According to the preamble of claim 1, this invention relates to a power distributed transmission comprising one variator.
Transmissions of this kind comprise continuously variable friction gear variators having at least two torus discs with toroidal races between which rolling bodies roll off. Friction gear variators have, together with the continuously variable ratio, a high torque capacity.
DE 196 29 213 A1 has disclosed a transmission which can be operated in two power ranges. The essential component parts of this known friction gear transmission are a continuously variable friction gear variator having two toroidal races interacting in pairs, one countershaft and one summarizing transmission. A power distribution is provided in the lower range (LOW). The input power is conveyed by the input shaft via a reduction step to the countershaft and then to the continuously variable transmission (friction gear variator) which is connected with the summarizing transmission on the output side. Via a second power branch the input power is conveyed via the countershaft and a reduction step directly to the summarizing transmission where the power of both power branches is added up and relayed to the output shaft.
In the second power range (HIGH) of this known transmission, the input power is conveyed via a reduction step to the countershaft and then to the continuously variable transmission. Another power portion is not provided in this case.
The Applicant's DE 197 03 544 A1 has disclosed another transmission where a power distribution is provided and a continuously variable transmission, especially a transmission with toroidal races (friction gear transmission) interacting in pair, is used. This known transmission also has an intermediate shaft or countershaft to make the desired power distribution possible.
In order to improve the efficiency degree of such a transmission in the overdrive, one gear can be provided in which no power flows via the variator. This can be a direct gear; but it is also possible to achieve one other ratio which corresponds to the ratio of the variator or implements another ratio step by way of planetary gear sets or spur gear stages or belt drives or sprocket wheel drives.
From EP 1 253 350 A2 a power distributed two-range transmission of the above mentioned kind has become known in which, to increase the total degree of efficiency in the overdrive, a gear is engaged in which no power flows via the variator since the variator, as a rule, has a poorer degree of efficiency than form-locking force or torque transmitting devices. The transmission comprises one reversing toroidal variator, one summarizing transmission containing a planetary gear set and one planetary gear set serving as reversal transmission, which are consecutively disposed in this sequence in power flow direction.
To engage the overdrive gear, an additional shifting element can be provided; in two-range transmissions, the overdrive gear can be engaged by closing of the range-shifting elements.
The disadvantage results that in a multi-range transmission, where the overdrive gear is engaged by closing of the range shifting elements; stresses are produced in the transmission in case of the smallest divergences of ratio in the variator in the overdrive operation, since in the circuit closed by the two clutches, rotational speed differences generate. These stresses can lead to power losses, to overheating and also to destruction of the transmission.
The problem on which this invention is based is to outline a power distributed transmission having one overdrive gear which overcomes the above mentioned disadvantages of the prior art. Om [articular, no stresses should occur in the overdrive operation.
This problem is solved by the features of claim 1. Other developments and advantages result from the sub-claims.
A power-distributed multi-range transmission is proposed having one variator which can be designed as toroidal or friction gear variator, as band or chain variator, as cone ring transmission or as continuously variable hydrostatic transmission and having one planetary gear set which, when engaged in power flow direction before the variator serves as distribution transmission and when engaged in power flow direction behind the variator serves as summarizing transmission for the power branches comprising shifting elements (range shifting elements) which, individually engaged, respectively change the lower and the upper drive ranges; the power of the variator being conveyed to the output via a variator output transmission or a shaft disposed paraxially with the variator, and there being provided a direct or overdrive gear in which no power flows via the variator and in which the variator is uncoupled from the power flow in the direct gear or overdrive operation.
With the inventive idea stresses are easily prevented in the transmission during the overdrive operation.
According to the invention, in the power flow of the variator, a device is provided which uncouples the variator on the input or output side. The device can be a shifting element, such as a clutch, a synchronizer unit, etc.
According to an advantageous development of the invention, one free wheel is provided as an uncoupling device. It is situated on a place of the transmission which has the same direction of rotation in all driving ranges, the same as in the reverse gear, so as to ensure a reliable uncoupling of the variator. The free wheel is preferably situated in a place in the transmission which, in relation to the power flow direction, is before the devices or parts of the transmission which can produce a reversal of direction of rotation. By using a free wheel as uncoupling device, the cost and installation space requirements are advantageously reduced.
The variator can be designed as toroidal or friction gear variator (single or double cavity, that is, with one or with two toroidal disc pairs), as band or chain gear variator or also as continuously variable hydrostatic transmission.
The invention is described herebelow in detail by way of example with reference to the enclosed figures which show:
The transmission shown in
The transmission shown in
The transmission is designed as power distributed reversing transmission. A sun gear 10 of the planetary gear set 9 of the variator output transmission 2 is connected on the input side with the variator output and a ring gear 11, on the output side, with a sun gear 15 of the planetary gear set 3. In addition, a web 13 of the planetary gear set 9 is attached to a housing 14. A web 18 of the planetary gear set 3 is attachable via one brake KR to the housing and, on the input side, is connectable via the clutch K2 with an input shaft 12, a ring gear 16 being connected with an output shaft 17. Besides, the ring gear 16 is connectable via the clutch K1 and the clutch K2 with the input shaft 12; the web 18 is also connectable via the clutch K1 with the ring gear 16.
In the first range (LOW), the clutch K1 is closed and the power flows only via the variator 1, the planetary gear set 9 and the planetary gear set 3 which rotates in the block operation. In the second range (HIGH), a power distribution is provided; the clutch K2 is closed so that the power is transmitted, on one side, by the input shaft 12 to the web 18 of the planetary gear set 3 and, on the other side, by the variator 1 via the planetary gear set 9 to the sun gear 15 of the planetary gear set 3. The total power is transmitted via the ring gear 16 to the output shaft 17. To implement the reverse gear, the shifting element KR is closed.
To engage the direct gear or overdrive gear, no additional shifting element is needed; the overdrive gear is engaged by closing of the clutches K1 and K2 so that the planetary gear set rotates in the block operation driven by the input shaft 12. As is to be inferred from the Figure, one free wheel F is located in power flow direction behind the variator output and before the variator output transmission 2 to prevent stresses in the transmission in the overdrive operation.
The object of
In the transmission shown in
In the transmission shown in
The transmission shown in
According to
In the embodiment shown in
In the transmission shown in
Every constructional design, particularly every spatial arrangement of the planetary gear sets and of the shifting elements, the same as of the free wheel or related to each other and, insofar as technically significant, obviously falls under the scope of protection of the claims without influencing the function of the transmission such as stated in the claims even if said design has not been explicitly shown in the figures or in the description.
1 variator 14 housing
2 variator output transmission 15 sun gear
3 planetary gear set 16 ring gear
4 variator disc pair 17 output shaft
5 variator disc pair 18 web
6, 6′ shaft K1 clutch
7, 7′ belt or sprocket wheel drive K2 clutch
8, 8′ spur gear stage KR brake
9 planetary gear set KD clutch
10 sun gear
11 ring gear AK starting clutch
12 input shaft W converter
13 web F free wheel
Number | Date | Country | Kind |
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10 2004 004 138.5 | Jan 2004 | DE | national |