DE1703538A1 - Axial piston unit - Google Patents

Description

BB 11 729

Gerlafingen

Axial piston unit

The invention relates to an axial piston unit, as used in oil hydraulics both as a pump and as Motor is used. Axial piston units are known in which the axis dos rotating cylinder block opposite those of the drive shaft with the feat associated drive flange sjur setting a particular Hubes is inclined and has therefore been designated as a Schiefachaenöunheit.

ΟΛΚϊίΝΑί. 109885/0403

The pistons, which are hinged to the drive flange with piston rods via ball joints, are on the front side of the drive flange Pressure medium is applied and ea is in each case the Half of the piston under pressure. As a result, considerable forces are exerted on the drive flange. For example, with a 7-piston unit with a piston diameter of 25 mm, with alternating 3 or 4 pistons from an operating pressure of 200 atti, with a small stroke, i.e. when the cylinder and drive shaft axis approximately flush., the axial force around 3 tons (with three loaded pistons) or around 4 tons (with four loaded piston).

These considerable forces must have suitable Bearings are forwarded to the housing. The compact design of the units means that there is only little space to accommodate the bearings. For this reason special roller bearing types have been developed, especially axial cylindrical roller bearings, which are now available in large Scope to be used. Nevertheless, not all needs can be met with these bearings, especially when it comes to applications where because of the örösae of the plant, also small downtimes cannot be accepted for the replacement of the bearings

10 * 8 * 6/0403

or where, for reasons of space, more heavily loaded units must be used where the service life of the mentioned bearing is not sufficient. It is therefore obvious to use plain bearings instead of roller bearings. Hydrostatic sliding bearings, in particular hydrostatic axial sliding bearings, are known, as is their application for axial piston units using the operating pressure a, and they are suitable to meet increased operating conditions. The hydrostatic axial plain bearing, consisting of from a ring field or a number of ring segment-shaped Fields, is fed by the throttled high pressure on the entire circumference, but only on in the unit itself the pressure side, i.e. half of the pistons. When idling, when there is feed pressure on both pressure sides, the load on the bearings is relatively double as high as if there was a pronounced high pressure, since then the throttled the thrust bearing suggested Pressure depending on the size of the bearing proportional corresponds to the pressure prevailing on both pressure sides, i.e. occurs in all pistons. Storage temperature measurements at idle confirm this peculiarity of the hydrostatic bearings operated in this way by the Storage temperature when idling rises above that when under load.

QAIf

10988S / 0403

Another property of the hydrostatic bearings is that they are normal in the presence of pressure run reliably. When starting, the pressure is missing at first, which is only calibrated when the lifting movement begins the piston begins to build up. The metallic contact of the bearing surfaces that occurs here can only then avoided when using a pipeline pressure source

before commissioning the hydrostatic bearing pressurized oil supplies and removes contact with the storage surfaces even when the machine is at a standstill.

So you have the hydrostatic bearing of the unit distinguish between three operating states:

The start-up state in which the pressure is still in the warehouse has not built up, the idle, in which because of the same Druoke on both sides of the print The bearing is relatively heavily loaded and your real one Operation in which the high pressure prevailing on only one pressure side is available to the whole camp.

Failure to observe these conditions can lead to considerable difficulties. Possibly lies this also explains the reason for the low level of application of the hydrostatic Camp, despite their undisputed superiority with regard to load capacity and service life compared to the Rolling bearings.

10988S / 0403

BAO OWGINAL

With the invention, a solution is shown how the hydrostatic plain bearings used in hydraulic units, In particular, the peculiarities adhering to the axial sliding bearing can be mastered, so that it is an operationally reliable and becomes a maintenance-free component. This solution is characterized in that the oil pressure is at least

a throttle device is fed to the hydrostatic sliding bearing, the throttling effect of which at low oil pressure at least partially canceled and becomes stronger with increasing oil pressure.

In OEEA figures, the invention is illustrated with reference to several examples. It shows:

1 shows a section (partially) through an axial piston constant unit with a first version of the axial bearing,

2 shows a section partly through a second embodiment of the axial bearing of an axial piston VeretelJ unit,

3 shows a section (partially) perpendicular to the section according to fig. 2,

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BATH

Pig.4 a section through an embodiment of the axial bearing according to Pig.2, applied to an axial piston constant unit ,

5 shows a throttle device in section, Pig. 6 a second throttle guide in section.

In Pig.l, 1 designates the housing of the constant unit, which is closed off by the drive flange cover 2 and the control plate cover 3. The bores (not shown) for the supply and discharge of the pressure medium are accommodated in the control plate cover 3, to which the corresponding lines are attached. The Triob shaft 4, which is made in one piece with the drive flange 5, has two radial bearings, the inner bearing 6 and the outer bearing 7, both shown as cylindrical roller bearings, housing 1 and bearing cover 2. The housing 1 is sealed against oil loss by the Seoktl 8, in the recess 9 of which a lip seal, which is not shown and which rests with its sealing lip on the raceway 10, is inserted.

The thrust bearing consists of the rotor ring 11 erρten, the cylindrical roller bearing 12, the second rotor ring 13 and the stator plate 14, which the near the Oehäuaeinnern

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directed part of the Triob flange cover 2 represents. The throttled operating medium flows through the connection 15 into the annular field 16 of the hydrostatic bearing. The Ringföld 16 can also be divided into a three-segment ring Fields be divided and each of these has a separate output from the terminal 15

Supply of the pressurized operating medium.

On the drive flange 5 are the cylinder 17 leading and mounted in the cover 3 support rod with ball joints 18 and the piston rods 19 r: it the piston 20 hinged.

The axial plain bearing works as follows: Through the At port 15, the operating medium flows in a throttled manner, as will be explained later, into ring field 16 and lifts the second rotor ring 13 until it is that pressure is set in the ring field 16 which is in equilibrium with the axial force exerted by the piston 20 stands. The ring 13 can thus rotate without touching the stator 14, so that only the frictional force The shear force of the operating medium originating from the operating medium acts.

The axial force of the piston is over that on the drive shaft 1 tightly fitting first rotor ring 6 on the

109885/0403

W & lalager 12 and transferred from there to the second rotor ring 13.

The frictional force of the roller bearing is dependent on the axial force of the piston 20 and is accordingly very small when idling, even less than 3 the frictional force of the hydrostatic plain bearing 13, 14 ·. This means that in this operating state the second rotor ring 13 acts as a stator, that is to say stands still or only wire at a very low speed. If the operating pressure increases, the friction of the roller bearing also increases and, from a certain operating pressure, becomes greater than the shear force of the operating medium in the hydrostatic plain bearing 13, 14, the latter essentially only depending on the viscosity and the gap height. It therefore grows much more slowly or hardly at all with the operating pressure, so that from a certain operating pressure on the second rotor ring 13 begins to rotate and the roller bearing stops or rotates only very slowly with respect to the two rotors.

The change from one to the other of the bsldon portrayed Operating states occurs at the transition from idling to Load on. First of all, the axial force is low, so that

100885/0403

BATH ORIGINAL

only the roller bearing is effective. If calibrated then during operation the pressure builds up, the point in time occurs when the hydrostatic plain bearing becomes fully effective and the roller bearing is practically at a standstill. Theoretically, the pail could occur that either of the two camps takes over half the speed. In practical operation However, one of the two operating states β always arises, where the rolling bearing and the hydrostatic plain bearing takes over almost the full speed.

In Fig. 2 and 3 again 4 represents the drive shaft, 5 the Drive flange, 6 the inner and 7 the outer radial bearing. The structure of the axial bearing ^ is similar to in Fig.l, but the individual parts are slightly different arranged. 11 is the first rotor ring, which is in direct contact with the drive flange 5, 12 is the cylindrical roller bearing and 13 the second rotor ring, which is supported by the inner radial bearing 6 on the drive shaft 4. The inner The radial bearing has an inner ring 6 ', alier no outer ring and therefore runs in the rotor ring, which is basically made of ball bearing steel or a similar material have to be.

The second rotor ring 13, the support surface of which as in Fig. 1 is ajfeärisoh, but it is by no means a necessity but is advantageous for processing, runs

109085/0403

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in the stator 14 * which has the shape of a shell with a spherically convex outer surface 21. The stator 14 is at a standstill is silent with respect to the rotor ring 13, but it is pivotable with respect to the housing 22. To this end is A slot 23 is recessed in the housing 22 (Pig. 3), in which the shaft 4 moves from the extreme position shown Can move maximum stroke over stroke zero to the other extreme position with maximum stroke.

In the stator 14 is the Planohbüch3e 14 *, the with the Yfelle 4 forms a gap through which the leakage oil is arranged between the rotor ring 13 and the stator 14 can abfljesaen hydrostatic plain bearing.

Bas hydrostatic plain bearings are operated by the respective high pressure via bore 24 »check valve 25 in the form of a Ball, the stroke of which is limited by screw 26, and channel 27 is acted upon. From the outside 21 of the stator 14 lead one or more channels, not shown in the drawing, to the hydrostatic bearing and feed it all over the ring circle. The respective low pressure side is through the check valve 25 of the High pressure side blocked.

109885/0403

ÖWGINAL

- li -

In Pig.4 a hydrostatic axial slide bearing is shown which is installed in a Konatanteinheit · The arrangement is essentially the same as in Pig.2 and 3, but because of the fixed pivoting angle, the stator shell 14 can be omitted. The first rotor ring on which the cylindrical roller bearing 12 runs is denoted by 11. A further bearing ring 12 lies in the second rotor ring 13, the back of which forms the hydrostatic sliding bearing with the stator surface 14. The stator surface 14 is arranged on the inside of the drive flange cover 2, as in Pig . The hydrostatic slide bearing 13, 14 is geapiesen via the supply line 15 and the pressure fluid is distributed through branch lines (not shown) into the spherical bearing ring surface arranged around the drive flange. The respective high pressure is applied to the hydrostatic sliding bearing outside the bearing by a switchover valve (not shown).

The stability of the hydrostatic plain bearing, ie the maintenance of a gap suitable for the puncture of the bearing, even if the load changes, is ensured in a known manner by the fact that the »

10 ^ 885/6 * 03

hydrostatic plain bearing is preceded by a fixed Vordroaael, while the Lagerapalt is a variable Throttle forms. If, for example, the bearing gap is too large compared to the state of equilibrium, the pressure drops in the bearing and the gap decreases instantly. Conversely, if the gap is too small, the pressure in the bearing increases and the rotor ring is raised until it is in equilibrium is reached *

The Vordrosselvantil shown in Figure 5 represents a pressure-dependent throttling in the sense that the throttling is increased as the pressure increases. This valve consists of the hollow throttle piston 28, which is pressed in its cylindrical bore by the spring 29 towards the inlet opening 30. When the operating pressure is low or when the system is idling, the spring 29 presses the piston 28 against the orifice 30 and thus releases at least partially free the throttle cross-section, so that the operating medium throttled slightly through channel 32 into space 33 and through the pierced nut 34, on which calibration the spring 29 is supported, in the space 35 fHess can, whose pressure is identical to the pressure in the hydrostatic plain bearing.

1Ö9805 / CU03

BAO OWIQINAL

The throttle cross section is formed by the conically tapering throttle piston 28 and the edge 31. The Drosaelkolben can rather be aylindriach and at least ine α have to at.iner / LuBseEfläohG lying groove, the effective length increases with increasing operating pressure. Ma Hut could also be in the. cylindrical wall of the space 33 be attached, while the Droasel flask is made smooth.

The whole throttle valve can be as shown in Pig. 5, in a hole, dia in the stator odai in a special Housing lies, be built in *

Pig.6 shows a slightly different design of the pre-throttle valve3 shown in Pig.5. So that the spring can be kept smaller than 29, the Droaselkplben 28 is preceded by a smaller Kssskolben 36 and the end face äzu iii * o33elkolbens 20 connected via channel 37 to a pressure-free space so that the pressure on the? JeBskolber. 36 on the one hand with the pressure acting on the Drosaol piston 28 in the space 33 and the force of the spring 29 on the other hand Lm is in equilibrium .

1 09885/0403

BATH

That acted upon by the operating pressure of an axial piston unit hydrostatic plain bearings with the Vordrosffelventil creates one for most of the Operating conditions efficient and reliable Storage. When starting, where the pressure has not yet built up in the plain bearing and when idling, this is also the case

Rolling bearings arranged in series with the plain bearing are a complement to the very insignificant start-up wear in the plain bearing is avoided, and the temperature increase that occurs when idling, which is already due to the throttle valve is effectively reduced, further reduced by taking over a portion of the speed and even avoided.

1 09885/0 A03 _{ftft0 oW} GiNM-

Claims (6)

Claims ). Axial piston unit with a cylinder axis inclined to the drive shaft and a bearing for the drive shaft, which is a dated Pressurized annular, hydrostatic axial sliding bearing with a rotor and stator part contains, thereby characterized in that the oil pressure is fed to the hydrostatic plain bearing via at least one throttle device whose throttling effect is at least partially canceled at low oil pressure and with increasing oil pressure gets stronger. 2. Axial piston unit according to claim 1, characterized in that that an axial roller bearing is arranged in series with the hydrostatic axial plain bearing. 3. Axial piston unit according to claims 1 and 2, characterized in that that between the housing (22, Fig. J5) and the second rotor part (13) a pivotable stator shell (14) is arranged. 4. Axial piston unit according to claims 1 and 2, characterized in that that the second rotor part carries both the axial and the inner radial roller bearing. ^% *. . , 103885/0 * 03 5 · Axial piston unit according to claim 1, characterized in that that the throttle device has a throttle piston tapering conically at the end. 6. Axial piston unit according to claim 1, characterized in that that the throttle cross-section is formed by at least one groove, the effective length of which differs from that of the Operating pressure-setting position of the cylindrical throttle piston is dependent. 7 · Axial piston unit according to claims 1, 5 and 6, thereby indicated that the operating pressure acts on the throttle piston via a volumetric piston (JJ6). 101185/0403 28 ^ 1968