JP2009197979A - Crankshaft and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crankshaft and its manufacturing method, easy in manufacture, without deteriorating forging performance, by reducing weight. <P>SOLUTION: This crankshaft 1 includes a counterweight 20 in a part opposed to a crank pin 15 of a web 14, and includes a crankshaft body 11 integrally molded with a part except for the counterweight 20, the counterweight 20 formed separately from the crankshaft body 11, and a connecting member 30 for connecting the crankshaft body 11 and the counterweight 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a crankshaft and a manufacturing method thereof.

  A crankshaft is a component for an internal combustion engine such as an automobile engine that converts a reciprocating motion of a piston in a reciprocating engine into a rotational motion. The crankshaft is provided with a crank portion corresponding to the number of cylinders of the engine. The crank portion is provided with a counterweight at a portion of each web facing the crankpin in order to reduce rotational error. In such a crankshaft, it is necessary to set a large counterweight in order to establish a weight balance.

  However, in crankshafts formed by hot forging, setting a large counterweight not only increases the weight of the crankshaft, but also reduces the life of the press die and increases the defective rate of the product. There is a risk that it will be worse.

On the other hand, Patent Document 1 below proposes a technique for inserting a substance having a large specific gravity into a part of the counterweight.
Japanese Utility Model Publication No. 61-146619

  However, even if a material having a large specific gravity is inserted into a part of the counterweight as in the technique described in Patent Document 1, it is still necessary to forge the counterweight with a material. Therefore, the problem that there is a possibility that not only an increase in weight but also a deterioration in forgeability may be caused by making the counterweight from a raw material.

  In addition, in the crankshaft of a V-type engine, a twist process that partially twists around the axis is necessary due to the forging draft gradient. That is, in the crankshaft of the V-type engine, the counterweight has a portion with a reverse draft (draft slope), so that a separate press for twisting is required, and the manufacturing becomes complicated.

  Accordingly, the present invention has been made in view of the above circumstances, and provides a crankshaft that can be reduced in weight and can be easily manufactured without degrading forgeability, and a method for manufacturing the crankshaft. With the goal.

  The object of the present invention is achieved by the following means.

  The present invention provides a crankshaft having a counterweight at a portion of the web that supports the crankpin that faces the crankpin, the crankshaft body in which a portion other than the counterweight is integrally formed, and the crankshaft body separately from the crankshaft body A crankshaft comprising: a counterweight formed of a body; and a connecting member that connects the crankshaft body and the counterweight.

The present invention also relates to a method of manufacturing a crankshaft having a counterweight at a portion of the web that supports the crankpin facing the crankpin, the step of integrally forming a crankshaft body other than the counterweight, A crankshaft manufacturing method comprising: a step of forming a counterweight separately from a shaft main body; and a step of connecting the crankshaft main body and the counterweight with a connecting member.

  According to the crankshaft and the manufacturing method thereof according to the present invention, the crankshaft main body other than the counterweight and the counterweight are separately formed and are connected by the connecting member. As a result, the weight can be reduced and the forgeability is not deteriorated, and the production is easy. In addition, there is an advantage that a twisting process is not required even for a crankshaft of a V-type engine.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing a first embodiment of a crankshaft according to the present invention.

  First, with reference to FIG. 1, the structure of the crankshaft 1 of this embodiment is demonstrated.

  The main body 11 of the crankshaft 1 includes a journal 12 as a shaft portion having a circular cross section. This journal 12 is rotatably supported by a reciprocating engine via a bearing (not shown). The journal 12 is provided with a number of crank portions 13 corresponding to the number of cylinders of the engine. Each crank portion 13 includes a pair of webs 14 and 14 and a crank pin 15 sandwiched between the webs 14 and 14. The crank pin 15 is slidably connected to a connecting rod (connecting rod) of a piston (not shown) and has a circular cross section.

  In summary, the crankshaft 1 of this embodiment is fastened to the crankshaft body 11, the counterweight 20 formed separately from the crankshaft body 11, and the crankshaft body 11 and the counterweight 20. And a connecting member 30 to be connected.

  The crankshaft body 11 is formed by, for example, forging or casting, and is adjusted to a predetermined shape by a post-process mainly including a grinding process after the heat treatment.

  A counterweight 20 formed separately from the crankshaft main body 11 is provided at a portion of each web 14 facing the crankpin 15 (on the opposite side) to reduce rotational error.

  The counterweight 20 of the present embodiment is a member that reduces the rotation error by imparting a balance weight to the crankshaft 1, and is formed of, for example, a fan-shaped weight material having a thickness. The weight material is selected from, for example, a metal material having a high specific gravity. The counterweight 20 is connected to a portion of the web 14 of the crankshaft body 10 facing the crankpin 15 by the connecting member 30.

In the present embodiment, the connecting member 30 is a bolt. The counterweight 20 is attached to the outer peripheral portion of the web 14 via a connecting member 30 by screw fastening. For example, the counterweight 20 can be fixedly attached to the connecting member 30 by lightly press-fitting the head (or shaft) of the bolt into the mounting groove (or mounting hole) of the counterweight 20 (FIG. 6). (See (A)). Here, the counterweight 20 is held in a state of being separated from the web 14 by the connecting member 30.

  Next, a method for manufacturing the crankshaft according to the present embodiment will be described together with the operation of the crankshaft 1 configured as described above.

  In the crankshaft manufacturing method according to the present embodiment, first, the crankshaft body 11 having a shape without the counterweight 20 is formed on the web 14. The crankshaft body 11 is usually formed by casting using ductile cast iron or the like, or hot forging using lead-free non-tempered or non-tempered steel. Then, after rough molding of the crankshaft body 11, after soft nitriding treatment or high-frequency heat treatment, a finished product shape is prepared through a post-process mainly including grinding.

  A counterweight 20 is formed separately from the crankshaft body 11. As described above, the counterweight 20 is formed into a fan shape having a thickness, and is formed of, for example, a weight material such as a metal material having a high specific gravity.

  Next, the crankshaft body 11 and the counterweight 20 are connected by a connecting member 30. That is, the counterweight 20 is attached to the outer peripheral portion of the web 14 via the connecting member 30 by screw fastening.

  As described above, according to the crankshaft 1 and the manufacturing method thereof of the present embodiment, the crankshaft body 11 having no counterweight portion and the counterweight 20 are formed separately, and these are connecting members that are bolts. Therefore, the crankshaft 1 can be easily manufactured without degrading forgeability, while improving the design freedom of the counterweight and reducing the weight. In addition, there is an advantage that a twisting process is not required even for a crankshaft of a V-type engine.

  Further, the counterweight 20 is formed in a fan shape, and the counterweight 20 is attached to the crankshaft main body 11 via the connecting member. Therefore, it is possible to balance efficiently and further reduce the weight.

  Further, since the connecting member 30 is a bolt, the connection between the crankshaft body 11 and the counterweight 16 is easy.

(Second Embodiment)
FIG. 2 is a perspective view showing a main part of the crankshaft according to the second embodiment. Hereinafter, the points different from the first embodiment will be mainly described. In addition, the same code | symbol is attached | subjected to the member which is common in 1st Embodiment, and the description is abbreviate | omitted suitably.

  Referring to FIG. 2, a counter formed separately from the crankshaft body 11 is provided at a portion of the crankshaft 101 a facing the crankpin 15 of each web 14 (on the opposite side) in order to reduce rotational error. A weight 20 is provided. In the present embodiment, the web 14 has a shape obtained by rounding a substantially pentagonal corner.

  The counterweight 20 of the present embodiment is connected to a portion of the web 14 of the crankshaft body 11 facing the crankpin 15 by a connecting member 30.

The connecting member 30 includes a stay 40 that holds the counterweight 20, and a fastening member 50 that fixes the stay 40 to the outer peripheral portion of the web 14. The stay 40 is a member that holds the counterweight 20, and is formed of a material having a specific gravity smaller than that of the counterweight 20, such as hard plastic. In the present embodiment, the stay 40 is formed by bifurcating the holding portions 42 and 43 in a U-shape from the base-end-side coupling portion 41 attached to the web 14. The holding portions 42 and 43 of the stay 40 are plate-like pieces, and the holding portions 42 and 43 hold the fan-shaped counterweight 20 so as to be sandwiched therebetween. Examples of a method for fixing the holding portions 42 and 43 and the counterweight 20 include press-fitting by elastic deformation of the stay 40 and bolting.

  Moreover, as the said fastening member 50, the volt | bolt 51 is mentioned, for example. In the present embodiment, the outer peripheral end of the web 14 is formed in a straight surface, and attachment portions 44 and 45 formed to protrude from the coupling portion 41 of the stay 40 to the left and right sides are brought into contact with the straight surface. The bolts 51 are inserted into the attachment portions 44 and 45 and fastened to the web 14 for attachment.

  Next, a method for manufacturing the crankshaft according to the present embodiment will be described together with the operation of the crankshaft 1 configured as described above.

  In the crankshaft manufacturing method according to the present embodiment, first, the crankshaft body 11 having a shape without the counterweight 20 is formed on the web 14. A counterweight 20 is formed separately from the crankshaft body 11. Next, the crankshaft body 11 and the counterweight 20 are connected by a connecting member 30. That is, first, the fan-shaped counterweight 20 is fixed and held so as to be sandwiched between the holding portions 42 and 43 of the stay 40 branched into two branches. Then, the mounting portions 44 and 45 of the stay 40 are brought into contact with the straight surface at the outer peripheral end of the web 14, and the bolts 51 are inserted through the mounting portions 44 and 45 to be fastened and attached to the web 14.

  As described above, according to the present embodiment, the following operational effects can be obtained in addition to the effects of the first embodiment.

  That is, since the connecting member 30 has the stay 40 that is attached so as to sandwich the counterweight 20 from both sides in the width direction, it is necessary to make a mounting hole in a portion (counterweight central portion) that has a large contribution to the balance ratio. No further weight reduction is possible.

  Moreover, since the connection member 30 is formed of a material having a specific gravity smaller than that of the counterweight 20, the weight of the portion having a small contribution to the balance ratio is reduced, and the weight is further reduced by setting the center of gravity position to the outer peripheral side. Is possible.

(Third embodiment)
FIG. 3 is a perspective view showing a main part of the crankshaft according to the third embodiment. Hereinafter, a description will be given centering on differences from the second embodiment. In addition, the same code | symbol is attached | subjected to the member which is common in 2nd Embodiment, and the description is abbreviate | omitted suitably.

  With reference to FIG. 3, in the crankshaft 101 b of the third embodiment, the curved portion 141 side in the plate-like stay 140 having a substantially U shape or a substantially Ω shape is hooked and held on the outer peripheral portion of the web 14. ing. The fan-shaped counterweight 20 is held so that the holding portions 142 and 143 on the distal end side of the stay 140 protrude from the web 14 and are sandwiched by the holding portions 142 and 143. Further, jaw portions 144 and 145 having a small curvature are present on the base end sides of the holding portions 142 and 143 of the stay 140, and the web 14 is firmly held. Here, the stay 140 constitutes the connecting member 30.

  The stay 140 can be further reduced in weight by being formed of a material having a small specific gravity such as hard plastic. The counterweight 20 is formed of a weight material such as a metal material having a large specific gravity, for example. For preventing the counterweight 20 from coming off, for example, press-fitting by elastic deformation of the stay 140, bolting, or the like can be mentioned.

  In this embodiment, the cross-sectional shape of the web 14 has an egg shape. The counterweight 20 is narrower than the second embodiment and is formed in a fan shape having a thickness.

  FIG. 4 is a perspective view showing a main part of a modification of the third embodiment.

  With reference to FIG. 4 (A), in this embodiment, the prevention portions 146, 147 for the counterweight 20 are formed at the tip portions of the holding portions 142, 143 of the stay 140, respectively. These drop prevention portions 146 and 147 are formed by bending the respective tip portions of the holding portions 142 and 143 so as to face each other, and are held flush with the arc surface of the counterweight 20. . That is, stepped portions 21 and 22 are formed at both ends of the arc surface of the counterweight 20, and the above-described removal preventing portions 146 and 147 are attached to the respective stepped portions 21 and 22 to hold the outer peripheral portion of the counterweight 20. Yes.

  With reference to FIG. 4B, in this embodiment, the slip-off preventing portions 148 and 149 formed at the tip portions of the holding portions 142 and 143 of the stay 140 are further L-shaped toward the inside of the counterweight 20. It is bent and formed. Therefore, L-shaped hooks 23 and 24 are also formed at both ends of the arc surface of the counterweight 20. That is, the hook portions 23 and 242 are formed at both ends of the arc surface of the counterweight 20, and the L-shaped drop prevention portions 148 and 149 are attached to the hook portions 23 and 24 to securely hold the counterweight 20. is doing.

  Note that the fastening member 50 is not attached to the crankshaft 101 of the third embodiment. Therefore, the weight of the portion other than the counterweight 20 can be reduced, but the fastening member 50 may be used in combination.

The crankshaft 101b of the present embodiment has basically the same operational effects as the crankshaft 101a of the second embodiment. In particular, in the third embodiment, the counterweight 20 is securely held and The counterweight 20 can be prevented from coming off. Further, it is possible to reduce the processing of the mounting hole and the use of the fixing member for mounting.
(Fourth embodiment)
FIG. 5 is a perspective view showing a main part of the crankshaft according to the fourth embodiment. Hereinafter, the points different from the first embodiment will be mainly described. In addition, the same code | symbol is attached | subjected to the member which is common in 1st Embodiment, and the description is abbreviate | omitted suitably.

  With reference to FIG. 5, in the crankshaft 201 of 4th Embodiment, the shape of the said web 14 is exhibiting the shape which combined the egg shape and the fan shape. The weight mounting surface of the web 14 is formed as an arc surface (curvature surface).

  Further, the counterweight 220 is formed in a thick fan shape or an arc shape having a thickness and a height. A mounting hole 221 for fixing a bolt 51 as a fixing member 50 is formed at the bottom of the counterweight 220. The attachment hole 221 penetrates in the height direction of the counterweight 220 (the direction perpendicular to the axis of the crankshaft 201), and is formed as an elongated hole along the longitudinal direction. Bolts 51 are inserted into the mounting holes 221 at two positions on the left and right sides of the counterweight 220 in the width direction and fastened to the web 14.

  Here, the bolt 51 as the fastening member 50 constitutes the connection member 30. The counterweight 220 is attached to the outer peripheral portion of the web 14 via the connecting member 30 by screw fastening. Here, it is more preferable that the counterweight 220 is held in a state of being separated from the web 14 by the connecting member 30 in order to further reduce the weight.

  As shown in FIG. 5B, if the position of the counterweight 220 is shifted along the mounting hole 221 that is a long hole by loosening the bolt 51, the mounting angle of the counterweight 220 can be changed. A fine balance angle adjustment can be performed.

  FIG. 6 is a schematic view showing a counterweight attachment method. As the connecting member 30, a fastening member 50 (bolt 51) is used.

  With reference to FIG. 6A, the counterweight 220 is lightly press-fitted with the head of the bolt 51 into the mounting groove 222 of the counterweight 220 or the shaft of the bolt 51 into the mounting hole 221. Can be fixed to the connecting member 30.

  Alternatively, referring to FIG. 6B, the bolt 51 is inserted by light press-fitting or clearance fitting so as to pass through the mounting hole 221 of the counterweight 220, and a nut 52 is screwed onto the bolt 51 and attached. Also good.

  FIG. 7 is a schematic view showing a method of attaching to the web.

  With reference to FIG. 7A, the connecting member 30 includes a fastening member 50 (bolt 51). In this case, the inner surface of the counterweight 220 is opposed to the outer peripheral surface of the web 14, the two bolts 51 on the left and right sides are inserted into the mounting holes 221 of the counterweight 220, and fastened to the web 14. Also good.

  The present invention is not limited to this, and as shown in FIG. 7B, the connecting member 30 may be constituted by a fastening member 50 including, for example, a bolt 51 and a nut 52. In this case, an insertion hole 18 is formed in the web 14. Then, the bolt 51 is inserted into the insertion hole 18, and the counterweight 220 is attached by fastening the nut 52 to the bolt tip protruding from the web 14.

  Further, referring to FIG. 7C, the connecting member 30 (bolt 51) may be attached to the web 14 by lightly press-fitting the bolt 51 into the web 14.

  FIG. 8 is a perspective view showing a main part of a modification of the fourth embodiment.

  With reference to FIG. 8A, in this aspect, a washer 231 is interposed as a weight adjusting member on the seat portion of the bolt 51 inserted and fixed in the mounting hole 221 of the counterweight 220. Since the washer 231 is interposed under one of the bolts 51, the balance can be adjusted by shifting the position of the center of gravity from the center of gravity of the weight. That is, a balance adjusting member can be attached to an attachment portion of the counterweight 220 to the bolt 51 that is a connecting member. In addition, since the attachment hole 221 is a long hole, the center of gravity can be further shifted by adjusting the attachment angle as described above.

  With reference to FIG. 8 (B), in this aspect, a weight spacer 232 is interposed under one bolt 51 in addition to a washer 231. Depending on the weight and number of the washers 231 and the weight spacers 232, balance adjustment with a high degree of freedom can be performed.

  Further, as shown in FIGS. 8A and 8B, the counterweights 220 of the two are different from each other with the center of gravity position shifted. That is, in the present embodiment, preferably, the counterweight 220 is configured to be exchangeable with another counterweight whose center of gravity is shifted.

The crankshaft 201 of the present embodiment has basically the same effects as the crankshaft 1 of the first embodiment, but in particular, in the third embodiment, the balance of the crankshaft 201 can be finely adjusted. In addition, the present invention has a specific effect that the conventional machining of the counterweight 220 for balance adjustment becomes unnecessary.
(Fifth embodiment)
FIG. 9 is a perspective view showing a main part of the crankshaft according to the fifth embodiment.

  Referring to FIG. 9, in the crankshaft 301 of the fifth embodiment, the counterweight 320 is formed of materials having different specific gravity. That is, the counterweight 320 having a substantially semicircular shape is formed using two kinds of metals 321 and 322 having different specific gravities. In this embodiment, a metal 321 having a larger specific gravity is disposed in the vicinity of the outer periphery of the substantially semicircular counterweight 320.

  The counterweight 320 is coupled to the web 14 via a connecting member 330. The connecting member 330 of the present embodiment has a concave fitting portion 331, and the convex portion 19 of the web 14 is press-fitted or fitted into the concave fitting portion 331.

  FIG. 10 is a perspective view showing a main part of another aspect of the fifth embodiment.

  Referring to FIG. 10, in this aspect, counterweight 320 is formed by overlapping materials having different specific gravity in the thickness direction. That is, the counterweight 320 having a substantially semicircular shape is formed by superimposing two kinds of metals 321 and 322 having different specific gravities.

  Further, the counterweight 320 is connected by using, as a connecting member 330, a convex portion 331 of two kinds of metals 321 and 322 having different specific gravities, and sandwiching the convex portion 19 of the web 14 with the convex portion 331.

  The crankshaft 301 of the present embodiment has basically the same function and effect as the crankshaft 1 of the first embodiment. In particular, in the fourth embodiment, the counterweight 320 is formed by combining materials having different specific gravities. Therefore, a specific effect that balance adjustment with a higher degree of freedom can be performed is exhibited.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims.

  The crankshaft and the manufacturing method thereof according to the present invention can be widely applied not only to a crankshaft of an automobile engine but also to a crankshaft for an internal combustion engine.

It is a schematic structure figure showing a 1st embodiment of a crankshaft concerning the present invention. It is a perspective view which shows the principal part in the crankshaft of 2nd Embodiment. It is a perspective view which shows the principal part in the crankshaft of 3rd Embodiment. It is a perspective view which shows the principal part of the deformation | transformation aspect of 3rd Embodiment. It is a perspective view which shows the principal part in the crankshaft of 4th Embodiment. It is the schematic which shows the attachment method of a counterweight. It is the schematic which shows the attachment method to a web. It is a perspective view which shows the principal part of the deformation | transformation aspect of 4th Embodiment. It is a perspective view which shows the principal part in the crankshaft of 5th Embodiment. It is a perspective view which shows the principal part of the other aspect of 5th Embodiment.

Explanation of symbols

1, 101a, 101b, 201, 301 crankshaft,
11 Crankshaft body,
20, 220, 320 counterweight,
30 connecting member,
40 stays,
50 Fastening member.

Claims (11)

A crankshaft provided with a counterweight at a portion facing the crankpin of the web supporting the crankpin,
A crankshaft body integrally formed with a portion other than the counterweight;
A counterweight formed separately from the crankshaft body;
A connecting member for connecting the crankshaft body and the counterweight;
A crankshaft characterized by comprising:   2. The crankshaft according to claim 1, wherein the counterweight is formed in a fan shape, and the counterweight is attached to the crankshaft main body through the connecting member.   The crankshaft according to claim 1 or 2, wherein the connecting member is formed of a material having a specific gravity smaller than that of the counterweight.   The crankshaft according to any one of claims 1 to 3, wherein the connecting member is a bolt.   The crankshaft according to any one of claims 1 to 3, wherein the connecting member has a stay attached so as to sandwich the counterweight from both sides in the width direction.   The crankshaft according to claim 5, wherein a counterweight removal prevention portion is formed at a tip portion of the stay.   The crankshaft according to any one of claims 1 to 4, wherein an angle of attachment of the counterweight to the connecting member is adjustable.   The crankshaft according to any one of claims 1 to 4, wherein a balance adjusting member is attached to an attachment portion of the counterweight to the connecting member.   The crankshaft according to any one of claims 1 to 4, wherein the counterweight is replaceable with another counterweight whose center of gravity is shifted.   The crankshaft according to any one of claims 1 to 9, wherein the counterweight is formed by combining substances having different specific gravities. A crankshaft manufacturing method comprising a counterweight at a portion of the web that supports the crankpin that faces the crankpin,
Integrally forming a crankshaft body other than the counterweight;
Forming a counterweight separately from the crankshaft body;
Connecting the crankshaft body and the counterweight with a connecting member;
A method for manufacturing a crankshaft, comprising:

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