Multiple-speed transmission for motor vehicles

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] The invention is described herebelow in further detail with reference to the drawing where advantageous embodiments are diagrammatically shown. In the drawings:

[0015] FIG. 1 is a partial section through a transmission having rear-mounted range change group and synchronizer unit; and

[0016] FIG. 2 is an enlarged sectional representation of the synchronizer unit.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] If the inner gearing 16 of the sliding sleeve 15 is connected with the clutch dogs via the gearing 17a, 18aof the synchronizer ring 18 and of the clutch 17, the rotational speed of the output shaft 4 is changed to the speed reduction ratio.

[0024] 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, 20aof 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.

[0025] 1 synchronizer unit

[0026] 2 output shaft

[0027] 3 sun gear

[0028] 4 output shaft

[0029] 5 planet carrier

[0030] 6 planetary gear

[0031] 7 ring gear

[0032] 8 housing

[0033] 9 housing

[0034] 10 flange

[0035] 11 end wall

[0036] 12 planetary transmission

[0037] 13 spindle shaft

[0038] 14 outer gearing

[0039] 15 sliding sleeve

[0040] 16 clutch teeth

[0041] 17 inner taper segment synchronizer unit

[0042] 18 inner taper segment synchronizer unit

[0043] 19 outer taper segment synchronizer unit

[0044] 20 outer taper segment synchronizer

[0045] 21 gearing

[0046] 22 locking body

[0047] 23 locking body

[0048] 24 spline

[0049] 25 spline