JP5369754B2 - Bearing unit for joint part of manipulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing for manipulator joint having a structure constituted by sealing the grease having superior lubrication performance irrespective of its biodegradability and preventing the grease from leaking and water from intruding into the bearing from the outside and being suitable for use as, in particular, a partner robot, a housework robot or the like. <P>SOLUTION: This bearing assembled in joints of a manipulator uses the grease containing at least one kind prepared from among vegetable oil and liquid paraffin as base oil and metallic soap as thickener and is put on an inner face of a pocket of a cage. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to a bearing unit incorporated in a joint portion of a manipulator.

  Manipulators are widely used in processing lines, assembly lines, conveyance lines, etc. for automobiles and electrical equipment for the purpose of labor saving and automation. In recent years, attention has been focused on human prosthetic hands and manipulators for performing detailed work, and it is expected to realize partner robots and armed robots with arms (finger) using them.

  Until now, there has been a mineral oil-urea grease that uses a versatile mineral oil as a base oil and a urea compound as a thickener in consideration of wear resistance, etc., for lubrication of joint bearings for industrial manipulators. Generally used. However, since partner robots and domestic robots require safety for the human body and environmental considerations, mineral oil-urea greases are not preferred because both base oil and thickener are poor in biodegradability.

  As a biodegradable grease, a grease mainly composed of a polyol ester (see Patent Document 1), a grease mainly composed of pentaerythritol (see Patent Document 2), and a grease mainly composed of a vegetable oil (Patent Document 3). However, greases based on polyol esters and greases based on pentaerythritol are inferior in lubrication performance compared to mineral oil-urea greases. Therefore, there is a problem that the performance is remarkably lowered when moisture enters.

JP-A-6-1989 JP-A-8-20789 JP 2002-323053 A

The present invention has been made in view of the above problems, and is composed of a grease that is biodegradable and excellent in lubrication performance, and further has a structure in which it is difficult for grease to leak and moisture hardly enters from outside. Another object of the present invention is to provide a bearing unit for a joint part of a manipulator of a partner robot or a domestic robot.

In order to achieve the above object, the present invention provides the following bearing unit for a joint part of a manipulator.
(1) A bearing unit for a joint part of a manipulator of a partner robot or a domestic robot used in a joint part that connects a first arm and a second arm so as to be relatively rotatable about a rotation axis. The bearing unit includes two sets of an outer ring housing that is inserted into a unit mounting hole formed in the first arm and a predetermined interval in the axial direction of the rotating shaft that is fitted in the outer ring housing. Each of the ball bearings and a shaft member that is fitted into the two sets of ball bearings and connected to the second arm, and the two sets of ball bearings are respectively fitted to the outer ring housing. An inner ring in which the shaft member is fitted, a plurality of balls that are provided between the outer ring and the inner ring, a cage that holds the balls at predetermined intervals in the circumferential direction, and a gap 0 and the following of the labyrinth seal .05mm, Things oil and a base oil at least one kind obtained from liquid paraffin, a metal soap as a thickener, the content of the thickener is 8 to 20 wt%, the grease supplied to the retainer If, joint bearing unit of the manipulator, characterized in that it comprises a.
( 2 ) The joint unit bearing unit for a manipulator according to ( 1) above, wherein the metal parts constituting the two sets of ball bearings are made of stainless steel.
(3) The outer ring housing is formed with an inward protruding portion that protrudes between the outer rings in order to separate the two sets of ball bearings at a predetermined interval in the axial direction at an intermediate portion in the axial direction. A bearing unit for a joint part of a manipulator according to the above (1) or (2).

In the joint unit bearing unit of the manipulator of the present invention, the sealed grease has biodegradability and is excellent in lubrication performance. For this reason, the labyrinth is specified to suppress grease leakage, but even if grease leakage occurs, there is little impact on the human body and the environment. Further, by specifying the labyrinth, it is possible to prevent moisture from entering from the outside, and it is possible to suppress deterioration of the grease.

It is a perspective view which shows an example of the joint unit part of a manipulator. It is the figure which looked at the joint part of FIG. 1 from upper direction. It is the figure which looked at the rotation arm provided with the bearing unit which comprises the joint part of FIG. 1 from upper direction. It is the sectional view on the AA line of FIG.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  1 is a perspective view showing an example of a joint unit portion of a manipulator, FIG. 2 is a view of the joint portion of FIG. 1 as viewed from above, and FIG. 3 is a rotation including a bearing unit constituting the joint portion of FIG. FIG. 4 is a cross-sectional view taken along line AA in FIG. 2.

  As shown in the drawing, the joint 41 connecting the base arm 43 and the rotating arm 44 includes a unit mounting hole 47 formed on one end side of the rotating arm 44 and a bearing fitted in the unit mounting hole 47. The unit 48, a connection screw 49 that is mounted at the rotation center P position of the bearing unit 48, is fixed to a connection plate 43c formed at one end of the base arm 43, and is fixed to the outer periphery of one end of the rotation arm 44. An arc-shaped arm gear 72 centering on the axis (rotation center P) of the connecting screw 49, and a rotary motor 73 including a helical gear (helical gear) 75 housed in the base arm 43 and meshing with the arm gear 72. I have.

  The unit mounting hole 47 is formed by opening one end of the rotating arm 44 in a circular shape in a direction perpendicular to the longitudinal direction, and four convex portions 47b are axially provided on the inner peripheral surface 47a at intervals of 90 ° in the circumferential direction. It extends in the direction. The bearing unit 48 is a component in which two sets of ball bearings 52, 53, a single outer ring housing 54, and a single shaft member 55 are integrated.

  Of the two sets of ball bearings, one of the ball bearings 52 includes an outer ring 52a and an inner ring 52b, and a plurality of balls 52c that are rotatably arranged between the raceway grooves of the outer ring 52a and the raceway grooves of the inner ring 52b. ing. Further, the other ball bearing 53 also has a large number of balls 53c that are rotatably arranged between the outer ring 53a and the inner ring 53b having the same shape as the one ball bearing 52, and the raceway grooves of the outer ring 53a and the raceway grooves of the inner ring 53b. And.

  The outer ring housing 54 is a cylindrical member that internally fits the outer rings 52 a and 53 a of the two sets of ball bearings 52 and 53 and is fitted into the unit mounting hole 47 of the rotating arm 44. Four concave portions 54b are extended in the axial direction on the outer peripheral surface 54a of the outer ring housing 54 at intervals of 90 ° in the circumferential direction. When the bearing unit 48 is mounted in the unit mounting hole 47 of the rotating arm 44, the concave portion 54 b engages with a convex portion 47 b formed on the inner peripheral surface 47 a of the unit mounting hole 47, and relative rotation between the rotating arm 44 and the bearing unit 48 is prevented. The shaft member 55 is a cylindrical member that is fitted into the inner rings 52b and 53b of the ball bearings 52 and 53, and a female screw to which the connecting screw 49 is screwed is formed on the inner peripheral surface.

  In addition, a through hole 44a is formed in the axially central portion on the outer periphery of one end of the rotating arm 44, and the outer ring housing 54 and the rotating arm are fitted in the unit mounting hole 47 of the rotating arm 44. The arm gear support portion 72a fixed to the outer periphery of the end portion 44 is provided with through holes 54c and 72b that overlap the through hole 44a, respectively, from one outer periphery side of the rotating arm 44, that is, from the outside of the arm gear support portion 72a. Pins 77 are attached, and these members are positioned.

  The arm gear 72 is fixed to the outer periphery of one end of the rotating arm 44 by welding or the like. In this embodiment, the input gear 72 is fixed to the rotating arm 44. However, the present invention is not limited to this, and the axial length of the outer periphery of one end of the rotating arm 44 is made shorter than the axial length of the bearing unit 48. The input gear 72 may be fixed to the outer periphery of the unit 48, that is, the outer periphery of the outer ring housing 54.

  In the manipulator configured as described above, when the helical gear 75 is rotated in the forward / reverse direction by driving the rotary motor 73 in the forward / reverse direction, the arm gear 72 is engaged with the helical gear 75 and the rotating arm 44 is rotated. It rotates in the direction opposite to the Y3 direction shown in FIG. 1 or the Y3 direction.

  The ball bearings 52 and 53 preferably include a labyrinth seal having a gap of 0.05 mm or less in order to prevent leakage of grease and intrusion of moisture from outside. Furthermore, as will be described later, in the present invention, biodegradable grease is encapsulated in consideration of the influence on the human body and the environment. Therefore, it is necessary to select an additive having a small influence on the human body and the environment. However, since some rust inhibitors and antioxidants contain substances that adversely affect the human body and the environment, it is preferable to refrain from using them, but on the other hand, rust is likely to occur. The member is preferably made of stainless steel. Specifically, the inner ring, the outer ring and the rolling element are made of stainless steel, and when a metal seal is used, it is made of stainless steel.

  In addition, in the seal having a configuration in which the core metal is covered with resin or rubber, the core metal is preferably made of stainless steel. However, as in the past, cold rolled metal plate, spring steel plate, aluminum alloy plate, copper alloy plate, etc. Can also be used. The resins include polyamide, polyacetal, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polyacrylate, modified polyphenyl oxide, polyphenylene sulfide, polysulfone, polyether ether ketone, polyimide and other thermoplastic resins, polyamide elastomer and polyester elastomer. And thermoplastic elastomers such as polyurethane elastomers, polyolefin elastomers, polystyrene elastomers, and polyvinyl chloride elastomers. Examples of rubbers include nitrile rubber, acrylic rubber, silicon rubber, fluorine rubber, and ethylene propylene rubber.

  Since grease has biodegradability, the base oil is at least one selected from vegetable oil and liquid paraffin. Examples of vegetable oils include rapeseed oil, sunflower oil, soybean oil, cottonseed oil, corn oil, and castor oil, and these can be used alone or in combination of two or more. Among them, rapeseed oil having an excellent balance between fluidity at low temperature and oxidation stability is preferable.

  As the thickener, metal soap is used because of its excellent base oil retention. Among them, lithium soaps such as 12-hydroxy lithium stearate soap and lithium complex soap are preferable. In particular, 12-hydroxy lithium stearate soap has excellent adhesion to steel and has an effect of improving fretting resistance and wear resistance. Therefore, it is preferable. The content of the thickener in the grease is suitably 8 to 20% by mass in order to impart appropriate flexibility to the grease without impairing the biodegradability of the vegetable oil or liquid paraffin. If it is less than 8% by mass, leakage of the grease tends to occur, and if it exceeds 20% by mass, the fluidity of the grease decreases and high torque is not preferable.

  In addition, the grease has a blending degree of NLGI No. 2 is preferable. If it is harder than this, sufficient lubricity cannot be obtained, and if it is softer than this, the amount of dust generation increases and the acoustic life becomes inferior.

  Various additives can be added to the grease as needed, but additives that interfere with biodegradability or adversely affect the human body and the environment are not preferred.

  In order to suppress the generation of rust, a rust inhibitor and an antioxidant can be added. However, when the metal part is made of stainless steel, it is not necessary to add it. It is necessary to keep it at 5 to 3% by mass. Examples of the rust inhibitor and antioxidant include dioctylphenylamine, 2,6-di-t-butyl-p-cresol, dinonylnaphthalene sulfonate calcium salt, and the like.

  In addition, for example, an extreme pressure agent can be added to improve the fretting resistance and wear resistance of the bearing.

  The method for preparing the grease is the same as that for general grease, and is obtained by synthesizing a thickener in the base oil. The additive may be dissolved in the base oil, or added to the base grease composed of the base oil and the thickener and kneaded.

  The grease is placed on the inner surface of the pocket of the cage. Thereby, compared with the case where the bearing space is filled with grease, the torque can be reduced while maintaining the lubrication performance.

  Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby.

(Examples 1-4, Comparative Examples 1-2)
As shown in Table 1, test greases containing base oil, thickener and additives were prepared. Further, the degree of biodegradation of the test grease was measured by a test method defined in L-33-A-93 of the CEC standard (European Standards Advisory Committee standard). The results are also shown in Table 1, and are preferably 80% or more and particularly preferably 90% or more.

  Then, test grease is applied to the inner surface of each pocket of a deep groove ball bearing (bearing name “SR168B-H-26T12”; inner diameter 6.35 mm, outer diameter 9.525 mm, width 3.175 mm) using a microsyringe. After supplying 2.5 mg each, a pair of two bearing units was assembled. In addition, the inner ring, the outer ring, and the rolling element were made of SUS440C, and the labyrinth gaps shown in Table 1 were used. Then, the following swing durability test was performed using the bearing unit. The results are also shown in Table 1.

(Swing endurance test)
Swinging was performed under the following two conditions, and the torque increase value was obtained from the torque difference before and after rocking. The results are also shown in Table 1, and are shown as relative values with the torque increase value of Example 1 as 1.
Atmosphere temperature and humidity: 30 ° C., 40% RH (condition 1) or 30 ° C., 90% RH (condition 2)
・ Preload load: 8.8N
・ Oscillation angle: 10 °
・ Oscillation frequency (constant): 10Hz
・ Time: 100 hours ・ Torque measurement: 25 ° C., preload 8.8 N, rotation speed 2 rpm

  As shown in Table 1, the test greases of Examples 1 to 4 according to the present invention have a biodegradability of approximately 90% or more and excellent biodegradability, and even when used as a test bearing, an increase in torque is suppressed. Moreover, it turns out that a torque raise can be suppressed more by adding animal oil like Example 3. FIG.

  Further, as for the bearing structure, as the labyrinth gap is smaller as in the fourth embodiment, the leakage of grease and the ingress of moisture are prevented, the durability of the grease is enhanced, and the torque increase is suppressed.

43 ... Base arm, 43c ... Connecting plate, 44 ... Rotating arm, 47 ... Unit mounting hole, 47b ... Projection, 48 ... Bearing unit, 49 ... Connecting screw, 52, 53 ... Ball bearing, 52a, 53a ... Outer ring, 52b, 53b ... Inner ring, 52c, 53c ... Ball, 54 ... Outer ring housing, 54b ... Recess, 55 ... Shaft member, 72 ... Arm gear, 73 ... Rotating motor, 75 ... Helical gear, 77 ... Pin

Claims (3)

A joint unit bearing unit for a manipulator of a partner robot or a domestic robot, which is used in a joint unit that connects the first arm and the second arm so as to be relatively rotatable about a rotation axis ,
The bearing unit is
An outer ring housing fitted into a unit mounting hole formed in the first arm;
Two sets of ball bearings fitted in the outer ring housing and provided at a predetermined interval in the axial direction of the rotating shaft;
A shaft member fitted in the two sets of ball bearings and connected to the second arm;
With
The two sets of ball bearings are respectively
An outer ring fitted in the outer ring housing;
An inner ring into which the shaft member is fitted;
A plurality of balls provided between the outer ring and the inner ring so as to be freely rollable;
A cage for holding the balls in the circumferential direction at predetermined intervals;
A labyrinth seal with a gap of 0.05 mm or less,
Grease to be supplied to the cage , wherein at least one kind obtained from vegetable oil and liquid paraffin is a base oil, metal soap is a thickener, and the content of the thickener is 8 to 20% by mass. ,
Joint bearing unit of the manipulator, characterized in that it comprises a. 2. The bearing unit for a joint part of a manipulator according to claim 1 , wherein the metal parts constituting the two sets of ball bearings are made of stainless steel. The outer ring housing is formed with an inward protruding portion that protrudes between the outer rings in order to separate the two sets of ball bearings in the axial direction at a predetermined interval in an axially intermediate portion. Item 3. A bearing unit for a joint part of a manipulator according to Item 1 or 2.

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