Variable camshaft timing sun gear cushion ring

An electrically-controlled camshaft phaser with a gearbox assembly, including a sun gear having outwardly-facing gear teeth; at least one planet gear, having outwardly-facing gear teeth, that moves radially relative to an axis of sun gear rotation; at least one pin that carries the planet gear; and a deformable outer ring, carried by the sun gear, that engages the planet gear and moves the planet gear radially toward a ring gear.

TECHNICAL FIELD

The present application relates to electric motors and, more particularly, to gearboxes driven by an output shaft of an electric motor.

BACKGROUND

Internal combustion engines include camshafts that open and close valves regulating the combustion of fuel and air within combustion chambers of the engines. The opening and closing of the valves are carefully timed relative to a variety of events, such as the injection and combustion of fuel into the combustion chamber and the location of the piston relative to top-dead center (TDC). Camshaft(s) are driven by the rotation of the crankshaft via a drive member connecting these elements, such as a belt or chain. In the past, a fixed relationship existed between the rotation of the crankshaft and the rotation of the camshaft. However, internal combustion engines increasingly use camshaft phasers that vary the phase of camshaft rotation relative to crankshaft rotation. Variable camshaft timing (VCT) devices—camshaft phasers—can, in some implementations, be actuated by electric motors that advance or retard the opening/closing of valves relative to crankshaft rotation.

Electrically-actuated camshaft phasers typically include a gearbox assembly having an input and an output as well as an electric motor. The electric motor can couple to the input of the gearbox assembly while the output of the assembly can be coupled to a camshaft of an internal combustion engine. The components of the gearbox assembly can include a defined amount of space between them that is tolerated. As the gearbox assembly is used, the defined amount of space can cause backlash, which can increase as components wear with use. It would be helpful to be able to reduce this amount of space to minimize the amount of backlash in the gearbox assembly.

SUMMARY

In one implementation, an electrically-controlled camshaft phaser with a gearbox assembly, including a sun gear having outwardly-facing gear teeth; at least one planet gear, having outwardly-facing gear teeth, that moves radially relative to an axis of sun gear rotation; at least one pin that carries the planet gear; and a deformable outer ring, carried by the sun gear, that engages the planet gear and moves the planet gear radially toward a ring gear.

In another implementation, an electrically-controlled camshaft phaser with a gearbox assembly, including a sun gear having outwardly-facing gear teeth in between one axial end and another axial end of the sun gear; a circumferential groove formed in the sun gear between the axial ends; at least one planet gear, having outwardly-facing gear teeth, that moves radially relative to an axis of sun gear rotation; at least one pin that carries the planet gear; and a deformable outer ring, received within the circumferential groove, that engages the planet gear and moves the planet gear radially toward a ring gear.

In yet another implementation, an electrically-controlled camshaft phaser with a gearbox assembly, including a sun gear having outwardly-facing gear teeth; at least one planet gear, having outwardly-facing gear teeth, that moves radially relative to an axis of sun gear rotation; at least one pin that carries the planet gear; an axial section of the sun gear adjacent a radial face of the gear teeth; a first deformable outer ring carried by the axial section; and a second deformable outer ring carried by the sun gear adjacent an opposite radial face of the gear teeth, wherein the first deformable outer ring and the second deformable outer ring engage the planet gear and move the planet gear radially toward a ring gear.

DETAILED DESCRIPTION

A gearbox assembly included with an electrically-controlled camshaft phaser can include a sun gear having a resiliently deformable outer ring that is outwardly facing and engages with one or more planet gears to urge the planet gear(s) radially-outwardly toward ring gears. The outer ring can engage the planet gear(s) in one of a variety of different positions. For example, the outer ring can engage the teeth of the planet gear or the outer ring can engage a hub of the planet gear. In one implementation, the planet gears can rotate about pins that move radially outwardly and inwardly relative to the sun gear so that they can be moved into engagement with the ring gears by the outer ring. Or in another implementation, the planet pins are fixed so that the pins do not move radially. An inner diameter of the planet gear can be slightly larger than an outer diameter of the planet pin. The outer ring can bias the planet gear radially outwardly relative to the planet pin. The outer ring can be formed from an elastomeric material that resists compression and forces the planet gear(s) radially outwardly toward and into engagement with ring gears. The force exerted by the outer ring can reduce lash in the gearbox. Due to the interface between a sun gear and one or more planet gears, an amount of backlash exists. The backlash can range from negative (unwanted binding) to an undesirable high level because of manufacturing tolerances. The outer ring in the present disclosure has the ability to control a center distance to have zero backlash while avoiding the negative binding. An added benefit is that the outer ring can also compensate for component wear that would otherwise lead to an increase in backlash as the camshaft phaser is used.

An embodiment of an electrically-actuated VCT assembly10(also referred to as an electrically-controlled camshaft phaser or “phaser”) is shown with respect toFIGS.1-3. The phaser10is a multi-piece mechanism with components that work together to transfer rotation from the engine's crankshaft and to the engine's camshaft, and that can work together to angularly displace the camshaft relative to the crankshaft for advancing and retarding engine valve opening and closing. The phaser10can have different designs and constructions depending upon, among other possible factors, the application in which the phaser is employed and the crankshaft and camshaft that it works with. In the embodiment presented inFIGS.1-3, for example, the phaser10includes a sprocket12, a planetary gear assembly14, and a camshaft plate or plate16.

The sprocket12receives rotational drive input from the engine's crankshaft and rotates about an axis x1. A timing chain or a timing belt can be looped around the sprocket12and around the crankshaft so that rotation of the crankshaft translates into rotation of the sprocket via the chain or belt. Other techniques for transferring rotation between the sprocket12and crankshaft are possible. Along an outer surface, the sprocket12has a set of teeth18for mating with the timing chain, with the timing belt, or with another component. In different examples, the set of teeth18can include thirty-eight individual teeth, forty-two individual teeth, or some other quantity of teeth spanning continuously around the circumference of the sprocket12. As illustrated, the sprocket12has a housing20spanning axially from the set of teeth18. The housing20is a cylindrical wall that surrounds part of the planetary gear assembly14.

A planetary gear stop can be included to limit the angular displacement between the camshaft and the crankshaft. The planetary gear stop can engage a portion of the planetary gear assembly14and prevent further angular displacement between the camshaft and the crankshaft in both an advancing direction and a retarding direction. It should be appreciated that the planetary gear stop can be implemented in a number of different ways. A variety of different planetary gear stops are described in U.S. patent application Ser. No. 15/635,281, the entirety of which is incorporated by reference.

In the embodiment presented here, the planetary gear assembly14includes planet gears24. A sun gear22is driven by an electric motor23for rotation about the axis X1. The sun gear22engages with the planet gears24and has a set of teeth32at its exterior that makes direct teeth-to-teeth meshing with the planet gears24. In different examples, the set of teeth32can include twenty-six individual teeth, thirty-seven individual teeth, or some other quantity of teeth spanning continuously around the circumference of the sun gear22. A skirt34in the shape of a cylinder spans from the set of teeth32. As described, the sun gear22is an external spur gear, but could be another type of gear. The electric motor23includes a stator and a rotor (not shown). The rotor can be coupled to a motor shaft100to prevent angular movement of the rotor relative to the motor shaft100. Electric current can be received by windings included with the stator to induce rotational movement of the rotor relative to the stator. The rotational movement of the rotor is communicated to the motor shaft100.

The planet gears24rotate about their individual rotational axes x2when in the midst of bringing the engine's camshaft among advanced and retarded angular positions. When not advancing or retarding, the planet gears24revolve together around the axis x1with the sun gear22and with the ring gears26,28. In the embodiment presented here, there are a total of three discrete planet gears24that are similarly designed and constructed with respect to one another, but there could be other quantities of planet gears such as one, two, four or six. However many there are, each of the planet gears24can engage with first and second ring gears26,28, included with the sprocket12and the plate16, respectively. Each planet gear24can have a set of teeth60along its exterior for making direct teeth-to-teeth meshing with the ring gears26,28. In different examples, the teeth60can include twenty-one individual teeth, or some other quantity of teeth spanning continuously around the circumference of each of the planet gears24. To hold the planet gears24in place and support them, a carrier assembly62can be provided. The carrier assembly62can have different designs and constructions. In the embodiment presented in the figures, the carrier assembly62includes a first carrier plate64on one side, a second carrier plate66on the other side, and slots68that serve as a hub for the rotating planet gears24. Planet pins or bolts70can be used with the carrier assembly62. The slots68can receive the pins70and permit the radial movement of the planet gears24toward and away from the sun gear22relative to axis x1. It should be appreciated that other implementations of the planetary gear assembly are possible and that term should be understood to include other such implementations. Implementations having one ring gear and a planet gear attached to a camshaft via a coupling are possible as well.

The first ring gear26receives rotational drive input from the sprocket12so that the first ring gear26and sprocket12rotate together about the axis x1in operation. The first ring gear26can be a unitary extension of the sprocket12—that is, the first ring gear26and the sprocket12can together form a monolithic structure. The first ring gear26has an annular shape, engages with the planet gears24, and has a set of teeth72at its interior for making direct teeth-to-teeth meshing with the planet gears24. In different examples, the teeth72can include eighty individual teeth, or some other quantity of teeth spanning continuously around the circumference of the first ring gear26. In the embodiment presented here, the first ring gear26is an internal spur gear, but could be another type of gear.

The second ring gear28transmits rotational drive output to the engine's camshaft about the axis x1. In this embodiment, the second ring gear28drives rotation of the camshaft via the plate16. The second ring gear28and plate16can be connected together in different ways, including by a cutout-and-tab interconnection, press-fitting, welding, adhering, bolting, riveting, or by another technique. In embodiments not illustrated here, the second ring gear28and the plate16could be unitary extensions of each other to make a monolithic structure. Like the first ring gear26, the second ring gear28has an annular shape, engages with the planet gears24, and has a set of teeth74at its interior for making direct teeth-to-teeth meshing with the planet gears. In different examples, the teeth74can include seventy-seven individual teeth, or some other quantity of teeth spanning continuously around the circumference of the second ring gear28. With respect to each other, the number of teeth between the first and second ring gears26,28can differ by a multiple of the number of planet gears24provided. So, for instance, the teeth72can include eighty individual teeth, while the teeth74can include seventy-seven individual teeth-a difference of three individual teeth for the three planet gears24in this example. In another example with six planet gears, the teeth72could include seventy individual teeth, while the teeth74could include eighty-two individual teeth. Satisfying this relationship furnishes the advancing and retarding capabilities by imparting relative rotational movement and relative rotational speed between the first and second ring gears26,28in operation. In the embodiment presented here, the second ring gear28is an internal spur gear, but could be another type of gear. The plate16includes a central aperture76through which a center bolt78passes to fixedly attach the plate16to the camshaft. In addition, the plate16is also secured to the sprocket12with a snap ring80that axially constrains the planetary gear assembly14between the sprocket12and the plate16.

Together, the two ring gears26,28constitute a split ring gear construction for the camshaft phaser10. However, it should be appreciated that other camshaft phaser designs can be used with the cushioned stops. For example, the camshaft phaser could be implemented using an eccentric shaft, a compound planet gear, and two ring gears. Or the camshaft phaser could include more than two ring gears. For instance, the camshaft phaser10could include an additional third ring gear for a total of three ring gears. Here, the third ring gear could also transmit rotational drive output to the engine's camshaft like the second ring gear28, and could have the same number of individual teeth as the second ring gear.

Turning toFIGS.4-7, an implementation of the sun gear22is shown. The sun gear22includes a circumferential groove82that bifurcates the teeth32such that the groove82is located in between one axial end84of the sun gear22and another axial end86of the sun gear22. The groove82can have a cross sectional shape that closely conforms to the cross-sectional shape of the resiliently deformable outer ring88. The outer ring88can be formed from any one of a variety of different materials, such as an elastomeric material, that is compressible and when loaded provides an opposite-direction return force. The surface of the outer ring88can engage the teeth60of one or more planet gears24to urge the planet gear(s)24radially-outwardly toward ring gears26,28. As the outer ring engages the teeth60of the planet gear(s)24, the pins70carrying the planet gears24can move radially-outwardly within the slots68toward the teeth72,74of the first and second ring gears26,28. The diameter of the outer ring88can closely conform to a base diameter of the sun gear22and/or the circumferential groove82, but the cross-sectional size of the outer ring88can be selected based on the amount of radial-outward force desired from the sun gear22on the planet gears24.

Turning toFIG.8, another implementation of sun gear22′ and planet gears24is shown. The sun gear22′ includes a plurality of outer rings88on opposite sides of the sun gear teeth32. A first outer ring88acan be positioned on the skirt34such that the ring88aabuts a radial face90of the gear teeth32. A second outer ring88bcan be positioned adjacent an opposite radial face92of the gear teeth32; a location that is also adjacent to motor shaft100. An axial section94of the sun gear22, adjacent to where the motor shaft100provides input to the sun gear22, can include a surface for receiving the second outer ring88b. The surface of the first outer ring88aand the surface of the second outer ring88bcan both engage the teeth60of the planet gear(s)24and urge the planet gear(s)24radially-outwardly toward ring gears26,28. As the first outer ring88aand the second outer ring88bengage the teeth60of the planet gear(s)24, the pins70carrying the planet gears24can move radially-outwardly within the slots68toward the teeth72,74of the first and second ring gears26,28.

Turning toFIG.9, another implementation of sun gear22′ and planet gears24′ is shown. The sun gear22′ includes a plurality of outer rings88on opposite sides of the sun gear teeth32. The first outer ring88acan be positioned on the skirt34such that the ring88aabuts a radial face90of the gear teeth32. The second outer ring88bcan be positioned adjacent an opposite radial face92of the gear teeth32; a location that is also adjacent to motor shaft100. An axial section94of the sun gear22, adjacent to where the motor shaft100provides input to the sun gear22, can include a surface for receiving the second outer ring88b. Planet gears24′ can include a first hub surface96adjacent a radial gear face98of teeth60and a second hub surface100adjacent an opposite radial gear face102of teeth60. The first and second hub surfaces96,100can extend circumferentially around the pin68and may be configured to engage the first and second outer rings88a,88b, respectively. The surface of the first outer ring88aand the surface of the second outer ring88bcan both engage the first and second hub surfaces96,100of the planet gear(s)24′ and urge the planet gear(s)24′ radially-outwardly toward ring gears26,28. As the first outer ring88aand the first and second hub surfaces96,100of the planet gear(s)24′, the pins70carrying the planet gears24′ can move radially-outwardly within the slots68toward the teeth72,74of the first and second ring gears26,28.