Linear guide bearing device

Details Linear guide bearing device Linear guide bearing device

1999-01-05

2001-01-16

Footland, Lenard A. (Department: 3682)

Bearings

Linear bearing

Recirculating

C384S625000, C384S912000

Reexamination Certificate

active

06174085

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a linear guide bearing device and, more particularly, to a linear guide bearing device in which rolling members are disposed between a rail and a bearing.
Linear guide bearing devices have been generally used in apparatuses which perform rectilinear motion, such as machining centers, lathes, grinders, robots, precision X-Y tables, measuring apparatuses, manufacturing facilities for semiconductor devices and liquid crystal display devices, and convey facilities. A linear guide bearing device used for these apparatuses comprises a rail, a bearing rectilinearly moving on the rail, and rolling members disposed in rolling contact between the rail and bearing.
The rolling theory of a rolling bearing is applied to linear guide bearing devices. The Lundberg-Palmgen theory in rolling bearings is also applied to the rolling fatigue in linear guide bearing devices.
Techniques obtained in the process of development of rolling bearings are utilized for materials, heat treatment conditions, and the like used in linear guide bearing devices. For example, the oxygen content in steel is suppressed to reduce nonmetallic inclusions that become the start points of separation as in rolling bearings. As for heat treatment, induction hardening and case-hardening are performed to introduce residual compression stress in the surface in order to prolong the service life as in rolling bearings.
A variety of techniques obtained in the process of development of rolling bearings are exploited in linear guide bearing devices. Higher workability is required for materials used for linear guide gearing apparatuses than those used for rolling bearings. In particular, excellent cold working like rail drawing is required. A material having a high carbon content used in rolling bearings may not often satisfy workability required in linear guide bearing devices.
Induction-hardened steel or case-hardening steel has been used for both the rail and bearing in conventional linear guide bearing devices. For example, “Special Steel” (February Issue, 1990, pp. 33 to 36) discloses a linear guide unit in which induction-hardened steel containing 0.53 wt % of carbon and 1.5 wt % of manganese and having an oxygen content of 10 ppm is used for both the rail and bearing. “NSK Technical Journal” (No. 645, pp. 45 to 59) reports use of degassified case-hardening steel for both the rail and bearing.
Of these steel materials, induction-hardened steel is most popular at present as the material for linear guide bearing devices because it can be relatively and easily heat-treated. It is, however, difficult to obtain excellent service life characteristics when induction-hardened steel is used for both the rail and bearing.
Along with recent developments of high-performance, high-speed, and high-precision mechanical apparatuses, demand has arisen for improving the performance of linear guide bearing devices. Durability is one of the performances to be improved most. For this reason, when durability is required, case-hardening steel is mainly used.
Case-hardening steel is better durability than induction-hardened steel. The use of case-hardening steel makes the heat treatment process more complex than the use of induction-hardened steel and requires bulky heat treatment facilities. The manufacturing cost becomes higher than that in the manufacture of a linear guide bearing device using induction-hardened steel.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made to solve the conventional problems described above, and has as its object to provide a linear guide bearing device excellent in life time characteristics and workability at low cost.
It is another object of the present invention to provide a linear guide bearing device excellent in life time characteristics.
In order to achieve the above objects, according to an aspect of the present invention, there is provided a linear guide bearing device comprising a rail, a bearing supported by the rail and rectilinearly movable along an axial direction of the rail, and rolling members interposed between the rail and the bearing to roll with the motion of the bearing, wherein at least one of the rail and the bearing is made of induction-hardened steel comprising 0.5 to 1.1 wt % of carbon, 0.05 to 0.25 wt % of silicon, 0.3 to 0.9 wt % of manganese, 0.1 to 0.5 wt % of chromium, 0.2 to 1.0 wt % of molybdenum, and residual portion as iron and unavoidable impurities, the induction-hardened steel having a total content of carbon, manganese, and molybdenum, which satisfies both inequalities (1) and (2) below.
Preferable modes of the linear guide bearing device will be described below.
(i) The rail is made of induction-hardened steel comprising 0.6 to 0.9 wt % of carbon, 0.05 to 0.25 wt % of silicon, 0.3 to 0.9 wt % of manganese, 0.1 to 0.5 wt % of chromium, 0.2 to 1.0 wt % of molybdenum, and residual portion as iron and unavoidable impurities, and the total content of carbon, manganese, and molybdenum in the induction-hardened steel satisfy both inequalities (1) and (2) below.
(ii) Both the rail and the bearing are made of the induction-hardened steel.
According to another aspect of the present invention, there is provided a linear guide bearing device comprising a rail, a bearing supported by the rail and rectilinearly movable along an axial direction of the rail, and rolling members interposed between the rail and the bearing to roll along with motion of the bearing, wherein the bearing is made of case-hardening steel, and a finished track surface of the bearing has a total content of carbon and nitrogen within a range of 0.7 to 1.4 wt %.
Preferable modes of the linear guide bearing device will be described below.
(i) Each of the rail and bearing is made of case-hardening steel, and each finished track surface of the bearing and the bearing has a total content of carbon and nitrogen within a range of 0.7 to 1.4 wt %.
(ii) The rail is made of induction-hardened steel comprising 0.5 to 1.1 wt % of carbon, 0.05 to 0.25 wt % of silicon, 0.3 to 0.9 wt % of manganese, 0.1 to 0.5 wt % of chromium, 0.2 to 1.0 wt % of molybdenum, and residual portion as iron and unavoidable impurities, and the total content of carbon, manganese, and molybdenum in the induction-hardened steel satisfy both inequalities (1) and (2) below.
(iii) The rail is made of induction-hardened steel comprising 0.6 to 0.9 wt % of carbon, 0.05 to 0.25 wt % of silicon, 0.3 to 0.9 wt % of manganese, 0.1 to 0.5 wt % of chromium, 0.2 to 1.0 wt % of molybdenum, and residual portion as iron and unavoidable impurities, and the total content of carbon, manganese, and molybdenum in the induction-hardened steel satisfy both:
0.8≦(C wt %−0.6)×10+Mn wt %  (1)
(C wt %−0.6)×10+Mn wt %+Mo wt %≦2.0  (2)
where C wt %, Mn wt %, and Mo wt % represent the weight percentages of carbon, manganese, and molybdenum to the induction-hardened steel.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.


REFERENCES:
patent: 5030017 (1991-07-01), Murakami et al.

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