JP2725807B2 - Ball screw penetrating servo motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cylindrical shape in which a ball screw shaft is inserted and a ball nut is fixed among a ball screw shaft and a ball nut mechanism which is a driving force transmission mechanism of a machine tool or the like. The present invention relates to a servomotor having a shaft.

[Conventional technology]

2. Description of the Related Art Conventionally, when a ball screw shaft / ball nut mechanism is directly connected to a motor shaft, a method of inserting a ball screw shaft through the motor shaft and fixing the ball nut to the motor shaft may be adopted. At this time, conventionally, the ball nut has been directly fixed to the motor shaft with a screw part or the like.

[Problems to be solved by the invention]

However, in order to directly fix the ball nut to the motor shaft, it is necessary to design the shaft shape to be adapted to the dimensional form corresponding to the ball nut,
There is a problem that the motor housing and the like must be designed so as to correspond to this. Further, when the ball nut is directly attached to the motor shaft, heat generated inside the motor is directly transmitted to the ball nut, and further to the ball screw shaft, which causes a problem that feed accuracy is deteriorated due to thermal expansion.

Therefore, in order to solve the problem, the present invention can fix ball nuts of various sizes to a certain motor shaft, and can reduce conduction of heat generated in the motor to the ball nut. The purpose of the present invention is to provide a simple ball screw penetrating servomotor.

[Means for solving the problem]

In view of the above object, the present invention provides a servomotor having a cylindrical shaft through which a ball screw shaft can be inserted at the center of the shaft, wherein one end of the cylindrical shaft has a series of ball screw shafts having various sizes. -Among the ball nuts, the ball nut has a nut receiving hole having a size capable of receiving the main body of the ball nut having the largest size, and one end of the shaft having the nut receiving hole has the various sizes. Provided corresponding to each of the ball nuts,
The ball nut is formed into a cylinder via an intervening member having a first engagement portion capable of fastening the corresponding ball nut and a second engagement portion capable of being fastened to the one end. Provided is a ball screw penetrating type servomotor which is mounted on a shaft.

(Operation)

One end of the shaft is provided with a nut receiving hole for accommodating the main body of the ball nut having the largest size among the ball screw shafts and ball nuts to be used, and therefore accommodates any of the ball nuts to be used. it can. Further, since an intervening member is used for each ball nut, it is possible to fix a smaller ball nut to one end of the shaft. Further, there is a gap between the peripheral wall of the nut receiving hole and the main body of each ball nut, and by using an appropriate intervening member, the amount of heat generated inside the motor is transmitted to the ball nut. Can be reduced.

〔Example〕

Hereinafter, the present invention will be described in more detail based on embodiments shown in the accompanying drawings. 1 and 2 have the same reference numerals for the same components. It is assumed that the ball screw shaft 18A and the ball nut 20A shown in FIG. 1 are of the maximum size to be used in the present design. Motor shaft
Numeral 10 is formed in a hollow cylindrical shape having a through hole 14 provided at the center over its entire length. The one end portion 12 is formed with a nut storage hole portion 16 having a hole diameter large enough to receive the main body portion 22A of the ball nut 20A of the maximum size. Further, the hole diameter of the hole portion 16 is set to be somewhat larger than the outer diameter of the main body portion 22A of the ball nut 20A in order to increase the heat conduction resistance from the shaft 10 to the ball nut 20A, and a gap is provided.

The ball screw shaft 18 is inserted into the motor shaft 10 having the above structure.
A and the ball nut 20A are inserted, and the ball nut 20A is fixed to the one end 12 of the shaft 10 via the flange portion 24A. In this case, a small ball screw shaft 18B and a ball nut 20B as shown in FIG. 2 are inserted into the shaft 10, and the ball nut 20B is inserted into the same end 12 as the shaft end 12 shown in FIG. In consideration of the fact that the flange portion 24B is fastened with a threaded component, an intervening member is required in order to be able to fasten a ball nut of any size within the range of use. The center position P1 of the screw component insertion hole provided in the flange portion 24A of the large size ball nut 20A and the center of the screw component insertion hole provided in the flange portion 24B of the small size ball nut 20B. The position P3 is, of course, a radially different position relative to the one end 12 of the motor shaft 10.
Therefore, it is necessary to prepare the intervening members 26A or 26B according to the ball nuts of the respective sizes such as the ball nuts 20A or 20B. In these intervening members 26A and 26B, screw holes provided on the distal end surface of the one end portion 12 of the motor shaft 10 and engaging with other screw components are provided at a radial dimension position P2. Members 26A and 26B are provided with screw component insertion holes corresponding to the same radial dimension position P2. Further, screw holes are provided in the intervening members 26A, 26B corresponding to the respective radial dimension positions P1, P3 of the respective flange portions 24A, 24B.

If the intervening member is configured as described above, first, the intervening member 26A (26B) is fastened and fixed to the one end portion 12 using a screw component at the radial dimension position P2, and then, the radial dimension position P1 ( In P3), the flange portion 24A (24B) of the ball screw 20A (20B) can be fastened and fixed to the interposition member 26A (26B) by using another screw component. For example, a screw hole corresponding to the radial dimension position P1 of the interposition member 26A shown in FIG. 1 and a screw component insertion hole corresponding to the other radial dimension position P2 are respectively described in the claims. A first engaging portion and a second engaging portion. In addition, even when the radial dimension positions P1 and P2 (P3 and P2) substantially coincide with each other, by appropriately shifting the positions of the actual screw holes and insertion holes in the circumferential direction, two types can be obtained. Holes do not interfere.

The inner diameter of the center holes 30A, 30B of the interposed members 26A, 26B is designed to be slightly larger than the outer diameter of the main body 22A, 22B of each ball nut so that heat generated inside the motor is not conducted to the ball nuts 20A, 20B. It is desirable to do. However, in order to hold the ball nut 20A (20B) concentrically with the motor shaft 10 at an appropriate position in the circumferential direction, a centering projection that comes into contact with the main body portion 22A (22B) of the ball nut is provided. is required. When configured in this manner, generally, only the end faces 28A, 28B of the intervening members 26A, 26B are connected to the respective ball nuts 20A, 20B.
Therefore, the amount of heat conducted inside the motor to the ball nut via the shaft 10 can be reduced. Further, although the motor shaft 10 is made of a material having relatively high thermal conductivity such as ordinary carbon steel, the intervening members 26A,
If 26B is made of a material having a low thermal conductivity such as ceramics, the amount of heat transferred to the ball nut can be further reduced. Also, the number of components called intervening members has increased compared to the conventional method, but these are small components, and the cost is significantly reduced as compared with preparing the same type of motor shaft and housing.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, it is possible to fix ball nuts of various sizes to the motor shaft without changing the motor shaft and the housing, thereby reducing costs and improving the motor interior. This makes it possible to reduce the amount of heat transfer to the ball nut.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of one end of a shaft of a servomotor according to the present invention, in which a large-sized ball screw shaft and a ball nut are mounted, and FIG. FIG. 2 is a longitudinal sectional view of one end of a shaft of a servomotor according to the present invention in a state where a small-sized ball screw shaft and a ball nut are mounted. 10 ... Motor shaft, 12 ... One end of shaft, 16 ... Nut accommodation hole, 18A, 18B ... Ball screw shaft, 20A, 20B ... Ball nut, 26A, 26B ... Intervening member, P1, P3 ... ... Position of the first engagement portion where the ball nut is attached to the intervening member. P2: Position of the second engaging portion for attaching the interposed member to one end of the shaft.

Claims (1)

(57) [Claims] 1. A servo motor having a cylindrical shaft through which a ball screw shaft can be inserted at the center of the shaft, wherein one end of the cylindrical shaft has a series of ball screw shafts / ball nuts having various sizes. Among them, a nut receiving hole having a dimension capable of receiving a main body of a ball nut having a maximum size is provided, and one end of the shaft having the nut receiving hole is provided with ball nuts of various sizes. An intervening portion provided correspondingly to each of the first engagement portion, which can fasten the corresponding ball nut, and the second engagement portion, which can be fastened to the one end portion. A ball screw penetrating servo motor, wherein a ball nut is attached to a cylindrical shaft via a member.