JPH0942409A - Hollow ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of working man-hours of the screw shaft of a hollow ball screw, and also improve mechanical property. SOLUTION: In a hollow ball screw which consists of a hollow screw shaft arranged an inner spiral groove on an outer peripheral surface, a ball nut which is penetrated the screw shaft 1 and arranged an outer side spiral groove opposing to the inner side spiral groove 2 of the screw shaft on an inner circumferential surface, and a plurality of ball which is rotatably arranged in a spiral ball circulating passage formed between the inner spiral groove 2 of the screw shaft 1 and the outer side spiral groove of the ball nut, the hollow hole 3 surface of the screw shaft 1 is formed on a first surface at the time of plastic work, and the cutting work of the hollow hole 3 surface is omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow ball screw used in various industrial equipment such as machine tools.

[0002]

2. Description of the Related Art In general, a ball screw has a spiral formed between an inner spiral groove provided on an outer peripheral surface of a screw shaft and an outer spiral groove provided on an inner peripheral surface of a ball nut inserted through the screw shaft. A plurality of balls are rotatably arranged in a ball-shaped ball circulation passage, and the rotational movement of the screw shaft is converted into the linear movement of the ball nut through the rolling circulation of the balls.

In the above ball screw, when the ball nut is moved by rotating the screw shaft at a high speed, the screw shaft may thermally expand due to frictional heat generated between the screw shaft and the ball and between the ball and the ball nut. In order to prevent this, a hollow ball screw having a hollow hole for flowing a cooling medium in a screw shaft is known.

Conventionally, the screw shaft of the above-mentioned hollow ball screw is manufactured by forming a hollow hole in a round bar by cutting such as a gun drill system or a BTA system, or a shaft having a certain quantity can be expected to have a seamless thick wall material. You are using a tube.

[0005]

However, in the above-mentioned screw shaft in which a hollow hole is formed in a round bar by cutting, a lot of man-hours are spent for cutting the hollow hole, resulting in a high processing cost. is there. Further, when the axial length is long, the hollow hole cannot be penetrated by cutting work from one end, so that the hollow hole is penetrated by cutting work from both ends. However, if the hollow hole is penetrated by cutting from both ends, the processing man-hour will increase, and there will be a step in the center of the hollow hole. Problems may occur when press-fitting or wiring. Moreover, for a screw shaft that penetrates the hollow hole by cutting from one end, the shaft center and the center of the hollow hole can be matched by cutting the outer peripheral surface with reference to the holes at both ends. For the screw shaft that penetrates the hollow hole by cutting from, the center of the shaft and the center of the hollow hole cannot be perfectly aligned, and with the recent increase in speed, it has become a factor of dynamic unbalance of the shaft. The positioning accuracy will be adversely affected.

On the other hand, in the screw shaft using the seamless thick-walled pipe, it is possible to omit the machining of the hollow hole to reduce the processing cost. However, in the process of expanding the seamless thick-walled pipe, the lubricant is applied to the surface of the hollow hole. Since the glass powder and scale used as a product adhere to the cooling medium and adversely affect the means for circulating the cooling medium, it is necessary to cut the surface of the hollow hole to remove it, which requires a lot of man-hours for this cutting process. Is spent.

The present invention has been proposed in view of the above problems, and an object of the present invention is to provide a hollow ball screw which reduces the number of working steps and improves the mechanical properties.

[0008]

In order to achieve the above-mentioned object, the present invention provides a hollow screw shaft having an inner spiral groove on the outer peripheral surface thereof, and an inner peripheral surface through which the screw shaft is inserted. A ball nut having an outer spiral groove facing the inner spiral groove of the screw shaft, and a spiral ball circulation passage formed between the inner spiral groove of the screw shaft and the outer spiral groove of the ball nut. A hollow ball screw consisting of multiple balls that can be rolled freely is characterized in that the surface of the hollow hole of the screw shaft is formed on the ground during plastic working.

Since the surface of the hollow hole of the screw shaft is formed on the surface of the plastic working, the conventional cutting process of the surface of the hollow hole can be omitted, and the man-hour of the screw shaft can be greatly increased. Can be reduced to

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
This will be described together with the illustrated example.

FIG. 1 is a side view showing a part of a hollow ball screw of the present invention in a sectional view. (1) is a screw shaft having an inner spiral groove (2) at the center of the outer peripheral surface, and the shaft center thereof. Has a hollow hole (3) penetrating therethrough and absorbs frictional heat generated from the screw shaft (1) by flowing cutting oil or the like based on water as a cooling medium into the hollow hole (3). As a result, thermal expansion of the screw shaft (1) can be suppressed. As a material of the screw shaft (1), a hollow rod-shaped material, for example, a hot-rolled finish material is adopted, and the surface of the hollow hole (3) is formed into a black skin texture at the time of hot-roll finish. This hollow rod-shaped hot rolled finish material can reduce the amount of eccentricity of the hollow hole (3) with respect to the axial center, and the surface of the hollow hole (3) is formed into a black skin texture during hot rolling finish. However, it does not adversely affect the means for supplying and circulating the cooling medium.
Reference numeral (4) is a ball nut having the screw shaft (1) inserted therein, and an outer spiral groove (not shown) is provided on the inner peripheral surface of the ball nut so as to face the inner spiral groove (2) of the screw shaft (1). A plurality of balls (not shown) are rotatably arranged in a spiral ball circulation passage formed between the outer spiral groove and the inner spiral groove (2) of the screw shaft (1). ) By rotating the ball through the ball circulation (4)
Can move linearly.

By the way, the hollow rod-shaped hot-rolled finishing material used as the material for the screw shaft (1) is a thick material having a thickness capable of forming the inner spiral groove (2) on the outer peripheral surface. Has been recently developed and has not been used as a material for the screw shaft (1) of a hollow ball screw. It should be noted that a hollow rod-shaped hot-rolled finish material having a thin wall has been manufactured for a long time, but this is because the screw shaft (1) of the hollow ball screw cannot be formed because the inner spiral groove (2) cannot be formed on the outer peripheral surface. Was not used as a material for. Therefore, until now, hollow holes have been formed in a round bar by machining, and seamless thick-walled pipes have been used as the raw material, but there were the above-mentioned problems.

In the hollow ball screw according to the embodiment having the above-mentioned structure, the hollow rod-shaped hot work in which the surface of the hollow hole (3) is formed as a material of the screw shaft (1) on the black leather surface at the time of hot rolling finish By adopting the rolled finish material, it is possible to omit the conventional cutting process of the hollow hole (3) (including the cutting process for scraping off the adhered material on the hollow hole surface of the seamless thick-walled pipe). The processing man-hour of 1) can be significantly reduced, and the eccentric amount of the hollow hole (3) with respect to the shaft center can be reduced, so that the reduction in positioning accuracy due to dynamic imbalance during high-speed rotation can be suppressed. .

Further, conventionally, when the hollow hole (3) is cut from both ends when the axial length is long, there is no step generated in the middle portion of the hollow hole (3), so that inside the hollow hole (3). No problems occur when press-fitting pipes or wiring. Furthermore, since it is possible to easily manufacture the screw shaft (1) made of a material that is conventionally difficult to cut and is not suitable for cutting the hollow hole (3) (for example, stainless steel or alloy steel),
The application can be expanded as a hollow ball screw that can be used in fields that have special requirements such as corrosion resistance and non-magnetism.

[0015]

As described above, according to the present invention, as the material of the screw shaft, the hollow rod-shaped material whose hollow hole surface is formed on the background of the plastic working is adopted, so that the number of man-hours for processing the screw shaft is increased. Can be significantly reduced, and the processing cost can be significantly reduced. In addition, it is possible to reduce the decrease in positioning accuracy due to dynamic imbalance during high-speed rotation, and to press fit a pipe-shaped object into the hollow hole,
Since no problem occurs even when wiring is performed, the mechanical properties of the ball screw can be improved.

[Brief description of drawings]

FIG. 1 is a side view in which a hollow ball screw of the present invention is partially sectioned.

[Explanation of symbols]

 1 Screw shaft 2 Inner spiral groove 3 Hollow hole 4 Ball nut

Claims (1)

[Claims] 1. A hollow screw shaft having an inner spiral groove formed on an outer peripheral surface thereof, and an outer spiral groove inserted through the screw shaft and facing the inner spiral groove of the screw shaft on an inner peripheral surface thereof. A hollow ball screw comprising a ball nut and a plurality of balls rollably arranged in a spiral ball circulation passage formed between an inner spiral groove of the screw shaft and an outer spiral groove of the ball nut. A hollow ball screw, wherein the surface of the hollow hole of the screw shaft is formed by the texture of the plastic working.