JPS59107805A - Main spindle unit of machine tool - Google Patents

Abstract

PURPOSE:To prevent fretting due to a microscopical vibration to be generated during machining from generating, by constituting part of each of main spindles touching mutually with ceramics, in a main spindle unit provided with a hollow main spindle and a boring main spindle which is fitted in the inner circumferential part of the hollow main spindle slidably. CONSTITUTION:The external circumferential part of a boring main spindle 1 is coated with ceramics at a part as shown by hatch C, in a device revolving the boring main spindle 1 which is fitted in a hollow spindle 2 and is connected with the same spindle 2 with a key through a revolution of the hollow shaft 2 to be revolved by a motor through an appropriate transmission device. An inner circumferential part of the hollow spindle 2 is coated with the ceramics at parts as shown by hatches A, B. In addition to the above, a bushing 4 is made of the ceramics or an inner circumferential surface of the same is coated with the ceramics at the hatched parts A', B'. With this construction, fretting to be generated between both the spindles 1, 2 due to the vibration at the time of machining processing by mounting tools on the spindle 1 can be prevented effectively from generating.

Description

[Detailed description of the invention] This invention relates to a spindle unit equipped with a hollow shaft and a boring spindle that is freely movable in the axial direction within the hollow shaft, and allows various machining to be performed using tools attached to each spindle. be.

A conventional seed spindle unit is shown in FIGS. 1 and 2. In the same figure, the boring spindle ■ has the rotational torque transmitted to the motor (not shown) through gears and belts.
Conveyed to the hollow shaft ■.

By the key ■ between the hollow shaft ■ and the boring spindle ■.

Torque is transmitted to the boring spindle ■, causing it to rotate. A tool is attached to the tip of this boring spindle 1 to perform cutting. Recent advances in tool materials have made tools able to withstand harsh conditions even when a certain amount of cutting vibration occurs. Micro-vibration wear (fretting) occurs between ■ and the hollow shaft ■, resulting in damage to both the boring main shaft ■ and the hollow shaft ■.

Traditionally, boring spindles have been made of hardened steel or nitrided steel to improve wear resistance and seizure resistance. Similarly, hollow shaft ■
Hardened steel or nitrided steel is used for the entire body, but as shown in Figure 2, the hollow shaft body is made of ordinary steel, and only the part that slides with the boring main shaft is made of wear-resistant and anti-seizure material. There are also some that are made of high-quality materials and have a low push button.

However, even with this consideration, the occurrence of fretting cannot be prevented in response to current cutting vibrations.

In view of the above-mentioned circumstances, an object of the present invention is to provide a spindle unit that prevents fretting between a hollow spindle and a boring spindle due to fine movement caused by cutting. It is characterized in that the mutually contacting parts of the inner peripheral part of the shaft and the outer peripheral part of the boring spindle mounted in the hollow shaft so as to be able to move in the axial direction are made of ceramic.

Embodiments according to the present invention will be described below based on the drawings.

FIG. 3 corresponds to FIG. 1 showing the conventional device, and FIG. 4 similarly corresponds to FIG. 2. In the figure, 1 is a boring spindle and 2 is a hollow shaft.

4 indicates Bunon, respectively. The outer periphery of the boring spindle l is coated with ceramic at the area indicated by the diagonal line ◎. Furthermore, the inner circumferential portion of the hollow shaft is coated with ceramic at the portions indicated by diagonal lines (■) and (■). Furthermore, the bushing 4 is made of ceramic, or its inner peripheral surface is coated with ceramic at the diagonal lines (1) and (2).

With this configuration, fretting is less likely to occur between the boring shaft 1 and the hollow shaft 2 due to vibrations that occur when a tool is attached to the boring main shaft 1 and cutting is performed. This is also clear from the experiments described below.

FIG. 5 shows the test equipment used to test the fretting resistance, and FIG. 6 shows the test piece. For the non-fretting resistance test, two test pieces were set, one on the top and one on the bottom, the lower test piece 5 was fixed, the upper test piece 6 was connected to the actuator 7, and the actuator 7 applied the load. It vibrates up and down in response to the

As a result, the 45° slopes of test pieces 5 and 6 slide while receiving the load, causing fretting. The magnitude of the load is measured by a load cell 8.

Since fretting in air involves an oxidation phenomenon, it is preferable to use a material that has a small difference in hardness between the sliding material and its oxide. The above test results revealed that ceramic is optimal for this purpose.

Types of ceramics include Cr2O3 ceramic, W
There are C-based ceramics and ZrO2-based ceramics, and these are used as test pieces for the above-mentioned fretting resistance test. According to a comparison of test results with

It is remarkable that the combination of ceramics is less likely to cause fretting than nitrided steel or the like.

As explained above, according to the present invention, the parts of the boring main spindle and the hollow shaft where they contact each other are made of ceramic, so that the micro-vibration (with respect to Ic) that occurs during machining with the tool attached to the boring main spindle is However, fretting does not occur, and therefore the machining capacity of the machine tool is increased and failures are prevented, so the operating rate is improved.

[Brief explanation of drawings]

FIGS. 1 and 2 are longitudinal sectional views showing a conventional device, FIGS. 3 and 4 are longitudinal sectional views showing an embodiment of the present invention, and FIG. 5 is a front view showing a testing device for a fretting resistance test. , FIG. 6 is a front view of the test specimen. 1... Boring spindle, 2... Hollow shaft, ■, ■
, ■...Ceramic coating part. Article E (a) Continued from page 1 0 Inventor: Kei Katayama - 4-6-22 Kannon-Shinmachi, Nishi-ku, Hiroshima City, Mitsubishi Heavy Industries, Ltd. Hiroshima Research Center 0 Inventor: Masaru Rokkaku 4-6, Kannon-Shinmachi, Nishi-ku, Hiroshima City No. 22, Mitsubishi Heavy Industries, Ltd., Hiroshima Research Center 0 Inventors: Sadato Shigemura, 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Tamabishi Heavy Industries, Ltd., Hiroshima Research Center

Claims (1)

[Scope of Claims] A spindle unit for a machine tool comprising a hollow spindle and a hollow nine spindle that is fitted into the inner circumference of the hollow spindle and configured to freely move in the axial direction. A spindle unit for a machine tool, characterized in that the inner circumferential portion of the hollow spindle and the outer circumferential portion of the boring spindle are made of ceramic.