EP1288495A2 - Hollow piston for a piston engine - Google Patents

Abstract

The invention relates to a hollow piston (1) for a piston machine, with a closed annular cavity (9), consisting of a first piston part (1a) with a base section (3), from which a joint part (4) extends in one axial direction. and in the other axial direction each extend in one piece with a circumferential wall (6) delimiting the ring cavity (9) and a mandrel (7) delimiting the ring cavity (9) on the inside, and consisting of a second piston part (1b) with a cover (8) which is connected to the ends of the peripheral wall (6) and the mandrel (7) facing away from the base section (3). The peripheral wall (6) and the mandrel (7) are formed on the base section (3) without cutting in order to achieve an inexpensive, simple manufacture while ensuring a stable construction. <IMAGE>

Description

The invention relates to a hollow piston for a Piston machine according to the preamble of claim 1.

A hollow piston according to the preamble of claim 1 is in DE 196 20 167 C2. With this previously known Hollow piston exists between the peripheral wall and the central mandrel is a ring hole made by deep drilling is machined. This is a labor and predetermined time-consuming manufacturing effort, by the relatively high manufacturing costs are required. there it should be borne in mind that the production of this known Hollow piston also with a relatively high Material loss occurs due to the cutting The ring hole is worked in. Furthermore, this points Hollow piston a ball joint part in the form of a joint ball on, which from the base portion of the hollow piston in the Cavity extends in opposite axial direction.

DE 26 53 867 A1 describes a hollow piston and a method described for its manufacture, the two separate Hollow piston parts is formed, namely one Base section, the peripheral wall and the ball joint part comprising first piston part and one the cover and one extending from this integral mandrel containing second piston part. For stabilization the connection between the first and the second Piston part holds the lid with a cone-shaped approach at the free edge of the peripheral wall in the hollow piston and that free end of the mandrel engages in a recess in the Base section, the two piston parts by soldering are connected to each other. In these known hollow pistons are on the one hand the peripheral wall of the first piston part and on the other hand through the mandrel of the other piston part Extrusion in one piece on the associated piston part molded, but are in this known embodiment two separate molding operations in two separate Molding tools required.

The invention has for its object a hollow piston of the type specified in such a way that at Ensuring a simple or inexpensive Manufacturing, a stable design is achieved, and a to specify the corresponding manufacturing process.

This object is achieved by the features of claim 1 solved.

In hollow pistons according to claim 1, the peripheral wall and the central mandrel without cutting to the base section of the hollow piston formed. This will not only be the one machining deep drilling caused material loss avoided, but also when deep drilling resulting, circumferential grooves in the Inner surface of the peripheral wall and the outer surface avoided the mandrel, making the hollow piston a receives much greater stability because the Circumferential scores significantly reduce that Resistance of the hollow piston against bending loads. In addition, the one-piece molding of the peripheral wall and the central mandrel easier to manufacture and perform faster without disposing of the Chips needed.

It is particularly advantageous to the peripheral wall and the to form the central mandrel by extrusion. This will not just a simple and quick transformation reached, but extrusion also result in the Longitudinal direction of the piston directed material fibers, whereby the peripheral wall and the mandrel a particularly large Resistance to bending stresses received and also are basically of great strength, which is also by extrusion due to material and Microstructure compaction is achieved.

In the context of the invention, the peripheral wall and the central mandrel can alternatively also be formed in that these parts with the base section made of sintered material exist and with which between the peripheral wall and the Mandrel extending ring hole are shaped and sintered. This also makes it not just a simple one Achieved inexpensive manufacture, but it can too the advantage can be exploited that a sintered material suitable as a sliding material, which can be attributed to that the pores present in a sintered material Form lubricant pockets that provide good lubrication and a relatively low wear of the sliding surfaces guarantee.

Another hollow piston consists of two cup-shaped ones Blank sections, the shape and size of their Internal shape, i.e. the shape of the cavity halves, identical are. This makes it possible, at least for the configuration the internal shapes of the hollow pistons have the same tools and To use manufacturing measures. This will Manufacturing process significantly simplified, and it can manufacturing costs are reduced considerably.

It is not particularly advantageous not to have the hollow piston made of two only in terms of their inner shape but also in terms of their Outer shape and thus identical blank sections or To assemble prefabricated parts. It is therefore necessary just a kind of prefabricated parts to be made, which are put together in opposite order and be connected to each other, especially by Welding, and thus form a piston blank.

Features are contained in the subclaims which are used for Solution of the object on which the invention is based contribute, enable further material savings and a shorter overall length of the hollow piston or Allow the piston engine as a whole. The latter will achieved in particular by the fact that the Base portion of the hollow piston extending ball joint part is formed by a ball socket, the Outer peripheral surface as the outer surface and sliding surface of the Hollow piston can be used, so that the piston guide can extend over the ball socket and consequently the axial length of the piston machine can be reduced can.

Fig. 1

einen erfindungsgemäßen Hohlkolben für eine Kolbenmaschine im axialen Schnitt;

Fig. 1a, 1b und 1c

drei Vorfertigungsteile, die zu einem Kolbenrohling weiter verarbeitet werden;

Fig. 1d

ein durch eine Stützscheibe stabilisiertes Vorfertigungsteil;

Fig. 1e

den Kolbenrohling im axialen Schnitt;

Fig. 2

einen Kolbenrohling in abgewandelter Ausgestaltung;

Fig. 3

ein Vorfertigungsteil für den Hohlkolben im axialen Schnitt mit angedeutetem Faserverlauf nach dem Stand der Technik;

Fig. 4

ein erfindungsgemäßes Vorfertigungsteil für den Hohlkolben mit angedeutetem Faserverlauf im axialen Schnitt;

Fig. 5

ein Vorfertigungsteil für den Hohlkolben im axialen Schnitt nach dem Stand der Technik;

Fig. 6

ein erfindungsgemäßes Vorfertigungsteil für den Hohlkolben im axialen Schnitt;

Fig. 7

einen erfindungsgemäßen Hohlkolben in abgewandelter Ausgestaltung im axialen Schnitt;

Fig. 7a, 7b

zwei einander gleiche Vorfertigungsteile für den erfindungsgemäßen Hohlkolben nach Fig. 7;

Fig. 7c

eine Kolbenrohling für den Hohlkolben nach Fig. 7 im axialen Schnitt;

Fig. 8

einen erfindungsgemäßen Hohlkolben im axialen Schnitt in weiter abgewandelter Ausgestaltung;

Fig. 8a, 8b

zwei Vorfertigungsteile für den Hohlkolben nach Fig. 8 im axialen Schnitt; und

Fig. 8c

einen Kolbenrohling im axialen Schnitt für einen Hohlkolben nach Fig. 8.

The invention and further advantages which can be achieved by means of preferred exemplary embodiments and drawings are explained in more detail below. Show it

Fig. 1

a hollow piston according to the invention for a piston machine in axial section;

1a, 1b and 1c

three prefabricated parts that are processed into a piston blank;

Fig. 1d

a prefabricated part stabilized by a support disc;

Fig. 1e

the piston blank in axial section;

Fig. 2

a piston blank in a modified configuration;

Fig. 3

a prefabrication part for the hollow piston in axial section with indicated fiber course according to the prior art;

Fig. 4

a prefabricated part according to the invention for the hollow piston with indicated fiber course in axial section;

Fig. 5

a prefabrication part for the hollow piston in axial section according to the prior art;

Fig. 6

a prefabricated part according to the invention for the hollow piston in axial section;

Fig. 7

a hollow piston according to the invention in a modified configuration in axial section;

7a, 7b

two identical prefabrication parts for the hollow piston according to the invention according to FIG. 7;

Fig. 7c

a piston blank for the hollow piston of Figure 7 in axial section.

Fig. 8

a hollow piston according to the invention in axial section in a further modified embodiment;

8a, 8b

two prefabrication parts for the hollow piston according to FIG. 8 in axial section; and

Fig. 8c

8 shows a piston blank in axial section for a hollow piston according to FIG. 8.

The hollow piston generally designated 1 with a cylindrical lateral surface 2 has a base section 3 on, of which there is a joint part in one longitudinal direction 4, a joint ball 5 in the present exemplary embodiment with a ball neck 5a, and in the other longitudinal direction a hollow cylindrical peripheral wall 6 and a cylindrical extend central mandrel 7, which at its the base portion 3 opposite ends through a cover 8 with each other are connected. Between the peripheral wall 6 and the mandrel 7 there is an annular cavity 9 which is closed on all sides is. In the present embodiment, the End face 11 at the front free end of the hollow piston 1 a frustoconical shape. However, it can also be one have another shape, e.g. a radial plane face his.

The hollow piston 1 is made of two or three parts assembled and manufactured, namely a base body part 1a according to FIG. 1a, a cover part 1b according to FIG. 1b and optionally a centering disc 1c according to FIG. 1c. The Base body part 1a and the cover part 1b are for the purpose Further training as a piston blank 1e according to FIG. 1e on a Gap 12 axially placed against each other, which are in Length range of the annular cavity 9 is, where preferably a distance a from the cover 8 and also one Has distance b from the base section 3. Consequently a section of the annular cavity 9 extends in each case both in the base part 1a and in the cover part 1b, whereby peripheral wall sections 6a, 6b and Mandrel sections 7a, 7b result, which face each other. The centering disc 1c is between the peripheral wall 6b and the mandrel section 7b of the base body part 1a inserted (s. Fig. 1d), with its central hole 13 and her Outside diameter to the cross-sectional size of the mandrel section 7b and the inner diameter of the peripheral wall portion 6b is adjusted. The diameter of the mandrel section 7b may be slightly tapered (not shown) or the Inner diameter of the peripheral wall portion 6b can be slightly expanded, so that in a small axial distance b from the free end of the base part 1a gives a contact shoulder 14 for the centering disc 1c. The centering disc 1c has a through hole 13a, preferably on its outer edge, e.g. a notch on that or through a flow passage between the two the centering disc 1c separate cavity sections guaranteed.

The outer diameter of the main body part 1a and Cover part 1b are each with respect to the diameter d of Hollow piston 1 prefabricated with an oversize x. The Base section 3 is on the base body part 1a by an axial Dimension c extended, which is dimensioned so long that the Joint ball 5 with its ball neck 5a are formed therefrom can, e.g. by cutting off.

The hollow piston 1 or the base body part 1a and that Cover part 1b exist in the present embodiment Made of metal, especially steel, which is suitable for extrusion suitable.

The base body part 1a and the cover part 1b are at Attachment to the surfaces of the division joint 12 by welding connected to each other, preferably by friction welding what by rotating one part relative to the other can be achieved, as is known per se. While of rubbing, the peripheral wall portions 6b and Mandrel section 7b in the area of the dividing joint 12 as strong heated so that they melt in the region of the dividing line 12 and weld them together, being inside and outside Weld beads 15 can form. During the rotation and of welding is in particular the mandrel section 7b supported radially by the centering disc 1c.

By welding the base part 1a and the Cover part 1b results in a piston blank 1e according to FIG. 1e, in which the radial and axial oversizes x by a dash-dotted representation of the final piston shape are made clear.

The embodiment of FIG. 2, in the same or Comparable parts with the same reference numerals shows a piston blank 1e, which differs from above-described embodiment only thereby distinguishes that the parting line 12 more to the free end the peripheral wall 6 is offset, e.g. near the Cover 8 or up to cover 8.

The base body part 1a and the cover part 1b are preferably one-piece moldings, d. H. your Are peripheral wall portions 6a, 6b and mandrel portions 7a, 7b each in one piece on the associated base section 3 or Molded lid 8. Preferred measures for this can e.g. Sintering and extrusion, in particular cold extrusion, his. In the first case, the base part 1a and that Cover part 1b shaped in that the respective sintered material in entered a corresponding cavity of a shape and is sintered. Extrusion takes place in itself known extrusion dies of the appropriate shape, wherein the peripheral wall portion 6b and the Mandrel section 7b and possibly also the Circumferential wall section 6a and the mandrel section 7a each a blank, not shown, formed by extrusion become. In both cases there is a sufficient one Shape accuracy for the main body part 1a and that Cover part 1b, with an additional sintered part good for a sliding function due to im Sintered pores contained in the functional mode act as lubrication pockets.

The extrusion gives one in the base area of the cavity 9 adjacent material area u-shaped extending fiber course 16, as shown in FIG. 4. This The course of the fibers also results on the inner surface of the Cavity 9, which in Fig. 6 by longitudinal lines and the reference numeral 16a is clarified. In contrast, exhibits by cutting, e.g. by deep drilling, manufactured cavity 9 in the base region of the cavity 9 a broken or axially opening fiber path 16b, which is due to the production of the starting material, e.g. by rolling, calibrating or drawing. Also points the inner wall of the cavity 9 in a cutting Manufacturing, e.g. by deep drilling, transverse to the longitudinal direction running grooves 16c, which - as already in the Base region of the cavity 9 interrupted fiber course 16b - lead to risk of breakage.

Another advantage is that both of the above Manufacturing measures no material is to be cut to the to achieve the desired shape of the annular cavity 9. The existing material is thus optimally used.

• Herstellen jeweils wenigstens eines Grundkörperteils 1a und eines Deckelteils 1b durch einstückiges Formen mit einem radialen Übermaß x. In solchen Fällen, in denen sich die Teilungsfuge 12 in der Nähe der Innenseite des Deckelteils 1b befindet, ist es im Rahmen der Erfindung gegebenenfalls praktikabel, den Umfangswandabschnitt 6b und den Dornabschnitt 7b des Deckelteils 1b nicht durch einstückiges Formen sondern spanabhebend einzuarbeiten, z.B. durch Bohren oder Fräsen. Längere axiale Abschnitte der Umfangswand 6 und des Dorns 7 werden dagegen in vorteilhafter Weise einstückig geformt, insbesondere durch Sintern oder Fließpressen, vorzugsweise Kaltfließpressen. Außerdem wird wenigstens eine Zentrierscheibe 1c ausgebildet, insbesondere durch Stanzen aus einer Platine.
• Einsetzen oder Einpressen der Zentrierscheibe 1c in das Grundkörperteil 1a.
• Verschweißen des Grundkörperteils 1a und des Deckelteils 1b zu einem Kolbenrohling 1e gemäß Fig. 1e.
• Einarbeiten einer koaxial durchgehenden Bohrung 21 im Kolbenrohling 1e nach oder vor dem Schweißen im Grundkörperteil 1a und Deckelteil 1b, sofern diese vorhanden ist.
• Härten oder Nitrierhärten des Kolbenrohlings 1e wenigstens im Bereich seiner Mantelfläche 18.
• Spanabhebendes Endbearbeiten der Oberfläche des Kolbenrohlings 1e durch z.B. Drehen und/oder Schleifen.

A method for producing a hollow piston 1 according to FIG. 1 with its method steps is described below.

• Manufacture at least one base body part 1a and one cover part 1b by one-piece molding with a radial oversize x. In such cases, in which the division joint 12 is located in the vicinity of the inside of the cover part 1b, it may be practical within the scope of the invention to incorporate the peripheral wall section 6b and the mandrel section 7b of the cover part 1b by machining rather than in one piece, for example by drilling or milling. Longer axial sections of the peripheral wall 6 and the mandrel 7, however, are advantageously formed in one piece, in particular by sintering or extrusion, preferably cold extrusion. In addition, at least one centering disc 1c is formed, in particular by stamping from a board.
• Inserting or pressing the centering disc 1c into the base body part 1a.
• Welding the base body part 1a and the cover part 1b into a piston blank 1e according to FIG. 1e.
• Incorporation of a coaxial through bore 21 in the piston blank 1e after or before welding in the base body part 1a and cover part 1b, if this is present.
• Hardening or nitriding the piston blank 1e at least in the area of its outer surface 18.
• Machining finishing of the surface of the piston blank 1e, for example by turning and / or grinding.

Machining can be carried out within the scope of the invention the surface of the piston blank 1d also in several Steps. So it is e.g. possible after Welding and before hardening the final shape of the Hollow piston 1 corresponding shape according to FIG. 1, e.g. by turning or grinding, with an oversize to produce at least on the outer surface 18 and after above-described hardness the entire lateral surface or only the hollow cylindrical surface e.g. by grinding finish, with the joint ball 5 already before Hardening can be finished.

The embodiment of FIGS. 7 to 7c, in the same or comparable parts with the same reference numerals differs from the above Embodiment in that the base part 1a and the cover part 1b at least in the area of it Circumferential wall sections 6b and mandrel sections 7b and Cavity sections are identical, preferably also on the outside and thus the same overall design and therefore can be identical parts. Because of the central arrangement of the parting line 12 with respect to the Annular cavity 9 the length of the peripheral wall portions 6a, 6b and mandrel sections 7b is reduced and these parts are more stable due to this reduction Centering disc 1c is omitted, as shown in FIGS. 7 and 7c. However, within the scope of the invention it is also possible at least one of the mandrel sections 7a, 7b, preferably both mandrel sections 7a, 7b, each by one Centering disc 1c to support, as in Fig. 7 to 7c is indicated by dash-dotted lines. With this Embodiment is before or after welding the Base body part 1a with the cover part 1b the latter to cut to dimension e in Fig. 7c. hereby a certain loss of material is predetermined, however the advantage is achieved that the base body part 1a and the cover part 1b are at least the same on the cavity side and therefore there is only one device for manufacturing each these parts are needed. This also reduces the Number of different parts, which means that Manufacturing process is simplified overall and the Manufacturing costs can be reduced.

8 to 8c, in the same or comparable parts with the same reference numerals are different from the prescribed ones Embodiments in that the lid part 1b a disc with a central hole 19, in particular one Through hole is formed, which depends on the cross-sectional size the mandrel 7 is adapted, the mandrel 7 in the hole 19 extends into and the peripheral wall 6 to disc-shaped cover part 1b extends. The Mandrel 7 in the case of a through hole 19 up to Extend the end face of the cover part 1b, as shown in FIG. 8c shows. In this embodiment, the cover part 1b can be Soldering or welding connected to the base body part 1a e.g. on the contact surfaces on the one hand between the cover part 1b and the peripheral wall 6 and the other between the wall of the hole 19 and the lateral surface of the Dorns 7. The parts are preferably by laser welding connected with each other. Otherwise, the hollow piston 1 in this embodiment with those already described Establish process steps. The cover part 1b e.g. be integrally formed by sintering, or it can be machined, especially by turning.

The hollow piston 1 can with in all embodiments a sliding shoe only indicated in Fig. 1 22, which is connected to the hollow piston 1 by an articulated connection 23 is connected to form a piston assembly 24 which at a Piston machine with a swash plate to move the Hollow piston 1 an axial support and an axial Drive of the hollow piston 1 enables. In the present Embodiment in which the hinge part 4 by a Joint ball 5 is formed, the slide shoe 22 instructs its side facing the hollow piston 1 hemispherical joint recess 25, whose Recess edge 26 over the equator 27 of the joint recess 25 is also extended and into a joint ball 5 backward form when ensuring a Movement play is flanged. That of the joint recess 25 opposite surface of the slide shoe 22 is one preferably flat sliding surface 28, which for articulated Support on the swash plate is used. The sliding shoe 22 consists of metal, e.g. a copper or brass alloy like bronze, or steel. The recess edge 26 can be cold or warm. This Flaring can be done before finishing the Shell surface 18 of the hollow piston or as the last Processing step after finishing the outer surface 18 of the hollow piston 1 take place.

In the presence of a coaxial through hole 21 in Hollow piston 1 is also in the shoe 22 in Connected bore section 21a is present, the the sliding surface 28 opens out. Furthermore, the sliding shoe 22 a flange 29, the one the joint recess 25th having radially protruding base portion 31.

Within the scope of the invention, the articulated connection 23 can also be formed in that the joint recess 25 with the Recess edge 26 are arranged on the hollow piston 1 and themselves extend towards the shoe 22, and the Slide shoe 22 has the joint ball 5, which in the Joint recess 25 is pivotally mounted.

Claims (5)

Hollow piston (1) for a piston machine with a closed annular cavity (9), consisting of a first piston part (1a) with a base section (3), of which a joint part (4) in one axial direction and each in the other axial direction extend in one piece a circumferential wall (6) which delimits the ring cavity (9) and a mandrel (7) delimiting the ring cavity (9) on the inside, and consisting of a second piston part (1b) with a cover (8) which is connected to the base section ( 3) opposite ends of the peripheral wall (6) and the mandrel (7) are connected,
characterized in that the peripheral wall (6) and the mandrel (7) are formed on the base section (3) without cutting. Hollow piston according to claim 1,
characterized in that the hollow piston (1) is composed of two cross-divided pieces, the dividing joint (12) of which is at an axial distance (a, b) from the cover (8) and from the base section (3) or is arranged in between, and that Circumferential wall section (6b) and the mandrel section (7b), which extend from the base section (3) and / or the circumferential wall section (6a) and the mandrel section (7a), which extend from the cover (8), without cutting at the base section (3) or The cover (8) are molded on. Hollow piston according to claim 1 or 2,
characterized in that the peripheral wall (6) or the peripheral wall section (s) (6a, 6b) and the mandrel (7) or the mandrel section (s) (7a, 7b) is or are formed by extrusion, in particular cold extrusion. Hollow piston according to claim 1 or 2,
characterized in that the first piston part (1a) with the base section (3) and the peripheral wall (6) or the peripheral section (6a, 6b) and the mandrel (7) or the mandrel section (7b) and / or the second piston part (1b ) is or are sintered with the peripheral wall section (6a) and the mandrel section (7a). Hollow piston according to one of the preceding claims,
characterized in that the joint part (4) is formed by a joint ball (5) or a hemispherical joint recess (25).

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