Plain bearing

Abstract

To provide a slide bearing having a sliding member and a resin housing, which has an excellent sliding characteristic of the sliding member, high bondability between the sliding member and the resin housing, and high inner diameter accuracy and roundness of the sliding member.SOLUTION: According to the invention, provided is a slide bearing in which a sliding member has a wound bushing with a joint extending in an axial direction; the wound bushing has a multilayer structure including at least a resin layer located on an inner diameter side and forming a sliding surface, an intermediate layer located on an outer diameter side of the resin layer, and a back metal located on an outer diameter side of the intermediate layer; and a resin material of a resin housing flows from an outer peripheral surface of the wound bushing toward an inner peripheral surface at the joint by 10 to 90% of a wall thickness.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a sliding bearing for slidably supporting a shaft member, and more particularly to a sliding bearing having a cylindrical sliding member and a resin housing formed by injection molding on the outer peripheral surface of the sliding member.

Background Art

[0002] A cylindrical sliding bearing 101 having a resin housing 140 formed by injection molding is known (Figs. 8 - 9). The sliding bearing 101 has an inner peripheral surface 142 that functions as a sliding surface for supporting a shaft member and an outer peripheral surface 144 that functions as a fixing surface fixed to a mating member.

[0003] Conventionally, methods such as adding an additive such as a solid lubricant to the resin to impart slidability to the resin housing itself or forming the sliding surface with a separate member and integrating it with the resin housing are known. However, the method of adding an additive makes it difficult to balance the function of the housing (mechanical properties) and the function of the bearing (sliding characteristics). Also, this method makes it difficult to obtain high inner diameter dimensional accuracy and cylindricity due to the problem of anisotropy of resin molding shrinkage.

[0004] Patent Document 1 proposes a method of using a thin - walled cylindrical metal split bushing having an axial cut as a sliding member in a sliding bearing and insert - molding the sliding member to be integrated with a resin housing. Cited Document 1 also mentions the necessity of preventing the resin from flowing out to the sliding surface of the split bushing in order to achieve high accuracy of the inner peripheral surface of the sliding bearing. Therefore, in insert molding, the split bushing is first attached to the core pin of the injection mold device in a state where the cuts are in close contact, and then the resin is injected into the cavity of the injection mold device (paragraphs 0016 - 0019 and 0070, etc.).

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-085243 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The sliding bearing described in Patent Document 1 uses a metal split bushing. However, when the sliding surface is metal, the sliding characteristics are insufficient in lubrication environments where solid contact occurs, such as boundary lubrication. Patent Document 1 also proposes applying a coating (such as PTFE coating) to the sliding surface to improve its sliding properties (paragraph 0020, etc.), but the coating does not have sufficient bonding force when subjected to high loads.

[0007] Furthermore, in the sliding bearing described in Patent Document 1, in order to ensure the joint between the resin housing and the metal split bush, it is necessary to increase the holding force of the split bush by the housing by filling the resin at high pressure during injection molding. However, if the rigidity of the split bush is insufficient, deformation occurs and the sliding performance is impaired, while if the rigidity of the split bush is too high, it is difficult to conform it to the shape of the mold, resulting in an unstable shape for the sliding bearing.

[0008] Therefore, an object of the present invention is to provide a sliding bearing having a sliding member and a resin housing in which the sliding member has sufficient sliding characteristics even when subjected to a high load, the bonding between the sliding member and the resin housing is high, and the inner diameter accuracy and roundness of the sliding member are high. [Means for solving the problem]

[0009] According to the present invention, a sliding bearing for slidably supporting a shaft member is provided, comprising a cylindrical sliding member and a resin housing formed on the outer circumferential surface of the sliding member, wherein the sliding member has a coiled bushing with a joint extending in the axial direction, and the coiled bushing has a multilayer structure including at least a resin layer located on the inner diameter side and forming a sliding surface, an intermediate layer located on the outer diameter side of the resin layer, and a backing plate located on the outer diameter side of the intermediate layer, and the resin material of the resin housing flows in at the joint from the outer circumferential surface of the coiled bushing toward the inner circumferential surface by 10 to 90% of the wall thickness of the coiled bushing.

[0010] According to one embodiment of the present invention, the wall thickness of the coiled bushing can be 5-20% of the inner diameter of the coiled bushing.

[0011] Furthermore, according to one embodiment of the present invention, the coiled bushing can have a three-layer structure consisting of a resin layer, an intermediate layer, and a backing plate.

[0012] In the present invention, the resin layer of the coiled bushing may contain a resin material and additives added to the resin material, and the resin material may contain polytetrafluoroethylene (PTFE).

[0013] Furthermore, the intermediate layer of the coiled bushing may include a porous metal material and a resin material impregnated into the porous metal material. [Effects of the Invention]

[0014] In the sliding bearing of the present invention, by using a multi-layered wrapped bushing having a resin layer on the inner diameter side, and particularly a three-layered wrapped bushing consisting of a resin layer, an intermediate layer, and a backing plate, a highly adhesive resin sliding layer is provided while improving sliding characteristics. With this configuration, the sliding layer is bonded by a physical anchoring effect, which is particularly effective when using a low-tack resin material such as PTFE for the resin layer.

[0015] Furthermore, although the coiled bushing is integrally formed with the resin housing by injection molding, by allowing resin material to flow into the joint of the coiled bushing, particularly by setting the flow rate to 10-90%, the holding force of the coiled bushing can be improved, preventing the coiled bushing from coming loose or rotating together with the housing. Furthermore, the inflow rate of resin material into the joint of a coiled bushing represents the ratio of the length of resin material inflow extending from the outer surface to the inner surface of the coiled bushing to the wall thickness (radial thickness) of the coiled bushing. Therefore, an inflow rate of 0% means that no resin material has flowed from the outer surface to the joint, and an inflow rate of 100% means that the resin material has flowed into the joint from the outer surface to the inner surface, across the entire wall thickness of the coiled bushing. Unlike the present invention, if the resin material inflow rate is less than 10%, the inflow amount is insufficient, and improvement in the holding force of the coiled bushing cannot be expected. Furthermore, if the resin material inflow rate exceeds 90%, the joint of the coiled bushing will open up, and the inner diameter accuracy will deteriorate. Moreover, if the resin material inflow rate exceeds 100% and flows into the inner circumferential surface, the sliding properties will be impaired.

[0016] Furthermore, according to the present invention, the rigidity of the coiled bushing may be appropriately adjusted by setting the wall thickness of the coiled bushing to 5-20% of the inner diameter. This makes it possible to achieve sufficient holding force for the coiled bushing and a coiled bushing shape with excellent sliding properties. The rigidity of a coiled bushing is determined by the ratio of its wall thickness to its inner diameter (wall thickness / inner diameter). If this ratio is 5% or higher, rigidity can be efficiently increased, making the coiled bushing less prone to deformation even under pressure during injection molding. If this ratio is 20% or lower, rigidity is high and the conformability to the mold does not decrease, resulting in a stable shape (and therefore higher roundness).

[0017] The configuration and advantages of the present invention will be described in more detail below with reference to the accompanying drawings. It will be understood that the drawings show non-limiting embodiments for illustrative purposes only. [Brief explanation of the drawing]

[0018] [Figure 1] Front view of the sliding bearing according to an embodiment of the present invention, as viewed in the axial direction. [Figure 2] Cross-sectional view taken along line A-A of the sliding bearing shown in FIG. 1. [Figure 3] Expanded view of a part B of the sliding bearing shown in FIG. 2, showing the cross-section of the wound bushing in detail. [Figure 4] Expanded view of a part C of the sliding bearing shown in FIG. 1, showing the joint of the wound bushing in detail. [Figure 5] View corresponding to FIG. 4 of the sliding bearing according to another embodiment of the present invention, showing another configuration of the joint of the wound bushing in detail. [Figure 6] Diagram for explaining an example of the manufacturing process of the sliding bearing. [Figure 7] Diagram for explaining an example of the manufacturing process of the sliding bearing. [Figure 8] Front view of a conventional sliding bearing, as viewed in the axial direction. [Figure 9] Cross-sectional view taken along line D-D of the conventional sliding bearing shown in FIG. 8.

Mode for Carrying Out the Invention

[0019] The sliding bearing 1 according to an embodiment of the present invention will be described in detail below.

[0020] (Structure of the sliding bearing) FIG. 1 is a front view of the sliding bearing 1 as viewed in the axial direction, and FIG. 2 is a cross-sectional view of the sliding bearing 1 in the axial direction. The sliding bearing 1 has a cylindrical shape and is composed of a wound bushing 20 as a sliding member located on the inner diameter side and a resin housing 40 located on the outer diameter side thereof. The resin housing 40 is joined to the outer peripheral surface 24 of the wound bushing 20 so as to hold the wound bushing 20. The outer peripheral surface 44 of the resin housing 40 functions as a fixing surface for fixing the sliding bearing 1 to a mating member (not shown), and the inner peripheral surface 22 of the wound bushing 20 functions as a sliding surface for slidably supporting a shaft member (not shown).

[0021] Figure 3 is an enlarged view of a part B of the sliding bearing 1 shown in Figure 2, and in particular shows a detailed axial cross-section of the coiled bushing 20. As can be seen from Figure 3, the coiled bushing 20 is formed by shaping a cylindrical thin plate with a three-layer structure consisting of a resin layer (sliding layer) 32 located on the innermost diameter side and forming the inner circumferential surface (sliding surface) 22, a backing plate 36 located on the outermost diameter side, and an intermediate layer 34 between the resin layer 32 and the backing plate 36. The intermediate layer 34 includes a porous metal material 34a formed on the backing plate 36 and a resin material 34b, the same as the resin layer 23, impregnated inside it. Although the coiled bushing in this embodiment has a three-layer structure, it may also have a four-layer structure, for example, by further having a plating layer on the outer circumferential surface side of the backing plate 36. The plating layer can be formed from, for example, copper, tin, zinc, etc. Alternatively, a five-layer structure can be formed by also forming a plating layer on the inner circumferential surface side of the backing plate 36. In this case, a porous metal material 34a is sintered on the plating layer on the inner circumferential surface side and impregnated with a resin material 34b. Furthermore, the inner circumferential surface side of the resin layer 32 can also be surface-treated.

[0022] As shown in detail in Figure 4, the coiled bushing 20 has a joint 26 that is the abutting portion between the circumferential end faces of the three-layer thin plate and extends in the axial direction. In this embodiment, the joint 26 has a gap that extends radially with a constant width W in the radial cross-section (Figure 4). At the joint, the resin material constituting the resin housing 40 flows from the outer circumferential surface 24 of the coiled bushing 20 toward the inner circumferential surface 22, up to 10-90% of the wall thickness (radial thickness) t of the coiled bushing 40.

[0023] The inner diameter d of the coiled bushing 20 can be, for example, 3 to 50 mm. Generally, when the inner diameter exceeds 50 mm, it becomes a bearing that can withstand higher loads. In this case, the wall thickness t of the coiled bushing 20 can be, for example, 0.5 to 2.5 mm in 0.5 mm increments, and the width W of the joint can be 0.1 to 0.3 mm. It is preferable that the ratio of the wall thickness to the inner diameter of the coiled bushing 20 be 5 to 20%, and in this case, the upper and lower limits of the inner diameter for each wall thickness in 0.5 mm increments are as shown in Table 1. [Table 1]

[0024] In other embodiments of the present invention, the joint of the coiled bushing 20 does not have to extend radially with a constant width W in the radial cross-section of the coiled bushing 20. Instead, as shown in Figure 5, the joint 26' may have a gap that has a predetermined width W on the outer circumferential surface 24 of the coiled bushing 20, but gradually decreases in width toward the inner circumferential surface 22 and closes approximately in the middle of the wall thickness. Such a joint 26' makes it easier to obtain a configuration in which the resin material flows in up to 10-90% of the wall thickness (radial thickness) t of the coiled bushing 40. The joint does not have to be a stepped shape or a dovetail groove, etc., where the width gradually decreases toward the inner circumferential surface 22. The width may also be varied in the axial direction.

[0025] (Material of sliding bearings) The resin material constituting the resin housing 4 can be any material that is injection moldable, for example, glass fiber-filled plant-derived polyamide 10T can be used. Alternatively, as a thermoplastic resin, general-purpose plastics (PP, PE, PS, ABS, PMMA, PVC, PLA), engineering plastics (PA, POM, PC, PBT, PVDF), and super engineering plastics (PPS, PEEK, LCP, PFA, FEP, PEI, PAR, PSF, PES, PI, PAI) can be used, and thermosetting resins (PF, UF, MF, EP, PUR) may also be used. Furthermore, the resin layer 32 of the coiled bushing 20 can be a mixture of a base resin and additives. The base resin can be, for example, PTFE, POM, PEEK, PA, etc., and the additives can include, for example, solid lubricants such as graphite and MoS2, and wear-resistant agents such as alumina and carbon fiber. The backing plate 36 of the coiled bushing 20 can be made from, for example, iron or carbon steel. The intermediate layer 34 of the coiled bushing 20 can be obtained, for example, by impregnating a sintered powder of copper and copper alloy with a resin material that constitutes the resin layer 32.

[0026] (Manufacturing method for sliding bearings) The sliding bearing 1 can be manufactured, for example, by the following injection molding method. First, as shown in Figure 6, a first mold 60 is provided having a core pin 61 and a cylindrical cavity 62 formed around it, and an insert material 20' (wound bushing 20) is fitted onto the core pin 61. Next, as shown in Figure 7, a second mold 64 is clamped onto the first mold 61, and resin material is filled into the cavity 62 through a sprue 65 formed in the second mold 64. After cooling and setting, the molded product is removed from the mold, thereby providing a sliding bearing in which a resin housing 40 is formed around the wound bushing 20. In this embodiment, the shape of the joint of the insert material 20' was made straight, its opening width was adjusted to 0.6 mm, and the injection pressure (holding pressure) was adjusted to 40 MPa, resulting in a resin material inflow ratio of 50% relative to the wall thickness of the rolled bushing 40. However, the inflow ratio will vary depending on the shape and type of the resin housing to be molded, so the desired inflow ratio can be achieved by adjusting the shape of the joint of the insert material, the opening width, the pressure applied to the resin being molded, etc. [Examples]

[0027] (Performance evaluation test) To evaluate the bushing retention force and roundness of the sliding bearing according to the present invention, performance evaluation tests were conducted on Examples 1 to 8 and Comparative Examples 1 to 2. The three-layer coiled bushing was formed by sintering a porous intermediate layer onto a backing plate and impregnating it with a resin sliding layer (PTFE). The housing was molded using Unitika Ltd.'s XecoT® XG510A30D with an injection molding machine (FANUC ROBOSHOT α-S50iA). The inflow rate of resin material into the joint of the coiled bushing was determined by measuring a cross-section perpendicular to the axial direction.

[0028] (Test results) Table 2 below summarizes the test results for measuring bushing retention force and roundness when the inflow rate of resin material into the joint of the wrapped bushing was changed using Examples 1-5 and Comparative Examples 1-2. Furthermore, the bushing retention force was determined by measuring the force required to push the coiled bushing out of the housing in the axial direction using an autograph, and the roundness was determined by measuring the roundness of the inner diameter of the bushing using a roundness measuring instrument. [Table 2]

[0029] (Test results) Furthermore, Table 3 below summarizes the test results for measuring bushing retention force and roundness when the ratio of wall thickness to inner diameter of the coiled bushing was changed using Examples 3 and 6-8. [Table 3]

[0030] The test results in Table 2 confirm that a sliding bearing with a good balance of bushing retention force and roundness can be obtained when the resin material inflow rate is between 10% and 90%. In particular, it can be seen that when the resin material inflow rate is low, as in Comparative Example 1, the retention force decreases, while when the resin material inflow rate is too high, as in Comparative Example 2, the roundness deteriorates. Furthermore, the test results in Table 3 confirm that the roundness can be improved while maintaining the bushing retention force by adjusting the ratio of the wall thickness to the inner diameter of the coiled bushing.

[0031] While embodiments and examples of the present invention have been described in detail above with reference to the drawings and in relation to performance evaluation tests, the specific configurations are not limited to these, and modifications that do not depart from the gist of the present invention as described in the claims are included in the present invention. [Explanation of Symbols]

[0032] 1. Plain bearing 20 wraps bush 22 Inner surface 24 Outer surface 26th joint 32. Resin layer (sliding layer) 34 Middle Class 34 a Porous metal material 34 b Resin material 36. Slush funds 40 Resin housing 44 Outer surface 20' Insert material (wound bushing 20) 60 First mold 61 core pins 62 Cavity 64. Second mold 65 Spruce

Claims

1. A sliding bearing for slidably supporting a shaft member, comprising a cylindrical sliding member and a resin housing formed on the outer circumferential surface of the sliding member, The sliding member has a coiled bushing with a joint extending in the axial direction, and the coiled bushing has a multilayer structure including at least a resin layer located on the inner diameter side and forming a sliding surface, an intermediate layer located on the outer diameter side of the resin layer, and a backing plate located on the outer diameter side of the intermediate layer, A sliding bearing characterized in that the joint has a gap extending radially from the outer circumferential surface to the inner circumferential surface of the coiled bushing, the resin material of the resin housing flows into the gap from the outer circumferential surface to the inner circumferential surface of the coiled bushing at a rate of 10 to 90% of the wall thickness of the coiled bushing, and the coiled bushing is fixed to the resin housing and does not move in the axial direction.

2. The sliding bearing according to claim 1, wherein the wall thickness of the coiled bushing is 5 to 20% of the inner diameter of the coiled bushing.

3. The sliding bearing according to claim 1, wherein the coiled bushing has a three-layer structure consisting of the resin layer, the intermediate layer, and the backing plate.

4. The sliding bearing according to claim 1, wherein the resin layer comprises a resin material and an additive added to the resin material.

5. The sliding bearing according to claim 1, wherein the resin material of the resin layer contains polytetrafluoroethylene.

6. The sliding bearing according to claim 1, wherein the intermediate layer comprises a porous metal material and a resin material impregnated in the porous metal material.

7. The sliding bearing according to claim 1, wherein in the radial cross-section of the coiled bushing, the width of the gap gradually decreases from the outer circumferential surface to the inner circumferential surface of the coiled bushing, and closes at a position of 10 to 90% of the wall thickness.

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