Ball screw device

Abstract

To provide a ball screw device that can automatically supply lubricating oil stably over a long period of time by assembling a solid lubricant without increasing the overall length of a nut, and can easily manage contact force of the solid lubricant with a screw shaft to suppress torque increase and abnormal heat generation, and can easily install and replace the solid lubricant.SOLUTION: A ball screw device 10 comprises a screw shaft 20, a nut 30, and a plurality of balls 26. The nut 30 is provided with a storage chamber 33 outside a circuit C in which the balls 26 circulate infinitely, which penetrates from an outer peripheral surface to an inner peripheral surface of the nut 30 and can store a solid lubricant 50. The solid lubricant 50 is stored in the storage chamber 33 with a protrusion part 52 in slide contact with an outer peripheral screw groove 21 of the screw shaft 20 and a recessed part 53 in slide contact with a land part 22 of the screw shaft 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a ball screw device, and more particularly to a ball screw device capable of supplying lubricant for a long period of time. [Background technology]

[0002] Ball screws used in general environments are lubricated by filling the space between the screw shaft and the nut that is screwed together via a large number of balls with grease or lubricating oil. In addition, to prevent dust and other particles from entering the nut, an annular recess is provided at the end of the nut, and a seal member is fitted into the recess.

[0003] However, such conventional ball screws using lubricating oil or grease lubrication have the problem that, especially when used in high-temperature environments, the lubricant filled inside the nut leaks out to the outside, causing rapid wear and requiring repeated replenishment of the lubricant in a short period of time.

[0004] To solve this problem, Patent Document 1 discloses a lubrication device for a ball screw in which a seal-shaped solid lubricant is placed on a nut in sliding contact only with the outer diameter part (land part) of the screw shaft, lubricant is supplied from the solid lubricant, and the lubricant attached to the screw groove is prevented from being scraped off during the reciprocating motion of the screw shaft, making it possible to effectively retain the lubricant. Patent Document 2 discloses an oil-retaining polymer-lubricated ball screw in which a backup deflector-shaped solid lubricant in sliding contact with the screw groove of the screw shaft is placed outside the circuit, which is the part other than the passage through which the balls circulate, and lubricant is supplied from the solid lubricant to the screw shaft over time to perform lubrication over a long period of time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3796972 [Patent Document 2] Japanese Patent Application Publication No. 11-201258 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the ball screw of Patent Document 1, the total length of the nut needs to be long to place the solid lubricant, and it is difficult to replace it with an existing model, and there are large restrictions on the device space. In addition, in the ball screw of Patent Document 2, although the impact on the nut dimensions is small, the shape of the solid lubricant is complex, and it is difficult to manage the contact force of the solid lubricant with the screw shaft. For example, if the contact force is large, there is a risk that the torque of the ball screw will increase and the heat generated therefrom will become a problem. In addition, if the contact force is small, it may be difficult to obtain the lubricating function. In addition, in both Patent Documents 1 and 2, if the solid lubricant is depleted or deformed due to a foreign object environment or the influence of heat, the solid lubricant cannot be replaced unless the nut is disassembled, and there is a risk that it will be used continuously in a state where the lubricating performance has been lost.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a ball screw device in which a solid lubricant can be arranged without increasing the overall length of the nut, lubricating oil can be automatically supplied stably over a long period of time, the contact force of the solid lubricant with the screw shaft can be easily managed to suppress torque increases and abnormal heat generation, and the solid lubricant can be easily installed and replaced. [Means for solving the problem]

[0008] Therefore, the above object of the present invention is achieved by the following configuration [1] relating to a ball screw device. [1] A screw shaft having a spiral outer peripheral screw groove formed on an outer peripheral surface and a land portion formed between the outer peripheral screw grooves adjacent in the axial direction; A nut having a helical inner circumferential screw groove formed on an inner circumferential surface so as to face the outer circumferential screw groove of the screw shaft; A ball rolling path formed by the outer circumferential screw groove and the inner circumferential screw groove; A plurality of balls rolling on the ball rolling path; At least one circulation part having a ball circulation passage for circulating the balls rolling in the ball rolling path; At least one circuit formed by the ball rolling path and the ball circulation passage, through which the balls circulate; A ball screw device comprising: the nut includes an accommodation chamber outside a circuit, the accommodation chamber penetrating from an outer peripheral surface of the nut to the inner peripheral surface and capable of accommodating a solid lubricant; The solid lubricant includes a protrusion portion that is in sliding contact with the outer peripheral thread groove of the screw shaft and a recess portion that is in sliding contact with the land portion of the screw shaft. Ball screw device. Effect of the Invention

[0009] According to the ball screw device of the present invention, lubricating oil can be automatically supplied stably over a long period of time, the contact force of the solid lubricant with the screw shaft can be easily managed, torque increase and abnormal heat generation can be suppressed, and the solid lubricant can be easily installed and replaced. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a ball screw device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view of the nut shown in FIG. [Diagram 3] FIG. 3 is an exploded perspective view of the nut. [Figure 4] FIG. 4 is a perspective view of the ball screw device showing the cross-sectional positions of FIGS. 5A and 5B. [Figure 5A] FIG. 5A is a cross-sectional view taken along line AA in FIG. [Figure 5B] FIG. 5B is a cross-sectional view taken along line BB of FIG. [Figure 6A] FIG. 6A is an enlarged perspective view of the storage chamber. [Figure 6B] FIG. 6B is a perspective view of the solid lubricant. [Figure 7]FIG. 7 is a perspective view showing a state in which the solid lubricant contained in the containing chamber is pressed down by a fixing member. [Figure 8A] FIG. 8A is a side view showing the positional relationship between the screw shaft and the solid lubricant. [Figure 8B] FIG. 8B is a perspective view of the solid lubricant. [Figure 9A] FIG. 9A is a side view showing the positional relationship between the screw shaft and another solid lubricant. [Figure 9B] FIG. 9B is a perspective view of another solid lubricant. [Figure 10] FIG. 10 is a perspective view of a modified nut. [Figure 11] FIG. 11 is an exploded perspective view of the modified nut shown in FIG. [Figure 12A] FIG. 12A is a side view of a nut of a ball screw device according to a second embodiment of the present invention. [Figure 12B] FIG. 12B is a perspective view of the solid lubricant. [Figure 13] FIG. 13 is a side view showing the positional relationship between a fixing hole of a nut and a pin hole of a solid lubricant in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a ball screw device according to the present invention will be described in detail with reference to the drawings. (First embodiment) As shown in Figures 1 to 5B, the ball screw device 10 is a mechanism that converts rotational motion into linear motion and includes a screw shaft 20 having a spiral outer peripheral thread groove 21 formed on its outer peripheral surface, a nut 30 having a spiral inner peripheral thread groove 31 formed on its inner peripheral surface opposite the outer peripheral thread groove 21 of the screw shaft 20, and a number of balls 26 rollably interposed in a ball rolling path 25 formed by the outer peripheral thread groove 21 of the screw shaft 20 and the inner peripheral thread groove 31 of the nut 30.

[0012] A roughly U-shaped circulation tube 40 (four in the embodiment shown in the figure), which is a circulation component for returning the balls 26 that have rolled in the ball rolling path 25 to a predetermined position in the ball rolling path 25, is attached to the nut 30.

[0013] The nut 30 has a cutout plane 32 formed by cutting out a portion of the outer circumferential surface, and a plurality of female threads 13 are formed in the radial direction on the cutout plane 32 (see FIG. 11). The circulation tube 40 is fixed to the cutout plane 32 by a set screw 11 that screws into the female threads 13, via a tube holder 12 that is a fixing member.

[0014] As shown in FIG. 5A, the circulation tube 40 has a ball circulation passage 41 therein for circulating the balls 26 rolling on the ball rolling path 25, and the ball circulation passage 41 and the ball rolling path 25 form a circuit C (four in the embodiment shown in the figure), which is an infinite circulation path for infinitely circulating the balls 26.

[0015] In addition, on both axial sides of each of the four circuits C consisting of the ball rolling paths 25 and the ball circulation passages 41, a ball non-circulation path is formed outside the circuit, where the outer peripheral screw groove 21 of the screw shaft 20 and the inner peripheral screw groove 31 of the nut 30 face each other but in which the balls 26 do not roll.

[0016] In other words, circuit C is an infinite circulation path (four in the embodiment shown in the figure) in which the ball rolling path 25 and the ball circulation passage 41 are continuous and a plurality of balls 26 circulate and roll inside, and the outside of the circuit is formed by parts of the ball rolling path 25 located on the axial outside of the four infinite circulation paths (both axial ends of the nut 30) and parts of the ball rolling path 25 located between each of the infinite circulation paths, and is a ball non-circulation path in which the balls 26 do not roll.

[0017] The nut 30 has two accommodating chambers 33 which are rectangular holes that penetrate the cutout plane 32 and the inner surface of the nut 30 on both axial sides of the four circuits C, i.e., on both axial ends of the nut 30 and on opposite sides of the axial center line CL of the cutout plane 32.

[0018] The storage chamber 33 contains a plate-shaped solid lubricant 50, which will be described in detail later, and a portion of the upper surface 51 of the solid lubricant 50 visible through the cutout plane 32 is pressed down by the tube presser 12 to prevent the solid lubricant 50 from falling out of the storage chamber 33 or rattling.

[0019] Next, the accommodation chamber 33 and the solid lubricant 50 will be described with reference to Fig. 4 to Fig. 8. The depth H of the accommodation chamber 33 reaches the inner peripheral thread groove 31 of the nut 30, and a part of the accommodation chamber 33 on the screw shaft 20 side penetrates the inner peripheral surface of the nut 30, while another part radially away from the screw shaft 20 forms a bottom 34 that is approximately parallel to the notch plane 32. The bottom 34 functions as a seat surface for positioning the solid lubricant 50 accommodated in the accommodation chamber 33 (see Fig. 5B and Fig. 6A).

[0020] 5A, 5B, 6B, and 8B, the solid lubricant 50 is a plate-like member having a substantially pentagonal shape with one corner of the rectangle cut out in an arc shape when viewed from the axial direction. The axial thickness t of the solid lubricant 50 corresponds to the sum of approximately 1 / 2 the width of the outer peripheral thread groove 21 of the screw shaft 20 and approximately 1 / 2 the width of the land portion 22 between the adjacent outer peripheral thread grooves 21.

[0021] In the arc-shaped notch of the solid lubricant 50, at the portion corresponding to the outer peripheral thread groove 21, a protrusion portion 52 that slides against the outer peripheral thread groove 21 is formed in approximately the same shape as the outer peripheral thread groove 21, and at the portion corresponding to the land portion 22, a recessed portion 53 that slides against the land portion 22 is formed in approximately the same shape as the land portion 22.

[0022] When the ball screw device 10 is operating, the protrusion portion 52 of the solid lubricant 50 comes into sliding contact with the outer peripheral screw groove 21 and the recessed portion 53 comes into sliding contact with the land portion 22, and the lubricating oil contained in the solid lubricant 50 gradually seeps out over time and is automatically supplied to lubricate the contact surfaces between the outer peripheral screw groove 21 and the inner peripheral screw groove 31 and the ball 26.

[0023] The solid lubricant 50 is a lubricant-containing polymer prepared by mixing a synthetic resin selected from a group of polyolefin resins having basically the same chemical structure, such as polyethylene, polypropylene, polybutylene, and polymethylpentene, with a lubricant such as paraffinic hydrocarbon oil such as poly-α-olefin oil, naphthenic hydrocarbon oil, mineral oil, ether oil such as dialkyl diphenyl ether oil, or ester oil such as phthalic acid ester, either alone or in the form of a mixture of oils, and then heating the raw material to a temperature above the melting point of the resin to plasticize it, and then cooling it to make it solid. Various additives such as antioxidants, rust inhibitors, anti-wear agents, antifoaming agents, and extreme pressure agents may also be added to the lubricant.

[0024] The composition ratio of the lubricant-containing polymer is 10-50% by mass of polyolefin resin and 90-50% by mass of lubricant based on the total mass. If the polyolefin resin is less than 10% by mass, a certain level of hardness and strength cannot be obtained, and it becomes difficult to maintain the initial shape when a load is applied. Also, if the polyolefin resin exceeds 50% by mass (i.e., if the lubricant is less than 50% by mass), the supply of lubricant is reduced, shortening the life of the ball screw.

[0025] The synthetic resin group has the same basic structure but different average molecular weights, ranging from 700 to 5×10 6 The average molecular weight ranges from 700 to 1×10 4 waxes with an average molecular weight of 1×10 4 ~1×10 6 and those with a relatively low molecular weight of 1×10 6 ~5×10 6 These ultra-high molecular weight compounds are used alone or in combination as required.

[0026] By combining a relatively low molecular weight material with a lubricant, a lubricant-containing polymer having a certain degree of mechanical strength, lubricant supplying ability, and oil retention can be obtained. If a part of the relatively low molecular weight material is replaced with a material classified as wax, the affinity with the lubricant increases because the difference in molecular weight between the material classified as wax and the lubricant is small, and as a result, the oil retention of the lubricant-containing polymer improves, making it possible to supply the lubricant for a long period of time. However, on the other hand, the mechanical strength decreases. In addition to polyolefin resins such as polyethylene wax, any wax having a melting point in the range of 100 to 130°C or higher (for example, paraffin-based synthetic wax) can be used as the wax.

[0027] On the other hand, if an ultra-high molecular weight polymer is used instead, the affinity with the lubricant will be lowered due to the large difference in molecular weight between the ultra-high molecular weight polymer and the lubricant, resulting in a decrease in oil retention and an increase in the seepage of the lubricant from the lubricant-containing polymer. This shortens the time it takes for the lubricant-containing polymer to reach the amount of lubricant that it can supply, shortening the life of the ball screw. However, the mechanical strength will improve.

[0028] Considering the balance of moldability, mechanical strength, oil retention, and lubricant supply amount, the composition ratio of the lubricant-containing polymer is preferably 0 to 5 mass% of a material classified as wax, 8 to 48 mass% of a relatively low molecular weight material, 2 to 10 mass% of an ultra-high molecular weight material, and a total of 10 to 50 mass% of the three resin components (with the remainder being 90 to 50 mass% lubricant).

[0029] In order to improve the mechanical strength of the lubricant-containing polymer of the present invention, the following thermoplastic resins and thermosetting resins can be added to the above-mentioned polyolefin resins. As the thermoplastic resins, various resins such as polyamide, polycarbonate, polybutylene terephthalate, polyphenylene sulfide, polyethersulfone, polyetheretherketone, polyamideimide, polystyrene, and ABS resins can be used.

[0030] On the other hand, as the thermosetting resin, various resins such as unsaturated polyester resin, urea resin, melamine resin, phenol resin, polyimide resin, epoxy resin, etc. These resins may be used alone or in combination.

[0031] Furthermore, in order to disperse the polyolefin resin and other resins in a more uniform state, a suitable compatibilizer may be added as necessary. Also, in order to improve the mechanical strength, a filler may be added. For example, inorganic whiskers such as calcium carbonate, magnesium carbonate, potassium titanate whiskers, and aluminum borate whiskers, inorganic fibers such as glass fibers and metal fibers, and those woven into a cloth, and organic compounds such as carbon black, graphite powder, carbon fibers, aramid fibers, and polyester fibers may be added.

[0032] Furthermore, in order to prevent deterioration of the polyolefin resin due to heat, an anti-aging agent such as N,N'-diphenyl-p-phenyldiamine or 2,2'-methylenebis(4-ethyl-6-t-butylphenol) may be added, and in order to prevent deterioration due to light, an ultraviolet absorber such as 2-hydroxy-4-n-octoxybenzophenone or 2-(2'-hydroxy-3'-t-butyl-5'-methyl-phenyl)-5-chlorobenzotriazole may be added.

[0033] The amount of all the above additives (other than the polyolefin resin and lubricant) added is preferably 20 mass % or less of the total amount of the molding raw materials in terms of maintaining the supply capacity of the lubricant.

[0034] As shown in Figures 6A to 8B, the solid lubricant 50 is accommodated in each of the two accommodation chambers 33 by abutting the protrusion portion 52 against the outer peripheral thread groove 21 and the recessed portion 53 against the land portion 22, and then the tube holder 12 is abutted against the upper surface 51 and fixed to the notched plane 32 with the set screw 11 for assembly.

[0035] Since the solid lubricant 50 is contained in the containing chamber 33 formed adjacent to the circuit C and outside the circuit, the axial length of the nut 30 can be made shorter than that of the ball screw of Patent Document 1, in which the lubricant-containing polymer member is covered with a seal cap and screwed to the end face of the nut, and a labyrinth seal is further arranged in the seal cap.

[0036] As shown in FIG. 5B, when the solid lubricant 50 is assembled with the protrusion 52 and the recess 53 abutting against the outer circumferential thread groove 21 and the land portion 22, respectively, the dimensions are set such that the upper surface 51 of the solid lubricant 50 protrudes slightly from the cutout plane 32 and there is a small gap between the lower surface 54 of the solid lubricant 50 and the bottom 34 of the accommodation chamber 33.

[0037] As a result, simply by fixing the solid lubricant 50 to the notched plane 32 via the tube presser 12, the protrusion 52 and the recess 53 are pressed against the outer circumferential thread groove 21 and the land 22 with a predetermined contact force. In other words, the contact force is easy to control, and problems such as increased torque and heat generation due to excessive contact force, and deterioration of the lubricating function due to insufficient contact force can be prevented, thereby obtaining suitable lubricating performance.

[0038] In addition, since the bottom 34 of the accommodation chamber 33 functions as a seat surface for positioning the solid lubricant 50 accommodated in the accommodation chamber 33, even if the solid lubricant 50 is inserted into the accommodation chamber 33 of the nut 30 alone without the screw shaft 20 assembled therein, a stable posture can be maintained, facilitating the assembly of the solid lubricant 50. In addition, the solid lubricant 50 accommodated in the accommodation chamber 33 can be prevented from rattling in the radial direction.

[0039] In the ball screw device 10 configured in this manner, when the screw shaft 20 rotates relative to the nut 30, the screw shaft 20 moves relatively in the axial direction. At that time, the lubricating oil contained in the solid lubricant 50 gradually seeps out due to kinetic frictional heat generated by the sliding contact between the screw shaft 20 and the solid lubricant 50, and is automatically supplied to the contact surfaces between the outer peripheral screw groove 21 and the inner peripheral screw groove 31 and the balls 26, thereby lubricating them.

[0040] In addition, the solid lubricant 50 can be replaced simply by removing the set screw 11 that secures the tube clamp 12, so that the solid lubricant 50 can be easily replaced even if it becomes depleted due to use in a high-temperature environment or long-term use.

[0041] As described above, according to the ball screw device 10 of this embodiment, the lubricating oil gradually seeps out from the solid lubricant 50 over time and is supplied thoroughly to the contact surfaces between the outer peripheral screw groove 21 and the inner peripheral screw groove 31 and the balls 26, providing stable lubrication for a long period of time without supplying lubricating oil from the outside to the ball screw device 10, enabling good operation with low torque. This allows the lubricating oil replenishment period to be extended.

[0042] In addition, the solid lubricant 50 is easy to install and replace, and the contact force of the solid lubricant 50 with the screw shaft 20 is easy to manage, making it possible to suppress torque increases and abnormal heat generation due to excessive contact force and to eliminate supply shortages due to insufficient contact force.

[0043] 9A and 9B, the solid lubricant 50 may be formed with a thick plate thickness t so that the protrusion 52 is in sliding contact with the entire width of the outer peripheral thread groove 21, and further the recessed streaks 53 formed on both sides of the protrusion 52 are in sliding contact with approximately half the width of the land portions 22 on both sides of the outer peripheral thread groove 21. This solid lubricant 50 can contain approximately twice the amount of lubricating oil compared to the solid lubricant 50 shown in FIG. 8B, and can maintain the oil supplying performance for a longer period of time.

[0044] (Modification) 10 and 11, the nut 30 of this modification has two shallow grooves 35 formed in a cutout plane 32, the shallow grooves 35 being rectangular in plan view. Each of the two shallow grooves 35 is formed to surround the entire periphery of the accommodation chamber 33 and include the accommodation chamber 33 inside the shallow groove 35. A female thread 36 is provided in a portion of the shallow groove 35 outside the accommodation chamber 33. The ball screw device 10 also has a screw hole 16 and a substantially rectangular pressing plate 15 that can be fitted into the shallow groove 35. The pressing plate 15 is fixed in the shallow groove 35 by a set screw 17 inserted through the screw hole 16.

[0045] In this modified example, the upper surface 51 of the solid lubricant 50 is set to a dimension such that it protrudes slightly from the bottom surface of the shallow groove 35 when the protrusion portion 52 and the recessed portion 53 (see Figure 6B) abut against the outer circumferential thread groove 21 and the land portion 22, respectively, and the solid lubricant 50 is contained in the containing chamber 33.

[0046] As a result, by simply fitting the pressure plate 15 into the shallow groove 35 and fixing it to the nut 30 with the set screw 17, a contact force can be applied between the solid lubricant 50 and the screw shaft 20. In addition, by adjusting the groove depth of the shallow groove 35, an interference can be provided between the solid lubricant 50 and the pressure plate 15, and the contact force between the solid lubricant 50 and the screw shaft 20 can be adjusted.

[0047] The other configurations and effects are similar to those of the ball screw device 10 of the first embodiment, so the same or corresponding reference numerals are used for the same parts and the description thereof will be omitted.

[0048] Second embodiment As shown in Figs. 12A to 13, the nut 30 of the ball screw device 10 of this embodiment has a fixing hole 37 penetrating from the axial side to the accommodation chamber 33, which is formed parallel to the central axis of the nut 30. The solid lubricant 50 also has a pin hole 55 penetrating in the plate thickness direction corresponding to the fixing hole 37. The fixing hole 37 and the pin hole 55 are formed so that they partially overlap when viewed from the axial direction, and their centers C2, C3 are shifted from each other. The center C2 of the fixing hole 37 is disposed radially inward from the center C3 of the pin hole 55. Specifically, the radius R1 from the center C1 of the nut 30 to the center C2 of the fixing hole 37 is set to be slightly shorter than the radius R2 from the center C1 of the nut 30 to the center C3 of the pin hole 55.

[0049] Then, a fixing pin (not shown) is inserted through the fixing hole 37 of the nut 30 and further through the pin hole 55 of the solid lubricant 50 accommodated in the accommodation chamber 33 , thereby positioning and fixing the solid lubricant 50 to the nut 30 .

[0050] At this time, since the radius R1 from the center C1 of the nut 30 to the center C2 of the fixing hole 37 is shorter than the radius R2 from the center C1 of the nut 30 to the center C3 of the pin hole 55, the insertion of the fixing pin moves the solid lubricant 50 in the inner diameter direction, and applies a contact force between the protrusion 52 and the recess 53 of the solid lubricant 50 and the outer peripheral thread groove 21 and the land 22 of the screw shaft 20. Note that the contact force between the solid lubricant 50 and the screw shaft 20 can be adjusted by adjusting the relative positional relationship between the center C1 of the nut 30 and the center C2 of the fixing hole 37.

[0051] In this way, the solid lubricant 50 is attached to the nut 30 by the fixing pin, so that the assembly is easy and the solid lubricant 50 can be easily replaced by simply pulling out the fixing pin. The fixing pin may be, for example, a male screw or a male screw with a pin. The above-mentioned method of fixing the solid lubricant 50 by the fixing pin can be used in combination with the bottom 34 of the accommodation chamber 33, which prevents the solid lubricant 50 accommodated in the accommodation chamber 33 from rattling in the radial direction (see FIG. 6A).

[0052] The present invention is not limited to the above-described embodiments and modifications, and can be modified, improved, etc., as appropriate. For example, in the above-described embodiment, the solid lubricant 50 is disposed at both axial ends of the nut 30, but the solid lubricant 50 may be disposed in a ball non-circulating path (outside the circuit) between any pair of circuits C in which the balls 26 do not roll. In this case, the length of the nut 30 can be further shortened. Also, three or more solid lubricants 50 can be disposed for one nut 30, and the oil supply performance can be maintained for a longer period of time.

[0053] As described above, the present specification discloses the following: (1) A screw shaft having a helical outer peripheral thread groove formed on an outer peripheral surface and a land portion formed between the outer peripheral thread grooves adjacent to each other in the axial direction; A nut having a helical inner circumferential screw groove formed on an inner circumferential surface so as to face the outer circumferential screw groove of the screw shaft; A ball rolling path formed by the outer circumferential screw groove and the inner circumferential screw groove; A plurality of balls rolling on the ball rolling path; At least one circulation part having a ball circulation passage for circulating the balls rolling in the ball rolling path; At least one circuit formed by the ball rolling path and the ball circulation passage, through which the balls circulate; A ball screw device comprising: the nut includes an accommodation chamber outside a circuit, the accommodation chamber penetrating from an outer peripheral surface of the nut to the inner peripheral surface and capable of accommodating a solid lubricant; The solid lubricant includes a protrusion portion that is in sliding contact with the outer peripheral thread groove of the screw shaft and a recess portion that is in sliding contact with the land portion of the screw shaft. Ball screw device. According to the above configuration, as the ball screw device operates, lubricating oil is gradually exuded from the solid lubricant and can be automatically supplied stably over a long period of time to the contact surfaces between the outer peripheral screw groove and the inner peripheral screw groove and the ball.

[0054] (2) The solid lubricant accommodated in the accommodation chamber has an exposed surface exposed to the outer circumferential surface of the nut, At least a portion of the exposed surface is pressed by a fixing member that fixes the circulatory component to the nut. A ball screw device as described in (1). According to the above-mentioned configuration, the solid lubricant can be easily attached and replaced, and the contact force of the solid lubricant with the screw shaft can be easily controlled. This also makes it possible to suppress torque increase and abnormal heat generation.

[0055] (3) A pressing plate for pressing the exposed surface of the solid lubricant is further provided between the exposed surface of the solid lubricant and the fixed member. A ball screw device as described in (2). According to the above-mentioned configuration, the contact force of the solid lubricant with the screw shaft can be easily controlled.

[0056] (4) The nut has a fixing hole formed parallel to a central axis of the nut, penetrating from an axial side surface into the accommodating chamber, The solid lubricant has a pin hole formed parallel to a central axis of the nut, The fixing hole and the pin hole are arranged so that their centers are offset from each other when viewed in the axial direction, the solid lubricant is accommodated in the accommodation chamber, and is positioned and fixed by inserting a fixing pin into the fixing hole into the pin hole; A ball screw device as described in (1). According to the above configuration, by inserting a fixing pin through the fixing hole of the nut and the pin hole of the solid lubricant to fix the solid lubricant to the nut, it becomes easy to manage the contact force of the solid lubricant and to install or replace the solid lubricant.

[0057] (5) The solid lubricant is a lubricant-containing polymer member formed by integrally molding a synthetic resin and a lubricant. The ball screw device according to any one of (1) to (4). According to the above-mentioned configuration, a solid lubricant containing a lubricant can be produced by molding.

[0058] (6) The circuit is an infinite circulation path formed by the ball rolling path and the ball circulation passage, in which the plurality of balls circulate and roll, The outside of the circuit is a ball non-circulating path formed by a portion of the ball rolling path axially outside the infinite circulation path and a portion of the ball rolling path between the plurality of the infinite circulation paths, and is a ball non-circulating path in which the balls do not roll. A ball screw device as described in (1). According to the above-mentioned configuration, the circuit in which the balls roll circulating can be clearly separated from the outside of the circuit in which the balls do not roll. [Explanation of symbols]

[0059] 10. Ball screw device 12 Tube holder (fixing member) 15 Pressing plate (fixing member) 20 Screw shaft 21 Outer Circumferential Thread Groove 22 Land Department 25 Ball Rolling Path 26 Ball 30 Nut 31 Internal thread groove 32 Notch plane (outer circumferential surface of nut) 33 Containment Room 37 Fixing hole 40 Circulation tube (circulation part) 41 Ball circulation passage 50 Solid lubricant (polymer material containing lubricant) 51 Top surface (exposed surface) 52 Projection part 53 Concave section 55 Pin hole C Circuit (Infinite Loop) C2 Fixation hole center C3 Pin hole center

Claims

1. A screw shaft having a spiral outer peripheral screw groove formed on an outer peripheral surface and a land portion formed between the outer peripheral screw grooves adjacent to each other in the axial direction; A nut having a helical inner circumferential screw groove formed on an inner circumferential surface so as to face the outer circumferential screw groove of the screw shaft; A ball rolling path formed by the outer circumferential screw groove and the inner circumferential screw groove; A plurality of balls rolling on the ball rolling path; At least one circulation part having a ball circulation passage for circulating the balls rolling in the ball rolling path; At least one circuit formed by the ball rolling path and the ball circulation passage, through which the balls circulate; A ball screw device comprising: the nut includes an accommodation chamber outside a circuit, the accommodation chamber penetrating from an outer peripheral surface of the nut to the inner peripheral surface and capable of accommodating a solid lubricant; The solid lubricant includes a protrusion portion that is in sliding contact with the outer peripheral thread groove of the screw shaft and a recess portion that is in sliding contact with the land portion of the screw shaft. Ball screw device.

2. the solid lubricant accommodated in the accommodation chamber has an exposed surface exposed to the outer circumferential surface of the nut, At least a portion of the exposed surface is pressed by a fixing member that fixes the circulatory component to the nut. The ball screw device according to claim 1 .

3. a pressing plate for pressing the exposed surface of the solid lubricant is further provided between the exposed surface of the solid lubricant and the fixed member. The ball screw device according to claim 2 .

4. The nut includes a fixing hole formed parallel to a central axis of the nut, the fixing hole penetrating into the accommodating chamber from an axial side surface, The solid lubricant has a pin hole formed parallel to a central axis of the nut, The fixing hole and the pin hole are arranged so that their centers are offset from each other when viewed in the axial direction, the solid lubricant is accommodated in the accommodation chamber, and is positioned and fixed by inserting a fixing pin into the fixing hole into the pin hole; The ball screw device according to claim 1 .

5. The solid lubricant is a lubricant-containing polymer member formed by integrally molding a synthetic resin and a lubricant. The ball screw device according to any one of claims 1 to 4.

6. the circuit is an infinite circulation path formed by the ball rolling path and the ball circulation passage, in which the plurality of balls circulate and roll; The outside of the circuit is a ball non-circulating path formed by a portion of the ball rolling path axially outside the infinite circulation path and a portion of the ball rolling path between the plurality of the infinite circulation paths, and is a ball non-circulating path in which the balls do not roll. The ball screw device according to claim 1 .

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