Torque limiter

Abstract

A torque limiter (10) is provided with: a first rotating part (12); a second rotating part (14) that is fitted to the outside of the first rotating part (12) so as to be rotatable with respect to the first rotating part (12) on the same axis as the first rotating part (12); a permanent magnet (16) fixed to the first rotating part (12); and a hysteresis member (18) that is fixed to the second rotating part (14) so as to face the permanent magnet (16) in the radial direction of the first rotating part (12), and that generates a hysteresis torque between the hysteresis member (18) and the permanent magnet (16). The permanent magnet (16) is a metal sintered magnet having radial anisotropy.

Description

Technical Field

[0001] The present invention relates to a torque limiter. Background Art

[0002] Torque limiters that utilize hysteresis torque are used in various devices, such as copiers and ATMs. For example, the torque limiter disclosed in Patent Document 1 comprises a first rotating body having a cylindrical outer periphery and a second rotating body having a cylindrical inner periphery opposite the cylindrical outer periphery. A permanent magnet is provided on one of the cylindrical outer periphery of the first rotating body and a hysteresis element is provided on the other. This torque limiter utilizes the hysteresis torque generated between the permanent magnet and the hysteresis element to transmit and interrupt rotation.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-153708 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The characteristics required of a torque limiter such as the one described above vary depending on the location and purpose of the torque limiter. For example, in order to prevent overlapping paper feeds, a torque limiter used in a paper feeder such as a copier is required to suppress torque reduction and accelerate torque increase. Regarding this, Patent Document 1 discloses a structure for suppressing torque reduction, but does not disclose a structure for improving torque increase characteristics.

[0008] Therefore, an object of the present invention is to provide a torque limiter having excellent torque increase characteristics.

[0009] Solutions for solving problems

[0010] The present invention is based on the following torque limiter.

[0011] (1) A torque limiter comprising: a first rotating portion; a second rotating portion embedded in the outer side of the first rotating portion on the same axis as the first rotating portion so as to be rotatable relative to the first rotating portion; a permanent magnet fixed to one of the first rotating portion and the second rotating portion; and a hysteresis member fixed to the other of the first rotating portion and the second rotating portion so as to be opposite to the permanent magnet in a radial direction of the first rotating portion and to generate a hysteresis torque between the permanent magnet and the hysteresis member, wherein the permanent magnet is a metal sintered magnet having radial anisotropy.

[0012] (2) In the torque limiter according to (1) above, the permanent magnet is an Nd—Fe—B magnet.

[0013] (3) In the torque limiter according to (1) or (2) above, the number of poles of the permanent magnet is 20 or more.

[0014] Effects of the Invention

[0015] According to the present invention, a torque limiter having excellent torque increase characteristics can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic cross-sectional view showing a torque limiter according to one embodiment of the present invention.

[0017] Figure 2 This is a diagram of a permanent magnet viewed from the axial direction.

[0018] Figure 3 This is a graph showing the comparison results of the torque values ​​of Example 1 and Comparative Example 1.

[0019] Figure 4 This is a graph showing the comparison results of the torque values ​​of Example 2 and Comparative Example 2.

[0020] Figure 5 This is a graph showing the comparison results of the torque values ​​of Example 3 and Comparative Example 3.

[0021] Figure 6 This is a diagram showing the comparison results of the torque values ​​of Examples 1 to 5 and Comparative Examples 1 to 5.

[0022] Figure 7 This is a diagram showing the comparison results of the torque values ​​of Examples 6 to 9 and Comparative Examples 6 to 9. DETAILED DESCRIPTION

[0023] Hereinafter, a torque limiter according to an embodiment of the present invention will be described with reference to the drawings.

[0024] (Structure of the torque limiter)

[0025] First, the basic structure of the torque limiter will be described. Figure 1 This is a schematic cross-sectional view showing a torque limiter according to one embodiment of the present invention.

[0026] like Figure 1As shown, the torque limiter 10 of this embodiment includes a cylindrical first rotating portion 12, a cylindrical second rotating portion 14 provided on the same axis as the first rotating portion 12, a cylindrical permanent magnet 16 fixed to the first rotating portion 12, and a cylindrical hysteresis member 18 fixed to the second rotating portion 14. In this embodiment, the first rotating portion 12, the second rotating portion 14, the permanent magnet 16, and the hysteresis member 18 each have a cylindrical shape.

[0027] The first rotating portion 12 includes a cylindrical shaft portion 12a and a protruding portion 12b that protrudes radially outward from the shaft portion 12a. In this specification, the radial direction of the first rotating portion refers to a direction orthogonal to the axial direction of the first rotating portion. Hereinafter, when simply referred to as the radial direction, this refers to the radial direction of the first rotating portion, and when simply referred to as the axial direction, this refers to the axial direction of the first rotating portion.

[0028] The first rotating portion 12 is made of, for example, a synthetic resin. Examples of synthetic resins include polyacetal resin, polybutylene terephthalate resin, polyamide resin, polyolefin resin, polyimide resin, polycarbonate resin, polyetheretherketone resin, polypropylene resin, polyetherimide resin, liquid crystal polymer, polyethernitrile resin, polyetherketone resin, polyphenylene sulfide resin, polyphenylene oxide resin, phenolic resin, epoxy resin, acrylonitrile-butadiene-styrene resin, and the like. Furthermore, the first rotating portion 12 may also be made of materials other than synthetic resins. For example, the first rotating portion 12 may also be made of metal. Examples of metals include aluminum, zinc, brass, stainless steel, and iron. The second rotating portion 14 and the sleeves 20, 22, and cap 24 described later may also be made of the same material. Furthermore, the first rotating portion 12, the second rotating portion 14, the sleeve 20, the sleeve 22, and the cap 24 may be constructed in the same manner as various known torque limiters.

[0029] The second rotating portion 14 is embedded in the outer side of the first rotating portion 12 in a manner that is rotatable relative to the first rotating portion 12. In the present embodiment, cylindrical sleeves 20 and 22 are embedded in the outer sides of both ends of the first rotating portion 12 (shaft portion 12a). In addition, a hollow circular plate-shaped cap 24 is fixed to the inner side of one axial end of the second rotating portion 14. The cap 24 is embedded in the outer side of the sleeve 20 in a manner that is slidable (rotatable) relative to the sleeve 20. The other axial end side of the second rotating portion 14 is embedded in the outer side of the sleeve 22 in a manner that is slidable (rotatable) relative to the sleeve 22. With such a structure, the second rotating portion 14 is supported on the first rotating portion 12 in a manner that is rotatable relative to the first rotating portion 12.

[0030] The permanent magnet 16 and the hysteresis component 18 are arranged so as to be radially opposed to each other. In this embodiment, the hysteresis component 18 is arranged radially outside the permanent magnet 16. In this specification, the state in which the permanent magnet 16 and the hysteresis component 18 are radially opposed refers to a state in which one of the permanent magnet 16 and the hysteresis component 18 is positioned inside the other. Therefore, even if another cylindrical member is inserted between the permanent magnet 16 and the hysteresis component 18, the state in which one of the permanent magnet 16 and the hysteresis component 18 is positioned inside the other still refers to the state in which the permanent magnet 16 and the hysteresis component 18 are radially opposed to each other.

[0031] In this embodiment, the permanent magnet 16 is fixed to the outer peripheral surface of the first rotating portion 12 (more specifically, the protruding portion 12b). A metal sintered magnet is used as the permanent magnet 16. The permanent magnet 16 will be described later.

[0032] In this embodiment, the hysteresis element 18 is fixed to the inner circumferential surface of the second rotating portion 14. The hysteresis element 18 is formed using a semi-hard magnetic material. Specifically, the hysteresis element 18 can be formed by subjecting a semi-hard magnetic material such as an Fe-Cr-Co alloy or an Fe-Co alloy to a predetermined magnetic field treatment. In this embodiment, the magnetic flux density of the hysteresis element 18 is preferably 0.7 T or greater, and the coercive force is preferably 2.5 to 12.5 kA / m.

[0033] Although not shown in the figure, a rotating shaft driven by a driving device is inserted into the shaft portion 12a of the first rotating portion 12. The rotating shaft is connected to the first rotating portion 12 so as to rotate integrally with the first rotating portion 12. In addition, the rotating shaft is inserted into the first rotating portion 12 so as to be rotatable relative to the second rotating portion 14.

[0034] A rotated member (not shown) is attached to the second rotating portion 14. When the torque limiter 10 of this embodiment is used in a paper feeding device, the rotated member is, for example, a retard roller (friction roller) provided in pressure contact with a feed roller (paper feeding roller).

[0035] In the torque limiter 10 of this embodiment, the first rotating portion 12 and the permanent magnet 16 are rotated by the aforementioned drive device (not shown). This generates a hysteresis torque between the permanent magnet 16 and the hysteresis element 18, causing the hysteresis element 18 and the second rotating portion 14 to rotate. As a result, a predetermined torque is applied to the rotated member.

[0036] (Structure of permanent magnet)

[0037] The permanent magnet 16 is a sintered metal magnet and does not contain an adhesive (binding material). The density of the permanent magnet 16 is, for example, 7.0 g / cm³ or greater. The density of the permanent magnet 16 is, for example, preferably 7.5 g / cm³ or greater. In this embodiment, the magnetic flux density of the permanent magnet 16 is preferably 1.0 T or greater, and the coercive force is preferably 800 kA / m or greater.

[0038] Figure 2 This is a diagram of the permanent magnet 16 viewed from the axial direction. Figure 2 As shown, in this embodiment, the permanent magnet 16 is a metal sintered magnet having radial anisotropy and being magnetized in a multi-pole manner in the circumferential direction. According to the research results of the present inventors, by using a metal sintered magnet having radial anisotropy as a permanent magnet, the rate of increase of torque becomes faster than when using an isotropic magnet as a permanent magnet. Therefore, in this embodiment, a metal sintered magnet having radial anisotropy is used as the permanent magnet 16. In addition, whether the permanent magnet has radial anisotropy and is magnetized in a multi-pole manner in the circumferential direction can be determined using a magnetic observer. Specifically, this can be determined by placing a magnetic observer on the end face of the permanent magnet and confirming the magnetization pattern.

[0039] In this embodiment, for example, a rare earth sintered magnet is used as the permanent magnet 16. More specifically, for example, an Nd-Fe-B magnet is used as the permanent magnet 16. Figure 2 As shown, in this embodiment, the number of poles of the permanent magnet 16 is 20. The number of poles of the permanent magnet 16 is preferably 20 or more, and more preferably 22 or more.

[0040] The permanent magnet 16 can be manufactured using a known manufacturing method, so detailed description is omitted. For example, it can be manufactured using a pressure sintering method. In this embodiment, the permanent magnet 16 is a hot pressed magnet manufactured using a hot pressing method, for example.

[0041] (Variation)

[0042] The shape of the torque limiter is not limited to the above-mentioned example. The present invention can be used in various torque limiters as follows, which include: a first rotating part; a second rotating part, which is embedded in the outer side of the first rotating part on the same axis as the first rotating part so as to be rotatable relative to the first rotating part; a permanent magnet, which is fixed to one of the first rotating part and the second rotating part; and a lag component, which is fixed to the other of the first rotating part and the second rotating part so as to be opposite to the permanent magnet in the radial direction of the first rotating part.

[0043] Therefore, for example, the hysteresis member may be fixed to the outer peripheral surface of the first rotating portion 12 , and the permanent magnet may be fixed to the inner peripheral surface of the second rotating portion 14 so as to be located radially outside the hysteresis member.

[0044] In addition, in the above embodiment, the second rotating portion 14 is composed of a single member, but the second rotating portion may also be composed of multiple members. For example, the second rotating portion may be composed of a first member and a second member separated in the axial direction, and the hysteresis element or the permanent magnet may be fixed to the first member and the second member in a manner connecting the first member and the second member.

[0045] In the above embodiment, the second rotating portion 14 and the cap 24 are rotatably supported on the first rotating portion 12 via the sleeves 20 and 22. However, the second rotating portion and / or the cap may be rotatably supported on the first rotating portion via other bearings such as ball bearings. Furthermore, the sleeves and bearings such as ball bearings may not be provided. In other words, the second rotating portion and / or the cap may be provided so as to be slidable relative to the first rotating portion.

[0046] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0047] Example

[0048] (Example 1 to Example 9)

[0049] The inventors have produced Figure 1 The torque limiter 10 shown has the same structure as the torque limiters of Examples 1 to 9. Furthermore, the first rotating portion 12 is made of aluminum, the second rotating portion 14 and the cap 24 are made of polybutylene terephthalate (PBT), and the sleeves 20 and 22 are made of polyacetal (POM).

[0050] As the permanent magnet 16, a metal sintered magnet (Nd-Fe-B sintered magnet) having radial anisotropy and multi-pole magnetization in the circumferential direction is used. In this embodiment, the permanent magnet 16 is a hot-pressed magnet manufactured by hot pressing. The magnetizing voltage of the permanent magnet 16 of the torque limiter of Examples 1 to 9 is 1700 V or 1100 V, and the number of magnetized poles is 18 to 30. The inner diameter of the permanent magnet 16 is 15.4 mm, the outer diameter is 18.6 mm, and the length is 18.7 mm. In addition, the density of the permanent magnet 16 of the torque limiter of Examples 1 to 9 is 7.55 g / cm3.

[0051] The hysteresis member 18 is manufactured by subjecting a semi-hard magnetic material (Fe-Cr-Co alloy) to magnetic field treatment. The hysteresis member 18 has an inner diameter of 19.08 mm, an outer diameter of 19.88 mm, and a length of 18 mm.

[0052] (Comparative Examples 1 to 9)

[0053] The torque limiters of Comparative Examples 1 to 9 are manufactured as follows. As permanent magnets, isotropic bonded magnets (Nd-Fe-B bonded magnets) that are multi-pole magnetized in the circumferential direction are used. Except for this, the torque limiters have the same structure as the torque limiters of Examples 1 to 9. As in Examples 1 to 9, the magnetization voltage of the permanent magnets of the torque limiters of Comparative Examples 1 to 9 is 1700V or 1100V, and the number of magnetization poles is 18 to 30. The inner diameter of the permanent magnet is 15.4mm, the outer diameter is 18.6mm, and the length is 18.7mm. In addition, the density of the permanent magnets of the torque limiters of Comparative Examples 1 to 9 is 6.0 to 6.3g / cm 3 Table 1 below shows the manufacturing conditions of the permanent magnets of the torque limiters of Examples and Comparative Examples.

[0054] [Table 1]

[0055] Table 1

[0056]

[0057] (Evaluation 1)

[0058] The present inventors evaluated the torque increase performance of torque limiters of Examples 1 to 3 and Comparative Examples 1 to 3 having the above-described structure. The torque values ​​were measured using a torque sensor (TS103) manufactured by MAGTROL. Specifically, the second rotating portion 14 of the torque limiter was fixed with a jig, and the first rotating portion 12 was fixed to the shaft of the torque sensor. The shaft was rotated at a speed of 2 rpm, and the torque acting on the torque limiter was measured. Figures 3 to 5 Indicates the measurement results of the torque value. Figure 3 The torque values ​​of the torque limiters of Example 1 and Comparative Example 1 are shown. Figure 4 The torque values ​​of the torque limiters of Example 2 and Comparative Example 2 are shown. Figure 5 The torque values ​​of the torque limiters of Example 3 and Comparative Example 3 are shown. Figures 3 to 5 In FIG. 5 , the horizontal axis represents the rotation angle of the first rotating portion 12 after the start of measurement, and the vertical axis represents the torque value (measured value) of the torque limiter.

[0059] like Figures 3 to 5As shown, the torque values ​​of each torque limiter in Examples 1 to 3 and Comparative Examples 1 to 3 initially peak within a rotation angle range of approximately 4° to 8°. The rate of increase in torque until this initial peak (peak torque value / rotation angle until the peak value) is defined as the torque rise rate. The rise rate of the examples is greater than that of the comparative examples at all magnetization pole counts. These results demonstrate that using a radially anisotropic, multi-pole magnetized metal sintered magnet as a permanent magnet can produce a torque limiter with excellent torque rise characteristics.

[0060] (Evaluation 2)

[0061] The torque limiters of Examples 4, 5, and Comparative Examples 4 and 5 were measured in the same manner as the torque limiters of Examples 1 to 3 and Comparative Examples 1 to 3, and the initial peak values ​​of the torque values ​​of the torque limiters of Examples 1 to 5 and Comparative Examples 1 to 5 were compared. The comparison results are shown in FIG. Figure 6 In addition, Figure 6 In FIG. 1 , the horizontal axis represents the number of magnetized poles, and the vertical axis represents the initial peak value of the torque value of the torque limiter.

[0062] like Figure 6 As shown, when comparing the cases of using radially anisotropic metal sintered magnets as permanent magnets (Examples 1 to 5) and the cases of using isotropic bonded magnets as permanent magnets (Comparative Examples 1 to 5), the initial peak torque value of the torque limiter is the same when the number of magnetic poles is 18, but a difference occurs when the number of magnetic poles is 22 or greater. Based on this result, it is believed that by using metal sintered magnets with 20 or more magnetic poles and radial anisotropy, the torque reduction can be prevented and the torque increase characteristics can be improved compared to the case of using bonded magnets with the same number of magnetic poles and isotropy. It is also found that by using metal sintered magnets with 22 or more magnetic poles and radial anisotropy, the torque value of the torque limiter can be reliably improved compared to the case of using bonded magnets with the same number of magnetic poles and isotropy.

[0063] (Rating 3)

[0064] The torque limiters of Examples 6 to 9 and Comparative Examples 6 to 9 were measured in the same manner as the torque limiters of Examples 1 to 3 and Comparative Examples 1 to 3, and the initial peak values ​​of the torque values ​​were compared. The comparison results are shown in FIG. Figure 7 In addition, Figure 7 In FIG. 1 , the horizontal axis represents the number of magnetized poles, and the vertical axis represents the initial peak value of the torque value of the torque limiter.

[0065] like Figure 7 As shown, even when the magnetizing voltage is 1100V, the same Figure 6 The results are similar to those obtained when the magnetizing voltage is 1700 V. Specifically, when comparing the cases of using radially anisotropic metal sintered magnets as permanent magnets (Examples 6 to 9) and the cases of using isotropic bonded magnets as permanent magnets (Comparative Examples 6 to 9), the initial peak torque values ​​of the torque limiter are comparable when the number of magnetic poles is 18, but differ when the number of magnetic poles is 22 or greater. These results suggest that, regardless of the magnetizing voltage, the use of radially anisotropic metal sintered magnets with a number of magnetic poles of 20 or greater prevents torque degradation and improves torque-building characteristics compared to the use of isotropic bonded magnets with the same number of magnetic poles. Furthermore, it is clear that the use of radially anisotropic metal sintered magnets with a number of magnetic poles of 22 or greater reliably improves the torque value of the torque limiter compared to the use of isotropic bonded magnets with the same number of magnetic poles.

[0066] Industrial applicability

[0067] According to the present invention, a torque limiter having excellent torque increase characteristics can be obtained.

[0068] Description of Reference Numerals

[0069] 10. Torque limiter; 12. First rotating unit; 14. Second rotating unit; 16. Permanent magnet; 18. Hysteresis element; 20, 22. Sleeve; 24. Cap.

Claims

1. A torque limiter, wherein: The torque limiter has: first rotating part; a second rotating portion fitted on the outer side of the first rotating portion so as to be rotatable relative to the first rotating portion on the same axis as the first rotating portion; a permanent magnet fixed to one of the first rotating portion and the second rotating portion; as well as a hysteresis member fixed to the other of the first rotating portion and the second rotating portion so as to face the permanent magnet in a radial direction of the first rotating portion and generating a hysteresis torque between the member and the permanent magnet; The permanent magnet is a metal sintered magnet with radial anisotropy.

2. The torque limiter according to claim 1, wherein: The permanent magnet is a Nd—Fe—B magnet.

3. The torque limiter according to claim 1 or 2, wherein: The number of poles of the permanent magnet is greater than 20.

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