Ball screw device

Abstract

To provide a ball screw which can maintain high accuracy by being efficiently cooled in a balanced manner while keeping costs low.SOLUTION: A ball screw device 100 includes: a screw shaft 10 having a spiral first screw groove 11 in an external peripheral face; a nut 20 having a spiral second screw groove 21 in an internal peripheral face and externally fit to the screw shaft 10; and a plurality of balls 30 accommodated in rolling paths 32 which are formed by the first screw groove 11 of the screw shaft 10 and the second screw groove 21 of the nut 20. In the screw shaft 10 and the nut 20, a first spiral groove 13 and a second spiral groove 23 which lie opposite each other are formed in a first land part 12 and a second land part 22 between the rolling paths 32, and a cooling pipe 40 is arranged in the second spiral groove 23 of the nut 20.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] A ball screw device is a device that puts balls into screw grooves provided on a screw shaft and a nut respectively, and converts rotational motion into linear motion with high efficiency by the balls rotating and revolving when the screw shaft or the nut rotates.

[0003] In order for this ball screw device to continuously convert rotational motion into linear motion, the balls circulate within a rolling path. As a circulation method for circulating the balls, there are various methods such as a tube type, a ball type, or an end cap type.

[0004] By the way, a ball screw device used as a precision feed mechanism for machine tools, injection molding machines, semiconductor element manufacturing devices, etc. may cause the screw shaft and the nut to thermally deform when the temperature rises. When such thermal deformation occurs, abnormal load distribution of the balls and deterioration of operability occur, affecting the positioning accuracy as a feed mechanism, etc., so it is used in a cooled state.

[0005] Patent Document 1 describes forming a coolant through-hole in a nut constituting a ball screw device, supplying and circulating coolant from a coolant source into this coolant through-hole, and directly cooling the nut, thereby reducing thermal deformation due to heat generation of the ball screw device.

[0006] Also, Patent Document 2 describes cooling a ball screw device by arranging a cooling pipe in a grinding relief groove formed in a spiral groove of a nut.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] By the way, in the ball screw device described in Patent Document 1, a coolant through hole for circulating coolant in the nut is formed in the axial direction. Therefore, particularly in the case of a nut having a large axial dimension, it is necessary to form an elongated coolant through hole, which increases the processing cost. In addition, since there is a distance between the coolant through hole and the rolling path which is a heat source, there is a risk of insufficient cooling under a high-temperature environment or severe usage conditions.

[0009] Also, in the ball screw device described in Patent Document 2, since a cooling pipe is arranged in the grinding relief groove, the outer diameter dimension of the cooling pipe that can be arranged is limited by the size of the grinding relief groove. In this ball screw device, if the maximum width dimension of the right-angled cross section of the grinding relief groove is 1 / 4 or more of the diameter of the ball used, the contact portion between the ball and the screw groove decreases, and the screw groove shape cannot be established. For this reason, for example, as the cooling pipe, it is limited to the width dimension of the grinding relief groove that is at most 1 / 4 of the diameter of the ball, and efficient cooling is difficult. Moreover, in recent years, the number of ball screw devices without a grinding relief portion by cutting finish has increased, and there may be no space for accommodating the cooling pipe.

[0010] Therefore, an object of the present invention is to provide a ball screw device capable of cooling efficiently with good balance while suppressing costs and maintaining high accuracy.

Means for Solving the Problems

[0011] The present invention has the following configuration. (1) A screw shaft having a spiral screw groove on the outer peripheral surface, A nut having a spiral screw groove on the inner peripheral surface and externally fitted to the screw shaft, A plurality of balls accommodated in a rolling path formed by the screw grooves of the screw shaft and the nut, A ball screw device comprising On the screw shaft and the nut, spiral grooves facing each other are formed on the land portions between the rolling paths, respectively. A cooling pipe is arranged in the spiral groove of the screw shaft or the nut. Ball screw device. (2) A screw shaft having a spiral screw groove on the outer peripheral surface, A nut having a spiral screw groove on the inner peripheral surface and externally fitted to the screw shaft, A plurality of balls accommodated in a rolling path formed by the screw grooves of the screw shaft and the nut, A ball screw device comprising On the screw shaft or the nut, a spiral groove is formed on the land portion between the rolling paths, A cooling pipe is arranged in the spiral groove. Ball screw device.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a ball screw device that can cool efficiently and evenly while suppressing costs and maintaining high accuracy.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) First, a ball screw device according to the first embodiment will be described. FIG. 1 is an axial cross-sectional view of a ball screw device 100 according to the first embodiment. As shown in FIG. 1, the ball screw device 100 according to the first embodiment includes a screw shaft 10, a nut 20, and a plurality of balls 30. The screw shaft 10 is formed in a circular cross-sectional shape centered on the central axis, and a spiral first screw groove (screw groove) 11 is formed on its outer peripheral surface.

[0015] The nut 20 has a substantially cylindrical shape, and its inner diameter is formed larger than the outer diameter of the screw shaft 10, and it is externally fitted to the screw shaft 10 with a predetermined gap. A flange 25 for coupling to the object to be guided is provided at one end of the nut 20.

[0016] On the inner peripheral surface of the nut 20, a second thread groove (thread groove) 21 having the same lead as the first thread groove 11 of the screw shaft 10 and facing the first thread groove 11 is formed. And a rolling path 32 having a substantially circular cross-section is formed by the first thread groove 11 of the screw shaft 10 and the second thread groove 21 of the nut 20. A plurality of balls 30 are filled and arranged in the rolling path 32 so as to be rollable.

[0017] The ball screw device 100 has a structure in which the balls 30 circulate in the rolling path 32 so that the screw shaft 10 or the nut 20 continuously converts the rotational motion into a linear motion. Thus, with the relative rotation of the screw shaft 10 with respect to the nut 20, the plurality of balls 30 circulate infinitely, enabling the screw shaft 10 and the nut 20 to move linearly relative to each other in the axial direction. Note that the circulation method for circulating the balls 30 may be any of a tube type, a ball type, or an end cap type.

[0018] FIG. 2 is a cross-sectional view along the axial direction at the boundary portion between the screw shaft 10 and the nut 20 of the ball screw device 100 according to the first embodiment. As shown in FIG. 2, between the first thread grooves 11 constituting the rolling path 32 of the screw shaft 10 is a first land portion (land portion) 12, and similarly, between the second thread grooves 21 constituting the rolling path 32 of the nut 20 is a second land portion (land portion) 22.

[0019] On the screw shaft 10, a first spiral groove (spiral groove) 13 is formed in the first land portion 12 between the rolling paths 32, and on the nut 20, a second spiral groove (spiral groove) 23 is formed in the second land portion 22 between the rolling paths 32. The first spiral groove 13 and the second spiral groove 23 formed on the screw shaft 10 and the nut 20 are formed at positions facing each other.

[0020] The first spiral groove 13 and the second spiral groove 23 have the same pitch P1 as the pitch P1 of the rolling path 32 formed by the first thread groove 11 and the second thread groove 21. Further, the first spiral groove 13 and the second spiral groove 23 are formed at the central positions of the first land portion 12 and the second land portion 22, whereby the dimensions between the rolling paths 32 on both sides are the same dimension A.

[0021] Note that the groove shapes of the first spiral groove 13 and the second spiral groove 23 may be arc-shaped similar to the first thread groove 11 and the second thread groove 21, but may also be shapes different from the arc-shaped, such as rectangular or trapezoidal. In this example, the first spiral groove 13 and the second spiral groove 23 have a groove shape of a smaller arc than the first thread groove 11 and the second thread groove 21.

[0022] The nut 20 is provided with a cooling pipe 40. For example, a refrigerant such as cooling water is passed through this cooling pipe 40. This cooling pipe 40 is arranged in the second spiral groove 23 of the nut 20 and is formed spirally along this second spiral groove 23. As the cooling pipe 40, for example, a copper pipe, a stainless steel pipe, a polyurethane tube, or a nylon tube is used. This cooling pipe 40 is fitted into the second spiral groove 23 and fixed to the nut 20. Note that this cooling pipe 40 may be fixed to the second spiral groove 23 with an adhesive.

[0023] The cooling pipe 40 provided in this nut 20 has an outer diameter that does not contact the screw shaft 10 facing the fixed side in a state of being fixed to the second spiral groove 23. Thereby, the cooling pipe 40 is arranged with a gap from the screw shaft 10.

[0024] FIG. 3 is a cross-sectional view taken along the axial direction of the nut 20 constituting the ball screw device 100 according to the first embodiment. As shown in FIG. 3, the nut 20 has insertion holes 26 with an L-shaped cross section formed at both ends thereof. The insertion holes 26 have a diameter hole portion 26a extending in the radial direction and an axial hole portion 26b extending in the axial direction. Each insertion hole 26 has the diameter hole portion 26a communicating with the second spiral groove 23 and the axial hole portion 26b opening at the end face of the nut 20. The cooling pipe 40 disposed in the second spiral groove 23 of the nut 20 is drawn out to the outside through these insertion holes 26. The cooling pipe 40 drawn out from the end face of the nut 20 to the outside is connected to a cooling source (not shown) such as a cooling water circulation device, and cooling water is circulated through the cooling pipe 40 by the cooling source.

[0025] In the ball screw device 100 having the above configuration, by circulating cooling water through the cooling pipe 40, it is cooled evenly in the axial direction as a whole. Thereby, abnormal load distribution of the balls 30 and deterioration of operability due to thermal deformation of the screw shaft 10 and the nut 20 can be suppressed.

[0026] As described above, according to the ball screw device 100 according to the first embodiment, the space between the rolling paths 32, which are heat generation sources, is cooled by the cooling pipe 40 along the second spiral groove 23, and heat generation in the rolling paths 32 can be suppressed with high cooling efficiency. Abnormal load distribution of the balls 30 and deterioration of operability due to thermal deformation of the screw shaft 10 and the nut 20 can be suppressed, and high accuracy can be maintained as a feed mechanism.

[0027] Moreover, the second spiral groove 23 in which the cooling pipe 40 is arranged can be easily machined when the second thread groove 21 is formed, so the cost can be reduced compared to a structure in which an axially elongated coolant through hole is formed in the nut. Moreover, compared with a structure in which a cooling pipe is arranged in the grinding relief groove, a cooling pipe 40 with a large diameter (about 4 times) is arranged spirally, and the cooling efficiency can be improved significantly (about 4 times or more).

[0028] Moreover, the cooling pipe 40 has an outer diameter that does not contact the screw shaft 10 facing the fixed side in a state of being fixed to the second spiral groove 23. Therefore, interference with the screw shaft 10 facing the fixed side of the cooling pipe 40 can be avoided, and the screw shaft 10 and the nut 20 can be rotated smoothly relative to each other.

[0029] Next, the ball screw device according to the second to fifth embodiments will be described. In addition, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

[0030] (Second Embodiment) FIG. 4 is a cross-sectional view along the axial direction at the boundary portion between the screw shaft 10 and the nut 20 of the ball screw device 200 according to the second embodiment.

[0031] As shown in FIG. 4, in the ball screw device 200 according to the second embodiment, the first spiral groove 13 and the second spiral groove 23 formed with the same pitch P1 as the pitch P1 of the rolling path 32 are formed at positions offset in one axial direction of the ball screw device 200 from the central positions of the first land portion 12 and the second land portion 22. As a result, in a cross-sectional view, the dimension B between the first spiral groove 13 and the rolling path 32 adjacent to one side and the dimension C between the first spiral groove 13 and the rolling path 32 adjacent to the other side are different. Specifically, the dimension C between the first spiral groove 13 and the rolling path 32 adjacent to the other side is made larger than the dimension B between the first spiral groove 13 and the rolling path 32 adjacent to one side. And the cooling pipe 40 is arranged in the second spiral groove 23 of the first spiral groove 13 and the second spiral groove 23 formed at such an offset position.

[0032] In the ball screw device 200 according to this second embodiment, for example, when a large load is always applied to one flank of the rolling path 32, by forming the first spiral groove 13 and the second spiral groove 23 near one flank of the rolling path 32 that receives the large load and arranging the cooling pipe 40, the heat generation occurring in the rolling path 32 can be suppressed more efficiently.

[0033] (Third Embodiment) FIG. 5 is a cross-sectional view along the axial direction of the ball screw device 300 according to the third embodiment. FIG. 6 is a front view and a side view of the ball screw device 300 according to the third embodiment viewed from one end side of the screw shaft 10 constituting the ball screw device 300. FIG. 7 is a side view of a part showing the end structure of the screw shaft 10 of the ball screw device 300 according to the third embodiment in a cross-sectional view.

[0034] As shown in FIG. 5, in the ball screw device 300 according to the third embodiment, a cooling pipe 40 is provided on the screw shaft 10. This cooling pipe 40 is fitted into the first spiral groove 13 and fixed to the screw shaft 10. Note that this cooling pipe 40 may be fixed to the first spiral groove 13 with an adhesive.

[0035] The cooling pipe 40 provided on this screw shaft 10 has an outer diameter that does not contact the nut 20 facing the fixed side in a state of being fixed to the first spiral groove 13. Thereby, the cooling pipe 40 is arranged with a gap from the nut 20.

[0036] As shown in FIG. 6, insertion holes 16 having an L-shaped side view are formed at both ends of the screw shaft 10. The insertion hole 16 has a diameter hole portion 16a extending in the radial direction and an axial hole portion 16b formed at the axis of the screw shaft 10 and extending in the axial direction. In each insertion hole 16, the diameter hole portion 16a communicates with the first spiral groove 13, and the axial hole portion 16b opens at the end face of the screw shaft 10. The cooling pipe 40 disposed in the first spiral groove 13 of the screw shaft 10 is drawn out to the outside through these insertion holes 16.

[0037] As shown in FIG. 7, the cooling pipe 40 drawn out from the end face of the screw shaft 10 is connected to a tube 46 extending from a cooling source such as a cooling water circulation device via a joint portion 45, and cooling water is circulated through the cooling pipe 40 by the cooling source. The joint portion 45 has a cylindrical body 47 connected to the end of the tube 46 and a seal member 48 provided on the side opposite to the connection side of the cylindrical body 47 with the tube 46. The seal member 48 has a seal hole 49 at its center, and the cooling pipe 40 is inserted into this seal hole 49. Then, the cooling pipe 40 is rotatably connected to the joint portion 45 in a sealed state by being inserted into the seal hole 49 of the seal member 48. Thereby, the supply and recovery of cooling water to the cooling pipe 40 of the rotating screw shaft 10 are smoothly performed.

[0038] Also in the case of the ball screw device 300 according to the third embodiment, between the rolling paths 32 which are heat sources, cooling is performed by the cooling pipe 40 along the first spiral groove 13, heat generation in the rolling paths 32 can be suppressed with high cooling efficiency, abnormal load distribution of the balls 30 and deterioration of operability due to thermal deformation of the screw shaft 10 and the nut 20 can be suppressed, and high accuracy can be maintained as a feed mechanism.

[0039] In addition, the first spiral groove 13 in which the cooling pipe 40 is arranged can be easily machined when the first thread groove 11 is formed, so the cost can be suppressed as compared with a structure in which an axially elongated coolant through hole is formed in the nut. Moreover, as compared with a structure in which a cooling pipe is arranged in a grinding relief groove, a cooling pipe 40 with a large diameter (about 4 times) is arranged in a spiral shape, and the cooling efficiency can be improved significantly (about 4 times or more).

[0040] Moreover, the cooling pipe 40 has an outer diameter that does not contact the screw shaft 10 facing the fixed side while being fixed to the first spiral groove 13. Therefore, interference with the nut 20 facing the fixed side of the cooling pipe 40 can be avoided, and the screw shaft 10 and the nut 20 can be rotated smoothly relative to each other.

[0041] (Fourth Embodiment) FIG. 8 is a cross-sectional view along the axial direction at the boundary portion between the screw shaft 10 and the nut 20 of the ball screw device 400 according to the fourth embodiment. As shown in FIG. 8, in the ball screw device 400 according to the fourth embodiment, the screw shaft 10 has no first spiral groove 13, the first land portion 12 is a smooth surface, and the second spiral groove 23 is formed only in the second land portion 22 of the nut 20. And the cooling pipe 40 is fitted and fixed to the second spiral groove 23 of this nut 20. Further, the cooling pipe 40 provided in this nut 20 has an outer diameter that does not contact the screw shaft 10 facing the fixed side while being fixed to the second spiral groove 23. Thereby, the cooling pipe 40 is arranged with a gap from the first land portion 12 of the screw shaft 10.

[0042] According to the ball screw device 400 according to this fourth embodiment, since only the nut 20 is formed with the second spiral groove 23, machining of the first spiral groove 13 on the screw shaft 10 can be made unnecessary, and the manufacturing cost can be reduced.

[0043] In addition, as shown in FIG. 9, as the cooling pipe 40 disposed in the second spiral groove 23, it is preferable that the outer diameter does not protrude from the inner peripheral surface of the second land portion 22 of the nut 20 in which the second spiral groove 23 is formed.

[0044] Also, in the above-described fourth embodiment, the second spiral groove 23 is formed only in the second land portion 22 of the nut 20, and the cooling pipe 40 is disposed in the second spiral groove 23. However, the first spiral groove 13 may be formed only in the first land portion 12 of the screw shaft 10, and the cooling pipe 40 may be disposed in the first spiral groove 13. In this case, the cooling pipe 40 fixed to the screw shaft 10 has an outer diameter that does not contact the nut 20 facing the fixed side in a state of being fixed to the first spiral groove 13, and a gap is provided between the cooling pipe 40 and the second land portion 22 of the nut 20.

[0045] Also, when the cooling pipe 40 is provided on the screw shaft 10 side, as the cooling pipe 40 disposed in the first spiral groove 13, it is preferable that the outer diameter does not protrude from the outer peripheral surface of the first land portion 12 of the screw shaft 10 in which the first spiral groove 13 is formed (see FIG. 9).

[0046] (Fifth Embodiment) FIG. 10 is a cross-sectional view taken along the axial direction at the boundary portion between the screw shaft 10 and the nut 20 of the ball screw device 500 according to the fifth embodiment.

[0047] As shown in FIG. 10, also in the case of the ball screw device 500 according to the fifth embodiment, the second spiral groove 23 is formed only in the second land portion 22 of the nut 20, and the cooling pipe 40 is disposed in the second spiral groove 23. Then, the cooling pipe 40 fixed to the nut 20 has an outer diameter that does not contact the screw shaft 10 facing the fixed side in a state of being fixed to the second spiral groove 23, and a gap is provided between the cooling pipe 40 and the first land portion 12 of the screw shaft 10.

[0048] In this ball screw device 500, the second spiral groove 23 of the nut 20 has a pitch P2 different from the pitch P1 of the rolling path 32. Specifically, the second spiral groove 23 has a pitch P2 larger than the pitch P1 of the rolling path 32. As a result, the dimensions D, E, and F between the second spiral groove 23 and the rolling path 32 adjacent to one side in the axial direction are gradually reduced. That is, the second spiral groove 23 of the nut 20 where the cooling pipe 40 is disposed is configured to gradually approach the rolling path 32 toward one side in the axial direction.

[0049] According to the ball screw device 500 according to this fifth embodiment, when used in a situation where the balance of the load acting in the axial direction gradually increases toward one side in the axial direction, cooling can be performed more effectively.

[0050] In addition, also in the case of the ball screw device 500 according to the fifth embodiment, as shown in FIG. 9, as for the cooling pipe 40 disposed in the second spiral groove 23, it is preferable that the outer diameter does not protrude from the inner peripheral surface of the second land portion 22 of the nut 20 in which the second spiral groove 23 is formed.

[0051] Also, in the fifth embodiment, the second spiral groove 23 is formed only in the second land portion 22 of the nut 20, and the cooling pipe 40 is disposed in the second spiral groove 23. However, the first spiral groove 13 may be formed only in the first land portion 12 of the screw shaft 10, and the cooling pipe 40 may be disposed in the first spiral groove 13. In this case, the cooling pipe 40 fixed to the screw shaft 10 has an outer diameter that does not contact the nut 20 facing the fixed side in a state of being fixed to the first spiral groove 13, and a gap is provided between the cooling pipe 40 and the second land portion 22 of the nut 20.

[0052] Also, when the cooling pipe 40 is provided on the screw shaft 10 side, as for the cooling pipe 40 disposed in the first spiral groove 13, it is preferable that the outer diameter does not protrude from the outer peripheral surface of the first land portion 12 of the screw shaft 10 in which the first spiral groove 13 is formed (see FIG. 9).

[0053] Note that, also in the ball screw devices 100, 200, and 300 according to the first to third embodiments, the first spiral groove 13 and the second spiral groove 23 may be formed so as to have a different pitch P2 from the pitch P1 of the rolling path 32. Also in this case, when used in a situation where the balance of the load acting in the axial direction gradually increases toward one side in the axial direction, cooling can be more effectively performed.

[0054] As described above, the present invention is not limited to the above embodiments, and it is also within the scope of the present invention for those skilled in the art to combine each configuration of the embodiments with each other, make changes and applications based on the description in the specification and well-known techniques, and these are included in the scope for which protection is sought.

[0055] As described above, the following matters are disclosed in this specification. (1) A screw shaft having a spiral screw groove on an outer peripheral surface, a nut having a spiral screw groove on an inner peripheral surface and externally fitted to the screw shaft, a plurality of balls accommodated in a rolling path formed by the screw grooves of the screw shaft and the nut, and a ball screw device comprising: on the screw shaft and the nut, spiral grooves facing each other are formed on land portions between the rolling paths, respectively, and a cooling pipe is disposed in the spiral groove of the screw shaft or the nut. According to this ball screw device, spiral grooves are formed on the land portions of the screw shaft and the nut, and a cooling pipe is disposed in the spiral groove of the screw shaft or the nut. Thereby, the space between the rolling paths, which is a heat generation source, is cooled by the cooling pipe along the spiral groove, and heat generation in the rolling path can be suppressed with high cooling efficiency. It is possible to suppress abnormal load distribution of the balls and deterioration of operability due to thermal deformation of the screw shaft and the nut, and to maintain high accuracy as a feed mechanism. In addition, since the spiral groove for arranging the cooling pipe can be easily machined during the formation of the thread groove, the cost can be suppressed as compared with the structure in which an axially elongated coolant through hole is formed in the nut. Moreover, as compared with the structure in which the cooling pipe is arranged in the grinding relief groove, a cooling pipe with a large diameter (about 4 times) can be arranged spirally, and the cooling efficiency can be improved significantly (about 4 times or more).

[0056] (2) The ball screw device according to (1), wherein the cooling pipe has an outer diameter that does not contact the screw shaft or the nut facing the fixed side while being fixed to the spiral groove. According to this ball screw device, interference with the screw shaft or the nut facing the fixed side of the cooling pipe can be avoided, and the screw shaft and the nut can be rotated relative to each other smoothly.

[0057] (3) The ball screw device according to (1) or (2), wherein the spiral groove is formed at a position biased toward the rolling path adjacent to one side. According to this ball screw device, for example, when a large load is always applied to one side flank of the rolling path, by forming a spiral groove near the flank of the rolling path on the side where the large load is applied and arranging the cooling pipe, the heat generation occurring in the rolling path can be suppressed more efficiently.

[0058] (4) The ball screw device according to any one of (1) to (3), wherein the spiral groove has a pitch different from the pitch of the rolling path. According to this ball screw device, when it is used in a situation where the balance of the load acting in the axial direction gradually increases toward one side in the axial direction, it can be cooled more effectively.

[0059] (5) A ball screw device comprising a screw shaft having a spiral thread groove on an outer peripheral surface, a nut having a spiral thread groove on an inner peripheral surface and externally fitted to the screw shaft, a plurality of balls accommodated in a rolling path formed by the thread grooves of the screw shaft and the nut, and On the screw shaft or the nut, a spiral groove is formed in a land portion between the rolling paths, A ball screw device in which a cooling pipe is disposed in the spiral groove. According to this ball screw device, a spiral groove is formed in the land portion of the screw shaft or the nut, and a cooling pipe is disposed in this spiral groove. Thereby, the space between the rolling paths, which is a heat generation source, is cooled by the cooling pipe along the spiral groove, and heat generation in the rolling paths can be suppressed with high cooling efficiency. Abnormal load distribution of the balls and deterioration of operability due to thermal deformation of the screw shaft and the nut can be suppressed, and high accuracy can be maintained as a feed mechanism. In addition, since the spiral groove in which the cooling pipe is disposed can be easily machined when the screw groove is formed, the cost can be suppressed as compared with a structure in which an axially elongated coolant through hole is formed in the nut. Moreover, as compared with a structure in which a cooling pipe is disposed in a grinding relief groove, a cooling pipe having a large diameter (about 4 times) can be spirally disposed, and the cooling efficiency can be improved significantly (about 4 times or more).

[0060] (6) The ball screw device according to (5), wherein the cooling pipe has an outer diameter that does not contact the screw shaft or the nut facing the fixed side while being fixed to the spiral groove. According to this ball screw device, interference with the screw shaft or the nut facing the fixed side of the cooling pipe can be avoided, and the screw shaft and the nut can be rotated relative to each other smoothly.

[0061] (7) The ball screw device according to (5) or (6), wherein the spiral groove is formed at a position biased toward the rolling path adjacent to one side. According to this ball screw device, for example, when a large load is always applied to one side flank of the rolling path, by forming a spiral groove near the flank of the rolling path on the side receiving the large load and disposing a cooling pipe, heat generation occurring in the rolling path can be suppressed more efficiently.

[0062] (8) The ball screw device according to any one of (5) to (7), wherein the spiral groove has a pitch different from the pitch of the rolling path. According to this ball screw device, when it is used in a situation where the balance of the load acting in the axial direction gradually becomes larger toward one side in the axial direction, it can be cooled more effectively.

Explanation of Signs

[0063] 10 Screw shaft 11 First screw groove (screw groove) 12 First land portion (land portion) 13 First spiral groove (spiral groove) 20 Nut 21 Second screw groove (screw groove) 22 Second land portion (land portion) 23 Second spiral groove (spiral groove) 30 Ball 32 Rolling path 40 Cooling pipe 100, 200, 300, 400, 500 Ball screw device P1, P2 Pitch

Claims

1. A screw shaft having a spiral thread groove on its outer peripheral surface, a nut having a spiral thread groove on its inner peripheral surface and externally fitted onto the screw shaft, a plurality of balls accommodated in a rolling path formed by the thread grooves of the screw shaft and the nut, A ball screw device comprising: on the screw shaft and the nut, spiral grooves facing each other are formed respectively on land portions between the rolling paths, a cooling pipe is disposed in the spiral groove of the screw shaft or the nut. Ball screw device.

2. The cooling pipe has an outer diameter that does not contact the screw shaft or the nut facing the fixed side while being fixed in the spiral groove. The ball screw device according to Claim 1.

3. The spiral groove is formed at a position biased toward the rolling path adjacent to one side. The ball screw device according to Claim 1 or Claim 2.

4. The spiral groove has a pitch different from that of the rolling path. The ball screw device according to any one of Claims 1 to 3.

5. A screw shaft having a spiral thread groove on its outer peripheral surface, a nut having a spiral thread groove on its inner peripheral surface and externally fitted onto the screw shaft, a plurality of balls accommodated in a rolling path formed by the thread grooves of the screw shaft and the nut, A ball screw device comprising: on the screw shaft or the nut, a spiral groove is formed on a land portion between the rolling paths, a cooling pipe is disposed in the spiral groove. Ball screw device.

6. The cooling pipe has an outer diameter that does not contact the screw shaft or the nut facing the fixed side while being fixed in the spiral groove. The ball screw device according to Claim 5.

7. The spiral groove is formed at a position biased toward the rolling path adjacent to one side. The ball screw device according to Claim 5 or Claim 6.

8. The spiral groove has a pitch different from that of the rolling path. The ball screw device according to any one of Claims 5 to 7.

Images