The present invention relates to rolling bearings in which rollers or balls are used as rolling elements and the infinite rectilinear motion is provided by endlessly circulating those rolling elements.
As the rolling bearings for providing the infinite rectilinear motion, the following arts have been conventionally proposed: namely, as shown in FIG. 29, the rollers of single row are used as the rolling elements (refer to Japanese Utility Model Application No. 61971/1980); as shown in FIG. 30, the rollers of total four rows consisting of respective two rows on the right and left sides are used as the rolling elements (refer to Japanese Patent Application Laid-open No. 622/1983); as shown in FIG. 31, the rollers of three rows are used as the rolling elements (refer to Japanese Patent Application Laid-open No. 101121/1982); as shown in FIG. 32, the balls of four rows are used as the rolling elements (refer to Japanese Patent Application Laid-open No. 72912/1980); and as shown in FIG. 33, the balls of six rows are used as the rolling elements (refer to Japanese Patent Application Laid-open No. 29936/1973), etc.
Any of the above-mentioned bearings belongs to the technical field of the rolling bearings for providing the endless rectilinear motion of the present invention.
The common points regarding the construction of the bearings of the foregoing prior arts are as follows.
(i) Rollers 30, 31 and 32, or balls 33 and 34 are used as the rolling elements.
(ii) The infinite circuits comprise: rectilinear track passages 35, 36, 37, 38, and 39 in the regions where some weight is applied thereto; rectilinear return passages 40, 41, 42, 43, and 44 in the regions where no weight is applied thereto; and direction reversing passages 45, 46, 47, 48, and 49 on both sides which respectively couple both ends of both rectilinear passages, thereby smoothly reversing the traveling direction of the rolling elements. The axial central line which passes on the centers of the cross sections perpendicular to the rolling direction of the rolling elements at each portion of the infinite circuit (therefore, the rolling locus of the centers of the rolling elements which roll in the infinite circuit) is located on the axial central plane as the same plane. This axial central plane is the plane which is perpendicular to the rolling axis of each roll in the case where the rolling elements are the rollers and it is the plane which passes through the center of each ball in the case where the rolling elements are the balls. Therefore, in the case where the infinite circuit is cut along the axial central plane, the rolling elements in the infinite circuit are represented as the cross sections of the circles having the same diameter which are sequential in the contact relation with each other as illustrated in FIGS. 1, 2, 30(C), 30(D), 31(B), and 32(B), etc.
The conventional rolling bearings as described above relatively satisfy the performances of the bearings such as service life, coefficient of friction, sliding resistance, and the like and are therefore used as the bearings for providing the rectilinear motion at the rectilinear moving portions of various equipment. However, recently, the development of the rolling bearings for the rectilinear motion whereby the sliding resistance is lower and the coefficient of friction is smaller than those of the conventional bearings is required.
In the conventional rolling bearings for the rectilinear motion, the infinite circuit is formed as an arbitrary proper construction. Thus, even if the degree of finishing accuracy of each part of the infinite circuit is improved, the stick slip as the bearings cannot be reduced, so that the sliding resistance as the entire bearings cannot be decreased. Particularly, in the case where the rollers 30, 31 and 32 are used as the rolling elements as shown in FIGS. 29, 30 and 31, and in case of the bearings having the complicated constructions whereby the rolling elements are endlessly circulated on track rails 51 and 53 along the track passages 36 and 38 of four rows as shown in FIGS. 30 and 32, the sliding resistance is increased due to the occurrence of a larger stick slip. Therefore, it is demanded to solve the occurrence of stick slip.