Composite Bearing

Abstract: A composite bearing has an outer ring 2 and an inner ring 1 arranged coaxially with a space between them, and ball grooves in the opposing surfaces of the inner ring and outer ring, with balls 3 which can rotate freely in the grooves. A friction bearing 4 is arranged between the outer ring and inner ring on at least on one side of the balls, which is cylindrically-shaped and has, for example, an outer part fixed to an outer ring sleeve 6, and an inner surface providing a bearing part against the inner ring 1, with a gap g having a specified value for restricting the permitted range of inclination of the inner and outer rings.

Description: The present invention relates to a composite bearing structure and more particularly to a composite bearing structure composed of a combination of single row ball bearings and cylindrical bearings. Single row ball bearings are simple in construction and low cost, and are therefore widely used for the bearings in the rotational support mechanism of the rotational axis in compact motors, etc. FIG 17 shows a sectional view through a single row ball bearing. In the single row ball bearing shown in FIG 17, when a single bearing 100 is used, the outer ring 101 freely inclines through an angle of  on top of ball 102. As a result, when a rotating body (not shown) such as the hub of a spindle motor is mounted on outer ring 101, this rotating body will vibrate in both the axial and radial directions with relation to inner ring 103, and so the rotation will be unstable. Similarly, if outer ring 101 is fixed and when a rotating body (not shown) such as the rotational shaft of a spindle motor is mounted on inner ring 103, this rotating body will vibrate in both the axial and radial directions with relation to outer ring 101, and so the rotation will be unstable. In order to prevent this vibratory rotation of the rotating body, as shown in FIG 18, two single row ball bearings 100 and 110 are fixed together in a parallel assembly, or, as shown in FIG 19, to further reduce the rotational vibration, a spacer 120 is mounted between the two single row ball bearings 100 and 110, increasing the space between ball bearing 100 and ball bearing 110, preventing rotational vibration and achieving stable high precision rotation. However, in response to the trend for smaller size in many kinds of device, when a rotating body of more compact dimensions is to be employed, it is desired to reduce the dimension L in FIGS 18 and 19 as much as possible. Accordingly, to make the dimensions as compact as possible, the arrangement is often used as shown in FIG 18 where single row ball bearings 100 and 110 are mounted side by side, instead of the arrangement where a spacer 120 is used between single row ball bearings 100 and 110 as shown in FIG C. If it is desired to reduce the minimum dimensions even more than this, the only solution is to specially manufacture thin multiple row ball bearings. Even if such special thin multiple row ball bearings are used, the dimensions are limited by the size of the balls in the 2 side-by-side parallel rows. A concrete example of this trend toward reducing the size of devices is the remarkable recent reduction in the size and thickness of floppy disk drives and hard disk drives for magnetic storage equipment. Demand is especially strong for more compact, thinner spindle motors for use in such drives. To respond to this demand for more compact, thinner spindle motors, a major point is to find some method for making the dimensions of the bearing section more compact (thinner). At present, the only ways to meet these requirements are by using a side-by-side double row of ball bearings, or specially produced multiple row ball bearings as mentioned above, and these methods have their limitations. For the bearing on one side of a spindle motor, it is desirable to use a single ball bearing in order to make the motor thinner, but in this case rotational vibration will occur as described above and such a method is not practical. Also, the use of 2 single row ball bearings for this purpose would increase the cost too much. The present invention has been acomplished in view of the above-mentioned problems and it is an object of the invention to provide a bearing struture in which a single ball bearing is used in such a way as to prevent rotational vibration in the same way as if two ball bearing were used, and in addition to provide a low cost, thin type ball bearing structure. FR-A-1464889 discloses a hydrodynamic needle or ball bearing. comprising the features of the preamble of claim 1. GB-A-1042549 discloses a needle bearing. According to the present invention, there is provided a composite bearing having a single row ball bearing and cylindrical bearing, comprising: an inner ring and an outer ring of said row ball bearing arranged coaxially with a space between them; balls disposed between ball grooves of the inner ring and the outer ring; wherein a cylindrical friction bearing mounted on one of the inner ring and the outer ring and spaced from the other of the inner ring and the outer ring by a gap, and disposed beside the ball bearing, for reducing inclination of the inner ring and the outer ring of said ball bearing relative to one another. The present invention provides a structure using one single row ball bearing (the smallest unit which can be used in a ball bearing), which, in order to solve the problem of inclination and vibration in the inner and outer rings, uses a sintered, oil-impregnated bearing or alternatively, a non-oil-impregnated dry bearing, a fluid bearing, etc.(There are defined with a friction bearing.) where an inner or an outer ring of the friction bearing is mounted either on one side or on both sides, in a structure which reduces inclined rotation. The radial load is mainly received by the ball, and when the inner and outer rings are about to vibrate and incline, a sintered, oil-impregnated bearing mounted either on one side or on both sides of the inner ring or outer ring closes the gap and slightly contacts the opposing inner or outer ring thus reducing the inclination, said contact surface being, because it is the inner or outer ring surface of the single row ball bearing, a very precisely finished surface, and thus the frictional loss from the inclination load is slight. Furthermore, the thrust load is all received by the ball. In this way, practically the whole of the radial load is received by the ball, the thrust load is also all received by the ball, and the friction loss received by the inclination-reducing sintered, oil-impregnated bearing is very slight, and therefore there is no great influence on either the rotational precision or the lifetime reliability. The present invention makes possible a bearing with minimal width, which can be formed by a composite bearing having an anti-collapse function, and which does not require much increase of the width of the single row ball bearing. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing embodiment No. 1 of the present invention, for a single composite bearing. FIG. 2 is a sectional view showing embodiment No. 2 of the present invention, for a single composite bearing. FIG. 3 is a sectional view showing embodiment No. 3 of the present invention, for a single composite bearing. FIG. 4 is a sectional view showing embodiment No. 4 of the present invention, for a single composite bearing. FIG. 5 is a sectional view showing embodiment No. 5 of the present invention, for a single composite bearing. FIG. 6 is a sectional view showing embodiment No. 6 of the present invention, for a single composite bearing. FIG. 7 is a sectional view showing embodiment No. 7 of the present invention, for a single composite bearing. FIG. 8 is a sectional view showing embodiment No. 8 of the present invention, for a single composite bearing. FIG. 9 is a sectional view showing embodiment No. 1 of the present invention, for a double composite bearing. FIG. 10 is a sectional view showing embodiment No. 2 of the present invention, for a double composite bearing. FIG. 11 is a sectional view showing embodiment No. 3 of the present invention, for a double composite bearing. FIG. 12 is a sectional view showing embodiment No. 4 of the present invention, for a double composite bearing. FIG. 13 is a sectional view showing embodiment No. 5 of the present invention, for a double composite bearing. FIG. 14 is a sectional view showing embodiment No. 6 of the present invention, for a double composite bearing. FIG. 15 is a sectional view showing embodiment No. 7 of the present invention, for a double composite bearing. FIG. 16 is a sectional view showing embodiment No. 8 of the present invention, for a double composite bearing. FIG. 17 is a sectional view showing a conventional ball bearing. FIG. 18 is a sectional view showing a conventional arrangement of two ball bearings fixed together in parallel. FIG. 19 is a sectional view showing the arrangement of a spacer between conventional ball bearings. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The basic structure of the composite bearing of the present invention can be divided into two types as follows. (1): A composite bearing comprising one single row ball bearing and one sintered, oil-impregnated bearing mounted on 1 side (hereafter referred to as a single composite bearing) This structure will be described in detail with reference to Figures 1 to 8. (2): A composite bearing comprising one single row ball bearing and two sintered, oil-impregnated bearings, one mounted on each side (hereafter referred to as a double composite bearing) This structure will be described in detail with reference to Figures 9 to 16. Next, the overall characteristics will be described. - 1. Single composite bearing: Because there is only 1 inclination reducing sintered, oil-impregnated bearing on 1 side, this type has production and cost advantages, but with regard to the accuracy of inclination, there are some drawbacks compared to the double type. -2. Double composite bearing: Because there are 2 inclination reducing sintered, oil-impregnated bearings mounted on 2 sides, this type has production and cost disadvantages, but it provides better accuracy of inclination compared to the single type. Next, the detailed structure of each type of composite bearing will be described. - 1. Single composite bearing As shown in FIG 1, a single composite bearing comprising an inner ring 1, having a width L of the size necessary to restrain the inclination of the axis within the permitted range, and an outer ring 2, having a width which is half the width of the above mentioned width L, which is mounted above the outside half of inner ring 1 and separated from inner ring 1 by a gap. A ball 3 is fitted into this gap between the rings and rests in grooves made in each ring. The ball 3 is prevented from escaping from the groove by retainer 5. Inner ring 1 has an external form which is superfinished to high precision in one piece and contains the ball groove described above. The outside of outer ring 2 is press fitted into outer ring sleeve 6, which is made of metal having a cylindrical form of width L. Cylindrically-shaped sintered, oil-impregnated bearing 4 is press fitted into the space formed by the inner parts of outer ring 2, ball 3 and retainer 5. The outer diameter of this sintered, oil-impregnated bearing 4 is the same as the inner diameter of outer ring sleeve 6, and its inner diameter is slightly larger than the outer diameter of inner ring 1. Because of this, sintered, oil-impregnated bearing 4 is press fitted firmly to the inner side of outer ring sleeve 6 and forms a small gap g above the peripheral face of inner ring 1. This inclination suppression gap g, in order to prevent the inclination from exceeding the permitted range, is determined by the dimensions A and B shown in FIG 1, and accordingly extremely high precision processing is required. During operation of the single composite bearing, if either outer ring 2 or inner ring 1 begins to incline, part of the surface B of sintered, oil-impregnated bearing 4 will contact surface A of inner ring 1 and prevent any further inclination from occurring. The size of the inclination of the axis can be determined by the size of inclination suppression gap g. FIGS 3, 5 and 7 show basically similar structures to the above, in which a single composite bearing has an inclination suppression gap g formed on the inner ring 1 side. These structures will be described in detail below. A single composite bearing shown in FIG 3 has a structure in which the single composite bearing and the inclination suppression gap g are established on the inner ring 1 side. Sintered, oil-impregnated bearing 4, processed to the dimensions outer diameter C, inner diameter B and width W, is combined with a single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5. As shown in FIG 3, there is no outer ring sleeve and instead the outer face of sintered, oil-impregnated bearing 4 is fitted or bonded to the other part in such a way as to maintain inclination suppression gap g. This embodiment does not require the outer ring sleeve 6 of the embodiment shown in FIG 1, and instead the parts can directly assembled together. This embodiment has the advantage of allowing the diametrical dimension to be reduced. A single composite bearing shown in FIG 5 has a structure in which the single composite bearing and the inclination suppression gap g are established on the inner ring 1 side. Sintered, oil-impregnated bearing 4 is combined with a single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5. Also, outer ring 2 has a stepped large diameter part F, and sintered, oil-impregnated bearing 4 is press fitted or bonded onto this stepped large diameter part F of outer ring 2 to form a structure which, together with inner ring 1, maintains inclination suppression gap g. In this embodiment, sintered, oil-impregnated bearing 4 is fixed together with outer ring 2 to make a one-piece single composite bearing. This embodiment is easy to use, easy to handle, and does not require an outer ring spacer, and is thus advantageous from the cost viewpoint and because it allows size reductions in the diametrical direction. Also, assembly precision is high. A single composite bearing shown in FIG 7 has a structure in which the single composite bearing and the inclination suppression gap g are established on the inner ring 1 side. Sintered, oil-impregnated bearing 4 is combined with a single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5. Sintered, oil-impregnated bearing 4 is press fitted or bonded onto the inner diameter part G of outer ring 2 to form a fixed structure which maintains inclination suppression gap g with the dimensions A and B on the inner ring side. In this embodiment, sintered, oil-impregnated bearing 4 is fixed together with outer ring 2 to make a one-piece single composite bearing, with the outer diameter of inner ring 1 and the inner diameter of outer ring 2 both processed to standard bearing dimensions. This embodiment is easy to use, easy to handle, does not require an outer ring spacer or outer ring step processing, and is thus most advantageous from the cost viewpoint and because it allows size reductions in the diametrical direction. Also, assembly precision is high. In another embodiment, as shown in FIG 2, a single composite bearing comprises an inner ring 1, having a width L of the size necessary to restrain the inclination of the axis within the permitted range, and an outer ring 2, having a width which is half the width of the above mentioned width L, which is mounted above the outside half of inner ring 1 and separated from inner ring 1 by a gap. A ball 3 is fitted into this gap between the rings and rests in grooves made in each ring. The ball 3 is prevented from escaping from the groove by retainer 5. Inner ring 1 has an external form which is superfinished to high precision in one piece and contains the ball groove described above. The outside of outer ring 2 is press fitted into outer ring sleeve 6, which is made of metal having a cylindrical form of width L. Sintered, oil-impregnated bearing 7 is arranged in the space formed by the inner parts of outer ring 2, ball 3 and retainer 5. As shown in FIG 2, this sintered, oil-impregnated bearing 7 has an outer diameter which is smaller than the inner diameter of outer ring sleeve 6, and an inner diameter of the same size as the outer diameter of inner ring 1. Because of this, sintered, oil-impregnated bearing 7 is press fitted firmly to the outer side of inner ring 1 and forms a small gap g with the inner peripheral face of outer ring 2. This inclination suppression gap g, in order to prevent the inclination from exceeding the permitted range, is determined by the dimensions C and D shown in FIG 2, and accordingly extremely high precision processing is required. During operation of the single composite bearing, if either outer ring 2 or inner ring 1 begins to incline, part of the surface C of sintered, oil-impregnated bearing 7 will contact surface D of outer ring sleeve 6 and prevent any further inclination from occurring. The size of the inclination of the axis can be determined by the size of inclination suppression gap g. FIGS 4, 6 and 8 show basically similar structures to the above, in which a single composite bearing has an inclination suppression gap g formed on the inner ring 1 side. These structures will be described in detail below. In a single composite bearing shown in FIG 4, the inclination suppression gap g is established with outer ring 2. Sintered, oil-impregnated bearing 7, having width I and outer diameter C which forms the specified inclination suppression gap g, is bonded or press fitted to inner ring 1 to make a structure which maintains the gap S with the edge face of outer ring 2. Outer ring 2 is assembled by bonding or press fitting to inner diameter E of the opposing part, thus forming inclination suppression gap g with inner diameter E of the opposing part. This composite bearing structure as shown in FIGS 3 and 4 has the advantage of allowing the diametrical dimension to be reduced. In the single composite bearing shown in FIG 6, the inclination suppression gap g is established with the side of outer ring 2. In the single composite bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5, outer ring 2 has a processed stepped section with large diameter F, and sintered, oil-impregnated bearing 7 is press fitted or bonded onto inner ring 1 to form a structure which maintains inclination suppression gap g with this stepped large diameter part F and also establishes gap S with the edge side of the outer ring. In this structure, sintered, oil-impregnated bearing 7 is fixed together with inner ring 1 to make a one-piece single composite bearing. This embodiment is easy to use, easy to handle, and does not require an outer ring spacer, and is thus advantageous from the cost viewpoint and because it allows size reductions in the diametrical direction. Also, assembly precision is high. In a single composite bearing shown in FIG 8, the inclination suppression gap g is established with the side of outer ring 2. In the single composite bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5, sintered, oil-impregnated bearing 7 is press fitted or bonded onto inner ring 1 to form a structure which creates inclination suppression gap g between the inner diameter part G of outer ring 2 and outer diameter part C of sintered, oil-impregnated bearing 7. In this structure, sintered, oil-impregnated bearing 7 is fixed together with inner ring 1 to make a one-piece single composite bearing, with the outer diameter of inner ring 1 and the inner diameter of outer ring 2 both processed to standard bearing dimensions. This structure is easy to use, easy to handle, does not require an outer ring spacer or outer ring step processing, and is thus most advantageous from the cost viewpoint and because it allows size reductions in the diametrical direction. Also, assembly precision is high. -2. Double composite bearing As shown in FIG 9, a double composite bearing comprises an inner ring 1, having a width L of the size necessary to restrain the inclination of the axis within the permitted range, and an outer ring 2, having a width which is the same as the above mentioned width L, which is mounted above the outside of inner ring 1 and separated from inner ring 1 by a gap. A ball 3 is fitted into the central space between the two rings and rests in a groove in the outside of inner ring 1 and a groove in the inside of outer ring 2. The ball 3 is prevented from escaping from the ball groove by retainers 5. Inner ring 1 is super finished in one piece to high precision in a shape having the ball groove described above. Half-sintered oil-impregnated bearings 8 and 9, each having width I, are fitted into the space between inner ring 1 and outer ring 2 on each side of ball 3. The outer diameters of half-sintered oil-impregnated bearings 8 and 9 are the same as the inner diameter of outer ring 2, and their inner diameters are slightly larger than the inner diameter of inner ring 1. Because of this, half-sintered, oil-impregnated bearings 8 and 9 are press fitted firmly to the inner side of outer ring 2 and form a small gap g with the peripheral face of inner ring 1. This inclination suppression gap g, in order to prevent the inclination from exceeding the permitted range, is determined by the dimensions A and B shown in FIG 9, and accordingly extremely high precision processing is required. During operation of the double composite bearing, if either outer ring 2 side or inner ring 1 side begins to incline, part of one surface B of half-sintered, oil-impregnated bearings 8 and 9 will contact surface A of inner ring 1 and prevent any further inclination of the axis from occurring. The size of the inclination of the axis can be determined by the size of inclination suppression gap g. FIGS 11, 13 and 15 show basically similar structures to the above, in which a double composite bearing has an inclination suppression gap g formed on the inner ring 1 side. These structures will be described in detail below. A double composite bearing shown in FIG 11 has a structure in which the inclination suppression gap g is established on the inner ring 1 side. Sintered, oil-impregnated bearings 8 and 9, processed to the dimensions outer diameter C, inner diameter B and width L, are press fitted onto either side of outer ring 2 of the single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5, thus forming a structure which establishes an inclination suppression gap g on the inner ring 1 side. In this case, the opposing parts may be freely designed as regards shape, and can be directly assembled together with the opposing parts with no need for an outer sleeve ring 6. This has the advantage of allowing the diametrical dimension to be reduced. A double composite bearing shown in FIG 13 has a structure in which the inclination suppression gap g is established on the inner ring 1 side. Sintered, oil-impregnated bearings 8 and 9, processed to the dimensions outer diameter C, inner diameter B and width L, are press fitted onto the inner diameter part of outer ring sleeve 6 and press onto either side of outer ring 2 of the single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5, thus forming a structure which establishes an inclination suppression gap g with outer ring sleeve 6. In this embodiment, the external diameter of the composite bearing becomes large, but the one-piece structure has the advantages of easy handling and assembly. A double composite bearing shown in FIG 15 has a structure in which the inclination suppression gap g is established on the inner ring 1 side. Sintered, oil-impregnated bearings 8 and 9, processed to the dimensions outer diameter F, inner diameter B and width I, are press fitted onto the inner diameter part of outer ring sleeve 6 and press into the large diameter F sections of either side of outer ring 2 of the single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5, thus forming a one-piece structure which establishes inclination suppression gap g with the side of inner ring 1. In this embodiment, no outer ring sleeve is required and the two sintered, oil-impregnated bearings 8 and 9 are directly assembled together with outer ring 2 as a one-piece assembly, thus offering the advantages of compactness and smaller size in the diametrical direction. In a further embodiment as shown in FIG 10, a double composite bearing comprises an inner ring 1, having a width L of the size necessary to restrain the inclination of the axis within the permitted range, and an outer ring 2, having a width which is the same as the above mentioned width L, which is mounted above the outside of inner ring 1 and separated from inner ring 1 by a gap. A ball 3 is fitted into the central space between the two rings and rests in a groove in the outside of inner ring 1 and a groove in the inside of outer ring 2. The ball 3 is prevented from escaping from the ball groove by retainers 5. Inner ring 1 is super finished in one piece to high precision in a shape having the ball groove described above. Half-sintered oil-impregnated bearings 10 and 11, each having width I, are fitted into the space between inner ring 1 and outer ring 2 on each side of ball 3. The outer diameters of half-sintered oil-impregnated bearings 10 and 11 are slightly smaller than the inner diameter of outer ring 2, and their inner diameters are the same as the outer diameter of inner ring 1. Because of this, half-sintered, oil-impregnated bearings 10 and 11 are press fitted firmly to the outer side of inner ring 1 and form a small gap g with the inner peripheral face of outer ring 2. This inclination suppression gap g, in order to prevent the inclination from exceeding the permitted range, is determined by the dimensions C and G shown in FIG 10, and accordingly extremely high precision processing is required. During operation of the double composite bearing, if either outer ring 2 side or inner ring 1 side begins to incline, part of one surface C of half-sintered, oil-impregnated bearings 10 and 11 will contact surface G of outer ring 2 and prevent any further inclination of the axis from occurring. The size of the inclination of the axis can be determined by the size of inclination suppression gap g. FIGS 12, 14 and 16 show basically similar structures to the above, in which a double composite bearing has an inclination suppression gap g formed on the outer ring 2 side. These structures will be described in detail below. A double composite bearing shown in FIG 12 has a structure in which the inclination suppression gap g is established on the outer ring 2 side. Sintered, oil-impregnated bearings 10 and 11, processed to the dimensions outer diameter C, inner diameter B and width L, are press fitted or bonded onto inner ring 1 and mounted, so as to preserve a gap S, on either side of outer ring 2 of the single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5, thus forming a structure which establishes inclination suppression gap g between the opposing parts. In this case, the assembly is formed as a single piece unlike the set shown in the example of FIG 14, and so both handling and assembly are easy. Also, the opposing parts may be freely designed as regards shape, and can be directly assembled together with the opposing parts with no need for an outer sleeve ring. This has the advantage of allowing the diametrical dimension to be made more compact. A double composite bearing shown in FIG 14 has a structure in which the inclination suppression gap g is established on the outer ring side. Sintered, oil-impregnated bearings 10 and 11, processed to the dimensions outer diameter C, inner diameter B and width I, are press fitted or bonded onto the outer diameter part of inner ring 1 and mounted, so as to preserve a gap S, on either side of outer ring 2 of the single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5, thus forming a structure which establishes inclination suppression gap g with outer ring sleeve 6. In this embodiment, the outer diameter dimension of the double composite bearing becomes large, but its one-piece construction offers the advantages of easy handling and assembly. A double composite bearing shown in FIG 16 has a structure in which the inclination suppression gap g is established on the outer ring 2 side. Sintered, oil-impregnated bearings 10 and 11, processed to the dimensions outer diameter C, inner diameter B and width I, are press fitted or bonded onto the outer diameter part of inner ring 1 and mounted, so as to preserve a gap S with the stepped faces of outer ring 2, on either side of outer ring 2 of the single row ball bearing formed by inner ring 1, outer ring 2, ball 3 and retainer 5, thus forming a one-piece structure which establishes inclination suppression gap g with the large diameter faces F formed by a step process on outer ring 2. In this embodiment, no outer ring sleeve 6 is required and the two sintered, oil-impregnated bearings 10 and 11 are directly assembled together with outer ring 2 as a one-piece assembly, thus offering the advantages of compactness and smaller size in the diametrical direction. The present invention has been described in terms of the above embodiments, but within the range of the gist of this invention various formats and applications are possible within the scope of the claims. For example, the use of inner ring 2 as a rotating and stopping axis with no hollow spaces, the use, as a substitute for the sintered, oil-impregnated bearings, of a not included dry bearing (including materials used as fixed bearings such as ceramics, plastics, and others), or a fluid bearing structure, or a magnetic bearing structure, the assembly of a seal plate (seal groove) with this composite bearing. As explained in detail above, the present invention provides a structure using one single row ball bearing with 1 ball (the smallest unit which can be used in a ball bearing), which, in order to solve the problem of inclination and vibration in the inner and outer rings, uses a sintered, oil-impregnated bearing with the objective of reducing inclination, where an inner or an outer ring of a single row ball bearing is mounted either on one side or on both sides, in a structure which reduces inclined rotation, and thus provides stable rotational support to the same extent as conventional ball bearings which require a minimum of 2 balls, and in which the bearing can be made thin in the direction of rotational support, and which, because only one ball bearing is required, can be made more inexpensively than conventional bearing structures.

Claims: A composite bearing having a single row ball bearing and cylindrical bearing, comprising: an inner ring (1) and an outer ring (2) of said row ball bearing arranged coaxially with a space between them; balls (3) disposed between ball grooves of the inner ring and the outer ring; characterised by a cylindrical friction bearing (4,7) mounted on one of the innerring (1) and the outer ring (2) and spaced from the other of the inner ring (1) and the outer ring (2) by a gap (g) and disposed beside the ball bearing, for reducing inclination of the inner ring and the outer ring of said ball bearing relative to one another. A composite bearing according to claim 1, wherein the ball groove of the inner or outer ring (1,2) is formed on a bearing portion and the gap in the cylindrical friction bearing (4) is formed between a cylindrical friction bearing face and a face of the bearing portion. A composite bearing according to claim 1,wherein the cylindrical friction bearing (4,7) has an inner ring and an outer ring and the gap is formed between the inner ring and the outer ring. A composite bearing according to claim 1, wherein the cylindrical friction bearing (4,7) is arranged on one side of the ball bearing. A composite bearing according to claim 1, wherein cylindrical friction bearings (8,9) are arranged on both sides of the ball bearing.

Inventors: OBARA RIKURO, OBARA, RIKURO, Obara, Rikuro, c/o Minebea Co.,Ltd.
Applicants: MINEBEA KK, MINEBEA CO., LTD.
Application year: 1999
Main classification: F16C21
IPC codes: F16C21