JP4368070B2 - Rolling element spacer of rolling guide device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a rolling guide device having an infinite circulation path of balls, such as a linear guide device and a ball screw device, and is interposed between adjacent balls in the infinite circulation path, so that the wear of these balls The present invention relates to a rolling element spacer that reduces heat generation and smoothes its rolling.
[0002]
[Prior art]
Conventionally, as a rolling guide device in which a pair of members continuously move relative to each other through an infinitely circulated ball train, it is used in a linear guide portion of a machine tool, a conveying device, etc., on a fixed portion such as a bed or a saddle. A linear guide device that guides a movable body such as a table, and a ball screw that is used together with the linear guide device and gives a stroke of a linear motion according to the rotation amount of a motor to the movable body are known.
[0003]
The former linear guide device is disposed on the fixed portion and has a track rail in which a ball rolling groove is formed along the longitudinal direction, and faces the rolling groove of the track rail through a large number of balls. And a slide that is provided with an infinite circulation path for the ball that rolls in the load rolling groove, and that supports the movable body along with the infinite circulation of the ball. Are configured to continuously linearly move along the track rail. On the contrary, the track rail may be configured to move with respect to the fixed slide.
[0004]
On the other hand, the latter ball screw has a screw shaft in which a spiral ball rolling groove is formed by a predetermined lead, and a load rolling groove facing the ball rolling groove through a number of balls. It consists of a nut member formed with an infinite circulation path of the ball rolling in the load rolling groove, and the ball circulates in the infinite circulation path with the relative rotational movement of the screw shaft and the nut member, The nut member and the screw shaft are configured to move relatively in the axial direction.
[0005]
On the other hand, in such a rolling guide device, since the individual balls circulating in the ball infinite circulation path come into contact with the balls positioned before and after the ball, when the balls are used at high speed, for example, the friction between the balls As a result, the balls wear out relatively early, and there is a risk that problems such as burning of the balls and load rolling grooves due to frictional heat may occur. In addition, when the movement direction is reversed, that is, when the ball circulation direction is reversed, the arrangement of the balls in the infinite circulation path is easily disturbed, and in an extreme case, a so-called lock phenomenon occurs in which the balls are clogged in the infinite circulation path, There is also a risk that the rolling guide device itself may become inoperable. For this reason, Japanese Patent Application Laid-Open No. 11-315835 discloses a rolling guide device in which rolling element spacers are interposed between balls adjacent to each other in an infinite circulation path as a means for eliminating such drawbacks.
[0006]
In the rolling guide device disclosed in the publication, synthetic resin rolling element spacers called separators are arranged alternately with balls in an infinite circulation path, thereby preventing contact between the balls. Yes. Such a separator is formed in a disk shape having an outer diameter smaller than the ball diameter, and ball holding seats having a curvature larger than the curvature of the ball spherical surface are formed on both front and back surfaces in contact with the ball. As a result, when the balls and the separators are alternately arranged in the endless circulation path without any gap, each ball is sandwiched between a pair of front and rear separators, and the row is disturbed even when the circulation direction is reversed. It circulates in the endless circuit with the separator.
[0007]
[Problems to be solved by the invention]
By the way, such a rolling element spacer is manufactured by injection molding of a synthetic resin or the like, and at that time, such a synthetic resin material is used from various viewpoints such as wear resistance to the ball and cushioning property in collision with the ball. You can choose the best one. However, since the rolling element spacer circulates in the endless circulation path of the nut member together with the balls, the rolling element spacer is also in sliding contact with the inner wall of the endless circulation path. For this reason, in selecting a synthetic resin material for molding the rolling element spacer, not only the relationship with the ball, but also the relationship with the infinite circuit must be taken into account. If required, there is a problem that either one must be sacrificed.
[0008]
The present invention has been made in view of such problems, and the object of the present invention is to satisfy both the suitability for the ball and the suitability for the infinite circuit at a high level by using different resin materials in combination. Another object is to provide a rolling element spacer that can be used.
[0009]
[Means for Solving the Problems]
That is, the present invention is used in a rolling guide device in which a pair of members performs a relative continuous motion through a ball train that circulates infinitely, and is interposed between adjacent balls in the infinite circulation path. A rolling element spacer that circulates together with the ball, comprising a disk-shaped inner member having a pair of ball holding seats in sliding contact with the ball, and an annular outer member that covers the outer peripheral surface of the inner member, The outer member and the inner member are formed from resin materials having different bending elastic moduli.
[0010]
According to such a rolling element spacer of the present invention, it is possible to select a molding material considering only sliding contact with the ball for the inner member, and mainly the relationship with the infinite circuit for the outer member. The molding material can be selected in consideration of the above, and both the suitability for the ball and the suitability for the infinite circuit can be satisfied.
[0011]
The resin material for molding the inner member and the outer member can be freely selected, for example, the bending elastic modulus of the resin material for molding the inner member may be larger than that of the resin material for molding the outer member, Conversely, the flexural modulus of the resin material forming the outer member may be larger than that of the resin material forming the inner member. The optimum one can be selected depending on the operating environment of the ball screw device in which the rolling element spacer is used, for example, whether it is under load capacity, operating speed, or the environment in which the coolant is used.
[0012]
Among such synthetic resins that can be used in the present invention, those having a low flexural modulus can include thermoplastic elastomers, polyamides, and the like. From the viewpoint of ball lubrication, a lubricant is contained in the resin. It is preferable to use a material obtained by kneading and molding a material in which a porous resin is impregnated with a lubricant. On the other hand, examples of the resin having a large flexural modulus include those having high durability and rigidity such as fiber reinforced plastic and liquid crystal polymer.
[0013]
Further, from the viewpoint of firmly integrating the outer member and the inner member, when the same type of resin material is used as these members, for example, when a thermoplastic elastomer is used for the inner member, the outer member is also thermoplastic. It is preferred to use an elastomer. By using the same series of resin material for the inner member and the outer member in this way, the adhesiveness between the two becomes good and the difference in coefficient of thermal expansion is also reduced. Even when the spacer becomes high temperature, it is possible to prevent a gap from being generated between the inner member and the outer member.
[0014]
Further, from the viewpoint of completely preventing troubles that the rolling element spacers are dropped from between adjacent balls, the outer member has an annular dropout projecting in the ball arrangement direction from the edge of the ball holding seat. It is preferable to form a prevention part. This drop-off prevention part is configured so that it is kept in non-contact with the ball seated on the ball holding seat, and the ball is lifted from the ball holding seat and hits the ball only when the rolling element spacer is about to fall out between the balls. The
[0015]
Furthermore, by providing a drop prevention portion that protrudes in the ball arrangement direction from the edge of the ball holding seat and is kept out of contact with the spherical surface of the ball, the gap between the drop prevention portion and the ball is lubricated. Since the agent can easily enter, the lubrication state of the ball can be maintained satisfactorily. Therefore, from the viewpoint of further improving the holding state of the lubricant in the rolling element spacer of the present invention, an annular groove is formed between the ball holding seat and the drop-off preventing portion surrounding the ball holding seat. Is preferably used as a lubricant reservoir. If comprised in this way, since the lubricant which flowed into the clearance gap between a ball | bowl and a drop-off prevention part is stored in the said annular groove, it will become possible to always apply | coat a lubricant to the surface of a ball | bowl.
[0016]
In addition, although the said fall prevention part may be formed in the continuous annular | circular shape, it does not interfere even if it arrange | positions the processus | protrusion cut | disconnected by the slit annularly.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the rolling element spacer of the present invention will be described in detail with reference to the accompanying drawings.
1 and 2 show an example of a ball screw device in which rolling element spacers of the present invention are arranged together with balls in an infinite circulation path. In the figure, reference numeral 1 is a screw shaft, reference numeral 2 is a ball, reference numeral 3 is a nut member, and the nut member 3 is screwed onto the screw shaft 1 via a plurality of balls 2.
[0018]
A spiral ball rolling groove 10 is formed on the outer peripheral surface of the screw shaft 1, while a spiral load rolling facing the ball rolling groove 10 of the screw shaft 1 is formed on the inner peripheral surface of the nut member 3. A groove 30 is formed, and the ball rolling groove 10 and the load rolling groove 30 form a spiral load ball passage between the screw shaft 1 and the nut member 3. That is, when a relative rotational movement occurs between the screw shaft 1 and the nut member 3, the ball 2 rolls spirally in the load ball passage while applying a load. The nut member 3 is connected to both ends of the load ball passage so as to communicate with each other, and a return pipe 4 constituting an infinite circulation path of the ball 2 is mounted. The ball 2 thus made is in a no-load state and rolls in the return pipe 4, jumps over the ball rolling groove 10 by several turns, and is returned to the entrance of the load ball passage. Accordingly, when the screw shaft 1 and the nut member 3 perform relative rotational movement, the ball 2 rolls from the load ball path to the return pipe 4 and from the return pipe 4 to the load ball path. It circulates in the endless circuit constituted by the return pipe 4.
[0019]
In this ball screw device, in order to prevent the balls 2 incorporated in the infinite circulation path from contacting each other, a rolling element spacer 5 is interposed between the adjacent balls 2 and 2.
[0020]
3 to 5 show an example of the shape of the rolling element spacer to which the present invention is applied. The rolling element spacer 5 includes an inner member 5a formed in a substantially disc shape and an annular outer member 5b that covers the outer peripheral surface of the inner member 5a. The inner member 5a and the outer member 5b cannot be separated from each other. Is bound to. Further, ball holding seats 50 with which the balls 2 are slidably contacted are formed on both front and back surfaces of the inner member 5a. The balls 2 and the rolling element spacers 5 are alternately arranged in the endless circulation path, thereby preventing contact between the balls 2 that roll in the endless circulation path, and smooth circulation of the balls 2, and consequently the screw shaft. In addition to facilitating the rotational movement of the nut member 3 with respect to 1, the occurrence of collision noise between balls during operation of the ball screw device is reduced.
[0021]
The ball holding seat 50 is formed in a concave spherical shape approximately approximate to the spherical surface of the ball 2, and the adjacent balls 2 are configured to contact the ball holding seat 50 with almost no gap. The outer member 5b is formed with an annular drop prevention portion 52 so as to surround the ball holding seat 50. The tip of the drop-off prevention portion 52 protrudes from the edge of the ball holding seat 50 in the arrangement direction of the balls 2 (the left-right direction in FIG. 5). However, as shown in FIG. 6, when the ball 2 is seated on the ball holding seat 50, a gap is formed between the ball 2 and the tip of the drop-off preventing portion 52.
[0022]
FIG. 7 shows a state in which the ball 2 is seated on the ball holding seat 50 of the rolling element spacer 5. As described above, since the ball holding seat 50 is formed in a concave spherical shape substantially approximate to the spherical surface of the ball 2, the seated ball 2 is in contact with the ball holding seat 50 with almost no gap as shown in this figure. ing. Thereby, when the ball 2 and the rolling element spacer 5 are arranged without gaps in the infinite circulation path of the ball screw device, the ball 2 does not swing unstably on the ball holding seat 50 of the rolling element spacer 5, The ball 2 and the rolling element spacer 5 can be circulated in the infinite circulation path without meandering.
[0023]
Further, the drop-off prevention portion 52 formed around the ball holding seat 50 is not in contact with the ball 2 seated on the ball holding seat 50, and a gap having a substantially wedge-shaped cross section is provided between the drop-off prevention portion and the ball. Therefore, the lubricant such as grease adhering to the ball 2 enters the gap. For this reason, the lubricant is easily caught between the ball 2 and the ball holding seat 50 that are in sliding contact with each other, and it is possible to reliably lubricate between the ball 2 and the rolling element spacer 5, and to pass through the gap. The lubricant easily adheres to the surface of the ball 2 that moves outward, and it is possible to reliably lubricate between the ball 2 and the rolling groove 10 of the ball screw device.
[0024]
9 to 11 show other examples of the shape of the rolling element spacer to which the present invention is applied.
The rolling element spacer 6 has substantially the same structure as that of the rolling element spacer 5 shown in FIGS. 3 to 5 except that an annular lubricant reservoir 51 is formed on the ball holding seat 50. The first embodiment is different in that an annular groove 53 is formed near the boundary between the holding seat 50 and the drop-off prevention portion 52, and a prevention portion 54 is provided on the inner member 5a from the outer member 5b. Different from the moving body spacer 5. Therefore, the same configurations as those in the example shown in FIGS. 3 to 5 are denoted by the same reference numerals in FIGS. 9 to 11, and detailed description thereof is omitted here.
[0025]
The lubricant reservoir 51 and the annular groove 53 are both formed for the purpose of favorably lubricating between the ball 2 and the rolling element spacer 6 and further improving the adhesion of the lubricant to the spherical surface of the ball 2. In particular, as shown in FIG. 12, by forming an annular groove 53 at the boundary between the ball holding seat 50 and the drop-off prevention part 52, lubricant such as grease adhering to the ball 2 can be removed from the drop-off prevention part 52 and the ball. 2 enters the annular groove 53 through a gap with the spherical surface of 2 and accumulates in the annular groove 53. For this reason, the lubricant is easy to be caught between the ball 2 and the ball holding seat 50 that are in sliding contact with each other, and the ball 2 and the rolling element spacer 6 can be reliably lubricated and passed through the annular groove 53. Thus, the lubricant easily adheres to the surface of the ball 2 that moves outward, and it is possible to reliably lubricate between the ball 2 and the rolling groove 10 of the ball screw device.
[0026]
Further, as shown in FIG. 10, the retaining member 54 protrudes from the outer peripheral surface of the inner member 5a, while the outer member 5b is formed with a locking hole 55 corresponding to the retaining member 54. When the outer member 5b is fitted to the outer peripheral surface of the inner member 5a, the retaining member 54 enters the locking hole 55, and the outer member 5b and the inner member 5a are firmly integrated. It is like that. The inner member 5a and the outer member 5b may be formed separately and integrated later. However, in order to manufacture the rolling element spacer 6 more simply, the outer member formed in advance may be used. The inner member 5a is preferably injection-molded with 5b inserted into the mold.
[0027]
First Embodiment Both the inner member 5a and the outer member 5b are made of synthetic resin, and both are made of polyester. However, although the flexural modulus of the polyester forming the inner member 5a is 0.055 GPa, the flexural modulus of the polyester forming the outer member is 0.157 GPa. Further, when the inner member 5a and the outer member 5b are combined, they may be formed separately and integrated later by bonding or the like. However, after forming the outer member 5b first, It is also possible to inject the inner member 5a in a mold having 5b inserted therein, thereby integrating the both. In this injection molding, the molten resin can be injected into the mold by using the locking hole 55 formed in the outer member 5b as a gate. While the retaining portion 54 is naturally formed in the stop hole 55, it is possible to avoid the gate cutting mark from remaining on the ball holding seat 50 of the inner member 5a. The reason why the outer member 5b is injection-molded before the inner member 5a is that the outer member 5b has a higher flexural modulus than the inner member 5a and is a harder material. If the inner member 5a that is softer than the outer member 5b is first injection molded, the soft inner member 5a may be pushed and deformed by the harder outer member 5b that is molded later, In order to avoid such trouble, a hard outer member is first injection molded.
[0028]
As another combination of resin materials, the inner member can be formed of polyester having a flexural modulus of 0.118 GPa and the outer member can be formed of polyester having a flexural modulus of 0.470 GPa.
[0029]
In this embodiment, since the inner member 5a on which the ball holding seat 50 is formed is made of a synthetic resin having a small bending elastic modulus, the rolling element spacer 5 serves as a cushion between the adjacent balls 2. Further, it is possible to reduce the fatigue of the ball 2 and the generation of noise that are generated when the ball 2 circulating in the endless circulation path repeatedly collides with the rolling element spacer 5. Furthermore, the ball 2 that rolls while applying a load between the nut member 3 and the screw shaft 1 due to the formation error of the load rolling groove 30 of the nut member 3 or the ball rolling groove 10 of the screw shaft 1. Even if the distance between the two is changed minutely, the inner member 5a formed of a soft synthetic resin can be deformed to absorb this change in distance, so that the balls 2 are in an infinite circulation path. Therefore, it is possible to prevent a problem that the balls 2 are clogged in the infinite circulation path. From the viewpoint of a ball screw device in which the rolling element spacers 5 are arranged in an infinite circulation path, this leads to the achievement of smooth movement with little torque fluctuation. From this point of view, it can be said that the resin material used for the inner member preferably has a flexural modulus of about 0.05 to 0.2 GPa.
[0030]
On the other hand, FIG. 8 shows a state in which the distance between adjacent balls 2 increases during circulation in the endless circulation path, and the balls 2 float from the ball holding seat 50 of the rolling element spacer 5. For example, it is difficult to arrange the balls 2 and the rolling element spacers 5 without gaps with respect to the infinite circulation path of the ball screw device, and the balls 2 and the rolling element spacers 5 wear due to use over time. Such a situation will occur somewhere in the endless circuit. When the ball 2 is lifted from the ball holding seat 50 in this way, the rolling element spacer 5 sandwiched between the balls 2 from both sides loses its support and tends to fall out between the balls 2. However, in the rolling element spacer 5 of the present embodiment, since the outer member 5b having a large bending elastic modulus covers the outer peripheral surface of the inner member 5a, the inner member 5a undergoes elastic deformation between the adjacent balls 2, Even if the outer member 5 b tries to fall out from between the balls 2, the outer member 5 b is caught on the spherical surface of the ball 2 without being deformed, and acts to prevent the rolling element spacer 5 from coming out from between the balls 2. In particular, in the rolling element spacer 5 of the present embodiment, the drop-off prevention part 52 is formed on the outer member 5b, and the tip of the drop-off prevention part 52 projects beyond the edge of the ball holding seat 50 in the arrangement direction of the balls 2. Therefore, when the rolling element spacer 5 is about to fall from between the balls 2 adjacent to each other, the falling prevention portion 52 that has been in a non-contact state with the ball 2 is effectively caught by the ball 2, and the rolling element spacer 5 Acts to prevent the ball from falling out between the balls 2. From this point of view, it can be said that the resin material used for the outer member preferably has a flexural modulus of about 0.15 to 2.0 GPa.
[0031]
That is, the rolling element spacer 5 of the first embodiment is intended to facilitate the circulation of the ball in the infinite circulation path while reducing the generation of the fatigue and noise of the ball due to the use over time. Furthermore, the rolling element spacer can also effectively prevent the trouble that the rolling element spacer falls from between adjacent balls.
[0032]
At this time, the bending elastic modulus of the outer member is about 3 times or more, preferably 4 times or more, that of the inner member.
[0033]
Second Embodiment In the second embodiment, contrary to the first embodiment, the inner member 5a is molded from polyester having a flexural modulus of 0.157 GPa and the outer member is molded from polyester having a flexural modulus of 0.055 GPa. did. When the inner member 5a and the outer member 5b are combined, they may be integrated by bonding or the like as in the first embodiment, but both may be integrated by injection molding. However, in this second embodiment, the bending elastic modulus of the inner member is greater than that of the outer member, so the order of such injection molding is reversed from that of the first embodiment. That is, the inner member 5a is injection-molded first, and the outer member 5b is injection-molded using a mold with the inner member 5a inserted. In the first embodiment, the inner member has to be injection-molded through the locking hole 55 of the outer member, but in this second embodiment, the inner member is molded before the outer member. Therefore, it can be formed more easily and at a lower cost than the rolling element spacer of the first embodiment.
[0034]
In this embodiment, the inner member 5a is made of a synthetic resin having a large flexural modulus, in other words, a hard synthetic resin. Therefore, after the ball 2 repeatedly collides with the ball holding seat 50 of the inner member 5a. However, the ball holding seat 50 will not be deformed. That is, the inner member 5a formed of a hard synthetic resin is excellent in dimensional stability, and the gap between the ball holding seat 50 and the ball 2 does not increase even when used over time. Therefore, it is possible to prevent the rolling element spacer 5 from falling off. Further, when the inner member 5a is formed of a hard synthetic resin, the wear resistance of the ball holding seat 50 is improved, and also in this respect, the gap between the ball holding seat 50 and the ball 2 increases with time. Can be prevented. From this point of view, it can be said that the resin material used for the inner member preferably has a flexural modulus of about 0.15 to 2.0 GPa.
[0035]
Further, when the ball screw device is used for a machine tool, the ball screw device may be exposed to the coolant liquid, and the synthetic resin rolling element spacer 5 may be swollen by the coolant liquid. The However, if a relatively hard synthetic resin is used for the inner member 5a, the swelling of the inner member 5a due to the coolant liquid is suppressed as compared with the case where a soft synthetic resin is used, and the ball screw device It is possible to prevent the ball 2 and the rolling element spacer 5 from coming into close contact with each other in the infinite circulation path. As a result, it is possible to avoid troubles such as the torque required for the rotation of the screw shaft 1 increasing with time and troubles such as the balls 2 and the rolling element spacers 5 being clogged in the infinite circulation path. Become.
[0036]
On the other hand, in this embodiment, a synthetic resin having a low bending elastic modulus, in other words, a soft synthetic resin, is used as the outer member 5b. For example, the rolling element spacer 5 circulates in an infinite circulation path of the ball screw device. Even when it is caught in the step of the infinite circulation path, the outer member 5b is elastically deformed so that the catch can be easily eliminated, and the rolling element spacer 5 and the ball 2 It is possible to facilitate circulation in the infinite circulation path. Further, since the toughness of the outer member 5b is increased, the outer member 5b is prevented from being damaged by a collision with the ball 2 or the inner wall of the infinite circulation path even when the outer member 5b is formed thin. It is also possible to do. From this point of view, it can be said that the resin material used for the outer member preferably has a flexural modulus of about 0.05 to 0.2 GPa.
[0037]
That is, according to the rolling element spacer 5 of the second embodiment in which the inner member 5a is formed of a resin material having a higher bending elastic modulus than the outer member 5b, the gap between the ball 2 and the rolling element spacer 5 is changed over time. It is possible to prevent the rolling element spacers 5 from being enlarged due to various uses and effectively prevent the rolling element spacers 5 from dropping out between the adjacent balls 2. The ball 2 can be smoothly circulated in the endless circulation path.
[0038]
【The invention's effect】
As described above, the rolling element spacer of the present invention is composed of a disk-shaped inner member having a ball holding seat and an annular outer member covering the outer peripheral surface of the inner member, and these outer member and inner member. Are formed from resin materials having different bending elastic moduli, and by combining different resin materials to form the inner member and the outer member, both the suitability for the ball and the suitability for the infinite circulation path are satisfied at a high level. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing an embodiment of a ball screw device in which rolling element spacers of the present invention are arranged in an endless circulation path together with balls.
FIG. 2 is a front sectional view of the ball screw device shown in FIG.
FIG. 3 is a perspective view showing an example of the shape of the rolling element spacer of the present invention.
4 is an exploded perspective view showing a state in which the rolling element spacer shown in FIG. 3 is disassembled into an inner member and an outer member. FIG.
5 is a longitudinal sectional view showing the rolling element spacer shown in FIG. 3. FIG.
6 is an enlarged cross-sectional view showing a relationship between a drop prevention portion of the rolling element spacer shown in FIG. 3 and a ball.
7 is a cross-sectional view showing a state in which a ball is seated on a ball holding seat of the rolling element spacer shown in FIG. 3;
8 is a cross-sectional view showing a state where a ball is lifted from a ball holding seat of the rolling element spacer shown in FIG. 3;
FIG. 9 is a perspective view showing another example of the shape of the rolling element spacer of the present invention.
10 is an exploded perspective view showing a state in which the rolling element spacer shown in FIG. 9 is disassembled into an inner member and an outer member. FIG.
11 is a longitudinal sectional view showing the rolling element spacer shown in FIG.
12 is an enlarged cross-sectional view showing the relationship between the falling prevention portion of the rolling element spacer and the ball shown in FIG. 9;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Screw shaft, 2 ... Ball, 3 ... Nut member, 5 ... Rolling element spacer, 5a ... Inner member, 5b ... Outer member, 50 ... Ball holding seat, 52 ... Fall-off prevention part

Claims (2)

A pair of members is used in a rolling guide device in which a pair of members make a relative continuous movement through an infinitely circulating ball train, and is interposed between adjacent balls in the infinite circulation path and circulates with the balls. A moving body spacer,
A disk-shaped inner member that is formed in a concave spherical shape approximately approximate to the spherical surface of the ball, and that has a pair of ball holding seats with which the ball is in sliding contact with no gap;
Annular fall prevention that is formed in an annular shape covering the outer peripheral surface of the ball holding seat, protrudes in the ball arrangement direction from the edge of the ball holding seat, and is kept in non-contact with the ball seated on the ball holding seat. An outer member having a portion,
The rolling element spacer according to claim 1, wherein the inner member is formed from a resin material having a higher bending elastic modulus than the outer member.   2. The rolling element spacer according to claim 1, wherein an annular groove is formed between the ball holding seat and the drop-off preventing portion, and the annular groove functions as a lubricating oil reservoir.

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