JP2011190489A - Method for manufacturing crankshaft in internal combustion engine, and crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a crankshaft in an internal combustion engine capable of reducing any deformation, shortening the quenching time, and reducing the cost, and to provide the crankshaft. <P>SOLUTION: In the manufacturing method of a crankshaft 1, in which a journal part 2 and a crank pin 3 are alternately connected to each other via a crank arm 4 having a balance weight 5, a circumferential surface 20 of the journal part 2 and a circumferential surface 30 of the crank pin 3 are subjected to the high-frequency quenching, and an R-part 6 formed at a boundary part between the circumferential surface 20 of the journal part 2 and the crank arm 4, and an R-part 7 formed at a boundary part between the circumferential surface 30 of the crank pin 3 and the crank arm 4 are respectively subjected to the laser beam quenching. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a crankshaft manufacturing method and a crankshaft in an internal combustion engine.

  In an internal combustion engine (hereinafter referred to as an engine) such as a diesel engine, a crankshaft 1 having a structure as shown in FIG. 4 is used. Note that the crankshaft 1 shown in FIG. 4 is a four-cylinder engine. In order to increase the wear resistance of the sliding portion, induction hardening is performed on the journal portion 2 and the crankpin 3 of the crankshaft 1 as shown in FIG. 4 (see, for example, Patent Documents 1 and 2). Hardened layers 21 and 31 are formed at places where induction hardening is performed (places indicated by bold lines), respectively. Further, in order to give the crankshaft 1 strength, a material subjected to induction hardening (called R induction hardening) up to the R portions 6 and 7 having the highest stress as shown in FIG. 5 is used. Reference numerals 60a and 70a denote hardened layers subjected to induction hardening.

JP 2005-180571 A JP 2005-195067 A

  By the way, in the crankshaft 1 shown in FIG.4 and FIG.5, since induction hardening is performed to R part 6 and 7, the deformation | transformation (bending) at the time of induction hardening is intense. Although it is forcibly re-bent with a press or the like after induction hardening, those with large deformation are not re-bent and partitioned, and are discarded. In other words, the yield is bad.

  If laser hardening is performed instead of induction hardening, deformation (bending) is eliminated, but this time the hardening time becomes very long, resulting in excessive capital investment and high costs.

  The present invention has been made in view of such points, and an object of the present invention is to provide a crankshaft manufacturing method and a crankshaft in an internal combustion engine that can be reduced in deformation, reduced in quenching time, and reduced in cost. It is in.

  In order to solve the above problems, a crankshaft manufacturing method in an internal combustion engine according to the present invention is the crankshaft manufacturing method in which journal portions and crankpins are alternately connected via a crank arm having a balance weight. The peripheral surface of the portion and the peripheral surface of the crank pin are induction hardened, and the R portion formed at the boundary point between the peripheral surface of the journal portion and the crank arm and the crank arm of the peripheral surface of the crank pin Each of the R portions formed at the boundary points is subjected to laser hardening.

  According to the above method, since the whole is not laser-quenched but only the R portion where deformation is increased, the treatment time is short and there is no need to increase the number of laser-quenching apparatuses.

  The laser applied to each of an R portion formed at a boundary point between the peripheral surface of the journal portion and the crank arm and an R portion formed at a boundary point between the peripheral surface of the crank pin and the crank arm. It is preferable to make the quenching depth of quenching shallower than the quenching depth of induction quenching applied to the peripheral surface of the journal part and the peripheral surface of the crankpin.

  According to the above method, the R portion where the deformation becomes large is quenched by making it shallower than the quenching depth applied to the peripheral surface of the journal portion and the peripheral surface of the crankpin. There is little deformation in the part.

  The crankshaft in the internal combustion engine of the present invention is a crankshaft in which journal portions and crankpins are alternately connected via a crank arm having a balance weight, and a high frequency is applied to the peripheral surface of the journal portion and the peripheral surface of the crankpin. High frequency is applied to each of the R portion formed at the boundary point between the peripheral surface of the journal portion and the crank arm and the R portion formed at the boundary point between the crank surface and the crank arm. It is characterized by being subjected to laser quenching which is shallower than the quenching depth of quenching.

  According to the crankshaft manufacturing method and the crankshaft in the internal combustion engine of the present invention, the deformation is small, the quenching time is short, and the cost can be reduced.

FIG. 1 is an external view showing a crankshaft according to an embodiment of the present invention. FIG. 2 is a schematic view showing a state in which laser hardening is applied to an R portion which is a part of the crankshaft of FIG. FIG. 3 is a schematic view showing a quenching depth in a part of the crankshaft of FIG. FIG. 4 is an external view showing a hardened portion when induction hardening is performed on a general crankshaft. FIG. 5 is a diagram showing a quenching depth when a general crankshaft is induction-hardened.

  A preferred embodiment of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected and demonstrated about the part similar to a prior art example.

  As shown in FIG. 1, the crankshaft 1 has journal portions 2 and crankpins 3 alternately connected via a crank arm 4 having a balance weight 5, and the journal portion 2 is a main bearing (not shown). The crankpin 3 is supported by a connecting rod bearing (not shown).

  The crankshaft 1 of this example is applied to a four-cylinder engine, and includes journal portions 2 and crank pins 3 that are alternately formed, and the journal portion 2 rotates on a cylinder block (not shown). The crank pin 3 is rotatably supported and is rotatably connected to one end of a connecting rod (not shown). The journal portion 2 and the crankpin 3 are connected via a crank arm 4, and a balance weight 5 extends from the crank arm 4 on the opposite side of the crankpin 3.

  As shown in FIG. 2, at both ends of the journal portion 2, corners (roots) between the peripheral surface 20 of the journal portion 2 and one side of the crank arm 4, that is, the crank arm 4 of the peripheral surface 20 of the journal portion 2. The R portion 6 is formed at the boundary point. Further, an R portion 7 is formed at a corner (base) between the peripheral surface 30 of the crankpin 3 and one side of the crank arm 4, that is, a boundary point between the peripheral surface 30 of the crankpin 3 and the crank arm 4.

  The crankshaft 1 in the engine converts linear thrust obtained by exploding fuel in a cylinder (not shown) into rotational motion of the crankpin 3 by a connecting rod (not shown). When this linear motion is converted into rotational motion, a strong bending load is applied to the crankshaft 1, particularly the crankpin 3. The maximum stress due to the bending load acts on the R portions 6 and 7 at the base of the crankpin 3 and the journal portion 2. The journal portion 2 and the crankpin 3 of the crankshaft 1 must withstand wear due to rotational movement.

  Since the crankshaft 1 rotates at a high speed, the oil in the radial direction of the journal portion 2 is circulated on the crankshaft 1 so that the oil circulates in the journal portion 2 and the crankpin 3 in order to prevent seizure during long-time operation. A hole 11 is formed, and an oil hole 12 is formed obliquely from the oil hole 11 toward the crankpin 3 to lubricate the surfaces of the journal portion 2 and the crankpin 3 with oil to reduce the coefficient of friction and to occur. Heat is released out of the crankshaft 1.

  In such a crankshaft 1, the crankpin 3 and the journal part 2 are integrally formed by forging a carbon steel for mechanical structure (for example, S53C, S48C, etc.). In order to harden the surface, induction hardening is performed using an induction hardening apparatus (not shown).

  In the induction hardening apparatus, for example, a heating coil is connected to an AC power source, an eddy current is generated in a metal by a magnetic field generated by passing an AC current having a high frequency through the heating coil, and heat treatment is performed by Joule heat. In the induction hardening applied to the peripheral surface 20 of the journal portion 2 of the crankshaft 1 and the peripheral surface 30 of the crankpin 3, heating coils are set on these peripheral surfaces 20, 30, and the crankshaft 1 is rotated around its central axis X. While rotating, an alternating current is passed through the heating coil to generate eddy currents on the peripheral surfaces 20 and 30, and this is performed by Joule heat.

  FIG. 3 shows the quenched area. A hardened layer 21 is formed on the peripheral surface 20 of the journal portion 2, and a hardened layer 31 is formed on the peripheral surface 30 of the crankpin 3. For example, if the diameter D1 of the journal part 2 is 60 to 75 mm, the depth (quenching depth) B1 of the hardened layer 21 is about 1 to 1.5 mm, and if the diameter D2 of the crankpin 3 is 60 to 75 mm, The depth (quenching depth) B2 of the hardened layer 31 is about 1 to 1.5 mm.

  Next, laser hardening is applied to the R portion 6 of the journal portion 2 and the R portion 7 of the crank pin 3.

  As shown in FIG. 2, the laser beam 8 a is irradiated from the laser hardening device 8 to the R portion 6 of the journal portion 2. Further, in order to make the laser beam 8 a correspond to the R portion 6, the laser hardening device 8 can change the irradiation angle by rotating an irradiation unit (not shown). As a result, a hardened layer 60 is obtained in the R portion 6 by quenching as shown in FIG. The hardening depth A1 of the hardened layer 60 is about 0.1 to 0.5 mm.

  Induction hardening is inevitably deep as 1 to 1.5 mm as described above, but laser hardening can easily reduce the hardening depth compared to induction hardening. The surface hardness is the same as in the case of induction hardening, but the deformation of the R portion 6 is reduced by reducing the amount of heat applied and reducing the quenching depth A1.

  Next, the laser hardening device 8 or the crankshaft 1 is moved so that the laser hardening device 8 is directed toward the R portion 7 of the crankpin 3, and similarly, the R portion 7 is irradiated with laser light 8 a from the laser hardening device 8. As a result, a hardened layer 70 is obtained in the R portion 7 by quenching as shown in FIG. The hardening depth A2 of the hardened layer 70 is about 0.1 to 0.5 mm.

  In order to change the quenching depths A1 and A2 of the hardened layers 60 and 70 by changing the amount of heat applied to the R portions 6 and 7, the amount of energy of the laser beam 8a to be applied can be increased or decreased. The irradiation output, irradiation time, or processing speed (rotation speed) of 8a is appropriately changed. Further, since the hardened portions for the R portions 6 and 7 have a small area, even if laser hardening is performed, an increase in processing time can be allowed to a low level.

  In the first place, there is a difference in deformation between induction hardening and laser hardening for the following reasons. That is, induction hardening has a wide and deep range to be heated. Therefore, it expands in a wide range. If it occurs in the R portion where the shape change is large, it cannot be uniformly expanded, resulting in a large deformation. On the other hand, laser quenching has a narrow and shallow range to be heated, so there are few parts to expand. Therefore, there is little deformation.

  As described above, according to the present invention, induction hardening is performed on the peripheral surface 20 of the journal portion 2 and the peripheral surface 30 of the crankpin 3 to form a hardened layer 21 having a quenching depth B1 and a hardened layer 31 having a quenching depth B2. In addition, by applying laser quenching to the R portions 6 and 7 having a large shape change, the quenching depth can be made shallower than the induction quenching and deformation of the R portions 6 and 7 can be reduced. Further, since the laser quenching is performed only for the R portions 6 and 7, the quenching time can be processed with a normal cycle time without excessively extending.

  As described above, according to the present invention, there is little deformation with respect to R induction hardening, the yield is improved, and the cost is reduced as a result. Moreover, since the whole is laser-quenched, only the R portion is used, so that the processing time is short. Therefore, excessive investment is not required and costs can be reduced.

DESCRIPTION OF SYMBOLS 1 Crankshaft 2 Journal part 3 Crankpin 4 Crank arm 5 Balance weight 6, 7 R part 8 Laser hardening apparatus 11,12 Oil hole 20,30 Peripheral surface 21,31,60,70 Hardened layer A1, A2, B1, B2 Quenching depth

Claims (3)

In a method for manufacturing a crankshaft in which journal portions and crankpins are alternately connected via a crank arm having a balance weight,
The peripheral surface of the journal portion and the peripheral surface of the crank pin are induction-hardened, and the R portion formed at the boundary point between the peripheral surface of the journal portion and the crank arm and the crank arm of the peripheral surface of the crank pin A method of manufacturing a crankshaft in an internal combustion engine, wherein each of the R portions formed at the boundary point is laser-quenched.   The laser hardening applied to each of an R portion formed at a boundary point between the peripheral surface of the journal portion and the crank arm and an R portion formed at a boundary point between the peripheral surface of the crank pin and the crank arm. 2. The method of manufacturing a crankshaft in an internal combustion engine according to claim 1, wherein a quenching depth of the internal combustion engine is made shallower than a quenching depth of induction hardening applied to a peripheral surface of the journal portion and a peripheral surface of the crankpin. In the crankshaft in which the journal portion and the crankpin are alternately connected via a crank arm having a balance weight,
Induction hardening is applied to the peripheral surface of the journal part and the peripheral surface of the crankpin,
From the quenching depth of induction hardening in each of the R portion formed at the boundary point with the crank arm on the peripheral surface of the journal portion and the R portion formed at the boundary point with the crank arm on the peripheral surface of the crank pin. A crankshaft in an internal combustion engine, which is subjected to shallow laser hardening.

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