JP2007146919A - Sliding bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved sliding bearing capable of further reducing friction compared with a conventional bearing. <P>SOLUTION: A plurality of narrow projecting reinforcements 2 are provided on the bearing surface of the sliding bearing 1 along a circumferential direction. When a pitch between the projecting reinforcements is (a), a bottom surface width between the projecting reinforcements is (b) and the width of the projecting reinforcement is (c), a ratio between the bottom surface width (b) and the projecting reinforcement width (c) is set to be b/c>14. The narrow projecting reinforcements formed along the circumferential direction make lubricating oil flowing between the surface of a rotating shaft and the surface of the bearing easy flow in the circumferential direction and make it difficult to flow in the axial direction, and the thickness of the oil film is increased. Further, the projecting reinforcements make the thickness of the main lubrication surface on the side where a gap between the shaft and the bearing is reduced by the act of a load to be thick, and friction is reduced, and oil film pressure is raised, and thus, the projecting reinforcements contribute to the effective increase of a load capacity to the load. By setting the ratio between the bottom surface width (b) and the projecting width (c) to be b/c>14, the friction of the sliding bearing can be further reduced compared with the conventional bearing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cylindrical slide bearing that rotatably supports a rotary shaft having a circular cross section.

In general, plain bearings for power machines such as engines often have cutting marks in the axial direction (bearing width direction) perpendicular to the circumferential direction of the bearing surface, which prevents oil flow and improves friction. It was a factor of unfamiliarity.
In order to solve this problem, in order to supply the lubricating oil to the bearing surface, there are ones in which many small grooves are formed at a narrow pitch in the circumferential direction to promote the flow of the lubricating oil in the circumferential direction. (Patent Document 1).
There has also been proposed a structure in which a plurality of thin protruding bars are provided in the circumferential direction of the bearing surface of the slide bearing and the lubricating oil passage between each protruding bar is trapezoidal to increase the amount of lubricating oil (patent) Fig. 7 in Literature 2.
Japanese Examined Patent Publication No. 63-11530 JP-A-7-259858

In the case of the sliding bearing of Patent Document 1, it is assumed that the load is mainly handled by the top surface of the projection of the groove, and the width of the top surface of the projection is relatively wide, and the top surface of the projection is relatively wide with respect to the groove. The area ratio is high. Friction can be reduced compared to conventional plain bearings without grooves, but at the initial stage of use without wear, the distance between the protrusions sandwiching the grooves and the rotating shaft is close, and the friction here is the main component. The friction is relatively large.
Friction is further increased when the top surface of the protrusion is displaced due to the familiarity between the rotating shaft and the bearing surface, and the width of the top surface is slightly larger than the initial width. However, if the familiarity between the rotating shaft and the bearing surface is worn out and the top surface of the protruding portion is worn and the width of the top surface is further increased, the friction is gradually reduced. As wear progresses asymptotically to a smooth plane, the friction has the potential to reduce to a flat state.

In the slide bearing described in FIG. 7 of Patent Document 2, the friction is reduced as compared with a conventional general slide bearing without a groove and a slide bearing described in Patent Document 1 as shown in the later experimental results. be able to.
However, Patent Document 2 does not describe at all how to set the ratio of the bottom surface width between the protruding muscles and the protruding muscles, and the width of each protruding muscle. It is unclear whether low friction can be obtained when the range is set.
In power machines such as engines, reducing friction of sliding bearings has become an even more important issue in order to improve efficiency. For this reason, the present invention provides a sliding bearing improved so that the friction can be further reduced as compared with the prior art.

  In the present invention, a plurality of thin projecting protrusions are provided in the circumferential direction of the bearing surface of the slide bearing, the pitch between the protrusions and the protrusions is a, the bottom width between the protrusions and the protrusions is b, and the width of each protrusion is c. In some cases, the ratio between the bottom surface width b and the protruding bar width c is set so that b / c> 14.

The thin protruding bar formed in the circumferential direction makes the lubricating oil flowing between the surface of the rotating shaft and the bearing surface easy to flow in the circumferential direction, makes it difficult to flow in the axial direction, and thickens the oil film. In addition, the above-mentioned protruding bar increases the oil film thickness of the lubricating surface, which is the main part on the side where the gap between the shaft and the bearing becomes thin due to the load acting, thereby reducing friction and increasing the oil film pressure to increase the load capacity against the load. Contributes to effectively increasing.
Unlike the case of supporting the load by using the top surface of the protrusion of the groove for controlling the flow as a lubricating surface as in Patent Document 1, the bottom surface of the groove is remarkably wide, and this wide and thick oil film is used to reduce the friction. And achieve a load capacity for high loads.
By setting the ratio between the bottom surface width b and the protruding bar width c so as to satisfy b / c> 14, extremely low friction can be realized as compared with the conventional case.

  Hereinafter, the present invention will be described with reference to the illustrated embodiment. FIG. 1 is a perspective view of a half slide bearing 1 according to the present invention. . In the figure, L indicates the bearing width. The other half-slide bearing (not shown) has the same configuration as the half-slide bearing 1 described above.

2 and 3 are enlarged cross-sectional views of the main part taken along the line II-II in FIG. 1, respectively, and FIG. 2 exaggerates each protruding bar 2 so that the dimensions of each part can be easily understood. Is displayed in a state close to the actual size.
In each figure, a is the pitch between the projecting muscles, b is the bottom surface width between the projecting muscles, and c is the width of each projecting muscle, and the projecting muscle width c corresponds to pitch a−bottom surface width b (c = Ab). H represents the height of the protruding muscle.
As can be understood from FIGS. 2 and 3, each protruding bar 2 is formed in a triangular shape in cross section, and as can be understood from FIG. 3 in particular, its apex has a considerably obtuse angle. The width of the top surface of each protruding bar 2 should be as narrow as possible. This is because when the width of the top surface of the protruding bar 2 is increased, a large shearing force is generated on the top surface to increase friction.

FIG. 4 shows the friction (power loss W) under variable load acting on the connecting rod of the engine by forming the protrusion 2 on the bearing surface and changing the ratio (b / c) of the bottom surface width b to the protrusion width c. It is what investigated the change of.
In the figure, ◯ indicates the test result of the slide bearing of the present invention having the above-described configuration. In this test, the height h of the protrusion 2 is set to 3 μm. In addition, the dotted line in the figure shows the test result of the sliding bearing in which the bearing surface is formed completely flat. In general, it is difficult to mass-produce plain bearings having a completely flat surface without roughness of the bearing surface, but for the purpose of testing, a plain bearing having a completely flat bearing surface was manufactured.
The test was conducted using a 1000 cc, in-line 4-cylinder engine at 5000 rpm and full load. Each plain bearing had a radius of 14 mm and a bearing width of 12 mm. Further, the power loss is indicated by the power (W), and the power loss per one large end of each connecting rod is indicated.
As shown in FIG. 4, in the sliding bearing of the present invention indicated by the above-mentioned circle, when the ratio (b / c) between the bottom surface width b and the protruding bar width c is 5, the friction of the sliding bearing with a completely flat bearing surface is obtained. As the value exceeds 5, the friction becomes lower than that of the flat sliding bearing, and stable friction reduction can be achieved at 14 times or more.

For comparison, FIG. 5 shows the test results of a conventional plain bearing performed under the same test conditions as those in FIG.
In the figure, Δ indicates a test result in a general slide bearing in which the bearing surface is processed by broaching, and □ indicates a test result in a slide bearing belonging to the category of Patent Document 1. Also, the dotted line in the figure shows the test result of the slide bearing in which the bearing surface is formed completely flat, as in FIG.
However, the protrusion top width e in FIG. 5 means the width of the flat end when the top of the protrusion 2 'is formed flat as shown in FIG. 6, and the groove width f is the flat section. The width of the groove portion between the protruding muscle 2 ′ and the protruding muscle 2 ′ is shown.
The general sliding bearing indicated by Δ is surface-treated by cutting in a direction substantially perpendicular to the circumferential direction of the rotating shaft, and thus has a protruding streak in the axial direction in many cases. The axial streak has a large amount of friction, and when the top width e increases due to wear or familiarity, the friction slightly decreases.
On the other hand, in the plain bearing of Patent Document 1 indicated by the above-mentioned □, when the protruding bar is in the circumferential direction, the friction is significantly lower than that in the axial direction. However, when the apex width e increases due to wear or familiarity, the friction approaches that of a plain bearing having a completely flat bearing surface.
Thus, in the conventional slide bearing, the tendency for friction to reduce is shown by expanding the top width e.

FIG. 7 shows the characteristics when the ratio (b / c) between the bottom surface width b and the protruding bar width c is greatly changed by changing the bottom surface width b. In the figure, ○ indicates the product of the present invention, and the dotted line indicates the test result of the slide bearing in which the bearing surface is completely flat.
As shown in FIG. 7, if the ratio is 14 or more, there is a considerable friction reduction, minimum at 40 to 50, and gradually increase above that.
From this test result, when the ratio (b / c) between the bottom face width b and the protrusion width c in the slide bearing of the present invention is set to be in the range of b / c> 14, a good low friction slide bearing is obtained. be able to.

FIG. 8 shows the difference in the magnitude of friction in various sliding bearings with respect to the magnitude of friction in a completely flat sliding bearing.
In the figure, A shows the friction level of a plain bearing with a completely flat bearing surface, and B shows the friction level of a plain bearing manufactured by a conventional broaching process. It is shown as the difference from the magnitude of friction of A. Similarly, C is a sliding bearing with a groove described in Patent Document 1, D is a sliding bearing described in FIG. 7 of Patent Document 2, and E is a ratio of the bottom surface width b to the protruding bar width c (b / Each of the plain bearings of the present invention with c) set to 40 is shown.
In addition, regarding FIG. 7 of patent document 2, there is no quantitative description about the effect of friction reduction, and there is no description about the ratio of the bottom face width b and the protrusion width c. Therefore, when the dimensions in the figure were measured, the ratio was 8. Accordingly, the symbol D indicates a test result in which the ratio of the bottom surface width b and the protruding bar width c is 8. Further, the protruding muscle in FIG. 7 of Patent Document 2 has an acute angle, and the text of Patent Document 2 also describes that it is an acute angle. This is different from the shape of FIG. 3 of the present invention.
As understood from the above test results, the grooved slide bearing C is effective for reducing friction with respect to the general slide bearing B, but it does not reach the completely flat slide bearing A. On the other hand, the slide bearings D and E having a larger bottom width b are effective in reducing friction, and the slide bearing E of the present invention having the above ratio of 40 is particularly suitable for the slide bearing D having the ratio of 8. In contrast, there is a reduction effect of about twice.

FIG. 9 is a diagram showing the factor of friction reduction. In the present invention, the plain bearing having a wide bottom width b is indicated by a thick line, and the completely flat slide bearing is indicated by a thin line. As understood from the figure, the product of the present invention has a lubrication period in which the minimum oil film thickness is about twice that of a completely flat plain bearing in the engine cycle, and this reduces friction.
The increase in the minimum oil film thickness is due to the fact that the circumferential flow is mainly caused by the protrusion 2 and the effect of increasing the oil pressure is produced by suppressing the lateral flow.

Next, the height h, the width c, and the size of the pitch a will be described.
First, the height h of the projecting muscle 2 will be described. The height of each projecting muscle must be lower than the reference gap width (clearance) and smaller than the minimum oil film thickness at each position during actual operation. It is known from numerical calculations that the load bearing of an engine or the like varies depending on the position of the bearing and is about 1/10000 to 2/10000 of the bearing diameter d.
Therefore, it is desirable that the height h of the protruding bar 2 is such that the diameter of the sliding bearing is d, and the height h of the protruding bar 2 <the bearing diameter d × 2/10000 = 2d / 10000 mm (h <2d / 10000).

Next, the width c of the protruding muscle 2 can be set in consideration of the height h of the protruding muscle 2.
A plain bearing often uses a soft material for the surface, and recently, a resin may be used. Therefore, the minimum width of the protruding bar 2 is determined based on the allowable shear force.
In a sliding bearing for an engine or the like, it must be sufficiently assumed that the oil film pressure p locally reaches 500 MPa (from the lubrication theory of a rigid bearing). In order to use the bearing with an allowable shear stress τ, the allowable shear stress τ × the protrusion width c> the oil film pressure p × the protrusion height h (τc> ph) must be satisfied. That is, the protrusion width c> the pressure p of the oil film × the protrusion height h / the allowable shear stress τ (c> ph / τ).
Stress due to bending in this, that is, the maximum principal stress = root section modulus at the root of the moment /突筋of突筋2 (= p × (h / c) 2/12 also acts.
This maximum principal stress is sufficiently smaller than the allowable shear stress τ, but it must be a protruding bar width c with some margin. Here, based on the yield point stress of the bearing material, the allowable shear stress is assumed to be half of the yield point stress. The tensile strength of the bearing surface material is 300 to 370 MPa, and the yield point stress is 100 to 150 MPa.
If the allowable shear stress is 50 to 75 MPa, which is half of the yield point stress, then using the lower value of 50 MPa and h = d / 10000, p = 500 MPa, c> ph / τ,
The ridge width c> 500 MPa × d / 10000/50 MPa = d / 1000 mm (c> d / 1000).

By the way, it is practically difficult to reduce the width c of the protrusion 2 when the diameter d of the slide bearing is small.
In cutting, shear stress is generated by cutting resistance, which affects the shape that can be processed. The cutting resistance can be lowered by reducing the processing speed, etc., but the shear stress is introduced as 130 MPa in pure aluminum (Mechanical Engineering Handbook B2 Bias Processing and Processing Equipment). The yield point stress of pure aluminum is about 180 MPa, and in determining the allowable stress, the allowable shear stress is often 80% of the allowable stress.
If the protrusion 2 is triangular, the shear stress of the bottom surface of the protrusion due to cutting resistance must be less than the allowable shear stress of the material. This is cosine (cos δ) of inclination angle δ (see FIG. 3) <shear stress due to cutting resistance / allowable shear stress. In the case of pure aluminum, angle δ is 25 ° or less (vertical angle 130 ° or more). Furthermore, it is thought that 95% of the energy of the cutting force is increased in temperature (Mechanical Engineering Handbook B2: Partial Machining / Machining Equipment). For heat conduction, δ is set to a value considerably smaller than 25 °. Heat transfer from the inside to the inside of the material must be facilitated.
When cutting with a lathe. The minimum width that can be machined, that is, the minimum width of the protrusion 2 must be determined from the feed accuracy. The accuracy inspection is described in JIS B6202, and the allowable value of accuracy in the precision lathe is 10 μm for the movement and runout of the main spindle in the main axis direction, 10 μm for the axial movement of the lead screw, and the position accuracy of the tool post in JIS B6331. The allowable value is marked as 5 μm.
Together these, the precision lathe feed tolerance is 25 μm. Even the precision grade throw-away tip with accuracy symbol G has a dimensional difference of ± 25 μm (Mechanical Engineering Handbook B2: Partial Machining and Processing Equipment). Even if the accuracy of the throw-away tip is relative and can be excluded, it is considered that the machining of the protruding bar 2 cannot be guaranteed in terms of cutting unless the cutting resistance or the width c of the protruding bar 2 has a feed accuracy of a precision lathe of 25 μm or more.
Therefore, it is desirable to set the width c of the ridge 2 so that it is 25 μm or more and c> d / 1000.

Furthermore, a preferable minimum value of the pitch a of the protrusion 2 will be described.
The pitch a = the protruding bar width c + the bottom surface width b, and the ratio of the bottom surface width b and the protruding bar width c is b / c> 14, that is, the bottom surface width b> 14 × the protruding bar width c. The width b = the protrusion width c + 14 × the protrusion width c = 15 × the protrusion width c (a> 15c).
As described above, since the width c of the protrusion 2 is required to be 25 μm or more, the pitch a is required to be 15 × 25 = 375 μm or more.
On the other hand, since pitch a> 15 × barrel width c> 15 × bearing diameter d × 10 ⁻³ , a> 15d / 1000.

FIGS. 10 and 11 illustrate the relationship between the pitch a and the bearing diameter d, respectively. FIG. 10 shows a region where the bearing diameter d is small, and FIG. 11 shows a region where the bearing diameter d is larger than that. ing.
In the same figure, the code | symbol X has shown the area | region described in patent document 1, and the line Y has shown the minimum pitch a based on this invention mentioned above. The region of the present invention is a region above the line Y. A line Z indicates a line in which the bottom width b / the protrusion width c = 19 in the present invention. If the ratio is 19 or more, a more excellent friction reducing effect is obtained. In the line Z of FIG. 10, the minimum pitch a when b / c = 19 is 500 μm. That is, since b = 19c and a = b + c, a = 20c, and since c is required to be 25 μm or more, the minimum pitch a is 20 × 25 = 500 μm.

Furthermore, in order to reduce axial side leakage to the outside of the slide bearing, improve the oil film pressure on the bearing surface that supports the load, increase the oil film thickness, reduce friction and improve lubrication performance, It is desirable to form the protruding bars 2 at both axial ends of the bearing. If at least two protruding bars 2 are formed on the bearing surface in addition to the protruding bars at both ends, the oil film pressure at the center can be increased to control the flow of oil.
Therefore, it is desirable that the maximum value of the pitch a of the present invention is set such that the bearing width is L and the pitch a <L / 3.

  Further, each protruding bar 2 may be formed in the circumferential direction of the slide bearing accurately, or may be formed in a spiral shape by being inclined at a required angle θ. When the protrusion 2 is formed to be inclined, assuming that the bearing width is equal to the bearing inclined diameter, tan θ <1 / (3π) is 6 degrees or less. Therefore, it is desirable to set the inclination angle θ of the protrusion 2 of the present invention to be ± 6 degrees or less with respect to the circumferential direction of the bearing.

The plain bearing of the present invention may not have a uniform pitch as long as it is within the range of the pitch a. The cross section perpendicular to the projecting muscle 2 can be approximated by a trapezoid, but the slope, top surface, and bottom surface of the projecting muscle 2 may be slightly bent or distorted.
Further, the height h of the protruding muscle may be different depending on the location as long as it is within the above range. In particular, when the height is low in the direction in which a large load is applied and the load is small or the bearing housing is soft, it is effective to increase the protrusion height.

The perspective view which shows one Example of this invention. FIG. 2 is an enlarged cross-sectional view of a main part taken along line II-II in FIG. 2. It is an expanded sectional view of the principal part in alignment with the II-II line | wire of FIG. 1, and sectional drawing nearer to an actual dimension than FIG. The test result figure which changed the ratio (b / c) of the bottom face width b and the protrusion width c in this-article product, and investigated the change of the friction (power loss W) under the variable load which acts on the connecting rod of an engine. FIG. 5 is a test result of a conventional plain bearing performed under the same test conditions as FIG. Sectional drawing for demonstrating the ridge top width e and groove width f in the test of FIG. The test result figure which investigated the influence which ratio (b / c) of the bottom face width b and the protrusion width | variety width c has on friction. With reference to the magnitude of friction of a plain bearing manufactured with a completely flat bearing surface, a plain bearing having a normal process (broaching), a grooved slide bearing described in Patent Document 1, and a patent document 2 Test results showing the difference in the magnitude of friction between the sliding bearing shown in FIG. 7 and the sliding bearing of the present invention in which the ratio (b / c) of the bottom surface width b to the protruding bar width c is set to 40 Figure. The figure explaining the reason of the friction reduction of the slide bearing which widened the bottom face width b of this invention using minimum oil film thickness. The figure which showed the relationship between the pitch a and the bearing diameter d. The figure which showed the relationship between the pitch a and the bearing diameter d in the area | region where the bearing diameter d is larger than FIG.

Explanation of symbols

1 Sliding bearing 2 Reinforcement a pitch b Bottom width c Reinforcement width d Bearing diameter h Height of protrusion

Claims (7)

  When a plurality of thin protruding protrusions are provided in the circumferential direction of the bearing surface of the sliding bearing, the pitch between the protruding bars and the protruding bars is a, the bottom width between the protruding bars and the protruding bars is b, and the width of each protruding bar is c. A plain bearing, characterized in that the ratio of the bottom surface width b to the protruding bar width c is set so that b / c> 14.   2. The plain bearing according to claim 1, wherein the pitch a is set to satisfy a <L / 3 when the bearing width of the plain bearing is L.   3. The plain bearing according to claim 1, wherein when the diameter of the plain bearing is d, the pitch a is set such that a ≧ 375 μm and a> 15d / 1000. .   4. The height h of the protrusion is set so that h <2d / 10000, where h is the height of the protrusion and d is the diameter of the plain bearing. A plain bearing according to any of the above.   5. The plain bearing according to claim 1, wherein the protruding bar width c is set such that c ≧ 25 μm and c> d / 1000.   The sliding bearing according to any one of claims 1 to 5, wherein the protruding bars are formed to be inclined with respect to a circumferential direction of the bearing surface, and an inclination angle thereof is ± 6 degrees or less. .   The sliding bearing according to any one of claims 1 to 6, wherein pitches a of the protruding bars are unequal pitches.

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