US20190211903A1 - Cycloidal differential - Google Patents
Cycloidal differential Download PDFInfo
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- US20190211903A1 US20190211903A1 US15/864,460 US201815864460A US2019211903A1 US 20190211903 A1 US20190211903 A1 US 20190211903A1 US 201815864460 A US201815864460 A US 201815864460A US 2019211903 A1 US2019211903 A1 US 2019211903A1
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- Prior art keywords
- cycloidal
- roller disk
- disk
- differential
- roller
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H1/00—Toothed gearings for conveying rotary motion
- F16H1/28—Toothed gearings for conveying rotary motion with gears having orbital motion
- F16H1/32—Toothed gearings for conveying rotary motion with gears having orbital motion in which the central axis of the gearing lies inside the periphery of an orbital gear
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H48/00—Differential gearings
- F16H48/06—Differential gearings with gears having orbital motion
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H1/00—Toothed gearings for conveying rotary motion
- F16H1/28—Toothed gearings for conveying rotary motion with gears having orbital motion
- F16H1/32—Toothed gearings for conveying rotary motion with gears having orbital motion in which the central axis of the gearing lies inside the periphery of an orbital gear
- F16H2001/325—Toothed gearings for conveying rotary motion with gears having orbital motion in which the central axis of the gearing lies inside the periphery of an orbital gear comprising a carrier with pins guiding at least one orbital gear with circular holes
Definitions
- the present disclosure relates to differentials for vehicles and more specifically to cycloidal differentials that include a pair of cycloidal drives arranged to allow independent rotation of the left and right wheels.
- Cycloidal drives are commonly used as speed-reducer mechanisms.
- a typical cycloidal drive includes an input shaft having an eccentric end connected to a cycloidal disk (also known as a cycloidal cam).
- the disk includes a plurality of lobes that intermesh with ring pins circumferentially surrounding the disk.
- the ring pins are typically stationary with the housing of the speed reducer.
- An output shaft includes an array of circumferentially arranged roller pins that are received within holes defined in the cycloidal disk.
- the input shaft drives the disk in an eccentric, cycloidal motion. Motion is transferred from the disk to the output shaft via the plurality of roller pins.
- the eccentric, cycloidal motion of the disk reduces the speed between the input shaft and the output shaft according to the number of lobes, holes, pins, and rollers.
- the difference between the number of rollers and the number of lobes is usually one, and the number of lobes usually matches the number of pins.
- a cycloidal differential includes a driven body and a coupling ring supported for rotation within the driven body.
- the coupling ring defines a first eccentric race and a second eccentric race on opposing sides of the coupling ring.
- the cycloidal differential further includes first and second cycloidal drives.
- the first cycloidal drive includes a first roller disk received in the first eccentric race and a first output member operably coupled to the first roller disk and configured to couple with a half shaft.
- the second cycloidal drive includes a second roller disk received in the second eccentric race and a second output member operably coupled to the second roller disk and configured to couple with another half shaft.
- a cycloidal differential includes a first cycloidal drive and a second cycloidal drive.
- the first cycloidal drive includes a first roller disk having internal rollers and axially extending pins, and a first cycloidal cam defining lobes configured to engage with the rollers and configured to couple with a half shaft.
- the second cycloidal drive includes a second roller disk having internal rollers and axially extending pins, and a second carrier disk defining holes that receive the pins of the second roller disk and configured to couple with another half shaft.
- a cycloidal differential includes a driven body, a coupling ring, and first and second cycloidal drives.
- the coupling ring is supported for rotation within the driven body and has a first eccentric race and a second eccentric race on opposing sides of the coupling ring.
- the first cycloidal drive includes a first roller disk received in the first eccentric race and defines a central opening having internal rollers circumferentially arranged around a perimeter of the opening.
- the first roller disk further has pins circumferentially arranged on a face of the first roller disk.
- a first cycloidal cam, of the first drive is supported within the central opening and defines lobes configured to engage with the rollers.
- the first cycloidal cam is configured to couple with a half shaft.
- a first side plate is attached to a first side of the driven body and defines circumferentially arranged holes that receive the pins therein.
- the second cycloidal drive includes a second roller disk received in the second eccentric race and defining a central opening having internal rollers circumferentially arranged around a perimeter of the opening.
- the second roller disk further has pins circumferentially arranged on a face of the second roller disk.
- a carrier disk is supported for rotation within the coupling ring between the first and second roller disks and defines holes that are circumferentially arranged and that receive the pins of the second roller disk therein.
- the carrier disk is configured to couple with another half shaft.
- the second drive further includes a second endplate is attached to a second side of the driven body and a second cycloidal cam rotationally fixed to the second endplate and supported for rotation with the central opening of the second roller disk.
- the second cycloidal cam defines lobes configured to engage with the rollers of the second roller disk.
- FIG. 1 is a perspective view of a cycloidal differential.
- FIG. 2 is an exploded perspective view of the cycloidal differential.
- FIG. 3 is a cross-sectional side view of the cycloidal differential.
- FIG. 4 is an exploded perspective view of the cycloidal differential during straight-line driving.
- FIG. 5 is an exploded perspective view of the cycloidal differential during cornering.
- Vehicles may include a differential on a driven axle to multiply torque of the powertrain and/or allow independent rotation of the left and right driven wheels during cornering.
- Differentials include a housing supported under the vehicle and have left and right connections configured to receive left and right half shafts of the driven axle.
- the half shafts transmit torque from the differential to the driven wheels. Used herein “half shaft” refers to any shaft that transmits power from a differential to a driven wheel.
- differentials are known including bevel-gear differentials and spur-gear differentials. These differentials include a gear train disposed within the differential case in order to transmit power from the driveshaft to the half shafts. These types of differentials tend to be bulky requiring a sizable packaging space.
- the following figures and related text describe a completely different type of differential that does not include a gear train and instead includes a pair of cycloidal drives coupled in tandem. This type of differential is referred to herein as a “cycloidal differential.” Cycloidal differentials are compact and require less packaging space on the vehicle than traditional differentials.
- a cycloidal differential 20 includes a driven body that is the power-receiving element of the differential.
- the driven body may be operably coupled to a driveshaft.
- the driven body may be a gear such as ring gear 26 .
- the driven body may be a bevel gear, a chain-driven sprocket, a belt-driven pully, a carrier, or the like.
- the differential 20 includes a first cycloidal drive 22 and a second cycloidal drive 24 disposed on opposing sides of a ring gear 26 .
- the ring gear 26 includes gear teeth 28 that may mesh with gear teeth of a pinion driven by a driveshaft.
- the first cycloidal drive 22 includes an input member configured to receive power from the ring gear 26 and an output member 30 configured to couple with a half shaft.
- the output member 30 may define a central bore that defines internal splines 34 for receiving external splines of the half shaft.
- the second cycloidal drive 24 includes an input member configured to receive power from the ring gear 26 and an output member 32 configured to couple with another half shaft.
- the output member 32 may define a central bore that defines internal splines 36 for receiving external splines of the another half shaft.
- the cycloidal drives 22 , 24 allow for a very compact differential.
- the first and second drives 22 , 24 may be completely disposed between the first and second faces 38 , 40 of the ring gear 26 .
- a carrier is attached to the bevel gear and axially extends significantly past a footprint of the bevel gear. This enlarges the differential housing and requires vehicle designers to provide a much larger packaging space for the bevel-gear differential.
- a case (not shown) for the differential 20 need not extend significantly past the ring gear 26 .
- a much smaller packaging space is required for the differential 20 as compared to traditional differentials.
- the first end face 38 and the second end face 40 are disposed on opposite sides of a hub 42 .
- the hub 42 defines a first recess portion 44 , a second recess portion 46 , and a central portion 48 .
- a coupling ring 50 is supported for rotation within the hub 42 .
- the couple ring 50 interconnects the first and second drives 22 , 24 .
- the coupling ring 50 includes an outer surface 52 that is seated on the central portion 48 .
- a bearing may be provided between the coupling ring 50 and the hub 42 to reduce friction.
- the inner surface of the coupling ring 50 defines a first eccentric race 54 , a second eccentric race 56 , and a concentric race 58 .
- the first and second races 54 , 56 may have different center points to create a phase difference.
- the phase difference between the first and second races 54 , 56 may be between 170 and 200 degrees, inclusive. In the illustrated embodiment, the phase difference is 180 degrees. A phase difference between the races may not be required in all applications.
- the first cycloidal drive 22 includes a roller disk 60 that is received in the first eccentric race 54 with an outer surface 62 of the roller disk disposed against the first eccentric race 54 .
- a bearing may be disposed between the outer surface 62 and the race 54 .
- the roller disk 62 is supported for eccentric, cycloidal motion (also known as wobbling or orbital motion) within the ring gear 26 via the coupling ring 50 .
- the roller disk 60 defines a central opening 64 having a plurality of internal rollers 66 circumferentially arranged around a perimeter of the opening 64 .
- the rollers 66 may be integrally formed with the disk 60 or may be separate components that are attached to the disk 60 .
- the rollers 66 are static components that are rotationally fixed with the disk 60 , and in others, the rollers 66 are configured to rotate relative to the disk 60 .
- a plurality of pins 68 are circumferentially arranged on a face of the disk 60 .
- the pins 68 project from the face in an axial direction of the differential 20 .
- the pins 68 may be integrally formed with the disk 60 or may be separate components that are attached to the disk 60 .
- the pins 68 are static components that are rotationally fixed with the disk 60 , and in others, the pins 68 are configured to rotate relative to the disk 60 .
- the number of pins 68 and the number of rollers 66 may be equal.
- the pins 68 may be attached to the roller disk 60 so that associated ones of the pins 68 and the rollers 66 have a common center point.
- the output member 30 is supported for rotation within the central opening 64 of the roller disk 62 .
- the output member 30 is a cycloidal cam.
- the cycloidal cam 30 includes a plurality of lobes 70 configured to engage with the internal rollers 66 .
- the number of lobes 70 may be less than the number of rollers 66 .
- the cam 30 includes eight lobes and the roller disk 60 includes nine rollers and nine pins.
- the first cycloidal drive 22 also includes a side plate 72 that is rotationally fixed to the ring gear 26 .
- the side plate 72 may be attached to the first end face 38 of the hub 42 by welding, fasteners, or the like.
- the side plate 72 defines a central opening 75 providing clearance for the half shaft to connect with the cam 30 and defines a plurality of holes 76 circumferentially arranged to receive the pins 68 .
- a diameter of the holes 76 is larger than a diameter of the pins 68 allowing for the eccentric, cycloidal motion of the roller disk 60 .
- Eccentric bearings may be provided between the pins 68 and the holes 76 .
- the first cycloidal drive 22 is configured to have relative rotation between its various components. For example, if the side plate 72 is held stationary and the cam 30 is rotated clockwise, then the roller disk 60 will have a counterclockwise eccentric, cycloidal motion. Since the roller disk 60 is connected with the coupling ring 50 , the coupling ring will rotate counterclockwise within the ring gear 26 when the cam 30 is rotated clockwise.
- the second cycloidal drive 24 includes a roller disk 90 that is received in the second eccentric race 56 with an outer surface 92 of the roller disk 90 disposed against the second eccentric race 56 .
- a bearing may be disposed between the outer surface 92 and the race 56 .
- the roller disk 90 is supported for eccentric, cycloidal motion within the ring gear 26 via the coupling ring 50 .
- the roller disk 90 defines a central opening 94 having a plurality of internal roller 96 circumferentially arranged around a perimeter of the opening 94 .
- the rollers 96 may be integrally formed with the disk 90 or may be separate components that are attached to the disk 90 .
- the roller 96 are static components that are rotationally fixed with the disk 90 , and in others, the rollers 96 are configured to rotate relative to the disk 90 .
- a plurality of pins 98 are circumferentially arranged on a face of the disk 90 .
- the pins 98 project from the face in an axial direction of the differential 20 .
- the pins 98 may be integrally formed with the disk 90 or may be separate components that are attached to the disk 90 .
- the pins 98 are static components that are rotationally fixed with the disk 98 , and in others, the pins 98 are configured to rotate relative to the disk 60 .
- the number of pins 98 and the number of rollers 96 may be equal.
- the pins 98 may be attached to the roller disk 90 so that associated ones of the pins 98 and the rollers 96 have a common center point.
- the output member 32 of the second cycloidal drive 24 is a carrier disk.
- the carrier disk 32 is supported for rotation within the coupling ring 50 .
- the carrier disk 32 includes an outer surface 100 that is seated on the central race 58 of the coupling ring 50 .
- a bearing may be disposed between the carrier disk 32 and the coupling ring 50 .
- the carrier disk 32 defines a plurality of circumferentially arranged holes 102 arranged to receive the pins 98 of the roller disk 90 .
- a diameter of the holes 102 is larger than a diameter of the pins 98 allowing for the eccentric, cycloidal motion of the roller disk 90 .
- Eccentric bearings may be provided between the pins 98 and the holes 102 .
- a cycloidal cam 104 of the second drive 24 , is supported for rotation within the central opening 94 of the roller disk 90 .
- the cycloidal cam 104 includes a plurality of lobes 106 configured to engage with the internal rollers 96 .
- the number of lobes 104 may be less than the number of rollers 96 .
- the cam 104 includes seven lobes and the roller disk 90 includes eight rollers 96 and eight pins 98 .
- a side plate 108 encloses the second drive 24 within the hub 42 .
- the side plate 108 is received within the second recessed portion 46 of the hub 42 and is rotationally fixed to the ring gear 26 .
- the side plate 108 may be attached to the hub 42 by welding, fasteners, or the like.
- the cam 104 is rotationally fixed to an inner face 110 of the side plate 108 .
- the cam 104 may be attached to the side plate 108 by welding, fasteners, pins, or the like, or may be integrally formed with the side plate 108 .
- the cam 104 is attached to the side plate 108 for on-axis rotation. Both the cam 104 and the side plate 108 may define a hole 112 allowing the other half shaft to extend into the differential 20 to connect with the carrier disk 32 .
- the second cycloidal drive 24 is configured to have relative rotation between its various components. For example, if the cam 104 is held stationary and the carrier disk 32 is rotated counterclockwise, then the roller disk 90 will have a counterclockwise eccentric, cycloidal motion. Since the roller disk 90 is connected with the coupling ring 50 , the coupling ring will rotate counterclockwise within the ring gear 26 when the carrier disk 32 is rotated counterclockwise.
- the first cycloidal drive 22 is an eighth-order drive (cam 30 has eight lobes) and the second cycloidal drive 24 is a seventh-order drive (cam 104 has seven lobes).
- the speed ratios between the output members are equal.
- the differential 20 may have any combination of an m order drive and an m+1 order drive, where m is greater than or equal to 2.
- the differential 20 is designed to have a 1: ⁇ 1 speed ratio between the output members, i.e., the output member 30 rotates clockwise if the output member 32 rotates counterclockwise.
- Various internal components of the cycloidal drives 22 , 24 e.g., the roller disks and the coupling ring, are designed to rotate within the ring gear 26 when the output members 30 , 32 rotate in opposite directions or at different speeds.
- the differential 20 is also designed to lock the first and second drives 22 , 24 relative to each other when the output members 30 , 32 rotate in the same direction at a same speed, e.g., straight-line driving.
- straight-line driving the various components of the first and second drives 22 , 24 are not rotating relative to the ring gear 26 so that the output members 30 and 32 rotate at the same speed and in the same direction as the ring gear 26 .
- the dashed arrows indicate would-be relative rotation between the illustrated parts—not actual relative rotation.
- the differential 20 is shown with the output members 30 and 32 rotating at the same speed and in the clockwise direction such as during straight-line driving of the vehicle. If first output member 30 is urged clockwise, the roller disk 60 is urged to have eccentric, cycloidal motion in the counterclockwise direction. If second output member 32 is also urged clockwise, the roller disk 90 is urged to have eccentric, cycloidal motion in the clockwise direction. Thus, the first and second roller disk 60 , 90 are urged in opposite directions.
- the coupling ring 50 prevents this causing the differential 20 to lock up, i.e., none of the individual components of the differential rotate relative to each other. Instead, all of the individual components rotate with the ring gear 26 .
- the ring gear 26 and the output members 30 , 32 rotate at the same speed and in the same direction.
- FIG. 5 the solid arrows indicate actual relative rotation between the illustrated parts—not overall rotation. (The entire illustrated assembly rotates clockwise with the ring gear during driving of the vehicle.)
- the differential 20 is shown during cornering of the vehicle with the output members 30 and 32 rotating at the different speeds.
- the output member 32 is connected to the inner wheel, and the output member 30 is connected to the outer wheel.
- the output member 30 is rotating faster than the ring gear 26 and is inputting rotation into the differential 20 .
- the clockwise rotation of the output member 30 i.e., increased angular speed, causes counterclockwise eccentric, cycloidal motion of the roller disk 60 due to rolling engagement between the rollers 66 and the lobes 70 .
- the counterclockwise eccentric, cycloidal motion of the roller disk 60 causes the coupling ring 50 rotate counterclockwise within the hub 42 .
- the coupling ring 52 causes the roller disk 90 to have a counterclockwise eccentric, cycloidal motion.
- the pins 98 engage with the holes 102 to transfer motion from the roller disk 90 to the carrier disk 32 causing the output member 32 to rotate in the counterclockwise direction.
- the counterclockwise direction of the output member 32 is being used as a relative term meaning that the output member 32 is rotating slower than the ring gear 26 and the output member 30 .
- both of the output members 30 and 32 rotate in the same direction, which is also the same direction of rotation as the ring gear, but at different speeds.
- cycloidal drives of the differential can be rearranged to form other types of cycloidal differentials.
- Applicant's co-pending applications U.S. patent application Ser. No. ______ (Attorney Docket SCHF 0130 PUS) and U.S. patent application Ser. No. ______ (Attorney Docket SCHF 0145 PUS), filed on the same day as this disclosure, which are incorporated in their entirety by reference herein—disclose other types of cycloidal differentials.
Abstract
Description
- The present disclosure relates to differentials for vehicles and more specifically to cycloidal differentials that include a pair of cycloidal drives arranged to allow independent rotation of the left and right wheels.
- Cycloidal drives are commonly used as speed-reducer mechanisms. A typical cycloidal drive includes an input shaft having an eccentric end connected to a cycloidal disk (also known as a cycloidal cam). The disk includes a plurality of lobes that intermesh with ring pins circumferentially surrounding the disk. The ring pins are typically stationary with the housing of the speed reducer. An output shaft includes an array of circumferentially arranged roller pins that are received within holes defined in the cycloidal disk. The input shaft drives the disk in an eccentric, cycloidal motion. Motion is transferred from the disk to the output shaft via the plurality of roller pins. The eccentric, cycloidal motion of the disk reduces the speed between the input shaft and the output shaft according to the number of lobes, holes, pins, and rollers. The difference between the number of rollers and the number of lobes is usually one, and the number of lobes usually matches the number of pins.
- According to one embodiment, a cycloidal differential includes a driven body and a coupling ring supported for rotation within the driven body. The coupling ring defines a first eccentric race and a second eccentric race on opposing sides of the coupling ring. The cycloidal differential further includes first and second cycloidal drives. The first cycloidal drive includes a first roller disk received in the first eccentric race and a first output member operably coupled to the first roller disk and configured to couple with a half shaft. The second cycloidal drive includes a second roller disk received in the second eccentric race and a second output member operably coupled to the second roller disk and configured to couple with another half shaft.
- According to another embodiment, a cycloidal differential includes a first cycloidal drive and a second cycloidal drive. The first cycloidal drive includes a first roller disk having internal rollers and axially extending pins, and a first cycloidal cam defining lobes configured to engage with the rollers and configured to couple with a half shaft. The second cycloidal drive includes a second roller disk having internal rollers and axially extending pins, and a second carrier disk defining holes that receive the pins of the second roller disk and configured to couple with another half shaft.
- According to yet another embodiment, a cycloidal differential includes a driven body, a coupling ring, and first and second cycloidal drives. The coupling ring is supported for rotation within the driven body and has a first eccentric race and a second eccentric race on opposing sides of the coupling ring. The first cycloidal drive includes a first roller disk received in the first eccentric race and defines a central opening having internal rollers circumferentially arranged around a perimeter of the opening. The first roller disk further has pins circumferentially arranged on a face of the first roller disk. A first cycloidal cam, of the first drive, is supported within the central opening and defines lobes configured to engage with the rollers. The first cycloidal cam is configured to couple with a half shaft. A first side plate is attached to a first side of the driven body and defines circumferentially arranged holes that receive the pins therein. The second cycloidal drive includes a second roller disk received in the second eccentric race and defining a central opening having internal rollers circumferentially arranged around a perimeter of the opening. The second roller disk further has pins circumferentially arranged on a face of the second roller disk. A carrier disk is supported for rotation within the coupling ring between the first and second roller disks and defines holes that are circumferentially arranged and that receive the pins of the second roller disk therein. The carrier disk is configured to couple with another half shaft. The second drive further includes a second endplate is attached to a second side of the driven body and a second cycloidal cam rotationally fixed to the second endplate and supported for rotation with the central opening of the second roller disk. The second cycloidal cam defines lobes configured to engage with the rollers of the second roller disk.
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FIG. 1 is a perspective view of a cycloidal differential. -
FIG. 2 is an exploded perspective view of the cycloidal differential. -
FIG. 3 is a cross-sectional side view of the cycloidal differential. -
FIG. 4 is an exploded perspective view of the cycloidal differential during straight-line driving. -
FIG. 5 is an exploded perspective view of the cycloidal differential during cornering. - Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.
- Vehicles may include a differential on a driven axle to multiply torque of the powertrain and/or allow independent rotation of the left and right driven wheels during cornering. Differentials include a housing supported under the vehicle and have left and right connections configured to receive left and right half shafts of the driven axle. The half shafts transmit torque from the differential to the driven wheels. Used herein “half shaft” refers to any shaft that transmits power from a differential to a driven wheel.
- Many types of differentials are known including bevel-gear differentials and spur-gear differentials. These differentials include a gear train disposed within the differential case in order to transmit power from the driveshaft to the half shafts. These types of differentials tend to be bulky requiring a sizable packaging space. The following figures and related text describe a completely different type of differential that does not include a gear train and instead includes a pair of cycloidal drives coupled in tandem. This type of differential is referred to herein as a “cycloidal differential.” Cycloidal differentials are compact and require less packaging space on the vehicle than traditional differentials.
- Referring to
FIG. 1 , acycloidal differential 20 includes a driven body that is the power-receiving element of the differential. The driven body may be operably coupled to a driveshaft. The driven body may be a gear such asring gear 26. Alternatively, the driven body may be a bevel gear, a chain-driven sprocket, a belt-driven pully, a carrier, or the like. In the illustrated embodiment, thedifferential 20 includes a firstcycloidal drive 22 and a secondcycloidal drive 24 disposed on opposing sides of aring gear 26. Thering gear 26 includesgear teeth 28 that may mesh with gear teeth of a pinion driven by a driveshaft. - The first
cycloidal drive 22 includes an input member configured to receive power from thering gear 26 and anoutput member 30 configured to couple with a half shaft. Theoutput member 30 may define a central bore that definesinternal splines 34 for receiving external splines of the half shaft. The secondcycloidal drive 24 includes an input member configured to receive power from thering gear 26 and anoutput member 32 configured to couple with another half shaft. Theoutput member 32 may define a central bore that definesinternal splines 36 for receiving external splines of the another half shaft. - The cycloidal drives 22, 24 allow for a very compact differential. The first and
second drives ring gear 26. In a traditional bevel-gear differential, a carrier is attached to the bevel gear and axially extends significantly past a footprint of the bevel gear. This enlarges the differential housing and requires vehicle designers to provide a much larger packaging space for the bevel-gear differential. In contrast, a case (not shown) for the differential 20 need not extend significantly past thering gear 26. Thus, a much smaller packaging space is required for the differential 20 as compared to traditional differentials. - Referring to
FIGS. 2 and 3 , thefirst end face 38 and thesecond end face 40 are disposed on opposite sides of ahub 42. Thehub 42 defines afirst recess portion 44, asecond recess portion 46, and acentral portion 48. Acoupling ring 50 is supported for rotation within thehub 42. Thecouple ring 50 interconnects the first andsecond drives coupling ring 50 includes anouter surface 52 that is seated on thecentral portion 48. A bearing may be provided between thecoupling ring 50 and thehub 42 to reduce friction. The inner surface of thecoupling ring 50 defines a firsteccentric race 54, a secondeccentric race 56, and aconcentric race 58. The first andsecond races second races - The first
cycloidal drive 22 includes aroller disk 60 that is received in the firsteccentric race 54 with anouter surface 62 of the roller disk disposed against the firsteccentric race 54. A bearing may be disposed between theouter surface 62 and therace 54. Theroller disk 62 is supported for eccentric, cycloidal motion (also known as wobbling or orbital motion) within thering gear 26 via thecoupling ring 50. Theroller disk 60 defines acentral opening 64 having a plurality ofinternal rollers 66 circumferentially arranged around a perimeter of theopening 64. Therollers 66 may be integrally formed with thedisk 60 or may be separate components that are attached to thedisk 60. In some embodiments, therollers 66 are static components that are rotationally fixed with thedisk 60, and in others, therollers 66 are configured to rotate relative to thedisk 60. A plurality ofpins 68 are circumferentially arranged on a face of thedisk 60. Thepins 68 project from the face in an axial direction of the differential 20. Thepins 68 may be integrally formed with thedisk 60 or may be separate components that are attached to thedisk 60. In some embodiments, thepins 68 are static components that are rotationally fixed with thedisk 60, and in others, thepins 68 are configured to rotate relative to thedisk 60. The number ofpins 68 and the number ofrollers 66 may be equal. Thepins 68 may be attached to theroller disk 60 so that associated ones of thepins 68 and therollers 66 have a common center point. - The
output member 30 is supported for rotation within thecentral opening 64 of theroller disk 62. In the illustrated embodiment, theoutput member 30 is a cycloidal cam. Thecycloidal cam 30 includes a plurality oflobes 70 configured to engage with theinternal rollers 66. The number oflobes 70 may be less than the number ofrollers 66. In the illustrated embodiment, thecam 30 includes eight lobes and theroller disk 60 includes nine rollers and nine pins. - The first
cycloidal drive 22 also includes aside plate 72 that is rotationally fixed to thering gear 26. Theside plate 72 may be attached to thefirst end face 38 of thehub 42 by welding, fasteners, or the like. Theside plate 72 defines acentral opening 75 providing clearance for the half shaft to connect with thecam 30 and defines a plurality ofholes 76 circumferentially arranged to receive thepins 68. A diameter of theholes 76 is larger than a diameter of thepins 68 allowing for the eccentric, cycloidal motion of theroller disk 60. Eccentric bearings may be provided between thepins 68 and theholes 76. - The first
cycloidal drive 22 is configured to have relative rotation between its various components. For example, if theside plate 72 is held stationary and thecam 30 is rotated clockwise, then theroller disk 60 will have a counterclockwise eccentric, cycloidal motion. Since theroller disk 60 is connected with thecoupling ring 50, the coupling ring will rotate counterclockwise within thering gear 26 when thecam 30 is rotated clockwise. - The second
cycloidal drive 24 includes aroller disk 90 that is received in the secondeccentric race 56 with anouter surface 92 of theroller disk 90 disposed against the secondeccentric race 56. A bearing may be disposed between theouter surface 92 and therace 56. Theroller disk 90 is supported for eccentric, cycloidal motion within thering gear 26 via thecoupling ring 50. Theroller disk 90 defines acentral opening 94 having a plurality ofinternal roller 96 circumferentially arranged around a perimeter of theopening 94. Therollers 96 may be integrally formed with thedisk 90 or may be separate components that are attached to thedisk 90. In some embodiments, theroller 96 are static components that are rotationally fixed with thedisk 90, and in others, therollers 96 are configured to rotate relative to thedisk 90. A plurality ofpins 98 are circumferentially arranged on a face of thedisk 90. Thepins 98 project from the face in an axial direction of the differential 20. Thepins 98 may be integrally formed with thedisk 90 or may be separate components that are attached to thedisk 90. In some embodiments, thepins 98 are static components that are rotationally fixed with thedisk 98, and in others, thepins 98 are configured to rotate relative to thedisk 60. The number ofpins 98 and the number ofrollers 96 may be equal. Thepins 98 may be attached to theroller disk 90 so that associated ones of thepins 98 and therollers 96 have a common center point. - The
output member 32 of the secondcycloidal drive 24 is a carrier disk. Thecarrier disk 32 is supported for rotation within thecoupling ring 50. Thecarrier disk 32 includes anouter surface 100 that is seated on thecentral race 58 of thecoupling ring 50. A bearing may be disposed between thecarrier disk 32 and thecoupling ring 50. Thecarrier disk 32 defines a plurality of circumferentially arrangedholes 102 arranged to receive thepins 98 of theroller disk 90. A diameter of theholes 102 is larger than a diameter of thepins 98 allowing for the eccentric, cycloidal motion of theroller disk 90. Eccentric bearings may be provided between thepins 98 and theholes 102. - A
cycloidal cam 104, of thesecond drive 24, is supported for rotation within thecentral opening 94 of theroller disk 90. Thecycloidal cam 104 includes a plurality oflobes 106 configured to engage with theinternal rollers 96. The number oflobes 104 may be less than the number ofrollers 96. In the illustrated embodiment, thecam 104 includes seven lobes and theroller disk 90 includes eightrollers 96 and eightpins 98. - A
side plate 108 encloses thesecond drive 24 within thehub 42. Theside plate 108 is received within the second recessedportion 46 of thehub 42 and is rotationally fixed to thering gear 26. Theside plate 108 may be attached to thehub 42 by welding, fasteners, or the like. Thecam 104 is rotationally fixed to aninner face 110 of theside plate 108. Thecam 104 may be attached to theside plate 108 by welding, fasteners, pins, or the like, or may be integrally formed with theside plate 108. Thecam 104 is attached to theside plate 108 for on-axis rotation. Both thecam 104 and theside plate 108 may define ahole 112 allowing the other half shaft to extend into the differential 20 to connect with thecarrier disk 32. - The second
cycloidal drive 24 is configured to have relative rotation between its various components. For example, if thecam 104 is held stationary and thecarrier disk 32 is rotated counterclockwise, then theroller disk 90 will have a counterclockwise eccentric, cycloidal motion. Since theroller disk 90 is connected with thecoupling ring 50, the coupling ring will rotate counterclockwise within thering gear 26 when thecarrier disk 32 is rotated counterclockwise. - In the illustrated embodiment, the first
cycloidal drive 22 is an eighth-order drive (cam 30 has eight lobes) and the secondcycloidal drive 24 is a seventh-order drive (cam 104 has seven lobes). By having one of the drives of m order and the other of m+1 order, the speed ratios between the output members are equal. While illustrated as having an eighth-order drive and a seventh-order drive, the differential 20 may have any combination of an m order drive and an m+1 order drive, where m is greater than or equal to 2. - The differential 20 is designed to have a 1:−1 speed ratio between the output members, i.e., the
output member 30 rotates clockwise if theoutput member 32 rotates counterclockwise. Various internal components of the cycloidal drives 22, 24, e.g., the roller disks and the coupling ring, are designed to rotate within thering gear 26 when theoutput members - The differential 20 is also designed to lock the first and
second drives output members second drives ring gear 26 so that theoutput members ring gear 26. - In
FIG. 4 the dashed arrows indicate would-be relative rotation between the illustrated parts—not actual relative rotation. (As will be explained below, the entire assembly is locked relative to each other and rotates in unison with the ring gear.) The differential 20 is shown with theoutput members first output member 30 is urged clockwise, theroller disk 60 is urged to have eccentric, cycloidal motion in the counterclockwise direction. Ifsecond output member 32 is also urged clockwise, theroller disk 90 is urged to have eccentric, cycloidal motion in the clockwise direction. Thus, the first andsecond roller disk coupling ring 50 prevents this causing the differential 20 to lock up, i.e., none of the individual components of the differential rotate relative to each other. Instead, all of the individual components rotate with thering gear 26. Thus, when the vehicle is driving in a straight line, thering gear 26 and theoutput members - In
FIG. 5 the solid arrows indicate actual relative rotation between the illustrated parts—not overall rotation. (The entire illustrated assembly rotates clockwise with the ring gear during driving of the vehicle.) The differential 20 is shown during cornering of the vehicle with theoutput members output member 32 is connected to the inner wheel, and theoutput member 30 is connected to the outer wheel. - During a corner, the
output member 30 is rotating faster than thering gear 26 and is inputting rotation into the differential 20. The clockwise rotation of theoutput member 30, i.e., increased angular speed, causes counterclockwise eccentric, cycloidal motion of theroller disk 60 due to rolling engagement between therollers 66 and thelobes 70. The counterclockwise eccentric, cycloidal motion of theroller disk 60 causes thecoupling ring 50 rotate counterclockwise within thehub 42. Thecoupling ring 52 causes theroller disk 90 to have a counterclockwise eccentric, cycloidal motion. Thepins 98 engage with theholes 102 to transfer motion from theroller disk 90 to thecarrier disk 32 causing theoutput member 32 to rotate in the counterclockwise direction. The counterclockwise direction of theoutput member 32 is being used as a relative term meaning that theoutput member 32 is rotating slower than thering gear 26 and theoutput member 30. In reality, both of theoutput members - This disclosure is not limited to the illustrated embodiments. The cycloidal drives of the differential can be rearranged to form other types of cycloidal differentials. Applicant's co-pending applications U.S. patent application Ser. No. ______ (Attorney Docket SCHF 0130 PUS) and U.S. patent application Ser. No. ______ (Attorney Docket SCHF 0145 PUS), filed on the same day as this disclosure, which are incorporated in their entirety by reference herein—disclose other types of cycloidal differentials.
- While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated.
Claims (20)
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US15/864,460 US10359099B1 (en) | 2018-01-08 | 2018-01-08 | Cycloidal differential |
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US15/864,460 US10359099B1 (en) | 2018-01-08 | 2018-01-08 | Cycloidal differential |
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US20190211903A1 true US20190211903A1 (en) | 2019-07-11 |
US10359099B1 US10359099B1 (en) | 2019-07-23 |
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CN113124131A (en) * | 2021-05-11 | 2021-07-16 | 温岭市绿能机电有限公司 | Speed reducing mechanism |
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EP3608558B1 (en) * | 2017-04-02 | 2023-05-10 | Zilong Ling | Cycloidal differential |
US10563729B2 (en) * | 2018-01-08 | 2020-02-18 | Schaeffler Technologies AG & Co. KG | Hyper-cycloidal differential |
JP7302578B2 (en) * | 2020-11-11 | 2023-07-04 | トヨタ自動車株式会社 | differential |
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US3499348A (en) | 1967-10-09 | 1970-03-10 | Powr Lok Corp | Locking differential |
US3791237A (en) | 1971-04-21 | 1974-02-12 | Aisin Seiki | Differential |
JP2966536B2 (en) | 1990-12-27 | 1999-10-25 | 加茂精工株式会社 | Rolling ball type differential reduction gear |
TWI223034B (en) * | 2002-08-30 | 2004-11-01 | Sumitomo Heavy Industries | Power transmission device |
US7217212B2 (en) | 2004-10-27 | 2007-05-15 | Orbiter Gears Marketing & Finance Ag | Differential gear system having a stably-oriented orbiting gear |
DE102007004710B4 (en) | 2007-01-31 | 2012-09-27 | Schaeffler Technologies Gmbh & Co. Kg | Spur gear |
US7749123B2 (en) | 2007-02-06 | 2010-07-06 | Gm Global Technology Operations, Inc. | Cycloid limited slip differential and method |
JP5374215B2 (en) | 2008-07-02 | 2013-12-25 | Ntn株式会社 | Cycloid reducer, in-wheel motor drive device, and vehicle motor drive device |
CN103542041B (en) * | 2012-07-13 | 2016-02-24 | 财团法人工业技术研究院 | Differential two-stage high-reduction-ratio cycloidal speed reducer |
EP2784347A1 (en) * | 2013-03-25 | 2014-10-01 | Spinea s.r.o. | Gearbox |
CN106461051B (en) | 2014-06-24 | 2019-03-19 | 武藏精密工业株式会社 | Differential gear |
JP2016031081A (en) | 2014-07-25 | 2016-03-07 | 武蔵精密工業株式会社 | Differential gear |
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2018
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CN113124131A (en) * | 2021-05-11 | 2021-07-16 | 温岭市绿能机电有限公司 | Speed reducing mechanism |
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