DESC:FIELD OF THE INVENTION
The present invention relates to a power drive system for an electric vehicle, and more specifically, to a power drive system for an electric vehicle, in which at least one planetary gear set, a motor, and a differential device are arranged on the same shaft in one housing to be concentrated, thereby reducing the volume, reducing an installation space, reducing the number of components, reducing the weight thereof, reducing noise and vibration since power generation and a reduction action are performed on one axis, and improving according to a fuel ratio.
BACKGROUND OF THE INVENTION
FIG. 1 is a schematic diagram illustrating a power transmission path having three axes in a conventional drive unit for an electric vehicle.
Referring to FIG. 1, a conventional drive unit for an electric vehicle includes a housing 10 surrounding a motor, a reducer 40 disposed on a shaft separately from the housing 10, and a differential device 90 to which driving force of the reducer 40 is transmitted.
The housing 10 includes a stator 30 and a rotor 20 forming a motor therein, and the first shaft S1 is connected to interlock with the rotor 20.
The stator 30 is fixed on the inner circumferential surface of the housing 10 in a state in which a coil is wound, and the rotor is rotated by a magnetic field generated when electric current is applied to the stator, and a rotational driving force of the rotor 20 is transmitted to the first shaft (driving shaft) S1.
Accordingly, the first shaft S1 is interlocked with the rotation of the rotor 20, and the driving force of the first shaft S1 is transmitted to the reducer 40 having a second shaft S2 not on the same horizontal line but at a different position.
The reducer 40 reduces the rotational driving force transmitted from the first shaft S1 and supplies to the differential device 90 in an arrow direction indicated in the drawing, and the differential device 90 transmits the rotational force to both wheels through a third shaft S3 (driven shaft) divided into left and right sides.
That is, the conventional art illustrated in FIG. 1 has a structure in which the driving power of the electric vehicle is transmitted to the wheels through the three shafts S1, S2 and S3 having different phase differences.
FIG. 2 is a cross-sectional view schematically illustrating a power transmission path of a drive unit for an electric vehicle in which a power transmission path is formed in two axes.
Referring to FIG. 2, a motor including a rotor 20 and a stator 30 is disposed in a housing 10, one end of a first shaft S1 is connected to interlock with the rotor 20, the other end of the first shaft S1 is connected to interlock with the differential device 90 on the same shaft, and the differential device 90 is connected to the reducer 40 having the second shaft S2 with another phase difference.
In this regard, Korean Patent No. 0195022 discloses “driving device for electric vehicle” (registration date: 02.10.1999).
The above-mentioned conventional arts have a structure that the reducer is separately disposed on the outer surface of the housing, and thus, have a spatial constraint in installation of the reducer and increase overall volume and weight.
Figure 12 illustrates a two-axis drive system according to a conventional art.
In comparison with the above-described conventional art, the present invention has a simple structure of a single shaft formed by combination of two planetary gear sets.
Therefore, the present invention is advantageous in terms of efficiency, noise reduction, and weight reduction since performing speed reduction without changing shafts.
Driving power of a motor is input to the sun gear of the first planetary gear and is output to the carrier.
The carrier for the first output is connected to the sun gear of the second planetary gear.
In the same way, the carrier of the second planetary gear outputs the driving power.
Then, the gear reduction ratio is as follows:
R = ((Zr1+Zr1) /Zs1)* ((Zr2+Zs2)/Zs2).
In order to solve the above problems, Korean Patent Laid Open No. 10-2012-116000 discloses a drive system for a hybrid electric vehicle. As illustrated in FIG. 3, the drive system for a hybrid electric vehicle includes: first and second electric motors A and B arranged inside one housing; a planetary gear set arranged inside the housing and coupled to interlock with the first electric motor A; a gear unit arranged inside the housing, transmitting rotation of the second electric motor to an output shaft and transmitting rotational force of the planetary gear set to a differential device through the output shaft; and a one-way clutch (OWC) arranged between a rotor of the first electric motor A and a second rotation element of the planetary gear set to be capable of blocking (lock mode) or connecting (overrun mode) the mechanical connection between the first electric motor A and the second rotation element, and capable of controlling the blocking and the connection by a control signal of a controller.
The first rotation element of the planetary gear set may be a carrier gear C, the second rotation element may be a sun gear S, and the third rotation element may be a ring gear R.
The one-way clutch may select a lock mode having the existing manual transmission ratio (fixed transmission ratio) or an overrun mode having a variable transmission ratio through the planetary gear set and the gear device according to the control signal of the controller.
The gear device is a reduction gear device, which decelerates the rotational force transmitted from the rotor of the second electric motor to transmit the same to the differential device, and reduces the rotational force transmitted from the third rotation element of the planetary gear set in the overrun mode to transmit the reduced rotational force to the differential device.
That is, the conventional art is provided with the planetary gear set and the gear device, which is a gear reduction device, in the housing, but includes the controllable one-way clutch to select a manual transmission ratio or a variable transmission ratio, since being a drive system for a hybrid electric vehicle.
In addition, the conventional art has at least three multiaxial driving shafts having a power transmission path between the rotor of the second electric motor B and the gear device and between the third rotation element R of the planetary gear set and the gear device and having a power transmission path connecting the gear device and the differential device with each other.
Since the conventional art having the multiaxial drive shafts cannot be arranged on one axis due to the connection structure of the first and second electric motors A and B and the planetary gear set for selecting different transmission ratios, the driving shafts must be arranged to have different phase differences.
Therefore, since the conventional multiaxial drive unit requires complicated connection components for connecting the driving shafts and transmitting driving power, and increases operational noise and vibration generated by mis-match between the driving shafts when the driving shafts rotate at high RPM due to eccentricity.
In addition, the conventional drive unit increases volume and weight and deteriorates fuel efficiency due to structural characteristics of the connection structure to connect multiple shafts.
Furthermore, the interlocking means of the present invention has a hollow formed at the center of the rotor and a spline gear formed at one side of the inner circumferential surface of the hollow so that a portion of the teeth of the first sun gear is tooth-meshed. So, the rotor and the first sun gear are gear-meshed and interlocked with each other.
In another aspect of the present invention, there is provided a power drive system for an electric vehicle including: a housing; a motor unit having a stator fixed on the inner circumferential surface of the housing and having a coil wound thereon, and a rotor arranged inside the stator to be rotated when electricity is applied to the coil; a first planetary gear set having a first sun gear rotated by the medium of the stator and an interlocking means and having a plurality of gear teeth formed on the outer circumferential surface thereof, a plurality of first planetary gears tooth-meshed with gear teeth of the first sun gear, a ring gear fixed inside the housing and having an internal gear formed on the inner circumferential surface and tooth-meshed with the first planetary gears, and a first carrier to which the first planetary gears are connected to interlock with each other; a second planetary gear set disposed on one side of the first planetary gear set and connected in parallel on the same axis line so as to interlock with the first planetary gear set; and a differential device having a differential gear case of which one side is connected to the second planetary gear set to interlock with the second planetary gear set, and right and left driving shafts split to right and left sides to transmit rotational force transmitted from the differential gear case to right and left wheels.
When the motor unit arranged inside the housing is driven, generation of driving power and speed reduction are simultaneously performed on one driving shaft through the first and second planetary gear sets and the differential device arranged on the same axis.
The second planetary gear set of the present invention includes: a second sun gear interlocked with the first carrier by the medium of a connection means; a plurality of second planetary gears engaged with the second sun gear and engaged with the internal gear of the ring gear; and a second carrier connected to each other and connected to interlock with the differential gear case.
The connecting means has a through hole formed at the center of the first carrier, and an inner gear is formed on one side of the inner circumferential surface of the through hole to be engaged with a portion of the gear of the second sun gear.
The present invention has the following effects.
First, since the motor unit, the first planetary gear set, and the differential device are arranged on the same axis in one housing, generation of driving force and the power transmission path for reduction are performed by left and right driving shafts, and there is no eccentric phase difference between the driving shafts, thereby significantly reducing operational noise and vibration when the rotor rotates at high RPM.
In addition, since the components are densely arranged in one housing, the volume and weight of the drive unit device can be reduced to increase fuel efficiency.
Second, since the rotor and the first sun gear of the present invention are directly connected in a gearing manner, the power transmission path is simplified, thereby reducing the number of components required for the connection structure of the motor unit and the first planetary gear set.
Third, in a second embodiment of the present invention, since the motor unit, the first and second planetary gear sets and the differential device are arranged on the same axis in the housing, the present invention can obtain a reduction ratio greater than the reduction ratio of the first embodiment.
Fourth, since the second carrier of the present invention is directly bolt-coupled to a differential gear case of the differential device, the power transmission path is simplified, thereby reducing the number of components required for the connection structure.
Fifth, in the second embodiment of the present invention, a through hole is formed at the center of a first carrier, and an inner gear geared with a portion of gear teeth of a second sun gear is formed at one side of the inner circumferential surface of the through hole. So, the power transmission structure between the first and second planetary gear sets is directly connected in a gearing manner, thereby reducing the number of components required for the connection structure of the first and second planetary gear sets.
SUMMARY
In first aspect of the present disclosure, a power drive system is provided.
A power drive system includes a motor that is adapted to provide input force, a rotor that is coupled with the motor and adapted to receive the input force from the motor, such that the rotor includes teeth, that are positioned on a peripheral inner circumference of the rotor, a first sun gear of one or more sun gears that is in mesh with the teeth associated with the peripheral inner circumference of the rotor, such that the first sun gear of one or more sun gears are adapted to rotate along with the rotor.
Further, the system provides a first planetary gear sets of one or more planetary gear sets that are positioned in mesh with the first sun gear of one or more sun gears and adapted to receive the input force from the first sun gear one or more one or more sun gears, such that the first planetary gear sets of one or more planetary gear sets includes one or more planetary gears, that are in mesh with the first sun gear of one or more sun gears and adapted to receive the input force from the first sun gear of one or more sun gears. And the system further includes a ring gear comprising teeth on inner surface, such that the teeth is in mesh with the one or more planetary gears and differential device that is coupled with a flange associated with the first planetary gear sets of one or more planetary gear sets and adapted to receive the input force transmitted from the first planetary gear sets of one or more planetary gear sets.
In some aspects of the present disclosure, the power drive system includes a housing to accommodate the system.
In some aspects of the present disclosure, the power drive, includes a stator which is coupled to the inner circumference of the housing and fixed by a fastening member such as a bolt, and has a coil wounded on the outer circumferential surface, such that the rotor is disposed inside the stator and is rotated by the magnetic force of a magnetic field generated when power is applied to the coil and plurality of magnets, are inserted into the rotor.
In some aspects of the present disclosure, the power drive system, first planetary gear sets of one or more planetary gear sets further comprises a first carrier connected such that the first planetary gears are connected to each other to interlock with each other, and rotating in the same direction as the first planetary gears by the binding force of the first planetary gears.
In some aspects of the present disclosure, the first sun gear of one or more sun gears coupled to interlock with the rotor by way of a plurality of gear teeth on the inner circumference of rotor with the plurality of gear teeth on the outer circumference of the first sun gear of one or more sun gear.
In some aspects of the present disclosure, the power drive system, the differential device is provided with a pinion gear and a worm gear in the differential gear case, and employs a general differential device in which the left and right driving shafts and are rotated according to the rotation of the differential gear case.
In some aspects of the present disclosure, the power drive system, such that the differential gear case transmits the rotational force of the first carrier to the left and right driving shafts, and drives the left and right driving shafts.
In some aspects of the present disclosure, the power drive system, a differential gear case is accommodated in the receiving space of the first carrier, and then, one side of the differential gear case is coupled to a flange formed at one side of the receiving space by a bolt.
In some aspects of the present disclosure, the power drive system, such that the rotor, sun gear, planetary gear set, and Ring gear are all aligned in a single axis.
BRIEF DESCRIPTION OF DRAWINGS
The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which:
FIG. 1 is a cross-sectional view schematically illustrating the concept of a three-axis drive unit in a conventional art electric vehicle drive unit;
FIG. 2 is a cross-sectional view schematically illustrating the concept of a two-axis drive unit in a conventional art electric vehicle drive unit;
FIG. 3 is a diagram illustrating an example of the conventional art;
FIG. 4 is a cross-sectional view schematically illustrating a power drive system for an electric vehicle according to a first embodiment of the present invention;
FIG. 5 is an exploded perspective view of a rotor and a first planetary gear set according to the first embodiment of the present invention;
FIG. 6 is a side view illustrating a coupled state of FIG. 5;
FIG. 7 is a cross-sectional view taken along the line A-A of FIG. 6;
FIG. 8 is a cross-sectional view schematically illustrating a power drive system for an electric vehicle according to a second embodiment of the present invention;
FIG. 9 is an exploded perspective view of a rotor and a first planetary gear set according to the second embodiment of the present invention;
FIG. 10 is a side view illustrating a coupled state of FIG. 9;
FIG. 11 is a cross-sectional view taken along the line B-B of FIG. 10; and
FIG. 12 illustrates a two-axis drive system in according to a conventional art.
BRIEF DESCRIPTION OF THE INVENTION
Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure. Thus, the following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, known details are not described in order to avoid obscuring the description.
References to one or an embodiment in the present disclosure can be references to the same embodiment or any embodiment; and, such references mean at least one of the embodiments.
Reference to "one embodiment", "an embodiment", “one aspect”, “some aspects”, “an aspect” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others.
The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Alternative language and synonyms may be used for any one or more of the terms discussed herein, and no special significance should be placed upon whether or not a term is elaborated or discussed herein. In some cases, synonyms for certain terms are provided.
A recital of one or more synonyms does not exclude the use of other synonyms.
The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and is not intended to further limit the scope and meaning of the disclosure or of any example term. Likewise, the disclosure is not limited to various embodiments given in this specification. Without intent to limit the scope of the disclosure, examples of instruments, apparatus, methods and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, technical and scientific terms used herein have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control.
Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims, or can be learned by the practice of the principles set forth herein.
According to the present invention, a motor unit, a planetary gear set, and a differential device are arranged on the same axis in a housing so as to generate driving force and reduce speed at the same time on the same axis.
Referring to FIGS. 4 to 7, a power drive system for an electric vehicle according to a first embodiment of the present invention includes a housing 10, a motor unit M disposed to be accommodated in the housing 10, a first planetary gear set G1 disposed to be accommodated in the housing 10 so as to reduce speed by receiving rotational force of the motor unit M, and a differential device 90 receiving the rotational force reduced from the first planetary gear set G1 to transmit driving force to left and right driving shafts 110 and 120 split to left and right sides.
Referring to FIG. 4, the motor M includes a stator 30 which is coupled to the inside of the housing 10 to be fixed by a fastening member, such as a bolt, and having a coil wound on the outer circumferential surface thereof, and a rotor 20 which is disposed inside the stator 30 and is rotated by magnetic force of a magnetic field generated when power is applied to the coil.
A plurality of magnets 25 are inserted into the rotor 20.
Referring to FIG. 5, One or more planetary gear sets (G) (of which first through second planetary gear sets are shown in figures and represented as G1 and G2 respectively) includes: One or more sun gears 70 (of which first through second gears are shown in figures and represented as 70A and 70B respectively) coupled to interlock with the rotor 20 by the medium of an interlocking means and having a plurality of gear teeth 72 formed on the outer circumferential surface thereof; a plurality of first planetary gears 60A having a plurality of gear teeth 62 formed on the outer circumferential surface to be tooth-meshed to the gear teeth 72 of the first sun gear 70A; a ring gear 50 fixed inside the housing and having an internal gear 52 formed on the inner circumferential surface to be tooth-meshed with the outer portion of the gear teeth 62 of the first planetary gears 60A, and a first carrier 80A connected such that the first planetary gears 60A are connected to each other to interlock with each other, and rotating in the same direction as the first planetary gears 60A by binding force of the first planetary gears 60A.
As illustrated in FIG. 4, the ring gear 50 is disposed inside the housing 10 and is fixed to the inner circumferential surface of the stator 30 or the housing 10.
Referring to FIG. 5, the interlocking means includes a hollow 21 formed at the center of the rotor 20 to open one side and the other side thereof, and a spline gear 22 formed on one side of the inner circumferential surface of the hollow 21 to be tooth-meshed with the gear teeth 72 of the first sun gear 70A.
Furthermore, the first planetary gears 60A are rotatably coupled to the first carrier 80A.
The first carrier 80A has a receiving space 83 formed in the inner center thereof to receive a differential gear case 92.
In addition, the first carrier 80A has three receiving parts 85 formed in the outer circumferential surface thereof so that the receiving space 83 can communicate with the outside and the first planetary gears 60A are accommodated therein.
Referring to FIGS. 5 and 6, each of the first planetary gears 60A is rotatably coupled to the first carrier 80A by each connection pin 65 in a state of being accommodated in the receiving part 85.
The differential device 90 is provided with a pinion gear and a worm gear in the differential gear case 92, and employs a general differential device in which the left and right driving shafts 110 and 120 are rotated according to the rotation of the differential gear case 92.
Referring to FIG. 7, the differential gear case 92 is accommodated in the receiving space 83 of the first carrier 80A, and then, one side of the differential gear case 92 is coupled to a flange 82 formed at one side of the receiving space 83 by a bolt.
The operation of the power drive system for an electric vehicle according to the first embodiment of the present invention is as follows.
According to the first embodiment of the present invention, when power is applied to the coil, a magnetic field is formed between the coil and the magnet 25 to rotate the rotor 20.
In this instance, since the rotor 20 is engaged with the first sun gear 70A, the rotational force is transmitted to the first sun gear 70A to rotate the first sun gear 70A when the rotor 20 rotates.
The first sun gear 70A rotates the engaged first planetary gears 60A.
In this instance, the first sun gear 70A and the first planetary gears 60A are rotated in opposite directions, and the first planetary gears 60A and the first carrier 80A are rotated in the same direction.
In addition, as illustrated in FIG. 7, since the inside of each first planetary gear 60A is geared with the first sun gear 70A and the outside thereof is geared with the internal gear 52 of the ring gear 50, the first planetary gears 60A make a revolution and a rotation.
Next, the first planetary gear 60A rotates the first carrier 80A and the differential gear case 92, which is bolt-coupled with the first carrier 80A.
The differential gear case 92 transmits the rotational force of the first carrier 80A to the left and right driving shafts 110 and 120, respectively, and drives the left and right driving shafts 110 and 120.
That is, the first embodiment of the present invention has a power transmission path through which the rotational force of the rotor 20 is transmitted to the differential device 90 through the first planetary gear set G1.
The power transmission path of the first embodiment of the present invention has a path progressed in sequence of the rotor 20, the first sun gear 70A, the first planetary gear 60A, the first carrier 80A, the differential gear case 92, the left and right driving shafts 110 and 120, and both wheels.
In this instance, the rotational force is reduced while being transmitted to the differential device 90 through the first planetary gear set G1, and the reduction ratio N1 is as follows:
Reduction ratio (N1)=(the number of teeth of internal gear 52 of ring gear 50 + the number of teeth of gear 72 of first sun gear 70A/the number of teeth 72 of first sun gear 70A.
In the first embodiment of the present invention, driving force is generated in a state where the motor unit M, the first planetary gear set G1, and the differential device 90 are disposed on the same axis as the left and right driving shafts 110 and 120, and speed reduction is achieved while driving power is transmitted.
Therefore, since the driving force is generated and reduced on the central line of the same shaft, the power drive system for an electric vehicle according to the first embodiment of the present invention can reduced operational noise and vibration generated during driving, compared with the conventional multi-axis drive unit which increases operational noise and vibration at high RPM rotation.
Additionally, as illustrated in FIG. 4, since the motor unit M, the first planetary gear set G1, and the differential device 90 are densely arranged in one housing 10, the power drive system for an electric vehicle according to the present invention can simplify the configuration, reduce the volume, and improve fuel efficiency by reducing the weight of the drive unit.
It will be apparent to those skilled in the art that the present invention is not limited to the embodiments and various modifications and variations can be made therein without departing from the spirit and scope of the present invention. Accordingly, such variations or modifications belong to the scope of the claims of the present invention.
,CLAIMS:I/We Claim

1. A power drive system (100) comprising:
a motor (M) that is adapted to provide input force;
a rotor (20) that is coupled with the motor (M) and adapted to receive the input force from the motor (M), such that the rotor comprising:
a plurality of teeth (22), that are positioned on a peripheral inner circumference of the rotor (20);
a first sun gear (70A) of one or more sun gears (70) that is in mesh with the teeth associated with the peripheral inner circumference of the rotor (20), such that the first sun gear (70A) of one or more sun gears (70) are adapted to rotate along with the rotor (20);
a first planetary gear sets (G1) of one or more planetary gear sets (G) that are positioned in mesh with the first sun gear (70A) of one or more sun gears (70) and adapted to receive the input force from the first sun gear (70A) one or more one or more sun gears (70), such that the first planetary gear sets (G1) of one or more planetary gear (G) sets comprising:
one or more planetary gears (60A), that are in mesh with the first sun gear (70A) of one or more sun gears (70) and adapted to receive the input force from the first sun gear (70A) of one or more sun gears (70);
a ring gear (50) comprising teeth (52) on inner surface, such that the plurality of teeth (52) is in mesh with the one or more planetary gears (60A); and
a differential device (90) that is coupled with a flange (82) associated with the first planetary gear sets (G1) of one or more planetary gear sets (G) and adapted to receive the input force transmitted from the first planetary gear sets (G1) of one or more planetary gear sets (G).

2. The power drive system (100) as claimed in claim 1, further comprises a housing (10) to accommodate the system (100).

3. The power drive system (100) as claimed in claim 1, further comprises a stator (30) which is coupled to the inner circumference of the housing (10) and fixed by a fastening member such as a bolt, and has a coil wounded on the outer circumferential surface,
wherein the rotor (20) is disposed inside the stator (30) and is rotated by the magnetic force of a magnetic field generated when power is applied to the coil and plurality of magnets (25), are inserted into the rotor (20).

4. The power drive system (100) as claimed in claim 1, wherein the first planetary gear sets (G1) of one or more planetary gear sets (G) further comprises a first carrier (80A) connected such that the first planetary gears (60A) are connected to each other to interlock with each other, and rotating in the same direction as the first planetary gears (60A) by the binding force of the first planetary gears (60A).

5. The power drive system (100) as claimed in claim 1, wherein the first sun gear (70A) of one or more sun gear (70) coupled to interlock with the rotor by way of a plurality of gear teeth (22) on the inner circumference of rotor (20) with the plurality of gear teeth (72) on the outer circumference of the first sun gear (70A) of one or more sun gear (70).

6. The power drive system (100) as claimed in claim 1, wherein the differential device (90) is provided with a pinion gear and a worm gear in the differential gear case (92) and employs a general differential device in which the left and right driving shafts (110) and (120) are rotated according to the rotation of the differential gear case (92).

7. The power drive system (100) as claimed in claim 1, wherein the differential gear case (92) transmits the rotational force of the first carrier (80A) to the left and right driving shafts (110) and (120), respectively, and drives the left and right driving shafts (110) and (120).

8. The power drive system (100) as claimed in claim 1, wherein the differential gear case (92) is accommodated in the receiving space (83) of the first carrier (80A), and then, one side of the differential gear case (92) is coupled to a flange (82) formed at one side of the receiving space (83) by a bolt.

9. The power drive system (100) as claimed in claim 1, wherein the rotor 20, sun gear (70), planetary gear set (G), and Ring gear (50) are all aligned in a single axis.