Ball screw device

Abstract

To provide a ball screw device high in reliability, which is advantageous for compactification and reduction of man-hours for assembly.SOLUTION: A ball screw device includes a ball screw (20) having a screw shaft (21), a nut (22), and a plurality of balls (23), and a support body (60) for supporting the ball screw (20). The ball screw (20) includes an inner ring raceway surface (250) provided to the screw shaft (21) or the nut (22). The support body (60) includes an outer ring raceway surface (350). The screw shaft (21) or the nut (22) is formed integrally with the inner ring raceway surface (250). A plurality of conical rollers (43) as rolling elements are arranged between the inner ring raceway surface (250) and the outer ring raceway surface (350).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ball screw device. [Background technology]

[0002] A ball screw includes a screw shaft, a nut, and a plurality of balls disposed between the screw shaft and the nut. In one example of a ball screw device, the rotational motion of the output shaft of a motor is converted into linear motion by a ball screw. In ball screw devices, a bearing is generally installed between the ball screw and a housing to support the rotation of the ball screw (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-284444 Summary of the Invention [Problem to be solved by the invention]

[0004] Ball screw devices are being used in a wide variety of fields, and there is a demand for compact and simple configurations.

[0005] An object of the present invention is to provide a ball screw device that is advantageous in terms of compactness and reduction in assembly steps, and has high reliability. [Means for solving the problem]

[0006] A ball screw device according to one aspect of the present invention includes a ball screw having a screw shaft, a nut, and a plurality of balls, and a support body supporting the ball screw. The ball screw has an inner ring raceway surface provided on the screw shaft or the nut, and the support body has an outer ring raceway surface. A plurality of tapered rollers are disposed as rolling elements between the inner ring raceway surface and the outer ring raceway surface. [Effects of the Invention]

[0007] According to a ball screw device according to one aspect of the present invention, it is possible to provide a ball screw device that is advantageous in terms of compactness and reduction in assembly steps, and that has high reliability. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view showing a ball screw device according to a first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of a nut. [Figure 3] FIG. 2 is a diagram for explaining a contact angle α in a tapered roller bearing. [Figure 4] FIG. 1 is a schematic partially enlarged cross-sectional view showing a ball screw device according to a first embodiment. [Figure 5] FIG. 6 is a schematic partially enlarged cross-sectional view showing a ball screw device according to a second embodiment. [Figure 6] FIG. 2 is a diagram for explaining dimensional values of a tapered roller bearing. [Figure 7] FIG. 10 is a schematic enlarged partial cross-sectional view showing a ball screw device according to a third embodiment. [Figure 8] FIG. 10 is a schematic partially enlarged cross-sectional view showing a ball screw device according to a fourth embodiment. [Figure 9] FIG. 10 is a schematic partially enlarged cross-sectional view showing a ball screw device according to a fifth embodiment. [Figure 10] 10(a), 10(b), and 10(c) are schematic partially enlarged cross-sectional views showing ball screw devices according to sixth, seventh, and eighth embodiments, respectively. [Figure 11] FIG. 13 is a schematic cross-sectional view showing a ball screw device according to a ninth embodiment. [Figure 12] FIG. 13 is a schematic partially enlarged cross-sectional view showing a ball screw device according to a ninth embodiment. [Figure 13] 13(a), 13(b), and 13(c) are schematic partially enlarged cross-sectional views showing ball screw devices according to tenth, eleventh, and twelfth embodiments, respectively. [Figure 14] FIG. 23 is a schematic cross-sectional view showing a ball screw device according to a thirteenth embodiment. [Figure 15] FIG. 23 is a schematic partially enlarged cross-sectional view showing a ball screw device according to a thirteenth embodiment. [Figure 16] FIG. 23 is a schematic partially enlarged cross-sectional view showing a ball screw device according to a fourteenth embodiment. [Figure 17] FIG. 23 is a schematic partially enlarged cross-sectional view showing a ball screw device according to a fifteenth embodiment. [Figure 18] FIG. 22 is a schematic cross-sectional view showing a ball screw device according to a sixteenth embodiment. [Figure 19] 16(a), 16(b), and 18(c) are schematic partially enlarged cross-sectional views showing ball screw devices according to sixteenth, seventeenth, and eighteenth embodiments, respectively. [Figure 20] FIG. 22 is a schematic cross-sectional view showing a ball screw device according to a nineteenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described with reference to the drawings. In one embodiment, a ball screw device is incorporated into various mechanical devices, such as an electric brake device for a vehicle, an automatic manual transmission (AMT), or a positioning device for a machine tool, and is used to convert the rotational motion of a drive source, such as an electric motor, into linear motion to operate a driven part (operating part). Various types of electric brake devices are applicable, such as an electro-mechanical brake (EMB) that applies braking force via a ball screw driven by a motor, and an electro-hydraulic brake (EHB) that controls the hydraulic pressure of a hydraulic brake via a ball screw driven by a motor. The ball screw device can also be applied to mechanical devices other than those mentioned above.

[0010] In the following description, unless otherwise specified, the axial direction, radial direction, and circumferential direction refer to the direction along the central axis of the ball screw, the radial direction of the ball screw, and the direction around the central axis of the ball screw, respectively. Furthermore, the direction from the input side to the output side along the central axis of the ball screw is referred to as the first direction (first orientation), and the direction from the output side to the input side is referred to as the second direction (second orientation).

[0011] (First embodiment) 1 is a schematic cross-sectional view of a ball screw device 10 according to a first embodiment. The ball screw device 10 includes a ball screw 20 and a support 60 that supports the ball screw 20.

[0012] As shown in FIG. 1, the ball screw 20 includes a screw shaft 21, a nut 22, and a plurality of balls 23 arranged between the screw shaft 21 and the nut 22. In one example, a first shaft 101 to which a driving force of a motor (not shown) is transmitted is connected to the nut 22. The ball screw 20 converts rotational motion into linear motion. A speed reducer may be additionally arranged between the ball screw 20 and the motor. In one example in which the ball screw device 10 is applied to an electric brake device for a vehicle, brake pads of the vehicle operate against a brake disc in response to the linear motion. The ball screw 20 and the mechanism using the same are not limited to this example, and various forms are applicable.

[0013] The screw shaft 21 has a shaft body 270 and a spiral thread groove (spiral outer peripheral rolling groove) 275 provided on the outer peripheral surface of the shaft body 270. In one example, at least a portion of the screw shaft 21 is made of metal. The thread groove 275 of the screw shaft 21 is formed by cutting or rolling the outer peripheral surface of the shaft body 270. In forming the thread groove 275, a grinding process can be additionally performed. The thread groove shape (groove bottom shape) of the screw shaft 21 is, for example, a Gothic arch groove or a circular arc groove. The number of threads of the thread groove 275 is set to one, two, or more. In other examples, various forms are applicable to the screw shaft 21.

[0014] The nut 22 has a cylindrical nut body 280 and a helical thread groove (helical inner peripheral rolling groove) 285 provided on the inner peripheral surface of the nut body 280. The screw shaft 21 is inserted into and disposed inside the nut 22. In one example, at least a portion of the nut 22 is made of metal. The thread groove 285 of the nut 22 is formed by cutting or rolling the inner peripheral surface of the nut body 280. In forming the thread groove 285, a grinding process can be additionally performed. The thread groove shape (groove bottom shape) of the nut 22 corresponds to the groove shape of the screw shaft 21, and is, for example, a Gothic arch groove or a circular arc groove. The number of threads of the thread groove 285 is set to one, two, or more. In other examples, various shapes are applicable to the nut 22.

[0015] A plurality of balls 23 are disposed between the screw shaft 21 and the nut 22. The plurality of balls 23 are disposed in a space (rolling path) formed by the opposing arrangement of the screw groove 275 of the screw shaft 21 and the screw groove 285 of the nut 22. In FIG. 1, two balls 23 are indicated by two-dot chain lines. In reality, the ball screw 20 includes a large number of balls 23. In one example, the plurality of balls 23 are made of metal (such as steel) or ceramics. The plurality of balls 23 roll in the rolling path in accordance with the relative rotation between the screw shaft 21 and the nut 22. In one example, the balls 23 return from the end point of the rolling path to the start point via a circulation path provided in the nut 22. The balls 23 disposed in the rolling path move while receiving a compressive load. The balls 23 disposed in the circulation path move by being pushed by the subsequent balls 23. The start point and end point of the rolling path are interchanged depending on the direction of relative displacement (direction of relative rotation) between the screw shaft 21 and the nut 22. In other examples, the ball screw 20 can have a different structure for circulating the balls 23 .

[0016] In this embodiment, the ball screw 20 has an inner ring raceway surface 250 provided on the nut 22. The support body 60 has an outer ring raceway surface 350 corresponding to the inner ring raceway surface 250. A plurality of tapered rollers 43 serving as rolling elements are arranged between the inner ring raceway surface 250 and the outer ring raceway surface 350. The tapered rollers 43 have a truncated cone shape. The inner ring raceway surface 250, the outer ring raceway surface 350, and the tapered rollers 43 form a tapered roller bearing 40. The plurality of tapered rollers 43 are held between the inner ring raceway surface 250 and the outer ring raceway surface 350 via a cage. The tapered roller bearing 40 can additionally have a seal structure that seals in a lubricant. The ball screw 20 is supported by the support body 60 via the tapered roller bearing 40.

[0017] The tapered roller bearing 40 is generally capable of bearing a radial load and an axial load in one direction, and has a high load capacity. The axial load in the second direction from the ball screw 20 is borne by the support 60 via the tapered roller bearing 40. In one example, the tapered roller bearing 40 is a single-row tapered roller bearing. The use of such a single bearing (a configuration that avoids a configuration in which two bearings are opposed to each other or a configuration in which two or more bearings are combined) is advantageous for making the ball screw device 10 more compact. In one example, the tapered rollers are held by a stamped steel cage or a plastic cage. In another example, the tapered rollers are held by a pin-type cage or another structure.

[0018] FIG. 2 is a cross-sectional view showing an example of a nut 22. The nut body 280 has a first portion 281 having a thread groove 285 and a second portion 282 having an inner ring raceway surface 250. Both the thread groove 285 and the inner ring raceway surface 250 are formed on the nut body 280. The nut 22 has the nut body 280 in which the thread groove 285 and the inner ring raceway surface 250 are integrally formed. The thread groove 285 and the inner ring raceway surface 250 are formed on the material of the nut body 280. In one example, the first portion 281 and the second portion 282 are arranged side by side in the axial direction. In another example, at least a portion of the second portion 282 is arranged to overlap the first portion 281 in the axial direction. For example, the entire inner ring raceway surface 250 or at least a portion of the inner ring raceway surface 250 may be located at the same axial position as the thread groove 285. Furthermore, the entire inner ring raceway surface 250 or at least a portion of the inner ring raceway surface 250 may be disposed radially outward of the thread groove 285. In one example, the diameter (maximum diameter, minimum diameter, center diameter, or average diameter) of the inner ring raceway surface 250 is set to be approximately the same as the outer diameter (maximum diameter, minimum diameter, center diameter, or average diameter) of the first portion 281. In another example, the diameter of the inner ring raceway surface 250 is set to be larger or smaller than the outer diameter of the first portion 281.

[0019] For example, when the maximum diameter (diameter of the large diameter portion) of the inner ring raceway surface 250 is D1 and the outer diameter of the first portion 281 is D2, D1 / D2 is greater than 0.5 and is equal to or less than 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 3.5, or 4.0. In one example, D1 / D2 is set to be equal to or greater than approximately 0.6 and equal to or less than 2.0. In another example, D1 / D2 is set to be equal to or greater than approximately 0.8 and equal to or less than 1.2. In other examples, ratios other than those listed above can be set. The above numerical values are merely examples and are not limiting.

[0020] Furthermore, for example, when the radial average thickness in the area where the inner ring raceway surface 250 is formed is T1 and the radial average thickness of the first portion 281 is T2, T1 / T2 is greater than 0.1 and is equal to or less than 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, or 3.0. In one example, T1 / T2 is set to be equal to or greater than approximately 0.4 and equal to or less than 2.0. In another example, T1 / T2 is set to be equal to or greater than approximately 0.5 and equal to or less than 1.5. In other examples, ratios other than those listed above can be set. The above numerical values are merely examples and are not limiting.

[0021] As shown in FIG. 2 , the second portion 282 has a first flange (large flange) 251 and a second flange (small flange) 252. The first flange 251 has a relatively large outer diameter, and the second flange 252 has a relatively small outer diameter. A groove (recess) 253 is provided between the first flange 251 and the second flange 252 in the axial direction, and an inner ring raceway surface 250 is provided at the bottom surface of the groove 253. The first flange 251 has an axial end face (outer axial end face) 415 facing the first direction. The second flange 252 has an axial end face (outer axial end face) 417 facing the second direction. In one example, the axial end face 417 is the axial end face (axial end face in the first direction) of the nut 22. In another example, the nut 22 may have an axial end face other than the axial end face 417 of the second flange 252.

[0022] The inner ring raceway surface 250 is a so-called tapered surface, and is inclined with respect to the central axis 800. A straight line passing through and along the inner ring raceway surface 250 intersects with the central axis 800 at a reference point 850. The reference point 850 coincides with the apex of a cone having the inner ring raceway surface 250 as its side surface. In one example, the reference point 850 is located at a position spaced apart in the second direction from an axial end face (axial end face in the second direction) 417 of the nut 22. In another example, the reference point 850 is located at the same position as the axial end face (axial end face in the second direction) 417 of the nut 22 or at a position spaced apart in the first direction from the axial end face 417. The inner ring raceway surface 250 is located between the thread groove 285 of the nut 22 and the reference point 850. In the tapered roller bearing 40 shown in Figure 1, the apex of the cone for the inner ring raceway surface 250, the apex of the cone for the tapered roller 43, and the apex of the cone for the outer ring raceway surface 350 are designed to converge at reference point 850 (Figures 2 and 3).

[0023] As shown in Figure 3, the contact angle α is appropriately set in tapered roller bearing 40. Bearings with a relatively small contact angle α generally have a relatively high load capacity against radial loads. Bearings with a relatively large contact angle α generally have a high load capacity against axial loads.

[0024] In this embodiment, the contact angle α is set to, for example, approximately 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35°. In one example, a tapered roller bearing with a contact angle of 20° or more is used in a ball screw device 10 with high load specifications. In another example, a tapered roller bearing with a contact angle of 25° or more is used in a ball screw device 10 with even higher load specifications. The above numerical values are by way of example only, and are not limiting.

[0025] Returning to FIG. 1, the support body 60 has an outer ring member 42 provided with an outer ring raceway surface 350, and a housing (support member) 30 to which the outer ring member 42 is attached.

[0026] The housing 30 supports the ball screw 20 via a tapered roller bearing 40 or the like. Various additional support structures can be applied to the housing 30. At least a portion of the ball screw 20 is enclosed by the housing 30. At least a portion of the ball screw 20 is disposed in the inner space of the housing 30. In one example, at least a portion of the housing 30 is made of metal. In another example, at least a portion of the housing 30 is made of a material other than metal. The housing 30 is fixed to a predetermined structure (not shown). In one example, the housing 30 has a substantially divided structure. The division position of the housing 30 is appropriately set in consideration of the assembly process. In another example, the housing 30 can have a different structure.

[0027] In this embodiment, the outer ring member 42 is attached to the housing 30. Additionally and / or alternatively, various structures including a separate member (not shown) (such as a thrust collar, a C-shaped retaining ring, or annular plate) for supporting the axial position of the outer ring member 42 relative to the housing 30 are applicable.

[0028] 4, the housing 30 has inner surfaces (inner wall surfaces) 301, 302, and 303 that are provided to surround the ball screw 20. The inner surface (inner peripheral surface) 302 is disposed between the inner surfaces 301 and 303 in the axial direction. The inner surface 302 has an inner diameter that corresponds to the outer diameter of the outer ring member 42. The inner surfaces 301, 302, and 303 face a space in which the ball screw 20 and structures connected to the ball screw 20 are disposed.

[0029] In this embodiment, the housing 30 has an axial surface (axial wall surface) 311 facing in a first direction and an axial surface (axial wall surface) 312 facing in a second direction. The axial surface 311 is provided between the inner surfaces 302 and 303 in the radial direction, and has, for example, a surface perpendicular to the axial direction. The axial surface 312 is provided between the inner surfaces 302 and 301 in the radial direction, and has, for example, a surface perpendicular to the axial direction.

[0030] The housing 30 is provided with a recess 450 including a space surrounded by the inner surface 302, the axial surface 311, and the axial surface 312. The outer ring member 42 is disposed in the recess 450. The bearing 40 is inserted into the recess 450 of the housing 30 so that the outer surface 421 of the outer ring member 42 faces the inner surface 302 of the housing 30, and the outer ring member 42 and the housing 30 are fitted together. An appropriate interference or gap (loose fit) is provided in the fit between the outer ring member 42 and the housing 30. The outer surface (outer peripheral surface) 421 of the outer ring member 42 is supported by the inner surface 302 of the housing 30. The outer ring member 42 has an axial surface (axial end surface) 425 facing the second direction. The axial surface 425 is provided at the end of the outer ring member 42 in the second direction and has, for example, a surface perpendicular to the axial direction. The axial surface 425 of the outer ring member 42 and the axial surface 311 of the housing 30 face each other and abut against each other. The end surface 425 of the outer ring member 42 is supported by the axial surface 311 of the housing 30.

[0031] 4, the outer diameter of the outer ring member 42 is larger than the outer diameter of the nut 22. In another example, the outer diameter of the bearing 40 can be smaller than the outer diameter of the nut 22. The outer ring member 42 is disposed substantially radially outward of the nut 22.

[0032] In this embodiment, during high-load driving, a high load (reaction force, axial load) acts in the second direction (first mode, high-load mode). In the ball screw 20, a high reaction force in the second direction caused by high-load driving acts on the nut 22 via the ball screw 20. In this first mode, the force in the second direction due to the high load is transmitted in this order: the nut 22, the tapered rollers 43, the outer ring member 42, and the housing 30. That is, the axial load from the nut 22 is received by the axial surface 311 of the housing 30 via the tapered rollers 43 and the outer ring member 42. In the tapered roller bearing 40, the nut 22 rotates relative to the outer ring member 42 while bearing a radial load and an axial load. In this ball screw device 10, even when a high axial load acts, the rotational motion of the rotating body (second assembly, inner assembly) 70, such as the nut 22, relative to the support body (first assembly, outer assembly) 60 is stably supported. The ball screw device 10 of this embodiment is preferably applied to high load specifications and is advantageous in terms of compactness.

[0033] In this embodiment, the inner ring raceway surface 250 is provided on the nut 22 of the ball screw 20. In other words, the ball screw device 10 has a configuration in which the nut 22 and the inner ring of the bearing 40 are integrally formed. The ball screw device 10 is advantageous in terms of compactness compared to a configuration in which the inner ring of the bearing, which is a separate member, is attached to the nut 22.

[0034] In this embodiment, the tapered roller bearing 40 has a structure that allows it to be relatively easily separated in the axial direction. The ball screw device 10 is advantageous in reducing the number of assembly steps. For example, the support 60 and the ball screw 20 can be relatively easily assembled by axially moving the ball screw 20 relative to the support 60 in the second direction. Furthermore, the ball screw 20 can be relatively easily removed from the support 60 by axially moving the ball screw 20 relative to the support 60 in the first direction.

[0035] (Second embodiment) FIG. 5 is a schematic partial cross-sectional view showing a ball screw device 11 according to a second embodiment. In the following description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. Unlike the first embodiment, this embodiment is provided with a regulating member 50 between the housing 30 and the nut 22. In this embodiment, the support body (first assembly, outer assembly) 60 includes the housing 30, an outer ring member 42, etc. The rotating body (second assembly, inner assembly) 70 includes the nut 22, the regulating member 50, etc.

[0036] In this embodiment, the nut 22 has an axial surface (axial end surface) 415 facing the first direction. The axial surface 415 is provided at an end of the second portion 282 of the nut 22 in the first direction in the axial direction, and has, for example, a surface perpendicular to the axial direction. The axial surface 415 is also provided between the outer surface 410 and the outer surface 412 in the radial direction.

[0037] In this embodiment, the ball screw 20 includes a regulating member 50. The regulating member 50 is provided as a separate member from the main body (screw shaft main body / nut main body) of the ball screw 20. The regulating member 50 has a ring shape and includes a first surface 501 facing a first direction and a second surface 502 facing a second direction. The regulating member 50 is attached to the nut 22. The regulating member 50 is incorporated as a part of a rotating body (second assembly, inner assembly) 70. The rotating body 70 is rotatably supported by a support body (first assembly, outer assembly) 60. In FIG. 5 , the axial surface 312 of the housing 30 is an axial surface integrally formed on the main body of the housing 30 and facing the second direction. The first surface 501 (first axial surface AX1) of the regulating member 50 and the axial surface 312 (second axial surface AX2) of the housing 30 are disposed facing each other. The first surface 501 and the shaft surface 312 face each other and abut against each other, or face each other with a gap therebetween. In one example, a member having a shape similar to that of a so-called sliding bearing is used as the restricting member 50. In another example, a member having a shape similar to that of a relatively simple spacer is used as the restricting member 50.

[0038] In this embodiment, similar to the first embodiment, even when a high axial load is applied, the rotational motion of the rotating body 70 (such as the nut 22) relative to the support body 60 (such as the housing 30) is stably supported. The ball screw device 11 of this embodiment is preferably applied to high load specifications and is advantageous for compactness.

[0039] In the first mode, the nut 22 receives a strong force in the second direction based on an axial load (reaction force). This force acts in a direction that causes the first surface 501 of the regulating member 50 attached to the nut 22 to move axially away from the axial surface 312 of the housing 30. In one example, the ball screw device 11 is designed so that a substantial gap 900 is generated between the axial surface 312 of the housing 30 and the first surface 501 of the regulating member 50 when a high load in the second direction is received. The design value of the gap 900 in the first mode (high load mode) is defined as the "allowable axial clearance (C1)." In another example, the ball screw device 11 is designed so that the gap 900 (allowable axial clearance C1) between the axial surface 312 of the housing 30 and the first surface 501 of the regulating member 50 is substantially zero when a high load in the second direction is received.

[0040] As the rotating body 70 rotates relative to the support body 60, a relative movement (relative rotation) occurs in the circumferential direction between the axial surface 312 of the housing 30 and the first surface 501 of the regulating member 50. In the ball screw device 11, when the allowable axial clearance C1 greater than zero is set, a rotational load (frictional load) due to contact between the housing 30 and the regulating member 50 in the first mode is avoided.

[0041] In the ball screw device 11, when the load in the second direction received from the ball screw 20 is relatively small or substantially zero (no load), relative axial movement tends to occur between the nut 22 and the outer ring member 42 (second mode, low-load mode). As described above, in the first mode, a substantial gap 900 may occur between the axial surface 312 of the housing 30 and the first surface 501 of the restricting member 50. Furthermore, in a low-load or no-load state, such as when the ball screw 20 is operated in an initial state or in a predetermined orientation, the substantial gap 900 may occur. When the substantial gap 900 exists between the axial surface 312 and the first surface 501, the nut 22 may tend to move in a direction (first direction) away from the outer ring member 42. This is due, for example, to the fact that the bearing 40 has a structure that is easily separated in the axial direction and / or that an axial component force is generated in the bearing 40 when a radial load is applied.

[0042] In this embodiment, the relative axial movement of the nut 22 in the first direction is restricted based on the axial positional relationship between the first surface 501 (first axial surface AX1) of the restricting member 50 and the axial surface 312 (second axial surface AX2) of the housing 30. That is, the relative axial movement of the nut 22 is restricted to within the range of a design value (allowable axial clearance C1) of the gap 900 between the first surface 501 (first axial surface AX1) and the axial surface 312 (second axial surface AX2).

[0043] In this embodiment, contact between the axial surface 312 of the housing 30 and the first surface 501 of the regulating member 50 is permitted. Based on the contact of the first surface 501 with the axial surface 312, relative axial movement of the nut 22 in the first direction is limited. The range of a region (sliding region, contact region, facing region) 910 where the axial surface 312 and the first surface 501 can contact each other is appropriately set in advance. In one example, the radial range of the sliding region 910 is set to include a position (region 910A) radially inward from the outer surface (outer peripheral surface) 412 of the nut 22. That is, contact between the housing 30 and the regulating member 50 is permitted at a position radially inward from the outer surface 412 of the nut 22. In other examples, the radial range of the sliding region 910 may be set to a range different from the above. Appropriate setting of the sliding region 910 contributes to stable operation of the bearing 40 and is advantageous for reducing rotational load and extending the life of the bearing 40.

[0044] In this embodiment, slippage is permitted between the axial surface 312 of the housing 30 and the first surface 501 of the regulating member 50. In the ball screw device 11, when the first surface 501 abuts against the axial surface 312 during rotation, relative circumferential movement (circumferential slippage) occurs between the axial surface 312 and the first surface 501 accompanied by contact. That is, slippage (contact slippage) occurs in at least a portion of the slip region 910. In the ball screw device 11, due to the configuration that permits contact slippage, relative axial movement of the nut 22 in the first direction is restricted even during rotation.

[0045] In this embodiment, a configuration can be employed in which the state of slippage changes depending on the magnitude of the load in the second direction from the ball screw 20. In one example in which the value of the allowable axial clearance C1 is designed to be greater than zero, contact slippage does not occur between the axial surface 312 and the first surface 501 in the first mode (high load mode). This is because the high axial load from the ball screw 20 pushes the nut 22 in the second direction, and the presence of the gap 900 prevents the first surface from contacting the axial surface 312 (non-contact slippage). On the other hand, in the second mode (low load mode), the axial load in the second direction from the ball screw 20 is relatively small or zero. Therefore, the position of the nut 22 with respect to the outer ring member 42 (axial relative position) tends to move in the first direction. When the first surface 501 abuts against the axial surface 312 during rotation, contact slippage occurs between the axial surface 312 and the first surface 501. In this example, the state of slippage changes between a non-contact state in the first mode and a contact state in the second mode. The rotational load generated in the sliding region 910 is suppressed to be relatively small.

[0046] In another example, the value of the allowable axial clearance C1 is designed to be substantially zero. In the first mode (high load mode), contact slippage occurs between the axial surface 312 and the first surface 501. For example, a rotational load (frictional load) based on preload occurs in the slip region 910. Furthermore, in the second mode (low load mode), contact slippage also occurs between the axial surface 312 and the first surface 501. In this example, the rotational load in the slip region 910 may change between the first mode and the second mode. Note that in this example, the change in the relative axial positions of the nut 22 and the outer ring member 42 between the first mode and the second mode is small, and the posture of the bearing 40 is kept relatively constant.

[0047] In this embodiment, contact slippage occurs between the first surface 501 of the regulating member 50 and the shaft surface 312 of the housing 30. Because the member that contacts the housing 30 is a separate member from the nut 22, there is a high degree of freedom in designing the regulating member 50 in terms of material, surface precision, surface roughness, surface shape, and the like. Appropriate design of the sliding structure can reduce wear, improve assembly, and improve positioning accuracy, which is advantageous for extending the life of the device.

[0048] In this embodiment, in the example of a tapered roller bearing shown in FIG. 6 , when the axial width of the outer ring is L and the distance between the tapered rollers (rolling elements) and the end of the outer ring is a, a / L is set to approximately 1 / 20, 1 / 18, 1 / 16, 1 / 14, 1 / 12, 1 / 10, 1 / 8, or 1 / 6 or more. In one example, a bearing with a / L of 1 / 10 or more is used. By appropriately setting the correspondence relationship between the value of a / L and the design value of the allowable axial clearance (gap 900 described below), problems such as damage to bearing 40 and abnormal noise due to relative axial movement can be reliably prevented. The above numerical values are merely examples and are not limiting.

[0049] As described above, according to this embodiment, high reliability and long life are achieved while having a compact configuration and high load specifications, based on the configuration that restricts relative axial movement of the bearing 40.

[0050] (Third embodiment) FIG. 7 is a schematic partial cross-sectional view showing a ball screw device 12 according to a third embodiment. In the following description of the third embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. In this embodiment, unlike the second embodiment, no restricting member is provided between the housing 30 and the nut 22. Also, in this embodiment, the support body (first assembly, outer assembly) 60 includes the housing 30 and the outer ring member 42, etc. The rotating body (second assembly, inner assembly) 70 includes the nut 22, etc.

[0051] In this embodiment, the axial end surface 415 (first axial surface AX1) of the nut 22 and the axial surface 312 (second axial surface AX2) of the housing 30 are arranged to face each other. The axial end surface 415 is an axial surface formed integrally with the body of the nut 22 and faces in a first direction. The axial surface 312 of the housing 30 is an axial surface formed integrally with the body of the housing 30 and faces in a second direction. The axial end surface 415 and the axial surface 312 face each other and abut each other, or face each other with a gap therebetween.

[0052] In this embodiment, during high-load driving, a force in the second direction due to the high load is transmitted in this order: nut 22, tapered rollers 43, outer ring member 42, and housing 30 (first mode, high-load mode). That is, the axial load from the ball screw 20 is received by the axial surface 311 of the housing 30 via the tapered rollers 43 and outer ring member 42. In the bearing 40, the nut 22 rotates relative to the outer ring member 42 while bearing a radial load and an axial load. In the ball screw device 12, even when a high axial load is applied, the rotational motion of the rotating body 70 (such as the nut 22) relative to the support body 60 (such as the housing 30) is stably supported. The ball screw device 12 of this embodiment is preferably applied to high-load specifications and is advantageous for compactness.

[0053] In the first mode, the nut 22 receives a strong force in the second direction based on an axial load (reaction force). This force acts in a direction that causes the axial end surface 415 of the nut 22 to move axially away from the axial surface 312 of the housing 30. In one example, the ball screw device 12 is designed so that a substantial gap 900 is generated between the axial surface 312 of the housing 30 and the axial end surface 415 of the nut 22 when a high load in the second direction is received. In other words, the allowable axial clearance C1 is set to be greater than zero. In another example, the ball screw device 12 is designed so that the gap 900 (allowable axial clearance C1) between the axial surface 312 of the housing 30 and the axial end surface 415 of the nut 22 is substantially zero when a high load in the second direction is received.

[0054] As the rotating body 70 rotates relative to the support body 60, a relative movement (relative rotation) occurs in the circumferential direction between the axial surface 312 of the housing 30 and the axial end surface 415 of the nut 22. In the ball screw device 12, when the allowable axial clearance C1 greater than zero is set, a rotational load (frictional load) due to contact between the housing 30 and the nut 22 in the first mode is avoided.

[0055] In this embodiment, the relative axial movement of the nut 22 in the first direction is restricted based on the axial positional relationship between the axial end surface 415 (first axial surface AX1) of the nut 22 and the axial surface 312 (second axial surface AX2) of the housing 30. That is, the relative axial movement of the nut 22 is restricted within the range of a design value (allowable axial clearance C1) of a gap 900 between the axial surface 312 and the axial end surface 415. The axial relative movement of the nut 22 in the first direction is limited based on the contact of the axial end surface 415 with the axial surface 312 in a sliding region 910. Furthermore, in this embodiment, sliding is permitted between the axial surface 312 of the housing 30 and the axial end surface 415 of the nut 22. In the ball screw device 12, the configuration that allows contact sliding restricts the relative axial movement of the nut 22 in the first direction even during rotation.

[0056] In this embodiment, contact slip occurs between the axial end surface 415 of the nut 22 and the axial surface 312 of the housing 30. Compared to the first embodiment, the ball screw device 12 has a reduced number of parts, which is advantageous in terms of cost reduction.

[0057] (Fourth embodiment) FIG. 8 is a schematic partial cross-sectional view showing a ball screw device 13 according to a fourth embodiment. In the following description of the fourth embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. In this embodiment, unlike the second embodiment, the housing 30 includes a regulating member 53. The regulating member 53 is provided as a separate member from the main body of the housing 30 (housing main body 330). In this embodiment, the support body (outer assembly, first assembly) 60 includes the housing 30, the outer ring member 42, etc. The housing 30 has the housing main body 330 and the regulating member 53. The rotating body (inner assembly, second assembly) 70 includes the nut 22, etc.

[0058] In this embodiment, the regulating member 53 has a ring shape and includes a first surface 531 facing a first direction and a second surface 532 facing a second direction. The regulating member 53 is fixed to the housing main body 330 with the first surface 531 facing and abutting against the axial surface 312 of the housing 30. In FIG. 8 , the axial end surface 415 (first axial surface AX1) of the nut 22 and the second surface 532 (second axial surface AX2) of the regulating member 53 are disposed facing each other. The axial end surface 415 and the second surface 532 face each other and abut against each other, or face each other with a gap therebetween. Additionally and / or alternatively, various structures including a separate member (not shown, such as a thrust collar, a C-shaped retaining ring, or annular plate) for fixing the regulating member 53 to the housing main body 330 are applicable. In one example, the regulating member 53 is a member having a shape similar to a sliding bearing. In another example, the regulating member 53 is a member having a relatively simple shape similar to a spacer.

[0059] Alternatively, various shapes can be applied to the regulating member 53. For example, the regulating member 53 has a diameter portion extending in the radial direction and a circumferential portion extending in the axial direction. Furthermore, one axial end of the regulating member 53 can abut against the axial surface 312 of the housing 30, and the other axial end can abut against the axial surface of the outer ring member 42. In one example, the regulating member 53 is sandwiched between the housing 30 and the outer ring member 42 with a preload. In another example, the regulating member 53 is disposed between the housing 30 and the outer ring member 42 with substantially no preload.

[0060] In this embodiment, during high load driving, as in the third embodiment, a force in the second direction due to the high load is transmitted in this order to the nut 22, tapered rollers 43, outer ring member 42, and housing 30 (first mode, high load mode). In the ball screw device 13, even when a high axial load is applied, the rotational motion of the rotating body 70 (such as the nut 22) relative to the support body 60 (such as the housing 30) is stably supported.

[0061] In the first mode, the nut 22 receives a strong force in the second direction based on an axial load (reaction force). This force acts in a direction that causes the axial end surface 415 of the nut 22 to move axially away from the axial surface 312 of the housing 30 (the second surface 532 of the regulating member 53). In one example, the ball screw device 13 is designed so that, when a high load in the second direction is received, a substantial gap 900 is generated between the second surface 532 of the regulating member 53 and the axial end surface 415 of the nut 22. In other words, the allowable axial clearance C1 is set to be greater than zero. In another example, the ball screw device 13 is designed so that, when a high load in the second direction is received, the gap 900 (allowable axial clearance C1) between the second surface 532 of the regulating member 53 and the axial end surface 415 of the nut 22 is substantially zero.

[0062] As the rotating body 70 rotates relative to the support body 60, a relative movement (relative rotation) occurs in the circumferential direction between the second surface 532 of the regulating member 53 and the axial end surface 415 of the nut 22. In the ball screw device 13, when the allowable axial clearance C1 greater than zero is set, a rotational load (frictional load) due to contact between the regulating member 53 and the nut 22 in the first mode is avoided.

[0063] In this embodiment, the relative axial movement of the nut 22 in the first direction is restricted based on the axial positional relationship between the axial end surface 415 (first axial surface AX1) of the nut 22 and the second surface 532 (second axial surface AX2) of the restricting member 53. That is, the relative axial movement of the nut 22 is restricted within the range of a design value (allowable axial clearance C1) of a gap 900 between the second surface 532 and the axial end surface 415. The axial relative movement of the nut 22 in the first direction is limited based on the contact of the axial end surface 415 of the nut 22 with the restricting member 53 in a sliding region 910. Furthermore, in this embodiment, sliding is permitted between the second surface 532 of the restricting member 53 and the axial end surface 415 of the nut 22. In the ball screw device 13, the configuration that allows contact sliding restricts the relative axial movement of the nut 22 in the first direction even during rotation.

[0064] In this embodiment, contact slippage occurs between the second surface 532 of the restricting member 53 and the axial end surface 415 of the nut 22. Because the member that comes into contact with the nut 22 is a member separate from the housing main body 330, appropriate design of the sliding structure can reduce wear, improve assembly, and improve positioning accuracy, which is advantageous for extending the life of the device.

[0065] (Fifth embodiment) FIG. 9 is a schematic partial cross-sectional view showing a ball screw device 14 according to a fifth embodiment. In the following description of the fifth embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. In this embodiment, unlike the second embodiment, a regulating member 54 is provided on a wall different from the wall adjacent to the tapered rollers 43. The regulating member 54 is provided as a separate member from the main body of the screw shaft 21 / nut 22. In this embodiment, the support body (outer assembly, first assembly) 60 includes the housing 30, the outer ring member 42, etc. The rotating body (inner assembly, second assembly) 70 includes the nut 22, the regulating member 54, etc.

[0066] In this embodiment, the housing 30 has another axial surface (axial end surface) 315 facing the second direction, different from the axial surface 312 facing the space in which at least a portion of the bearing 40 is disposed. The axial surface 315 is provided at a position spaced apart from the axial surface 312 in the first direction. The nut 22 of the ball screw 20 has another axial surface 226 facing the first direction, different from the axial surface 415 provided on the wall adjacent to the tapered rollers 43. The axial surface 226 is provided at a position spaced apart from the axial surface 415 in the first direction. The axial surface 315 and the axial surface 226 are disposed opposite to each other. The regulating member 54 is disposed between the axial surface 315 and the axial surface 226. The regulating member 54 has a ring shape and has a first surface 541 facing the first direction and a second surface 542 facing the second direction. The regulating member 54 is fixed to the nut 22 in a state facing and abutting against the nut 22. A first surface 541 (first axial surface AX1) of the regulating member 54 and an axial surface 315 (second axial surface AX2) of the housing 30 are disposed facing each other. The first surface 541 and the axial surface 315 face and abut each other, or face each other with a gap therebetween. Additionally and / or alternatively, various structures including a separate member (not shown) for fixing the regulating member 54 to the nut 22 (such as a thrust collar, a C-shaped retaining ring, or an annular plate) are applicable. In one example, a member having a shape similar to that of a sliding bearing is used as the regulating member 54. In another example, a member having a shape similar to that of a relatively simple spacer is used as the regulating member 54.

[0067] In this embodiment, during high load driving, as in the second embodiment, a force in the second direction due to the high load is transmitted in this order to the nut 22, tapered rollers 43, outer ring member 42, and housing 30 (first mode, high load mode). In the ball screw device 14, even when a high axial load is applied, the rotational motion of the rotating body 70 (such as the nut 22) relative to the support body 60 (such as the housing 30) is stably supported.

[0068] In the first mode, the nut 22 receives a strong force in the second direction based on an axial load (reaction force). This force acts in a direction that causes the axial surface 226 of the nut 22 (the first surface 541 of the restricting member 54) to move axially away from the axial surface 315 of the housing 30. In one example, the ball screw device 14 is designed so that, when a high load in the second direction is received, a substantial gap 900 is generated between the axial surface 315 of the housing 30 and the first surface 541 of the restricting member 54. In other words, the allowable axial clearance C1 is set to be greater than zero. In another example, the ball screw device 14 is designed so that, when a high load in the second direction is received, the gap 900 (the allowable axial clearance C1) between the axial surface 315 of the housing 30 and the first surface 541 of the restricting member 54 becomes substantially zero.

[0069] As the rotating body 70 rotates relative to the support body 60, a relative movement (relative rotation) occurs in the circumferential direction between the axial surface 315 of the housing 30 and the first surface 541 of the regulating member 54. In the ball screw device 14, when the allowable axial clearance C1 is set to be greater than zero, a rotational load (frictional load) due to contact between the housing 30 and the regulating member 54 in the first mode is avoided.

[0070] In this embodiment, the relative axial movement of the nut 22 in the first direction is restricted based on the axial positional relationship between the first surface 541 (first axial surface AX1) of the restricting member 54 and the axial surface 315 (second axial surface AX2) of the housing 30. That is, the relative axial movement of the nut 22 is restricted within the range of a design value (allowable axial clearance C1) of a gap 900 between the axial surface 315 and the first surface 541. The first surface 541 of the restricting member 54 contacts the axial surface 315 of the housing 30 in a sliding region 910, thereby restricting the relative axial movement of the nut 22 in the first direction. Furthermore, in this embodiment, sliding is permitted between the axial surface 315 of the housing 30 and the first surface 541 of the restricting member 54. In the ball screw device 14, the configuration that allows contact sliding restricts the relative axial movement of the nut 22 in the first direction even during rotation.

[0071] In this embodiment, contact sliding occurs between the axial surface 315 of the housing 30 and the first surface 541 of the regulating member 54. Appropriate design of the sliding structure can reduce wear, improve assembly ease, and improve positioning accuracy, which is advantageous for extending the life of the device. The distance (axial distance) between the sliding structure and the bearing 40 in the axial direction can be set arbitrarily. In one example, the axial distance between the axial surface 541 (or the axial surface 226) and the axial surface 415 is set to be equal to or less than the axial length of the bearing 40 (or the length of the tapered rollers 43). In another example, the axial distance between the axial surface 541 (or the axial surface 226) and the axial surface 415 is set to be greater than the axial length of the bearing 40 (or the length of the tapered rollers 43).

[0072] Furthermore, in this embodiment, the radial range of the slip region 910 is set to include a position (region 910A) radially inward relative to the outer surface (outer peripheral surface) 412 of the nut 22, and a position (region 910B) radially inward relative to the tapered rollers 43. In other words, contact between the housing 30 and the restricting member 54 is permitted at a position radially inward relative to the tapered rollers 43. Appropriate setting of the slip region 910 contributes to stable operation of the bearing 40 and is advantageous for reducing the rotational load and extending the life of the bearing 40.

[0073] 9, the radial range of the slip region 910 is set at a position radially inward relative to the tapered rollers 43. Alternatively, at least a part of the radial range of the slip region 910 may be set at a position radially outward relative to the tapered rollers 43. Also, at least a part of the radial range of the slip region 910 may be set at a position radially outward relative to the outer surface (outer peripheral surface) 412 of the nut 22.

[0074] In the example shown in FIG. 9 , the ball screw 20 is provided with a regulating member 54. In the modified example of FIG. 9 , a configuration in which a regulating member is provided on the housing 30 at a position axially spaced from the bearing 40 can be applied. That is, a regulating member fixed to the housing 30 may be disposed between the axial surface of the housing 30 and the axial surface of the ball screw 20. In this example, the relative axial movement of the nuts 22 in the first direction is restricted based on the axial positional relationship between the axial surface (first axial surface AX1) of the nut 22 and the axial surface (second axial surface AX2) of the regulating member provided on the housing 30. Furthermore, in another modified example, the sliding structure may be configured without a regulating member, as in the third embodiment. In this configuration, the axial surface of the nut 22 and the axial surface of the housing 30 directly face each other at a position axially spaced from the bearing 40, and contact sliding occurs between the axial surface of the nut 22 and the axial surface of the housing 30. The axial surface of the nut 22 and the axial surface of the housing 30 face each other and abut against each other, or face each other with a gap therebetween.

[0075] (Sixth, Seventh, and Eighth Embodiments) FIG. 10 is a schematic cross-sectional view showing ball screw devices 15, 16, and 17 according to sixth, seventh, and eighth embodiments. FIG. 10(a) shows a ball screw device 15 according to a sixth embodiment, which is a modified version of the second embodiment. FIG. 10(b) shows a ball screw device 16 according to a seventh embodiment, which is a modified version of the third embodiment. FIG. 10(c) shows a ball screw device 17 according to an eighth embodiment, which is a modified version of the fourth embodiment. In the following description, the same components as those in the above embodiments are denoted by the same reference numerals, and their description will be omitted or simplified. In each embodiment, the ball screw devices 15, 16, and 17 further include a preload member 801.

[0076] In the sixth embodiment shown in FIG. 10(a), the ball screw device 15 is configured so that the first surface 501 (first axial surface AX1) of the regulating member 50 and the axial surface 312 (second axial surface AX2) of the housing 30 approach each other due to the preload of the preload member 801. In one example, the preload member 801 is an elastic member, such as a disc spring. For example, the preload member 801 is disposed between the axial end surface 425 of the outer ring member 42 and the axial surface 311 of the housing 30 in a pre-elastically deformed state. The preload member 801 applies a biasing force (preload) in a first direction to the outer ring member 42 based on the elastic deformation. Furthermore, the shape (elastic deformation state) of the preload member 801 changes in response to a load acting on the bearing 40 in a second direction. In other examples, a preload mechanism other than those described above is applied.

[0077] In this embodiment, in both the high load state (first mode) and the low load state (second mode), the preload from the preload member 801 acts on the bearing 40. Furthermore, in the second mode, the preload from the preload member 801 causes the first surface 501 (first axial surface AX1) of the regulating member 50 and the axial surface 312 (second axial surface AX2) of the housing 30 to come into contact with each other. This is also the case in the seventh embodiment shown in FIG. 10(b) and the eighth embodiment shown in FIG. 10(c). Similarly, a configuration further including the preload member 801 can also be applied to the fifth embodiment.

[0078] In each of the sixth, seventh, and eighth embodiments, the preload applied by the preload member 801 suppresses axial movement of the bearing 40 relative to the gap 900. As a result, problems such as damage to the bearing 40 and abnormal noise are reliably prevented, for example, noise vibration is reduced.

[0079] (Ninth embodiment) 11 and 12 are schematic cross-sectional views showing a ball screw device 80 according to a ninth embodiment. In the following description, the same components as those in the above-described embodiments are denoted by the same reference numerals, and their description will be omitted or simplified. In this embodiment, the ball screw device 80 is configured so that the screw shaft 21 of the ball screw 20 rotates relative to the housing 30.

[0080] 11, in the ninth embodiment, a first shaft 101 to which a driving force of a motor (not shown) is transmitted is connected to a screw shaft 21 (shaft main body 270). In the ball screw 20, rotational motion is converted into linear motion.

[0081] In this embodiment, an inner ring raceway surface 250 is provided on the screw shaft 21 (shaft body 270) of the ball screw 20. An outer ring member 42 of a bearing 40 is attached to the housing 30. Tapered rollers 43 are arranged between the inner ring raceway surface 250 of the screw shaft 21 and an outer ring raceway surface 350 of the outer ring member 42. Additionally and / or alternatively, various structures can be applied that include a separate member (not shown) (such as a thrust collar, a C-shaped retaining ring, or annular plate) for supporting the axial position of the outer ring member 42 relative to the housing 30.

[0082] The shaft body 270 has a first portion 271 provided with a screw groove 275 and a second portion 272 provided with an inner ring raceway surface 250. Both the screw groove 275 and the inner ring raceway surface 250 are formed on the shaft body 270. The threaded shaft 21 has a shaft body 270 in which the screw groove 275 and the inner ring raceway surface 250 are integrally formed. The screw groove 275 and the inner ring raceway surface 250 are formed on the material of the shaft body 270. In one example, the first portion 271 and the second portion 272 are arranged side by side in the axial direction. In another example, at least a portion of the second portion 272 is arranged to overlap the first portion 271 in the axial direction. For example, the entire inner ring raceway surface 250 or at least a portion of the inner ring raceway surface 250 may be located at the same position as the screw groove 275 in the axial direction. Furthermore, the entire inner ring raceway surface 250 or at least a portion of the inner ring raceway surface 250 may be disposed radially outward of the thread groove 275. In one example, the diameter (maximum diameter, minimum diameter, center diameter, or average diameter) of the inner ring raceway surface 250 is set to be approximately the same as the outer diameter (maximum diameter, minimum diameter, center diameter, or average diameter) of the first portion 271. In another example, the diameter of the inner ring raceway surface 250 is set to be larger or smaller than the outer diameter of the first portion 271.

[0083] For example, when the maximum diameter (diameter of the large diameter portion) of the inner ring raceway surface 250 is D1 and the outer diameter of the first portion 271 is D2, D1 / D2 is greater than 0.5 and is equal to or less than 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 3.5, or 4.0. In one example, D1 / D2 is set to be equal to or greater than approximately 0.6 and equal to or less than 2.0. In another example, D1 / D2 is set to be equal to or greater than approximately 0.8 and equal to or less than 1.2. In other examples, ratios other than those listed above can be set. The above numerical values are merely examples and are not limiting.

[0084] Furthermore, for example, when the radial average thickness in the area where the inner ring raceway surface 250 is formed is T1 and the radial average thickness of the first portion 271 is T2, T1 / T2 is greater than 0.1 and is equal to or less than 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, or 3.0. In one example, T1 / T2 is set to be equal to or greater than approximately 0.4 and equal to or less than 2.0. In another example, T1 / T2 is set to be equal to or greater than approximately 0.5 and equal to or less than 1.5. In other examples, ratios other than those listed above can be set. The above numerical values are merely examples and are not limiting.

[0085] 12, the outer diameter of the bearing 40 (outer diameter of the outer ring member 42) is larger than the outer diameter of the screw shaft 21. In another example, the outer diameter of the bearing 40 (outer diameter of the outer ring member 42) can be smaller than the outer diameter of the screw shaft 21. In FIG. 12, the bearing 40 is disposed substantially radially outward of the screw shaft 21.

[0086] In this embodiment, during high-load driving, a high load (reaction force, axial load) acts in the second direction (first mode, high-load mode). In the ball screw 20, a high reaction force in the second direction caused by high-load driving acts on the screw shaft 21 via the ball screw 20. In this first mode, the force in the second direction due to the high load is transmitted in this order: screw shaft 21, tapered rollers 43, outer ring member 42, and housing 30. That is, the axial load from the screw shaft 21 is received by the axial surface 311 of the housing 30 via the tapered rollers 43 and outer ring member 42. In the tapered roller bearing 40, the screw shaft 21 rotates relative to the outer ring member 42 while bearing a radial load and an axial load. As in the first embodiment, in the ball screw device 80 of this embodiment, the rotational motion of a rotating body (second assembly, inner assembly) 70, such as the screw shaft 21, relative to the support body (first assembly, outer assembly) 60 is stably supported, even when a high axial load acts. The ball screw device 80 of this embodiment is preferably applied to high load specifications and is advantageous for compactness. The support body (outer assembly, first assembly) 60 includes a housing 30, an outer ring member 42, etc. The rotating body (inner assembly, second assembly) 70 includes a screw shaft 21, etc.

[0087] In this embodiment, an inner ring raceway surface 250 is provided on the screw shaft 21 of the ball screw 20. The ball screw device 80 has a configuration in which the screw shaft 21 and the inner ring of the bearing 40 are integrally formed. The ball screw device 80 is advantageous in terms of compactness compared to a configuration in which the inner ring of the bearing is attached to the screw shaft 21 as a separate member.

[0088] In this embodiment, the tapered roller bearing 40 has a structure that allows it to be relatively easily separated in the axial direction. The ball screw device 80 is advantageous in reducing the number of assembly steps. For example, the support body 60 and the ball screw 20 can be relatively easily assembled by axially moving the ball screw 20 in the second direction relative to the support body 60. Furthermore, the ball screw 20 can be relatively easily removed from the support body 60 by axially moving the ball screw 20 in the first direction relative to the support body 60.

[0089] (10th, 11th, and 12th embodiments) FIG. 13 is a schematic cross-sectional view showing ball screw devices 81, 82, and 83 according to the tenth, eleventh, and twelfth embodiments. FIG. 13(a) shows a ball screw device 81 according to the tenth embodiment, which is a modified version of the second embodiment. FIG. 13(b) shows a ball screw device 82 according to the ninth embodiment, which is a modified version of the third embodiment. FIG. 13(c) shows a ball screw device 83 according to the twelfth embodiment, which is a modified version of the fourth embodiment. In the following description, the same components as those in the above embodiments are denoted by the same reference numerals, and their description will be omitted or simplified.

[0090] In each embodiment shown in FIG. 13 , similarly to the ninth embodiment, ball screw devices 81, 82, and 83 are configured so that the screw shaft 21 of the ball screw 20 rotates relative to the housing 30. Tapered rollers 43 are arranged between an inner ring raceway surface 250 of the screw shaft 21 and an outer ring raceway surface 350 of the outer ring member 42. The support body (outer assembly, first assembly) 60 includes the housing 30, the outer ring member 42, and the like. The rotating body (inner assembly, second assembly) 70 includes the screw shaft 21, and the like. The ball screw devices 81, 82, and 83 are advantageous in terms of compactness.

[0091] 13(a), a restricting member 50 is disposed between the axial surface 312 of the housing and the axial surface 415 of the screw shaft 21. The restricting member 50 is fixed to the screw shaft 21.

[0092] In this embodiment, similarly to the second embodiment, the relative axial movement of the screw shaft 21 in the first direction is restricted based on the axial positional relationship between the first surface 501 (first axial surface AX1) of the restricting member 50 and the axial surface 312 (second axial surface AX2) of the housing 30. That is, the relative axial movement of the screw shaft 21 is restricted within the range of the design value (allowable axial clearance C1) of the gap 900 between the first surface 501 (first axial surface AX1) and the axial surface 312 (second axial surface AX2). The first surface 501 of the restricting member 50 contacts the axial surface 312 of the housing 30, thereby restricting the relative axial movement of the screw shaft 21 in the first direction. Furthermore, based on the contact sliding in the sliding region 910, the relative axial movement of the screw shaft 21 in the first direction is restricted even during rotation.

[0093] Thus, in this embodiment, even in a configuration in which the screw shaft 21 rotates with respect to the housing 30, similar to the second embodiment, high reliability and long life are achieved while maintaining a compact configuration and high load specifications based on a configuration that restricts relative axial movement of the bearing 40. The same applies to the eleventh embodiment shown in FIG. 13(b) and the twelfth embodiment shown in FIG. 13(c). Similarly, in the fifth embodiment shown in FIG. 9, a configuration in which an inner ring raceway surface 250 is provided on the screw shaft 21 instead of the nut 22 can be applied. Furthermore, in each embodiment, a configuration including a preload member can be applied, as shown in FIG. 10.

[0094] (Thirteenth embodiment) 14 and 15 are schematic cross-sectional views showing a ball screw device 91 according to a thirteenth embodiment. In the following description, the same components as those in the above-described embodiments are denoted by the same reference numerals, and their description will be omitted or simplified. In this embodiment, the ball screw device 91 includes a regulating member 150 attached to the outer ring member 42.

[0095] 14, in this embodiment, an inner ring raceway surface 250 is provided on the nut 22 of the ball screw 20. An outer ring member 42 is attached to the housing 30. Tapered rollers 43 are arranged between the inner ring raceway surface 250 of the nut 22 and an outer ring raceway surface 350 of the outer ring member 42. Additionally and / or alternatively, various structures can be applied that include a separate member (not shown) (such as a thrust collar, a C-shaped retaining ring, or annular plate) for supporting the axial position of the outer ring member 42 relative to the housing 30.

[0096] In this embodiment, the bearing 40 includes a restricting member 150 attached to the outer ring member 42. The restricting member 150 has a circumferential portion 1511 extending in the axial direction and a diameter portion 1512 extending in the radial direction. In one example, the cross-sectional shape of the restricting member 150 is substantially L-shaped. In other examples, various shapes can be applied to the restricting member 150.

[0097] In this embodiment, the regulating member 150 has a structure in which a circumferential portion 1511 and a radial portion 1512 are connected via a bent portion. The outer ring member 42 has an outer surface 421 and an outer surface 422 having a smaller diameter than the outer surface 421. A step is provided between the outer surfaces 421 and 422. The circumferential portion 1511 of the regulating member 150 has an inner diameter corresponding to the outer surface 422 of the outer ring member 42 and an outer diameter corresponding to the outer surface 421 of the outer ring member 42. For example, the outer diameter of the outer surface of the circumferential portion 1511 is set to be smaller than the outer diameter of the outer surface 421 of the outer ring member 42 and smaller than the inner diameter of the inner surface 302 of the housing 30. This is advantageous for improving the ease of assembly of the bearing 40 to the housing 30. In one example, the circumferential portion 1511 of the regulating member 150 is axially press-fitted into the outer surface 422 of the outer ring member 42, thereby fixing the regulating member 150 to the outer ring member 42. In other examples, various configurations for attaching the restricting member 150 to the outer ring member 42 are applicable.

[0098] In this embodiment, a diameter portion 1512 of the regulating member 150 is disposed between the axial surface 312 of the housing 30 and the axial surface 415 of the nut 22. The diameter portion 1512 of the regulating member 150 has a first surface 1501 facing a first direction and a second surface 1502 facing a second direction. The first surface 1501 is disposed at a position axially spaced apart from the axial surface 312 of the housing. At least a portion of the second surface 1502 is disposed facing the axial surface 415 of the nut 22. At least a portion of the second surface 1502 and the axial surface 415 face and abut each other, or face each other across a gap. The regulating member 150 is incorporated as part of a support body (outer assembly, first assembly) 60. The rotating body (inner assembly, second assembly) 70 is rotatably supported by the support body 60. In this embodiment, the support body 60 includes the housing 30, the outer ring member 42, the regulating member 150, etc. The rotating body 70 includes the nut 22 and the like.

[0099] In this embodiment, during high-load driving, a high load (reaction force, axial load) acts in the second direction (first mode, high-load mode). In the ball screw 20, a high reaction force in the second direction caused by high-load driving acts on the nut 22 via the ball screw 20. In this first mode, the force in the second direction due to the high load is transmitted in this order: the nut 22, the tapered rollers 43, the outer ring member 42, and the housing 30. That is, the axial load from the ball screw 20 is received by the axial surface 311 of the housing 30 via the tapered rollers 43 and the outer ring member 42. In the bearing 40, the nut 22 rotates relative to the outer ring member 42 while bearing a radial load and an axial load. In this ball screw device 91, the rotational motion of the rotating body 70 (such as the nut 22) relative to the support body 60 (such as the housing 30) is stably supported even when a high axial load acts. The ball screw device 91 of this embodiment is preferably applied to high-load specifications and is advantageous for compactness.

[0100] In the first mode, the nut 22 of the ball screw 20 receives a strong force in the second direction based on an axial load (reaction force). This force acts in a direction that causes the axial surface 415 of the nut 22 to move axially away from the second surface 1502 of the regulating member 150. In one example, the ball screw device 91 is designed so that a substantial gap 900 is generated between the second surface 1502 of the regulating member 150 and the axial surface 415 of the nut 22 when a high load is applied in the second direction. The design value of the gap 900 in the first mode (high load mode) is defined as the "allowable axial clearance (C1)." In another example, the ball screw device 91 is designed so that the gap 900 (allowable axial clearance C1) between the second surface 1502 of the regulating member 150 and the axial surface 415 of the nut 22 is substantially zero when a high load is applied in the second direction.

[0101] As the rotating body 70 rotates relative to the support body 60, a relative movement (relative rotation) occurs in the circumferential direction between the second surface 1502 of the regulating member 150 and the axial surface 415 of the nut 22. In the ball screw device 91, when the allowable axial clearance C1 greater than zero is set, a rotational load (frictional load) due to contact between the nut 22 and the regulating member 150 in the first mode is avoided.

[0102] In the ball screw device 91, when the load in the second direction received from the ball screw 20 is relatively small or substantially zero (no load), relative axial movement tends to occur between the nut 22 and the outer ring member 42 (second mode, low-load mode). As described above, in the first mode, a substantial gap 900 may occur between the second surface 1502 of the restricting member 150 and the axial surface 415 of the nut 22. Furthermore, in a low-load or no-load state, for example, when the ball screw 20 is operated in an initial state or in a predetermined direction, the substantial gap 900 may occur. When the substantial gap 900 exists, there is a possibility that the nut 22 will attempt to move in a direction (first direction) away from the outer ring member 42. This is due, for example, to the fact that the bearing 40 has a structure that is easily separated in the axial direction and / or that an axial component force is generated in the bearing 40 when a radial load is applied.

[0103] In this embodiment, the relative axial movement of the nut 22 in the first direction is restricted based on the axial positional relationship between the axial surface 415 (first axial surface AX1, third axial surface AX3) of the nut 22 and the second surface 1502 (second axial surface AX2, fourth axial surface AX4) of the restricting member 150. In other words, the relative axial movement of the nut 22 is restricted to within the range of the design value (allowable axial clearance C1) of the gap 900 between the axial surface 415 (first axial surface AX1, third axial surface AX3) and the second surface 1502 (second axial surface AX2, fourth axial surface AX4).

[0104] In this embodiment, contact between the axial surface 415 of the nut 22 and the second surface 1502 of the restricting member 150 is permitted. Relative axial movement of the nut 22 in the first direction is restricted based on the contact of the axial surface 415 of the nut 22 with the second surface 1502 of the restricting member 150. The range of an area (sliding area, contact area, facing area) 910 in which the axial surface 415 and the second surface 1502 can come into contact with each other is appropriately set in advance. Appropriate setting of the sliding area 910 contributes to stable operation of the bearing 40 and is advantageous for reducing the rotational load and extending the life of the bearing 40.

[0105] In this embodiment, slippage is permitted between the axial surface 415 of the nut 22 and the second surface 1502 of the regulating member 150. In the ball screw device 91, when the axial surface 415 of the nut 22 abuts against the second surface 1502 of the regulating member 150 during rotation, relative axial movement (circumferential slippage) occurs between the second surface 1502 and the axial surface 415 accompanied by contact. That is, slippage (contact slippage) occurs in at least a portion of the slip region 910. In the ball screw device 91, due to the configuration that permits contact slippage, relative axial movement of the nut 22 in the first direction is restricted even during rotation.

[0106] In this embodiment, a configuration can be employed in which the state of slippage changes depending on the magnitude of the load in the second direction from the ball screw 20. In an example in which the allowable axial clearance C1 is designed to be greater than zero, in the first mode (high load mode), contact slippage does not occur between the axial surface 415 of the nut 22 and the second surface 1502 of the regulating member 150. This is because the nut 22 is pushed in the second direction by the high axial load from the ball screw 20, and the presence of the gap 900 prevents the axial surface 415 of the nut 22 from contacting the second surface 1502 of the regulating member 150 (non-contact slippage). On the other hand, in the second mode (low load mode), the axial load in the second direction from the ball screw 20 is relatively small or zero. Therefore, the position of the nut 22 with respect to the outer ring member 42 (axial relative position) tends to move in the first direction. When the axial surface 415 of the nut 22 abuts against the second surface 1502 of the restricting member 150 during rotation, contact slippage occurs between the axial surface 415 and the second surface 1502. In this example, the slippage state changes between a non-contact state in the first mode and a contact state in the second mode. The rotational load generated in the slippage region 910 is suppressed to a relatively small value.

[0107] In another example, the value of the allowable axial clearance C1 is designed to be substantially zero. In the first mode (high load mode), contact slippage occurs between the axial surface 415 of the nut 22 and the second surface 1502 of the restricting member 150. For example, a rotational load (frictional load) based on preload occurs in the slip region 910. Also, in the second mode (low load mode), contact slippage occurs between the axial surface 415 and the second surface 1502. In this example, the rotational load in the slip region 910 may change between the first mode and the second mode. Note that in this example, the change in the relative axial positions of the nut 22 and the outer ring member 42 between the first mode and the second mode is small, and the posture of the bearing 40 is kept relatively constant.

[0108] In this embodiment, contact slip occurs between the shaft surface 415 of the nut 22 and the second surface 1502 of the regulating member 150. By appropriately designing the sliding structure, such as the material, surface precision, surface roughness, and surface shape of the regulating member 150, it is possible to reduce wear, improve assembly ease, and improve positioning accuracy, which is advantageous for extending the life of the device.

[0109] In this embodiment, the regulating member 150 is disposed to surround the side of the bearing 40 facing the first direction. In one example, the regulating member 150 has a continuous surface 1550 that surrounds at least a portion of the axial surface (axial end surface) 415 of the nut 22, at least a portion of the axial surface (axial end surface) 424 of the outer ring member 42, and the gap (gap space) 405 between the axial surface 415 and the axial surface 424. The continuous surface 1550 faces the gap 405 of the bearing 40 and is disposed in the vicinity thereof. The ball screw device 91 may have a seal structure 47 that includes a portion of the regulating member 150 (e.g., the continuous surface 1550). Such a configuration may have a sealing function and / or a function that assists sealing. For example, this configuration contributes to preventing leakage of lubricant from the bearing 40 and is advantageous in improving the device life.

[0110] As described above, according to this embodiment, high reliability and long life are achieved while having a compact configuration and high load specifications, based on the configuration that restricts relative axial movement of the bearing 40.

[0111] (Fourteenth embodiment) 16 is a schematic partial cross-sectional view showing a ball screw device 92 according to a fourteenth embodiment. In the following description of the fourteenth embodiment, the same components as those in the thirteenth embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. In this embodiment, unlike the thirteenth embodiment, no step for attaching the restricting member 152 is provided in the outer ring member 42.

[0112] 16 , the housing 30 further includes an inner surface (inner wall surface) 305 having a diameter larger than that of the inner surface 302. A step is provided between the inner surfaces 305 and 302. For example, the housing 30 has a divided structure including a first element 391 and a second element 392 that are coupled to each other, with the first element 391 being provided with the inner surface 302 and the second element 392 being provided with the inner surface 305. The circumferential portion 1511 of the regulating member 152 has an outer diameter that is the same as or smaller than that of the inner surface 305 of the housing 30 and an inner diameter that corresponds to the outer surface 422 of the outer ring member 42. For example, the circumferential portion 1511 of the regulating member 152 is press-fitted axially into the outer surface 421 of the outer ring member 42, thereby attaching the regulating member 52 to the outer ring member 42.

[0113] In this embodiment, processing of the bearing 40, such as forming a step on the outer surface of the outer ring member 42, is avoided. In addition, the restricting member 150 is housed in a space formed by the step provided in the housing 30. The ball screw device 92 simplifies the processing and assembly processes, which is advantageous for reducing costs.

[0114] (Fifteenth embodiment) 17 is a schematic partial cross-sectional view showing a ball screw device 93 according to a fifteenth embodiment. In the following description of the fifteenth embodiment, the same components as those in the thirteenth embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. In this embodiment, the shape of a regulating member 153 is different from that of the regulating member 150 in the thirteenth embodiment.

[0115] In this embodiment, as shown in FIG. 17 , the restricting member 153 has a radial portion 1512 extending radially, a first circumferential portion 1531 extending from the radial portion 1512 in a first direction, and a second circumferential portion 1532 extending from the radial portion 1512 in a second direction. An outer peripheral surface 1535 of the restricting member 153 includes the outer peripheral surface of the first circumferential portion 1531 and the outer peripheral surface of the second circumferential portion 1532. For example, the outer peripheral surface 1535 has a diameter corresponding to the inner surface 302 of the housing 30. In one example, the radial thickness of the first circumferential portion 1531 of the restricting member 153 is greater than the radial thickness of the second circumferential portion 1532. The radial thicknesses of the circumferential portions 1531 and 1532 can be set arbitrarily. In another example, the radial thickness of the first circumferential portion 1531 can be the same as or smaller than the radial thickness of the second circumferential portion.

[0116] In this embodiment, the restricting member 153 and the outer ring member 42 are arranged side by side in the axial direction. The restricting member 153 is arranged between the axial surface 312 of the housing 30 and the axial surface 424 of the outer ring member 42. In one example, the restricting member 153 is sandwiched between the axial surface 312 and the axial surface 424 with a preload. In another example, the restricting member 153 is arranged between the axial surface 312 and the axial surface 424 with substantially no preload. An axial end surface of the first circumferential portion 1531 can abut against the axial surface 312 of the housing 30. An axial end surface of the second circumferential portion 1532 can abut against the axial surface 424 of the outer ring member 42.

[0117] In this embodiment, similar to the thirteenth embodiment, the relative axial movement of the nut 22 in the first direction is restricted based on the axial positional relationship between the axial surface 415 (first axial surface AX1, third axial surface AX3) of the nut 22 and the second surface 1502 (second axial surface AX2, fourth axial surface AX4) of the restricting member 153. That is, the relative axial movement of the nut 22 is restricted within the range of the design value (allowable axial clearance C1) of the gap 900 between the axial surface 415 (first axial surface AX1, third axial surface AX3) of the nut 22 and the second surface 1502 (second axial surface AX2, fourth axial surface AX4) of the restricting member 153. The axial surface 415 of the nut 22 contacts the second surface 1502 of the restricting member 153, thereby restricting the relative axial movement of the nut 22 in the first direction. Furthermore, based on the contact sliding in the sliding region 910, the relative axial movement of the nut 22 in the first direction is restricted even during rotation.

[0118] In this embodiment, the regulating member 153 has a diameter portion 1512 provided for the nut 22 of the bearing 40 and a second circumferential portion 1532 provided for the outer ring member 42. The ball screw device 93 has a reduced number of parts and a simplified assembly process, which is advantageous for reducing costs. The ball screw device 93 can also have a seal structure 47 that includes a portion of the regulating member 153 (for example, the continuous surface 1550). In this case, the seal structure 47 contributes to preventing leakage of lubricant from the bearing 40, which is advantageous for improving the life of the device.

[0119] (16th, 17th, and 18th embodiments) 18 and 19 are schematic cross-sectional views showing ball screw devices 95, 96, and 97 according to sixteenth, seventeenth, and eighteenth embodiments. FIGS. 18 and 19(a) show a ball screw device 95 according to a sixteenth embodiment, which is a modification of the thirteenth embodiment. FIG. 19(b) shows a ball screw device 96 according to a seventeenth embodiment, which is a modification of the fourteenth embodiment. FIG. 19(c) shows a ball screw device 97 according to an eighteenth embodiment, which is a modification of the fifteenth embodiment. In the following description, the same components as those in the above embodiments are denoted by the same reference numerals, and their description will be omitted or simplified. In each embodiment, the ball screw devices 95, 96, and 97 are configured so that the screw shaft 21 of the ball screw 20 rotates relative to the housing 30.

[0120] 18, in the sixteenth embodiment, a first shaft 101 to which a driving force of a motor (not shown) is transmitted is connected to a screw shaft 21. In the ball screw 20, rotational motion is converted into linear motion.

[0121] In this embodiment, an inner ring raceway surface 250 is provided on the screw shaft 21 of the ball screw 20. An outer ring member 42 is attached to the housing 30. Tapered rollers 43 are arranged between the inner ring raceway surface 250 of the screw shaft 21 and an outer ring raceway surface 350 of the outer ring member 42. .

[0122] 9, the screw shaft 21 has an axial surface (axial wall surface) 415 facing the second direction. The axial surface 415 is provided between the outer surface 410 and the outer surface 412 in the radial direction, and has, for example, a surface perpendicular to the axial direction.

[0123] In this embodiment, the support body (outer assembly, first assembly) 60 includes the housing 30, the outer ring member 42, and the restricting member 150. The rotating body (inner assembly, second assembly) 70 includes the screw shaft 21 and the like.

[0124] In this embodiment, a high reaction force in the second direction caused by driving under a high load acts on the screw shaft 21 via the ball screw 20. In this first mode, the force in the second direction due to the high load is transmitted in the following order: screw shaft 21, tapered rollers 43, outer ring member 42, and housing 30. In the ball screw device 95, even when a high axial load is applied, the rotational motion of the rotating body 70 (such as the screw shaft 21) relative to the support body 60 (such as the housing 30) is stably supported.

[0125] In this embodiment, similarly to the thirteenth embodiment, the relative axial movement of the screw shaft 21 in the first direction is restricted based on the axial positional relationship between the axial surface 415 (first axial surface AX1, third axial surface AX3) of the screw shaft 21 and the second surface 502 (second axial surface AX2, fourth axial surface AX4) of the regulating member 150. That is, the relative axial movement of the screw shaft 21 is restricted within the range of the design value (allowable axial clearance C1) of the gap 900 between the axial surface 415 (first axial surface AX1, third axial surface AX3) of the screw shaft 21 and the second surface 502 (second axial surface AX2, fourth axial surface AX4) of the regulating member 150. The axial surface 415 of the screw shaft 21 comes into contact with the second surface 1502 of the regulating member 150, thereby restricting the relative axial movement of the screw shaft 21 in the first direction. Furthermore, based on the contact sliding in the sliding region 910, the relative axial movement of the screw shaft 21 in the first direction is restricted even during rotation.

[0126] Thus, in this embodiment, even in a configuration in which the screw shaft 21 rotates relative to the housing 30, similar to the thirteenth embodiment, high reliability and long life are achieved while having a compact configuration and high load specifications based on a configuration that restricts relative axial movement of the bearing 40. The same is true for the seventeenth embodiment shown in Fig. 19(b) and the eighteenth embodiment shown in Fig. 19(c).

[0127] (19th embodiment) 20 is a schematic partial cross-sectional view showing a ball screw device 98 according to a nineteenth embodiment. In the following description, the same components as those in the above-described embodiments are denoted by the same reference numerals, and the description thereof will be omitted or simplified.

[0128] In this embodiment, a ball screw device 98 is configured so that the screw shaft 21 of the ball screw 20 rotates relative to the housing 30. In FIG. 20(a), a shaft to which the driving force of a motor is transmitted is connected to the screw shaft 21, and rotational motion is converted into linear motion via the ball screw 20, causing the nut 22 to move in a first direction and a second direction. As shown in the schematic enlarged view of FIG. 20(c), an inner ring raceway surface 250 is provided on the screw shaft 21 of the ball screw 20. An outer ring member 42 is attached to the housing 30. Tapered rollers 43 are arranged between the inner ring raceway surface 250 of the screw shaft 21 and an outer ring raceway surface 350 of the outer ring member 42.

[0129] In this embodiment, the bearing 40 includes a regulating member 157 attached to the outer ring member 42. As shown in FIG. 20( c), the regulating member 157 has a circumferential portion 1571 extending in the axial direction and a diameter portion 1572 extending in the radial direction. The diameter portion 1572 of the regulating member 157 has a first surface 1501 facing a first direction and a second surface 1502 facing a second direction. In this embodiment, at least a portion of the first surface 1501 is disposed radially inward relative to the outer surface of the nut 22. In one example, the regulating member 157 may be formed by plastic processing, and then the first surface 1501 and / or the second surface 1502 may be subjected to additional processing such as grinding. In other examples, various methods can be applied to processing the regulating member 157. In this embodiment shown in FIG. 20, the support body (outer assembly, first assembly) 60 includes the housing 30, the outer ring member 42, the regulating member 157, and the like. The rotating body (inner assembly, second assembly) 70 includes the screw shaft 21 and the like.

[0130] In this embodiment, similarly to the above-described embodiment, the relative axial movement of the bearing 40 is restricted by the second surface 1502 (second axial surface AX2, fourth axial surface AX4) of the restricting member 157. Furthermore, in this embodiment, the movement of the nut 22 in the second direction relative to the housing 30 is restricted by the first surface 1501 (fifth axial surface AX5) of the restricting member 157. That is, the restricting member 157 has a stopper function against the movement of the ball screw 20.

[0131] 20(a), when the screw shaft 21 of the ball screw 20 rotates in a predetermined direction, the nut 22 moves in the second direction. In Fig. 20(b), when the shaft surface 227 of the nut 22 abuts against the first surface 1501 of the regulating member 157, the movement of the nut 22 in the second direction is stopped.

[0132] Here, when the nut 22 abuts against the axial surface of the screw shaft 21, the components may bite together, which may require excessive torque when restarting, etc. This is because the axial surface of the nut 22 in a non-rotating state abuts against the axial surface of the screw shaft 21 in a rotating state. In this embodiment, the nut 22 in a non-rotating state abuts against the restricting member 157 in a non-rotating state, so the phenomenon of the components biting together due to the abutment is avoided. This is advantageous for improving reliability and lifespan.

[0133] Furthermore, in this embodiment, similar to the above embodiment, high reliability and long life are achieved while having a compact configuration and high load specifications based on a configuration that restricts relative axial movement of the bearing 40.

[0134] The technical scope of the present invention is not limited to the scope of the embodiments. Various modifications or improvements can be made to the embodiments. Forms incorporating such modifications or improvements can also be included in the technical scope of the present invention. Furthermore, the present invention is not limited to the described embodiments, and any combination of these configurations may be used.

[0135] The present disclosure may be combined as follows: (1) In one embodiment, a ball screw device includes a ball screw having a screw shaft, a nut, and a plurality of balls, and a support body that supports the ball screw. The ball screw has an inner ring raceway surface provided on the screw shaft or the nut. The support body has an outer ring raceway surface. The screw shaft or the nut is integrally formed with the inner ring raceway surface. A plurality of tapered rollers are arranged as rolling elements between the inner ring raceway surface and the outer ring raceway surface. (2) In the ball screw device described in (1) above, the ball screw is assembled to the support body so as to be removable in a first direction, and an axial load from the ball screw along a second direction is borne by the support body. (3) In the ball screw device described in (1) or (2) above, the ball screw has a first axial surface facing the first direction, and the support body has a second axial surface facing the second direction. When the screw shaft or the nut rotates relative to the support body, relative circumferential movement occurs between the first axial surface and the second axial surface. Relative axial movement of the ball screw in the first direction relative to the support body is restricted based on the axial positional relationship between the first axial surface and the second axial surface. (4) In the ball screw device according to any one of (1) to (3) above, the first shaft surface and the second shaft surface are allowed to come into contact with each other. (5) In the ball screw device according to any one of (1) to (4) above, sliding is permitted between the first shaft surface and the second shaft surface. (6) In the ball screw device described in (5) above, the state of the slippage changes depending on the magnitude of the axial load from the ball screw. (7) In the ball screw device described in any one of (1) to (6) above, the ball screw has an axial surface as the first axial surface formed on the screw shaft or the main body of the nut, or is provided with a regulating member having the first axial surface as a separate member from the screw shaft or the main body of the nut. (8) In the ball screw device described in any one of (1) to (7) above, the support body has an axial surface as the second axial surface formed on the main body of the support body, or is provided with a regulating member having the second axial surface as a separate member from the main body of the support body. (9) The ball screw device according to any one of (1) to (8) above further comprises a preload member that applies a preload so that the first shaft surface and the second shaft surface approach each other. (10) In the ball screw device described in any one of (1) to (9) above, the support body has an outer ring member provided with an outer ring raceway surface. The ball screw has a third axial surface oriented in the first direction. The support body further has a regulating member arranged in contact with the outer ring member, the regulating member having a fourth axial surface arranged facing the third axial surface. The third axial surface and the fourth axial surface face and abut each other, or face each other across a gap. When the screw shaft or the nut rotates relative to the support body, relative axial movement in the first direction of the ball screw relative to the support body is regulated based on the axial positional relationship between the third axial surface and the fourth axial surface. (11) In the ball screw device described in (10) above, the regulating member is attached to the outer ring member. (12) In the ball screw device described in (10) or (11) above, contact between the third shaft surface and the fourth shaft surface is permitted. (13) In the ball screw device according to any one of (10) to (12) above, sliding is permitted between the third shaft surface and the fourth shaft surface. (14) In the ball screw device described in (13) above, the state of the slippage changes depending on the magnitude of the axial load from the ball screw. (15) In the ball screw device according to any one of (10) to (14) above, movement of the nut in the second direction relative to the support body is restricted by the restricting member. (16) The ball screw device according to any one of (1) to (15) above further comprises a seal structure including at least a part of the regulating member. [Explanation of symbols]

[0136] 10~17, 80~83, 91~93, 95~98 Ball screw device, 20 ball screws, 21 screw shaft, 22 nuts, 23 balls, 30 housing, 40 bearings, 42 outer ring member, 43 Tapered rollers, 50, 52-54, 150, 152, 153, 157 Regulating members; 60 support, 70 rotating bodies, 250 inner ring raceway, 350 outer ring raceway, 801 preload member, 900 gap, AX1 1st axis plane, AX2 Second axis surface.

Claims

1. a ball screw having a screw shaft, a nut, and a plurality of balls; a support for supporting the ball screw; Equipped with The ball screw has an inner ring raceway surface provided on the screw shaft or the nut, the support body has an outer ring raceway surface; the screw shaft or the nut is formed integrally with the inner ring raceway surface, a plurality of tapered rollers as rolling elements are disposed between the inner ring raceway surface and the outer ring raceway surface; Ball screw device.

2. the ball screw is assembled to the support so as to be removable in a first direction; An axial load from the ball screw along a second direction is received by the support body. The ball screw device according to claim 1 .

3. the ball screw has a first axial surface facing the first direction; the support has a second axial surface oriented in the second direction; When the screw shaft or the nut rotates relative to the support, a relative movement in the circumferential direction occurs between the first axial surface and the second axial surface, Axial relative movement of the ball screw in the first direction with respect to the support body is restricted based on an axial positional relationship between the first axial surface and the second axial surface. The ball screw device according to claim 2 .

4. The ball screw device according to claim 3 , wherein the first shaft surface and the second shaft surface are allowed to contact each other.

5. The ball screw device according to claim 3 , wherein sliding is permitted between the first shaft surface and the second shaft surface.

6. 6. The ball screw device according to claim 5, wherein the state of the slippage changes depending on the magnitude of the axial load from the ball screw.

7. 7. The ball screw device according to claim 3, wherein the ball screw has an axial surface as the first axial surface formed on the screw shaft or the body of the nut, or includes a regulating member having the first axial surface as a separate member from the screw shaft or the body of the nut.

8. 7. A ball screw device according to claim 3, wherein the support body has an axial surface as the second axial surface formed on a main body of the support body, or is provided with a regulating member having the second axial surface as a separate member from the main body of the support body.

9. 7. The ball screw device according to claim 3, further comprising a preload member that applies a preload so that the first shaft surface and the second shaft surface approach each other.

10. the support body has an outer ring member provided with an outer ring raceway surface, the ball screw has a third axial surface oriented in the first direction; the support body further includes a regulating member that is arranged in contact with the outer ring member, the regulating member having a fourth axial surface that is arranged facing the third axial surface, When the screw shaft or the nut rotates relative to the support, a relative movement in the circumferential direction occurs between the third axial surface and the fourth axial surface, 4. The ball screw device according to claim 2, wherein axial relative movement of the ball screw in the first direction relative to the support body is restricted based on the axial positional relationship between the third axial surface and the fourth axial surface.

11. The ball screw device according to claim 10 , wherein the restricting member is attached to the outer ring member.

12. The ball screw device according to claim 10 , wherein contact between the third shaft surface and the fourth shaft surface is permitted.

13. The ball screw device according to claim 10 , wherein sliding is permitted between the third axial surface and the fourth axial surface.

14. 14. The ball screw device according to claim 13, wherein the state of the slippage changes depending on the magnitude of the axial load from the ball screw.

15. The ball screw device according to claim 10 , wherein movement of the nut in the second direction relative to the support body is restricted by the restricting member.

16. The ball screw device according to claim 10, further comprising a seal structure including at least a part of the restricting member.

Images