Loosening-prevention device
The anti-loosening device addresses the issue of center of gravity shift in high-speed applications by using a nut with a protrusion and a recess, combined with a center of gravity correction notch, improving stability and reducing vibrations.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HARD LOCK IND CO LTD
- Filing Date
- 2025-10-30
- Publication Date
- 2026-05-15
AI Technical Summary
Conventional anti-loosening devices for shafts, such as bearings, cause vibrations and repeated loads due to the slight shift in the center of gravity when fastened on high-speed rotating shafts.
The anti-loosening device incorporates a first nut with a protrusion and a second nut featuring an eccentric recess and a notch for center of gravity correction, which reduces the shift in the center of gravity by offsetting the eccentricity through a concentrically designed notch on the outer or inner surface of the second nut.
The solution effectively minimizes the shift in the center of gravity, reducing vibrations and tilting during fastening, thereby enhancing the stability and performance of the anti-loosening mechanism.
Smart Images
Figure JP2025038188_15052026_PF_FP_ABST
Abstract
Description
Anti-loosening device
[0001] The present invention relates to an anti-loosening device comprising first and second nuts that are eccentrically fitted to each other.
[0002] The applicant of the present application has hitherto been developing a hard lock nut ( "Hard Lock" is a trademark of the applicant of the present application), which is an anti-loosening nut that exhibits a high anti-loosening function, and is disclosed in, for example, Patent Documents 1 to 5 described below.
[0003] In particular, as an anti-loosening nut for a shaft, product development suitable for bearings has been advanced under the product names "Hard Lock Bearing Nut" and "HLB" ( "HLB" is a trademark of the applicant of the present application).
[0004] These anti-loosening nuts are composed of a convex nut (first nut) having a screw hole that is screwed onto a screw shaft and a concave nut (second nut) having a screw hole that is screwed onto the screw shaft. The convex nut has a convex portion that protrudes axially toward the concave nut. The convex portion has an outer peripheral surface in the shape of a truncated cone having a predetermined taper angle. A concave portion into which the convex portion of the convex nut fits is provided on the end face of the concave nut facing the convex nut. This concave portion has an inner peripheral surface in the shape of a truncated cone having a predetermined taper angle. Either the outer peripheral surface of the convex portion or the inner peripheral surface of the concave portion is eccentric with respect to the corresponding screw hole, and the other is concentric with the corresponding screw hole.
[0005] In a state where the convex nut screwed onto the screw shaft and the concave nut screwed onto the screw shaft are fastened, the convex portion and the concave portion are eccentrically fitted, and the outer peripheral surface of the convex portion and the inner peripheral surface of the concave portion interfere with each other in a part in the circumferential direction so as to generate a pressing force along a direction orthogonal to the axis of the screw shaft in the convex nut and the concave nut. Thereby, a strong anti-loosening action is generated in the convex nut and the concave nut.
[0006] Japanese Patent No. 6762591 Japanese Patent Application Laid-Open No. 2016-125622 Japanese Patent Application Laid-Open No. 2016-133136 Japanese Patent Application Laid-Open No. 2002-195236 Japanese Patent Application Laid-Open No. Sho 61-244912
[0007] When the above-mentioned conventional anti-loosening device is used to attach bearings to a rotating shaft, the eccentric fitting of the convex and concave portions causes the center of gravity of the entire convex and concave nut in the fastened state to be slightly off from the axis of the rotating shaft. However, in the case of a rotating shaft that rotates at high speed, this slight shift in the center of gravity can cause vibrations and repeated loads on the bearings supporting the rotating shaft, which can be problematic.
[0008] The present invention aims to reduce the shift in the center of gravity when fastened in a hard lock nut.
[0009] The anti-loosening device according to the present invention comprises a first nut having a screw hole that screws onto a screw shaft, and a second nut having a screw hole that screws onto the screw shaft. The outer circumference of the second nut may be circular in shape concentric with the screw hole of the second nut when viewed from the axial direction. Similarly, the outer circumference of the first nut may be circular in shape concentric with the screw hole of the first nut when viewed from the axial direction.
[0010] The first nut has a projection that protrudes axially toward the second nut, and this projection may have an outer surface that is a cut-off cone shape with a predetermined taper angle. The outer surface of the projection may be concentric with the threaded hole of the first nut.
[0011] The end face of the second nut facing the first nut is provided with a recess into which the convex portion fits, and the recess has a truncated conical inner surface with a predetermined taper angle, and the inner surface of the recess may be eccentric with respect to the screw hole of the second nut.
[0012] In a state where the first nut and the second nut, which are screwed onto the screw shaft, are fastened together, the convex portion and the concave portion are eccentrically fitted together, and the convex portion and the concave portion can be configured such that a pressing force is generated on the first nut and the second nut in a direction perpendicular to the axis of the screw shaft, with the outer surface of the convex portion and the inner surface of the concave portion interfering with each other in a part of the circumferential direction of the concave portion. Furthermore, the second nut is provided with a notch for center of gravity correction that cancels out at least a portion of the shift in the center of gravity that occurs in the second nut due to the eccentric formation of the concave portion.
[0013] In a first embodiment of the present invention, a notch for center of gravity correction is formed on the outer circumference of the second nut, and the notch for center of gravity correction has an outer surface that is eccentric in the same direction as the inner surface of the recess with respect to the threaded hole of the second nut, and is in the shape of a cut cone or cylindrical shape. The outer surface of the notch for center of gravity correction may be located radially inward from the outer circumference of the second nut.
[0014] According to this first embodiment, the thickness of the radially outer portion of the eccentric recess of the second nut is thinnest on the side in the eccentric direction and thickest on the side opposite to the eccentric direction, causing the center of gravity of the second nut to shift slightly in the direction opposite to the eccentric direction.
[0015] On the other hand, the notch for center of gravity correction formed on the outer circumference of the second nut has an outer surface that is eccentric in the same direction as the inner surface of the recess. Therefore, the amount of material removed from the virtual profile where the notch is not formed is smallest on the side in the eccentric direction and largest on the side opposite to the eccentric direction. As a result, the notch for center of gravity correction slightly shifts the center of gravity of the second nut in the eccentric direction. Furthermore, by providing the notch for center of gravity correction on the outer circumference of the second nut, the ratio of the amount of material removed to the amount of center of gravity correction can be maximized.
[0016] In the first embodiment, the eccentricity of the outer circumferential surface of the center of gravity correction notch with respect to the threaded hole of the second nut can be equal to the eccentricity of the inner circumferential surface of the recess with respect to the threaded hole of the second nut. This eliminates the need to reattach the second nut to the chuck of the turning machine when forming the recess and the center of gravity correction notch by turning, and makes it possible to manufacture the second nut by sequentially turning with a recess cutting tool and a notch cutting tool.
[0017] In the first embodiment, the eccentricity of the outer circumferential surface of the notch for center of gravity correction with respect to the screw hole of the second nut may be greater than the eccentricity of the inner circumferential surface of the recess with respect to the screw hole of the second nut. This allows for a greater center of gravity correction amount by the notch for center of gravity correction.
[0018] The notch for center of gravity correction may be formed on the outer edge of the end face of the second nut. In this case, the recess and the notch for center of gravity correction are in the same position in the axial direction, and the center of gravity correction is performed at the same position in the axial direction, so the generation of moment during rotation can be suppressed.
[0019] The outer circumferential surface of the notch for center of gravity correction may extend around the entire circumference of the second nut. This allows for center of gravity correction to be performed by a gradually changing shape around the entire circumference of the second nut, without localized weight reduction.
[0020] In a second embodiment of the present invention, a notch for correcting the center of gravity is formed on the inner circumferential surface of the recess of the second nut, and the notch for correcting the center of gravity may have a cylindrical inner circumferential surface that is concentric with the screw hole of the second nut.
[0021] According to this second embodiment, the thickness of the radially outer portion of the eccentric recess of the second nut is thinnest on the side in the eccentric direction and thickest on the side opposite to the eccentric direction, thereby causing the center of gravity of the second nut to shift slightly in the direction opposite to the eccentric direction.
[0022] On the other hand, the notch for center of gravity correction formed on the inner circumferential surface of the recess of the second nut has an inner circumferential surface that is concentric with the screw hole. Therefore, the amount of material removed from the virtual profile where the notch is not formed is smallest on the side in the eccentric direction and largest on the side opposite to the eccentric direction. As a result, the notch for center of gravity correction slightly shifts the center of gravity of the second nut in the eccentric direction.
[0023] In a second embodiment, the notch for center of gravity correction may be formed on the inner side in the depth direction of the recess of the second nut. This allows for center of gravity correction by the structure within the recess while suppressing the influence of interference between the outer surface of the convex portion and the inner surface of the recess on the wedge action.
[0024] The inner circumferential surface of the notch for center of gravity correction may extend over the entire circumference of the second nut. This allows for center of gravity correction to be performed by a gradually changing shape over the entire circumference of the second nut, without localized weight reduction.
[0025] According to the present invention, at least a portion of the shift in the center of gravity that occurs in the second nut due to the formation of an eccentric recess can be offset by the formation of a notch for center of gravity correction. Furthermore, an eccentric structure can be eliminated for the first nut having a protrusion, and the occurrence of tilting of the first nut during fastening can be reduced.
[0026] This is a partial cross-sectional perspective view showing the fastening state of a loosening prevention device according to the first embodiment of the present invention. This shows the second nut of the loosening prevention device, where (a) is a plan view, (b) is a left side view, (c) is a front view, (d) is a right side view, and (e) is a bottom view. This is an enlarged cross-sectional view of line A-A in Figure 2(b). This is an enlarged perspective view of the bottom side of the second nut. This shows the second nut of a loosening prevention device according to the second embodiment of the present invention, where (a) is a plan view, (b) is a left side view, (c) is a front view, and (d) is a bottom view. This is an enlarged cross-sectional view of line B-B in Figure 5(b). This is an enlarged perspective view of the bottom side of the second nut. This is a cross-sectional view showing another embodiment of the second nut.
[0027] Preferred embodiments of the present invention will be described below.
[0028] Figure 1 shows a loosening prevention device according to the first embodiment of the present invention. This loosening prevention device consists of a convex nut 1 (first nut) and a concave nut 2 (second nut), and is used to fix a bearing B to a rotating shaft S (screw shaft) in which a male thread is formed in part of the axial direction. In Figure 1, a thrust bearing is shown as an example of the bearing, but the bearing may also be a radial bearing, and the loosening prevention device can also be used to attach other appropriate parts besides the bearing.
[0029] The convex nut 1 has a cylindrical nut body 11 with a seating surface at one axial end, and a convex portion 12 that protrudes axially from the other axial end of the nut body 11 toward the concave nut 2. A screw hole 13 is formed in the axial center of the convex nut 1, passing through the nut body 11 and the convex portion 12 in the axial direction, and this screw hole 13 is screwed onto the male thread of the rotating shaft S.
[0030] The outer circumference of the nut body 11 is formed in a circular shape concentric with the screw hole 13 when viewed from the axial direction. However, since multiple rotary tool engagement grooves 11a are formed on the outer circumference of the nut body 11 at equal intervals in the circumferential direction, the outer shape of the nut body 11 is not a perfect circle.
[0031] The protrusion 12 has a truncated cone-shaped outer surface with a predetermined taper angle, and the outer surface gradually decreases in diameter towards the tip (upper end in Figure 1). The taper angle can be appropriately designed according to the required performance and function, but can be, for example, 5° to 10°. The outer surface of the protrusion 12 is concentric with the screw hole 13.
[0032] As shown in detail in Figures 2 to 4, the concave nut 2 is cylindrical in shape with a recess 22 formed on the end face opposite the convex nut 1. A threaded hole 23 is formed in the central part of the shaft of the concave nut 2, and this threaded hole 23 is screwed onto the male thread of the rotating shaft S.
[0033] The outer circumference of the recessed nut 2 is formed in a circular shape concentric with the screw hole 23 when viewed from the axial direction. However, since multiple rotary tool engagement grooves 21a are formed on the outer circumference of the recessed nut 2 at equal intervals in the circumferential direction, the outer shape of the recessed nut 2 is not a perfect circle.
[0034] A recess 22 is provided on one axial end face of the recessed nut 2, into which the convex portion 12 of the convex nut 1 fits. The recess 22 has a truncated conical inner surface with a predetermined taper angle, and the inner surface gradually decreases in diameter towards the back of the recess 22. The taper angle of the inner surface of the recess 22 is equal to or approximates the taper angle of the outer surface of the convex portion 12 of the convex nut 1. The axis O2 of the inner surface of the recess 22 is slightly eccentric with respect to the axis O1 of the screw hole 23 of the recessed nut 2. Note that the axis O1 of the screw hole 23 is also the axis of rotation S.
[0035] As shown in Figure 1, when the first and second nuts 1 and 2, which are screwed onto the rotating shaft S, are fastened, the convex portion 12 and the concave portion 22 are eccentrically fitted, and the outer surface of the convex portion 12 and the inner surface of the concave portion 22 interfere with each other in a part of the circumferential direction of the concave portion 22, such that a pressing force is generated on both nuts 1 and 2 in a direction perpendicular to the axis O1 of the rotating shaft S. As a result, a pressing force is generated in a direction perpendicular to the axial direction at the contact point with the male thread of the rotating shaft S, and a strong anti-loosening effect is exerted. On the other hand, because the concave nut 2 has a fitting gap between the male thread and the female thread of the screw hole 22, and a fitting gap between the convex portion 12 and the concave portion 22, the eccentric fitting of the convex portion 12 and the concave portion 22 causes it to be pressed radially in the opposite direction to the eccentric direction of the inner surface of the concave portion, and the shift of the center of gravity caused by the formation of the eccentric concave portion 22 tends to become larger.
[0036] To reduce the amount of deviation in the center of gravity of the recessed nut 2, in this embodiment, a notch 24 for center of gravity correction is formed on the outer circumference of the recessed nut 2. The notch 24 has a truncated conical outer surface that is eccentric in the same direction as the inner surface of the recess 22 with respect to the screw hole 23 of the recessed nut 2. The outer surface of this notch 24 has a shape as if the outer edge of one axial end of the recessed nut 2 has been cut off by a rotating body shape with the axis O2 as the center of rotation. In the illustrated example, the notch 24 is composed of a chamfer formed on the outer edge of the axial end face of the recessed nut 2. It is preferable that the notch 24 extends over the entire circumference of the recessed nut 2, but it may be formed only in a part of the circumferential range.
[0037] Furthermore, the recessed nut 2 can be configured by forming the recessed portion 22 and the notch portion 24 for center of gravity correction on a lock nut for rolling bearings as defined in JIS B1554.
[0038] According to the anti-loosening device of the first embodiment, the amount of displacement of the center of gravity of the recessed nut 2 caused by the eccentric recess 22 for generating the anti-loosening effect can be reduced by forming a notch 24 on the outer circumference of the recessed nut 2 that is eccentric in the same direction as the inner surface of the eccentric recess 22 with respect to the screw hole axis O1.
[0039] Figures 5 to 7 show the recessed nut of the anti-loosening device according to the second embodiment of the present invention. The convex nut and screw shaft are the same as in the first embodiment and are therefore omitted from the illustration. The configuration that differs from the recessed nut of the first embodiment will be described below.
[0040] In the recessed nut 2 of the second embodiment, a notch 26 for center of gravity correction is formed on the inner circumferential surface of the recess 22. The notch 26 has a cylindrical inner circumferential surface that is concentric with the screw hole 23 of the recessed nut 2. The inner circumferential surface of this notch 26 has a shape as if a part of the inner circumferential surface of the recess 22 has been cut out by a rotating body shape with the axis O1 as the center of rotation. In the illustrated example, the notch 26 is formed on the inner side in the depth direction of the recess 22 and extends over approximately half the circumference. The notch 26 may also be formed to extend over the entire circumference of the recessed nut 22.
[0041] According to the anti-loosening device of the second embodiment, the amount of displacement of the center of gravity of the recessed nut 2 caused by the eccentric recess 22 for generating the anti-loosening effect can be reduced by forming a notch 24 concentric with the screw hole axis O1 on the inner circumference of the recess 22.
[0042] The present invention is not limited to the above embodiments, and the design can be modified as appropriate within the scope of the invention described in the claims. For example, the notch 24 for center of gravity correction provided on the outer circumference of the recessed nut may have a cylindrical outer surface, for example, by turning it into a cylindrical shape parallel to the axis O2, as shown in Figure 8.
[0043] 1. First nut 12. Protrusion 13. Screw hole 2. Second nut 22. Recess 23. Screw hole 24, 26. Notch for center of gravity adjustment S. Screw shaft O1. Axis of the screw hole O2. Axis of the eccentric recess?
Claims
1. The assembly comprises a first nut having a screw hole for screwing onto a screw shaft, and a second nut having a screw hole for screwing onto the screw shaft, wherein the outer circumference of the second nut is circular and concentric with the screw hole of the second nut when viewed from the axial direction, the first nut has a convex portion projecting axially toward the second nut, the convex portion having a truncated conical outer surface with a predetermined taper angle, the end face of the second nut facing the first nut is provided with a recess into which the convex portion fits, the recess has a truncated conical inner surface with a predetermined taper angle, the inner surface of the recess is eccentric with respect to the screw hole of the second nut, and in a state in which the first nut screwed onto the screw shaft and the second nut screwed onto the screw shaft are fastened together, the convex portion and the recess are eccentrically fitted together, and the outer surface of the convex portion and the inner surface of the recess interfere with each other in a part of the circumferential direction of the recess such that a pressing force is generated on the first nut and the second nut in a direction perpendicular to the axis of the screw shaft. A loosening prevention device comprising a second nut having a notch for center of gravity correction that cancels out at least a portion of the shift in the center of gravity of the second nut caused by the eccentric formation of the recess.
2. An anti-loosening device according to claim 1, wherein the notch for correcting the center of gravity is formed on the outer circumference of the second nut, and the notch for correcting the center of gravity has an outer circumference that is eccentric in the same direction as the inner circumference of the recess with respect to the screw hole of the second nut, in a head cone shape to a cylindrical shape.
3. An anti-loosening device according to claim 2, wherein the amount of eccentricity of the outer circumferential surface of the notch for center of gravity correction with respect to the screw hole of the second nut is equal to the amount of eccentricity of the inner circumferential surface of the recess with respect to the screw hole of the second nut.
4. An anti-loosening device according to claim 2, wherein the amount of eccentricity of the outer circumferential surface of the notch for center of gravity correction with respect to the screw hole of the second nut is greater than the amount of eccentricity of the inner circumferential surface of the recess with respect to the screw hole of the second nut.
5. An anti-loosening device according to claim 2, wherein the notch for correcting the center of gravity is formed on the outer peripheral edge of the end face of the second nut.
6. The anti-loosening device according to claim 2, wherein the outer circumferential surface of the notch for center of gravity correction extends over the entire circumference of the second nut.
7. The anti-loosening device according to claim 1, wherein the notch for correcting the center of gravity is formed on the inner circumferential surface of the recess of the second nut, and the notch for correcting the center of gravity has a cylindrical inner circumferential surface that is concentric with the screw hole of the second nut.
8. The anti-loosening device according to claim 2, wherein the notch for correcting the center of gravity is formed on the inner side in the depth direction of the recess of the second nut.
9. The anti-loosening device according to claim 2, wherein the inner circumferential surface of the notch for center of gravity correction extends over the entire circumference of the second nut.