Bearing arrangement for a deep drilling device

A bearing arrangement is disclosed for a drilling head, through which flushing liquid flows, of a deep drilling device, having multiple radially outer and radially inner bearing rings. Radially outer bearing rings are arranged coaxially over radially inner bearing rings, balls roll in raceways of the bearing rings, and the raceways are delimited axially on both sides by shoulders with mutually opposite shoulder surfaces. In order for a bearing arrangement to be of short axial extent and to simplify the construction, the internal diameter (Di) of the shoulder surfaces of the radially outer bearing rings and the external diameter (Da) of the shoulder surfaces of the radially inner bearing rings are dimensioned such that the shoulder surfaces perform the function of parallel radial plain bearings with a radial clearance (S).

BACKGROUND

The invention relates to a bearing arrangement for a drill head of a deep drilling device, wherein a flushing liquid flows through this drill head, with multiple radially outer and radially inner bearing rings in which the radially outer bearing rings are arranged coaxial over the radially inner bearing rings, in which balls are arranged radially between the bearing rings, wherein these balls roll in raceways of the bearing rings and in which the raceways are bounded axially on both sides by shoulders with shoulder surfaces that are opposite each other and extending parallel to a bearing longitudinal axis.

Such a bearing arrangement of a deep drilling device is known from DE 101 62 473 B4. It comprises a larger number of ball bearings that are arranged axially one behind the other and are constructed as 4-point ball bearings and combined to form a ball bearing assembly. For these 4-point ball bearings, the radially outer bearing rings and the radially inner bearing rings have a divided construction. It is known that 4-point ball bearings can transmit both axial forces and also radial forces, but frequently a sliding or plain bearing is still arranged axially in front of and/or behind the ball bearing assembly, in order to relieve the 4-point ball bearing from radial forces that are too large. Here, the bearing arrangement is extended axially around this at least one plain bearing, so that such a bearing arrangement requires a larger packaging space in the longitudinal direction and the minimum possible radius for changes in direction is disadvantageously increased for articulated drill heads.

SUMMARY

In light of this information, the invention is based on the object of providing a bearing arrangement that has both radial plain bearings and also axial ball bearings and whose axial extent corresponds essentially to a bearing arrangement made exclusively from 4-point ball bearings.

This object is achieved by a bearing arrangement with one or more features of the invention as described below. Advantageous refinements are defined in the subordinate claims.

Accordingly, the invention starts from a bearing arrangement for a drill head of a deep drilling device, wherein a flushing liquid flows through this drill head, with multiple radially outer and radially inner bearing rings, in which the radially outer bearing rings are arranged coaxial over the radially inner bearing rings, in which balls are arranged radially between the bearing rings, wherein these balls roll in raceways of the bearing rings and in which the raceways are bounded axially on two sides by shoulders with shoulder surfaces that are opposite each other and extend parallel to a bearing longitudinal axis. For this bearing arrangement and for meeting the stated object, it is provided that the inner diameter of the shoulder surfaces of the radially outer bearing rings and the outer diameter of the shoulder surfaces of the radially inner bearing rings are dimensioned so that there is a radial play producing the function of parallel radial plain bearings.

Therefore, because the shoulder surfaces of the shoulders on both sides of the raceways of the 4-point ball bearing form plain bearings, a combination bearing is created that has multiple axial-radial rolling bearings and radial plain bearings whose length corresponds exactly to the length that has a bearing assembly consisting only from 4-point ball bearings. A separate plain bearing to be arranged axially behind or in front of the assembly made from 4-point ball bearings according to the prior art is not needed, which saves costs. In addition, the integration of the radial guidance into the axial bearings can reduce the axial length of the entire bearing arrangement. Here, the distance between the drill head and a bend for directed holes can be shortened. This allows advantageously smaller radii of the drill string.

According to one advantageous embodiment, the shoulder surfaces of the radially inner and/or radially outer bearing rings have grooves for guiding the flushing liquid if the flow rate through the bearing arrangement is not sufficient due to the adjusted radial bearing play. Preferably, the grooves can be arranged with respect to the bearing longitudinal axis at an angle to cause only a break in the lubricating film of the plain bearing based on the width of the grooves.

To simplify the assembly of a 4-point ball bearing of the ball bearing area of the bearing arrangement according to the invention, the radially outer and/or radially inner bearing rings can have a split design in a plane that runs perpendicular to the bearing longitudinal axis centrally through the raceways.

The bearing arrangement has at least one row of balls with the associated bearing rings. The axially end-side end rings of the bearing arrangement can be longer than is typical for 4-point ball bearings for drill heads for comparable operating loads, especially for reducing the wear and the surface pressure in the radial plain bearing.

Preferably it is provided that multiple rows of balls are assembled with the associated bearing rings to form a bearing assembly and that the end rings have a longer construction than the bearing rings arranged between these end rings.

By integrating the radial plain bearings into the axial-radial rolling bearings formed as 4-point bearings, the axial distance of the radial support points is reduced, which increases the tipping moment for the same applied force. To reduce this effect, the number of rows of balls with the associated bearing rings can be greater than is typical for conventional 4-point bearings for drill heads for comparable operating loads.

Because a flushing liquid flows through the bearing arrangement and this liquid contains unavoidable contaminants that lead to quick wear of the bearing arrangement, it can be provided that at least the shoulder surfaces of the radially outer bearing rings and/or the shoulder surfaces of the radially inner bearing rings are provided with a friction-reducing and/or wear-reducing coating that preferably is formed of a tribological coating system. This tribological coating system can be applied by means of the Triondur® method. Triondur® is a registered trademark of the applicant. In particular, the friction-reducing and/or wear-reducing coating can be made from diamond layers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Accordingly, a bearing arrangement1of a drive shaft of a drill head is shown inFIG. 1. The drive shaft is arranged radially within the bearing arrangement1and is constructed as a hollow shaft3. The hollow shaft3is supported by the bearing arrangement1in a rotationally locked housing2and transmits a drive torque from a drive turbine (not shown) to the drill head (not shown). A flushing liquid is introduced into the hollow shaft3according to the direction of flow4with which the drive turbine is operated. A part of the flushing liquid is guided through outlet openings10in the hollow shaft3into the bearing arrangement1axially in front of the bearing arrangement1, in order to cool and lubricate the rolling bearings there and also to form a load-bearing film in the plain bearing integrated into the bearing arrangement. With a greater portion of the flushing liquid that is discharged from the hollow shaft3in the area5through openings in this shaft, the drill head is then cooled and lubricated. Because the flushing liquid is always somewhat contaminated, contaminants are constantly coming into the bearing arrangement1.

FIG. 2shows the bearing arrangement1ofFIG. 1that is formed according to a first embodiment and supports the hollow shaft3in the housing2. In this bearing arrangement1, multiple full-sphere radial-axial ball bearings (4-point bearings) are arranged in a row axially one behind the other to form an assembly. Each of the 4-point bearings has two radially outer bearing rings6,6* and two radially inner bearing rings7,7*. Every two axially directly adjacent radially outer bearing rings6,6* together form a radially outer running groove6aand every two axially directly adjacent radially inner bearing rings7,7* together form a radially inner running groove7a. The two raceways6a,7aof each 4-point bearing are consequently radially divided by a separating plane that is perpendicular to the bearing longitudinal axis11.

The bearing arrangement1shown inFIG. 2has, on each axial end side, an end ring6′,7′ that is shorter in comparison with the other bearing rings6,7. Accordingly, the end rings6′,7′ are formed in the second embodiment according toFIG. 3geometrically and length-wise identical to the other bearing rings6,6*,7,7*. The axially longer end rings6′,7′ are advantageous for reducing the wear and the surface pressure in the end rings6′,7′ through applied tilting moments. In this case, it is also possible to form the end rings6′,7′ without the half raceways shown inFIG. 3.

In the raceways6a,7a, there are load-bearing balls8that are preferably formed as ceramic balls. Between two of the load-bearing ceramic balls8there is a preferably somewhat smaller separating ball9made from steel. The arrangement of the balls8,9made from steel and ceramic is shown inFIG. 4in a radial cross section through the bearing arrangement1. In every individual 4-point bearing of the bearing arrangement1, load-bearing ceramic balls8and separating steel balls9are inserted. The radially outer bearing rings6,6*,6′ and the radially inner bearing rings7,7*,7′ consist of steel. The steel balls9can be made from a rolling bearing steel, a stainless rolling bearing steel, or a wear-resistant steel.

The radially outer bearing rings6,6* and the radially inner bearing rings7,7* have axial shoulders6bor7bthat end in radial shoulder surfaces6c,7c. Accordingly, these radial shoulder surfaces6c,7cextend axially between the adjacent raceways6a,7a. The inner diameter Di of the shoulder surfaces6cof the shoulders6bon the radially outer bearing rings6,6*,6′ and the outer diameter Da of the shoulder surfaces7cof the shoulders7bon the radially inner bearing rings7,7*,7′ are dimensioned so that a radial play S is formed between the radially opposite shoulder surfaces6c,7c. This radial play S allows these shoulder surfaces6c,7cto exert the function of parallel radial plain bearing surfaces. The radial play S between the radially opposite shoulder surfaces6c,7conly equals a few hundredths of a millimeter. In these embodiments, in the shoulders7bof the radial inner bearing rings7,7*,7′ there are grooves13and grooves12in the shoulders6bof the radially outer bearing rings6,6*,6′, in order to guarantee a sufficient flow rate of the flushing liquid through the bearing arrangement1. These grooves12,13are shown running in the axial direction inFIG. 3, but it is preferred that these grooves12,13are formed at an angle to the bearing longitudinal axis11, in order to not break the load-bearing film of the flushing liquid over the entire width of the bearing rings6,6*,6′,7,7*,7′.

FIG. 4shows a row of balls of a 4-point bearing of the bearing arrangement in the axial top view. The load-bearing ceramic balls8recognizably have a diameter8athat is slightly larger than the diameter9aof the circumferentially adjacent steel balls9. In this figure it is clearly shown that the ceramic balls8have, as rolling partners, only bearing components, namely the steel balls9and the two allocated bearing rings6,6*,6′,7,7*,7′. The smaller steel balls9in diameter9amust be much smaller than the ceramic balls8so that for a maximum loading of the bearing arrangement1, these separating steel balls9do not become load-bearing balls. The ceramic balls8can be made from solid ceramic or from a carrier material that is coated with ceramic. The ceramic material can be made, for example, from silicon nitride or zirconium oxide.

FIG. 4also shows the play S produced between the shoulder surfaces6cand7c, because the inner diameter Di of the shoulder surfaces6cis slightly larger than the outer diameter Da of the shoulder surfaces7c. In addition, the grooves12and13can also be seen in the shoulders6band7bthat benefit the flow rate of the flushing liquid through the bearing arrangement1.

At least the shoulder surfaces6cof the radially outer bearing rings6,6*,6′ and/or the shoulder surfaces7cof the radially inner bearing rings7,7*,7′ are provided with a friction-reducing and/or wear-reducing coating14,15that is preferably made from a tribological coating system that is applied, for example, by the Triondur® method. Preferably, but not exclusively, these friction-reducing and/or wear-reducing coatings14,15are diamond layers.

LIST OF REFERENCE NUMBERS

1Bearing arrangement2Housing3Hollow shaft, drive shaft4Direction of flow of the flushing liquid5Outlet of the flushing liquid6,6* Radially outer bearing rings6aRaceways in the outer bearing rings6,6*6bShoulders on the outer bearing rings6,6*,6′6cShoulder surfaces on the shoulders6b6′ Radially outer end ring7,7* Radially inner bearing rings7aRaceways in the inner bearing rings7,7*7bShoulders on the inner bearing rings7,7*,7′7cShoulder surfaces on the shoulders7b7′ Radially inner end ring8Load-bearing ceramic balls8aDiameter of load-bearing ceramic balls9Separating steel balls9aDiameter of separating steel balls10Outlet openings in the hollow shaft for the flushing liquid11Bearing longitudinal axis12Grooves in the shoulders6b13Grooves in the shoulders7b14Coating15CoatingDi Inner diameter of shoulder surfaces6cDa Outer diameter of shoulder surfaces7cS Radial play between the shoulder surfaces6cand7c