DE202004021158U1 - Sliding shoe, for an excavator diesel motor or a hydrostatic piston motor, has a sliding sole composed of an alloy of copper and tin and titanium with local bonding between the sole and the shoe body - Google Patents

Abstract

The sliding shoe (1), e.g. for the diesel motor of an excavator or a hydrostatic piston motor, has a body (3) fitted with a sliding sole (2) bonded locally together. The running surface of the sole is of a spray compacted alloy composed of 13.5-20.0 wt.% tin, 0.05-0.5 wt.% titanium and the remainder of copper. Selective additives can include silicon, chromium and zirconium to a total weight of 1.0 wt.% plus any unavoidable impurities.

Description

The Invention relates to a sliding body, consisting of a basic body and one on the main body arranged sliding sole with a tread.

The power transmission from the diesel engine to the wheels and work equipment takes place in earthmoving machinery, for example Excavators or cranes, by so-called hydrostatic drives. at The swashplate pumps often used as a drive become the torque the crankshaft over a slope Disc with variable angle of attack transmitted to reciprocating pistons. The pistons sit in a rotating cylinder housing. A sliding connection to the fixed swash plate by means of sliding shoe causes a reciprocation of the pistons at each revolution. Of the Stroke is due to the respective angle of attack of the swash plate certainly. The thus driven pistons provide a pressure build-up in oil pressure lines, over the in turn, a hydraulic motor can be driven.

During the Diesel engine usually operates in nominal load operation, the transmitted pressure by oblique position the disc and the changed with it Stroke movements of the piston varies stepless within certain limits become.

at Drivers is the increase in power density of principle Interest. This also increases the demands on the sliding shoes in terms of Strength and runflat because performance at higher speeds and higher To press must be applied. The increase the pressures reinforces the specific load and claimed as a result, the sliding surfaces stronger. On Reason of higher Speeds associated increase the centrifugal forces have to all rotating components are made lighter. This can be, for example achieved by a minimized component size become.

The to an increase the load capacity requirements are placed on the shoe primarily by materials such as coated steel but also met by some special brasses. In practice one finds frequently either sliding shoes made of steel, on which a high leaded bronze on the tread is poured or sliding shoes, made entirely of special brass consist.

Stahlgleitschuhe have high strengths, depending on the variety. They represent a preferred one Material of the basic body The bad tribological properties can through the infusion high-leaded cast bronzes on the tread already improved. The disadvantage here is the casting structure created by the pouring process with a low strength of the sliding layer.

Corresponding sliding shoes are for example in the document GB 1 355 325 described. The document discloses an axial piston pump or motor comprising a sliding shoe with friction reducing layers at the contact surfaces between the shoe and ball of the joint. These friction-reduced layers are metallically bonded to the shoe, for example, by friction welding, plating or by powder metallurgy. Optionally, intermediate layers of molybdenum are also used.

Of Further are sliding shoes for hydrostatic piston machines from the document OS 2 025 169 known opposite larger temperature fluctuations should be less sensitive in operation with good sliding properties. This will be on a re opposite the sliding sole lying surface a shoe with a layer of the same material as the soleplate fixed, so that due to appropriate arrangement of materials with different coefficients of expansion an otherwise occurring disadvantageous bulge of the Sliding sole can be largely avoided.

Of the Invention has for its object to provide a slider, the over a composite material improved tribological and mechanical Features.

The Invention is related a slider represented by the features of claim 1. The others refer back claims relate to advantageous embodiments and further developments of the invention.

The Invention includes in terms of a method for producing a slider, consisting of a body and one on the main body arranged sliding sole with a tread, the technical teaching, through the sliding sole and the main body by means of capacitor discharge welding together get connected.

the joining methods For connecting the sliding sole with the main body is of particular importance to. The microstructure should be in the connection area between the tread from the proposed Tin bronze and the main body made of steel as possible little disturbed become.

The invention is based on the consideration that forms a locally narrow heat affected zone of a few micrometers in this joining process. For welding, only as much energy is brought to the joint as necessary. The surrounding matrix remains unaffected and there is no hardening waste due to high temperatures during joining. Due to the low heat input form a favorable Schweißgutgefüge and a narrow heat affected zone. The heat-affected zone is limited in particular by an extremely short joining time in the range of approximately 10 ms and a high current flow of up to 500 kA. For the small amount of heat usually no electrode cooling is necessary.

Of the particular advantage is that it due to the extremely short joining time to no significant structural change or oxidation comes. The cut can be seen in the joining area no cracks or pores. With this joint connection can also mechanical forces be transferred from the soleplate to the base body and thereby In addition, the different thermal expansion behavior of the used Attention to materials.

In Preferred embodiment of the invention, the sliding sole and the main body locally connected. In such a connection can for heating contributing current flow are controlled accordingly targeted.

A of the two joining surfaces, the usually made of material with higher Strength and lower conductivity, steel, in this case, is designed constructively so that in the touch area one or more surveys are arranged. The surveys, in Technical jargon called "hump", can as be formed all around extending ring hump, which has the contact surface a minimum reduced. The welding energy and the welding pressure are In capacitor discharge welding, the most important setting parameters. These parameters are adapted to the component to be welded. At the welding is a capacitor bank on the for the welding process provided energy is charged with a constant current. A welding press drives electrodes on the component and builds up the set welding pressure. Then the capacitors are discharged, which over the joining partner the welding current flows. The humps are through the current passage in contact with the joining partner melted and connected by the load pressure with this. The joining process is canceled before both joining surfaces complete meet each other. This creates a gap or cavity between the parts to be joined. Excessive melt Can be accommodated by constructive collecting bags.

advantageously, The soleplate and the body are about a peripheral in the outer edge region Ring hump alone or with a centrally located ring hump connected with each other. Particularly preferred is a compound of one in the outer edge area circumferential ring hump in conjunction with a centrally located Ring hump. As a result, in the operation acting on the tread Force targeted at the supporting Transferred basic body. This can also the different expansion behavior of the various Materials are taken into account. By further, on the respective Expansion behavior when heated adapted humps, the bulge described in the prior art Edge areas are even reduced.

One Another aspect of the invention with respect to a slider closes the technical teaching that the slider body and a body one on the main body arranged sliding sole having a tread, wherein at least the tread the sliding sole made of a spray-compacted Consists of non-ferrous metal bearing material. As non-ferrous metal bearing materials In particular copper-based alloys are used.

Prefers For example, the non-ferrous metal bearing material consists of one by means of spray compacting produced copper-tin-titanium alloy from 13.5 to 20 wt .-% Tin, 0.05 to 0.5 wt .-% titanium, balance copper and optionally from one or more of the elements of the group silicon, chromium and zirconium bis to a total content of 1.0% by weight and unavoidable impurities.

The Invention is based on the consideration, that for himself sliding in their composition optimized tin bronzes are suitable, in the spray compacting can be produced causing the slider a higher one Withstand load under operating conditions. Macroscopic segregations, as with conventional casting methods already occur from 6 wt .-% tin content, are up to the Löslichkeitsgrenze of tin in copper at 13.5 wt% Sn practically not observed. Only when exceeded the specified solubility limit can yourself for the tribological applications desired Form second phases. This can especially at higher tin contents also a higher one Titanium content to be contained in the alloy.

at the second phase is a delta phase with a tin content of about 25 wt .-%, which is extremely hard. The structure of the basic matrix It consists of copper and tin dissolved in copper up to a maximum soluble Content of about 13.5 wt .-%.

A optional addition of the elements chromium, silicon and zirconium causes during further processing in forming operations a grain refining of the alloy.

The production of the tread material in Round discs with a thickness of about 5 mm follow conventional semi-finished products. For further processing following the spray-compacting process, the material is hot-pressed, whereby the rod diameter, depending on the subsequent degree of cold-working, can already be selected close to the final dimensions. Due to the cold forming process different states can be set safely and reproducibly.

One Extrusion process and the subsequent cold deformation provide for this, that the delta phase precipitates are aligned in the direction of deformation become.

When Alternative is the production of a band. By vote The production parameters can be adjusted here also different material conditions. The necessities Round discs can finally be punched out of the finished strip.

ever after manufacturing via a press bar or a rolled strip differ the microstructures. While in pressed rods, the precipitates are arranged perpendicular to the tread are, lie in the rolled state horizontal to the surface. By Abrasion of the softer base matrix forms a network of voids that ensure a safe lubricant transport.

Of the body can consist of a steel alloy. The slider is Accordingly, formed from a composite material, with respect to its sliding properties and re its stability in use made of completely different materials is constructed. The joining process For the production of the composite material is of particular importance to. The steel body serves to absorb the forces generated during operation on the tread.

The particular advantages of the invention are that a high strength steel body with a tribologically optimized lead-free Copper material is used together. So are sliding body with excellent tribological and mechanical properties as well with increasing power density for a wide range of applications to disposal.

In Advantageous embodiment of the invention, the copper-tin-titanium alloy of the slider 14.0 contain up to 17.0 wt .-% tin. This becomes the solubility limit for tin already exceeded, causing yourself the desired ones Can train second phases. This narrower Element content opened for tin a sufficient and variable in its parameters process window for one with respect to their Material properties reproducible and high quality Alloy.

advantageously, For example, the copper-tin-titanium alloy of the slider may be 0.1 to 0.3% by weight of titanium contain. A Titanzusatz requires an increase in the density of Alloy. Titanium is able to form nitrides, thereby which was used as the spray gas in the manufacturing process of spray compacting Nitrogen can be tied off as titanium nitride. Shares over 0.3 Wt .-% lead in the current practice to no further improvement of the alloy properties.

In preferred embodiment The invention can be the tread of the slider a directed biphasic structure from the copper-tin-titanium alloy.

In particularly preferred embodiment that the entire sliding sole of the slider with the tread consists of copper-tin-titanium alloy. Such sliding soles meet by their preferred sliding properties in conjunction with appropriate mechanical properties both requirements regarding tribological and mechanical requirements in one.

In preferred embodiment can the basic body consist of a steel alloy. This will be done accordingly high strength already ensured in the body.

advantageously, the sliding sole can be connected to the main body over the entire surface. alternative Advantageously, the soleplate may be local to the base body be connected.

In Another advantageous embodiment of the invention, the sliding sole with the main body over an outer ring hump and / or a centrally located ring hump be connected to each other. This arises in particular using the method according to the invention of capacitor discharge welding a reliable connection of basic body and sliding sole with low heat in the manufacturing process at the joining surfaces.

such Sliders according to the invention can as Sliding shoe for hydrostatic piston engines are used.

embodiments The invention will be explained in more detail with reference to a schematic drawing.

In this demonstrate:

1 a cross section of the connecting surface of a base body with a sliding sole, and

2 an enlarged section of a connection surface.

each other corresponding parts are in all figures with the same reference numerals Mistake.

1 shows a cross section of a connecting surface formed by capacitor discharge welding 4 of a basic body 3 with a sliding sole 2 a sliding shoe 1 , The microstructure is at the interface 4 between the tread of the proposed tin bronze and the base made of steel by a low heat input of the manufacturing process almost not disturbed. A locally limited heat-affected zone only forms in the range of a few micrometers. The surrounding matrix remains unaffected and there is no hardening drop in the material. In this example, the joining surface was the sliding sole 2 The joining process was already stopped before both joining surfaces met completely, creating the cavity between the joining parts, which can absorb excessive melt.

2 shows an enlarged section of a connection surface 4 a sliding shoe 1 , The method of capacitor discharge welding leads to an intensive toothing of the connection surface 4 of sliding sole 2 and basic body 3 under local heat. The joint does not show any cracks or pores in the joint area.

1

Sliding body, sliding shoe

2

soleplate

3

body

4

interface

Claims (7)

Sliding body ( 1 ), consisting of a basic body ( 3 ) and one on the main body ( 3 ) sliding sole ( 2 ) having a tread, characterized in that - at least the tread of the sole ( 2 ) of a sliding bearing material made of a copper-tin-titanium alloy produced by spray-compacting from 13.5 to 20 wt .-% tin, 0.05 to 0.5 wt .-% titanium, balance copper and optionally one or more of the elements consists of silicon, chromium and zirconium up to a total content of 1,0% by weight and unavoidable impurities, and - that the sliding sole ( 2 ) and the basic body ( 3 ) are only locally connected. Sliding body according to claim 1, characterized in that the sliding sole ( 2 ) with the basic body ( 3 ) are connected to each other via an outer ring hump and / or a centrally located ring hump. sliding according to claim 1 or 2, characterized in that the copper-tin-titanium alloy 14.0 contains up to 17.0 wt .-% tin. sliding according to one of the claims 1 to 3, characterized in that the copper-tin-titanium alloy Contains 0.1 to 0.3 wt .-% titanium. sliding according to one of the claims 1 to 4, characterized in that the tread is a directional biphasic structure from the copper-tin-titanium alloy having. Sliding body according to one of claims 1 to 5, characterized in that the sliding sole ( 2 ) is made with the tread of the copper-tin-titanium alloy. Sliding body according to one of claims 1 to 6, characterized in that the basic body ( 3 ) consists of a steel alloy.