Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
2002-07-25
2004-10-05
Lewis, Tisha (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C074S337500
Reexamination Certificate
active
06799484
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns an actuating apparatus for an automatic multiple-ratio transmission of a motor vehicle. The term “multiple-ratio transmission” is understood hereinafter to mean both automated gear-shifting transmissions, for example non-on-load-shiftable automated manual gear-shifting transmissions, and automatically on-load-shiftable double-clutch transmissions.
BACKGROUND OF THE INVENTION
Actuating apparatuses having shifter drums have already been used for some time in the field of motorcycles, since a particularly favorable coupling between a force actuation system and an implemented shifting logic is provided here by means of shifter drums. For engaging and disengaging ratios of the transmission, it is usual to use a shifter drum that has a circumferential track in which an axially displaceable guide element is guided, and that can have a defined rotary motion imparted to it by way of a foot lever with an associated pawl device.
Known shifter drums that have guides—usually in the form of grooves with pins, which sit on the corresponding selector rods or shift forks of the transmission and move them, running in them—are usually used in practice where simple actuation upon shifting is desired, e.g. in the context of a motorcycle, where only sequential shifting into the next gear is performed.
Since there are limited possibilities for implementing a logic for shifting ratios by the application of corresponding guides on the shifter drum and by transferring shifting force from an energy source to the shifting point, actuating apparatuses having shifter drums have hitherto been utilized in four-wheeled vehicles principally in racing.
Since shifter drums have the advantage, as components of actuating apparatuses, that they can easily be electrically motor-driven, and require considerably less complexity as compared to hydraulic shifting apparatuses with their requisite hydraulic circuits, efforts have recently become apparent to transfer the principle of an actuating apparatus with a shifter drum in particular to passenger cars having an automatic gear-shifting transmission. A purely sequential shifting capability as in the case of a motorcycle cannot be imposed in the context of a car, however, because of the unavoidable driver convenience drawbacks that necessarily result therefrom. To allow shifter drum technology also be used in an automated gear-shifting transmission, appropriate modifications to the shifter drums must be made.
DE 195 16 651 A1 describes a gear-shifting transmission, in particular for motor vehicles, in which the individual gear ratios are selected sequentially by the rotation of a shifter drum. The shift forks of the gear-shifting transmission are guided on the shifter drum, thereby eliminating the selector rods. Decoupling of the shift forks from the positive control system of the shifter drum means that the constrained sequence for selection of the individual gears can be eliminated.
DE 199 24 335 A1 furthermore discloses an actuating apparatus for a multiple-ratio transmission of a motor vehicle which has a shifter drum with a circumferential track. Guided in the circumferential track are at least two axially displaceable guide elements, which are coupled to one another in such a way that a shifting prong in the circumferential track can be used, depending on the rotational position of the shifter drum, for axial movement of two actuating members. This shifter drum can be combined with at least one further shifter drum, the underlying idea being, by way of two shifter drums rotatable independently of one another, to perform at least some gear changes in the shortest possible time while skipping over one or more gears, even without decoupling the axial guidance; and moreover to perform a gear change with overlapping actuation of two shift clutches, any interruption in tractive force during the shifting operation being minimized. Achieving this solution requires, however, an extraordinarily high level of design complexity.
It is generally problematic with shifter drums to actuate transmissions having many ratios and transmissions requiring a great deal of shifting force, and especially a combination of the two, for example as exists in the case of split-range transmissions.
In order to convert the torque present at the shifter drum into a shifting force, two geometric variables are known to be important, namely the shifter drum diameter and the angle of the circumferential track or groove. Increasing the actuation force in terms of the applied torque would necessitate reducing the diameter of the shifter drum or the groove angle.
On the other hand, an increase in the shifter drum diameter is more desirable so that the entire logic (in the form of grooves) can be accommodated on its surface. For a transmission having more than five ratios, for example, at least four grooves are necessary if four shift forks (for four shift packets to be operated) are each to be guided in a groove. Negative factors associated with an enlargement of the shifter drums, however, include not only limited installation space but also increased pressure on the groove and (as described above) the greater force needed to move the shifter drum.
For modern automated multiple-ratio transmissions having more than five ratios it is therefore difficult to control only one shifter drum with an actuator, since the developed surface of that one shifter drum usually no longer has sufficient space for optimum configuration of the guides.
It is the object of the present invention to create, for an automated multiple-ratio transmission of a motor vehicle having at least one shifter drum, an actuating apparatus with which the requirements in terms of guides on the shifter drum surface configured optimally for the shifting logic, minimal actuation force, and little installation space requirement can very largely be met.
This object is achieved, according to the present invention, with an actuating apparatus in accordance with the features of claim
1
.
SUMMARY OF THE INVENTION
An actuating apparatus for an automated multiple-ratio transmission of a motor vehicle, having a first shifter drum and at least one further separate shifter drum that are kinematically coupled to one another, yields the advantage that the guides can be distributed onto at least two separate shifter drums, so that the shifter drums can be of correspondingly small dimensions and sufficient space is available for optimum configuration of the guides on the developed surface of the shifter drums. The term “multiple-ratio transmission” is understood here to mean both automated gear-shifting transmissions, for example non-on-load-shiftable automated manual transmissions, and automated on-load-shiftable multiple-ratio transmissions, for example double-clutch transmissions.
For example, the arrangement of two shifter drums coupled kinematically to one another can be used to associate one shifter drum with a principal transmission and the further shifter drum with a split-range transmission, so that a very large number of ratios can be shifted by means of two relatively small shifter drums.
The overall actuation force required is also greatly reduced. Corresponding to the lower energy required for transferring the shifting force, preferably only a single energy source is provided for driving the shifter drums; that energy source can be implemented by way of a manually actuated actuating drive or one equipped with electrical, pneumatic, or hydraulic devices.
The actuating drive can be connected to the shifter drums via a constant conversion ratio system, for example in the form of a belt drive or a tooth set; or by way of a non-constant conversion ratio system or non-constant conversion transmission.
Kinematic coupling between the shifter drums can also be implemented by way of a constant conversion or non-constant conversion transmission. Suitable as a constant conversion transmission is any kind of conversion device in which the conversion ratio is constant during one rotation of the shifter drums. A
Baasch Detlef
Dreibholz Ralf
Gumpoltsberger Gerhard
Davis & Bujold P.L.L.C.
Lewis Tisha
ZF Friedrichshafen AG
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