Engine ladder frame

Abstract

The objective is to provide an engine ladder frame in which the occurrence of cracks in the frame section is suppressed. [Solution] An engine ladder frame comprising a cast iron crank cap portion and an aluminum alloy frame portion integrally molded with the crank cap portion, wherein the crank cap portion supports a crankshaft and has an arc-shaped support surface concentric with the axis of the crankshaft and includes a first peripheral portion extending in an arc shape concentric with the axis, and the frame portion includes a second peripheral portion extending in an arc shape along the first peripheral portion on the opposite side of the support surface, and the boundary line between the first peripheral portion and the second peripheral portion includes an arc-shaped region extending in an arc shape along the support surface, a first curved region curving from one end of the arc-shaped region in the arc direction to the other end of the arc-shaped region on the opposite side of the support surface, and a second curved region curving from the first curved region to the one end on the opposite side of the support surface.

Description

Technical Field

[0001] The present invention relates to a ladder frame of an engine.

Background Art

[0002] There is a ladder frame of an engine including a crank cap portion made of cast iron and a frame portion made of an aluminum alloy formed integrally with the crank cap portion (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The crank cap portion rotatably supports the crankshaft. Therefore, a large load is applied to the crank cap portion and the frame portion around the crank cap portion. For example, if the boundary line between the crank cap portion and the frame portion bends at an acute angle, stress may concentrate in the acute angle region. As a result, there is a risk of cracks occurring in the frame portion.

[0005] Therefore, an object of the present invention is to provide a ladder frame of an engine in which the occurrence of cracks in the frame portion is suppressed.

Means for Solving the Problems

[0006] The above objective can be achieved by an engine ladder frame comprising a cast iron crank cap portion and an aluminum alloy frame portion integrally formed with the crank cap portion, wherein the crank cap portion supports the crankshaft and has an arc-shaped support surface concentric with the axis of the crankshaft and includes a first peripheral portion extending in an arc shape concentric with the axis, and the frame portion includes a second peripheral portion extending in an arc shape along the first peripheral portion on the side opposite to the support surface, and the boundary line between the first peripheral portion and the second peripheral portion includes an arc-shaped region extending in an arc shape along the support surface, a first curved region curving from one end of the arc-shaped region in the arc direction toward the other end of the arc-shaped region on the side opposite to the support surface, and a second curved region curving from the first curved region toward the one end on the side opposite to the support surface.

[0007] The first peripheral portion includes a first front surface continuous with the support surface and intersecting the direction of the axis, and a first arc surface continuous with the first front surface and extending concentrically with the axis in the direction of the axis; the second peripheral portion includes a second front surface continuous flush with the first front surface, and a second arc surface continuous with the second front surface, extending concentrically with the axis in the direction of the axis and continuous with the first arc surface; the arc region and the first curved region are the boundary between the first front surface and the second front surface, and the second curved region may be the boundary between the first front surface and the second front surface and the boundary between the first arc surface and the second arc surface.

[0008] The crank cap portion includes a recessed portion located below the first peripheral portion and recessed in the direction of the axis compared to the first front surface, and a columnar portion that curves downward from one end of the first peripheral portion in the arc direction, the columnar portion having a raised portion that curves and rises on the other end of the first peripheral portion in the arc direction, the second front surface covering the recessed portion, the first curved region being defined by the first peripheral portion, the columnar portion and the raised portion, and the second curved region being defined by the raised portion. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an engine ladder frame in which the occurrence of cracks in the frame portion is suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1A is a schematic diagram of the engine, and Figure 1B is a schematic diagram of the ladder frame. [Figure 2] Figure 2 is a magnified view of the crank cap. [Figure 3] Figure 3 is a magnified view of a portion of Figure 2. [Figure 4] Figure 4 is a magnified view of a comparative example. [Figure 5] Figure 5 is a schematic diagram of the crank cap before casting. [Modes for carrying out the invention]

[0011] [Engine Overview] Figure 1A is a schematic diagram of engine 1. Engine 1 is a V6 engine having a pair of banks 2L and 2R projecting in a V shape from the top of a cylinder block 6. Engine 1 is mounted in a vehicle, for example, but is not limited to that. Engine 1 may also be an inline cylinder engine. Bank 2L has a cylinder head 5L and a head cover 4L. Cylinder head 5L is located at the upper end of the cylinder block 6. Head cover 4L is attached to the upper end of cylinder head 5L. Similarly, bank 2R has a cylinder head 5R and a head cover 4R.

[0012] Within the cylinder block 6, there are three cylinders in each of the banks 2L and 2R. Each cylinder contains a piston. Each piston transmits power to the crankshaft 8. In Figure 1A, the axis C of the crankshaft 8 is shown by a dotted line. A ladder frame 10 is attached to the underside of the cylinder block 6. The crankshaft 8 is rotatably supported by the cylinder block 6 and the ladder frame 10. An oil pan 9, which stores lubricating oil, is attached to the underside of the ladder frame 10.

[0013] [Outline of ladder frame] Figure 1B is a schematic diagram of the ladder frame 10. The ladder frame 10 includes four crank cap sections 20 and a frame section 40. The crank cap sections 20 are made of cast iron. The frame section 40 is made of aluminum alloy. The four crank cap sections 20 and the frame section 40 are molded as a single unit. These four crank cap sections 20 are cast from molten aluminum alloy into a mold. This forms a molded product in which the four crank cap sections 20 are joined to the frame section 40. After that, the molded product is subjected to predetermined machining to be manufactured as the ladder frame 10.

[0014] The frame portion 40 has side wall portions 41a and 41b that are facing each other and arranged substantially parallel to one another. The four crank cap portions 20 are joined to the side wall portions 41a and 41b and are aligned in the direction of the axis C. Of the four crank cap portions 20, the crank cap portion 20 located closest to the viewer in Figure 1B has a different shape at the joint with the frame portion 40 from the other crank cap portions 20. The crank cap portion 20 has a semi-circular support surface 23s formed on its upper side, centered on the axis C. The support surface 23s rotatably supports the crankshaft 8 from below.

[0015] [Structure of the crank cap and frame] Figure 2 is an enlarged view of the crank cap portion 20. Figure 2 is an enlarged view of the crank cap portion 20 located on the foreground side of Figure 1B. The crank cap portion 20 has a first peripheral portion 22. The frame portion 40 has a second peripheral portion 42. The second peripheral portion 42 is continuous with the side wall portions 41a and 41b. The second peripheral portion 42 is integrally formed on the front side of the first peripheral portion 22 of the crank cap portion 20.

[0016] The first peripheral portion 22 includes a support surface 23s, a first front surface 24s, and a first arcuate surface 26s. The support surface 23s is substantially arcuate in shape and concentric with the axis C. The first front surface 24s is continuous with the support surface 23s. The support surface 23s is substantially perpendicular to the axis C. The support surface 23s extends in a substantially arcuate shape concentric with the axis C. The first arcuate surface 26s protrudes from the first front surface 24s along the direction of the axis C. The first arcuate surface 26s extends in a substantially arcuate shape concentric with the axis C. The first arcuate surface 26s includes both a portion protruding from one end of the first front surface 24s in the arcuate direction along the direction of the axis C and a portion protruding from the other end of the first front surface 24s in the arcuate direction along the direction of the axis C.

[0017] Furthermore, the crank cap portion 20 has upper surfaces 28s and 29s formed on either side of the support surface 23s. The upper surfaces 28s and 29s are in contact with the lower end surface of the cylinder block 6. Bolt holes H1 and H2 are formed in each of the upper surfaces 28s and 29s. Bolts that connect the cylinder block 6 and the ladder frame 10 are inserted into each of the bolt holes H1 and H2.

[0018] The second peripheral portion 42 includes a second front surface 44s, a second arc surface 46s, an end surface 47s, an upper surface 48s, and an upper surface 49s. The second peripheral portion 42 is formed outside the first peripheral portion 22. The second front surface 44s is flush with the first front surface 24s. That is, the second front surface 44s, like the first front surface 24s, is substantially orthogonal to the axis C and extends in a substantially arc shape. The second arc surface 46s protrudes from the second front surface 44s along the direction of the axis C. The second arc surface 46s extends in a substantially arc shape concentric with the axis C. The second arc surface 46s and the first arc surface 26s are continuous in the arc direction. The second arc surface 46s and the first arc surface 26s have the same arc radius. The second arc surface 46s includes a portion located between the two first arc surfaces 26s and a portion continuously extending in the arc direction from this portion.

[0019] The end surface 47s is continuous with the second arc surface 46s. The end surface 47s is substantially orthogonal to the axis C. The end surface 47s extends in a substantially arc shape concentric with the axis C. The upper surface 48s continuously extends from one end in the arc direction of the second arc surface 46s and the end surface 47s to the side wall portion 41a in a substantially straight line. The upper surface 48s is flush with the upper surface 28s. The upper surface 49s continuously extends from the other end in the arc direction of the second arc surface 46s and the end surface 47s to the side wall portion 41b in a substantially straight line. The upper surface 49s is flush with the upper surface 29s.

[0020] As shown in FIG. 2, the boundary line between the first peripheral portion 22 and the second peripheral portion 42 is shown. The boundary line includes an arc region B1, a first curved region B2, a second curved region B3, an arc region B4, a first curved region B5, a second curved region B6, and an arc region B7. The arc region B1 extends in a substantially arc shape concentric with the axis C along the support surface 23s. The first curved region B2 curves from one end in the arc direction of the arc region B1 to the side opposite the support surface 23s and toward the other end side in the arc direction of the arc region B1. Curving to the side opposite the support surface 23s means curving to the side away from the support surface 23s. The second curved region B3 curves from the first curved region B2 to the side opposite the support surface 23s and toward one end side in the arc direction of the arc region B1. The arc region B4 extends from the second curved region B3 in an arc shape toward the upper surface 48s side.

[0021] Similarly, the first curved region B5 curves from the other end in the arc direction of the arc region B1, on the side opposite to the support surface 23s and toward one end side in the arc direction of the arc region B1. The second curved region B6 curves from the first curved region B5, on the side opposite to the support surface 23s and toward the other end side in the arc direction of the arc region B1. The arc region B7 extends in an arc shape from the second curved region B6 toward the upper surface 49s. Note that "curving" means curving in a curved or arcuate shape, that is, curving in a curved line.

[0022] The arc region B1, the first curved regions B2 and B5 are the boundary between the first front surface 24s and the second front surface 44s. The second curved regions B3 and B6 are the boundary between the first front surface 24s and the second front surface 44s and the boundary between the first arc surface 26s and the second arc surface 46s. The arc regions B4 and B7 are the boundary between the first arc surface 26s and the second arc surface 46s.

[0023] Figure 3 is a partial enlarged view of Figure 2. The first curved regions B2 and the second curved region B3 are curved. The first curved region B5 and the second curved region B6 are the same. Figure 4 is a partial enlarged view of a comparative example. Figure 4 corresponds to Figure 3. The first curved region B2x is the boundary between the first front surface 24sx of the first peripheral portion 22x of the crank cap portion 20x and the second front surface 44sx of the second peripheral portion 42x of the frame portion 40x. The acute angle region B3x is the boundary between the first arc surface 26sx and the second arc surface 46sx.

[0024] The first curved region B2x of the comparative example is not curved as much as the first curved region B2 of the present embodiment. The acute angle region B3x is continuous from the first curved region B2x, bends at an acute angle, and is continuous with the arc region B4x. Thus, the acute angle region B3x is an acute angle. Stress is likely to concentrate in the acute angle region B3x during the operation of the engine. As a result, cracks may occur around the acute angle region B3x. In the present embodiment, as shown in Figure 3, the second curved region B3 is curved. Therefore, stress concentration in the second curved region B3 is suppressed, and the occurrence of cracks in the frame portion 40 is suppressed. Note that "bending at an acute angle" means bending at an acute angle, that is, bending linearly.

[0025] [Schematic diagram of the crank cap before casting] Figure 5 is a schematic diagram of the crank cap portion 20 before casting. The crank cap portion 20 includes a first peripheral portion 22, a recessed portion 32, column portions 34 and 36, raised portions 35 and 37, and outer column portions 38 and 39. The recessed portion 32 is located below the first peripheral portion 22. The recessed portion 32 is recessed in the direction of the axis C more than the first peripheral portion 22. The column portion 34 curves downward from one end of the first peripheral portion 22 in the arc direction. That is, the edge on the recessed portion 32 side, continuous from one end of the first peripheral portion 22 to the base portion 341 of the column portion 34, is curved in an arc shape. The column portion 36 curves downward from the other end of the first peripheral portion 22 in the arc direction. The edge on the recessed portion 32 side, continuous from the other end of the first peripheral portion 22 to the base portion 361 of the column portion 36, is curved in an arc shape. The column sections 34 and 36 extend approximately parallel to each other. The column sections 34 and 36 sandwich the recessed section 32.

[0026] The outer column section 38 is located further out than the column section 34. The outer column section 39 is located further out than the column section 36. The outer column sections 38 and 39 extend approximately parallel to the column sections 34 and 36. Bolt holes H1 are formed inside each of the column sections 34 and 36. Bolt holes H2 are formed inside each of the outer column sections 38 and 39 by subsequent machining. Strength is ensured by the column sections 34 and 36 and the outer column sections 38 and 39.

[0027] The raised portion 35 curves and rises from the column portion 34 towards the other end of the first peripheral portion 22 in the arc direction, i.e., towards the column portion 36. The raised portion 37 curves and rises from the column portion 36 towards one end of the first peripheral portion 22 in the arc direction, i.e., towards the column portion 34. In other words, the raised portions 35 and 37 are each hemispherical. The raised portion 35 includes an upper part 351 and a lower part 352 of the raised surface. The upper part 351 is the portion of the raised portion 35 on the side of the first peripheral portion 22. The lower part 352 is the portion of the raised portion 35 opposite to the first peripheral portion 22. Similarly, the raised portion 37 includes an upper part 371 and a lower part 372 of the raised surface.

[0028] In the molded product after the crank cap portion 20 has been cast into the mold using molten aluminum alloy, the second front surface 44s of the second peripheral portion 42 covers the lower side of the first front surface 24s of the recessed portion 32. By machining this molded product to reduce the thickness in the direction of the axis C around the first peripheral portion 22, the ladder frame 10 shown in Figure 2 is formed.

[0029] The arc region B1 described above is defined by the substantially arc-shaped lower edge 241 of the first front surface 24s of the first peripheral portion 22. The first curved region B2 is defined by one end of the lower edge 241 of the first front surface 24s, the base 341 of the column portion 34, and the upper part 351 of the raised portion 35. Similarly, the first curved region B5 is defined by the other end of the lower edge 241 of the first front surface 24s, the base 361 of the column portion 36, and the upper part 371 of the raised portion 37. The second curved region B3 is defined by the lower part 352 of the raised portion 35. The second curved region B6 is defined by the lower part 372 of the raised portion 37.

[0030] In this way, the raised portions 35 and 37 of the crank cap portion 20 cause the first curved region B2, the second curved region B3, the first curved region B5, and the second curved region B6 to curve. This suppresses stress concentration and prevents the occurrence of cracks in the frame portion 40. Furthermore, the crank cap portion 20 having the raised portions 35 and 37 suppresses the increase in mass of the crank cap portion 20 while also suppressing the occurrence of cracks in the frame portion 40.

[0031] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0032] 1 Engine 8 Crankshaft 10 Ladder Frames 20 Crank cap section 22 First Peripheral Area 23s support surface 24s 1st front 26s First circular arc surface 32 Recessed area 34, 36 Column section 35, 37 ridges 40 Frame section 42 Second Peripheral Area 44s 2nd front 46s Second circular arc surface B1 Arc Region B2, B5 1st curved area B3, B6 Second Curved Region C axis center

Claims

1. The cast iron crank cap section, It comprises an aluminum alloy frame portion molded integrally with the crank cap portion, The crank cap portion supports the crankshaft and has an arc-shaped support surface concentric with the axis of the crankshaft, and includes a first peripheral portion that extends in an arc shape concentric with the axis. The frame portion includes a second peripheral portion that extends in an arc shape along the first peripheral portion on the side opposite to the support surface, The boundary line between the first peripheral area and the second peripheral area is An arc-shaped region extending along the aforementioned support surface, A first curved region that curves from one end of the arc region in the arc direction to the other end of the arc region in the arc direction, opposite to the support surface, and Including the first curved region, a second curved region that is on the opposite side of the support surface and curved toward the one end, The engine's ladder frame.

2. The first peripheral portion is, A first front surface continuous with the support surface and intersecting in the direction of the axis, It includes a first arcuate surface that is continuous with the first front surface and extends concentrically with the axis in the direction of the axis from the first front surface, The second peripheral portion is, A second front surface continuous with the first front surface, and It includes a second arc surface that is continuous with the second front surface, extends concentrically with the axis in the axial direction from the second front surface, and is continuous with the first arc surface, The arc region and the first curved region are the boundary between the first front surface and the second front surface. The ladder frame of the engine according to claim 1, wherein the second curved region is the boundary between the first front surface and the second front surface and the boundary between the first arc surface and the second arc surface.

3. The aforementioned crank cap portion is A recessed portion located below the first peripheral portion and recessed in the direction of the axis compared to the first front surface, and It includes a columnar portion that curves downward from one end in the arc direction of the first peripheral portion, The column portion has a curved, raised portion on the other end side in the arc direction of the first peripheral portion, The second front surface covers the recessed portion, The first curved region is defined by the first peripheral portion, the column portion, and the raised portion. The ladder frame of the engine according to claim 2, wherein the second curved region is defined by the raised portion.

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