JPH0134735Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a bearing combination device, and more specifically, to a combination of angular contact ball bearings for supporting the main shaft of a machine tool.

Bearings in rotating machines are generally located at both ends of the shaft, and the selection and combination of bearings is extremely important in order to fully utilize the functions of the bearings.

In particular, the main shaft of a machine tool, with a workpiece or tool attached to its free end, is supported and rotated by a front bearing and a rear bearing. During cutting operations performed by rotating the main shaft, bearings are subjected to radial loads acting in a direction perpendicular to the main axis and the central axis of the bearing, and thrust loads acting in a direction parallel to the central axis. The size and orientation are influenced by processing conditions in a broad sense.

Moreover, the direction of the thrust load is often
It is from the side of the workpiece or tool, that is, from the front to the rear of the spindle.

[Prior Art] With the demands for high speed, high load capacity, and high precision of machine tools, and especially automatic operation such as numerical control, it has become important to reduce heat generation in bearings. To meet this requirement, conventional machine tool spindle bearings used a combination of only tapered roller bearings or a combination of cylindrical roller bearings and angular contact ball bearings, but instead of using angular contact ball bearings. There is a growing trend to use bearings in combination.

Angular contact ball bearings (hereinafter referred to as "ball bearings"), including angular contact ball bearings, are advantageous in supporting high-speed rotating shafts, but they are difficult to handle due to the load and especially the rigidity required for bearings for the main shaft of machine tools. It has the disadvantage of being low. To compensate for these disadvantages, it is common practice to increase the number of ball bearings used.

By the way, when ball bearings are used on the front fixed side of the main spindle of a machine tool, there are generally two main combinations.
Rows, three rows or four row combinations are used. However, in consideration of limitations on bearing temperature rise, required rigidity, cost, etc., three-row combinations are most common, and some are five-row combinations.
In the case of a combination of even numbered ball bearings such as two or four rows, the preload acting on each ball bearing can be made equal; however, in the case of a combination of odd numbered rows, the preload applied to each ball bearing can be made equal. Unable to apply preload evenly to the bearing.

Therefore, when using an odd number of ball bearings on the front fixed side of the main shaft, a large number of ball bearings in the main bearing are arranged to receive thrust loads, and the ball bearings are arranged so that they receive thrust loads that mainly act in one direction. The rigidity and load capacity of the bearing are increased.

The amount of preload has an optimal value depending on the rotation speed of the spindle, cutting resistance, required rigidity, temperature rise limit, bearing life, etc. However, if the preload is not evenly applied to each ball bearing, it is impossible to apply the optimum preload value. Also, even if a certain tolerance is considered for the optimal value of preload,
The selection is extremely difficult, and becomes even more difficult as the rotational speed required of the spindle increases.

[Purpose of the invention] Considering the above points, the main purpose of this invention is to provide a bearing combination device that can equalize the preload acting on each ball bearing even when ball bearings are combined in an odd number of rows. It is in.

Particularly, the object of this invention is to provide a combination device of angular contact ball bearings consisting of an odd number of rows to be arranged on the front fixed side of the main shaft of a machine tool, which can achieve the above object.

[Structure of the invention] In order to achieve the above object, the bearing combination device of this invention is a combination of angular contact ball bearings in which the front bearings are arranged in odd number rows and the rear bearing is one piece, Furthermore, the front surface of each ball bearing and the back surface of the adjacent ball bearing are arranged so that they do not face each other.

In order to achieve the above-mentioned objectives and achieve remarkable effects, the bearing combination device of this invention will be described in detail, particularly when used for the main shaft of a machine tool.

FIG. 1 shows a bearing combination device of this invention: a front bearing consisting of three rows of angular contact ball bearings 10, 12, 14, and a rear row of angular contact ball bearings 16.
FIG. 2 is a schematic cross-sectional view showing a bearing constructed by and applied to a bearing for a main shaft 18 of a machine tool.

Since the structure of each part of the ball bearing is generally well known, its explanation will be omitted.
It is supported by a ball bearing 10, a second ball bearing 12, and a third ball bearing 14. The mounting method is also well known and is not the gist of this invention, but in FIG. An inner race spacer 24 is provided between the second ball bearing 12 and the third ball bearing 14.
is arranged, and the third ball bearing 14 is brought into contact with an inwardly protruding portion 26 of the housing 20.

The main shaft 18 is then supported at its rear by a row of rear ball bearings 16 . A rear outer race spacer 30 equipped with a spring 28 is interposed between the rear ball bearing 16 and the inward protrusion 26 of the housing 20, and the rear ball bearing 16 is connected to a preload nut 32 disposed behind it. It is held in

As described above, when the main shaft 18 is supported by three rows of ball bearings 10, 12, 14 at the front and one row of rear ball bearings 16 at the rear, in the combination of this invention, the front The front surface F and the rear surface B of adjacent ball bearings in odd-numbered rows do not face each other.

That is, in the embodiment shown in FIG. 1, as shown in FIG. 2, the first ball bearing 10 has one surface, for example, the front surface F, facing the front (left side in FIG. 1) of the main shaft 18. , second ball bearing 12
has its back surface B facing the front of the main shaft 18,
The front surface F and the rear surface B of the adjacent first ball bearing 10 and second ball bearing 12 do not face each other. next,
The third ball bearing 14 has its front face F facing the front of the main shaft 18, and the front face F of the second ball bearing 12 and the third ball bearing
The back surfaces B of the ball bearings 14 are arranged so that they do not face each other.

For the embodiment shown in FIG.
The state where preload is applied to 0, 12, and 14, that is, the transmission path (balance) of preload, is shown by a broken line with an arrow.
As shown in Figure 2. Note that in the same figure, parallel oblique lines indicating a cross section are omitted.

FIG. 3 shows an example of a conventional combination of ball bearings of this type. A similar bearing combination is also found in the magazine "Machine Design" Vol. 25, No. 13 (October 31, 1981, published by Nikkan Kogyo Shimbun) "Bearing/lubrication design application drawings" page 50. Published.

As is clear from FIG. 3, in the conventional bearing combination, when three rows of ball bearings 41, 42, 43 are used to support the front part of the main shaft 18, adjacent rows of ball bearings 41, 42, 43 are Rear side B of ball bearing 41 of No. 1
and the front surface F of the second ball bearing 42 face each other.

Figure 4 compares the conventional combination of ball bearings shown in Figure 3 with the combination of this invention, and shows the transmission path of the preload (balance of preload) applied to each ball bearing with a dashed line with an arrow. Similarly to FIG. 2, the parallel diagonal lines indicating the cross section are omitted in FIG. 4 as well.

[Effect of the invention] As can be easily seen by comparing FIG. 2 and FIG. 4, in this invention, the preload is equal to each ball bearing 10, 12, and It is understood that the preload on the rear ball bearing 16 is also equal to the preload on each of the front ball bearings.

On the other hand, in the conventional combination shown in FIG.
1 in that the preload is not evenly distributed on each ball bearing. By NSK Ltd.
In the catalog of "High-speed angular contact ball bearings" published in March 1984, on page 5, it is stated that "When angular contact ball bearings are used as fixed side bearings of the main shaft, the combination is generally a two-row combination. , 3-column combinations or 4-column combinations are used.
In the case of a row combination, the preload load distribution for each bearing is not equal (the preload on the first row bearing is greater than the second row bearing), so the optimal preload setting range is narrow;
Not suitable for high speed rotation. ” is explained.

Next, a case where five rows of ball bearings are used in the front section will be explained. FIG. 5 shows the combination of this invention according to FIG. 2, and the first to fifth ball bearings 51, 52, 53, 54, and 55 are arranged toward the front end of the main shaft, from the front F to the back, respectively. They are arranged in the order of B-Front F-Back B-Front F. As can be seen from the dashed lines with arrows in FIG. 5, preload is applied equally to each of the ball bearings 51-55.

On the other hand, Fig. 6 shows a conventional combination similar to Fig. 4, in which the first to fifth ball bearings 61, 62, 63, 64, and 65 are oriented toward the front end of the main shaft, respectively. They are arranged in the direction of F-F-F-back side B-B. The state of preload can be seen from the dashed lines with arrows shown in FIG.
For 63, preload is added at a ratio of 2,
Ball bearings 64 and 65 are preloaded at a ratio of 3.

As described in detail above, the bearing combination device of the present invention evenly distributes the preload to each of the odd rows of front ball bearings, so it can exhibit effects superior to those of the prior art.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing a case where the ball bearing combination device of this invention is constructed of three rows of angular contact ball bearings in the front part and one row in the rear part, and is used as a bearing device for the main shaft of a machine tool. The figure is a schematic diagram illustrating the state in which preload is applied to each ball bearing in the device shown in FIG. is a schematic diagram illustrating the state in which preload is applied to each ball bearing of the device shown in FIG. 3, and FIG. FIG. 6 is a schematic diagram illustrating a state in which preload is applied to each ball bearing in a conventional example using five rows of ball bearings at the front of the main shaft. In the drawings, the symbols indicating the main parts of this invention are as follows. 10...first ball bearing, 12...
Second ball bearing, 14... Third ball bearing, 16... Rear ball bearing, 18... Main shaft, 51... First ball bearing,
52... Second ball bearing, 53... Third ball bearing, 54... Fourth ball bearing, 55... Fifth ball bearing, B... Back side of bearing, F... Front side of bearing.

Claims (1)

[Claims for Utility Model Registration] 1. In a combination of angular contact ball bearings that support a rotating shaft divided into a front part and a rear part,
The front ball bearings are arranged in odd number rows, and the front surface of each ball bearing and the back surface of the adjacent ball shaft do not face each other, and the adjacent bearings are arranged in a direct force transmission relationship. , a bearing combination device characterized by having ball bearings arranged in one row at the rear. 2. The bearing combination device according to claim 1, wherein the adjacent bearings are arranged in a force transmission relationship via a spacer.