Neck bushing as part of oil film bearing

Abstract

The present invention relates to a neck bush (100) as part of an oil film bearing in a roll stand, which is used to accommodate the conical roll neck of the roll of the roll stand, in particular the backup roll. The oil film bearing with the neck bush is used to support the roll in the roll stand. In order to form a sufficiently large lubricant film gap in the area between the inside of the neck bush (100) and the outside of the roll neck when passing through the angular area with the highest pressure load during the rolling operation, and at the same time to prevent the axial forces acting on the fixing ring (230) that holds the neck bush (100) axially on the roll neck from becoming too large, the present invention contemplates designing the neck bush according to the following formula: 0.35<3.6 / a(DB)+kD<0.5, where D is the outside diameter of the neck bush, a is the drawn cone length of the longitudinal part of the cone, k is the slip coefficient and B is the cone major diameter.

Description

[Technical Field]

[0001] The present invention relates to a neck bushing as part of an oil film bearing in a roll stand, the neck bushing being used to accommodate the conical roll neck of a roll, particularly a backup roll. The oil film bearing with the neck bushing is used to support the roll in the roll stand. The roll stand is typically used in a rolling mill for cold or hot rolling of metal stock. [Background technology]

[0002] In the prior art, neck bushes for oil film bearings are basically known.

[0003] DE-A-2 843 658 states that the design of the conical neck bushing is advantageous in that the bearing can be easily mounted and removed from the similarly conical roll neck during maintenance work. The relatively tight fit of the conical neck bushing on the conical roll neck is not so tight that limited relative rotation of the neck bushing relative to the roll neck is not possible. These minimal relative rotations (also called "micro-creep" in DE-A-2 843 658) can cause microscopically small wear ("fretting") on the contact surfaces. This can cause permanent damage to the rotating components, especially the surfaces of the roll neck.

[0004] The invention of DE-A-2843658 aims to provide an improved device for lubricating the transition between the roll neck and the co-rotating neck bush without removing so much oil from the load area that it would impair the function of the oil film bearing. This is achieved by additional secondary lubrication grooves located inside the rotating neck bush, which are supplied with oil from the primary lubrication grooves. A network of multiple, separated grooves distributed around the periphery promotes lubrication of the contact surface between the roll neck and the neck bush.

[0005] WO 2011 / 096672 presents another method / apparatus for arranging lubrication grooves in oil film bearings for rolling mill rolls.

[0006] EP 1213061 presents a thin-walled neck bushing with a high load capacity due to its significantly greater elastic deformation under load than the prior art. It specifies a minimum taper angle of 3 degrees for the cone, below which "self-locking" occurs, and a minimum (thinnest) thickness of 10 mm ~ 0.024D + 14.5 (D = bearing barrel diameter) for the neck bushing mounted on the outer tapered part of the roll neck.

[0007] The increase in load capacity referred to in this patent (those skilled in the art speak of an increase in EHD; elastohydrodynamic load capacity) is caused by the fact that the neck bushing can be displaced axially away from the roll barrel under radial load (hydraulic pressure in the load area). This displacement is limited by a fixing unit at the tapered end of the roll neck, as described, for example, in DE 102016214011 A1 and DE 102017217562 A1. In addition, simulation studies have shown that this axial sliding of the neck bushing (due to the gradient resistance "Hangabtriebskraft" on the conical taper angle) does not occur evenly around the circumference, but is maximized when rotating through the load area. This sliding of the neck bush, which varies around its circumference, causes a sinusoidal back and forth sliding of both friction pairs, which ensures that oil can also reach the contact surface between the roll neck and the neck bush via the oil lubrication grooves (mentioned above) - where no lubrication grooves are arranged (i.e. between the lubrication grooves).

[0008] The sliding of the neck bushings generates axial forces in the fixed unit that must be supported at or held by the roll neck ends. The magnitude of these axial forces (gradient resistance) is directly related to the cone taper angle. In fact, due to the construction, it has been found that if the angle is too large, damage can occur at the roll ends (where the axial forces are taken up by the rolls). This leads to conflicting design goals: The neck bushing must slide axially so that the lubricant (oil) applied through the lubrication grooves can reach the surfaces located between the lubrication grooves. The neck bush must not apply excessive force to the axial fixing unit to avoid damaging the axial fixing unit. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] West German Patent Application Publication No. 2843658 [Patent Document 2] International Publication No. 2011 / 096672 [Patent Document 3] European Patent No. 1213061 [Patent Document 4] German Patent Application Publication No. 102016214011 [Patent Document 5] German Patent Application Publication No. 102017217562 Summary of the Invention [Problem to be solved by the invention]

[0010] The problem underlying the present invention is to develop the known neck bush as part of an oil film bearing, and the known roll stand having a neck bush, so as to satisfy both of the aforementioned conflicting design goals. [Means for solving the problem]

[0011] This problem is solved with respect to the neck bush by the subject matter of claim 1. This solution provides, with respect to the neck bush (100): 0.35<3.6 / a(DB)+kD<0.5 (1) however, a [m] Cone length of neck bush D [m] Outer diameter of neck bush B [m] Conical major diameter of neck bush k=0.15[1 / m] Slip coefficient The present invention is characterized in that the relationship

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

[0013] The inventors have discovered that a neck bushing satisfying the newly claimed design conditions according to formula (1) solves the problem of the present invention. In other words, with such a neck bushing, during rolling operations, when large rolling loads due to angular position-dependent axial neck bushing displacement or deformation occur, sufficient lubricant reaches the area between the roll neck and the neck bushing, so that no damage occurs to the surface of the roll neck there. Furthermore, with a neck bushing designed according to formula (1), the axial forces that occur during elastic axial neck bushing displacement or deformation due to normal rolling loads are advantageously tolerable, i.e., within the range of tolerable forces. Axial forces within this range can be absorbed by a fixing device equipped with a spring ring. In other words, with a neck bushing designed according to the present invention, the axial forces that occur during neck bushing displacement or deformation are so small that there is no risk of the end of the roll neck being torn off from the rest of the roll neck or of the fixing system itself being overloaded or damaged due to the (axial) forces introduced into the roll neck by the fixing system being so large. The spring constant of the spring ring must be designed so that at maximum bearing stress the resulting gradient resistance (calculated with a known cone angle) produces a minimum axial displacement of the neck bushing of 1 / 10 mm, preferably 3 / 10 mm.

[0014] According to one embodiment, the conical neck bushing, like the outside of the conical roll neck, is provided on the inside with at least one groove for partially accommodating a feather key. The feather key engages in both grooves, thereby forming a circumferential rotational connection between the roll neck and the neck bushing attached to and rotating with the roll neck. According to the invention, at least one of these two grooves of each groove pair is dimensioned so that the feather key is positioned therein with axial and / or radial play. Both plays facilitate or enable said axial displacement or deformation of the neck bushing only when it passes through the area of ​​highest load during the rolling operation.

[0015] The above object of the present invention is furthermore solved by a roll stand according to claim 5. The advantages of this solution correspond to those stated above for the claimed neck bush.

[0016] Further advantageous configurations of the neck bush and the roll stand are the subject of the dependent claims.

[0017] The specification is accompanied by five figures. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a longitudinal section through a neck bush according to the present invention; [Figure 2] Dimensional tolerances of the neck bush according to the present invention [Figure 3] Neck bushing according to the invention free from the loading caused by the rolling forces associated with feather keys [Figure 4] Typical pressure distribution on the surface of a neck bush in an oil film bearing when loaded by a rolling load. [Figure 5] FIG. 1 is a longitudinal section through a neck bushing according to the invention under a rolling load and a roll neck supported in this neck bushing. DETAILED DESCRIPTION OF THE INVENTION

[0019] The invention will be explained in detail below by way of example with reference to the mentioned figures, in which the same technical elements are designated by the same reference numerals.

[0020] 1 shows a longitudinal cross-sectional view of a neck bushing 100 according to the present invention. The neck bushing has a cylindrical outer periphery and constitutes an oil film bearing together with a bearing bushing (not shown in FIG. 1) in which the neck bushing is housed within a cylindrical cavity. Between the bearing bushing and the neck bushing there is a lubricant gap filled with the lubricant of the oil film bearing.

[0021] The neck bushing according to the invention comprises a conical longitudinal section 110, the length of which, extending around the cylindrical circumference of the neck bushing, is designated by the symbol a. The conical longitudinal section 110 defines a conical cavity with a major conical diameter B and a minor conical diameter A. The conical longitudinal section 110 has a cone angle β. In the region of the minor conical diameter A, the conical longitudinal section 110 is seamlessly joined to the neck bushing by a cylindrical end section 120. The end section 120 defines a cylindrical cavity whose diameter corresponds to the diameter of the minor conical diameter A.

[0022] Both the conical cavity defined by the conical longitudinal portion 110 and the cylindrical cavity defined by the end portion 120, which connects to the conical cavity, are used to accommodate the corresponding complementary-shaped necks of the rolls in the roll stand. The cylindrical outer side of the neck bushing has an outer diameter D. The cylindrical outer side of the neck bushing is connected to the lubrication groove 112 on the inner side of the neck bushing via a connecting passage 113.

[0023] During operation of a roll supported in this way, the oil film of lubricant is formed between the bearing bush and the outside of the neck bush 100. Via the connecting passage 113, the lubricant reaches the lubrication groove 112. However, as long as the neck bush 100 is fixedly mounted on the roll neck, the lubricant remains in the lubrication groove 112 and cannot spread from there to the contact surface between the neck bush and the roll neck.

[0024] According to the present invention, the neck bush (100) 0.35<3.6 / a(DB)+k*D<0.5 (1) however, B [m] Cone major diameter D[m] Body outer diameter a [m] The length of the conical longitudinal part of the cylindrical circumference of the neck bushing k=0.15[1 / m] Slip coefficient The relationship applies.

[0025] Preferably, the lower limit is 0.37 (instead of 0.35) and / or the upper limit is 0.49 (instead of 0.5).

[0026] The claimed lower and upper limits are specifically illustrated in Figure 2. The lower and upper limits constitute a structurally acceptable range. That is, as long as the neck bushing satisfies the claimed formula (1) with the claimed upper and lower limits, preferably with an increased lower limit and / or a decreased upper limit, the neck bushing satisfies the problem underlying the present invention, i.e., the conflicting design goals to be solved. These conflicting design goals and their solution by the present invention are further explained in detail below with reference to Figures 3-5.

[0027] Figure 3 shows a supplement to Figure 1. In Figure 3, the neck bush 100 is also fixedly mounted on the roll neck 210. That is, the conical longitudinal section 110 of the neck bush 100 rests without play on the substantially complementary conical roll neck section 212, and the cylindrical end section 120 of the neck bush rests on the cylindrical roll neck end section 214 of the roll neck. There is essentially a frictional engagement between the neck bush 100 and the roll neck 210, that is, the neck bush 100 rotates together with the roll neck 210 due to the existing static friction. The frictional engagement rotational coupling is fixed by at least one feather key 20, which is partly located in an axially aligned groove 122 on the inside of the neck bush and partly located in an axially extending groove 216 on the outside of the roll neck.

[0028] The father key 20 is positioned in both of these grooves 122, 216 with axial play Sa and / or radial play Sr.

[0029] The neck bushing 100 is on the one hand axially fixed on the roll neck by a spring ring 220 and a fixing ring 230 .

[0030] 3 shows the arrangement of the neck bush and roll neck in an unloaded state, i.e., when no rolling load is applied or when a rolling load so small as not to cause deformation of the neck bush is applied. In this state, no lubricating film is formed between the neck bush and the roll neck.

[0031] Figure 4 shows a real pressure distribution as it occurs in the bearing gap between a rotating neck bushing and a stationary bearing bushing during a rolling operation. By way of example, the pressure distribution is shown here for the case where the upper backup roll neck 210, fitted with a neck bushing 100, is supported in a rolling stand and rotates in the direction of the arrow during the rolling operation (see the left and right views of Figure 4). It is important to note that the pressure load on the bearing, and in particular on the neck bushing, is not distributed evenly around the periphery, but rather a maximum load M is formed in the area of ​​the surface of the neck bushing opposite the rolling load action FR.

[0032] The pressure distribution shown in Fig. 4 is substantially stationary within a certain circumferential angular region during the rolling operation, at least as long as the direction in which the rolling load FR acts remains unchanged, which is consistent with the fact that the rolling load can fundamentally change its amount.

[0033] The stationary pressure distribution results in that a point on the surface of the roll neck or on the surface of the co-rotating neck bushing is only exposed to the indicated high pressure loads when, during its rotation, it passes through a pressure region with a high maximum pressure load M, as shown in Figure 4. In this situation, i.e. when passing through an angular region with a high pressure load, the radial compressive force FP on the neck bushing resulting from the rolling load FR and the resulting gradient resistance, particularly in connection with the conical longitudinal portion 110, can become so great that the neck bushing 100 is locally displaced or deformed, as shown in Figure 5. The local deformation consists in that the part of the neck bushing that is currently passing through the region of high pressure load M during the respective rotation is displaced or deformed on the roll neck in the direction of the gradient resistance, and thus locally peels off from the roll neck.

[0034] The separation of the neck bushing from the roll neck 210 occurs while a microscopically narrow and locally restricted lubricant gap 130 is formed between the neck bushing 100 and the roll neck 210. This microscopically narrow lubricant gap 130 does not extend over the entire circumference either, but is substantially limited in the circumferential direction to the region of high pressure load shown in Figure 4. Therefore, when passing through the angular region of high pressure load M, the lubricant oil is forced from the original lubricant film between the bearing bushing and the neck bushing 100 as shown in Figure 4, via the connecting passage 113 into the lubricant groove 112, and from there into the lubricant gap 130 as shown in Figure 5. The portion of the neck bushing 100 passing through the angular region of high pressure load slides on the lubricant film 130 due to the compressive force FP as also shown in Figure 5, pressing against the spring ring 220 and deforming the spring ring as well. During deformation / displacement, the axial and radial play Sa, Sr in the neck bushing groove 122 and / or the roll neck groove 216 is utilized by the feather key being pressed to its limit based on the displacement of the roll neck according to FIG. 5.

[0035] It is noteworthy that the neck bushing is only slightly deformed on the opposite side, i.e., the bottom in FIG. 5, so that it sits almost unchanged on the roll neck in a press fit without a lubricant gap.

[0036] The inventive design of the neck bushing 100 according to formula (1) ensures, on the one hand, the formation of the lubricant gap 130, which ensures that the lubricant between the neck bushing and the roll neck does not remain locally confined to the region of the lubrication grooves 112, but is also distributed in the region between the lubrication grooves 112. This is desirable despite the fact that an essentially immovable fit of the neck bushing on the roll neck still exists, in order to prevent the fretting known from the prior art, i.e., the microscopically small wear that occurs in the region of the contact surface between the neck bushing and the roll neck when passing through angular regions that would otherwise have high pressure loads. This wear is prevented by the lubricant gap 130, which is itself realized or promoted by making the gradient resistance FH as large as possible. The gradient resistance increases, in particular, the greater the difference between the major cone diameter B and the minor cone diameter A. On the other hand, however, the gradient resistance FH must not be too large, because otherwise the spring ring 220 and the fixing ring 230 will no longer be able to receive and direct the gradient resistance FH to the roll neck 210. In the worst case, i.e., if the gradient resistance FH is too large, the cylindrical roll neck end portion 214 may be thrown axially off the conical roll neck portion 212.

[0037] As stated above, the structural design of the neck bushing 100 in accordance with equation (1) ensures that both of the conflicting design goals can be realized or adhered to.

[0038] The double-headed arrow shown in FIG. 5 pointing from the right toward the fixing ring 230 indicates a reaction force FG against the grade resistance FH that must be received by the roll neck, particularly the cylindrical roll neck end portion 214, when the grade resistance is introduced into the roll neck 210 via the fixing ring 230. [Explanation of symbols]

[0039] 100 Neck Bush 110 Vertical part of the cone 112 Lubrication groove 113 Connecting Road 120 Termination section 122 Feather key groove 130 Lubricant gap 20 Feather Key 200 rolls 210 Roll Neck 212 Conical roll neck 214 Cylindrical roll neck end 216 Feather key groove 220 Spring Ring 230 Fixing ring A Cone minor diameter B Cone large diameter D Outer diameter of neck bush M maximum load Sa Axial play Sr Radial play β cone angle FG Reaction force against gradient resistance FH FP Compressive force resulting from rolling load FR FR rolling load FH Grade Resistance a) Cone length of the longitudinal part of the cone (drawn out)

Claims

1. A neck bush (100) as part of an oil film bearing in a roll stand for accommodating a conical roll neck of a roll, in particular a backup roll, comprising: The neck bushing is - be elastically deformable under the action of the rolling load applied by the roll stand; The outside is formed into a cylindrical shape with a body outer diameter D, - comprising an internally conical longitudinal section (110) formed conically with a major cone diameter B and a cone angle β to accommodate the conical roll neck of the roll over a cone length a, The conical longitudinal section (110) is provided on the inside with a lubrication groove (112) for introducing a lubricant into the space between the inside of the neck bush and the outside of the conical roll neck, Regarding the neck bush (100), 0.35<3.6 / a(DB)+kD<0.5 (1) where k = 0.15 / m is the coefficient of slip The neck bushing (100) is characterized in that the relationship:

2. Regarding the neck bush (100), 0.37<3.6 / a(DB)+kD<0.49 (2) 2. The neck bushing (100) of claim 1, wherein the relationship:

3. 3. The neck bush (100) according to claim 1 or 2, characterized in that it is provided with a terminal portion (120) formed as a hollow cylinder, the internal diameters of which match and connect with the conical longitudinal portion at the position of the conical minimum diameter A of the conical longitudinal portion.

4. A neck bush (100) according to any one of claims 1 to 3, characterized in that the neck bush (100) is provided on the inside with a groove (122) for partially accommodating the feather key (20).

5. At least one bearing housing formed as an oil film bearing having an internally conical neck bush (100) according to any one of claims 1 to 4; At least one roll (200) whose roll neck (210) is formed to have a conical roll neck portion (212) and preferably also a cylindrical roll neck end portion (214) for receiving in the neck bush (100).

5. A roll stand comprising: a roll neck, the roll neck being supported in a bearing housing, the roll neck being supported in a bearing bush of the bearing housing, the roll neck being supported in a bearing bush of the bearing housing.

6. 6. The roll stand according to claim 5, characterized in that the roll neck (210) is provided with an external groove, that a feather key (20) is provided, a first part of which is received by an internal groove of the neck bush (100) and a second part of which is received by an external groove (216) of the roll neck (210), and that at least one of the two grooves is dimensioned in relation to the dimensions of the feather key (20) such that the feather key (20) sits in the groove in an unloaded state, in particular outside the rolling operation, with an axial play of Sa>0.0 mm and a radial play of Sr>0.5 mm.

7. the neck bush (100) is fixed on the roll neck (210) against slipping off the roll neck in the axial direction by a fixing ring (230) and a spring ring (220) arranged axially between the neck bush (100) and the fixing ring (230); and the spring constant of the spring ring (220) is designed such that at maximum stress of the bearing, the resulting gradient resistance calculated with a known cone angle results in a minimum axial displacement of the neck bush of 1 / 10 mm, preferably 3 / 10 mm; 7. A roll stand according to claim 6, characterized in that

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