Multiple-speed transmission for motor vehicles

A multiple-speed transmission for motor vehicles has a main transmission and a planetary design range change group rear-mounted thereon. The multiple-speed transmission has a synchronizer assembly situated upon an output shaft of the main transmission which is, at the same time, the input shaft of the range change group. The synchronizer assembly is locked either against a rotation relative to a sun gear to create a reduction ratio between the input shaft to the planetary transmission and the output shaft of the planetary transmission or against a rotation relative to the planet carrier, and thus to the output shaft of the planetary transmission, to create a direct drive between the input shaft to the planetary transmission and the output shaft of the planetary transmission.

BACKGROUND OF THE INVENTION
 This invention relates to a multiple-speed transmission for motor vehicles
 having one main transmission and one range change group of planetary
 design rear-mounted thereon and having a synchronizer unit situated on the
 output shaft of the main transmission which, at the same time, is the
 input shaft of the range change group.
 Multiple-speed transmission for industrial vehicles cannot be built with
 adjacently disposed gear pairs, since one such known transmission made so
 long has a strong bending of the shaft under load and a poor contact
 pattern of the gears. Therefore, with more than six gears the
 transmissions are usually designed in multi-group construction, i.e. to
 the main transmission is attached a front-mounted or rear-mounted group
 which can also be integrated in the main transmission. A differentiation
 has to be made here between a split and a range change group.
 The split group doubles the number of gears, i.e. in a four-gear
 counter-shaft transmission as a main transmission, the ratio range in the
 center is halved. This results in eight fine gear gradations in the total
 range of ratios.
 The range change group is rear-mounted, short, one-step planetary
 transmission which, nevertheless, does not concentrate but lengthens the
 gear sequence. This means that the first gear step of the range change
 group to be engaged attaches itself to the directly driving step of the
 last step of the main transmission. This is obtained by the speed ratio
 change of the range change group being higher than the total ratio change
 in the main transmission. Combined with a front-mounted split group and a
 main transmission, a transmission with sixteen gears can thus be
 implemented. Such a transmission satisfies all requirements the same as
 the economical use of heavy industrial vehicles in street traffic. The
 already known multiple group transmissions of this design have a high
 mechanical, total ratio of about 10 to 17.5.
 DE-A 31 29 414 has disclosed a planetary wheels reversing transmission for
 a continuously adjustable, traction roller transmission of a motor vehicle
 having a planetary wheel transmission disposed coaxially relative to the
 input shaft and to the primary shaft of the traction roller transmission,
 which surrounds it as hollow shaft and having its input element connected
 with the input shaft and its output element with the primary shaft. Two
 additional components for shifting a forward and a reverse gear range can
 be fastened by a brake or by a clutch, an idle or neutral range being
 shifted when the devices are loosened. In a planet gear carrier provided
 as input element and having two intermeshed planetary gear sets of which,
 one is meshed with the sun gear provided as an output element and the
 other with the ring gear provided as a reaction element, the ring gear is
 used in its periphery as synchronizer hub for a synchronizer sleeve which,
 on one side, interacts via a synchronizer ring with a synchronizer taper
 ring non-rotatably fasted on the transmission cover or via a synchronizer
 ring with a synchronizer taper disc built on the planet gear carrier.
 This known transmission has a small installation space and a low
 construction cost for its control; the hollow gear serves, in addition, as
 a clutch carrier with the interacting synchronizer taper segment and the
 shift sleeve, wherein it is laterally settled as a disc part and axially
 retained by means of two thrust washers against the web and transmission
 cover. This known transmission has an upper synchronous assembly position
 with an axially fixed ring gear, a reduction of shift jerks being obtained
 by intercalated synchronizer rings.
 EP-PS 239 555 has disclosed a planetary transmission having an axially
 movable ring gear, which is also designed as a sliding sleeve and has, on
 the ends, meshing teeth which converge toward inner teeth which mesh with
 the planetary gears. The meshing teeth interact in an axial direction with
 a clutch body, the synchronizer rings are provided with outer locking
 teeth and friction surfaces which grind as tapered segments on the clutch
 body. By means of a spring device, outer teeth of the synchronizer rings
 are under spring tension against the outer gearing of the synchronizer
 ring. Thereby resulting in an angular play of tooth width in the
 tangential direction. The spring device in the inner gearing of the ring
 gear produces an abutting position of the synchronizer rings, i.e. an
 angular movement relative to the ring gear. To obtain a compact design, an
 upper synchronous assembly position is provided, wherein the ring gear is
 axially movable and drafted as a shift sleeve while the locking takes
 place via tangentially disposed spring devices in the ring gear.
 EP-PS 423 863 finally describes a transmission in which an axially movable
 ring gear is, at the same time, designed as a sliding sleeve, thus, ends
 having on the inner gearing, meshing teeth, which converge toward inner
 teeth which mesh with the planetary gears. The meshing teeth can mesh in
 an axial direction with the clutch body; synchronizer rings with outer
 locking teeth and friction surfaces which grind as tapered segments on the
 clutch body are provided with outer bolts. The outer gearing of the
 synchronizer ring presses, via a spring device upon a bolt; an the angular
 play, in the tangential direction of the synchronizer ring, amounts to the
 width of a tooth.
 A spring device lies in recesses on the axial ends of the ring gear, the
 locking body pressing upon the synchronizer ring from outside. Here is
 also obtained a compact design by an upper synchronous assembly position
 with axially movable ring gear drawn up as a shift sleeve. Likewise, the
 locking takes place via radially disposed spring devices in the ring gear.
 The problem on which this invention is based is to provide a multiple-speed
 transmission for motor vehicles having a main transmission and
 rear-mounted thereon a range change group of planetary design, wherein the
 range change group has a one-step planet drive with a high ratio, the two
 gears of which can be shifted by means of a synchronizer unit and which
 makes possible a short shifting time, a quick unlocking, extensively
 reduced grinding, considerably less meshing hindrances and elimination of
 transmission noises.
 SUMMARY OF THE INVENTION
 According to the invention, therefore, it is proposed that a one-step
 planetary transmission be rear-mounted on the main transmission, wherein
 the output shaft of the main transmission forms at the same time the input
 shaft of the planetary transmission upon which a synchronizer unit is
 provided which can be locked either against a rotation relative to the sun
 gear of the planetary transmission to create a reduction ratio between the
 input shaft and the output shaft of the planetary transmission or against
 a rotation relative to the planet carrier and thus to the output shaft of
 the planetary transmission to create a direct input between the shafts.
 The transmission, according to the invention, has the advantage of small
 mass, inertia torque and of small drag torque, since the ring gear in both
 shifting positions is firmly connected with the housing. Thereby also
 fewer rotary parts are needed with a simultaneous reduction of the
 shifting forces. The dimensions of the synchronizer unit can be reduced in
 comparison to the convention transmission; in quick travel a direct torque
 and power flow occur, since planet gears and sun gear rotate free of
 torque. A surface flattening of the gearing is also prevented.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 In the partial section shown in FIG. 1, housing 9 is designated the rear
 section of a housing for a main transmission on which a flange 10 of an
 open housing 8 of a range change group is screwed on in planetary design.
 The rear end wall 11 of the housing 9 thus forms, at the same time, the
 front end wall of the housing 8 of the range change group.
 The main transmission has an output shaft 2 which extends into the housing
 8 of the range change group and forms, at the same time, the input shaft
 of said range change group; the planetary transmission 12 of the range
 change group has an output shaft 4 provided with a flange for connection
 with the input shaft of the vehicle.
 The planetary transmission 12 comprises a sun gear, which meshes with
 planet gears 6, supported in a planet carrier 5 and fastened on spindle
 shafts 13 which are carried by the planet carrier 5, the planet carrier
 forming the output shaft. The planetary gears 6 mesh with the ring gear of
 a ring gear 7 which, in every shifting position, is firmly connected by
 means of an outer gearing 14 with the housing 8.
 To shift the range change group now involves a synchronizer unit (assembly)
 1 which is situated on the side of the out put shaft 2. In the position,
 shown in the drawing of the sliding sleeve 15 with inner clutch teeth 16,
 the former gets to mesh with the out put shaft 2, via corresponding teeth
 on the latter. The sliding sleeve 15 is axially movable and shifts in one
 direction the inner tapered segment synchronizer unit 17, 18 and in an
 opposite direction the outer tapered segment synchronizer unit 19, 20.
 The sun gear 3 is built on the side of the out put shaft 2 as clutch body
 17 with tapered segment upon which grinds the synchronizer ring 18 which,
 on one side, is to a limited extent rotatable relative to the sun gear 3
 and, on the other side, has outer locking teeth 18a.
 During the gear shift movement, the axial displacement of the sliding
 sleeve 15 and the coupling with the clutch body 17,19 concerned are locked
 until reaching the synchronous movement. For this purpose at the end of
 each synchronizer ring 18, 20, a recess is placed in which the locking
 bodies 22, 23 are disposed in the form of ring springs which act radially
 inwardly upon the synchronizer ring 18 or radially outwardly upon the
 synchronizer ring 20 and thus transmit the axial force of the sliding
 sleeve 15 via a radial spline 24, 25 of the gearing 16, 21 to the
 synchronizer rings 18, 20 and, in this manner, a contact is produced
 between the friction surfaces (tapered segments) of the synchronizer rings
 18, 20 and of the clutch bodies 17,19.
 If the inner gearing 16 of the sliding sleeve 15 is connected with the
 clutch dogs via the gearing 17a, 18a of the synchronizer ring 18 and of
 the clutch 17, the rotational speed of the output shaft 4 is changed to
 the speed reduction ratio.
 The clutch body 19 is firmly connected with the planet carrier 4, via an
 outer gearing. If the outer gearing 21 of the shift sleeve 15 is connected
 via the gearing 19a, 20a of the synchronizer ring 20 and of the clutch
 body 19, then the output shaft 4 is driven with direct ratio, i.e. i=1.0.
 REFERENCE NUMERAL
 1 synchronizer unit
 2 output shaft
 3 sun gear
 4 output shaft
 5 planet carrier
 6 planetary gear
 7 ring gear
 8 housing
 9 housing
 10 flange
 11 end wall
 12 planetary transmission
 13 spindle shaft
 14 outer gearing
 15 sliding sleeve
 16 clutch teeth
 17 inner taper segment synchronizer unit
 18 inner taper segment synchronizer unit
 19 outer taper segment synchronizer unit
 20 outer taper segment synchronizer
 21 gearing
 22 locking body
 23 locking body
 24 spline
 25 spline