Patent Application
20050133338
The invention concerns a parking lock for an automatic transmission with a parking lock gear directly bound to the transmission output shaft in accord with the concept of the principal claim 1.
Such a parking lock has been disclosed by DE 36 36 978 A1. The output of this transmission is directly connected to a parking lock gear, so that, when in parking mode, a locking member in the form of a parking lever, upon option, can be lockingly brought into engagement with toothing of the parking lock gear. A push-rod, which is indirectly connected with a selection lever of the transmission, carries a conical cam, which, in the parking position of the said selection lever, brings the locking member into such a position, that the parking lock brake gear is in the locked condition. Thereby, by this establishment of the parking position and with even an unfavorable relative position of the park locking gear, an engagement can securely be made, if the said cam is spring loaded and slidably placed on the insertion rod. To this end, the said push-rod carries a molded on connection, upon which a compression spring can anchor, which then exerts force on the said cam. So that, in a case of extreme vibration, which can act upon this known transmission, the lock member, which is in the driving mode, can undesirably contactingly engage with the parking lock gear, there is provided on the insertion rod a braking member spring in the form of a leaf-spring. This spring is so designed, that in a driving gear stage, it exerts its resilient force on the lock member, and works against an engagement of the lock member in the parking lock gear.
In cases of increased demands, in regard to resistance of a parking lock mechanism to vibratory disturbance, in order hold the locking lever free from engagement in the parking lock gear, the force of the leaf spring must be made greater. Due to substantial friction caused by the spring, an increased expenditure of force is created between the leaf spring and the locking lever. As a result, an axial sliding of the cam is initiated, and thus an increased expenditure of force appears at the selector lever. Such increased demands can, for example, occur with motor vehicles equipped with such parking locks, if these are driven at excessive speeds over unlevel obstructions or in off-the-road courses.
Giving consideration to this background, thus the purpose of the invention is to create a parking lock for an automatic transmission of such a nature, that in the driving mode, even at extreme accelerations acting upon the transmission, contact between the locking lever and the parking lock gear is avoided.
The achievement of this purpose is to be found in the features of claim 1 of the present text, while advantageous embodiments and improvements of the invention are to be taught by the dependent claims.
The invention stipulates, that the conflict of purpose in the layout of the lock member spring cannot be solved by variations of the force of this lock member spring.
Accordingly, the invention provides an arrester which can be brought into contact with the lock member and immobilizes the same. The parking lock mechanism, when in the park position, releases this arrester in such a manner, that the lock member enters into engagement with the parking lock gear.
Advantageous, when this occurs, is that the arrester is conducive to a strict division of function in the parking lock, wherein the respective components can be dedicated to such functions as they were intended to perform. The true parking lock mechanism, which leads directly to a displacement of the lock member, can, to the greatest extent, be given entire freedom, for example, in the form of the known placement of a spring loaded, slidable cam on a push bar.
The lock member spring can be so directly placed, that the lock member, in all selector level positions, can be brought out of the parking position, withdrawn from the parking lock gear and placed in a position, wherein the separate arrester can make an engagement therewith. The spring force thereof can also be optimized for this purpose, and must not be adjustingly set to function only in a case of the eventually occurring, extreme acceleration. In this way, the activation forces directed at the selector lever remain at a minimum value.
By means of the separately designed arrester, forces acting on the lock member, which have been evoked by recurring accelerations, have been blocked, this being due to an effective transfer of force into the parking lock gear by means of the lock member.
In an advantageous embodiment, the said arrester is designed to be somewhat springlike in resilience, that is, it is made of band of thin, resilient sheet metal, somewhat extended in surface and capable of making a shape-fit with, and also restraining, the lock member. Preferentially, the said arrester is anchored at one end in the transmission housing, while on its free end, a component of the parking brake mechanism activates its release.
In an embodiment, which is particularly simple to construct and to install, the sheet metal band is placed to run essentially parallel to the lock member and is provided with an angled section, which engages itself into a corresponding recess of the said lock member.
In another preferred embodiment of the arrester, this appears, for example, as a spring loaded, piston-like arrester rod, which abuts itself on a transmission wall and vertically penetrates into a corresponding opening in the lock member.
For further clarification of the invention, a drawing is hereto attached. With the aid of this said drawing, in the following an embodiment of the invention will be described and explained in greater detail: There is shown in:
Within a housing 1 of an automatic transmission for a motor vehicle, is placed a parking lock gear underneath the plane of the drawing. This is fully connected to a transmission output drive. Outside of the drawing, in the direction of the said parking lock gear, and inside the housing, is placed a movable lock member 2, which is subjected to the force of a lock member spring 3, which in the form of a helical spring. The helical spring penetrates in common with an angular arm 4 thereof into a recess 5 in the lock member 2 and transmits in this way its spring force onto the lock member 2 in such a way, that this force acts counter to an engagement with the parking lock gear.
Between the housing inner wall 6 and the lock member 2 is placed an arrester 7 in the form of a springlike, resiliently designed sheet metal band. This band extends itself in a direction essentially parallel to the lock member 2 and one end is rigidly affixed to the housing inner wall 6 by means of a fastener 8. The generally leaf spring design of the sheet metal band 7 possesses on its free end an angular section 9, which, by means of the inherent force of the said springlike sheet metal band 7, in accord with
A piston 13, which forms a part of the parking lock mechanism is placed within the housing 1, slidably situated perpendicularly to the lock member 2. The part of the parking lock mechanism, which displaces the said lock member 2 need not be further described here, and can be manufactured by known methods in accord with the state of the technology.
The manner of functioning of the parking lock is as follows. In
If the (not shown) selective lever is placed in the parking position, than by means of a known, mechanical transfer element, the piston 13 is advanced to the position shown in
Reference Numerals
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 59 326.8 | Dec 2003 | DE | national |
