JP2010112488A - Support structure of crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the durability of a lower thrust bearing 9 mounted between the balance weight 2c of a crankshaft 2 and a crank cap 5 to stably support the crankshaft 2 over a long period of time in the structure in which the crank journal 2a of the crankshaft 2 is sandwiched between the cylinder block 1 and crank cap 5 of an engine to support it rotatably. <P>SOLUTION: The lower thrust bearing 9, which has a shape made by forming a projection 9b projecting outward in the diameter direction integrally with a half washer 9a in a predetermined position on the outer diameter side, is fitted into the depression (5b, 5c) provided to the crank cap 5 while approximately fitting with the depression. The projection 9b and the portion of the half washer 9a in which the half washer 9a is connected with projection 9b are formed so as to have a smaller thickness as compared with the other portion to be in non-contact with a balance weight 2c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a structure for rotatably supporting a crank journal of a crankshaft between an engine cylinder block and a crank cap. In particular, the present invention relates to an improvement in a lower thrust bearing interposed between a balance weight of a crankshaft and a crank cap.

  In general, a crankshaft that outputs rotational power generated by an engine has a crank journal that is rotatably supported by a cylinder block, a crankpin that is rotatably supported by a connecting rod, and a balance for balancing the rotation. It includes a weight (or counterweight) and the like.

  The crank journal of the crankshaft is rotatably supported in a state of being sandwiched between a substantially U-shaped pedestal provided on the lower side of the cylinder block and a substantially U-shaped crank cap attached thereto with a bolt or the like. It is like that.

  Thrust bearings are interposed between the balance weight of the crankshaft and the crank cap, and between the balance weight of the crankshaft and the base of the cylinder block.

  This thrust bearing is generally a sliding bearing in which a disc-shaped washer is divided in half, and is formed of a metal having an appropriate self-lubricating property. For this reason, the thrust bearing that is normally interposed between the balance weight of the crankshaft and the crank cap is called the “lower thrust bearing”, and is interposed between the balance weight of the crankshaft and the base of the cylinder block. The thrust bearing that is mounted is called the “uppass thrust bearing”.

  In order to prevent the rotation of the two pairs of thrust bearings, the lower thrust bearing is provided with a rotation-preventing projecting piece. Further, in order to prevent erroneous mounting of the front and back of the lower thrust bearing, The projecting piece is provided at a position slightly shifted from the approximate center in the arc length direction of the lower thrust bearing (see, for example, Patent Documents 1 and 2).

For reference, the two pairs of thrust bearings are treated to prevent seizure on only one side of the front and back, taking into consideration the manufacturing cost, so the wrong mounting of the front and back as described above is prevented. The idea to do is given.
Japanese Utility Model Publication No. 58-184017 Japanese Utility Model Publication No. 61-191521

  The pair of thrust bearings of the above-described conventional example has the following concerns because both the front and back surfaces are flat surfaces.

  In other words, during the rotation of the crankshaft, the balance weight may bend as the piston moves up and down, which causes the thrust load to repeatedly act on the two thrust bearings, as well as the tensile load in the circumferential direction. Compressive loads can act repeatedly. Due to the effects of such thrust load, tensile load and compressive load, stress is concentrated particularly on the root of the protrusion of the lower thrust bearing, so there is a concern that the durability may be lowered.

  In view of such circumstances, the present invention provides a structure in which a crank journal of a crankshaft is rotatably supported by being sandwiched between an engine cylinder block and a crankcap, and is interposed between the crankshaft balance weight and the crankcap. The purpose is to make it possible to improve the durability of the lower thrust bearing and to support the crankshaft stably over a long period of time.

  The present invention has a structure in which a crank journal of a crankshaft is rotatably supported by being sandwiched between an engine cylinder block and a crankcap, and a lower thrust bearing is interposed between the balance weight of the crankshaft and the crankcap. The lower thrust bearing has a shape in which a projecting piece projecting radially outward is integrally formed at a predetermined position on the outer diameter side of the half washer portion, and is substantially formed in a recess provided in the crank cap. Compared to other regions so that the region connected to the projecting piece in the projecting piece and the half washer is in non-contact with the balance weight. It is characterized by being thin.

  In this configuration, since the projecting piece of the lower thrust bearing and the region connected to the projecting piece in the half washer portion are not in contact with the balance weight, the balance weight is bent when the crankshaft rotates, for example. Accordingly, even if a thrust load acts on the lower thrust bearing, it acts on the thick part of the half washer part of the lower thrust bearing, and the projecting piece on the lower thrust bearing and the half washer part Thrust load no longer acts on the continuous area.

  As a result, it is possible to prevent stress from concentrating on the base of the projecting piece, so that the lower thrust bearing can be prevented from being damaged from the base side of the projecting piece. Therefore, the durability of the lower thrust bearing is improved, and it is possible to contribute to the improvement of reliability.

  Preferably, the recess of the crank cap includes a semicircular arc-shaped step and a linear groove provided radially outward on the outer diameter side of the predetermined position, and the crank cap has a straight line and a step. The cross wall portion is removed by forming a hole in the wall portion where the groove intersects, and the connecting portion between the half washer portion and the projecting piece is curved in the lower thrust bearing, The curvature radius is set to a size that does not interfere with the remaining wall portion at the intersection of the semicircular step and the straight groove.

  In this configuration, in addition to the above-described merit, the base of the projecting piece is a curve with a large radius of curvature, and the strength of the base of the projecting piece is improved due to the absence of crack initiation. .

  Thereby, in addition to the effect of the above configuration, even if a circumferential tensile load or compressive load acts on the lower thrust bearing during rotation of the crankshaft, the stress is dispersed throughout the curved portion. The effect of avoiding damage from the base side of the projecting piece is increased.

  Preferably, a hole penetrating in the thickness direction is provided in a region connected to the projecting piece in the projecting piece of the lower thrust bearing and the half washer.

  In this configuration, in addition to the above structural advantages, the balance weight, the lower thrust bearing, and the crank when the thrust load is applied to the lower thrust bearing and the crank cap by bending the balance weight when the crankshaft rotates. The lubricating oil film existing between the cap and the cap is pulled out to the straight groove side of the crank cap through the hole of the lower thrust bearing.

  As a result, in addition to the effects of the above-described configuration, the oil film pressure is less likely to act on the projecting piece in the lower thrust bearing and the region connected to the projecting piece in the half washer, so stress concentration at the base of the projecting piece is further increased. It becomes possible to reduce, and the effect which avoids the damage from the base side of a protrusion comes to increase.

  By the way, the present invention relates to a lower thrust bearing interposed between a crankshaft balance weight and a crank cap in a structure in which a crank journal of a crankshaft is rotatably supported by being sandwiched between an engine cylinder block and a crank cap. The halved washer has a shape formed integrally with a projecting piece projecting radially outward at a predetermined position on the outer diameter side of the half washer, and is fitted and mounted in a state of substantially matching a recess provided in the crank cap. The region connected to the protruding piece in the protruding piece and the half washer portion is formed to be thinner than other regions so as to be non-contact with the balance weight. It can be.

  The lower thrust bearing of the present invention can contribute to the improvement of reliability, such as the durability being improved. Further, the crankshaft support structure of the present invention can contribute to improving the reliability of the engine, such as being able to support it stably over a long period of time.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1)
1 to 5 show Embodiment 1 of the present invention. First, a crankshaft support structure according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  1 and 2, 1 is a cylinder block, 2 is a crankshaft, and 3 is a connecting rod.

  The crankshaft 2 is a type used for a four-cylinder engine in this embodiment, and has five crank journals 2a, four crankpins 2b, and eight balance weights 2c.

  The crank journal 2a of the crankshaft 2 is rotatably supported in a state of being sandwiched between a lower pedestal 1a of the cylinder block 1 and a crank cap 5 coupled thereto with a bolt 6 or the like.

  The pedestal 1 a is provided with a recess 1 b that is recessed in a substantially U-shaped cross section toward the upper side of the cylinder block 1. The crank cap 5 is provided with a recess 5a that is recessed in a substantially U-shaped cross section toward the cylinder block 1 side.

  And between the rotation support part of each crank journal 2a of the crankshaft 2, specifically, the outer peripheral surface of the crank journal 2a of the crankshaft 2, and the recess 1b inner surface of the base 1a and the recess 5a inner surface of the crank cap 5, Radial bearings 7 and 8 are interposed.

The radial bearings 7 and 8 are generally plain bearings in which a cylindrical one is divided in half, and are formed of a metal having an appropriate self-lubricating property. Of the pair of radial bearings 7, 8, one radial bearing 7 is fitted and mounted on the inner surface of the recess 1 b of the pedestal 1 a, and the other radial bearing 8 is fitted and mounted on the inner surface of the recess 5 a of the crank cap 5. . In the following description, the radial bearing 7 disposed on the pedestal 1a side of the cylinder block 1 is referred to as an apparel bearing, and the radial bearing 8 disposed on the crank cap 5 side is referred to as a radial bearing. In addition, the large end of the connecting rod 3 is swingably attached to the crank pin 2b of the crankshaft 2, and a piston is attached to the small end of the connecting rod 3. (Not shown) is attached.

  The large end portion of the connecting rod 3 is substantially U-shaped, and a crank pin 2b is sandwiched by attaching a substantially U-shaped cap to the large end portion with a bolt or the like. A radial bearing (not shown) as a radial slide bearing is also interposed between the crank pin 2b and the large end of the connecting rod 3 in the same manner as the crank journal 2a.

  Thrust bearings 9 and 10 are interposed between the balance weight 2 c of the crankshaft 2 and the crank cap 5, and between the balance weight 2 c of the crankshaft 2 and the base 1 a of the cylinder block 1.

  The thrust bearings 9 and 10 are generally plain bearings in which a disc-shaped washer is divided in half, and are formed of a metal having an appropriate self-lubricating property. Due to this relationship, the thrust bearing 9 that is usually interposed between the balance weight 2c of the crankshaft 2 and the crank cap 5 is called a “lower thrust bearing”. Also, the balance weight 2c of the crankshaft 2 and the cylinder block 1 The thrust bearing 10 interposed between the pedestal 1a and the pedestal 1a is called an “uppass thrust bearing” and is used in pairs.

  The lower thrust bearing 9 has a shape in which a protruding piece 9b protruding outward in the radial direction is integrally formed at a predetermined position on the outer diameter side of the half washer portion 9a. The upper thrust bearing 10 has a half washer shape and is not provided with the protruding piece 9b as described above.

  In order to prevent the two thrust bearings 9 and 10 from rotating, the lower thrust bearing 9 is provided with a rotation-preventing protruding piece 9b, and further, to prevent erroneous mounting of the lower thrust bearing 9 on both sides. Further, the projecting piece 9b is provided at a position slightly shifted from the approximate center of the lower thrust bearing 9 in the arc length direction. In addition, the corner of the base of the projecting piece 9b is rounded.

  In addition, in order to prevent erroneous mounting of the upper thrust bearing 10 on the front and back, the concave portions 9c and 10a and the convex portions 9d and 10b that are concavo-convexly fitted to each other at the mating ends of the lower thrust bearing 9 and the upper thrust bearing 10 are provided. Is provided.

  Such a pair of thrust bearings 9 and 10 is processed in order to prevent seizure on only one side of the front and back in consideration of the manufacturing cost. Ingenuity to prevent it is given.

  A pedestal 1 a of the cylinder block 1 is provided with a semicircular arc-shaped step 1 c for fitting and mounting the up-last bearing 10.

  On the other hand, the crank cap 5 is also provided with recesses (5b, 5c) for fitting and mounting the lower thrust bearing 9, and this recess is a combination of the semicircular arc-shaped step 5b and the linear groove 5c. It is a thing. The semicircular arc-shaped step 5b is provided on one side of the crank cap 5 along the edge of the recess 5a. The straight groove 5 c is provided along the height direction of the crank cap 5 near the center of the semicircular arc-shaped step 5 b.

  As shown in FIG. 2, the straight groove 5c is formed deeper than the semicircular arc-shaped step 5b. The reason will be explained. In FIG. 2, the depth of the straight groove 5c is exaggerated.

  In the first place, the semicircular arc-shaped step 5b and the linear groove 5c are processed separately. However, if the linear groove 5c is formed shallower than the semicircular arc-shaped step 5b due to manufacturing tolerances or the like, the bottom of the linear groove 5c protrudes. It can be. In such a case, when the balance weight 2c bends due to the piston (not shown) moving up and down due to the rotation of the crankshaft 2, when it hits the lower thrust bearing 9, it thrusts locally against the projecting piece 9b. A load will act, stress may concentrate on the base of the protrusion 9b, and the protrusion 9b may be easily damaged from the base.

  Therefore, if the straight groove 5c is made deeper than the semicircular arc-shaped step 5b, it is possible to avoid stress concentration at the root of the protruding piece 9b as described above. For this reason, the setting is made as described above.

  In this embodiment, the lower thrust bearing 9 is devised to prevent cracks and breakage of the projecting piece 9b, and will be described in detail below.

  The area of the lower thrust bearing 9 that is connected to the protruding piece 9b on the surface of the protruding piece 9b and the half washer 9a on the balance weight 2c side is thinner than the other areas of the half washer 9a. The thin portion is denoted by reference numeral 9e. In addition, the thin part 9e of the half washer part 9a is formed of the groove | channel along a radial direction.

  With such a configuration, for example, when a thrust load is applied to the lower thrust bearing 9 from the balance weight 2c side with the rotation of the crankshaft 2, as shown in FIG. It acts on the thick part of 9a and does not act on the thin part 9e and the protruding piece 9b of the lower thrust bearing 9.

  In the first place, when the crankshaft 2 rotates, the balance weight 2c may bend as described above, and therefore, a thrust load is likely to act on the protruding piece 9b of the lower thrust bearing 9. With such a configuration, it is possible to avoid such a thrust load from acting on the protruding piece 9b and the thin portion 9e.

  As a result, it is possible to prevent stress from concentrating on the base of the projecting piece 9b, so that it is possible to prevent the occurrence of problems such as the lower thrust bearing 9 cracking or breaking from the base side of the projecting piece 9b. As a result, the durability of the lower thrust bearing 9 is improved, and the reliability can be improved.

(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, in the lower thrust bearing 9, the connecting portion between the half washer portion 9a and the protruding piece 9b is formed in a curved shape, and the radius of curvature R thereof is between the semicircular arc-shaped step 5b and the linear groove 5c. The size is set so as not to interfere with the remaining wall portions 5e and 5e at the intersection.

  By the way, if the corner of the wall portion where the semicircular arc-shaped step 5b of the crank cap 5 and the linear groove 5c intersect is sharply sharp, the half washer portion 9a and the protruding piece in the lower thrust bearing 9 are provided. The connecting portion with 9b also needs to have an acute angle, and it is physically impossible to increase the radius of curvature R of the connecting portion as much as possible.

  Therefore, by forming the holes 5d and 5d as shown in FIG. 6 in the wall portion where the semicircular arc-shaped step 5b of the crank cap 5 and the linear groove 5c intersect, the intersecting wall portion itself is removed. I have to. The holes 5d and 5d have a shape in which the back is closed, but it is also possible to make them through holes.

  As the inner diameters of the holes 5d and 5d are increased, the curvature radius R of the connecting portion of the half washer portion 9a and the projecting piece 9b in the lower thrust bearing 9 can be increased as much as possible. Thus, as shown in FIG. 7, the curvature radius R is linear with the semicircular arc-shaped step 5b in the crank cap 5 in a state where the lower thrust bearing 9 is fitted and mounted in the recesses (5b, 5c) of the crank cap 5. The size is set so as not to interfere with the remaining wall portions 5e and 5e at the intersection with the groove 5c.

  The operation in the case of the second embodiment will be described.

  That is, when the thrust load is applied to the lower thrust bearing 9 and the crank cap 5 by bending the balance weight 2c when the crankshaft 2 rotates as described in the first embodiment, the half washer portion of the lower thrust bearing 9 is applied. In addition to the thrust load acting as a whole on 9a and the projecting piece 9b, a circumferential tensile load or a compressive load acts on the lower thrust bearing 9 when the crankshaft 2 rotates. It is inevitable that stress concentrates on the base of the protruding piece 9b.

  However, the root of the projecting piece 9b is a curve having a large radius of curvature R, and the stress is distributed over the entire curved portion due to the fact that the crack starting point is eliminated. The strength of the roots in the is improved.

  Therefore, in the case of the second embodiment, as in the case of the first embodiment, it is possible to prevent the lower thrust bearing 9 from being broken or broken from the base side of the protruding piece 9b. As a result, the durability of the lower thrust bearing 9 is improved, and the reliability can be improved.

  By the way, the configuration of the second embodiment can be combined with the configuration of the first embodiment as shown in FIG. In that case, in addition to the merit by the structure of the said Embodiment 1, the effect which avoids the damage from the base side of the protrusion 9b increases.

(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIGS. 9 and 10. In the third embodiment, the lower thrust bearing 9 is provided with a hole 9f penetrating in the thickness direction in a region continuous with the protruding piece 9b in the protruding piece 9b and the half washer portion 9a.

  Specifically, as shown in the drawing, a plurality of holes 9f are arranged in the radial direction of the lower thrust bearing 9 in the radial direction of the lower thrust bearing 9 in the region connecting to the protruding piece 9b in the protruding piece 9b and the half washer portion 9a. Is formed.

  In this case, as described in the first embodiment, the balance weight 2c bends during the rotation of the crankshaft 2, so that a thrust load acts on the lower thrust bearing 9 and the crank cap 5. At that time, a lubricating oil film exists between the balance weight 2c, the lower thrust bearing 9 and the crank cap 5, but when the hole 9f as described above is provided in the lower thrust bearing 9, the oil film is formed in the hole. The crank cap 5 is pulled out to the straight groove 5c side through 9f.

  As a result, the thrust load from the crankshaft 2 is less likely to act on the region of the lower thrust bearing 9 that is continuous with the protruding piece 9b in the protruding piece 9b and the half washer portion 9a, and stress is applied to the root of the protruding piece 9b. It will be possible to prevent concentration.

  Therefore, in the case of the third embodiment as well, in the same way as in the first and second embodiments, it is possible to prevent the occurrence of problems such as the lower thrust bearing 9 being damaged from the base side of the protruding piece 9b. The durability of the last bearing 9 is improved and it is possible to contribute to the improvement of reliability.

  By the way, the configuration of the third embodiment can be combined with the configurations of the first and second embodiments. In that case, in addition to the merit by the structure of the said Embodiment 1 and 2, the effect which avoids the damage from the base side of the protrusion 9b increases. For example, FIG. 11 shows a combination of the first and third embodiments.

  As described above, in Embodiments 1 to 3 to which the features of the present invention are applied, it is possible to stably support the crankshaft 2 over a long period of time, which contributes to improvement in engine reliability.

  In addition, this invention is not limited only to the said embodiment, All the deformation | transformation and application included in the range equivalent to the claim and the said range are possible. Examples are given below.

  (1) In each of the above embodiments, an example in which individual crank caps 5 are coupled to each of the plurality of crank journals 2a provided on the crankshaft 2 is described, but the present invention is not limited thereto. Alternatively, it is possible to use a so-called ladder beam structure in which the crank caps 5 are integrally connected. In this case, the present invention can be applied in the same manner as in the above embodiment.

  (2) In each of the above embodiments, the shape of the mating end of the lower thrust bearing 9 and the uppass thrust bearing 10 is not particularly limited. For example, the shape shown in Japanese Utility Model Laid-Open No. 61-191521 is used. It is possible.

It is sectional drawing which shows typically Embodiment 1 of the crankshaft support structure which concerns on this invention. It is a disassembled perspective view which shows the state which isolate | separated the cylinder block shown in FIG. 1, a crank cap, and a crankshaft. It is an arrow view of the (3)-(3) line cross section of FIG. It is a figure which expands and shows a part (leftmost crank journal part) of FIG. It is a figure which shows the state which looked down the lower thrust bearing periphery in FIG. 3 from upper direction. FIG. 6 is a view corresponding to FIG. 3 in Embodiment 2 of the crankshaft support structure according to the present invention. In Embodiment 2 of FIG. 6, it is a figure which shows the state which attached the two thrust bearings. FIG. 7 is a diagram corresponding to FIG. 3 and FIG. 6 in an example in which the first embodiment and the second embodiment are combined. FIG. 6 is a view corresponding to FIG. 3 in Embodiment 3 of the crankshaft support structure according to the present invention. FIG. 10 is a diagram corresponding to FIG. 5 in Embodiment 3 of FIG. 9. FIG. 10 is an example in which the first embodiment and the third embodiment are combined, and corresponds to FIGS. 3 and 9.

Explanation of symbols

1 Cylinder block
1a Pedestal of cylinder block
2 Crankshaft
2a Crankshaft crank journal
2b Crankshaft crankpin
2c Crankshaft balance weight
3 Connecting rod
5 Crank cap
5b Semi-circular step of crank cap
5c Crank cap straight groove
5d Crank cap hole
9 Lower thrust bearing for crank journal
9a Half washer of lower thrust bearing
9b Lower thrust bearing protrusion
9e Thin part of lower thrust bearing
9f Lower thrust bearing hole
10 Uppass Last Bearing for Crank Journal

Claims (3)

In the structure that supports the crank journal of the crankshaft so as to be rotatable by sandwiching it between the cylinder block and crank cap of the engine,
A lower thrust bearing is interposed between the balance weight of the crankshaft and the crank cap,
The lower thrust bearing has a shape in which a projecting piece projecting radially outward is integrally formed at a predetermined position on the outer diameter side of the half washer portion, and substantially matches a recess provided in the crank cap. Are fitted and installed,
Crank characterized in that a region connected to the projecting piece in the projecting piece and the half washer portion is formed thinner than other regions so as to be in non-contact with the balance weight. Shaft support structure. The crankshaft support structure according to claim 1,
The recess of the crank cap includes a semicircular arc-shaped step and a linear groove provided radially outward on the outer diameter side of the predetermined position,
In the wall portion where the semicircular arc-shaped step of the crank cap and the straight groove intersect, the intersecting wall portion is removed by forming a hole,
In the lower thrust bearing, the connecting portion between the half washer and the projecting piece is curved, and the radius of curvature is such that it does not interfere with the remaining wall at the intersection of the semicircular arc step and the straight groove. A crankshaft support structure characterized by being set. The crankshaft support structure according to claim 1 or 2,
A crankshaft support structure, wherein a hole penetrating in a thickness direction is provided in a region of the lower thrust bearing projecting piece and the half washer portion continuous with the projecting piece.

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