JPS6244372A - Spindle structure - Google Patents

Abstract

PURPOSE:To improve a degree of flexural rigidity in a spindle, by forming a static pressure pad of a thrust bearing so as to receive the resultant force of a vertical component of force and a feed component of force of drinding force to be produced at the time of grinding. CONSTITUTION:A rotative driving pulley 36 is locked to one end of a spindle 24 and a cupped stone holder 27 to the other end, respectively, and a grindstone 29 is installed in an end face of this holder 27. A static pressure thrust bearing 32 is installed in a direction of the resultant force of a vertical component of force fN and a feed component of force fS of grinding force acting on the spindle 24 at the time of face grinding by this grindstone 29. Thus the static pressure thrust bearing 32 is installed whereby bending force and bending displacement are not produced on a bearing surface but vertical force alone comes to be added in consequence, so that performance of a hydrostatic bearing in itself is securable and, what is more, flexural rigidity in the spindle is enlargeable.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides sufficient rigidity and accuracy when processing is performed using a cup-shaped tool provided on the end face of a rotating shaft, such as in face grinding or face milling. This relates to the structure of the rotating shaft and tool to provide the same.

[Conventional technology]

Conventionally, the structure of a spindle and a tool used when face processing is performed using a cup-shaped tool such as face grinding and face milling is generally as shown in FIG. 2 as an example of face grinding. FIG. 2 shows an example in which the @ is held by a hydraulic hydrostatic bearing, and the grindstone is connected by a taper at the end of the spindle shaft.

The grinding resistance in face grinding is usually the ratio of the vertical component fS and the feed component force ``3'' (10 = 1 to 6:1), and the spindle is subjected to a large bending force due to the resultant force of the 2 component forces, and also due to the torque load. is subjected to a tangential force (perpendicular to the plane of the paper) ft.

[Problem that the invention seeks to solve]

However, as shown in the example of face grinding in Figure 2, the grinding resistance rN,r is applied to the end of the grinding wheel in the figure and results in a large bending force, but the conventional spindle and tool structures are not strong enough to withstand this force. There was a problem in obtaining bending rigidity.

To explain Figure 2 in detail, slide 2 on top of bed 1.
, and processing feed is performed in the direction of the arrow. A corrugated workpiece 6 is provided on the slide 2.

Spindle @4 is long and has hydrostatic radial bearings 10.11
supported by and opposed hydrostatic thrust bearing section 12.1
3 in the thrust direction. A hydraulic pressure supply path 14 and a discharge path 15 are provided inside the spindle outer cylinder 17 . Note that piping lines are omitted and not shown in the figure. Outer cylinder 1
7 is fixed at ℃ by the housing 18, and the housing 1
8 is not shown, but it is assumed that it is fixed to a column placed on the bed 1.

A taper 6 is provided at the end of the spindle 41 ] 4 , which is connected to a cup-shaped grindstone holder 7 and fixed with a screw 8 . The grindstone portion 9 is provided at the end of the holder 7.

In the spindle structure shown in FIG. 2, the bending force due to the grinding resistances fN and fll is supported by the bending rigidity of the bearings 10 and 11. The deflection of the spindle shaft 4 itself, the deflection of the holder 7, etc. overlap, and it is normal that sufficient rigidity cannot be obtained at the processed portion, that is, at the end of the grindstone. Therefore, during grinding, machining accuracy is poor due to uncut parts, and when truing the grindstone, it is impossible to form the grindstone with high accuracy with less end face runout.

It is an object of the present invention to provide a spindle and tool structure that can sufficiently withstand the bending forces generated by the grinding forces applied to the end of a cup-shaped grinding wheel.

[Means for solving problems]

The present invention includes a spindle in which a tool mounting portion is formed at one end;
In the main shaft structure consisting of a housing in which radial and thrust bearings are formed to support the spindle, the housing is characterized in that a static pressure pad of the thrust bearing is formed so as to receive the resultant force of grinding resistances fS4 and f3 generated during grinding. It is something.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a cross-sectional view of the spindle and grindstone.

The spindle shaft 24 has a roughly H-shaped cross section (actually consists of three parts), and both outer ends are held by hydrostatic thrust bearings 62 and 66, giving it a strong bending rigidity.
Further, it is rotatably supported within the housing 67 by a static pressure radial bearing 30. Hydraulic supply path 34 inside housing 67
, a discharge passage 65 is provided. Note that piping lines are omitted and not shown in the figure.

A rotation drive pulley 66 is fixed to one end of the spindle shaft 24, and a cup-shaped grindstone holder 27 is fixed to the other end. Whetstone 2
9 is provided on the end surface of the holder 27.

The grinding wheel 29 and the grinding wheel holder 27 do not have any narrow constricted parts as seen in the structure of FIG. 2, and the spindle shaft 2
Since it is directly fixed to the end face of 4, the grinding resistance fN, f
It is characterized by the fact that there are no locations where 9" deflection occurs due to S.

Next, the grinding point at the end of the grinding wheel 29 and the static pressure thrust bearing 62
About the positional relationship.

In the case of face grinding, the vertical component of grinding resistance fN and the feed component force f
It is widely known that the l+ ratio is in the range of 10:1 to 6:1. Since the resultant force of fN and fs acts on the spindle shaft 24 in the direction of the arrow shown in the figure, if the hydrostatic thrust bearing 62 is provided in the direction of this resultant force, no bending force or bending displacement will occur on the bearing surface. With the addition of an honest sword, it is possible to bring out the original performance of the hydrostatic bearing.

In addition, in the conventional structure shown in FIG. 2, the hydrostatic bearings 1o and 11 were subjected to bending force and bending displacement as well as the above-mentioned "deflection" of the structure. In principle, +C is weak against bending inclinations, and its usage has impaired its original performance.

〔Effect of the invention〕

As is clear from the above explanation, the shaft shape, bearing shape, and bearing arrangement shown in the present invention are 10:1 to 10:1 to 6:1 from the end of the grinding wheel.
: By providing the thrust bearing at a position opposite the vector of the combined grinding resistance of 1, the original performance of the bearing can be obtained, and the spin hydrostatic radial bearings 1o and 11, which have high bending rigidity, each have a rigidity of 3oKv/μ. There is something that is 3K at the end of the whetstone.
g/μ and 1/101C stiffness were decreased. In the structure shown in Fig. 1, the hydrostatic thrust bearing 62'? :30 and 97μ, the same rigidity value can be obtained at the end of the grindstone.

In the above embodiments, the hydraulic hydrostatic bearing was used as an example, but it goes without saying that the same effect can be obtained with other bearings, such as air bearings, sliding bearings, rolling bearings, etc.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a spindle and grindstone according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a spindle and grindstone according to the prior art. 1...Ped, 2...Table, 6...
...Workpiece, 4.24...Spindle axis,
5... Thrust receiver is flange, 6... Taper, 7... Grinding wheel holder, 8
...Screw, 9...Whetstone, 10.11.
60...Static pressure radial bearing, 12.13.62
．． 66...Static pressure thrust bearing, 14.35...
...Hydraulic supply path, 15.64...Discharge path, 16.66...
・Pulley, 17...Spindle outer cylinder,

Claims (1)

[Claims] In a main shaft structure consisting of a spindle with a tool mounting portion formed at one end and a housing formed with radial and thrust bearings that support the spindle, the housing receives the resultant force of the grinding resistance f_N and f_S generated during grinding. The main shaft structure is characterized by the formation of a static pressure pad.