Patent Description:
One or more transmissions are utilised along a powertrain of a vehicle to adapt an output of a torque source, such as an internal combustion engine and/or an electric machine, to the drive wheels of the vehicle.

A transmission may be shifted into different gears in order to adapt the torque and rotational speed provided by the torque source to the drive wheels of the vehicle depending on current driving and/or operating conditions of the vehicle.

Shifting of gears may be manually or automatically initiated and/or performed. Actuators of the transmission may shift gears in the transmission upon manual or automatic input to the transmission. The actuators may be controlled by a control unit which determines when gear shifting is due and which automatically shifts gears in the gearbox.

In order to shift gears, the rotational speeds of at least a first component of the transmission and a second component have to be synchronised. This may be done in different ways e.g., with a mechanical synchronisation mechanism utilising friction for synchronising the relevant components, or by controlling the matching of the rotational speeds of the relevant components under the control of a control unit of the transmission. In the former case, reference is made to synchronised gears and in the latter case, reference is made to unsynchronised gears. One and the same transmission may comprise synchronised gears as well as unsynchronised gears.

A transmission may comprise at least one section of gears. One or more further sections of gears may be arranged downstream or upstream of the one section of gears. The one section of gears may comprise a planetary gearset, which may be shifted between a low gear and a high gear. The one section of gears may form a so-called range section of a transmission.

One example of a transmission in the form of a transfer case comprising a planetary gearset is disclosed in <CIT>.

In modern vehicles space is sparse. Small sized transmissions are thus, easier to build into modern vehicles.

It would be advantageous to achieve a transmission that provides conditions for enabling a small sized transmission. In particular, it would be desirable to enable mechanical synchronization in a transmission within limited dimensions.

According to independent claim <NUM> the invention provides a transmission comprising an input shaft, an output shaft, and a planetary gearset being driven by the input shaft and being couplable to the output shaft in a high gear mode and a low gear mode of the transmission, the input and output shafts being arranged rotatably and coaxially along an axis. The planetary gearset comprises a sun gear connected to the input shaft, a ring gear that is axially movable, and at least one planet gear rotatably supported on a planet gear carrier that is connected to the output shaft. The transmission further comprises a coupling disc connected to the input shaft, an axially moveable coupling sleeve being configured to selectively connect the planet gear carrier with the coupling disc in an engaged position of the coupling sleeve to provide the high gear mode, and a synchronizer ring arranged between the coupling sleeve and the ring gear. The synchronizer ring is configured to transfer an axial motion of the ring gear in a first direction towards the coupling sleeve and the coupling disc. The coupling sleeve is moveable from an unengaged position into the engaged position at least in part by the synchronizer ring.

Since the transmission comprises the coupling disc connected to the input shaft, since the synchronizer ring is configured to transfer an axial motion of the ring gear in a first direction towards the coupling sleeve and the coupling disc, and since the coupling sleeve is moveable from an unengaged position into the engaged position at least in part by the synchronizer ring - a compact mechanically synchronized transmission is provided. A length of the transmission along the axis is only affected by the coupling disc and as such the axial extension beyond that of the planetary gearset itself is limited. Particularly so, since the synchronizer ring and at least part of the coupling sleeve fit within the axial extension of the planetary gearset as such.

The transmission may form part of a powertrain of a vehicle. A torque source of the powertrain may be connected directly or indirectly to the input shaft of the transmission. Downstream of the output shaft, the powertrain may comprise one or more drive wheels for propelling the vehicle. The torque source may form the only torque source of the vehicle. Alternatively, the torque source may form one of at least two torque sources of the vehicle.

Herein, the term vehicle relates to e.g., heavy goods vehicle, lorry, truck, pickup, van, wheel loader, bus, tracked vehicle, tank, quad bike, car or other similar motorized manned or unmanned vehicle, designed for land-based propulsion.

The transmission may comprise one or more further sections of gears in addition to the planetary gearset. The one or more further sections of gears may be arranged downstream or upstream of the planetary gearset.

In the high gear mode, the input shaft is connected to the output shaft and rotationally locked to the output shaft such that the input and output shafts rotate at the same rotational speed. In the high gear mode, the ring gear is rotatable with the synchronizer ring and the coupling disc. In the high gear mode, torque is transmitted from the input shaft via the coupling disc, the coupling sleeve, and the planet gear carrier to the output shaft.

In the low gear mode, the input shaft is connected to the output shaft via the at least one planet gear and the planet gear carrier while the ring gear is rotationally locked to a stationary portion of the transmission. In the low gear mode, torque is transmitted from the input shaft via the sun gear, the at least one planet gear, and the planet gear carrier to the output shaft.

In the low gear mode, no torque is transmitted via the coupling sleeve which is rotating with the planet gear carrier but not engaged with the coupling disc. This means that the coupling sleeve rotates with a lower rotational speed than the sun gear in the low gear mode. Accordingly, drag losses are reduced in the low gear mode.

Terms used herein, such as axial extension, axially movable, circumferential, rotation, rotational direction, and other similar references are used in relation to the axis of the input and output shafts, if not otherwise noted.

The coupling disc as such has only a limited axial extension. The axial extension of the coupling disc may fit within a length of the input shaft along the axial extension. As such, the axial extension of the transmission may be extended to a limited and even negligible extent by the coupling disc.

The coupling sleeve and the synchronizer ring may be rotationally locked to the planet gear carrier.

The synchronizer ring is sometimes referred to as a latch cone. The ring gear is sometimes be referred to as an annular gear.

The synchronizer ring is configured for frictional engagement with the ring gear. Thus, during shifting the transmission into the high gear mode, as the ring gear is moved in the first direction, the frictional engagement between the rotating synchronizer ring and the ring gear, causes the ring gear to rotate at the same rotational speed as the coupling sleeve, the synchronizer ring, and the planet gear carrier.

Since the synchronizer ring is configured to transfer the axial motion of the ring gear in the first direction and since the synchronizer ring is arranged between the coupling sleeve and the ring gear, the coupling sleeve is moveable from the unengaged position into the engaged position at least in part by the synchronizer ring.

Put differently, the coupling sleeve being moveable from an unengaged position into the engaged position at least in part by the synchronizer ring, means that the coupling sleeve is moveable from an unengaged position into the engaged position directly and/or indirectly by the synchronizer ring.

An actuator, such as a hydraulic, pneumatic, or electric actuator may be arranged to move the ring gear in the first direction. A further option may be to manually actuate the ring gear to move in the first direction.

The actuator may be controlled by a control unit. The control unit may determine when gear shifting is due, such as shifting between low and high gear modes. Alternatively, or additionally, the control unit may be configured to receive manual input causing the control unit to control specific actuators to shift one or more gears in the transmission.

According to independent claim <NUM> the invention provides a method of shifting a transmission according to any of aspects and/or embodiments discussed herein. Accordingly, the transmission comprises an input shaft, an output shaft, and a planetary gearset being driven by the input shaft and being couplable to the output shaft in a high gear mode and a low gear mode of the transmission, the input and output shafts being arranged rotatably and coaxially along an axis. The planetary gearset comprises a sun gear connected to the input shaft, a ring gear that is axially movable, and at least one planet gear rotatably supported on a planet gear carrier that is connected to the output shaft. The transmission further comprises a coupling disc connected to the input shaft, an axially moveable coupling sleeve, and a synchronizer ring arranged between the coupling sleeve and the ring gear. In order to connect the planet gear carrier with the coupling disc in an engaged position of the coupling sleeve to provide the high gear mode, the method comprises steps of:.

Accordingly, shifting into a high gear mode of a compact transmission is provided.

According to embodiments, the synchronizer ring may be arranged to engage with the coupling sleeve in a circumferential direction and arranged with a rotational play in relation to the coupling sleeve. In this manner, the synchronizer ring may be arranged in different rotational positions in relation to the coupling sleeve. This may be utilised for controlling axial movement of the synchronizer ring, preventing axial movement of the synchronizer ring in one relative rotational position and permitting axial movement in a different relative rotational position.

According to embodiments, the rotational play may also be utilised for controlling axial movement of the coupling sleeve into engagement with the coupling disc. Namely, the rotational play may be utilised for permitting a relative rotation between the coupling sleeve and the synchronizer ring, such that the coupling sleeve may be permitted to rotate in relation to the coupling disc for reaching the engaged position.

The rotational play provides a clearance in the rotational direction. The rotational play provides a limited relative rotational shift between the synchronizer ring and coupling sleeve.

Since the coupling sleeve may be rotationally locked to the planet gear carrier, the synchronizer ring may also be arranged with a rotational play in relation to the planet gear carrier.

Further features of, and advantages with, the invention will become apparent when studying the appended claims and the following detailed description.

Various aspects and/or embodiments of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:.

Aspects and/or embodiments of the invention will now be described more fully.

<FIG> schematically illustrates a land-based vehicle <NUM> according to embodiments. The vehicle <NUM> is a heavy goods vehicle. The vehicle <NUM> is configured to be propelled by a powertrain.

During propelling of the vehicle <NUM> at different speeds, a transmission of the powertrain may be shifted into, and operated, in a high gear mode and a low gear mode, depending e.g., on a torque output from a torque source of the powertrain and a traveling speed of the vehicle <NUM>.

<FIG> schematically illustrates embodiments of a powertrain <NUM> of a land-based vehicle <NUM>. The vehicle <NUM> may be a vehicle <NUM> as shown in <FIG>.

The powertrain <NUM> comprises a transmission <NUM>. The transmission <NUM> is a transmission according to any one of aspects and or embodiments discussed herein.

The powertrain <NUM> further comprises at least one torque source <NUM>. According to embodiments, the at least one torque source may comprise an electric machine.

In the illustrated example, the torques source <NUM> comprises a main torque source <NUM>' and an additional torque source <NUM>".

The main torque source <NUM>' and/or the additional torque source <NUM>" may comprise an electric machine.

Specifically, the at least one torque source includes a rotor. The rotor is connected to the transmission <NUM>.

The rotor may comprise a rotor of an electric machine and/or a crankshaft of an ICE.

The powertrain <NUM> may comprise one or more further components. Mentioned purely as examples, the powertrain <NUM> may comprise one or more of a further transmission (not shown), a clutch <NUM>, a shaft <NUM> leading to the transmission <NUM>, a propeller shaft <NUM>, a differential <NUM>, drive axels <NUM>, and drive wheels <NUM>.

A control unit <NUM> may be provided for controlling at least the transmission <NUM>. The control unit <NUM> may be configured to control shifting of gears in the transmission <NUM>. The control unit <NUM> may be configured to shift gears based on input from a driver of the vehicle <NUM>. Sensors for providing input to the control unit <NUM> may be connected to the control unit <NUM>. Data from such sensors may be utilised by the control unit prior to, and/or during, a gear shifting process.

The control unit <NUM> may be configured to perform a method <NUM> as discussed inter alia below with reference to <FIG>.

<FIG> schematically illustrate embodiments of a transmission <NUM> of a powertrain for a vehicle. The transmission may be a transmission <NUM> of a powertrain as illustrated in <FIG>.

The transmission <NUM> comprises an input shaft <NUM>, an output shaft <NUM>, and a planetary gearset <NUM>. The input shaft <NUM> is arranged coaxially with the output shaft <NUM> along an axis <NUM>. The planetary gearset <NUM> is driven by the input shaft <NUM>, which is couplable to the output shaft <NUM> in a high gear mode and a low gear mode of the transmission <NUM>.

The high gear mode is shown in <FIG> and the low gear mode is shown in <FIG>.

The transmission may comprise one or more further gear stages (not shown) connected to the input shaft <NUM> and/or to the output shaft <NUM>. Such further gear stages may comprise shiftable and/or non-shiftable gears.

The planetary gearset <NUM> comprises a sun gear <NUM>, a ring gear <NUM>, at least one planet gear <NUM>, and a planet gear carrier <NUM>.

The sun gear <NUM> is connected to the input shaft <NUM> and rotationally locked to the input shaft <NUM>. The ring gear <NUM> is axially movable along the axis <NUM>. The at least one planet gear <NUM> is rotatably supported on the planet gear carrier <NUM>. The planet gear carrier <NUM> is fixedly connected to the output shaft <NUM> and thus, rotationally locked to the output shaft <NUM>.

The transmission <NUM> further comprises a coupling disc <NUM>, a coupling sleeve <NUM>, and a synchronizer ring <NUM>. The synchronizer ring <NUM> may also be referred to as a high gear synchronizer ring <NUM>.

The coupling disc <NUM> is fixedly connected to the input shaft <NUM> and thus, rotationally locked to the input shaft <NUM>. The coupling sleeve <NUM> is axially moveable. The coupling sleeve <NUM> is configured to connect the planet gear carrier <NUM> with the coupling disc <NUM> in an engaged position. In the engaged position of the coupling sleeve <NUM>, the high gear mode of the transmission <NUM> is provided.

The synchronizer ring <NUM> is arranged between the coupling sleeve <NUM> and the ring gear <NUM>. The synchronizer ring <NUM> is configured to transfer an axial motion of the ring gear <NUM> in a first direction <NUM>. The first direction <NUM> extends in a direction from the ring gear <NUM> towards the coupling sleeve <NUM> and the coupling disc <NUM>. The first direction <NUM> extends in parallel with the axis <NUM>. Accordingly the first direction <NUM> may alternatively be referred to as a first axial direction <NUM>.

The coupling sleeve <NUM> is moveable from an unengaged position into the engaged position at least in part by the synchronizer ring <NUM>.

Accordingly, in the high gear mode (<FIG>), the input shaft <NUM> is coupled to the output shaft <NUM> via the coupling disc <NUM>, the coupling sleeve <NUM> in its engaged position with the coupling disc <NUM>, and the planet gear carrier <NUM>. Thus, in the high gear mode, a ratio of the transmission is <NUM>:<NUM> from the input shaft <NUM> to the output shaft <NUM>.

The ring gear <NUM> and the synchronizer ring <NUM> are utilised for shifting the transmission into the high gear mode as will be further discussed below with reference to <FIG>.

In the low gear mode (<FIG>), the input shaft <NUM> is coupled to the output shaft <NUM> via the sun gear <NUM>, the at least one planet gear <NUM>, and the planet gear carrier <NUM>. In the low gear mode, the ring gear <NUM> is rotationally locked to a stationary portion of the transmission <NUM>, such as to a housing of the transmission <NUM>. Also, the ring gear <NUM> is positioned to engage with the at least one planet gear <NUM>. Thus, in the low gear mode, a rotational speed reduction is provided by the transmission <NUM> from the input shaft <NUM> to the output shaft <NUM>. The reduction of rotational speed is determined by the number of teeth of the sun gear <NUM>, the at least one planet gear <NUM>, and the ring gear <NUM>.

In the high gear mode, the ring gear <NUM> does not form part of a torque transmission path through the planetary gearset <NUM>. The torque transmission path, in the high gear mode, leads via the coupling sleeve <NUM> directly from the coupling disc <NUM> to the planet gear carrier <NUM>.

In the low gear mode, the ring gear <NUM> is included in a torque transmission path through the planetary gearset <NUM>. Since, the ring gear <NUM> in the low gear mode is fixed in relation to a stationary portion of the transmission <NUM> and with the at least one planet gear <NUM> engaged with the ring gear <NUM>, the ring gear <NUM> forms a counter member for engagement of the at least one planet gear <NUM> as the sun gear <NUM> rotates the at least one planet gear <NUM> in the planet gear carrier <NUM>.

The ring gear <NUM> may have an intermediate position. In the intermediate position the ring gear <NUM> is neither engaged with the stationary portion of the transmission <NUM> nor with the synchronizer ring <NUM>.

An actuator <NUM> is arranged for shifting the transmission <NUM> into the high gear mode. That is, the actuator <NUM> is arranged for moving the ring gear <NUM> axially in the first direction <NUM> to cause the coupling sleeve <NUM> to engage with the coupling disc <NUM>.

The actuator <NUM> may also be arranged for shifting the transmission <NUM> into the low gear mode. That is, the actuator <NUM> may be arranged for moving the ring gear <NUM> axially in a direction opposite to the first direction <NUM> to cause the ring gear <NUM> to engage with the at least one planet gear <NUM> and the stationary portion of the transmission <NUM>.

A non-shown further synchronizer ring may be provided for reducing the rotational speed of the ring gear <NUM> to facilitate engagement between the ring gear <NUM> and the stationary portion of the transmission <NUM>. See also below with reference to <FIG>.

The actuator <NUM> may also be arranged to disengage the coupling sleeve <NUM> from the coupling disc <NUM>.

The actuator <NUM> may be controlled by a control unit of the transmission <NUM>. The actuator <NUM> may be activated upon input of a driver of the vehicle and/or by the control unit when a control algorithm of the control unit so dictates.

The transmission <NUM> may be provided in a compact format. As also shown in the context of <FIG> below, the herein discussed transmission <NUM> only extends axially beyond the dimensions of the basic components of the planetary gearset <NUM>, i.e. beyond the sun gear <NUM>, the ring gear <NUM>, the at least one planet gear <NUM>, and the planet gear carrier <NUM>, by an axial extension of the coupling disc <NUM>. In a direction perpendicularly to the axis <NUM>, the dimensions of the transmission <NUM> do essentially not have to extend beyond that of the basic components of the planetary gearset <NUM>. At one angular position around a circumference of the ring gear <NUM>, the actuator <NUM> may have to be arranged, at which angular position the transmission <NUM> may require to extend beyond the ring gear <NUM> in the direction perpendicularly to the axis <NUM>.

<FIG> illustrate partial cross sections through a transmission <NUM> according to embodiments. The transmission <NUM> may be a transmission as discussed above with reference to <FIG>. Accordingly, in the flowing reference is also made to <FIG>.

In <FIG>, the transmission <NUM> is shown in the high gear mode and in <FIG>, the transmission <NUM> is shown in the low gear mode.

With reference to <FIG>, in the high gear mode the coupling sleeve <NUM> is engaged with the coupling disc <NUM> and with the planet gear carrier <NUM>.

During shifting into the high gear mode, the ring gear <NUM> is moved in the first direction <NUM> by the actuator <NUM> and the rotational speed of the ring gear <NUM> is synchronized with that of the planet gear carrier <NUM> by the synchronizer ring <NUM> which rotates with the planet gear carrier <NUM>. For instance, a wire spring <NUM> abutting against the coupling sleeve <NUM> may provide resistance to axially moving the coupling sleeve <NUM> in the first direction <NUM>, see <FIG>. The resistance is overcome by the actuator <NUM>.

Since the synchronizer ring <NUM> is engaged with the coupling sleeve <NUM>, also the synchronizer ring <NUM> will be subjected to resistance to axial movement in the first direction <NUM>. During overcoming the resistance from the wire spring <NUM>, the synchronizer ring <NUM> may be rotationally positioned in a blocking position in relation to the coupling sleeve <NUM>. The blocking position is further discussed below with reference to <FIG>. The ring gear <NUM> is sped up in the rotational direction of the planet gear carrier <NUM> by frictional engagement with the synchronizer ring <NUM>.

After rotational speed synchronization, the ring gear <NUM> is further moved in the first direction <NUM> and the coupling sleeve <NUM> is moved into the engaged position shown in <FIG>, directly and/or indirectly by the ring gear <NUM>. That is, one and or both of the ring gear <NUM> and the synchronizer ring <NUM> may abut against the coupling sleeve <NUM> to transfer the movement in the first direction <NUM> of the ring gear <NUM>.

Further details of the engagement between the coupling sleeve <NUM> and the coupling disc <NUM> are discussed below with reference to <FIG>.

With reference to <FIG>, in the low gear mode, the ring gear <NUM> is engaged with a stationary portion of the transmission <NUM>. Thus, the ring gear <NUM> is maintained stationary in the low gear mode. In <FIG>, a lefthand portion of the ring gear <NUM> is engaged with a stationary portion of the transmission <NUM>.

During shifting into the low gear mode, the ring gear <NUM> is moved in a direction opposite to the first direction <NUM> and the rotational speed of the ring gear <NUM> is reduced to zero by a low gear synchronizer ring <NUM>. The low gear synchronizer ring <NUM> is axially moveable and is only rotationally moveable to a limited degree to provide a blocking position. A wire spring <NUM> may provide resistance against axial movement of the low gear synchronizer ring <NUM> in an initial portion of the synchronization of the ring gear <NUM> during shifting into the low gear mode. The axial resistance is overcome by the actuator <NUM>. When the rotation of the ring gear <NUM> has stopped, the ring gear <NUM> is further moved into engagement with stationary portion of the transmission <NUM>.

A shift fork <NUM> forming part of the actuator <NUM> arranged for shifting the transmission <NUM> is shown in <FIG>.

The shift fork <NUM> of the actuator <NUM> is arranged for moving the ring gear <NUM> axially in the first direction <NUM> to cause the coupling sleeve <NUM> to engage with the coupling disc <NUM> and thus, shift the transmission <NUM> into the high gear mode. The shift fork <NUM> of the actuator <NUM> is also arranged for moving the ring gear <NUM> axially in the direction opposite to the first direction <NUM> to cause the ring gear <NUM> to engage with a stationary portion of the transmission <NUM> and thus, shift the transmission <NUM> into the low gear mode.

Moreover, the shift fork <NUM> of the actuator <NUM> may be arranged to disengage the coupling sleeve <NUM> from the coupling disc <NUM>. As shown in sequence in <FIG>, the shift fork <NUM> of the actuator <NUM> engages with the coupling sleeve <NUM> and axially moves the coupling sleeve <NUM> out of its engaged position with the coupling disc <NUM> as the shift fork <NUM> of the actuator <NUM> is moved in the direction opposite to the first direction <NUM>. Together with the coupling sleeve <NUM>, also the synchronizer ring <NUM> is moved in the direction opposite to the first direction <NUM>. Thus, the synchronizer ring <NUM> and the coupling sleeve <NUM>, in Fig. 4c, are in position for shifting the transmission <NUM> into the high gear mode.

Similarly, as shown in <FIG>, the shift fork <NUM> of the actuator <NUM> may be arranged to axially move the low gear synchronizer ring <NUM> in the first direction <NUM> when the ring gear <NUM> is moved in the first direction <NUM>. Thus, the low gear synchronizer ring <NUM> is in position for shifting the transmission <NUM> into the low gear mode.

<FIG> illustrate a transmission <NUM> according to embodiments in two different exploded views. The transmission <NUM> may be a transmission as discussed above with reference to <FIG>. Accordingly, in the flowing reference is also made to <FIG>.

Accordingly, from the left in <FIG>, the transmission <NUM> comprises, the input shaft <NUM>, the coupling disc <NUM>, the coupling sleeve <NUM>, the synchronizer ring <NUM>, the planet gear carrier <NUM>, the at least one planet gear <NUM>, the ring gear <NUM>, and the output shaft <NUM>. The sun gear <NUM> is not visible in <FIG>.

The transmission <NUM> may further comprise one or more of a high gear wire spring <NUM>, a low gear synchronizer ring <NUM>, a low gear wire spring <NUM>, and a set of outer splines <NUM> included in a stationary portion of the transmission <NUM>.

According to embodiments, the ring gear <NUM> may comprise an outer conical surface <NUM> and the synchronizer ring <NUM> comprises one or more inner surfaces <NUM> configured to abut against the outer conical surface <NUM>. In this manner, the ring gear <NUM> and the synchronizer ring <NUM> may be brought to frictionally engage with each other via the outer conical surface <NUM> and the one or more inner surfaces <NUM>.

The outer conical surface of the ring gear <NUM> and the one or more inner surfaces of the synchronizer ring <NUM> are also visible in <FIG> and 4c.

For instance, the outer conical surface <NUM> may be a circumferentially continuously extending surface portion of the ring gear <NUM>. The one or more inner surfaces <NUM> may form part of a lining, such a s a carbon fibre lining, and/or may be surfaces of protrusions facing radially inwardly from the synchronizer ring <NUM>.

According to embodiments, the coupling sleeve <NUM> may be rotationally locked to the planet gear carrier <NUM> by a first splined connection <NUM>, <NUM>. The first splined connection <NUM>, <NUM> may comprise external splines <NUM> arranged on the planet gear carrier <NUM> and internal splines <NUM> arranged at a radially inner portion of the coupling sleeve <NUM>. In this manner, the coupling sleeve <NUM> may be provided axially movable on the planet gear carrier <NUM> while being rotationally locked thereto.

The first splined connection <NUM>, <NUM> may ensure that the coupling sleeve <NUM> rotates with the planet gear carrier <NUM>.

The first splined connection <NUM>, <NUM> may herein alternatively be referred to as the splined connection <NUM>, <NUM> of the coupling sleeve <NUM> and the planet gear carrier <NUM>.

The synchronizer ring <NUM> may be arranged to engage with the coupling sleeve <NUM> in a circumferential direction of the coupling sleeve <NUM>. Thus, it may be ensured that the rotational speed of the ring gear <NUM> is synchronized with that of the coupling sleeve <NUM> and the synchronizer ring <NUM> before the coupling sleeve <NUM> is permitted to be move in the first direction <NUM> by the ring gear <NUM>. The synchronizer ring <NUM> may take a blocking position while the rotational speed of the ring gear <NUM> is synchronized, as discussed below with reference to <FIG>.

Moreover, the synchronizer ring <NUM> may be arranged with a rotational play in relation to the coupling sleeve <NUM>.

The rotational play is provided in combination by axial recesses <NUM> in the coupling sleeve <NUM>, radially inwardly directed protrusions <NUM> in the synchronizer ring <NUM>, and circumferential gaps <NUM> in the external splines <NUM> of the planet gear carrier <NUM>.

The synchronizer ring <NUM> may be engaged with the coupling sleeve <NUM> at one or more circumferential positions of the synchronizer ring <NUM> and the coupling sleeve <NUM>, such as at circumferential positions of the radially inwardly directed protrusions <NUM>. That is, the radially inwardly directed protrusions <NUM> may extend radially inwardly through the circumferentially extending axial recesses <NUM> of the coupling sleeve <NUM>.

See below with reference to <FIG> concerning details about the rotational play and how the coupling sleeve <NUM> is moved in the first direction <NUM> after synchronization of the ring gear <NUM>.

According to embodiments, the coupling sleeve <NUM> and the coupling disc <NUM> may be engageable in the engaged position via a second splined connection <NUM>, <NUM>. The second splined connection <NUM>, <NUM> may comprise external splines <NUM> arranged on the coupling disc <NUM> and internal splines <NUM> arranged at a radially inner portion of the coupling sleeve <NUM>. In this manner, the engagement between the coupling sleeve <NUM> and the coupling disc <NUM> in the high gear mode of transmission <NUM> may be provided by the second splined connection <NUM>, <NUM>.

The second splined connection <NUM>, <NUM> is selectively engageable to provide the high gear mode of the transmission <NUM>.

The internal splines <NUM> of the coupling sleeve <NUM> of the second splined connection <NUM>, <NUM> may form part of the internal splines <NUM> of the coupling sleeve <NUM> of the first splined connection <NUM>, <NUM>. Alternatively, the internal splines <NUM> of the coupling sleeve <NUM> of the second splined connection <NUM>, <NUM> may be separate from the internal splines <NUM> of the coupling sleeve <NUM> of the first splined connection <NUM>, <NUM>.

See below with reference to <FIG> concerning details about how the engaged position of the coupling sleeve <NUM> with the coupling disc <NUM> is achieve with the second splined connection <NUM>, <NUM>.

The second splined connection <NUM>, <NUM> may herein alternatively be referred to as the splined connection <NUM>, <NUM> of the coupling sleeve <NUM> and the coupling disc <NUM>.

<FIG> illustrate partial axially and circumferentially extending cross sections of the transmission <NUM> of <FIG>. The cross sections of <FIG> are taken along lines VI - VI in <FIG> and 4c. Accordingly, the cross sections extend through the first and second splined connections <NUM>, <NUM>, <NUM>, <NUM> of the planet gear carrier <NUM>, the coupling sleeve <NUM>, and the coupling disc <NUM>, and through the radially inwardly directed protrusions <NUM> of the synchronizer ring <NUM>, see discussion of <FIG> above. In the following, reference is also made to <FIG>.

<FIG> also show steps of a method <NUM> of shifting a transmission as discussed below with reference to <FIG>.

More specifically, in all of <FIG> there are shown:.

<FIG> show how the coupling sleeve <NUM> reaches its engaged position with the coupling disc <NUM>. Accordingly, <FIG> show relative axial and circumferential movements of the synchronizer ring <NUM> (comprising the protrusions <NUM>) and the coupling sleeve <NUM> (comprising the internal splines <NUM>, <NUM>) in relation to the planet gear carrier <NUM> (comprising the external splines <NUM>) and the coupling disc <NUM> (comprising the external splines <NUM>).

As mentioned above, and as shown in <FIG>, the synchronizer ring <NUM> is arranged with a rotational play in relation to the coupling sleeve <NUM>. More specifically, in <FIG> the inwardly directed protrusions <NUM> of the synchronizer ring <NUM> are shown in three different positions in relation to the internal splines <NUM>, <NUM> of the coupling sleeve <NUM>.

Also, the synchronizer ring <NUM> and the planet gear carrier <NUM> are configured such that the synchronizer ring <NUM> can change relative rotational position in relation to the planet gear carrier <NUM>. The relative rotational positions are at least in part enabled by the circumferential gaps <NUM> in the external splines <NUM> of the planet gear carrier <NUM>.

In <FIG>, the rotational direction of the planet gear carrier <NUM>, the coupling sleeve <NUM>, the synchronizer ring <NUM>, and the coupling disc <NUM> is downwardly. During synchronization of the rotational speed of the ring gear <NUM> from zero to that of the planet gear carrier <NUM>, the synchronizer ring <NUM> and its protrusions <NUM> are subjected by the ring gear <NUM> to an upwardly directed force in the figures. Thus, during synchronization, the synchronization ring <NUM> and its protrusions <NUM> are circumferentially positioned in relation to the coupling sleeve <NUM> such that the protrusions <NUM> are arranged at one circumferential end of the circumferential recess <NUM> of the coupling sleeve <NUM>.

When the rotational speed of the ring gear <NUM> has been synchronized with that of the planet gear carrier <NUM> via the synchronizer ring <NUM> and the coupling sleeve <NUM>, the at least one planet gear <NUM> does no longer rotate in relation to the sun gear <NUM> and the ring gear <NUM>.

According to embodiments, in a blocking position of the synchronizer ring <NUM>, the synchronizer ring <NUM> may be prevented from axial movement in the first direction <NUM>. The blocking position may be maintained while there remains a rotational speed difference between the ring gear <NUM> on the one hand and the synchronizer ring <NUM> and the coupling sleeve <NUM> on the other hand. In this manner, since the coupling sleeve <NUM> is rotationally locked to the planet gear carrier <NUM>, the synchronization of the ring gear <NUM> by the synchronizer ring <NUM> with planet gear carrier <NUM> and the coupling sleeve <NUM> may be ensured before the coupling sleeve <NUM> is permitted to move in the first direction <NUM>.

In the blocking position the radially inwardly directed protrusions <NUM> of the synchronizer ring <NUM> may be at least partially axially aligned with at least some of the external splines <NUM> of the planet gear carrier <NUM>. Thus, in the blocking position, the synchronizer ring <NUM> is prevented from moving in the first direction <NUM> by the splines <NUM>. The blocking position remains as long as the rotational speed difference between the ring gear <NUM> and the planet gear carrier <NUM> remains.

In <FIG>, the synchronizer ring <NUM> is in the blocking position. The protrusions <NUM> of the synchronizer ring <NUM> are at least partially aligned with the splines <NUM> and thus, prevented from being moved axially in between the splines <NUM> of the planet gear carrier <NUM>.

According to embodiments, in a release position of the synchronizer ring <NUM>, the synchronizer ring <NUM> may be axially moveable in the first direction <NUM>. In the release position the coupling sleeve <NUM> is axially moveable in the first direction <NUM> by the synchronizer ring <NUM> and/or the ring gear <NUM>. In this manner, movement of the coupling sleeve <NUM> in the first direction <NUM> toward its engaged position with the coupling disc <NUM> may be enabled when the rotational speed of the ring gear <NUM> has been synchronized with that of the planet gear carrier <NUM>.

In the release position the protrusions <NUM> of the synchronizer ring <NUM> may be aligned with circumferential interspaces between the external splines <NUM> of the planet gear carrier <NUM>.

In <FIG>, the synchronizer ring <NUM> is in the release position. The protrusions <NUM> of the synchronizer ring <NUM> are circumferentially positioned between the splines <NUM> of the planet gear carrier <NUM> and thus, axially moveable in between the splines <NUM>.

According to embodiments, the release position of the synchronizer ring <NUM> may be reachable by a first relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM> in a first circumferential direction. The first relative rotation may be permitted by the rotational play i.e., the rotational play between the synchronizer ring <NUM> and the coupling sleeve <NUM>. In this manner, the release position may be provided.

Since the first circumferential direction represents a relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM>, the first circumferential direction may be e.g. counter-clockwise for the synchronizer ring <NUM> and clockwise for the coupling sleeve <NUM>.

What is relevant is that the first relative rotation causes the synchronizer ring <NUM> to rotate in the direction opposite to the direction, in which the synchronizer ring <NUM> was forced by the ring gear <NUM> while the synchronizer ring <NUM> synchronized the speed of the ring gear <NUM>.

The first relative rotation in the first circumferential direction may be achieved by respective angled axial surfaces <NUM>, <NUM> of the protrusions <NUM> of the synchronizer ring <NUM> and the splines <NUM> of the planet gear carrier <NUM>.

In the blocking position, during the synchronization of the ring gear <NUM>, the angled axial surfaces <NUM>, <NUM> of the protrusions <NUM> and the splines <NUM> may abut against each other. As long as the rotational speed difference during synchronization forces the synchronizer ring <NUM> with the protrusion <NUM> against the rotational direction of the coupling sleeve <NUM>, no relative sliding between the protrusions <NUM> and the splines <NUM> along the angled axial surfaces <NUM>, <NUM> may occur. Once the rotational speeds are synchronized, relative sliding between the protrusions <NUM> and the splines <NUM> along the angled axial surfaces <NUM>, <NUM> may occur.

The above discussed first relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM> has been performed in <FIG> by relative sliding along the angled axial surfaces <NUM>, <NUM> of between the protrusions <NUM> and the splines <NUM>, see also <FIG>.

According to embodiments, in the release position of the synchronizer ring <NUM>, the coupling sleeve <NUM> may be moveable in the first direction <NUM> towards the engaged position.

In <FIG>, the synchronizer ring <NUM>, in its release position, has been moved in the first direction <NUM> with the protrusions <NUM> in between the splines <NUM> of the planet gear carrier <NUM>. Accordingly, also the coupling sleeve <NUM> has been moved in the first direction <NUM>. That is, in the release position of the synchronizer ring <NUM>, the coupling sleeve <NUM> is further moveable in the first direction <NUM> by the ring gear <NUM> and/or the synchronizer ring <NUM>.

According to embodiments, upon movement of the coupling sleeve <NUM> in the first direction <NUM> when the synchronizer ring <NUM> is in the release position, the rotational play may permit a second relative rotation between on the one hand the planet gear carrier <NUM> and the coupling sleeve <NUM> and on the other hand the coupling disc <NUM>. In this manner, the second relative rotation may provide for the external and internal splines <NUM>, <NUM> of the second splined connection <NUM>, <NUM> to be rotationally arranged for engagement therebetween in the engaged position of the coupling sleeve <NUM> with the coupling disc <NUM>.

According to embodiments, in the release position, the synchronizer ring <NUM> may be subjectable to a second relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM> in the first circumferential direction. The second relative rotation may be permitted by the rotational play. After the second relative rotation, the external splines <NUM> arranged on the coupling disc <NUM> and the internal splines <NUM> arranged at a radially inner portion of the coupling sleeve <NUM> are arranged circumferentially offset from each other such that the coupling sleeve <NUM> is moveable in the first direction <NUM> to reach the engaged position. In this manner, the external and internal splines <NUM>, <NUM> of the second splined connection <NUM>, <NUM> may be arranged for engagement therebetween in the engaged position of the coupling sleeve <NUM> with the coupling disc <NUM>.

According to embodiments, the external splines <NUM> arranged on the coupling disc <NUM> and the internal splines <NUM> arranged at a radially inner portion of the coupling sleeve <NUM> may comprise angled axial end surfaces <NUM>, <NUM> facing each other, wherein an abutment between the angled axial end surface <NUM>, <NUM> of the external and internal splines <NUM>, <NUM> while the coupling sleeve <NUM> is moved in the first direction <NUM> towards the engaged position may causes the second relative rotation. In this manner, the external and internal splines <NUM>, <NUM> of the second splined connection <NUM>, <NUM> may be arranged for engagement therebetween in the engaged position of the coupling sleeve <NUM> with the coupling disc <NUM>.

In <FIG>, the angled axial surfaces <NUM>, <NUM> of the external and internal splines <NUM>, <NUM> of the second splined connection <NUM>, <NUM> are shown in abutment with each other. The movement of the coupling sleeve <NUM> in the first direction <NUM> and the angle of the angled surfaces <NUM>,<NUM> causes the external and internal splines <NUM>, <NUM> to slide in relation to each other and thus, cause the second relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM>.

More specifically, the movement of the coupling sleeve <NUM> in the first direction <NUM> and the abutment and sliding between the angled surfaces <NUM>,<NUM> causes the coupling disc <NUM> to rotated in relation to the coupling sleeve <NUM>. Thus, the external and internal splines <NUM>, <NUM> will be positioned to reach the engaged position, as shown in <FIG>. Moreover, since the coupling disc <NUM> is rotationally locked to the input shaft <NUM> and the sun gear <NUM>, the rotation of the coupling disc <NUM> in relation to the coupling sleeve <NUM> will adjust the rotational position of the ring gear <NUM> and the synchronizer ring <NUM> in relation to the ring gear carrier <NUM> and the coupling sleeve <NUM> via the at least one planet gear <NUM>.

The thus, adjusted rotational position of the ring gear <NUM> and the synchronizer ring <NUM> in relation to the ring gear carrier <NUM> and the coupling sleeve <NUM> corresponds to the second relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM>.

In <FIG>, the second relative rotation has been completed and the second splined connection <NUM>, <NUM> can be brought into engagement by moving the coupling sleeve <NUM> further in the first direction <NUM>.

The circumferential gaps <NUM> in the external splines <NUM> of the planet gear carrier <NUM> provide space for the protrusions <NUM> of the synchronizer ring <NUM> and thus, permit the second relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM>. Put differently, without providing for the second relative rotation, engagement of the second splined connection <NUM>, <NUM> and the reaching of the engaged position might be difficult or not possible.

<FIG> illustrates a partial axial cross section through the planet gear carrier <NUM>, the coupling sleeve <NUM>, and the synchronizer ring <NUM> along line VII - VII in <FIG>.

In <FIG>, also the axial recesses <NUM> in the coupling sleeve <NUM>, the radially inwardly directed protrusions <NUM> of the synchronizer ring <NUM>, and the circumferential gaps <NUM> in the external splines <NUM> of the planet gear carrier <NUM> are clearly shown.

From <FIG> also the rotational play of the synchronizer ring <NUM> in relation to the coupling sleeve <NUM>, which permits the first and second relative rotations are visible.

As in <FIG>, also in <FIG>, the synchronizer ring <NUM> is in the release position of the synchronizer ring <NUM>. The protrusions <NUM> are axially aligned with the splines <NUM> of the coupling sleeve <NUM>. The release position has been reached by the first relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM> in the first circumferential direction, as discussed above.

The first relative rotation has caused a first gap <NUM> within the axial recess <NUM> of the coupling sleeve <NUM> between a first radial edge <NUM> of the axial recess <NUM> and a first radial edge <NUM> of the protrusions <NUM> of the synchronizer ring <NUM>.

Space for the protrusions <NUM> and the second relative rotation between the synchronizer ring <NUM> and the coupling sleeve <NUM> is provided by the circumferential gaps <NUM> in the splines <NUM> of the planet gear carrier <NUM> and a second gap <NUM> within the axial recess <NUM> between a second radial edge <NUM> of the axial recess <NUM> and a second radial edge <NUM> of the protrusions <NUM>.

<FIG> illustrates embodiments of a method <NUM> of shifting a transmission. The transmission may be a transmission <NUM> as discussed herein. Accordingly, in the following reference is also made to <FIG>.

Accordingly, the transmission <NUM> comprises an input shaft <NUM>, an output shaft <NUM>, and a planetary gearset <NUM> being driven by the input shaft <NUM> and being couplable to the output shaft <NUM> in a high gear mode and a low gear mode of the transmission <NUM>, the input and output shafts <NUM>, <NUM> being arranged rotatably and coaxially along an axis <NUM>. The planetary gearset <NUM> comprises a sun gear <NUM> connected to the input shaft <NUM>, a ring gear <NUM> that is axially movable, and at least one planet gear <NUM> rotatably supported on a planet gear carrier <NUM> that is connected to the output shaft <NUM>. The transmission <NUM> further comprises a coupling disc <NUM> connected to the input shaft <NUM>, an axially moveable coupling sleeve <NUM>, and a synchronizer ring <NUM> arranged between the coupling sleeve <NUM> and the ring gear <NUM>. In order to connect the planet gear carrier <NUM> with the coupling disc <NUM> in an engaged position of the coupling sleeve <NUM> to provide the high gear mode, the method <NUM> comprises steps of:.

The step of moving <NUM> the ring gear <NUM> in an axial motion in the first direction <NUM> may lead to the ring gear <NUM> frictionally engaging with the synchronizer ring <NUM> to synchronize the rotational speed of the ring gear <NUM> with that of the planet gear carrier <NUM> and the coupling sleeve <NUM>.

The step of transferring <NUM> via the synchronizer ring <NUM> the axial motion of the ring gear <NUM> to the coupling sleeve <NUM>, may be performed once the rotational speed of the ring gear <NUM> has been synchronizer with that of the planet gear carrier <NUM> and the coupling sleeve <NUM>.

The at least partial movement of the step of at least partially moving <NUM> is shown in sequence in <FIG> and discussed above and/or in sequence in <FIG> and discussed above.

The full movement of the coupling sleeve <NUM> from the unengaged position into the engaged position is shown in sequence in <FIG> and discussed above.

According to embodiments, the method <NUM> may comprise further steps of:.

For instance, the step of preventing <NUM> the synchronizer ring <NUM> from axial movement in the first direction <NUM> in a blocking position and the step of maintaining <NUM> the blocking position while the rotational speed difference remains, may be performed after the step of moving <NUM> the ring gear <NUM> in an axial motion in the first direction <NUM> and before the step of transferring <NUM> via the synchronizer ring <NUM> the axial motion of the ring gear <NUM> to the coupling sleeve <NUM>.

According to embodiments, after the step of maintaining <NUM> the blocking position, the method <NUM> may comprise a step of:.

In this manner, the rotational speed of the ring gear <NUM> may be synchronized with that of the synchronizer ring <NUM>, the coupling sleeve <NUM>, and the planet gear carrier <NUM>, to thereafter move the synchronizer ring <NUM> into its release position in order to move the coupling sleeve <NUM> towards the engaged position.

The step of rotating <NUM> the synchronizer ring <NUM> a first relative rotation in a first circumferential direction relative to the coupling sleeve <NUM> into a release position is shown in sequence in <FIG>.

According to embodiments, wherein the coupling sleeve <NUM> and the coupling disc <NUM> are engageable in the engaged position via a splined connection <NUM>, <NUM> between the coupling sleeve <NUM> and the coupling disc <NUM>, the splined connection <NUM>, <NUM> between the coupling sleeve <NUM> and the coupling disc <NUM> comprising external splines <NUM> arranged on the coupling disc <NUM> and internal splines <NUM> arranged at a radially inner portion of the coupling sleeve <NUM>, the method <NUM> may comprise further steps of:
from the release position,.

The steps of rotating <NUM> the synchronizer ring <NUM> the second relative rotation and further moving <NUM> the coupling sleeve <NUM> in the first direction <NUM> to reach the engaged position are shown in sequence in <FIG>.

As discussed above with reference to <FIG>, the step of rotating <NUM> the synchronizer ring <NUM> a second relative rotation in the first circumferential direction relative to the coupling sleeve <NUM> may be provided by a rotation of the coupling disc <NUM> in relation to the coupling sleeve <NUM>, which rotation will provide the second relative rotation by adjust the rotational position of the ring gear <NUM> and the synchronizer ring <NUM> in relation to the ring gear carrier <NUM> and the coupling sleeve <NUM> via the at least one planet gear <NUM>.

The step of further moving <NUM> the coupling sleeve <NUM> in the first direction <NUM> to reach the engaged position may form part of, or may be performed subsequently to, the step of at least partially moving <NUM> the coupling sleeve <NUM> with the synchronizer ring <NUM> from an unengaged position towards the engaged position.

External splines discussed herein relate to splines extending radially outwardly from a member, such as the coupling disc or the planet gear carrier. Consequently, internal splines discussed herein relate to splines extending radially inwardly from a member, such as the coupling sleeve.

Claim 1:
A transmission (<NUM>) comprising an input shaft (<NUM>), an output shaft (<NUM>), and a planetary gearset (<NUM>) being driven by the input shaft (<NUM>) and being couplable to the output shaft (<NUM>) in a high gear mode and a low gear mode of the transmission (<NUM>), the input and output shafts (<NUM>, <NUM>) being arranged rotatably and coaxially along an axis (<NUM>), wherein
the planetary gearset (<NUM>) comprises a sun gear (<NUM>) connected to the input shaft (<NUM>), a ring gear (<NUM>) that is axially movable, and at least one planet gear (<NUM>) rotatably supported on a planet gear carrier (<NUM>) that is connected to the output shaft (<NUM>), wherein
the transmission (<NUM>) further comprises a coupling disc (<NUM>) connected to the input shaft (<NUM>), an axially moveable coupling sleeve (<NUM>) being configured to selectively connect the planet gear carrier (<NUM>) with the coupling disc (<NUM>) in an engaged position of the coupling sleeve (<NUM>) to provide the high gear mode, and a synchronizer ring (<NUM>) characterized in that the synchronizer ring is arranged between the coupling sleeve (<NUM>) and the ring gear (<NUM>), wherein
the synchronizer ring (<NUM>) is configured to transfer an axial motion of the ring gear (<NUM>) in a first direction (<NUM>) towards the coupling sleeve (<NUM>) and the coupling disc (<NUM>), and wherein
the coupling sleeve (<NUM>) is moveable from an unengaged position into the engaged position at least in part by the synchronizer ring (<NUM>).