Compact two-speed transmission with compound planetary stage

A transmission comprises: a first planetary stage including a first ring gear defining first internal teeth; a ground component defining second internal teeth; a compound planetary stage including a one-way clutch with an inner race and an outer race, the outer race having a first tapered surface; and an adaptor defining external teeth and a second tapered surface, the adaptor being movable into at least a first position where the first tapered surface and the second tapered surface are connected with each other, and into a second position where instead the first internal teeth are gear coupled with the second internal teeth.

TECHNICAL FIELD

This document relates to a compact two-speed transmission with a compound planetary stage.

BACKGROUND

In some electric vehicles presently available, an electric motor may be designed to operate without a gearbox. As a result, such a motor operates with a fixed gear ratio at all times, which limits its performance and efficiency. Other electric vehicles use a gearbox that allows shifting between two gears. However, these gearboxes are complex mechanisms that take up significant space, they may have low efficiency and/or deliver low initial torque, and they place a significant inertia load on the drivetrain (e.g., an excessive jerk when shifting).

SUMMARY

In a first aspect, a transmission comprises: a first planetary stage including a first ring gear defining first internal teeth; a ground component defining second internal teeth; a compound planetary stage including a one-way clutch with an inner race and an outer race, the outer race having a first tapered surface; and an adaptor defining external teeth and a second tapered surface, the adaptor being movable into at least a first position where the first tapered surface and the second tapered surface are connected with each other, and into a second position where instead the first internal teeth are gear coupled with the second internal teeth.

Implementations can include any or all of the following features. The compound planetary stage has a common shaft with the first planetary stage. The adaptor is also movable into at least a third position where the first tapered surface and the second tapered surface are not connected with each other, and where the first internal teeth are not gear coupled with the second internal teeth. The first position corresponds to a first gear ratio for the transmission, and wherein the second position corresponds to a second gear ratio for the transmission. The first gear ratio is greater than the second gear ratio. The first planetary stage further comprises: a sun gear to be rotated about an axis by a rotor shaft; and a first planetary gear that is gear coupled to the sun gear. The first planetary stage comprises multiple first planetary gears that are gear coupled to the sun gear. The compound planetary stage further comprises: a second planetary gear; a second ring gear that is gear coupled to the second planetary gear; and a carrier member carrying the first and second planetary gears. The first planetary gear has a first diameter, wherein the second planetary gear has a second diameter, and wherein the first diameter is greater than the second diameter. The carrier member is coaxial with the sun gear. The inner race of the one-way clutch is coupled to the second ring gear. The compound planetary stage comprises multiple second planetary gears that are gear coupled to the second ring gear. The second planetary gear has a common shaft with the first planetary gear. The transmission further comprises another one-way clutch coupled between the first ring gear and ground in the transmission.

In a second aspect, a transmission comprises: a first planetary stage including a first ring gear; a ground component; a compound planetary stage including a second ring gear; and means for selectively i) connecting the second ring gear to the ground component, wherein the transmission has a first gear ratio, and ii) instead connecting the first ring gear to the ground component, wherein the transmission has a second gear ratio.

In a third aspect, a vehicle comprises: a first electric motor having a first rotor shaft; and a first transmission coupled to the first rotor shaft of the first electric motor, the first transmission comprising: a first planetary stage including a first ring gear defining first internal teeth; a ground component defining second internal teeth; a compound planetary stage including a one-way clutch with an inner race and an outer race, the outer race having a first tapered surface; and an adaptor defining external teeth and a second tapered surface, the adaptor being movable into at least a first position where the first tapered surface and the second tapered surface are connected with each other, and into a second position where instead the first internal teeth are gear coupled with the second internal teeth.

Implementations can include any or all of the following features. In the first position of the adaptor the first transmission has a first gear ratio, wherein in the first gear ratio the first transmission: does not provide regenerative braking; and provides a reverse gear mode by reversing a rotation direction of the first rotor shaft; and in the second position of the adaptor the first transmission has a second gear ratio, and wherein in the second gear ratio the first transmission: does provide the regenerative braking; and does not provide the reverse gear mode. The vehicle further comprises: a second electric motor having a second rotor shaft; and a second transmission coupled to the second rotor shaft of the second electric motor; wherein: in the first gear ratio of the first transmission the vehicle uses the second transmission for regenerative braking using; and in the second gear ratio of the first transmission the vehicle uses the second transmission for the reverse gear mode.

In a fourth aspect, a transmission comprises: a first planetary stage comprising: a sun gear to be rotated about an axis by a rotor shaft; a first planetary gear that is gear coupled to the sun gear; and a first ring gear defining first internal teeth, the first ring gear being gear coupled to the first planetary gear by the first internal teeth; a ground component defining second internal teeth; a compound planetary stage comprising: a second planetary gear having a common shaft with the first planetary gear; a second ring gear that is gear coupled to the second planetary gear; a carrier member carrying the first and second planetary gears, the carrier member coaxial with the sun gear; and a one-way clutch having an inner race that is coupled to the second ring gear, and an outer race having a first tapered surface being tapered along the axis; and an adaptor defining i) external teeth being gear coupled to the second internal teeth, and ii) a second tapered surface being tapered along the axis, the adaptor being movable into at least: a first position where the first tapered surface and the second tapered surface are connected with each other, and where the first internal teeth are not gear coupled with the second internal teeth; and a second position where the first tapered surface and the second tapered surface are not connected with each other, and where the first internal teeth are gear coupled with the second internal teeth.

Implementations can include the following feature. The transmission further comprises another one-way clutch coupled between the first ring gear and ground in the transmission.

DETAILED DESCRIPTION

This document describes examples of systems and techniques relating to a compact two-speed transmission with a compound planetary stage. With this architecture, a two-speed transmission can provide smooth shifting for vehicles with electric motors and be implemented within a reduced packaging space. Such a two-speed transmission can generate a high initial torque and also operate at high efficiency zones of the motor at all speeds.

Examples herein refer to a vehicle. A vehicle is a machine that transports passengers or cargo, or both. A vehicle can have one or more electric motors. Examples of vehicles include, but are not limited to, cars, trucks, buses, motorcycles, and scooters. The number of wheels can differ between types of vehicles, and one or more (e.g., all) of the wheels can be used for propulsion of the vehicle. The vehicle can include a passenger compartment accommodating one or more persons. A vehicle can be powered exclusively by electricity, or can use one or more other energy sources in addition to electricity, to name just a few examples.

Examples described herein refer to an electric motor. As used herein, an electric motor includes any type of electric motor, including, but not limited to, a permanent-magnet motor, an induction motor, a synchronous motor, or a reluctance motor.

Examples described herein refer to a ground component that is part of a transmission. As used herein, a ground component is a component not subject to rotation or translation relative to the rest of the transmission during operation. Examples of ground components include, but are not limited to, a housing or case of the transmission.

Examples described herein refer to a one-way clutch. As used herein, a one-way clutch is a mechanical component that limits relative rotation between two components to single-direction rotation. Examples of one-way clutches include, but are not limited to, one-way roller clutches and one-way sprag clutches.

Examples described herein refer to two gears being on a common shaft. As used herein, two gears being on a common shaft signifies that the two gears cannot rotate independently of each other; rather, at any moment the two gears either both rotate with the same angular frequency, or both do not rotate. Examples of two gears being on a common shaft include, but are not limited to, the gears being welded together or being cut on the same blank.

Examples described herein refer to a component having external teeth or internal teeth. As used herein, external teeth face radially outward from a rotation axis of the component. As used herein, internal teeth face radially inward from a rotation axis of the component.

Examples described herein refer to two or more components being connected with each other. As used herein, being connected signifies that the components touch each other, wherein if at least one of the components is currently being held stationary, the other also does not move.

FIGS.1A-1Cshow an example of an electric motor100with a transmission102according to the present subject matter.FIG.1Ashows a perspective view,FIG.1Ba side view, andFIG.1Ca cross section taken along the line A-A inFIG.1B, of the electric motor100. Here, the transmission102is mounted at one end of a motor housing104. The electric motor100and/or the transmission102can be used with one or more other examples described elsewhere herein. The electric motor100can have a single-side transmission or can have an active-core style dual planetary transmission, to name just two examples.

The transmission102has an output shaft106. For example, the output shaft106can be coupled to a wheel axle (e.g., welded to a drive shaft) or any other load to be driven by the electric motor100. The electric motor100has a stator108and a rotor110within the motor housing104. The rotor110is coupled to a rotor shaft112so as to be rotatable. For example, the electric motor100can rotate the rotor shaft112in one direction to drive the vehicle forward using any of multiple gears of the transmission102. As another example, in at least one of the gears of the transmission102, the rotor shaft112can instead be rotated in the opposite direction to drive the vehicle in reverse. As another example, in at least one of the gears of the transmission102, regenerative braking can be performed to convert torque from a rotating road wheel into electric energy. In some implementations, the electric motor100has a transmission114mounted at the opposite end of the motor housing104from the transmission102. The transmission114has an output shaft116and can be similar or identical to the transmission102.

FIGS.2A-2Bschematically show examples of a transmission200according to the present subject matter. The transmission200is schematically represented using rectangular shapes. WhileFIGS.2A-2Bare schematical illustrations and not pure sections, the perspectives presented in them approximately represent the view of a section taken along the line B-B inFIG.1C, in an implementation where the transmission102includes the components of the transmission200. The transmission200can be used with one or more other examples described elsewhere herein.

The transmission200includes a sun gear201that is driven by a component labeled “Input”. In some implementations, the sun gear201can be coupled to a rotor shaft of an electric motor with which the transmission200is being used (e.g., the rotor shaft112inFIGS.1A-1C). The transmission200includes one or more planetary gears202that are gear coupled to the sun gear201. Each of the planetary gears202can rotate about an axis. Each of the planetary gears202can also rotate about the axis of the sun gear201, for example using a carrier. The transmission200includes a ring gear203that is gear coupled to the planetary gear(s)202. The sun gear201, the planetary gear(s)202and the ring gear203can collectively be referred to as a first planetary stage of the transmission200.

The transmission200includes one or more planetary gears204having a common shaft (sometimes referred to as a common pin) with the corresponding planetary gear(s)202. The planetary gear202has a first diameter, and the planetary gear204has a second diameter, the first diameter being greater than the second diameter. The transmission200includes a ring gear205that is gear coupled to the planetary gear(s)204. The planetary gear(s)204and the ring gear205can collectively be referred to as a compound planetary stage of the transmission200.

FIG.2Ashows an example of a first mode of operation of the transmission200. The first mode corresponds to a first gear ratio for the transmission200. For example, the first gear ratio can be referred to as a first gear for the vehicle. In the first mode of operation, the ring gear205is held stationary, which is here schematically illustrated by the ring gear205being connected to a ground206. For example, a one-way clutch coupled to the ring gear205can be selectively coupled through a spline adaptor to the ground206. By contrast, the ring gear203is not held stationary in the first mode of operation.

FIG.2Bshows an example of a second mode of operation of the transmission200. The second mode corresponds to a second gear ratio for the transmission200. For example, the second gear ratio can be referred to as a second gear for the vehicle. The first gear ratio (ofFIG.2A) can be greater than the second gear ratio. In the second mode of operation, the ring gear203is held stationary, which is here schematically illustrated by the ring gear203being connected to a ground207. For example, a spline adaptor can selectively couple the ring gear203to the ground207. By contrast, the ring gear205is not held stationary in the second mode of operation.

The rotor shaft of the electric motor can rotate in either of two directions. InFIG.2A, an arrow at the input for the sun gear201schematically illustrates a rotation direction. The input rotation direction can be a clockwise, or counterclockwise, rotation when viewed from the electric motor toward the transmission200. InFIG.2B, an arrow at the carrier of the planetary gears204schematically illustrates the same rotation direction as that of the input. As such, the carrier output rotation can be a clockwise, or counterclockwise, rotation when viewed from the electric motor toward the transmission200. The two different gear ratios of the transmission200facilitate that the electric motor can always be run in high-efficiency regions. For example, the larger reduction ratio is used at lower revolutions per minute (rpm) for increased initial torque. As another example, the lower reduction ratio is used at higher rpm for higher top speed.

FIGS.3A-3Bschematically show additional examples of a transmission300according to the present subject matter. The transmission300is schematically represented using rectangular shapes. WhileFIGS.3A-3Bare schematical illustrations and not pure sections, the perspectives presented in them approximately represent the view of a section taken along the line B-B inFIG.1C, in an implementation where the transmission102includes the components of the transmission300. The transmission300can be used with one or more other examples described elsewhere herein.

The transmission300includes a sun gear302that is driven by a component represented by the label “Input”. In some implementations, the sun gear302can be coupled to a rotor shaft of an electric motor with which the transmission300is being used (e.g., the rotor shaft112inFIGS.1A-1C). The transmission300includes one or more planetary gears304that are gear coupled to the sun gear302. Each of the planetary gears304can rotate about an axis. Each of the planetary gears304can also rotate about the axis of the sun gear302using a carrier, for example as described below. The transmission300includes a ring gear306that is gear coupled to the planetary gear(s)304. The ring gear306defines internal teeth308that extend parallel with the axis of the sun gear302. The ring gear306can be coupled to a ground component310by a one-way clutch312. The one-way clutch312can help with mechanically synchronizing the ring gear306to zero speed to provide smooth shifting between gears (e.g., as described below). The sun gear302, the planetary gear(s)304and the ring gear306can collectively be referred to as a first planetary stage of the transmission300.

The transmission300includes one or more planetary gears314having a common shaft (sometimes referred to as a common pin) with the corresponding planetary gear(s)304. The planetary gear304has a first diameter, and the planetary gear314has a second diameter, the first diameter being greater than the second diameter. The transmission300includes a ring gear316that is coaxial with the sun gear302and gear coupled to the planetary gear(s)314. The transmission300includes a one-way clutch318. The one-way clutch318is positioned radially outward of the ring gear316. The one-way clutch318has an outer race318A with a tapered surface320. The tapered surface320is tapered along the rotation axis of the sun gear302. The one-way clutch318has an inner race318B. The inner race318B is connected to the ring gear316. Between the outer and inner races318A-318B, the one-way clutch318includes sprags, or rollers biased by springs toward wedging planes, so as to provide single-direction rotation between the outer and inner races318A-318B. The transmission300includes a carrier member322carrying the planetary gears304and314, the carrier member322being coaxial with the sun gear302. The carrier member322can define a bearing nest for at least the planetary gear(s)314. For example, in this sectional view a portion of the carrier member322is visible radially outward of the shaft of the planetary gears304and314. The planetary gear(s)314, the ring gear316and the one-way clutch318can collectively be referred to as a compound planetary stage of the transmission300.

The transmission300includes a ground component324that can be used for selectively holding either the ring gear306or the ring gear316stationary. The ground component324can be part of the same structure as the ground component310(e.g., a case or housing of the transmission300). The ground component324defines internal teeth326that extend parallel with the axis of the sun gear302.

The transmission300includes an adaptor328that can be translated along the axis of the sun gear302. The adaptor328defines external teeth330. The external teeth330mesh with the internal teeth326of the ground component324. The adaptor328defines a tapered surface332. The tapered surface332is tapered along the rotation axis of the sun gear302so as to face the tapered surface320.

The transmission300includes a solenoid334that is fixed (coupled to ground, not shown) and can directly or indirectly actuate the adaptor328to move in either or both directions.

FIG.3Ashows an example of a first mode of operation of the transmission300. The first mode corresponds to a first gear ratio for the transmission300. For example, the first gear ratio can be referred to as a first gear for the vehicle. In the first mode of operation, the ring gear316is held stationary, whereas the ring gear306, by contrast, is not held stationary. In the first mode of operation, the adaptor328is moved toward the right in the present illustration into a first position where the tapered surfaces320and332are connected with each other, and where the external teeth330of the adaptor328do not mesh with the internal teeth308of the ring gear306. For example, the solenoid334is energized to actuate the adaptor328into the first position. As another example, the solenoid334is deenergized so that a bias member acting on the adaptor328advances the adaptor328into the first position. The external teeth330of the adaptor328can mesh with the internal teeth326of the ground component324in the first position of the adaptor328and also in other positions. That is, the ring gear316is held stationary in the first mode of operation by the ground component324through the one-way clutch318and the adaptor328.

FIG.3Bshows an example of a second mode of operation of the transmission300. The second mode corresponds to a second gear ratio for the transmission300. For example, the second gear ratio can be referred to as a second gear for the vehicle. The first gear ratio (ofFIG.3A) can be greater than the second gear ratio. In the second mode of operation, the ring gear306is held stationary, whereas the ring gear316, by contrast, is not held stationary. In the second mode of operation, the adaptor328is moved toward the left in the present illustration into a second position where the tapered surfaces320and332are not connected with each other, and where the external teeth330of the adaptor328mesh with the internal teeth308of the ring gear306. For example, the solenoid334is energized to actuate the adaptor328into the second position. As another example, the solenoid334is deenergized so that a bias member acting on the adaptor328advances the adaptor328into the second position. The external teeth330of the adaptor328can mesh with the internal teeth of the ground component324in the second position of the adaptor328and also in other positions. That is, the ring gear306is held stationary in the second mode of operation by the ground component324through the adaptor328.

Between the first mode (FIG.3A) and the second mode (FIG.3B) the transmission300can have a third mode of operation. The third mode of operation can temporarily occur while the transmission300is shifting from the first gear to the second gear, and also while the transmission300is shifting from the second gear to the first gear. In the third mode, neither of the ring gear306or the ring gear316is held stationary. As such, both the ring gear306and the ring gear316can be free to rotate in the third mode.

The described examples illustrate that a transmission (e.g., the transmission300) can include: a first planetary stage including a first ring gear (e.g., the ring gear306) defining first internal teeth (e.g., the internal teeth308); a ground component (e.g., the ground component324) defining second internal teeth (e.g., the internal teeth326); a compound planetary stage including a one-way clutch (e.g., the one-way clutch318) with an inner race (e.g., the inner race318B) and an outer race (e.g., the outer race318A), the outer race having a first tapered surface (e.g., the tapered surface320); and an adaptor (e.g., the adaptor328) defining external teeth (e.g., the external teeth330) and a second tapered surface (e.g., the tapered surface332), the adaptor being movable into at least a first position (e.g., as shown inFIG.3A) where the first tapered surface and the second tapered surface are connected with each other, and into a second position (e.g., as shown inFIG.3A) where instead the first internal teeth are gear coupled with the second internal teeth.

FIG.4shows a cross section of an example of a transmission400according to the present subject matter. The cross section is taken along the line C-C inFIG.1C, in an implementation where the transmission102includes the components of the transmission400. The transmission400can be used with one or more other examples described elsewhere herein.

The transmission400includes a sun gear402that is driven by a component such as the rotor shaft of an electric motor (e.g., the rotor shaft112inFIGS.1A-1C). The transmission400includes one or more planetary gears404that are gear coupled to the sun gear402. Each of the planetary gears404can rotate about an axis. Each of the planetary gears404can also rotate about the axis of the sun gear402using a carrier, for example as described below. The transmission400includes a ring gear406that is gear coupled to the planetary gear(s)404. The ring gear406defines internal teeth408that that extend parallel with the axis of the sun gear402. The ring gear406can be coupled to a ground component410by a one-way clutch412. The sun gear402, the planetary gear(s)404and the ring gear406can collectively be referred to as a first planetary stage of the transmission400.

The transmission400includes one or more planetary gears414having a common shaft (sometimes referred to as a common pin) with the corresponding planetary gear(s)404. The planetary gear404has a first diameter, and the planetary gear414has a second diameter, the first diameter being greater than the second diameter. The transmission400includes a ring gear416that is coaxial with the sun gear402and gear coupled to the planetary gear(s)414. The transmission400includes a one-way clutch418. The one-way clutch418is positioned radially outward of the ring gear416. The one-way clutch418has an outer race418A with a tapered surface420. The tapered surface420is tapered along the rotation axis of the sun gear402. The one-way clutch418has an inner race418B. The inner race418B is connected to the ring gear416. Between the outer and inner races418A-418B, the one-way clutch418includes sprags, or rollers biased by springs toward wedging planes, so as to provide single-direction rotation between the outer and inner races418A-418B. The transmission400includes a carrier member422carrying the planetary gears404and414, the carrier member422being coaxial with the sun gear402. The carrier member422can define a bearing nest for at least the planetary gear(s)414. For example, in this sectional view a portion of the carrier member422is visible radially outward of the shaft of the planetary gears404and414. The planetary gear(s)414, the ring gear416and the one-way clutch418can collectively be referred to as a compound planetary stage of the transmission400.

The transmission400includes a ground component424that can be used for selectively holding either the ring gear406or the ring gear416stationary. The ground component424can be part of the same structure as the ground component410(e.g., a case or housing of the transmission400). The ground component424defines internal teeth426that extend parallel with the axis of the sun gear402.

The transmission400includes an adaptor428that can be translated along the axis of the sun gear402. The adaptor428defines external teeth430. The external teeth430mesh with the internal teeth426of the ground component424. The adaptor428defines a tapered surface432. The tapered surface432is tapered along the rotation axis of the sun gear402so as to face the tapered surface420.

FIG.4shows an example of a first mode of operation of the transmission400. The first mode corresponds to a first gear ratio for the transmission400. For example, the first gear ratio can be referred to as a first gear for the vehicle. In the first mode of operation, the ring gear416is held stationary, whereas the ring gear406, by contrast, is not held stationary. In the first mode of operation, the adaptor428is moved toward the left in the present illustration into a first position where the tapered surfaces420and432are connected with each other, and where the external teeth430of the adaptor428do not mesh with the internal teeth408of the ring gear406. For example, a solenoid is energized to actuate the adaptor428into the first position. As another example, the solenoid is deenergized so that a bias member acting on the adaptor428advances the adaptor428into the first position. The external teeth430of the adaptor428can mesh with the internal teeth426of the ground component424in the first position of the adaptor428and also in other positions. That is, the ring gear416is held stationary in the first mode of operation by the ground component424through the one-way clutch418and the adaptor428.

A second mode of operation of the transmission400can correspond to a second gear ratio (e.g., a lower gear ratio), in which the ring gear406is held stationary, the ring gear416is not held stationary, and in which the adaptor428is moved toward the right in the present illustration into a second position where the tapered surfaces420and432are not connected with each other, and where the external teeth430of the adaptor428mesh with the internal teeth408of the ring gear406. That is, the ring gear406is held stationary in the second mode of operation by the ground component424through the adaptor428.

Between the first mode (FIG.4) and the second mode (described above) the transmission400can have a third mode of operation. The third mode of operation can temporarily occur while the transmission400is shifting from the first gear to the second gear, and also while the transmission400is shifting from the second gear to the first gear. In the third mode, neither of the ring gear406or the ring gear416is held stationary. As such, both the ring gear406and the ring gear416can be free to rotate in the third mode.

FIGS.5A-5Cshow examples of a transmission500according to the present subject matter. The transmission500can be used with one or more other examples described elsewhere herein. The transmission500is here shown partially transparent to present its various components. The transmission500includes a sun gear502that is driven by a component such as the rotor shaft of an electric motor (e.g., the rotor shaft112inFIGS.1A-1C). The transmission500here includes four planetary gears504that are gear coupled to the sun gear502. Each of the planetary gears504can rotate about an axis. Each of the planetary gears504can also rotate about the axis of the sun gear502using a carrier (e.g., the carrier member322inFIGS.3A-3B). The transmission500includes a ring gear506that is gear coupled to the planetary gears504. The ring gear506defines internal teeth508; the cusp of each of the internal teeth508defines a ridge that extends parallel with the axis of the sun gear502. Each of the planetary gears504is gear coupled to only the sun gear502and the ring gear506. The ring gear506can be coupled to a ground component (e.g., the ground component310inFIGS.3A-3B) by a one-way clutch (e.g., the one-way clutch312inFIGS.3A-3B). The sun gear502, the planetary gear(s)504and the ring gear506can collectively be referred to as a first planetary stage of the transmission500. As such, the first planetary stage can include multiple planetary gears.

The transmission500here includes four planetary gears510each having a common shaft (sometimes referred to as a common pin) with a corresponding one of the planetary gear(s)504. The planetary gears504have a first diameter, and the planetary gears510have a second diameter, the first diameter being greater than the second diameter. The transmission500includes a ring gear512that is coaxial with the sun gear502and gear coupled to the planetary gears510. Each of the planetary gears510is gear coupled to only the ring gear512. The planetary gear(s)510and the ring gear512can collectively be referred to as a compound planetary stage of the transmission500. As such, the compound planetary stage can include multiple planetary gears.

The transmission500can selectively hold either the ring gear506or the ring gear512stationary. In some implementations, an adaptor (e.g., the adaptor328inFIGS.3A-3B, or the adaptor428inFIG.4) can be used to either couple the ring gear506, or the ring gear512, to a ground component (e.g., the ground component324inFIGS.3A-3B, or the ground component424inFIG.4). In such examples, the ground component can be positioned radially outward of the ring gear512, and the adaptor can be positioned radially inward of the ground component. For example, the adaptor can be actuated directly or indirectly by a solenoid.

FIG.5Ashows an example of a first mode of operation of the transmission500. The first mode corresponds to a first gear ratio for the transmission500. For example, the first gear ratio can be referred to as a first gear for the vehicle. In the first mode of operation, the ring gear512is held stationary, whereas the ring gear506, by contrast, is not held stationary. The sun gear502can be driven to rotate in either direction. Here, a rotation514of the ring gear506is shown as an example. The rotation514causes each of the planetary gears504and510to undergo a rotation516about its respective common shaft. Also, the planetary carrier for the planetary gears504and510will undergo a rotation518, as schematically indicated at each of the common shafts of the planetary gears504and510. The planetary carrier can be the component that delivers motor torque from the transmission500to the traction wheel of the vehicle, and as such the rotational speed of the planetary carrier can indicate the rotational speed of the traction wheel. The ring gear506, finally, will undergo a rotation520that is in the opposite direction of both the rotation514of the ring gear506and the rotation518of the carrier of the planetary gears504and510.

FIG.5Bshows an example of an operation of the transmission500in shifting between gears. During this transition, the grounding of the ring gear512is removed so that both of the ring gears506and512are free to rotate. The sun gear502can undergo a rotation522that is slower than the rotation514inFIG.5A. The planetary carrier for the planetary gears504and510can undergo the rotation518, the same as inFIG.5A. The ring gear506can undergo a rotation524that is in the same direction as, and slower than, the rotation520inFIG.5A. The ring gear512can undergo a rotation526that is in the opposite direction of the rotations520and524of the ring gear506.

FIG.5Cshows an example of a second mode of operation of the transmission500. The second mode corresponds to a second gear ratio for the transmission500. For example, the second gear ratio can be referred to as a second gear for the vehicle. In the second mode of operation, the ring gear506is held stationary and the ring gear512is not held stationary. The sun gear502can undergo a rotation528that is slower than the rotation514inFIG.5A. The planetary carrier for the planetary gears504and510can undergo the rotation518, the same as inFIGS.5A-5B. The ring gear512can undergo a rotation530that is in the opposite direction of the rotations520and524of the ring gear506and that is faster than the rotation526inFIG.5B.

FIG.6shows a diagram600with graphs exemplifying angular velocities for a rotor shaft speed602, a planetary carrier speed604, and ring gear speeds606and608, respectively, of a transmission. The diagram600shows angular velocity on a vertical axis as a function of time on a horizontal axis. The diagram600and/or any of its graphs can be used with one or more other examples described elsewhere herein.

A section610of the diagram600corresponds to operation using a first gear ratio (e.g., driving the vehicle in first gear). In the section610, a ring gear of a compound planetary stage of the transmission is held stationary by being connected to ground. The rotor shaft can rotate with a speed612defined by motor control circuitry, for example based on accelerator pedal depression. The planetary carrier rotates with a speed614which can be reflective of the current rotation of the vehicle's road wheels. The ring gear having the ring gear speed606(e.g., a ring gear of a first planetary stage) rotates with a speed616that has the opposite rotation direction of the speed612. A speed618of the ring gear having the ring gear speed608(e.g., a ring gear of a compound planetary stage) is zero.

A section620of the diagram600corresponds to a shift time in moving between the first gear ratio and a second gear ratio. In the section620, both the ring gears (e.g., a ring gear of a compound planetary stage, and a ring gear of a first planetary stage) are free to rotate because neither of them is connected to ground. The rotor shaft can rotate with a speed622that is decreasing from the speed612in the section610. The planetary carrier rotates with the same speed614as in the section610due to the load on the carrier. The ring gear having the ring gear speed606rotates with a speed624whose absolute value increases towards zero from the speed616in the section610. For example, the one-way clutch312(FIGS.3A-3B) can help mechanically synchronize the speed624of the ring gear having the ring gear speed606towards zero. The ring gear having the ring gear speed608rotates with a speed626that increases from the speed618in the section610.

A section630of the diagram600corresponds to operation using a second gear ratio (e.g., driving the vehicle in second gear). In the section630, a ring gear of a first planetary stage of the transmission is held stationary by being connected to ground. The rotor shaft can rotate with a speed632that is lower than the speed612in the section610. The planetary carrier rotates with the same speed614as in the section610due to the load on the carrier. The ring gear having the ring gear speed606rotates with the speed618that is zero. The ring gear having the ring gear speed608rotates with a speed634, the rotation being in the same direction as that of the rotor shaft.

Some examples of a vehicle with multiple electric motors will now be described.FIG.7schematically shows an example of a vehicle700with at least two electric motors702and704, at least one of which has a transmission according to the present subject matter. Here, the electric motor704has a transmission706according to the present subject matter where one of the corresponding ring gears of respective planetary stages can be selectively grounded to effectuate different gear ratios. The electric motor704can also have a transmission708according to the present subject matter.

The vehicle700is schematically illustrated using a rectangle710. For example, the rectangle710here represents the body, passenger cabin, chassis, wheels, energy storage (e.g., battery pack), electrical system, and thermal system of the vehicle700. At least one aspect of the examples inFIG.7can be used with one or more other examples described elsewhere herein.

The electric motor702can be configured to work with an axle712of the vehicle700. Similarly, the electric motor704can be configured to work with an axle714of the vehicle700. Each of the axles712and714is here schematically illustrated as a dashed line and can be coupled to one or more respective road wheels (not shown) of the vehicle700. In some implementations, the electric motor702can be referred to as a front motor, and the electric motor704as a rear motor, of the vehicle700. In other implementations, the electric motor704can be referred to as a front motor, and the electric motor702as a rear motor, of the vehicle700. The electric motor702can have only a transmission716or can also have a transmission718.

To drive the vehicle700forward, either or both of the electric motors702or704can operate in a forward direction. For example, the transmission706can begin operating in first gear and subsequently be shifted into second gear. Similarly, the transmission716can begin operating in first gear and subsequently be shifted into second gear, which shifting may occur at the same time as or at a different time than the shifting of the transmission706.

To obtain regenerative braking, the vehicle700can either first ensure that the transmission706is in second gear (because the first gear may not facilitate regenerative braking), and then use the electric motor704for the regenerative braking. Alternatively, the vehicle700can use the electric motor702, where the transmission716provides regenerative braking in all (e.g., both) gears, for the regenerative braking regardless of the current gear of the transmission706of the electric motor704.

To drive the vehicle700in reverse, the vehicle700can either first ensure that the transmission706is in first gear (because the second gear may not facilitate driving in reverse), and then operate the electric motor704in the opposite direction to drive the vehicle700in reverse. Alternatively, the vehicle700can use the electric motor702, where the transmission716facilitates driving in reverse in all (e.g., both) gears, to facilitate driving in reverse and not energize the electric motor704while in reverse.

The vehicle700can have three or more electric motors. For example, two electric motors can power the axle712, with one or more electric motors powering the axle714. As another example, two electric motors can power the axle714, with one or more electric motors powering the axle712.

The terms “substantially” and “about” used throughout this Specification are used to describe and account for small fluctuations, such as due to variations in processing. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Also, when used herein, an indefinite article such as “a” or “an” means “at least one.”

In addition, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other processes may be provided, or processes may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.