Apparatus for manufacturing forged crankshaft

Abstract

An apparatus for manufacturing a forged crankshaft includes a pair of upper and lower dies and a first tool. The pair of dies deforms first excess portions and thereby thickens both side portions of a rough crank arm, in a region near a rough pin adjacent thereto. The first tool is fitted in an open space made in the pair of dies, and is capable of coming into contact with a rough-journal-facing surface of the rough crank arm, except the side portions in the region near the adjacent rough pin. The first pair of dies and the first tool have first guides to guide the first tool from a retracting position to a contacting position. The first guides include a first guide disposed on at least one of an upper surface and a lower surface of the first tool.

Claims

1. A manufacturing apparatus for processing a forged blank from which flash has been removed, the forged blank including rough journals, rough pins, rough crank arms and rough counterweights, the rough pins decentered from the journals so as to define a rough pin decentering direction, and at least one of the rough crank arms including a first excess portion protruding from a side portion in a region near an adjacent one of the rough pins; the manufacturing apparatus comprising: a pair of upper and lower dies configured for deforming the first excess portion and thereby thickening the side portion of the rough crank arm including the first excess portion in the region near the adjacent rough pin; and a first tool fitted in an open space made in the pair of dies, the first tool configured for coming into contact with a rough-journal-facing surface of the rough crank arm, except the side portion in the region near the adjacent rough pin, before deformation of the first excess portion by the pair of upper and lower dies, the first tool retaining a shape of the rough-journal facing surface during deformation of the first excess portion, wherein: the pair of dies and the first tool have first guides to guide the first tool from a retracting position to a contacting position; and the first guide of the first tool is disposed on at least one of an upper surface and a lower surface of the first tool; and further comprising: a first jig movable in the rough pin decentering direction, wherein: the first jig supports the first tool such that the first tool is movable in a first slide direction that is at an angle to a first guide direction in which the first tool is guided by the first guides; and the first tool moves in the first guide direction along with a movement of the first jig.

2. The manufacturing method according to claim 1, wherein the pair of upper and lower dies are dies to apply coining to the forged blank.

3. The manufacturing apparatus according to claim 1, wherein the forged blank includes a second excess portion protruding from an outer periphery of a side portion of at least one of the rough crank arms with no rough counterweights in a region near an adjacent one of the rough journals, the manufacturing apparatus further comprising: a second tool fitted in an open space made in the pair of dies, the second tool capable of coming into contact with a rough-pin-facing surface of the rough crank arm, except the side portion in the region near the rough journal, wherein the pair of dies is further capable of deforming the second excess portion and thereby thickening the side portion in the region near the adjacent rough journal; and further wherein the pair of upper and lower dies and the second tool have second guides to guide the second tool from a retracting position to a contacting position; and the second guide of the second tool disposed on at least one of an upper surface and a lower surface of the second tool.

4. The manufacturing method according to claim 3, wherein the pair of upper and lower dies are dies to apply coining to the forged blank.

5. A manufacturing apparatus for processing a forged blank from which flash has been removed, the forged blank including rough journals, rough pins, rough crank arms and rough counterweights, and at least one of the rough crank arms including a first excess portion protruding from a side portion in a region near an adjacent one of the rough pins, the forged blank including a second excess portion protruding from an outer periphery of a side portion of at least one of the rough crank arms with no rough counterweights in a region near an adjacent one of the rough journals; the manufacturing apparatus comprising: a pair of upper and lower dies configured for deforming the first excess portion and thereby thickening the side portion of the rough crank arm including the first excess portion in the region near the adjacent rough pin; and a first tool fitted in an open space made in the pair of dies, the first tool configured for coming into contact with a rough-journal-facing surface of the rough crank arm, except the side portion in the region near the adjacent rough pin, before deformation of the first excess portion by the pair of upper and lower dies, the first tool retaining a shape of the rough-journal facing surface during deformation of the first excess portion, wherein: the pair of dies and the first tool have first guides to guide the first tool from a retracting position to a contacting position; and the first guide of the first tool is disposed on at least one of an upper surface and a lower surface of the first tool, and further comprising: a second tool fitted in an open space made in the pair of dies, the second tool capable of coming into contact with a rough-pin-facing surface of the rough crank arm, except the side portion in the region near the rough journal, wherein the pair of dies is further capable of deforming the second excess portion and thereby thickening the side portion in the region near the rough journal; and further wherein the pair of upper and lower dies and the second tool have second guides to guide the second tool from a retracting position to a contacting position; and the second guide of the second tool disposed on at least one of an upper surface and a lower surface of the second tool.

6. The manufacturing method according to claim 5, wherein the pair of upper and lower dies are dies to apply coining to the forged blank.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1A is a schematic diagram of a billet during a conventional process of manufacturing a forged crankshaft.

(2) FIG. 1B is a schematic diagram of a rolled blank during the conventional process of manufacturing a forged crankshaft.

(3) FIG. 1C is a schematic diagram of a bent blank during the conventional process of manufacturing a forged crankshaft.

(4) FIG. 1D is a schematic diagram of a rough forged blank during the conventional process of manufacturing a forged crankshaft.

(5) FIG. 1E is a schematic diagram of a finish forged blank during the conventional process of manufacturing a forged crankshaft.

(6) FIG. 1F is a schematic diagram of a crankshaft during the conventional process of manufacturing a forged crankshaft.

(7) FIG. 2 is a diagram showing a four-cylinder four-counterweight crankshaft having an exemplary configuration.

(8) FIG. 3A is a top view showing the positional relationship between a forged blank and tools.

(9) FIG. 3B is a perspective view of a mechanism for moving the tools.

(10) FIG. 3C is a top view showing a state where the tools are in contacting positions.

(11) FIG. 3D is a top view showing a state where the tools are in retracting positions.

(12) FIG. 3E is a sectional view along the line IIIE-IIIE in FIG. 3C.

(13) FIG. 4A is a perspective view schematically showing the shape of an arm of a crankshaft having a first exemplary configuration according to the present invention.

(14) FIG. 4B is a top view schematically showing the shape of the arm of the crankshaft having the first exemplary configuration according to the present invention.

(15) FIG. 4C is a side view schematically showing the shape of the arm of the crankshaft having the first exemplary configuration according to the present invention.

(16) FIG. 4D is a sectional view along the line IVD-IVD in FIG. 4B.

(17) FIG. 5A is a perspective view schematically showing the shape of a rough arm of a forged blank with no flash for the first exemplary configuration according to the present invention.

(18) FIG. 5B is a front view schematically showing the shape of the rough arm of the forged blank with no flash for the first exemplary configuration according to the present invention.

(19) FIG. 5C is a side view schematically showing the shape of the rough arm of the forged blank with no flash for the first exemplary configuration according to the present invention.

(20) FIG. 5D is a sectional view along the line VD-VD in FIG. 5B.

(21) FIG. 6A is a front view schematically showing the shape of an arm of a crankshaft having a second exemplary configuration according to the present invention.

(22) FIG. 6B is a sectional view along the line VIB-VIB in FIG. 6A.

(23) FIG. 7A is a front view schematically showing the shape of a rough arm of a forged blank with no flash for the second exemplary configuration according to the present invention.

(24) FIG. 7B is a sectional view along the line VIIB-VIIB in FIG. 7A.

(25) FIG. 8A is a perspective view schematically showing a forged crankshaft manufacturing apparatus according to an embodiment.

(26) FIG. 8B is an enlarged perspective view of the forged crankshaft manufacturing apparatus according to the embodiment from a direction indicated by the arrow in FIG. 8A.

(27) FIG. 8C is a top view showing a state where tools are in contacting positions in the forged crankshaft manufacturing apparatus according to the embodiment.

(28) FIG. 8D is a top view showing a state where the tools are in retracting positions in the forged crankshaft manufacturing apparatus according to the embodiment.

(29) FIG. 9 is a diagram showing a forged crankshaft manufacturing apparatus having another exemplary configuration different from the configuration shown in FIGS. 8A to 8D.

(30) FIG. 10 is a top view showing the positional relationship between tools according to the embodiment and a forged blank.

(31) FIG. 11A is a top view showing a state where, in a forged crankshaft manufacturing apparatus according to an embodiment further including a second tool, the second tool is in a contacting position.

(32) FIG. 11B is a top view showing a state where, in the forged crankshaft manufacturing apparatus according to the embodiment further including a second tool, the second tool is in a retracting position.

DESCRIPTION OF EMBODIMENTS

(33) A forged crankshaft manufacturing apparatus according to an embodiment of the present invention processes a forged blank with no flash during a process of manufacturing a forged crankshaft. The forged crankshaft includes journals serving as an axis of rotation, pins decentered from the journals, and crank arms connecting the journals and the pins. The forged crankshaft further includes one or more counterweights integrated with one or more of the rough arms. The forged blank includes rough journals, rough pins, rough crank arms and rough counterweights, which correspond to the journals, the pins, the crank arms and the counterweights, respectively, of the forged crankshaft. At least one of the rough crank arms has a first excess portion protruding from the outer periphery of a side portion in a region near an adjacent one of the rough pins.

(34) The forged crankshaft manufacturing apparatus includes a pair of upper and lower dies, and a first tool. The pair of dies is capable of deforming the first excess portion and thereby thickening the side portion of the rough crank arm in the region near the adjacent rough pin. The first tool is fitted in an open space made in the dies, and is capable of coming into contact with the rough-journal-facing surface of the rough crank arm having the first excess portion, except the side portion in the region near the adjacent rough pin. The pair of dies and the first tool have first guides to guide the first tool from a retracting position to a contacting position. The first guide of the first tool disposed on at least one of the upper surface and the lower surface of the first tool.

(35) It is preferred that the forged crankshaft manufacturing apparatus further includes a first jig movable in a pin decentering direction in which the pins are decentered. The first jig preferably supports the first tool such that the first tool is movable in a first slide direction that is at an angle to a first guide direction in which the first tool is guided by the first guides. The first tool preferably comes into contact with the rough-journal-facing surface of the rough crank arm having the first excess portion, except the side portion in the region near the adjacent rough pin. The first tool preferably moves in the first guide direction along with a movement of the first jig.

(36) The forged crankshaft manufacturing apparatus is to manufacture a forged crankshaft in which every one of the crank arms has a counterweight integrated therewith.

(37) When only some of the crank arms of the forged crankshaft have counterweights integrated therewith, the forged crankshaft manufacturing apparatus may have a configuration as described below.

(38) In the forged crankshaft, at least one of the rough crank arms with no rough counterweights includes a second excess portion protruding from an outer periphery of a side portion in a region near an adjacent one of the rough journals. The pair of dies is further capable of deforming the second excess portion and thereby thickening the side portion of the rough crank arm with no rough counterweight in the region near the adjacent rough journal. The manufacturing apparatus is placed in an open space made in the dies. The manufacturing apparatus further includes a second tool. The second tool is capable of coming into contact with the rough-pin-facing surface of the rough crank arm having the second excess portion, except the side portion in the region near the adjacent rough journal. The pair of dies and the second tool have second guides to guide the second tool from a retracting position to a contacting position. The second guide of the second tool disposed on at least one of an upper surface and a lower surface of the second tool.

(39) The dies of the manufacturing apparatus are preferably dies to apply coining to the forged blank.

(40) A forged crankshaft manufacturing apparatus according to an embodiment of the present invention will hereinafter be described with reference to the drawings.

(41) 1. Shape of Crankshaft

(42) A forged crankshaft that is the target of the present embodiment includes journals serving as an axis of rotation, pins decentered from the journals, and arms connecting the journals and the pins. The forged crankshaft further includes one or more weights integrated with one or more of the arms. Every one of the arms may have a weight integrated therewith. Such a crankshaft may have, for example, a first exemplary configuration as shown by FIGS. 4A to 4D or a second exemplary configuration as shown by FIGS. 6A and 6B.

(43) Whether the forged crankshaft has the first exemplary configuration or the second exemplary configuration, the forged crankshaft includes at least one arm having a recess in the journal-facing surface. The crankshaft having the second exemplary configuration includes at least one arm with no weight integrated therewith. The arm with no weight has a recess in the pin-facing surface.

(44) FIGS. 4A to 4D are diagrams showing the shape of an arm of a crankshaft after processed in the coining step, the crankshaft having the first exemplary configuration according to the present invention. FIG. 4A is a perspective view, FIG. 4B is a front view from the journal-facing surface, FIG. 4C is a side view, and FIG. 4D is a sectional view along the line IVD-IVD in FIG. 4B. In FIGS. 4A to 4D, an arm representing the arms (having weights integrated therewith) of the crankshaft is shown, and the other arms are omitted. FIG. 4C is a view from the direction indicated by the dashed arrow in FIG. 4B.

(45) The arm A of the crankshaft having the first exemplary configuration, as shown in FIGS. 4A to 4D, has a recess in the journal J-facing surface, in a region near the adjacent pin P, in an area As inside of both side portions Aa and Ab. The side portions Aa and Ab in the region near the adjacent pin P bulge toward the journal J. The thicknesses of the side portions Aa and Ab are greater than the thickness of the recess in the inner area As.

(46) In the first exemplary configuration, the arm A has thick side portions As and Ab in the region near the adjacent pin P, and has a recess in the journal J-facing surface. According to the present embodiment, the recess made in the arm A leads to a weight reduction of the forged crankshaft. Besides, the thick side portions Aa and Ab of the arm A ensure stiffness.

(47) In the crankshaft having the first exemplary configuration, both side portions Aa and Ab of the arm A in the region near the adjacent pin P are thick. However, only one side portion of the arm A in the region near the adjacent pin P may be thick. Even in this case, the thick portion of the arm A in the region near the adjacent pin P ensures the arm A stiffness.

(48) FIGS. 5A to 5D are diagrams showing the shape of a rough arm of a forged blank with no flash before processed in the coining step, the forged blank being for the forged crankshaft having the first exemplary configuration according to the present invention. FIG. 5A is a perspective view, FIG. 5B is a front view from the journal-facing surface, FIG. 5C is a side view, and FIG. 5D is a sectional view along the line VD-VD in FIG. 5B. In FIGS. 5A to 5D, a rough arm representing the rough arms (having rough weights integrated therewith) of the forged blank is shown, and the other rough arms are omitted. FIG. 5C is a view from the direction indicated by the dashed arrow in FIG. 5B. To make the drawings easy to understand, FIG. 5D further shows a first tool 20 and a jig 30 of a manufacturing apparatus which will be described later.

(49) As shown in FIGS. 5A to 5D, the rough arm A before processed in the coining step has the same surface shape as the finished product after processed in the coining step, in the rough-journal J-facing surface, in a region near the adjacent rough pin P, in an area As inside of both side portions Aa and Ab. The surface shape extends smoothly to the side portions Aa and Ab in the region near the adjacent rough pin P. Accordingly, the thicknesses of the side portions Aa and Ab are smaller than the thicknesses of the side portions of the finished product after processed in the coining step.

(50) The rough arm has first excess portions Aaa and Aba protruding from the outer peripheries of the side portions Aa and Ab in the region near the adjacent rough pin P. The first excess portions Aaa and Aba are plate-shaped, and are disposed along the outer periphery of the side portion Aa and the outer periphery of the side portion Ab, respectively, in the region near the adjacent pin P. The thicknesses of the first excess portions Aaa and Aba are comparable to or less than the thicknesses of the side portions Aa and Ab which are the bases thereof.

(51) In the forged blank for the first exemplary configuration, all of the rough arms A of the forged blank may have such first excess portions Aaa and Aba. Alternatively, some of the rough arms A may have such first excess portions Aaa and Aba. In the above-described first exemplary configuration, the rough arm A has two first excess portions Aaa and Aba. However, the rough arm A may have only one first excess portion. In this case, in the finished crankshaft, the arm has one thick side portion in the region near the adjacent pin.

(52) FIGS. 6A and 6B are diagrams showing the shape of an arm of a crankshaft after processed in the coining step, the crankshaft having the second exemplary configuration according to the present invention. FIG. 6A is a front view from the pin-facing surface, and FIG. 6B is a sectional view along the line VIB-VIB in FIG. 6A. In the second exemplary configuration, the crankshaft includes a plurality of arms, and only some of the arms have weights integrated therewith. In FIGS. 6A and 6B, an arm with no weight extracted from the crankshaft is shown, and the other arms of the crankshaft are not shown.

(53) In the second exemplary configuration, as in the first exemplary configuration, the arm A has thick side portions in the region near the adjacent pin P and has a recess in the journal-facing surface although it is not shown in the drawings. In the second exemplary configuration, the arm A, which does not have a weight, additionally has another recess in the pin P-facing surface, in a region near the adjacent journal J, in an area At inside of both side portions Ac and Ad. The side portions Ac and Ad in the region near the adjacent journal J bulge toward the adjacent pin P. The thicknesses of the side portions Ac and Ad are greater than the thickness of the recess.

(54) In the second exemplary configuration, the arm A has thick side portions in the region near the adjacent P and has a recess in the journal J-facing surface. The arm A, which does not have a weight, further has thick side portions Ac and Ad in the region near the adjacent journal J and has a recess in the pin P-facing surface. In the second exemplary configuration, the recesses formed in the journal J-facing surface and the pin P-facing surface of the arm A lead to a weight reduction of the forged crankshaft. Besides, the thick side portions in the region near the adjacent pin P and the thick side portions Ac and Ad in the region near the journal J ensure the arm A stiffness.

(55) In the second exemplary configuration, both side portions of the arm A in the region near the adjacent pin P are thick, and both side portions Ac and Ad of the arm A in the region near the adjacent journal J are thick. However, only one side portion of the arm A in the region near the adjacent pin P may be thick, and only one side portion of the arm A in the region near the adjacent journal J may be thick. Even in this case, the thick side portion of the arm A in the region near the adjacent pin P and the thick side portion in the adjacent journal J ensure the arm A stiffness.

(56) FIGS. 7A and 7B are diagrams showing a rough arm of a forged blank with no flash before processed in the coining step, the forged blank being for the second exemplary configuration according to the present invention. FIG. 7A is a front view from the rough-pin-facing surface, and FIG. 7B is a sectional view along the line VIIB-VIIB in FIG. 7A. In FIGS. 7A to 7B, one of the rough arms with no rough weights extracted from the forged blank is shown, and the other rough arms are omitted.

(57) As in the forged blank for the first exemplary configuration, the rough arm A before processed in the coining step has the same surface shape as the finished product after processed in the coining step, in the rough-journal J-facing surface, in a region near the adjacent rough pin P, in an area inside of both side portions, though it is not shown in the drawings. As in the forged blank for the first exemplary configuration, the rough arm A has first excess portions Aaa and Aba protruding from the outer peripheries of the side portions Aa and Ab in the region near the adjacent rough pin P.

(58) Unlike in the forged blank for the first exemplary configuration, the rough arm A with no rough weight before processed in the coining step, as shown in FIGS. 7A and 7B, has the same surface shape as the finished product after processed in the coining, in the rough-pin P-facing surface, in a region near the adjacent rough journal J, in an area At inside of both side portions Ac and Ad. The surface shape extends smoothly to the side portions Ac and Ad in the region near the adjacent rough journal J. Accordingly, the thicknesses of the side portions Ac and Ad in the region near the adjacent rough journal J are smaller than the thicknesses of the side portions of the finished product after processed in the coining step.

(59) The rough arm A with no rough weight further has second excess portions Aca and Ada protruding from the outer peripheries of side portions Ac and Ad in a region near the adjacent rough journal J. The second excess portions Aca and Ada are plate-shaped, and are disposed along the outer periphery of the side portion Ac and the outer periphery of the side portion Ad, respectively, in the region near the adjacent rough journal J. The thicknesses of the second excess portions Aca and Ada are comparable to or less than the thicknesses of the side portions Ac and Ad which are the bases thereof.

(60) In the forged blank for the second exemplary configuration, all of the rough arms A may have such second excess portions Aca and Ada. Alternatively, some of the rough arms A may have such second excess portions Aca and Ada. In the second exemplary configuration, the rough arm A has two first excess portions Aaa and Aba, and two second excess portions Aca and Ada. However, the rough arm A may have only one first excess portion and may have only one second excess portion. When the rough arm A has only one second excess portion, in the finished crankshaft, the arm has one thick side portion in the region near the adjacent pin.

(61) 2. Forged Crankshaft Manufacturing Apparatus

(62) FIGS. 8A to 8D are diagrams showing a forged crankshaft manufacturing apparatus having an exemplary configuration. FIG. 8A is a perspective view, FIG. 8B is an enlarged perspective view from the direction indicated by the arrow in FIG. 8A, FIG. 8C is a top view showing a state where tools are in contacting positions, and FIG. 8D is a top view showing a state where the tools are in retracting positions. In FIGS. 8A to 8D, a forged blank 91 with no flash, a part of a lower die of the pair of dies 10, a first tool 20 and a first jig 30 are shown. To make the drawings easy to understand, in FIGS. 8B to 8D, the forged blank 91 is omitted.

(63) The forged blank 91 shown in FIG. 8A is a forged blank for a four-cylinder four-counterweight crankshaft. The first, the fourth, the fifth and the eighth rough arms of the forged blank 91 have rough weights integrated therewith. As in the forged blank shown in FIG. 5A, at least one of the rough arms has first excess portions protruding from the outer peripheries of both side portions in a region near the adjacent rough pin.

(64) The first tool 20 comes into contact with the rough journal-facing surface of the rough arm except the side portions. For example, a front face 20a of the first tool 20 comes into contact with the rough-journal J-facing surface of the rough arm A, and specifically the inner area As inside of the side portions Aa and Ab in the region near the adjacent rough pin P, that is, an area to become a recess after the process.

(65) The manufacturing apparatus includes several first tools. In FIG. 8A, only two of the first tools are shown, and the other first tools are omitted. The two first tools shown in FIG. 8A are in contact with the rough-journal-facing surfaces of two rough arms (the fourth rough arm and the fifth rough arm) that are plane symmetrical with respect to the rough journal therebetween. FIGS. 8B to 8D show the two first tools shown in FIG. 8A and the surrounding area thereof.

(66) The pair of dies 10 is composed of an upper die and a lower die. To make the drawings easy to understand, in FIGS. 8A to 8D, the upper die is not shown, and only a part of the lower die is shown.

(67) The upper die and the lower die are to process the forged blank with no flash. The upper die and the lower die deform the protruding excess portions. The upper die and the lower die have impressions. Impressions 10a shown in FIGS. 8A to 8D is a part of the impression of the lower die.

(68) The impressions of the upper die and the lower die reflect the shape of the finished crankshaft except a part thereof. Specifically, when recesses are to be formed in the respective journal-facing surfaces of arms (see FIGS. 4A to 4D), the dies 10 (the upper die and the lower die) have open spaces 10b for the first tools 20. Accordingly, the impressions of the dies 10 do not reflect the recesses in the journal-facing surfaces of the arms.

(69) When recesses are to be formed in the respective pin-facing surfaces of arms (see FIGS. 6A and 6B), the impressions of the dies 10 do not reflect the recesses in the pin-facing surfaces of the arms. If the impressions reflect the shapes of the recesses, parts of the impressions will have a reverse draft. In this case, the dies 10 (the upper die and the lower die) may have open spaces for a second tool, which will be described later.

(70) The dies 10 (the upper die and the lower die) may have groove-like open spaces 10c for first jigs 30 (see FIG. 8A).

(71) In order to guide each of the first tools 20 from a retracting position to a contacting position, projections 20d extending in a first guide direction (see the solid arrows in FIGS. 8C and 8D) are formed on an upper surface 20b and a lower surface 20c of each of the first tools 20. The dies 10 have groove-like recesses 10d formed at the bottoms of the open spaces 10b for each of the first tools 20, and the projections 20d of the first tool 20 are fitted in the groove-like recesses 10d. Then, the first tool 20 moves from the retracting position to the contacting position along the side walls of the recesses 10d made in the open space 10b (in the dies 10) and the side surfaces 20e of the projections 20d of the first tool 20. Accordingly, the side walls of the recesses 10d made in the open space 10b (in the dies 10) and the side surfaces 20e of the projections 20d formed on the upper surface 20b and the lower surface 20c of the first tool 20 function as guides (first guides).

(72) The forged crankshaft manufacturing apparatus according to the present embodiment does not need to use the side surfaces of each of the first tools 20 as first guides. In the forged crankshaft manufacturing apparatus according to the present embodiment, each of the first tools 20 has at least one first guide on at least one of the upper surface 20b and the lower surface 20c. Therefore, the side surfaces of the first tool 20 need not be flat. The shapes of the side surfaces of the first tool 20 may be changed appropriately. For example, the side surfaces of the first tool 20 may be beveled or rounded. This leads to a decrease of the width of the first tool 20, which prevents interference of the first tool 20 with the first jig 30 or the dies 10. This ensures the first tool 20 a sufficiently wide movable range.

(73) During a process by use of the dies 10, the first excess portions are deformed to increase the thicknesses of the side portions of a rough arm in the region near the adjacent rough pin. Thereby, in the produced crankshaft, the arm has thick side portions and has a recess in the journal-facing surface. Accordingly, the produced crankshaft has a reduced weight and assured stiffness.

(74) Before deformation of the first excess portions, the first tools are brought into contact with the respective rough-journal-facing surfaces of the rough arms, whereby the recesses and other shapes in the rough-journal-facing surfaces can be retained during the process. In this manner, each of the arms obtains thick side portions in the region near the adjacent pin, whereby the inner area is recessed. Accordingly, in the produced crankshaft, each of the arms has an accurate shape.

(75) Forged crankshaft manufacturing apparatuses according to the present invention is not limited to that shown in FIGS. 8A to 8D, wherein two first tools come into contact with two rough arms which are plane symmetrical with respect to a rough journal therebetween.

(76) FIG. 9 is a diagram showing a forged crankshaft manufacturing apparatus having another exemplary configuration according to the present invention that is different from the configuration shown in FIGS. 8A to 8D. FIG. 9 is a top view showing a state where a tool is in a contacting position. In the case of FIG. 9, one first tool 20 is supported by a first jig 30. There are no other differences in configuration from the manufacturing apparatus shown in FIGS. 8A to 8D. The manufacturing apparatus shown in FIG. 9 can be used for manufacture of a four-cylinder eight-counterweight crankshaft as shown in FIG. 1F and for manufacture of a four-cylinder four-counterweight crankshaft as shown in FIG. 2, for example. This will be described with reference to FIG. 10.

(77) FIG. 10 is a top view showing the positional relationship between tools according to the present embodiment and a forged blank. In FIG. 10, a first jig 30 supporting two first tools 20 and another first jig 30 supporting one first tool 20 are shown. For example, the second rough pin P2 is in the same phase as the third rough pin P3. The fourth rough arm A4 and the fifth rough arm A5 are plane symmetrical with respect to the third rough journal J3. Therefore, the first jig 30 located to face the third rough journal J3 support two first tools 20. In this case, the two first tools 20 are capable of coming into contact with the fourth rough arm A4 and the fifth rough arm A5, respectively.

(78) The first rough pin P1 is in a different phase from that of the second rough pin P2. Therefore, the first jig 30 located to face the second rough journal J2 supports one first jig 20. In this case, the first tool 20 is capable of coming into contact with either one of the second rough arm A2 or the third rough arm A3. FIGS. 9 and 10 show a first tool 20 contacting the third rough arm A3.

(79) As described above, when two first tools are to come into contact with two rough arms which are plane symmetrical with respect to a rough journal therebetween, if both side portions of each of the tools are used as guides, the two tools will be likely to interfere with each other. This will decrease the movable range of each of the first tools. For ensuring of a sufficiently wide movable range for each of the tools, it is preferred that the two first tools to come into contact with the two rough arms which are plane symmetric with respect to a rough journal therebetween each have at least one first guide on at least one of the upper surface and the lower surface. As mentioned above, the two rough arms which are plane symmetric with respect to a rough journal therebetween are two rough arms connecting with one rough journal and connecting with rough pins which are in the same phase.

(80) Diverging from the exemplary configuration shown in FIGS. 8A to 8D, the first tools 20 could be fixed to the first jigs 30. In this case, each of the first tools can be moved in the first guide direction by a movement of the first jig in the first guide direction. However, in the configuration, the first guide directions in which the plurality of tools are to be moved are different, and therefore, the plurality of first jigs 30 shall be moved different directions. Then, the first jigs 30 may interfere with drive units (not shown), which decreases the movable ranges of the first tools.

(81) In order to prevent the interferences between the first jigs 30 and the drive units (not shown) and in order to meet the conditions for the first jigs 30 to be moved in the same direction, as shown in FIGS. 8A to 8D, the jigs 30 in the manufacturing apparatus are preferably movable in a pin decentering direction in which the pins are decentered from the journals. In this case, the first tools 20 are supported by the first jigs 30. Each of the first tools 20 is movable in a first slide direction (see the dashed arrows in FIGS. 8C and 8D) that is at an angle to the first guide direction of the first tool 20. In the manufacturing apparatus including such first jigs 30, the first tools can be moved in the respective first guide directions by movements of the first jigs in the pin decentering direction. This allows each of the first tools 20 to be located between two adjacent rough arms, which prevents the first tools 20 from interfering with the forged blank. The first jigs 30 are moved in the pin decentering direction, that is, in the same direction. This allows one drive unit to be shared between the first jigs 30, which leads to simplification of the configuration of the manufacturing apparatus. This ensures each of the first tools a sufficiently wide movable range and allows each of the first tools to be located in a smaller space.

(82) The first slide direction of each of the first tools can be set appropriately in accordance with the first guide direction. For example, the first slide direction may be a direction along the part of the rough arm which the first tool is to come into contact with.

(83) When two first tools are brought into contact with two rough arms which are plane symmetrical with respect to a rough journal therebetween, it is preferred that the two first tools are movably supported by one first jig. This also leads to simplification of the configuration of the manufacturing apparatus and ensures each of the first tools a sufficiently wide movable range.

(84) Next, with reference to FIGS. 11A and 11B, another exemplary configuration of the manufacturing apparatus is described. In this configuration, the manufacturing apparatus further includes second tools, each of which is to come into contact with the rough-pin-facing surface of a rough arm with no rough weight.

(85) FIGS. 11A and 11B are diagrams showing a manufacturing apparatus having an exemplary configuration according to the present embodiment, the manufacturing apparatus further including second tools. FIG. 11A is a top view showing a state where the second tools are in contacting positions. FIG. 11B is a top view showing a state where the second tools are in retracting positions. In FIGS. 11A and 11B, the dies 10, a second tool 40 and a second jig 50 are shown. In FIGS. 11A and 11B, a part of a lower die of the dies 10 are shown. To make the drawings easy to understand, in FIG. 11A, the outline of the forged blank 91 with no flash is indicated by a chain line. In FIGS. 11A and 11B, the first tools 20 are omitted.

(86) The forged blank 91 indicated by a chain line in FIG. 11A is, for example, a forged blank for a four-cylinder four-counterweight crankshaft shown in FIG. 2. FIG. 11A shows two adjacent rough arms A across a rough pin P, the rough pin P located between the two adjacent rough arms A, and two rough journals J which the two rough arms A connect with, respectively. One of the two rough arms A is a rough arm with no rough weight, and the other is a rough arm with a rough weight.

(87) In the forged blank 91, as in the forged blank shown in FIG. 7A, the rough arm with no rough weight additionally has second excess portions protruding from the outer peripheries of both side portions in a region near the adjacent rough journal. In FIGS. 11A and 11B, the second excess portions are omitted.

(88) The second tool 40 comes into contact with the rough arm with no rough weight, the rough-pin-facing surface thereof, except both side portions. For example, a front face 40a of the second tool 40 comes into contact with the rough-pin P-facing surface of the rough arm A, and specifically the inner area At inside of the side portions Ac and Ad in the region near the adjacent rough journal J, that is, an area to become a recess after the process. FIGS. 11A and 11B show one of the second tools 40 of the manufacturing apparatus and the surrounding area thereof.

(89) The dies 10 (the upper die and the lower die) have open spaces for the second tools 40. Further, the dies (the upper die and the lower die) have groove-like open spaces 10c for the second jigs 50.

(90) As with the first tools, in order to guide each of the second tools 40 from a retracting position to a contacting position, projections 40d extending in a second guide direction (see the solid arrows in FIGS. 11A and 11B) are formed on an upper surface 40b and a lower surface of each of the second tools 40. The dies 10 also have groove-like recesses 10d which the projections 40d of the second tools 40 are fitted in. Then, each of the second tools 40 moves from the retracting position to the contacting position along the side walls of the recesses 10d made in the dies 10 and the side surfaces 40e of the projections 40d of the second tool 40. Accordingly, the side walls of the recesses 10d made in the dies 10 and the side surfaces 40e of the projections 40d formed on the upper surface 40b and the lower surface of the second tool 40 function as guides (second guides).

(91) By providing at least one second guide to each of the second tools 40 such that the second guide is located on at least one of the upper surface 40b and the lower surface, it is possible to prevent interference of the second tool 40 with the second jig 50 or the dies 10. This ensures the second tool 40 a sufficiently wide movable range. During a process by use of the dies 10, the second excess portions are deformed to increase the thicknesses of the side portions of each of the rough arms with no rough weights in the region near the adjacent rough journal. This allows manufacture of a crankshaft having a reduced weight and assured stiffness as shown in FIGS. 6A to 6D. During the process, also, each of the rough arms with no rough weights can retain the surface shape of the rough-pin-facing surface by the contact with the second tool. In this manner, each of the arms with no weights obtains thick side portions in the region near the adjacent journal, whereby the inner area is recessed. Accordingly, in the finished crankshaft, each of the arms has an accurate shape.

(92) As with the first jigs 30, in order to prevent interferences between the second jigs 50 and drive units (not shown) and in order to meet the conditions for the second jigs 50 to be moved in the same direction, the jigs 50 in the manufacturing apparatus are preferably movable in the pin decentering direction (see the hatched arrows in FIGS. 11A and 11B). In this case, as with the jig shown in FIGS. 8A to 8D, the second jigs 50 support the second tools 40 such that each of the second tools 40 is movable in a second slide direction (see the dashed arrows in FIGS. 11A and 11B) that is at an angle to the second guide direction in which the second tool 40 is guided by the second guides.

(93) The second slide direction of each of the second tools can be set appropriately in accordance with the second guide direction. For example, the second slide direction may be a direction along the part of the rough arm which the second tool is to come into contact with.

(94) 3. Forged Crankshaft Manufacturing Method

(95) A method for manufacturing a forged crankshaft by use of the above-described manufacturing apparatus according to the present embodiment will hereinafter be described. A case where the manufacturing apparatus according to the present embodiment is used in a coining step will be described below.

(96) The manufacturing process may have the same configuration as a conventional manufacturing process. For example, the manufacturing process includes a preforming step, a die forging step, a trimming step and a coining step. In this case, in order to obtain a forged blank with no flash as shown in FIG. 5A, in the die forging step, a forged blank with flash, which includes rough arms each having first excess portions protruding from the outer peripheries of side portions in a region near an adjacent rough pin, is formed. Thereafter, in the trimming step, the flash is removed from the forged blank with flash.

(97) In the coining step, the forged crankshaft manufacturing apparatus shown in FIGS. 8A to 8D is used. First, the upper die and the lower die of the pair of dies 10 are separated from each other, and the first tools are placed in the retracting positions. Then, the forged blank with no flash is carried in and placed between the upper die and the lower die.

(98) Next, the first tools are moved to the contacting positions, and the first tools come into contact with the rough-journal-facing surfaces of the rough arms of the forged blank. In this state, the upper die and the lower die are moved toward each other. More specifically, the upper die is moved to the bottom dead point, and the forged blank is slightly reduced by the pair of dies 10. Accordingly, coining is applied to the forged blank, and the forged blank is corrected to have the size and the shape of the finished product.

(99) In the forged crankshaft manufacturing apparatus according to the present embodiment, during the coining, the first excess portions are deformed so that each of the rough arms obtains thickened side portions in the region near the adjacent rough pin. The deformation of the first excess portions is carried out, for example, by crashing of the first excess portions by use of the dies 10. Alternatively, the first excess portions are bent toward the rough journals along the impressions of the dies 10. In this way, the first excess portions are deformed into shapes along the impressions of the dies 10 and caused to bulge toward the journals.

(100) After completion of the coining and the deformation of the first excess portions, the upper die and the lower die are separated from each other. More specifically, the upper die is moved to the top dead point, and the first tools are moved to the retracting positions. Thereafter, the processed forged blank is taken out. In this way, a crankshaft as shown in FIGS. 4A to 4D can be obtained.

(101) When the forged crankshaft manufacturing apparatus further includes second tools to come into contact with the rough-pin facing surfaces of rough arms with no rough weights, a forged blank with flash further including second excess portions as shown in FIG. 7A is formed in the die forging step. In the coining step, the second tools are moved to the contacting positions and the retracting positions in the same manner as the first tools. In this way, a crankshaft including arms as shown in FIG. 6A can be obtained.

(102) A case where the manufacturing apparatus according to the present embodiment is used in the coining step has been described. However, the manufacturing apparatus according to the present embodiment can be used in any other step than the coining step. For example, when the manufacturing method includes an additional processing step before or after the coining step, the manufacturing apparatus according to the present embodiment may be used in the additional processing step. When the coining step is not needed, another processing step shall be added after the trimming step, and the manufacturing apparatus according to the present embodiment shall be used in the processing step. In sum, the manufacturing apparatus according to the present embodiment is used to process excess portions of a forged blank from which flash has been removed.

INDUSTRIAL APPLICABILITY

(103) The present invention is efficiently utilized for manufacture of a forged crankshaft to be mounted in a reciprocating engine.

LIST OF REFERENCE SYMBOLS

(104) 1: forged crankshaft

(105) J, J1 to J5: journal

(106) P, P1 to P4: pin

(107) Fr: front

(108) FI: flange

(109) A, A1 to A8: crank arm

(110) W, W1 to W8: counterweight

(111) J: rough journal

(112) P: rough pin

(113) A: rough crank arm

(114) W: rough counterweight

(115) Aa, Ab: side portion of an arm in a region near a pin

(116) Aa, Ab: side portion of a rough arm in a region near a rough pin

(117) Aaa, Aba: first excess portion

(118) Ac, Ad: side portion of an arm in a region near a journal

(119) Ac, Ad: side portion of a rough arm in a region near a rough journal

(120) Aca, Ada: second excess portion

(121) As: inner area of a journal-facing surface of an arm, inside of side portions

(122) At: inner area of a pin-facing surface of an arm, inside of side portions

(123) 10: pair of dies

(124) 10a: impression

(125) 10b: open space for tool

(126) 10c: open space for jig

(127) 10d: recess

(128) 20: first tool

(129) 20a: front face (impression)

(130) 20b: upper surface

(131) 20c: lower surface

(132) 20d: projection

(133) 20e: side surface of projection (first guide)

(134) 30: first jig

(135) 30a: projection

(136) 40: second tool

(137) 40a: front face (impression)

(138) 40b: upper surface

(139) 40d: projection

(140) 40e: side surface of projection (second guide)

(141) 50: second jig

(142) 50a: projection

(143) 91: forged blank with no flash

(144) 92: tool having side surfaces to serve as guides

(145) 92a: front face (impression)

(146) 92b: side surface (guide)

(147) 92c: recessed portion

(148) 92d: groove

(149) 93: jig

(150) 93a: projection