PLANET CARRIER ASSEMBLY AND METHOD

Abstract: A planet carrier assembly (20) has a pair of side plates (36) with axially aligned bores (40) in which are disposed pins (44) for rotatably supporting pinion gears (68). Each pin has a slot (48) which is alignable with a groove (50) formed in one of the side plates. A latching plate (52) has radially extending locking tabs (54) which are positionable in respective ones of the groove and slots by simultaneous rotation of the pins and latching plate about their respective axis during assembly. A spring pin or roll pin (58) is secured in an aperture in the grooved side wall and cooperates with a notch (60) in the latching plate to prevent rotation thereof relative to the side plate after assembly with the pins.

Description: This invention relates to planetary gear structures and more particularly to the planet carrier assembly of such structures, and a method of assembling the planet carrier assembly. Prior art planet carrier assemblies generally provide for one of three methods for retaining the pinion mounting pins in the carrier housing. The pins are either pressfit within the housing or retained therein by a cover held to the housing by threaded fasteners or through the use of a snap ring or locking ring (as, for example, disclosed in US-A-4,756,212). Generally with the use of a snap ring or locking ring, the carrier is manufactured to have a shoulder for reduced diameter in one portion thereof to limit the movement of the pins in one direction and the locking ring is secured in another portion of the carrier to prevent movement of the pin in the other direction. An arrangement in accordance with the preamble of claim 1 is shown in GB-A-1205009. Another common method of securing the pins in the carrier housing is to utilize a light pressfit followed by a swaging operation which offsets the ends of the pins to provide a secure assembly. While these prior art mechanisms provide useful articles, the present invention provides for a simpler assembly with less machining operations. A planet carrier assembly, and a method of assembly thereof, in accordance with the present invention are characterised over GB-A-1205009 by the features specified in the characterising portions of claims 1 and 3 respectively. The present invention provides for a planet carrier assembly wherein the side plates of the planet housing are through-bored to provide a mounting bore for the pins which are placed therein. One of the side plates has a radially extending groove which intersects a radially inward portion of the through-bore. The pin has a slot formed in a segmental portion of its cylindrical envelope. The pins are assembled in the through-bore such that the slot is aligned with but oblique to the groove in the side plate. To complete the assembly, a latching plate having a plurality of locking tabs is installed in the side plate and rotated relative to the central axis thereof to move into registration with the slot in the pins. The pins are simultaneously rotated on their individual axes to permit the complete registration of the locking tabs within the slot. The latching plate is prevented from further rotation relative to the planet carrier assembly by the installation of a roll pin in a notch formed on the latching plate and the locking tabs prevent rotation of the pins. It is therefore an object of this invention to provide an improved planet carrier assembly, wherein a planet housing has a pair of spaced side plates each having a plurality of bores formed therein, and wherein one of the side plates has an annular groove intersecting the bores, and further wherein a plurality of (pinion mounting) pins are disposed between the side plates and rotatably mounted within the bores, and also wherein each pin has a slot which is aligned with the interrupted groove and registers with a locking tab on a latching plate which is nonrotatably maintained on the side plate by a retaining member. It is another object of this invention to provide an improved method of assembling a planet carrier assembly wherein a plurality of pins each having a slot therein are installed in bores formed in the planet housing and aligned with a groove also formed in the planet housing, after which a latching plate having radially extending locking tabs is rotated with the locking tabs registering in the grooves and slots thereby preventing axial and rotary movement of the pins, and further wherein means is provided for connecting the latching plate with the planet housing to prevent relative rotation therebetween. The present invention will be described, by way of example, with reference to the following description and the accompanying drawings, in which:- Figure 1 is a cross-sectional elevational view of a portion of a planetary gear arrangement of a transmission incorporating planet carrier assemblies utilizing the present invention; Figure 2 is a view taken along line 2--2 of Figure 1; and Figure 3 is a diagrammatic representation of the interconnection occurring between the pinion pin and the latching plate. Referring to the drawings, wherein like characters represent the same or corresponding parts throughout the several views, there is seen in Figure 1 a planetary gear arrangement, generally designated 10, which includes a pair of sun gears 12 and 14, a pair of ring gears 16 and 18, and a pair of planet carrier assemblies 20 and 22. The sun gears 12 and 14 are connected with a hub 24 and sleeve shaft 26, respectively. The planet carrier assembly 20 is connected with a hub 28 and a hub 30. The hubs 24 and 28 and sleeve shaft 26 may be selectively connected with a transmission input through the use of selectively engageable friction clutch devices in a well known manner. Each of these hubs 24, and 28 and sleeve shaft 26 may also be connected with a selectively operable brake member to provide a reaction element within the planetary gear arrangement 10. The hub 30 can be connected with a brake member which is selectively engageable to establish the planet carrier assembly 20 as a reaction member within the planetary gear arrangement 10. The ring gear 16 is drivingly connected with the planet carrier assembly 22, which in turn can be connected with the transmission output shaft. The ring gear 18 is connected with a hub 32 which may be held stationary by a selectively engageable brake, not shown. The operation of planetary gear arrangement 10 is well known and such gear arrangements have been utilized in commercially available transmissions. Through the judicious selection of clutches and brakes, the planetary gear arrangement 10 is operable to provide four forward speed ratios, a neutral condition and a reverse speed ratio between a prime mover, such as an internal combustion engine and a vehicle final drive mechanism. The operation of such planetary gear arrangements is well known and it is not believed that a description is necessary at this point for a full understanding of the present invention. The present invention is concerned with the planet carrier assemblies 20 and 22 and in particular, the assembly of pins and gears within the planet carrier assemblies 20 and 22. The planet carrier assembly 20 includes a planet housing 34 having a pair of side plates 36 and 38. The side plates 36 and 38 are interconnected and generally manufactured as a single casting. The side plate 36 has a plurality of bores 40 and the side plate 38 has a plurality of bores 42. These bores 40 and 42 are axially aligned in pairs and each pair of bores 40 and 42 has disposed therein a pin 44. As seen in Figure 2, there may be four such pins 44 distributed substantially equiangularly in the planet housing 34. The pins 44 are sized to have a sliding fit within the bores 40 and 42 and each pin 44 has formed therein a drive opening 46. Each pin 44 also has formed therein a slot 48. As best seen in Figures 2 and 3, the slot 48 removes only a segment of the cylindrical material of the pin 44 laterally inward of end 49 and is in the form of a segmental groove. The side plate 36 has an annular groove or slot 50 formed therein which will be aligned with each slot 48 when the pins 44 are assembled within the side plate 36. A latching plate or locking plate 52 has a plurality of locking tabs 54 which are aligned in the annular groove 50 and the slots 48. As seen in Figure 1, the locking tabs 54 will be effective to prevent longitudinal movement of the pin 44 along its rotary axis, and as seen in Figure 2, the interaction between the locking tab 54 and slot 48 will prevent rotation of the pin 44 about its rotary axis. The side plate 36 has a plurality of circumferentially extending openings 56 formed therein at a radius A from the centre of the side plate 36 which interrupt the annular groove 50. The outer surface of locking tabs 54 have a maximum radius B which is less than the radius A of circumferentially extending openings 56. To assemble the latching plate 52 and the side plate 36, the locking tabs 54 are axially aligned with the circumferentially extending openings 56 and the latching plate 52 is moved longitudinally until the locking tabs 54 align with the annular groove 50. At this point, the pins 44 have been assembled within their respective bores 40, 42. As seen in Figure 3, the pins 44 are rotatably positioned so that the slot 48 is skewed to the outer surface of locking tab 54 and also to the annular groove 50. To complete the assembly of the locking tab 54 in the slot 48, the latching plate 52 is rotated about its axis in the direction of Arrow C while the pins 44 are simultaneously rotated about their axis in the direction of Arrow D. As the pins 44 are rotated in the direction of Arrow D, the slot 48 will be fully aligned with the annular groove 50 and the locking tab 54. By establishing the depth of slot 48 and the radius B of locking tab 54, it is possible to utilize the registration of the pins 44 and latching plate 52 to prevent the rotation of the pins 44 about their axis. It is likewise possible to prevent the rotation of latching plate 52 about its axis. However, since the two members can be rotated into engagement, it stands to reason they can be rotated out of engagement. To prevent this from accordingly occurring, a roll pin or spring pin 58 is secured in an aperture formed in the side plate 36 in overlapping relationship with a notch 60 formed in the latching plate 52. Thus, the latching plate 52 will not rotate relative to the side plate 36. As seen in Figure 2, there are a plurality of notches 60 such that orientation of any particular locking tab 54 of the latching plate 52 is not critical during assembly. The latching plate 52 also has a plurality of notches 64 which are formed facing radially inward such that in some assemblies, the roll pin 58 could be placed in an aperture radially inward from the locking tab 54, depending on the design of the side plates 36. Both sets of notches 60 and 64 are not required since only one roll pin is needed to establish the relative angular positions of the latching plate 52 and planet housing 34. The pins 44 each have a roller bearing 66 and pinion gear 68 mounted thereon. The pinion gears 68 are components of the planet carrier assembly 20 and establish an intermeshing relationship between the sun gear 12 and the ring gear 16 in a well known manner. The planet carrier assembly 22 includes a planet housing having a pair of side plates 72 and 74 which provide a structure similar to that described above for side plates 36 and 38. The side plate 72 has an annular groove 76 in which is disposed a latching or locking plate 78. The latching plate 78 has locking tabs 80 which engage respective ones of a plurality of pins 82 which are rotatably mounted in bores 84 and 86 formed in the side plates 72 and 74, respectively. Each pin 82 has formed therein a slot 88 which cooperates with the locking tab 80 in the same manner as described above for locking tab 54 and slot 48. The pins 82 each have disposed thereon a roller bearing 90 and pinion gear 92. Each pinion gear 92 meshes with the sun gear 14 and ring gear 18 in a well known manner. The assembly of the pins 82 and latching plate 78 are similar to that described above for pins 44 and latching plate 52. It should now be apparent that the assembly of the planet carrier with the pins and gears is accomplished very simply and easily. It does not require staking operations or the insertion of snap rings, such as required by the prior art. The only pressing operation required is the pressfit between the roll pin 58 and the side plate 36. This operation does not require the use of heavy equipment such as that required to pressfit pinion pins into the carrier side plates or the heavy equipment necessary for a staking operation. The side plates are through-bored to form the bores 40 and 42 or 84 and 86. This is a much simpler machining operation than the use of a step bore. As described above, the step bore is used by the prior art to locate one end of the (pinion) pins. Also, the (pinion) pins in the present invention, being a single diameter cylinder, can be finish machined on a centreless grinder without the use of specially designed grinding wheels. In the prior art, wherein a stepped or shouldered pinion is utilized, special grinding operations are required.

Claims: A planet carrier assembly comprising a pair of spaced side plates (36,38,72,74); pins (44,82) extending between the side plates (36,38,72,74); gear means (68,92) supported on each pin (44,82); a plurality of pairs of bores (40,42,84,86) axially aligned in the side plates (36,38,72,74) and which are equally radially and circumferentially spaced thereon, one of the pins (44,82) being disposed in each pair of bores (40,42,84,86); a slot (48,88) being formed in each pin (44,82); and a latching plate (52,78) having a plurality of locking tabs (54,80), the locking tabs (54,80) being registerable with respective ones of the slots (48,88) in the pins (44,82) and cooperating with the slots (48,88) for preventing axial and rotary movement of the pins (44,82) relative to the side plates (36,38,72,74); characterised in that one of the side plates (36,72) has an inner periphery with an annular groove (50,76) formed therein and facing radially inward, and a plurality of circumferentially extending openings (56) for permitting access to the annular groove (50,76) in an axial direction; in that the bores (40,84) in the said one side plate (36,72) intersect the annular groove (50,76); in that the slot (48,88) in each pin (44,82) is alignable with the annular groove (50,76); in that the latching plate (52,78) has an outer periphery less than the inner periphery of the said one side plate (36,72); in that the circumferentially extending openings (56) are adapted to be axially aligned with the locking tabs (54,80); and in that the locking tabs (54,80) extend radially outward from the periphery of the latching plate (52,78) and each have an outer arcuate dimension (B) substantially equal to the outermost radial dimension (A) of the annular groove (50,76) to allow cooperation with the annular groove (50,76). A planet carrier assembly as claimed in claim 1, wherein the slot (48,88) in each pin (44,82) is in the form of a segmental groove; and further comprising retaining means (58) secured to the one side plate (36,72) and registering in a notch (60,64) in the latching plate (52,78) for limiting relative rotary motion between the latching plate (52,78) and the one side plate (36,72). A method of assembling a planet carrier assembly (20,22) according to claim 2, wherein retaining means (58) are finally inserted in one of the side plates (36,72) for connecting the latching plate (52,78) with the side plate (36,72) in a manner to prevent relative rotation therebetween; the method being characterised by aligning the latching plate (52,78) with the locking tabs (54,80) in the circumferentially extending openings (56) and coplanar with respective ones of the slots (48,88) and the annular groove (50,76) and being disposed adjacent the pins (44,82); positioning the pins (44,82) to establish the slots (48,88) in facing relation with the respective locking tabs (54,80); and simultaneously rotating the pins (44,82) on their respective axes and the latching plate (52,78) on its axis to register the locking tabs (54,80) in the slots (48,88) and the annular groove (50,76).

Inventors: LEGGAT, ANGUS BRUCE
Applicants: GENERAL MOTORS CORPORATION
Application year: 1989
Main classification: F16H57
IPC codes: F16H57, F16H1