JP2003329102A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformly secure the rigidity of a ball screw device in the circumferential direction, to improve rotation accuracy and the service life of the device, and to particularly make the device optimum for high-load application such as an injection molding machine. <P>SOLUTION: This ball screw device 10 is provided with: a screw shaft 3 having a spiral thread groove 2 on the circumferential surface; a ball nut 6A having a thread groove 4 corresponding to the thread groove 2 on its inside surface and loosely fitted to the screw shaft 3; a lot of rolling bodies 5 rotatably mounted in a load track formed between both thread grooves 2 an 4; and a ball circulation tube 20 mounted to the ball nut 6A so as to endlessly circulate the rolling bodies 5 rolling in the load track. The scooping direction of the rolling bodies 5 of the circulation tube 20 is set in a nearly radial direction or a lead direction passing the centers of the screw shaft 3 and the ball nut 6A. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor manufacturing apparatus,
The present invention relates to a ball screw device used as a feed mechanism for various devices such as an injection molding machine and an industrial robot.

[0002]

2. Description of the Related Art As a conventional ball screw device of this type, for example, one shown in FIG. 13 is known. In this ball screw device 1, a ball nut 6 having a spiral screw groove 4 on its inner peripheral surface is loosely fitted to a screw shaft 3 having a spiral screw groove 2 on its outer peripheral surface and extending in the axial direction. .

The screw groove 4 of the ball nut 6 and the screw groove 2 of the screw shaft 3 face each other to form a spiral load track between them, and a large number of rolling elements 5 are formed on the load track. It is loaded so that it can roll. The rotation of the screw shaft 3 (or the ball nut 6) causes the ball nut 6 (or the screw shaft 3) to linearly move through the rolling of the rolling element 5.

When the ball nut 6 linearly moves, the rolling element 5 moves while rolling on a spiral load track formed by the screw grooves 2 and 4, but the ball nut 6 is continued. In order to move the rolling element 5, the rolling element 5 must be infinitely circulated. For this reason, for example, a part of the outer peripheral surface of the ball nut 6 is made into a flat surface, and a pair of two holes 7 communicating with both screw grooves 2 and 4 is formed on this flat surface so as to straddle the screw shaft 3. A ball circulation tube 8 having a substantially U shape in a set of holes 7.
By fitting both ends of the rolling element 5, the rolling element 5 revolving along the load track between the screw grooves 2 and 4 is scooped up by the ball circulation tube 8 from the middle of the load track and returned to the original load track. The rolling element 5 is infinitely circulated.

[0005]

By the way, in the above-mentioned conventional ball screw device, the ball circulation tube 8 is attached so as to cross the screw shaft 3 obliquely and to straddle the screw shaft 3. The ball circulating tube 8 scoops the rolling element 5 rolling on the load track in a direction substantially tangential to the load track.

However, when the rolling element 5 is scooped up by the ball circulation tube 8 in the direction substantially tangential to the load raceway, the rolling element 5 is scooped up by the ball circulation tube 8 before it revolves an integral number of times on the load raceway. As a result, the number of rolling elements 5 that receive a load in the circumferential direction becomes uneven, and it becomes impossible to ensure uniform rigidity in the circumferential direction. Moreover, the rolling elements that try to enter the ball circulation tube 8 cannot be ensured. There is a problem that the moving body 5 easily collides with the tongue or the tip of the tube, which causes the life of the device to be shortened.

Further, since the ball circulation tube 8 is obliquely crossed with respect to the screw shaft 3 and attached to the ball nut 6, the flat portion formed on the ball nut 6 for the attachment is made relatively wide and the section D Since it is necessary to cut the ball nut 6 into a uniform shape, in the ball screw device of the type in which the ball nut 6 is rotated, the inertia around the rotation center of the ball nut 6 is not uniform, and it is necessary to improve the rotation accuracy and torque stability. Considered disadvantageous.

As an example of solving such a problem, there has been proposed a ball screw device in which a plurality of ball circulation tubes are divided on the circumference of a ball nut and are attached. In this case, the ball circulation tube is Since a large number of rolling elements are provided, the cost increases, and at the same time, the rolling elements move in and out between the ball circulation tube and the load raceway, which is likely to cause a defect.

The present invention has been made in order to eliminate such inconvenience, and it is possible to uniformly secure the rigidity in the circumferential direction and to improve the rotation accuracy and the life of the apparatus. An object of the present invention is to provide a ball screw device that can be optimized for high load applications such as injection molding machines.

[0010]

In order to achieve the above object, the invention according to claim 1 provides a screw shaft having a spiral screw groove on the outer peripheral surface, and a screw groove corresponding to the screw groove of the screw shaft. A ball nut having an inner peripheral surface that is loosely fitted to the screw shaft, a number of rolling elements rotatably mounted on a load track formed between the screw grooves, and the load track. In a ball screw device provided with a ball circulation tube attached to the ball nut so as to infinitely circulate a moving rolling element, a scooping-up direction of the rolling element of the ball circulation tube is set to a center of the screw shaft and the ball nut. A ball screw device having a substantially radial direction or a lead direction passing through.

According to a second aspect of the present invention, in the first aspect, the ball circulation tube is attached in parallel with the screw shaft. According to a third aspect of the present invention, in the first or second aspect, a retaining piece or a spacer ball is interposed between the rolling elements of the plurality of rolling elements.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory sectional view for explaining a ball screw device which is an example of an embodiment of the present invention, FIG. 2 is a right side view of FIG. 1, FIG. 3 is a plan view of FIG. 1, and FIG. 4 is an example of the present invention. And FIG. 6 are graphs comparing the distribution of the screw shaft contact load in the axial direction of the screw shaft, and FIG. 5 is an enlarged view showing an example of the scooping part, and FIGS. 6 to 10 are modification examples of the scooping part. 11 and 12 are explanatory views for explaining a ball screw device according to another embodiment of the present invention. In each embodiment, the same parts as those of the conventional ball screw device described in FIG. 13 will be described with the same reference numerals.

As shown in FIGS. 1 to 3, this ball screw device 10 has a screw shaft 3 extending in the axial direction with a spiral thread groove 2 on the outer peripheral surface, and a spiral screw thread on the inner peripheral surface. A ball nut 6A having a groove 4 is loosely fitted. Ball nut 6
The screw groove 4 of A and the screw groove 2 of the screw shaft 3 face each other to form a spiral load track between them, and a large number of rolling elements 5 are rotatably loaded on the load track. Has been done.

The screw shaft 3 (or the ball nut 6)
By rotating A), ball nut 6A (or screw shaft 3)
Moves linearly through the rolling of the rolling element 5. Further, on the outer peripheral surface of the ball nut 6A, the rolling element 5 that revolves along the load track between the screw grooves 2 and 4 is scooped up from the middle of the load track and returned to the original load track to move the rolling element 5 In order to attach the ball circulation tube 20 for infinite circulation, a cutout portion 11 having a concave cross section is formed by cutting out a part of the outer peripheral surface along the axial direction.

Both screw grooves 2 and 4 are formed on the bottom surface of the notch 11.
Is formed in the axial direction of the screw shaft 3 so as to be separated from each other, and by fitting both ends of the ball circulation tube 20 having a substantially U shape into these holes 12, the ball circulation tube 20 is arranged parallel to the screw shaft 3 and revolves along the load trajectory between the screw grooves 2 and 4 by the ball circulation tube 20 in a radial direction passing through the center of the screw shaft 3, that is, a screw. The structure is such that the shaft 3 can be scooped up in a radial direction perpendicular to the rotation direction of the shaft 3.

As a result, the outlet portion and the inlet portion of the ball circulation tube 20 are in the same phase in the circumferential direction of the ball nut 6A, and the rolling element 5 has an integral number of revolutions along the load track between the screw grooves 2 and 4. Ball circulation tube 20 after revolving
Be scooped up by. In the figure, reference numeral 30 is a pressing member for the ball circulation tube 20, and the pressing member 30 has a shape corresponding to the cutout portion 11 of the ball nut 6A and has a recess 31 corresponding to the ball circulation tube 20. Then, the ball circulation tube 20 is accommodated in the recess 31 and is fitted into the notch portion 11 and fixed to the ball nut 6A by screwing or the like.

FIG. 5 is an enlarged view of the scooping portion of the ball circulation tube 20. A tongue 21 is provided at the tip of the ball circulation tube 20. As described above, in the conventional ball circulation tube, since the rolling element 5 is scooped up in the tangential direction of the load raceway or in a direction close thereto, the rolling element 5 attempting to enter the ball circulation tube collides with the tongue or the tip of the tube. Although it was easy, in this embodiment, since the rolling element 5 is scooped up in the radial direction at right angles to the rotation direction of the screw shaft 3, as shown in FIG.
Can be scooped up against the abdomen of the tongue 21, and as a result, the rolling element 5 trying to enter the ball circulation tube 20 from the load track can be scooped up smoothly.

The tongue 21 in the figure is bent toward the inner diameter side of the ball circulation tube 20.
The scooping of the rolling element 5 onto the ball circulation tube 20 is facilitated. An R-shaped crowning 32 is provided on the nut track immediately before the connection between the ball nut 6A and the ball circulation tube 20 so as to gradually reduce the load on the rolling elements 5.

As described above, in this embodiment, the outlet and inlet of the ball circulation tube 20 are provided at the ball nut 6.
The rolling element 5 has the same phase in the circumferential direction of A, and
Since it is revolved along the load trajectory between the four by an integral number of revolutions and then scooped up by the ball circulation tube 20, the number of rolling elements 5 that receive a load in the circumferential direction becomes even, and moreover, the rolling elements 5 Is scooped up in the radial direction at right angles to the rotation direction of the screw shaft 3, so that the rolling element 5 trying to enter the ball circulation tube 20 from the load track can be scooped up smoothly.

As a result, the rigidity in the circumferential direction can be uniformly ensured, the rotation accuracy and the life of the apparatus can be improved, and it is most suitable for high load applications such as injection molding machines. It is possible to obtain the action and effect. Further, since the ball circulation tube 20 is attached in parallel to the screw shaft 3, the cut amount of the notch portion 11 formed in the ball nut 6A for the attachment is cut into a D-shaped cross section as in the conventional case and a flat surface is formed. This is much smaller than in the case where the ball nut 6 is formed, and since the pressing member 30 is fitted in the space of the cutout portion 11, the ball nut 6 is rotated even when the ball nut 6A is rotated.
The inertia around the rotation center of A can be made substantially uniform, and as a result, the rotation accuracy and torque stability can be improved.

FIG. 4 shows the ball screw device of FIG. 1 in which the rolling element 5 revolves along the load track for an integral number of revolutions and is picked up by the ball circulation tube 20. FIG. 13 is a view showing the distribution of the screw shaft contact loads of the two along the screw axis direction, using the ball screw device of FIG. 13 scooped up by the ball circulation tube 8 before revolving an integral number of times as a conventional example.

The basic specifications of the ball screw device are the same in both the present invention example and the conventional example. As is apparent from FIG. 4, in the conventional example, the contact load varies greatly in the screw axis direction, whereas in the example of the present invention, the contact load variation is small, and it is understood that the contact load is greatly improved.

The ball screw device of the present invention is not limited to the above-mentioned embodiment, and can be appropriately modified without departing from the scope of the present invention. For example, FIGS. 6 and 7 are enlarged views of modifications of the scooping portion, and FIG. 7 is a view of the ball circulation tube 50 of FIG. 6 viewed from the upper side. Unlike this embodiment, this scooping portion is a tongue in which a first scooping guide member 51 for guiding the rolling element 5 is provided at the tip of the ball circulation tube 50, as shown in FIG. .

The guide surface of the first scooping guide member 51 is a concave curved surface larger than the radius of the rolling element 5, so that the ball circulating tube 50 of the rolling element 5 can move in and out between the load raceway. I try to make it happen smoothly.
As the material of the first scooping guide member 51, a metal material having a high hardness may be used to have strength, and a polymer material such as rubber or plastic may be used to avoid noise.

In the ball screw device of the present invention, since the rolling element 5 that has moved in the load track is scooped up in the radial direction perpendicular to the rotation direction of the screw shaft 3, a large load acts on the tongue. Therefore, particularly when the tongue is operated at a high speed, it is desirable to form the tongue by the first scooping guide member 51 which is a member different from the ball circulation tube 50 as described above to increase the strength.

A tongue 52 is provided at the tip of the ball circulation tube 50 on the opposite side of the first scooping guide member 51 so as to warp to the outer diameter side of the ball circulation tube 50. As can be seen from FIG. 6, when the tip of the ball circulation tube 50 on the opposite side of the first scooping guide member 51 is angular, the rolling element 5 to be scooped up or the ball circulation tube 50 enters the load track. There is a high possibility that the rolling elements 5 to be interfered with each other at this angle.

Therefore, by providing the tongue 52 as shown in the figure and guiding the rolling element 5, such interference of the rolling element 5 is avoided. A crowning 53 that gradually expands radially outward is provided on the load raceway surface of the ball nut 6A near the ball circulation tube 50, so that the load applied to the rolling element 5 is gradually released. Thus, the load on the tongue 52 is reduced.

8 to 10 are enlarged views showing another embodiment of the modified example of the scooping portion, FIG. 9 is a perspective view showing the scooping portion of FIG. 8 in three dimensions, and FIG. It is the figure which looked at the 2nd scooping guide member of FIG. 8 from the left side. This scooping part is a first scooping guide member 51 for scooping up the rolling element 5 provided at the tip of the ball circulation tube 60 as in FIG.
6 is different from FIG. 6 in that the cushioning material 61 is provided on the back surface of the first scooping guide member 51 as shown in FIG.

This cushioning material 61 further reduces the impact on the first scooping guide member 51 of the rolling element 5 during scooping to prevent damage to the rolling element 5 and the guide member 51, noise, etc. We are trying to improve In this case, the first scooping guide member 51 is made of a metal material having high hardness,
Since it is possible to use a method in which the cushioning material 62 is a polymer material such as rubber, a high effect can be expected by combining the materials.

Further, a second scooping guide member 62 is provided at the tip of the ball circulation tube 60 on the opposite side of the first scooping guide member 51, instead of the tongue 52 in FIG. The guide surface of the second scooping-up guide member 62 is a concave curved surface larger than the radius of the rolling element 5 similarly to the first scooping-up guide member 51, whereby the rolling element 5 is continuously guided. The rolling element 5 can be guided more smoothly than the tongue 52 of FIG.

The second scooping guide member 62 is also the first
The ball circulation tube 6 as well as the scooping guide member 51 of
Since it is composed of a member different from that of No. 0, there is an advantage that the material can be freely selected, and it is generally desirable to use a polymer material such as rubber or plastic that alleviates shock and noise. In addition, since the second scooping guide member 62 has a slightly complicated shape, it is advantageous to use a polymer material suitable for forming a complicated shape also from this point.

Further, similarly to FIG. 6, a crowning 63 that gradually expands radially outward is provided on the load raceway surface of the ball nut 6A in the vicinity of the ball circulation tube 60 to gradually release the load applied to the rolling element 5. Thus, the load applied to the second scooping guide member 62 is reduced. FIG. 11 is an example in which the retaining piece 70 is interposed between the rolling elements 5 of FIG. 8, and even when the retaining piece 70 is used in this manner, the first scooping guide member 51 and the It is possible to scoop up without interfering with the second scooping guide member 62.

By using the retaining piece 70, it is possible to alleviate competition or collision between rolling elements in the load track or the ball circulation tube 60.
Further higher performance of the device can be realized. In addition,
Even if a spacer ball is provided between the rolling elements 5 instead of the retaining piece 70, the same effect can be obtained.

In FIG. 12, the ball circulation tube 80 is arranged in parallel with the screw shaft 3, and the rolling element 5 revolving along the load track between the screw grooves 2 and 4 is led by the ball circulation tube 80 to the lead of the screw shaft 3. It has a structure that can be scooped up in the angular direction. Even in this way, the ball circulation tube 80
Of the ball nut 6A has the same phase in the outlet portion and the inlet portion, and the rolling element 5 revolves for an integral number of revolutions along the load track between the screw grooves 2 and 4 and then scooped into the ball circulation tube 80. Raised, and rolling element 5 in the direction of the lead angle
The ball circulation tube 8 of the rolling element 5
It is possible to smoothly move in and out between 0 and the load track. The scooping portion of the rolling element 5 may have any of the configurations described above.

[0035]

As is apparent from the above description, according to the ball screw device of the present invention, the rigidity in the circumferential direction can be uniformly ensured, and the rotation accuracy and the life of the device can be improved. In particular, it is possible to obtain the effect that it can be optimized for high load applications such as an injection molding machine.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view for explaining a ball screw device that is an example of an embodiment of the present invention.

FIG. 2 is a right side view of FIG.

FIG. 3 is a plan view of FIG.

FIG. 4 is a graph comparing the axial distribution of the screw shaft contact load of the present invention example and the conventional example.

FIG. 5 is an explanatory view showing an enlarged example of the scooping portion.

FIG. 6 is an explanatory view showing a modification of the scooping portion in an enlarged manner.

FIG. 7 is a view of the ball circulation tube of FIG. 6 viewed from the upper side.

FIG. 8 is an explanatory diagram showing an enlarged example of a modification of the scooping portion.

9 is an explanatory perspective view showing the scooping portion of FIG. 8 in three dimensions.

10 is a view of the second scooping guide member of FIG. 8 as viewed from the left side.

FIG. 11 is an explanatory diagram for explaining a ball screw device that is another embodiment of the present invention.

FIG. 12 is an explanatory cross-sectional view for explaining a ball screw device that is another embodiment of the present invention.

FIG. 13 is an explanatory cross-sectional view for explaining a conventional ball screw device.

[Explanation of symbols]

2… Screw groove (screw shaft side) 3 ... Screw shaft 4… Screw groove (ball nut side) 5 ... rolling elements 6A ... Ball nut 10 ... Ball screw device 20, 50, 60, 80 ... Ball circulation tube 70 ... Retaining piece

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Claims (3)

[Claims] 1. A screw shaft having a spiral thread groove on an outer peripheral surface, and a ball nut having a thread groove corresponding to the thread groove of the screw shaft on an inner peripheral surface and being loosely fitted to the screw shaft. A large number of rolling elements rotatably loaded on a load track formed between the screw grooves, and a ball circulation tube attached to the ball nut for endless circulation of the rolling elements rolling the load movement. A ball screw device comprising: a ball circulating tube, wherein the scooping-up direction of the rolling element of the ball circulation tube is a substantially radial direction or a lead direction passing through the centers of the screw shaft and the ball nut. 2. The ball screw device according to claim 1, wherein the ball circulation tube is attached in parallel with the screw shaft. 3. The ball screw device according to claim 1, wherein a retaining piece or a spacer ball is interposed between the rolling elements of the plurality of rolling elements.