JPH0611434Y2 - Ball screw - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a ball screw used particularly in vacuum equipment, space equipment, high and low temperature equipment and the like.

<Prior Art> Conventionally, internal lubrication of a ball screw used under normal conditions is performed with grease, oil, or the like. However, when used in environments where such lubricants such as grease and oil cannot be used, such as vacuum equipment, space equipment, and high and low temperature equipment, the screw shaft, nut raceway surface, and metal ball outer peripheral surface cannot be used. A lubrication method in which a solid lubricant such as molybdenum sulfide or tungsten disulfide is coated in layers or a soft metal such as silver is ion plated is applied.

<Problems to be Solved by the Invention> However, the conventional example having such a configuration has the following disadvantages.

That is, the coated layered solid lubricant is worn and separated at an early stage, and the ball screw causes lubrication failure in an extremely short time, and each component is significantly worn or adhered in a short period of time. The result was At a high temperature in the presence of a certain amount of air, these solid lubricants are oxidized, causing poor lubrication at an early stage and making them unusable. Further, the silver ion plated product also suffered from peeling in a short period of time and had a short life.

As described above, at present, a ball screw that can withstand long-term use in a severe environment such as vacuum equipment, space equipment, and high / low temperature equipment has not been established.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a ball screw that can be stably used for a long period of time in an environment where a lubricant such as grease or oil cannot be used.

<Means for Solving the Problem> The present invention has the following configuration in order to achieve such an object.

That is, the ball screw according to the present invention comprises a stainless steel screw shaft, a stainless steel nut equipped with a circular tube for ball circulation, and a ball interposed between the screw shaft and the nut. As the ball, a ceramic ball and a carbon ball having a Vickers hardness of 1.5 times or more higher than that of the stainless steel forming the screw shaft and the nut are used together as the balls, and they are alternately arranged at a predetermined ratio. It is characterized by being placed in.

<Operation> The operation of the configuration of the present invention is as follows.

That is, the ceramic balls and the carbon balls come into contact during rolling, whereby the lubrication component of the carbon balls is transferred to the rolling parts between the ceramic balls and the screw shaft and the nut through the ceramic balls, and the lubrication of the rolling parts is performed. Is done.
In addition, since the hardness of the carbon balls is 1.5 times or more the Vickers hardness of the stainless steel forming the screw shaft and the nut, the lubricating component will not be consumed early due to peeling and the like. Period lubrication is possible.
Moreover, the ceramic balls and the carbon balls themselves have low thermal expansion, heat resistance, and excellent corrosion resistance, and can sufficiently withstand use in the harsh environment described in the conventional example.

According to the lubrication method using the combination of the ceramic balls and the carbon balls, it is clear from the experimental results in the examples that stable use can be achieved for a long period of time.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 and 2 show an embodiment of the present invention.
FIG. 1 is a partially cutaway perspective view showing a ball screw, and FIG. 2 is a vertical sectional view showing a ball arrangement mode.

In these figures, 1 is a screw shaft, and the screw shaft 1 is provided with a spiral groove 1a. Reference numeral 2 denotes a nut, and the spiral groove 2a is also formed in this nut. Reference numerals 3a and 3b are two types of balls which are interposed in a spiral passage formed by the spiral groove 1a of the screw shaft 1 and the spiral groove 2a of the nut 2. Further, the nut 2 is provided with a circular tube 4 for circulating the balls 3a and 3b in the spiral passage.

Then, the screw shaft 1 and the nut 2 are made of SUS440C, the circular tube 4 is made of stainless steel, and one of the two types of balls 3a and 3b is sintered, for example, one ball 3a containing silicon nitride as a main component. The body is a ceramic ball, and the other ball 3b is a carbon ball made of, for example, glassy carbon.
The ceramic balls 3a and the carbon balls 3b are alternately arranged in the spiral passage.
In this embodiment, the diameter of the carbon ball 3b is set smaller than that of the ceramic ball 3a by, for example, 40 to 60 μm, and the carbon ball 3b serves as a spacer. These ceramic balls 3a and carbon balls 3b have a Vickers hardness of 1.5 or more than stainless steel.
It is configured to have a hardness (Hv: 1700) more than double.

Next, the results of the non-lubrication durability test will be described.

The test conditions are: rotation speed 850 [rpm] movement stroke 100 [mm] axial load 1 [Kgf] reciprocating movement cycle time 4.2 [sec] (forward 1.5 sec, return 1.5 sec, folding back 1.2 sec)
c)

Then, in the test, in the ball screw having the above-mentioned configuration, the material of the ball was variously changed as shown in (a) to (d).

(a) All balls are SUS440C, (b) All balls are sintered bodies (ceramics) whose main component is silicon nitride, (c) All balls are carbon balls, (d) Ceramics When every other ball and carbon ball are used, as a result, in the case of (a), the wear of each part becomes large in an extremely short time, and when the life time is 1, the cases of (b) and (c) Example 2) is about twice as large as example (a), and example (d) corresponding to this example is about 100 times or more as large as example (a).

That is, in the case of the example (d), the ceramic balls 3a and the carbon balls 3b come into contact with each other during rolling, and the abrasion powder of the carbon balls 3b is transferred to the rolling portions, so that the rolling portions are stably lubricated. It is considered that long-term lubrication can be achieved because the entire ball is made of a carbon material having lubricity unlike the case where the layered solid lubricant is coated and wear of each part is suppressed to a small extent.

Although the above test results are obtained at room temperature, the ceramic balls 3a and the carbon balls 3b themselves have low thermal expansion, heat resistance, and excellent corrosion resistance, so that they can be used for a long time even in a high temperature atmosphere. It can be said that it can be used without problems.

By the way, the present invention includes the following configurations as examples.

That is, regarding the arrangement ratio of the ceramic balls 3a and the carbon balls 3b, for example, as shown in FIG. 3, two ceramic balls 3a are continuously arranged, and one carbon ball 3b is interposed between them. It is also possible to do it. Also in this case, since the carbon balls 3b always contact the ceramic balls 3a, the same lubricating effect as in the above-described embodiment in which one carbon ball 3a is alternately arranged can be exhibited, and moreover, since the number of the ceramic balls 3a is large, the load bearing capacity is large. There is an incidental effect that the value can be increased. Further, as the material of the circular tube 4, a fluorine resin,
For example, when polytetrafluoroethylene is used, the frictional resistance is extremely small, and therefore the fluororesin component contributes to lubrication. Further, the materials of the screw shaft 1 and the nut 2 are not limited to those described in the above embodiment.

<Effects of the Invention> According to the present invention, the following effects are exhibited.

Since the carbon balls having lubricity are used and the structure in which the carbon balls and the ceramic balls are used in combination, the friction component is reduced and the lubricity is improved due to the lubricating component of the carbon balls. In addition to the fact that the lubricating component is not consumed at an early stage due to peeling or the like, the life time can be remarkably improved as compared with that of the conventional example, as is clear from the experimental results in the above-mentioned examples. Furthermore, because the ceramic balls and carbon balls themselves have low thermal expansion, high heat resistance, and excellent corrosion resistance, such ball screws cannot be used in lubricants such as grease or oil in vacuum or in high or low temperature environments. It can be used stably for a long time in a special environment.

[Brief description of drawings]

1 and 2 relate to an embodiment of the present invention.
FIG. 1 is a partially cutaway perspective view showing a ball screw, and FIG. 2 is an enlarged sectional view showing a ball arrangement form. 3 is an enlarged sectional view corresponding to FIG. 2 according to another embodiment of the present invention. 1 ... screw shaft, 2 ... nut, 3a ... ceramic ball, 3b ... carbon ball, 4 ... circular tube.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshiaki Wakamatsu, 2nd Nishinomachi, Unagiya, Minami-ku, Osaka-shi, Osaka Prefecture Koyo Seiko Co., Ltd. (72) Takaya Doi 2-34, Minamiuematsucho, Yao-shi, Osaka Koyo Machine Industry Co., Ltd. (56) Reference Japanese Unexamined Patent Publication No. 63-152762 (JP, A) No. 60-175942 (JP, U) No. 63-51957 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A ball screw comprising a stainless steel screw shaft, a stainless steel nut equipped with a ball circulation circular tube, and a ball interposed between the screw shaft and the nut. As the balls, ceramic balls and carbon balls having a Vickers hardness of 1.5 times or more higher than that of the stainless steel forming the screw shaft and the nut are used together, and the balls are alternately arranged at a predetermined ratio. Ball screw characterized by.