JP5287400B2 - Radial plain bearing - Google Patents

Description

  The present invention relates to a radial slide bearing, and more particularly to a radial slide bearing in which lubricating oil is filled between a rotating shaft and a bearing inner peripheral surface and a shaft load is supported via the lubricating oil.

  A radial plain bearing is also called a journal plain bearing, and is a plain bearing that receives a load perpendicular to the radial direction of the rotating shaft supported by the bearing. The load capacity with respect to the load is large. Here, the load received by the bearing is a load acting on the inner peripheral surface of the bearing and means an axial load from the rotating shaft (hereinafter referred to as an axial load or simply a load). A typical example of a bearing that receives a dynamic load is a radial slide bearing that supports a crankshaft of an engine. For example, an explosion load, a reciprocating inertia load, and a rotary inertia load are applied to the bearing at the large end of the connecting rod connecting the piston and the crankshaft, and the magnitude and direction of the axial load change.

  In general, in a four-stroke engine, four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke are one cycle. On the inner peripheral surface of the bearing, at the compression top dead center, a high load acts on the piston side (upper side) due to the explosive force. A high load acts on the opposite side (lower side) of the piston due to the force. Thus, the position where the high load acts is changed by each stroke. Along with this, the thickness of the lubricating oil film interposed between the crank pin that is the rotating shaft and the inner peripheral surface of the bearing changes. In particular, when a high load due to an explosion stroke is applied, the oil film thickness is significantly reduced, which may cause the oil film to run out. When oil film breakage occurs, the frictional resistance between the crankpin and the bearing inner peripheral surface increases, and the power loss increases, and at the same time, the bearing inner peripheral surface may be damaged.

  In view of such a situation, several techniques have been developed for the purpose of ensuring the oil film thickness at the time of high load action. For example, in Patent Document 1, the crank pin has a non-circular cross-sectional shape, and the minimum position (minimum gap position) of the bearing gap between the cross-sectional shape and the slide bearing is the center of rotation of the crank journal. A crankshaft that is not on the axis connecting the center of the bearing is disclosed. And in patent document 1, what processed the cross-sectional shape of the crankpin into the elliptical shape is disclosed.

  Further, in Patent Document 2, in the combustion stroke of an internal combustion engine, in order to suppress load transmission to a region where the oil film becomes thin between the large end portion of the connecting rod and the crank pin, the rigidity of the portion corresponding to that region is described. There is disclosed a connecting rod having an asymmetric shape in which the height is lower than other portions. Patent Document 2 discloses a specific form in which a through hole is formed in a column portion and a part of rigidity is lowered.

JP 2003-278739 A JP 2008-82522 A

  However, the crankshaft of Patent Document 1 requires a special technique for non-circular machining of the crankpin, and there is room for improvement from the viewpoint of cost. In addition, the connecting rod of Patent Document 2 secures the oil film thickness by reducing a part of rigidity in order to suppress load transmission to the region where the oil film becomes thin. For example, a column that requires high strength is used. It is necessary to form a through hole in the part, and there is room for improvement from the viewpoint of mechanical strength.

  An object of the present invention is to provide a radial slide bearing capable of increasing the load capacity of a load by ensuring a sufficient thickness of a lubricating oil film even when a high load is applied without degrading other performance. is there.

The radial plain bearing according to the present invention is a radial plain bearing that receives axial load along the radial direction of the rotating shaft via lubricating oil filled in a gap between the inner peripheral surface and the rotating shaft. Is the maximum position on the inner peripheral surface in the range of 16 ° to 21 ° around the center point of the inner peripheral cross section toward the upstream side in the axial rotation direction of the rotary shaft with reference to the direction in which the axial load acts. It has a bulging portion bulging inward as a bulging position.

  According to the above configuration, the gap between the bulging portion and the rotating shaft is reduced, the generation range of the oil film pressure due to the wedge effect is increased as compared with the perfect circular bearing, and the stable position of the rotating shaft is greater than that of the true circular bearing. Move downstream in the direction of rotation. That is, in the perfect circle bearing, the axial load is concentrated at one point on the inner peripheral surface. However, in the above configuration, the axial load is dispersed in a part of the bulging portion and the downstream portion. Accordingly, the pressure acting on the oil film (oil film pressure) is reduced, and it is possible to ensure a sufficient thickness of the lubricating oil film even when a high load is applied.

Further, the radial plain bearing according to the present invention is used for a large end portion of a connecting rod having a small end portion connected to a piston and a large end portion connected to a crankshaft. In the radial slide bearing to be supported, the shape of the inner peripheral surface is a portion located at least on the small end side with respect to a center line passing through the centers of the small end portion and the large end portion of the connecting rod, It has a bulging portion that bulges inward with the position on the inner circumferential surface in the range of 16 ° to 21 ° advanced about the center point of the inner circumferential section toward the upstream side in the axial rotation direction as the maximum bulging position. It is characterized by.

  According to the above configuration, it is possible to secure a sufficient thickness of the lubricating oil film and increase the load capacity of the load due to the wedge effect of the bulging portion, particularly during a high load action due to an explosion stroke. That is, the axial load can be distributed to a part of the bulging part and the downstream part of the bulging part, so that the oil film thickness can be improved and the oil film pressure can be reduced.

  In addition, it is preferable that the bulging portion bulges at least to a position intersecting with the center line, and the degree of bulging decreases from the maximum bulging position toward the end portion.

  According to the above configuration, it is further easy to secure a sufficient lubricating oil film thickness and reduce the oil film pressure.

  According to the radial plain bearing according to the present invention, it is possible to secure a sufficient thickness of the lubricating oil film and increase the load capacity of the load even when a high load is applied, without reducing other performance. Further, the configuration of the radial slide bearing according to the present invention has an effect of increasing the load capacity of the load even when applied to a bearing other than the large end bearing of the connecting rod.

It is a figure which shows the connecting rod to which the large end part bearing of the connecting rod in embodiment which concerns on this invention and this bearing is applied. It is a figure which shows the principal part cross section of the crankpin inserted by the large end bearing and large end bearing of FIG. Form of the bulging part that minimizes the maximum oil film pressure Pmax (a), form of the bulging part that maximizes the minimum oil film thickness Hmin (b), and bearing form of a perfect circle having no bulging part (c) ). In each form shown in FIG. 3, it is a figure which shows the oil film pressure distribution with respect to the circumferential direction angle. In each form shown in FIG. 3, it is a figure which shows oil film thickness distribution with respect to the circumferential direction angle. It is a figure which shows the principal part cross section of the rotating shaft inserted in the static load bearing and static load bearing in embodiment which concerns on this invention.

  Embodiments according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a view showing a connecting rod large end bearing and a connecting rod to which the bearing is applied, and FIG. 2 shows a crank pin inserted into the large end bearing and the large end bearing shown in FIG. It is a figure which shows the principal part cross section. In addition, in each figure including FIG. 1 and FIG. 2, the size of the bulging portion, the crankpin, and the clearance between the bearing inner peripheral surfaces is shown larger than the actual size. Moreover, the shaft rotation direction of the crankpin is indicated by an arrow along the arc of the crankpin.

  In the following description, the large end bearing 30 of the connecting rod 10 shown in FIG. 1 will be described as an example of the radial slide bearing in the embodiment according to the present invention. The radial slide bearing according to the present invention is, for example, a cam Bearings for other engine members such as shaft bearings, suspension and steering member bearings such as power steering oil pump bearings, various bearings such as bearings for OA equipment such as spindle bearings of magnetic drums, etc. Can be applied to.

  The connecting rod 10 is a component that converts the reciprocating linear motion of the piston 11 to a crankshaft (not shown) and converts it into rotational motion. As shown in FIG. 1, the connecting rod 10 includes a small end portion 12 on the piston 11 side, a large end portion 13 on the crankshaft side, and a column portion 14 that connects between the small end portion 12 and the large end portion 13. It is composed of The connecting rod 10 is made of a material such as nickel / chromium steel, chromium / molybdenum steel, or titanium alloy, and is a member that requires high mechanical strength.

  The small end portion 12 is a connection portion with the piston 11, and a small end portion through-hole 16 through which the piston pin 15 coupled to the piston 11 is inserted is formed. The small end through hole 16 is provided with a small end bearing 17 for supporting the piston pin 15. Since the small end bearing 17 receives, for example, a high load in the explosion stroke via the piston 11, a high load capacity is required. The movement form of the small end 12 is a swinging movement from the combination of the reciprocating movement of the entire connecting rod 10 and the rotational movement of the large end 13, so that the small end bearing 17 has a wide range of bearing inner peripheral surfaces. A high load acts over the range. Therefore, for example, lubricating oil is supplied to the inner peripheral surface of the bearing from a jet hole or a communication hole (not shown) formed in the large end portion 13 to support the axial load via the lubricating oil.

  The large end portion 13 is a connecting portion with the crankshaft, and a large end through hole 19 into which the crankpin 18 of the crankshaft is inserted is formed. The large end through hole 19 is provided with a large end bearing 30 for supporting the crank pin 18. The large end portion 13 includes a large end body 20 integrally formed with the column portion 14 and a cap 21 fastened to the large end portion body 20. The large end portion main body 20 is fastened with the cap 21. A large end bearing 30 having a half structure is attached to the large end through-hole 19 to be formed.

  As described above, the column portion 14 is a portion that connects between the small end portion 12 and the large end portion 13. Generally, the column portion 14, the small end portion 12, and the large end portion main body 20 are integrated. Molded. For example, a communication hole (not shown) is formed in the column portion 14 in order to supply the lubricating oil from the large end portion 13 to the small end portion 12. Further, as described above, the crankpin 18 is a shaft that connects the crankshaft and the large end portion 13 and is rotated by receiving the force due to the reciprocating motion of the piston 11 and transmits the force to the crankshaft. It is a member for.

  As described above, when the connecting rod 10 connects the piston 11 and the crank pin 18 of the crankshaft, when the piston 11 reciprocates in a cylinder (not shown) during operation of the engine, the reciprocating motion is transmitted through the connecting rod 10. It is converted into the rotational motion of the crankshaft, and this rotational force is obtained as engine output.

  The large end bearing 30 is a radial slide bearing that supports the crank pin 18 that is a rotating shaft. As shown in FIG. 1, the large end bearing 30 has a halved structure, and generally a bimetal material in which a back metal and a lining are joined is used. The types of lining are broadly classified into copper-lead alloys and aluminum alloys. The surface of the lining is an inner peripheral surface 31 that is a bearing sliding surface.

  An oil supply passage is formed in the crankshaft, and lubricating oil is supplied to the inner peripheral surface 31 which is a bearing sliding surface of the large end bearing 30 through the oil supply passage. With the supplied lubricating oil, an oil film is formed between the inner peripheral surface 31 and the crank pin 18 to prevent friction between both members. In addition, this lubricating oil is supplied to the bearing sliding surface (inner peripheral surface) of the small end bearing 17 through, for example, the communication hole formed in the column portion 14.

  Here, the main role of the lubricating oil is to form an oil film to operate the engine without seizing the shaft and the bearing, and to reduce friction loss and wear between the shaft and the inner peripheral surface of the bearing. Also plays a role of cooling, cleaning, rust prevention and so on. The lubricating oil is obtained by adding a friction modifier, a viscosity index improver, an antioxidant and the like to the base oil.

  As described above, the inner peripheral surface 31 that is a bearing sliding surface is a surface that receives an axial load from the crank pin 18 that is a rotating shaft. Lubricating oil is filled between the inner peripheral surface 31 and the crank pin 18, and the axial load acts on the inner peripheral surface 31 via the lubricating oil. On the inner peripheral surface 31, the position where the high load acts is the downstream region in the axial rotation direction of the crankpin 18 from the position where the center line α passing through the center of the small end portion 12 and the center of the large end portion 13 intersects. . Here, the center of the small end portion 12 and the center of the large end portion 13 are the center point 17C of the inner peripheral section of the small end bearing 17 and the center point 30C of the inner peripheral section of the large end bearing 30, respectively. .

  Specifically, when the number of reciprocating motions of the piston 11 is small, a minimum oil film thickness position where the oil film thickness of the lubricating oil becomes the smallest occurs near the intersection with the center line α. On the other hand, as the reciprocating motion of the piston 11 increases, the rotational speed of the crankpin 18 increases, and the crankpin 18 is deviated from the crossing position in the axial direction. The thickness position shifts. For example, as shown in FIG. 3C, which will be described later, when the shaft rotation speed is 2000 rpm, the oil film thickness of the lubricating oil is the thinnest at a position advanced from the intersection with the center line α to the downstream side in the shaft rotation direction. (Minimum oil film thickness position), oil film breakage may occur.

  Here, as described above, the center line α is a line passing through the center point 17C of the inner peripheral section of the small end bearing 17 and the center point 30C of the inner peripheral section of the large end bearing 30, and The acting direction is a direction along the center line α. Specifically, the acting direction of the axial load of the crankpin 18 is the direction toward the piston 11 along the center line α at the compression top dead center (intake bottom dead center, exhaust bottom dead center), and at the intake top dead center. , And the direction toward the opposite side of the piston 11 along the center line α. In addition, as shown in FIG. 4 described later, when the oil film pressure distribution is plotted with respect to the circumferential direction angle of the bearing, the resultant force of the oil film pressure distribution is in the opposite direction (balanced) in the same direction as the axial load.

  As shown in FIG. 1, the large end bearing 30 has a bulging portion 32 on an inner peripheral surface 31 in order to prevent oil film breakage. The bulging portion 32 is a portion that swells more than the other inner peripheral surface 31 with respect to the inside of the large end bearing 30, that is, the crankpin 18 side, and between the crankpin 18 and the inner peripheral surface 31 in that portion. The gap becomes narrower. Therefore, the axial load of the crankpin 18 acts on a part of the bulging portion 32 due to the wedge effect.

  The bulging portion 32 is a portion located at least on the small end portion 12 side with respect to the center line α, and around the center point 30C of the inner peripheral section toward the upstream side in the axial rotation direction of the crankpin 18. A position on the inner peripheral surface 31 advanced by a predetermined angle is formed as the maximum bulging portion 33. At the intake top dead center, a high load also acts on the inner peripheral surface 31 opposite to the piston 11, so that the portion located on the opposite side of the small end 12 as shown by the dotted line in FIG. A bulging portion 32 can be provided. As shown in the figure, when the two bulging portions 32 are provided, they are preferably provided at positions facing each other.

  The maximum bulging portion 33 is a portion bulging inwardly in the bulging portion 32. The bulging portion 32 is formed over a predetermined range with the maximum bulging portion 33 as the center. That is, as shown in detail in FIG. 2, the bulging portion 32 does not have only the largest bulging portion 33 bulging, but the degree of bulging decreases from the largest bulging portion 33 toward the end portion. It bulges gently. Note that the bulging length of the maximum bulging portion 33 varies depending on the size of the bearing and the like, but is preferably about several μm for the large end bearing 30.

  As described above, the maximum bulging portion 33 is determined based on the center line α. Specifically, as shown in FIG. 2, an inner portion advanced from the center line α toward the upstream side in the axial rotation direction of the crankpin 18 by an angle A that is the predetermined angle around the center point 30C of the inner peripheral section. The position on the peripheral surface 31 is the maximum bulge portion 33. Here, the angle A is preferably 16 to 21 °. If the angle A is within this range, it becomes easier to secure a sufficient lubricating oil film thickness and reduce the maximum oil film pressure.

  The angle B that defines the range of the bulging portion 32 in the circumferential cross section is preferably 60 ° or more. As described above, the bulging portion 32 bulges from the maximum bulging portion 33 toward the end portion. It is preferable to bulge so that the degree is small and at least to a position intersecting with the center line α. In addition, as shown in FIG. 2, the bulging portion 32 preferably has the same length from the left and right ends with the maximum bulging portion 33 as the center, from the viewpoint of securing the oil film thickness and improving the workability. If the angle B is within this range, it becomes easier to secure a sufficient lubricating oil film thickness and reduce the oil film pressure. Note that the bulging portion 32 maintains a uniform shape along the axial direction of the crankpin 18 and is usually formed over both ends of the bearing in the axial direction.

  Examples of a method for forming the bulging portion 32 include the following method. For example, a method of forming a thickness distribution in the bearing metal casting process, a method of forming a thickness distribution on the back metal, a method of depositing a thickness of several μm on the back surface of the back metal by plating, etc., and raising the back surface of the back metal with a shim or the like The bulging part 32 can be formed easily and inexpensively by the method of applying.

  3 to 5, when the form of the bulging portion 32 is changed, specifically, the oil film pressure distribution and the oil film thickness distribution when the angle A that defines the position of the maximum bulging portion 33 is changed. Will be described. Here, FIG. 3A shows the form of the bulging portion 32 that minimizes the maximum oil film pressure Pmax as Example 1, and FIG. 3B shows that the minimum oil film thickness Hmin is maximum as Example 2. FIG. 3 (c) is a view showing a perfect-circular bearing form having no bulging part 32 as a comparative example. FIG. 4 is a diagram showing the oil film pressure distribution with respect to each circumferential angle, with the horizontal axis representing the circumferential angle and the vertical axis representing the oil film pressure in each embodiment shown in FIG. The fine dotted line, Example 2 is shown as a rough dotted line, and the comparative example is shown as a solid line. The same applies to FIG. 5.), FIG. FIG. In addition, the circumferential direction angle refers to a line (perpendicular: not shown) perpendicular to the center line α drawn from the center point 30C toward the right side in FIG. An angle formed by a line (angle line: not shown) drawn from an arbitrary position with respect to the center point 30C (circumferential angle at an arbitrary position), and a circle at a position where the angle line and the perpendicular line coincide with each other. The circumferential angle is 0 °, and the circumferential angle at the position where the angle line coincides with the center line α is 90 °.

  The analysis conditions such as the oil film pressure (FIG. 4) are all the same. The diameter of the crankpin 18 is 44 mm, the shaft load is 100 kN, the shaft rotation speed is 2000 rpm, and the average of the inner peripheral surface 31 and the crankpin 18. The gap was 20 μm and the lubricating oil viscosity was 10 mPa · s. The bulge length of the maximum bulge portion 33 was 3 μm, and the angle B was 60 °. The values of oil film pressure and oil film thickness were calculated by known fluid lubrication calculation (Reynolds equation).

  As shown in FIG. 3A, the bulging portion 32 of Example 1 is formed with an angle A of 21 ° (angle B is 60 ° and the maximum bulging length is 3 μm). According to the configuration having such a bulging portion 32, the maximum oil film pressure Pmax can be reduced to 0.72 GPa as shown in FIG. It can be seen that Pmax can be greatly reduced (58% reduction) compared to (FIG. 3C). Also, the minimum oil film thickness Hmin can be improved from 0.268 μm (comparative example) to 0.465 μm.

  On the other hand, as shown in FIG. 3B, the bulging portion 32 of the second embodiment is set to an angle A of 16 °, which is smaller than that of the first embodiment. The angle B and the maximum bulge length are 60 ° and 3 μm as in the first embodiment. According to the configuration having such a bulging portion 32, as shown in FIG. 5, the minimum oil film thickness Hmin can be increased to 0.67 μm. It can be seen that Hmin can be significantly increased (increase by 150%) as compared with the bearing (FIG. 3C). Also, the maximum oil film pressure Pmax can be reduced from 1.69 GPa (comparative example) to 1.02 GPa.

  As shown in FIGS. 4 and 5, the large-end bearing 30 of the example has two peaks indicating the oil film pressure and the oil film thickness, and the axial load is different from that of the comparative example bearing only one peak. The way of working is very different. That is, in the large end bearing 30 of the embodiment, the axial load is dispersed by the effect of the bulging portion 32. When the shaft rotation speed increases, the peak position of the oil film pressure shifts to the downstream side in the axial rotation direction, and when the shaft rotation speed decreases, the peak position of the oil film pressure shifts to the upstream side in the axial rotation direction. The range of the angle A and the like suitable for reducing H and increasing Hmin hardly change.

  As described above, the large end bearing 30 is a portion located at least on the small end 12 side with respect to the center line α passing through the centers of the small end 12 and the large end 13 of the connecting rod 10. The position on the inner peripheral surface 31 advanced by the angle A around the center point of the inner peripheral cross section toward the upstream side in the axial rotation direction of the crankpin 18 is defined as the maximum bulging portion 33, and the inner side over the range of the angle B. Therefore, the gap between the bulging portion 32 and the crank pin 18 is reduced and the wedge effect is exhibited, so that a sufficient lubricating oil film thickness can be ensured even when a high load is applied. Thus, the load capacity of the load can be increased.

  In the above description, the large-end bearing 30 has been described as an example of the radial slide bearing according to the present invention. However, as shown in FIG. 6, the rotational speed of the rotating shaft is slow and the eccentricity of the shaft is ignored. For the static load bearing 40 in which the axial load due to the large gravity acts in one direction, the bulging portion 42 is provided on the inner peripheral surface 41, thereby ensuring a sufficient thickness of the lubricating oil film and reducing the load capacity of the load. It is possible to increase. Here, FIG. 6 is a schematic diagram showing a static load bearing 40 in which an axial load due to gravity G acts in the direction of the arrow. In the figure, the position of the rotating shaft when the bulging portion 42 does not exist is indicated by a dotted line, and the position of the rotating shaft 44 in the static load bearing 40 having the bulging portion 42 is indicated by a solid line.

  As shown in FIG. 6, the static load bearing 40 has an inner peripheral cross section toward the upstream side in the axial rotation direction of the rotary shaft 44 with reference to the direction in which gravity G as an axial load acts on the inner peripheral surface 41. A bulging portion 42 having a maximum bulging portion 43 at a position on the inner peripheral surface 41 advanced by an angle A around the center point 40C. The bulging portion 42 bulges gently so that the degree of bulging gradually decreases from the maximum bulging portion 43 toward both ends. By providing such a bulging portion 42, the generation range of the oil film pressure due to the wedge effect is increased as compared with the perfect circle bearing, and the stable position of the rotary shaft 44 is located downstream of the true circle bearing in the axial rotation direction. Moving. Therefore, the oil film pressure is such that the axial load is distributed to a part of the bulging portion 42 and the downstream portion, thereby reducing Pmax and ensuring a sufficient thickness of the lubricating oil film even during a high load operation. become.

  Further, when there are a plurality of peak values of the oil film pressure with respect to the circumferential angle of the bearing, that is, when there are a plurality of high load application positions, for example, the upstream side of the shaft rotation direction with respect to each high load application direction. The bulging portion can be provided on the basis of the direction of the maximum load. In the latter case, when the acting direction of the maximum load changes with time depending on the rotation speed of the rotating shaft, it is preferable to provide the bulging portion based on the load acting direction when the rotation of the rotating shaft is stopped. Note that the range of the angle A suitable for reducing Pmax and increasing Hmin can also be applied when the formation position or the like of the bulging portion changes.

  10 connecting rod, 11 piston, 12 small end, 13 large end, 14 column, 15 piston pin, 16 small end through hole, 17 small end bearing, 18 crank pin, 19 large end through hole, 20 Large end body, 21 cap, 30 large end bearing, 31 inner peripheral surface, 32 bulge portion, 33 maximum bulge portion, 40 static load bearing, 41 inner peripheral surface, 42 bulge portion, 43 maximum bulge portion 44, rotation axis, α center line, center point of inner peripheral section of 17C small end bearing, center point of inner peripheral section of 30C large end bearing, center point of inner peripheral section of 40C static load bearing.

Claims (3)

In the radial plain bearing that receives the axial load along the radial direction of the rotating shaft through the lubricating oil filled in the gap between the inner peripheral surface and the rotating shaft,
The shape of the inner peripheral surface is
The position on the inner peripheral surface in the range of 16 ° to 21 ° advanced around the center point of the inner peripheral cross section toward the upstream side in the axial rotation direction of the rotary shaft with respect to the direction in which the axial load acts is maximized. A radial slide bearing characterized by having a bulging portion bulging inward as a position. In a radial slide bearing that is used for a large end of a connecting rod having a small end connected to a piston and a large end connected to a crankshaft, and supports a crankpin via lubricating oil,
The shape of the inner peripheral surface is
A portion located at least on the small end side with respect to a center line passing through the centers of the small end and large end of the connecting rod, and the center of the inner peripheral section toward the upstream side in the axial rotation direction of the crankpin A radial slide bearing characterized by having a bulging portion bulging inward with a position on the inner peripheral surface in a range of 16 ° to 21 ° advanced around a point as a maximum bulging position. In the radial plain bearing according to claim 2,
The bulge is
A radial plain bearing characterized in that it swells at least to a position that intersects the center line, and the degree of bulge decreases from the maximum bulge position toward the end.

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