218 may be rotationally coupled to the synchronizer shaft 240 via the first clutch 230 by way of the first clutch gear 222 and the gear 252 that are meshed. Similarly, when the second clutch 240 is engaged, the input shaft 218 may be rotationally coupled to the synchronizer shaft 240 via the second clutch 240 by way of the second clutch gear 234 and the gear 276 that are meshed.

As noted, the gear 252 and the gear 276 may both rotationally couple to synchronizer shaft 246. The synchronizer 270 may couple to the synchronizer shaft 246 as well. The synchronizer 270 may comprise a selector 242, a first synchronizer gear 272, and a second synchronizer gear 274. The selector 242 may be a selector fork, in some examples, and may enable movement of the synchronizer 270 to engage or disengage one or more gears of the idler shaft 232, such as gear 248 or gear 250, depending on a selected gear ratio. For example, the first synchronizer gear 272 may selectively engage gear 248 and the second synchronizer gear 274 may selectively engage gear 250. The first synchronizer gear 272 and gear 248 may together form the third gear train 260 and the second synchronizer gear 274 and gear 250 may together form the fourth gear train 262. Synchronizer movement may be based on input from various sensors of the control system of FIG. 1, and may include but are not limited to transmission range, vehicle speed, throttle pedal position, ambient temperature, steering angle, brake inputs, electric motor speed and torque (for both the first and second electric motors 202, 204), and transmission input shaft speed.

Gears 248 and 250 may both be positioned on (e.g., rotationally coupled to) the idler shaft 232 such that selective engagement of one of them from the synchronizer 270 transfers rotational power to the idler shaft 232 in different gear ratios. The second gear train 220 may be configured such that rotational power has to pass through the synchronizer 270 in either a first position or a second position in order to transfer power to the idler shaft 232 when the first clutch 230 is engaged. The first position of the synchronizer 270 may be with the first synchronizer gear 272 engaged with the gear 248, thereby defining a first gear ratio of the available three gear ratios. The second position of the synchronizer 270 may be with the second synchronizer gear 274 engaged with the gear 250, thereby defining a third gear ratio of the available three gear ratios. The fifth gear train 236 may be configured such that rotational power may bypass the synchronizer 270 via gears 276 and 244 to be transferred to the idler shaft 232 when the second clutch 240 is engaged, thus defining a second gear ratio of the available three gear ratios.

Thus, as herein described, the synchronizer shaft 246 may be rotationally coupled to the idler shaft 232 via the synchronizer 270, in one of its two positions, or the second clutch 240. For example, when the second clutch 240 is engaged, the fifth gear train 236 may couple the input shaft 218 to the synchronizer shaft 246 via the second clutch gear 234 and the gear 276 and may couple the synchronizer shaft 246 to the idler shaft 232 via the gear 276 and the gear 244. When the first clutch 230 is engaged and the synchronizer 270 is in the first position, the synchronizer shaft 246 may be coupled to the idler shaft 232 via the third gear train 260 (e.g., via the first synchronizer gear 272 and the gear 248). When the first clutch 230 is engaged and the synchronizer 270 is in the second position, the synchronizer shaft 246 may be rotationally coupled to the idler shaft 232 via the fourth gear train 262 (e.g., the second synchronizer gear 274 and the gear 250).

The synchronizer 270, in some examples, may only be in either the first or the second position. Thus, when the second clutch 240 is engaged, rotational power may bypass the synchronizer 270 even when in one of the first and second positions. In other examples, the synchronizer 270 may have a neutral position as well in which neither the gear 248 nor the gear 250 are engaged by a synchronizer gear. In this way, the transmission system 200 may have three available gear ratios with two clutches and the synchronizer.

Turning briefly to FIG. 6, available gear ratios and clutch engagements thereof are shown. FIG. 6 shows a table 600 of clutch engagements for gear ratios for both configurations of the transmission 200 herein described. In the first gear ratio, the first clutch (e.g., first clutch 230) is engaged and the synchronizer (e.g., synchronizer 270) is in the first position while the second clutch (e.g., second clutch 240) is disengaged. In the second gear ratio, the first clutch is disengaged, the second clutch is engaged, and the synchronizer is bypassed. As described above, in the second gear ratio the synchronizer may be in any available position (e.g., first position, second position, or a neutral position) as rotational power may bypass the synchronizer when the second clutch is engaged and the first clutch is disengaged. In the third gear ratio, the first clutch is engaged and the synchronizer is in the second position while the second clutch is disengaged.

Returning to FIG. 2, the idler shaft 232 may further rotationally couple to the sixth gear train 256 via gear 254. The sixth gear train 256 may comprise gear 254 and output gear 264. Gear 254 may mesh with output gear 264, which may rotationally couple to output shaft 266. The output shaft 266 may couple to one or more output interface 268. The one or more output interfaces may be designed to attach to axles (not shown) via shafts, couplings, combinations thereof, and/or the like. Such axles may include components such as differentials, axle shafts, and drive wheels (e.g., front vehicle wheels 156 and rear vehicle wheels 157 of FIG. 1). The output shaft 266 may thus be configured to transfer rotational torque to the axles. The output interfaces 268 may be flanges, yokes, splines, joints, combinations thereof, or the like.

As noted, output gear 264 may mesh with gear 254 in one of two positions. In FIG. 2, output gear 264 meshes with gear 254 in the first position. The first position may be with the output shaft 266 vertically below an axis of the input shaft 218 by a first distance 278. The first position may thus define the short drop configuration for the output shaft 266. The short drop configuration may be utilized in applications that demand a relatively short distance between the transmission and the axles, for example in applications in which the transmission is positioned in a vertical position close to an axis of the axles.

The first, second, and third clutches as herein described may be wet friction clutches, in some examples. In other examples, the clutches may be dog clutches, dry friction clutches, or other type of clutch. Wet friction clutches may allow for a smoother transition between engagement and disengagement, as compared to dog clutches. Further, lubrication of we friction clutches may decrease degradation to the clutches over time, thereby increasing the longevity of the transmission system 200.

Turning now to FIG. 3, the transmission system 200 is again shown. Components of the transmission system 200 are unchanged compared to FIG. 2 and thus are given similar component numbering. The transmission system 200 as depicted in FIG. 3 includes the output shaft 266 in the second position, as previously noted.

In the second position, the output gear 264 may mesh with gear 254 such that the output gear 264 is vertically below the gear 254. As such, the output shaft 266 may be positioned vertically below the axis of the input shaft 218 by a second distance 370. The second distance 370 may be longer than the first distance 278 such that in the second position the axis of the output shaft 266 is further from the axis of the input shaft 218 than in the first position. In this way, the second position of the output gear 264 may be a long drop configuration of the transmission system 200. The long drop configuration may allow for the transmission system to be utilized for applications that demand a long drop between a main section of the transmission (e.g., about the axis of the input shaft) and the output. For example, loaders may demand a long drop due to the transmission being assembled/positioned higher with respect to the axles.

Inclusion of the synchronizer in the transmission system 200 herein disclosed may reduce a number of clutches, e.g., wet friction clutches, in the transmission system. Therefore, efficiency of the transmission system may be increased.

Turning now to FIGS. 4A-4C, power paths through the transmission system 200 are shown. Power paths are provided for both potential configurations of the transmission system 200, for example with the output arranged in either the short or long drop configurations described above. FIG. 4A specifically shows a power path through the transmission system 200 when in the first gear ratio, FIG. 4B specifically shows a power path through the transmission system 200 when in the second gear ratio, and FIG. 4C specifically shows a power path through the transmission system 200 when in the third gear ratio.

In the power path of the first gear ratio as depicted in FIG. 4A, power of the first and second electric motors 202, 204 is transferred into the input shaft 218 via the first and second rotor shafts 206, 208 and the first gear train 210. Specifically, power of the first electric motor 202 may be transferred from the first rotor shaft 206 into gear 212, from gear 212 to gear 214 and from gear 214 to input shaft 218. Power of the second electric motor 204 may be transferred from the second rotor shaft 208 into gear 216, from gear 216 into gear 214, and from gear 214 to input shaft 218. Power is then transferred from the input shaft 218 into the first clutch 230 via gear 258 when the first clutch 230 is engaged. From the first clutch 230, power is transferred into the first clutch gear 222 and then into the synchronizer shaft 246 via the gear 252. With the synchronizer 270 in the first position, power is transferred from the synchronizer shaft 246 to the first synchronizer gear 272 and then into the idler shaft 232 via the gear 248. From the idler shaft 232, power is transferred into gear 254 and then into the output gear 264. From the output gear 264, power is transferred to output shaft 266, to output interfaces 268, and finally to downstream components thereafter.

In the power path of the second gear ratio as depicted in FIG. 4B, power of the first and second electric motors 202, 204 is transferred into the input shaft 218 via the first and second rotor shafts 206, 208 and the first gear train 210. Specifically, power of the first electric motor 202 may be transferred from the first rotor shaft 206 into gear 212, from gear 212 to gear 214 and from gear 214 to input shaft 218. Power of the second electric motor 204 may be transferred from the second rotor shaft 208 into gear 216, from gear 216 into gear 214, and from gear 214 to input shaft 218. Power is then transferred from the input shaft 218 into the second clutch 240 via gear 258 when the second clutch 240 is engaged. When the second clutch 240 is engaged, power is transferred into the second clutch gear 234, from the second clutch gear 234 to the gear 246, and from the gear 246 to the gear 244, bypassing the synchronizer 270. From the gear 244, power is transferred into the idler shaft 232. From the idler shaft 232, power is transferred into gear 254 and then into the output gear 264. From the output gear 264, power is transferred to output shaft 266, to output interfaces 268, and finally to downstream components thereafter.

In the power path of the third gear ratio as depicted in FIG. 4C, power of the first and second electric motors 202, 204 is transferred into the input shaft 218 via the first and second rotor shafts 206, 208 and the first gear train 210. Specifically, power of the first electric motor 202 may be transferred from the first rotor shaft 206 into gear 212, from gear 212 to gear 214 and from gear 214 to input shaft 218. Power of the second electric motor 204 may be transferred from the second rotor shaft 208 into gear 216, from gear 216 into gear 214, and from gear 214 to input shaft 218. Power is then transferred from the input shaft 218 into the first clutch 230 via gear 258 when the first clutch 230 is engaged. From the first clutch 230, power is transferred into the first clutch gear 222 and then into the synchronizer shaft 246 via the gear 252. With the synchronizer 270 in the second position, power is transferred from the synchronizer shaft 246 to the second synchronizer gear 274 and then into the idler shaft 232 via the gear 250. From the idler shaft 232, power is transferred into gear 254 and then into the output gear 264. From the output gear 264, power is transferred to output shaft 266, to output interfaces 268, and finally to downstream components thereafter.

Referring now to FIG. 5, a flowchart illustrating a method 500 for operation of a transmission system is shown. For example, the transmission system 200 described with respect to FIGS. 2-4C may be operated according to the method 500 as herein presented. However, the method 500 may be carried out via other suitable transmissions, in other examples. Furthermore, the method 500 may be implemented by a controller than includes a processor and memory, according to instructions stored in the memory that are executable by the processor. For example, the method