JP2018071787A - Sliding bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding bearing with low abrasion and low torque which comprises a bearing surface contacting with a peripheral surface of a shaft, can reduce friction abrasion between the bearing surface and the shaft, can drain abrasion flour generated in initial abrasion from a sliding surface, and is superior in feeding and holding of grease.SOLUTION: A sliding bearing 1 comprises a bearing surface 3 contacting with a peripheral surface of a shaft 4, and non-vertical unbalanced load is burdened in the bearing surface 3 for the axis of the shaft 4. The bearing surface 3 is a cylindrical surface or partly cylindrical surface along the peripheral surface of the shaft 4, and there is a groove 5 along the axis direction of the shaft 4 at the part of the bearing surface 3 contacting with the shaft 4 and receiving load.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sliding bearing. In particular, a slip applied to an application for supporting a rotating shaft of a roller such as a fixing roller or a pressure roller of a fixing unit in an image forming apparatus such as a copying machine, a multifunction machine, a printer (laser beam printer, LED printer, etc.), a facsimile, or the like. Related to bearings.

  A fixing device of an image forming apparatus such as a copying machine or a printer fixes unfixed toner transferred from a photosensitive drum to a sheet by heat and pressure. The fixing device applies heat and pressure at the same time by allowing the paper to enter between a fixing roller with a built-in heat source such as a halogen heater or a ceramic heater in a cylinder and a pressure roller installed opposite to the fixing roller. A mechanism for fixing toner is common. The outer peripheral surface of one of the fixing roller and the pressure roller is an elastic body such as synthetic rubber, and the other is a rigid body. Further, instead of the pressure roller, a mechanism for pressing an endless belt made of stainless steel, polyimide resin or the like to the fixing roller side through an elastic body is also employed.

  The fixing roller and the pressure roller are rotatably supported by bearings at both ends of the rotation shaft. As this bearing, a ball bearing (rolling bearing), a resin sliding bearing, or the like is used. As a resin sliding bearing used for such an application, a cylindrical shape or a U-shaped shape having an opening is often used. In use, grease is often applied to the bearing surface.

  Copiers and printers are becoming increasingly faster printing speeds and lower power consumption year by year, and bearings are required to support high load / high speed conditions, lower torque, and improved wear resistance. Further, depending on the structure of the fixing device, conductivity is also required. Ball bearings have higher load resistance and lower torque than resin sliding bearings, but have high costs and abnormal noise due to ball rolling vibration. Such high cost and abnormal noise have recently been regarded as a problem in the office environment, and application of a resin sliding bearing is desired even in a model having a high printing speed.

  Conventionally, various proposals for improving the bearing material have been made in order to improve the performance of the resin sliding bearing. For example, as a bearing material, a heat-resistant / lubricating resin composition in which polytetrafluoroethylene (PTFE) resin or the like is blended with a predetermined heat-resistant / thermoplastic resin has been proposed. However, there is a limit to reducing the torque only by improving the bearing material, so attempts have been made to reduce the rotational torque by designing the shape of the bearing surface. There are mainly two methods, a method of reducing the contact area between the bearing surface and the rotating shaft, and a method of improving the lubrication effect by providing a portion where grease accumulates on the bearing surface.

  Patent Documents 1 and 2 have been proposed as methods for reducing the contact area between the bearing surface and the rotating shaft. In Patent Document 1, the bearing surface is a convex portion having a contact surface substantially similar to the outer peripheral surface shape of the rotating shaft, and the contact area with the rotating shaft before and after wear is made constant. This design prevents an increase in contact area due to wear and stabilizes the torque. Moreover, in patent document 2, it is supposed that a torque will be reduced by setting the length of the axial direction of the part where a bearing surface contacts a rotating shaft shorter than the full length of the axial direction of a sliding bearing.

  Patent Document 3 has been proposed as a method for improving the lubrication effect by providing a portion where grease is accumulated on the bearing surface. An oil groove for storing grease is formed on the bearing surface, and a part of the periphery surrounding the open portion of the oil groove has a portion along the direction intersecting with the rotation direction, so that a wide range of the bearing surface can be obtained. In order to improve the lubrication effect.

JP 2000-035034 A JP 05-026228 A JP 2000-242113 A

  However, with the further increase in printing speed of image forming apparatuses in recent years, the required characteristics for bearings have become stricter, and it can be said that the proposals of Patent Documents 1 to 3 and the like sufficiently reduce the torque and increase the load. Absent. Also, when the shaft diameter is made the minimum diameter due to cost reduction, the rotating shaft bends due to the increased load, so the contact between the bearing and the shaft cannot be received over the entire bearing inner diameter width. Take the load. For this reason, the bearing edge portion is easily worn and a lot of wear powder is generated. Further, the generated wear powder is held by the grease, and the retained wear powder causes a vicious cycle in which the bearing is further worn, which adversely affects the friction wear characteristics. Furthermore, even when a grease groove is formed on the bearing surface, the effect may be adversely affected depending on the shape, position, and use conditions, and there is a possibility that a sufficient effect cannot be obtained.

  The present invention has been made to cope with these problems, and includes a bearing surface that contacts an outer peripheral surface of a rotating shaft, and in particular, a sliding bearing that is loaded with a non-perpendicular load with respect to the axis of the rotating shaft. Can reduce the frictional wear between the bearing surface and the rotating shaft, discharge the wear powder generated by the initial wear from the sliding contact surface, and also have excellent grease supply and retention, low wear and low torque An object of the present invention is to provide a plain bearing.

  The sliding bearing of the present invention is a sliding bearing comprising a bearing surface that contacts the outer peripheral surface of the rotating shaft, and the bearing surface is a cylindrical surface or a partial cylindrical surface along the outer peripheral surface of the rotating shaft. Further, the bearing surface has a groove along the axial direction of the rotary shaft in a portion that receives a load by sliding contact with the rotary shaft. In particular, a lubricant is applied to the bearing surface.

  A non-perpendicular load is applied to the bearing surface with respect to the axis of the rotary shaft. In addition, the bearing surface is formed such that the diameter of the bearing surface is increased toward the outer side in the axial direction at the axial end portion on the side where the load received by the eccentric load is large, of both axial end portions of the bearing surface. It is characterized by having an inclined groove. Alternatively, a chamfer of 20 degrees or less is provided at the axial end of the bearing surface in the axial direction on the side where the load received by the offset load is large.

  The sliding bearing is a resin composition comprising a base resin of at least one thermoplastic resin selected from polyphenylene sulfide (PPS) resin, aromatic polyether ketone resin, thermoplastic polyimide resin, and polyamideimide (PAI) resin. It is a molded body. The resin composition contains a PTFE resin and lithium phosphate. Further, the resin composition is a conductive resin composition containing at least one selected from carbon black and carbon nanotubes.

  The sliding bearing is a bearing that supports a rotating shaft of a fixing roller or a pressure roller in the image forming apparatus.

  The sliding bearing of the present invention can smoothly discharge wear powder due to initial wear between the bearing surface and the rotating shaft, compared with a case where there is no predetermined groove, and rotational torque and wear are reduced. Further, the predetermined groove can avoid receiving a load at the edge portion of the bearing surface, and the load can be distributed and received on both sides of the bearing surface across the groove. In addition, it plays a role of retaining a lubricant such as grease. By providing the groove in the portion where the bearing and the rotating shaft are in sliding contact, that is, the portion receiving the load, the generated wear powder is quickly taken in, and the grease in the groove is continuously supplied to the rotating shaft in sliding contact. A good sliding state can be maintained. In particular, even when a non-perpendicular load is applied to the bearing surface with respect to the axis of the rotating shaft, the initial wear powder generated by the initial sliding contact of the rotating shaft with the edge portion of the bearing surface Can be discharged quickly.

  The slide bearing is a molded product of a resin composition containing a thermoplastic resin such as a PPS resin, an aromatic polyether ketone resin, a thermoplastic polyimide resin, or a PAI resin as a base resin, and containing a PTFE resin and lithium phosphate. Therefore, it is excellent in load resistance, heat resistance, lubricity, etc., and can suppress wear.

It is the perspective view and sectional drawing which show an example of the slide bearing of this invention. It is the perspective view and sectional drawing which show the other example of the slide bearing of this invention. It is the bearing surface enlarged view and sectional drawing which show the shape of the groove | channel of a bearing surface. It is a perspective view which shows the other example of the slide bearing of this invention. FIG. 2 is a schematic diagram (side view) illustrating a configuration of a fixing unit of the image forming apparatus. FIG. 2 is a schematic diagram (cross section) illustrating a configuration of a fixing unit of the image forming apparatus. It is a perspective view which shows the sliding bearing (partially cylindrical type) without a groove | channel. It is the perspective view and sectional drawing which show the sliding bearing (partially cylindrical type) from which a groove | channel differs. (Example 1) which is a figure which shows the time-dependent change of rotational torque. It is a figure which shows a time-dependent change of rotational torque (comparative example 1). It is a figure which shows a time-dependent change of rotational torque (comparative example 2). It is a figure which shows a time-dependent change of rotational torque (comparative example 3). It is a perspective view which shows the sliding bearing (cylindrical type) from which a groove | channel does not differ / a groove | channel. It is a figure which shows a time-dependent change of a dynamic friction coefficient (Example 2). It is a figure which shows a time-dependent change of a dynamic friction coefficient (comparative example 4). It is a figure which shows a time-dependent change of a dynamic friction coefficient (comparative example 5). It is sectional drawing which shows the other example of the slide bearing of this invention.

  The configuration of the fixing unit of the image forming apparatus using the slide bearing of the present invention will be described with reference to FIGS. FIG. 5 is a schematic diagram of the configuration of the fixing unit viewed from the side. The image forming apparatus forms an image captured by an optical unit with toner on a transfer belt at a developing unit and a photosensitive unit. As shown in FIG. 5, in the fixing unit, the toner 9 is transferred to the paper 10 and printed on the paper 10. At that time, the sheet 10 passes between the fixing roller 6 including the heater 12 and the pressure roller 7 (nip portion), and is heated and pressed at about 160 to 200 ° C. in order to burn the toner 9. A peeling member 8 is provided at a position in contact with or close to the fixing roller 6 so that the paper 10 that has passed through the nip portion can be peeled from the fixing roller 6. The fixing roller 6 and the pressure roller 7 are rotatably supported by bearings at their respective rotation shafts. Here, the pressure roller 7 is pressed against the fixing roller 6 by a spring 11 or the like via the sliding bearing 1 of the present invention.

  An offset load acting on the sliding bearing 1 will be described with reference to FIG. FIG. 6 is a schematic sectional view of the fixing unit. The sliding bearing 1 that supports the rotating shaft 4 of the pressure roller 7 is always pressed in a direction perpendicular to the axis of the rotating shaft 4 with a load in one direction. A load is received at the edge portion 3 a of the bearing surface 3. The amount of deflection depends on the shaft diameter of the rotating shaft, but is about 0.2 to 1 degree. Thus, the magnitude | size of the load received in the axial direction position in the bearing surface 3 differs. Due to the deflection or thermal expansion of the rotating shaft 4, both an axial load and a radial load are applied to the bearing surface 3, and an offset load in a non-perpendicular direction (oblique direction) is applied to the axis of the rotating shaft. When the printing speed is increased, since it is necessary to burn the toner in a short time, both the temperature of the fixing roller 6 and the pressing force of the pressure roller 7 are increased, and the use conditions of the bearing become severe.

  An example of the sliding bearing of the present invention will be described with reference to FIG. FIG. 1A is a perspective view of the sliding bearing, and FIG. 1B is an axial sectional view of the sliding bearing. As shown in FIGS. 1 (a) and 1 (b), the sliding bearing 1 of this embodiment includes a U-shaped bearing body 2 having a predetermined axial thickness, and the bearing body 2 includes a pressure roller. It has the bearing surface 3 which contacts the outer peripheral surface of the rotating shaft 4, and supports this. The bearing surface 3 is formed on the U-shaped bottom side of the bearing body 2, and the U-shaped upper side is open. The bearing surface 3 is a partial cylindrical surface (arc surface) along the outer peripheral surface of the rotating shaft 4. On the surface of the bearing surface 3, a concave groove 5 is provided along the axial direction of the rotary shaft (X-ray in FIG. 1B). The distance between the inner wall surfaces 2a and 2b of the bearing body 2 is slightly larger than the diameter of the rotating shaft 4 supported by the slide bearing 1, specifically 0.2 to 5% of the diameter of the rotating shaft 4, Preferably it is 0.3 to 3% larger.

  The groove 5 is provided in a portion of the bearing surface 3 that is in sliding contact with the rotating shaft 4 and receives a load. In the form shown in FIG. 1, the U-shaped bearing body 2 is provided at the bottom of the inner wall surfaces 2 a and 2 b, and this part is the part that receives the most load. By forming the groove 5 in the portion of the bearing surface 3 that receives the load, it is possible to avoid receiving the load at the edge portion of the bearing surface 3, and to receive the load distributed on both sides of the bearing surface across the groove. Can do. Further, generated abrasion powder is discharged into the groove 5 without entering the sliding contact surface. Further, when the grease held in the groove 5 and the rotating shaft 4 come into contact with each other, a good sliding state can be obtained. Since the sliding bearing of the present invention receives the load of the rotating shaft on both sides of the bearing surface sandwiching the groove as described above, in order to further distribute the load, as shown in FIG. It is desirable to chamfer the edge portion 3b in the axial direction formed at both boundaries with the bearing surface 3. Although this chamfering depends on the depth of the groove, it is R 0.05 mm to 0.5 mm or C 0.05 mm to 0.5 mm.

  Another example of the slide bearing of the present invention will be described with reference to FIG. FIG. 2A is a perspective view of the sliding bearing, and FIG. 2B is an axial sectional view of the sliding bearing. As shown in FIGS. 2A and 2B, the plain bearing 1 of this embodiment has an inclined groove 13 in the edge portion 3a of the bearing surface 3 that is in sliding contact with the rotating shaft 4 in the initial stage of operation. The edge portion 3a is an end portion in the axial direction on the bearing surface 3 on the side where a large load is received due to the offset load. The inclined groove 13 is formed in the edge portion 3a so as to expand the diameter of the bearing surface 3 which is an arc surface toward the outer side in the axial direction (outside of the bearing). By providing such an inclined groove 13, it becomes easy to receive the above-described uneven load. Further, when the rotating shaft 4 rotates, initial wear powder is generated by the initial sliding contact at the edge portion 3 a of the bearing surface 3. Even when the initial wear powder is generated, the wear powder is quickly discharged to the outside by the groove 5 and the inclined groove 13 and does not enter the sliding contact surface.

  The inclined groove 13 has a length of 1/4 or less, preferably 1/5 or less of the bearing width (axial dimension of the bearing body), preferably 0.5 to 20 ° or less with respect to the bearing surface. The inclination is preferably 0.5 to 10 ° or less, more preferably 0.5 to 5 ° or less.

  Another example of the sliding bearing of the present invention will be described with reference to FIG. FIG. 17 is a longitudinal sectional view of the sliding bearing. As shown in FIG. 17, the plain bearing 1 of this embodiment has a gentle chamfer 14 at the edge portion 3a of the bearing surface 3 that is in sliding contact with the rotating shaft in the initial stage of operation. The edge portion 3a is an end portion in the axial direction on the bearing surface 3 on the side where a large load is received due to the offset load. The chamfer 14 is formed on the edge portion 3a so as to expand the diameter of the bearing surface 3 that is an arc surface toward the outer side in the axial direction (outside of the bearing). Providing such a chamfer 14 makes it easier to receive the above-described offset load. Further, when the rotating shaft rotates, initial wear powder is generated due to initial sliding contact at the edge portion 3a of the bearing surface 3, but this generation can be suppressed by the chamfer 14. Even when the initial wear powder is generated, the wear powder is quickly discharged to the outside by the groove 5 and the chamfer 14 and does not enter the sliding contact surface.

  The chamfer 14 is in the range of 1/4 or less of the bearing width (axial dimension of the bearing body), preferably in the range of 1/5 or less, and the angle θ with respect to the bearing surface is 0.5 to 20 °, preferably 0. It is attached as a chamfer of 5 to 10 ° or less, more preferably 0.5 to 5 ° or less.

  In each embodiment, the circumferential width of the groove is preferably 2 to 10%, particularly preferably 2 to 6%, of the outer peripheral length of the rotating shaft. The depth of the groove is preferably 0.05 to 1.0 mm at the deepest portion regardless of the groove width. Here, the depth of the groove is a distance from the bearing surface (virtual surface) to the groove bottom, and when the groove is an inclined groove or an arc groove, the depth of the deepest portion of the groove is within the above range. It is preferable to do. It is preferable that the axial length of the groove penetrates both end surfaces of the bearing in the axial direction.

  The groove in the present invention is along the axial direction of the rotation axis, but is not limited to being completely along (parallel or coincident), and may be slightly inclined. The allowable tilt angle is, for example, about 0 ° to 20 °. This inclination is the same in both the load direction and the horizontal direction (direction perpendicular to the load direction). Since the axial direction of the rotary shaft and the cylindrical center axis direction of the cylindrical surface of the bearing body or a part of the cylindrical surface substantially coincide, the groove also extends along the cylindrical center axis direction of the cylindrical surface of the bearing body or a part of the cylindrical surface. It will be.

  In the form shown in FIGS. 1 and 2, one groove is formed near the center of the arc of the bearing surface (arc surface). The width, shape, formation range, and the like of the groove can be set as appropriate. As shown in FIG. 5 and FIG. 6 described above, the sliding bearing 1 supports the rotating shaft 4 with the bearing surface 3 while being pressed upward from the U-shaped lower side, but receives no load over the entire bearing surface. Particularly, in the initial stage, it slides at the edge portion 3a and receives a load at the portion. The groove is preferably arranged so as to pass through at least a portion including the edge portion 3a in the bearing surface 3.

  Another shape of the groove on the bearing surface will be described with reference to FIG. FIG. 3 is an enlarged view of the bearing surface and a radial sectional view of the bearing surface. As the shape in the depth direction of the groove, shapes as shown in FIGS. 3A to 3C can be adopted. The groove 5 in FIG. 3A is a groove having the form shown in FIGS. 1 and 2, and is a circular groove whose depth direction is an arc. The groove 5 ′ in FIG. 3B is a rectangular groove having a rectangular depth direction, and the groove 5 ″ in FIG. 3C is a triangular groove having a triangular depth direction. 3 (a) to FIG. 3 (c), the bearing body is not forcibly removed during injection molding, and the groove portion can be easily formed integrally with the bearing body, so that the groove is post-processed. It can be unnecessary.

  1, 2, and 17, the embodiment in which the bearing surface is a partially cylindrical surface along the outer peripheral surface of the rotating shaft has been described. However, a cylindrical body is used for the bearing body, and the bearing surface is the outer periphery of the rotating shaft. The structure may be a cylindrical surface along the surface.

  Another example of the slide bearing of the present invention will be described with reference to FIG. FIG. 4 is a perspective view of the sliding bearing. The sliding bearing 1 ′ in this form includes a substantially cylindrical bearing body 2 having a predetermined axial thickness, and the bearing body 2 is in contact with and supports the outer peripheral surface of the rotating shaft 4 such as a pressure roller. Bearing surface 3 to be provided. The bearing surface 3 is formed on the inner peripheral surface of the bearing body 2, and the shape thereof is a cylindrical surface along the outer peripheral surface of the rotating shaft 4. A concave groove 5 along the axial direction of the rotary shaft 4 is provided on the surface of the bearing surface 3. The cylindrical inner diameter of the bearing body 2 is slightly larger than the diameter of the rotating shaft 4 supported by the sliding bearing 1 ′, specifically 0.2 to 5% of the diameter of the rotating shaft 4, preferably 0. 3 to 3% larger.

  In the sliding bearing 1 ′ in FIG. 4, a load is received on the bearing surface on the lower side of the cylinder. The groove 5 is formed in a portion that receives the load on the inner peripheral surface (bearing surface 3) of the main body in consideration of the fixing direction of the bearing main body 2. Thereby, it can avoid receiving a load in the edge part of a bearing surface like the form of FIG. 1, etc., and can receive a load disperse | distributing to both sides of the bearing surface which pinched | interposed the groove | channel. Further, the generated abrasion powder does not enter the sliding contact surface and is discharged from the groove 5, and the grease held in the groove 5 and the rotary shaft 4 come into contact with each other, so that a good sliding state is obtained. In addition, as the structure of the groove in FIG. 4, the same structure as that of the above-described FIG. 3 can be adopted. Further, chamfering of the edge of the groove and the bearing surface, inclined groove in the edge portion of a part of the cylindrical surface, and chamfering of 20 degrees or less can be similarly employed.

  As mentioned above, although the form of the sliding bearing was demonstrated based on FIGS. 1-4, the whole shape of the sliding bearing of this invention is not limited to these, It can change suitably according to the specification of the image forming apparatus to apply. For example, when the bearing surface is partially cylindrical, it is not U-shaped as shown in FIG. 1 and the like, but the entire bearing body 2 is formed of a partially cylindrical body (30 to 300 degrees in central angle). It may be. In this case, the groove is partially formed in a portion that receives the load on the inner peripheral surface of the cylindrical body.

  The material of the rotating shaft that is the counterpart material of the sliding bearing of the present invention is not particularly limited, but the rotating shaft such as a pressure roller in the image forming apparatus may be a soft metal such as aluminum or an aluminum alloy (A5052, A5056, A6063). Hard metal such as stainless steel is used.

  A resin material is preferably used as the bearing material forming the sliding bearing of the present invention. As the base resin of the resin material, for example, PPS resin, aromatic polyether ketone resin, thermoplastic polyimide resin, polycyanoaryl ether resin, PAI resin, polyetherimide resin, polyether sulfone resin, etc. are used. it can. Among these thermoplastic resins, it is preferable to use a PPS resin, an aromatic polyether ketone resin, or a thermoplastic polyimide resin.

  As the resin material, it is preferable to use a resin composition containing PTFE resin and lithium phosphate in the above base resin. As each compounding ratio, for example, 35 to 74% by weight of thermoplastic resin, 10 to 45% by weight of PTFE resin, and 16 to 30% by weight of lithium phosphate are preferable with respect to the entire resin composition. By making the slide bearing into a molded body of such a resin material, it is possible to form a transition film on the rotating shaft that has the required heat resistance and good lubricity, even if it is a soft aluminum alloy. It shows good lubrication properties without damaging the surface.

Examples of the lithium phosphate include Li ₃ PO ₄ or 2Li ₃ PO ₄ .H ₂ O. Anhydrides are preferred because there is no foaming due to dehydration. Lithium phosphate can be used mainly in powder form, and the particle size is preferably in the range of 0.5 to 100 μm.

When the sliding bearing requires conductivity due to the structure of the fixing portion, the conductivity can be imparted by adding one or both of carbon black and carbon nanotube to the resin composition. Although these compounding quantities will not be specifically limited if it is the quantity which can provide desired electroconductivity, For example, 0.03 to 10 weight% is mix | blended with respect to the whole resin composition. The volume resistivity of the molded body of this resin composition is preferably 10 ⁵ Ω · cm or less.

  As carbon black, furnace black, acetylene black, and ketjen black (registered trademark) are preferably used from the viewpoint of conductivity, and ketjen black is more preferable because of its excellent conductivity.

  As the carbon nanotube, a single-walled carbon nanotube (SWNT) or a multi-walled carbon nanotube (MWNT) can be used alone or in combination. In addition, the surface of the single-walled or multi-walled carbon nanotube may be chemically modified to improve the affinity with the base resin. Single-walled and multi-walled carbon nanotubes can be obtained by a known method such as a method using arc discharge such as graphite, a thermal decomposition method using a catalyst, a laser evaporation method, a CVD method, or a method for removing silicon atoms from SiC. .

  In addition, a known resin additive may be added to the resin composition to the extent that the effects of the present invention are not impaired.

  The method for forming a sliding bearing from this resin composition is not particularly limited. Although it may be formed by machining a material molded body obtained by compression molding or extrusion molding, injection molding is preferred from the viewpoint of cost. Further, after injection molding, necessary portions such as grooves may be machined.

  In the sliding bearing of the present invention, it is preferable that a lubricant such as grease or lubricating oil is interposed in the sliding portion between the bearing surface and the rotating shaft that is the counterpart material. By interposing a lubricant in the sliding portion, torque can be reduced, wear can be suppressed, and the performance life can be greatly extended. The grease and lubricating oil are not particularly limited as long as the torque can be reduced, and those usually used for sliding bearings can be used. A sliding bearing that supports a fixing roller, a pressure roller, and the like of a fixing unit in an image forming apparatus needs heat resistance of 150 ° C. or higher. Under such conditions, it is preferable to use fluorine grease or urea grease having high heat resistance. In addition, when the slide bearing requires conductivity, conductive grease containing conductive carbon or the like may be used.

Example 1, Comparative Example 1 to Comparative Example 3 [partially cylindrical (U-shaped)]
Table 1 shows the resin compositions used in the production of the sliding bearings of the examples and comparative examples. Using the resin composition of Table 1, Example 1 shows a plain bearing having the shape shown in FIG. 1, Comparative Example 1 and Comparative Example 2 have a shape shown in FIG. 7, and Comparative Example 3 shows FIG. Each shaped plain bearing was manufactured by injection molding. Here, in the plain bearing 21 shown in FIG. 7, the bearing surface 23 of the bearing body 22 is an arc surface (no groove) along the outer peripheral surface of the rotating shaft, and the bearing inner diameter dimension (distance between the inner wall surfaces of the bearing body). Is 8.1 mm, and the bearing width (axial dimension of the bearing body) is 6 mm. In the plain bearing 31 shown in FIG. 8, the bearing surface 33 in the bearing body 32 is an arc surface along the outer peripheral surface of the rotating shaft, and a circumferential groove 34 is formed at the approximate center in the axial direction of the bearing surface 33. In the slide bearing of FIG. 1 (FIG. 1), the axial groove 5 (groove width 1 mm, groove depth 0.5 mm) was machined after the slide bearing having the shape shown in FIG. 7 was manufactured by injection molding. Further, in the sliding bearing of Comparative Example 3 (FIG. 8), the circumferential groove 34 (groove width 1 mm, groove depth 0.5 mm) was machined after the sliding bearing having the shape shown in FIG. 7 was manufactured by injection molding.

  0.2 g of fluorine grease was applied to the bearing surface of the manufactured sliding bearing, and a frictional wear test was performed in a manner in which the bearing surface of the sliding bearing and the outer peripheral surface of the rotating shaft slide with a radial type testing machine. The test conditions were a continuous operation at a rotational speed of 0.25 m / min, a radial load of 150 N (2.5 MPa when converted to surface pressure with the sliding bearing of FIG. 7), and a temperature of 150 ° C. for 63 hours. The material of the rotating shaft was nickel-plated on free-cutting steel S45C (surface roughness Ra 0.3 μm). The shaft diameter of the rotating shaft is 7.95 mm and the operating gap is 0.15 mm. Under the test conditions described above, the amount of wear was determined from the rotational torque (frictional force) after 50 hours from the start of operation and the bearing height (thickness difference) before and after the test. The results are shown in Table 1. Moreover, the time-dependent change of rotational torque (friction force) is shown in FIGS.

  As shown in Table 1 and FIGS. 9 and 10, Example 1 and Comparative Example 1 are the same resin composition, but Example 1 using the shape of the present invention is stable with low friction (low torque). The result was excellent in wear resistance. Moreover, as shown in Table 1 and FIGS. 9 and 12, Example 1 and Comparative Example 3 are the same resin composition, but Example 1 using the shape of the present invention has a low rotational torque from the beginning of operation. The result was stable and excellent in wear resistance.

Example 2, Comparative Example 4, Comparative Example 5 [cylindrical type]
In Example 2, a slide bearing having the shape shown in FIG. 4 was prepared by blending 20 wt% lithium phosphate, 25 wt% PTFE resin, 5 wt% graphite and aramid fibers, and 3 wt% carbon black into PPS resin. It was manufactured by injection molding using the composition. In Comparative Example 4, a slide bearing having the shape shown in FIG. 13A is manufactured, and in Comparative Example 5, a slide bearing having the shape shown in FIG. 13B is manufactured by injection molding using the same resin composition as in Example 2. did. Here, in the sliding bearing 41 shown in FIG. 13A, the bearing surface 43 of the bearing body 42 is a cylindrical surface (no groove) along the outer peripheral surface of the rotating shaft, the bearing inner diameter is 20 mm, and the bearing width is 6 mm. It is. In the sliding bearing 51 shown in FIG. 13B, the bearing surface 53 of the bearing body 52 is a cylindrical surface along the outer peripheral surface of the rotating shaft, and the portion of the bearing surface 53 that receives the load of the rotating shaft has three circumferential directions. This is a three-surface receiving structure in which convex portions 54 are formed, and a groove 55 is formed between the convex portions. In addition, the sliding bearing (FIG. 4) of Example 2 was manufactured by manufacturing the axial groove 5 (groove width 1 mm, groove depth 0.8 mm) after manufacturing the sliding bearing having the shape shown in FIG. 13A by injection molding. processed. Further, the sliding bearing (FIG. 13B) of Comparative Example 5 has three convex portions 54 (protruding width 1.2 mm, convex height 0 after the sliding bearing having the shape shown in FIG. 13A is manufactured by injection molding. .5 mm, convex-convex distance 1.2 mm).

  0.05 g of lubricating oil was applied to the manufactured sliding bearing, and a frictional wear test was performed in a manner in which the bearing surface of the sliding bearing and the outer peripheral surface of the rotating shaft slide with a radial type testing machine. The test conditions were a continuous operation for 50 hours at a rotation speed of 1.5 m / min, a radial load of 152 N (1.3 MPa when converted to a surface pressure with a sliding bearing of FIG. 13A), and a temperature of 150 ° C. The material of the rotating shaft is A5052 (surface roughness Ra 0.4 μm), the shaft diameter of the rotating shaft is 19.7 mm, and the operating gap is 0.3 mm. 14 to 16 show changes with time in the dynamic friction coefficient from the start of operation to 50 hours under the test conditions described above.

  As shown in FIGS. 14 to 16, Example 2 using the shape of the present invention was a result that the coefficient of friction was stably lower than that of Comparative Example 4 and Comparative Example 5, and excellent in low friction characteristics. In particular, the coefficient of friction after 10 hours was stable lower than 0.01, which was very excellent compared to Comparative Examples 4 and 5.

  The sliding bearing of the present invention can reduce frictional wear between the bearing surface and the rotating shaft, can discharge wear powder generated by initial wear from the sliding contact surface, and is excellent in grease supply and retention, Since it has a low torque, it can be suitably used as a sliding bearing that supports the rotating shaft of a fixing roller or a pressure roller of a fixing unit in an image forming apparatus such as a copying machine, a multifunction machine, a printer, or a facsimile machine.

DESCRIPTION OF SYMBOLS 1 Sliding bearing 2 Bearing body 3 Bearing surface 4 Rotating shaft 5 Groove 6 Fixing roller 7 Pressure roller 8 Peeling member 9 Toner 10 Paper 11 Spring 12 Heater 13 Inclined groove 14 Chamfer

Claims (9)

A sliding bearing comprising a bearing surface in contact with the outer peripheral surface of the rotating shaft,
The bearing surface is a cylindrical surface or a partial cylindrical surface along the outer peripheral surface of the rotary shaft, and a portion of the bearing surface that is in sliding contact with the rotary shaft and receives a load is along the axial direction of the rotary shaft. A slide bearing having a groove.   The sliding bearing according to claim 1, wherein a lubricant is applied to the bearing surface.   3. The plain bearing according to claim 1, wherein a non-perpendicular load is applied to the bearing surface with respect to the axis of the rotary shaft.   Of the axial end portions of the bearing surface, an inclination formed so as to expand the diameter of the bearing surface toward the axially outer side of the end portion at the axial end portion on the side where the load received by the offset load is large The sliding bearing according to claim 3, further comprising a groove.   4. A plain bearing according to claim 3, wherein a chamfer of 20 degrees or less is provided at an axial end portion on a side where a load received by the offset load is larger among both axial end portions of the bearing surface.   The sliding bearing is a molded article of a resin composition comprising a base resin of at least one thermoplastic resin selected from polyphenylene sulfide resin, aromatic polyether ketone resin, thermoplastic polyimide resin, and polyamideimide resin. The plain bearing according to any one of claims 1 to 5, wherein the slide bearing is characterized in that   The sliding bearing according to claim 6, wherein the resin composition contains a polytetrafluoroethylene resin and lithium phosphate.   The sliding bearing according to claim 6 or 7, wherein the resin composition is a conductive resin composition containing at least one selected from carbon black and carbon nanotubes.   The sliding bearing according to any one of claims 1 to 8, wherein the sliding bearing is a bearing that supports a rotating shaft of a fixing roller or a pressure roller in an image forming apparatus.

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