Crankshaft support structure

Abstract

To provide a crank shaft support structure capable of constituting a beam-integrated bearing cap without increasing the size of a crank case with further structural improvements, to improve strength and rigidity of a crank case.SOLUTION: A crank shaft support structure is provided with a bearing cap body B in which a plurality of bearing caps 18 for pivotally supporting a crank shaft 5 at a lower part of a cylinder block 1 is integrated with a beam 19 extending in an axial core P direction of the crank shaft 5. The beam 19 is configured to have a cross section along or similar to a cross-sectional shape of a gap S, where the gap S is an outside region of a rotational trajectory t of the crank shaft 5 and an inside region of a lower crank case 1C assembled under the cylinder block 1.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a crankshaft support structure for an engine equipped with a bearing cap that supports a bearing of a crankshaft from below.

Background Art

[0002] Generally, in engines for industrial use, automobiles, etc., as disclosed in Patent Document 1, a cylinder block having a shape in which a cylinder portion and a crankcase portion are integrated is used. A crankshaft provided in the lower portion of the cylinder block, that is, the crankcase portion, is pivotally supported by a journal portion machined in the upper portion of the crankcase portion and a bearing cap assembled to the central lower surface of the crankcase portion.

[0003] For example, in a multi-cylinder diesel engine assumed to be mounted on an agricultural tractor, since the crankcase portion (lower portion of the cylinder block) often has a structure that also serves as the body frame of the tractor (such as Patent Document 1), strength and rigidity are required for the crankcase portion. That is, when the crankcase portion also serves as the body frame, as shown in the schematic diagram of FIG. 7(B), a configuration in which a lower crankcase 57 is provided is often adopted so that sufficient strength and rigidity can be obtained.

[0004] In FIG. 7(B), 51 is a cylinder block, 51A is a cylinder portion, 51B is a crankcase portion, 52 is a piston, 53 is a connecting rod, 54 is a crankshaft, and a bearing cap 55 for pivotally supporting the crankshaft 54 is bolted to the central lower surface of the crankcase portion 51B. And a lidless box-shaped (concave-shaped) lower crankcase 57 is bolted to the lower surfaces of both left and right ends of the crankcase portion 51B so as to cover the bearing cap 55.

[0005] That is, by adopting a structure in which the lower crankcase 57, which is a strength member, is assembled and integrated under the crankcase portion 51B, the strength and rigidity as the crankcase portion k are enhanced so that the function of the airframe frame can be exerted.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the case of increasing the output of the engine while maintaining the conventional structure in specification changes, new product development, etc., since the load (behavior) on the bearing cap increases due to an increase in combustion load (increase in explosion pressure), some countermeasures are required. As countermeasures, a plan to integrate the bearing cap with the lower crankcase and a plan to add a beam to the bearing cap can be considered.

[0008] The former plan (integration of the bearing cap and the lower crankcase) is large-scale and has a large cost burden, and it is very difficult to implement. Therefore, the latter plan is more practical. However, when adopting the means of adding a beam, which has an advantage in terms of cost, since the bearing cap is covered by the lower crankcase with little gap, it is not easy to newly provide a beam without increasing the size of the lower crankcase or the crankcase portion (see Fig. 7(B)).

[0009] In view of the above circumstances, an object of the present invention is to focus on the latter (beam addition) solution, which is cost-effective among the above two solutions, and by further structural improvements, to configure a bearing cap body in which the beam is integrated without increasing the size of the crankcase, and to provide a crankshaft support structure capable of improving the strength and rigidity of the crankcase.

Means for Solving the Problems

[0010] The present invention relates to a crankshaft support structure, a bearing cap body is provided in which a plurality of bearing caps for axially supporting a crankshaft at the lower part of a cylinder block are integrated by a beam extending in the axial direction of the crankshaft, the beam is configured to have a cross-section similar or similar to the cross-sectional shape of the void portion in an outer region of the rotation locus of the crankshaft and in an inner region of a lower crankcase assembled under the cylinder block.

[0011] In this case, the peak portion of the beam corresponding to the maximum rotation locus of the crankshaft is set to a cross-sectional shape having a radially inner surface close to the maximum rotation locus exist Other aspects of the present invention constituent elements For details, refer to the Claims 1 to 5 claims.

Advantages of the Invention

[0012] According to the present invention, a beam is installed in the rotation locus of the crankshaft (rotation locus of the large end portion and counterweight) and the bolt seat surface of the bearing cap and the triangular portion (void portion) covered by the lower crankcase, and the bearing cap and the beam are connected to form a bearing cap body. Since the beam has a cross-section along or similar to the cross-sectional shape of the void portion, a larger cross-sectional area can be obtained than before without changing the lower crankcase.

[0013] Therefore, by adding the beam, the combustion load that was previously borne by four bolts with the bearing caps being independent of each other can now be shared by the bolts of the adjacent bearing caps, reducing the movement of the bearing caps and suppressing the deterioration of vibration and noise.

[0014] As a result, a beam-integrated bearing cap body can be configured without increasing the size of the lower crankcase (crankcase), enabling the provision of a crankshaft support structure that can improve the strength and rigidity of the crankcase at low cost.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the crankshaft support structure according to the present invention will be described with reference to the drawings for an industrial in-line multi-cylinder diesel engine. In an industrial diesel engine (hereinafter abbreviated as "engine") E, the side with the cooling fan 10 is the front, the side with the flywheel 7 (flywheel housing 7A) is the rear, the side with the exhaust manifold 31 is the left, and the side without the exhaust manifold 31 [the side with the intake manifold (not shown)] is the right.

[0017] As shown in FIGS. 1 to 3, in an engine [vertical in-line four-cylinder (multi-cylinder) water-cooled engine] E, a cylinder head 2 is assembled on a cylinder block 1, a head cover 3 is assembled on the cylinder head 2, and an oil pan 4 is assembled under the cylinder block 1. 5 is a crankshaft, 6 is a piston, 7 is a flywheel, 8 is a transmission belt, 9 is a water pump, 10 is a cooling fan, and 11 is a radiator. 32 is a supercharger, and 33 is an exhaust treatment device.

[0018] The upper part of the cylinder block 1 is formed with a cylinder part 1A into which the piston 6 is fitted, and the lower side of the cylinder part 1A is formed with a crankcase part C. The crankcase part k is composed of an upper crankcase 1B integrally formed with the cylinder part 1A and a lower crankcase 1C (see also FIG. 6(A)) assembled under the upper crankcase 1B. The oil pan 4 is assembled under the lower crankcase 1C.

[0019] As shown in FIG. 3, the crankshaft 5 is pivotally supported by the upper crankcase 1B and a bearing cap body B assembled under the upper crankcase 1B by a plurality of bolts. That is, the lower crankcase 1C and the bearing cap body B are assembled on the lower surface of the upper crankcase 1B, and the bearing cap body B is configured to be accommodated in the lower crankcase 1C without a gap.

[0020] As shown in FIGS. 4 and 5, the bearing cap body B is configured as a substantially ladder-shaped structure [see FIG. 4(A)] including a plurality of (five) bearing caps (bearing cap portions) 18 arranged in the front and rear, and a total of eight beams (beam portions) 19 that connect and integrate adjacent bearing caps 18. That is, a bearing cap body B is provided in which a plurality of bearing caps 18 that pivotally support the crankshaft 5 at the lower part of the cylinder block 1 are integrated by beams 19 extending in the axial direction P of the crankshaft 5.

[0021] Each bearing cap 18 is bolted at two locations on the left and right to the lower surfaces of a plurality of bearing walls 20 formed to hang down from the upper crankcase 1B. That is, the bearing cap body B is attached to the upper crankcase 1B by ten bolts 21 [see FIG. 7(A)].

[0022] The bearing cap 18 is formed with a semi-circular inner peripheral surface 18a on which a bearing (such as a sliding bearing) 22 is placed, and a pair of left and right mounting seat surfaces 18b on the cap main body 18A, and beams 19 are connected to both the left and right ends at the lower part thereof. The bearing 22 is a portion that pivotally supports the journal 5a of the crankshaft 5 and is also mounted on the journal portion (reference numeral omitted) at the lower part of the bearing wall 20 (see FIG. 5).

[0023] As shown in FIGS. 4, 5, and 6(B), the beam 19 has a front beam portion 19a and a rear beam portion 19b that are continuous with the bearing cap 18, and an intermediate portion 19c. In addition, in the four beams 19 on the left and right at the front and rear ends, the front beam portion 19a and the rear beam portion 19b are formed in a shape like a diagonal beam by restricting the overhang to the left and right [see FIG. 4(A)]. The beam 19 is configured to have a cross-section along or similar to the cross-sectional shape of the gap portion S in the outer region of the rotation locus t of the crankshaft 5 and in the inner region of the lower crankcase 1C (see FIG. 5).

[0024] In the crankshaft 5, the locations where the rotation locus t becomes large are the large end portion 23A of the connecting rod 23 that pivotally supports the piston 6 at the upper end portion, and the counterweights 24, 24 that are disposed in the vicinity of both sides (front and rear) of the large end portion 23A. The location with the largest rotation locus (rotation radius) (maximum rotation locus st) is the large end portion 23A. Therefore, in order to avoid interference with the pair of counterweights 24, 24 and the large end portion 23A, the beam 19 has side inner surfaces 19s, 19s and a central inner surface 19d in the outer region of the rotation locus (maximum rotation locus) t of these three members 24, 23A, 24, and in a state of having the shape shown in substantially V-shaped when viewed in the left-right direction [see Fig. 6(B)].

[0025] As shown in Figs. 1, 2, 5, and 6(A), the lower crankcase 1C has a front wall 25, a rear wall 26, a left side wall 27, a right side wall 28, and a bottom wall 29 in the front-rear middle. In addition, three locations in the front and rear corresponding to the bearing wall 20 are formed with reinforcing rib walls 30 extending left and right. Notches 25A, 26A (see Fig. 6(A)) that are recessed downward from the upper end in the left-right central portions are formed in the front wall 25 and the rear wall 26 to allow the crankshaft 5 to pass through.

[0026] As shown in Fig. 5, the left and right outer surfaces 19L, 19R of each beam 19 are set to be close to and along the corresponding left and right inner surfaces 27A, 28A of the lower crankcase 1C, and the bottom surface 19B of each beam 19 is set to be close to and along the upper surface 29A of the bottom wall 29. In addition, the central inner surface 19d, which is the upper surface (inclined upper surface) of the intermediate portion 19c located at the location of the maximum rotation locus st where the rotation locus t is the largest in the front-rear direction, is set to be close to and along the rotation locus t. As a result, the intermediate portion 19c has a cross-sectional shape of an irregular quadrilateral having a left outer surface 19L, a right outer surface 19R, an inclined central inner surface 19d, and short side surfaces 19e on the left and right central sides.

[0027] That is, an intermediate portion (an example of a "peak portion") 19c corresponding to the maximum rotation locus st of the crankshaft 5 in the beam 19 is set to a cross-sectional shape having a central inner surface (an example of a "radial inner surface") 19d close to the maximum rotation locus st. And the cross-sectional area of the beam 19 (the area of the cross-section cut in the left-right direction) is set in a gradually increasing state that becomes larger as it goes forward and backward from the intermediate portion 19c which is the peak portion (as it goes to the connection portion to the bearing cap 18). The intermediate portion 19c has outer surfaces 19L and 19R along the inner surfaces 27A and 28A of the lower crankcase 1C, and a bottom surface 19B along the upper surface 29A of the lower crankcase 1C.

[0028] The left-right width of the intermediate portion 19c, that is, the position of the short side surface 19e in the left-right direction, is set to a short length such that a rectangular cross-section having a certain length is ensured so that stress concentration hardly occurs in the intermediate portion 19c (so that the bottom surface 19B and the central inner surface 19d do not directly intersect to form an acute-angled tip). Also, it can be said that the short side surface 19e is provided at a position as close as possible to the inside in the left-right direction within the range where the attachment and detachment of bolts (not shown) for attaching the bearing cap 18 to the bearing wall 20 and the operation of the turning tool can be performed.

[0029] 〔Regarding the effects〕 Since the lower crankcase 1C is attached to the upper crankcase 1B, the strength and rigidity of the crankcase portion k are greatly improved, and the crankcase portion k can be suitably used for a working machine (such as an agricultural tractor) that also serves as the body frame. And since the beam 19 that connects adjacent ones of the bearing caps 18 for pivotally supporting the crankshaft 5 is provided and integrated, the strength and rigidity of the bearing cap 18 are improved, and even if the combustion load increases due to increased output, the behavior of the bearing cap 18 (the bearing cap body B) does not become large.

[0030] In the present invention, as shown in FIG. 7(A), a beam is provided so as to have as large a cross-sectional area as possible in the outer region of the maximum rotation locus st of the crankshaft 5 and within the range that fits within the inner region of the lower crankcase (liner case) 1C. Thus, a beam 19 having strength and rigidity can be formed without changing the size of the lower crankcase 1C. Therefore, sufficient strength and rigidity can be provided to the bearing cap body B. In FIG. 7(A), the substantially triangular portions with hatching on the left and right indicating the gap portion S are drawn including the space where the head of the bolt 21 (reference numeral omitted) is arranged. In the portion without the bolt 21, the upper surface 29A (see FIG. 5) of the lower crankcase 1C approaches the bottom of the bearing cap 18, and the bottom of the aforementioned substantially triangular portion may rise to the position of the bottom of the bearing cap 18 and become even smaller.

[0031] That is, a beam 19 is installed in the rotation locus t of the crankshaft 5 (such as the rotation locus of the large end portion 23A and the counterweight 24), the bolt seating surface of the bearing cap 18, and the triangular portion (gap portion S) covered by the lower crankcase 1C, and the bearing cap 18 and the beam 19 are connected to form the bearing cap body B. Due to the addition of the beam 19, the combustion load that was conventionally borne by four bolts with the bearing caps being independent of each other can also be borne by the bolts 21 of the adjacent bearing caps, the behavior of the bearing cap 18 can be reduced, and the deterioration of vibration and noise can be suppressed.

[0032] And as shown in FIG. 6(B), since the front and rear beam portions 19a and 19b are formed such that the cross-sectional area increases as the beam 19 approaches the bearing cap 18 from the intermediate portion 19c, the portion with the minimum cross-sectional area is only the intermediate portion 19c, the strength and rigidity of the beam 19 are greatly improved, and as a result, the strength and rigidity of the bearing cap body B are also greatly improved.

[0033] 〔Alternative Embodiment〕 The cross-sectional shape of the middle part 19c of the beam 19 (the part corresponding to the maximum rotation locus st) may be enlarged to a large area in the vicinity of the inner surface of the lower crankcase 1C or the maximum rotation locus st within the range allowed by the dimensional tolerance of the component clearance. (Summary) In this embodiment, as shown in FIG. 4(A), with the axial direction of the crankshaft as the front-rear direction and the width direction of the bearing cap intersecting the front-rear direction in plan view as the left-right direction, the beam 19 includes connection portions 19A to the respective bearing caps 18 disposed on the left and right sides of each bearing cap 18, peak portions 19c·19c disposed on the front and rear sides of the connection portion 19A, and front and rear connecting walls 19b·19a connecting the connection portion 19A and the front and rear peak portions 19c·19c, respectively. As shown in FIG. 4(C), in a left-right direction view, the front and rear connecting walls 19b·19a protrude forward and backward from the positions of the front and rear end faces 18c·18c of the bearing cap 18, respectively, and each has front and rear wall surfaces 19sb·19sa at the front and rear protruding ends. The front and rear wall surfaces 19sb·19sa are inclined downward from the height of the lower end portion 18aa of the inner peripheral surface 18a of the cap toward the front and rear peak portions 19c·19c, respectively. Also, as shown in FIG. 4(C), the upper surface 19d of the peak portion 19c and the front and rear wall surfaces 19sb·19sa of the front and rear connecting walls 19b·19a disposed on the front and rear sides of the upper surface 19d of the peak portion 19c are formed in a V shape with the upper surface 19d of the peak portion 19c as the base in a left-right direction view. When expressed in terms of the relative arrangement with the connection portion 19A as a reference, as described above, the front beam portion 19a becomes the rear connecting wall 19a, the rear beam portion 19b becomes the front connecting wall 19b, the side inner surface 19s becomes the front side wall surface 19sb or the rear side wall surface 19sa, and the central inner surface 19d of the intermediate portion 19c becomes the upper surface 19d of the peak portion 19c.

Explanation of Signs

[0034] 1 Cylinder block 1C Lower crankcase 5 Crankshaft 18 Bearing cap 19 Beam 19L, 19R Outer surface 19c Peak location 19d Inner diameter surface 27A, 28A Inner surface B Bearing cap body P Axis center S Gap location t Rotation locus st Maximum rotation locus

Claims

1. A bearing cap body is provided, in which a plurality of bearing caps that pivotally support a crankshaft at the lower part of a cylinder block are integrated by a beam extending in the axial direction of the crankshaft. The beam is configured to have a cross-section along or similar to the cross-sectional shape of the void portion in an outer region of the rotation locus of the crankshaft and in a void portion that is an inner region of a lower crankcase assembled under the cylinder block. A peak portion corresponding to the maximum rotation locus of the crankshaft in the beam is configured to have a cross-sectional shape having a radially inner surface close to the maximum rotation locus. Taking the axial direction of the crankshaft as the front-rear direction and the width direction of the bearing cap intersecting the front-rear direction in plan view as the left-right direction, the beam includes connection portions to the respective bearing caps disposed on the left and right sides of each bearing cap, peak portions disposed on the front and rear sides of the connection portions, and front and rear connecting walls connecting the connection portions and the front and rear peak portions respectively. Viewed in the left-right direction, the front and rear connecting walls project forward and backward from the positions of the front and rear end faces of the bearing cap, and each has a front and rear wall surface at the front and rear protruding ends. The front and rear wall surfaces are each inclined downward from the height of the lower end portion of the inner peripheral surface of the cap toward the front and rear peak portions. A crankshaft support structure characterized by this.

2. The crankshaft support structure according to claim 1, wherein the cross-sectional area of the beam is set in an increasing state such that it becomes larger as it goes from the peak portion to the connection portion to the bearing cap.

3. The crankshaft support structure according to claim 1, wherein the peak portion has an outer surface along the inner surface of the lower crankcase and a bottom surface along the upper surface of the lower crankcase.

4. The upper surface of the peak portion and the front and rear wall surfaces of the front and rear connecting walls disposed on the front and rear sides of the upper surface of the peak portion are formed in a V shape having the upper surface of the peak portion as the bottom, in the crankshaft support structure according to claim 1.

5. The beam is provided on each of the left and right sides with respect to the axis of the crankshaft, in the crankshaft support structure according to any one of claims 1 to 4.

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