JP2007155010A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for imparting an adequate groove perpendicular sectional shape to a shaft raceway groove of a ball screw device requiring high load and high speed drive in stroke. <P>SOLUTION: The ball screw device 1 comprises a screw shaft 3 having a spiral shaft raceway groove 5 formed in the outer peripheral face, and a nut 9 having a nut raceway groove 10 formed in the inner peripheral face in opposition to the shaft raceway groove 5, the shaft raceway groove 5 being threaded to the nut raceway groove 10 via a plurality of balls 2. One shaft raceway groove 5 of the screw shaft 3 consists of two shaft raceway grooves 5 each having a groove perpendicular sectional shape, namely, a high load shaft raceway groove 5a and a high speed shaft raceway groove 5b, which are connected to each other via a connection portion 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ball screw device used in a feed mechanism for positioning, transporting, and transmitting power of a moving table of a machine device such as a machine tool, an industrial machine, a semiconductor manufacturing apparatus, an injection molding machine, or a press molding machine.

  In a conventional ball screw device that needs to withstand a high axial load such as an injection molding machine or a press molding machine, a shaft raceway groove formed in a spiral shape on the outer peripheral surface of the screw shaft and an inner peripheral surface of the nut The nut raceway groove opposed to the shaft raceway groove formed on the shaft is screwed together via a plurality of balls to constitute a ball screw device. For example, the shaft raceway groove is formed by a Gothic arc groove, and the groove of the shaft raceway groove is formed. The radius of the arc of the rolling arc surface forming the gothic arc groove in the cross-sectional shape perpendicular to the groove (referred to as the cross-sectional shape of the groove) is in the range of 52% to 55% of the ball diameter. The increase in PVmax that occurs in the contact ellipse with the groove is suppressed to extend the life of the ball screw device under a high load (for example, see Patent Document 1).

In addition, in a conventional ball screw device that requires high-speed driving with a relatively low load, such as for positioning in a semiconductor manufacturing device, the shaft raceway groove of the ball screw device having the same configuration as described above is formed by a Gothic arc groove. The arc portion of the rolling arc surface forming the gothic arc groove in the cross-sectional shape of the groove and the shoulder portion of the outer peripheral surface of the screw shaft is chamfered in an arc shape with a radius 1/2 to 2 times the radius of the ball. Smooth connection, the impact force on the arc portion due to the collision of the ball during high-speed operation of the return portion where the ball returns from the communication path to the shaft raceway groove is reduced to prevent damage to the arc portion (for example, Patent Documents) 2).
Japanese Patent Laying-Open No. 2005-3104 (page 3, paragraph 0011 to page 4, paragraph 0016, FIG. 2) JP-A-7-158715 (mainly, page 3, paragraphs 0013-0015, FIG. 1)

  However, in the techniques of Patent Document 1 and Patent Document 2 described above, a ball screw device suitable for high-load and high-speed drive applications of each mechanical device is provided using a shaft raceway groove having a single cross-sectional shape perpendicular to the axis. Therefore, in the case of a ball screw device that is required to be applied to a high load and a high-speed drive at the same time between strokes of the ball screw device, for example, a ball screw device used for mold clamping of an injection molding machine, it is biased to either application A shaft raceway groove or an intermediate shaft raceway groove is used, and there is a problem that the requirements for the ball screw device cannot be properly satisfied.

  That is, in a ball screw device used for mold clamping of an injection molding machine, as shown in the stroke / load diagram in FIG. 10 and the stroke / velocity diagram in FIG. In the stroke range indicated by HS, a low load is required to shorten the cycle time, but high speed driving is required. In the stroke range indicated by HL where mold clamping is performed, a low speed but high load is required so that the mold does not open. It is done.

When the technique of Patent Document 1 is used for such a demand, it operates properly in the stroke range HL, but in the stroke range HS, the return portion has a high speed on the shoulder between the gothic arc groove and the outer peripheral surface of the screw shaft. There is a problem that it is difficult to increase the driving speed because the impact force caused by the collision of the ball with driving tends to cause damage.
Further, when the technique of Patent Document 2 is used, it operates properly in the stroke range HS, but in the stroke range HL, a ball and a gothic arc groove are formed on the arc portion of the shoulder between the gothic arc groove and the outer peripheral surface of the screw shaft. This causes a problem that it is difficult to increase the load for mold clamping.

This results in a reduction in the life of the ball screw device that requires a plurality of characteristics for the stroke at the same time.
The present invention has been made to solve the above-mentioned problems, and provides means for making the right-angle cross-sectional shape of the axial raceway groove of a ball screw device that is required to have a high load, high-speed drive, etc. with respect to the stroke. The purpose is to do.

  In order to solve the above problems, the present invention has a screw shaft in which a spiral shaft raceway groove is formed on the outer peripheral surface, and a nut in which a nut raceway groove facing the shaft raceway groove is formed on the inner peripheral surface. In the ball screw device in which the shaft raceway groove and the nut raceway groove are screwed together via a plurality of balls, a shaft raceway groove having a plurality of groove perpendicular cross-sectional shapes is formed on one shaft raceway groove of the screw shaft. It is provided.

  As a result, the present invention can easily change the required characteristics such as high load and high-speed driving with respect to the stroke of the ball screw device, and the shaft raceway grooves and nuts having a right-angle cross-sectional shape appropriately formed according to the required characteristics. It is possible to form a load path with the raceway groove, and it is possible to obtain an effect that it is possible to extend the life of the ball screw device that requires a plurality of characteristics with respect to the stroke at the same time.

  Embodiments of a ball screw device according to the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view showing a cross section of the ball screw device of the first embodiment, and FIG. 2 is an explanatory view showing a cross-sectional shape perpendicular to the groove of the axial raceway groove of the first embodiment.
In FIG. 1, 1 is a ball screw device.
Reference numeral 2 denotes a ball as a rolling element of the ball screw device 1, which is a sphere made of a steel material such as alloy steel.

Reference numeral 3 denotes a screw shaft of the ball screw device 1, which is a rod-shaped member made of a steel material such as alloy steel, and has a groove perpendicular to the outer circumferential surface thereof formed by a circular arc as shown in FIG. A shaft raceway groove 5 which is a Gothic arc groove in which the two rolling arc surfaces 4a and 4b are circumscribed on the spherical surface of the ball 2 and arranged in a V shape is formed in a spiral shape with a predetermined lead.
The shaft raceway groove 5 of the present embodiment is formed by connecting two shaft raceway grooves 5 formed of the same lead and having a cross-sectional shape perpendicular to the groove through a connecting portion 6, and is one of the screw shafts 3 shown in FIG. In the stroke range HL set at a relatively short range at the end of the shaft, a shaft raceway groove 5 (referred to as a high load shaft raceway groove 5a) made of a gothic arc groove that can withstand a high load is set in a relatively long range. In the stroke range HS, a shaft raceway groove 5 (referred to as a high-speed shaft raceway groove 5b) made of a gothic arc groove that can withstand high-speed driving is formed.

  The high-load shaft raceway groove 5a is adapted so that the arc radius R of the rolling arc surface 4a or 4b shown in FIG. 2 is as close to the radius of the ball 2 as possible so as to be suitable for a high load, and the contact angle α (rolling arc surface 4a, 4b Of the ball 2 and the contact point of the rolling arc surface 4a or 4b circumscribing the spherical surface of the ball 2 and the vertical line drawn from the center C of the ball 2 to the axis CL of the screw shaft 3 (see FIG. 1). In order to prevent the contact ellipse from climbing, the outer peripheral surface of the screw shaft 3 (referred to as the shaft outer peripheral surface 3a) and the rolling arc surface 4a or 4b are used. The chamfer of the shoulder chamfer 7 is reduced to a chamfer start angle β (the vertical line, the connection point between the rolling arc surface 4a or 4b and the chamfer 7 and the center C of the ball 2). Is set to a groove perpendicular cross-sectional shape with a larger angle.

The arc radius R of the high load shaft raceway groove 5a of this embodiment is about 0.51 to 0.52 times the ball diameter Da, the contact angle α is about 45 to 55 degrees, and the chamfering start angle β is 75 degrees or more. Is set.
Further, the high-speed shaft raceway groove 5b sets the arc radius R to be relatively large so as to be suitable for high-speed driving, suppresses the collision of the ball 2 with the chamfered portion 7 as much as possible, makes the contact angle α small, In order to reduce the stress generated at the time of the collision with the chamfered portion 7, the chamfering start angle β is decreased to set the chamfered portion 7 to a groove right-angled cross-sectional shape having the largest R chamfer.

The arc radius R of the high-speed shaft raceway groove 5b of this embodiment is about 0.54 to 0.6 times the ball diameter Da, the contact angle α is about 35 to 45 degrees, and the chamfering start angle β is about 60 to 70 degrees. Is set to
The connecting portion 6 is preferably formed in a stroke range Lc that is one time or less of the lead of the shaft raceway groove 5.
In this case, the right-angle cross-sectional shape of the shaft raceway groove 5 of the connecting portion 6 continuously changes from the right-angle cross-sectional shape of the high-load shaft raceway groove 5a to the right-angle cross-sectional shape of the high-speed shaft raceway groove 5b. The ball pitch circle diameter of the ball brought into contact with the shaft raceway groove 5 of the connecting portion 6 is the ball pitch circle diameter of the shaft raceway groove 5 in another portion, that is, the high load shaft raceway groove 5a and the high speed shaft raceway groove 5b. It is formed to have a smaller diameter.

9 is a nut of the ball screw device 1, which is a cylindrical member made of a steel material such as an alloy steel, and a nut raceway groove having a single right-angle cross-sectional shape formed as a Gothic arc groove on its inner peripheral surface 10 is formed of the same lead as the shaft raceway groove 5.
Reference numeral 11 denotes a mounting portion of the screw shaft 3, which is coaxial with the screw shaft 3 for mounting a mating machine element such as a rolling bearing (not shown) for rotating and supporting the screw shaft 3 and a motor (not shown) for rotating the screw shaft 3. It is a column-shaped or stepped shaft-shaped part provided in the.

  The ball 2 of the present embodiment has an over-diameter that is larger than the diameter of a sphere inscribed in a load path composed of four arcuate surfaces formed by an axial raceway groove 5 and a nut raceway groove 10 which are gothic arc grooves arranged opposite to each other. A ball of a size is configured such that an appropriate preload is applied to the ball screw device 1 when the axial raceway groove 5 and the nut raceway groove 10 which are opposed to each other are screwed together via the ball 2.

A load path on which the ball 2 rolls is formed by the shaft raceway groove 5 and the nut raceway groove 10 arranged opposite to each other, and both ends thereof are communicated by a return tube as a communication path (not shown) to form a circulation path. The
The circulation path is filled with a plurality of balls 2 and a predetermined amount of lubricant, for example, grease, and the shaft raceway groove 5 and the nut raceway groove 10 are screwed together with a preload applied through the balls 2. As the screw shaft 3 rotates, the ball 2 circulates in the circulation path, and the ball 2 rolling on the load path supports the load applied to the nut 9 so as to be able to reciprocate. It is supported so that it can reciprocate linearly along the longitudinal direction. Thereby, the rotational motion of the screw shaft 3 is converted into the linear motion of the nut 9.

  If comprised as mentioned above, in the stroke range HL required to endure a high load, a load path is formed by the high load shaft raceway groove 5a of the screw shaft 3 and the nut raceway groove 10 of the nut 9. In the stroke range HS in which the load capacity for tightening and the like can be increased and the high-speed driving is required, the load path is formed by the high-speed shaft raceway groove 5b of the screw shaft 3 and the nut raceway groove 10 of the nut 9. The chamfered portion 7 is damaged even if an impact force due to the collision of the ball due to high-speed operation is applied to the chamfered portion 7 of the high-speed shaft raceway groove 5b at the return portion of the ball 2 from the return tube (not shown). It does not occur, and the operating speed of the ball screw device 1 can be increased.

  Further, the stroke range Lc of the connecting portion 6 is formed by continuously changing the shape from the cross-sectional shape of the high-load shaft raceway groove 5a to the cross-sectional shape of the high-speed shaft raceway groove 5b. Therefore, the ball 2 guided to the nut raceway groove 10 of the nut 9 is smoothly passed from the high load shaft raceway groove 5a to the high speed shaft raceway groove 5b or in the opposite direction while maintaining the spiral arrangement. Can do.

  As described above, in this embodiment, one shaft raceway groove of the screw shaft is formed by connecting two shaft raceway grooves having a cross-sectional shape perpendicular to the groove, whereby the stroke of the ball screw device. It is possible to easily change the required characteristics of high load and high-speed drive, and to form a load path with the axial raceway groove and nut raceway groove with a right-angle cross-sectional shape appropriately formed according to the required characteristics In addition, it is possible to extend the life of the ball screw device that requires a plurality of characteristics for the stroke at the same time.

  In addition, the cross-sectional shape at right angles to the groove is two, one of which is a high-load shaft raceway groove formed at the end of the screw shaft, and the other is a high-speed shaft raceway groove connected to this high-load shaft raceway groove. Therefore, in the stroke range HL where the high load shaft raceway groove is formed, the load capacity of the load path formed with the nut raceway groove is increased, and in the stroke range HS where the high speed shaft raceway groove is formed, the nut raceway groove is formed. It is possible to increase the operation speed of the ball screw device by preventing damage due to the collision of the ball due to the high speed operation of the chamfered portion at the return portion of the axial raceway groove of the load path formed by.

  This is particularly effective as a ball screw device for mold clamping.

FIG. 3 is an explanatory view illustrating a side surface of the screw shaft according to the second embodiment.
In addition, the same part as the said Example 1 attaches | subjects the same code | symbol, and abbreviate | omits the description.
The shaft raceway groove 5 of the screw shaft 3 of the present embodiment is similar to the above-described embodiment 1 in that the high-speed shaft raceway groove 5a formed in the stroke range HL and the high-speed shaft raceway shape formed in the stroke range HS. The shaft raceway groove 5b is configured to be connected to the cross-sectional shape perpendicular to the groove through the connecting portion 6, but the configuration of the connecting portion 6 is different.

In FIG. 3, reference numeral 15 denotes a relief groove, which is a relief of a grinding wheel at the time of groove grinding formed in the circumferential direction of the connecting portion 6 of the shaft raceway groove 5, and is a bottom surface 16 parallel to the axial direction of the screw shaft 3. And an annular groove having a rectangular cross-sectional shape formed over the entire circumference in the circumferential direction of the screw shaft 3 constituted by both ends of the bottom surface 16 and a plane 17 orthogonal to the axial direction.
The diameter of the bottom surface 16 (referred to as the bottom diameter Dc) is such that the ball 2 guided in the nut raceway groove 10 of the nut 9 passing through the stroke range Lc is maintained in a spiral arrangement while maintaining a spiral arrangement. In order to smoothly pass from the groove 5a to the high-speed shaft raceway groove 5b or in the opposite direction, the ball pitch diameter of the ball 2 and the diameter Da of the ball 2 and a predetermined clearance allowance (0% of the diameter Da of the ball 2) Larger and less than 25% length).

  When the predetermined clearance for forming the bottom diameter Dc is 0% or less of the diameter Da of the ball 2, that is, if the bottom diameter Dc is too large, the ball 2 passes from one of the two shapes of the axial raceway grooves 5 to the other. If the predetermined clearance margin is larger than 25% of the diameter Da of the ball 2, that is, if the bottom diameter Dc is too small, the ball 2 is displaced in the radial direction and cannot maintain the spiral arrangement. This is because it may be difficult to smoothly pass from one to the other.

In this case, it is desirable to make the stroke range Lc, which is the axial width of the relief groove 16, as narrow as possible within the range that can be used as relief when grinding the shaft raceway groove 5. This is because if the stroke range Lc is too large, the number of balls 2 that receive a load when the nut 9 passes through the stroke range Lc decreases.
Specifically, if the stroke range Lc is set to be twice or less of the lead of the shaft raceway groove 5, grinding of the shaft raceway grooves 5 of the high load shaft raceway groove 5a and the high speed shaft raceway groove 5b is facilitated. It is possible to suppress the decrease in the number of balls 2 that receive a load when the nut 9 passes through the stroke range Lc.

As described above, in this embodiment, in addition to the same effects as in the first embodiment, the escape groove which is an annular groove having a rectangular cross-sectional shape over the entire circumference in the circumferential direction at the coupling portion of the shaft raceway groove. By forming the shaft raceway grooves, the shaft raceway grooves for the high load and the shaft raceway grooves for the high speed can be easily formed by grinding.
Further, by setting the bottom diameter of the escape groove to a diameter obtained by subtracting the ball diameter Da and the predetermined clearance margin from the ball pitch circle diameter of the ball, the escape groove is guided to the nut raceway groove of the nut passing through the stroke range Lc of the connecting portion. The balls can be smoothly passed from the high load shaft raceway groove to the high speed shaft raceway groove or in the opposite direction while maintaining the spiral arrangement.

4 is an explanatory view showing the side surface of the screw shaft of Example 3, FIG. 5 is an explanatory view showing a cross section along the AA cross section line of FIG. 4, and FIG. 6 is along the BB cross section line of FIG. It is explanatory drawing which shows a cross section.
In addition, the same part as the said Example 1 and Example 2 attaches | subjects the same code | symbol, and abbreviate | omits the description.
The shaft raceway groove 5 of the screw shaft 3 of the present embodiment is similar to the embodiment 1 in that the high-load shaft raceway groove 5a formed in the stroke range HL and the high-speed shaft raceway shape formed in the stroke range HS. The shaft raceway groove 5b is connected to the groove perpendicular cross-sectional shape via the connecting portion 6, and the escape groove is formed in the connecting portion 6 as in the second embodiment. Different.

  In FIG. 4, reference numeral 21 denotes a relief groove, which is a relief of a grinding wheel at the time of groove grinding formed along the groove of the shaft raceway groove 5. As shown in FIG. 5, the shaft raceway groove 5 is formed in an arcuate cross-sectional shape including the groove width W of the groove perpendicular cross-sectional shape inside, and the bottom diameter Dc of the groove bottom is the same as that of the second embodiment. Is formed. In this case, it is desirable that the valley diameter of the cross-sectional shape of the shaft raceway groove 5 is equal to the bottom diameter Dc.

Further, as shown in FIG. 6, a chamfer 23 along the groove is formed at the corner of the stepped portion 22 with the shaft groove 5 at both ends of the clearance groove 21 in the cross section along the groove of the shaft groove 5. Is formed. The chamfer 23 in this embodiment is a C chamfer.
The stroke range Lc of the escape groove 21 is set to a range as narrow as possible that can be used as a relief when grinding the shaft raceway groove 5 within a range of 1 times or less of the lead of the shaft raceway groove 5. With this setting, the shaft raceway grooves 5 of the high load shaft raceway groove 5a and the high speed shaft raceway groove 5b can be easily ground and the nut 9 passes through the stroke range Lc. It is possible to further suppress a decrease in the number of balls 2 that receive a load of.

  If the relief groove 21 having the bottom diameter Dc equivalent to the valley diameter of the groove perpendicular to the axial raceway groove 5 is formed in the connecting portion 6 of the shaft driving groove 5, the axial direction of the nut 9 of the ball screw device 1 is achieved. When a seal body (not shown) having a tip along the groove of the shaft raceway groove 5 is provided at both ends of the shaft raceway, the tip end of the seal body is a clearance between the valley portion of the shaft raceway groove 5 and the connecting portion 6. It is possible to smoothly slide on the groove bottom of the groove 21 and to prevent foreign matter from entering the nut 9 and leakage of the lubricant to the outside. This is particularly effective in the case of the ball screw device 1 having a seal body.

  Further, since the chamfer 23 is provided at the corner portion of the step portion 22 with the shaft raceway groove 5, the ball 2 that has rolled while receiving one load on the shaft raceway groove 5 in the stroke range Lc of the connecting portion 6. When the ball enters the escape groove 21, the load is once released, and then, when the ball enters the other shaft raceway groove 5 and rolls again, the stepped portion 22 can be smoothly passed over. The corner portion of the stepped portion 22 is not damaged due to the collision.

Such a chamfer 23 is the same when the chamfer 23 is provided in the escape groove 15 of the second embodiment.
As described above, in the present embodiment, the same effect as in the second embodiment can be obtained also by forming a relief groove having an arcuate cross-sectional shape along the axial raceway groove of the screw shaft.
In addition, in the case of a ball screw device in which a seal body is provided at both ends of the nut by forming the bottom diameter Dc of the escape groove equal to the valley diameter of the cross section of the shaft raceway groove, the seal body The tip can smoothly slide on the bottom of the escape groove of the connecting portion, and foreign matter can be prevented from entering the nut and leakage of the lubricant to the outside.

  Furthermore, by forming a chamfer at the corner of the cross section along the groove of the axial raceway groove between the axial raceway groove and the escape groove, the stroke range Lc of the connecting portion passes through the escape groove from one axial raceway groove. The ball entering the other shaft raceway groove can smoothly get over the stepped portion, prevent damage to the corner of the stepped portion, and extend the life of the ball screw device that requires multiple characteristics for the stroke at the same time. Can be planned.

In the present embodiment, the chamfer 23 provided in the stepped portion 22 has been described as being a C chamfer, but may be an R chamfer shown in FIG. Even in this way, the corners can be prevented from being damaged due to the collision of the ball with the stepped portion 22.
Further, as shown in FIG. 8, the direction toward the escape groove 21 along the groove line at the corner of each stepped part 22 on both sides of the cross section along the groove line of the shaft track groove 5 with the shaft track groove 5. You may make it provide the crowning 25 dug deeply gradually. If such a crowning 25 is provided, an edge load generated in the shaft raceway groove 5 can be effectively prevented.

This crowning 25 is used for the high load at the corner of the connecting portion between the shaft raceway groove 5 in the connecting portion 6 of the first embodiment and the high load shaft raceway groove 5a and the high speed shaft raceway groove 5b connected thereby. Even if it forms as the crowning 25 which goes to the connection part 6 along the groove of the shaft track groove 5a and the high-speed shaft track groove 5b, the edge load which arises in the shaft track groove 5 can be prevented effectively.
Further, as shown in FIG. 9, a chamfer 23 having a C chamfering or an R chamfering may be provided on the clearance groove 21 side of the crowning 25. In this way, damage to the corners and edge loading due to ball collision can be prevented at the same time.

  In each of the above-described embodiments, the shaft raceway groove is described as being formed by connecting two groove perpendicular cross-sectional shapes of the high load shaft raceway groove and the high speed shaft raceway groove. Even in this case, the required characteristics for the stroke of the ball screw device can be easily changed by connecting between three or more perpendicular cross-sectional shapes of the grooves via the connecting portions in the same manner as described above. A load path according to the required characteristics can be formed by the shaft raceway groove and the nut raceway groove having a right-angle cross-sectional shape.

In each of the above embodiments, the case where the present invention is applied to a ball screw device using a tube-type circulation system in which a ball is circulated using a return tube as a communication path has been described as an example. However, the communication path is not limited to the above. Even if the present invention is applied to a circulation type ball screw device in which the communication path is a top type or an end cap type, the same effect can be obtained.
In this embodiment, the screw shaft of the ball screw device is rotated and the nut is moved in the axial direction. However, the present invention is applied to a ball screw device of the type in which the nut is rotated and the screw shaft is moved in the axial direction. Even if the invention is applied, the same effect can be obtained.

Explanatory drawing which shows the cross section of the ball screw apparatus of Example 1. Explanatory drawing which shows the groove | channel perpendicular | vertical cross-sectional shape of the axial track groove of Example 1. FIG. Explanatory drawing which shows the side surface of the screw shaft of Example 2. Explanatory drawing which shows the side surface of the screw shaft of Example 3. Explanatory drawing which shows the cross section along the AA cross section line of FIG. Explanatory drawing which shows the cross section along the BB cross section line of FIG. Explanatory drawing which shows the other form of chamfering of Example 3. Explanatory drawing which shows the other form of the level | step-difference part of Example 3. Explanatory drawing which shows the other form of the level | step-difference part of Example 3. Stroke and load diagram of ball screw device used for mold clamping Stroke / speed diagram of ball screw device used for mold clamping

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 2 Ball 3 Screw shaft 3a Shaft outer peripheral surface 4a, 4b Rolling circular arc surface 5 Shaft raceway groove 5a High load shaft raceway groove 5b High speed shaft raceway groove 6 Connection part 7 Chamfering part 9 Nut 10 Nut raceway groove DESCRIPTION OF SYMBOLS 11 Mounting part 15, 21 Escape groove 16 Bottom face 17 Plane 22 Level difference part 23 Chamfering

Claims (9)

A screw shaft having a spiral shaft raceway groove formed on an outer peripheral surface; and a nut having a nut raceway groove formed on an inner peripheral surface opposed to the shaft raceway groove, wherein the shaft raceway groove and the nut raceway groove are plural. In the ball screw device screwed through the ball,
A ball screw device, wherein a single shaft raceway groove of the screw shaft is provided with a plurality of shaft raceway grooves having a cross-sectional shape perpendicular to the groove. In claim 1,
A ball screw device characterized in that the groove has a right-angle cross-sectional shape of two, one is a high-load shaft raceway groove, and the other is a high-speed shaft raceway groove connected to the high-load shaft raceway groove. In claim 1 or claim 2,
The plurality of shaft raceway grooves are connected to each other via a connecting portion in which a ball pitch circle diameter of a ball brought into contact with the shaft raceway grooves is smaller than a ball pitch circle diameter of the plurality of shaft raceway grooves. Ball screw device to play. In claim 3,
A ball screw characterized by forming a crowning shape toward the connecting portion along a groove of the plurality of shaft raceway grooves at a connection portion between the shaft raceway groove of the connecting portion and the plurality of shaft raceway grooves. apparatus. In claim 1 or claim 2,
A ball screw device, wherein a relief groove having a bottom diameter obtained by subtracting a diameter of the ball and a predetermined clearance from the ball pitch circle diameter of the ball is formed in the shaft raceway groove. In claim 5,
2. The ball screw device according to claim 1, wherein the escape groove is an annular groove having a rectangular cross-sectional shape formed over the entire circumference in the circumferential direction of the screw shaft. In claim 5,
2. The ball screw device according to claim 1, wherein the relief groove is a groove having an arcuate cross-sectional shape formed along the axial raceway groove of the screw shaft. In any one of Claims 5 thru | or 7,
A ball screw device, wherein a chamfer is formed at a corner of a cross section along the groove of the shaft raceway groove between the shaft raceway groove and the escape groove. In any one of Claims 5 thru | or 8,
A ball screw device, wherein a crowning shape toward the escape groove is formed at a corner of a cross section of the axial raceway groove and the escape groove along a groove of the axial raceway groove.