Multi-speed gearbox, in particular a six-speed gearbox

Details Multi-speed gearbox, in particular a six-speed gearbox Multi-speed gearbox, in particular a six-speed gearbox

2001-03-26

2003-02-25

Wright, Dirk (Department: 3681)

Planetary gear transmission systems or components

Fluid drive or control of planetary gearing

Fluid resistance inhibits relative rotation

Reexamination Certificate

active

06524208

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-speed gearbox, and in particular, a six-speed gearbox for use with automatic transmissions.
2. Description of the Related Art
Multi-speed gearboxes in the form of automatic transmissions are known in a plurality of designs based primarily on a mechanical gearbox portion associated with an appropriate starting element. In particular, hydraulic torque converters or hydraulic couplings are used as starting elements in vehicle construction. The operating range of the hydraulic components is limited thereby primarily to the starting range. Gearbox designs are also possible with division of power in which, during the transmission of power the hydraulic component is used in the lower gears.
Automatic transmissions with starting elements in the form of hydraulic speed/torque converters are known, e.g., from Voith: “Hydrodynamics in Drive Technology”, Engineer Digest, Vereinigte Fachverlage Krausskopf-Verlag. Hydraulic torque converters can be divided into so-called converter gearboxes and differential converter gearboxes.
Converter gearboxes include all gearboxes in which a converter is connected to additional mechanical elements in order to bring about a change or expansion of the operating range of the gearbox. The converter can remain filled thereby during operation of the mechanical gear steps or can also be bridged filled or emptied. If the converter is placed into an outer power branch, it then no longer participates in the transmission of power in the mechanical gear steps and can remain filled.
Differential converter gearboxes are gearboxes with power branching in which the power flow is divided into a hydraulic branch and into a mechanical branch. A distinction can be made thereby between inner and outer power branching. A planetary gear set, as a rule a differential, can be combined, e.g., with a torque converter in such a manner that one element is connected to the pump impeller of the converter, the second element of the planetary gear set is connected to the drive shaft and the third element to the driven shaft. As the output speed increases, the hydraulically transmitted power component is reduced on account of the action of the differential whereas the mechanically transmitted component increases. This results in a higher degree of total efficiency for the gearbox than is the case for a purely hydraulic transmission of energy. Finally, the hydraulic converter is automatically bridged approximately at the operating point of its best efficiency and the power is transmitted purely mechanically.
A disadvantage of converter gearboxes is essentially the fact that the range which can be used for driving and which represents a certain translation ratio can only be achieved with relatively large converter units, which require a significant amount of space and are very expensive. All previously known solutions for planetary coupling gearboxes for bus gearboxes are characterized by translations which require a torque converter as an additional gear. These gearboxes can not be readily used because the first gear is always constituted by an individual planetary gear set for which the translation can not be increased further. A further disadvantage is the fact that the hydraulic converter is not self-regulating. It must therefore be adapted to each drive machine by changing the pump impeller and/or turbine and the differential.
SUMMARY OF THE INVENTION
The invention therefore has the basic problem of developing a gearbox unit of the initially cited type further in such a manner that the disadvantages cited are avoided. Specifically, a solution which is simple in design and can be realized with low expense for control technology is to be developed which makes it possible to realize a simple adaptation to various requirements, especially to drive engines, without significant additional expense.
According to the invention, in order to realize a multispeed gearbox the hydraulic converter is eliminated, such that the translation achievable with the converter is realized in a more cost-advantageous manner and with less complexity regarding the required construction space of an additional gear. This means that the mechanical gearbox portion is expanded by an additional gear. Another planetary gear set is preferably used to this end. The starting then takes place with a braking device for one of the gearbox elements of the planetary gear sets, preferably the ring gear, in which instance the braking device must be dimensioned as an inch brake. The dynamic viscosity of the oil forms the basis for this. The solution in accordance with the invention has the advantage of simpler control, since no centrifugal forces have to be compensated. Moreover, the braking device always cooperates during starting with the lowest engine speed, which speed can not be achieved with a converter. This results in a reduction of the fuel consumption.
There is a plurality of possibilities for the design of the gearbox. However, there is always a mechanical gearbox portion, which consists of a plurality of spur gear sets or planetary gear sets, as well as another mechanical gearbox set which is associated with an inch device, either in the form of an inch brake or an inch coupling.
The use of a so-called inch brake or also inch coupling offers yet another advantage over a hydraulic converter, namely, the possibility of remote control. An inch brake is preferably constructed with laminar design. The torque of an inch brake is controlled with the modulated oil pressure for the lamination pressure. As a result, the gearbox can be adapted to different engines and vehicle masses over a wide range exclusively by software.
The construction space is reduced in its axial length by using the inch device since large hydraulic converters can be eliminated. The mounting length could therefore be shortened for the entire gearbox or the gearbox could also be designed as a housing variant. The control for the shifting devices and the inch device can be placed above in mounting position. This means a simpler and more economical design than the previously known design for hydraulic converters with oil sump.
An inch device, preferably in the form of a multiple disk brake device, is used in the gearbox which device is also a shifting brake for the first gear and the reverse gear at the same time. The outer laminations are surrounded by an annular chamber. The latter is filled with oil during starting so that the laminations run fully in the oil. The oil exits at the inner diameter and flows from there into the oil sump. The oil inflow into the annular chamber is controlled with a magnet valve in the central control block of the gearbox. In the case of flooded laminations the torque is transmitted only by the shearing force of the oil. The laminations do not touch each other thereby. This can be calculated with the formula for the dynamic viscosity of the oil:
Vis
=(N×s/m
2
)
or also, unshortened,
Vis
=N×m/(m/s'm
2
)
in which
Vis=The viscosity of the oil at the instantaneous temperature
N (Newton)=The circumferential force on the laminations
m (m)=The oil slot between the laminations
m/s (m/s)=The average circumferential speed of the laminations
m
2
(m
2
)=The entire lining surface moistened in the oil slot.
The product of N×Rm (Nm) is then the torque transmitted by the brake. Rm indicates the average lamination radius.
During starting the greatest circumferential speed is present right at the beginning. This speed becomes smaller and smaller as the travel speed increases, so that the slot for constant torque must also become smaller and smaller until the lining contacts the counterlamination. Then, the outer oil is cut off and the laminations function just as in the other multiple disk brakes in the gearbox. The described property of the oil is also used in converter-inch couplings, in large control couplings, in wheel brakes in large construction machines, in VISCO coupl

Affiliated with

Also associated with

Rating

Multi-speed gearbox, in particular a six-speed gearbox does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Multi-speed gearbox, in particular a six-speed gearbox, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-speed gearbox, in particular a six-speed gearbox will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3135681