WO2008041427A1 - Rolling bearing, shaft rotating mechanism using the rolling bearing, linear actuator using the rolling bearing - Google Patents

Abstract

A rolling bearing comprises an inner ring (2), an outer ring (3), and rolling elements (4) interposed therebetween. The inner diameter of the inner ring (2) is larger than the outer diameter of a shaft member (6) disposed inside the inner ring. The shaft member (6) has a size allowing the rotation and the axial movement thereof. An annular body (5) formed of a member with a higher elastic modulus than the inner ring (2) is installed on the inner peripheral surface of the inner ring (2). The annular body (5) is so formed that there is a gap between its inner surface and the outer surface of the shaft member (6) to allow the rotation and the axial movement of the shaft member (6). The coefficient of friction of the inner peripheral surface of the annular body (5) is lower than that of the inner peripheral surface of the inner ring (2). The rolling bearing (1) is applied to a support member for supporting the shaft member at the axial intermediate position in a device such as a linear actuator having a shaft rotating mechanism for rotating the shaft member. Consequently, the axial intermediate portion of the rotating shaft member can be supported while the shaft member is smoothly rotated.

Description

 Specification

Rolling bearing, shaft rotation mechanism using the rolling bearing, and rolling bearing

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to a rolling bearing that can rotatably support a shaft member, a shaft rotating mechanism that uses this rolling bearing, and a linear actuator that uses this rolling bearing. This is suitable for preventing stagnation of the shaft member. Background art

 In general, in a precision ball screw mechanism used in a machine tool, in order to increase a feed rate, a screw lead is increased or a rotation speed is increased. For machine tools that require a mechanical resolution of the servo motor's built-in encoder for precise position control, the maximum screw lead is limited to 10 mm or less. The means is high-speed rotation of the screw.

 [0003] However, there are various restrictions on increasing the feed speed of the cutting tool, and in particular, there is a problem of the critical speed of the ball screw. When the ball screw rotates at a high speed, the centrifugal force causes stagnation and a so-called jumping phenomenon occurs. Therefore, normal operation cannot be ensured at a critical speed exceeding the allowable range. Theoretically, the allowable rotational speed from the critical speed of the ball screw is expressed by the following equation.

[0004] N = λ ² Χ (d / L ² ) X 10 ⁷ (min—. (1)

 max 1

 (N: Maximum allowable rotational speed of the ball screw from the critical speed (critical rotational speed))

 max

 λ: fulcrum support coefficient

 d: Valley diameter of the borehole screw (mm)

 1

 L: Distance between fulcrums (mm)

 [0005] From equation (1), in order to increase the allowable rotational speed N of the ball screw, the ball screw diameter is increased and max

It can be seen that it is desirable to adopt at least one of the above methods or the method of shortening the distance between the fulcrums. In this respect, the method of shortening the distance between the fulcrums is extremely effective in theory because it acts on the critical rotation speed as a quadratic function. [0006] However, the distance between the fulcrums is determined by the maximum moving amount of the machine. For this reason, in the case of a feed mechanism intended for long stroke movement, it is necessary to set a long distance between the fulcrums, thereby realizing a long stroke movement amount. In other words, there was a trade-off between improving the feed rate and shortening the distance between fulcrums.

 [0007] For the purpose of solving this problem, a technique described in Patent Document 1 has been proposed. In this Patent Document 1, a drive motor, a first feed ball screw connected to the drive motor, a moving support body having a plurality of support points for supporting the first feed ball screw while sliding, A first feed nut arranged between the support points and screwed into the first feed ball screw; a movable body arranged to be movable on the movable support body and to which the first feed nut is attached; a first feed ball screw; A second feed ball screw having the same lead and arranged in parallel; a second feed nut fixed to the moving support body and screwed into the second feed ball screw; and a moving support body A linear actuator comprising transmission means for transmitting the rotation of the first feed ball screw to the second feed ball screw so that the first feed nut moves relative to the support point in synchronization with the movement of the moving support body. Is described.

 [0008] However, in the linear actuator described in Patent Document 1, the screw mechanism becomes very complicated, and accordingly, the apparatus configuration becomes large. As described above, when the device configuration is increased in size, the production cost of the linear actuator is increased and the weight is increased.

 [0009] On the other hand, the patent applicant of the present application has already disclosed an invention for solving this problem in Patent Document 2.

 [0010] On the other hand, in the field of rolling bearings! /, Rolling bearings are strong! / When external force is applied from a shaft member attached by fitting, this external force is caused to interfere and the rolling bearing from the shaft member. In recent years, technology has been developed to try to prevent external forces from being transmitted as much as possible.

[0011] For example, Patent Document 3 discloses an invention in which a sleeve is provided on the inner peripheral surface of an inner ring, and this functions as a cushioning material. Patent Document 4 discloses a ceramic rolling bearing in which a sleeve functioning as a cushioning material is attached to the inner peripheral surface of the inner ring and the outer peripheral surface of the outer ring. Patent Document 1: Japanese Patent Laid-Open No. 2001-336596

 Patent Document 2: JP-A-2005-249120

 Patent Document 3: Japanese Patent Application Laid-Open No. 2004-108463

 Patent Document 4: Japanese Unexamined Patent Application Publication No. 2004-144154

 Disclosure of the invention

 Problems to be solved by the invention

[0013] The linear actuator disclosed in Patent Document 2 described above is excellent in that the support member supports the screw shaft that penetrates the support member while freely rotating the support member. The patent applicant of the present application has been researching to realize further high-speed movement of the moving member in the linear actuator.

On the other hand, the rolling bearings disclosed in Patent Document 3 and Patent Document 4 are fitted with a strong tightening force to a shaft member disposed inside the inner ring, and these rolling bearings are used. Thus, it cannot be used as a means for supporting the shaft member while rotating it relative to the rolling bearing.

Accordingly, in the present invention, a rolling bearing capable of smoothly rotating a rotating shaft member and supporting an intermediate portion in the axial direction, a shaft rotating mechanism using the rolling bearing, and the rolling bearing A linear actuator that uses is provided.

 Means for solving the problem

 In the present invention, firstly, in order to solve the above-mentioned problem, an inner ring, an outer ring, and rolling elements interposed between the inner ring and the outer ring are provided, and the inner diameter of the inner ring is A rolling bearing having a gap with respect to the outer diameter of the shaft member disposed inside the shaft member and having a dimension that allows the shaft member to rotate with respect to the inner ring and move in the axial direction is employed.

 In the present invention, in the force and rolling bearing, an annular body made of a member having a higher elastic modulus than the inner ring is provided on the inner peripheral surface of the inner ring, and the inner diameter of the annular body is the shaft member. The outer diameter of the annular member is formed to have a size that allows the shaft member to rotate and move in the axial direction with respect to the annular member, and the friction coefficient of the inner peripheral surface of the annular member is the inner ring. It was decided to adopt a rolling bearing that has a lower coefficient of friction than the inner peripheral surface.

Second, in the present invention, a shaft member that is rotationally driven by a drive source, and an axial direction of the shaft member And a support member that supports the outer periphery of the shaft member. The support member includes an inner ring, an outer ring, and an inner ring and an outer ring interposed between the inner ring and the outer ring. A rolling bearing having a rolling element is provided, and an inner diameter of the inner ring has a gap with respect to an outer diameter of the shaft member disposed inside the inner ring, and rotation of the shaft member with respect to the inner ring, and A shaft rotating mechanism formed to have a dimension that allows movement in the axial direction was adopted.

Furthermore, in the present invention, in this shaft rotation mechanism, an annular body made of a member having a higher elastic modulus than the inner ring is provided on the inner peripheral surface of the inner ring, and the inner diameter of the annular body is the shaft There is a gap with respect to the outer diameter of the member, the shaft member is formed in a dimension that allows rotation and movement in the axial direction of the shaft member, and the shaft member on the inner peripheral surface of the ring member is formed. A shaft rotation mechanism having a lower frictional resistance than the frictional resistance against the shaft member on the inner peripheral surface of the inner ring was adopted.

 [0020] In these shaft rotation mechanisms, the support member is moved in the axial direction of the shaft member so that the force S can be freely moved to a position where the stagnation generated as the shaft member rotates is maximized. It is good to move freely.

 Thirdly, in the present invention, a race member, a screw shaft that is supported at both ends and whose axial direction is aligned with the longitudinal direction of the race member, and the screw shaft are passed through, A moving member that is moved along the raceway member as the screw shaft rotates, and is arranged on both sides of the moving member in the axial direction of the screw shaft. A rolling bearing having an inner ring, an outer ring, and rolling elements interposed between the inner ring and the outer ring, and the inner diameter of the inner ring is A linear actuator having a clearance with respect to the outer diameter of the screw shaft disposed inside the inner ring and having a dimension that allows the screw shaft to rotate and move in the axial direction with respect to the inner ring. Adopted.

[0022] Further, in the present invention, with regard to the force and linear actuator, an annular body made of a member having a higher elastic modulus than the inner ring is provided on the inner peripheral surface of the inner ring, and the inner diameter of the annular body is The screw shaft has a gap with respect to the outer diameter, is formed to have a size that allows the screw shaft to rotate and move in the axial direction with respect to the annular body, and the inner circumferential surface of the annular body Friction resistance against the screw shaft From the friction resistance against the screw shaft on the inner peripheral surface of this inner ring Low! / A linear actuator is used.

 [0023] In these linear actuators, the support member is supported by the track member so as to be movable in the axial direction of the screw shaft.

 [0024] The linear actuator is substantially U-shaped in section having inner wall surfaces facing each other, and the moving member and the support member are sandwiched between the inner wall surfaces. A rolling element rolling part is formed on the inner wall surface, and a load rolling element rolling part corresponding to the rolling element rolling part is provided on the moving member and the support member, and the moving member and The support member is further provided with a rolling element return passage and a direction changing path through which the rolling elements rolling between the rolling element rolling portion and the loaded rolling element rolling portion can be circulated. A moving body return passage is configured in parallel with each other at a predetermined interval from the load rolling body rolling section, and the direction changing path connects the load rolling body rolling section and the rolling body return path. Configured, on the outer peripheral surface of the screw shaft, A rolling rolling element rolling part for a screw shaft is provided, a load rolling element rolling part for a screw shaft corresponding to the rolling element rolling part for the screw shaft is provided in a through hole of the moving member, and the moving member Further, there is provided a screw shaft rolling element return passage for circulating the screw shaft rolling element rolling between the screw shaft rolling element rolling part and the screw shaft load rolling element rolling part. It is characterized.

 The invention's effect

 [0025] According to the rolling bearing of the present invention, the shaft member arranged inside the inner ring is allowed to rotate and move in the axial direction. For this reason, the intermediate position in the axial direction of the shaft member can be supported while realizing smooth rotation of the shaft member. In addition, the desired position of the shaft member can be supported by moving the rolling bearing in the axial direction of the shaft member or by moving the shaft member in the axial direction with respect to the rolling bearing. Even if a pulling force or scale is generated between the inner ring and the shaft member, the inner ring rotates freely with respect to the outer ring, so that the shaft member and the inner ring can rotate smoothly. Realize rotation.

 [0026] Further, when an annular body is provided on the inner peripheral surface of the inner ring of the rolling bearing, such an effect can be obtained. However, when an annular body is provided, the following effects are further achieved.

[0027] That is, the rolling bearing is configured such that the shaft member is not in contact with the rolling bearing while suppressing the stagnation of the shaft member. Supporting force to rotate freely When suppressing the stagnation of this shaft member, the shaft member force and other loads act on the rolling bearing. However, since the annular body is provided on the inner peripheral surface of the inner ring, the load force S transmitted from the shaft member to the rolling bearing is buffered by the annular body. For this reason, it is possible to effectively prevent the rolling bearing from being damaged. Even if the rolling bearing itself is damaged and the inner ring does not rotate with respect to the outer ring, the annular member allows the shaft member to rotate, so that the rotation of the shaft member is not hindered.

[0028] A shaft member that is rotationally driven by a drive source with such a rolling bearing, and a support member that is disposed at an intermediate position in the axial direction of the shaft member and penetrates the shaft member to support the outer periphery thereof. When applied to a support member of a shaft rotation mechanism comprising the support member, the support member ensures smooth rotation while preventing the shaft member from stagnation. In this case, by providing the support member so as to be movable in the axial direction of the shaft member, the support member can be appropriately arranged at the maximum position of the stagnation caused by the rotation of the shaft member.

 [0029] Further, by applying to the support member of the linear actuator, smooth rotation of the screw shaft is maintained while preventing the screw shaft from being squeezed. For this reason, it is possible to move the moving member along the track member with high accuracy.

 [0030] In the above-described shaft rotation mechanism and this linear actuator, the shaft member or the screw shaft can significantly improve the dangerous rotation speed based on the long stroke, and the so-called jumping phenomenon due to stagnation. Suppress. In particular, in the linear actuator, since such an effect is obtained, the moving member can be moved at a high speed with extremely high accuracy. Brief Description of Drawings

 FIG. 1 is an enlarged partial sectional view of a rolling bearing according to an embodiment of the present invention.

 [FIG. 2] FIG. 2 is an enlarged partial cross-sectional view schematically showing a state in which the rotating shaft is supported by the rolling bearing shown in FIG.

 FIG. 3 is a partial cross-sectional perspective view showing a linear actuator according to an embodiment of the present invention.

 FIG. 4 is a partial sectional perspective view showing a linear actuator according to an embodiment of the present invention.

FIG. 5 is a top view and side view showing a linear actuator according to an embodiment of the present invention. FIG.

 FIG. 6 is a sectional view showing an inner block and a water rail according to one embodiment of the present invention.

 FIG. 7 is a cross-sectional view showing a support member and an water rail according to an embodiment of the present invention.

 FIG. 8 is a perspective view showing another example of the linear actuator according to one embodiment of the present invention.

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, an embodiment of the rolling bearing of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows an enlarged partial cross-sectional view of a radial contact ball bearing which is an example of a rolling bearing 1. The rolling bearing 1 includes an inner ring 2, an outer ring 3, and a plurality of balls 4 interposed between the inner ring 2 and the outer ring 3 to allow the inner ring 2 and the outer ring 3 to rotate relative to each other in the circumferential direction. . In addition, a cage is provided between the balls 4... For holding the balls 4. An annular sleeve 5 is fitted on the inner periphery of the inner ring 2, and the inner peripheral surface of the inner ring 2 is covered with the sleeve 5.

Each member constituting the rolling bearing 1 itself is composed of a member such as a ceramic material in addition to a generally used material such as a bearing steel. On the other hand, the sleeve 5 is formed of a member having a higher elastic modulus than the member of the inner ring 2. The inner diameter of the sleeve 5 has a weak fitting dimension capable of rotating the rotating shaft 6 in relation to the outer diameter of the rotating shaft 6 disposed inside the rolling bearing 1. Formed. In addition, the friction coefficient of the inner peripheral surface of the sleeve 5 is formed to be lower than the friction coefficient of the inner peripheral surface of the inner ring 2, and the friction resistance of the sleeve 5 to the rotating shaft 6 is higher than the friction resistance to the rotating shaft of the inner ring 2. Is configured to be small. Specifically, the sleeve 5 is formed of a fluororesin such as a polymer of tetrafluorotechylene. However, a member having a higher elastic modulus than that of the inner ring of the rolling bearing may be formed in a ring shape, and the inner peripheral surface thereof may be coated with a fluororesin. Note that the sleeve made of other members is the same as that of the linear actuator described later. Details will be explained.

 [0036] As described above, when the sleeve 5 is fitted into the inner peripheral surface of the inner ring 2 of the rolling bearing 1, the following operational effects are obtained. That is, when the rolling bearing 1 is arranged in the intermediate portion in the axial direction of the rotating shaft 6, the rotating shaft 6 is supported while suppressing the stagnation of the rotating shaft 6. However, as the rolling bearing 1 suppresses the stagnation of the rotating shaft 6, the rolling bearing 1 receives a load from the rotating shaft 6 as shown in FIG. The sleeve 5 functions as a buffer material for the load that the rotating shaft 6 gives to the rolling bearing 1. For this reason, the external force received from the rotating shaft 6 is not transmitted to the rolling bearing 1, and damage to the rolling bearing 1 is effectively prevented.

 [0037] Further, since the friction resistance force S of the inner peripheral surface of the sleeve 5 with respect to the rotation shaft 6 and the friction resistance of the inner peripheral surface of the inner ring 2 with respect to the rotation shaft 6 are formed smaller, Even if it interferes with the sleeve, the rotating shaft 6 rotates smoothly. However, even if the rotating shaft 6 interferes with the sleeve 5, the inner ring 2 rotates freely with respect to the outer ring 5, so that the inner ring 2 rotates together with the rotating shaft.

 [0038] Even if a pulling force or a scale is generated between the rotating shaft 6 and the sleeve 5, the inner ring 2 rotates freely with respect to the outer ring. Therefore, the rotating shaft 6 rotates the inner ring 2 around. It just turns. On the other hand, even if the rolling bearing itself is damaged and the inner ring 2 cannot rotate with respect to the outer ring 3, the sleeve 5 allows the rotation shaft 6 to rotate with respect to the inner ring. For this reason, even if these failures occur, smooth rotation of the rotating shaft 6 is ensured.

 [0039] In addition to the force described above using the radial contact ball bearing as an example, the present invention can also be applied to an angular contact ball bearing and a radial contact roller bearing. It can be applied not only to end row rolling bearings but also to double row rolling bearings.

 [0040] Further, the case where the sleeve 5 that is an annular body is provided on the inner peripheral surface of the inner ring 2 has been described as an example of fitting, but the present invention is not limited to this, and the sleeve 5 is fixed to the inner peripheral surface of the inner ring 2 It is possible to provide it with a configuration other than fitting.

As described above, the rolling bearing 1 can be configured without the force S and the sleeve 5 described for the rolling bearing 1 provided with the sleeve 5 on the inner peripheral surface of the inner ring 2. In this case, the inner diameter of the inner ring 2 is formed so as to have a gap with respect to the outer diameter of the rotating shaft 6 disposed inside the inner ring 2, so that the rotating shaft 6 rotates with respect to the inner ring 2 and moves in the axial direction. It is configured to allow dimensions. [0042] Next, the above-described rolling bearing is disposed at a shaft member that is rotationally driven by a drive source and an axially intermediate position of the shaft member, and the shaft member is penetrated to support the outer periphery thereof. What is applied to a linear actuator having a shaft rotation mechanism having a support member will be described. FIG. 3 shows the overall structure of the linear actuator according to one embodiment, and FIG. 4 shows the main part of the linear actuator. Fig. 5 shows a side view and top view of the linear actuator, and Fig. 6 shows a cross-sectional view of the inner block.

 As shown in FIG. 3, the linear actuator according to this embodiment is provided in the outer rail 7 as a race member having a substantially U-shaped cross section, guide portions on both side surfaces, and in the center. An inner block 8 as a moving member assembled in a reciprocating manner with a ball screw portion as an integral structure, and a screw shaft 9 rotatably supported at both ends in the longitudinal direction of the water rail 7 are provided.

 [0044] First, the guide portion of the linear actuator will be described.

 [0045] As shown in FIG. 4, the water rail 7 is provided with a pair of inner wall surfaces 7a extending in parallel so as to face each other. A concave groove 10 is engraved on the inner wall surface 7a over its entire length. At the upper and lower corners of each concave groove 10, ball rolling grooves 11 are formed as two rolling element rolling grooves as rolling element rolling portions. In other words, the ball rolling grooves 11 are provided in total on the upper and lower sides of the pair of inner wall surfaces 7a of the water rail 7, four in total. The ball rolling groove 11 is composed of a single circular arc, a so-called circular arc groove whose cross section has a curvature slightly larger than the radius of the ball.

 [0046] The inner block 8 sandwiched between the inner wall surfaces 7a of the water rail 7 is composed of a block main body 8a and end plates 8b attached to both front and rear end surfaces in the traveling direction of the block main body 8a. The inner block 8 is inserted into the outer rail 7 and supported so as to be sandwiched between the inner wall surface 7a via a ball 28 as a rolling element.

 Further, as shown in FIGS. 5A and 5B, housings 13 and 14 force S for rotatably supporting the screw shaft 9 are provided at both ends in the longitudinal direction of the water rail 7. The housings 13 and 14 and the water rail 7 are coupled by a coupling means such as a bolt.

In addition, as shown in FIG. 6, on both side surfaces of the block body 8a, a load ball rolling groove 19 serving as two upper and lower load rolling element rolling grooves facing the ball rolling groove 11 of the water rail 7 is provided. But Is formed. In other words, the load ball rolling grooves 19 are provided in total on the upper and lower sides of both sides of the block body 8a, for a total of four. The loaded ball rolling groove 19 is also composed of a single circular arc having a slightly larger curvature than the half diameter of the ball, a so-called circular arc groove. Between the ball rolling groove 11 of the outer rail 7 and the load ball rolling groove 19 of the inner block 8, a load ball rolling path that forms part of a ball circulation path (rolling element circulation path) for circulating the ball is formed. Yes.

 [0049] In addition, two through holes 21 are formed on the left and right sides of the block body 8a so as to extend in parallel from the upper and lower two load ball rolling grooves 19 at a predetermined interval.

 [0050] The inner block 8 is provided with a U-shaped pipe-shaped turning path that connects the loaded ball rolling path and the ball return path to circulate the ball. These loaded ball rolling path, direction turning path, and ball return path form a circuit-like ball circulation path. This ball circulation path is formed on the left and right sides of the inner block 8 with a total of 4!

 [0051] In addition, the outer peripheral side of the direction changing path is formed by an end plate 8b as a direction changing path outer peripheral side constituent member, and the inner peripheral side of the direction changing path is formed by a resin molded body provided in the block body 8a. Has been. A plurality of balls 28 are arranged and accommodated in each ball circulation path.

 [0052] Next, support members provided at the front and rear along the axial direction of the inner block 8 will be described.

As shown in FIG. 3 and FIG. 6, in the water rail 7, a pair of support members 100 provided with guide portions on both side surfaces are arranged on the front and rear sides along the axial direction of the inner block 8. Yes. The support member 100 has a configuration in which the inner block 8 is narrowed in the direction of the screw shaft 9 and is not screwed into the screw shaft 9 so as not to be affected by the rotation of the screw shaft 9. It is configured. Therefore, the support member 100 is configured to be able to reciprocate along the screw shaft 9 while being firmly supported by the outer rail 7. The pair of supporting members 100 are connected to each other by two connecting members 101 and supported by the outer rail 7 so that a reaction force is applied from the inner wall surface 7 a of the outer rail 7. Further, unlike the inner block 8, the support member 100 is provided with a through-hole through which the screw shaft 9 passes, similar to the inner block 8, and the ball rolling groove 9a for the screw shaft of the screw shaft 9 is provided. In order to avoid interference by! /, Balls 33 etc. are provided!

As shown in FIG. 7, the rolling bearing S 1 shown in FIG. 1 is fitted into the through hole formed in the support member 100. As described above, the rolling bearing 1 includes the inner ring 2 and the outer ring 3 having a plurality of balls 4 interposed therebetween, and the sleeve 5 is fitted on the inner periphery of the inner ring 2. In this rolling bearing 1, the outer peripheral surface of the outer ring 3 is strongly held by the inner peripheral surface of the through hole of the holding member 100 by being press-fitted into the through hole formed in the support member 100, and moves relative to the holding member 100. Is prevented. On the other hand, the sleeve 5 is formed such that its inner diameter is weakly fitted to the outer diameter of the screw shaft 9, and allows the screw shaft 9 to rotate inside the sleeve 5. For this reason, the screw shaft 9 rotates while smoothly sliding with respect to the inner peripheral surface of the sleeve 5 covering the inner peripheral surface of the inner ring 2. At this time, even if the rolling bearing 1 is affected by the friction generated between the screw shaft 9 and the sleeve 5, the inner ring 2 rotates freely with respect to the outer ring 3. Is rotated by. For this reason, smooth rotation of the screw shaft 9 is realized as compared with a case where only an annular body such as a resin molded body is fitted into the through hole of the support member 100. Even if the screw shaft 9 is sagged and interferes with the sleeve 9, the inner ring 2 rotates with the screw shaft 9 because the inner ring 2 rotates freely with respect to the outer ring 3 in this support member 100. The support member 100 supports the screw shaft 9 and realizes its smooth rotation.

[0055] As the force and rolling bearings, in addition to radial contact ball bearings, angular contact ball bearings and radial contact roller bearings can be applied. Further, either an end row rolling bearing or a double row rolling bearing can be applied, and an appropriate one may be applied according to the dimensions of the support member.

 [0056] The sleeve 5 fitted into the inner peripheral surface of the inner ring 2 of the rolling bearing 1 is formed of a fluororesin such as a polymer of tetrafluoroethylene. Alternatively, a member having an elastic modulus higher than that of the inner ring of the rolling bearing may be formed in an annular shape and the inner peripheral surface thereof may be coated with a fluororesin, and may be used as the sleeve.

However, this sleeve 5 has a higher elastic modulus than the inner ring 2 of the rolling bearing 1, has a lower frictional resistance than the inner peripheral surface of the inner ring 2, and the material has the required mechanical strength. Ordinary synthetic resins can be used. It is preferable to use a material having a tensile strength of 30 to 50 kg / cm ² , an elongation of 300 to 500%, and a rebound resilience of about 30 to 60%. It can also be used. For example, open-cell foamed polyurethane with 30-50% by weight of lubricant absorbed and retained. Besides foamed polyurethane, open-celled foam such as sintered resin, and fiber entangled bodies such as wool felt It is also possible that the fiber entangled body absorbs and holds the lubricant after it is formed into a predetermined shape. When the sleeve 5 is formed of a synthetic resin, the lubricant is mixed and held in advance in the synthetic resin material and then molded into a predetermined shape, or the monomer is polymerized at the stage of polymerizing the monomer to produce the synthetic resin. It is also possible to use a synthetic resin containing a lubricant obtained by mixing a lubricant with a resin molded into a predetermined shape.

 [0058] Further, the configuration in which the annular sleeve 5 is provided on the inner peripheral surface of the inner ring 2 may be provided by a configuration other than fitting, such as being fixed to the inner peripheral surface of the inner ring 2.

 [0059] The support member 100 is configured in the same manner as the inner block 8 except for the points described above. In addition, the force supporting member 100 that can make the supporting member 100 the same size as the inner block 8 is provided in order to suppress the jumping phenomenon in the high rotation range of the screw shaft 9 and is used as a moving member. Considering not to use it, it is desirable to make it smaller than the inner block 8.

 [0060] The distance between the pair of support members 100 connected by the two connection members 101 (the distance between the centers of the two support members 100) is the fulcrum of the respective housings 13 and 14 that support the screw shaft 9 at both ends. The distance L between the fulcrums is preferably half of the distance U between the fulcrums, that is, about L / 2. The distance between the centers of the pair of support members 100 is not necessarily limited to this distance. is not.

 The connecting member 101 is provided on the upper surface of the inner block 8 so as not to come into contact with the recessed corner portions 102 formed at two positions on both sides with respect to the axial direction of the screw shaft 9. Therefore, when the support member 100 is moved, when the screw shaft 9 is rotated by the electric motor and the inner block 8 linearly moves along the outer rail 7 in a predetermined direction, first, the inner block 8 is moved to the inner part of the support member 100. Touch the block 8 side. The support member 100 is pushed by the movement of the inner block 8, and the one support member 100 becomes almost integrated with the inner block 8 and moves in the moving direction of the inner block 8.

Next, the thread portion of the linear actuator will be described. As shown in FIG. 3, the screw shaft 9 passes through the center portion of the inner block 8. Further, as shown in FIG. 4, a screw shaft ball rolling groove 9a is formed on the outer peripheral surface of the screw shaft 9 as a spiral rolling element rolling portion for the screw shaft. The cross-sectional shape of the screw shaft ball rolling groove 9a is formed as a Gothic arch composed of two arcs having a slightly larger radius of curvature than the radius of the ball 33 for the screw shaft.

 [0064] On the other hand, a threaded shaft rolling ball rolling groove 15a as a threaded shaft rolling element rolling portion corresponding to the threaded shaft ball rolling groove 9a is also formed in the through hole of the block body 8a. The cross-sectional shape of the threaded ball rolling groove 15a for the screw shaft is also formed as a Gothic arch composed of two arcs having a radius of curvature slightly larger than the radius of the ball 33. A ball raceway load rolling path is formed between the screw shaft ball rolling groove 9a of the screw shaft 9 and the load ball rolling groove 15a for the screw shaft of the block body 8a.

 [0065] The screw shaft ball rolling groove 9a of the screw shaft 9 and the ball 33 are in contact at two points, and the screw ball load ball rolling groove 15a of the block body 8a and the ball 33 are in contact at two points. As a method for applying pressure, a so-called oversize method in which an oversized ball having a diameter slightly larger than the gap between the screw shaft 9 and the block body 8a is filled.

 [0066] The inner block 8 is provided with a return pipe 34 for circulating a ball rolling between the screw shaft ball rolling groove 9a and the screw shaft load ball rolling groove 15a. The return pipe 34 forms a screw shaft ball return path (screw shaft rolling element return path) that connects one end and the other end of the load rolling path.

[0067] The return pipe 34 has a circular cross section, and both end portions thereof are bent by about 90 ° with respect to the main body portion, and is formed in a substantially portal shape. The legs are twisted in accordance with the lead angle. At both ends of the return pipe 34, cuts for rolling the load rolling path ¾ and scooping up the ball are formed. Both sides of the return pipe 34 are inserted into the load rolling path with a few pitch intervals. The return pipe 34 is provided on the lower surface of the inner block 8, that is, on the side facing the upper surface of the water rail 7, and is fixed to the inner block 8 by a pipe presser. By providing the return pipe 34 on the lower surface side of the inner block 8, the upper surface side of the inner block 8 can be used freely, and assembly of a table or the like can be facilitated. When the screw shaft 9 is rotated, the ball 33 that rolls in the circumferential direction while receiving a load in the load rolling path is lifted / raised by the ends of both ends of the return pipe 34. The scooped-up ball 33 passes through the return pipe 34, and is returned to the load rolling path again from the ends of both ends separated by a few pitches. When the rotation direction of the screw shaft 9 is reversed, the ball 33 is circulated through this reverse path.

 [0069] As described above, the screw shaft 9 is configured, and the screw shaft 9 is rotated by the electric motor, whereby a linear actuator is configured to move the inner block 8 as a moving member. .

 [0070] As described above, according to the linear actuator according to this embodiment, since the guide portion and the ball screw portion have a body structure, high rigidity and high accuracy are achieved in a minimum space. And a pair of support members 100 that support the screw shaft 9 and are supported by the outer rail 7 along the axial direction of the screw shaft 9 of the inner block 8. Since there is always a support member 100 between the inner block 8 that penetrates the shaft 9 and one end of the screw shaft 9, the distance between the fulcrums that contributes to the calculation of the dangerous rotational speed must be reduced. It is possible to prevent the bending of the screw shaft 9 and suppress the so-called jumping phenomenon.

 Accordingly, since it is possible to avoid the limit of the dangerous rotational speed, it is physically possible to greatly improve the upper limit of the moving speed of the inner block 8. Further, since the support member 100 is accommodated in the water rail 7 provided with the inner block 8, the support member 100 can be accommodated in the passage region of the inner block 8. For this reason, the upper limit of the permissible rotational speed (dangerous rotational speed) can be significantly increased without increasing the size as compared with the conventional linear actuator.

 [0072] Then, the rolling bearing 1 is provided in the through hole of the support member 100, and the sleeve 5 is fitted on the inner periphery of the inner ring constituting the rolling bearing 1, so that the conventional linear actuator is provided. As described above, the screw shaft 9 can be smoothly rotated.

[0073] As described above, the force S specifically described for one embodiment of the present invention, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. . [0074] For example, in the above-described embodiment, the force S adopting the configuration using the outer rail 7 as the track member and the inner block 8 as the moving member, as shown in FIG. A screw shaft whose both ends are supported by a drive motor (not shown) for moving the block 8 'using a rail 8' as a moving member and a block 8 'extending over the rail 7' as a moving member. It is also possible to adopt a configuration in which 9 ′ is provided outside rail 7 ′ and block 8 ′.

 That is, the linear actuator shown in FIG. 8 has a nut 41 through which a screw shaft 9 ′ is passed, and the nut 41 and the block 8 ′ are connected by, for example, a connecting rod 42. . A pair of support members 100 ′ similar to the support member 100 in the above-described embodiment is provided in front and rear along the axial direction of the nut 41, and is connected to each other by a connecting member 10Γ. Yes. The present invention can be applied even when the linear actuator is configured as shown in FIG. 8, and the same operational effects as the operational effects of the embodiment of the present invention can be achieved.

 [0076] Further, in the above-described embodiment, the support member 100 has the same configuration as the inner block 8 except that the front-rear width along the axial direction of the screw shaft 9 is narrowed. Thus, the force configured to move using the ball 28 as a rolling element is not necessarily limited to this configuration, and slides into a recess such as a recess 10 provided in the inner wall surface 7a of the water rail 7. When the support member moves, the inner wall surface 7a is configured to support the screw shaft 9 while being supported by the outer rail 7 with a reaction force acting from the concave portion of the inner wall surface 7a. It is also possible to adopt a structure that moves while being slid.

As described above, the force described in the case where the support member 100 is applied to a member that supports the screw shaft 9 of the linear actuator is not limited to this. An apparatus having a mechanism in which both ends in the axial direction are rotatably supported by rolling bearings and a shaft member that is not threaded is provided on the outer peripheral surface, and the shaft member is rotationally driven by a drive source. However, this support member can be applied. That is, when the shaft member is driven to rotate, there is a risk that the shaft center of the shaft member may crawl as the shaft member rotates. If the support member is disposed at a position where the stagnation is maximum in the axial direction of the shaft member with respect to the device having such a mechanism, the support member stagnate while allowing the shaft member to rotate smoothly. Preventing the occurrence of In the linear actuator having the above-described shaft rotation mechanism, the force S and the sleeve are not described as an example in which the support member is provided with a rolling bearing provided with a sleeve on the inner peripheral surface of the inner ring. A rolling bearing can also be provided on the support member. In this case, the inner diameter of the inner ring is formed so as to have a gap with respect to the outer diameter of the screw shaft disposed on the inner side of the inner ring so that the screw shaft can be rotated with respect to the inner ring and moved in the axial direction. Constitute.

Claims

The scope of the claims  [1] An inner ring, an outer ring, and rolling elements interposed between the inner ring and the outer ring,  An inner diameter of the inner ring has a gap with respect to an outer diameter of a shaft member disposed on the inner side of the inner ring, and is formed to have a size that allows the shaft member to rotate with respect to the inner ring and move in the axial direction. Rolling bearing characterized by  [2] In the rolling bearing according to claim 1,  An annular body made of a member having a higher elastic modulus than the inner ring is provided on the inner peripheral surface of the inner ring,  The inner diameter of the annular member has a gap with respect to the outer diameter of the shaft member, and is formed to have a dimension that allows the shaft member to rotate and move in the axial direction with respect to the annular member. A rolling bearing characterized in that a friction coefficient of an inner peripheral surface is lower than a friction coefficient of an inner peripheral surface of the inner ring. [3] a shaft member that is rotationally driven by a drive source;  A support member that is disposed at an intermediate position in the axial direction of the shaft member, penetrates the shaft member, and supports the outer periphery of the shaft member;  The support member is provided with a rolling bearing having an inner ring, an outer ring, and rolling elements interposed between the inner ring and the outer ring,  The inner diameter of the inner ring has a gap with respect to the outer diameter of the shaft member arranged inside the inner ring, and is formed to have a dimension that allows the shaft member to rotate with respect to the inner ring and move in the axial direction. A shaft rotation mechanism characterized by that. [4] In the shaft rotating mechanism according to claim 3,  An annular body made of a member having a higher elastic modulus than the inner ring is provided on the inner peripheral surface of the inner ring,  The inner diameter of the annular member has a gap with respect to the outer diameter of the shaft member, and is formed to have a dimension that allows the shaft member to rotate and move in the axial direction with respect to the annular member. Friction resistance force of the inner peripheral surface against the shaft member A shaft rotation mechanism characterized by being lower than the friction resistance against the shaft member of the inner peripheral surface of the inner ring. [5] In the shaft rotation mechanism according to claim 3 or 4, The shaft rotation mechanism, wherein the support member and the shaft member are relatively movable in the axial direction of the shaft member. [6] raceway members;  A screw shaft that is supported at both ends and whose axial direction is aligned with the longitudinal direction of the track member;  A moving member that penetrates the screw shaft and moves along the track member as the screw shaft rotates;  A support member disposed on both sides of the moving member in the axial direction of the screw shaft, the screw shaft penetrating through and supporting the outer periphery thereof;  Comprising  The support member is provided with a rolling bearing having an inner ring, an outer ring, and rolling elements interposed between the inner ring and the outer ring,  An inner diameter of the inner ring has a gap with respect to an outer diameter of the screw shaft disposed on the inner side of the inner ring, and is formed to have a dimension that allows the screw shaft to rotate with respect to the inner ring and move in the axial direction. This is a linear actuator. [7] In the linear actuator according to claim 6,  An annular body made of a member having a higher elastic modulus than the inner ring is provided on the inner peripheral surface of the inner ring,  The inner diameter of the annular body has a gap with respect to the outer diameter of the shaft member, and is formed to have a dimension that allows rotation of the screw shaft relative to the annular body and movement in the axial direction. Friction resistance force of inner peripheral surface to the screw shaft A linear actuator having a lower friction resistance than the inner peripheral surface of the inner ring to the screw shaft. [8] In the linear actuator according to claim 6 or 7,  The linear actuator is characterized in that the support member is supported by the track member so as to be movable in the axial direction of the screw shaft. [9] The linear actuator according to claim 8, The track member is substantially U-shaped in cross section having inner wall surfaces facing each other, the moving member and the support member are provided sandwiched between the inner wall surfaces, A rolling element rolling part is formed on the inner wall surface, and a load rolling element rolling part corresponding to the rolling element rolling part is provided on the moving member and the support member,  The moving member and the support member further include a rolling element return passage and a direction changing path through which a rolling element rolling between the rolling element rolling portion and the loaded rolling element rolling portion can be circulated. Provided in  The rolling element return passages are respectively formed in parallel with a predetermined interval from the load rolling element rolling portion, and the direction changing path is formed between the load rolling element rolling portion and the rolling element return passage. Configured to connect between,  A spiral rolling element rolling part for a screw shaft is provided on the outer peripheral surface of the screw shaft, and the load rolling element rolling for the screw shaft corresponding to the rolling element rolling part for the screw shaft is provided in the through hole of the moving member. Part is provided,  The moving member is provided with a screw shaft rolling element return passage for circulating the screw shaft rolling element that rolls between the screw shaft rolling element rolling part and the screw shaft load rolling element rolling part. A linear actuator characterized by