JP2003314569A - Industrial robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrial robot for reducing external contamination with a lubricant for lubricating a rolling bearing used for a joint and implementing easy maintenance by space savings. <P>SOLUTION: In the industrial robot in which the rolling bearing is employed for the joint, polymer containing the lubricant consisting of synthetic resin by involving and solidifying a grease containing the lubricating oil as a base oil, is filled into the inside space of the rolling bearing. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial robot, and more particularly to improvement of a rolling bearing used for joints.

[0002]

2. Description of the Related Art As illustrated in FIG. 1, an industrial robot 100 has a large number of joints (joints I to VI in the illustrated example).
6 locations). Rolling bearings are incorporated in these joints, and grease is the most common lubrication means, and in some cases, new grease is regularly supplied from a pipe provided for lubrication. Also,
In addition to grease, lubricating oil using a supply means such as air is also used.

[0003]

However, since grease and lubricating oil are semi-solid or liquid, they are likely to leak, and the leak becomes more remarkable during greasing. As a result, the environment in which the industrial robot 100 is operating is contaminated, and the leaked grease or lubricating oil causes the industrial robot 1
It is assumed that 00 will adhere to the products handled and cause some trouble. Further, since the greasing pipe is required, it is assumed that the robot becomes unnecessarily large and that the greasing work is electrically controlled, which makes the handling difficult. Further, except for the case where the seal is integrated, the bearing part is generally provided with an oil seal or a metal shield (for example, niros ring) separately in order to prevent foreign matter from entering the bearing. This led to higher costs and larger device dimensions.

Therefore, the present invention is intended to solve the above-mentioned problems, and is for industrial use in which there is little external contamination by a lubricant for lubricating a rolling bearing used in a joint portion, space saving and easy maintenance. The purpose is to provide a robot.

[0005]

In order to achieve the above object, the present invention relates to an industrial robot in which a rolling bearing is used in a joint portion, and a lubricating oil or the lubricating oil is provided in an internal space of the rolling bearing. An industrial robot characterized by being filled with a lubricant-containing polymer made of a synthetic resin containing and solidifying a grease containing as a base oil.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The industrial robot of the present invention will be described in detail below.

In the present invention, the structure and configuration of the industrial robot itself is not limited, and all industrial robots using rolling bearings in the joints are targeted, and even the industrial robot 100 shown in FIG. Good.

The structure and structure of the rolling bearing itself are not limited, and for example, a tapered roller bearing as shown in FIGS. 2 and 3 can be exemplified. The tapered roller bearing 1 shown in FIG. 2 is called a single-row tapered roller bearing, and includes an inner ring 2, an outer ring 3, a tapered roller 4 and a tapered roller 4 which are rolling elements interposed between the inner ring 2 and the outer ring 3. Holder 5 to hold
Is equipped with. The inner ring 2 and the outer ring 3 form a hollow rotating body whose cross-sectional shape shown in the figure is a track that is rotated about a rotation axis II ′. The inner ring 2 has a concave portion on the outer peripheral side thereof that accommodates the tapered rollers 4 obliquely, and in the portion that accommodates the tapered rollers 4, there are a thick portion and a thin portion in the radial direction of the inner ring 2. The concave portion of the inner ring 2 has a surface 21 on the large flange portion side and a surface 22 on the small flange portion side. On the other hand, the outer ring 3 also has a thick portion and a thin portion in the radial direction. The cage 5 has a bent portion.
In the present invention, the tapered roller bearing 1 has a lubricant-containing polymer 6 containing a lubricating oil filled in the internal space formed by the inner ring 2, the outer ring 3 and the tapered rollers 4. The lubricant-containing polymer 6 is made of a synthetic resin that is solidified in a state where the lubricating oil is included therein, and has a property that the lubricating oil contained inside gradually exudes from the surface thereof.

In the above tapered roller bearing 1, when the outer ring 3 receives a radial load (arrow A in FIG. 2) or a thrust load (arrow B in FIG. 2), the force is transmitted from the outer ring 3 to the tapered roller 4. And is transmitted from the tapered roller 4 to the inner ring 2. Here, since the end surface of the tapered roller 4 and the surface 21 on the side of the large flange portion are in sliding contact, it is desirable to make the coefficient of friction as small as possible. However, the lubricating oil exudes from the lubricant-containing polymer 6 to cause the sliding contact. It is supplied to the part, and smooth lubrication is maintained for a long time. Further, the lubricating oil exuded from the lubricant-containing polymer 6 is also supplied to the portion from the end surface of the tapered roller 4 to the surface 22 on the side of the small flange portion of the inner ring 2 for lubrication. At the time of lubrication, the amount of lubricating oil is extremely small, so that the torque associated with rotation can be reduced.
Further, since the lubricant-containing polymer 6 does not exist between the end surface of the tapered roller 4 and the surface 21 of the inner ring 2 on the side of the large flange portion of the recess, the movement of the tapered roller due to the presence of the lubricant-containing polymer 6 is hindered. There is no problem of

Further, as shown in FIG. 3, the present invention is also applicable to a combined tapered roller bearing 1a which is constructed by arranging a pair of tapered cone bearings 1 with side faces of inner and outer rings facing each other with a spacer 10 interposed therebetween. is there. In the combined tapered roller bearing 1a, by using the individual tapered roller bearings as the tapered roller bearing 1 shown in FIG. 2, for example, stable lubrication can be realized for a long period of time by the action of the lubricant-containing polymer 6. Incidentally, FIG.
2, the same parts as those in FIG. 2 are denoted by the same reference numerals.

Further, the present invention can be applied to ball bearings as well as tapered roller bearings. For example, the ball bearing 1 illustrated in FIG.
b, between the inner ring 30 and the outer ring 31, a plurality of rolling elements balls 32 are held by a retainer 33 at substantially equal intervals, and between the inner ring 30, the outer ring 31, the balls 32 and the retainer 33. The lubricant-containing polymer 35 is filled in the formed internal space. In addition, in such a rolling bearing 1b, a seal 34 is generally mounted in order to more reliably prevent the leakage of the lubricating oil and prevent the intrusion of foreign matter from the outside. The seal 34 is reinforced by a cored bar 34b, one end of which is fixed to the outer peripheral edge of the outer ring 31, and the other end of the lip 34a is attached so as to contact the inner ring 30. Also in this ball bearing 1b, the lubricant-containing polymer 35
The lubricating oil gradually exudes from the surface of the ball 32, the inner ring 3
The raceway surface of 0 and the raceway surface of the outer ring 31 are lubricated.

The lubricant-containing polymers 6 and 35 will be described below. This lubricant-containing polymer is a synthetic resin, preferably a polyolefin resin having basically the same chemical structure such as polyethylene, polypropylene, polybutylene, and polymethylpentene, and a paraffin hydrocarbon such as poly α-olefin oil as a lubricant. Oil, naphthenic hydrocarbon oil, mineral oil, ether oil such as dialkyldiphenyl ether oil, ester oil such as phthalate ester, etc., which are prepared individually or mixed in the form of a mixed oil, at a temperature not lower than the melting point of the resin. It is solidified by heating to plasticize it and then cooling. Incidentally, various additives such as an antioxidant, a rust inhibitor, an antiwear agent, a defoaming agent and an extreme pressure agent may be added to the lubricant in advance. Further, the lubricant may be grease using the above-mentioned lubricating oil as a base oil, and in that case, metal soap, urea, etc. are used as the thickener.

[0013] Lubricating oils used as the base oil or lubricant is preferably 100 to 1000 mm ² / s at a kinematic viscosity of 40 ° C., more preferably in the range of 150~500mm ² / s. If the kinematic viscosity is less than 100 mm ² / s,
When used at a relatively low speed and with a heavy load like an industrial robot, the oil film strength is low, and seizure easily occurs on the sliding surface of the bearing. If the kinematic viscosity exceeds 1000 mm ² / s, the dynamic torque of the bearing becomes high and the viscosity cannot be maintained only by the base oil, so the addition of a thickener becomes essential and stable lubrication becomes difficult. , The practicality is reduced. In the above viscosity range, particularly when the following load-bearing additives are added, the load-bearing performance is improved, and practically no problem is posed without using a lubricating oil having such a high viscosity.

As load-bearing additives, higher fatty acids such as oleic acid and stearic acid, higher alcohols such as oleyl alcohol, sulfur compounds such as dibenzyl disulfide,
Chlorinated paraffins, halogenated compounds such as methyl trichlorostearate, phosphorus compounds such as tricresyl phosphate, tributyl phosphite, zinc dialkyldithiophosphate (Zn-DTP; chemical formula I), molybdenum dialkyldithiophosphate (Mo-DTP; chemical formula) II), molybdenum dialkyldithiocarbamate (Mo-DTC; chemical formula III), and other organometallic compounds are effective. Among the above, the most effective additive for improving the load resistance is Mo-DTP.
And Mo-DTC, and when Zn-DTP is used in combination, the formation of a film of these organic molybdenum on the metal is facilitated, which is more preferable.

[0015]

[Chemical 1]

In the chemical formulas I to III, R is an alkyl group having 3 to 15 carbon atoms.

The addition amount of the load-bearing additive is in the range of 0.1 to 5% by weight, preferably 0.5 to 3% by weight, based on the lubricant. When the addition amount is less than 0.1% by weight, almost no improvement in load bearing performance is observed. On the other hand, addition of more than 5% by weight is not preferable because the improvement level of load resistance is hardly changed and the oil content is reduced.

The composition ratio of the lubricant-containing polymer is 10 to 50% by weight of the polyolefin resin with respect to the total weight.
Lubricating oil or grease is 90 to 50% by weight. When the content of the polyolefin resin is less than 10% by weight, hardness and strength above a certain level cannot be obtained, and it becomes difficult for the lubricant-containing polymer to maintain the initial shape when a load is applied by rotation of the bearing, There is a high possibility that a problem such as detachment from the inner space of the bearing will occur. Also, when the synthetic resin exceeds 50% by weight (that is, the lubricant is 50% by weight).
If less than), the supply of lubricant to the bearing is reduced,
Bearing life is shortened.

The above polyolefin-based resins have the same basic structure but different average molecular weights, and are 700 to 5 × 1.
It ranges from 0 to ⁶ . Average molecular weight 700-4 × 10 ⁴
Those having a relatively low molecular weight of 1 × 10 ⁴ to 1 × 10 ⁶ , and those having an average molecular weight of 1 × 10 ^{6 to} 5 ×.
An ultrahigh molecular weight of 10 ⁶ is used alone or as a mixture if necessary. The combination of a relatively low molecular weight one and a lubricant gives a lubricant-containing polymer having a certain level of mechanical strength, lubricant supply ability and oil retention. Replacing some of the relatively low molecular weight ones with those classified as waxes, the affinity with the lubricating oil becomes high because the difference in the molecular weight between the wax classified and the lubricating oil is small. As a result, the oil retaining property of the lubricant-containing polymer is improved, and the lubricant can be supplied for a long period of time. However, on the other hand, the mechanical strength is reduced. As the wax, in addition to a polyolefin resin such as polyethylene wax, a hydrocarbon type wax having a melting point in the range of 100 to 130 ° C. or higher (for example, paraffin type synthetic wax) can be used. On the other hand, if you replace it with an ultra-high molecular weight one, the affinity with the lubricating oil will decrease due to the large difference in molecular weight between the ultra-high molecular weight one and the lubricating oil,
As a result, the oil retaining property is lowered, and the leaching of the lubricant from the lubricant-containing polymer is accelerated. This shortens the time required to reach the amount of lubricant that can be supplied from the lubricant-containing polymer and shortens the life of the bearing. However, the mechanical strength is improved.

Considering the balance among moldability, mechanical strength, oil retaining property, and lubricant supply amount, the lubricant-containing polymer has a composition ratio of 0 to 5% by weight classified as wax, and a relatively low molecular weight composition. 8 to 48% by weight, ultra high molecular weight 2 to 2
It is preferable that the total amount of the three resin components is 0 to 50% by weight (the balance is 90 to 50% by weight of the lubricant).

As one of the mechanical strength, the hardness [HD _A ] of the lubricant-containing polymer is preferably in the range of 65 to 95, more preferably 70 to 90. When the hardness [HD _A ] is less than 65, the strength is weak and the rotation of the bearing may damage the lubricant-containing polymer.
On the other hand, if the hardness [HD _A ] exceeds 95, the force that restrains the rolling elements is large, which increases the torque of the bearing and the heat generated by the rotation of the bearing, which increases the temperature of the bearing. There is a fear.

Further, in order to improve the mechanical strength of the lubricant-containing polymer, the following thermoplastic resin and thermosetting resin may be added to the polyolefin resin.

As the thermoplastic resin, various resins such as polyamide, polycarbonate, polybutylene terephthalate, polyphenylene sulfide, polyether sulfone, polyether ether ketone, polyamide imide, polystyrene and ABS resin can be used.

As the thermosetting resin, various resins such as unsaturated polyester resin, urea resin, melanin resin, phenol resin, polyimide resin and epoxy resin can be used.

These resins may be used alone or as a mixture. Further, in order to disperse the polyolefin resin and the other resin in a more uniform state, a suitable compatibilizing agent may be added if necessary.

In addition, a filler may be added to improve the mechanical strength. For example, powder fillers such as calcium carbonate, magnesium carbonate, carbon black and graphite powder, inorganic whiskers such as potassium titanate whiskers and aluminum borate whiskers, or inorganic fibers such as glass fibers and metal fibers, carbon fibers, aramid. Organic fibers such as fibers and polyester fibers, or cloth-like braids of these fibers may be added.

Further, for the purpose of preventing deterioration of the polyolefin resin due to heat, N, N'-diphenyl-p-phenyldiamine, 2,2'-methylenebis (4-ethyl-).
6-t-butylphenol) and the like, and 2-hydroxy-4-n- for the purpose of preventing deterioration by light.
Octoxybenzophenone, 2- (2'-hydroxy-
An ultraviolet absorber such as 3'-t-butyl-5'-methyl-phenyl) -5-chlorobenzotriazole may be added.

The addition amount of all the above-mentioned additives (other than polyolefin resin + lubricant) is 20% by weight or less of the total amount of the forming raw materials as the whole additive, so that the lubricant supply ability is maintained. It is preferable above.

As the synthetic resin which can be used in the present invention, in addition to the resin based on the polyolefin resin as described above, any thermoplastic resin which can be injection-molded can be used, in which the oil content is large. Examples of materials that can be used include polyester elastomers and polyamide elastomers.

In the present invention, the method of filling the bearing-containing space of the rolling bearing with the lubricant-containing polymer is not limited, but a molding raw material containing the above-mentioned synthetic resin, lubricant and additive is used by using an injection molding machine. A simple method is to fill the bearing space with a specified amount and cool the entire rolling bearing to solidify the forming raw material.
In addition, it is preferable because a good filling state can be obtained. At this time, for example, it is preferable that the injection molding machine described in JP-A-8-309793 is improved in the hopper and the mold is arranged vertically so that the filling amount can be controlled and the filling state can be improved. The filling amount is appropriately selected depending on the type of rolling bearing, the part to be used, the specification requirements, and the like.

[0031]

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Examples 1 to 9 and Comparative Examples 1 and 2) High-density polyethylene (relatively low molecular weight) 10% by weight, ultra high molecular weight polyethylene (ultra high molecular weight) 12.5% by weight and polyethylene wax (Classified as wax) 2.5
% By weight and 75% by weight of various mineral oils having different kinematic viscosities at 40 ° C. as shown in Table 1, and further, as shown in Table 1, Mo-DTC and Mo-DTP which are load bearing additives.
And Zn-DTP were added to prepare a molding raw material. Then, the bearing durability comparison test shown below was performed.

[0033]

[Table 1]

◎ Bearing durability comparison test Tapered roller bearing HR32024XJ (inner diameter 120 mm,
An outer diameter of 180 mm and a width of 38 mm) was filled with the molding raw materials of Examples 1 to 9 and Comparative Example 1 by using an injection molding machine, and the whole was cooled and solidified, thereby interposing the spacer shown in FIG. A combined tapered roller bearing was manufactured. Further, as Comparative Example 2, a mineral oil-Li soap-based grease (base oil viscosity: 100 mm ² / s at 40 ° C.) was filled in place of the lubricant-containing polymer, and a Niros ring was attached to the outside to produce a combined tapered roller bearing. did. Then, a bearing durability comparison test was performed on each of the combined tapered roller bearings under the following conditions assuming use in the joint portion of an industrial robot. ·Test condition,

The rotation was continued under the above-mentioned test conditions, and when the initial vibration value exceeded 10 times, it was defined as the durable life, and the time until then was measured. The results are shown in Table 2 relative to the life time of the grease-filled bearing (Comparative Example 2) as 1.

[0036]

[Table 2]

As is clear from Table 2, it is understood that the life of the lubricant-filled polymer is longer than that of the conventional grease-filled polymer. In addition, from the comparison between the example and the comparative example 1, 100 to 1000 mm ² / s at 40 ° C.
By using a lubricating oil having a kinematic viscosity in the range of 1, the load resistance is further improved and the life is extended. Further, it can be seen that the life is further improved by adding the load bearing additive as in Examples 6 to 9.

Observation of the combined tapered roller bearing after completion of the bearing durability comparison test revealed that the leakage of lubricant was extremely small in each of Examples and Comparative Example 1.

[0039]

Since the industrial robot of the present invention is made of a solid polymer containing a lubricant for the appearance of the rolling bearing of the joint portion, parts such as a niros ring for preventing foreign matter from entering the pipe for supplying the lubricant and the bearing. Since it can be omitted, the compact, low weight and low maintenance cost can be satisfied. Further, since the kinematic viscosity of the lubricating oil supplied from the lubricant-containing polymer is 100 to 1000 mm ² / s at 40 ° C., the load bearing property is excellent, so that stable operation of the robot for a long time can be maintained. It is possible. Furthermore, there is little lubricant leakage during operation, and operation that does not pollute the work environment is possible.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of an industrial robot.

FIG. 2 is a sectional view showing an example of a rolling bearing (single row tapered roller bearing) to which the present invention is applied.

FIG. 3 is a sectional view showing another example of a rolling bearing (combined tapered roller bearing) to which the present invention is applied.

FIG. 4 is a sectional view showing still another example (ball bearing) of a rolling bearing to which the present invention is applied.

[Explanation of symbols] 1 Single-row tapered roller bearing 1a Combined tapered roller bearing 1c ball bearing 2 inner ring 3 outer ring 4 tapered rollers 5 cage 6 Polymer containing lubricant 10 zaza 30 inner ring 31 outer ring 32 balls 33 cage 34 seal 35 Solid lubricant polymer 100 industrial robots

Continued front page    (72) Inventor Kazuhiko Otaka             1-5-50 Kumei, Kugenuma, Fujisawa-shi, Kanagawa             Within NSK Ltd. F-term (reference) 3C007 BS12 CY27                 3J101 AA01 AA32 AA62 CA01 CA11                       EA52 EA64 FA13 FA32 FA48                       FA53 GA32

Claims (3)

[Claims] 1. An industrial robot in which a rolling bearing is used in a joint portion, and a lubrication made of a synthetic resin containing lubricating oil or grease containing the lubricating oil as a base oil and solidifying the internal space of the rolling bearing. An industrial robot characterized by being filled with an agent-containing polymer. 2. The lubricating oil contains at least one of zinc dialkyldithiophosphate (Zn-DTP), molybdenum dialkyldithiophosphate (Mo-DTP), and molybdenum dialkyldithiocarbamate (Mo-DTC). The industrial robot according to claim 1. 3. The kinematic viscosity of the lubricating oil at 40 ° C. is 100.
It is -1000 mm < ² > / s and it is characterized by the above-mentioned.
Or the industrial robot described in 2.