JPH05215548A - Vertical axis structure of survey instrument - Google Patents

Abstract

PURPOSE:To obtain high vertical accuracy with a manufacturing cost suppressed. CONSTITUTION:The upper end of a bearing 2 supporting a vertical axis 1 is tapered, a plurality of bearing balls 3 are placed on this tapered face 2a, a thrust bearing face la of the vertical axis 1 is supported via these balls 3, and a plurality of bearing balls 4 held by a ball retainer 5 along a peripheral direction are rotatably pressed between an outer peripheral face on a lower part of the vertical axis 1 and an inner peripheral face on a lower part of the bearing 2. Thus rattling along a radial direction of the vertical axis 1 is suppressed while automatic centripetal function due to the bearing balls placed on the tapered face 2a of the bearing 2 can be sufficiently exhibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical axis structure of a surveying instrument, and more particularly to a vertical axis structure of a surveying instrument such as a theodolite or a total station.

[0002]

2. Description of the Related Art A conventional vertical shaft structure is shown in FIGS.
As shown in FIG. 3, the upper end of the bearing 12 that supports the vertical shaft 11 is tapered, a plurality of bearing balls 13 are arranged on the tapered surface 12 a, and the thrust receiving surface 11 a of the vertical shaft 11 is interposed via these balls 13. There is a structure in which the lower part of the vertical shaft 11 is fitted to the lower part of the bearing 12.

As another conventional vertical shaft structure, as shown in FIG. 4, a bearing ball 104 held along a circumferential direction by a ball retainer 105 is provided on the outer peripheral surface of the vertical shaft 101 and the inner peripheral surface of the bearing 102. Press in between the vertical shaft 10
There is one in which the thrust ball bearing 107 receives the thrust of No. 1 (JP-A-54-1659).

[0004]

However, the vertical accuracy required for a surveying instrument is as high as several arcseconds, and in order to obtain such high vertical accuracy with the former vertical axis structure, the vertical axis 1
There is 1-2 μm of fitting play in the lower part of 1, but it is necessary to further reduce this fitting play, and a more advanced processing technique is required to reduce this. However, even if the fitting gap becomes small, the grease oil film becomes thin, and another problem of occurrence of baking occurs.

On the other hand, in the latter vertical shaft structure, since the bearing balls 104 are press-fitted, there is no play and the vertical accuracy is high, but the bearing balls 104 must be arranged on the entire outer peripheral surface of the vertical shaft 101. Therefore, roundness and cylindricity are required in a wide range over the entire length of the vertical shaft 101 and the bearing 102, and high processing accuracy is required.

In order to manufacture the latter vertical shaft structure,
Since it is necessary to find the difference between the outer diameter of the vertical shaft 101 and the inner diameter of the bearing 102 and select and use the bearing ball 105 suitable for the difference, it is necessary to prepare a large number of various bearing balls 105 having different diameters in advance. I have to. Therefore, the dimensional accuracy of many bearing balls 105 must be controlled, and the manufacturing cost becomes high.

Furthermore, the press-fitting of the bearing balls is performed with a preload amount of 1 to 2 μm from the viewpoint of Hertz stress.
Therefore, the sum of cylindricity and variation in ball diameter is 1 μm
It is practically difficult to prepare a large number of bearing balls within this accuracy range.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a vertical axis structure of a surveying instrument which is inexpensive and can obtain high vertical accuracy.

[0009]

A vertical axis structure of a surveying instrument of the present invention for solving the above-mentioned problems has a structure in which an upper end portion of a bearing for supporting the vertical axis is tapered and a plurality of bearing balls are provided on the tapered surface. In the vertical shaft structure of the surveying instrument in which the thrust receiving surface of the vertical shaft is supported through these balls, a plurality of bearing balls held along the circumferential direction by a ball retainer are attached to the vertical shaft. It was rotatably press-fitted between the outer peripheral surface of the lower part and the inner peripheral surface of the lower part of the bearing.

[0010]

As described above, the plurality of bearing balls held by the ball retainer in the circumferential direction are rotatably press-fitted between the outer peripheral surface of the lower vertical shaft and the inner peripheral surface of the lower bearing. Therefore, the play in the radial direction can be suppressed, and the automatic centering action of the bearing balls arranged on the tapered surface of the bearing can be sufficiently exerted to improve the vertical accuracy.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a vertical sectional view showing a vertical axis structure of a surveying instrument according to an embodiment of the present invention.

The upper end of the bearing 2 supporting the vertical shaft 1 is formed in a tapered shape, and a plurality of bearing balls 3 are arranged on the tapered surface 2a.
The thrust receiving surface 1a of the vertical shaft 1 is supported via the.

A collar portion 2b is provided on the upper portion of the bearing 2,
A horizontal scale plate (not shown) is fixed to the collar portion 2b. A flange portion 2c is provided below the bearing 2, and the flange portion 2c is fixed to a leveling table (not shown) with screws.

Between the inner peripheral surface of the lower portion of the bearing 2 and the outer peripheral surface of the lower portion of the vertical shaft 1, 10 to 30 bearing balls 4 are press-fitted in a rollable manner. These bearing balls 4
Are held by the ball retainer 5 in a row at equal intervals along the circumferential direction.

A retaining nut 6 is screwed onto the lower end of the vertical shaft 1.

The 10 to 30 bearing balls 4 held by the ball retainer 5 as described above are connected to the vertical shaft 1
Since it is press-fitted between the outer peripheral surface of the bearing and the inner peripheral surface of the bearing 2 so as to be freely rollable, it is possible to suppress backlash in the radial direction without causing seizure and to obtain high vertical accuracy. Further, since the press-fitting portion of the bearing ball 4 is limited between the lower portion of the vertical shaft 1 and the lower portion of the bearing 2, if the range in which the roundness and the cylindricity should be secured is large compared with the conventional vertical shaft structure. That is, roundness and cylindricity are not required in a wide range over the entire length of the vertical shaft 1 and the bearing 2, and the number of bearing balls 4 whose dimensional accuracy is to be controlled is significantly reduced. as a result,
Processing becomes easier and the cost required for processing can be reduced.

Further, as described above, as the press-fitting portion of the bearing ball 4, a portion between the lower portion of the vertical shaft 1 and the lower portion of the bearing 2 is selected, and 10 to 30 which are held by the ball retainer 5 at equal intervals in the circumferential direction. Since the outer peripheral surface of the vertical shaft 1 is supported only by the individual bearing balls 4, the bearing 2
The automatic centering action of the bearing balls 3 arranged on the tapered surface 2a is sufficiently exerted, and a higher vertical accuracy can be obtained.

In the above-mentioned embodiment, the case where the plurality of bearing balls 4 are held in a line at equal intervals along the circumferential direction by the ball retainer 5 has been described. However, as a modification, the bearing balls 4 are equally spaced along the circumferential direction. Even if the bearing ball groups held in a line are arranged in two stages in the axial direction, it is possible to obtain the same effects as the above-described embodiment.

However, when three or more bearing ball groups are arranged side by side, the automatic centripetal action on the taper surface 2a at the upper end portion does not function sufficiently, which is not preferable.

Further, even in the case of providing the bearing ball group of two stages in the axial direction, it is preferable to provide the bearing ball group in the narrowest axial range below the vertical shaft in order to fully exert the automatic centripetal action.

[0022]

As described above, according to the vertical shaft structure of the surveying instrument of the present invention, it is possible to suppress the play in the radial direction, and the automatic centering action by the bearing balls arranged on the tapered surface of the bearing is sufficient. The vertical range and cylindricity required for processing vertical shafts and bearings are greatly limited, and the number of bearing balls that must be controlled for dimensional accuracy is significantly increased. Since the amount is reduced, the processing is facilitated and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a vertical axis structure of a surveying instrument according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a conventional surveying instrument having a vertical shaft structure.

FIG. 3 is an enlarged vertical sectional view showing the vertical axis structure of FIG.

FIG. 4 is a vertical cross-sectional view showing another conventional vertical axis structure.

[Explanation of symbols]

 1 ... Vertical shaft 1a ... Vertical shaft thrust receiving surface 2 ... Bearing 2a ... Bearing tapered surface 3, 4 ... Bearing ball 5 ... Ball retainer

Claims (2)

[Claims] 1. A surveying instrument, wherein an upper end portion of a bearing for supporting a vertical shaft is tapered, a plurality of bearing balls are arranged on the tapered surface, and the thrust receiving surface of the vertical shaft is supported through these balls. In the vertical shaft structure of the machine, a plurality of bearing balls held along the circumferential direction by a ball retainer are press-fitted between the outer peripheral surface of the lower vertical shaft and the inner peripheral surface of the lower bearing so as to be rollable. The vertical axis structure of the surveying instrument. 2. The vertical shaft structure for a surveying instrument according to claim 1, wherein the plurality of bearing balls are arranged in one or two stages in the axial direction.