JPH06200947A - Rolling element holder and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a roller holder where the lubricant is contained in pores of a porous material by executing the pressurization and hot forming of particulates of polyethylene of super high molecular weight in a mixed condition with the lubricant, and efficiently provide a holder excellent in lubricity. CONSTITUTION:A rolling element holder 1, e.g. a holder 1 for ball bearing of a machine tool has a number of pockets 10 formed in the outer circumferential part. The holder 1 is formed of the porous material of polyethylene of super high molecular weight, and reinforced with the reinforcing fiber. In addition, the lubricant is contained in pores. The holder 1 where the lubricant is contained in the pores of the porous material composed of particulates is provided by executing pressurization and hot forming in the condition where the particulates of polyethylene of superhigh molecular weight are mixed with the lubricant. On the other hand, the reinforcing fiber is added to the particulates and the lubricant during the pressurization and hot forming. This constitution allows the efficient manufacture of the holder 1 excellent in lubricity which does not generate where seizing or the like immediately even when running out of lubricant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling element cage used for holding rolling elements in, for example, rolling bearings and a method for manufacturing the cage.

[0002]

2. Description of the Related Art Conventionally, a cage for holding rolling elements in a rotating device such as a rolling bearing is formed of metal or engineering plastic, and is lubricated to ensure lubricity. It is necessary to separately supply agents (grease, oil, etc.). Therefore, the assembled device is filled with a certain amount of lubricant in advance, or the lubricant is supplied to the device during rotation. However, if the lubricant filled in advance runs out or the supply of the lubricant stops, problems such as seizure and stoppage occur immediately.

As a non-lubricated bearing, a solid lubricant coating is applied to the surface of the cage and the surface of the rolling elements, but the material is special and the coating requires special technology and equipment. Therefore, it is not suitable for general use in terms of cost, mass productivity, etc., and is currently used only for special purposes. It is possible to use a so-called sintered metal having a porous structure formed by sintering metal powder to impregnate the pores with a lubricant, but the oil content of the sintered metal is at a practical level. It is about 15 to 20% by volume, and is not suitable for practical use because it has an insufficient oil content as a rolling element retainer.

The present invention has been made in view of the above circumstances, and has no possibility of causing troubles such as seizure and stop immediately even if the lubricant runs out or the supply thereof is stopped. An object of the present invention is to provide an excellent cage for rolling elements and an efficient manufacturing method thereof.

[0005]

Means and Actions for Solving the Problems In order to solve the above problems, the inventors of the present invention have an average molecular weight of 1,000,000-6.
It was studied to manufacture a cage for rolling elements using ultra-high molecular weight polyethylene, which is about 1,000,000. This ultra-high molecular weight polyethylene has a high melting point of about 100 to 140 ° C and excellent heat resistance as compared with general high density polyethylene (average molecular weight of about 20,000 to 200,000, melting point of about 80 to 90 ° C). Compared with high density polyethylene and other engineering plastics, it has excellent wear resistance, impact resistance, self-lubrication and chemical resistance. However, when a solid cage is manufactured from ultra high molecular weight polyethylene, problems such as seizure and stoppage may still occur when the lubricant runs out or the supply is stopped. Therefore, as a result of further study, if the cage is made of a porous body formed by pressurizing and heat-molding the above-mentioned ultra-high-molecular-weight polyethylene powder, and if a lubricant is impregnated in the hole, In combination with the self-lubricating property of high-molecular-weight polyethylene itself, it was found that a cage for rolling elements having excellent lubricity, which is free from problems such as seizure and stoppage, can be obtained, and to complete the present invention I arrived.

That is, the cage for rolling elements of the present invention is characterized by being made of a porous body of ultra high molecular weight polyethylene. The lubricant is contained in the holes as described above. The rolling element cage is preferably reinforced with reinforcing fibers. Further, the method for manufacturing a rolling element cage according to the present invention comprises pressurizing and heat-molding the above-mentioned ultra-high-molecular-weight polyethylene powder and granules in a state of being mixed with a lubricant to form pores in the porous body made of powder and granules. It is characterized in that a cage for rolling elements in which a lubricant is contained is manufactured.

In the cage for rolling elements of the present invention having the above structure, the cage itself is made of ultra-high molecular weight polyethylene having excellent self-lubricating property, and the ultra-high-molecular-weight polyethylene powder or granular material is used. Since the lubricant can be impregnated into the pores of the porous body, even if the lubricant runs out or the supply is stopped, there is no risk of problems such as seizure and stop immediately.

Further, according to the present invention, the porosity of the cage after molding, that is, the oil content of the lubricant can be freely adjusted by adjusting the molding conditions such as molding temperature and molding pressure, and the particle size of the powder and granules. It also has the advantage of being adjustable. Further, in the case of the production method of the present invention in which the powder and granules are pressed and heat-molded together with the lubricant, the oil content can be freely adjusted by adjusting the mixing ratio of both.

Further, since a porous body made of ultra-high molecular weight polyethylene powder and granules has a structure in which the powder and granules are melt-bonded to each other by pressure and heat molding, the metal powders are not completely melt-bonded to each other. Porosity (= oil content) can be higher than that of metal, for example 50% by volume depending on the conditions.
The above oil content is also possible. Further, the cage for rolling elements of the present invention can be made to have mechanical strength comparable to that of a resin cage having a normal solid structure by strengthening by adding reinforcing fibers. Is.

Further, according to the above-mentioned manufacturing method of the present invention, since the cage can be molded and the lubricant can be impregnated in one step, it is more efficient than the case where the cage molded earlier is impregnated with the lubricant later. In addition, the lubricant can be uniformly impregnated into the inside of the cage. Incidentally, as similar to the rolling element cage of the present invention, between the inner and outer races of the rolling bearing,
Alternatively, after filling a paste-like mixture (commonly called “plastic grease”) of the same ultra-high molecular weight polyethylene powder and lubricant into the gap between the cage and the rolling elements, the entire rolling bearing is made into ultra-high molecular weight polyethylene. There is a technique in which the mixture is appropriately solidified by heating and melting the powder and granules to each other by heating above the melting temperature (about 150 to 200 ° C.) (JP-A-55-109824 and JP-A-56).
-49418 gazette etc.).

However, the purpose of these prior arts is only a lubricant, and the cage itself is different from the present invention in that it is made of ordinary metal or plastic. ing. Further, in the above-mentioned conventional technique, the lubricant is solidified in order to prevent the outflow at the time of rotation, and the mechanical strength or the like is hardly required unless the outflow occurs, so the plastic grease is filled in the space inside the bearing. It can only be used in the form of doing. On the other hand, the rolling element cage of the present invention, while using almost the same raw material as in the prior art, for example, by blending reinforcing fibers and the like or selecting molding conditions appropriately,
The present invention also differs from the prior art in that it is formed into a state that can be handled as one independent cage.

Further, in the above-mentioned prior art, it is necessary to fill the assembled rolling bearing with the plastic grease and then heat it to the above-mentioned high temperature, so that it cannot be applied to the rolling bearing for precision use where precision is required. In addition to the above problem, it is necessary to add a step of heating the assembled rolling bearing to the normal production line, which causes a problem of reduced production efficiency. On the other hand, in the present invention, the retainer that has been previously pressure-molded and heat-molded is
Since it only needs to be incorporated into a rolling device such as a rolling bearing as in a normal process and does not include a step of heating the entire rotating device to a high temperature, it can be applied to, for example, a rolling bearing for precision applications in which precision is required. There is no fear that the application will be limited. Further, since the assembly in the conventional production line is possible, there is no fear that the production efficiency will decrease.

Further, in the former case of the above-mentioned conventional techniques, since the plastic grease is solidified in such a manner that the plastic grease enters all the gaps in the bearing, the rotational torque of the bearing is remarkably increased, or the bearing ring, rolling Since there is no escape area for heat generation from the moving body, cage, etc., there arises a problem that the temperature rise during rotation becomes large, and high-speed rotation cannot be performed. On the other hand, the rolling element cage according to the present invention can be molded into a shape that does not hinder the rotation of bearings and the dissipation of heat, as in the case of a normal cage, so that the above problems do not occur.

The present invention will be described below. As the ultra-high molecular weight polyethylene, those having an average molecular weight of about 1,000,000 to 6,000,000, particularly 2,000,000 or more and a melting point of about 100 to 140 ° C are suitably used as described above.
The particle size of the ultra-high molecular weight polyethylene powder is not particularly limited in the present invention, and as described above, the oil content in the cage after molding, or the mechanical strength of the cage, etc. may be taken into consideration. The average particle size is preferably about 10 to 130 μm, but is preferably 10 to 30
More preferably, it is about μm. If the particle size of the ultra-high-molecular-weight polyethylene powder is less than the above range, the porosity of the porous body obtained by pressurizing and heating this will be insufficient, and a sufficient amount of lubricant cannot be impregnated with oil. There is a risk. On the contrary, when the particle size of the powder or granules exceeds the above range, the melt adhesion ratio of the powder or granules may be decreased, and the mechanical strength of the cage may be insufficient.

If necessary, various known additives such as antioxidants, stabilizers, and colorants are added to the ultra-high-molecular-weight polyethylene powder or granules in the same proportion as in the past. You can also leave it. In order to improve the mechanical strength and heat resistance of the cage, the reinforcing fibers that may be added to the ultra-high molecular weight polyethylene powder or granules include glass fibers, carbon fibers, and other reinforcing fibers for ordinary resin kneading. , Can be used in various ways. Since ultra-high molecular weight polyethylene is difficult to melt-knead, and it is difficult to mix the reinforcing fiber into the powder or granular material, the reinforcing fiber is preferably mixed with the manufactured powder or granular material and used for molding.

The fiber length of the reinforcing fiber is not particularly limited in the present invention, and an appropriate range is set according to the type of the reinforcing fiber. The reinforcing fiber having a longer fiber length improves the strength of the cage. Excellent effect, especially fiber length 5
Reinforcing fibers of about 10 mm are most suitable. However, in consideration of the mixing property with the powder and granules, the pressurizing property, the dispersibility at the time of heat molding, etc., the short fiber length (0.
Reinforcing fibers of about 2 to 0.8 mm) may be used together. The reinforcing fibers having the above short fiber length may be used alone, but in that case, the strength and application of the cage are limited.

The addition amount of the reinforcing fiber is not particularly limited in the present invention, but it is preferable to add the reinforcing fiber at a ratio of 10 to 50% by weight based on the total amount including the ultra high molecular weight polyethylene. If the addition amount of the reinforcing fiber is less than the above range, it may not be possible to obtain a sufficient addition effect,
On the contrary, if the amount of reinforcing fiber added exceeds the above range,
Welding of the powder and granules may be insufficient, and sufficient strength may not be obtained.

In the cage for rolling elements of the present invention, a mixture having the above-mentioned ultra-high-molecular-weight polyethylene powder and granules and, if necessary, reinforcing fibers is filled into a die having a cavity in the shape of the cage. It is manufactured by applying pressure and heat molding,
At this time, if a lubricant is further added to the above mixture based on the structure of the manufacturing method of the present invention, the cage formation and the oil impregnation of the lubricant can be performed in one step. The production efficiency can be improved as compared with the case where the agent is impregnated. It is also possible to uniformly impregnate the inside of the cage. However, the lubricating oil may be impregnated after forming the porous material.

As the lubricant, various conventionally known lubricants such as grease and oil can be used. Especially, these components react with ultra-high molecular weight polyethylene and reinforcing fibers at the time of pressurizing and heat molding, and these components are added. A stable lubricant that does not deteriorate the characteristics of (1) is preferably used. Specific examples of usable grease include, but are not limited to, lithium soap mineral oil grease, sodium soap mineral oil grease, aluminum soap mineral oil grease, lithium soap diester grease, lithium soap diester mineral oil grease. Examples thereof include grease, non-soap diester grease, silicone grease and the like. Specific examples of usable oils include, but are not limited to, silicone oils, paraffin oils, synthetic oils, fluorine oils, and the like.

The amount of the lubricant added is not particularly limited in the present invention, but the ratio (weight ratio) of the ultra-high molecular weight polyethylene powder A to the lubricant B A: B = 95: 5-2.
It is preferable to add the lubricant so as to be in the range of 0:80. If the amount of lubricant added is less than the amount represented by the above ratio A: B = 95: 5, the oil content in the cage after molding may be insufficient, and conversely the amount of lubricant added If the amount is larger than the amount represented by the ratio A: B = 20: 80, the mechanical strength of the cage after molding may decrease. Even if the amount of the lubricant added is within the above range, the mechanical strength of the cage tends to decrease in the vicinity of the upper limit of the range, so the reinforcing fiber may be added, or the molding conditions may be changed. Therefore, it is desirable to secure strength.

If necessary, an inorganic filler may be added to the mixture containing the above components. There are no particular restrictions on the molding conditions when pressurizing and heat-molding the mixture containing the above components, but the molding temperature is such that the particles can be sufficiently melt-bonded to each other, and the particles are completely melted. It is preferable that the temperature is such that the porous structure is not crushed. Specifically, the lower limit is near the melting point of the ultrahigh molecular weight polyethylene, and a range up to about 200 ° C. is suitable. Further, the molding pressure is preferably a pressure at which the particles can be sufficiently melt-bonded to each other and the porous structure is not crushed. Specifically 1
It is preferably about 00 kg / cm ² or less.

The molded rolling element retainer is used by incorporating it into a rolling bearing or the like. The configuration of the rolling element cage of the present invention can be applied to cages having various conventionally known shapes and uses. When the rolling element cage of the present invention is incorporated into a rolling bearing, and if the rolling bearing has a dust-proof sealing member, the sealing member is used as the rolling element holding member of the present invention. Like the container, it is made of a porous material by pressing and heat molding ultra-high molecular weight polyethylene powder, or a ring-shaped spacer made of the same porous material between the metal seal member and the cage. By inserting the member and impregnating the lubricant in the hole, it is possible to further improve the effect of preventing seizure and stop of the rolling bearing.

As a matter of course, since the seal member and the spacer member are formed in a shape that does not hinder the rotation of the rolling bearing, the rotational torque of the bearing is remarkably increased as in the prior art using the plastic grease described above. There is no fear. In addition, since a sufficient space can be secured inside the bearing, there is no fear that the temperature rise during rotation will be large. Moreover, since the preformed seal member and spacer member are incorporated into the bearing, the bearing can be assembled in the conventional bearing production line and the production efficiency is good.

The above-mentioned ones are formed by pressing and heat-molding ultra-high-molecular-weight polyethylene powder particles to form a porous body, while pellets are pressed and heat-formed by a porous body. It may be configured as. Furthermore, by injection molding,
It is possible to form a porous body by adding an inert gas.

[0025]

[Example] Ultra high molecular weight polyethylene (average molecular weight 200
30 parts by weight of powdered particles having an average particle size of 20 μm, and 20 parts by weight of glass fiber (fiber length 5 mm) as a reinforcing fiber,
70 parts by weight of silicone oil (viscosity 100 cSt at 40 ° C.) as a lubricant was stirred and mixed to prepare a paste-like mixture. After this mixture was poured into a mold, it was molded under the conditions of a molding pressure of 20 kg / cm ² and a molding temperature of 150 ° C., and had a shape shown in FIGS. 1 (a) and (b), and an outer diameter D ₁ = 9.
4.8 mm, inner diameter D ₂ = 87 mm, inner diameter D _{3 of} pocket 10
A retainer 1 for machine tool ball bearings having an oil content (= porosity) of 30% by volume was obtained.

The cage 1 obtained in the above-mentioned example and, as a comparative example, a cage made of solid 66 nylon having the same shape were respectively incorporated in ball bearings for machine tools to obtain oil and air. Rotation speed: 200 under lubrication condition
When the oil supply was stopped after rotating for a fixed time under the conditions of 00r.pm and a rotating load of 60 kg, the bearing incorporating the cage of the comparative example burned within 10 minutes and stopped. However, the bearing in which the cage of the example was incorporated did not cause seizure even if it was rotated for another hour thereafter.

[0027]

The cage for rolling elements according to the present invention is excellent in lubricity because it is constructed as described above. Even if the lubricant runs out or the supply is stopped, it will seize immediately,
There is no risk of problems such as stoppage. According to the method for manufacturing a rolling element cage of the present invention, the rolling element cage of the present invention can be efficiently manufactured.

[Brief description of drawings]

FIG. 1 (a) is a partially enlarged vertical cross-sectional view of a cage for ball bearings for machine tools as an embodiment of the cage for rolling elements of the present invention, and FIG. It is a partially expanded transverse cross-sectional view.

[Explanation of symbols]

 1 cage

Claims (5)

[Claims] 1. A cage for rolling elements, which is made of a porous body of ultra high molecular weight polyethylene. 2. The cage for rolling elements according to claim 1, which is reinforced with reinforcing fibers. 3. The rolling element cage according to claim 1, wherein a lubricant is contained in the hole. 4. A structure in which a lubricant is impregnated in the pores of a porous body made of powder and granules by pressing and heat-molding a powder and granules of ultra-high molecular weight polyethylene mixed with a lubricant. A method of manufacturing a cage for rolling elements, which comprises manufacturing a cage. 5. The method for producing a rolling element cage according to claim 4, wherein reinforcing fibers are further added to the powder and granules and the lubricant at the time of pressurization and heat molding.