Eccentric gears with reduced bearing span

An electrically-controlled eccentric camshaft phaser (10) that adjusts phase between a camshaft and a crankshaft includes a sprocket (12), configured to connect to the crankshaft and rotate about a center axis (x), having a sprocket ring gear (14); a camshaft plate (20) configured to connect to the camshaft and rotate about the center axis (x), having a camshaft ring gear (22); an eccentric shaft (28) that includes a crankshaft eccentric section (52) and a camshaft eccentric section (54); a sprocket bearing (16) that is received by the crankshaft eccentric section (52); a camshaft bearing (64), having a different diameter than the sprocket bearing (16), that is received by the camshaft eccentric section (54).

TECHNICAL FIELD

The present application relates to camshaft phasers and, more particularly, to electrically-actuated camshaft phasers that use eccentric gears.

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. Increasingly, internal combustion engines now use camshaft phasers that vary the phase of camshaft rotation relative to crankshaft rotation.

A variety of different camshaft phaser designs exist. Some camshaft phasers rely on hydraulic fluid to adjust the angular position of the camshaft relative to the crankshaft while others are actuated by electric motors that advance or retard the opening/closing of valves relative to crankshaft rotation. Camshaft phasers that are actuated by electric motors can use a plurality of gears to vary the angular position of a camshaft relative to a crankshaft. Vehicle designers work to create vehicle engines that consume less space while producing the same, if not more, horsepower. Designing vehicle engines having smaller physical dimensions can be furthered by reducing the size of engine components, such as camshaft phasers.

SUMMARY

In one embodiment, an electrically-controlled eccentric camshaft phaser that adjusts phase between a camshaft and a crankshaft and includes a sprocket, configured to connect to the crankshaft and rotate about a center axis, having a sprocket ring gear that includes a plurality of radially-inwardly facing gear teeth; a camshaft plate, configured to connect to the camshaft and rotate about the center axis, having a camshaft ring gear that includes a plurality of radially-inwardly facing gear teeth; an eccentric shaft that includes a crankshaft eccentric section and a camshaft eccentric section; a sprocket bearing that is received by the sprocket and the crankshaft eccentric section; a camshaft bearing, having a different diameter than the sprocket bearing, that is received by the camshaft eccentric section, wherein at least a portion of the sprocket bearing and the camshaft bearing abut each other; and a compound planetary gear including a sprocket planetary gear engaging the sprocket ring gear and a camshaft planetary gear engaging the camshaft ring gear.

In another embodiment, an electrically-controlled eccentric camshaft phaser that adjusts phase between a camshaft and a crankshaft includes a sprocket, configured to connect to the crankshaft and rotate about a center axis, having a sprocket ring gear that includes a plurality of radially-inwardly facing gear teeth; a sprocket bearing that is received via an axial side of the sprocket and abuts the sprocket ring gear; a camshaft bearing, having a different diameter than the sprocket bearing, that is received via the axial side; a camshaft plate, including a camshaft ring gear axially spaced from the sprocket ring gear, configured to rotationally couple with the camshaft and rotate about the center axis, includes a plurality of radially-inwardly facing gear teeth; an eccentric shaft including a crankshaft eccentric section that is engaged with an inner diameter of the sprocket bearing and a camshaft eccentric section that is engaged with an inner diameter of the camshaft bearing, wherein the eccentric shaft is adapted for insertion into the camshaft phaser via the axial side of the sprocket passing through the inner diameter of the sprocket bearing and the inner diameter of the camshaft bearing; and a compound planetary gear including a sprocket planetary gear engaging the sprocket ring gear and a camshaft planetary gear engaging the camshaft ring gear.

In yet another embodiment, an electrically-controlled eccentric camshaft phaser that adjusts phase between a camshaft and a crankshaft includes a sprocket, configured to connect to the crankshaft and rotate about a center axis (x), having a sprocket ring gear that includes a plurality of radially-inwardly facing gear teeth; a camshaft plate, configured to connect to the camshaft and rotate about the center axis (x), having a camshaft ring gear that includes a plurality of radially-inwardly facing gear teeth; a sprocket bearing that is received by the sprocket; a camshaft bearing, having a different diameter than the sprocket bearing, received by the camshaft plate; a compound planetary gear including a sprocket planetary gear engaging the sprocket ring gear and a camshaft planetary gear engaging the camshaft ring gear; and an eccentric shaft that includes a crankshaft eccentric portion engaging the sprocket bearing, a camshaft eccentric portion engaging the camshaft bearing, and a bearing spacer, wherein the bearing spacer does not extend radially-outwardly beyond the camshaft eccentric portion.

DETAILED DESCRIPTION

An electrically-controlled camshaft phaser includes an eccentric shaft, a compound planetary gear, and a plurality of ring gears that vary the angular position of the camshaft relative to the crankshaft. A sprocket housing or crankshaft sprocket includes a sprocket ring gear having a plurality of inwardly-facing gear teeth and sprocket teeth that connect to the crankshaft via an endless loop, such as a timing chain. A bearing opening in an end of the sprocket receives a sprocket bearing. A camshaft bearing, having a different diameter than the sprocket bearing, can be positioned axially adjacent to the sprocket bearing such that in some implementations a portion of the camshaft bearing abuts or touches the sprocket bearing and in other implementations they are slightly separated by a bearing spacer. An eccentric shaft fits within the inner diameter of both the sprocket bearing and the camshaft bearing when inserted from one side of the camshaft phaser and can include one or more features that constrain the bearings from axial movement. A compound planet gear having an inner diameter and an outer diameter can attach to an outer diameter surface of the camshaft bearing. A camshaft plate connects to a camshaft and includes a camshaft ring gear having a plurality of inwardly-facing gear teeth. The compound planet gear engages the sprocket ring gear and the camshaft ring gear. An electric motor is coupled to the eccentric shaft, which rotates the compound planet gear to vary the angular position of the camshaft relative to the crankshaft.

The electrically-controlled camshaft phaser uses bearings having different diameters that are axially close together or abutting so that, during assembly, the phaser bearings and the eccentric shaft are inserted into the camshaft phaser from one side. The close or abutting relationship between the phaser bearings can minimize moment loading on the phaser bearings from the eccentric shaft. When the gears of the eccentric camshaft phaser are loaded, the camshaft bearing and the sprocket bearing prevent excessive tipping of the eccentric shaft. The phaser bearings, implemented as single row bearings, can transmit the load radially as needed. By single row bearings, this means that the bearings use a single row of ball bearings. Further, the eccentric shaft can allow a larger inner diameter that provides additional clearance for a bolt that attaches the camshaft phaser to the camshaft or use of a larger bolt. In contrast, past camshaft phasers use eccentric shafts that receive one phaser bearing on one end of the eccentric shaft and another phaser bearing on an opposite end. These bearings are installed on opposite sides of the eccentric shaft because of a shoulder having a larger diameter than the eccentric shaft located in between the phaser bearings. Assembling such a camshaft phaser involves accessing both sides of the camshaft phaser or at least both sides of the eccentric shaft, which makes assembly more challenging. Also, separating the bearings with the eccentric shaft shoulder can increase the overall axial length of the camshaft phaser as well as the moment loading relative to the camshaft phaser.

An embodiment of an electrically-controlled camshaft phaser that is controlled using an electric motor and an eccentric shaft is shown inFIGS. 1-2. The camshaft phaser10includes a crankshaft sprocket12that connects to a crankshaft and includes a sprocket ring gear14and a sprocket bearing16. The sprocket ring gear14includes a set of inwardly-facing gear teeth18. A camshaft plate20attaches to a camshaft and includes a camshaft ring gear22comprising a separate set of inwardly-facing gear teeth24. A compound planetary gear26uses two sets of outwardly facing gear teeth that each engage with the camshaft ring gear22and the sprocket ring gear14. An eccentric shaft28connects to the crankshaft sprocket12or the camshaft plate20such that a portion of the eccentric shaft28rotates about the axis (x). The eccentric shaft28also connects to the compound planetary gear26along an eccentric axis (ex). The crankshaft sprocket12and the camshaft plate20each rotate about axis (x). A portion of the eccentric shaft28is rotationally driven by an electric motor30about axis x according to desired phasing such that the compound planetary gear26rotates about the eccentric axis ex.

Operating the electric motor30so that an output shaft32rotates the eccentric shaft28at the same speed as the crankshaft sprocket12maintains an existing angular position of the camshaft relative to the crankshaft. Changing the rate at which the output shaft32rotates relative to the rate at which the crankshaft sprocket12rotates changes the angular position (also called “phase”) of the camshaft relative to the crankshaft. For example, when the output shaft32rotates faster than the crankshaft sprocket12, the eccentric shaft28rotates the compound planetary gear26relative to the sprocket ring gear14and the camshaft ring gear22thereby displacing the camshaft plate20relative to the crankshaft sprocket12to advance the phase of the camshaft relative to the crankshaft. And when the output shaft32rotates slower than the crankshaft, the eccentric shaft28rotates the compound planetary gear26relative to the sprocket ring gear14and the camshaft ring gear22thereby displacing the camshaft plate20relative to the camshaft sprocket12to retard the phase of the camshaft relative to the crankshaft.

The crankshaft sprocket12receives rotational drive input from the engine's crankshaft and rotates about the axis x. An endless loop power transmission member, such as 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 sprocket12via the member. Other techniques for transferring rotation between the sprocket12and crankshaft are possible. Along an outer surface, the sprocket12has a plurality of sprocket teeth34for mating with the timing chain, with the timing belt, or with another component. As shown, the sprocket12has a housing36spanning axially from the sprocket teeth34. The housing36includes the sprocket ring gear14within the housing36spaced axially and radially inward from the teeth34. The sprocket ring gear14includes a plurality of inwardly-facing gear teeth18and an end plate38at least partially closing one end of the sprocket12. The end plate38includes a bearing opening40that is roughly the same diameter as the sprocket bearing16. The sprocket bearing16is received by the sprocket12in the bearing opening40and abuts a bearing shoulder44. The gear teeth18of the sprocket ring gear14can be offset axially from the sprocket teeth34and the sprocket bearing16. In one implementation, all of the components of the camshaft phaser10are located in the axial space of the housing36.

The eccentric shaft28includes a crankshaft portion52and a camshaft portion54one of which is eccentric to the other. The crankshaft portion52and the camshaft portion54are not separated by a shoulder having an outer diameter larger than either the crankshaft portion52or the camshaft portion54that would separate the phaser bearings. Instead, the crankshaft portion52and the camshaft portion54are each sized to permit the phaser bearings to both slide over the eccentric shaft28from one end and, in some implementations, abut each other when the camshaft phaser10is assembled. Put differently, the sprocket bearing16and the camshaft bearing64can both be inserted into the sprocket12and the eccentric shaft28can then be inserted into the inner diameters of both bearings at the same time from one side of the eccentric phaser10.

The crankshaft portion52can be substantially annular having an outside surface that closely conforms to an inner diameter of the sprocket bearing16. The camshaft portion54can be eccentric relative to the crankshaft portion52. An outer surface of the camshaft portion54may be smaller in diameter relative to a camshaft bearing64and includes a recess69(shown inFIG. 5) for receiving a planetary biasing member68. The camshaft bearing64can have a larger inner and outer diameter than the sprocket bearing16. The increased diameter size of the camshaft bearing64can permit insertion of the eccentric shaft28even after the sprocket bearing16has been inserted into the bearing opening40and the sprocket bearing16has been placed into the sprocket12. The planetary biasing member68can help forcibly engage the compound planetary gear26with the sprocket ring gear14and the camshaft ring gear22. One end of the planetary biasing member68can engage the eccentric shaft28at the recess69and another end of the member68can direct force radially outwardly and toward an internal surface70of the camshaft bearing64. The recess69is located on the outer surface of the camshaft portion54and includes a reduced diameter section that can prevent movement of the planetary biasing member68.

The compound planetary gear26includes a sprocket planetary gear72and a camshaft planetary gear74. The sprocket planetary gear72and the camshaft planetary gear74include a set of outwardly-facing sprocket planetary gear teeth76that engage with the sprocket ring gear14and a set of outwardly-facing camshaft planetary gear teeth78that engage with the camshaft ring gear22, respectively. The number of gear teeth76used by the sprocket planetary gear72is different than the number of gear teeth18used by the sprocket ring gear14by more than one. And the camshaft ring gear22includes one or more additional gear teeth24relative to number of gear teeth78on the camshaft planetary gear74. In one implementation, the number of gear teeth differ by two.

The camshaft plate20is configured to be attached to the camshaft and includes the camshaft ring gear22. A camshaft plate end80substantially closes one end of the camshaft plate20and includes a bolt aperture82through which a retention bolt84passes and couples the camshaft to the camshaft plate20. While in this embodiment a single retention bolt84is shown, other implementations could use a plurality of retention bolts. In addition, the camshaft plate20includes an outer surface86that abuts the inwardly-facing surface48of the sprocket12so that the outer surface86of the camshaft plate20is radially-inward from the inwardly-facing surface48of the sprocket12.

Another implementation of the camshaft phaser10is shown inFIG. 3. In this implementation, the sprocket12includes a feature17that is formed after the sprocket bearing16has been inserted into the bearing opening40. The feature17then prevents the axial movement of the sprocket bearing16. The feature17can be created from the sprocket12shown inFIGS. 1-2after the sprocket bearing16has been inserted into the bearing opening40. A portion of the bearing opening40can be roller formed in a radially-inwardly direction to create a diameter-reduced portion that secures the sprocket bearing16against the bearing shoulder44. After the camshaft bearing64is installed in the camshaft phaser10, it can be axially separated from the sprocket bearing16to allow space for feature17. The sprocket bearing16may be separated from the camshaft bearing64by as much as 1.0 mm.

Turning toFIGS. 4a-4b, the sprocket bearing16and the camshaft bearing64have different diameters, one larger than the other, as discussed above. And in one implementation, the camshaft bearing64is larger in diameter than the sprocket bearing16by at least two times the eccentricity of the eccentric shaft28. As shown inFIG. 4a, this relates to the relationship between the camshaft ring gear22having radius rcand the sprocket ring gear14having radius rsas well as the sprocket planetary gear72having radius rp1and the camshaft planetary gear74having radius rp2. The diameters of the camshaft ring gear22and the sprocket ring gear14as well as the camshaft planetary gear74and the sprocket planetary gear72are shown. A first line402is drawn through the center (Cp1) of the camshaft planetary gear74and the center (Cp2) of the crankshaft planetary gear72. A second line404is drawn through the center (Cc) of the camshaft ring gear22and the center (Cs) of the crankshaft ring gear14. The eccentricity (e) of the sprocket ring gear14relative to the crankshaft ring gear22is indicated by the distance between the first line402and the second line404. Given that first line402and the second line404are parallel, e represents the difference between rp2and rcas well as the difference between rp1and rs. These differences of radial dimensions result in 2e , a diameter constraint. The diameter of the camshaft bearing64is sized relative to the diameter of the sprocket bearing16by a value of 2e or greater. This relationship can be appreciated fromFIG. 4bin which the sprocket bearing16rotates about a central axis (x) while the camshaft bearing64rotates about an eccentric axis (ex).

A compact design can be realized when a positive gear ratio exists between the sprocket gear14having radius rsand the camshaft gear22having radius rc. A positive gear ratio occurs when rsis larger than rc. Such a relationship facilitates fitting the camshaft plate20radially inward from the sprocket12thereby reducing the overall axial length of the camshaft phaser10. The gear ratios (gr) and eccentricity (e) can be determined for the case of identical gear module among all the gears by using the following formulas, wherein Ns represents the number of gear teeth on the sprocket ring gear14, NCrepresent the number of gear teeth on the camshaft ring gear22, Np1represents the number of gear teeth on the sprocket planetary gear72, and Np2represents the number of gear teeth on the camshaft planetary gear74:

The sprocket bearing16and the camshaft bearing64are rolling element bearings and can be implemented in a variety of ways. For example, the bearings could be single-row ball bearings or needle bearings. Or the bearings could be crossed-roller bearings or four-point contact bearings to provide increased moment carrying capacity over the single-row bearings. And it is possible for the sprocket bearing16, the camshaft bearing64, or both to have an inner race and outer race of different widths. For example, the inner races of the sprocket bearing16and the camshaft bearing64can be slightly larger than the outer races of the bearings. The varied widths of the inner race and the outer race can help ensure that the races and/or cages do not interfere with one another. This will be discussed below in more detail.

When the camshaft phaser10is assembled, the sprocket12can be articulated so that the end plate38is facing downward before assembly begins and remains in this position until after assembly is complete. In the downward position, the sprocket bearing16can be inserted, from a side42of the sprocket12that is open during assembly, into the bearing opening40until it abuts the bearing shoulder44and is prevented from further downward axial movement. The camshaft bearing64can then be placed on top of and axially adjacent to the sprocket bearing16. The eccentric shaft28can then be inserted into the inner diameter of the sprocket bearing16an axial distance that can be defined by a side of the camshaft portion54that is eccentric to the crankshaft portion52and abuts the sprocket bearing16. A shoulder29included on one end of the eccentric shaft28can axially constrain the sprocket bearing16and the camshaft bearing64after insertion along an inner diameter of the camshaft bearing64. The compound planetary gear26can then be fit over the outside diameter of the camshaft bearing64. In this implementation, the compound planetary gear26includes an inner diameter having a shoulder46that axially constrains the camshaft bearing64along the outer diameter of the bearing64. The planetary biasing member68can be compressed and inserted between the camshaft bearing64and the camshaft portion54of the eccentric shaft28. The camshaft plate20is fit in close proximity to the compound planetary gear26so that the gear teeth24of the camshaft ring gear22contact the camshaft planetary gear74and are located radially outwardly from gear74. The sprocket bearing16, the eccentric shaft28, the camshaft bearing64, the compound planetary gear26, and the camshaft plate20can be located within the sprocket housing36. A cam ring90can be forcibly fit into a radial groove in the sprocket12to axially constrain the elements of the camshaft phaser10within the sprocket housing36.

Turning toFIG. 5, another implementation of the eccentric shaft28is shown that includes an integral bearing spacer31that prevents the sprocket bearing16from abutting the camshaft bearing64. In this implementation, the bearing spacer31extends in an axial direction (x) away from the camshaft eccentric portion54. In some implementations, the bearing spacer31can extend from the camshaft eccentric portion54as much as 1.0 mm. The integral bearing spacer31can be a solid uninterrupted element that extends the entire side of the eccentric portion54or it could be segmented such that one or more protuberances extend from the side of the eccentric portion54. And it should be appreciated that the bearing spacer31does not extend radially outwardly from the eccentric shaft28beyond the surface of the camshaft eccentric portion54. The bearing spacer31maintains space between the sprocket bearing16and the camshaft bearing64thereby minimizing the possibility of interference between the bearing races. While the bearing spacer31shown inFIG. 5as an integral part of the eccentric shaft28, it should be understood that other implementations of bearing spacers are possible. For example, it is possible to create space between the sprocket bearing16and the camshaft bearing64using a separate element, such as a washer, that is inserted between the sprocket bearing16and the camshaft bearing64.

The bearing spacer between the sprocket bearing16and the camshaft bearing64can be implemented in other ways as well. Turning toFIG. 6, another implementation of a bearing spacer31′ is shown. There, an inner race92of the camshaft bearing16can be wider than the outer race94of the camshaft bearing16. The difference in width between the inner race and the outer race of the camshaft bearing can create a gap between the sprocket bearing16and the camshaft bearing64. In this implementation, the inner race92has a width (Wi) and the outer race94has an outer race94(WO) such that W1is greater than W0. The inner race92can abut or contact a side of the eccentric shaft28thereby creating an axial space along axis x equal to WO. The embodiment shown includes a sprocket bearing16received by the sprocket12and a camshaft bearing64received by a compound planetary gear26. However, it should be appreciated that other implementations could also be realized with a sprocket bearing16received by a compound planetary gear26and a camshaft bearing64received by a camshaft plate20.