Field of the invention

The invention relates to a monitoring system of an oil film bearing, e.g., provided in a rolling mill stand or roll casting device or coil forming system.

Background art

The rolls are supported by bearings in the rolling mill stands for sheets and strips, as well as in other similar applications (e.g., continuous roll casting devices, profile product rolling mills, coil forming systems).

One of the main technologies used for these bearings is the oil film solution, in which a shaft, most often covered by a replaceable sleeve, rotates inside a static bushing. To limit friction and wear between the parts, an amount of oil is injected between the bushing and the sleeve to create a layer of oil capable of reducing or almost eliminating friction and preventing massive contact between the two parts subject to relative motion.

In principle, it is understood that this rotation is free of friction and wear, and the shaft is coaxial to the bushing which acts as a guiding element. Actually, friction and wear are minimized but are still present, and a shaft deformation and a related displacement with respect to the bushing are possible, determining working conditions which create wear on the parts. Furthermore, these conditions can create a non-uniform distance between the shaft and the bushing, pressure peaks, and oil heating. Therefore, the temperature, pressure and thickness of the oil film vary in the gap between the two components in response to load, rotation speed, and other operating conditions.

At present, these conditions are mainly predicted with some approximation by a theoretical or empirical model, and their evaluation makes it possible to estimate the load on the parts, the residual wear, and the bearing life.

Disadvantageously, the level of prediction is not sufficient to anticipate premature and occasional failures or to determine the actual achievable performance, due to the low accuracy of the prediction but also to the variability of the working conditions. Having the ability to estimate the oil film operating conditions in the field could reduce uncertainty and allow for improved prediction accuracy, eliminating uncertainties about actual operating conditions, with the beneficial effect of improving the performance and life of the bearing, and improving operating practices to optimize the bearing behavior.

The need is thus felt to make a monitoring system of the operating conditions of an oil film bearing capable of overcoming the aforesaid drawbacks.

Summary of the invention

It is an object of the present invention to make a novel solution for a more efficient monitoring of operating conditions in an oil film bearing.

It is a further aim of the present invention to provide a monitoring system which allows the continuous monitoring of three parameters inherent in oil film bearings: pressure, temperature, and layer thickness of the lubricating oil injected between shaft and bushing or between shaft sleeve and bushing.

The present invention achieves these and other purposes, which will be apparent in light of the present description, by means of a system for monitoring parameters representative of the operating conditions of an oil film bearing according to claim 1 , wherein an oil film is present between a static component and at least one rotating component both defining an axis, said at least one rotating component being arranged inside said static component, the monitoring system comprising

- at least one pressure sensor to detect the oil pressure of said oil film;

- at least one distance sensor to detect the distance between said static component and said at least one rotating component and thereby the thickness of said oil film;

- at least one temperature sensor to detect the temperature of said oil film; wherein the at least one pressure sensor, the at least one distance sensor, and the at least one temperature sensor are housed in said at least one rotating component. Therefore, the solution makes it possible to map the three main parameters: oil film temperature, oil film thickness, and oil pressure.

Advantageously, the three types of sensors are installed in the rotating shaft, or in the sleeve attached to it, instead of on the static housing.

Advantageously, since the sensors can rotate together with the rotating component, the aforesaid three parameters of the oil film can be measured in different areas and mapping can be achieved. With the solution of the invention, these three parameters can be measured for each point of the oil film along one or more circumferences having substantially the center on the axis X and being arranged spaced apart, in particular along the width of the bearing (parallel to the axis X, Figure 1 ), to allow a correct reconstruction of the real working conditions, but also of possible deformations of the shaft inside the bearing, which are often unpredictable but can appreciably affect the local stresses on the mechanical components, thus causing damage and wear.

Three types of sensors can be used to measure, for example, temperature, pressure and thickness of the oil film at the same time:

- a set of pressure sensors, such as piezoresistive sensors or other suitable sensors, which can produce an electrical signal based on the applied pressure;

- a set of temperature sensors, such as thermocouples or other suitable sensors, which can produce an electrical signal based on the measured temperature;

- a set of distance sensors, such as inductive sensors or other suitable sensors, capable of reading the distance between the bushing and the sleeve, or between the bushing and the shaft, in the presence of an oil gap between them.

Advantageously, a monitoring system according to the invention makes it possible to obtain a correct mapping of the aforementioned three parameters, at high resolution, using a reduced number of sensors, unlike other possible monitoring systems in which high numbers of sensors are installed in the static part of the bearing to simplify supplying power to them, and the sensors monitor only one of the mentioned parameters.

Instead, in the present invention, the sensors are mounted on the sleeve, if present, or directly on the shaft, so that, for example, a single row of sensors with two or more sensors, can be installed for each type of sensor with appropriate spacing in the axial direction. Thus, a regular measurement grid is obtained due to the rotation imposed on the shaft.

Alternatively, only one sensor can be provided per sensor type.

The sensors can be powered by sliding contacts, batteries, wirelessly, or otherwise, such as by a device equipped with an alternator and a flywheel. In this manner, existing installations can also be conditioned without complex technical interventions. Some advantages of the solution of the present invention over the prior of the art are listed below:

- efficient monitoring of the bearing operating conditions;

- possibility of anticipating possible accidents, and thus reducing accidents;

- possibility of leaving the bearings in operation beyond the conventional operating hours if the measured conditions are favorable;

- cost reduction;

- possibility of monitoring the aforesaid three parameters independently;

- possibility of installation on existing machines without generation of new encumbrances.

The invention further relates to a rolling mill stand according to claim 11 ; a continuous roll casting device according to claim 12; and a coil forming system according to claim 13.

Further features and advantages of the invention will be more apparent in light of the detailed description of the preferred, but not exclusive embodiments.

The dependent claims describe particular embodiments of the invention.

Brief description of the figures

The description of the invention refers to the accompanying drawings, which are provided by way of non-limiting example, in which:

Figure 1 shows a section view of a monitoring system according to the invention;

Figure 2 show a section view taken along a plane vertical and perpendicular to the sheet of Figure 1 .

The same elements or components are referred to using the same reference numerals.

Detailed description of some embodiments of the invention

Exemplary embodiments of a monitoring system according to the invention are described with reference to the figures.

The monitoring system can advantageously be used, in particular it can be implemented, e.g., in a rolling mill stand, in a continuous roll casting device, or in a coil forming system.

The monitoring system is used, in particular, for monitoring the parameters representative of operating conditions of an oil film bearing, wherein an oil film is arranged between a static component 2 and at least one rotating component 3, 4 defining an axis X, said at least one rotating component 3, 4 being arranged inside said static component 2.

The term "rotating component" in particular refers to a component which is capable of rotation, i.e., a rotatable component. More in particular, the component is capable of rotating about the axis X.

The term "static component" in particular means a component which remains fixed in position, in particular during rotation of the rotating component.

In all embodiments, the monitoring system comprises:

- at least one pressure sensor 5 to detect the oil pressure of said oil film;

- at least one distance sensor 8 to detect the distance between said static component 2 and said at least one rotating component 3, 4 and thus the thickness of said oil film;

- at least one temperature sensor 9 to detect the temperature of said oil film.

Advantageously, the at least one pressure sensor 5, the at least one distance sensor 8 and the at least one temperature sensor 9 are housed in said at least one rotating component 3, 4.

In particular, said at least one pressure sensor 5, said at least one distance sensor 8 and said at least one temperature sensor 9 are housed in said at least one rotatable component 3, 4 so as to be able to rotate together with said at least one rotatable component 3, 4, e.g., so as to be able to rotate integrally with said at least one rotatable component 3, 4.

Advantageously, when each sensor 5, 8, 9 makes a full rotation about the axis X, a measurement of the parameter detected by the sensor along the circumference it has traveled can be obtained. Therefore, advantageously, each sensor 5, 8, 9 can detect the respective parameter at different angular positions.

Preferably, each sensor 5, 8, 9 is arranged in a peripheral zone of the rotating component 3, 4.

Preferably, but not exclusively, part of each sensor 5, 8, 9 defines a portion of the periphery of the rotating component 3, 4. The periphery of the rotating component 3, 4 is the portion of the rotating component 3, 4 proximal to the static component 2. Said at least one pressure sensor 5, said at least one distance sensor 8, and said at least one temperature sensor 9 are preferably arranged in one or more holes or cavities of said at least one rotating component 3, 4.

Preferably, each hole or cavity is appropriately plugged to prevent unwanted infiltration of oil. For example, each hole or cavity can be plugged by a respective sensor 5, 8, 9 and/or by sealing means.

In particular, the wall which delimits each hole or cavity extends about a respective axis J (one of which is shown in Fig. 1 ), which is preferably transverse to the axis X. Preferably, said axes J of the holes or cavities are mutually parallel. In a first variant, the axes J of the holes, or cavities, are perpendicular to the axis X, whereby the sensors are arranged radially with respect to the axis X.

In a second variant each of said axes J of holes, or cavities, forms an angle other than 90° with respect to the axis X, whereby the sensors are not arranged radially with respect to the axis X.

Preferably, said at least one pressure sensor 5 is housed in a first hole or cavity obtained in said at least one rotating component 3, 4; said at least one distance sensor 8 is housed in a second hole or cavity obtained in said at least one rotating component 3, 4; and said at least one temperature sensor 9 is housed in a third hole or cavity obtained in said at least one rotating component 3, 4. In particular, the first hole, or cavity, the second hole, or cavity, and the third hole, or cavity, are mutually distinct.

Alternatively, two of either the at least one pressure sensor 5, the at least one distance sensor 8 or the at least one temperature sensor 9 are housed in a first hole or cavity obtained in said at least one rotating 3, 4, and the other one is housed in a second hole or cavity obtained in said at least one rotating component 3, 4. For example, one or more pressure sensors 5 and one or more distance sensors 8 are housed in the first hole or cavity; and one or more temperature sensors 9 are housed in the second hole or cavity.

Alternatively, the at least one pressure sensor 5, the at least one distance sensor 8, and the at least one temperature sensor 9 are housed in a single hole or cavity obtained in said at least one rotating component 3, 4. For example, a pressure sensor 5, a distance sensor 8, and a temperature sensor 9 can be arranged in a same hole or cavity. For example, two or more holes, or cavities, can be provided, in each of which a pressure sensor 5, a distance sensor 8, and a temperature sensor 9 are housed.

Preferably, two or more pressure sensors 5, two or more distance sensors 8, and two or more temperature sensors 9 are provided.

Preferably, the two or more pressure sensors 5 are axially separated from each other with respect to the axis X; and/or the two or more distance sensors 8 are axially separated from each other with respect to the axis X; and/or the two or more temperature sensors 9 are axially separated from each other with respect to the axis X.

Preferably, there are provided a row of pressure sensors 5, a row of distance sensors 8, and a row of temperature sensors 9, each row being arranged along a direction parallel to the axis X.

In other words, two or more pressure sensors 5 are arranged to form a row. In particular, the two or more pressure sensors 5 are aligned with each other, in particular along a direction parallel to the axis X. Similarly for the distance sensors 8 and the temperature sensors 9.

Advantageously, the three parameters can thus be measured at different positions along the axis X.

Preferably, the row of pressure sensors 5, the row of distance sensor 8, and the row of temperature sensors 9 are arranged along the periphery of said at least one rotating component 3, 4, preferably in a zone which corresponds to a convex central angle.

Preferably, the pressure sensors 5 are at a same distance from each other; the distance sensors 8 are at a same distance from each other; and the temperature sensors 9 are at a same distance from each other.

In a preferred variant, the distance between one pressure sensor 5 and the next is equal to both the distance between one distance sensor 8 and the next and the distance between one temperature sensor 9 and the next.

Preferably, each triad consisting of a pressure sensor 5, a distance sensor 8, and a temperature sensor 9 is arranged along a portion of circumference having its center on the axis X. However, it is possible to provide only one pressure sensor 5, only one distance sensor 8, and only one temperature sensor 9, in particular arranged along the periphery of said at least one rotating component 3, 4, preferably in a zone which corresponds to a convex central angle. Preferably, this single triad of sensors 5, 8, 9 is arranged along a portion of a circumference having its center on the axis X.

In all the embodiments, the at least one pressure sensor 5, the at least one distance sensor 8, and the at least one temperature sensor 9 are connected by means of a respective cable 6, in particular an electrical cable, to a digitalization device 7. The digitalization device 7 is configured to digitize the signals generated by the respective sensors 5, 8, 9. Preferably, the digitalization device 7 is adapted to transmit the digitized signals either by means of a rotary joint, or wirelessly.

The digitalization device 7 preferably comprises a casing containing electronic hardware capable of amplifying and transforming, in particular digitizing, the signals of the sensors 5, 8, 9.

The digitalization device 7, in particular its casing, is preferably mounted on the rotating component 3, 4, in particular on the rotating component 4 which, for example, is a shaft pin. More in detail, the digitalization device 7 is preferably fixed to the rotating component 4 so that it can rotate therewith, e.g., integrally therewith. Preferably, the digitalization device 7 is fixed to an axial end (axial relative to the axis X) of the rotating component 4. Preferably, the digitalization device 7 is arranged so as to be crossed by the axis X.

In all the embodiments, the at least one pressure sensor 5, the at least one distance sensor 8, and the at least one temperature sensor 9 can be powered by means of sliding contacts, batteries, wirelessly, or by means of a device provided with an alternator and a flywheel.

In particular, said device is fixed to the rotating component 4 so that it can rotate integrally therewith. The rotating component 4 and the device are arranged to be mutually coaxial (with respect to the axis X).

When the rotating component 4 rotates about the axis X, the flywheel is placed in rotation and, as it rotates, generates energy by means of the alternator. In this manner, the sensors 5, 8, 9 can be powered without the need for batteries.

The static component 2 is, for example, a bushing 2. Said at least one rotating component 3, 4, for example, consists of a shaft pin 4 (or end pin) or a sleeve 3 into which a shaft pin 4 is inserted.

The shaft pin 4 is, for example, a neck or pin of a roll 11 of a rolling mill stand or continuous casting device or coil forming system.

In the illustrated example, said sensors 5, 8, 9 are housed in a sleeve 3. The oil film is present between the sleeve 3 and the bushing 2. In particular, the oil film is in contact with the sleeve 3 and the bushing 2. Preferably, the surface of the sleeve 3 and the surface of the bushing 2, between which the oil film is present, are cylindrical or substantially cylindrical.

A pin is inserted into the sleeve 3, in particular a shaft pin 4 or end pin.

Preferably, the sleeve 3 is arranged about a portion of the shaft pin 4 the outer surface of which is tapered, e.g., conical-frustum shaped. In this case, the inner surface of the sleeve 3 is also tapered, e.g., conical-frustum shaped, in particular in a direction opposite to the tapering direction of the surface portion of the shaft pin 4. Preferably, the thickness, parallelly to axis Y, of the sleeve wall 3 is increasing outwardly along the axis X. The axis Y is orthogonal to the axis X.

The shaft pin 4 is adapted to rotate. The sleeve 3 and the shaft pin 4 are fixed to each other, in particular so that the sleeve 3 and the shaft pin 4 are adapted to rotate integrally with each other.

If the sensors 5, 8, 9 are housed in the sleeve 3 the axes J of the holes, or cavities, are preferably perpendicular to the axis X, whereby the sensors are arranged in said holes radially with respect to the axis X.

If the overall dimensions of the sensors used exceed the thickness of the sleeve 3 along the axis Y, it is preferable that the axes J of the holes, or cavities (Figure 1 ), are inclined forming an angle other than 90° with respect to the axis X so that the sensors are not arranged radially with respect to the axis X. This solution makes it possible to leave the shaft pin 4 unchanged and modify only the sleeve 3, whereby this solution can be applied in case of retrofitting.

In an alternative example (not shown), said sensors 5, 8, 9 are housed in the rotating component 4 which is, for example, a pin, in particular a shaft pin 4, or end pin 4. In particular, the sleeve 3 is not provided. The oil film is present between the shaft pin 4 and the bushing 2. In particular, the oil film is in contact with the shaft pin 4 and the bushing 2. Again, it is preferable for the axes J of the holes, or cavities, to be perpendicular to the axis X. However, the axes J of the holes, or cavities, can be inclined to form an angle other than 90° with respect to the axis X.

Fig. 1 shows part of a roll 1 1 . The roll 1 1 has a portion which is adapted to come into contact with the material to be processed.

The roll 1 1 is provided with two shaft pins 4, or end pins 4, one of which is shown in Fig. 1 . The shaft pins 4 are in particular the axial (relative to the axis X) end portions of the roll 1 1 . The aforesaid portion adapted to come into contact with the material to be processed extends between the two shaft pins 4.

Each end pin 4 is supported by a respective chock 1 . The static component 2 is housed in each chock 1 , in particular in a through hole of each chock 1 , and is internally crossed by said at least one rotating component 3, 4.

For each roll 1 1 , the monitoring system can be implemented for both pairs of static component 2 and rotating component 3, 4, opposite to each other relative to a plane perpendicular to the axis X, in particular parallel with respect to the axis Y drawn in Fig. 1. The two monitoring systems implemented for each roll 1 1 preferably comprise the same components which are preferably arranged symmetrically relative to said plane.

As anticipated above, the invention further relates to a rolling mill stand or continuous roll casting device or coil forming system, wherein each roll 1 1 has end pins 4 supported by a respective chock 1 , wherein a static component 2, crossed internally by at least one rotating component 3, 4, is housed in a through-hole of each chock 1 , said static component 2 and said at least one rotating component 3, 4 defining an axis X; wherein an oil film is arranged between said static component 2 and said at least one rotating component 3, 4; wherein said at least one rotating component 3, 4 consists of an end pin 4 of a respective roll 1 1 or a sleeve 3 into which said end pin 4 is inserted; and wherein a monitoring system of parameters representative of the operating conditions of the oil film, as described above, is provided.

The rolling mill stand, the continuous roll casting device, and the coil forming system each comprise one or more rolls 1 1 .