JPH077046Y2 - A device that keeps the preload of the spindle bearing of a machine tool using bimetal constant. - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) This invention uses a bimetal to maintain a constant preload applied to a spindle bearing attached to a spindle of a machine tool such as a machining center, thereby ensuring accurate precision. The present invention relates to a device for performing work.

(Prior Art) An outer ring spacer and an inner ring spacer are interposed between the main shaft bearings of a machine tool, and the outer ring has a hydraulic pressure or a set screw so that the main shaft rotates properly during machining. Is always given a constant preload.

However, as the machining is performed, heat generated in the main shaft and the main shaft bearing is transferred to the inner and outer ring spacers, so that both spacers expand. On the other hand, the main shaft is cooled by cooling oil,
The outer ring spacer, which is located far from the main shaft, has a relatively high temperature compared to the inner ring spacer that is close to the main shaft.
The outer ring spacer tends to expand more than the inner ring spacer.

For this reason, an extra force is applied to the preload applied to the outer ring, the slip of the ball of the main shaft bearing becomes large, the regular rotation is not performed, and accurate machining cannot be performed. This tendency becomes more remarkable as the number of rotations of the main shaft increases.

Therefore, in order to keep the preload of the outer ring constant, measures such as detecting the number of rotations of the main shaft and automatically changing the hydraulic pressure or adjusting the push screw are taken.

(Problems to be Solved by the Invention) However, the means for changing the hydraulic pressure according to the rotational speed of the main shaft has a complicated structure and is expensive. Further, the means for adjusting the push screw has drawbacks that it is difficult to adjust and the cost becomes higher.

(Means for Solving Problems) The present invention has an object to provide a device for maintaining a constant preload applied to an outer ring at a low cost without using a complicated structure.

That is, at least a pair of bimetals are provided between outer rings of a main shaft bearing mounted on a main shaft of a machine tool so as to be opposed to each other with a space therebetween to press the two outer rings in opposite directions, and at the same time, reduce the space as the temperature rises. The idea is to wear it.

(Operation) The heat transmitted to the outer ring by the heat generation of the main shaft and the main shaft bearing raises the temperature of the bimetal interposed between the outer rings. Since the distance between the pair of bimetals shrinks as the temperature rises, extra force due to thermal expansion does not act on the outer ring,
The amount of preload given to the outer ring is kept constant.

(Effect) Since the amount of preload given to the outer ring is always kept constant by the bimetal interposed between the outer rings, the adjustment by the push screw is unnecessary. Moreover, a complicated structure such as using hydraulic pressure and a push screw is unnecessary.

(Example) In the drawings, 1a and 1b are main shaft bearings, 2a and 2b are outer rings thereof, and 3a and 3b are inner rings thereof. Reference numeral 4 is an inner ring spacer interposed between the inner rings.

5a and 5b are push rings, the front push ring 5a is in contact with the inner ring surfaces of the front outer ring 2a, and the rear push ring 5b is in contact with the inner ring surfaces of the rear outer ring, which are opposed to each other.

6a and 6b are a pair of bimetals, and a material having a small coefficient of thermal expansion (for example, iron) is provided on the inner side facing each other with a gap.
The metal piece A is formed by pressure-bonding a metal piece B made of a material (for example, copper) having a large coefficient of thermal expansion to the outside thereof.
The upper portions of the bimetals 6a and 6b are fitted in the recesses 13 provided on the inner peripheral surface of the spindle housing 12, which will be described later. The lower portion of the front bimetal 6a is the lower portion of the front push ring 5a and the lower portion of the rear bimetal 6b. Are arranged so as to come into contact with the opposing inner end surfaces of the rear pressing environment 5b.

Reference numeral 7 denotes a disc spring stretched between the upper portions of the pair of bimetals 6a and 6b. The pair of bimetals are connected by pressing the pair of bimetals in opposite directions with an appropriate force, and are supported by a support shaft 8. The disc spring 7 is provided at several places between the bimetals 6a and 6b.

Therefore, the heat of the main shaft and the main shaft bearing is transferred to the push ring 5a,
It is transmitted to the pair of bimetals 6a and 6b via 5b, and as the temperature rises, the bimetals are bent inward toward each other and the distance therebetween is shortened.

In addition, 11 is a main shaft, 12 is a main shaft housing, and 13 is a recess provided in the inner peripheral surface of the main shaft housing. Reference numeral 14 denotes a front flange that also serves as a main shaft bearing retainer, and is attached to the main shaft housing 12 by a push screw 15 and preloads the main shaft bearings 1a and 1b.

In the above embodiment, the pair of bimetals is interposed between the outer rings via the front and rear push rings, but it is also possible to dispose one or both of the push rings and directly insert between the outer rings.

It is also possible to provide a plurality of pairs of bimetals.

[Brief description of drawings]

 FIG. 1 is a vertical cross-sectional view of the main part of the spindle. 1a, 1b …… Outer ring 5a, 5b …… Push ring 6a, 6b …… Bimetal 11 …… Spindle

Claims (1)

[Scope of utility model registration request] 1. At least a pair of bimetals, which are disposed between the outer races of a main shaft bearing of a machine tool so as to be opposed to each other with a gap therebetween, press the outer races in opposite directions to each other, and reduce the gap as the temperature rises. A device that maintains a constant preload of the spindle bearing of a machine tool that uses bimetal.