A kind of memory alloy self-adjusting gap based roll

Abstract

The application discloses a kind of based on memory alloy self-adjusting gap's carrier roller, belong to the sealing technical field of belt conveyor equipment.The carrier roller includes bearing seat, bearing, rotating shaft and sealing assembly.Sealing assembly includes first pole shoe, second pole shoe, third pole shoe, permanent magnet, magnetic isolation shaft sleeve and the elastic element made of memory alloy.First, second pole shoe is fixed on magnetic isolation shaft sleeve with rotating shaft rotation, and third pole shoe is slidably arranged in bearing seat and is abutted with the outer ring of bearing by elastic element.Permanent magnet generates magnetic field, and forms magnetic circuit between pole shoe, and adsorbs magnetic liquid in sealing gap.Low temperature start, elastic element keeps sealing gap as larger value, and starting torque is small;After running temperature rises, elastic element elongation pushes third pole shoe to move, and makes sealing gap reduce, and enhances sealing capacity.The application realizes that sealing gap is self-adapting adjustment with temperature, and considers low temperature startability and high temperature sealing property, and structure is reliable.

Description

Technical Field

[0001] This invention belongs to the field of sealing technology for belt conveyor equipment, and specifically relates to a sealing structure for conveyor idlers, and in particular a high-performance sealing idler based on shape memory alloy to achieve adaptive adjustment of the sealing gap with temperature changes. Background Technology

[0002] Idler rollers are a key basic component in belt conveyors, and their operational reliability directly affects the safety and energy consumption level of the conveying system. Idler rollers typically operate in complex environments with high dust concentration, high humidity, strong particle impact, and large temperature fluctuations, making bearing sealing performance one of the key factors affecting their service life.

[0003] Existing idler roller sealing structures mainly include labyrinth seals, contact rubber seals, and magnetic fluid seals. Among them, magnetic fluid seals are increasingly being used in the idler roller sealing field due to their advantages such as non-contact operation, zero wear, and stable sealing performance. However, existing magnetic fluid seal idler rollers still have the following shortcomings: On the one hand, in order to improve the sealing pressure resistance, existing magnetic fluid seals usually adopt a smaller sealing gap or a stronger magnetic field strength design, which results in a higher viscosity of the magnetic fluid at low temperatures or during the start-up stage, and a significant increase in the starting torque, which is not conducive to low-temperature start-up and energy-saving operation. On the other hand, increasing the sealing gap or reducing the magnetic field strength in order to reduce the starting resistance will reduce the pressure resistance and resistance to external contamination of the magnetic fluid seal during the operation of the idler roller, and the seal is prone to failure under high load or high temperature conditions.

[0004] Therefore, how to reduce the starting torque of the magnetic liquid seal during the low-temperature start-up phase, while improving the seal's pressure resistance and reliability during idler operation, has become a technical problem that magnetic liquid seal idlers urgently need to solve. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a self-adjusting gap idler roller based on shape memory alloy. This invention aims to resolve the contradiction between the large starting torque during the low-temperature start-up stage and the insufficient sealing pressure resistance during operation of existing magnetic liquid sealed idlers, thereby achieving the dual goals of low low-temperature start-up resistance and reliable sealing during operation.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A self-adjusting gap idler roller based on shape memory alloy includes a roller body and a rotating shaft assembly disposed in the roller body. The rotating shaft assembly includes a rotating shaft and bearing assemblies disposed at both ends of the rotating shaft. Each bearing assembly includes a bearing housing, a bearing, and a sealing assembly disposed between the bearing housing and the rotating shaft. The sealing assembly includes: a first pole shoe, a second pole shoe, a third pole shoe, a permanent magnet, a magnetic shielding bushing, and an elastic element made of shape memory alloy; The first pole shoe and the second pole shoe are fixedly mounted on the magnetic shielding bushing, which is fitted and fixed on the rotating shaft. The first pole shoe and the second pole shoe rotate synchronously with the rotating shaft. The third pole shoe is fitted inside the bearing seat and slides with the bearing seat. The third pole shoe abuts against the outer ring of the bearing through the elastic element. The permanent magnet is sandwiched between the first pole piece and the second pole piece to generate a magnetic field. The magnetic field forms a magnetic circuit between the first pole piece, the second pole piece, and the third pole piece, and attracts the magnetic liquid into the sealed gap between the third pole piece and the first and second pole pieces. The elastic element is configured to maintain its initial length when the temperature is below a preset threshold, so that the sealing gap maintains a first spacing; when the temperature is above the preset threshold, the elastic element extends and pushes the third pole shoe to move axially toward the first pole shoe and the second pole shoe, so that the sealing gap is reduced to a second spacing.

[0007] Furthermore, the elastic element is a shape memory alloy spring, one end of which is fixedly connected to the outer ring of the bearing, and the other end is fixedly connected to the third pole shoe.

[0008] Furthermore, both the first pole piece and the second pole piece are annular magnetic conductors, and the end faces of the first pole piece and the second pole piece facing the third pole piece are arranged radially flush.

[0009] Furthermore, the permanent magnet is a radiatively magnetized ring-shaped permanent magnet, with its inner ring being either the N pole or the S pole, and its outer ring being the other pole.

[0010] Furthermore, the magnetic shielding bushing is made of a non-magnetic material, the first pole shoe and the magnetic shielding bushing are in an interference fit, and the magnetic shielding bushing and the rotating shaft are in an interference fit.

[0011] Furthermore, a sealing element is provided between the third pole shoe and the bearing housing to achieve a static seal between the third pole shoe and the bearing housing.

[0012] Furthermore, it also includes a dustproof ring, which is disposed on the rotating shaft and located at the port of the bearing housing.

[0013] Furthermore, both the first pole shoe and the second pole shoe are provided with stepped structures for fixing the permanent magnet.

[0014] Furthermore, the elastic element is configured such that when the internal temperature of the idler roller rises, the shape memory alloy undergoes a phase transformation, generating a driving force that pushes the third pole shoe to overcome the frictional force between it and the bearing housing.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) By using an elastic element made of shape memory alloy, the adaptive adjustment of the magnetic fluid sealing gap with temperature changes is achieved. During the low-temperature start-up stage, the sealing gap is larger, the magnetic field strength is lower, and the viscosity of the magnetic fluid is smaller, thus significantly reducing the starting torque. During the operation of the idler roller, the temperature rises, and the shape memory alloy pushes the third pole shoe to move, automatically reducing the sealing gap, enhancing the magnetic field strength and gradient, and improving the sealing pressure resistance and resistance to external contamination. This structure solves the contradiction between starting torque and sealing capacity in the prior art.

[0016] (2) It fully utilizes the heat generated by the roller itself as the driving source, without the need for any external sensors, controllers or energy input. It has a simple and compact structure, high reliability, and no contact wear, which extends the service life of the roller.

[0017] (3) It is especially suitable for harsh working conditions such as high dust, high humidity and large temperature difference, ensuring the stable and efficient operation of the conveyor in various environments. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 This is a schematic diagram of one end of the magnetic liquid sealing roller based on shape memory alloy self-adjusting gap provided by the present invention.

[0020] Figure 2 This is a simulation calculation diagram of the magnetic field in the initial state of the present invention.

[0021] Figure 3 This is a simulation calculation diagram of the magnetic field under the operating state of the present invention.

[0022] Figure 4 This is a schematic diagram of the structure of the magnetic liquid sealing roller based on the self-adjusting gap of shape memory alloy in an example of the present invention. Detailed Implementation

[0023] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0024] like Figure 1As shown, the present invention provides a magnetic liquid sealing roller based on shape memory alloy self-adjusting gap, which mainly includes a roller body 14 and a rotating shaft assembly disposed in the roller body 14. The rotating shaft assembly includes a rotating shaft 12 and bearing assemblies disposed at both ends of the rotating shaft 12. Each bearing assembly includes a bearing seat 1, a bearing 2, and a sealing component disposed between the bearing seat 1 and the rotating shaft 12.

[0025] The sealing assembly is used to realize the adaptive adjustment of the sealing gap in the magnetic liquid sealing idler of the present invention, and specifically includes: a first pole shoe 8, a second pole shoe 6, a third pole shoe 4, a permanent magnet 7, a magnetic shielding bushing 10, and an elastic element 3 made of shape memory alloy.

[0026] In this idler roller, the bearing housing 1 is fixedly installed inside the roller body 14. The outer ring of the bearing 2 is fixed inside the bearing housing 1, and the inner ring cooperates with the rotating shaft 12 or the magnetic shielding sleeve 10 to bear the radial load and allow the rotating shaft 12 to rotate smoothly. The magnetic shielding sleeve 10 is fixedly sleeved on the rotating shaft 12. The first pole shoe 8 and the second pole shoe 6 are both fixed on the magnetic shielding sleeve 10, so the first pole shoe 8 and the second pole shoe 6 rotate synchronously with the rotating shaft 12. The third pole shoe 4 is sleeved inside the bearing housing 1 and can slide axially. Its right side abuts against the left side of the outer ring of the bearing 2 through the elastic element 3. The permanent magnet 7 is sandwiched between the first pole shoe 8 and the second pole shoe 6. The magnetic field generated forms a closed magnetic circuit through the first pole shoe 8, the second pole shoe 6, and the third pole shoe 4. The magnetic fluid is adsorbed in the axial sealing gap between the third pole shoe 4 and the first pole shoe 8 and the second pole shoe 6, thereby realizing a rotary dynamic seal.

[0027] In the magnetic liquid-sealed idler roller thus constructed, the phase change characteristics of the shape memory alloy elastic element 3 allow the sealing gap to automatically adjust with temperature changes. During low-temperature startup, the elastic element 3 maintains its initial length, resulting in a larger sealing gap, a weaker magnetic field within the gap, and lower magnetic liquid viscosity, thus significantly reducing the starting torque. As the idler roller generates heat during operation, and the temperature rises above the shape memory alloy phase change point, the elastic element 3 elongates, pushing the third pole shoe 4 towards the first pole shoe 8 and the second pole shoe 6, reducing the sealing gap and strengthening the magnetic field within the gap. This significantly improves the pressure resistance and contamination resistance of the magnetic liquid seal. This solution requires no external control, has a reliable structure, and resolves the contradiction between high low-temperature startup resistance and insufficient sealing capacity during operation in existing technologies.

[0028] The following section further elaborates on the specific configuration of each component in this magnetic liquid-sealed idler roller based on shape memory alloy self-adjusting gap.

[0029] The bearing housing 1 in this magnetic liquid-sealed idler roller has a cylindrical structure with a multi-step inner bore for positioning the outer ring of the bearing 2 and the third pole shoe 4. The bearing housing 1 is sealed and fixedly installed in the ports at both ends of the roller body 14.

[0030] As an example, the bearing housing 1 can be made of carbon structural steel or cast iron to ensure sufficient rigidity and wear resistance.

[0031] The bearing 2 in this idler roller is a deep groove ball bearing or a cylindrical roller bearing. Its outer ring is interference-fitted with the inner hole of the bearing housing 1, and its inner ring is interference-fitted with the rotating shaft 12 or the magnetic shielding bushing 10. The bearing 2 bears the radial load of the idler roller and allows a certain axial clearance to ensure that the third pole shoe 4 can move to the right under the push of the elastic element 3.

[0032] The rotating shaft 12 in this idler roller is a hollow or solid shaft, made of medium carbon steel or alloy steel, and its outer surface is interference-fitted with the inner hole of the magnetic shielding bushing 10.

[0033] The magnetic isolation bushing 10 in this idler roller is made of non-magnetic material, such as austenitic stainless steel, aluminum alloy or non-metallic material. Its function is to prevent the magnetic field generated by the permanent magnet 7 from leaking through the rotating shaft 12, and to ensure that the magnetic lines of force are mainly concentrated in the working gap between the pole shoes.

[0034] Furthermore, the outer circle of the magnetic shielding bushing 10 is provided with a step for positioning the first pole shoe 8, and its inner hole is interference-fitted with the rotating shaft 12 to ensure synchronous rotation with the rotating shaft 12.

[0035] The first pole shoe 8 and the second pole shoe 6 in this idler roller are both made of high-permeability materials (such as electrical pure iron, low-carbon steel, or soft magnetic alloys), possessing high magnetic permeability and low coercivity. Both are annular structures, and their end faces facing the third pole shoe 4 are flush axially to ensure uniform sealing gaps. Both have stepped structures in their inner holes for clamping and fixing the permanent magnet 7 from both sides.

[0036] Specifically, the inner hole of the first pole shoe 8 is interference-fitted with the outer circle of the magnetic shielding bushing 10, so that the assembly formed by the first pole shoe 8, the second pole shoe 6 and the permanent magnet 7, together with the magnetic shielding bushing 10 and the rotating shaft 12, becomes an integral rotating component.

[0037] The permanent magnet 7 in this idler roller adopts a ring structure and is made of high-performance permanent magnet materials such as neodymium iron boron or samarium cobalt. The magnetization method is radial radiation magnetization, that is, the inner ring is N pole (or S pole) and the outer ring is S pole (or N pole). This magnetization method can generate a magnetic field that diverges or converges radially from the inner ring to the outer ring, which is beneficial to forming a high gradient magnetic field in the axial gap between the pole shoes, thereby enhancing the sealing ability of the magnetic fluid.

[0038] The third pole shoe 4 in this idler roller is also made of a highly magnetically permeable material, is annular, and is fitted into the inner hole of the bearing housing 1. A sealing groove is provided between the outer circle of the third pole shoe 4 and the inner hole of the bearing housing 1 for installing the seal 5. The third pole shoe 4 can slide along the axial direction of the bearing housing 1. Its end face facing the bearing 2 (taking the position shown in the figure as an example, i.e., the left end face) abuts against the elastic element 3, and its other end face is opposite to the first pole shoe 8 and the second pole shoe 6, forming an axial sealing gap.

[0039] The elastic element 3 in this idler roller is a shape memory alloy spring made of Ni-Ti based shape memory alloys (such as NiTi, NiTiCu, etc.). This type of alloy exhibits a shape memory effect; in the low-temperature phase (martensitic phase), the spring is softer and shorter (or maintains its initial length), while in the high-temperature phase (austenitic phase), the spring recovers its preset shape, generating significant elongation and restoring force. The phase transformation temperature of the shape memory alloy can be controlled within, for example, a range of 30℃ to 60℃ by adjusting the composition. One end of the elastic element 3 (in the illustrated orientation, i.e., the left end face) is fixedly connected (e.g., by welding or snap-fit) to the end face of the outer ring of the bearing 2 facing the third pole shoe 4 (in the illustrated orientation, i.e., the right end face), and the other end of the elastic element 3 (in the illustrated orientation, i.e., the right end face) is fixedly connected to the end face of the third pole shoe 4 facing the bearing 2 (in the illustrated orientation, i.e., the left end face).

[0040] Furthermore, the initial length of the elastic element 3 determines the size of the sealing gap during low-temperature startup, and its elongation determines the amount of reduction in the sealing gap during high-temperature operation.

[0041] The sealing element 5 in this idler roller is specifically an O-ring made of oil-resistant rubber (such as nitrile rubber or fluororubber). It is installed in the sealing groove on the outer circle of the third pole shoe 4 and forms a compression seal with the inner hole of the bearing seat 1 to achieve a static seal between the third pole shoe and the bearing seat, preventing magnetic liquid or grease from leaking from the gap between the third pole shoe 4 and the bearing seat 1.

[0042] The dustproof ring 11 in this idler roller is made of polyurethane or rubber and is specifically installed on the rotating shaft 12 and located at the port of the bearing seat 1. It can contact the outer circle of the rotating shaft 12 or the magnetic shielding bushing 10 to form a labyrinth seal or contact seal, which plays a role in initially blocking large particles of dust from the outside.

[0043] The elastic retaining rings 9 and 13 in this idler roller are installed in the grooves on the rotating shaft 12 and are distributed on both sides of the bearing 2. They respectively mate with the end faces of the two sides of the bearing 2 to limit the axial position of the rotating shaft 12 relative to the bearing 2 and prevent the rotating shaft 12 from moving axially relative to the bearing 2. As an example, the elastic retaining rings 9 and 13 can be retaining rings.

[0044] The magnetic liquid sealing roller based on the above scheme, which is based on the shape memory alloy self-adjusting gap, can effectively achieve adaptive adjustment of the sealing gap during operation.

[0045] Combination Figure 1 As shown, the magnet 7 in this magnetic liquid sealed idler roller is magnetized radially. Taking the inner ring as the N pole and the outer ring as the S pole as an example, the magnetic field lines generated by the permanent magnet 7 are as follows: Starting from the inner ring (N pole) of the permanent magnet 7, it enters the inner side of the first pole shoe 8, passes through the body of the first pole shoe 8, reaches the left end face of the first pole shoe 8 (the face opposite to the third pole shoe), crosses the axial sealing gap between the first pole shoe 8 and the third pole shoe 4, enters the upper right end face of the third pole shoe 4, passes through the body of the third pole shoe 4, exits from the lower right end face of the third pole shoe 4 (the face opposite to the second pole shoe), crosses the axial sealing gap between the second pole shoe 6 and the third pole shoe 4, enters the left end face of the second pole shoe 6, passes through the body of the second pole shoe 6, and returns to the outer ring (S pole) of the permanent magnet 7.

[0046] In the aforementioned magnetic circuit, the two axial sealing gaps are crucial locations where the magnetic fluid is adsorbed and forms a seal. Since the magnetic shielding sleeve 10 is made of a non-magnetic material, the magnetic field will not leak through the rotating shaft 12, ensuring that the magnetic field energy is concentrated in the working gap.

[0047] Meanwhile, the apparent viscosity of magnetic fluids is positively correlated with the strength of the magnetic field; that is, the stronger the magnetic field, the more pronounced the chain-like structure of magnetic particles in the magnetic fluid, and the higher the viscosity; the weaker the magnetic field, the lower the viscosity. Furthermore, the pressure resistance of magnetic fluid seals is directly proportional to the magnetic field strength gradient; that is, the smaller the gap, the lower the magnetic resistance, and the greater the magnetic field strength and gradient, the higher the pressure resistance of the seal.

[0048] Based on this, the temperature change is converted into a change in the sealing gap by the shape memory alloy elastic element 3, thereby regulating the magnetic field strength and the viscosity of the magnetic liquid.

[0049] Thus, during the low-temperature start-up phase, the magnetic liquid-sealed idler roller has a low overall temperature (e.g., below the phase transformation temperature of the shape memory alloy), and the shape memory alloy elastic element 3 is in the martensitic phase, maintaining its initial length. At this time, the axial gap between the third pole shoe 4 and the first pole shoe 8 and the second pole shoe 6 is relatively large. A larger gap results in higher magnetic reluctance and a weaker magnetic field strength within the gap (e.g., ...). Figure 2 (As shown in the simulation diagram of the medium magnetic field). The viscosity of the magnetic fluid is low under a weak magnetic field, so the viscous resistance when the roller rotates is very small, the starting torque is significantly reduced, and it is easy to start.

[0050] As the idler roller continues to rotate, the rolling friction of bearing 2 generates heat. This heat is conducted through the outer ring of bearing 2 to the elastic element 3, which is fixedly connected to the outer ring. When the temperature of the elastic element 3 rises above the phase transformation temperature of the shape memory alloy (e.g., 40℃~50℃), the shape memory alloy undergoes a martensitic-to-austenitic phase transformation, and the elastic element 3 generates a restoring force and elongates significantly. When the elongation force exceeds the static friction between the third pole shoe 4 and the bearing housing 1 and O-ring 5, the elastic element 3 pushes the third pole shoe 4 to the right (i.e., towards the first pole shoe 8 and the second pole shoe 6). The distance of movement depends on the elongation of the elastic element 3, resulting in a reduction in the sealing gap.

[0051] During stable operation, as the sealing gap decreases, the magnetic reluctance at the gap decreases, the magnetic flux density increases significantly, and the magnetic field strength and gradient are significantly enhanced (e.g., Figure 3 (As shown in the simulation diagram of the medium magnetic field). The strong magnetic field more firmly adsorbs the magnetic fluid in the gap, forming a high-pressure-resistant seal, effectively preventing external dust and moisture from entering bearing 2, while also preventing internal grease leakage. Since the idler roller is already in normal operation at this time, the increase in viscous resistance caused by the reduction in the sealing gap has little impact on the overall energy consumption.

[0052] Once the idler roller reaches thermal equilibrium and the temperature stabilizes, the length of the elastic element 3 also remains stable, maintaining the sealing gap at a small, constant value, thus ensuring long-term stable high sealing performance. If temperature fluctuations occur due to load changes or ambient temperature variations, the length of the elastic element 3 will be finely adjusted accordingly, achieving dynamic self-adaptation of the sealing gap. If the temperature drops below the phase change temperature after the idler roller stops, the elastic element 3 returns to its initial length, and the sealing gap automatically returns to its maximum value, preparing for the next low-temperature start-up.

[0053] To further illustrate the performance of the magnetic liquid sealing roller based on shape memory alloy self-adjusting gap provided by this invention, this invention calculates and simulates the magnetic field of the magnetic liquid sealing roller in its initial state (when the gap is large) and its state after operation (when the gap is small), respectively. See [link to relevant documentation]. Figure 2 and Figure 3 , Figure 2 The figure shown is a simulation diagram of the magnetic field of the structure in its initial state (large gap). Figure 3 The diagram shown is a simulation calculation of the magnetic field of the structure under operating conditions (small gap).

[0054] from Figure 2 and Figure 3 The line graph shown (i.e.) Figure 2 and Figure 3 As can be seen from the first figure, the magnetic field generated by the permanent magnet 7 forms a magnetic circuit, proving the rationality of the design structure.

[0055] Next, compare Figure 2 and Figure 3 The last figure shows that the initial gap is large and the magnetic field strength within the gap is low. Since the weaker the magnetic field, the lower the viscosity of the magnetic fluid, the starting torque is small. After operation, due to the rightward thrust generated by spring 3, the sealing gap decreases, the magnetic field within the gap strengthens, and the magnetic field strength gradient also increases, thus enhancing the pressure resistance of the seal.

[0056] The simulation results above confirm that the present invention can effectively achieve adaptive adjustment of the magnetic liquid sealing gap as the temperature changes.

[0057] The following is a specific implementation example using idlers applied to belt conveyors.

[0058] Combination Figure 4 As shown, in this embodiment, the overall structure of the idler roller is as follows: the roller body 14 is a cylindrical steel roller skin, and its two end holes are fixedly connected to the left and right bearing seats 1, respectively. The rotating shaft 12 passes through the roller body 14, and a bearing 2 is installed at each end of the rotating shaft 12, and is axially positioned from both sides of the bearing 2 by elastic retaining rings 9 and 13, respectively. Each bearing seat 1 is provided with a set of self-adjusting sealing components.

[0059] The following parameter ranges can be used for each component: the inner diameter of bearing housing 1 is determined according to the specifications of the idler roller, and the material is carbon structural steel; bearing 2 is selected according to the load and is a deep groove ball bearing of the appropriate model; the diameter of shaft 12 matches the inner diameter of the bearing, and the material is alloy steel; the magnetic shielding sleeve 10 is made of austenitic stainless steel; the first pole shoe 8 and the second pole shoe 6 are made of electrical pure iron, and their end faces toward the third pole shoe 4 are flush; the permanent magnet 7 is made of annular neodymium iron boron, radially radiating magnetization, with the inner ring being the N pole and the outer ring being the S pole; the third pole shoe 4 is made of electrical pure iron; the elastic element 3 is a NiTi memory alloy spring, and its phase change temperature is set at approximately 45°C; the O-ring 5 is made of nitrile rubber; and the dustproof ring 11 is made of polyurethane.

[0060] In this example, the idler rollers are assembled using the following deployment and assembly sequence: (1) Press the magnetic shielding bushing 10 into the rotating shaft 12 and fix it; (2) Press the first pole shoe 8 into the magnetic isolation bushing 10 until it is positioned on the step; (3) Insert the permanent magnet 7 into the magnetic isolation bushing 10, so that one side of it fits against the step of the first pole shoe 8; (4) Press the second pole shoe 6 into the magnetic shielding sleeve 10 so that its step presses against the other side of the permanent magnet 7; (5) Install the bearing 2 on the rotating shaft 12 so that its inner ring mates with the rotating shaft 12 or the magnetic shielding bushing 10; (6) Install elastic retaining rings 9 and 13 on the rotating shaft 12, respectively, on both sides of the bearing 2, to fix the bearing 2 axially; (7) Install the dust seal 11 into the left port of the bearing housing 1; (8) Fix one end of the elastic element 3 to the left end face of the outer ring of the bearing 2; (9) After installing the O-ring 5 on the third pole shoe 4, insert the bearing seat 1 from the right side so that its right end face abuts against the other end of the elastic element 3. (10) Fit the assembled bearing housing assembly into the rotating shaft assembly so that the third pole shoe 4 is opposite to the first pole shoe 8 and the second pole shoe 6; (11) Inject an appropriate amount of magnetic liquid (such as kerosene-based or ester-based Fe3O4 magnetic liquid). (12) Fix the bearing housing 1 to the roller body 14. Assemble the other end bearing assembly in the same way.

[0061] Taking the startup in a low-temperature environment (such as winter) as an example, the working process of the idler roller in this example is explained.

[0062] Low-temperature start-up stage: In a low-temperature environment (below the phase transformation temperature of the shape memory alloy), the shape memory alloy elastic element 3 is in the martensitic phase, maintaining its initial length. At this time, the axial sealing gap between the third pole shoe 4 and the first pole shoe 8 and the second pole shoe 6 is relatively large. The larger gap results in a weaker magnetic field strength and a lower viscosity of the magnetic fluid within the gap, thus the starting torque when the idler roller rotates is smaller, making it easier to start.

[0063] During the heating and gap adjustment phase: As the idler roller continues to run, the rolling friction of bearing 2 generates heat. This heat is conducted to the elastic element 3 through the outer ring of bearing 2. When the temperature of the elastic element 3 rises above its phase transformation temperature, the shape memory alloy undergoes a phase transformation, and the elastic element 3 generates a restoring force and elongates. When the elongation force exceeds the static friction between the third pole shoe 4 and the bearing housing 1 and O-ring 5, the elastic element 3 pushes the third pole shoe 4 towards the first pole shoe 8 and the second pole shoe 6, reducing the sealing gap.

[0064] Stable operation phase: After the sealing gap is reduced, the magnetic resistance at the gap decreases, and the magnetic flux density and magnetic field strength gradient are significantly enhanced. The strong magnetic field firmly attracts the magnetic fluid, forming a high-pressure-resistant seal, effectively preventing external dust and moisture from entering bearing 2, while also preventing internal grease leakage.

[0065] Thermal equilibrium and dynamic response: Once the idler roller reaches thermal equilibrium, the temperature stabilizes, the length of the elastic element 3 remains stable, and the sealing gap is maintained at a small, constant value, ensuring long-term stable high sealing performance. If the temperature drops below the phase change temperature after the idler roller stops, the elastic element 3 returns to its initial length, and the sealing gap automatically returns to its maximum value, preparing for the next low-temperature start-up.

[0066] As can be seen from the above specific implementation process, the present invention has the following technical features and beneficial effects: (1) Fully automatic and maintenance-free: No sensors, controllers or external energy are required. It is driven entirely by the heat of the roller itself to achieve adaptive adjustment of the sealing gap.

[0067] (2) Resolving performance contradictions: Maintaining a large sealing gap during low-temperature startup results in a small starting torque; automatically reducing the sealing gap after the operating temperature rises, resulting in high sealing pressure resistance.

[0068] (3) Compact structure and controllable cost: It only adds a memory alloy spring to the conventional magnetic liquid sealing roller, which is a small modification and easy to implement.

[0069] (4) Wide temperature adaptability: By selecting shape memory alloys with different phase transformation temperatures, they can be applied to different climate conditions and working conditions.

[0070] (5) Long service life: There is no direct contact between the pole shoes during the sealing gap adjustment process, and there is no mechanical wear. The magnetic liquid seal itself is a non-contact seal, so the service life of the idler roller is significantly better than that of the contact seal idler roller.

[0071] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A self-adjusting gap idler roller based on shape memory alloy, mainly comprising a roller body (14) and a shaft assembly disposed within the roller body (14), the shaft assembly comprising a shaft (12) and bearing assemblies disposed at both ends of the shaft (12), each bearing assembly comprising a bearing housing (1), a bearing (2), and a sealing assembly disposed between the bearing housing (1) and the shaft (12), characterized in that, The sealing assembly includes: The first pole shoe (8), the second pole shoe (6), the third pole shoe (4), the permanent magnet (7), the magnetic shielding bushing (10), and the elastic element (3) made of shape memory alloy; The first pole shoe (8) and the second pole shoe (6) are fixedly mounted on the magnetic shielding bushing (10), and the magnetic shielding bushing (10) is sleeved and fixed on the rotating shaft (12). The first pole shoe (8) and the second pole shoe (6) rotate synchronously with the rotating shaft (12). The third pole shoe (4) is fitted inside the bearing seat (1) and slides with the bearing seat (1). The third pole shoe (4) abuts against the outer ring of the bearing (2) through the elastic element (3). The permanent magnet (7) is sandwiched between the first pole shoe (8) and the second pole shoe (6) to generate a magnetic field. The magnetic field forms a magnetic circuit between the first pole shoe (8), the second pole shoe (6) and the third pole shoe (4), and adsorbs the magnetic liquid into the sealed gap between the third pole shoe (4) and the first pole shoe (8) and the second pole shoe (6). The elastic element (3) is configured to maintain its initial length when the temperature is below a preset threshold, so that the sealing gap maintains a first spacing; when the temperature is above the preset threshold, the elastic element (3) extends and pushes the third pole shoe (4) to move axially toward the first pole shoe (8) and the second pole shoe (6), so that the sealing gap is reduced to a second spacing.

2. The idler roller based on shape memory alloy self-adjusting gap according to claim 1, characterized in that, The elastic element (3) is a memory alloy spring, one end of which is fixedly connected to the outer ring of the bearing (2), and the other end is fixedly connected to the third pole shoe (4).

3. The idler roller based on shape memory alloy self-adjusting gap according to claim 1, characterized in that, The first pole piece (8) and the second pole piece (6) are both annular magnetic conductors, and the end faces of the first pole piece (8) and the second pole piece (6) facing the third pole piece (4) are arranged radially flush.

4. The idler roller based on shape memory alloy self-adjusting gap according to claim 1, characterized in that, The permanent magnet (7) is a ring-shaped permanent magnet that is radiatively magnetized, with its inner ring being either the N pole or the S pole, and its outer ring being the other pole.

5. A roller based on a shape memory alloy self-adjusting gap according to claim 1, characterized in that, The magnetic shielding bushing (10) is made of non-magnetic material. The first pole shoe (8) and the magnetic shielding bushing (10) are in an interference fit. The magnetic shielding bushing (10) and the rotating shaft (12) are in an interference fit.

6. A roller based on a shape memory alloy self-adjusting gap according to claim 1, characterized in that, A sealing element (5) is provided between the third pole shoe (4) and the bearing seat (1) to achieve a static seal between the third pole shoe (4) and the bearing seat (1).

7. A roller based on a shape memory alloy self-adjusting gap according to claim 1, characterized in that, It also includes a dustproof ring (11), which is disposed on the rotating shaft (12) and located at the port of the bearing seat (1), and can form a labyrinth seal with the rotating shaft (12) or the magnetic shielding bushing (10).

8. A roller based on a shape memory alloy self-adjusting gap according to claim 1, characterized in that, Both the first pole shoe (8) and the second pole shoe (6) are provided with stepped structures for fixing the permanent magnet (7).

9. A roller based on a shape memory alloy self-adjusting gap according to claim 1, characterized in that, The elastic element (3) is configured such that when the internal temperature of the roller increases, the shape memory alloy undergoes a phase change, generating a driving force that pushes the third pole shoe (4) to overcome the friction between it and the bearing seat (1).

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