JPH0418722Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bearing structure for a ceramic main shaft in a machine tool or the like.

[Conventional technology]

Many of today's electronic devices and various mechanical devices pursue extremely high precision, and the parts that make up these devices and various devices are required to be processed with high precision. Processed using a Motsuta ultra-high precision lathe. For the spindle of such ultra-high precision lathes, instead of a metal spindle, lathes have been developed that use a spindle made of lightweight ceramic material with a small coefficient of thermal expansion (for example, Utility Model Application No. 59-53161). ), which is effective in ultra-high precision machining on the submicron scale.

For example, as shown in Figure 2, machine tool M
, a main shaft 1 made of ceramic material (or metal material) has a front bearing 3 disposed on a headstock 2,
The main shaft 1 is supported by a rear bearing 4, and is configured such that movement of the main shaft 1 in the thrust direction is controlled by a front thrust seat 5 and a rear thrust seat 6 on both sides of the front bearing 3.

[Problems with conventional technology]

In the case of such a bearing structure for the main shaft 1, it may be caused by a minute precision defect in the sliding surface A of the front bearing 3 and the front thrust seat 5, or a minute defect in perpendicularity with the main shaft thrust direction. However, there is a drawback in that the main spindle 1 is moved slightly forward and backward in the thrust direction during rotation, which tends to reduce the machining accuracy of the workpiece held at the tip of the main spindle 1.

In addition, the large number of mechanical parts that make up the bearing makes it difficult to assemble the parts, making it unsuitable for the spindle structure of machine tools that require ultra-high precision on the so-called submicron level of 1 μm or less. Ta. Furthermore, when the main shaft 1 rotates, lubricating oil is supplied by a separately installed hydraulic pump through an oil supply hole (not shown) provided in the tapered surface of the front bearing 3. Even if an appropriate oil film is maintained in case B, on sliding surface A especially when a load is applied to the main spindle 1 in the thrust direction, that is, machining in a direction perpendicular to the main axis of the workpiece held at the tip of the main spindle 1. When attempting to do this, if a large load is applied, it becomes difficult to maintain an appropriate oil film on the sliding surface A, and problems such as seizure and abnormal wear occur due to lack of the oil film.

[Means for solving problems]

Therefore, in order to solve the above problem, two tapered surfaces with different angles were formed in the front bearing part of the main spindle, with the angle becoming wider towards the tip of the main spindle, and the angle of the tapered surface closer to the tip of the main spindle was changed from 45 to 75 degrees. I made it within the range to support it.

〔Example〕

FIG. 1 shows a bearing structure as a machine tool M according to an embodiment of the present invention. In this, the same parts as in the conventional example will be explained using the same reference numerals.

Reference numeral 1 denotes a main shaft made of metal or ceramic material, to which a workpiece is attached at the tip;
Front bearing 30 and rear bearing 4 arranged on the headstock 2
The shaft is supported by a power transmission mechanism (not shown), and is rotatably driven from the rear end by a power transmission mechanism (not shown).

The main shaft 1 is supported at one end by the front bearing 30, but the main shaft 1 is supported by the front bearing 30.
Tapered surfaces C and D are formed, therefore, the inner surface of the front bearing 30 is also provided with a tapered shape corresponding to the tapered surfaces C and D, so that it slides on the tapered surfaces C and D of the main shaft 1. The rear thrust seat 6 constitutes one of the bearings.

Note that the angle of the tapered surface C is 1 to
Preferably within a range of 5°.

In addition, if the angle of the tapered surface D becomes too small, the main shaft may bite into the front bearing due to a wedge-like effect, causing excessive stress to be applied to the sliding surface and cause it to seize up. It also becomes less resistant to On the other hand, if the angle of the tapered surface D becomes too large, the oil film becomes uneven and uneven, and the oil film tends to run out on the sliding surface.

Therefore, the angle of the tapered surface D is preferably within the range of 45 to 75 degrees.

[Effect of idea]

As mentioned above, according to the present invention, tapered surfaces with different angles are formed on the main shaft, and the main shaft is supported by bearings corresponding to the tapered surfaces. This eliminates the need for a front thrust seat, and the number of parts can be reduced, making it possible to reduce the number of man-hours and costs required for manufacturing parts, and to facilitate assembly and adjustment.

Furthermore, while the spindle is rotating, it is possible to minimize minute displacements in the front direction of the spindle that occur due to slight precision defects in the front bearing. It is possible to dramatically improve the surface machining accuracy in the direction.

Also, during the rotation of the main shaft, the sliding surface with the bearing is
The oil film of the lubricating oil on the two tapered surfaces can be maintained at an optimal value, and in particular, the oil film on the tapered surface D, which mainly receives loads in the thrust direction, can be maintained at an optimal value, so that it can withstand high loads in the thrust direction. It has many effects, such as increased durability under high loads during cutting, and the ability to provide high-precision rotation necessary for high-precision machining and finishing.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a bearing structure of a main shaft according to an embodiment of the present invention. FIG. 2 is a sectional view showing a conventional main shaft bearing structure. 1... Main shaft, 2... Headstock, 3, 30... Front bearing, 4... Rear bearing.

Claims (1)

[Scope of utility model registration request] In order to rotate the workpiece, the rear and front sides of the main spindle made of ceramic material are supported by rear bearings and front bearings, respectively, and the front bearing has two different angles that widen toward the tip of the main spindle. A bearing structure for a main spindle in a machine tool, etc., characterized in that it is supported by angular tapered surfaces C and D, and the angle of the tapered surface D near the tip of the main spindle is 45° to 75°.