WO2012104065A2

WO2012104065A2 - Piston arrangement of a hydraulic piston machine

Info

Publication number: WO2012104065A2
Application number: PCT/EP2012/000424
Authority: WO
Inventors: Stephan Geise; Carsten Tuechert
Original assignee: Robert Bosch Gmbh
Priority date: 2011-02-04
Filing date: 2012-02-01
Publication date: 2012-08-09
Also published as: DE102011010296A1; WO2012104065A3

Abstract

A piston arrangement for a hydraulic piston machine is disclosed, with a piston and with a sliding block which is produced from a plastic, wherein a piston foot and a joint socket arranged on the sliding block form a joint, and the piston foot has a tapered portion, behind which a collar of the joint socket engages. According to the invention, the collar is caulked here towards the tapered portion. Furthermore, a manufacturing method for manufacturing the piston arrangement is disclosed.

Description

Piston arrangement of a hydraulic piston machine

description

The invention relates to a piston assembly of a hydraulic piston machine with a sliding shoe made of plastic according to the preamble of patent claim 1 and a method for manufacturing the piston assembly, according to the preamble of

Patent claim 6.

It is known that a hydraulic piston machine has a piston assembly with a working piston and a non-ferrous metal or steel sliding shoe attached thereto. The working piston is supported on the slide shoe on a sliding surface of a swash plate.

Making the shoe over a machining process is costly and time consuming. In addition, non-ferrous metals are expensive and contain environmentally harmful lead. For water hydraulics, sliding shoes are made, for example, from steel with a plastic coating, which means that another complex assembly step has to be integrated.

DE 10 2004 060 945 A1 shows the possibility of producing the sliding shoe completely from plastic and directly by means of an assembly injection molding method to the

To mold working piston. A disadvantage of the method is that the molded plastic tends to adhere to the metallic working piston.

A solution for a gasoline pump shown in US Pat. No. 6,181,321 B1, in which plastic sliding shoes are clipped to the working pistons, is not applicable to hydraulic reciprocating engines since the high-strength or wear-resistant plastics required in hydraulics only have a low elasticity, so that a Clipping is not possible without damaging the shoe. DE 10 2008 038 767 A1 shows a solution in which the sliding shoe made of plastic can also be clipped onto the working piston. For this purpose, the sliding block and a head of the working piston on coupling projections and coupling receptacles, on the between the head and the shoe a rotatable or pivotable

Snap connection is created. Again, it is also disadvantageous that the appropriately elastic plastic used does not have the optimum wear resistance.

In contrast, the invention is based on the object to provide a cost-effective piston assembly for a hydraulic piston engine with a sliding shoe made of plastic.

This object is achieved by a piston arrangement having the features of patent claim 1 and by a method for producing the piston arrangement having the features of patent claim 6.

Advantageous developments of the piston assembly are described in the claims 2 to 5. Advantageous developments of the method for manufacturing the

Piston assembly are described in the dependent claims 7 to 12.

The piston assembly according to the invention for a hydraulic piston machine has a piston and a sliding shoe, which consists of plastic. The sliding shoe has a sliding surface, via which it can be supported on a support surface of the hydraulic piston machine. The piston is rotatably or pivotally connected to the sliding shoe via a joint which is formed by a piston foot and a joint mount arranged on the sliding shoe. In this case, the piston foot on a taper, which is engaged behind by a collar of the joint receptacle. According to the collar is caulked towards the taper. Preferably, the collar has been caulked warm in the heated state. The plastic shoe is lighter than the metal and therefore saves weight. At the same time, the material costs are much lower compared to non-ferrous metals. Since non-ferrous metal contains lead, plastic sliding shoes are more environmentally friendly. Another advantage is that over the caulked Collar of the shoe, the joint is not solvable. The thus created articulated connection between the piston and the shoe also has the advantage that during a suction stroke of the shoe is taken from the piston (once per revolution) and no separate driving device must be provided. The advantages mentioned make the piston assembly cost.

In a particularly preferred embodiment of the shoe is made of a

made of thermoplastic material. Due to their processability and good mechanical strength, polyetheretherketone (PEEK),

Polyphthalamide (PPA) or polyamide (PA) suitable. It is particularly advantageous if the thermoplastic material is reinforced with at least one filler.

To caulk the collar well for rejuvenation, this has at least one approximately axially disposed slot. So are avoided from the caulking resulting unwanted accumulation of material in the collar.

Particularly preferably, the piston is spherical and form-fitting of the

Envelope included. The joint receptacle is thus preferably formed hollow spherical. About the fit the entrainment of the shoe during the suction stroke of the piston is further improved. In addition, it results from the positive connection that the transition from suction to a pressure stroke of the piston due to a small clearance between the joint partners a pressure surge is minimized on the shoe, which increases its life.

To minimize in continuous operation a contact pressure of the shoe to the support surface of the piston engine and wear between the shoe and the support surface of the piston and the shoe is penetrated by a pressure medium channel, which opens into the sliding surface. Through this pressure fluid channel pressure medium is passed into a space between the shoe and the support surface, whereby the shoe is hydrostatically relieved. The method for manufacturing a piston assembly according to the invention comprises according to the invention the step "caulking the collar of the joint receptacle towards the taper of the piston foot", whereby the piston assembly can be produced by a procedural low-cost and favorable step.

In this case, the collar is preferably caulked by pressing at least one jaw or a heating jaw of a tool for rejuvenation.

It proves to be particularly advantageous if, prior to the caulking step, a step "heating of the collar" takes place, so that caulking is a hot caulking, or if after the caulking step a step "cooling of the collar" takes place. When warm caulking is a temperature of the heated

Plastic or thermoplastic below its melt temperature. The collar can thus be more easily caulked and adheres due to the moderate in comparison with a prior art assembly injection molding process

Temperature not at the piston base. After caulking, the collar must be brought back to ambient temperature. This happens the fastest, where he experiences a cooling.

The step of heating is carried out in a preferred embodiment of the method either by infrared irradiation of the collar, or by heat conduction from a heating jaw of a tool towards the collar. The cooling down step takes place

Device-technically little complicated by convection of air flow, which covers the collar or by heat conduction from the collar to a cooled jaw of a tool. Meanwhile, to prevent springback upon cooling, regardless of whether a cooling method is selected, the jaw of the tool or other fixture should remain supported on the collar.

The heating jaw is preferably heated by applying a voltage or by magnetic induction. In particular, the magnetic induction proves to be a fast and safe method for heating the heating jaw. It is particularly preferred if, in a process step preceded by caulking, the sliding shoe is formed by injection molding via a single step, whereby a high number of sliding shoes can be produced at low unit costs in a short time. The shoes do not have to be cut individually to your final contour, but fall urgeformt from the injection mold. Post-processing is minimized.

In a preferred embodiment of the method takes place to any

Time after the initial shaping of the shoe, but preferably before caulking with the piston, a drilling of an approximately coaxial through hole in the shoe over which the pressure medium channel is formed. The bore can be made with a special plastic drill or a plastic drill suitable for plastics, for example a C02 laser, a Nd: YAG or excimer laser, which leaves no plastic particles or glass fibers behind.

In the following, an embodiment of a piston assembly according to the invention in a drawing, and three embodiments of an inventive

Method for manufacturing the piston assembly based on three schematic

Drawings explained in more detail. Show it:

Figure 1 shows an embodiment of a piston assembly in a longitudinal section;

Figure 2 shows a first embodiment of a method for manufacturing the

Piston assembly according to Figure 1;

Figure 3 shows a second embodiment of a method for manufacturing the

Piston assembly according to Figure 1; and

Figure 4 shows a third embodiment of a method for manufacturing the

Piston arrangement according to FIG. 1 FIG. 1 shows an embodiment of a piston arrangement 1 according to the invention in a longitudinal section. The piston assembly 1 has a piston 2, which is only partially shown, and a shoe 4. The shoe is made of the thermoplastic PEEK in an injection molding process. On a lower side in FIG. 1, the sliding shoe 4 has a sliding surface 6, via which it is supported on a sliding surface of a swashplate of a swashplate-type axial piston machine (not shown). The sliding shoe 4 has a circumferential radial

Extension 8, so that a Kippfestigkeit of the shoe 4 is increased on the sliding surface of the swash plate.

At a lower portion in FIG. 1, the piston 2 has a piston foot 10, which is received in a form-fitting manner in a joint receptacle 12 of the sliding shoe 4. The piston foot is spherical in shape, the joint receptacle 12 accordingly as well. The piston foot has at a portion where it is connected to the piston 2, a taper 14 which is engaged behind by a collar 16 of the shoe 4. The collar is inventively heat stiffened by means of heat conduction towards the taper 14.

For a hydrostatic relief of the sliding surface 6 with pressure medium from a working space (not shown) of the piston 2, this has a continuous bore 18th

Together with a funnel-shaped inlet 20 and a through hole 22, which opens into the sliding surface 6, the bore 18 forms a pressure medium channel 24. The piston foot has an axial flattening 26 at its end portion, so that upon pivoting of the piston 2 from an axis Z, the pressure medium connection between the sliding surface 6 and the bore 18 is not interrupted. The piston 10 is bordered in the shoe 4 with a very small game.

Figure 2 shows a first embodiment of a method for manufacturing the

Piston arrangement 1 according to FIG. 1

A first step of injection molding A takes place in an injection mold 130, which is designed as a multi-cavity mold and preferably with a hot runner system is operated. In this case, the sliding shoe 4 is molded in the injection mold 130 from a reinforced with fillers thermoplastic polyetheretherketone (PEEK).

After a predetermined cooling time, the sliding shoe 4, or in mass production, the sliding shoes 4, removed in steps B and C and fed to a device which generates the through hole 22 in a step D. The through-bore 22 is for this purpose with a special plastic drill or a CO2 laser drill 132, which leaves no plastic particles or glass fibers produced.

In the next process step, the fixed sliding block 4 is supplied to a caulking device 134, in which it is joined to the piston 2. In this case, the piston 10 is fixed vertically in the joint seat 12. The projecting collar 16 of the shoe 4, which is provided with slots (covered by the piston 2) is caulked by 3 lateral heating jaws 136 (only two visible) to the taper 14 towards warm.

Since the temperature of the heating jaws 136 is between a heat distortion temperature and a melting temperature of the thermoplastic, the plastic of the sliding shoe 4 does not adhere to the piston base 10. The heating jaws 136 are made of steel and in the vicinity of the collar 16 cooling channels 138 are introduced. Through this, a cooling medium is introduced after the hot caulking of the collar 16 to cool the plastic in the caulked position. Since a contact force of the heating jaws, which now have cooling function, is withdrawn only after cooling, springback of the collar can be prevented. A brought into contact with the collar 16 surface of the heating jaws 136 is provided with a non-stick coating, so that the plastic can not adhere.

The hot caulking of the protruding collar can still be carried out by alternative heating methods. Two preferred methods are shown in FIGS. 3 and 4.

Figure 3 shows a second embodiment of a method for manufacturing the piston assembly 1. Shown is the heating of the collar 16 by irradiation with Infrared radiation of an infrared radiation source 240, in which the collar 16 of the shoe 4 can be heated in a very short time. As soon as the softening temperature of the plastic is reached, contour-adapted jaws 237 of a caulking device 234 press the collar 16 against the taper 14 of the piston foot 10. At the same time, the infrared radiation is switched off. The jaws 237 rapidly cool by convection of airflow and the plastic of the collar 16 solidifies in the new position.

FIG. 4 shows a third exemplary embodiment of a method for producing the piston assembly 1. Shown is the heating of the collar 16 by contour-matched heating jaws 336, which are heated by induction. A copper inductor 342 heats up the heating jaws 336 in just a few seconds. As soon as the heating jaws 336 have reached the softening temperature of the plastic, springs 344 press the heating jaws 336 and these push the collar 16 against the taper 14 of the piston foot 10. At the same time, the induction is switched off. The Hetzbacken 336 quickly cooled by an air purge and the plastic solidifies in the new position.

Notwithstanding the exemplary embodiments shown, the through-bore 22 can be drilled with an Nd: YAG or excimer laser, or with a special plastic drill.

Deviating from the exemplary embodiments shown, possible heating methods are convection by means of hot gas, laser heating, as well as internal and external friction by means of ultrasound, rotation or vibration.

Disclosed is a piston assembly for a hydraulic piston machine with a piston and with a sliding shoe made of plastic, wherein a piston base and arranged on the sliding shoe pivot receptacle form a joint and the piston foot has a taper which is engaged behind by a collar of the joint receptacle.

According to the collar of this case is caulked towards the taper. Disclosed is still a manufacturing process for manufacturing the piston assembly.

Claims

claims

A piston assembly for a hydraulic piston machine, comprising a piston (2) and a sliding shoe (4) made of plastic and having a sliding surface (6) via which it can be supported on a support surface of the piston engine, the piston (2) via a joint which is formed by a piston foot (10) and a joint receptacle (12) arranged on the sliding shoe (4), is connected to the sliding shoe (4), and wherein the piston foot (10) has a taper (14) characterized by a collar (16) of the joint receptacle (12) is engaged behind, characterized in that the collar (16) is caulked towards the taper (14).

2. Piston assembly according to claim, wherein the plastic is a thermoplastic.

3. Piston arrangement according to claim 1 or 2, wherein the collar (16) has at least one approximately axially disposed slot.

4. Piston arrangement according to one of the preceding claims, wherein the piston foot (10) is spherical and positively engages around the joint receptacle (12).

5. Piston arrangement according to one of the preceding claims, wherein the piston (2) and the sliding block (4) are penetrated by a pressure medium channel (24) which opens into the sliding surface (6).

6. A method for manufacturing a piston assembly according to one of

Claims 1 to 5, characterized by caulking the collar (16) of the joint receptacle (12) towards the taper (14) of the piston foot (10).

7. The method according to claim 6, wherein the step by caulking

Pressing at least one jaw (237) or a heating jaw (136; 336) of a

Tool on the collar (16).

8. The method of claim 6, wherein prior to the caulking step, a step of heating the collar (16), or wherein after the caulking step, a step of cooling the collar (16).

9. The method of claim 8, wherein the step is heated by

Infrared irradiation of the collar (16), or by heat conduction from a heating jaw (136; 336) of a tool to the collar (16), or wherein the step cooling by convection of an air flow to the collar (16), or through

Heat conduction from the collar (16) to a cooled jaw of a tool takes place.

10. The method according to claim 9, wherein the heating jaw (136, 336) by

Applying a voltage or is heated by magnetic induction.

1 1. A method according to any one of the claims 6 to 10, wherein the sliding shoe (4) is urgeformt via a step injection molding.

12. The method according to any one of claims 6 to 1 1, wherein about a step drilling in the shoe (4) an approximately coaxial through hole (22) is formed.