DE102019217959A1 - Eccentric axis with bearing sleeves and method for producing an eccentric axis - Google Patents

Abstract

Disclosed is an eccentric axis for a control device for an axial piston machine, with a molded core of the eccentric axis being formed in / around bearing sleeves so that these are finally attached to the outer circumference of the eccentric axis. Furthermore, a method for manufacturing such an eccentric axis is disclosed.

Description

The present invention relates to an eccentric axis with bearing sleeves for a control device of an axial piston machine according to claim 1 and a method for producing an eccentric axis.

The EP 0 903 494 B1 discloses a hydraulic pump with a bearing bush made of bearing metal, in which an eccentric of a drive axle, that is to say an eccentric axle, is mounted. In a plain bearing, the bearing bush is pressed into an inner circumference of a bearing ring and additionally secured in a form-fitting manner with interlocking stop means against rotation and in the axial direction.

From the DE 10 2011 120 750 A1 The applicant is aware of a control device for an axial piston machine with an eccentric axis referred to as a bearing pin. The eccentric axis is rotatably mounted in a bearing bore of a housing. This has an intermediate piece which is eccentric to an axis of rotation and on which a return lever and a first and a second leg are each rotatably mounted independently of one another.

The disadvantage of the aforementioned solutions is that the eccentric axles, regardless of whether they are one-piece or two-piece, are made from a solid material, and that the machining outlay for producing such eccentric axles is great. The costs for producing such eccentric axles are correspondingly high, since the processing steps for dimensionally accurate production with very low tolerances and at the same time high surface hardness are complex.

In contrast, the invention is based on the object of creating an inexpensive eccentric axis for a control device of an axial piston machine, with very tight dimensional tolerances being maintained and high wear resistance guaranteed, and a method for producing such an eccentric axis.

This object is achieved by an eccentric axis with bearing sleeves for a control device of an axial piston machine with the features of claim 1 and a method for producing an eccentric axis according to claim 13.

The eccentric axis according to the invention can also be referred to as an eccentric pin and is designed for use in a control device of an axial piston machine, in particular an axial piston pump. The eccentric axis has two concentric areas and an eccentric sleeve made of metal. The two areas and the sleeve have a circular cylindrical outer peripheral surface. The outer peripheral surfaces of the concentric regions define an axis of rotation of the eccentric axis, while the outer peripheral surface of the eccentric sleeve defines a central axis. The central axis is arranged at a distance parallel to the axis of rotation. A core of the eccentric axis is formed in one piece from a molded material. The core is adapted in such a way that it rests against the eccentric sleeve without play, so that it is preferably held in a form-fitting manner over its entire length transversely to the axis of rotation. The eccentric sleeve is preferably held positively in a first axial direction with respect to the axis of rotation.

In contrast to the eccentric axes known from the prior art, the eccentric axis according to the invention can be produced with significantly less effort while maintaining the required tolerances of the eccentric area. The eccentric sleeve is also designed with an outer circumferential surface, the tribological properties of which also meet the very high requirements, which correspond to the requirements of an eccentric axis in a control device of an axial piston pump.

Preferably, concentric sleeves, which are also made of metal and are concentric to the axis of rotation, are also provided in the two concentric areas, the eccentric sleeve being arranged between the two concentric sleeves as seen in the direction of the axis of rotation. The concentric sleeves are referred to below as the first and second concentric sleeves.

In this development, the core is adapted so that it rests against the concentric sleeves and the eccentric sleeve without play, so that these are each held in a form-fitting manner, preferably over their entire length transversely to the axis of rotation. The concentric sleeves and the eccentric sleeve are preferably held in a form-fitting manner in a first axial direction with respect to the axis of rotation. At least some of the sleeves are preferably held in a form-fitting manner in a second axial direction which is opposite to the first direction.

All of the sleeves mentioned are preferably bearing sleeves.

It is particularly preferred if only one of the concentric sleeves, that is to say the first concentric sleeve or the second concentric sleeve, is held in a form-fitting manner with respect to the second axial direction.

In contrast to the eccentric axes known from the prior art, the eccentric axis according to the invention can be produced with significantly less effort while maintaining the required tolerances. The first and the second concentric sleeves each have an outer circumferential surface, the outer circumferential diameter of which adhere to the tolerances, which are, for example, in the μm range. The eccentric sleeve is also designed with an outer circumferential surface, the tribological properties of which also meet the very high requirements, which correspond to the requirements of an eccentric axis in a control device of an axial piston pump.

Further advantageous refinements of the invention are described in the dependent claims.

In a preferred embodiment, the molded material of the core has a coefficient of thermal expansion which essentially corresponds to the coefficient of thermal expansion of the metal of the sleeves.

In this way, distortion of the eccentric axis is advantageously prevented when it is exposed to temperature changes. This can be the case in particular when the eccentric axis is removed from a mold, for example a casting mold, after the core has been introduced.

The sleeves are preferably made of the same metal.

In a particularly preferred embodiment of the eccentric axis according to the invention, the eccentric sleeve is made of a different metal than the first and the second concentric sleeve. As already stated above, the eccentric sleeve must meet higher tribological properties than the first and second concentric sleeves. It can therefore be advantageous if the eccentric sleeve, compared to the first and second concentric sleeve, is made of a harder metal.

In a further exemplary embodiment, the material of the core that can be molded in the original manner is a plastic. This plastic can be composed of a thermosetting and / or thermoplastic base material and an inorganic filler material. The filler has a share of at least 50%.

It has been found to be advantageous that when such a plastic is used, a tendency to creep is reduced by a factor of 10 compared to otherwise customary plastics. The above-mentioned coefficient of thermal expansion of the core can be adjusted via a corresponding amount of fillers.

The inorganic material of the filler can be provided as glass spheres, glass fibers or other mineral substances. These are preferably used in pure form, it being conceivable to combine different organic fillers.

Depending on the design, it can be advantageous if a thermoplastic plastic is selected as the base material, the proportion of filler being at least 55%, but in particular at least 60% of the core material.

In an advantageous embodiment, the base material is polyphenylene sulfide.

Alternatively, the base material can also be a thermosetting plastic, the proportion of fillers being at least 75%, but particularly preferably at least 80%.

In this alternative embodiment, it is particularly preferred if the base material is a phenoplast.

In a preferred development, the sleeves are each made in one piece. Each sleeve consists of a steel which has a martensitic structure at least in the area of the respective outer circumferential surface.

The sleeves are preferably hardened throughout and accordingly have a continuous martensitic structure. It goes without saying that in addition to the martensitic structure, other structural components could also be present in order to adjust the hardness of the respective sleeve as desired. In particular, an identical microstructure is conceivable for the first and the second concentric sleeve, while that of the eccentric sleeve varies therefrom in order to meet the requirements set out above with regard to the tribological properties.

It is particularly preferred if the sleeves are each designed as a hollow cylinder and each have a constant wall thickness.

If, according to a further exemplary embodiment, the eccentric axis has at least one sealing section, then this or these are advantageously formed from a sealing ring made from a thermoplastic elastomer. The at least one sealing ring is cohesively connected to the molded material in a region of the core provided for this purpose.

In a particularly preferred embodiment of the eccentric axis according to the invention, the core runs in the area of an end face of one of the sleeves, at an angle offset by approximately 90 ° to the axis of rotation. It is advantageous for one occurring axial load prevents breakage of the core in this area.

• - Herstellung der Hülsen, einschließlich Wärmebehandlung und exakter Endbearbeitung der Außenumfangsfläche;
• - Einsetzen der Hülsen in eine Gussform, insbesondere eine Spritzgussform, in der diese zumindest formschlüssig gehalten sind;
• - Einfüllen des urformbaren Materials, insbesondere eines fließfähigen Kunststoffmaterials, bestehend aus dem Basismaterial und dem anorganischen Füllstoff;
• - Aushärten des urformbaren Materials, insbesondere des fließfähigen Kunststoffmaterials, bestehend aus dem Basismaterial und dem anorganischen Füllstoff;
• - Entnehmen der Exzenterachse aus der Gussform.

A method according to the invention for producing an eccentric axis is carried out with the following steps, which are carried out one after the other in the order given:

• - Manufacture of the sleeves, including heat treatment and precise finishing of the outer peripheral surface;
• - Insertion of the sleeves into a mold, in particular an injection mold, in which they are held at least positively;
• - Filling in the molded material, in particular a flowable plastic material, consisting of the base material and the inorganic filler;
• - Curing of the molded material, in particular the flowable plastic material, consisting of the base material and the inorganic filler;
• - Removing the eccentric axis from the mold.

The eccentric axis has an eccentric bearing section, designed here as an eccentric sleeve, which supports a so-called return lever and a pair of levers. A diameter of this bearing section is designed eccentrically to a recess in a housing of the control device. The diameter tolerance is very tight and must be ground with a conventional eccentric axis made of a solid material. Since the pair of levers and the return lever move on the bearing section, this must have a high surface hardness to protect against wear. For this purpose, this is heat-treated with conventional eccentric axles and a connecting layer obtained in this way should be retained, so it should not be reground. The dimensional distortion and the growth of the diameter due to the heat treatment thus contradict the requirements for the diameter tolerance.

The contradiction between surface hardness and diameter tolerance is advantageously eliminated by the manufacturing method according to the invention. The complex production with the steps: eccentric turning, eccentric grinding, heat treatment and eccentric grinding is significantly simplified and accelerated by the above method, i.e. the casting around of prefabricated sleeves and can thus be used much more cost-effectively.

For reasons of process optimization, it is advisable to insert the thermoplastic elastomer sealing ring into the mold in the region of the at least one sealing section after curing and before removing the eccentric axis in order to form the at least one sealing section.

• 1 eine Ansicht eines Ansteuergerätes;
• 2 eine Schnittansicht des Ansteuergerätes gemäß 1 mit einer erfindungsgemäßen Exzenterachse, und
• 3 eine geschnittene Ansicht einer erfindungsgemäßen Exzenterachse aus 2 mit Hülsen.

Preferred exemplary embodiments of the invention are explained in more detail below with reference to drawings. Show it

• 1 a view of a control device;
• 2 a sectional view of the control device according to 1 with an eccentric axis according to the invention, and
• 3rd a sectional view of an eccentric axle according to the invention 2 with pods.

1 shows a view of a housing 2 a control device 1 . Such a control device 1 is, for example, part of an adjusting device, not shown, to which an actuating piston can also belong. The adjusting device can be used, for example, to adjust a swivel angle of a hydrostatic axial piston machine with a swash plate design. The actuating piston can be designed in a known manner, for example in that known from the introduction DE 10 2011 120 750 A1 the mode of operation of such an actuating piston and also of a corresponding adjusting device are described in detail.

For feedback of an actuating movement of the actuating piston, a recess is provided in the actuating piston, in which a driver head 4th a return lever 6th of the control device 1 is arranged. The return lever 6th is on an eccentric axle according to the invention, which is in a recess 8th of the control device 1 is used, and from the in 1 just a pretender 12th is shown, rotatably mounted. The actuating movement of the actuating piston leads to a rotation of the feedback lever 6th . On one of the driving head 4th remote end of the return lever 6th a driving pin is arranged. When the actuating piston moves and the feedback lever rotates therewith 6th the driving pin moves in the opposite direction to the movement of the actuating piston.

In the recess 8th of the housing 2 the eccentric axis is rotatably mounted. This has a central axis eccentric to an axis of rotation, that is to say offset in parallel, which is described in more detail below. At an end region of the eccentric axis that extends outwards, the eccentric axis has a radially protruding, circumferential collar 10 on, in a corresponding expansion of the recess 8th of the housing 2 is used.

According to 2 is one out of the case 2 protruding adjusting end 12th coaxial with a Polygonal socket 14th provided, in which an adjustment tool can be inserted around the eccentric axis 24 around the axis of rotation 42 to twist.

In parallel at a distance next to the recess 8th is in the housing 2 a threaded hole 16 formed in which a fixing screw 18th with hexagon socket 20th is screwed in. A screw head of the fixing screw 18th clamps the threaded hole 16 surrounding tension ring 22nd against the housing 2 as well as the collar 10 so that the collar 10 is braced against a floor of the extension.

This means that the eccentric axis is fixed in its set position and cannot adjust itself.

In 2 is a section of a control device 1 shown. In the case 2 is the eccentric axis 24 in the recess 8th recorded. The eccentric axis 24 points away from the adjuster 12th seen from several sections. First is the collar 10 in a receptacle provided for this purpose in the area of the recess 8th brought in. Below the collar 10 is a seal in the form of a sealing ring 26th around a core 28 the eccentric axis 24 intended. This sealing ring 26th is in the present embodiment around the core 28 molded around, so that a mount of the sealing ring 26th after the eccentric axis has been manufactured 24 not applicable.

Below the sealing ring 26th is a second concentric bearing sleeve, hereinafter referred to as the second concentric sleeve 30th labeled, at the core 28 the eccentric axis 24 attached. On another, eccentric part of the eccentric axis 24 , is an eccentric bearing sleeve, hereinafter referred to as an eccentric sleeve 32 designated, attached. At one of the pretenders 12th opposite area of the eccentric axis 24 is a first concentric bearing sleeve, as the first concentric sleeve 34 designated, attached.

The first concentric sleeve 34 and the second concentric sleeve 30th are in the recess 8th of the housing 2 stored and designed with optimized dimensions. The eccentric sleeve 32 is optimized in terms of surface hardness and diameter tolerance.

On an outer peripheral surface of the eccentric sleeve 32 are the feedback lever 6th and the pair of levers 36 stored. About the driving pin 38 is the return lever 6th with the pair of levers 36 in operative connection to transmit a movement of the actuating piston (not shown).

The outer peripheral surface of the eccentric sleeve 32 defines a central axis 40 , while outer peripheral surfaces of the first and second concentric sleeves 34,30 have an axis of rotation 42 define. The central axis 40 is spaced parallel to the axis of rotation 42 .

3rd shows an eccentric axis according to the invention 24 in a sectional view. Based on 3rd is also a possible manufacturing process according to the invention for the eccentric axis 24 described.

The sectional view shows the eccentric axis 24 with the adjuster 12th , the core 28 , the sealing ring 26th , the second concentric sleeve 30th , the eccentric sleeve 32 and the first concentric sleeve 34 . In the opposite of the 2 isolated and enlarged view of the eccentric axis 24 it can be clearly seen that in the area of the eccentric sleeve 32 an eccentric offset along the central axis 42 opposite the axis of rotation 40 is present.

To each of the person making the adjustment 12th pointing faces of the sleeves 30th , 32 , 34 are contact surfaces 44 , 46 , 48 intended. The second concentric sleeve 30th has the contact surface 44 who have favourited The Eccentric Sleeve 32 has the contact surface 46 and the first concentric sleeve 34 has the contact surface 48 . These contact surfaces 44 , 46 , 48 serve to position the sleeves 30th , 32 , 34 into a form, not shown, which in the case of the exemplary embodiment described here is an injection mold.

The pods 30th , 32 , 34 are placed in the injection mold after their production. The contact surfaces are used for exact positioning within the injection mold 44 , 46 , 48 . These are oriented to opposite stop surfaces in the injection mold and applied to them. So are the pods 30th , 32 , 34 , which can be designed as standard parts, positioned in a fixed position in the form.

In a subsequent step, the injection mold is closed and the core 28 is introduced. In the present case, a reinforced plastic, consisting of a base material and a filler material, is introduced into the injection mold. Of course, it is also conceivable that a ceramic, a metal green compact, a sintered metal or the like can alternatively be used as the core in an alternative manufacturing process 28 is introduced.

The core 28 So is in openings of the sleeves 30th , 32 , 34 injected so that the pods 30th , 32 , 34 be held positively on the core. With an additional overmold 50 the eccentric sleeve 32 becomes their hold on the core 28 optimized.

After the core 28 is introduced, the sealing ring can in a further step 26th with a another material, for example a thermoplastic elastomer, onto the core 28 be injected. This creates an integral connection between the sealing ring 26th and the core 28 reached.

After the eccentric axis has cooled down 24 this can then be removed from the mold as a part.

In contrast to the previously known, fully metallic eccentric axes, the complex production, which includes eccentric turning, eccentric grinding, heat treatment and eccentric grinding, can be significantly simplified. A contradiction between the required surface hardness and diameter tolerance can be overcome in this way.

The pods 30th , 32 , 34 can be manufactured much more easily, also fully hardened and with tribological and geometric properties optimized for the respective requirement profile, while the core 28 Does not experience such high loads during operation and does not have to be made as precisely as the sleeves with regard to diameter tolerances 30th , 32 , 34 . In addition, the sealing ring is sprayed on 26th a separate sealing ring is unnecessary, so that a further source of error in production can be excluded.

Disclosed is an eccentric axis for a control device for an axial piston machine, with a molded core of the eccentric axis being formed in / around bearing sleeves so that these are finally attached to the outer circumference of the eccentric axis. Furthermore, a method for manufacturing such an eccentric axis is disclosed.

List of reference symbols

1

Control device

2

casing

4th

Driving head

6th

Return lever

8th

Recess

10

collar

12th

Pretending

14th

Polygonal socket

16

Threaded hole

18th

Fixing screw

20th

Hexagon socket

22nd

Bracing ring

24

Eccentric axis

26th

poetry

28

core

30th

second concentric sleeve

32

eccentric sleeve

34

first concentric sleeve

36

Pair of levers

38

Driving pin

40

Central axis

42

Axis of rotation

44

Third sleeve contact surface

46

Second sleeve contact surface

48

Contact surface first sleeve

50

Encapsulation

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• EP 0903494 B1 [0002]
• DE 102011120750 A1 [0003, 0036]

Claims (15)

Eccentric axis for use in a control device (1) of an axial piston machine, two concentric areas (30, 34) and an eccentric sleeve (32) are provided, each having a circular cylindrical outer peripheral surface, the sleeve (32) being made of metal, the Outer circumferential surfaces of the concentric regions (30, 34) define an axis of rotation (42), the outer circumferential surface of the eccentric sleeve (32) defining a central axis (40) which is arranged at a distance parallel to the axis of rotation (42), with a one-piece core (28 ) is provided from a primary formable material which is adapted to the eccentric sleeve (32) without play in such a way that it is held in a form-fitting manner. Eccentric axis after Claim 1 , characterized in that the two concentric areas are formed by concentric sleeves (34, 30) made of metal, which are concentric to the axis of rotation (42). Eccentric axis after Claim 1 or 2 , characterized in that the coefficient of thermal expansion of the malleable material of the core (28) is substantially equal to the coefficient of thermal expansion of the metal of the sleeve (32) or the sleeves (30, 32, 34). Eccentric axis according to one of the preceding claims, characterized in that the moldable material of the core (28) is composed of a thermoplastic or thermosetting base material and an inorganic filler, the proportion of filler being at least 50%. Eccentric axis after Claim 4 , characterized in that the base material is a thermoplastic plastic, the proportion of filler material being at least 55%, preferably at least 60%. Eccentric axis after Claim 5 , characterized in that the base material is polyphenylene sulfide. Eccentric axis after Claim 4 , characterized in that the base material is a thermosetting plastic, the proportion of filler being at least 75%, preferably at least 80%. Eccentric axis after Claim 7 , characterized in that the base material is phenoplast. Eccentric axis according to one of the Claims 2 to 8th , characterized in that the metal of the concentric sleeves (30, 34) and / or the eccentric sleeve (32) is steel, which has a martensitic structure at least in the area of the respective outer circumferential surface. Eccentric axis according to one of the Claims 2 to 9 , characterized in that the concentric sleeves (30, 34) and / or the eccentric sleeve (32) is / are each designed in the form of a hollow cylinder with a constant wall thickness. Eccentric axis according to one of the preceding claims, characterized in that the eccentric axis (24) comprises at least one sealing ring (26) which consists of a thermoplastic elastomer, which is firmly connected to the molded material of the core (28). Eccentric axis according to one of the preceding claims, characterized in that the core (28) runs inclined to the axis of rotation (40) at an angle different from 90 ° in the area of an end face of a sleeve (30, 32, 34). Method for producing an eccentric axis (24) according to one of the preceding claims with the following steps, which are carried out one after the other in the specified order: - Manufacture of the eccentric sleeve (32), including heat treatment and precise finishing of the outer peripheral surface; - Inserting the eccentric sleeve (32) into a casting mold in which they are held at least in a form-fitting manner; - Filling in the primordial material in flowable form; - hardening of the molded material; - Removing the eccentric axis (24) from the mold. Procedure according to Claim 13 , characterized in that the primary moldable material is a flowable plastic material, mixed from a base material and inorganic fillers. Procedure according to Claim 14 to produce an eccentric axis (24) according to Claim 11 , characterized in that the thermoplastic elastomer is poured into the casting mold between the last two process steps in the region of the at least one sealing ring (26).

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