DE102011079180A1 - Actuating element of a motor vehicle transmission - Google Patents

Abstract

The invention relates to an actuating element (15) of a motor vehicle change gear for adjusting a switching element (16), with which it is detachably brought into contact, wherein those sliding portions (17) of the actuating element (15), which contact the switching element (16) when adjusting in, a sliding material wherein the sliding material contains PTFE.

Description

Field of the invention

The invention relates to an actuating element of a motor vehicle change gear for adjusting a switching element, with which it can be detachably brought into contact, wherein the actuating element has sliding portions with a sliding material, which contact the switching element during adjustment.

Background of the invention

By means of actuators of switching devices manual transmission in motor vehicles switching elements are operated directly or indirectly to the gear selection. It also components must be moved to each other while they move. An example of such a switching device are shift forks, which engage as actuators with sliding shoes in a groove of a sliding sleeve. The sliding sleeve usually rotates when switching under frictional contact with the shoe relative to the shift fork. During switching operations, a sliding force is transmitted from the shift fork to the sliding sleeve via the sliding shoes. The load of the sliding shoes is strengthened when shift shocks are added to the displacement force. The shift shocks are caused by errors when switching or when operating the clutch of the motor vehicle or by wear of the synchronizer.

Plastic sliding shoes are usually relatively wear-resistant and have acceptable self-lubricating or sliding properties. They are simple and inexpensive to manufacture and have a low weight. Despite partial lack of strength properties, they are increasingly used in modern manual transmissions. In order for such sliding shoes to be used despite the high loads, according to the current state of knowledge, two concepts are pursued in their application, each concept representing only a compromise solution, with a view to the requirements imposed.

The one concept provides to make the shoe replaceable for switching element. So z. In DE 195 39 967 A1 a Kunststoffgleitbacke described, which is plugged onto a shift fork end and can be replaced if necessary against a new one. If the shoe is broken or sheared due to high load, it will be replaced. The use of replaceable sliding shoes is advantageous in itself. In the case of a repair then, for example, not the entire switching element, but only a relatively cheap shoe has to be replaced. The associated with the change of the shoe repair work, however, are very expensive, since the transmission must be opened. With regard to the use of maintenance-free transmissions, which is becoming increasingly important, such a solution is unsatisfactory.

The second concept provides to embed such sliding shoes in the wall or the body of the switching element. In DE 40 17 955 A1 is z. Example, a shift fork described in their manufacture, the shoes are embedded in the material of the body. The shoe is thus at least partially, in particular laterally, surrounded by metal and thus more resistant to stress. The production costs for the production of switching elements with embedded sliding shoes is correspondingly higher and thus the production of the switching element is more expensive.

With the application of the above concepts, the cost advantage that arises during manufacture, at least partially offset by the costs incurred for repairs or in the further production of the switching elements.

The requirements that are placed on the coupling point actuator with the switching element, in particular their wear resistance and the equipment with self-lubrication or sliding properties are partly contrary to a simple and cost-effective production, especially in mass production, their secure adhesion to the actuator or switching element, the Interception of shock and shear loads and their long-term stability.

Object of the invention

The object of the invention is therefore to provide an actuating element which optimally combines the aforementioned properties in itself.

Solution of the task

The object is achieved by a device according to claim 1. An actuating element is understood to mean a transmission component which can be brought into contact with an already moving, generally rotating switching element during a switching operation. In another position, the actuating element is preferably not in contact with the switching element in order to protect the sliding material. The switching element is a transmission component that can move spatially by the actuator in its position regardless of its previous movement.

According to the invention, the actuating element on a sliding material containing polytetrafluoroethylene. In experiments it has been found that PTFE has sufficient long-term stability, especially in combination with hardened counterparts. PTFE is known as one of the most inert substances. The strong chemical fluorine-carbon compounds can not be broken even by aggressive substances, which benefits the long-term stability of the shift fork coating. Furthermore, PTFE has extremely low coefficients of friction.

Due to its good sliding properties relatively little rotational energy is converted into heat energy, so that the coating can also be very thin. This allows new concepts for the way of applying the sliding material. Alternatively, sliding blocks are made separately from the PTFE sliding material, which are connected to the actuating element.

PTFE is badly wetted by the gear oil. Due to its low coefficient of friction, it is suitable as a good dry lubricant, so that a shift of the switching element is possible without converting much rotational energy by friction into heat and thus reduce the life of the actuator or the coating too much.

In one embodiment, the sliding material is polyamide-based. Polyamide-based coatings are very resistant to friction and can nevertheless be applied well to a metal base body.

As a coating of actuators and / or switching elements Durotect P716, a Polyamidgleitlack containing PTFE, has been found to be particularly suitable. Although this PTFE-based coating also serves for corrosion protection and wear protection; their main function, however, is to reduce the friction between the friction partners, so that as little friction heat is generated during the switching process.

In a first application of the invention, the actuating element is a shift fork and the rotating switching element is a sliding sleeve. The shift fork may have sliding shoes at its fork ends which are either coated with or entirely made of the PTFE-containing slip material. The PTFE-containing sliding shoes can be formed thin-walled. The actuating element can also be designed as a rocker arm.

In one variant, only the actuating element, in another variant, both the actuating element and the switching element on the sliding material. It can be provided with the sliding material only the areas of the two components that are in direct contact with each other when switching and the whole components, which may be easier to manufacture. In particular, two juxtaposed PTFE layers slide very well together.

In a next embodiment, the actuating element is formed from a metallic material which is dip-coated. For this purpose, it is produced, for example, in forming technology and then brought into contact with a coating in a dip, which wets at least parts of the actuating element.

By dip coating the required accuracy can be more easily maintained compared to the encapsulation, since the shift fork can be formed sufficiently accurate and the paint forms a relatively thin and uniform coating. The high tool costs required for encapsulation with the required accuracy are eliminated. Also, no sliding blocks need to be mounted or welded to the shift forks.

The coating by dip coating is very process efficient. This eliminates the need to attach individual sliding blocks, and it can be driven simultaneously multiple switching forks in a dip. Dipping is a very efficient coating method, especially for mass production.

Another advantage is that the dip coating is a very thin layer compared to the sliding blocks. While the sliding blocks must have certain minimum axial thickness to be securely attached to the fork ends and to receive the required forces, the slide coating applied by dip painting forms a uniform layer of low thickness. Thereby, the axial space of the shift fork can be further shortened, which allows a narrower groove of the sliding sleeve and ultimately a shorter gear building.

Ideally, by dispensing with the relatively thick sliding blocks, it is possible to reduce the backlash between the dip-coated shift fork and the groove walls of the sliding sleeve to a width which is not only significantly smaller than in the prior art, but also smaller than the sheet thickness used the shift fork is.

Preferably, a thickness of the applied by the dip coating coating of 10 microns-20 microns is provided.

The temperature of the immersion bath and the duration of the immersion are determined by the painting and determines the material used for the shift fork.

The shift fork as a substrate to be coated can be mechanically pretreated as by grinding or blasting or chemically pretreated to ensure uniform adhesion and good resistance to dip coating. Alternatively, an adhesion promoter serves for better adhesion due to less compatible interfacial layers.

In a particularly advantageous manner, the dip coating is suitable for profiled thin sheet metal forks. Due to the good Umgriffsverhalten the dip coating U-shaped profiles of shift forks, which engage in an annular groove of a sliding sleeve or embrace a ring, and also very complex shaped shift forks can be safely coated. Thus, even mass and load optimized and therefore more complicated shaped shift forks can be well coated.

Preferably, the dip coating is used in its variant as a cathodic dip coating.

In one embodiment of the invention, only the fork ends are dip-painted. The fact that only the parts of the fork body are coated, which are actually later in frictional contact, only little dip is needed. If the shift fork is not only supported at its fork ends on the sliding sleeve, which is now easier due to the fact that the sliding layer is very thin compared to sliding shoes and the fork body can be accurately shaped, other areas can also be dip-painted.

In a further embodiment, in particular with very dimensionally manufactured shift forks, the entire fork body is dip-coated in the areas in which it contacts the sliding sleeve. The shift fork can then be supported over larger areas, whereby the shift fork is less deformed.

The actuator can first ur- or reshaped from a metallic material. The finished in its geometric basic structure actuator is then immersed in a dip with a paint. After immersion, the coating cures. Depending on the selected dip coating curing can be triggered by temperature or accelerated. Alternatively, a catalyst can accelerate the cure and reduce the required temperatures down to room temperature.

When curing, the molecules of the dip coating usually crosslink with one another and form a common structure.

The curing is preferably carried out at a constant temperature. To initiate or accelerate the curing, it is intended to cure the finished coated components in an oven.

Brief description of the drawings

In the following an embodiment of the invention will be explained in more detail with reference to drawings. Show it:

1 the front view of a gear unit for a sliding sleeve with sliding sleeve, which is shown partially cut,

2 the too 1 corresponding plan view of the transmission unit,

3 the corresponding side view, from the direction B according to 3 considered

4 the too 1 corresponding side view, viewed from the direction C according to, and

5 the gear unit including sliding sleeve in perspective view.

6 another transmission assembly with a shift fork, which has sliding blocks.

Detailed description of the drawings

In the figures is a gear unit 1 to see, with a sliding sleeve 2 can be operated, ie with the sliding sleeve 2 in the axial direction A can be moved to perform a switching operation in a change-speed gearbox in a known manner. A functionally essential part of the transmission unit 1 First is the shift fork 5 that have a shift fork body 14 with two arms 3 and 4 which is in an annular groove 12 on the circumference of the sliding sleeve 2 intervention. This is an axial displacement of the sliding sleeve 2 with appropriate movement of the shift fork 5 possible. At the fixed shift fork 5 it comes with the rotating sliding sleeve 2 to sliding friction. To protect against occurring especially at high differential speeds and short switching times high synchronization performance and thus associated with the sliding friction wear are the ends 10 . 11 the poor 3 . 4 dip-coated with PTFE, and the ring groove 12 the sliding sleeve 2 is hardened.

Furthermore, the transmission unit 1 at least one guide element in the Embodiment by the two elements 6 and 7 is formed. With these pin-shaped elements 6 . 7 becomes the transmission unit 1 stored and guided in a transmission housing, not shown.

Another part of the transmission unit 1 is the driver element 8th that can interact with an actuator. The actuator may be a part of a shift linkage or a differently shaped actuator with which a controlled movement in the axial direction A can be generated. The driver element 8th So absorbs the switching force generated by the actuator.

All three described parts of the shift fork 5 So the two arms 3 . 4 , the guiding element 6 . 7 and the driver element 8th , are formed in one piece or in one piece. The transmission unit 1 For this purpose, it is formed from a flat metal sheet which, in the initial state, that is to say before the start of sheet metal forming, has a flat contour and has a constant sheet thickness d.

From the flat sheet is by folding, punching, bending and possibly deep drawing the shift fork 5 produced without cutting, ie transformed, as it can be seen in the figures. For this purpose, a part of a metal sheet is first punched so that the required developed contour of the gear unit results. This punched-out part is then further formed without cutting. After forming, the dip coating and curing takes place.

It is further provided that in particular the arm 3 the shift fork 5 from the base 9 out in the direction of the end 10 of the arm 3 rejuvenated. In the end area 10 of the arm 3 shows this, as well as the arm 4 , only one width in the axial direction A, that of the annular groove 12 matches or runs with game in this.

6 shows a shift fork 5 with sliding blocks 18 at the fork ends 10 . 11 are arranged. The sliding block 18 is with a reinforcement 20 provided and inserted with a plug element 19 in a through hole 21 the shift fork 5 , The reinforcement 10 forms the core of the plug-in element 19 , The sliding block 18 rests on the reinforcement 20 and the plug element 19 under load in the through hole 21 from and is in the axial direction by means of a circumferential bead 22 secured against losing. The bead 22 is at the free end of the plug element 19 formed and engages behind the wall of the shift fork in the radial direction 5 , The sliding block 18 is on the reinforcement 20 coated with PTFE.

LIST OF REFERENCE NUMBERS

1

transmission unit

2

sliding sleeve

3

poor

3 '

Part of the arm

3 ''

Part of the arm

4

poor

5

shift fork

6

guide element

7

guide element

8th

dogging

9

Base of the shift fork

10

End of the arm

11

End of the arm

12

ring groove

13

strip-shaped contour

14

Shift fork body

15

actuator

16

switching element

17

sliding

18

slide

19

plug-in element

20

reinforcement

21

Through Hole

22

bead

A

axially

d

Thickness of the sheet

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19539967 A1 [0004]
• DE 4017955 A1 [0005]

Claims (8)

Actuating element ( 15 ) of a motor vehicle change gear for adjusting a switching element ( 16 ), with which it is detachably brought into contact, wherein the actuating element ( 15 ) Sliding sections ( 17 ) having a sliding material, which the switching element ( 16 ) contact during adjustment, characterized in that the sliding material contains PTFE. Actuating element according to claim 1, characterized in that the sliding material consists of PTFE. Actuating element according to claim 1, characterized in that the sliding material consists of a PTFE-containing Polyamidgleitlack. Actuating element according to one of claims 1 to 3, characterized in that the sliding material is formed as a dip-coated coating. Actuating element according to one of claims 1 to 3, characterized in that the sliding material in the form of prefabricated sliding blocks ( 18 ) with the actuating element ( 15 ) connected is. Actuating element according to claim 5, characterized in that the coating, the actuating element ( 15 ) as a shift fork ( 5 ) or a rocker arm is formed. Actuating element according to one of claims 1 to 4, characterized in that the actuating element ( 15 ) as a sliding sleeve ( 2 ) is trained. Use of PTFE-containing substances for coating an actuating element ( 15 ) a gear unit ( 1 ).

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