CA2923468C - Strengthening method for fillet part of crankshaft and stengthening device therefor - Google Patents
Strengthening method for fillet part of crankshaft and stengthening device therefor Download PDFInfo
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- CA2923468C CA2923468C CA2923468A CA2923468A CA2923468C CA 2923468 C CA2923468 C CA 2923468C CA 2923468 A CA2923468 A CA 2923468A CA 2923468 A CA2923468 A CA 2923468A CA 2923468 C CA2923468 C CA 2923468C
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- pressing
- slope surface
- fillet part
- pressing member
- fillet
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
- B21J5/02—Die forging; Trimming by making use of special dies ; Punching during forging
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- Mechanical Engineering (AREA)
- Shafts, Cranks, Connecting Bars, And Related Bearings (AREA)
- Forging (AREA)
Abstract
A device for strengthening a fillet part of a crankshaft, not only in a radial direction, but also in an axial direction, is provided. The device is configured to press a pressing member from a direction perpendicular to an axis line of a pin part or a journal part, against a portion in a circumferential direction of the fillet part of the pin part or the journal part, which is configured to receive at least one of bending load and torsional stress at the maximum degree, thereby applying compressive residual stress. The device includes a holder 52, which has a slope surface 55 at an end thereof, and a pressing piece 60, which has a sliding surface 61 that is slidable along the slope surface 55 and has a protrusion 62 that is finable to the fillet part. The slope surface 55 is uniformly tilted relative to the pressing direction of the pressing piece 60 so as to face the fillet part.
Description
STRENGTHENING METHOD FOR FILLET PART OF CRANKSHAFT AND
STRENGTHENING DEVICE THEREFOR
BACKGROUND OF THE INVENTION
Technical Field [0001] The present invention relates to a strengthening method for a fillet part of a crankshaft and a strengthening device therefor, and in particular relates to a technique for strengthening the fillet part not only in a radial direction, but also in an axial direction.
Background Art
STRENGTHENING DEVICE THEREFOR
BACKGROUND OF THE INVENTION
Technical Field [0001] The present invention relates to a strengthening method for a fillet part of a crankshaft and a strengthening device therefor, and in particular relates to a technique for strengthening the fillet part not only in a radial direction, but also in an axial direction.
Background Art
[0002] For example, a crankshaft includes a crank pin and a journal pin, and the crank pin rotatably supports a large end part of a connecting rod, whereas the journal pin is rotatably supported by a journal bearing of an engine block.
Each of the crank pin and the journal pin has a corner part, at which a groove (fillet part) is formed so as to have a cross section of a semicircular shape in order to avoid interference with a mating member. The fillet part is a part having low strength, but receives great bending moment when an explosion occurs in an internal combustion engine. Therefore, it is desired to strengthen top portions of the pin of the fillet part (at phases of 0 degrees and 180 degrees in the case of an in-line four cylinder engine).
Each of the crank pin and the journal pin has a corner part, at which a groove (fillet part) is formed so as to have a cross section of a semicircular shape in order to avoid interference with a mating member. The fillet part is a part having low strength, but receives great bending moment when an explosion occurs in an internal combustion engine. Therefore, it is desired to strengthen top portions of the pin of the fillet part (at phases of 0 degrees and 180 degrees in the case of an in-line four cylinder engine).
[0003] A forging device including a punch with slope surfaces is disclosed in Japanese Patent No. 3899246. The slope surface is formed at each side of an end of the punch so as to have a circular arc shape in a side view, and a convex die is slidably arranged thereto. In this forging device, when the convex die presses the fillet part, it protrudes outwardly along the slope surface and also axially presses the fillet part so as to obtain a strengthened portion in a wide area.
[0004] However, in the technique disclosed in Japanese Patent No. 3899246, the above effect cannot be obtained. This is because the slope surface used as a cam surface for making the convex die protrude outwardly is a conical surface (in [0011]), and a space is formed between the convex die and the conical surface when the convex die protrudes outwardly even at a small degree, whereby the convex die tilts against the punch.
SUMMARY OF THE INVENTION
SUMMARY OF THE INVENTION
[0005] Accordingly, an object of the present invention is to provide a strengthening method for a fillet part of a crankshaft not only in a radial direction, but also in an axial direction and to provide a strengthening device therefor.
[0006] The present invention provides a strengthening method for a fillet part of each of a pin part and a journal part of a crankshaft, and the method includes pressing a pressing member from a direction perpendicular to an axis of the pin part or the journal part, against a portion configured to receive at least one of bending load and torsional stress at the maximum degree in a circumferential direction of the fillet part when the crankshaft is practically used, so as to apply compressive residual stress to the portion. In this method, the pressing member is slidably supported in a direction tilted with respect to the axial direction against the pressing direction and is slidingly moved in a direction tilted with respect to the axial direction when pressing the fillet part.
[0007] In the present invention, the pressing member is slidingly moved in the axial direction when pressing the fillet part, whereby the fillet part is pressed in the axial direction by the pressing member. Therefore, the fillet part can be strengthened not only in the radial direction, but also in the axial direction.
[0008] In the present invention, the pressing member desirably includes a guide member that is provided at a trailing end side thereof. The guide member desirably has a convex slope surface, which faces the pressing member.
The pressing member is desirably constructed of a pair of pressing pieces, which are configured to come into contact with or separate from each other, and desirably has a concave slope surface, which faces the convex slope surface and has the same shape as the convex slope surface. In this case, the convex slope surface desirably presses the concave slope surface so that the pressing member slides while pressing the fillet part.
The pressing member is desirably constructed of a pair of pressing pieces, which are configured to come into contact with or separate from each other, and desirably has a concave slope surface, which faces the convex slope surface and has the same shape as the convex slope surface. In this case, the convex slope surface desirably presses the concave slope surface so that the pressing member slides while pressing the fillet part.
[0009] In addition, the present invention also provides a strengthening device for a fillet part of each of a pin part and a journal part of a crankshaft, and the device is configured to press a pressing member from a direction perpendicular to an axis of the pin part or the journal part, against a portion configured to receive at least one of bending load and torsional stress at the maximum degree in a circumferential direction of the fillet part when the crankshaft is practically used, so as to apply compressive residual stress to the portion. The device includes a guide member, which has a slope surface at an end thereof, and a pressing member, which has a sliding surface slidable along the slope surface and has a pressing surface with a configuration along the fillet part. The slope surface is uniformly tilted relative to a pressing direction of the pressing member so as to face the fillet part.
[0010] In the present invention, when the pressing surface of the pressing member presses the fillet part, the pressing member slides along the slope surface of the guide member and moves in the axial direction. Therefore, the pressing surface presses the fillet part in the axial direction, whereby the fillet part is strengthened not only in the radial direction, but also in the axial direction.
[0011] In the present invention, the slope surface of the guide member preferably has a convex shape so as to face the pressing member. The pressing member is preferably constructed of a pair of pressing pieces, which are configured to come into contact with or separate from each other, and preferably has a concave slope surface, which faces the convex slope surface and has the same shape as the convex slope surface. In this case, the convex slope surface preferably presses the concave slope surface so that the pressing member slides while pressing the fillet part.
[0012] In the present invention, the pressing member desirably includes a pressing surface for pressing the fillet part at a predetermined pressing amount, and the pressing surface desirably includes a forming area in a range within degrees from a normal direction to each side in a circumferential direction and desirably includes a gradually changing area in a range within 90 degrees from the normal direction to each side in the circumferential direction beyond the forming area. The forming area is formed of an approximately cylindrical curved surface having a curvature radius that is obtained by subtracting the predetermined pressing amount from a curvature radius of a cross section of the fillet part. The gradually changing area has a curvature radius that gradually increases to a relief radius that is obtained by adding a relief amount to the curvature radius of the fillet part.
[0001] In the above case, the curvature radius of the forming area is smaller than that of the shaft member, whereby strengthening can be performed in a wider area (in an area of 45 degrees of one side at the maximum). In addition, the pressing member includes the gradually changing area having the radius that gradually increases until the relief radius in which the relief amount is added to the curvature radius of the shaft member. Therefore, the compressive residual stress applied to the shaft member is gradually decreased in accordance with the gradually changing area, and the strengthened portion reaches a portion without the compressive residual stress, whereby tensile residual stress is decreased at the portion adjacent to the portion to which the compressive residual stress is applied. The forming area is preferably formed within a range of 30 to 45 degrees from the normal direction to each side in the circumferential direction.
The gradually changing area is preferably formed in a range of 60 to 75 degrees from the normal direction to each side in the circumferential direction beyond the forming area.
[0002] In this case, an imaginary straight line that is perpendicular to the slope surface in a cross section including the axis line desirably passes a working part of the pressing surface for pressing the fillet part. This is because if the working part of the pressing surface for pressing the fillet part is separated from the imaginary straight line, the pressing member is difficult to slide along the slope surface of the guide member when the pressing surface presses the fillet part in a direction perpendicular to the axis line.
[0015] In addition, the slope surface is preferably a cylindrical curved surface, for example. In this case, the guide member may be tilted and be secured on a milling machine or the like, and the slope surface can be processed by milling the guide member with a milling tool. On the other hand, the pressing member has an approximately semi-ring shape, for example, and has a sliding surface with a columnar curved surface so as to slide in the axial direction of the columnar curved surface relative to the slope surface. Moreover, the pressing surface may be provided at a side edge of an inner circumferential surface of the pressing member. The pressing surface may be formed into a protrusion that protrudes toward the fillet part and that also protrudes in the axial direction of the fillet part.
[0016] According to the present invention, the fillet part of the crankshaft is strengthened not only in the radial direction, but also in the axial direction.
Moreover, the strengthening can be performed in a wider area of the fillet part, and tensile residual stress is decreased at the portion adjacent to the portion to which the compressive residual stress is applied.
BRIEF DESCRIPTION OF DRAWINGS
[0017] Fig. 1 is a side view showing a crankshaft to be strengthened in an embodiment of the present invention.
Fig. 2 is a side view showing a condition in which a crank pin is strengthened in an embodiment of the present invention.
Fig. 3 is a side view showing a condition in which a journal pin is strengthened in an embodiment of the present invention.
Fig. 4A is a front view showing an upper punch in an embodiment of the present invention, and Fig. 4B is a sectional side view of the upper punch.
Fig. 5A is a front view showing a holder of an embodiment of the present invention, and Fig. 5B is a sectional side view of the holder.
Fig. 6 is an enlarged side view showing a condition in which a crank pin is strengthened in an embodiment of the present invention.
Fig. 7 is a cross sectional view taken along the line of the arrows VII ¨
VII in Fig. 2 for showing a strengthening method for a shaft member of an embodiment of the present invention.
Fig. 8 is an enlarged view showing details of a machined part.
PREFERRED EMBODIMENTS OF THE INVENTION
[0018] An embodiment of the present invention will be described with reference to the figures hereinafter. Fig. 1 is a side view showing a crankshaft 1 to be strengthened in this embodiment. The crankshaft 1 is formed by hot forging, and it is made by forming radially protruding crank arms 12 at journal pins 11, which function as a rotating shaft, arranging a crank pin 13 between sides of each of a pair of the crank arms 12, and forming a balance weight 14 at an end of one of the pair of the crank arms 12. Each of the journal pins 11 and the crank pins 13 has a fillet part 15 that is formed on each side thereof, and the fillet part 15 is a groove having a cross section with an approximately semicircular shape.
[0019] Fig. 2 shows a condition in which the fillet parts 15 of the crank pins
[0001] In the above case, the curvature radius of the forming area is smaller than that of the shaft member, whereby strengthening can be performed in a wider area (in an area of 45 degrees of one side at the maximum). In addition, the pressing member includes the gradually changing area having the radius that gradually increases until the relief radius in which the relief amount is added to the curvature radius of the shaft member. Therefore, the compressive residual stress applied to the shaft member is gradually decreased in accordance with the gradually changing area, and the strengthened portion reaches a portion without the compressive residual stress, whereby tensile residual stress is decreased at the portion adjacent to the portion to which the compressive residual stress is applied. The forming area is preferably formed within a range of 30 to 45 degrees from the normal direction to each side in the circumferential direction.
The gradually changing area is preferably formed in a range of 60 to 75 degrees from the normal direction to each side in the circumferential direction beyond the forming area.
[0002] In this case, an imaginary straight line that is perpendicular to the slope surface in a cross section including the axis line desirably passes a working part of the pressing surface for pressing the fillet part. This is because if the working part of the pressing surface for pressing the fillet part is separated from the imaginary straight line, the pressing member is difficult to slide along the slope surface of the guide member when the pressing surface presses the fillet part in a direction perpendicular to the axis line.
[0015] In addition, the slope surface is preferably a cylindrical curved surface, for example. In this case, the guide member may be tilted and be secured on a milling machine or the like, and the slope surface can be processed by milling the guide member with a milling tool. On the other hand, the pressing member has an approximately semi-ring shape, for example, and has a sliding surface with a columnar curved surface so as to slide in the axial direction of the columnar curved surface relative to the slope surface. Moreover, the pressing surface may be provided at a side edge of an inner circumferential surface of the pressing member. The pressing surface may be formed into a protrusion that protrudes toward the fillet part and that also protrudes in the axial direction of the fillet part.
[0016] According to the present invention, the fillet part of the crankshaft is strengthened not only in the radial direction, but also in the axial direction.
Moreover, the strengthening can be performed in a wider area of the fillet part, and tensile residual stress is decreased at the portion adjacent to the portion to which the compressive residual stress is applied.
BRIEF DESCRIPTION OF DRAWINGS
[0017] Fig. 1 is a side view showing a crankshaft to be strengthened in an embodiment of the present invention.
Fig. 2 is a side view showing a condition in which a crank pin is strengthened in an embodiment of the present invention.
Fig. 3 is a side view showing a condition in which a journal pin is strengthened in an embodiment of the present invention.
Fig. 4A is a front view showing an upper punch in an embodiment of the present invention, and Fig. 4B is a sectional side view of the upper punch.
Fig. 5A is a front view showing a holder of an embodiment of the present invention, and Fig. 5B is a sectional side view of the holder.
Fig. 6 is an enlarged side view showing a condition in which a crank pin is strengthened in an embodiment of the present invention.
Fig. 7 is a cross sectional view taken along the line of the arrows VII ¨
VII in Fig. 2 for showing a strengthening method for a shaft member of an embodiment of the present invention.
Fig. 8 is an enlarged view showing details of a machined part.
PREFERRED EMBODIMENTS OF THE INVENTION
[0018] An embodiment of the present invention will be described with reference to the figures hereinafter. Fig. 1 is a side view showing a crankshaft 1 to be strengthened in this embodiment. The crankshaft 1 is formed by hot forging, and it is made by forming radially protruding crank arms 12 at journal pins 11, which function as a rotating shaft, arranging a crank pin 13 between sides of each of a pair of the crank arms 12, and forming a balance weight 14 at an end of one of the pair of the crank arms 12. Each of the journal pins 11 and the crank pins 13 has a fillet part 15 that is formed on each side thereof, and the fillet part 15 is a groove having a cross section with an approximately semicircular shape.
[0019] Fig. 2 shows a condition in which the fillet parts 15 of the crank pins
13 are subjected to plastic working by a lower die 2 and an upper die 3, and the crankshaft 1 is placed on the lower die 2 so that the crank pins 13 are directed in the vertical direction. The lower die 2 includes a first lower punch 21, which is provided at one side thereof and extends upwardly at a longer length, and includes a second lower punch 22, which is provided at the other side thereof and extends upwardly at a shorter length. Similarly, the upper die 3 includes a first upper punch 31, which is provided at one side thereof and extends downwardly at a longer length, and includes a second upper punch 32, which is provided at the other side thereof and extends downwardly at a shorter length.
[0020] Fig. 3 shows a condition in which the fillet parts 15 of the journal pin 11 are subjected to plastic working by a lower die 4 and an upper die 5. The lower die 4 is provided with a lower punch 41 that extends upwardly. The upper die 5 is provided with an upper punch 51 that extends downwardly.
[0021] Fig. 4A is a front view showing the upper punch 51, and Fig. 4B is a cross sectional view of the upper punch 51. In these figures, the reference symbol 52 represents a holder (guide member). The holder 52 is made by forming a semicircular hole 54 at one side of a rectangular plate 53, as shown in Fig. 5A. The hole 54 has a center as shown by the alternate long and short dashed line in Fig. 5B and is formed into a circular shape when viewed from a direction tilted with respect to one of the front and the back sides of the plate 53 in the thickness direction. The hole 54 has an edge part, at which a slope surface 55 having a V-shaped cross section is formed. The slope surface 55 is made to have a sloped angle 0 of 60 to 150 degrees in the cross section passing through the center of the plate 53. The holder 52 having such a structure is mounted with a pair of pressing pieces (pressing members) 60.
[0022] The pressing piece 60 has an approximately semi-circular ring shape and has a sliding surface 61, which is formed at the outer circumference thereof and has the same shape as the slope surface 55. The pressing piece 60 also has a protrusion (pressing surface) 62, which is formed at an edge of the inner circumference thereof at a side opposite to the other pressing piece 60 and protrudes to the inner circumference and outwardly in the thickness direction thereof. The pair of the pressing pieces 60 have a symmetrical shape in the cross section shown in Fig. 4B and have the sliding surfaces 61 that form a concave part, and the slope surface 55 of the plate 53 fits to the concave part in a wedge-shaped manner. The pressing piece 60 is formed with a hole 63 that penetrates in the thickness direction, and a bolt 64 and nuts 65 are attached to the hole 63. The bolt 64 and the nuts 65 prevent the pair of the pressing pieces 60 from being separated from each other more than a predetermined distance.
In addition, the holder 52 has a stopper 66 that is attached at a lower surface thereof so as to prevent falling off of the pair of the pressing pieces 60 therefrom.
[0023] Fig. 6 is a cross sectional view showing the details of the pressing piece 60. As shown in Fig. 6, the protrusion 62 of the pressing piece 60 has a cross section with an approximately semicircular shape and has a curvature radius that is smaller than that of the fillet part 15. In addition, the protrusion 62 protrudes to the crank arm 12, thereby forming a space between the protrusion 62 and the crank arm 12 over the protrusion 62. Moreover, an imaginary straight line "L" (refer to Fig. 6) that is perpendicular to the slope surface 55 passes a working part "F" of the protrusion 62 for pressing the fillet part 15. It should be noted that the first upper punch 31, the first lower punch 21, the second lower punch 22, the lower punch 41, and the second upper punch 32, are also formed as in the case of the upper punch 51 described above.
[0024] Fig. 7 shows shapes of the lower punch 41 and the upper punch 51, which are viewed from a side. The protrusion 62 of the upper punch 51 has a forming area "A" in a range within 45 degrees from a normal line "1" direction (direction from the curvature center "0" to the center line of the upper punch 51) to each side in the circumferential direction. The forming area "A" is formed of an approximately cylindrical curved surface with a curvature radius that is obtained by subtracting a pressing amount from the curvature radius of the cross section of the fillet part 15. Here, the "pressing amount" is a thickness to be worked on the fillet part 15 along the normal line "1" by the protrusion 62. The protrusion 62 approximately uniformly works in the forming area "A".
[0025] As shown in Fig. 8, a gradually changing area "B" is provided in a range within 90 degrees from the normal line "1" direction to each side in the circumferential direction, beyond the forming area "A". In this area, the curvature radius is gradually increased to a relief radius "N" that is obtained by adding a relief amount to the curvature radius of the fillet part 15. In Fig.
8, the solid line represents a circle of a radius "R" of the fillet part 15, the broken line represents a circle of a target radius "S" after forming (the radius of the fillet part 15 ¨ the pressing amount), and the alternate long and two short dashed line represents a circle of the relief radius "N" (the radius of the fillet part 15 +
the relief amount). In the gradually changing area "B", the shape of the protrusion 62 is set by measuring a cam profile around the curvature center "0"
and by setting the distance from the curvature center "0" at each angle point.
[0026] Specifically, first, the angle ranges of the forming area "A" and the gradually changing area "B" are set, and then angle points are determined by setting a radius every 10 degrees from an end point of the forming area "A".
In this case, the angle range of the gradually changing area "B" is divided by degrees so that the angle point number is calculated, and a difference between the relief radius "N" and the target radius "S" is calculated. Next, the curvature radius of the protrusion 62 is enlarged every 10 degrees by a calculated value that is obtained by dividing the calculated difference by the angle point number. Thus, the distance from the curvature center "0" is gradually increased as the angle increases from the normal line "1" direction to each side in the circumferential direction beyond the forming area "A", and it agrees with the radius "R" of the fillet part 15 at the point "P". Moreover, when the angle further increases in the circumferential direction, the protrusion 62 is protruded in a direction reverse to the forming area "A", and the distance from the curvature center "0" reaches the relief radius "N".
[0027] The lower punch 41 is constructed in a manner similar to that of the upper punch 51. That is, the protrusion 62 of the lower punch 41 has a forming area "A" in a range within 45 degrees from the normal line "1"
direction to each side in the circumferential direction. The forming area "A" is formed of an approximately cylindrical curved surface with a curvature radius that is obtained by subtracting a pressing amount from the curvature radius of the cross section of the fillet part 15. In addition, a gradually changing area "B" is provided in a range within 90 degrees from the normal line "1" direction to each side in the circumferential direction, beyond the forming area "A". In this area, the curvature radius is gradually increased to a curvature radius that is obtained by adding a relief amount to the curvature radius of the fillet part 15.
[0028] Next, a method of strengthening the fillet part 15 by using the lower punch 41 and the upper punch 51 having the above structures will be described.
In this embodiment, the fillet part 15 is strengthened by plastic working at ordinary temperature. When the upper die 5 is lowered, the forming area "A"
of the protrusion 62 of the upper punch 51 contacts the fillet part 15 of the crank pin 13 and presses the fillet part 15 in conjunction with the forming area "A"
of the protrusion 62 of a first lower punch 121. At this time, as shown in Fig.
6, the slope surface 55 of the holder 52 comes between the pair of the pressing pieces 60 in a wedge-shaped manner, thereby separating the pair of the pressing pieces 60 from each other. Then, the protrusion 62 presses a portion of the fillet part 15 in the axial direction side. By performing this processing, compressive residual stress is applied to portions of the fillet part 15 in the radial direction side and in the axial direction side. In the forming area "A", since approximately the entirety of the portion of the fillet part 15 is formed in the vertical direction by the pressing amount, the compressive residual stress is approximately uniform. The compressive residual stress offsets tensile stress, which may occur when a bending moment is applied to the fillet part 15.
[0029] On the other hand, in the gradually changing area "B", the pressing amount is gradually decreased from the normal line "1" direction in the circumferential direction, and the pressed portion of the fillet part 15 reaches a portion that is not pressed. Therefore, the compressive residual stress that is applied to the fillet part 15 is gradually decreased in the gradually changing area "B" and becomes zero at the portion that is not pressed. Accordingly, tensile residual stress, which occurs at a portion in the vicinity of the portion provided with the compressive residual stress, is decreased.
[0030] Here, the crankshaft 1 is designed for an in-line four cylinder engine, and in such a case, portions at the phase angles of 0 degrees and 180 degrees, that is, the top point and the bottom point of the fillet part 15 as shown in Fig. 7 receive at least one of the bending load and the torsional stress at the maximum degree when explosive combustion occurs in the internal combustion engine.
For example, in the case of the crank pin 13, the bottom point of the fillet part 15 is located at a position in a direction reverse to the direction of the balance weight 14 by 180 degrees. In another example, in the case of the journal pin 11, the bottom point of the fillet part 15 is located at a position in the direction of the balance weight 14.
[0031] In this embodiment, the portions of the fillet part 15, to which at least one of the bending load and the torsional stress at the maximum degree is to be applied, are pressed by the upper punch 51 and the lower punch 41, whereby compressive residual stress is applied to the portions of the fillet part 15 in the radial direction side and in the axial direction side. In addition, the compressive residual stress is applied only to the portions that need to be strengthened, and therefore, the processing is efficiently performed.
Moreover, , the fillet part 15 is partially plastic worked, whereby elongation in the axial direction due to the plastic working is reduced.
[0032] In particular, in the above embodiment, since the forming area "A" and the gradually changing area "B" are provided to the upper punch 51 and the lower punch 41, a wide area of the fillet part 15 is strengthened while the tensile residual stress, which occurs at portions in the vicinity of the portions provided with the compressive residual stress, is decreased. In addition, since the imaginary straight line "L" that is perpendicular to the slope surface 55 of the holder 52 passes the working part "F" of the protrusion 62 for pressing the fillet part 15, the pressing pieces 60 are reliably slid and are moved in the axial direction.
[0033] Next, the crankshaft 1 is turned upside down and is placed on the lower die 2 so that a left end crank pin 13 and a crank pin 13 on the right side of the left end crank pin 13 face the vertical direction, and the fillet parts 15 are subjected to the plastic working in the same manner as described above. In addition, the fillet parts 15 of the journal pin 11 are subjected to the plastic working by the lower die 4 and the upper die 5 shown in Fig. 3. In these cases, the same effects can also be obtained as in the case described above.
[0034] Although two crank pins 13 are strengthened by using the upper punches 31 and 32 and the lower punches 21 and 22 as shown in Fig. 2 in the above embodiment, the crank pins 13 may be strengthened one by one by a pair of the upper and lower punches. Alternatively, all of the crank pins 13 and all of the journal pins 11 may be strengthened at one time by using a die assembly for the entire shape.
[0020] Fig. 3 shows a condition in which the fillet parts 15 of the journal pin 11 are subjected to plastic working by a lower die 4 and an upper die 5. The lower die 4 is provided with a lower punch 41 that extends upwardly. The upper die 5 is provided with an upper punch 51 that extends downwardly.
[0021] Fig. 4A is a front view showing the upper punch 51, and Fig. 4B is a cross sectional view of the upper punch 51. In these figures, the reference symbol 52 represents a holder (guide member). The holder 52 is made by forming a semicircular hole 54 at one side of a rectangular plate 53, as shown in Fig. 5A. The hole 54 has a center as shown by the alternate long and short dashed line in Fig. 5B and is formed into a circular shape when viewed from a direction tilted with respect to one of the front and the back sides of the plate 53 in the thickness direction. The hole 54 has an edge part, at which a slope surface 55 having a V-shaped cross section is formed. The slope surface 55 is made to have a sloped angle 0 of 60 to 150 degrees in the cross section passing through the center of the plate 53. The holder 52 having such a structure is mounted with a pair of pressing pieces (pressing members) 60.
[0022] The pressing piece 60 has an approximately semi-circular ring shape and has a sliding surface 61, which is formed at the outer circumference thereof and has the same shape as the slope surface 55. The pressing piece 60 also has a protrusion (pressing surface) 62, which is formed at an edge of the inner circumference thereof at a side opposite to the other pressing piece 60 and protrudes to the inner circumference and outwardly in the thickness direction thereof. The pair of the pressing pieces 60 have a symmetrical shape in the cross section shown in Fig. 4B and have the sliding surfaces 61 that form a concave part, and the slope surface 55 of the plate 53 fits to the concave part in a wedge-shaped manner. The pressing piece 60 is formed with a hole 63 that penetrates in the thickness direction, and a bolt 64 and nuts 65 are attached to the hole 63. The bolt 64 and the nuts 65 prevent the pair of the pressing pieces 60 from being separated from each other more than a predetermined distance.
In addition, the holder 52 has a stopper 66 that is attached at a lower surface thereof so as to prevent falling off of the pair of the pressing pieces 60 therefrom.
[0023] Fig. 6 is a cross sectional view showing the details of the pressing piece 60. As shown in Fig. 6, the protrusion 62 of the pressing piece 60 has a cross section with an approximately semicircular shape and has a curvature radius that is smaller than that of the fillet part 15. In addition, the protrusion 62 protrudes to the crank arm 12, thereby forming a space between the protrusion 62 and the crank arm 12 over the protrusion 62. Moreover, an imaginary straight line "L" (refer to Fig. 6) that is perpendicular to the slope surface 55 passes a working part "F" of the protrusion 62 for pressing the fillet part 15. It should be noted that the first upper punch 31, the first lower punch 21, the second lower punch 22, the lower punch 41, and the second upper punch 32, are also formed as in the case of the upper punch 51 described above.
[0024] Fig. 7 shows shapes of the lower punch 41 and the upper punch 51, which are viewed from a side. The protrusion 62 of the upper punch 51 has a forming area "A" in a range within 45 degrees from a normal line "1" direction (direction from the curvature center "0" to the center line of the upper punch 51) to each side in the circumferential direction. The forming area "A" is formed of an approximately cylindrical curved surface with a curvature radius that is obtained by subtracting a pressing amount from the curvature radius of the cross section of the fillet part 15. Here, the "pressing amount" is a thickness to be worked on the fillet part 15 along the normal line "1" by the protrusion 62. The protrusion 62 approximately uniformly works in the forming area "A".
[0025] As shown in Fig. 8, a gradually changing area "B" is provided in a range within 90 degrees from the normal line "1" direction to each side in the circumferential direction, beyond the forming area "A". In this area, the curvature radius is gradually increased to a relief radius "N" that is obtained by adding a relief amount to the curvature radius of the fillet part 15. In Fig.
8, the solid line represents a circle of a radius "R" of the fillet part 15, the broken line represents a circle of a target radius "S" after forming (the radius of the fillet part 15 ¨ the pressing amount), and the alternate long and two short dashed line represents a circle of the relief radius "N" (the radius of the fillet part 15 +
the relief amount). In the gradually changing area "B", the shape of the protrusion 62 is set by measuring a cam profile around the curvature center "0"
and by setting the distance from the curvature center "0" at each angle point.
[0026] Specifically, first, the angle ranges of the forming area "A" and the gradually changing area "B" are set, and then angle points are determined by setting a radius every 10 degrees from an end point of the forming area "A".
In this case, the angle range of the gradually changing area "B" is divided by degrees so that the angle point number is calculated, and a difference between the relief radius "N" and the target radius "S" is calculated. Next, the curvature radius of the protrusion 62 is enlarged every 10 degrees by a calculated value that is obtained by dividing the calculated difference by the angle point number. Thus, the distance from the curvature center "0" is gradually increased as the angle increases from the normal line "1" direction to each side in the circumferential direction beyond the forming area "A", and it agrees with the radius "R" of the fillet part 15 at the point "P". Moreover, when the angle further increases in the circumferential direction, the protrusion 62 is protruded in a direction reverse to the forming area "A", and the distance from the curvature center "0" reaches the relief radius "N".
[0027] The lower punch 41 is constructed in a manner similar to that of the upper punch 51. That is, the protrusion 62 of the lower punch 41 has a forming area "A" in a range within 45 degrees from the normal line "1"
direction to each side in the circumferential direction. The forming area "A" is formed of an approximately cylindrical curved surface with a curvature radius that is obtained by subtracting a pressing amount from the curvature radius of the cross section of the fillet part 15. In addition, a gradually changing area "B" is provided in a range within 90 degrees from the normal line "1" direction to each side in the circumferential direction, beyond the forming area "A". In this area, the curvature radius is gradually increased to a curvature radius that is obtained by adding a relief amount to the curvature radius of the fillet part 15.
[0028] Next, a method of strengthening the fillet part 15 by using the lower punch 41 and the upper punch 51 having the above structures will be described.
In this embodiment, the fillet part 15 is strengthened by plastic working at ordinary temperature. When the upper die 5 is lowered, the forming area "A"
of the protrusion 62 of the upper punch 51 contacts the fillet part 15 of the crank pin 13 and presses the fillet part 15 in conjunction with the forming area "A"
of the protrusion 62 of a first lower punch 121. At this time, as shown in Fig.
6, the slope surface 55 of the holder 52 comes between the pair of the pressing pieces 60 in a wedge-shaped manner, thereby separating the pair of the pressing pieces 60 from each other. Then, the protrusion 62 presses a portion of the fillet part 15 in the axial direction side. By performing this processing, compressive residual stress is applied to portions of the fillet part 15 in the radial direction side and in the axial direction side. In the forming area "A", since approximately the entirety of the portion of the fillet part 15 is formed in the vertical direction by the pressing amount, the compressive residual stress is approximately uniform. The compressive residual stress offsets tensile stress, which may occur when a bending moment is applied to the fillet part 15.
[0029] On the other hand, in the gradually changing area "B", the pressing amount is gradually decreased from the normal line "1" direction in the circumferential direction, and the pressed portion of the fillet part 15 reaches a portion that is not pressed. Therefore, the compressive residual stress that is applied to the fillet part 15 is gradually decreased in the gradually changing area "B" and becomes zero at the portion that is not pressed. Accordingly, tensile residual stress, which occurs at a portion in the vicinity of the portion provided with the compressive residual stress, is decreased.
[0030] Here, the crankshaft 1 is designed for an in-line four cylinder engine, and in such a case, portions at the phase angles of 0 degrees and 180 degrees, that is, the top point and the bottom point of the fillet part 15 as shown in Fig. 7 receive at least one of the bending load and the torsional stress at the maximum degree when explosive combustion occurs in the internal combustion engine.
For example, in the case of the crank pin 13, the bottom point of the fillet part 15 is located at a position in a direction reverse to the direction of the balance weight 14 by 180 degrees. In another example, in the case of the journal pin 11, the bottom point of the fillet part 15 is located at a position in the direction of the balance weight 14.
[0031] In this embodiment, the portions of the fillet part 15, to which at least one of the bending load and the torsional stress at the maximum degree is to be applied, are pressed by the upper punch 51 and the lower punch 41, whereby compressive residual stress is applied to the portions of the fillet part 15 in the radial direction side and in the axial direction side. In addition, the compressive residual stress is applied only to the portions that need to be strengthened, and therefore, the processing is efficiently performed.
Moreover, , the fillet part 15 is partially plastic worked, whereby elongation in the axial direction due to the plastic working is reduced.
[0032] In particular, in the above embodiment, since the forming area "A" and the gradually changing area "B" are provided to the upper punch 51 and the lower punch 41, a wide area of the fillet part 15 is strengthened while the tensile residual stress, which occurs at portions in the vicinity of the portions provided with the compressive residual stress, is decreased. In addition, since the imaginary straight line "L" that is perpendicular to the slope surface 55 of the holder 52 passes the working part "F" of the protrusion 62 for pressing the fillet part 15, the pressing pieces 60 are reliably slid and are moved in the axial direction.
[0033] Next, the crankshaft 1 is turned upside down and is placed on the lower die 2 so that a left end crank pin 13 and a crank pin 13 on the right side of the left end crank pin 13 face the vertical direction, and the fillet parts 15 are subjected to the plastic working in the same manner as described above. In addition, the fillet parts 15 of the journal pin 11 are subjected to the plastic working by the lower die 4 and the upper die 5 shown in Fig. 3. In these cases, the same effects can also be obtained as in the case described above.
[0034] Although two crank pins 13 are strengthened by using the upper punches 31 and 32 and the lower punches 21 and 22 as shown in Fig. 2 in the above embodiment, the crank pins 13 may be strengthened one by one by a pair of the upper and lower punches. Alternatively, all of the crank pins 13 and all of the journal pins 11 may be strengthened at one time by using a die assembly for the entire shape.
14 [0035] The present invention can be utilized for strengthening the fillet parts of a crankshaft.
Claims (5)
1. A strengthening method for a fillet part of each of a pin part and a journal part of a crankshaft, the method comprising:
pressing a pressing member from a normal direction that is perpendicular to an axis line of the pin part or the journal part, against a portion in a circumferential direction of the fillet part, which is configured to receive at least one of bending load and torsional stress at a maximum degree, thereby applying compressive residual stress, wherein the pressing member is slidably supported in a direction tilted with respect to the axis line direction against the pressing direction and is slidingly moved in a direction tilted with respect to the axis line direction when pressing the fillet part, wherein the pressing member includes a guide member that is provided at a trailing end side thereof, the guide member has a convex slope surface, which faces the pressing member, the pressing member is constructed of a pair of pressing pieces, which are configured to come into contact with or separate from each other, and has a concave slope surface, which faces the convex slope surface and has the same shape as the convex slope surface, and the convex slope surface presses the concave slope surface so that the pressing member slides while the pressing member presses the fillet part.
pressing a pressing member from a normal direction that is perpendicular to an axis line of the pin part or the journal part, against a portion in a circumferential direction of the fillet part, which is configured to receive at least one of bending load and torsional stress at a maximum degree, thereby applying compressive residual stress, wherein the pressing member is slidably supported in a direction tilted with respect to the axis line direction against the pressing direction and is slidingly moved in a direction tilted with respect to the axis line direction when pressing the fillet part, wherein the pressing member includes a guide member that is provided at a trailing end side thereof, the guide member has a convex slope surface, which faces the pressing member, the pressing member is constructed of a pair of pressing pieces, which are configured to come into contact with or separate from each other, and has a concave slope surface, which faces the convex slope surface and has the same shape as the convex slope surface, and the convex slope surface presses the concave slope surface so that the pressing member slides while the pressing member presses the fillet part.
2. A strengthening device for a fillet part of each of a pin part and a journal part of a crankshaft, the device being configured to:
press a pressing member from a normal direction that is perpendicular to an axis line of the pin part or the journal part, against a portion in a circumferential direction of the fillet part, which is configured to receive at least one of bending load and torsional stress at a maximum degree, thereby applying compressive residual stress, wherein the device includes a guide member, which has a slope surface that is tilted in the axis line direction with respect to the pressing direction and provided at an end thereof, and includes the pressing member, which has a sliding surface slidable along the slope surface and has a pressing surface with a configuration along the fillet part, and the slope surface is uniformly tilted relative to a pressing direction of the pressing member so as to face the fillet part, wherein the slope surface of the guide member has a convex shape so as to face the pressing member, the pressing member is constructed of a pair of pressing pieces, which are configured to come into contact with or separate from each other, and has a concave slope surface, which faces the convex slope surface and has the same shape as the convex slope surface, and the convex slope surface presses the concave slope surface so that the pressing member slides while the pressing member presses the fillet part.
press a pressing member from a normal direction that is perpendicular to an axis line of the pin part or the journal part, against a portion in a circumferential direction of the fillet part, which is configured to receive at least one of bending load and torsional stress at a maximum degree, thereby applying compressive residual stress, wherein the device includes a guide member, which has a slope surface that is tilted in the axis line direction with respect to the pressing direction and provided at an end thereof, and includes the pressing member, which has a sliding surface slidable along the slope surface and has a pressing surface with a configuration along the fillet part, and the slope surface is uniformly tilted relative to a pressing direction of the pressing member so as to face the fillet part, wherein the slope surface of the guide member has a convex shape so as to face the pressing member, the pressing member is constructed of a pair of pressing pieces, which are configured to come into contact with or separate from each other, and has a concave slope surface, which faces the convex slope surface and has the same shape as the convex slope surface, and the convex slope surface presses the concave slope surface so that the pressing member slides while the pressing member presses the fillet part.
3. The strengthening device according to claim 1 or 2, wherein the pressing member includes a pressing surface for pressing the fillet part at a predetermined pressing amount, the pressing surface includes a forming area in a range within 45 degrees from the normal direction to each side in the circumferential direction and includes a gradually changing area in a range within 90 degrees from the normal direction to each side in the circumferential direction beyond the forming area, the forming area is formed of an approximately cylindrical curved surface having a curvature radius that is obtained by subtracting the predetermined pressing amount from a curvature radius of a cross section of the fillet part, and the gradually changing area has a curvature radius that gradually increases to a relief radius that is obtained by adding a relief amount to the curvature radius of the fillet part.
4. The strengthening device according to claim 1 or 2, wherein an imaginary straight line that is perpendicular to the slope surface in a cross section including the axis line passes a working part of the pressing surface for pressing the fillet part.
5. The strengthening device according to claim 1 or 2, wherein the slope surface is a cylindrical curved surface.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015049375A JP6042472B2 (en) | 2015-03-12 | 2015-03-12 | Method and device for strengthening fillet portion of crankshaft |
| JP2015-049375 | 2015-03-12 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2923468A1 CA2923468A1 (en) | 2016-09-12 |
| CA2923468C true CA2923468C (en) | 2018-02-13 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2923468A Expired - Fee Related CA2923468C (en) | 2015-03-12 | 2016-03-10 | Strengthening method for fillet part of crankshaft and stengthening device therefor |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP6042472B2 (en) |
| CN (1) | CN105964848B (en) |
| CA (1) | CA2923468C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102017113066B3 (en) * | 2017-06-14 | 2018-11-15 | Maschinenfabrik Alfing Kessler Gmbh | Method for impact hardening of transition radii of a crankshaft |
| CN109408874B (en) * | 2018-09-14 | 2023-03-21 | 广东电网有限责任公司 | Simulation method for bending radian of end part of explosion-proof device of high-voltage cable joint |
| DE102020200153A1 (en) * | 2020-01-08 | 2021-07-08 | Mahle International Gmbh | Method for machining an annular groove |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1442344A (en) * | 1973-10-13 | 1976-07-14 | Brown Tractors Ltd | Method of treating crankshafts |
| JPS5537276A (en) * | 1978-09-11 | 1980-03-15 | Hino Motors Ltd | Work method for fillet portion of crankshaft |
| JP3899246B2 (en) * | 2001-09-13 | 2007-03-28 | 株式会社神戸製鋼所 | Crankshaft forging method and forging device |
| DE102005021793B4 (en) * | 2005-05-11 | 2007-03-29 | Maschinenfabrik Alfing Kessler Gmbh | Method and system for hardening transition radii of a shaft |
| JP2007030115A (en) * | 2005-07-28 | 2007-02-08 | Nissan Motor Co Ltd | Fillet roll machining method for crankshaft for internal combustion engine |
| EP1779972B1 (en) * | 2006-10-23 | 2008-12-17 | Cornelius Reuss | Method and apparatus for hardening crankshafts |
| DE102007028888B4 (en) * | 2007-06-20 | 2015-07-23 | Maschinenfabrik Alfing Kessler Gmbh | Method for increasing the strength of a component |
| CN201511080U (en) * | 2009-10-23 | 2010-06-23 | 秦皇岛方华埃西姆机械有限公司 | Dimpling mould for circular tube |
| CN202079161U (en) * | 2011-03-14 | 2011-12-21 | 广州花都通用集团有限公司 | Mould of pigtail taper sleeve for manufacturing elevator |
| CN201931018U (en) * | 2011-03-29 | 2011-08-17 | 日佳力机电工业(昆山)有限公司 | Formation stamping die for bolt via hole bushing |
| CN202690720U (en) * | 2012-07-18 | 2013-01-23 | 道依茨一汽（大连）柴油机有限公司 | Fillet rolling ductile iron crankshaft |
| CN203357448U (en) * | 2013-06-23 | 2013-12-25 | 四川海普工控技术有限公司 | Mechanical arm with replaceable anti-sliding structure |
| CN104368693A (en) * | 2014-11-24 | 2015-02-25 | 常州市永安保安服务有限公司 | U-shaped piece bending and correcting die |
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2015
- 2015-03-12 JP JP2015049375A patent/JP6042472B2/en not_active Expired - Fee Related
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2016
- 2016-03-10 CN CN201610136333.6A patent/CN105964848B/en active Active
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Also Published As
| Publication number | Publication date |
|---|---|
| JP2016168605A (en) | 2016-09-23 |
| CN105964848B (en) | 2019-03-19 |
| JP6042472B2 (en) | 2016-12-14 |
| CN105964848A (en) | 2016-09-28 |
| CA2923468A1 (en) | 2016-09-12 |
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