Ball socket structure

Abstract

To provide a ball socket structure having a novel configuration in which a socket is improved.SOLUTION: A ball socket structure of this invention includes a ball and a socket mutually sliding, and a sliding surface of the socket is made of a PVD coating layer. The sliding surface of the socket is a concave spherical surface, and a value of a ratio (Ds / Rs) between a depth Ds and a curvature radius Rs of the sliding surface is 0.05-0.70.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an improvement in the ball socket structure.

Background Art

[0002] In a tilting pad bearing used for a journal bearing, a ball socket structure may be adopted. The socket portion is fixed to the housing of the journal bearing, a pad is disposed on a ball portion that slides with respect to the socket portion, and this pad is tiltable. In such a tilting pad bearing having such a configuration, it has generally been the case that both the sliding surface of the ball portion and the sliding surface of the socket portion are made of a metal for a shaft. Since both the sliding surface of the ball portion and the sliding surface of the socket portion are made of metal, it is necessary to supply lubricating oil between the two. Therefore, recesses (point shape, groove shape) for collecting lubricating oil are formed on at least one of the sliding surfaces (see Patent Document 1). By providing such recesses, the following effects are achieved. As the two sliding surfaces slide, the lubricating oil collected in the recesses is drawn between the two sliding surfaces, thereby maintaining the slidability between the two sliding surfaces. Thereby, a good tilt function is ensured for the pad disposed on the ball portion. Please also refer to Patent Documents 2 and 3 that disclose technologies related to the present invention.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the studies by the present inventors, providing recesses for lubricating oil collection on the sliding surfaces of the ball part and the socket part had the following problems. The region where the recesses are formed does not contribute to the sliding between the sliding surface of the ball part and the sliding surface of the socket part. In other words, by providing the recesses, the effective area of both sliding surfaces becomes smaller than that without the recesses, which causes an increase in the friction coefficient. The tilt angle required for the pads arranged in the circumferential direction of the shaft in a journal bearing is very small (for example, about 0.1 degree). As a result, the sliding amount of the sliding surface of the ball part with respect to the sliding surface of the socket part is also very small. When the sliding amount is so small, the amount of lubricating oil drawn from the recesses for lubricating oil collection between both sliding surfaces may be insufficient, which may cause an increase in the friction coefficient.

Means for Solving the Problems

[0005] This invention solves such problems, and the first aspect is defined as follows. A ball socket structure comprising a ball part and a socket part that slide relative to each other, wherein the sliding surface of the socket part is composed of a PVD coating layer, the sliding surface of the socket part is a concave spherical surface, and the value of the ratio (Ds / Rs) of the depth Ds of the sliding surface to its radius of curvature Rs is 0.05 to 0.70, a ball socket structure.

[0006] In the bearing of the first aspect defined in this way, as shown in FIG. 1A, the value of the ratio (Ds / Rs) of the depth Ds of the sliding surface 43a in the socket part 43 to its radius of curvature Rs was set to 0.05 to 0.70. That is, the sliding surface 43a was made into a relatively shallow concave spherical surface. Thereby, when the metal socket part 43 is used as a cathode and particles generated by an evaporation source and plasma are made to collide therewith, the particles are likely to collide evenly over the entire area of the sliding surface 43a.

[0007] Note that when the ratio value (Ds / Rs) exceeds 0.70, the sliding surface 43a of the socket portion 43 becomes too deep, and there is a possibility that particles may not be able to collide with sufficient energy at the deep position of the sliding surface 43a. On the other hand, when the ratio value (Ds / Rs) is less than 0.05, the sliding surface 43a becomes too shallow, which is not preferable. That is, when the sliding surface 43a becomes shallow, a large area is required on the sliding surface 43a to effectively tilt the pad 20 (see FIG. 4) supported by the ball portion 41 by rotating the ball portion 41, and the ball socket structure becomes larger. From the viewpoint of ease of processing, a more preferable ratio value of (Ds / Rs) is 0.3 to 0.6. The most preferable ratio value is 0.4 to 0.6.

[0008] Here, when performing PVD (Physical Vapor Deposition, the same in this specification) treatment, it is common to perform plasma cleaning on the surface to be grown as the first pretreatment step. However, since the sliding surface 43a is formed shallowly, plasma such as Ar+ collides evenly over the entire area of the concave spherical surface. Therefore, the entire concave spherical surface is surely and uniformly cleaned, and then the coating layer 433 laminated by PVD treatment adheres uniformly (see FIG. 1B). That is, sufficient adhesion can be ensured between the PVD coating layer 433 and the base 431 of the socket portion. Of course, the particles of the material of the coating layer 433 laminated by PVD treatment also collide evenly with the concave spherical surface and are laminated there, so the film thickness and density of the PVD coating layer 433 also become uniform. The material of the PVD coating layer shall have characteristics such as high lubricity and wear resistance as constituting the solid sliding layer of the bearing sliding surface. Examples of such materials include DLC and CrN exemplified in the embodiments, as well as CrC, SiC, SiN, TiN, TiC, etc.

[0009] In this way, by forming the sliding surface 43a of the socket portion 43 with the PVD coating layer 433, it is possible to reduce the coefficient of friction between the sliding surface 43a of the socket portion 43 and the sliding surface 41a of the ball portion 41 without providing any recesses for collecting lubricating oil. Here, it is preferable to form the PVD coating layer 433 on the entire surface of the sliding surface 43a of the socket portion 43, but the PVD coating layer 433 may also be formed only on the portion of the sliding surface 43a of the socket portion 43 where the ball portion 41 contacts. Since the film thickness and density of this PVD coating layer 433 are uniform, it is possible to achieve thinning and high durability of the film.

[0010] The second aspect of this invention is defined as follows. That is, In the ball socket structure defined in the first aspect, the outer periphery of the sliding surface of the socket portion is chamfered. According to the ball socket structure of the second aspect defined in this way, as shown in FIG. 2A, since the outer periphery of the sliding surface 43a of the socket portion 43 is chamfered, the edge is removed from the socket portion 43 as the cathode that receives the collision of particles. Here, the outer periphery of the sliding surface 43a refers to the portion of the maximum diameter in the concave spherical surface. By chamfering in this way, the electric field at this portion becomes stable and the collision of particles becomes stable and uniform. As a result, the film thickness and density of the PVD coating layer 433 become more uniform over the entire surface of the sliding surface 43a.

[0011] It is preferable that the chamfering curvature radius Rc of the chamfered portion satisfies a ratio value (Rc / Rs) in comparison with the curvature radius Rs of the sliding surface 43a or a ratio value (Dc / Rs) of the curvature radius Rs to the depth Dc of the chamfered C surface to be 0.02 or more (third aspect). By setting these ratio values to 0.02 or more, it is possible to suppress the disturbance of the electric field due to the edge effect. When the ratio value (Rc / Rs or Dc / Rs) is less than 0.02, the chamfering curvature radius of the chamfered portion becomes too small, resulting in an edge effect and possibly disturbing the electric field in its vicinity. The chamfering curvature radius Rc refers to the curvature radius of the cross section when the C surface of the chamfered portion is formed into a hemispherical shape bulging outward. The chamfered shape is not limited to the above-described curved surface as long as it can suppress the disturbance of the electric field. For example, as shown in FIG. 2B, the angle Ac of the planar C surface may be 60 degrees or less.

[0012] The fourth aspect of this invention is defined as follows. That is, in the ball socket structure defined in any one of the first to third aspects, a through hole is formed in the central portion of the socket portion. Here, the central portion of the socket portion refers to the deepest portion on the sliding surface. According to the ball socket structure of the fourth aspect defined as above, as shown in FIG. 3, since the through hole 48 is formed at the deepest position on the sliding surface 41a of the socket portion 43, a strong electric field can be generated around the opening 48c of the through hole 48. Thereby, the electric field strength at the deep position of the sliding surface 43a where the electric field strength tends to be weak can be compensated. Furthermore, as shown in FIG. 4, it is preferable to chamfer the periphery of the opening 48c of the through hole 48 to stabilize the electric field at the periphery of the opening 48c (fifth aspect). The degree of chamfering can be made equivalent to the outer periphery of the sliding surface 43a.

[0013] The sixth aspect of this invention is defined as follows. That is, in the ball socket structure defined in the first to fifth aspects, the PVD coating layer is made of diamond-like carbon (which may be abbreviated as DLC in this specification). According to the ball socket structure of the sixth aspect defined as above, since the PVD coating layer 433 is made of DLC, high durability, which is a characteristic of DLC, can be obtained.

[0014] The seventh aspect of this invention is defined as follows. That is, in the ball socket structure defined in the first to sixth aspects, the thickness of the PVD coating layer occupies 0.001 to 0.300% with respect to the thickness Ts of the central portion of the socket portion. As described above, the central part of the socket part 43 refers to the deepest part on the sliding surface 43a. In other words, the central part is the thinnest part in the socket part 43. Therefore, as defined in the seventh aspect, by designing the thickness of the PVD coating layer 433 to account for 0.001 to 0.300% of the thickness Ts of the central part of the socket part 43, the necessary mechanical strength of the socket part 43 is ensured, and the necessary film thickness is also ensured for the PVD coating layer 433.

[0015] Here, if the proportion of the thickness of the PVD coating layer 433 in the central part of the socket part 43 is less than 0.001%, the PVD coating layer 433 becomes too thin and its film thickness life decreases. On the other hand, if the proportion of the thickness of the PVD coating layer 433 exceeds 0.300%, while the PVD coating layer 433 becomes uselessly thick, the proportion of the substrate in the central part of the socket part 43 decreases and the rigidity decreases. As a result, its mechanical strength decreases. A more preferable proportion of the thickness of the PVD coating layer 433 in the central part of the socket part 43 is 0.010 to 0.100%. The most preferable proportion is 0.020 to 0.050%. This facilitates the adjustment of the thickness of the PVD coating layer 433.

[0016] The eighth aspect of this invention is defined as follows. That is, in the ball socket structure defined in any one of the first to seventh aspects, the sliding surface of the ball part is composed of a PVD coating layer. The thickness of the PVD coating layer accounts for 0.001 to 0.300% of the thickness Tb of the central part of the ball part. According to the eighth aspect defined in this way, as shown in FIG. 1B, since the PVD coating layer 413 is also laminated on the sliding surface 41a of the ball part 41, in combination with the PVD coating layer 433 on the sliding surface 43a of the socket part 43, the friction coefficient of the ball socket structure can be reduced. By designing such that the thickness of the PVD coating layer 413 occupies 0.001 to 0.300% with respect to the wall thickness Tb at the center of the ball portion 41, it is possible to ensure the mechanical strength required for the ball portion 41 and also ensure the required film thickness for the PVD coating layer 413.

[0017] Here, the central portion of the ball portion 41 refers to the portion of the ball portion 41 that faces the central portion of the socket portion 43 in the no-load state. Here, if the ratio of the thickness of the PVD coating layer 413 at the center of the ball portion 41 is less than 0.001%, the PVD coating layer 413 may become too thin and its durability may be insufficient. On the other hand, if the ratio of the thickness of the PVD coating layer 413 exceeds 0.300%, while the PVD coating layer 413 becomes uselessly thick, the central portion of the ball portion 41 may become too thin and its mechanical strength may become insufficient. A more preferable ratio of the thickness of the PVD coating layer 413 at the center of the ball portion 41 is 0.010 to 0.030%. The most preferable ratio is 0.010 to 0.025%.

[0018] The ninth aspect of this invention is defined as follows. That is, A method for manufacturing the socket portion of a ball socket structure including a ball portion and a socket portion that slide relative to each other, A preparation step of preparing a metal socket portion substrate having a concave spherical surface that serves as a sliding surface, and the value of the ratio (Ds / Rs) of the depth Ds of the concave spherical surface to its radius of curvature Rs is 0.05 to 0.70, A first pretreatment step of plasma cleaning the concave spherical surface of the substrate, A second pretreatment step of laminating a primer layer on the plasma-cleaned concave spherical surface by PVD treatment, A manufacturing method of the socket portion including a lamination step of laminating diamond-like carbon on the primer layer by PVD treatment.

[0019] According to the manufacturing method defined in the ninth aspect, the value of the ratio (Ds / Rs) of the depth Ds of the concave spherical surface of the base body 431 of the socket portion 43 to its radius of curvature Rs is set to 0.05 to 0.70. That is, the concave spherical surface of the base body 431 is made shallow. Thereby, when the base body 431 of the metal socket portion 43 is used as a cathode and particles generated by an evaporation source and plasma are made to collide therewith, the particles are likely to collide evenly over the entire area of the concave spherical surface. When performing PVD treatment, it is common to perform plasma cleaning on the surface to be grown as a first pretreatment step. Here, according to the manufacturing method defined in the ninth aspect, since the concave spherical surface of the base body 431 of the socket portion 43 is formed shallowly, particles such as Ar+ generated by plasma collide evenly over the entire area of the concave spherical surface. Therefore, the entire surface of the concave spherical surface of the base body 431, which is the surface to be grown, is surely and uniformly cleaned.

[0020] Also, at the time of laminating the primer layer (second pretreatment step) performed thereafter, since the particles constituting the primer layer collide evenly with the plasma-cleaned concave spherical surface, the primer layer has a uniform film thickness and density over the entire surface of the concave spherical surface. Examples of materials for such a primer layer include Ti, Cr, W, Ni, NiCr, Si, Zr, Ta, Mo, and the like. Furthermore, at the time of laminating the diamond-like carbon layer (laminating step) performed thereafter, since the particles constituting the diamond-like carbon layer collide evenly with the primer layer on the concave spherical surface, the diamond-like carbon layer has a uniform film thickness and density over the entire surface of the primer layer.

[0021] The manufacturing method of the tenth aspect of this invention is defined as follows. That is, In the manufacturing method defined in the ninth aspect, in the preparation step, the outer periphery of the concave spherical surface of the base body is chamfered. According to the manufacturing method of the tenth aspect defined in this way, since the outer periphery of the concave spherical surface of the substrate 431 is chamfered, the electric field there is stable, and when the substrate 431 is used as the cathode, the collision of particles becomes stable and uniform. As a result, the first pretreatment step, the second pretreatment step, and the lamination step are each stably executed over the entire surface of the concave spherical surface. In addition, as defined in the eleventh aspect, it is preferable that the chamfering radius of curvature Rc satisfies a ratio value (Rc / Rs) in comparison with the radius of curvature Rs of the sliding surface 43a or a ratio value (Dc / Rs) of the radius of curvature Rs to the depth Dc of the chamfered C surface to be 0.02 or more. By setting the ratio value (Rc / Rs or Dc / Rs) to be 0.02 or more, the disturbance of the electric field due to the edge effect can be suppressed.

[0022] The twelfth aspect of this invention is defined as follows. That is, it is the manufacturing method defined in any one of the ninth to eleventh aspects, and in the preparation step, a through hole 48 is formed in the central portion of the concave spherical surface. According to the manufacturing method of the twelfth aspect defined in this way, since the through hole 48 is formed at the deepest position in the substrate 431, when the substrate 431 is used as the cathode, a strong electric field is generated around the opening 48c of the through hole 48. As a result, particles can collide stably even at a deep position on the concave spherical surface. Furthermore, as defined in the thirteenth aspect, it is preferable to chamfer the periphery of the opening 48c of the through hole 48 to stabilize the electric field at the periphery of the opening 48c.

[0023] The fourteenth aspect of this invention is defined as follows. That is, it is the manufacturing method defined in any one of the ninth to thirteenth aspects, and in the lamination step, the thickness of the DLC layer is set to be 0.001 to 0.300% with respect to the thickness Ts of the central portion of the socket portion. According to the manufacturing method of the fourteenth aspect defined in this way, by designing so that the thickness of the PVD coating layer 433 occupies 0.001 to 0.300% with respect to the thickness Ts of the central portion of the socket portion 43, the necessary mechanical strength of the socket portion 43 is ensured, and at the same time, the necessary film thickness of the PVD coating layer 433 is ensured.

[0024] The 15th aspect of this invention is defined as follows. That is, a step of preparing a socket part manufactured by the manufacturing method defined in any one of 9 to 14, and a step of preparing a ball part, and an assembling step of assembling the ball part and the socket part, a manufacturing method of a ball socket structure including the above. In the ball socket structure manufactured in this way, the socket part 43 is provided with a PVD coating layer 433 made of diamond-like carbon. Therefore, the friction coefficient between the sliding surface 41a of the ball part 41 and the sliding surface 43a of the socket part 43 can be reduced.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0026] Hereinafter, the ball socket structure according to the embodiment of this invention will be described. The ball socket structure of the embodiment constitutes a tilting pad bearing 40 (see FIG. 4). As shown in FIGS. 5 and 6, this tilting pad bearing 40 is assembled to the journal bearing 1. This journal bearing 1 includes semi-cylindrical housings 11, 11 and four pads 20 disposed on the inner peripheral surface thereof. Reference numeral 3 denotes a rotating shaft, and reference numeral 50 denotes an oil supply portion. The pads 20 are disposed with respect to the housing 11 via the tilting pad bearing 40 and the second tilting pad bearing 30 shown in FIG. 4. The second tilting pad bearing 30 is composed of a liner disposed on the pad 20 and a spherical pivot disposed on the housing 11. The ball socket structure of the embodiment can also be applied to the thrust bearing of the tilting pad.

[0027] The tilting pad bearing 40 includes a ball portion 41 and a socket portion 43. The ball portion 41 includes a base body 411 and a PVD coating layer 413 (see FIG. 1B). The base body 411 is formed of a part of a sphere having a radius of curvature Rs, and includes a convex spherical surface and a planar mounting portion 41b. A through hole 47 is formed at the center thereof. The material of the base body 411 is not particularly limited as long as it has rigidity that does not deform or break under the force applied to the pad 20. For example, a general-purpose bearing steel material such as high-chromium carbon steel can be used. The mounting portion 41b is in a sliding state with the anchor member 42, and this anchor member 42 is embedded in the pad 20. The PVD coating layer 413 is laminated on the convex spherical surface of the base body 411. The convex spherical surface of the base body 411 thus PVD-coated becomes the sliding surface 41a of the ball portion 41, and the sliding surface 41a is composed of the PVD coating layer 413.

[0028] This PVD coating layer 413 has higher lubricity than the material of the base body 411. In other words, the forming material of the PVD coating layer 413 has a lower friction coefficient than the high-chromium carbon steel or the like constituting the base body 411. As a result, wear of the sliding surface 41a of the ball portion 41 and, consequently, wear of the sliding surface 43a of the socket portion 43 are suppressed.

[0029] The socket portion 43 includes a base body 431 and a PVD coating layer 433 (see FIG. 1B). A concave spherical surface is formed on the base body 431, and this concave spherical surface has the same radius of curvature Rs as the sliding surface 41a (convex spherical surface) of the ball portion 41. The material of the base body 431 is not particularly limited as long as it has rigidity that does not deform or break under the force applied to the pad 20. For example, a general-purpose shaft steel material such as high-chromium carbon steel can be used. The PVD coating layer 433 is laminated on the concave spherical surface of the base body 431. In this way, the concave spherical surface of the PVD-coated base body 431 becomes the sliding surface 43a of the socket portion 43, and the sliding surface 43a is composed of the PVD coating layer 433.

[0030] A through hole 48 is formed at the center of the socket portion 43. This through hole 48 communicates with the through hole 47 of the ball portion 41. The anchor member 42 is fitted and fixed to the pad 20. By inserting a measuring instrument into the through holes 48 and 47, the amount of movement of the pad 20 can be measured. From this amount of movement, it is possible to measure the clearance between the shaft 3 and the bearing diameter in the journal bearing 1. A solid lubricating layer (for example, a DLC coating layer) may be laminated on at least one surface of the mounting portion 41b of the ball portion 41 and the anchor member 42 that slide relative to each other. Recesses for collecting lubricating oil can be provided on the sliding surface of the ball portion 41 and / or the sliding surface of the socket portion 43.

[0031] Hereinafter, the PVD coating layers 413 and 433 will be described. In order to form a coating layer on a base body made of high-chromium carbon steel by PVD treatment, it is necessary to perform plasma cleaning on the surface to be treated (coating layer growth surface) of the base body. Therefore, when selecting the sputtering method as the PVD process, set the substrate 411 of the ball portion 41 and the substrate 431 of the socket portion 43 on the cathode of the sputtering apparatus, and cause argon particles generated by plasma to collide with their convex spherical surfaces and concave spherical surfaces. Then, set the coating material source in the sputtering apparatus and deposit the coating material on the surface to be treated. The surface to be treated in this case is the convex spherical surface of the substrate 411 of the ball portion 41 and the concave spherical surface of the substrate 431 of the socket portion 43. When adopting a method other than the sputtering method, for example, general ion plating, as the PVD process, the same procedure is followed.

[0032] When performing such a PVD process, when uniformly plasma cleaning the surface to be treated on the substrate set on the cathode or uniformly depositing the coating material, it is a prerequisite that the electric field strength on the entire surface to be treated is uniform. Here, on the convex spherical surface that becomes the surface to be treated of the substrate 411 of the ball portion 41, the electric field is likely to be uniform. Therefore, it is possible to stack a uniform coating layer by applying a general PVD process.

[0033] However, on the concave spherical surface that becomes the surface to be treated of the substrate 431 of the socket portion 43, since the electric lines of force vertically emitted from the surface interfere with each other, the electric field strength on the concave spherical surface is canceled or becomes non-uniform. In particular, the disturbance of the electric field at the bottom of the concave spherical surface is large. As a result, it may not be possible to deposit the coating material on the bottom, or even if it is deposited, the adhesion deteriorates. Therefore, there was no socket portion whose sliding surface 43a was composed of a PVD coating layer. The inventors of the present invention conducted intensive studies to give the same electric field strength as other parts even at the bottom of the concave spherical surface, and obtained the following findings. That is, if the concave spherical surface of the socket portion 43 is designed as follows, the electric field strength is stable even at the bottom of the concave spherical surface of the substrate 431 of the socket portion 43, and the PVD coating layer 433 can be uniformly laminated up to the bottom with strong adhesion to the substrate 431.

[0034] The design condition is that the value of the ratio (Ds / Rs) of the depth Ds of the concave spherical surface of the base of the socket portion 43 to its radius of curvature Rs is 0.05 to 0.70. By making the concave spherical surface shallow in this way, the interference of the electric lines of force emitted from the concave spherical surface is suppressed, the disturbance of the electric field at the bottom of the concave spherical surface is reduced, and sufficient energy can be given to the particles that collide with the bottom of the concave spherical surface.

[0035] According to the study by the inventors, by chamfering the outer periphery of the concave spherical surface under the following conditions, in combination with the above ratio value (Ds / Rs = 0.05 to 0.70), the PVD coating layer 433 constituting the sliding surface 43a becomes uniform, and it has been found that the adhesion to the base 431 is also improved. This is because by removing the edge from the outer periphery of the concave spherical surface which is the surface to be treated, the disturbance of the electric field caused by the so-called edge effect can be suppressed. That is, the value of the ratio (Rc / Rs) of the radius of curvature Rs of the concave spherical surface to the chamfer radius of curvature Rc of the chamfered outer periphery is set to 0.02 or more (see Fig. 2A). Alternatively, the value of the ratio (Dc / Rs) of the radius of curvature Rs to the depth Dc of the chamfered C surface may be set to 0.02 or more (see Fig. 2B). In this case, the chamfer angle Ac is 60 degrees or less.

[0036] When a through hole 48 is provided at the bottom of the concave spherical surface of the base 431, since the electric lines of force diffuse into the space of the through hole 48, the electric field of the concave spherical surface can be strengthened at the periphery of the opening 48c of the through hole 48. Therefore, stronger energy can be given to the particles that collide with the bottom of the concave spherical surface. It is preferable that the periphery of the opening 48c of this through hole 48 is also chamfered in the same manner as the outer periphery of the concave spherical surface (see Fig. 3). In the above description, the parameters (Rs, Rc) regarding the radius of curvature of each element are described based on the base of the socket portion without the PVD coating layer. However, in terms of the value of the ratio of the radius of curvature, the presence or absence of the PVD coating layer can be almost ignored. Therefore, in the invention of the ball socket structure, the same value of parameters is also used to describe the socket portion provided with the PVD coating layer.

Example

[0037] Hereinafter, examples and comparative examples of the present invention will be described. The substrates of the ball part 41 and the socket part 43 in the examples and comparative examples were formed by cutting from a bulk of high chromium carbon steel. In the examples and comparative examples, the specifications of the ball part 41 and the socket part 43 were as follows. Thickness of the central part of the ball part 41: Tb = 6 to 30 mm Thickness of the central part of the socket part 43: Ts = 5 to 10 mm Thickness of the PVD coating layer 433: 0.1 to 10 μm Depth Ds of the sliding surface 43a formed by the concave spherical surface of the socket part 43: 5 to 25 mm Radius of curvature Rs of the sliding surface 43a: 10 to 45 mm Chamfering radius of curvature Rc of the outer periphery of the sliding surface 43a = 1 to 5 mm (depth Dc is the same) The thickness of the PVD coating layer 413 of the ball part 41 was the same as that of the socket part 43.

[0038] In the examples and comparative examples, substrates were created by changing the specifications of the above elements, and a PVD coating layer was laminated thereon. The conditions for plasma cleaning of the concave spherical surface of the substrate 411 were as follows. Bias voltage: 500 V, pressure: 0.2 Pa, gas: Ar, time: 40 minutes. After cleaning, a Cr layer was deposited as a primer layer on the entire surface of the concave spherical surface under the following conditions. Target Cr, output: 1.8 kw, bias voltage: 100 V, pressure: 0.5 Pa, gas: Ar, time: 23 minutes. A coating layer was deposited on the primer layer by sputtering under the following conditions. For DLC, target: graphite, output: 2.8 kw, bias voltage: 100 V, pressure: 0.5 Pa, gas: Ar:CH4 = 1:1, time: 300 minutes. Regarding CrN, target: Cr, output: 1.8 kw, bias voltage: 100 V, pressure: 0.5 Pa, gas: Ar:N2 = 1:1, time: 300 minutes.

[0039] In the ball portion 41 of the ball socket structure of the examples and comparative examples, the pad 20 was connected to form the tilting pad bearing 40 of FIG. 4. The material of the pad 20 is a bimetal material such as white metal, PEEK, PTFE (specifically, a bimetal using white metal, PEEK, PTFE, etc. as the sliding layer and steel, etc. as the backing metal). The journal bearing 1 shown in FIGS. 5 and 6 provided with such a tilting pad bearing 40 was configured. The diameter of the shaft 3 is 170 mm. The housing 11 of such a journal bearing 1 was fixed, and the shaft 3 was rotated under the conditions of 8000 rpm and a bearing surface pressure of 3 MPa. The conditions and results of the examples and comparative examples are shown in Table 1.

[0040]

Table 1

[0041] In Table 1, the friction coefficient was calculated from the eccentricity of the shaft center. The peeling rate (%) is the ratio of the area where the PVD coating layer has peeled off on the sliding surface 43a of the socket portion 43 after the shaft 3 has been rotated for 2 hours. This peeling rate is obtained by photographing the sliding surface 43a planarly and processing the obtained image.

[0042] From the comparison results of the friction coefficients and peeling rates between Examples 1 and 2 and Comparative Examples 1 and 2 in Table 1, it can be seen that the value of the ratio (Ds / Rs) of the depth Ds of the sliding surface, which is the concave spherical surface of the socket portion, to the radius of curvature Rs of the sliding surface is preferably 0.05 to 0.70. From the comparison results of the friction coefficients and peeling rates between Example 4 and Example 5, it can be seen that it is preferable to chamfer the outer periphery of the sliding surface of the socket portion and make the value of the ratio (Rc / Rs or Dc / Rs) of the chamfer radius of curvature Rc to the radius of curvature Rs of the sliding surface 0.02 or more.

[0043] From the comparison results of the friction coefficients and peeling rates between Examples 1 and 2 and Examples 3 and 4, it can be seen that the thickness (%) of the PVD coating layer at the center of the socket portion is preferably 0.0010 to 0.3000. From the comparison results of the friction coefficients between Example 6 and Examples 7 to 9, it can be seen that the thickness (%) of the PVD coating layer at the center of the ball portion is preferably 0.0010 to 0.3000.

[0044] The present invention is not limited to the descriptions of the embodiments and examples of the above invention. Various modifications are also included in the present invention within the scope that those skilled in the art can easily conceive without departing from the description of the claims.

Explanation of Reference Numerals

[0045] 1 Journal bearing 3 Shaft 20 Pad 40 Tilt pad bearing 41 Ball portion 41a Sliding surface of the ball portion 43 Socket portion 43a Sliding surface of the socket portion 47 Through hole 48 Through hole 48c Opening 411 Substrate 413 PVD coating layer 431 Substrate 433 Coating layer 433 PVD coating layer

Claims

1. A ball socket structure comprising a ball part and a socket part that slide relative to each other, wherein the sliding surface of the socket part is composed of a PVD coating layer, the sliding surface of the socket part is a concave spherical surface, and the value of the ratio (Ds / Rs) of the depth Ds of the sliding surface to its radius of curvature Rs is 0.05 to 0.70, and the outer periphery of the sliding surface of the socket part is chamfered to an R surface with the edge removed, a ball socket structure.

2. A ball socket structure comprising a ball part and a socket part that slide relative to each other, wherein the sliding surface of the socket part is composed of a PVD coating layer, the sliding surface of the socket part is a concave spherical surface, and the value of the ratio (Ds / Rs) of the depth Ds of the sliding surface to its radius of curvature Rs is 0.05 to 0.70, the outer periphery of the sliding surface of the socket part is chamfered, and the value of the ratio (Rc / Rs) of the radius of curvature Rs of the sliding surface to the chamfer radius of curvature Rc of the chamfered outer periphery or the value of the ratio (Dc / Rs) of the radius of curvature Rs to the depth Dc of the chamfered C surface is 0.02 or more, a ball socket structure.

3. A ball socket structure comprising a ball part and a socket part that slide relative to each other, wherein the sliding surface of the socket part is composed of a PVD coating layer, the sliding surface of the socket part is a concave spherical surface, and the value of the ratio (Ds / Rs) of the depth Ds of the sliding surface to its radius of curvature Rs is 0.05 to 0.70, a through hole is formed in the central portion of the socket part, and the periphery of the opening of the through hole is chamfered, a ball socket structure.

4. A ball socket structure comprising a ball part and a socket part that slide relative to each other, wherein the sliding surface of the socket part is composed of a PVD coating layer, the sliding surface of the socket part is a concave spherical surface, and the value of the ratio (Ds / Rs) of the depth Ds of the sliding surface to its radius of curvature Rs is 0.05 to 0.70, a through hole is formed as a cavity in the central portion of the socket part, and the periphery of the opening of the through hole is chamfered, a ball socket structure.

5. The ball socket structure according to any one of Claims 1 to 4, wherein the PVD coating layer is made of diamond-like carbon.

6. The ball socket structure according to any one of Claims 1 to 5, wherein the thickness of the PVD coating layer occupies 0.0010 to 0.3000% of the wall thickness Ts of the central portion of the socket part.

7. The sliding surface of the ball part is composed of a PVD coating layer, The ball socket structure according to any one of claims 1 to 6, wherein the thickness of the PVD coating layer occupies 0.0010 to 0.3000% with respect to the wall thickness Tb of the central part of the ball part.

8. A method for manufacturing the socket part of a ball socket structure including a ball part and a socket part that slide relative to each other, A preparation step of preparing a metal socket part substrate having a concave spherical surface serving as a sliding surface, wherein the value of the ratio (Ds / Rs) of the depth Ds of the concave spherical surface to its radius of curvature Rs is 0.05 to 0.70, the outer periphery of the sliding surface of the socket part is chamfered, and the value of the ratio (Rc / Rs) of the radius of curvature Rs of the sliding surface to the chamfered radius of curvature Rc of the chamfered outer periphery or the value of the ratio (Dc / Rs) of the radius of curvature Rs to the depth Dc of the chamfered C surface is 0.02 or more; A first pretreatment step of plasma cleaning the concave spherical surface of the substrate; A second pretreatment step of laminating a primer layer on the plasma-cleaned concave spherical surface by PVD treatment; A manufacturing method of the socket part, comprising a laminating step of laminating diamond-like carbon on the primer layer by PVD treatment.

9. A method for manufacturing the socket part of a ball socket structure including a ball part and a socket part that slide relative to each other, A preparation step of preparing a metal socket part substrate having a concave spherical surface serving as a sliding surface, wherein the value of the ratio (Ds / Rs) of the depth Ds of the concave spherical surface to its radius of curvature Rs is 0.05 to 0.70, and the substrate is provided with a through hole having a chamfered peripheral edge at the center of the concave spherical surface; A first pretreatment step of plasma cleaning the concave spherical surface of the substrate; A second pretreatment step of laminating a primer layer on the plasma-cleaned concave spherical surface by PVD treatment; A manufacturing method of the socket part, comprising a laminating step of laminating diamond-like carbon on the primer layer by PVD treatment.

10. The manufacturing method according to claim 8 or 9, wherein in the laminating step, the thickness of the diamond-like carbon layer is 0.0010 to 0.3000% with respect to the wall thickness Ts of the central part of the socket part.

11. A step of preparing a socket part manufactured by the manufacturing method according to any one of claims 8 to 10; A step of preparing a ball part; A manufacturing method of a ball socket structure comprising an assembling step of assembling the ball part and the socket part.

12. A tilting pad bearing comprising the ball socket structure according to any one of Claims 1 to 7.

13. A journal bearing comprising the tilting pad bearing according to Claim 12.

14. A thrust bearing comprising the tilting pad bearing according to Claim 12.

15. A manufacturing method of the socket part of a ball socket structure comprising a ball part and a socket part that slide relative to each other, a preparation step of preparing a metal base body of the socket part, the base body having a concave spherical surface serving as a sliding surface, a value of a ratio (Ds / Rs) of a depth Ds of the concave spherical surface to its radius of curvature Rs being 0.05 to 0.70, an outer periphery of the sliding surface of the socket part being chamfered, and a value of a ratio (Rc / Rs) of the radius of curvature Rs of the sliding surface to a chamfer radius of curvature Rc of the chamfered outer periphery or a value of a ratio (Dc / Rs) of the radius of curvature Rs to a depth Dc of a chamfered C surface being 0.02 or more; a lamination step of performing PVD treatment on the concave spherical surface to laminate a solid sliding layer. A manufacturing method of the socket part comprising the above steps.

16. A manufacturing method of the socket part of a ball socket structure comprising a ball part and a socket part that slide relative to each other, a preparation step of preparing a metal base body of the socket part, the base body having a concave spherical surface serving as a sliding surface, a value of a ratio (Ds / Rs) of a depth Ds of the concave spherical surface to its radius of curvature Rs being 0.05 to 0.70, and having a through hole with a chamfered peripheral edge of its opening at a central portion of the concave spherical surface; a lamination step of performing PVD treatment on the concave spherical surface to laminate a solid sliding layer. A manufacturing method of the socket part comprising the above steps.

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