JP2006329420A - Bearing device for robot arm joint part, and ball bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To receive a radial load, and an axial load and a moment load in both directions as a matter of course, and attain rigidity improvement, rotation accuracy improvement, cost reduction, torque reduction, heating reduction, and space saving. <P>SOLUTION: The bearing device for the robot arm joint part is provided with the joint part 23 of an articulated robot arm provided with a linkage 21 composed of a plurality of links 21a-21d, and a rolling bearing incorporated in the joint part 23. A single row ball bearing 100 wherein a cross sectional aspect ratio B/H of an axial cross sectional width B and a radial cross sectional height H is less than 0.63 is used as the rolling bearing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bearing device for a joint part of a multi-joint robot arm used for various industrial machines and the like, and a ball bearing incorporated in the joint part.

The articulated robot arm equipped with a link device composed of multiple links is a prosperous industry in recent years for digital equipment in addition to industrial machine processing lines, assembly lines or transport processes for the purpose of labor saving and automation. Along with this, they are also often used in semiconductor manufacturing equipment and liquid crystal panel manufacturing equipment lines.
FIG. 31 shows an example of an articulated robot arm for transferring a silicon wafer in a semiconductor manufacturing process.

  The multi-joint robot arm includes a link device 21 that, for example, combines four links 21a to 21d by pairs (joint portions). Each of the links 21a and 21b has a base end rotatably connected to the drive device 20 via a joint (not shown) and a distal end rotatable to the links 21c and 21d via a joint 22. It is connected. The tips of the links 21c and 21d are rotatably connected to a support hand 25 that supports the silicon wafer 24 via joint portions 23 (see FIG. 32). A predetermined rolling bearing is incorporated in each joint part, and the support hand 25 and the joint part 23 enter a chamber for processing a silicon wafer.

  Two rows of direct drive motors (not shown) are arranged in the drive device 20 in the axial direction. By performing rotation control in synchronization with the two rows of direct drive motors, the rotational motion of the entire robot arm ( 31 (the direction of arrow A in FIG. 31) and the link 21a and the link 21b can be rotated (in the directions of arrows B1 and B2 in FIG. 31). As a result, the support hand 25 can be freely moved in the arm extending / contracting direction (X direction) and the arm turning direction (θ direction).

  By the way, in the semiconductor manufacturing process, the liquid crystal panel manufacturing process, and the like, the above-described robot arm is used to put a silicon wafer, a liquid crystal panel, and the like into and out of a processing chamber maintained in a clean environment or a vacuum environment atmosphere. In order to quickly and surely isolate the outside environment and the inside of the chamber in these steps, it is necessary to make the opening area of the gate of the chamber as small as possible. In other words, the smaller the opening area of the gate, the smaller the variation in the atmosphere in the chamber, and the shorter the gate opening and closing time, the shorter the opening and closing time of the chamber allows the chamber atmosphere to be restored to the optimum processing conditions. This is because production efficiency is improved.

Usually, since a silicon wafer and a liquid crystal panel are thin-walled, the gate is narrow in the vertical direction and wide in the horizontal direction. Accordingly, it is desired that the robot arm carrying these members also has a thin-walled shape in the horizontal direction so as not to interfere with the narrow gate.
On the other hand, in a processing line, an assembly line, or a conveyance process of an industrial machine, if the robot arm in each process becomes compact, the area of the line can be reduced, and the entire process can be saved. As described above, if the robot arm can be thinned in the horizontal direction, two or more rows of robot arms are arranged in the vertical direction, so that the loading and unloading of members in a specific processing step can be performed simultaneously. This makes it possible to shorten the cycle time of the work process and greatly improves production efficiency.

Therefore, as a rolling bearing incorporated in the joint part of the articulated robot arm used for these applications, high rigidity (especially high moment rigidity), high rotation accuracy (ensuring high positioning accuracy of the arm, low vibration) In addition to low noise and low cost, space saving is required, and in particular, space saving of the joint portion 23 of the support hand 25 is required.
Conventionally, as a rolling bearing incorporated in the joint portion of the robot arm, for example, a thin two-row combination ball bearing, a four-point contact ball bearing, and a cross roller bearing have been proposed for the purpose of space saving.

(1) Two-row combination ball bearings (see, for example, Patent Document 1 and Patent Document 2)
First, FIG. 33 is an example in which standard angular ball bearings in which a plurality of balls 9 are rotatably arranged between the inner ring 7 and the outer ring 8 are combined in two rows. Is the same as that incorporated in In FIG. 32, a standard two-row angular contact ball bearing is incorporated in the joint 23 to constitute a robot arm joint bearing device, which eliminates rattling or tilting of the bearing when subjected to moment load. In order to reduce the contact angle, the combination direction of the two rows of angular contact ball bearings is the rear combination (the contact angle is a “C” and the distance between the action points of the moment is increased), and high moment rigidity is achieved. . Further, the bearing is loaded with a preload to eliminate rattling of the bearing.

However, in the case of a two-row combination of standard ball bearings, naturally, twice as much axial space as that of a single-row bearing is required, the axial thickness of the bearing cannot be reduced, and space saving cannot be achieved. Increases in size and costs.
Therefore, for the purpose of space saving of the bearing, a combination of two rows of extremely thin deep groove ball bearings and angular contact ball bearings (see FIG. 34) has been proposed. For example, as shown in FIG. 8 is fastened to the shaft 12 and the housing 13 using bolts 14 via the inner ring presser 10 and the outer ring presser 11, respectively. The outer ring presser 11 is a part of the outer diameter surface of the outer ring 8, and the inner ring presser 10 is connected to the outer side of the shaft 12. The bearing is positioned so as not to deviate from the bearing via the shaft 12 by being fitted to a part of the radial surface.

  Although such an ultra-thin two-row combination ball bearing is advantageous in terms of space saving, the inner and outer rings 7 and 8 have a very thin ring wall and the inner and outer rings 7 and 8 have low rigidity. Is difficult to generate (especially roundness), and when it is assembled into the shaft 12 or the housing 13 (particularly when it is assembled by clearance fitting with the shaft 12 or the housing 13), the pressing force of the inner ring presser 10, the outer ring presser 11, etc. Therefore, there are problems such as being easily deformed, requiring time and effort for securing the mounting accuracy, and increasing the cost. Further, depending on the case, the raceway grooves of the inner and outer rings 7 and 8 are distorted due to deformation at the time of incorporation, and an uneven load is applied between the contact portions between the balls 9 and the raceway grooves, or the smooth rolling motion of the balls 9 is hindered. Sometimes.

(2) Four-point contact ball bearing (see, for example, Patent Document 3 and Patent Document 4) As shown in FIG. 36, a four-point contact ball bearing has a large number of balls 6 rolling between the inner ring 4 and the outer ring 5. It is arranged freely, and can receive radial load, axial load in both directions, and moment load with a single bearing, and can save space.
In the case of a four-point contact ball bearing, the rolling element is a ball, so when receiving a pure axial load, or when the axial load is superior to the radial load, the torque is almost the same as that of the angular ball bearing of the same size. On the other hand, when the radial load is dominant, or when receiving a pure radial load, each ball 6 contacts the raceway grooves 4a and 5a at four points, and therefore the spin slip between the ball 6 and each raceway groove 4a and 5a is large. The torque also increases, causing problems of heat generation and wear.
Like angular contact ball bearings, preload is often applied to the bearings in order to achieve high rotational accuracy (ensuring precise positioning accuracy of the arm, low vibration and low noise) and high rigidity. Since the ball 6 always contacts the inner and outer ring raceway grooves 4a and 5a at four points, the torque further increases.

(3) Cross roller bearing (see, for example, Patent Document 5 and Patent Document 6)
As shown in FIG. 37, in the cross roller bearing, a large number of cylindrical rollers 3 are arranged between an inner ring 1 and an outer ring 2 so as to be able to roll, and a radial load and an axial load in both directions are provided by one bearing. It can receive moment load and can save space.
However, in the cross roller bearing, since the rolling element is a roller and the rolling contact surface of the roller 3 is in line contact with the raceway grooves 1a and 2a, the raceway is compared with a ball bearing using a ball as the rolling element. The torque for rotating the wheel becomes relatively large.

In addition, slight deformation when incorporated in the shaft or the housing makes the contact state of the line contact portion unstable, and torque unevenness is likely to occur, which may hinder malfunction or smooth movement of the robot arm.
In addition, preload is often applied to the bearings in order to achieve high rotational accuracy (ensuring precise positioning accuracy of the arm, low vibration and noise) and high rigidity. Increases and torque fluctuations are likely to occur, leading to an increase in space and cost, such as an increase in drive motor capacity.

Japanese Utility Model Publication No. 5-66327 JP 2003-278765 A Japanese Patent Laid-Open No. 11-62990 JP 2003-139145 A Japanese Utility Model Publication No. 1-444806 JP 63-213457 A

  The present invention has been made to eliminate such inconveniences, and can receive radial load, axial load in both directions, and moment load, as well as high rigidity, high rotational accuracy, low cost, An object of the present invention is to provide a robot arm joint unit bearing device and a ball bearing which can achieve low torque and low heat generation and can further save space.

In order to achieve the above object, an invention according to claim 1 is a robot comprising a joint part of an articulated robot arm provided with a link device constituted by a plurality of links, and a rolling bearing incorporated in the joint part. A bearing device for an arm joint,
As the rolling bearing, a single-row ball bearing in which the sectional dimension ratio (B / H) between the axial sectional width B and the radial sectional height H is (B / H) <0.63 is used. Features.

The invention according to claim 2 is an articulated robot arm including a link device in which a large number of balls are rotatably arranged between a raceway groove of an outer ring and a raceway groove of an inner ring, and includes a link device constituted by a plurality of links. In single-row ball bearings built into joints,
The sectional dimension ratio (B / H) between the axial sectional width B and the radial sectional height H is (B / H) <0.63.

The invention according to claim 3 is a bearing device for a robot arm joint part comprising a joint part of an articulated robot arm provided with a link device constituted by a plurality of links, and a rolling bearing incorporated in the joint part. And
As the rolling bearing, a double-row ball bearing in which the sectional dimension ratio (B2 / H2) between the axial sectional width B2 and the radial sectional height H2 is (B2 / H2) <1.2 is used. Features.

The invention according to claim 4 is provided with a multi-link device comprising a plurality of links in which a large number of balls are rotatably arranged between the double-row raceway grooves of the outer ring and the double-row raceway grooves of the inner ring. In double-row ball bearings incorporated in the joints of joint robot arms,
A sectional dimension ratio (B2 / H2) between the axial sectional width B2 and the radial sectional height H2 is (B2 / H2) <1.2.

  The invention according to claim 5 is the invention according to claim 2, wherein a seal housing groove is formed on at least one side end surface between the outer ring and the inner ring, an annular seal body is disposed in the seal housing groove, A cage for positioning a number of balls in the circumferential direction is disposed, and the cage is formed with annular portions on both sides in the axial direction of the pockets for holding the plurality of balls, Any one of the inner peripheral surfaces of the outer ring is used as a guide surface, and a concave groove portion is formed in the circumferential direction at a position facing the intersection edge portion between the guide surface and the seal housing groove portion to avoid contact with the intersection edge portion. It is characterized by that.

  In the invention according to claim 1 or 2, as the rolling bearing incorporated in the joint portion of the robot arm, for example, as shown in FIG. 2, a large number of rolling bearings are provided between the raceway groove 101a of the outer ring 101 and the raceway groove 102a of the inner ring 102. The ball 103 is arranged so as to be able to roll, and the cross-sectional dimension ratio (B / H) between the axial cross-sectional width B and the radial cross-sectional height H (= (outer ring outer diameter D−inner ring inner diameter d) / 2) is A ball bearing 100 in which (B / H) <0.63 is used.

Here, FIG. 26 and FIG. 27 show ultrathin ball bearings (bearing inner diameter: φ38.1 mm, bearing outer diameter: φ47.625 mm, bearing width: 4.762 mm, standard sectional ratio ( B / H) = 1) as a reference, the inner and outer ring rings of the inner and outer ring rings when the inner diameter of the bearing is changed without changing the outer diameter and the bearing width (that is, when the value of (B / H) is changed). radial deformation characteristic (see FIG. 24: illustrates the inner ring) and radial cross-sectional secondary moment I (see Figure 25): shows the I = bh ^3/12) result of comparison.

  Also for FIGS. 28 and 29, the standard thin ball bearings (bearing inner diameter: φ63.5 mm, bearing outer diameter: φ76.2 mm, bearing width: 6.35 mm, cross-sectional dimension ratio ( B / H) = 1) as a reference, the inner and outer ring rings of the inner and outer ring rings when the inner diameter of the bearing is changed without changing the outer diameter and the bearing width (that is, when the value of (B / H) is changed). The result of having compared the deformation characteristic of radial direction and the cross-sectional secondary moment I of radial direction is shown.

In either case, (B / H) is less than 0.63, and the change in the rigidity increase rate gradient is noticeable. That is, the increase in the secondary moment I of the cross section becomes significant, and the decrease in the deformation amount of the inner and outer ring in the radial direction becomes saturated.
Therefore, in the present invention, bearing deformation such as roundness and uneven thickness can be prevented by preventing lathe processing during inner and outer ring production and processing force during polishing, which is a problem with conventional ultra-thin bearings. Can be improved.

In addition, when incorporated in a shaft or housing (especially when assembled by clearance fitting with the shaft or housing), deformation of the inner and outer rings when the bearing is fixed with an inner ring retainer or outer ring retainer (especially worse roundness) In addition to torque failure and rotational accuracy failure caused by deformation, problems such as increased heat generation, wear, and seizure can be prevented.
That is, as compared with the conventionally used ultra-thin ball bearings, it is possible to achieve both space saving and high rotational accuracy.

In addition, each ball always contacts the inner and outer ring raceway grooves at two points. As in the case of a cross roller bearing, the increase in torque and torque caused by the roller contact surface of the roller making linear contact with the raceway groove. There is no problem of unevenness, low heat generation, and wear can be prevented.
Furthermore, when the width dimension is about half that of the conventional standard single-row ball bearing, the ball diameter is also about half that of the conventional ball bearing. Increased against ball bearings.

Furthermore, when incorporated in the joint part of a robot arm, the load capacity of the bearing is reduced by reducing the ball diameter, since the low-speed rotation or oscillating rotation conditions occupy most of the ratio compared to other applications. The rolling fatigue life time does not become a practical problem even if the decrease is reduced.
Single-row ball bearings are difficult to apply preload or moment load in one row, but by combining two or more rows, radial load, axial load in both directions and moment load It becomes possible to load.

  On the other hand, in the standard ball bearings whose dimension series prescribed by the International Organization for Standardization (ISO) are 18 (for example, 6810), 19 (for example, 6912), 10 (for example, 7010A), 02 (for example, 7214A), 03 (for example, 7313A) When the inner diameter of the bearing is φ5 mm to φ500 mm, the cross-sectional dimension ratio (B / H) is set to 0.63 to 1.17.

Therefore, the width of the cross-sectional dimension ratio (B / H) of these ball bearings is set to about 1/2 times the maximum value of 1.17, that is, less than 0.63. The ball bearings according to claim 1 or 2 can be arranged in combination with each other within a space narrower than that of the conventional ball bearing and within an axial space of a conventional standard single row ball bearing.
For example, if the sectional dimension ratio (B / H) of a conventional ball bearing is (B / H) = 0.9, the sectional dimension ratio (B / H) of the bearing of the present invention is (B / H) = 0. .45. In the case of this example, the sectional dimension ratio (B / H) of the two ball bearings to be combined need not be the same. For example, one may be 0.50 and the other may be 0.40. .

  In the invention according to claim 3 or 4, as the rolling bearing incorporated in the joint portion of the robot arm, for example, as shown in FIG. 20, the double row raceway grooves 201a and 201b of the outer ring 201 and the double row raceway groove 202a of the inner ring 202 are provided. , 202b, a large number of balls 203 are rotatably arranged, and the cross-sectional dimension of the axial cross-sectional width B2 and the radial cross-sectional height H2 (= (outer ring outer diameter D2-inner ring inner diameter d2) / 2). A double row ball bearing 200 in which the ratio (B2 / H2) is (B2 / H2) <1.2 is used.

  In the double row ball bearing, by setting the cross-sectional dimension ratio (B2 / H2) as described above, the single row narrow ball bearing according to claim 1 or 2 is combined into two rows, It becomes possible to arrange the double-row ball bearing according to claim 3 or 4 in the axial width space of the conventional standard single-row ball bearing, and it is also possible to apply a preload or apply a moment load. Become. Other functions and effects are the same as in the case where the single row narrow ball bearings according to claim 1 or 2 are combined in two rows.

  FIG. 30 is a comparison of calculated moment stiffness of various bearings. When the same size (calculation example is equivalent to bearing name No. 7906A (contact angle 30 °) and the inner and outer diameter dimensions are the same: inner ring inner diameter φ30 mm, outer ring outer diameter φ47 mm), the width of the single row according to claim 1 or 2 is narrow. Inventive examples A to E in which angular contact ball bearings (contact angle 30 °: calculation example of total ball bearing) are combined in two rows and the raceway radius of curvature of the inner and outer rings are changed are cross roller bearings, standard 2 The moment rigidity is larger than that of the row combination angular contact ball bearing and the 4-point contact ball bearing. For example, the present invention example B can maintain moment rigidity 2.4 times that of a cross roller bearing, 1.9 times that of a standard two-row angular contact ball bearing, and 3.3 times that of a 4-point contact ball bearing. It is.

The design preload clearances are -0.010 mm for the invention examples A to E, standard two-row angular contact ball bearings and 4-point contact ball bearings, and -0.001 mm for the cross roller bearings. (If the pre-load setting is less than -0.001 mm with a cross roller bearing, the torque may be excessive and may not be usable in practice).
The appropriate ball diameter of the narrow ball bearing according to the present invention varies depending on whether or not a seal or the like is attached, but in order to increase rigidity, if the ball diameter is extremely reduced, the ball and the inner and outer ring raceway grooves Since the surface pressure between the contact portions increases and the pressure scar resistance decreases, the bearing width (B) or (B2 / 2) is preferably approximately 30% to 90%.

Furthermore, when the present invention is applied to an angular ball bearing, the contact angle of the bearing is selected depending on the required rigidity (for example, moment rigidity) and the required torque, but is preferably in the range of approximately 10 to 60 °.
Further, according to the direction and magnitude of the load, the contact angle of each combined single row bearing or the contact angle between each row in the case of a double row bearing may be changed as necessary.
Further, the radius of curvature of the inner and outer ring raceway grooves is 51 to 60% Da (Da: ball diameter), preferably 52 to 56% Da, more preferably 52 to 54%, depending on the required rigidity and torque characteristics. It is about Da. Further, the radius of curvature of each raceway groove of the inner and outer rings may not be the same, or may be different between single row bearings to be combined or between rows of double row bearings.

  Still further, in the invention according to claim 5 or 6, in the single-row ball bearing according to claim 1 or 2, a seal housing groove is formed on at least one end face of each of the outer ring and the inner ring, and an annular seal is formed in the seal housing groove. The inner ring outer circumferential surface and the outer ring inner circumferential surface formed on both sides in the axial direction of the pocket for holding a large number of balls of the cage, when the body is disposed and the cage for positioning the large number of balls in the circumferential direction is disposed. Since the concave groove portion is formed in the circumferential direction at the position facing the intersection edge portion between the guide surface and the seal receiving groove portion on the annular portion having one of the surfaces as the guide surface, the width is narrow as described above. Even in the case of a bearing having a shape, wear of the annular portion due to edge contact can be reliably prevented by avoiding contact of the annular portion of the cage with the intersection edge portion by the concave groove portion.

  According to the present invention, in the ball bearing incorporated in the joint portion of the robot arm, in the case of the single row ball bearing, the sectional ratio (B / H) between the axial sectional width B and the radial sectional height H is (B / H). /H)<0.63, and in the case of a double row ball bearing, the sectional ratio (B2 / H2) between the axial sectional width B2 and the radial sectional height H2 is (B2 / H2) <1.2. In addition to being able to receive radial load, axial load in both directions, and moment load, it is possible to achieve high rigidity, high rotational accuracy, low cost, low torque and low heat generation. Space saving can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a view for explaining an example in which a single row ball bearing which is an example of an embodiment of the first aspect of the present invention (corresponding to claim 1 or 2) is incorporated in a joint portion of a robot arm to constitute a bearing device. FIG. 2 is a cross-sectional view of an essential part showing a single-row ball bearing incorporated in the joint part of FIG. 1, and FIG. 3 is a cross-sectional view of an essential part showing a state in which two single-row ball bearings of FIG. 4 to 15 are diagrams for explaining another embodiment of the first aspect of the present invention, and FIGS. 16 to 19 are diagrams and figures for explaining a modification of the first aspect of the present invention. 20 is a cross-sectional view of an essential part for explaining a double-row ball bearing for a robot arm joint, which is an example of an embodiment of the second aspect of the present invention (corresponding to claim 3 or 4). These are the figures for demonstrating other embodiment of the 2nd aspect of this invention.

  In each of the embodiments, the ball bearing according to the present invention is incorporated into the joint portion 23 (see FIG. 32) between the tips of the links 21c and 21d of the multi-joint robot arm already described in FIG. However, the present invention is not limited to this and may be applied to a ball bearing incorporated in a joint portion of another known robot arm.

  As shown in FIG. 2, a single row ball bearing 100 as an example of an embodiment of the first aspect (corresponding to claim 1 or 2) of the present invention includes a raceway groove 101 a of the outer ring 101 and a raceway groove of the inner ring 102. A single-row angular contact ball bearing in which a large number of balls 103 are rotatably arranged between the ball 102a and an axial section width B and a radial section height H (= (outer ring outer diameter D−). The sectional dimension ratio (B / H) with the inner ring inner diameter d) / 2) is (B / H) <0.63.

In this embodiment, as shown in FIGS. 1 and 3, the angular contact ball bearings 100 are assembled into the joint portion 23 of the robot arm as a two-row back combination, thereby constituting a robot arm joint portion bearing device. ing.
The outer ring 101 and the inner ring 102 are fastened to the shaft 32 of the support hand 25 and the housing 23a of the joint 23 using bolts or the like via the outer ring presser 30 and the inner ring presser 31, and the outer ring presser 30 is formed on the outer diameter surface of the outer ring 101. A part of the inner ring presser 31 is fitted to a part of the outer diameter surface of the shaft 32 and is positioned via the shaft 32 so that the bearing and the core are not displaced.

Here, in this embodiment, a case where the double-row back side angular contact ball bearing 100 is replaced with a 7208A (contact angle 30 °) double-row combination angular ball bearing is taken as an example.
Since the 7208A angular contact ball bearing has an inner ring inner diameter d: φ40 mm, an outer ring outer diameter: Dφ80 mm, and an axial sectional width (bearing single body width) B is 18 mm, the sectional dimension ratio (B / H) = 0.9. Therefore, in the angular ball bearing 100 of the present embodiment, the cross-sectional dimension ratio (B / H) = 0.45 (the inner ring inner diameter and the outer ring outer diameter remain the same, and the axial sectional width (bearing unit width) B is 9 mm). It is said.

As a result, radial load, axial load in both directions, and moment load can be received, as well as high rigidity, high rotational accuracy, low cost, low torque and low heat generation. It is possible to save space by ½ in the directional dimension, and it is possible to design a narrow opening width in the vertical direction of the gate of the processing chamber in a semiconductor manufacturing process, a liquid crystal panel manufacturing process, or the like.
Of course, if necessary, the cross-sectional dimension ratio (B / H) of the angular ball bearing 100 may be set to be less than 0.45 or more than 0.45 (where (B / H) <0.63). Absent. Incidentally, the contact angle of the angular ball bearing 100 is, for example, 30 °.

In this embodiment, the pitch circle diameter of the balls 103 is as shown in the following formula (1). However, when it is desired to increase the moment rigidity by increasing the number of balls per row of the bearing, the following formula (2) is used. 4 and the pitch circle diameter of the ball 103 may be shifted to the outer ring side, and the structure shown in FIG. 4 may be adopted, or the following equation (3) may be adopted as necessary to change the pitch circle diameter of the ball 103 to the inner ring. You may shift to 102 side (not shown).
Ball pitch circle diameter = (inner ring inner diameter + outer ring outer diameter) / 2 (1)
Ball pitch circle diameter> (inner ring inner diameter + outer ring outer diameter) / 2 (2)
Ball pitch circle diameter <(inner ring inner diameter + outer ring outer diameter) / 2 (3)

  Further, as shown in FIG. 5, the ball pitch circle diameters of the left and right ball bearings to be combined may not be the same value as shown in FIG. 5, and the diameters of the balls 103 of the right and left ball bearings to be combined are set to the same value. It does not have to be. In addition, the sectional dimension ratio (B / H) of the two ball bearings to be combined is not the same. For example, the smaller ball diameter is (B / H) = 0.28, and the larger ball diameter is (B / H). ) = 0.62. Further, the axial pitch of the balls 103 may not be the center of the axial direction, and the axial pitch of the balls 103 may be shifted in the axial direction in order to secure the distance between the application points of the moment and the moment of attachment of the seal and the cage. Good.

  FIG. 6 shows a combination of two rows of angular ball bearings 100 each having an annular seal body 104 mounted at one end in the axial direction. After the angular ball bearings 100 having the annular seal body 104 mounted on one end in the axial direction are combined in two rows and attached to a machine or the like (combined with the seal mounting surface facing outward), the external ball bearing 100 is used while the bearing is in use. It is possible to prevent entry of foreign matter, dust, etc. and leakage of the enclosed grease to the outside. In this embodiment, the annular seal body 104 is a non-contact type (non-contact with the inner ring 102) inserted into the seal groove 104a of the outer ring 101 and a reinforcing rubber seal (for example, nitrile rubber / acrylic rubber) of the metal core 105. Or fluorine rubber) 106, and an annular seal body 104 is attached only on the side opposite to the combined end face to save space.

FIG. 7 shows an angular ball bearing 100 in which annular seal bodies 104 are mounted at both ends in the axial direction.
After the angular ball bearing 100 with the annular seal body 104 mounted on both ends in the axial direction is attached to a machine or the like, it prevents foreign matter and dust from entering from outside during use of the bearing, Even when it is assembled into the housing, it is possible to prevent intrusion of foreign matter, dust, etc. and leakage of the enclosed grease to the outside. As for the combination, in order to increase the moment stiffness in two rows, it is desirable to adopt the back combination (the contact angle is in the direction of the letter C in FIG. 3 etc.) that allows the moment action point distance to be increased. .

  If further rigidity is required, as shown in FIGS. 8 and 9, a multi-row combination of three or more rows may be used. For some reason (for example, misalignment is unavoidable when the bearing is installed, the internal load of the bearing is For example, when it is desired to suppress the load as much as possible and to reduce the moment rigidity, an arrangement such as a frontal combination (the contact angle direction is reverse C) may be used as shown in FIG.

Furthermore, in order to apply moment load or both axial loads, it is necessary to use two or more rows of combined bearings. You can use it.
In this embodiment, the angular ball bearing is used, but other ball bearings such as a deep groove ball bearing may be used. The annular seal body is not the non-contact type shown in FIGS. 6 and 7, but may be a contact type metal core reinforcing type rubber seal (the rubber material is, for example, nitrile rubber, acrylic rubber or fluororubber), or the outer ring 101. A metal shield plate that is swaged into the seal groove may be used. Further, the annular seal body may be inserted by being inserted into the seal groove on the inner ring 102 side, or may be attached by caulking (a structure in contact with or non-contact with the outer ring).

The material of the inner ring 102, the outer ring 101, and the ball 103 is a bearing steel (eg, SUJ2, SUJ3, etc.) under standard usage conditions, but depending on the usage environment, a stainless steel material (eg, SUS440C, etc.) that is a corrosion resistant material. Martensitic stainless steel materials, austenitic stainless steel materials such as SUS304, precipitation hardening stainless steel materials such as SUS630, etc., titanium alloys and ceramic materials (for example, Si ₃ N ₄ , SiC, Al ₂ O ₃ , ZrO _2, etc.) ) May be adopted.

The lubrication method is not particularly limited, and mineral oil-based grease or synthetic oil-based grease (for example, lithium-based or urea-based grease) or oil can be used in a general usage environment. Fluorine-based grease or fluorine Series lubricants or solid lubricants such as fluororesin and MoS ₂ can be used.
FIG. 11 shows an angular contact ball bearing provided with an annular seal body 104 at one end in the axial direction (end opposite to the end face on the combination side) and a cage 110 that holds the ball 103 in a rollable manner. 100 is a combination of two rows on the back.

  As the cage 110, for example, as shown in FIGS. 12 to 15 (a), an annular portion 111 and one end portion of the annular portion 111 project in the axial direction at a plurality of locations at substantially equal intervals in the circumferential direction. A flexible crown-shaped cage including the pillars 112 and pockets 113 formed between the pillars 112 to hold the balls 103 so as to roll in the circumferential direction is employed. The material of the cage 110 is, for example, a synthetic resin material such as polyamide, polyacetal, or polyphenylene sulfide, and a material in which a reinforcing material such as glass fiber or carbon fiber is mixed into the synthetic resin material is used as necessary.

In this embodiment, in order to increase the load capacity and rigidity of the bearing, the circumferential pitch between adjacent balls 103 is made as small as possible, and the number of balls is increased as much as possible. Furthermore, the axial pitch of the balls 103 is shifted as much as possible to the opposite side of the combination side end face (FIG. 11: X ₁ > X ₂ ), and the ring portion 111 of the cage 110 is arranged to be on the bearing combination end face side. In order to increase the moment rigidity, the distance between the operating points can be increased.

  In the case of a full ball bearing, the axial pitch of the balls is not the center of the width in the same way as necessary, such as whether or not an annular seal body is mounted. It can be shifted to the opposite side. When a ball bearing with a cage is used as a full ball bearing under conditions where the rotation speed tends to vary due to changes in the contact angle of each ball, such as continuous rotation in one direction or a large moment load. It is more effective in terms of low torque, low heat generation, etc.

  Furthermore, in this embodiment, if the entrance portion of the pocket portion 113 is slightly smaller than the ball diameter and is provided with a hook (pachin allowance), the ball 103 can be assembled without being dropped when the inner ring 102 and the outer ring 101 are assembled. Easy. The shape of the cage is not limited to this embodiment, and any system other than the separator type cage disposed between the balls 103 may be used. Also, the material may be a metal material instead of a synthetic resin material.

15 (b) is a crown-shaped cage having the same basic structure as FIG. 15 (a), but the pocket portion 113 adjacent to each other at least at one place in the circumferential direction of the annular portion 111 is cut in advance. And it is set as the structure which gave the predetermined clearance gap between each cut surface.
By adopting such a structure, the rolling element pitch circle diameter and the cage pitch circle diameter have shifted due to differences in the thermal expansion coefficient between the cage and the raceway and variations in the dimensional accuracy and roundness of the cage. Even in this case, the ball 103 and the pocket have both the flexibility in the radial direction due to the cantilever shape and the elastic deformation in the circumferential direction (the flexibility in the circumferential direction) due to the gaps between the cut surfaces. The tension force between the portions 113 can be buffered to prevent the cage from being damaged and worn, and torque unevenness and heat generation due to sliding contact resistance between the balls 103 and the pocket portions 113 can be further reduced.

  In addition, since the ball bearing of the present invention has a structurally small ball diameter, the radial thickness of the annular portion 111 of the cage cannot be increased (as can be understood from FIG. 11, the cage is an inner ring). It is necessary to position the gap between the outer diameter and the inner diameter of the outer ring by providing an appropriate gap, and the gap between the outer diameter of the inner ring and the inner diameter of the outer ring is substantially proportional to the ball diameter and is narrow) Furthermore, due to the narrow structure, the gap in the axial direction is also narrow and the axial thickness has to be reduced. For this reason, since the annular portion of the cage is extremely smaller than a standard size bearing and it is difficult to obtain dimensional accuracy such as roundness, the cage structure having the annular portion 111 as shown in FIG. In particular, the effects described above can be obtained with respect to the above-described cage damage and wear prevention effect, and torque unevenness and reduction of heat generation.

In addition, the intended application is when the dmn value of the bearing (dm: product of rolling element pitch circle diameter (mm) of rolling bearing and n: rotational speed (min ⁻¹ )) is at most 100,000 to 200,000 or less. In many cases, when the present invention is applied to these uses, even if the cage structure as shown in FIG. If necessary, the circular portion 111 may have two or more cut portions in the circumferential direction. In this case, it is desirable that the cut portions are equally divided in the circumferential direction as much as possible. In addition, when these ball bearings are applied to the joints of robot arms, they are usually used with a preload in order to increase the rigidity. However, depending on the conditions or for other purposes, allow clearance. May be used.

Furthermore, with reference to FIG. 16, a modified example of the first embodiment described above (corresponding to claim 5 or 6) will be described.
In this modification, an annular seal body 120 is provided on one side of a single row ball bearing 100 constituted by a single row full-ball angular ball bearing shown in FIG. 1, and a plurality of balls 103 are positioned in the circumferential direction. A container 130 is provided.

That is, as shown in FIG. 16, seal housing grooves 121 and 122 for housing the annular seal body 120 are arranged on one end face on the right side of the outer ring 101 and the inner ring 102, for example.
The annular seal body 120 is composed of a reinforced rubber seal (for example, nitrile rubber / acrylic rubber or fluororubber) 126 reinforced by a metal core 125 formed in an inverted L shape. The rubber seal 126 has a fitting portion 126a that fits the outer ring 101 on the outer peripheral portion, and a lip portion 126b that contacts the inner ring 101 on the inner peripheral portion.

  The seal housing groove 121 of the outer ring 101 has a relatively shallow step portion 121a on the right end side of the inclined inner peripheral surface 101b connected to the raceway groove 101a of the outer ring 101, and an annular shape formed in the circumferential direction at the bottom portion of the step portion 121a. It is set as the structure which has the shallow fitting recessed part 121b which pushes in and inserts the fitting part 126a of the seal body 120. FIG. Further, the seal receiving groove 122 of the inner ring 102 includes a relatively deep step portion 122a on the right end side on the right side of the track groove 102a on the cylindrical outer peripheral surface 102b connected to the left and right ends of the track groove 102a of the inner ring, and a bottom surface of the step portion 122a. And a shallow receiving recess 122b with which a lip 126b formed on the inner peripheral surface of the annular seal body 120 formed in the circumferential direction contacts.

Furthermore, the retainer 130 has a pair of annular portions 132 a and 132 b extending in the axial direction across the pocket portion 131 that accommodates the ball 103, and these annular portions 132 a and 132 b are the cylindrical outer peripheral surface 102 b of the inner ring 102. Is installed as a guide surface.
The annular portion 132b on the annular seal body 120 side is connected to the intersection edge portion 123 on the inner circumferential surface facing the intersection edge portion 123 formed at the intersection between the cylindrical outer circumferential surface 102b of the inner ring 102 and the seal housing groove 122. A concave groove 133 having a semicircular cross section that avoids contact is formed in the circumferential direction.

  The cage 130 is made of a metal material such as a copper alloy manufactured by cutting, a synthetic resin material such as polyamide, polyacetal, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), or glass fiber or carbon fiber. It is made of a synthetic resin material containing a reinforcing material with a reinforcing material added. When the cage 130 is formed of a resin material, either cutting molding or injection molding can be applied.

  As described above, since the concave groove 133 is formed in the circumferential direction on the inner peripheral surface facing the intersection edge portion 123 formed on the right end side of the guide surface of the cage 130, the intersection edge portion 123 is formed in the cage. The retainer 130 can be reliably prevented from coming into contact with the inner peripheral surface of the ring 130, while ensuring the strength by increasing the width of the annular portion 132b on the annular seal body 120 side to increase the cross-sectional area. Can be reliably prevented.

  In addition, in the case of grease lubrication, the concave groove 133 provided in a part of the guide surface can serve as a reservoir for holding grease, and in addition, since it is located in the vicinity of the guide surface, There is also an effect of appropriately supplying the lubricating oil, and the wear resistance can be maintained for a long time from the viewpoint of the lubrication characteristics. This effect becomes more conspicuous when concave grooves 133 and 134 are formed in both annular portions 132a and 132b as shown in FIG.

  Normally, when the annular seal body 120 is disposed on at least one side of the ball bearing 100, the inner diameter surface of the outer ring 101 and the outer diameter surface of the inner ring 102 are used as the guide surfaces of the cage 130. Since the intersection edge portion 123 is formed at a position where the groove 122 is in contact with the groove 122, the cage 130 is worn due to the contact between the intersection edge portion 123 and the annular portion 132b of the cage 130.

In order to prevent the wear of the cage 130, conventionally, when the inner ring guide is used, as shown in FIG. 17, the axial length or width of the annular portion 132b on the intersection edge 123 side of the cage 130 is shown. It is considered that the annular portion 132b and the intersection edge portion 123 do not come into contact with each other.
However, in the case of the narrow ball bearing 100 as in this embodiment, there is a problem that the width of the annular portion 132b becomes very thin and sufficient strength cannot be ensured.

For this purpose, as shown in FIG. 18, it is necessary to increase the width of the annular portion 132b to ensure strength, but in this case, as described above, the intersection with the inner peripheral surface of the annular portion 132b. Since the edge portion 123 is opposed, when the cage 130 is inclined with respect to the guide-side raceway during rotation of the ball bearing 100, the inner peripheral surface of the annular portion 132b is edged to the intersection edge portion 123. As a result, the cage 130 is worn.
In particular, since the seal receiving grooves 121 and 122 are often heat-treated surfaces after cutting, the surface roughness is poor, and burrs are likely to be formed at the intersecting portions that come into contact with the cage 130, so that wear occurs. It's easy to do.

  Furthermore, since the ball bearing 100 according to the present invention has a structurally very small ball diameter with respect to the ball pitch circle diameter of the bearing, the cross section of the annular portion 132b of the cage 130 is correspondingly reduced. The radial strength of the cage 130 (the radial strength of the annular portion 132b) is also reduced. In addition to this, the application of the ball bearing 100 according to the present invention is likely to cause a large moment load to be applied during rotation of the bearing, and the bearing is liable to tilt due to its usage conditions. Therefore, due to the change in the contact angle of each ball 103, the revolution speed of each ball 103 varies, and the deformation of the cage 130 due to the tension force between the ball 103 and the pocket portion 131 also increases, so it is easier to hit the edge. Further, the surface pressure of the contact portion also increases and wear tends to proceed.

  However, as described above, in the present embodiment, as shown in FIG. 16, the width of the annular portion 132 b on the annular seal body 120 side of the retainer 130 is increased to increase the cross-sectional area while increasing the cross-sectional area. Since the concave groove 133 is formed in a portion that may contact the intersection edge portion 123 at the boundary with the cylindrical surface 102b serving as the guide surface, even if the cage 130 is inclined, the intersection edge portion 123 and the concave shape are formed. Since a sufficient space can be ensured between the groove 133 and the contact between the concave groove 133 and the intersection edge portion 123 can be surely prevented, and wear of the cage 130 can be surely prevented. .

In the above modification, the case where the annular seal body 120 is disposed on the right side of the ball bearing 100 has been described. However, the present invention is not limited to this, and the annular seal body 120 is disposed on the left side of the ball bearing 100. Alternatively, the annular seal body 120 may be disposed on both sides.
Moreover, although the case where the concave groove 133 formed in the annular portion 132b is formed in a semicircular cross section has been described in the above modification, the present invention is not limited to this, and is not limited to this. Any shape can be used as long as contact with the intersection edge portion 123 such as a shape can be avoided.

Furthermore, although the case where the annular seal body 120 is in contact with the inner ring seal housing groove 122 has been described in the above modification, the present invention is not limited to this, and a non-contact rubber seal that does not contact the inner ring seal housing groove 122 shown in FIG. A metal seal that is caulked in a mold (attached to a metal core) or an outer ring seal groove can be applied.
Furthermore, in the above-described modification, the case where the guide surface of the cage 130 is the outer peripheral surface of the inner ring 102 has been described, but the present invention is not limited to this, and the inner peripheral surface of the outer ring 101 is used as the guide surface. May be.

  Furthermore, in the above-described modification, the case where the concave groove 133 is formed in the annular portion 132b on the annular seal body 120 side of the annular portions 132a and 132b of the cage 130 has been described. However, the present invention is not limited to this. 19, the annular groove 132a on the opposite side of the annular seal body 120 also has a concave groove at a plane symmetrical position across the vertical groove passing through the concave groove 133 of the annular portion 132b and the center of each ball 103. 134 may be provided. As described above, when the concave groove portions are formed in the left and right annular portions 132a and 132b, it is possible to assemble from any direction without confirming the formation position of the concave groove portions of the retainer 130 during the assembly, thereby improving the assembling work. be able to.

Next, with reference to FIG. 20, the double row ball bearing which is an example of embodiment of the 2nd aspect (corresponding to Claim 3 or 4) of this invention is demonstrated.
In this double row full ball angular contact ball bearing 200, a large number of balls 203 are arranged between the double row raceway grooves 201a and 201b of the outer ring 201 and the double row raceway grooves 202a and 202b of the inner ring 202 so as to roll freely. The sectional dimension ratio (B2 / H2) between the direction sectional width B2 and the radial section height H2 (= (outer ring outer diameter D2−inner ring inner diameter d2) / 2) is (B2 / H2) <1.2. The ball pitch circle diameter is set at the center of the radial section height.

Referring to FIG. 1, the double-row angular contact ball bearing 200 is incorporated into the joint portion 23 of the robot arm to constitute a robot arm joint portion bearing device.
Here, in this embodiment, a case where the double row angular contact ball bearing 200 is replaced with a double row combination angular contact ball bearing of 7208A (contact angle 30 °) is taken as an example.
7208A has an inner ring inner diameter φ40 mm, an outer ring outer diameter φ80 mm, and an axial cross-sectional width (bearing single body width): B is 18 mm, so the cross-sectional dimension ratio (B / H) = 0.9. Therefore, in the double-row angular contact ball bearing 200 of the present embodiment, the sectional dimension ratio (B2 / H2) = 0.9 (the inner ring outer diameter and the outer ring outer diameter remain the same, and the axial sectional width (bearing unit width): B2 18 mm).

  As a result, radial load, axial load in both directions, and moment load can be received, as well as high rigidity, high rotational accuracy, low cost, low torque and low heat generation. It is possible to save space by ½ in the directional dimension, and it is possible to design a narrow opening width in the vertical direction of the gate of the processing chamber in a semiconductor manufacturing process, a liquid crystal panel manufacturing process, or the like.

Of course, if necessary, the cross-sectional dimension ratio (B2 / H2) may be set to be less than 0.90 or more than 0.90 (provided that (B2 / H2) <1.2). Incidentally, the contact angle of the double-row angular contact ball bearing 200 is, for example, 30 °.
FIG. 21 is an example in which the ball pitch circle diameter is shifted to the outer diameter side in the double row full ball angular contact ball bearing 200 in order to increase the moment rigidity, and FIG. FIG. 23 shows an example in which the ball diameter and ball pitch circle diameter of the row are changed. FIG. 23 shows a double row full ball angular contact ball bearing 200 having annular seal bodies 104 attached to both ends in the axial direction. This is an example in which the pitch circle diameter is shifted to the outer diameter side.

In any case, in addition to the structure of the annular seal body, the cage, etc., whether or not it is mounted, application examples related to the structure are the same as those of the single row ball bearing described in the embodiment of the first aspect. Moreover, you may use on any conditions of a preload and a clearance gap similarly to embodiment of the said 1st aspect.
The configurations of the link, the link device, the articulated robot arm, the joint, the outer ring, the outer ring raceway groove, the inner ring, the inner ring raceway groove, the ball, the cage and the like of the present invention are those exemplified in the above embodiments. The present invention is not limited to this, and can be appropriately changed without departing from the gist of the present invention.

Schematic cross section for explaining an example in which a single row ball bearing which is an example of an embodiment of the first aspect of the present invention (corresponding to claim 1 or 2) is incorporated in a joint portion of a robot arm to constitute a bearing device FIG. It is principal part sectional drawing which shows the single row ball bearing integrated in the joint part of FIG. It is principal part sectional drawing which shows the state which combined the single row ball bearing of FIG. 2 with 2 rows. It is principal part sectional drawing which shows the state which combined the single row ball bearing which is other embodiment of the 1st aspect of this invention in two rows. It is principal part sectional drawing which shows the state which combined the single row ball bearing of FIG. 2 and the single row ball bearing which is other embodiment in two rows. It is principal part sectional drawing which shows the state which combined the single row ball bearing which is other embodiment of the 1st aspect of this invention in two rows. It is principal part sectional drawing for demonstrating the single row ball bearing which is other embodiment of the 1st aspect of this invention. It is principal part sectional drawing which shows the state which combined the single row ball bearing of FIG. 2 with 3 rows. It is principal part sectional drawing which shows the state which combined the single row ball bearing of FIG. 2 with 4 rows. It is principal part sectional drawing which shows the state which combined the single row ball bearing of FIG. 1 by 2 row front combination. It is principal part sectional drawing which shows the state which combined the single row ball bearing which is other embodiment of the 1st aspect of this invention in two rows. It is sectional drawing in alignment with the radial direction of a holder | retainer. It is the fragmentary perspective view which looked at the holder | retainer from radial direction inner side. It is the figure seen from the arrow B direction of FIG. (A) is the figure seen from the arrow A direction of FIG. 12, (b) is a figure which shows the modification of (a). It is principal part sectional drawing for demonstrating the single row ball bearing for robot arm joint parts which is an example of the modification (corresponding to Claim 5 or 6) of the 1st aspect of this invention. It is principal part sectional drawing for demonstrating the single row ball bearing for robot arm joint parts. It is principal part sectional drawing for demonstrating the modification of the single row ball bearing for robot arm joint parts. It is principal part sectional drawing for demonstrating the single row ball bearing for robot arm joint parts which is an example of the other modification of the 1st aspect of this invention. It is principal part sectional drawing for demonstrating the double row ball bearing for robot arm joint parts which is an example of embodiment of the 2nd aspect (corresponding to Claim 3 or 4) of this invention. It is principal part sectional drawing for demonstrating the double row ball bearing which is other embodiment of the 2nd aspect of this invention. It is principal part sectional drawing for demonstrating the double row ball bearing which is other embodiment of the 2nd aspect of this invention. It is principal part sectional drawing for demonstrating the double row ball bearing which is other embodiment of the 2nd aspect of this invention. It is explanatory drawing for demonstrating the deformation amount of the radial direction of an inner ring | wheel. It is explanatory drawing for demonstrating the calculation method of the cross-sectional secondary moment of an inner ring | wheel. It is a graph which shows the relationship between a cross-sectional dimension ratio (B / H) and the deformation amount of the inner and outer ring | wheels of a radial direction. It is a graph which shows the relationship between a cross-sectional dimension ratio (B / H) and a cross-sectional secondary moment I. It is a graph which shows the relationship between a cross-sectional dimension ratio (B / H) and the deformation amount of the inner and outer ring | wheels of a radial direction. It is a graph which shows the relationship between a cross-sectional dimension ratio (B / H) and a cross-sectional secondary moment I. It is a graph which shows the comparison of the calculated moment rigidity in various bearings. It is the schematic for demonstrating an example of an articulated robot arm. It is sectional drawing which shows the conventional bearing apparatus of a robot arm joint part. It is principal part sectional drawing of the conventional 2 row combination angular contact ball bearing. It is principal part sectional drawing of the conventional 2 row combination angular contact ball bearing of an ultra-thin wall section. It is sectional drawing which shows the state which attached the conventional 2 rows combination angular contact ball bearing of the ultra-thin wall section to the axis | shaft. It is principal part sectional drawing of a 4-point contact ball bearing. It is principal part sectional drawing of a cross-roller bearing.

Explanation of symbols

21a to 21d Link 21 Link device 23 Robot arm joint part 100 Single row ball bearing 101 Outer ring 101a Outer ring raceway groove 102 Inner ring 102a Inner ring raceway groove 103 Ball 120 Ring seal body 121, 122 Seal receiving groove 123 Intersection edge part 130 Cage 131 Pocket Parts 132a, 132b annular part 133 concave groove part 200 double row ball bearing 201 outer ring 201a, 201b outer ring raceway groove 202 inner ring 202a, 202b inner ring raceway groove 203 ball

Claims (6)

A robot arm joint part bearing device comprising a joint part of an articulated robot arm provided with a link device constituted by a plurality of links, and a rolling bearing incorporated in the joint part,
As the rolling bearing, a single-row ball bearing in which the sectional dimension ratio (B / H) between the axial sectional width B and the radial sectional height H is (B / H) <0.63 is used. A bearing device for a joint portion of a robot arm. A plurality of balls are rotatably arranged between the outer ring raceway groove and the inner ring raceway groove, and are incorporated into the joint portion of the multi-joint robot arm having a link device constituted by a plurality of links. In ball bearings,
A ball bearing characterized in that a cross-sectional dimension ratio (B / H) between an axial cross-sectional width B and a radial cross-sectional height H is (B / H) <0.63. A robot arm joint part bearing device comprising a joint part of an articulated robot arm provided with a link device constituted by a plurality of links, and a rolling bearing incorporated in the joint part,
As the rolling bearing, a double-row ball bearing in which the sectional dimension ratio (B2 / H2) between the axial sectional width B2 and the radial sectional height H2 is (B2 / H2) <1.2 is used. A bearing device for a joint portion of a robot arm. A large number of balls are rotatably arranged between the double-row raceway groove on the outer ring and the double-row raceway groove on the inner ring, and incorporated into the joint part of an articulated robot arm having a link device constituted by a plurality of links. Double row ball bearing
A ball bearing characterized in that a cross-sectional dimension ratio (B2 / H2) between the axial cross-sectional width B2 and the radial cross-sectional height H2 is (B2 / H2) <1.2.   The ball bearing has a seal housing groove formed on at least one end face between the outer ring and the inner ring, an annular seal body is disposed in the seal housing groove, and a plurality of balls are positioned in the circumferential direction. The retainer has an annular portion formed on both sides in the axial direction of the pocket for holding the plurality of balls, and the annular portion is either one of the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring. A concave groove portion that avoids contact with the intersection edge portion is formed in a circumferential direction at a position facing the intersection edge portion between the guide surface and the seal housing groove portion. The bearing device for a robot arm joint part according to 1.   A seal housing groove is formed on at least one end surface between the outer ring and the inner ring, an annular seal body is disposed in the seal housing groove, and a cage for positioning the plurality of balls in the circumferential direction is disposed. The retainer has an annular portion formed on both axial sides of a pocket for holding the plurality of balls, and the annular portion has one of an inner ring outer peripheral surface and an outer ring inner peripheral surface as a guide surface, and the guide surface The ball bearing according to claim 2, wherein a concave groove portion that avoids contact with the intersection edge portion is formed in a circumferential direction at a position facing an intersection edge portion between the seal receiving groove portion and the seal housing groove portion.

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