JPH08285030A - Ball screw and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide a method of manufacturing a ball screw, used for a linear bearing or the like, at a low cost by rolling. CONSTITUTION: Insert material with a fusing point Ti lower than the fusing, point Tb of metallic material with a lower fusing point between metallic materials forming a screw shaft 1 and an extended member 3 is inserted between the screw shaft 1 with a thread groove previously machined on the peripheral surface by rolling, and the extended member 3 to be jointed to the end face of the screw shaft 1. A joint part is heated at the temperature of Ti<T< Tb while applying pressure to the faying surface and held to this temperature for the fixed time so as to joint the extended member 3 to the screw shaft 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw used for a linear bearing or the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art As is well known, a ball screw is arranged so that a ball rolls in a screw groove formed on the outer peripheral surface of a screw shaft, and is often used as a precision bearing for machine tools etc. as a bearing having an extremely small friction coefficient. Has been done. By the way, in order to manufacture the screw shaft of this ball screw, conventionally, a method of forming a screw groove by cutting the outer peripheral surface of the steel round bar of the material,
There has been a method of forming a screw groove by rolling a steel round bar as a raw material with a rolling machine. The latter manufacturing method by rolling is highly demanded because it has higher productivity and can reduce manufacturing cost as compared with the former cutting method.

[0003]

However, since the rolling method involves rolling the material by sandwiching it between a pair of rolling dies, a portion having a diameter larger than that of a round steel bar, such as a flange, is provided at one end. However, there is a problem that it is not possible to machine a shape in which the blades are integrally extended.Therefore, in such a shape, the screw groove must be processed by cutting, and when the material size increases, the material yield increases. In addition, the productivity is lowered and the manufacturing cost is significantly increased.

Therefore, if a member having a desired shape can be joined to one end of the screw shaft manufactured by rolling, the above problems can be solved and the productivity is improved. However, carbon steel for machine structure, which is generally used as a material for the screw shaft of ball screws,
There is a problem that cracking is likely to occur when welding is performed by a fusion welding method such as arc welding, and a change in joint size and deformation due to solidification and shrinkage of weld metal is large. Further, even if the joining method by friction welding which does not involve melting of the material is used, there is a problem that burrs are generated around the joined portion and a burr removing step is required. For these reasons, there has been a strong demand for a joining method suitable for manufacturing a ball screw, which is constructed by joining members whose respective parts are processed in advance.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and an object thereof is to manufacture a highly functional ball screw with high efficiency. Therefore, the method for manufacturing a ball screw according to the present invention includes a screw shaft formed by processing a screw groove on the outer peripheral surface in advance by rolling, and an extending member that is joined to the end face of the screw shaft and is made of the metal material. Among them, an insert material having a melting point T _i lower than the melting point T _b of the metal material having a lower melting point is inserted, and the bonding portion is heated to a temperature of T _i <T <T _b while applying pressure to the bonding surface. The extension member is joined to the screw shaft by maintaining the temperature for a certain period of time. Further, the present invention is characterized in that, in the above-mentioned method for manufacturing a ball screw, the joint portion is heated by using a high frequency induction heating method. Further, the present invention is characterized in that, in the above-mentioned method for manufacturing a ball screw, the joint portion is shielded and joined with an inert gas. Further, the present invention is characterized in that, in the method for manufacturing a ball screw, the screw shaft including the joint and the extending member are heat-treated after the joint. Furthermore, the ball screw manufacturing apparatus according to the present invention includes a heating means for the joint, a means for measuring the temperature of the joint, a means for applying pressure to the joint surface, a means for measuring the pressure, and It is characterized in that it comprises means for flowing an active gas and means for controlling them. Further, the ball screw according to the present invention is characterized in that an extension member is joined by liquid phase diffusion joining to one end of a screw shaft having a screw groove formed on the outer peripheral surface by rolling.

[0006]

The joint is heated to a temperature of T _i <T <T _b to melt the insert material and maintain the temperature at the same temperature for bonding, so that the screw shaft and the extending member are not melted. Moreover, they can be joined in an extremely narrow range. Therefore, since there is no region of low hardness such as weld metal when joining using the arc welding method, it is possible to prevent local wear of the joining portion and to cause welding cracks when joining using the arc welding method. do not do. Further, since the welding can be performed in a shorter time than the arc welding method, deterioration of the material can be suppressed. Therefore, a high quality ball screw can be manufactured at low cost.

[0007]

Embodiments of the present invention will now be described with reference to the drawings.
Fig. 1 shows the outline of the ball screw manufacturing apparatus.
Is a screw shaft having an outer diameter of 23.6 mm formed by rolling a screw groove on the outer peripheral surface of a carbon steel (S55C) rod by rolling, 2 is a fixed chuck holding the screw shaft 1, and 3 is An extension member 4 made of carbon steel (S55C) to be joined to the end portion of the screw shaft 1 is a movable chuck that holds the extension member 3, and 5 is inserted between the joint surfaces of both members. Insert material,
6 is a high frequency induction coil for heating the joint, 7 is a radiation thermometer for detecting the temperature of the joint, and 8 is a gas spray nozzle for spraying an inert gas such as N ₂ gas to seal the joint. Reference numerals 9 are strain gauges or pressure gauges (load cells) provided on the fixed chuck 4 for detecting the pressure of the joint extending from the screw shaft 1 to the extending member 3, and 10 is heating by the high frequency induction coil 6 and a movable chuck. 2 is a control device for controlling the pressure applied by the control device 10.
The temperature of the joint detected by the radiation thermometer 7 and the pressure of the joint detected by the strain gauge or pressure gauge (load cell) 9 are fed back to
We are trying to control them exactly as they are set.

The insert material 5 has a melting point of the screw shaft 1 (140
0 ° C.) and N _i -S _i -B (mp 1040 ° C. with a melting point lower than that of the extended members 3 (1400 ° C.)) or N _i -S _i -C _r -B such (melting point 1100 ° C.) The nickel alloy is used in the form of a sheet having a thickness of about 40 μm or in a powder state. Then, the movable chuck 4 is inserted between the joint surfaces of both members, the movable chuck 4 is moved forward and the joint portion is kept at a pressure of 5 MPa, the joint portion is heated to 1200 ° C. by induction heating by the induction coil 6, and the heating state is maintained. Hold for at least 60 seconds. As a result, the insert material 5 is melted, penetrates and diffuses from the joint surfaces of the screw shaft 1 and the extending member 3 into each metal structure, and firmly joins the joint surfaces.

Table 1 shows the results of the tensile test when the materials of the insert material 5, the combination of the members, the bonding temperature and other conditions were variously changed to carry out the bonding. It should be noted that the combination A of the members in the table is a case where a shaft-shaped extending member 3 having a larger diameter than that is joined to the end surface of the screw shaft 1 as shown in FIG. 2, and the combination B is as shown in FIG. In the case where the extension members 3 having axial spline grooves formed at equal intervals on the outer peripheral surface are joined to the end face of the screw shaft 1, the combination C has mutually reverse screw relationships as shown in FIG. This is the case where the screw shafts 1R and 1L are joined.

[Table 1]

In Table 1, Example 1 is a comparative example when no insert material is used, Examples 2 to 4 are inventive examples, Example 5 is a comparative example when no pressure is applied to the joining surfaces, and Example 6 is joining. Comparative examples when the temperature is lower than the melting temperature of the insert material, Example 7 is a comparative example when no time was taken to maintain the bonding temperature, and all of these comparative examples were fractured from the bonding surface in the tensile test. However, sufficient tensile strength was not obtained. In addition, Example 8 is an example of the invention when joined without using a shielding gas. In this case, the surface of the screw shaft 1 is oxidized, and even if it is polished later due to the oxide scale, the screw precision is as high as that of the other examples of the invention. Does not get better. The "accuracy of screw part" in Table 1 is based on the accuracy notation specified in JISB1192. No burr was generated at the joint.

Further, Table 2 shows a comparative example in which the combination A of the form shown in Example 9 is machined integrally by machining.
What was joined by the invention example shown in Examples 10 and 11,
Both were subjected to high-frequency heating at 950 ° C., then immersed in water, rapidly cooled and subjected to quenching treatment, and the results of measuring the surface hardness and the quenching depth (where Vickers hardness H _v is recognized to be 550 or more) are also shown. is there.

[Table 2]

As in Examples 10 and 11, the screw shaft 1 and the extending member 3 which have been hardened after joining have the same quench hardening as that manufactured by the shaving in Example 9 and have a high quality. A product with no discoloration was obtained. However, shaving requires a very long processing time as compared with rolling, resulting in poor productivity and markedly different manufacturing costs.

[0013]

As described above, according to the present invention, it is possible to manufacture a high quality ball screw at a low cost by joining the extending member with high strength to the end surface of the screw shaft in which the screw groove is machined in advance by rolling. effective.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a ball screw manufacturing apparatus according to the present invention.

FIG. 2 is a side view showing an example of joining a screw shaft and an extending member.

FIG. 3 is a side view showing an example of joining a screw shaft and an extending member.

FIG. 4 is a side view showing an example of joining the screw shaft and the extending member.

[Explanation of symbols]

 1 Screw Shaft 2 Fixed Chuck 3 Extension Member 4 Movable Chuck 5 Insert Material 6 High Frequency Induction Coil 7 Radiation Thermometer 8 Gas Spray Nozzle 9 Strain Gauge 10 Controller

Claims (6)

[Claims] 1. A metal material having a lower melting point between a screw shaft formed by forming a screw groove on an outer peripheral surface in advance by rolling and an extending member to be joined to an end surface of the screw shaft. Insert material having a melting point T _i lower than the melting point T _b of the metal material is heated to a temperature of T _i <T <T _b while applying pressure to the bonding surface and kept at that temperature for a certain time. A method for manufacturing a ball screw, characterized in that the extension member is joined to the screw shaft by holding it. 2. The method of manufacturing a ball screw according to claim 1, wherein the joint portion is heated by using a high frequency induction heating method. 3. The method of manufacturing a ball screw according to claim 1, wherein the joint portion is shielded and joined with an inert gas. 4. The method of manufacturing a ball screw according to claim 1, wherein the screw shaft and the extending member including the joint are heat treated after the joining. 5. A heating means for the joint, a means for measuring the temperature of the joint, a means for applying a pressure to the joint surface, a means for measuring the pressure, and a means for flowing an inert gas in the vicinity of the joint. , A ball screw manufacturing apparatus comprising these control means. 6. A ball screw, wherein an extension member is joined by liquid phase diffusion joining to one end of a screw shaft having a screw groove formed on the outer peripheral surface by rolling.