Patent ID: 12196293

DETAILED DESCRIPTION

The illustrations presented herein are not meant to be actual views of any particular gear drive or component thereof, but are merely idealized representations employed to describe illustrative embodiments. The drawings are not necessarily to scale.

As used herein, the term “about,” when used in reference to a numerical value for a particular parameter, is inclusive of the numerical value and a degree of variance from the numerical value that one of ordinary skill in the art would understand is within acceptable tolerances for the particular parameter. For example, “about,” in reference to a numerical value, may include additional numerical values within a range of from 90.0 percent to 110.0 percent of the numerical value, such as within a range of from 95.0 percent to 105.0 percent of the numerical value, within a range of from 97.5 percent to 102.5 percent of the numerical value, within a range of from 99.0 percent to 101.0 percent of the numerical value, within a range of from 99.5 percent to 100.5 percent of the numerical value, or within a range of from 99.9 percent to 100.1 percent of the numerical value.

As used herein, the term “substantially” in reference to a given parameter means and includes to a degree that one skilled in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially met may be at least about 90% met, at least about 95% met, at least about 99% met, or even at least about 100% met.

As used herein, relational terms, such as “first,” “second,” “top,” “bottom,” etc., are generally used for clarity and convenience in understanding the disclosure and accompanying drawings and do not connote or depend on any specific preference, orientation, or order, except where the context clearly indicates otherwise.

As used herein, the term “and/or” means and includes any and all combinations of one or more of the associated listed items.

As used herein, the terms “vertical” and “lateral” refer to the orientations as depicted in the figures.

As described above, gear drives and/or gear boxes are used in many different applications. The mechanical advantages or speed modifications may be determined by a size difference between gears in the associated gear drive. The size difference is often captured as a difference in the number of teeth on each gear. For example, a large gear (e.g., large diameter gear) and a small gear (e.g., small diameter gear) may have teeth that are substantially the same size. This may result in the large gear having a larger number of teeth than the small gear. An interface of the teeth between the small gear and the large gear may result in the small gear rotating multiple times for every rotation of the large gear. Thus, if a rotational input is coupled to the large gear and an output is coupled to the small gear, the output would rotate multiple times for every rotation of the input. Similarly, a torque input into the small gear would be multiplied at an output from the large gear due to the difference in diameter of the large gear while the output from the large gear would have a slower rotational speed than the input.

As the size difference between gears increases the size of the gear drive also increases, such that larger gear ratios result in large gear drives that may be difficult to install in a smaller applications. Some types of gears assemblies are able to achieve larger gear ratios in smaller packages. For example, planetary gear sets are able to achieve larger gear ratios due to an interface between multiple nested gears.

FIG.1illustrates a gear drive100. The gear drive100may be configured to receive a first input102and/or a second input104, where the first input102rotates in a first direction and the second input104rotates in a second opposite direction. In some embodiments, the gear drive100may be configured to receive a single input through the first input102. The first input102may be a shaft coupled to internal gears in the gear drive100. The second input104may be coupled to a housing108. The housing108may be configured to rotate independent from the first input102.

The housing108may form an outer case configured to house (e.g., surround) the internal gears of the gear drive100. The housing108may shield the internal gears from debris and other damage causing elements. The housing108may also be configured to maintain internal fluid, such as lubricants (e.g., oil, grease, etc.) within the housing108to reduce the wear on the internal gears, reduce friction losses in the internal gears, and extend the life of the internal gears. As described in further detail below, the housing108may be directly coupled to one or more of the internal gears to transfer motion to the internal gears and/or secure the internal gears relative to other internal gears.

The gear drive100may be suspended from one or more brackets106. The brackets106may be configured to mount and/or secure the gear drive100to a component that is stationary relative to the gear drive100. For example, if the gear drive100is mounted to an automobile or other vehicle, the brackets106may mount the gear drive100to a frame or body component of the vehicle that is stationary relative to the vehicle, such that the moving component of the vehicle that is coupled to the first input102and/or the second input104may move or rotate relative to the relatively stationary component. The brackets106may be configured to facilitate the housing108rotating relative to the bracket106. For example, the housing108may be rotatably coupled to the brackets106through one or more bearings110(e.g., roller bearings, ball bearings, needle bearings, etc.).

FIG.2illustrates a perspective view of an output side of the gear drive100. The gear drive100may include a first output202and a second output204. The first output202and the second output204may rotate in opposite directions. The second output204may rotate in a same direction as the first input102and the first output202may rotate in a second opposite direction. If a second input104is provided the first output202may rotate in the direction of the second input104. If no second input104is provided, the first output202may continue to rotate in a direction opposite the direction of the first input102. Thus, the gear drive100may output two distinct counter rotating outputs from a single input in a single direction.

The first output202and the second output204may exit the housing108through an aperture206defined in an end surface208of the housing108. The end surface208may be formed from an end plate210secured to the housing108. The end plate210may be removable to facilitate servicing the internal gears of the gear drive100(e.g., repairing components, replacing components, changing lubricant, etc.). The end surface208of the end plate210may further be configured to interface with another member such as a generator or a brake to control the rotation of the housing108via the bearings110. The brake or generator may be utilized to control a perceived gear ratio of the gear drive100.

The internal gears of the gear drive100may be planetary gears.FIG.3illustrates a perspective view of a planetary gear300. The planetary gear300includes a ring gear306, planet gears304, and a sun gear302. The planet gears304may be coupled together by a carrier310, such that the planet gears304move together between the ring gear306and the sun gear302. The carrier310may be coupled to each of the planet gears304through spindles308. The planet gears304may rotate about the spindles308while the carrier310rotates relative to the ring gear306and the sun gear302. The ring gear306may include inward facing teeth314, which may interface with teeth312of the planet gears304. The teeth312of the planet gears304may subsequently interface with teeth316of the sun gear302. Thus the planet gears304may transfer motion to at least one of the ring gear306and the sun gear302. In some cases the planet gears304may transfer motion between the ring gear306and the sun gear302.

Conventionally, one of the ring gear306, the carrier310, or the sun gear302is held stationary while the other two of the ring gear306, the carrier310, and the sun gear302is attached to a rotational input or a rotational output. The gear ratio of the planetary gear300is based on a difference in a number of teeth314in the ring gear306(R) and a number of teeth316in the sun gear302(S). The gear ratio also changes based on which of the ring gear306, carrier310, or sun gear302is held stationary. For example, if the ring gear306is held stationary the gear ratio is:

SR+S

If the sun gear302is held stationary the gear ratio is:

RR+S

If the carrier310is held stationary the gear ratio is:
S/R

In some instances, all three of the ring gear306, the carrier310, and the sun gear302may rotate. For example, two inputs and/or two outputs, may result in a single input coupled to one of the ring gear306, the carrier310, or the sun gear302and each of two outputs being coupled to one of the remaining ring gear306, carrier310, or sun gear302. Alternatively, two inputs may be coupled to two of the ring gear306, the carrier310, or the sun gear302and an output may be coupled to the remaining ring gear306, carrier310, or sun gear302. If all three of the ring gear306, carrier310, and sun gear302are rotating the gear ratio may be larger. The relative rotation of each of the ring gear306, carrier310, and the sun gear302become a function of the relative rotational speeds of the other components. For example, if the ring gear306and the carrier310are each coupled to separate inputs, such as the first input102and the second input104, the rotational speed of the sun gear302is determined as follows:

T⁢s=(R+S)⁢T⁢y-T⁢r⁢RS

Where Ts is the rotational speed of the sun gear302, Ty is the rotational speed of the carrier310and Tr is the rotational speed of the ring gear306. If the ring gear306and the carrier310are rotating in opposite directions, the ratio increases significantly. For example, rotating the ring gear306and the carrier310in opposite directions may result in gear ratios of greater than 9:1, such as greater than 10:1 or greater than 12:1. Therefore, rotating the ring gear306and the carrier310in opposite directions through separate inputs may increase the output speed of the sun gear302relative to conventional applications.

FIG.4illustrates a cross-sectional view of the gear drive100. The gear drive100may include a first planetary gear402and a second planetary gear404. The first planetary gear402and the second planetary gear404may be axially aligned with the inputs102,104, and the outputs202,204. The first input102may be coupled to a first carrier422of the first planetary gear402. In some embodiments the first carrier422may be formed as part of the first input102. For example, the first input102may be a shaft extending from the first carrier422. Thus, the first carrier422and the associated first planet gears420may rotate in substantially the same direction and at substantially the same speed as the first input102.

The first carrier422may be coupled to a second ring gear406of the second planetary gear404through a first input coupler426. The first input coupler426may be coupled to the first carrier422through the first spindles418extending through the first planet gears420. For example, the first input coupler426may be an extension of an interior portion of the first carrier422on an opposite side of the first planetary gear402from the first input102. The first input coupler426may transfer rotation from the first input102to the second ring gear406, such that the second ring gear406may rotate at substantially the same direction and at substantially the same speed as the first input102and the first carrier422.

The housing108may be coupled to the first ring gear424and to the second carrier408, such that the first ring gear424and the second carrier408may be fixed relative to the housing108. The second carrier408may maintain second planet gears410in position relative to the housing108through second spindles412. The first output202may be coupled to a first sun gear416of the first planetary gear402and the second output204may be coupled to a second sun gear414of the second planetary gear404. If the housing108remains in a fixed position, the first input102may cause the first sun gear416to rotate in a same direction as the first input102at a speed multiplied by the gear ratio of (ring teeth+sun teeth):sun teeth of the first planetary gear402. The first input coupler426may also cause the second ring gear406to rotate, which may cause the second sun gear414to rotate in a direction opposite the first input102at a speed multiplied by the gear ratio of ring teeth:sun teeth of the second planetary gear404. Thus, the first sun gear416and the second sun gear414may rotate in opposite directions when a single input is received from the first input102. The first sun gear416may cause the first output202to rotate in the direction of the first input102at the speed defined by the gear ratio of the first planetary gear402and the second sun gear414may cause the second output204to rotate in a direction opposite the first input102as the speed defined by the gear ratio of the second planetary gear404.

As described above, the housing108may be coupled to the second input104, such that the housing108may rotate in a direction opposite the first input102. This may cause the first ring gear424of the first planetary gear402to rotate relative to the first carrier422and the second carrier408to rotate relative to the second ring gear406. As described above, rotating each component of the planetary gears402,404may increase the mechanical advantage of the planetary gears402,404. For example, if each of the first input102and the second input104are rotating at substantially the same speed in opposite directions, the gear ratio becomes:

2⁢R+SS

The housing108rotating in an opposite direction from the first input102similarly maintains the counter rotation of the second sun gear414relative to the first sun gear416, such that the first output202and the second output204rotate in opposite directions. Furthermore, the first output202and the second output204may rotate at a higher rate of speed due to the increase gear ratio described above. The relative rotational speed between the first output202and the second output204may be about double the rotational speed of each individual output202,204due to the counter rotation.

In some embodiments, the gear ratios of the first planetary gear402and the second planetary gear404may be different. As illustrated inFIG.4, the second sun gear414may have a larger diameter than the first sun gear416. For example, the larger diameter of the second sun gear414may facilitate the first output202passing through a central portion of the second sun gear414to reach the first sun gear416. An output bearing428may be positioned between the first output202and the second output204. The output bearing428may reduce friction between the first output202and the second output204, which may increase efficiency of the gear drive100and may reduce wear between the first output202and the second output204.

The outputs202,204may be shafts configured to create an interference connection with the respective sun gears414,416. For example, the shafts may include splines (e.g., teeth) configured to interface with complementary splines in the sun gears414,416. In another example, the shafts may have an interference fit with the respective sun gears414,416such that compression forces between a surface of the shafts and the respective sun gears414,416transfer the rotation. In another example, the shafts may be secured to the sun gears414,416through a hardware connection (e.g., bolts, pins, studs, screws, rivets, etc.) or a welded, brazed, or soldered connection.

FIG.5illustrates an embodiment of the gear drive100configured to receive linear input motion. The gear drive100may be configured to receive oscillating linear motion, such as from vehicle suspension or waves on a body of water, through one or more input arms502. The input arms502may be coupled to the gear drive100through first input brackets504and second input brackets506. For example, each of the input arms502may be coupled to the first input102through first input brackets504. The first input brackets504may be coupled to the first input102through one-way bearings508(e.g., sprag bearings) configured to transmit rotation in a first direction and rotate freely in a second direction, such that rotation is only transmitted to the first input102in the first direction. Each of the input arms502may also be coupled to the second input104(FIG.1) through second input brackets506. The second input brackets506may similarly be coupled to the second input104(FIG.1) through one-way bearings508in an opposite orientation, such that the one-way bearings508only transmit rotation to the second input104(FIG.1) in a second direction. Thus, when the oscillating linear motion causes the input arms502to rotate in the first direction the input arms502transmit the rotation to the first input102while rotating freely about the second input104(FIG.1) and when the oscillating linear motion causes the input arms502to rotate in the second direction the input arms502transmit the rotation to the second input104(FIG.1) while rotating freely about the first input102. Thus, the oscillating motion may cause the first input102and the second input104(FIG.1) to rotate in opposite directions, which may be multiplied through the gear drive100as described above.

The embodiments of the disclosure may enable the capture of oscillating motion and/or rotational motion in one or two directions and its transmission into two counter rotating outputs. Counter rotating outputs may increase relative rotational speed between two components, such as a stator and rotor of an electrical generator. The increase relative rotational speed may increase an output of the electrical generator. In other embodiments, the counter rotating outputs may be used to drive counter rotating components, such as impellers, heads, bits, paddles, etc., of a device through a single input.

Embodiments of the disclosure may provide two counter rotating inputs. As described above, the counter rotating inputs may provide larger gear ratios in relatively small gear drives with planetary gears. The larger gear ratios may facilitate capturing energy from smaller movements and/or may facilitate greater mechanical advantages generated from smaller forces.

In the example shown above, the gear drive100includes two planetary gears402,404. In some examples, a gear drive may include more than two planetary gears based on a desired gear ratio. The planetary gears may be modular such that any number of planetary gears may be incorporated into a gear drive to achieve a desired gear ratio.

FIG.6Aillustrates a perspective view of a gear drive andFIG.6Billustrates a cross-sectional view of the gear drive ofFIG.6A. InFIGS.6A and6B, a gear drive600may comprise brackets602(similar to brackets106discussed above) for mounting the gear drive600to a component that is stationary relative to the gear drive600. The gear drive600may comprise a housing604that may form an outer case configured to house (e.g., surround) the internal gears of the gear drive600(similar to housing108described above).

In this example, the gear drive600may comprise a first input606. The first input may be a shaft coupled to internal gears in the gear drive600. Bearings607may be provided to facilitate rotation of the first input606relative to the brackets602. The gear drive600may further comprise an intermediate member608. The intermediate member608may be a shaft coupled to internal gears in the gear drive600. The intermediate member608may be disposed to be aligned with the first input606. Additional bearings607may facilitate rotation of the intermediate member608relative to the first input606.

The gear drive600may further comprise a first output610. The first output610may be a shaft coupled to internal gears of the gear drive600. The first output610may be aligned with the intermediate member608and the first input606. Additional bearings607may facilitate rotation of the first output610relative to the intermediate member608. The gear drive600may also comprise a second output612. The second output612may comprise a hollow shaft that surrounds the first output610and that is coupled to internal gears of the gear drive600. The second output612may rotate independent of the first output610via bearings607. The gear drive600may also comprise a third output614surrounding the second output612and being configured to rotate independently relative to the second output612via bearings607. The third output614may also be coupled to internal gears of the gear drive600.

As mentioned above, a gear drive may have any number of planetary gears based on a desired gear ratio. In this example, the gear drive600may comprise a first planetary gear616, a second planetary gear618, and a third planetary gear620. The first planetary gear616, the second planetary gear,618, and the third planetary gear620may be axially aligned with the first input606, the intermediate member608, and the outputs610,612,614. The first and second planetary gears616,618may be similar to the first and second planetary gears402,404discussed above. In the gear drive600, the third planetary gear620and the intermediate member608may be considered modular members that may be added to the first and second planetary gears616,618to achieve a desired gear ratio. Furthermore, while just the third planetary gear620and the intermediate member608are shown inFIGS.6A and6B, there may be additional modular members added to a gear drive depending on a desired gear ratio.

The first input606may be coupled to a carrier622of the third planetary gear620. In some examples, the first input606may be formed integrally with the carrier622. The first input606may also be formed separately from the carrier622and may be press fit into the carrier622or may otherwise be coupled thereto such as via a fastener, welding, or other suitable joining method. The carrier622is attached to the planet gears624of the third planetary gear620via spindles. The teeth of the planet gears624may interface with the interior teeth of a ring gear626of the third planetary gear620and may interface with teeth of the sun gear628of the third planetary gear620.

The sun gear628of the third planetary gear620may be coupled to the intermediate member608. The intermediate member608may be further coupled to a carrier630of the first planetary gear616. The carrier630may support planet gears632and may also comprise or otherwise be connected to a coupler634connecting the carrier630to a ring gear636of the second planetary gear618. Teeth of the planet gears632may interface with inner teeth of a ring gear639of the first planetary gear616. The ring gear639may be coupled to the housing604and may thus rotate with (or be fixed with) the housing604. The teeth of the planet gears632may also interface with teeth of a sun gear638of the first planetary gear616. The sun gear638of the first planetary gear616may be coupled with the first output610of the gear drive600to rotate the first output610.

The ring gear636of the second planetary gear618may have inner teeth that interface with planet gears642associated with a carrier640. The planet gears642may interface with a sun gear644of the second planetary gear618. The sun gear644may be coupled with the second output612to rotate the second output612. With the above-described connections between the first input606, the intermediate member608, and the first through the third planetary gears616,618,620, the first output610and the second output612may be operable to rotate in opposite directions based on a rotational input to the first input606.

The carrier640of the second planetary gear618may be coupled to the third output614. The third output614may be coupled with the housing604, and thus the third output may be operable to rotate with (or remain fixed with) the housing604. In this example, by utilizing a modular, third planetary gear620, the gear ratio between the first input606and the counter rotating first and second outputs610,612may be increased by a desired amount. In other examples, additional modular, planetary gears may be added depending on a desired gear ratio.

FIG.7Aillustrates a perspective view of a gear drive andFIG.7Billustrates a cross-sectional view of the gear drive ofFIG.7A. In this example, a gear drive700may comprise counter rotating inputs that are operable to drive an output to power a generator. The gear drive700may comprise brackets702that may be operable to mount the gear drive700to a component that is stationary relative to the gear drive700. The gear drive700also comprises a housing704that may form an outer case configured to house (e.g., surround) the internal gears of the gear drive700(similar to housing108described above).

The counter rotating inputs of the gear drive700may comprise a first input706and a second input708. The first input706may comprise a shaft coupled to internal gears of the gear drive700. The second input708may comprise a hollow shaft that is configured to surround the first input706and is operable to rotate independent of the first input706via bearings707. The second input708may couple with internal gears of the gear drive700. The gear drive700may further comprise a first output710and a second output712. The first output710may comprise a shaft and the second output712may comprise a hollow shaft that is configured to surround the first output710. The first output710may rotate independently of the second output712via bearings707. The first output710may couple with internal gears of the gear drive700. The second output712may be coupled with the housing704such that it rotates with (or remains stationary with) the housing704.

In this example, the gear drive may comprise a first planetary gear716and a second planetary gear718. The first and second planetary gears716,718may be axially aligned with the first and second inputs706,708and the first and second outputs710,712. The first and second planetary gears716,718may be similar to the first and second planetary gears402,404discussed above.

The first input706may be coupled to the sun gear720of the first planetary gear716. In some examples, the first input706may be formed integrally with the sun gear720. In some examples, the first input706may be formed separately from the sun gear720and may be press fit into the sun gear720or may otherwise be coupled thereto such as via a fastener, welding, or other suitable joining method. The sun gear720may interface with planet gears722of the first planetary gear716. The planet gears722are coupled to the carrier724of the first planetary gear by way of spindles. In this example, the first output710may be coupled to the carrier724of the first planetary gear716. The carrier724may further be coupled with the ring gear728of the second planetary gear718via a coupler726.

The ring gear728of the second planetary gear718may interface with planet gears730of the second planetary gear718. The planet gears730may interface with the sun gear732of the second planetary gear718. The second input708may be coupled with the sun gear732of the second planetary gear718.

It is noted that the above-described features of the gear drive700may be substantially similar to the gear drive100shown inFIG.4. However, the gear drive700is operable in the reverse direction as compared to the gear drive100. In other words, the first and second inputs706,708of the gear drive700correspond with the first and second outputs202,204of the gear drive100. Similarly, the first and second outputs710,712of the gear drive700correspond with the first and second inputs102,104of the gear drive100. This allows a gear drive (e.g., the gear drive100or the gear drive700) to be operable in either direction. By operating a gear drive in one direction, the gear drive may “gear down” from the inputs to the outputs, and by operating the gear drive in the opposite direction, the gear drive may “gear up” from the inputs to the outputs.

In this example, the gear drive700may further comprise an electric generator734that may be operable to provide resistance to one or more components of the gear drive700to dynamically control a gear ratio of the gear drive700. The generator734may comprise a rotor736. The rotor may be coupled to the second output712, which is coupled to the housing704. Thus, the rotor may be operable to rotate with the housing704. The generator734may further comprise stator coils738. The generator734may thus provide resistance to the rotation of the second output712and the housing704to dynamically control the gear ratio of the gear drive700.

WhileFIGS.7A and7Bshow an example with one generator coupled to an output of the gear drive, it may also be beneficial to utilize more than one generator to control a gear ratio of a gear drive.FIG.8Aillustrates a perspective view of a gear drive800andFIG.8Billustrates a cross-sectional view of the gear drive800ofFIG.8A. The gear drive800may comprise brackets802(similar to brackets106discussed above) for mounting the gear drive800to a component that is stationary relative to the gear drive800. The gear drive800may also comprise a housing804that may form an outer case configured to house (e.g., surround) the internal gears of the gear drive800(similar to housing108discussed above).

The gear drive800may comprise a first input806. The first input may be a shaft coupled to internal gears in the gear drive800. The gear drive800may further comprise a second input808that is coupled to internal gears of the gear drive800. The second input808may be axially aligned with the first input806and may comprise a hollow shaft that is configured to surround the first input806and rotate independently from the first input806via bearings807.

The gear drive800may further comprise a first output812. The first output812may be a shaft coupled to internal gears of the gear drive800. The first output812may be axially aligned with the first and second inputs806,808. The gear drive800may comprise a second output814. The second output814may comprise a hollow shaft that is axially aligned with and surrounds the first output812and that rotates independently from the first output812via bearings807.

The gear drive800may have a number of planetary gears depending on a desired gear ratio. In this example, the gear drive800may comprise a first planetary gear818and a second planetary gear820. The first and second planetary gears818,820may be axially aligned with the first and second inputs806,808and the first and second outputs812,814. The first and second planetary gears818,820may be similar to the first and second planetary gears402,404discussed above.

The first input806may be coupled to a carrier822of the first planetary gear818. In some examples, the first input806may be formed integrally with the carrier822. The first input806may also be formed separately from the carrier822and may be press fit into the carrier822or may otherwise be coupled thereto such as via a fastener, welding, or other suitable joining method. The carrier822may comprise a coupler824that is coupled with a ring gear826of the second planetary gear820. The carrier822may support planet gears828of the first planetary gear818via spindles.

The planet gears828may interface with a ring gear829of the first planetary gear818. The ring gear829may be coupled to the housing804such that the ring gear829rotates with the housing804. The second input808may be coupled to the housing804and thus the ring gear829such that the second input808rotates with the housing804and the ring gear829of the first planetary gear818. The planet gears828further interface with the sun gear830of the first planetary gear818. The sun gear830may be coupled to the first output812to rotate the first output812.

The ring gear826of the second planetary gear820may interface with the planet gears832of the second planetary gear820. The planet gears832may be supported by a carrier836via spindles. The planet gears832may interface with a sun gear834of the second planetary gear820. The sun gear834may interface with the second output814to rotate the second output814.

Similar to the gear drive700discussed above, the gear drive800may be dynamically control via a generator. In this example, the gear drive800may comprise a first generator838disposed on an output side of the gear drive800. The first generator838may comprise a rotor840that is coupled to the second output814of the gear drive. The generator may further comprise stator coils842that are supported by the brackets802. Similar to the generator734discussed above, the generator838may provide variable resistance to the second output to dynamically control the gear ratio of the gear drive.

In addition to the first generator838attached to the second output814, the gear drive800may comprise a second generator844disposed on an input side of the gear drive800. In this example, the second generator844may comprise a rotor846that is coupled to the second input808. The generator844may further comprise stator coils848supported by the brackets802. The generator844may dynamically control resistance to the second input808to control the gear ratio of the gear drive800. By providing an additional generator in the gear drive800, further refinement and control of the gear ratio of the gear drive may be achieved.

In some embodiments, the second generator844may be configured as an electric motor configured to input rotation into the second input808. The rotational input from the second generator844acting as a motor may control rotation of the housing804, which may add to the dynamic control of the gear drive800. For example, the second generator844may control rotation of the ring gear829and the carrier836, while the first generator838controls rotation of the sun gear834. Thus, the perceived gear ratio of the gear drive800may be controlled through both the second generator844inputting rotation to the respective components and the first generator838limiting rotation of the respective components.

The embodiments of the disclosure described above and illustrated in the accompanying drawing figures do not limit the scope of the invention, since these embodiments are merely examples of embodiments of the invention, which is defined by the appended claims and their legal equivalents. Any equivalent embodiments are intended to be within the scope of this disclosure. Indeed, various modifications of the present disclosure, in addition to those shown and described herein, such as alternative useful combinations of the elements described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims and their legal equivalents.