BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view showing a bearing, on which grooves are formed;
FIG. 2 is a cross-sectional view showing a bearing having a cylindrical member connected to an outer member of a bearing;
FIG. 3 is a perspective view, partially cross-sectioned, showing the same bearing shown in FIG. 2;
FIG. 4 is a side view showing an outer member of a bearing, on which grooves are formed;
FIG. 5 is a side view showing an outer member of a bearing, on which V-shaped grooves are formed;
FIG. 6 is a side view showing an outer member of a bearing, on which grooves in another shape are formed;
FIG. 7 is a drawing showing an outer surface of the outer member shown in FIG. 4, spreading in a plane;
FIG. 8 is a cross-sectional view showing a press-die for forming grooves on an outer surface of an outer member of a bearing; and
FIG. 9 is a graph showing a length of a groove projected on an axial line and on a peripheral line of a bearing relative to an inclination degree of the groove.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will be described with reference to accompanying drawings. FIG. 1 shows a bearing composed of a bearing-inner 102, a bearing-outer 101, and rolling members disposed between the bearing-inner 102 and the bearing-outer 101. An inner ring of the bearing is referred to as “the bearing-inner”, and an outer ring of the bearing is referred to as “the bearing-outer” in this specification. In a center of the bearing 1, a through-hole H is formed. On an outer surface 103 of the bearing-outer 101, grooves 104, a first groove 104a and a second groove 104b, are formed.
The grooves 104 are inclined relative to a center axis of the bearing 1. A direction of the inclination of the first groove 104a is different from that of the second groove 104b. The grooves 104 are formed to firmly connect a cylindrical member (explained later in detail) on the outer surface 103 of the bearing-outer 101. Though two grooves 104 are shown in FIG. 1, it is possible to form more grooves on the outer surface 103 of the bearing-outer 101.
FIGS. 2 and 3 show another example of a bearing. In this example, an outer ring 2 is connected to the outer surface of the bearing-outer 101. On an outer surface 201 of the outer ring 2, grooves 202 are formed so that a cylindrical member 3 made of resin is firmly connected to the outer ring 2. The shape of the grooves 202 is the same as the grooves 104 shown in FIG. 1. That is, the grooves are inclined relative to the center axis of the bearing 1, and two grooves incline in different directions. Two grooves 202 are formed not to cross each other.
The grooves 104 formed on the bearing-outer 101 or the grooves 202 formed on the outer ring 2 can be variously modified as explained below. Since the grooves are formed on the bearing-outer 101 or the outer ring 2 in the same manner, the bearing-outer 101 and the outer ring 2 are collectively referred to as an “outer member” in the following description.
The grooves (104, 202) on the outer member (101, 2) may be formed in a shape shown in FIG. 4. In this example, the outer surface (103, 201) of the outer member is divided into four areas A, each corresponding to a center angle of 90° of the bearing. A space S is formed between neighboring areas. In each area A, plural grooves (104, 202) are formed not to cross each other and to incline relative to the center axis of the bearing. The directions of the inclination are alternately reversed area by area. Though the inclination angle θ relative to the center axis can be arbitrarily selected, it is preferable to make it 45° for the reasons explained later. A depth of the grooves and an interval of the grooves can be variously selected. The side view of the outer member shown in FIG. 4 is shown in FIG. 7 in a spread form.
As shown in FIG. 5, the grooves (104, 202) formed on the outer member (101, 2) may be made in a V-shape pattern. The patterns are reversed alternately area by area. The groove pattern is not limited to the V-shape pattern, but other patterns such as a sine-curve pattern may be employed. As shown in FIG. 6, the inclination directions of the grooves are not necessarily alternately reversed area by area. In the example shown in FIG. 6, the inclination direction is reversed in an area at the right side of a center area while it is not reversed in the left side area.
The grooves on the outer member (101, 2) can be formed in various methods. One example is shown in FIG. 8. In this example, the grooves are formed by press-work. Four press-dies 401-404, each having projected lines 405 corresponding to the grooves to be formed, are forcibly pressed against the outer surface (103, 201) of the outer member. In this manner, grooves in a desired shape can be formed. In this example, a space S is formed between neighboring areas.
The cylindrical member 3 is connected to the outer surface (103, 201) of the outer member (101, 2) in a known method such as molding. The cylindrical member may be formed with a resin material or a power material by molding. The material forming the cylindrical member 3 softened by heat in the molding process enters into the grooves (104, 202) to thereby firmly connect the cylindrical member 3 to the outer member.
FIG. 9 shows a length of the groove (104, 202) projected on the axial line (a line parallel to the center axis of the bearing) and a length of the groove projected on a peripheral line (a line perpendicular to the center axis) relative to the inclination angle θ. The former is referred to as a projected axial length, and the latter is referred to as a projected peripheral length, both being shown in FIG. 4.
As seen in FIG. 9, the projected axial length becomes smaller as the inclination angle θ becomes larger, while the projected peripheral length becomes larger as the inclination angle E becomes larger. The projected axial length contributes to increase in a force of preventing a relative rotation between the cylindrical member 3 and the outer member (101, 2). On the other hand, the projected peripheral length contributes to is increase in a force of preventing a relative movement in the axial direction between the cylindrical member 3 and the outer member. When the inclination angle E of the grooves is 45°, the relative movements in both directions are equally suppressed. Therefore, it is preferable to make the inclination angle θ 45°. The gripping force between the outer member and cylindrical member 3 in both of the rotational direction and the axial can be further increased by alternately reversing the inclination directions area by area.
The present invention is not limited to the embodiment or examples described above, but it may be variously modified. For example, the shape of the grooves is not limited to those shown above, but it may be formed in other shapes. The grooves may be formed by other methods than the press-work described above. The grooves may be formed by rolling. While the present invention has been shown and described with reference to the foregoing preferred embodiment, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.
Patent Application
20080069487
