Torque limited variable camshaft timing assembly

Abstract

An electrically variable camshaft timing (VCT) assembly includes a variator assembly including an input; an electric motor having a rotor, a stator, and a motor shaft coupled with the input of the variator assembly, wherein the motor shaft includes an etching on an outer surface of the motor shaft that releasably couples the motor shaft to a central bore of the rotor when an amount of torque exerted on the motor shaft via the variator assembly is less than or equal to a predetermined torque value, and the etching is further configured to decouple the motor shaft from the rotor when the amount of torque exerted on the motor shaft is greater than the predetermined torque value.

Description

Technical Field

[0001] This application relates to variable camshaft timing, and more specifically, to an electrically variable camshaft timing assembly. Background Technology

[0002] The vehicle may include motors that perform various vehicle functions, including, for example, adjusting the angular position of one or more camshafts relative to the crankshaft, or adjusting the position of a passenger or driver's seat. The motors can be used to operate camshaft phasers to advance or decelerate camshaft timing relative to the crankshaft. The camshaft phasers may include a transmission driven by the motors. Mechanical stops that limit the range of motion of the camshaft phasers may be included in the transmission. When the camshaft phasers reach the end of said range, the movement of the transmission may stop relatively abruptly and a relatively large torque may be applied to the output shaft of the motor. This relatively large torque may cause undue stress to the camshaft phasers, which this helps to reduce. Summary of the Invention

[0003] In one embodiment, the electrically variable variable camshaft timing (VCT) assembly includes a gearbox assembly including an input end; a motor having a rotor, a stator, and a motor shaft coupled to the input end of the gearbox assembly, wherein the motor shaft includes an etching on its outer surface that releasably engages a central bore of the rotor when the amount of torque applied to the motor shaft by the gearbox assembly is maintained at or below a predetermined torque value.

[0004] In another embodiment, the electric VCT assembly includes a first ring gear configured to receive rotational input from a crankshaft; a second ring gear configured to be coupled to a camshaft; a gearbox assembly coupled to the first and second ring gears to move the first ring gear at an angle relative to the second ring gear and having an input end; and a motor having a rotor, a stator, and a motor shaft coupled to the input end of the gearbox assembly, wherein the motor shaft includes etched features on its outer surface that releasably engage a central bore of the rotor. Attached Figure Description

[0005] Figure 1 This is an exploded view depicting an embodiment of the electric variable camshaft timing (VCT) assembly;

[0006] Figure 2 This is an exploded view depicting an embodiment of a transmission assembly used with an electric VCT assembly; and

[0007] Figure 3 It is a cross-sectional view depicting an embodiment of the electric VCT assembly;

[0008] Figure 4It is a cross-sectional view depicting an embodiment of a motor used with an electric VCT assembly;

[0009] Figure 5 It is a perspective view depicting an embodiment of the rotor and motor shaft used with an electric motor;

[0010] Figure 6 It is a perspective view depicting an embodiment of the rotor and motor shaft used with an electric motor;

[0011] Figure 7 It is a perspective view depicting an embodiment with an etched motor shaft;

[0012] Figure 8 This is a perspective view depicting another embodiment of a motor shaft with etched details;

[0013] Figure 9 It is a outline drawing depicting an embodiment of the rotor; and

[0014] Figure 10 It is a outline diagram depicting an embodiment of the rotor. Detailed Implementation

[0015] An electrically operated variable camshaft timing (VCT) assembly may include a motor having a rotor and a stator, the motor having a motor shaft including an etched outer surface. The etching may extend axially along the outer surface of the motor shaft and may be produced by laser ablation. The electrically operated VCT assembly or camshaft phaser may include a gearbox having an output coupled to the camshaft and an input coupled to the motor shaft. The motor shaft may control the angular position or phase of the camshaft relative to the crankshaft. The gearbox may include mechanical stops that limit the angular displacement of the camshaft relative to the crankshaft. During assembly, the motor shaft and its etched outer surface may be forced into a central bore of the rotor, thereby creating a defined amount of frictional resistance between the motor shaft and the rotor. The etching may mechanically deform the surface of the central bore, thereby creating the defined frictional resistance.

[0016] The defined frictional resistance can be selected to generate a torque value at or below which the motor shaft will not angularly displace relative to the rotor, as occurs during normal operation, for example, when the phaser changes the phase of the camshaft relative to the crankshaft. However, when the camshaft is angularly displaced relative to the crankshaft to cause the mechanical gearbox engagement stop of the camshaft phaser, the amount of torque applied to the motor shaft by the gearbox can rise above a defined torque value, thus allowing relative angular rotation between the rotor and the shaft. Once the torque applied to the motor shaft drops below the defined torque value, the laser-etched outer surface again prevents angular displacement between the motor shaft and the rotor. This function can be repeated, where the etched outer surface holds the rotor relative to the shaft while the torque applied to the shaft is below a threshold limit, allowing the relative angular movement between the shaft and the gearbox to repeatedly exceed that limit. Etching and / or ablation patterns of different axial lengths can alter the defined torque value.

[0017] Compared to Figures 1 to 3 An embodiment of an electric VCT assembly 10 (also known as an electric camshaft phaser) is shown. The phaser 10 is a multi-piece mechanism having components that work together to transmit rotation from the engine crankshaft to the engine camshaft, and that can work together to angle the camshaft relative to the crankshaft for advancing and decelerating the opening and closing of engine valves. The phaser 10 can have different designs and constructions depending on, among other possible factors, the application in which the phaser is employed and the crankshaft and camshaft on which it operates. Figures 1 to 3 In the embodiments presented, for example, phaser 10 includes sprocket 12, planetary gear assembly 14, and camshaft plate or plate 16.

[0018] Sprocket 12 receives a rotational drive input from the crankshaft of the engine and rotates about axis X1. A timing chain or timing belt may be wound around sprocket 12 and crankshaft, such that rotation of the crankshaft is converted into rotation of the sprocket via the chain or belt. Other techniques for transmitting rotation between sprocket 12 and crankshaft are possible. Along its outer surface, sprocket 12 has a set of teeth 18 for engaging with a timing chain, timing belt, or another component. In various examples, this set of teeth 18 may include 38 individual teeth, 42 individual teeth, or some other number of teeth continuously spanning the circumference of sprocket 12. As shown, sprocket 12 has a housing 20 extending axially from this set of teeth 18. Housing 20 is a cylindrical wall surrounding a portion of planetary gear assembly 14.

[0019] Planetary gear stop 13 may be included on the inward-facing surface of sprocket 12 to limit angular displacement between the camshaft and crankshaft. Planetary gear stop 13 is one embodiment of a range limiting element. Planetary gear stop 13 engages a buffer stop and prevents further angular displacement between the camshaft and crankshaft in the advance and deceleration directions. However, planetary gear stop 13 can be implemented in several different ways. For example, the planetary gear stop may be movable rather than existing as a fixed protrusion extending radially inward from sprocket 12. For example, in one embodiment, the planetary gear stop may be an element that engages in a cavity of the camshaft ring gear, such that the planetary gear stop moves to engage an element included on the planetary gear assembly. In one embodiment, the planetary gear stop may be pivotable about an axis or may slide radially inward or radially outward to engage or disengage the planetary gear assembly 14. Various different planetary gear stops are described in U.S. Patent Application No. 15 / 635,281, the entire contents of which are incorporated herein by reference.

[0020] In the embodiment presented herein, planetary gear assembly 14 includes planetary gear 24. A sun gear 22 is driven by a motor 23 to rotate about axis X1. The sun gear 22 meshes with planetary gear 24 and has a set of teeth 32 on its exterior that directly mesh with planetary gear 24. In various examples, this set of teeth 32 may include 26 individual teeth, 37 individual teeth, or some other number of teeth that continuously span the circumference of the sun gear 22. A cylindrical skirt 34 spans across this set of teeth 32. As described, the sun gear 22 is an external spur gear, but may be another type of gear. The motor 23 includes a stator and a rotor (not shown). The rotor may be coupled to motor shaft 100 in a manner discussed in more detail below. Current may be received through windings included in the stator to induce rotational motion of the rotor relative to the stator. The rotational motion of the rotor is coupled to motor shaft 100. A key 102 may be coupled to the distal end of motor shaft 100. The key 102 can be shaped to engage the sun gear 22 and transmit rotational motion from the motor shaft 100 to the planetary gear assembly 14.

[0021] Planetary gear 24 rotates about its individual axis of rotation X2 when bringing the engine camshaft into advancing and decelerating angular positions. When not advancing or decelerating, planetary gear 24, sun gear 22, and ring gears 26, 28 rotate together about axis X1. In the embodiment presented herein, there are a total of three discrete planetary gears 24, which are designed and constructed similarly to each other, but other quantities of planetary gears may be present, such as one, two, four, or six. Regardless of the number, each of the planetary gears 24 can be engaged, respectively, with the first ring gear 26 and the second ring gear 28 included in the sprocket 12 and plate 16. Each planetary gear 24 may have a set of teeth 60 along its outer side for direct meshing with the ring gears 26, 28. In different examples, the teeth 60 may include 21 individual teeth, or some other quantity of teeth that continuously span the circumference of each of the planetary gears 24. To hold the planetary gears 24 in place and support them, a carrier assembly 62 may be provided. The carrier assembly 62 may have different designs and constructions. In the embodiment shown in the accompanying drawings, the carrier assembly 62 includes a first carrier plate 64 on one side, a second carrier plate 66 on the other side, and a cylinder 68 serving as the hub for rotating the planetary gear 24. Planetary pins or bolts 70 may be used with the carrier assembly 62. It should be understood that other embodiments of the planetary gear assembly are possible, such as using an eccentric shaft and a compound planetary gear or using another type of gear driven by harmonics. Embodiments in which a ring gear and a planetary gear are attached to a camshaft via a coupling are also possible.

[0022] The first ring gear 26 receives a rotational drive input from the sprocket 12, causing the first ring gear 26 and the sprocket 12 to rotate together about axis X1. The first ring gear 26 may be an integral extension of the sprocket 12, that is, the first ring gear 26 and the sprocket 12 may form an integral structure together. The first ring gear 26 has a ring shape, meshes with the planetary gear 24, and has a set of teeth 72 inside it for direct meshing with the planetary gear 24. In different examples, the teeth 72 may include 80 individual teeth or some other number of teeth that continuously span the circumference of the first ring gear 26. In the embodiment presented herein, the first ring gear 26 is an internal spur gear, but may be another type of gear.

[0023] The second ring gear 28 transmits rotational drive output to the engine camshaft about axis X1. In this embodiment, the second ring gear 28 drives the rotation of the camshaft via plate 16. The second ring gear 28 and plate 16 can be joined together in various ways, including by interlocking with cuts and tabs, press-fitting, welding, adhesion, bolting, riveting, or by another technique. In embodiments not shown herein, the second ring gear 28 and plate 16 can be integral extensions of each other to form a single structure. Like the first ring gear 26, the second ring gear 28 has a ring shape that meshes with planetary gears 24, and contains a set of teeth 74 for direct meshing with the planetary gears. In various examples, teeth 74 may include 77 individual teeth, or some other number of teeth that continuously span the circumference of the second ring gear 28. The number of teeth between the first ring gear 26 and the second ring gear 28 relative to each other may be a multiple of the number of planetary gears 24 provided. Thus, for example, teeth 72 may include 80 individual teeth, while teeth 74 may include 77 individual teeth, in this example, the three planetary gears 24 differ by three individual teeth. In another example with six planetary gears, tooth 72 may include 70 individual teeth, while tooth 74 may include 82 individual teeth. Satisfying this relationship provides propulsion and deceleration capabilities by transmitting relative rotational motion and relative rotational speed between the first ring gear 26 and the second ring gear 28 in operation. In the embodiment presented here, the first ring gear 28 is an internal spur gear, but could be another type of gear. Plate 16 includes a central bore 76 through which a central bolt 78 passes to securely attach plate 16 to the camshaft. Furthermore, plate 16 is fastened to sprocket 12 using a retaining ring 80, which axially constrains the planetary gear assembly 14 between sprocket 12 and plate 16.

[0024] The two ring gears 26 and 28 together constitute a separate ring gear configuration for the camshaft phaser 10. However, it should be understood that other camshaft phaser designs can be used with a damping stop. For example, the camshaft phaser can be implemented using an eccentric shaft, a compound planetary gear, and two ring gears. Alternatively, the camshaft phaser may include more than two ring gears. For example, the camshaft phaser 10 may include an additional third ring gear for a total of three ring gears. Here, the third ring gear can also transmit the rotary drive output to the engine camshaft, just like the second ring gear 28, and may have the same number of individual teeth as the second ring gear.

[0025] Figure 4A cross-sectional view of motor 23 is shown. Motor 23 is shown as having a rotor 104, a stator 106, and a motor shaft 100 mechanically forced into a central bore 108 of the rotor 104. Etching 110 has been performed along the axial length of the shaft 100 on the outer surface of the motor shaft 100. Etching 110 abuts and connects to the central bore 108 of the rotor 104. Etching 110 may be a portion of the surface area of ​​the motor shaft 100 that has a different coefficient of friction relative to the remaining surface area of ​​the shaft 100. Etching 110 can be produced by applying a laser to the desired portion of the surface area for a defined period of time before assembly with the rotor 104. The application of the laser can change the coefficient of friction of the portion of the surface area by melting the outer surface of the motor shaft 100. In one embodiment, a laser can apply a laser beam to the surface of the motor shaft 100 for a defined period of time. The energy of the laser beam and the duration of application can be affected by the material of the motor shaft 100 and the shape of the portion of the surface area of ​​the motor shaft 100 to be etched.

[0026] The motor shaft 100 with etching 110 and rotor 104 is in Figure 5 It is shown in the pre-assembled state and Figure 6 The components are shown in the diagram. The motor shaft 100 can be mechanically pressed into the center hole 108 of the rotor 104 until the etching 110 is axially aligned with the rotor 104 along the axis of rotation (x). The etching 110 engages the rotor 104 via the center hole 108, thereby resisting angular displacement of the motor shaft 100 relative to the rotor 104. The coefficient of friction of the etching 110 can be increased or decreased according to the amount of torque required to make angular displacement of the motor shaft 100 relative to the rotor 104.

[0027] The etching on a portion of the surface area of ​​the motor shaft 100 can be shaped in different ways to control the amount of torque required to cause angular displacement of the motor shaft 100 relative to the rotor 104. In some embodiments, the surface area of ​​the motor shaft 100 may include an added pattern in the axially extending surface area. (Go to...) Figure 7 Etching 110a is shown as a triangular spline 116, which increases the circumferential width around the circumference of the motor shaft 100, moving from the distal end 112 of the shaft 100, which is first inserted into the central hole 108, toward the motor 23. The triangular spline extends the axial length (y) of the motor shaft 100 and includes a plurality of etched points 114 that together form a triangular shape.

[0028] For example, an etched point 114a can be positioned at the beginning of etch 110a, at an axial position along the rotation axis (x), and additional points 114a with increasingly larger circumferential widths can be placed at axial positions increasingly farther from the distal end 112. Then, two points 114b can be positioned along the rotation axis (x) at axial points farther from the distal end 112 and points 114a. The two points 114b increase the circumferential width when the additional points 114b are placed away from the distal end 112 on the surface of the motor shaft 100. The narrower width of etch 110a towards the distal end 112 can contribute to a stronger bond between etch 110a and the rotor 104 after insertion into the center hole 108. When the motor shaft 100 is pressed into the center hole 108 such that etch 110a engages the rotor material, the portion of etch 110a closest to the distal end 112 agitates the material of the rotor 104 it is engaging, such as point 114a. However, based on the axial movement of the motor shaft 100 relative to the rotor 104, a subsequent wider etching 110a (such as dot 114b) connects the fresh rotor material disturbed by another part (such as dot 114a) that was not previously etched 110a.

[0029] Figure 8 Another embodiment of etching 110b is shown. Etching 110b includes a rectangular spline 118 of a relatively uniform length extending along the axial length (y) of the motor shaft 100. The rectangular spline 118 may include a plurality of uniformly formed points 114 extending a portion of the axial length (y) of the motor shaft 100. A first set of rectangular splines 118 may extend axially along a first axial segment (y1) of the motor shaft 100, and a second set of rectangular splines 118 may extend axially along a second axial segment (y2) of the motor shaft 100. The first set of rectangular splines 118 may be angularly displaced from the second set of rectangular splines 118 relative to the axis of rotation (x).

[0030] Turn Figure 9 and Figure 10 An embodiment of a rotor 104a with a non-circular center bore 108a is shown. The non-circular center bore 108a allows the bore 108a or hole to elastically deform or bend to facilitate the assembly of the motor shaft 100 into the rotor 104a. Compared to press-fit assemblies using circular center bores, the non-circular center bore 108a can also help regulate the pressure or force between the motor shaft 100 and the rotor 104a after assembly. In one embodiment, a plurality of protrusions 120 may be used to create the non-circularity, these protrusions extending radially inward toward the axis of rotation (x) and circumferentially spaced radially inward toward the aperture surfaces of the etched 110 and the outer surface of the motor shaft 100.

[0031] It should be understood that the foregoing description 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 defined solely by the following claims. Furthermore, the statements contained in the foregoing description relate to specific embodiments and should not be construed as limiting the scope of the invention or the definition of terms used in the claims, unless the terms or phrases are expressly defined above. Various other embodiments, as well as various changes and modifications to the disclosed embodiments, will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to fall within the scope of the appended claims.

[0032] The terms “for example,” “e.g.,” “for example,” “such as,” “for instance,” and “like,” as well as the verbs “comprising,” “having,” “including,” and other verb forms thereof, used in this specification and claims, when used with a list of one or more parts or other items, shall be interpreted as open-ended, meaning that the list shall not be construed as excluding other, additional parts or items. Other terms shall be interpreted using their broadest reasonable meaning unless used in a context requiring a different interpretation.

Claims

1. An electrically variable camshaft timing (VCT) assembly, comprising: A transmission assembly configured to change the angular position of a camshaft relative to a crankshaft, the transmission assembly including an input end; and An electric motor, comprising a rotor, a stator, and a motor shaft coupled to the input terminal, wherein the outer surface of the motor shaft includes an etching configured to releasably couple the motor shaft to the rotor at the center bore of the rotor when the amount of torque applied to the motor shaft via the gearbox assembly is less than or equal to a predetermined torque value, and the etching is further configured to disengage the motor shaft from the rotor when the amount of torque applied to the motor shaft is greater than the predetermined torque value.

2. The electric VCT assembly according to claim 1, wherein, The etching forms multiple triangular splines.

3. The electric VCT assembly according to claim 1, wherein, The etching forms multiple rectangular splines.

4. The electric VCT assembly according to claim 1, wherein, The etching involves multiple points.

5. The electric VCT assembly according to claim 3, wherein, The plurality of rectangular splines includes a first group of rectangular splines and a second group of rectangular splines that are angularly displaced from the first group of rectangular splines.

6. The electric VCT assembly according to claim 1, wherein, The central aperture is a non-circular central aperture.

7. The electric VCT assembly of claim 6, wherein the non-circular central aperture includes one or more radially inwardly extending protrusions.

8. The electric VCT assembly according to claim 1, wherein, The gearbox assembly also includes a plurality of planetary gears and a sun gear meshing with the plurality of planetary gears.

9. An electrically variable camshaft timing (VCT) assembly, comprising: A first ring gear, the first ring gear being configured to receive rotational input from a crankshaft; A second ring gear, the second ring gear being configured to be coupled to a camshaft; A transmission assembly configured to connect a first ring gear and a second ring gear such that the first ring gear is angularly displaced relative to the second ring gear, the transmission assembly including an input terminal; and An electric motor, comprising a rotor, a stator, and a motor shaft coupled to the input terminal, wherein the outer surface of the motor shaft includes an etching configured to releasably engage a central aperture of the rotor.

10. The electric VCT assembly according to claim 9, wherein, The etching forms multiple triangular splines.

11. The electric VCT assembly according to claim 9, wherein, The etching forms multiple rectangular splines.

12. The electric VCT assembly according to claim 9, wherein, The etching involves multiple points.

13. The electric VCT assembly according to claim 11, wherein, The plurality of rectangular splines includes a first group of rectangular splines and a second group of rectangular splines that are angularly displaced from the first group of rectangular splines.

14. The electric VCT assembly according to claim 9, wherein, The central aperture is a non-circular central aperture.

15. The electric VCT assembly according to claim 14, wherein, The non-circular center aperture includes one or more radially inwardly extending protrusions.

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