PIPE SUSPENSION AS PART OF AN OIL FILM BEARING

Description

[0001] The invention relates to a journal bushing as part of an oil film bearing in a rolling stand. The journal bushing serves to accommodate the conical roll neck of a roll, in particular a backup roll of the rolling stand. The oil film bearing with the journal bushing serves to support the roll in the rolling stand. The rolling stand is typically used for cold or hot rolling of metallic rolled stock in a rolling mill.

[0002] In the state of the art, journal bushings of oil film bearings are basically known.

[0003] German Patent Application DE 2843658 A1 describes the design of a conical journal bushing as advantageous in that the bearing can be more easily pulled on and off the likewise conical roll neck during maintenance work. This relatively tight fit of the conical journal bushing on the conical roll neck is not so tight that limited relative rotation of the journal bushing to the roll neck is prevented. These minute relative rotations (also referred to as "microcreep" in DE 2843658) can lead to microscopic wear ("fretting") on the contact surfaces. Permanent damage to the rotating components, particularly to the surface of a roll neck, can result.

[0004] The invention according to DE 2843658 A1 aims to create an improved device for lubricating the transition between the roll neck and the co-rotating neck bushing, without the disadvantageous removal of excessive oil from the load zone for the function of the oil film bearing. This is achieved by additional secondary lubrication grooves arranged on the inside of the rotating neck bushing, which are fed with oil from the primary lubrication grooves. Several separate groove networks distributed around the circumference promote the lubrication of the contact surfaces between the roll neck and neck bushing.

[0005] The published application (WO 2011 / 096672) presents another method / device for arranging lubrication grooves in an oil film bearing for rolling mill rolls.

[0006] EP 1213061 B1 presents a thin-walled journal bushing designed to achieve increased load-bearing capacity due to its greater elastic deformation under load compared to the state of the art at the time. A minimum taper angle of 3 degrees is specified for the cone, below which "self-locking" occurs, and a minimum (thinnest) thickness of the journal bushing of 10 mm to 0.024 D + 14.5 (D = bearing race diameter) is specified. The bushing is mounted on an externally tapered section of the roll neck.

[0007] The load-bearing capacity increase addressed in this patent (known as EHD; Elasto-Hydro-Dynamic Load-Bearing Increase) arises from the fact that, under radial load (oil pressure in the load zone), the journal bushing can shift axially away from the roll barrel. This displacement is limited by a fastening unit at the tapered end of the roll journal, as described, for example, in the published patent applications (DE102016214011A1, DE102017217562A1). Furthermore, simulation studies show that this axial sliding of the journal bushing (caused by the slope force acting on the cone taper angle) does not occur uniformly around the circumference, but rather maximizes during rotational passage through the load zone.This sliding of the journal bushing, which varies around the circumference, creates a sinusoidal back and forth sliding of the two friction pairs, which ensures that oil can reach the contact surfaces between the roll neck and the journal bushing via the oil lubrication grooves (described above) where no lubrication grooves are located (i.e. between the lubrication grooves).

[0008] The sliding of the journal bushing creates axial forces in the mounting unit, which are supported on the roll neck end or must be held by it. The magnitude of these axial forces (downward force) is directly proportional to the cone taper angle. Practice has shown that, due to the design, excessively large angles can lead to damage at the roll end (where the axial force is absorbed by the roll). This results in a contradictory design objective: The journal bushing must slide axially far enough to allow the lubricating medium (oil) added via lubrication grooves to reach the surfaces located between the lubrication grooves; and the journal bushing must not exert excessive forces on the axial fastening unit to prevent damage.

[0009] German patent application DE 31 50 496 A1 discloses a journal bushing for use as part of an oil film bearing according to the preamble of patent claim 1.

[0010] The invention is based on the object of developing a known journal bushing as part of an oil film bearing and a known rolling stand with the journal bushing in such a way that they meet the two previously mentioned contradictory design objectives.

[0011] This object is achieved for the pin bushing by the subject matter of claim 1. This solution is characterized in that the following applies to the pin bushing: 0 , 35 < 3 , 6 a D − B + kD < 0 , 5 with a [m]cone length of the journal bushing, D [m]outer running diameter of the journal bushing, B [m]large cone diameter of the journal bushing; and k = 0.15 [1 / m]sliding coefficient.

[0012] Preferably, the lower limit value is 0.37 and / or the upper limit value is 0.49.

[0013] It is to the inventors' credit that they have discovered that journal bushings which satisfy the newly claimed design condition according to formula (1) also achieve the object of the invention. This means that with such journal bushings, when large rolling forces are applied during rolling operations due to an angular position-dependent axial journal bushing displacement or deformation, sufficient lubricating oil reaches the area between the roll neck and journal bushing so that no damage occurs to the surface of the roll neck. Furthermore, with the journal bushings designed according to formula 1, the axial forces resulting from the elastic axial journal bushing displacement or deformation due to rolling forces of typical magnitude are advantageously tolerable, i.e. they lie within a permissible force range. The axial forces from this force range can be absorbed by a fastening device with an associated spring ring.In other words: With the journal bushings designed according to the invention, the axial forces occurring in the event of a journal bushing displacement or deformation are so low that there is no risk of the end of the roll neck tearing off from the rest of the roll neck due to the (axial) forces introduced into it by the fastening system being too great, or of the fastening systems themselves being overloaded or damaged. The spring rate of the spring ring must be designed so that, at maximum load on the bearing, the resulting downhill force (calculated using a known cone angle) leads to a minimum axial displacement of the journal bushing of 1 / 10 mm, preferably 3 / 10 mm.

[0014] According to one embodiment, the conical journal bushing on its inner side, as well as the conical roll neck on its outer side, each have at least one groove for partially receiving a feather key. The feather key engages in both grooves and thereby forms a rotational coupling in the circumferential direction between the roll neck and the journal bushing mounted thereon and rotating therewith. According to the invention, at least one of these two grooves of each pair of grooves is dimensioned such that the feather key sits in the grooves with axial play and / or radial play. These two plays facilitate or enable the aforementioned axial displacement or deformation of the journal bushing when it passes through the area of ​​highest load during rolling operation.

[0015] The above-mentioned object of the invention is further achieved by a rolling stand according to claim 5. The advantages of this solution correspond to the advantages mentioned above with reference to the claimed journal bushing.

[0016] Further advantageous embodiments of the journal bushing and the rolling stand are the subject of the dependent claims.

[0017] The description includes 5 figures, where Figure 1 a longitudinal section through the pin bushing according to the invention; Figure 2 the permissible range for the dimensioning of the pin bushing according to the invention; Figure 3 the pin bushing according to the invention without loading by a rolling force in conjunction with a key in longitudinal section; Figure 4 a typical pressure distribution on the journal bushing surface in an oil film bearing when subjected to a rolling force; and Figure 5a longitudinal section through the journal bushing according to the invention and the roll neck mounted therein under load by the rolling force; shows.

[0018] The invention is described in detail below with reference to the figures mentioned in the form of exemplary embodiments. In all figures, identical technical elements are designated by identical reference numerals.

[0019] Figure 1 shows the inventive journal bushing 100 in a longitudinal section. It has a cylindrical outer circumference and, together with a bearing bushing, in whose cylindrical cavity it is received, forms an oil film bearing; in Figure 1 Not shown. Between the bearing bush and the journal bush is the lubricant-filled lubricant gap of the oil-film bearing.

[0020] The pin bushing according to the invention consists of a conical longitudinal section 110, the length of which projected onto the cylindrical outer circumference of the pin bushing is designated by the reference symbol a. The conical longitudinal section 110 defines a conical cavity with a large cone diameter B and a small cone diameter A. The conical longitudinal section 110 has a cone angle β. In the region of the small cone diameter A, a cylindrical end section 120 of the pin bushing seamlessly adjoins the conical longitudinal section 110. The end section 120 defines a cylindrical cavity whose diameter corresponds to the diameter of the small cone diameter A.

[0021] Both the conical cavity defined by the conical longitudinal section 110 and the adjacent cylindrical cavity defined by the end section 120 serve to accommodate a corresponding, complementary journal of a roll in a rolling stand. The outer diameter of the externally cylindrical journal bushing is D. The cylindrical outer side of the journal bushing is connected via connecting channels 113 to lubrication grooves 112 on the inner side of the journal bushing.

[0022] During operation of the roll mounted in this way, the aforementioned lubricating film of lubricant forms between the bearing bush and the outer surface of the journal bushing 100. The lubricant enters the lubrication grooves 112 via the connecting channels 113. However, as long as the journal bushing 100 is firmly mounted on the roll neck, the lubricant remains in the lubrication grooves 112 and cannot spread from there into the contact surface between the journal bushing and the roll neck.

[0023] According to the invention, the following applies to the pin bushing 100: 0 , 35 < 3 , 6 / a D − B + k * D < 0 , 5 with B [m] large cone diameter D [m] outer running diameter a [m] length of the conical longitudinal section projected onto the cylindrical outer circumference of the journal bush k=0.15 [1 / m] sliding coefficient.

[0024] Preferably, the lower limit is 0.37 (instead of 0.35) and / or the upper limit is 0.49 (instead of 0.5).

[0025] The claimed lower and upper limits are clearly shown in Figure 2 They span a structurally permissible range. This means that as long as a journal bushing satisfies the claimed formula (1) with the claimed upper and lower limits, preferably with the increased lower limit and / or with the reduced upper limit, the journal bushing satisfies the object underlying the invention, i.e. the contrary design objective to be solved. This contrary design objective and its inventive solution are described below again with reference to the Figure 3 to 5 explained in more detail.

[0026] Figure 3 shows a supplement to Figure 1 . Also in Figure 3the journal bushing 100 is tightly fitted onto the roll neck 210. This means that the conical longitudinal section 110 of the journal bushing 100 sits gap-free on the essentially complementary conical roll neck section 212, and the cylindrical end section 120 of the journal bushing sits on the cylindrical roll neck end section 214 of the roll neck. There is essentially a frictional connection between the journal bushing 100 and the roll neck 210, i.e. the journal bushing 100 rotates with the roll neck 210 due to the existing static friction. The rotational, frictional coupling is secured by at least one key 20, which is partly seated in an axially aligned groove 122 on the inside of the journal bushing and partly in an axially extending groove 216 on the outside of the roll neck. The key 20 sits in these two grooves 122, 216 with axial play Sa and / or with radial play Sr.

[0027] In the axial direction, the journal bushing 100 is secured on the roll journal by a spring ring 220 and a fastening ring 230.

[0028] Figure 3 shows the configuration of the journal bushing and roll neck in an unloaded state, i.e., without the application of a rolling force or with the application of a rolling force that is so small that it does not lead to deformation of the journal bushing. In this state, no lubricating film is formed between the journal bushing and the roll neck.

[0029] Figure 4shows the actual pressure distribution as it occurs in the bearing gap between the rotating journal bushing and the stationary bearing bushing during rolling operations. The pressure distribution is shown here as an example for the case where an upper backup roll neck 210 with a mounted journal bushing 100 is rotatably mounted in a rolling stand and rotates in the direction of the arrow during rolling operations; see left and right figures in Fig. 4 It is important to note that the compressive load for the bearing and in particular the journal bushing is by no means evenly distributed over the circumference, but that a load maximum M is formed in the area of ​​the surface of the journal bushing opposite the rolling force FR.

[0030] The Figure 4The pressure distribution shown is essentially stationary within a circumferential angular range during rolling operation, at least as long as the direction in which the rolling force FR acts does not change. This is not contradicted by the fact that the rolling force can fundamentally change its magnitude.

[0031] The said stationary pressure distribution means that a point on the surface of the roll neck or the co-rotating neck bushing is only exposed to the high pressure load shown if it has the Figure 4shown pressure range with the large maximum pressure load M. In this situation, ie when passing through the angular range with the large pressure load, the pressure force FP resulting from the rolling force FR on the journal bush in the radial direction and in particular the resulting downhill force FH in connection with the conical longitudinal section 110 can become so large that the journal bush 100, as in Figure 5 shown, locally shifts or deforms. The local deformation consists in the fact that, in particular, the part of the journal bushing that currently passes through the area of ​​high compressive load M during rotation shifts or deforms on the roll neck in the direction of the slope force FH and thus locally detaches from the roll neck.

[0032] The detachment of the journal bushing from the roll neck 210 takes place with the formation of a microscopically narrow and locally limited lubricant gap 130 between the journal bushing 100 and the roll neck 210. This microscopically narrow lubricant gap 130 also does not extend over the entire circumference, but is essentially circumferentially limited to the Figure 4 When passing through the angular range of the high pressure load M, lubricating oil is thus released from the actual lubricating film between a bearing bush and the journal bush 100, as shown in Figure 4 shown, pressed via the connecting channels 113 into the lubrication grooves 112 and from there into the said lubricant gap 130, as in Figure 5 The part of the journal bushing 100 passing through the angular range of high compressive load deforms due to the compressive force FP, as also shown in Figure 5shown, in such a way that it slides on the lubricant film 130 and presses against the spring ring 220 and also deforms it. During the deformation / displacement, the axial and radial play Sa, Sr of the key 20 in the groove 122 in the journal bush and / or in the groove 216 in the roll neck is utilized, in that the key is displaced due to the displacement of the roll neck according to Figure 5 is pushed into its limits.

[0033] It is noteworthy that the pin bushing is on the opposite side, in Figure 5 below, only slightly deformed and thus sits almost unchanged with a press fit without a lubricant gap on the roll neck.

[0034] The inventive design of the journal bushing 100 according to formula (1) ensures, on the one hand, that the aforementioned lubricant gap 130 is formed, which guarantees that the lubricating oil between the journal bushing and the roll neck is not locally restricted to the area of ​​the lubrication grooves 112, but is also distributed into the areas between the lubrication grooves 112. This is desired, despite the still existing fundamentally tight fit of the journal bushing on the roll neck, in order to prevent fretting, i.e. the microscopic wear known from the prior art, which would otherwise arise in the area of ​​the contact surfaces between the journal bushing and the roll neck when passing through the angular range with the high pressure load. This wear is prevented by the lubricant gap 130, which in turn is realized or promoted by making the slope force FH as large as possible.The slope force becomes particularly greater the greater the difference between the large and small cone diameters B, A. On the other hand, however, the slope force FH must not be too large, because otherwise the spring ring 220 and the fastening ring 230 would no longer be able to absorb the slope force FH and transfer it to the roll neck 210. In the worst case, i.e., if the slope force FH were to become too large, it could happen that the cylindrical roll neck end section 214 were to be blown off from the conical roll neck section 212 in the axial direction.

[0035] As stated, the structural design of the journal bushing 100 according to formula (1) ensures that both contradictory design objectives can be realized or maintained.

[0036] The Figure 5The two arrows shown, which point from the right towards the fastening ring 230, represent the counterforce FG to the slope force FH, which must be absorbed by the roll neck, in particular by the cylindrical roll neck end section 214, when the slope force is diverted into the roll neck 210 via the fastening ring 230. List of reference symbols

[0037] 100Tee journal bushing 110Conical longitudinal section 112Lubrication groove 113Connecting channel 120End section 122Keyway 130Lubricant gap 20Keyway 200Roll 210Roll neck 212Conical roll neck section 214Cylindrical roll neck end section 216Keyway 220Lock washer 230Fastening ring Asmall cone diameter Blarge cone diameter Douter running diameter of the journal bush Mload maximum Saaxial play Srradial play βCone angle FGGopposing force to the downhill force FH FPcompressive force resulting from the rolling force FR FRrolling force FHDownhill force a(projected) cone length of the conical longitudinal section

Claims

1. Journal bush (100) for use as part of an oil film bearing in a roll stand for reception of a conical roll journal of a roll, particularly a backing roll; wherein the journal bush - is resiliently deformable under the action of a rolling force exerted by the roll stand; - is formed at its outer side to be cylindrical with an outer running diameter D; - has an inwardly conical length section (110) which is formed at its inner side over a cone length a to be conical with a major cone diameter B and a cone angle β for reception of the conical roll pin of the rolls; and wherein the conical length section (110) has at its inner side lubricant grooves (112) for introduction of lubricant into the intermediate space between the inner side of the journal bush and the outer side of the conical roll journal; characterised in that for the journal bush (100) there applies: 0.35 < 3.6 a D − B + kD < 0.5 wherein k = 0.15 / m coefficient of sliding friction.

2. Journal bush (100) according to claim 1 characterised in that for the journal bush (100 there applies: 0.37 < 3.6 / a D − B + kD < 0.

493. Journal bush (100) according to one of the preceding claims, characterised by an end section (120) which is of hollow-cylindrical form and which by its inner diameter adjoins in aligned manner the conical length section at the location of the smallest cone diameter A thereof.

4. Journal bush (100) according to any one of the preceding claims, characterised in that the journal bush (100) has at its inner side a groove (122) for partial reception of a key (20).

5. Roll stand comprising at least one bearing housing configured as an oil film bearing with an inner conical journal bush (100) according to any one of the preceding claims; and at least one roll (200), the roll journal (210) of which is formed with a conical roll journal section (212) and preferably also a cylindrical roll journal end section (214), for reception in the journal bush (100), wherein the journal bush together with the roll journal is rotatably mounted in the bearing housing, preferably in a bearing bush in the bearing housing.

6. Roll stand according to claim 5, characterised in that the roll journal (210) has a groove at its outer side; a key (20) is provided, of which a first part is received by the groove at the inner side of the journal bush (100) and a second part is received by the groove (216) at the outer side of the roll journal (210); and at least one of the two grooves is so dimensioned with respect to the dimensions of the key (20) that the key (20) in the load-free state, particularly outside of rolling operation, is seated in the grooves with an axial play of Sa > 0.0 mm and with a radial play Sr > 0.5 mm.

7. Roll stand according to claim 6, characterised in that the journal bush (100) is with the help of a fastening ring (230) and a spring ring (220) arranged in axial direction between the journal bush (100 and the fastening ring (230) secured on the roll journal against slipping off the roll journal (210) in axial direction; and the spring rate of the spring ring (220) is designed so that in the case of maximum loading of the bearing the then-arising downward slope force computed on the basis of the known cone angle leads to a minimum axial displacement of the journal bush of 1 / 10 mm, preferably 3 / 10 mm.