Patent Application
20080116030
This application claims priority from German Application Serial No. 10 2006 050 010.5 filed Oct. 24, 2006.
The invention relates to a gear brake device for a multi-speed manual transmission.
Modern manual transmissions are generally designed in such a way that a plurality of gear wheels fixedly arranged on a drive shaft continuously mesh with freely rotatable gear wheels that are respectively assigned to them and are arranged on a second drive shaft. In order to engage a gear, one of the idlers is rotationally coupled with the assigned drive shaft so that the drive torque of the first drive shaft is transferred to the second drive shaft and from there, ultimately, to a transmission output shaft.
In order to have shock-free, noiseless and low-wear shifting when engaging a gear, it must be ensured that the idler to be coupled and the assigned transmission shaft have at least approximately the same speed. For this kind of speed synchronization, small dimension friction couplings can be used inside the transmission, which, before engaging, frictionally mesh by positive locking coupling devices, thus adjusting the two different speeds to each other.
In another synchronization process, the input side drive shaft, which carries either the fixed wheels or the idlers, is brought to a speed, either through acceleration, by way of the drive engine, or by braking using a gear brake, at which the speeds of the idler to be coupled and assigned gear shaft are essentially equal, so that in this way synchronization is possible without friction clutches.
By definition, in the present invention the gear shafts that can be connected to the drive engine of a motor vehicle, via the input clutch or the drive clutch, are subsumed under the terms “input side gear shaft arrangement”, while the shafts that are permanently connected to the drive gears are designated as “output side shafts” in the present invention.
As is generally known, in order to shift into a lower gear, the input gear shaft arrangement must be brought to a higher rotational speed. This is achieved in that after disengaging the previous gear, the starting clutch is engaged, and the engine speed is increased, via an engine control unit, until the speed required for engaging the positive locking clutch is reached. In order to upshift, the speed of the input gear shaft arrangement must be reduced. This is achieved in that after disengaging the previous gear, the input gear shaft arrangement is braked using a gear brake that acts on one of the gear shafts until the speed required for engaging the clutch is reached.
Conventional manual transmissions comprise an input shaft that is connected to the drive engine via a drive clutch; a countershaft that is connected to it, via a fixed gear wheel connection, which carries a plurality of fixed gears, and a drive-coupled output shaft that is permanently connected with the drive wheels of the vehicle. The idlers assigned to the fixed gears wheels are arranged on the output shaft, the idlers being individually connectable in a rotationally fixed manner with the output shaft in the way described above. In addition, manual transmissions with two countershafts are also known, which allow a particularly short manual transmission design. The present invention is exemplified on the basis of this type of manual transmission where it should be pointed out that the invention is applicable analogously to other transmission designs.
Synchronization by way of the drive engine or by way of a gear brake is applicable in a simple manner particularly to automatic transmissions that already have an engine control unit and transmission control. However, the functional principle can also be applied to manually shifted transmissions.
In general, gear brakes are designed solely for their synchronization function. However, it has been demonstrated that the possibilities of a gear brake are by no means exhausted by the synchronization function. A process is known from DE 10 2004 045 828 A1, by way of which the function of a gear brake can be considerably expanded. According to this process, the use of the gear brake control and regulation goes beyond transmission synchronization without, or as the case may be, with only minimal additional hardware, in order to implement additional drive chain-relevant functions. The additional functions concern the comfort and speed of shifting operations, protection against or identification of error status in sensors, drive clutch, or engine control, as well as avoiding undesirable transmission conditions.
Regarding the possibilities of expanding the functions of a gear brake device, which is also the subject matter of the present invention, express reference is made to DE 10 2004 045 828 A1, the entire disclosure of which is incorporated herein by reference. In order for the gear brake to perform the additional functions effectively and quickly, the design of the gear brake for a braking torque that enables the performance of the additional functions is provided, where this braking torque will, in general, be higher than the braking torque required for the mere synchronization function. For speed synchronization when upshifting the manual transmission, this braking torque is too high as a rule and should, therefore, be controlled though electric impulse modulation. In the case of functional variations in which the additional functions described in the above mentioned document are not required, the gear brake would obviously be over-dimensioned. This would mean that the gear brake would need to produce only part of its potential braking torque for the by far most frequently occurring applications.
Against this background, the task of the present invention is to provide a gear braking device for a multi-speed manual transmission in which, despite the possibility of performing other functions, in addition to the synchronization function, over-dimensioning of the gear brake is avoided.
The present invention is based on the knowledge that the total construction and design complexity can be minimized, compared to known transmission brake devices, if the construction and design complexity serving the numerically most frequent synchronization function can be kept to a minimum.
The aim of the present invention is, therefore, a gear brake device for a multi-speed manual transmission that comprises a gear brake assigned to an input gear shaft arrangement; the gear brake being controlled by a transmission control.
In order to achieve this, it is provided that in addition to a first gear brake designed for a synchronization function, at least a further gear brake, which acts on a gear element, which is drive connected and/or can be drive connected to the auxiliary brake that is controllable by the transmission control, independently of the first gear brake.
The auxiliary brake is designed so that it can perform certain auxiliary functions alone or together with the first gear brake. Depending on the provided auxiliary functions, it can have a greater braking torque than the first transmission brake.
In an embodiment of the present invention, apart from the first gear brake, an auxiliary brake is provided inside the transmission housing. In terms of construction and design, it can be completely integrated into the transmission, so that there is no additional assembly effort, nor is a separate auxiliary brake housing required.
According to a further embodiment of the present invention, the first gear brake and the auxiliary brake can act jointly on a gear shaft on a countershaft of the type of manual transmission described above.
The first gear brake and the auxiliary brake can consist of a single two-stage brake arrangement which, when operated, first meshes with the first gear brake and subsequently with the auxiliary brake.
Another embodiment of the present invention provides that the first gear brake and the auxiliary brake act respectively on different gear shafts of the input gear shaft arrangement. Thus, in cases where the transmission has two countershafts, it is provided that the first gear brake acts on one of the countershafts and the auxiliary brake on the other countershaft, such that better load distribution is simultaneously achieved and reinforcement of a countershaft that would have to absorb the braking force of two brakes, is avoided.
A further embodiment of the present invention for a transmission with at least one power take-off shaft external to the transmission, which is drive-connected with the input gear shaft arrangement or can alternatively be drive-connected and provides that at least one auxiliary brake acts on one of the powertake-off shafts. Powertake-off shafts serve to drive auxiliary equipment and are permanently drive-connected with the input gear shaft arrangement or, as in the case of utility vehicles or agricultural vehicles, they serve to drive attached devices, such as hydraulic equipment, which are generally drive-connected with the gear shaft arrangement via clutches. By way of one or a plurality of auxiliary brakes acting on power take-off shafts, the speed of the gear shaft arrangement can also be braked in cases where large rotating masses are driven by way of the power take-off shafts, the masses, after being driven, rotating for a period lasting too long for a shifting operation when unbraked.
A further embodiment of the present invention provides that the first gear brake and further additional auxiliary brake(s) can be actuated consecutively. This means that the gear brake is always actuated first and that at least one auxiliary brake is activated only after the braking force of the gear brake has been determined to be insufficient.
Another embodiment provides that a first gear brake or further auxiliary brake(s) can be actuated simultaneously, the combined braking force being controlled or regulated by the transmission control, both with regard to strength and length of application.
The invention will now be described, by way of example, with reference to the accompanying drawings in which:
According to the present invention, an auxiliary brake 16 is also provided inside the transmission housing 12 and also interacts with a gear shaft of the input gear shaft arrangement when the brake is actuated. As described above, if the transmission has two countershafts, in order to distribute the braking load, the gear brake can interact with one countershaft and the auxiliary brake can interact with the other countershaft.
As
| Number | Date | Country | Kind |
|---|---|---|---|
| 102006050010.5 | Oct 2006 | DE | national |
