JP2019152103A - Ladder frame - Google Patents

Abstract

To make a fastening force of a bolt efficiently act as surface pressure acting between a lower end face of a ladder frame and an oil pan.SOLUTION: A lower end face of an end transverse frame 60 comprises: first joining faces 62 which are arranged in the same positions as those of bolt holes 54c with respect to an extension direction of the end transverse frame 60, and positioned at one side of a crankshaft rather than the bolt holes 54c in an axial line direction with respect to the axial line direction of the crankshaft; and a second joining faces 64 positioned between the two blot holes 54c with respect to the extension direction of the end transverse frame 60. The second joining faces 64 are larger than the first joining faces 62 in dimensions with respect to the axial line direction of the crankshaft, and extend up to the other side of the crankshaft in the axial line direction rather than a linear line L for virtually connecting tow connecting holes N with respect to the axial line direction of the crankshaft.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a ladder frame.

  Patent Document 1 discloses a ladder frame disposed between a cylinder block of an internal combustion engine and an oil pan. The ladder frame includes a pair of vertical frames that extend along the axial direction of the crankshaft, and a plurality of horizontal frames that are spanned between the pair of vertical frames. A crankshaft is rotatably supported between each horizontal frame and the cylinder block in the ladder frame.

  The lower end surface of each vertical frame in the ladder frame and the lower end surface of the horizontal frame located at the end in the axial direction of the crankshaft of each horizontal frame are joint surfaces that contact the upper end surface of the oil pan. Yes. And a ladder frame and an oil pan are fixed with a volt | bolt, and the sealing performance between the joining surface of a ladder frame and the upper end surface of an oil pan is ensured.

JP 2003-314358 A

  As in the ladder frame of Patent Document 1, when securing the sealing property between the joining surface of the ladder frame and the upper end surface of the oil pan with the fastening force of the bolt, depending on the positional relationship between the joining surface of the bolt and the ladder frame, The pressure (surface pressure) acting between the joining surface of the ladder frame and the upper end surface of the oil pan changes. Therefore, depending on the shape of the horizontal frame in the ladder frame, the pressure expected from the fastening force of the bolt may not be applied between the joint surface of the horizontal frame and the upper end surface of the oil pan.

  A ladder frame for solving the above-described problem is a ladder frame that is disposed between a cylinder block and an oil pan of an internal combustion engine and supports a crankshaft between the cylinder block and in the axial direction of the crankshaft. A pair of vertical frames extending along the plurality of horizontal frames arranged between the pair of vertical frames and arranged in the axial direction of the crankshaft, the cylinder block in the horizontal frame A bearing portion for supporting the crankshaft is recessed at the upper end surface, which is an end surface on the side, and the ladder frame is fixed to the cylinder block on both sides of the bearing portion with respect to the extending direction of the horizontal frame. Bolt holes through which the bolts to be inserted pass respectively, and a plurality of the horizontal frames Among these, when the horizontal frame located at the end on the most axial side of the crankshaft is an end horizontal frame, the lower end surface, which is the end surface on the oil pan side of the end horizontal frame, Two coupling holes into which bolts for fixing the oil pan and the ladder frame are screwed are recessed, and one of the coupling holes is on the opposite side of the bearing portion across the one bolt hole. And the other coupling hole is located on the opposite side of the bearing portion across the other bolt hole, and the lower end surface of the end horizontal frame is in the extension direction of the end horizontal frame. A first joint surface disposed at the same position as the bolt hole and positioned on one side in the axial direction of the crankshaft with respect to the axial direction of the crankshaft; A second joint surface that is continuous with the joint surface and is positioned between the two bolt holes with respect to the extending direction of the end lateral frame, wherein the second joint surface is in the axial direction of the crankshaft The dimension of the crankshaft is larger than that of the first joint surface, and the axial direction of the crankshaft is the other in the axial direction of the crankshaft rather than a straight line that virtually connects the central axes of the two coupling holes. It extends to the side.

  In the above configuration, the dimension of the second joint surface in the axial direction of the crankshaft is larger than the dimension of the first joint surface. For this reason, the contact area between the lower end surface of the ladder frame and the oil pan is increased. Furthermore, in the said structure, the 2nd joining surface is arrange | positioned ranging over the straight line which tied the central axis line of two coupling holes virtually in the crank-axis direction. From this, it becomes possible to make the fastening force of the bolt act efficiently as a surface pressure acting between the lower end surface of the ladder frame and the oil pan.

1 is a cross-sectional view schematically showing an internal combustion engine. The top view which looked at the ladder frame from the oil pan side.

  Hereinafter, an embodiment of an internal combustion engine to which a ladder frame is applied will be described with reference to the drawings. In this embodiment, it is assumed that the internal combustion engine is mounted on the vehicle. And the up-down direction in the state in which the internal combustion engine is mounted on the vehicle is defined as the up-down direction of the internal combustion engine.

  As shown in FIG. 1, the internal combustion engine 10 includes a cylinder block 20 having a substantially rectangular parallelepiped shape as a whole. A cylindrical cylinder 22 is defined in the cylinder block 20. The axis of the cylinder 22 extends in the vertical direction. In this embodiment, four cylinders 22 are provided (only one is shown in FIG. 1). The four cylinders 22 are arranged in a line in the axial direction of the crankshaft 100 of the internal combustion engine 10. In each cylinder 22, a piston (not shown) that reciprocates in the cylinder 22 is disposed.

  In the cylinder block 20, a gap 23 is defined below each cylinder 22. The gap 23 continues to the lower surface of the cylinder block 20. That is, each cylinder 22 communicates with the lower side of the lower surface of the cylinder block 20 via the gap 23. In each gap 23, a connecting rod (not shown) connected to the piston in each cylinder 22 can operate. The connecting rod is connected to the crankshaft 100, and when the internal combustion engine 10 is operated, the reciprocating movement of the piston in the vertical direction is converted into the rotational motion of the crankshaft 100 via the connecting rod.

  As described above, since the four gaps 23 are arranged side by side, partitions that divide the gaps 23 between the neighboring gaps 23 and at both ends of the cylinder block 20 in the axial direction of the crankshaft 100. There is a wall 21. That is, there are a total of five partition walls 21 including two partition walls 21 constituting side walls on both sides in the axial direction of the crankshaft 100 in the cylinder block 20 and three partition walls 21 between each of the four gap portions 23. is doing. When the direction perpendicular to both the axial direction and the vertical direction of the crankshaft 100 is defined as the width direction of the internal combustion engine 10, both end portions in the width direction of the five partition walls 21 are side walls at both ends in the width direction of the cylinder block 20. It is connected to the outer wall 24 which comprises.

On the lower surface of each partition wall 21, a semicircular bearing portion 21a in plan view is recessed upward. The bearing portion 21 a is located at the approximate center of the partition wall 21 in the width direction.
An aluminum alloy ladder frame 50 is fixed to the lower side of the cylinder block 20. As shown in FIG. 2, the ladder frame 50 includes a pair of plate-like vertical frames 52 that extend in the axial direction of the crankshaft 100. The pair of vertical frames 52 are disposed to face each other in the width direction of the internal combustion engine 10. Between the pair of vertical frames 52, five plate-like horizontal frames 54 are bridged. The extending direction of the five horizontal frames 54 coincides with the width direction of the internal combustion engine 10. The five horizontal frames 54 are arranged at substantially equal intervals in the axial direction of the crankshaft 100. The intervals between the five horizontal frames 54 coincide with the intervals between the five partition walls 21 in the cylinder block 20. Of the five horizontal frames 54, the horizontal frames 54 positioned at both ends in the axial direction of the crankshaft 100 connect the ends in the extending direction of the pair of vertical frames 52. As a result, the horizontal frames 54 located at both ends of the crankshaft 100 in the axial direction and the pair of vertical frames 52 are connected in a rectangular frame shape. The outer peripheral dimension of the frame is substantially the same as the outer peripheral dimension of the lower surface of the cylinder block 20. The vertical dimensions of the pair of vertical frames 52 and the five horizontal frames 54 are the same, and the upper end surface of the vertical frame 52 and the upper end surface of the horizontal frame 54 are substantially flush with each other. Further, the lower end surface of the vertical frame 52 and the lower end surface of the horizontal frame 54 are substantially flush with each other.

  As shown in FIG. 1, in a state where the ladder frame 50 is fixed to the cylinder block 20, each vertical frame 52 is disposed at a position facing each outer wall 24 in the cylinder block 20. The upper end surface of the vertical frame 52 is in contact with the lower surface of the outer wall 24. A sealing material such as a liquid gasket is interposed between the upper end surface of the vertical frame 52 and the lower surface of the outer wall 24. Further, the five horizontal frames 54 are arranged at positions facing the five partition walls 21 of the cylinder block 20. The upper end surface of the horizontal frame 54 is in contact with the lower surface of the partition wall 21. A sealing material such as a liquid gasket is interposed between the upper end surface of the horizontal frame 54 and the lower surface of the partition wall 21.

  As shown in FIG.1 and FIG.2, in the lower end surface of each vertical frame 52, the cylindrical recessed part 52a is dented upward. For each vertical frame 52, four recesses 52a are provided at substantially equal intervals in the axial direction of the crankshaft 100 (the extending direction of the vertical frame 52).

  In each vertical frame 52, an end bolt hole 52 b penetrates in the vertical direction from the upper surface (bottom surface) of each recess 52 a to the upper end surface of the vertical frame 52. As shown in FIG. 1, a bolt B2 is inserted into each end bolt hole 52b from below. The bolt B <b> 2 passes through the vertical frame 52 and is screwed into the cylinder block 20. That is, the ladder frame 50 is fixed to the cylinder block 20 by the bolt B2. The head of the bolt B2 is located in the recess 52a of the vertical frame 52. That is, the head of the bolt B <b> 2 is located above the lower end surface of the vertical frame 52.

  As shown in FIG. 2, columnar coupling holes P are recessed upward at the lower end surface of each vertical frame 52. The coupling hole P is located between the adjacent end bolt holes 52b in each vertical frame 52. That is, three coupling holes P are provided for each vertical frame 52. The inner wall surface of the coupling hole P is threaded.

  As shown in FIGS. 1 and 2, on the upper end surface of each horizontal frame 54, a semicircular bearing portion 54 a in plan view is recessed downward. The bearing portion 54 a is located substantially at the center in the extending direction of the horizontal frame 54, and is disposed to face the bearing portion 21 a of the partition wall 21 in the cylinder block 20. As shown in FIG. 1, the crankshaft 100 is rotatably supported between the bearing portions 54 a of the horizontal frames 54 and the bearing portions 21 a of the partition walls 21 in the cylinder block 20.

  As shown in FIG. 2, among the plurality of horizontal frames 54, when the horizontal frame 54 positioned at the end on the most axial side (the lower side in FIG. 2) of the crankshaft 100 is the end horizontal frame 60. On the lower end surfaces of the four horizontal frames 54 excluding the end horizontal frame 60, the recesses 54b are recessed upward. With respect to the extending direction of the horizontal frame 54, the recess 54 b is provided in a central portion of each horizontal frame 54. Specifically, with respect to the extending direction of the horizontal frame 54, the recessed portion 54b extends over both sides of the bearing portion 54a across the bearing portion 54a. With respect to the axial direction of the crankshaft 100, the recess 54 b extends to both ends of the horizontal frame 54. In other words, the recess 54 b penetrates the horizontal frame 54 in the axial direction of the crankshaft 100.

  In the four horizontal frames 54 described above, the bolt holes 54c penetrate vertically from the upper surface (bottom surface) of the recess 54b to the upper end surface of the horizontal frame 54. One bolt hole 54 c is provided on each side of the bearing portion 54 a in the extending direction of the horizontal frame 54.

  On the lower end surface of the end lateral frame 60, a recess 60a is recessed upward. With respect to the extending direction of the end horizontal frame 60, the recess 60 a is provided at a central portion of the end horizontal frame 60. Specifically, with respect to the extending direction of the end lateral frame 60, the recess 60a extends over both sides of the bearing portion 54a across the bearing portion 54a. With respect to the axial direction of the crankshaft 100, the recess 60a is located on the other side of the end lateral frame 60 as a whole. That is, the recess 60a is open on the other side in the axial direction of the crankshaft 100 in the end horizontal frame 60, but is not open on one side in the axial direction. Specifically, the central portion in the extending direction of the end horizontal frame 60 in the recess 60 a is provided on the other side of the center of the end horizontal frame 60 with respect to the axial direction of the crankshaft 100. It reaches to the end. The dimension in the axial direction of the crankshaft 100 is larger at the end portion of the recess 60a in the extending direction of the end horizontal frame 60 than at the center portion. Moreover, the site | part of the edge side of the extending direction of the end side frame 60 in the recessed part 60a has extended to the other end.

  In the end horizontal frame 60, a bolt hole 54 c penetrates in the vertical direction from the upper surface (bottom surface) of the recess 60 a to the upper end surface of the end horizontal frame 60. One bolt hole 54c is provided at each end portion of the recess 60a in the extending direction of the end horizontal frame 60, that is, on both sides of the bearing portion 54a.

  As shown in FIG. 1, in each horizontal frame 54 including the end horizontal frame 60, a bolt B1 is inserted into each bolt hole 54c from below. The bolt B1 passes through the horizontal frame 54 and is screwed into the cylinder block 20. That is, the ladder frame 50 is fixed to the cylinder block 20 by the bolt B1. Note that the heads of the bolts B <b> 1 are located in the recesses 54 b of the four horizontal frames 54 and the recesses 60 a of the end horizontal frame 60. That is, the head of the bolt B <b> 1 is located above the lower end surface of each horizontal frame 54.

  As shown in FIGS. 1 and 2, a cylindrical coupling hole N is recessed upward on the lower end surface of the end lateral frame 60. The inner wall surface of the coupling hole N is threaded. One coupling hole N is provided in the vicinity of the connection position with each vertical frame 52 in the end horizontal frame 60. That is, one coupling hole N is provided at each end of the end horizontal frame 60 in the extending direction with the recess 60 a of the end horizontal frame 60 interposed therebetween. One coupling hole N is located on the opposite side of the bearing portion 54a with one of the two bolt holes 54c interposed therebetween. The other coupling hole N is located on the opposite side of the bearing portion 54a across the other of the two bolt holes 54c.

  As shown in FIG. 1, a substantially square box-shaped oil pan 90 is fixed to the lower side of the ladder frame 50 as a whole. The oil pan 90 is configured such that a substantially rectangular box-shaped storage case 94 opened upward is connected to a lower side of a substantially rectangular box-shaped crankcase 92 opened upward. Specifically, the crankcase 92 includes a substantially rectangular plate-shaped bottom wall and a rectangular cylindrical peripheral wall extending upward from the outer peripheral edge of the bottom wall. The outer peripheral edge of the upper end surface of the peripheral wall extends along the outer peripheral edge of the lower end surface of the ladder frame 50. The four sides constituting the upper end surface of the peripheral wall of the crankcase 92, the pair of vertical frames 52 in the ladder frame 50, and the lower end surface of the horizontal frame 54 positioned on both ends in the axial direction of the crankshaft 100 The crankcase 92 is fixed to the ladder frame 50 in a state in which the abutment is in contact. In addition, between the upper end surface of the peripheral wall of the crankcase 92 and the pair of vertical frames 52 in the ladder frame 50 and the lower end surface of the horizontal frame 54 positioned on both ends in the axial direction of the crankshaft 100, A sealing material such as a liquid gasket is interposed.

  A bolt B <b> 3 is inserted into the peripheral wall of the crankcase 92 from below. The bolt B <b> 3 is arranged at a position that is vertically below each coupling hole P of each vertical frame 52 and each coupling hole N of the end horizontal frame 60 in the ladder frame 50. Each bolt B <b> 3 passes through the peripheral wall of the crankcase 92 and is screwed into each coupling hole P of each vertical frame 52 and each coupling hole N of the end horizontal frame 60 in the ladder frame 50. That is, the crankcase 92 is fixed to the ladder frame 50 by the bolt B3. The head of the bolt B <b> 3 is located in a recess that is recessed upward from the lower end surface of the peripheral wall of the crankcase 92.

  The bottom wall of the crankcase 92 is provided with an opening that penetrates the bottom wall in the vertical direction, and the inside of the crankcase 92 communicates with the inside of the storage case 94 through this opening. ing.

  As described above, the lower end surface of the end lateral frame 60 is a joint surface that comes into contact with the upper end surface of the peripheral wall of the crankcase 92. Here, as described above, from the lower end surface of the end lateral frame 60, the recess 60a is recessed upward. The recess 60 a is provided at the central portion in the extending direction of the end lateral frame 60. Moreover, the recessed part 60a is located in the axial direction other side of the crankshaft 100 in the end side frame 60 as a whole. That is, the joint surfaces in the end horizontal frame 60 are both end portions in the extending direction of the end horizontal frame 60 and the portion of the end horizontal frame 60 on the center side in the extending direction of the end horizontal frame 60. 100 is located on one side in the axial direction.

  Of the joint surfaces of the end lateral frame 60, the part of the end lateral frame 60 that is located on the center side in the extending direction can be broadly divided into a first joint surface 62 and a second joint surface 64. The first joint surface 62 is a portion that is disposed at substantially the same position as the two bolt holes 54 c in the extending direction of the end lateral frame 60. That is, there are two first joint surfaces 62 corresponding to the two bolt holes 54c. Since the opening of the bolt hole 54c is located in the recess 60a of the end lateral frame 60, the two first joint surfaces 62 are located on one side in the axial direction of the crankshaft 100 with respect to the two bolt holes 54c. Yes.

  The second joint surface 64 is a portion located between the two bolt holes 54 c with respect to the extending direction of the end lateral frame 60, and connects the two first joint surfaces 62 to the extending direction of the end lateral frame 60. ing. The dimension of the second joint surface 64 in the axial direction of the crankshaft 100 increases toward the center in the extending direction of the end lateral frame 60. Further, with respect to the axial direction of the crankshaft 100, the dimension K <b> 2 of the second joint surface 64 on the center side in the extending direction of the end lateral frame 60 is larger than the dimension K <b> 1 of the first joint surface 62.

  In the second joint surface 64, the central portion in the extending direction of the end lateral frame 60 is one on the axial direction of the crankshaft 100 rather than on the straight line L virtually connecting the central axes of the two coupling holes N. It extends from one side to the other. That is, a portion of the second joint surface 64 on the center side in the extending direction of the end horizontal frame 60 is disposed across the straight line L with respect to the axial direction of the crankshaft 100.

Next, the operation and effect of this embodiment will be described.
As described above, a recess 60 a for avoiding interference between the head of the bolt B <b> 3 and the upper end surface of the crankcase 92 is recessed from the lower end surface of the end side frame 60. Here, it is difficult to think of making the shape of the concave portion distorted in order to avoid complication of processing steps. Therefore, in the prior art (for example, Patent Document 1), the dimension of the concave portion in the axial direction of the crankshaft is constant throughout the extending direction of the end horizontal frame. In other words, the recess is located in the axial direction of the crankshaft both at the position between the two bolt holes in the extending direction of the end horizontal frame and at the substantially same position as the two bolt holes in the extending direction of the end horizontal frame. It extends from the vicinity of the end on one side to the end on the other side. As a result, the lower end surface of the end horizontal frame is located on one side in the axial direction of the crankshaft rather than the two bolt holes over the entire extending direction of the end horizontal frame.

  On the other hand, in the present embodiment, the dimension of the recess 60a in the axial direction of the crankshaft 100 is deliberately reduced at a position between the two bolt holes 54c in the extending direction of the end lateral frame 60. The dimension of the second joint surface 64 is increased. Specifically, with respect to the axial direction of the crankshaft 100, the second joint surface 64 extends from one side to the other side of the straight line L virtually connecting the central axes of the two coupling holes N. Yes. As a result, the dimension of the second joint surface 64 in the axial direction of the crankshaft 100 is larger than the dimension of the first joint surface 62, and the lower end surface of the end lateral frame 60 and the upper end surface of the crankcase 92 are in contact with each other. Increases area. Further, according to the above configuration, the surface pressure acting between the lower end surface of the end lateral frame 60 and the upper end surface of the crankcase 92 is easily applied to the fastening force of the bolt B3 on the second joint surface 64 of the end lateral frame 60. As a result, it becomes possible to act efficiently.

  Here, the ladder frame 50 of the present embodiment is made of an aluminum alloy. Therefore, for example, the weight is reduced compared to an iron ladder frame. On the other hand, the ladder frame 50 of the present embodiment, which is made of an aluminum alloy, is easily deformed so as to bend the end lateral frame 60 in accordance with vibration or the like accompanying the driving of the internal combustion engine 10. Temporarily, when the conventional structure where the lower end surface of the end horizontal frame is located on one side in the axial direction of the crankshaft rather than the two bolt holes over the entire extending direction of the end horizontal frame is adopted There is a possibility that the surface pressure expected from the fastening force of the bolt cannot be applied between the lower end surface of the end lateral frame and the upper end surface of the crankcase. In this case, when vibration is generated in the internal combustion engine, there is a possibility that the sealing performance between the lower end surface of the end side frame and the upper end surface of the crankcase cannot be secured.

  On the other hand, in the end horizontal frame 60 of this embodiment, as described above, the fastening force of the bolt B3 is efficiently used as a surface pressure acting between the lower end surface of the end horizontal frame 60 and the upper end surface of the crankcase 92. Can be activated. Therefore, even when vibration occurs in the internal combustion engine 10, the sealing performance between the lower end surface of the end lateral frame 60 and the upper end surface of the crankcase 92 can be ensured. That is, in the present embodiment in which an aluminum alloy is used as the material of the ladder frame 50, the effect of ensuring the sealing performance between the lower end surface of the end lateral frame 60 and the upper end surface of the crankcase 92 can be enjoyed.

  Further, in the end horizontal frame 60 of the present embodiment, the dimension of the second joint surface 64 in the axial direction of the crankshaft 100 is larger than the dimension of the first joint surface 62. Therefore, compared to the case where the dimension of the second joint surface 64 in the axial direction of the crankshaft 100 is the same as the dimension of the first joint surface 62, the flesh portion of the end horizontal frame 60 is increased in this embodiment. ing. Therefore, in the present embodiment, the rigidity of the end lateral frame 60 is improved.

  Here, the second joint surface 64 is located between the two bolt holes 54c with respect to the extending direction of the end horizontal frame 60, and extends in the extending range of the bearing portion 54a with respect to the extending direction of the end horizontal frame 60. It is. By reinforcing the rigidity of the end lateral frame 60 at the position corresponding to the extending range of the bearing portion 54a as described above, sufficient rigidity for supporting the crankshaft 100 can be ensured.

In addition, this embodiment can be implemented with the following modifications. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.
-The shape and dimension of the recessed part 60a of the end side frame 60 can be changed suitably. In other words, the shapes and dimensions of the first joint surface 62 and the second joint surface 64 can be changed as appropriate. In short, the dimension of the second joint surface 64 is larger than the first joint surface 62 with respect to the axial direction of the crankshaft 100, and the second joint surface 64 has two coupling holes N in the axial direction of the crankshaft 100. What is necessary is just to extend from the one side of the axial direction of the crankshaft 100 to the other side rather than on the straight line L which connected each center axis line virtually.

-The outer periphery of the ladder frame 50 should just be roughly square shape, and the detailed shape of the outer periphery can be changed.
-The number and position of the recessed part 52a and the end bolt hole 52b in the vertical frame 52, and the number and position of the coupling hole P can be changed suitably. The shape of the recess 52a is not limited to a cylindrical shape. The recessed part 52a should just be a shape which can arrange | position the head of volt | bolt B2 inside the said recessed part 52a.

-The material of the ladder frame 50 is not limited to an aluminum alloy. The material of the ladder frame 50 may be an alloy containing iron as a main component (iron-based alloy) such as cast iron.
It is not essential that a liquid gasket is interposed between the ladder frame 50 and the crankcase 92. For example, a metal gasket may be interposed between the two. Further, the gasket may be omitted as long as the sealability between the ladder frame 50 and the crankcase 92 can be secured without these gaskets. The same modification can be applied to the gasket interposed between the ladder frame 50 and the cylinder block 20.

  -The structure of the cylinder block 20, the crankcase 92, and the storage case 94 in the said embodiment is illustrated schematically to the last, and those dimensions and shapes can be changed suitably.

  The number of cylinders 22 can be changed. The number of partition walls 21 and the number of horizontal frames 54 in the ladder frame 50 may be changed according to the number of cylinders 22.

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Cylinder block, 50 ... Ladder frame, 52 ... Vertical frame, 54 ... Horizontal frame, 54a ... Bearing part, 54c ... Bolt hole, 60 ... End side frame, 62 ... First joint surface, 64 ... 2nd joint surface, 90 ... oil pan, 100 ... crankshaft, N ... coupling hole.

Claims (1)

A ladder frame that is disposed between a cylinder block and an oil pan of an internal combustion engine and supports a crankshaft between the cylinder block,
A pair of vertical frames extending along the axial direction of the crankshaft, and a plurality of horizontal frames that are spanned between the pair of vertical frames and aligned in the axial direction of the crankshaft;
In the upper end surface, which is the end surface on the cylinder block side of the horizontal frame, a bearing portion for supporting the crankshaft is recessed,
Bolt holes through which bolts for fixing the ladder frame to the cylinder block are inserted respectively on both sides of the bearing portion with respect to the extending direction of the horizontal frame,
Among the plurality of horizontal frames, when the horizontal frame located at the end on the most one side in the axial direction of the crankshaft is defined as an end horizontal frame, the bottom frame is an end surface on the oil pan side of the end horizontal frame. In the end surface, two coupling holes into which bolts for fixing the oil pan and the ladder frame are screwed are recessed,
One of the coupling holes is located on the opposite side of the bearing portion across the one bolt hole, and the other of the coupling holes is located on the opposite side of the bearing portion across the other bolt hole. And
The lower end surface of the end horizontal frame is disposed at the same position as the bolt hole in the extending direction of the end horizontal frame, and is one of the crankshaft axial directions than the bolt holes in the axial direction of the crankshaft. A first joint surface located on the side, and a second joint surface that is continuous with the first joint surface and located between the two bolt holes in the extending direction of the end lateral frame. Prepared,
The second joint surface has a size larger than that of the first joint surface in the axial direction of the crankshaft, and virtually connects the central axes of the two coupling holes in the axial direction of the crankshaft. A ladder frame extending to the other side in the axial direction of the crankshaft rather than on a straight line.