COMPREHENSIVE SPLITTER COMPOUND TRANSMISSION WITH FIXED DRIVE RATIO

Abstract

Transmission (60), comprising: a drive element (24); an output element (32); a first electrical device (36); a second electrical device (38); a first planetary gear set (40) coupled to the first electrical device (36) and including a first sun gear (42), a first ring gear (44), and a plurality of first planet gears mounted on a first planet carrier (46); a second planetary gear set (48) coupled to the second electrical device (38) and including a second sun gear (50), a second ring gear (52), and a plurality of second planet gears mounted on a second planet carrier (54); wherein the output element (32) is connected to both the first planetary gear set (40) and the second planetary gear set (48); wherein the drive element (24) is connected to the first planetary gear set (40); a fixed gear ratio system (56) connecting the input member (24) and the second planetary gear set (48) and operable to transmit rotation from the input member (24) to the second planetary gear set (48) at reduced speed and increased torque; characterized in that the fixed gear ratio system (56) comprises: an intermediate gear (62) connected to the drive element (24); a countershaft (64) having a first fixed gear (66) meshing with the intermediate gear (62); and a second fixed gear (68) connected to the second planetary gear set (48); wherein the first fixed gear (66) and the second fixed gear (68) are fixed to the countershaft (64) and are rotatable with the countershaft (64).

Description

TECHNICAL FIELD

[0001] The disclosure relates generally to an electromechanical transmission for a vehicle, specifically to a transmission according to the preamble of claim 1, as is essentially known from DE 10 2014 118 199 A1. BACKGROUND

[0002] An electromechanical transmission includes a gear set connecting one or more electrical devices and a final drive of the vehicle, such as an axle, wheels, etc. The gear set modifies the speed and torque output from electrical devices and transmits them to the final drive. The transmission can be further configured to receive torque from another power source, such as, but not limited to, an internal combustion engine. The transmission must also modify the speed and torque received from the engine and transmit it to the final vehicle drive system. One or more of the electrical devices can be operated simultaneously with the engine or can operate with the engine off and decoupled from the system to provide traction for the vehicle. SUMMARY

[0003] According to the invention, a transmission is presented which is characterized by the features of claim 1.

[0004] Accordingly, the transmission provides a splitter assembly that directs torque between the first electrical device and the second electrical device and is capable of providing a wide range of output gear ratios through the use of planetary gear sets with appropriate gear sizes, which in turn are suitable for use in a vehicle.

[0005] The foregoing features and advantages, as well as other features and advantages of the present teachings, will be readily apparent from the following detailed description of the best modes for carrying out the teachings when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a lever diagram of a transmission in a vehicle. Fig. 2 is a chain diagram of a first embodiment of the transmission according to the invention, designed for use in a front-wheel drive vehicle. Fig. 3 is a chain diagram of the first embodiment of the transmission designed for use in a rear-wheel drive vehicle. Fig. 4 is a chain diagram of a second embodiment of the transmission not according to the invention, designed for use in a front-wheel drive vehicle. Fig. 5 is a chain diagram of the second embodiment of the transmission designed for use in a rear-wheel drive vehicle. Fig. Figure 6 is a chain diagram of the second embodiment of the transmission designed for use in a heavy-duty rear-wheel drive vehicle and operable to provide a reverse mode. Fig. 7 is a chain diagram of the third embodiment of the transmission not according to the invention, designed for use in a heavy-duty rear-wheel drive vehicle and operable to provide a reverse mode. DETAILED DESCRIPTION

[0006] In the figures, where the components are numbered in multiple views, 20 generally represents the transmission. The transmission 20 is for a vehicle. The vehicle may include, but is not limited to, a car, a truck, a tractor, or other form of vehicle. The transmission 20 is part of, or is a powertrain. The powertrain may include a hybrid powertrain including a motor 22 (e.g., an internal combustion engine 22) and a pair of electrical devices.

[0007] With reference to Fig. 1, the transmission 20 is generally shown as a lever diagram. The description of the transmission 20 below, with reference to Fig. 1, is applicable to the different embodiments of the transmission 20, which is shown in the Fig. 2 to 6. Fig. 2 to 6 show bar diagrams of various embodiments and specific applications of each embodiment of the transmission 20, which is generally shown in the lever diagram Fig. 1 is shown.

[0008] With reference to Fig. 1, the transmission 20 includes an input member 24. The input member 24 may be connected to the engine 22 if the driveline is equipped with an engine 22. As noted above, the engine 22 may include, but is not limited to, an internal combustion engine 22, such as a gasoline engine or a diesel engine 22. The engine 22 is selectively operable to generate torque, which is applied to the input member 24. Accordingly, the input member 24 receives torque from the engine 22. The specific nature and configuration of the engine 22 and the operation of the engine 22 are not relevant to the teachings of this disclosure and, therefore, are not described in detail herein.

[0009] The transmission 20 may be equipped with a drive brake 26. The drive brake 26 is selectively actuable to ground the drive member 24. The drive brake 26 may, for example, include a selectively actuable drive clutch 28 for engaging the drive member 24 with a stationary member 30 to prevent or resist rotation of the drive member 24. The stationary member 30 may, for example, include a housing of the transmission 20 or another fixed structure of the transmission 20. Thus, when the drive clutch 28 is engaged, the drive brake 26 prevents or limits rotation of the drive member 24 relative to the stationary member 30. When the drive clutch 28 is released, the drive brake 26 permits rotation of the drive member 24 relative to the stationary member 30.The drive brake 26 can be engaged and / or released to switch between hybrid operation, in which the engine 22 and one or more of the electrical devices are used to propel the vehicle, and a fully electric mode when only the electrical devices are used to propel the vehicle.

[0010] The transmission 20 further includes an output member 32. The output member 32 is connected to a final drive system 34 of the driveline. The final drive system 34 may include, but is not limited to, a driveshaft, a differential, a gear ratio system, an axle, one or more wheels, etc. The output member 32 transmits or outputs torque from the transmission 20 to the final drive system 34. The specific nature and configuration of the final drive system 34 and the operation of the final drive system 34 are not relevant to the teachings of this disclosure and are therefore not described in detail herein.

[0011] The transmission 20 further includes a first electrical device 36 and a second electrical device 38. Each first electrical device 36 and second electrical device 38 may include, but is not limited to, an electric motor or an electric motor / generator. It should be noted that the first electrical device 36 and the second electrical device 38 may include another device in addition to the electric motor or electric motor / generator as described herein. It should further be noted that each of the first electrical device 36 and the second electrical device 38 may include an electric motor or an electric motor / generator, respectively, as described herein.Alternatively, it should be noted that one of the first electrical device 36 and the second electrical device 38 may include an electric motor or other device, and the first electrical device 36 and the second electrical device 38 may include an electric motor / generator or other device.

[0012] The transmission 20 includes a first planetary gear set 40 connected to the first electrical device 36. The first planetary gear set 40 includes a first sun gear 42, a first ring gear 44, and a plurality of first planet gears fixed to a first planet carrier 46. As is known in the art, the first sun gear 42 is concentric with a central axis. The first planet gears are arranged in an intermeshing pattern with the first sun gear 42 and are each supported or carried by the first planet carrier 46. The first ring gear 44 surrounds the first planet gears and is arranged in an intermeshing pattern with the first planet gears.

[0013] The first electrical device 36 is connected to one of the first sun gears 42, the first ring gear 44, and the first planet carrier 46. As used in this detailed description, the term "connected" is defined as being coupled in a manner that provides a direct, one-to-one rotary connection without increasing or decreasing speed and / or torque therebetween. As used herein, the term "connected" includes a first device directly connected to a second device with no intermediate components therebetween, and also includes a first device directly connected to a second device with one or more components between the first device and the second device. However, the first device is connected to the second device, and therefore, speed and torque are not changed between the first device and the second device.As shown in the figures and as described herein, the first electrical device 36 is connected to the first sun gear 42. However, it should be understood that the first electrical device 36 may be selectively connected to either the first ring gear 44 or the first planetary carrier 46.

[0014] The transmission 20 includes a second planetary gear set 48 connected to the second electrical device 38. The second planetary gear set 48 includes a second sun gear 50, a second ring gear 52, and a plurality of second planet gears fixed to a second planet carrier 54. As is known in the art, the second sun gear 50 is concentric with a central axis. The second planet gears are arranged in an intermeshing pattern with the second sun gear 50 and are each supported or carried by the second planet carrier 54. The second ring gear 52 surrounds the second planet gears and is arranged in an intermeshing pattern with the second planet gears.

[0015] The second electrical device 38 is connected to one of the second sun gears 50, the second ring gear 52, and the second planet carrier 54. As shown in the figures and as described herein, the second electrical device 38 is connected to the second sun gear 50. However, it should be understood that the second electrical device 38 can be selectively connected to either the second ring gear 52 or the second planet carrier 54.

[0016] The output is connected to both the first planetary gear set 40 and the second planetary gear set 48. The output is connected to one of the first sun gears 42, the first ring gear 44, and the first planet carrier 46. As shown in the figures and as described herein, the output is connected to the first ring gear 44. However, it should be understood that the output can be selectively connected to either the first sun gear 42 or the first planet carrier 46. The output is also connected to one of the second sun gears 50, the second ring gear 52, and the second planet carrier 54. As shown in the figures and as described herein, the output is connected to the second planet carrier 54. However, it should be understood that the output can be selectively connected to either the second sun gear 50 or the second ring gear 52.

[0017] The input is connected to the first planetary gear set 40. As shown in the figures and as described herein, the input is connected to the first sun gear 42, the first ring gear 44, and the first planet carrier 46. More specifically, the input is connected to the first planet carrier 46. However, it should be understood that the input can be selectively connected to the first sun gear 42 or the first ring gear 44.

[0018] Accordingly, with respect to the first planetary gear set 40, the input is connected to the first sun gear 42, the first ring gear 44, and the first planet carrier 46. The output is connected to another one of the first sun gear 42, the first ring gear 44, and the first planet carrier 46, and the first electrical device 36 is connected to another one of the first sun gear 42, the first ring gear 44, and the first planet carrier 46. It should be noted that the first sun gear 42, the first planet carrier 46, and the first ring gear 44 each define a respective node of the first planetary gear set 40, and that the input, the output, and the first electrical device 36 are each connected to a respective node of the first planetary gear set 40. Accordingly, only one of the input, the output, and the first electrical device 36 can be connected to a node of the first planetary gear set 40.If the first electrical device 36 as such is connected to the first sun gear 42, then the input and output cannot be connected to the first sun gear 42 either. Likewise, if the input is connected to the first planetary carrier 46, then the output and the first electronic device 36 cannot be connected to the first planetary carrier 46 either. Furthermore, if the output is connected to the first ring gear 44, then the first electrical device 36 and the input cannot be connected to the first ring gear 44 either. As shown in the figures and as described herein, the first electrical device 36 is connected to the first sun gear 42, the input is connected to the first planetary carrier 46, and the output is connected to the first ring gear 44.

[0019] A fixed gear ratio system 56 connects the input and the second planetary gear set 48. The fixed gear ratio system 56 is operable to transmit rotation from the input of the second planetary gear set 48 at reduced speed and with increased torque. Preferably, the fixed gear ratio system 56 provides a gear ratio between 3:1 and 6:1. More preferably, the gear ratio of the fixed gear ratio system 56 is between 4:1 and 5:1. As shown in the figures and as described herein, the fixed gear ratio system 56 is connected to the second ring gear 52.

[0020] With respect to the second planetary gear set 48, the fixed gear ratio system 56 is connected to the second sun gear 50, the second ring gear 52, and the second planet carrier 54. The output is connected to another one of the second sun gear 50, the second ring gear 52, and the second planet carrier 54, and the second electrical device 38 is connected to another one of the second sun gear 50, the second ring gear 52, and the second planet carrier 54. It should be noted that the second sun gear 50, the second planet carrier 54, and the second ring gear 52 each define a respective node of the second planetary gear set 48, and that the fixed gear ratio system 56, the output, and the second electrical device 38 are each connected to a respective node of the second planetary gear set 48.Accordingly, only one of the fixed gear ratio system 56, the output, or the second electrical device 38 can be connected to a single node of the second planetary gear set 48. As such, if the second electrical device 38 is connected to the second sun gear 50, then the fixed gear ratio system 56 and the output also cannot be connected to the second sun gear 50. Likewise, if the fixed gear ratio system 56 is connected to the second ring gear 52, the output and the second electrical device 38 also cannot be connected to the second ring gear 52. Furthermore, if the output is connected to the second planet carrier 54, then the second electrical device 38 and the fixed gear ratio system 56 also cannot be connected to the second planet carrier 54.As shown in the figures and as described herein, the second electrical device 38 is connected to the second sun gear 50. The fixed gear ratio system 56 may be connected to the second ring gear 52 or, alternatively, to the second planetary carrier 54. The output may be connected to the second planetary carrier 54 or, alternatively, to the second ring gear 52.

[0021] With reference to the Fig. 2 and Fig. 3, a first embodiment of the transmission 60 is generally illustrated at 60. The first embodiment of the transmission 60 includes the fixed gear ratio system 56 as an offset of the countershaft 64 with fixed gears. Fig. Figure 2 shows the first embodiment of the transmission 60, which is designed for use in a front-wheel drive vehicle, while Fig. 3 shows the first embodiment of the transmission 60, which is designed for use in a rear-wheel drive vehicle. During the description of the first embodiment of the transmission 60, the reference numbers of the various components will be explained with reference to Fig. 1, as described above, also used to represent the corresponding components in the first embodiment of the transmission 60, as shown in the Fig. 2 and Fig. 3. Unless otherwise stated, the description of the transmission 20 is with reference to Fig. 1, as mentioned above, including the description of the connections between the various components, applicable to the first embodiment of the transmission 60, as shown in the Fig. 2 and Fig. 3 shown.

[0022] With reference to the Fig. 2 and Fig. 3, the fixed gear ratio system 56 includes an intermediate gear 62 connected to the drive. Fig. 2 shows the intermediate gear 62 which is directly connected to the drive, while Fig. 3 shows the intermediate gear 62 indirectly connected to the input via the first planetary carrier 46. The fixed gear ratio system 56 further includes a countershaft 64 having a first fixed gear 66 and a second fixed gear 68. The first fixed gear 66 is arranged in an intermeshing pattern with the intermediate gear 62. The second fixed gear 68 is connected to the second planetary gear set 48. More specifically, the second fixed gear 68 is arranged in an intermeshing pattern with the second ring gear 52. The first fixed gear 66 and the second fixed gear 68 are both fixed to the countershaft 64 and are rotatable with the countershaft 64. Referring to Fig. 2, the first gear ring 44 is connected to the second planet carrier 54, which in turn is connected to the output. With reference to Fig. 3, the first gear ring 44 and the second planet carrier 54 are connected to each other and also to the output.

[0023] With reference to the Fig. 4 and Fig. 6, a second embodiment of the transmission 70 is generally illustrated at 70, but is not claimed. The second embodiment of the transmission 70 includes the fixed gear ratio system 56 as a third planetary gear set 72. Fig. Figure 4 shows the second embodiment of the transmission 70, which is designed for use in a front-wheel drive vehicle, while Fig. Figure 5 shows the second embodiment of the transmission 70 designed for use in a rear-wheel drive vehicle and Fig. Figure 6 shows the second embodiment of the transmission 70, which is designed for use in a heavy-duty rear-wheel drive vehicle. During the description of the second embodiment of the transmission 70, the reference numbers of the various components will be referred to with reference to Fig. 1, as described above, is also used to identify the corresponding components in the second embodiment of the transmission 70, as shown in the Fig. 4 to 6. Unless otherwise stated, the description of the transmission 20 is with reference to Fig. 1, as mentioned above, including the description of the connections between the various components, applicable to the second embodiment of the transmission 70, as shown in the Fig. 4 to 6.

[0024] With reference to the Fig. 4 and Fig. 5, the fixed gear ratio system 56 includes the third planetary gear set 72. The third planetary gear set 72 includes a third sun gear 74, a third ring gear 76, and a plurality of third planet gears fixed to a third planet carrier 78. As is known in the art, the third sun gear 74 is concentric with a central axis. The third planet gears are arranged in an intermeshing pattern with the third sun gear 74 and are each supported or carried by the third planet carrier 78. The third ring gear 76 surrounds the third planet gears and is arranged in an intermeshing pattern with the third planet gears.

[0025] The third ring gear 76 is grounded to a stationary member 30. The stationary member 30 may include, but is not limited to, a housing of the transmission 20 or another feature that prevents relative rotation of the third ring gear 76. The input is connected to the third sun gear 74. The third planet carrier 78 is connected to the second planetary gear set 48. Referring to Fig. 4, the third planet carrier 78 is connected to the second planet carrier 52 and the second planet carrier 54 is connected to the output. With reference to Fig. 5, the third planet carrier 78 is preferably shown connected to the second planet carrier 52 by a solid line, and the second planet carrier 54 is connected to the output by a solid line. As shown in Fig. 5, an alternative division shows the third planetary gear carrier 78, which is connected by a dashed line to the second planetary carrier 54, and the second gear ring 52, which is connected by a dashed line to the output.

[0026] With reference to Fig. 6 generally illustrates a specific application of the second embodiment of the transmission 70. As with the applications in the Fig. 4 and Fig. 5, the application of the second embodiment of the transmission 70 in Fig. 6 the fixed gear ratio system 56, which is represented as the third planetary gear set 72. However, the application in Fig. 6 a compound planetary gear set. The compound planetary gear set provides a fourth node, thereby enabling a reverse gear for the transmission 70. The compound planetary gear set in Fig. 6 includes two ring gears, i.e., a fourth ring gear 80 and a fifth ring gear 82, respectively, two planet carriers, i.e., a fourth planet carrier 84 carrying a plurality of the fourth planet gears, and a fifth planet carrier 86 carrying a plurality of the fifth planet gears, respectively, and a fourth sun gear 88. The fourth planet gears and the fifth planet gears are both arranged in an intermeshing pattern with the sun gear 88. The fourth ring gear 80 is arranged in an intermeshing pattern with the fourth planet gears. The fifth ring gear 82 is arranged in an intermeshing pattern with the fifth planet gears.

[0027] A first transmission ratio brake 90 selectively connects the fourth planetary carrier 84 to a stationary member 30, such as, but not limited to, the housing of the transmission 70. The first transmission ratio brake 90 is selectively engaged and released with a first transmission ratio clutch 94 to respectively prevent and permit rotation of the fourth planetary carrier 84 relative to the stationary member 30. Accordingly, when the first transmission ratio clutch 94 is engaged, the first transmission ratio brake 90 prevents or limits rotation of the fourth planetary carrier 84 relative to the stationary member 30, and when the first transmission ratio clutch 94 is released, the first transmission ratio brake 90 permits rotation of the fourth planetary carrier 84 relative to the stationary member 30.

[0028] A second gear ratio brake 92 couples the fifth ring gear 82 to a stationary member 30, such as, but not limited to, the housing of the transmission 70. The second gear ratio brake 92 can be selectively engaged and released with a second ratio clutch 96 to respectively prevent or permit rotation of the fifth ring gear 82 relative to the stationary member 30. Accordingly, when the second gear ratio clutch 96 is engaged, the second gear ratio brake 92 prevents or limits rotation of the fifth ring gear 82 relative to the stationary member 30, and when the second ratio clutch 96 is released, the second gear ratio brake 92 permits rotation of the fifth planetary carrier 82 relative to the stationary member 30.

[0029] The fourth ring gear 80 is connected to the fifth planetary carrier 86. The fifth planetary carrier 86 is connected to the second ring gear 52. The first gear ratio brake 90 and the second gear ratio brake 92 can each be independently engaged and / or released to provide the reverse gear for the transmission 70. For example, the transmission 70 can be operated in a forward gear when the first gear ratio brake 90 is released to allow rotation of the fourth planetary carrier 84 relative to the stationary member 30 and the second gear ratio brake 92 is engaged to prevent rotation of the fifth ring gear 82 relative to the stationary member 30.Alternatively, the transmission 70 may be operated in a reverse gear when the first transmission ratio brake 90 is engaged to prevent rotation of the fourth planetary carrier 84 relative to the stationary member 30 and the second transmission ratio brake 92 is released to allow rotation of the fifth ring gear 82 relative to the stationary member 30.

[0030] The first gear ratio brake 90 and the second gear ratio brake 92 can each be applied simultaneously to ground the drive member 24 or resist rotation of the drive member 24. As such, the first gear ratio brake 90 and the second gear ratio brake 92 can be applied simultaneously to transition between hybrid operation, in which the engine 22 and one or more of the electrical devices are used to propel the vehicle, and a fully electric mode when only the electrical devices are used to propel the vehicle.

[0031] With reference to Fig. 7 generally shows a second embodiment of the transmission 100, which is also not claimed. Similar to the second embodiment of the transmission in Fig. 6 includes the third embodiment of the transmission 100, as shown in Fig. 7, the fixed gear ratio system 56, which is represented as the third planetary gear set 72. However, the application in Fig. 7 a stacked planetary gear set. The stacked planetary gear set provides a fourth node, enabling a reverse gear for the transmission 100. The stacked planetary gear set in Fig.7 includes a sixth sun gear 102, a sixth planet carrier 104 supporting a plurality of sixth planet gears, a sun gear / ring gear combination 106, a seventh planet carrier 108 supporting a plurality of seventh planet gears, and a seventh ring gear 110. The sixth sun gear 102 and the sixth planet gears of the sixth planet carrier 104 are arranged in an intermeshing pattern. The sixth planet gears of the sixth planet carrier 104 and the sun gear / ring gear combination 106 are arranged in an intermeshing pattern. The sun gear / ring gear combination 106 and the seventh planet gears of the seventh planet carrier 108 are arranged in an intermeshing pattern. The seventh planet gears of the seventh planet carrier 108 and the seventh ring gear 110 are arranged in an intermeshing pattern.

[0032] The first transmission ratio brake 90 selectively connects the sun gear and ring gear combination 106 to the stationary member 30, such as, but not limited to, the housing of the transmission 100. The first transmission ratio brake 90 is selectively engaged and disengaged with the first transmission ratio clutch 94 to respectively prevent and permit rotation of the sun gear and ring gear combination 106 relative to the stationary member 30. Accordingly, when the first transmission ratio clutch 94 is engaged, the first transmission ratio brake 90 prevents or limits rotation of the sun gear and ring gear combination 106 relative to the stationary member 30, and when the first transmission ratio clutch 94 is disengaged, the first transmission ratio brake 90 permits rotation of the sun gear and ring gear combination 106 relative to the stationary member 30.

[0033] The second transmission ratio brake 92 couples the seventh ring gear 110 to a stationary member 30, such as, but not limited to, the housing of the transmission 100. The second transmission ratio brake 92 can be selectively engaged and released with the second transmission clutch 96 to respectively prevent or permit rotation of the seventh ring gear 110 relative to the stationary member 30. Accordingly, when the second transmission ratio clutch 96 is engaged, the second transmission ratio brake 92 prevents or limits rotation of the seventh ring gear 110 relative to the stationary member 30, and when the second transmission clutch 96 is released, the second transmission ratio brake 92 permits rotation of the seventh ring gear 110 relative to the stationary member 30.

[0034] The first ring gear 44 is connected to the sixth sun gear 102. The sixth planetary carrier 104 and the seventh planetary carrier 108 are simultaneously connected to the second ring gear 52. The first gear ratio brake 90 and the second gear ratio brake 92 can each be independently engaged and / or released to provide the reverse gear for the transmission 100. For example, the transmission 100 can be operated in a reverse gear when the first gear ratio brake 90 is released to allow rotation of the sun gear-ring gear combination 106 relative to the stationary member 30 and the second gear ratio brake 92 is engaged to prevent rotation of the seventh ring gear 110 relative to the stationary member 30.The transmission 100 may alternatively be operated in a forward gear when the first gear ratio brake 90 is engaged to prevent rotation of the sun gear-ring gear combination 106 relative to the stationary member 30 and the second gear ratio brake 92 is released to allow rotation of the seventh ring gear 110 relative to the stationary member 30.

[0035] The first gear ratio brake 90 and the second gear ratio brake 92 can each be applied simultaneously to ground the drive member 24 or resist rotation of the drive member 24. As such, the first gear ratio brake 90 and the second gear ratio brake 92 can be applied simultaneously to transition between hybrid operation, in which the engine 22 and one or more of the electrical devices are used to propel the vehicle, and a fully electric mode when only the electrical devices are used to propel the vehicle.

Claims

[1] Transmission (60), comprising: a drive element (24); an output element (32); a first electrical device (36); a second electrical device (38); a first planetary gear set (40) coupled to the first electrical device (36) and including a first sun gear (42), a first ring gear (44), and a plurality of first planet gears mounted on a first planet carrier (46); a second planetary gear set (48) coupled to the second electrical device (38) and including a second sun gear (50), a second ring gear (52), and a plurality of second planet gears mounted on a second planet carrier (54); wherein the output element (32) is connected to both the first planetary gear set (40) and the second planetary gear set (48); wherein the drive element (24) is connected to the first planetary gear set (40); a fixed gear ratio system (56) connecting the input member (24) and the second planetary gear set (48) and operable to transmit rotation from the input member (24) to the second planetary gear set (48) at reduced speed and increased torque; characterized by , that the fixed gear ratio system (56) comprises: an intermediate gear (62) connected to the drive element (24); a countershaft (64) having a first fixed gear (66) meshing with the intermediate gear (62); and a second fixed gear (68) connected to the second planetary gear set (48); wherein the first fixed gear (66) and the second fixed gear (68) are fixed to the countershaft (64) and are rotatable with the countershaft (64). [2] The transmission (60) of claim 1, wherein the first electrical device (36) is connected to the first sun gear (42). [3] Transmission (60) according to claim 2, wherein the output element (32) is connected to the first gear ring (44). [4] Transmission (60) according to claim 3, wherein the drive element (24) is connected to the first planet carrier (46). [5] The transmission (60) of claim 1, wherein the second electrical device (38) is connected to the second sun gear (50). [6] Transmission (60) according to claim 5, wherein the output element (32) is connected to the second planet carrier (54).

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