JP2004034226A - Bearing arrangement for joints - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing arrangement for joints of a robot arm, which is employed for the inside chamber of a general industrial machinery or a spattering system or the like, prevents a misregistration of a work by damping the oscillation of the work at the time of transfer, and improves a conveyance speed. <P>SOLUTION: The both inner rings of a combined bearing 30 are gripped with a pair of gripping members 41 and 42 from axial outer end surface, and are screwed with a fixing screw 46 in contact with each axial opposed surface simultaneously. Further, a wave washer 50 is inserted between the axial inner end surfaces of both the outer rings of the combined bearing 30, and next both the outer rings are attached at each axial direction outside in such a state that the axial opposite surfaces 47 and 48 of the pair of gripping members 41 and 42 are contacted together, and precompression is applied to each pair of rolling bearing 31 and 32 of the combined bearing 30. <P>COPYRIGHT: (C)2004,JPO

Description

このように構成された関節部用軸受装置によると、ベース４１の軸方向対向面４７とキャップ４２の軸方向対向面４８を当接させて固定ネジ４６でねじ止めした状態で、ウェーブワッシャ５０にて一対の転がり軸受３１，３２に予圧が付与される、いわゆる定圧予圧付与構造をしている。このため、作業者の手作業によって行われる定位置予圧付与構造のように、転がり軸受３１，３２に付与される予圧にばらつきが発生せず、各転がり軸受３１，３２に充分な予圧を付与することができ、軸受のがたつきによって振動が発生するのを防止できる。
【００５４】
第１の組合せ軸受３０Ａと第２の組合せ軸受３０Ｂに付与される予圧の差を２０％以内とすることで、第１の組合せ軸受３０Ａと第２の組合せ軸受３０Ｂのトルク差を低減でき、トルク差による振動の発生も防止できる。
【００５５】
以上のようにして、搬送時における板状ワーク２１の振動を低減することにより、板状ワーク２１の位置ずれを防止でき、かつ、搬送速度も高めることができる。しかも、振動を低減することで、関節部用軸受装置の長寿命化も図れる。
【００５６】
ウェーブワッシャ５０は、リンク１４，１６の環状部材４０と、転がり軸受３２の外輪３６間に介装してもよい。
【００５７】
予圧付与部材は、外輪３５，３６間に介装されて外輪３５，３６を軸方向外方に付勢することにより、組合せ軸受３０の一対の転がり軸受３１，３２に各々予圧を付与するものであればよい。
【００５８】
組合せ軸受３０を構成する転がり軸受３１，３２は、深溝玉軸受や、円すいころ軸受等の各種転がり軸受であってもよい。
【００５９】
本発明の関節部用軸受装置は、１つの組合せ軸受に一対のリンクを連結させた構成のものにも適用できる。
【００６０】
例えば、搬送用多関節ロボットのアーム１１，１２の関節部１８，１９におけるリンク１４，１６とリンク１５，１７の連結部分に適用してもよい。
【００６１】
すなわち、関節部１８，１９において、一対の転がり軸受を軸方向に組合わせてなる組合せ軸受が設けられ、転がり軸受の内輪にリンク１４，１６が圧入されると共に、外輪にリンク１５，１７が圧入され、両外輪の軸方向内端面間にウェーブワッシャ５０が介装される。両内輪は軸方向外端面からカバー等の一対の把持部材にて把持され、把持部材の互いの軸方向対向面を当接させてねじ止めされ、ウェーブワッシャ５０にて両外輪が各々軸方向外方に付勢されて一対の転がり軸受に予圧が付与される。
【００６２】
このように、１つの組合せ軸受に一対のリンクを連結させた関節部用軸受装置においても、定圧予圧付与構造とすることで、転がり軸受に付与される予圧にばらつきが発生するのを防ぎ、各転がり軸受に充分な予圧を付与することができ、軸受のがたつきによって振動が発生するのを防止できる。よって、板状ワーク２１の位置ずれを防止でき、かつ、搬送速度も高めることができる。
【００６３】
【発明の効果】
本発明の関節部用軸受装置によると、搬送時におけるワークの振動を低減することにより、ワークの位置ずれを防止でき、かつ、搬送速度も高めることができるという効果が得られる。
【図面の簡単な説明】
【図１】本発明の一実施形態における関節部用軸受装置の断面図である。
【図２】本発明の一実施形態における関節部用軸受装置の部分拡大断面図である。
【図３】本発明の一実施形態における関節部用軸受装置の要部拡大断面図である。
【図４】（Ａ）（Ｂ）は、本発明の一実施形態における関節部用軸受装置の予圧付与部材の平面図ならびに側面図である。
【図５】ウェハの振動実験の結果を示すグラフである。
【図６】搬送用多関節ロボットの概略平面図である。
【図７】従来例における関節部用軸受装置の部分拡大断面図である。
【符号の説明】
１３　ウェハホーク（リンク）
１４，１５，１６，１７　リンク
１８，１９，２０，２１　関節部
３０　組合せ軸受
３１，３２　転がり軸受
３３，３４　内輪
３５，３６　外輪
３７，３８　玉（転動体）
４１　ベース（把持部材）
４２　キャップ（把持部材）
４６　固定ネジ
４７，４８　軸方向対向面
５０　ウェーブワッシャ（予圧付与部材）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bearing device for a joint portion of a robot arm used inside a chamber of a general industrial machine or a sputtering apparatus.
[0002]
[Prior art]
Conventionally, as shown in FIG. 6, a transfer articulated robot for transferring a plate-like workpiece such as a wafer or a liquid crystal substrate in a vacuum processing apparatus has been used.
[0003]
The transfer articulated robot includes a robot body 10 incorporating a motor and the like, a pair of left and right arms 11 and 12 extending from the robot body 10, and a wafer hawk 13 serving as a link provided at the tip of both arms 11 and 12. Has been.
[0004]
Each of the arms 11 and 12 includes a pair of links 14, 15, 16, and 17 and joint portions 18 and 19 that link the links 14 and 16 and the links 15 and 17 so as to be swingable. The tips of the links 14 and 16 and the wafer hawk 13 are connected to each other via a joint 20 so as to be swingable. The base ends of the links 15 and 17 are connected to a swing mechanism provided in the robot body 10.
[0005]
The operation of the transfer articulated robot will be described.
[0006]
With the plate-like workpiece 21 placed on the wafer fork 13, the links 15 and 17 are swung by a swinging mechanism provided in the robot body 10. Then, the arms 11 and 12 expand and contract, the wafer hawk 13 repeatedly moves linearly, and the plate-like workpiece 21 is conveyed.
[0007]
FIG. 7 shows a cross-sectional view of the joint 20.
[0008]
The joint portion 20 includes a combination bearing 30 formed of an angular ball bearing in which a pair of rolling bearings 31 and 32 having balls 37 and 38 interposed between inner rings 33 and 34 and outer rings 35 and 36 are combined in the axial direction. It has.
[0009]
An annular member 40 provided at the tip of the link 14 (16) is interposed between the outer rings 35 and 36 of the combination bearing 30.
[0010]
Both inner rings 33 and 34 of the combined bearing 30 are gripped by gripping members 41 and 42 from the axially outer end surface. The gripping member 41 is composed of a base, and the gripping member 42 is composed of a cap fitted into the opening of the cover 43. The cover 43 is overlapped with the base 41 and the cap 42 is fitted, and the inner rings 33 and 34 of the combination bearing 30 are loosely fitted to the step portion 44 of the base 41 and the step portion 45 of the cap 42. Is gripped from the axially outer end surface.
[0011]
A fixing screw 46 is inserted through the cap 42 and fastened to the base 41. By fastening the fixing screw 46, the annular member 40 is clamped and fixed between the outer rings 35 and 36, and the inner rings 33 and 34 are also fixed to the step portion 44 of the base 41 and the step portion 45 of the cap 42, A preload is applied to each of the pair of rolling bearings 31 and 32. The preload applied to each of the rolling bearings 31 and 32 is performed by adjusting the tightening force of the fixing screw 46.
[0012]
[Problems to be solved by the invention]
When performing various processes with respect to the plate-shaped workpiece 21 etc., high precision is required for alignment of the plate-shaped workpiece 21. For this reason, it is required for the articulated robot for transfer used during the above processing to prevent the displacement of the plate-shaped workpiece 21 during transfer.
[0013]
However, the above process is generally performed in a vacuum environment. In such processing, the plate-like workpiece 21 cannot be held by vacuum suction at the time of conveyance, and the plate-like workpiece 21 must simply be conveyed in a state of being placed on the object mounting table. According to this conveyance, the vibration greatly affects the positional deviation of the plate-like workpiece 21, and high anti-vibration performance is required for the articulated robot for conveyance.
[0014]
The joint portion 20 shown in FIG. 7 has a fixed position preload application structure in which preload is applied to the rolling bearings 31 and 32 by the tightening force of the fixing screw 46. That is, by adjusting the tightening amount of the fixing screw 46, the spacing distance between the base 41 and the cap 42 in the axial direction is adjusted, and a preload corresponding to the spacing distance is applied to the rolling bearings 31 and 32.
[0015]
In order to prevent vibration, it is generally desirable to increase the preload of the rolling bearings 31 and 32. However, in the fixed position preload application structure, the preload applied to the rolling bearings 31 and 32 varies greatly depending on whether the fixing screw 46 is tightened or not. Since the fixing screw 46 is tightened manually by the operator, the tightening accuracy is deteriorated. Therefore, excess and deficiency is likely to occur in the preload applied to the rolling bearings 31 and 32. In particular, when the preload applied to the rolling bearings 31 and 32 is insufficient, vibration is generated due to rattling of the bearings.
[0016]
When a pair of combined bearings 30 are arranged in parallel in the horizontal direction as in the joint portion 20 shown in FIG. 6, if the preload applied to the rolling bearings 31 and 32 is too large, the torque difference between the two combined bearings 30 Is likely to occur. When a torque difference is generated between the two combined bearings 30, vibration is generated.
[0017]
As described above, there is a problem that if the vibration is generated during the conveyance, the plate-like workpiece 21 is displaced. Moreover, there is a problem that the conveyance speed cannot be increased due to the occurrence of vibration.
[0018]
SUMMARY OF THE INVENTION An object of the present invention is to provide a joint bearing device that can prevent the displacement of a workpiece and increase the conveyance speed by reducing the vibration of the workpiece during conveyance.
[0019]
[Means for Solving the Problems]
The joint bearing device according to the present invention includes a pair of links and a joint for connecting these links in a swingable manner. The joint includes an inner ring to which one link is fixed and the other link is fixed. A combined bearing formed by combining axially a rolling bearing composed of an outer ring and a rolling element interposed between the inner and outer rings, and both inner rings of the combined bearing are gripped from the outer end surface in the axial direction. A pair of gripping members that are screwed by abutting the axially opposed surfaces of the paired bearings and the axially inner end surfaces of both outer rings of the combined bearing, and abutting the axially opposed surfaces of the pair of gripping members In this state, each of the outer rings is urged outward in the axial direction, and a preload applying member for applying a preload to each of the pair of rolling bearings is included.
[0020]
Examples of the part to which the joint unit bearing device is applied include a joint part of an arm of a transfer multi-joint robot, a wrist part provided with a wafer hawk at the tip of the arm, and the like.
[0021]
According to the joint bearing device of the present invention, the preload is applied to the pair of rolling bearings by the preload applying member in a state where the axially opposed surfaces of the pair of gripping members are brought into contact with each other and screwed, so-called constant pressure preload. Has a grant structure. Therefore, unlike the fixed-position preload application structure that is performed manually by the operator, there is no variation in the preload applied to the rolling bearing, and sufficient preload can be applied to each rolling bearing. Vibrations due to rattling can be prevented.
[0022]
The joint bearing device according to the present invention includes a pair of links and a joint portion that connects the links in a swingable manner. The joint portion includes an inner ring, an outer ring to which one link is fixed, and an inner and outer ring. A pair of rolling bearings comprising a rolling element interposed therebetween, a first combination bearing that is combined in the axial direction, and a parallel arrangement in the horizontal direction with respect to the first combination bearing, an inner ring, A second combination bearing comprising a pair of rolling bearings comprising an outer ring to which the other link is fixed and a rolling element interposed between the inner and outer rings in the axial direction; and the first and second Between the pair of gripping members that are gripped from the outer end surface in the axial direction and screwed by bringing the opposing surfaces in the axial direction into contact with each other, and between the inner end surfaces in the axial direction of the two outer rings of each combination bearing Intervening, and abutting the axially opposed surfaces of the pair of gripping members State, said outer ring biased in each direction outward, the is intended to include a preload applying member which respectively impart a preload to the pair of rolling bearings of each duplex bearing.
[0023]
The difference in preload applied to the first and second combination bearings is set to 20% or less.
[0024]
Examples of the part to which the joint unit bearing device is applied include a wrist part provided with a wafer hawk at the tip of an arm of a transfer multi-joint robot.
[0025]
According to the joint bearing device of the present invention, the preload is applied to the pair of rolling bearings by the preload applying member in a state where the axially opposed surfaces of the pair of gripping members are brought into contact with each other and screwed, so-called constant pressure preload. Has a grant structure. Therefore, unlike the fixed-position preload application structure that is performed manually by the operator, there is no variation in the preload applied to the rolling bearing, and sufficient preload can be applied to each rolling bearing. Vibrations due to rattling can be prevented.
[0026]
Furthermore, the torque difference between the first combination bearing and the second combination bearing can be reduced by setting the difference between the preloads applied to the first combination bearing and the second combination bearing within 20%. Generation of vibration can be prevented.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0028]
1 is a cross-sectional view of the joint bearing device according to the present embodiment, FIG. 2 is a partially enlarged cross-sectional view of the joint bearing device, FIG. 3 is an enlarged cross-sectional view of the main part of the joint bearing device, and FIG. FIGS. 5A and 5B are a plan view and a side view of the preload imparting member, and FIG. 5 is a graph showing the results of a wafer vibration experiment.
[0029]
The joint bearing device according to the present embodiment is incorporated in the wrist portion provided with the wafer hawk 13 at the end of the arm of the articulated robot for conveyance shown in FIG. In addition, the same code | symbol is attached | subjected to the same part as the example shown in FIG. 6, and the description is abbreviate | omitted.
[0030]
As shown in FIG. 1, the joint 20 in the wrist is composed of a first combination bearing 30A and a second combination bearing 30B arranged in parallel in the horizontal direction. The first and second combination bearings 30A and 30B are similarly configured as shown in the enlarged views of FIGS.
[0031]
The first and second combination bearings 30A and 30B are formed by combining a pair of rolling bearings 31 and 32, each having balls 37 and 38 interposed between inner rings 33 and 34 and outer rings 35 and 36, in the axial direction. An angular ball bearing.
[0032]
An annular member 40 provided at the tip of the link 14 is interposed between the outer rings 35 and 36 of the first combination bearing 30A. An annular member 40 provided at the tip of the link 16 is interposed between the outer rings 35 and 36 of the second combination bearing 30B.
[0033]
A preload applying member 50 is interposed between each annular member 40 and the axially inner end surface of the outer ring 35 of the rolling bearing 31.
[0034]
As shown in FIG. 4, the preload applying member 50 is configured by a wave washer that is an annular wave spring. Reference numeral 51 denotes the top of a corrugated mountain valley.
[0035]
Both the inner rings 33 and 34 of the first and second combination bearings 30A and 30B are gripped from the outer end surface in the axial direction by a base 41 serving as a gripping member and a cap 42 fitted into the opening of the cover 43. That is, the cover 43 is overlapped with the base 41 and the cap 42 is fitted. The inner ring 34 of each combination bearing 30A, 30B is loosely fitted to the stepped portion 44 of the base 41, and the inner ring 33 is fitted to the stepped portion 45 of the cap 42. Is loosely fitted.
[0036]
With the axially facing surface 47 of the base 41 and the axially facing surface 48 of the cap 42 in contact with each other, a fixing screw 46 is inserted through the cap 42 and fastened to the base 41. In this state, both the outer rings 35 and 36 are urged outward in the axial direction by the wave washer 50, preload is applied to the rolling bearings 31 and 32, and the rolling bearings 31 and 32 are fixed.
[0037]
The magnitude of the preload applied to the rolling bearings 31 and 32 is 2 to 10% of the static load rating. Here, if a preload smaller than 2% of the static load rating is applied, a rolling element that is not loaded with load is generated, resulting in insufficient rigidity and reduced bearing performance. Moreover, if a preload greater than 10% of the static load rating is applied, the contact area of the rolling elements exceeds 200 kgf / mm, which leads to a decrease in life when considering an environment in a vacuum, which is not preferable. Therefore, the elastic force of the wave washer 50 is set in order to apply a preload having a magnitude of 2 to 10% of the static load rating.
[0038]
The difference in preload applied to the first combination bearing 30A and the second combination bearing 30B is set to be within 20%. This is because when a difference in preload amount of 20% occurs, a difference of 28% occurs in the starting torque of each rolling bearing (30A, 30B). In the stroke test under the current load conditions, when the starting torque difference between the rolling bearings (30A, 30B) becomes 30% or more, the repetitive linear motion of the wafer hawk 13 to which the rolling bearings (30A, 30B) are attached is generated. The vibration increases and the plate-like workpiece 21 placed on the wafer fork 13 is displaced. Therefore, the elastic accuracy of the wave washer 50 is set so that the difference in preload is within 20%.
[0039]
The preload is set by separately obtaining the relationship between the wave washer crushing amount and the load, calculating the wave washer crushing amount according to each component design, and applying the value to the above relationship.
[0040]
The ends of the links 14 and 16 are meshed with each other via a gear 22 formed on the outer peripheral surfaces of the links 14 and 16.
[0041]
The operation of the transfer articulated robot will be described.
[0042]
In a state where the plate-like workpiece 21 is placed on the wafer fork 13, the links 15 and 17 are rocked by the rocking mechanism provided in the robot body 10. Then, the arms 11 and 12 are expanded and contracted while the links 14 and 16 engaged with the gear 22 are swung, the wafer hawk 13 is repeatedly linearly moved, and the plate-like workpiece 21 is conveyed.
[0043]
FIG. 5 shows the result of a vibration experiment of a workpiece placed on the wafer hawk 13 of the transfer articulated robot.
[0044]
Experimental conditions will be described.
[0045]
As shown in FIG. 6, an 8-inch wafer 21 is placed on the wafer fork 13 as a plate-like workpiece.
[0046]
A distance X from the load application point B of the wafer 21 to the center A of the combination bearing 30 of the joint 20 is 140 mm. A total load 500 gf of the wafer 21 and the wafer fork 13 is applied to the load application point B.
[0047]
A distance Y from the center point C of the wafer 21 at the time of reduction to the center point C ′ of the wafer 21 at the time of extension is set to 600 mm.
[0048]
The expansion / contraction speed of the arms 11 and 12 is 300 mm / sec.
[0049]
A vibration meter pickup is installed on the wafer 21 to measure vibrations when the arms 11 and 12 are expanded and contracted. The vibration measurement direction is horizontal to the wafer 21 and perpendicular to the direction of expansion and contraction of the arms 11 and 12. In the measurement, the arms 11 and 12 were reciprocated 10 times, and vibrations between them were measured.
[0050]
In FIGS. 5A and 5B, when the joint device for constant pressure preload by the wave washer 50 of the present invention is used, C, D, and E in FIG. The experimental result in the case of using the bearing device for a vehicle is shown.
[0051]
The vertical axis in FIG. 5 represents the vibration value (G) of the wafer. In this graph, the expansion / contraction operation is performed 10 reciprocations (20 reciprocations), the vibration value of each operation is measured with the maximum value per operation as the vibration value of the operation, and the maximum value, the minimum value, and the average value. Is shown. Note that G of the vibration value (G) is gravitational acceleration.
[0052]
FIG. 5 shows that in the case of the constant pressure preloads A and B, the average value of vibration becomes small and the difference between the maximum value and the minimum value becomes small. Table 1 below shows the average value, maximum value, and minimum value of vibration in each of the experimental examples A to E.
[0053]
[Table 1]

According to the joint bearing device configured as described above, the wave washer 50 is attached to the wave washer 50 in a state where the axially opposed surface 47 of the base 41 and the axially opposed surface 48 of the cap 42 are brought into contact with each other and fixed with the fixing screw 46. Thus, a so-called constant pressure preload application structure is provided in which preload is applied to the pair of rolling bearings 31 and 32. For this reason, unlike the fixed-position preload application structure that is performed manually by the operator, the preload applied to the rolling bearings 31 and 32 does not vary, and sufficient preload is applied to the rolling bearings 31 and 32. It is possible to prevent vibrations from occurring due to the shakiness of the bearing.
[0054]
By setting the difference between the preloads applied to the first combination bearing 30A and the second combination bearing 30B to be within 20%, the torque difference between the first combination bearing 30A and the second combination bearing 30B can be reduced. Generation of vibration due to the difference can also be prevented.
[0055]
As described above, by reducing the vibration of the plate-like workpiece 21 at the time of conveyance, it is possible to prevent the displacement of the plate-like workpiece 21 and to increase the conveyance speed. In addition, the life of the joint bearing device can be extended by reducing vibration.
[0056]
The wave washer 50 may be interposed between the annular member 40 of the links 14 and 16 and the outer ring 36 of the rolling bearing 32.
[0057]
The preload applying member is provided between the outer rings 35 and 36 to apply a preload to the pair of rolling bearings 31 and 32 of the combined bearing 30 by urging the outer rings 35 and 36 outward in the axial direction. I just need it.
[0058]
The rolling bearings 31 and 32 constituting the combination bearing 30 may be various rolling bearings such as a deep groove ball bearing and a tapered roller bearing.
[0059]
The joint bearing device of the present invention can also be applied to a configuration in which a pair of links are connected to one combination bearing.
[0060]
For example, you may apply to the connection part of the links 14 and 16 and the links 15 and 17 in the joint parts 18 and 19 of the arms 11 and 12 of the articulated robot for conveyance.
[0061]
In other words, the joint portions 18 and 19 are provided with a combination bearing in which a pair of rolling bearings are combined in the axial direction, the links 14 and 16 are press-fitted into the inner ring of the rolling bearing, and the links 15 and 17 are press-fitted into the outer ring. A wave washer 50 is interposed between the inner end surfaces in the axial direction of both outer rings. Both inner rings are gripped by a pair of gripping members such as a cover from the outer end surface in the axial direction, screwed by bringing the opposing surfaces in the axial direction of the gripping members into contact with each other. And a preload is applied to the pair of rolling bearings.
[0062]
In this way, even in the joint bearing device in which a pair of links are connected to one combination bearing, by adopting a constant pressure preload application structure, it is possible to prevent variation in the preload applied to the rolling bearing, Sufficient preload can be applied to the rolling bearing, and vibrations due to rattling of the bearing can be prevented. Therefore, the position shift of the plate-shaped workpiece 21 can be prevented, and the conveyance speed can be increased.
[0063]
【The invention's effect】
According to the joint bearing device of the present invention, it is possible to prevent the positional deviation of the workpiece and to increase the conveyance speed by reducing the vibration of the workpiece during the conveyance.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a joint bearing device according to an embodiment of the present invention.
FIG. 2 is a partial enlarged cross-sectional view of a joint bearing device according to an embodiment of the present invention.
FIG. 3 is an enlarged cross-sectional view of a main part of the joint bearing device according to the embodiment of the present invention.
FIGS. 4A and 4B are a plan view and a side view of a preload imparting member of the joint bearing device according to the embodiment of the present invention.
FIG. 5 is a graph showing the results of a wafer vibration experiment.
FIG. 6 is a schematic plan view of a transfer articulated robot.
FIG. 7 is a partially enlarged cross-sectional view of a joint bearing device in a conventional example.
[Explanation of symbols]
13 Wafer Hawk (Link)
14, 15, 16, 17 Link 18, 19, 20, 21 Joint 30 Combination bearing 31, 32 Rolling bearing 33, 34 Inner ring 35, 36 Outer ring 37, 38 Ball (rolling element)
41 Base (gripping member)
42 Cap (gripping member)
46 Fixing screws 47, 48 Axial facing surface 50 Wave washer (preloading member)

Claims (3)

A bearing device for a joint portion of a link mechanism comprising a pair of links and a joint portion that connects these links in a swingable manner,
The joint is a combination of axially combined rolling bearings composed of an inner ring to which one link is fixed, an outer ring to which the other link is fixed, and rolling elements interposed between the inner and outer rings. A bearing,
A pair of gripping members that grip both the inner rings of the combination bearing from the axially outer end surface and are screwed by bringing the opposing surfaces in the axial direction into contact with each other,
With the axially opposed surfaces of the pair of gripping members in contact with each other between the inner end surfaces in the axial direction of both outer rings of the combined bearing, the outer rings are each biased outward in the axial direction, A joint bearing device comprising: a preload applying member that applies a preload to each of the pair of rolling bearings. A bearing device for a joint portion of a link mechanism comprising a pair of links and a joint portion that connects these links in a swingable manner,
The joint portion includes a first combination bearing in which a pair of rolling bearings including an inner ring, an outer ring to which one link is fixed, and a rolling element interposed between the inner and outer rings are combined in the axial direction. ,
A pair of rolling bearings arranged in parallel to the first combined bearing in the horizontal direction and comprising an inner ring, an outer ring to which the other link is fixed, and a rolling element interposed between the inner and outer rings, A second combination bearing in combination with
A pair of gripping members for gripping both inner rings of the first and second combination bearings from the axially outer end surface and screwing with the axially opposed surfaces abutting each other;
In the state where the axially opposed surfaces of the pair of gripping members are in contact with each other between the inner end surfaces in the axial direction of both outer rings of the combination bearings, the outer rings are each biased outward in the axial direction. A joint bearing device, comprising: a preload application member that applies a preload to each of the pair of rolling bearings of each combination bearing. The joint bearing device according to claim 2,
The joint bearing device according to claim 1, wherein a difference in preload applied to the first and second combination bearings is within 20%.

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