JP7111470B2 - Half thrust bearings, thrust bearings, bearing devices and internal combustion engines - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-annular half-split thrust bearing for receiving the axial force of a crankshaft in internal combustion engines such as automobiles, ships, and general industrial machinery. The present invention relates to a half-split thrust bearing having a sliding surface and a back surface on the opposite side of the sliding surface, wherein a soft metal coating layer coated on a substrate forms the sliding surface. Furthermore, the present invention also relates to a thrust bearing comprising this half thrust bearing, a bearing device comprising this thrust bearing, and an internal combustion engine comprising this bearing device.

A crankshaft of an internal combustion engine is rotatably supported in a lower portion of a cylinder block of the internal combustion engine via a main bearing formed by combining a pair of half bearings in a cylindrical shape at a journal portion. One or both of the pair of half bearings are used in combination with a half thrust bearing that receives the axial force of the crankshaft. The half thrust bearing is arranged on one or both of the axial end faces of the half bearing. The half thrust bearing receives the axial forces that occur on the crankshaft. That is, it is arranged for the purpose of supporting the axial force that is input to the crankshaft when the crankshaft and the transmission are connected by the clutch.

As a half-split thrust bearing, a bimetal is used in which a thin bearing alloy layer is adhered to a backing metal layer made of steel or the like, but it is also well known that a soft metal layer is further coated thereon (Patent Document 1, etc.). By coating the bearing alloy with a soft metal layer with high corrosion resistance, it is possible to prevent corrosion of the bearing alloy and suppress seizure and wear.

JP 2013-72449 A

In recent years, the performance and functions of engines have been improved. Along with this, the rigidity of mating members such as shafts has been reduced, and there has been a demand for higher surface pressure of bearings. Such conditions are severe operating environments for bearings. In particular, it is desired to have excellent anti-seizure performance due to the application of idling stop and hybrid vehicles.

In such a bearing, during operation, a fluid lubricating film such as lubricating oil is formed between the surface of a mating member (for example, a shaft member) and the sliding surface of the sliding member, thereby preventing sliding on the surface of the mating member. Direct contact with the sliding surface of the member is prevented. The soft metal coating layer applied to thrust bearings by conventional technology has a uniform layer thickness, but the oil film pressure is insufficient, resulting in insufficient bearing capacity, which can lead to seizure under the above operating environment. have a nature. In order to prevent seizure, it is necessary to form an oil film on the entire sliding surface, but the above-mentioned prior art is insufficient to achieve excellent anti-seizure performance in a severe engine environment.

SUMMARY OF THE INVENTION An object of the present invention is to provide a half thrust bearing, and thus a thrust bearing, which has excellent anti-seizure performance by promoting the formation of an excellent oil film. A further object of the present invention is to provide a bearing device and an internal combustion engine equipped with this thrust bearing.

According to one aspect of the present invention, a soft body having a semi-annular shape and having a sliding surface for receiving an axial force and a back surface opposite to the sliding surface is coated on a substrate. A half thrust bearing is provided in which a metallized layer forms a sliding surface. This half thrust bearing is characterized in that the thickness of the soft metal coating layer is maximum at the circumferential central portion of the half thrust bearing and decreases toward both circumferential ends of the half thrust bearing. .
Here, the term "semi-circular shape" means a shape whose inner circumference and outer circumference are defined by two semicircles, but these are not necessarily geometrically strictly semicircular. For example, a portion of the outer or inner surface may project radially (e.g., at the circumferential edge), and there may be an extension from the circumferential edge (e.g., perpendicular to the circumferential edge).

According to one embodiment of the invention, it is preferred that the circumferential central portion lies at a circumferential angle of between 75° and 105°.

According to a specific example of the present invention, when the half thrust bearing is viewed along the circumferential end surface of the half thrust bearing, the sliding surface of the half thrust bearing has a convex shape that protrudes at the center in the circumferential direction. It preferably has contours.

According to one embodiment of the invention, the profile of the sliding surface preferably consists of curvilinear lines.

According to one embodiment of the invention, the profile of the sliding surface preferably consists of straight lines.
Also, according to an embodiment of the present invention, the contour of the sliding surface may consist of curved lines and straight lines.

According to one embodiment of the present invention, the thickness of the soft metal coating layer is preferably defined by the following formula with respect to the circumference angle.
t(θ)/t _max ×100=A×exp[−{(θ−B)/C} ² ]+D (1)
where t(θ) is the thickness of the soft metal coating layer at the circumference angle θ, t _max is the maximum thickness of the soft metal coating layer, and B is the thickness of the soft metal coating layer. is the maximum circumferential angle (°), and A, C, and D are constants satisfying 10≦C≦100 and 30≦D≦95, where A=100−D.

According to a specific example of the present invention, the position where the slope of the curve of the thickness of the soft metal coating layer defined by the formula (1) with respect to the circumferential angle is maximum is 15° to 65° away from the position B. It is preferred that they are positioned, and more preferred that they are separated by 20° to 60°.

According to one embodiment of the present invention, the maximum slope of the tangent of the curve to the circumference angle of t(θ)/t _max ×100 defined by formula (1) is 0.10 to 1.20. is preferred, and 0.15 to 0.90 is more preferred.

According to another aspect of the present invention, the present invention is a thrust bearing comprising two half thrust bearings, wherein at least one of the two half thrust bearings is the above half thrust bearing of the present invention. A bearing, a thrust bearing, is provided.

According to one embodiment of the invention, the half thrust bearing is preferably a half thrust bearing for receiving axial forces of a crankshaft of an internal combustion engine.

According to still another aspect of the present invention, the present invention also provides a bearing device comprising the above-described half thrust bearing of the present invention.

According to still another aspect of the present invention, the present invention also provides an internal combustion engine equipped with the above bearing device of the present invention.

The half thrust bearing coated with the soft metal coating of the present invention promotes the formation of an oil film by controlling the thickness distribution of the soft metal coating layer in the circumferential direction, thereby improving the anti-seizure performance without impairing the corrosion resistance. can be made

The configuration of the invention and its many advantages are described in more detail below with reference to the accompanying schematic drawings. The drawings show, for illustrative purposes, some non-limiting examples.

FIG. 2 is an exploded perspective view of the bearing device; Sectional drawing of a bearing device. 1 is a front view of an example of a half thrust bearing of the present invention; FIG. Y1 arrow side view of the half thrust bearing of FIG. FIG. 2 is an exploded view of a cross section of an example of the half thrust bearing of the present invention cut in the circumferential direction at the center portion in the radial direction; FIG. 4 is a developed view of a cross section of another example of the half thrust bearing of the present invention, cut in the circumferential direction at the center portion in the radial direction; FIG. 10 is a development view of a cross section of still another example of the half thrust bearing of the present invention, cut in the circumferential direction at the center portion in the radial direction; FIG. 10 is a development view of a cross section of still another example of the half thrust bearing of the present invention, cut in the circumferential direction at the center portion in the radial direction; FIG. 10 is a development view of a cross section of still another example of the half thrust bearing of the present invention, cut in the circumferential direction at the center portion in the radial direction; FIG. 2 is a schematic diagram showing an example of a plating apparatus used for forming the soft metal coating layer of the half thrust bearing of the present invention; FIG. 11 is a schematic diagram showing the positional relationship between a cathode (substrate), an anode and a slit plate in the plating apparatus of FIG. 10; FIG. 11 is a diagram showing the principle of thickness control of the soft metal coating layer by the plating apparatus of FIG. 10;

First, the overall configuration of an example of a bearing device 1 having a half thrust bearing 8 of the present invention will be described with reference to FIGS. 1 and 2. FIG. As shown in FIGS. 1 and 2, a bearing housing 4 configured by attaching a bearing cap 3 to a lower portion of a cylinder block 2 is formed with a bearing hole (holding hole) 5 which is a circular hole penetrating between both side surfaces. Circular recessed seats 6, 6 are formed on the peripheral edge of the bearing hole 5 on the side surface. Into the bearing hole 5, half bearings 7, 7 for rotatably supporting a journal portion 11 of the crankshaft are fitted together in a cylindrical shape. Half thrust bearings 8, 8 which receive an axial force f (see FIG. 2) via a thrust collar surface 12 of the crankshaft are fitted to the seats 6, 6 in an annular manner. The half thrust bearings 8 may be fitted only on the cylinder block 2 side, for example, without being combined in an annular shape.

Next, FIGS. 3 and 4 show a front view and a perspective view of an example of the half thrust bearing 8 of the present invention. The half thrust bearing 8 has a soft metal coating layer 88 on a substrate 89 formed in a semi-annular flat plate. Substrate 89 is generally preferably constructed of a bimetal with a thin layer of bearing alloy adhered to a steel backing layer, but may be of a backing-only construction or of other constructions. The half thrust bearing 8 has a sliding surface 81 (bearing surface) facing in the axial direction, and the sliding surface 81 is composed of a soft metal coating layer. The sliding surface 81 is formed with at least one oil groove 81a (two oil grooves are shown in FIG. 3) between both circumferential end surfaces 83, 83 in order to improve the lubricating oil retention. may be

The half thrust bearing 8 defines an axially vertical reference plane 84 in which a substantially flat back surface 84 a adapted to be placed on the seat 6 of the cylinder block 2 . (see FIG. 4). The back surface 84 a is also the bottom surface of the substrate 89 . The substrate 89 has a top surface 82 axially opposite from a reference surface 84 (back surface 84a), and a soft metal coating layer 88 is coated on the top surface of the substrate. The surface of the soft metal coating layer 88 forms a sliding surface 81 axially spaced from the reference surface 84 (back surface 84a), and the sliding surface 81 receives the axial force f (See FIG. 2).

FIG. 5 is a developed cross-sectional view of the half thrust bearing 8 cut at a predetermined radius. Both lateral ends of the half thrust bearing 8 shown in FIG. Both end faces 83 (circumferential angles of 0° and 180°) and the lateral center of the half thrust bearing 8 shown in FIG. . The circumferential angle refers to the angle from both circumferential direction end faces 83 centering on the center of the annular shape of the half thrust bearing 8 . In this specification, the rear end face in the sliding direction (indicated by arrow SD in FIG. 3) of the crankshaft is taken as 0°, and the front end face in the sliding direction is taken as 180° (see FIG. 3). (However, even if the sliding direction front side end surface is set to 0°, the scope of the present invention is not affected.)

FIG. 5 shows soft metallization layer 88 on substrate 89 . The thickness of the soft metal coating layer 88 is maximum at the circumferential central portion 86 of the half thrust bearing and decreases toward the circumferential end portions 83 of the half thrust bearing. It should be noted that the circumferential central portion 86 does not have to be positioned strictly at the circumferential central portion 85 (circumferential angle of 90°), and the thickness distribution of the soft metal coating layer 88 seen in the sliding direction as a whole should be convex. just show it. A preferred circumferential central portion 86 is at a circumferential angle of 75° to 105°.
The soft metal coating layer preferably has a maximum thickness of about 2 to 30 μm and a minimum thickness of about 1 to 28 μm. When the maximum and minimum thicknesses are within this range, early exposure of the substrate and deterioration of fatigue resistance due to abrasion of the soft metal coating layer can be prevented, thereby further improving seizure resistance.

Controlling the distribution shape in this manner facilitates the formation of an oil film of the lubricating oil, improving the anti-seizure performance without impairing the corrosion resistance. This mechanism is as follows.
The soft metal undergoes elastic deformation under low load and plastic deformation under high load, which causes stretching (expansion and contraction). Therefore, the soft metal coating layer exhibits stretching mainly in the central part in the circumferential direction where the thickness is large. As a result, an oil film pressure is generated due to the flow distribution of the lubricating oil, which promotes the formation of an excellent oil film over the entire thrust bearing surface, thereby improving seizure resistance.

Furthermore, the thickness distribution of the soft metal coating layer 88 in the circumferential direction preferably has a distribution defined by the following formula with respect to the circumferential angle.
t(θ)/t _max ×100=A×exp[−{(θ−B)/C} ² ]+D (1)
where t(θ) is the value of the thickness of the soft metal coating layer 88 at the circumferential angle θ, t _max is the maximum thickness of the soft metal coating layer, and B is the thickness of the soft metal coating layer. is the value of the circumferential angle (°) at which the is the maximum, and A, C, and D are constants satisfying 10≦C≦100 and 30≦D≦95, where A=100−D.

(1) The position where the slope of the tangent of the curve with respect to the circumferential angle of the thickness of the soft metal coating layer 88 defined by the formula is maximum is 15° to 65° away from the B position (circumferential center portion 86) It is preferably at the B position, and more preferably at a distance of 20° to 60° from the B position. In addition, the maximum slope of the tangent line of the curve with respect to the circumference angle of t (θ) / t _max × 100 defined by the formula (1) is preferably 0.10 to 1.20, and the maximum slope of the tangent line is , 0.15 to 0.90. Satisfying these conditions facilitates the formation of an oil film and further improves the anti-seizure performance.

It is preferable that the circumferential thickness distribution of the soft metal coating layer 88 is established at any radial position. However, it suffices if this thickness distribution is established at the radial position in the center in the radial direction. Even in this case, oil film formation is facilitated. Note that even if the circumferential thickness distribution of the soft metal coating layer 88 is established at any radial position, the circumferential angles of the circumferential central portion 86 do not need to match. However, it is preferable that the circumferential angle of the circumferential central portion 86 is 75° to 105° at any radial position.

The thickness distribution in the circumferential direction of the soft metal coating layer 88 is the overall distribution, and small irregularities exist when viewed locally, but such local irregularities may exist.

The upper surface 82 of the substrate 89 of the half thrust bearing 8 is preferably flat as shown in FIG. In this case, the thickness distribution of the soft metal coating layer 88 becomes the contour shape of the sliding surface 81 . In this case, it is preferable that the height difference between the circumferential central portion and the circumferential end portion of the contour shape of the sliding surface 81 is about 1 to 17 μm.
However, the top surface 82 of the substrate 89 need not be flat. For example, as shown in FIG. 6, the central part in the circumferential direction may be raised, or it may be lowered toward the central part in the circumferential direction as shown in FIGS. 8 and 9, or other shapes may be used. In this case, the contour shape of the sliding surface 81 may be raised at the center (FIG. 6), flat (FIG. 8), lowered at the center (FIG. 9), or may have other shapes.
A thrust relief 87 may be formed in any shape (FIG. 7). The thrust relief 87 is a wall thickness decreasing region formed in a region adjacent to both circumferential end faces on the side of the sliding surface 81 such that the wall thickness gradually decreases toward the end face. It extends over the entire radial length of the circumferential end face. The thrust relief 87 is designed to prevent misalignment between the circumferential end surfaces 83, 83 of the pair of half thrust bearings 8, 8 due to misalignment when the half thrust bearing 8 is assembled in the split bearing housing 4, or the like. formed to alleviate

Further, in the half thrust bearing 8 of the present invention, the axial distance from the reference surface 84 to the sliding surface 81 is equal to the circumferential center of the half thrust bearing 8 at any radial position of the half thrust bearing 8 . It is preferably formed to be maximum at portion 86 and to become smaller toward circumferentially opposite ends 83 of the half thrust bearing. That is, when the half thrust bearing 8 is viewed along the circumferential direction of the half thrust bearing 8, the sliding surface 81 of the half thrust bearing 8 has a protruding contour at the center in the circumferential direction. The contour of the sliding surface 81 may be composed of curved lines or straight lines.

When the upper surface 82 of the substrate 89 of the half thrust bearing 8 is a flat surface, the contour of this sliding surface 81 is determined by the thickness distribution of the soft metal coating layer 88, and the maximum thickness of the soft metal coating layer 88 is determined by the thickness distribution of the soft metal coating layer 88. The sliding surface 81 protrudes at the point. During operation of the internal combustion engine, due to the protruding profile at the circumferential center portion, oil film pressure is generated due to the wedge film action around the circumferential center portion as the mating shaft member rotates. Furthermore, together with the generation of oil film pressure due to the stretching action of the soft metal coating layer described above, it is possible to promote the formation of an excellent oil film on the entire thrust bearing surface, thereby improving the seizure resistance and suppressing wear.
Even if the upper surface 82 of the substrate 89 of the half thrust bearing 8 is not flat and the maximum protrusion of the contour of the sliding surface 81 does not coincide with the maximum thickness of the soft metal coating layer 88, Since the maximum protrusion of the outline of the sliding surface 81 and the maximum thickness of the soft metal coating layer 88 are located close to the center 85 in the circumferential direction, the same effect as described above can be obtained.

The soft metal that forms the soft metal coating layer 88 is made of a pure metal selected from soft metals such as Pb, Sn, Bi, In, Ag, Al, Cu, Sn, Mg, or an alloy thereof, and is harder than the base metal. forming a metal layer with a small thickness. Elements such as Ni, Cr, Ti, and Zr may be contained as long as the hardness of the soft metal coating layer 88 is lower than that of the underlying metal.
Furthermore, the soft metal coating layer may contain hard particles in addition to the soft metal. The hard particles include, for example, one or more selected from oxides such as aluminum oxide and iron oxide, nitrides such as aluminum nitride and silicon nitride, carbides such as molybdenum carbide and silicon carbide, and diamond, which are preferable. The hard particle content is between 0.1 and 10% by volume. By containing these hard particles, it becomes possible to improve the wear resistance of the sliding layer.

As described above, the substrate 89 of the half thrust bearing 8 preferably has a backing metal layer and a bearing alloy layer provided on the backing metal layer. A metal plate such as an Fe alloy, Cu, or a Cu alloy can be used as the back metal layer, and the bearing alloy layer can be formed from an alloy such as a copper alloy, an aluminum alloy, or a tin alloy. It is also possible to use only a high-strength bearing alloy layer such as an aluminum alloy or a copper alloy without the back metal layer.

The soft metal coating layer 88 is preferably formed by electroplating, PVD, CVD vapor deposition, thermal spraying, or the like. An example method of forming the soft metallization layer 88 on the substrate 89 is described below.

FIG. 10 shows an example of a plating apparatus 90 used for forming the soft metal coating layer of the half thrust bearing of the present invention. An anode 93 and a cathode 95 are placed facing each other in a plating solution 94 , and a substrate 89 on which a soft metal coating layer is to be formed on one surface is attached to the cathode 95 . Between an anode 93 and a cathode 95 a slit plate 91 made of insulating material with slits 92 is arranged. FIG. 11 shows the positional relationship of the substrate 89 on the cathode 95, the anode 93, and the slit plate 91. As shown in FIG. In FIG. 11, the slit 92 has a single elongated shape, but other shapes of the slit 92 can be used to obtain the desired coating layer distribution. Normally, the plating thickness is determined by the current value and the plating time. It becomes possible to change the plating thickness at each position of . By appropriately selecting these parameters, the layer thickness distribution over the entire sliding surface can be controlled.

FIG. 12 shows the principle of thickness control of the soft metal coating layer by the plating apparatus 1. As shown in FIG. When a voltage is applied by connecting a power supply 96 between the anode 93 and the cathode 95, current flows from the anode 93 to the cathode 95, and metal ions 97 move toward the cathode. Since the insulating slit plate 91 is arranged between the anode 93 and the cathode 95 , the current is blocked by the slit plate 91 and flows through the slit 92 toward the cathode 95 . Since the size of the current density 99 is governed by the moving distance from the substrate 95 to the anode 93 , the current density is distributed according to the positional relationship between the substrate 89 and the slit 92 . The plating becomes thicker where the current density is high, and conversely, the plating becomes thinner where the current density is low. In the case shown in FIG. 12, the thickness of the central portion of the substrate 89 facing the slit 92 is large, and the thickness of the edge portion is small. Therefore, the film thickness distribution can be controlled by controlling the slit width and slit position.
The thickness control of the soft metal coating layer using this slit can also be applied to PVD, CVD, and the like.

A flat semicircular substrate (outer diameter 75 mm, inner diameter 55 mm, thickness 1.5 mm) was prepared by adhering a copper alloy (Cu—Zn) bearing alloy layer on a steel backing. A Pb—Sn alloy was used as the soft metal. Pb—Sn alloy is plated using the plating apparatus described with reference to FIGS. A soft metal coating layer with a smaller thickness was formed (this shape is hereinafter referred to as a convex portion). A sample A of the half thrust bearing having such protrusions and a sample B having a soft metal coating layer with a substantially uniform thickness (no protrusions) were prepared. The thickness of the soft metal coating layer of Sample A was 10 μm (circumferential angle of 70°) at the central portion in the circumferential direction and 6 μm at the end portions in the circumferential direction. The thickness of the soft metal coating layer of sample B was set to approximately uniform 10 μm. The thickness of the soft metal coating layer was measured by cutting out a sample at each circumferential angle in the center in the radial direction and observing the cross section with an optical microscope.

A seizure test was conducted using the samples A and B under the conditions shown in Table 2. S55C was used as the mating shaft material, and the load was increased at a rate of 1 MPa/10 min while rotating the mating shaft material at 1500 rpm. VG22 was supplied as a lubricating oil at 100° C. at a rate of 200 cc/min. As shown in Table 1, the test results were as follows: sample B, which had a soft metal coating layer with a substantially uniform thickness, had a non-seizure surface pressure of 4 MPa; The non-seizure surface pressure was 5 MPa, and the result was that the seizure resistance was improved by having the convex portion in the center in the circumferential direction.

Next, in order to investigate the effect on seizure resistance of the position where the thickness of the soft metal coating layer of the half thrust bearing is maximum (hereinafter referred to as the position of the convex portion), the shape, material, and manufacturing method were the same as that of sample A. Samples 1 to 7 were prepared by changing only the position of the convex portion from 70° to 110° in circumferential angle while keeping the same. These samples were subjected to the seizure test under the above conditions. Table 3 shows the results. The non-seizure surface pressure was 6 MPa for the samples where the projections were positioned at a circumferential angle of 75° to 105°. 5 MPa. It is considered that this is because the formation of the oil film is facilitated by having the convex portions at the circumferential angle of 75° to 105°, and the anti-seizure surface pressure is improved.

Next, the distribution of the thickness of the soft metal coating layer with respect to the circumferential angle was varied while the position of the convex portion was fixed at 90°. Equation (1) expresses this distribution
t(θ)/t _max ×100=A×exp[−{(θ−B)/C} ² ]+D (1)
The distribution was assumed to follow t(θ) is the thickness of the soft metal coating layer at the position of the circumferential angle θ, and t _max is the thickness of the soft metal coating layer at the convex position, which is set to 10 μm. B is the circumferential angle of 90° at the convex position. At the convex position θ=B, t(θ)= _tmax , so A+D=100, and if D is determined, A is also determined.
Therefore, the effects on seizure resistance were investigated by changing the values of C and D. Table 4 shows the changed C and D and the non-seizure surface pressure.

From the results in Table 4, Samples 11-14 had a higher non-seizure surface pressure than Samples 15-18. From this, it was found that the seizure resistance is improved when the parameters C and D in the formula (1) satisfy 10≤C≤100 and 30≤D≤95. Even if either one of C and D was out of this range, the non-seizure surface pressure was reduced.
Next, the parameters C and D were further varied within this range, and the relationship between the circumferential angle of the maximum tilt position and the seizure resistance in that case was investigated. Table 5 shows the results.

From the results in Table 5, Samples 22 to 26 obtained higher non-seizure surface pressure than Samples 21 and 27, and Samples 23 to 25 obtained even higher non-seizure surface pressure. As a result, among parameters C and D in formula (1) satisfying 10≦C≦100 and 30≦D≦95, the circumferential angle at the maximum tilt position is 15° to 15° from the circumferential angle at the projection position. It was found that the seizure resistance was improved at a position separated by 65°, and the seizure resistance was further improved at a position separated by 20° to 60°.
Then, the tangent to the curve A×exp[−{(θ−B)/C} ² ]+D (ie, t(θ)/t _max ×100) represented by equation (1) at its maximum tilt position The relationship between the value of the slope (maximum slope) and seizure resistance was investigated. Table 6 shows the results.

From the results in Table 6, Samples 32 to 41 obtained higher non-seizure surface pressure than Samples 31 and 42, and Samples 33 to 37 obtained even higher non-seizure surface pressure. From this, it was found that the seizure resistance is improved when the maximum slope value is 0.10 to 1.20, and the seizure resistance is further improved when the maximum slope value is 0.15 to 0.90.

Furthermore, in order to investigate the effect of the thickness of the soft metal coating layer on the seizure resistance, a convex portion was provided at a circumferential angle of 90°, satisfying 10 ≤ C ≤ 100 and 30 ≤ D ≤ 95, and the maximum inclination The thickness of the soft metal coating layer when the circumferential angle of the position is 20° to 60° away from the circumferential angle of the convex position and the maximum inclination value is adjusted to 0.15 to 0.90 were changed as shown in Table 7 to prepare samples 43 to 47. That is, the thickness of the soft metal coating layer at the positions of the convex portions was varied from 2 to 30 μm, and the minimum thickness of the soft metal coating layer was varied from 1 to 28 μm. However, as shown in Table 7, the non-seizure surface pressure was 13 MPa for all samples, and constant results were obtained regardless of the thickness of the soft metal coating layer. Therefore, it was found that if the above requirements are set, excellent seizure resistance can be obtained regardless of the absolute thickness of the soft metal coating layer.

Reference Signs List 1 bearing device 11 journal portion 12 thrust collar surface 2 cylinder block 3 bearing cap 4 bearing housing 5 bearing hole (holding hole)
6 receiving seat 7 half bearing 8 half thrust bearing 81 sliding surface 81a oil groove 82 upper surface of substrate 83 both circumferential direction end surfaces 84 reference surface 84a rear surface 85 circumferential center 86 circumferential center portion 87 thrust relief 88 soft metal coating layer 89 Substrate f Axial force SD Sliding direction 90 Plating device 91 Slit plate 92 Slit 93 Anode 94 Plating solution 95 Cathode 96 Power source 97 Metal ion 98 Current density vector

Claims (12)

A semi-annular half-split thrust bearing having a sliding surface for receiving an axial force and a rear surface opposite to the sliding surface, and a soft metal coating layer coated on a substrate. In the half thrust bearing forming the sliding surface,
The soft metal coating layer has a maximum thickness at a circumferential central portion of the half thrust bearing and decreases toward both circumferential ends of the half thrust bearing. is defined by the following formula for the circumference angle,
t(θ)/t _max ×100=A×exp[−{(θ−B)/C} ² ]+D (1)
where t(θ) is the thickness value of the soft metal coating layer at the circumference angle θ, t _max is the maximum thickness of the soft metal coating layer, and B is the soft metal coating layer is the value of the circumferential angle (°) at which the thickness of the
The center portion in the circumferential direction is positioned at a circumferential angle of 75° to 105°, and the height difference between the center portion in the circumferential direction and the end portions in the circumferential direction of the contour shape of the sliding surface is in the range of 1 to 17 μm. A half thrust bearing characterized by: 2. The half thrust bearing according to claim 1, wherein the soft metal coating layer has a maximum thickness of 2 to 30 μm . When the half thrust bearing is viewed along the circumferential direction of the half thrust bearing, the sliding surface of the half thrust bearing has a protruding convex contour at the center portion in the circumferential direction. 3. A half thrust bearing according to claim 1 or 2, characterized in that: 4. A half thrust bearing according to claim 3, wherein said profile of said sliding surface consists of curved lines. The position where the slope of the tangent line of the curve with respect to the circumferential angle of the thickness of the soft metal coating layer defined by the formula (1) is maximum is located at a distance of 15° to 65° from the position B. A half thrust bearing according to any one of claims 1 to 4 , wherein 6. The half thrust bearing according to claim 5 , wherein the position where the slope of the tangent line of the curve is maximum is at a position separated from position B by 20° to 60°. Claims 1 to 1, characterized in that the maximum slope of the tangent line of the curve with respect to the circumference angle of t(θ)/t _max ×100 defined by the formula (1) is 0.10 to 1.20. A half thrust bearing according to any one of items up to item 6 . 8. The half thrust bearing according to claim 7 , wherein the maximum inclination of said tangent line is 0.15 to 0.90. A thrust bearing comprising two half thrust bearings, wherein at least one of the two half thrust bearings is a half thrust bearing according to any one of claims 1 to 8 . A thrust bearing characterized by: 9. A half thrust bearing according to any one of claims 1 to 8 , characterized in that it is a half thrust bearing for receiving an axial force of a crankshaft of an internal combustion engine. A bearing device comprising the half thrust bearing according to any one of claims 1 to 8 . An internal combustion engine comprising a bearing arrangement according to claim 11 .

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