JP2007127284A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device of high work efficiency and durability, capable of being properly used for a small lead screw of a narrow clearance between thread grooves, and a multiple thread screw. <P>SOLUTION: In this ball screw device 30 having a ball circulation groove 21 making a load raceway formed between a thread groove 12 of a screw shaft 13 communicate with a thread groove 14 of a nut 16 for rolling a number of balls 15, and a ball return passage 17 of the nut 16, comprising a circulation piece 40 fitted to the end face of the nut 16, and a tongue 20 mounted on the tip of the ball circulation groove 21 in a state of being fitted to the thread groove 12 for scooping the balls 15 rolling between both thread grooves 12, 14, an axial inner part of the nut 16 of the ball circulation groove 21 including the tongue portion 20 of the circulation piece 40 is cut out. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ball screw device suitable for use in, for example, industrial machines and the like, particularly when high rigidity, long life, high speed feed and low noise are required.

As a conventional ball screw device of this type, for example, the one shown in FIGS. 9 and 10 is known (see German Utility Model Publication DE 2437497).
The ball screw device 10 includes a screw shaft 13 having a spiral thread groove 12 on the outer peripheral surface and extending in the axial direction, and a nut having a screw groove 14 corresponding to the screw groove 12 of the screw shaft 13 on the inner peripheral surface. 16, and the screw groove 14 of the nut 16 and the screw groove 12 of the screw shaft 13 are opposed to each other to form a spiral load track. A large number of balls 15 as rolling elements are slidably loaded on the load track, and the nut 16 (or screw shaft 16) causes the balls 15 to roll by rotation of the screw shaft 13 (or nut 16). It moves in the axial direction.

By the way, when the nut 16 (or the screw shaft 13) moves in the axial direction, the ball 15 moves while rolling on the spiral load track formed by the two screw grooves 12, 14, but the nut 16 ( Alternatively, in order to continuously move the screw shaft 13), it is necessary to circulate the ball 15 infinitely.
As a system for circulating the ball infinitely, a circulation tube type, an end cap type, or the like is generally used. In a compact type ball screw device, a ball return passage 17 penetrating in the axial direction is formed in the nut 16, and the nut 16 A notch 19 is formed on the end face of the stub, and a notch 19 is fitted with a circulating top 18 that communicates the ball return passage 17 and the load track between the screw grooves 12 and 14 so that the circulating top 18 is a nut. It is fixed to 16 with screws or retaining rings.

  The circulation top 18 is made of, for example, a synthetic resin molded product, and has a curved shape that communicates between the ball return passage 17 and the load track between the screw grooves 12 and 14 as shown in FIGS. A ball circulation groove (ball circulation path) 21 and a ball which is provided at the tip of the ball circulation groove 21 and is fitted to the screw groove 12 of the screw shaft 13 to roll on the load track between the screw grooves 12 and 14. And a tongue portion 20 for scooping up 15. The ball circulation groove 21 including the tongue 20, the load trajectory between the screw grooves 12 and 14, and the ball return passage 17 form an infinite circulation passage of the ball 15.

In the conventional ball screw device described above, the circulating top 18 is axially pushed into the notch 19 from the end face side of the nut 16 to be fitted, so that both sides of the nut 16 of the ball circulating groove 21 including the tongue 20 in the axial direction. Are provided with meat portions, and the end surfaces of the meat portions on both sides are parallel to each other along a plane perpendicular to the axis.
However, with such a shape of the circulating top 18, in the case of a small lead screw having a narrow space between the thread grooves or a multi-threaded screw, as shown in FIG. Since the ball 15 interferes with the flesh of the inner part, adaptation becomes difficult, and for the same reason, it is also difficult to increase the ball diameter and increase the dynamic load rating.

Further, if the width B of the circulating top 18 (see FIG. 12A) is shortened in order to adapt to the small lead screw, the path bending R (see FIG. Since b)) becomes smaller, the ball 15 may be bent suddenly and there may be a problem in the operability and durability of the apparatus.
The present invention has been made to eliminate such inconveniences, and can be suitably used for small lead screws having a narrow space between screw grooves and multi-threaded screws, and has excellent operability and durability. Another object is to provide a ball screw device.

  In order to achieve the above object, an invention according to claim 1 includes a screw shaft having a helical thread groove on an outer peripheral surface, and a thread groove corresponding to the screw groove of the screw shaft on an inner peripheral surface and in an axial direction. A ball return passage that penetrates the screw shaft and a nut that is loosely fitted to the screw shaft, and a ball circulation passage that communicates between the two screw grooves and the ball return passage, and is fitted to the end face of the nut. And a plurality of balls loaded so as to be able to circulate between the screw grooves, the ball return passage and the ball circulation path, and the circulation top at the tip of the ball circulation path. In the ball screw device comprising a tongue portion that scoops up the ball that is fitted in the screw groove of the screw shaft and rolls between the two screw grooves, the ball circulation path including the tongue portion in the circulation top Nut axially inside It was excised minutes, instead of as part of the ball circulation path of the cut portion, and performs a screw groove provided on the nut side.

The invention according to a second aspect is characterized in that, in the first aspect, a projection is provided in addition to the ball circulation path of the circulation top, and a recess into which the projection is fitted is provided in the nut.
According to a third aspect of the present invention, in the first or second aspect, the length of the tongue portion along the screw groove of the back surface facing the screw groove side of the screw shaft is 1.5 times or more the radial dimension of the ball. It is characterized by being 10 times or less.

  The invention according to claim 4 has a screw shaft having a helical thread groove on the outer peripheral surface, and a ball return passage having a thread groove corresponding to the screw groove of the screw shaft on the inner peripheral surface and penetrating in the axial direction. A nut that is loosely fitted to the screw shaft, a circulation top that has a ball circulation path that communicates between the two screw grooves and the ball return passage, and is fitted to an end face of the nut; A plurality of balls loaded so as to be able to circulate while rolling between the balls, the ball return path and the ball circulation path, and fitted into a thread groove of the screw shaft at the tip of the ball circulation path. In the ball screw device having a tongue portion that scoops up the ball that rolls between both screw grooves, the tongue portion has a cross-sectional area on the base end side of the back portion facing the screw groove side of the screw shaft of the tongue portion. The cross-sectional area of the tip is reduced and the tongue The tip, characterized in that the non-contact to the screw groove of the screw shaft

  As is apparent from the above description, according to the present invention, the ball can be prevented from interfering with the circulation top even in the case of a small lead screw having a narrow space between the screw grooves or a multi-thread screw. In addition, it can be suitably used for small lead screws with narrow gaps between thread grooves and multi-threaded screws, and it is also possible to increase the dynamic load rating by increasing the ball diameter. The effect that the operability and durability can be improved is obtained.

Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view of a ball screw device as an example of an embodiment of the present invention viewed from the axial direction, FIG. 2A is a right side view of FIG. 1, and a partial cross-sectional view taken along line XX of FIG. FIG. 2 (b) is a diagram showing a state before the circulation top of FIG. 2 (a) is mounted, FIG. 3 is a diagram showing the circulation top, (b) is a front view, and (a) is (b). 4C is a right side view of FIG. 4B, FIG. 4 is a perspective view of the circulating top of FIG. 3, FIG. 4A is a view seen from the back side of the tongue portion, and FIG. FIG. 5 is a diagram viewed from the groove side, FIG. 5 is an explanatory diagram for explaining the function and effect of the present invention, FIG. 6 is a graph diagram showing the relationship between tongue portion rear surface length L / ball diameter Dw and acoustic energy ratio, FIG. FIG. 8 is a perspective view showing a modified example of the circulating top, and FIG. 8 is an explanatory cross-sectional view for explaining the difference between the tongue portion distal end shape and the tongue portion proximal end side rear surface shape. In addition, about the part which overlaps with the prior art example shown in FIG. 9 and FIG. 10, the same code | symbol is attached | subjected and demonstrated to each figure.

As shown in FIGS. 1 and 2, the ball screw device 30 corresponds to a screw shaft 13 having a spiral thread groove 12 on the outer peripheral surface and extending in the axial direction, and to the screw groove 12 on an inner peripheral surface. A nut 16 having a thread groove 14 is fitted.
The screw groove 14 of the nut 16 and the screw groove 12 of the screw shaft 13 are opposed to each other to form a spiral load raceway between which a large number of balls 15 as rolling elements are rolled. It is loaded movably. The nut 16 (or the screw shaft 13) is moved in the axial direction via the rolling of the ball 15 by the rotation of the screw shaft 13 (or the nut 16).

  In order to reduce the noise between the balls 15 of a large number of balls 15 rolling on the load trajectory between the screw grooves 12 and 14 by eliminating the collision noise between the balls during driving, You may interpose the holding piece which has concave surfaces, such as circular arc shape, in the both opposing side surfaces, respectively. This holding piece may be either a type in which the holding pieces are interposed between the balls 15 or a type in which the holding pieces are connected to each other.

A ball return passage 17 penetrating in the axial direction is formed in the wall portion of the nut 16, and circulating tops 40 shown in FIGS. 3 and 4 are fitted to both end surfaces of the nut 16 with a predetermined tightening allowance. A notch 41 is formed in communication with the load track between the ball return passage 17 and the screw grooves 12 and 14.
The circulating top 40 is made of, for example, a synthetic resin molded product, and has a curved shape that communicates between the ball return passage 17 and the load track between the screw grooves 12 and 14, as shown in FIGS. A ball circulation groove (ball circulation path) 21 and a ball 15 provided at the tip of the ball circulation groove 21 and fitted on the screw groove 12 of the screw shaft 13 to roll on the load track between the two screw grooves 12 and 14. And a tongue section 20 for scooping up An infinite circulation path of the ball 15 is formed by the tongue portion 20, the ball circulation groove 21, the load track between the screw grooves 12 and 14, and the ball return path 17.

In a state where the circulating top 40 is fitted and fixed to the notch 41, the circulating top 40 is restrained in the notch 41 in the radial direction and the circumferential direction.
Here, in this embodiment, a meat part is provided on the outer side in the axial direction of the nut 16 of the ball circulation groove 21 including the tongue part 20, and an end surface of the meat part is a surface along a direction perpendicular to the axis, The flesh portion of the inner portion in the axial direction of the nut 16 of the ball circulation groove 21 including the tongue portion 20 is cut off.

  Thereby, even in the case of a small lead screw having a narrow space between the thread grooves or a multi-thread screw, it is possible to avoid the ball 15 from interfering with the circulating top 40 as schematically shown in FIG. As a result, it can be suitably used in the case of a small lead screw having a narrow space between the thread grooves and a multi-thread screw, and it is also possible to increase the dynamic load rating by increasing the ball diameter. The operability and durability of the device can also be made excellent.

  Incidentally, in this embodiment, the ball diameter / thread groove pitch can be accommodated up to about 0.8. In the case of a screw shaft diameter of 40 mm, a lead of 30 mm, and a double thread, the ball diameter is 5 in the conventional circulating top 18. It was confirmed that the ball diameter can be accommodated up to about 7.14 mm in the circulating top 40 of the present embodiment, whereas it could only cope up to about .5 mm. Thereby, the dynamic load rating can be increased by about 40% from 43700N to 61000N, and the life can be improved to about 2.7 times the conventional one.

  In this embodiment, the flesh portion of the inner side of the nut 16 in the axial direction of the nut 16 of the ball circulation groove 21 including the tongue portion 20 of the circulation top 40 is cut out, and a part of the ball circulation groove 21 in the cut portion is removed. As a guide, a guide screw groove (see FIG. 2B) continuous from the screw groove 14 of the nut 16 is formed on the nut 16 side, and the guide screw groove and the ball circulation groove 21 of the circulation top 40 are formed. Thus, the ball 15 picked up by the tongue portion 20 is guided to the ball return passage 17.

  It is desirable that the guide thread groove be a smooth path connecting the thread groove 14 of the nut 16 and the ball return passage 17. Further, it is desirable that the joint between the guide screw groove and the screw groove (spiral path) 14 of the nut 16 should have as few steps as possible. The size of this step needs to be determined from the relationship between the scooping angle and the circulation path diameter, but if it is 3% or less of the ball diameter (step of 0.2 mm or less for φ6.35 mm steel balls), the noise will be reduced. This is advantageous.

The main purpose of the circulating top 40 is to scoop up the ball 15 from the load trajectory between the screw grooves 12 and 14 and change the direction of movement of the ball 15 to the ball return passage 17 of the nut 16. The ball 15 receives a reaction force that changes direction and receives a rotational force. Therefore, a fixing force is required to counter this rotational force.
In this embodiment, as described above, since the meat part of the inner part in the axial direction of the nut 16 of the ball circulation groove 21 including the tongue part 20 of the circulation top 40 is cut out, in order to obtain such a fixing force. In addition, the back surface of the tongue 20 is disposed in the thread groove 12 of the screw shaft 13 until light contact or fine clearance, and a strip-shaped protruding piece (protrusion) extending in the circumferential direction of the nut 16 on the end face side of the nut 16 of the circulating top 40. 50 and the protruding piece 50 is fitted into a recess 51 provided on the end face of the nut 16 with a predetermined tightening allowance.

  Here, the back surface portion of the tongue portion 20 includes the side facing the groove surface of the screw groove 12 of the portion protruding from the screw groove 12 of the screw shaft 13 in order to scoop up the ball 15, and along the screw groove 12. A portion having substantially the same shape as the formed screw groove 12 is said. In addition, in the rotational direction of the circulating top 40, the rotational direction is fixed by light contact with the screw groove 12 on the back surface of the tongue portion 20 or by the arrangement of a minute gap, and also fixed in the thread groove direction. A piece 50 is provided.

Further, the fixing force at the back surface of the tongue portion 20 is important. In this case, it is preferable that the clearance between the screw shaft 13 on the back surface of the tongue portion and the thread groove 12 is 1 to 10% of the ball diameter Dw. Considering the thermal expansion of the circulating top 40, it is optimal to set it to 3 to 5% of the ball diameter.
Furthermore, the length L (see FIG. 4A) along the screw groove 12 on the back surface of the tongue 20 is also important. In order to scoop up the ball 15, the thickness of the tip of the tongue portion 20 may be about 30% of the ball diameter as in the tube tongue of the tube circulation type ball screw device. The circulation top 40 is fixed so as not to rotate by extending the back surface portion of the tongue portion 20 along the screw groove 12 of the screw shaft 13 and making the back surface portion of the tongue portion 20 lightly contact or slightly gap the screw groove 12. is doing.

At this time, the length L along the thread groove 12 on the back surface of the tongue 20 is 1. 5 to 10 times is preferable. FIG. 6 shows the relationship between the length L / ball diameter Dw of the tongue portion rear surface portion and the acoustic energy ratio.
In the acoustic test, sound pressure was measured with a microphone at a height of 400 mm from the axis at the center of the measurement stroke. The measurement uses an A filter. In addition, the vertical axis of FIG. 6 is expressed as a relative value where the acoustic energy ratio is 1 when the length L of the tongue portion / the ball diameter Dw is 1.

The test conditions are as follows.
Test ball screw device: Model number NSK ball screw 40 × 40 × 1000C5 (ball diameter 7/32 inch) manufactured by NSK Ltd.
Test machine name: NSK Ltd., ball screw acoustic measurement tester Preload: 500N
Test load (acceleration load): 750 to 1500 N
Maximum rotational speed: 3000 min ^-1
Stroke: 500mm
Lubrication: Oil VG # 68
As is apparent from FIG. 6, when the length L / ball diameter Dw of the tongue portion is less than 1.5 and the length L of the tongue portion is short, the noise increases, and the length L of the tongue portion back portion is the ball. It can be seen that the noise is greatly reduced when the diameter Dw is 1.5 times or more. However, even if it is 10 times or more, the effect is not changed only by increasing the length of the nut, so 1.5 times or more and 10 times or less are desirable.

  In the case of a small lead ball screw device, the value of the length L of the tongue portion / the ball diameter Dw can be relatively large. Further, when the pitch between the thread grooves is small, as shown in FIG. 7, the convex portion 60 fitted to the screw groove 12 adjacent to the screw groove 12 fitted to the rear face portion of the tongue portion on the end face side of the nut 16 is provided. It may be provided in the circulation top 40 to increase the fixing force. The same applies to the case of a multi-thread screw, and in the case of a multi-thread screw, a thread groove 12 having an adjacent pitch that is not used can be used.

  Further, the tip shape of the tongue portion 20 is important in order to smoothly lift the ball 15 from the screw groove 12 of the screw shaft 13. In this embodiment, in order to avoid the tip of the tongue portion 20 from coming into contact with the screw groove 12 of the screw shaft 13 and being damaged when the ball screw device is driven, the tip of the tongue portion 20 should not be in contact with the screw groove 12. Specifically, as shown in FIG. 8, the area of the groove perpendicular section at the distal end of the tongue section 20 is made smaller than the area of the groove perpendicular section of the back face section on the proximal end side of the tongue section 20. The tip is prevented from directly hitting the thread groove 12. That is, even if the rear surface portion on the proximal end side of the tongue portion 20 comes into contact with the screw groove 12, the tip of the tongue portion 20 does not hit the screw groove 12.

  However, the fact that the tip of the tongue 20 is close to the thread groove 12 is important for scooping up the ball 15, and this leads to low noise, so the length of the tip of the tongue 20 is the length of the tongue 20. It may be longer than the back part. Also in this case, it is necessary to consider the cross-sectional shape of the back surface portion of the tongue portion 20 so that the front end of the tongue portion 20 does not directly contact the screw groove 12 and is not damaged.

  Note that the configurations of the screw shaft, nut, circulating top, protrusion, and recess of the ball screw device of the present invention are not limited to the above-described embodiments, and can be appropriately changed without departing from the gist of the present invention. .

It is explanatory drawing which looked at the ball screw apparatus which is an example of embodiment of this invention from the axial direction. (A) is a right side view of FIG. 1, partially showing a cross-sectional view taken along line XX of FIG. 1, (b) is a diagram showing a state before the circulating top of (a) is mounted. It is a figure which shows an example of a circulation top, (b) is a front view, (a) is a left view of (b), (c) is a right view of (b). It is the perspective view of the circulation top of FIG. 3, (a) is the figure seen from the back side of the tongue part, (b) is the figure seen from the ball circulation groove side. It is explanatory drawing for demonstrating the effect of this invention. It is a graph which shows the relationship between tongue part back surface length L / ball diameter Dw, and acoustic energy ratio. It is a perspective view which shows the modification of a circulation top. It is explanatory sectional drawing for demonstrating the difference of a tongue part front end shape and a tongue part base end side back surface shape. It is explanatory drawing which looked at the conventional ball screw apparatus from the axial direction. It is a figure which shows the XX sectional drawing of FIG. 9 in part by the right view of FIG. It is a figure which shows an example of the conventional circulation top, (b) is a front view, (a) is a left view of (b), (c) is a right view of (b). FIG. 12 is a perspective view of the circulating top of FIG. 11, (a) is a view from the back side of the tongue portion, and (b) is a view from the ball circulation groove side. It is explanatory drawing for demonstrating the conventional problem.

Explanation of symbols

12 ... Thread groove (screw shaft side)
13 ... Screw shaft 14 ... Thread groove (Nut side)
15 ... Ball 16 ... Nut 17 ... Ball return passage 20 ... Tang part 21 ... Ball circulation groove (ball circulation passage)
30 ... Ball screw device 40 ... Circulating top 41 ... Notch 50 ... Projection piece (projection)
51 ... concave

Claims (4)

A screw shaft having a spiral thread groove on the outer peripheral surface, a thread return corresponding to the screw groove of the screw shaft on the inner peripheral surface, and a ball return passage penetrating in the axial direction. A nut that is connected to the end of the nut with a ball circulation path that communicates between the two screw grooves and the ball return path, and between the two screw grooves, the ball return path, and A plurality of balls loaded so as to be able to circulate while rolling in the ball circulation path, and the circulation top is fitted into the thread groove of the screw shaft at the tip of the ball circulation path, In a ball screw device comprising a tongue portion for scooping up the ball rolling
A screw provided on the nut side to cut out the axially inner portion of the nut of the ball circulation path including the tongue portion in the circulation top, and to replace the removed part as a part of the ball circulation path A ball screw device characterized by being performed in a groove.   The ball screw device according to claim 1, wherein a protrusion is provided in addition to the ball circulation path of the circulation top, and a recess in which the protrusion is fitted is provided in the nut.   The length along the screw groove of the back surface portion of the tongue portion facing the screw groove side of the screw shaft is set to be 1.5 times or more and 10 times or less of the diameter of the ball. The ball screw device described. A screw shaft having a spiral thread groove on the outer peripheral surface, a thread return corresponding to the screw groove of the screw shaft on the inner peripheral surface, and a ball return passage penetrating in the axial direction. A nut that is connected to the end of the nut with a ball circulation path that communicates between the two screw grooves and the ball return path, and between the two screw grooves, the ball return path, and And a plurality of balls loaded so as to be able to circulate while rolling in the ball circulation path, and fitted between the screw grooves of the screw shaft at the tip of the ball circulation path to roll between the two screw grooves. In the ball screw device having a tongue portion for scooping up the ball,
The cross-sectional area of the front end of the tongue portion is made smaller than the cross-sectional area of the base end side of the back surface portion facing the screw groove side of the screw shaft of the tongue portion, and the front end of the tongue portion is used as the screw groove of the screw shaft A ball screw device characterized by non-contact.

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