Process for improving resistance to false brinelling wear in friction-reducing mechanisms and mechanisms obtained through this procedure

Abstract

The invention is a process for increasing the resistance to false brinelling wear of the rolling surfaces for one or more rolling elements in mechanisms used to reduce friction between two parts moving according to a relative rotational or linear motion, wherein the rolling elements perform incomplete oscillatory rotations. The process includes the step of applying a coating to at least part of the rolling surfaces of one or both of these parts, that is, the surfaces on which said one or more rolling elements roll, and wherein said coating is a DLC or WC / C coating deposited using the PACVD technique at 180 °C or in any case at a temperature between 150 and 210 °C.

Description

[0001] PROCESS FOR IMPROVING RESISTANCE TO FALSE BRINELLING WEAR IN FRICTION-REDUCING MECHANISMS AND MECHANISMS OBTAINED THROUGH THIS PROCEDURE DESCRIPTION

[0002] The present patent concerns mechanisms for reducing friction in relative movements of the rotational or linear type, and in particular it concerns a new process for coating at least part of said mechanisms. The present patent also concerns the recirculating ball bearings, screws and sleeves, linear guides, etc. obtained through this process.

[0003] In mechanical systems, to increase energy efficiency and movement accuracy, the relative movement between parts is often achieved by interposing at least one ball or other rolling element between the parts.

[0004] If the relative movement is fast and / or there is a high compression force between the parts, the use of rolling elements is necessary. The use of rolling elements, such as balls, rollers, barrel rollers, etc., makes it possible to almost nullify the effects of the friction forces that inevitably develop between the moving parts.

[0005] The following, for example, are typical mechanisms used to reduce friction between two parts that rotate or move linearly with respect to each other: recirculating ball bearings / recirculating roller bearings; recirculating ball linear guides / recirculating roller linear guides, such as sleeves, carriages, rollers, etc.;

[0006] - ball screws, which basically have the function of transforming a rotary movement into a linear movement, and in some cases vice versa.

[0007] All these systems work well, ensuring high load capacities and long service life, and make it possible to develop machines with outstanding performance levels.

[0008] It is known that, in order to ensure the proper operation of these mechanisms and their long service life, lubricants are applied between the rolling bodies and their sliding surfaces. When the rolling body performs a complete rotation on itself, the lubricant layer remains correctly distributed between the rolling body and the friction surface. When, instead, its movement is oscillatory, meaning such that the rolling body does not rotate completely but only within a certain angle in one direction and in the opposite direction, the lubricant layer is progressively destroyed and the rolling surfaces quickly wear out at the contact points, even with very low loads, and grooves with loss of material appear on the rolling surfaces themselves.

[0009] This phenomenon is known as “false brinelling” and is called in this way because the signs of wear are similar to those of brinelling, which instead is a permanent deformation due to excessive loads and does not lead to any loss of material.

[0010] False brinelling, on the other hand, occurs due to vibrations even under moderate loads.

[0011] Wear-resistant coating processes are known, which can be generally applied to ball or roller bearings, that is, when a rolling body makes an indefinite number of complete rotations during the normal operation of the bearing. However, said coating processes are not effective in the specific case where the wear is due to false brinelling, which, as explained above, occurs when the rolling body does not perform complete rotations, but incomplete rotations according to a very fast oscillatory motion.

[0012] The subject of the present patent is a new process for limiting false brinelling wear on the surfaces of rolling elements in mechanisms used to reduce friction. The process can be applied, for example, to ball bearings, roller bearings, etc., linear guides, recirculating ball screws and sleeves.

[0013] The subject of the present patent includes also the mechanism constructed according to the new process, which is thus a high-strength mechanism in which at least the friction surfaces of one or more rolling bodies are completely or partially coated with a material characterized by high hardness, low thickness, very high chemical-physical adhesion. More specifically, the hardness of said coating is in the order of 1000-5000HV and its thickness is in the order of 1-4 pm.

[0014] The coating consists of a material that can be applied at a temperature lower than the tempering temperature of steel, so that the mechanical properties of the steel itself are not affected.

[0015] It was found that the application of said coating extends the service life of a bearing up to 10 times compared to bearings without said coating, under oscillatory loads with the rolling element performing incomplete oscillatory rotations.

[0016] Said coating is preferably aDLC (Diamond-Like Carbon) coating, deposited using the PACVD technique at 180 °C, in any case preferably at a temperature between 150 and 210 °C.

[0017] Alternatively, according to the invention, the coating can be made of WC / C (tungsten carbide), deposited using the PACVD technique at 180 °C, in any case preferably at a temperature between 150 and 210 °C.

[0018] The coating process for at least part of the rolling surfaces includes the deposition of a DLC or WC / C coating by means of the PACVD technique at 180 °C, in any case preferably at a temperature between 150 and 210 °C.

[0019] In fact, it was found that the coating obtained at these particular temperature values is particularly resistant to false brinelling wear, under oscillatory loads with the rolling element performing incomplete oscillatory rotations.

[0020] The new process can also include the step of coating, as described above, the entirety or part of the surface of said one or more rolling elements.

[0021] The subject of the present patent includes also a new type of angular bearing suited to withstand axial thrusts in screw actuators, comprising an inner ring, an outer ring and a plurality of balls or rolling bodies interposed between said inner ring and said outer ring. The mutually opposing sides of said rings are provided with grooves in which said rolling bodies roll, wherein at least part of the surfaces of said grooves of said outer ring and / or said inner ring, that is, the rolling surfaces of said rolling bodies, are covered with said coating according to the process described above.

[0022] According to the invention, also said one or more balls or rolling bodies can be completely or partially coated according to the described process.

[0023] The subject of the present patent includes also a linear guide comprising a guide and a slider sliding on said guide, and wherein said guide has one or more grooves in which one or more rolling bodies roll. The surfaces of said one or more grooves, that is, the rolling surfaces of said rolling bodies, are completely or partially covered with said coating according to the process described above.

[0024] According to the invention, also said one or more rolling bodies can be completely or partially coated according to the process described above.

[0025] The subject of the present patent includes also a new recirculating ball screw comprising a screw, a nut screwed on the screw and a plurality of balls between said nut and said screw, and wherein the rolling surfaces of said screw and of said nut, on which said balls roll, are completely or partially covered with said coating according to the process described above.

[0026] According to the invention, also said one or more balls can be completely or partially coated according to the described process.

[0027] The subject of the present patent includes also a bearing for rotary motors, wherein the rolling surfaces for the rolling elements of the bearing are completely or partially covered with said coating according to the process described above.

[0028] According to the invention, also said rolling bodies can be completely or partially coated according to the described process.

[0029] The subject of the present patent includes also a new rod for the sliding movement of ball sleeves, wherein the surface of said rod is completely or partially covered with said coating according to the process described above.

[0030] Therefore, with reference to the above description, the following claims are made.

Claims

CLAIMS1. Process for increasing the resistance to false brinelling wear of the rolling surfaces for one or more rolling elements in mechanisms used to reduce friction between two parts moving according to a relative oscillatory motion of the rotary type, that is, in the condition in which said rolling elements perform incomplete oscillatory rotations, characterized in that it comprises the step of applying a coating to at least part of the rolling surfaces of one or both of said parts, that is, the surfaces on which said one or more rolling elements roll, and wherein said coating is a DLC or WC / C coating deposited using the PACVD technique at 180 °C or in any case at a temperature between 150 and 210 °C.

2. Process according to claim 1, characterized in that the hardness of said coating is in the order of 1000-5000HV and its thickness is in the order of 1-4 pm.

3. Process according to claim 1, characterized in that it comprises the step of applying said coating also to the entirety or part of the surface of one or more of said rolling elements.

4. Mechanism used to reduce friction between two parts moving according to a relative rotational or linear motion with one or more rolling elements interposed therebetween, characterized in that at least part of the surfaces of one or both of said two parts, on which said one or more rolling elements roll, is coated by applying the process according to claims 1 or 2, in order to increase the resistance of said coated surface to false brinelling wear.

5. Mechanism according to claim 4, characterized in that it comprises one or more angular bearings suited to withstand axial thrusts in screw actuators, wherein said angular bearing in turn comprises an inner ring, an outer ring and a plurality of balls or rolling bodies interposed between said inner ring and said outer ring, and wherein the mutually opposing sides of said rings are provided with grooves in which said rolling bodies roll, and wherein at least part of the surfaces of said grooves of said outer ring and / or of said inner ring, that is, the rolling surfaces ofsaid rolling bodies, are covered with said coating by applying the process according to claim 1 or 2.

6. Mechanism according to claim 4, characterized in that it comprises a linear guide in turn comprising a guide and a slider sliding on said guide, and wherein said guide has one or more grooves in which one or more rolling bodies roll, and wherein the surfaces of said one or more grooves, that is, the rolling surfaces of said rolling bodies, are completely or partially covered with said coating by applying the process according to claim 1 or 2.

7. Mechanism according to claim 4, characterized in that it comprises a recirculating ball screw in turn comprising a screw, a nut screwed on the screw and a plurality of balls between said nut and said screw, and wherein the rolling surfaces of said screw and of said nut, on which said balls roll, are completely or partially covered with said coating by applying the process according to claim 1 or 2.

8. Mechanism according to claim 4, characterized in that it comprises one or more bearings for rotary motors, wherein the rolling surfaces for the rolling elements of the bearing are completely or partially covered with said coating by applying the process according to claim 1 or 2.

9. Mechanism according to claim 4, characterized in that it comprises a rod for the sliding movement of ball sleeves, wherein the surface of said rod is completely or partially covered with said coating by applying the process according to claim 1 or 2.

10. Mechanism according to one or more of claims from 4 to 8, characterized in that the outer surface of one or more of said rolling elements is completely or partially coated according to claim 3.