JPS61111867A - Constitution member for machine tool - Google Patents

Abstract

PURPOSE:To secure the working precision of a machine tool by preventing the thermal deformation of a hollow constitution member due to the difference of the temperature response speed in the same member for the change of the outside air temperature by charging liquid into the hollow part of the hollow constitution member. CONSTITUTION:When a temperature difference is generated between the parts of a constitution member 21, natural convection is generated in the liquid 22 in a hollow part by the change of liquid density. Since the heat transfer from the high-temperature part of the constitution member 21 to the low-temperature part through the liquid 22 in the hollow part by the natural convection in this case, the generated temperature difference is offset, and the max. temperature difference generated between the parts of the constitution member 21 is kept at a small value. Further, by charging liquid into the hollow part of the constitution member 21, the heat capacity of the liquid 22 is added, and the same effect to the increase of the body thickness of the constitution member 21 can be obtained, and the following of the temperature of the constitution member 21 to the change of the outside air temperature can be suppressed, and also the temperature difference generated between the parts of the constitution member 21 is reduced, and the thermal deformation can be suppressed, and a machine tool having a high precision can be obtained.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to structural members of machine tools, and is intended to maintain the machining accuracy of machine tools by preventing uneven thermal deformation of the structural members due to temperature changes. This is what I did.

<Prior Art> Generally, machine tools are composed of structural members such as columns, cross rails, and saddles. For example, as shown in FIG. 2 showing an overview of a portal machine tool, a pair of columns 12 are erected on both sides of a table 11 that can be moved back and forth in the horizontal direction, and a bridge 13 is provided at the upper end of the column 12. are strung across to form a gate shape, and a cross rail 14 is attached to this column 12 so as to be movable up and down. A saddle 15 is attached to the cross rail 14 so as to be movable horizontally left and right along the cross rail 14.
A ram 16 is attached to the ram 5 so as to be movable up and down, and a tool 17 is held at its lower end. In such a machine tool, as shown in FIG. 3 showing a cross-sectional perspective view of the column 12, for example, a guide surface 12a is formed on the front surface of the column 12 to guide the vertical movement of the cross rail 14. As a result, the accuracy of the guide surface 12a greatly influences the positional accuracy of the tool 17. For this reason, the guide surface 12
It is necessary to increase the thickness of the part a to ensure rigidity, and there is a large dimensional difference between this and the thickness of the opposite side. That is, the front surface of the column 12 where the guide surface 12a is formed has a thick wall, and the opposite side B has a thin wall thickness. Circumstances like B are not limited to Column 12.
The same applies to the cross rail 4, the saddle 15, etc., and the thicknesses of the constituent members of the machine tool are not necessarily uniform.

<Problems to be solved by the invention> Machine tools for precision machining were generally installed in thermostatic chambers due to the need for thermal rigidity, but in recent years they have been installed in factories without constant temperature equipment. High machining accuracy is also required for machine tools. When a machine tool is placed in an environment with temperature changes, the temperature changes cause thermal deformation. Especially in large machine tools, even a slight temperature change causes the component parts to deform significantly, making it difficult to obtain the necessary machining accuracy. The problem arises that there is no.

In other words, as shown in Fig. 4, which is a graph showing an example of the calculated value of the room temperature tracking of steel sheet temperature of various wall thicknesses, the thinner the wall thickness, the smaller the heat capacity, and the faster the response speed to surrounding temperature changes. In structural members whose wall thicknesses are not uniform, temperature differences occur within the same member, and deformation occurs due to differences in thermal expansion of the materials caused by this. To explain this using the above-mentioned column 12 as an example, as shown in FIG. 5, the eight thinner sides of the column 12 follow the room temperature faster than the thicker side A with respect to changes in room temperature. Therefore, for example, 5
At points P and M, the temperature of surface 8 is higher than that of surface A, while the temperature of surface 5 is higher than that of surface A.
At times A and M, the temperature of surface 8 is lower than surface A. Therefore, due to the difference in thermal expansion between the A side and the 8th side due to the temperature difference, the column 12 is 5P0M and the A side is 5P0M as shown in FIG.
It is inclined toward the surface side, and in 5A and M, it is inclined toward the 8th surface side.

Means for Solving the Problems> The present invention aims to prevent thermal deformation of structural members due to differences in temperature response speed within the same member to changes in outside air temperature as described above. In order to achieve this object, the present invention provides a method for filling a hollow part of a hollow component of a machine tool with a liquid.

In this way, heat transfer between the respective parts of the component is promoted by natural convection of the liquid within the component, and the temperature difference within the component is reduced.

In addition, the apparent thickness of the component increases due to the heat capacity of the liquid (i.e., the ability of the component to follow temperature changes in the outside air is suppressed).

Example of implementation Embodiments of the present invention will be described in detail below with reference to FIG.

FIG. 1 ta+ is a longitudinal sectional view of a first embodiment of the present invention. In this embodiment, a hollow portion of a columnar structural member z1 such as a column constituting a machine tool is filled with a liquid 22 such as water or 'nb until its M surface 22a reaches approximately the ceiling surface of the structural member 21. .

Further, FIG. 1 [bl is a longitudinal cross-sectional view of a second embodiment of the present invention. In this embodiment, as in the previous example, the liquid 22 is filled into the hollow portion of a columnar structural member 21 such as a column.
In this embodiment, a dummy mounting member 23 that is non-absorbent and lightweight, such as foamed polystyrene, is installed in the hollow portion in order to save the amount of liquid 22 and reduce the overall weight. The dummy personnel 23 is held in the center of the component 21 by a fixture (not shown), and the liquid 22 is filled between the inner surface of the component 21 and the outer surface of the dummy personnel 23.

FIG. 1 (CL is a cross-sectional view of a third embodiment of the present invention, in which a liquid 22 is filled into the hollow part of a cross-beam-like structural member 21 such as a bridge or a cross rail constituting a machine tool. It is something.

Further, a tammy-equipped human body 23 is provided in the hollow portion as in the previous example.

According to such a configuration, when a temperature difference occurs between each part of the component 21, natural convection occurs in the liquid 22 in the hollow part due to a change in liquid density. At this time, the liquid 2 in the hollow part 2 is transferred from the high temperature part of the component 21 by natural convection heat transfer.
2 to the colder parts, the temperature differences that occur are canceled out and the maximum temperature difference occurring between the parts of the component 21 is kept at a small value.

In other words, the prediction formula for natural convection heat transfer due to the inner wall of a container with a fluid sealed inside is Ra - 'βΔtD'
,,,Llla ν Nu = 0.0516 Ra
-f2)λ α= Nu −-431 where, Ra: Ray number [-koΔt: temperature difference between wall and fluid [℃] D: Representative dimension [mko Nu: Nusselt number [-] a: Heat transfer Coefficient [kcal/m'h°C] β: Body expansion coefficient of fluid [1/k] a: Temperature conductivity of fluid [m'/s] ν: Kinematic viscosity coefficient of fluid [m'/s] 'λ: It is given by the thermal conductivity of the fluid [kcal/mh'c]. Now, FIG. 7 shows the results calculated using equations (1) to (3) for cases in which water and air are respectively sealed as fluids. As shown in FIG. 7, the heat transfer when liquid (water) is sealed is more than 10 times that of air, so the temperature difference is reduced to less than one-tenth.

Furthermore, by filling the hollow part of the component 21 with the liquid 22, the heat capacity of the liquid 22 is added, so there is an effect equivalent to increasing the thickness of the component 21, as shown in FIG. As described above, the temperature tracking of the component 21 itself with respect to changes in the outside air temperature is suppressed, and therefore the temperature difference occurring between the respective parts of the component 21 is also reduced. for example,
The heat capacity of a water film with a thickness of 100 mm is equivalent to that of a steel plate with a thickness of approximately 100 mm, and the resulting reduction in temperature difference is significant.

<Effects of the Invention> As described above in detail with reference to the embodiments, according to the present invention, in a hollow structural member constituting a machine tool, the hollow part is filled with a liquid, so that changes in outside temperature can be avoided. For the same - the depletion between each part within the component 7
Once the difference is reduced, thermal deformation of the constituent members can be prevented, making it possible to provide a highly accurate machine tool.

[Brief explanation of the drawing]

FIG. 1 (al, (bl, fc)) is the first embodiment of the present invention.
, sectional views of the second and third embodiments, Fig. 2 is an overview of the column type machine tool, Fig. 3 is a cross-sectional perspective view of the column, and Fig. 4 shows room temperature changes in the form of a sine curve with an amplitude of 10°C Figure 5 is a graph showing the temperature change of the A side and B side of the column with respect to the room temperature change. Figure 6 is the graph showing the temperature change of the column deformation. The explanatory diagram, FIG. 7, is a graph showing an example of calculated values of internal convection heat transfer when water and air are enclosed. In the drawing, 21 is a component of the machine tool, 22 is a liquid, and 23 is a dummy personnel. (ri.)Military-9μ retroactive, J-,,,,.

Claims (1)

[Claims] 1. A hollow structural member constituting a machine tool, characterized in that the hollow portion thereof is filled with a liquid.