JPH0687764U - Feed screw shaft system - Google Patents

Abstract

(57) [Summary] [Purpose] The positioning accuracy is high immediately after the start of driving, and
Develop a feed screw shaft system that has less backlash when starting and switching between forward and reverse drive. [Structure] A screw shaft 1 having right-angled grooves 21 and 22 formed in a spiral shape on its outer surface, and right-angled grooves 56, 57 formed in a spiral shape on its inner surface, and a return path 55 formed therein. A feed screw shaft system including a nut 5 and a cross roller bearing 3 in which the frame is flexibly connected in an annular shape.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a feed screw shaft system for NC machines (numerical control machines) and precision machines. The feed screw shaft system consists of a screw shaft, nuts and bearings. The screw shaft is rotated using a drive motor and the nut is precisely translated.

[0002]

[Prior art]

 Conventionally, a ball screw has been used as the feed screw shaft system. FIG. 3 is a partial sectional view of the ball screw. A semicircular groove 23 is provided in a spiral shape on the surface of the screw shaft 1. A semicircular groove 59 is spirally provided on the inner surface of the nut 5 so as to face the semicircular groove 23 of the screw shaft 1. Further, although not shown, a return path is embedded in the inner portion of the nut 5 so as to connect both ends of the semicircular groove 59. A ball bearing is interposed between the semicircular groove 23 of the screw shaft 1 and the semicircular groove 23 of the nut 5. The radius of the semicircular groove 23 and the radius of the semicircular groove 59 are both larger than the radius of the ball bearing. When the ball screw shaft is rotated, the nut 5 moves linearly, with the ball bearings pressing each other, moving along the semicircular groove 59, entering the return path, and extending again in a spiral shape. It returns to the other end of the semicircular groove 59.

[0003]

[Problems to be solved by the device]

 However, in the ball screw, the ball bearing and the ball screw shaft, and the ball bearing and the nut are in a state close to point contact, and high pressure acts on this contact portion. Therefore, when stopped, this contact part is elastically deformed and dented. Therefore, the positioning accuracy at the start of driving is poor and the variation is large, which is a problem particularly in NC machines.

Since the ball bearing has a smaller size than the semicircular groove, the ball bearing is unevenly distributed when the ball screw is rotated. Play is a problem when starting to drive from a stop. Also, the play when switching the ball screw rotation direction between forward and reverse is particularly remarkable.

Therefore, an object of the present invention is to develop a feed screw shaft system with high positioning accuracy immediately after the start of driving. Another object of the present invention is to develop a feed screw shaft system that has a small play at the time of starting or switching between forward and reverse drive.

[0006]

[Means for Solving the Problems]

 The above object is to provide a feed screw shaft system according to the first aspect of the present invention, that is, a screw shaft in which a right-angled groove is spirally formed on its outer surface and a right-angled groove is spirally formed on its inner surface. This is achieved by a feed screw shaft system including a nut formed in the shape of a ring and having a return path formed therein, and a cross roller bearing in which the frame is flexibly connected in an annular shape.

Further, the above object is to provide a feed screw shaft system according to a second aspect of the present invention, that is, a screw shaft having a right-angled groove spirally formed on the outer surface thereof, and the same. A nut with a rectangular groove spirally formed on the inner surface, and a return path of square cross section formed inside, and a plurality of rollers without using a frame, the rotation axes of adjacent rollers are It is also achieved by a feed screw shaft system consisting of cross roller bearings arranged so as to make an angle of contact with each other.

[0008]

[Action]

 The right-angled groove formed on the outer surface of the screw shaft and the right-angled groove formed on the inner surface of the nut face each other, and a cross roller bearing is interposed therebetween. Then, the rollers of the cross roller bearing rotate while contacting one of the planes of the right-angled groove. As a result, the screw shaft and the nut perform a smooth spiral motion relative to each other while maintaining an equal distance. In addition, the frame of the cross roller bearing is flexibly connected in an annular shape, and infinitely circulates along the right-angled groove and then the return path inside the nut. In the second invention, the rollers move while rolling along the right-angled groove and the adjacent rollers press each other, so that the entire cross roller circulates in the forward and reverse directions.

[0009]

【Example】

 FIG. 1 is a schematic diagram of a feed screw shaft system according to an embodiment. FIG. 2 is a partial sectional view of the feed screw shaft system of the embodiment.

The feed screw shaft 1 has right-angled grooves 21 and 22 spirally formed on the outer surface of a round bar. The planes of the right-angled grooves 21 and 22 form an angle of 90 °. The feed screw shaft 1 is normally and reversely rotated by a precision motor (not shown).

The nut 5 has a substantially hollow cylindrical shape. In FIG. 1, a cross section of the nut 5 is shown, but a flange is provided for mounting the device. Right-angled grooves 56 and 57 are spirally formed on the inner surface of the nut 5. The pitches are the same so that the right-angled grooves 21 and 22 of the feed screw shaft and the right-angled grooves 56 and 57 of the nut face each other. The width of the flat part of these right-angled grooves corresponds to the height of the roller of the cross roller bearing. A return passage 55 penetrates the inside of the nut 5 and connects both ends 53 and 54 of the right-angled groove. The size and curvature of the return path 55 are designed with consideration for smooth circulation of the cross roller bearing.

The cross roller bearing is a flexible frame, for example, a frame made of vinyl chloride, plastics, resin, hard rubber, metal or the like, which is connected in an annular shape. Then, the rotating shafts of the rollers are alternately arranged so as to form an angle of 45 ° and −45 ° with respect to the frame surface in a vertical plane perpendicular to the longitudinal direction of the annular frame so that the rollers can rotate freely. It is attached. Therefore, the adjacent rollers are in a positional relationship of being twisted by 90 ° with respect to each other.

In this embodiment, the right-angled groove of the feed screw shaft has one thread, but it may have two threads. In that case, the nut has two right-angled grooves and two return paths in the nut.

Although not shown in the drawings, the embodiment of the second invention is such that the cross-sectional shape of the return path formed inside the nut is substantially square, and the side surface of each roller of the cross roller bearing is Comes into contact with the inner wall of the return path and rolls. Also, for the cross roller bearings, do not use a frame, but only use cylindrical rollers of approximately the same diameter and height. The rollers are arranged so that the rotation axes of the rollers adjacent to each other form 90 ° and are in direct contact with each other.

[0015]

[Effect of device]

 In the feed screw shaft system of the present invention, each roller of the cross roller bearing is in line contact with the right-angled groove of the screw shaft on the one hand, and is in line contact with the right-angled groove of the nut on the other hand. Since the contact area is much wider and the contact pressure is lower than before, there is almost no elastic deformation or dent in the contact area. As a result, the positioning accuracy at start-up is extremely high, and there is almost no play or play. Furthermore, the impact resistance is more than 7 times higher than the conventional ball screw, and the durability and life are greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a feed screw shaft system according to an embodiment.

FIG. 2 is a partial cross-sectional view of the feed screw shaft system according to the embodiment.

FIG. 3 is a partial cross-sectional view of a ball screw.

[Explanation of symbols]

 1 Screw Shaft 21 Right Angle Groove 22 Right Angle Groove 23 Semicircular Groove 3 Cross Roller Bearing 31 Roller 32 Rotating Shaft 33 Roller 34 Rotating Shaft 35 Frame 5 Nut 53 Right Angle Groove End 54 Right Angle Groove End 55 Return Path 56 Right Angle Groove 57 Right-angled groove 59 Semi-circular groove

Claims (2)

[Scope of utility model registration request] 1. A screw shaft having a right-angled groove spirally formed on its outer surface, a nut having a right-angled groove spirally formed on its inner surface, and a return path formed inside the nut. A feed screw shaft system consisting of a cross roller bearing that flexibly connects the frame in an annular shape. 2. A nut having a screw shaft having a right-angled groove formed in a spiral shape on its outer surface, and a right-angled groove formed in a spiral shape on its inner surface, and a return path having a square cross section formed therein. And a cross roller bearing in which a plurality of rollers are arranged such that the rotation axes of adjacent rollers make 90 ° with each other and are in contact with each other, and a feed screw shaft system.