JP2002226917A - Induction hardening method of crank shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction hardening method of a crank shaft capable of suppressing the bend of the crank shaft after a pin part is hardened. SOLUTION: The heating start time T1 of a plurality of pin parts (for example, two pin parts P2 and P3) located between two pin parts (for example, two pin parts P1 and P4) out of a plurality of pin parts (for example, four pin parts P1-P4) disposed along the X-direction of the axis of the multi-cylinder crank shaft (for example, four-cylinder crank shaft) with spaces therebetween is set to be earlier than the heating start time T2 of two pin parts (for example, pin parts P2 and P3) located on both end sides in the X-direction of the axis, and the heating finish time T3 of all pin parts P1-P4 is set to be the same, and distortion of the pin parts P1-P4 is reduced thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction hardening method for induction hardening (fillet R quenching) a pin portion of a crankshaft for a gasoline engine or a diesel engine.

[0002]

2. Description of the Related Art FIG. 4 shows a crankshaft 1 for a four-cylinder gasoline engine or a diesel engine. The crankshaft 1 is an integrally molded product formed by forging, and journals J ₁ , J ₂ , J ₃ , J ₄ , J ₄ arranged along the central axis X of the crank shaft 1.
₅ and counter weight sections CW ₁ , CW ₂ , CW ₃ , CW ₄ , CW ₅ , CW ₅ connected to these journal sections.
₆ , CW ₇ , CW ₈ and pin portions P ₁ , P ₂ , P ₃ , P ₄ erected respectively between a pair of counter weight portions disposed to face each other. Further, a pair of pin portions P on both sides in the direction along the central axis X
_1, the P ₄ has the same axis Y ₁ together, a pair of pin portions P _2, P ₃ of the intermediate portion has the same axial line Y ₂ together in the direction along the central axis X. Note that these axis lines Y ₁ and Y ₂ correspond to the journals J _{1 to} J ₅
Are offset by an equal distance from the center axis (corresponding to the center axis X of the crankshaft 1), and the phases of the pin portions P ₁ and P ₄ and the pin portions P ₂ and P ₃ are shifted from each other by 180 degrees.

[0003] Such a pin portion P of the crankshaft 1
Surface of ₁ to P ₄ (the cylindrical peripheral surface) during the quenching process,
The upper half portion of each pin portion P ₁ to P ₄ with a slight gap the semi-open saddle type high frequency induction heating coil was placed, high frequency to the rotation by the rotary drive about a central axis X of the crank shaft 1 High-frequency induction heating is performed while following the induction heating coil, and then rapid cooling is performed.

The shapes of the above-mentioned journal portions J _{1 to} J ₅ and pin portions P _{1 to} P ₄ are the same as those of the journal portion J ₅ and pin portion P _4.
This will be described as follows. That is,
Journal portion J _5, as shown in FIG. 5, the cylindrical portion 3a
And a fillet R (corner) 3b following the column 3a.
And a fillet portion (thrust portion) 3c that follows the fillet R portion 3b and is formed at right angles to the central axis X of the crankshaft 1. As shown in FIG. 5, the pin portion P ₄ is connected to the cylindrical portion 4 a, a fillet R portion (corner portion) 4 b following the cylindrical portion 4 a, the fillet R portion 4 b, and And a fillet portion (thrust portion) 4c formed at a right angle to the central axis X.

In FIG. 5, α and β are journal portions J.
Shows a hardened layer formed on the ₅ and the pin portion P _4. Note that the hardened layer alpha, a hardened layer obtained by cooling the cylindrical portion 3a of the journal portion J _5, the fillet R portion 3b and the fillet portion 3c after high frequency induction heating, respectively, hardened layer β is the pin portion P ₄ cylindrical portion 4a, the fillet R portion 4b and the fillet portion 4c
Is a quenched and hardened layer obtained by subjecting each to high-frequency induction heating and then cooling. Such a method of quenching is referred to as “fillet R quenching”.

[0006] normal quenching processing procedure in the conventional case where the pin portion P ₁ and the journal portion J ₁ through J ₅ of the crank shaft 1 to the fillet R quenching, first, four-cylinder crankshaft 1 which is an object to be hardened body All the pin portions P _{1 to} P ₄ located at a position １ ／ stroke away from the central axis X of the _first shaft are simultaneously quenched, and thereafter, the journal portions J _{1 to} J ₅ located at the axis of the crankshaft 1 are hardened. I am trying to enter. The reason is to perform the quenching of the journal portion J ₁ through J ₅ after quenching of the thus pin portion P ₁ to P ₄ are baked as compared with the case where the reverse this procedure after turning This is because the amount of bending of the crankshaft 1 as a whole is small.

In the four-cylinder crankshaft 1 as shown in FIG. 4, the pin portions P ₁ , P ₄ and the pin portions P ₂ , P ₃ have top portions thereof (portions farther from the center axis X). Since the directions of M are different from each other by 180 degrees, when the quenching hardened layer pattern of the top side portion and the bottom side portion (the portion near the center axis X) N of the pin portion is made uniform, the pin portion P ₂ , P ₃ and the pin portions P ₁ , P ₄ that are 180 degrees out of phase with each other, as separate groups, and the power supplied to the high-frequency induction heating coil for each pin portion is supplied to the crankshaft 1 (hence, the pin portion). It changes according to the rotation angle.

[0008]

When all the pins P _{1 to} P ₄ are simultaneously subjected to high-frequency induction heating for the same heating time, the shapes of the pins P _{1 to} P ₄ are complicated.
Crankshaft in after quenching of the pin portion P ₁ to P ₄ 1
Tend to be large. And the pin P
_When the journals J _{1 to} J ₅ coaxial to the center axis X of the crankshaft 1 are all quenched after the quenching of _{1 to} P _4, the amount of bending of the crankshaft 1 is equal to the reference value (TI
In fact, it far exceeds 0.3 mm in R). Table 1 below shows the journal J ₃ for each quenching process.
Shows the direction and amount of bending.

[0009]

[Table 1]

[0010] The crankshaft 1 having a large bend has a problem that it hinders polishing after quenching. In other words, since the completed dimensions after polishing are predetermined, there is a limit to the polishing allowance. Therefore, in the case of the crankshaft 1 having a large amount of bending, there is a problem that polishing remains and the product cannot be provided as a product. There is a risk of coming.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a high-frequency crankshaft capable of suppressing the amount of bending of the crankshaft after quenching of a pin portion. It is to provide a quenching method.

[0012]

First, each of the pin portions P _{1 to} P ₁
If the strain before and after quenching in Step ₄ is almost the same,
_2, P ₃ is the crankshaft than the pin portion P _1, P _{4 1}
Is located on the center side in the longitudinal direction (direction along the central axis X) of the crankshaft 1, which greatly affects the bending of the crankshaft 1. Therefore, the degree of influence on the bending is large (FIGS. 6A and 6B). b)). Specifically, 2
Normal depth (for example, about 2 mm) at the two pin portions P ₁ and P ₄
When only these are subjected to high-frequency induction heating to form a quenched hardened layer, the center axis Z of the center journal portion J _{3 is at} a distance from the center axis X of the crank shaft 1 as shown in FIG. displaced by L ₁ in the crankshaft 1 1
2 o'clock bending occurs. On the other hand, two pin portions P ₂ ,
If only these were high-frequency induction heating to form a hardened layer of the normal depth P ₃ is the axis Z crank link shaft 1 of the center of the journal portion J ₃ as shown in FIG. 6 (b) bending occurs from the central axis X of the distance L ₂ only displaced to the crankshaft 1 by 6 o'clock. Incidentally, the bending direction of the crank shaft 1 is the direction as viewed from the side of the journal portion J ₁ when the pin portion P ₁ was 12 o'clock direction.

The relationship between the above-mentioned distances L ₁ and L ₂ , that is, the mutual relationship between the deviations L ₁ and L ₂ of the axis Z of the journal J ₁ from the central axis X of the crankshaft 1 is determined by the pin P _2, since the P ₃ is in the center side of the pin portion P _1, P _4, the L ₁ <L _2. Therefore, all the pin portions P _{1 to} P
_{When the} high-frequency induction heating is performed for the same heating time and at the same time, the quenching conditions for the _two inner (center side) pin portions P ₂ and P ₃ greatly affect the degree of bending of the crankshaft 1. It is.

FIG. 7 shows the relationship between the hardened layer pattern formed on the pin portion P ₂ and the strain, and the relationship between the hardened layer pattern and the crankshaft 1.
This is to explain the effect on the bend. As shown in FIG. 7, in the pin portion P ₂ , the shape of a top portion M farther from the center axis X of the crankshaft 1 and a shape of a bottom portion N closer to the center axis X are greatly different. Top portion M, the height of the thrust surface S ₁ is relatively low,
Bottom portion N is relatively large height of the thrust surface S _2. Further, since a balance weight, which is a pendulum, may be formed in the bottom portion N, the mass (heat capacity) is relatively larger than that of the top portion M. Thus upon shape mass is quenched different pin portion P ₂ in the complex and each part is power supplied from the shape and the mass difference to the top portion M with respect to the bottom portion N (heating output)
Is reduced by about 10 to 30% and high-frequency induction heating is performed to obtain a uniform hardened and hardened layer.

However, due to differences in shape and mass, the depths of the hardened layers formed on the top side portion M and the bottom side portion N are not uniform, and the thrust size C after quenching is not sufficient.
(See FIG. 7) changes. With the change in the thrust dimension C, the pin portion P ₂ is moved in the A or B direction. And
The pin portion P ₂ from that position next to the journal portion J ₃ of the center, as a result of the journal portion J ₃ are hung to the movement of the pin portion P ₂ is moved, resulting in bending to the entire crankshaft 1. Incidentally, the bending in the quenching of the pin portion P ₃ is the pin portion P ₂ and the pin portion P ₃ is because it is located symmetrically journal portion J _3, a similar tendency.

Therefore, in the present invention, a semi-open saddle-type high-frequency induction heating coil is mounted on the cylindrical peripheral surface of the cylindrical portion of the pin portion of the multi-cylinder crankshaft, and the multi-cylinder crankshaft is moved with its central axis set. While rotating to the center and making the high-frequency induction heating coil follow the cylindrical peripheral surface of the cylindrical portion,
The cylindrical portion, the fillet R portion following the cylindrical portion, and the fillet portion following the fillet R portion are each subjected to high-frequency induction heating, and then the pin portion is cooled, thereby firing the surface of the pin portion. In the method of inserting, of the plurality of pin portions disposed at intervals along the center axis direction of the multi-cylinder crankshaft, two The heating start timing of the plurality of pin portions located in between is earlier than the heating start timing of the two pin portions located at both ends in the central axis direction, and the heating end timing of all the pin portions is set. At the same time, the distortion in the pin portion is reduced. Further, in the present invention, a semi-open saddle-type high-frequency induction heating coil is mounted on a cylindrical peripheral surface of a cylindrical portion of a pin portion of a four-cylinder crankshaft, and the four-cylinder crankshaft is rotated about its central axis. At least the high-frequency induction heating coil follows the cylindrical peripheral surface of the cylindrical portion, and the cylindrical portion, the fillet R portion following the cylindrical portion, and the fillet portion following the fillet R portion are each subjected to high-frequency induction heating. Then, in a method of cooling the pin portion and then quenching the surface of the pin portion with a fillet R, the four pins arranged at intervals along the center axis direction of the four-cylinder crankshaft. Of the parts, the time to start the high-frequency induction heating of the two inner pins is earlier than the time to start the high-frequency induction heating of the two outer pins, and these four End timing of the high frequency induction heating of the pin portion is simultaneous, this way, so as to reduce the distortion in pin part. Further, in the present invention, when supplying power to the high-frequency induction heating coil for high-frequency induction heating of the pin portion, the high-frequency induction heating when the high-frequency induction heating coil is opposed to a top portion of the pin portion. The power supplied to the coil is set to be smaller than the power supplied to the high-frequency induction heating coil when the high-frequency induction heating coil is opposed to the bottom portion of the pin portion. Further, in the present invention, the heating time of the four pin portions is high-frequency induction heating, and the heating time of the two pin portions located inside is
2 seconds from the heating time of the two pin portions located on the outside
It is set to be longer than c. In the present invention, four semi-open saddle-type high-frequency heating coils respectively corresponding to the four pin portions are used, and the four pin portions are subjected to high-frequency induction heating and cooled at the same station.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIGS. 1 to 3, the same parts as those in FIGS. 4 to 7 are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 shows an induction hardening apparatus 21 used for carrying out the induction hardening method for a crankshaft according to the present invention. This induction hardening device 21
As shown in FIG. 1, a pair of brass side plates (coil holding plates) 22a and 22b are disposed in parallel and opposed to each other.
A semi-open saddle-type high-frequency induction heating coil 20 attached between the pair of side plates 22a, 22b, and power supply lead conductors 23a, 23b
A high-frequency power supply 24 for supplying a high-frequency current through the power supply, connection terminals 25a and 25b for connecting the high-frequency power supply 24 and the power supply lead conductors 23a and 23b, and these connection terminals 25
a, 25b and feeding the lead conductors 23a, side plates 22a to protect 23b, a block 26 made of an insulating material attached to the upper portion of 22b, and the heated portion (e.g. cylindrical portion 4a of the pin portion P ₄₎ A plurality (for example, 3) for maintaining a slight gap in the space between the high-frequency induction heating coil 20
Pieces) of ceramic or cemented carbide contacts (tip members) 27a, 27b, 27c, and the pair of side plates 22a, 22b below the high-frequency induction heating coil 20.
And a pair of cooling liquid injection rings 28a and 28b for quenching and cooling attached to the lower end of the cooling water injection ring.

The above-described high-frequency induction heating coil 20
Is a pair of side plates 22 in a hanging state by a support mechanism (not shown).
a, 22b, and the high-frequency induction heating coil 20 is moved with respect to the cylindrical peripheral surface γ while the contacts 27a, 27b, 27c are in contact with the cylindrical peripheral surface γ of the cylindrical portion 4a. It is placed on the column 4a with a small gap. Then, as the crankshaft 1 is rotated about the central axis X, the high-frequency heating coil 20 is placed on the cylindrical portion 4a with a slight gap by a work following mechanism (not shown). It is configured to be able to move following the rotation of the unit. As shown in FIG. 2, the high-frequency induction heating coil 20 is connected to an oscillator (power supply) 60 via a thin transformer 40 and a capacitor 50.

Further, the above-mentioned pair of coolant injection rings 28a,
A coolant supply pipe 29 is connected to 28b.
A coolant is supplied from a cooling supply source (not shown) to the coolant injection rings 28a and 28b through these pipes 29, and the coolant is injected from the coolant injection rings 28a and 28b toward the cylindrical portion 4a at a predetermined timing. It is configured to be.

FIG. 2 schematically shows the positional relationship between the induction hardening device 21 and the crankshaft 1 described above. Both ends of the crankshaft 1 are fixed by chucks 30a and 30b, and are driven to rotate about a central axis X by a rotation driving mechanism (not shown). Pin portion P ₁ ~P ₄
When high-frequency heating of the is placed over the contact 27a~27c respectively on each high-frequency induction heating coil 20 is lowered by the non-illustrated downward movement mechanism pin portion P ₁ to P _4,
High-frequency induction heating coil 20 is configured to a high-frequency induction heating while following the rotation of the pin portion P ₁ to P ₄ (revolving around the center axis X) is performed by an unillustrated follow-up mechanism.

The pin P₁~ P_FourHigh frequency induction heating
Is controlled as shown in FIG.
You. FIG. 3A shows the pin portion P₁, P_FourAbout
FIG. 3B shows a thermal control program._Two, P
_Three3 shows a heating control program for the first embodiment. Heating system
More specifically, the crankshaft 1
Four spaced apart along the axis X direction
Pin part P₁~ P_FourOf which are located at both ends in the central axis X direction
Two pin portions P₁, P_FourLocated between the inner
Two pins P_Two, P_ThreeHeating start time T₁The central axis
Two outer pins located at both ends in the X direction
P₁, P_FourHeating start time T_TwoBefore
P of all pins₁~ P_FourHeating end time T_ThreeAt the same time
are doing. That is, the pin portion P_Two, P_ThreeHigh frequency induction
Heat is first started, and after a predetermined time elapses, the pin P₁,
P_FourStart high-frequency induction heating of these
The wave induction heating is terminated at the same time. Therefore,
Pin part P₁, P_FourHeating start time T_TwoPin P for
_Two, P_ThreeHeating start time T₁The delay time of₀, Pin
P ₁, P_FourHeating time of H₁, Pin part P_Two, P_ThreeHeating
H for hours_TwoThen, H_Two= H₀+ H₁So that
I have decided. In this case, the delay time H₀Is 2 sec
That is all.

In the present embodiment, the pin portion P ₁
The to P ₄ upon supplying power to the high-frequency induction heating coil 20 for high-frequency induction heating, high frequency induction heating when a high-frequency induction heating coil 20 is opposed to the top portion of the pin portion P ₁ to P ₄ M The high-frequency induction heating coil 20 when the high-frequency induction heating coil 20 is opposed to the bottom portion N of the pin portions P _{1 to} P ₄ is supplied to the coil 20.
(For example, about 20 to 30% lower).

In this embodiment, four semi-open saddle-type high-frequency heating coils 20 respectively corresponding to the four pin portions P _{1 to} P ₄ are used, and these four pin portions P ₁ to P 4 are used in the same station. the P ₄ are cooled by high-frequency induction heating. The cooling process after the high-frequency induction heating of the pin portion P ₁ to P _4, each pin portion P ₁ to P
_{4 is} done simultaneously.

Pin P_Two, P_ThreeOf quenched hardened layer depth and
The relationship between the bending of the link shaft 1 and the pin portion P_Two, P_Three
Bend in the direction of 12 o'clock as the hardened hardening layer
Is determined by experiments,
According to the induction hardening method of the ink shaft, the inner (center
Side) two pin parts P_Two, P_ThreeHeating period H_TwoThe both sides
Pin P₁, P_FourHeating time H₁Longer than
As a result, the bend toward 12 o'clock is promoted.
You. Therefore, the above-described delay time H₀And heating time H₁, H
_Two(Especially heating time H_Two) Can be adjusted accordingly.
And the pin P₁~ P_FourPin P after quenching is completed₁
~ P_FourCan be reduced. In addition,
Part P₁~ P_FourJar of crankshaft 1 after quenching
Null part J₁~ J _FiveCrankshaft generated during quenching
Absorbs the bend at 6 o'clock (the opposite direction)
(Can be offset), quenching process in the journal
The amount of overall bending of the crankshaft 1 after
Can also be reduced. In the present embodiment,
Pin part P₁~ P_FourEnd time of high frequency induction heating
At the same time and the cooling start time at the same time
Therefore, at the time of quenching,₁~ P_FourUniform stress
And thus the bending of the crankshaft 1
Variations in the amount can be reduced.

Hereinafter, specific examples of the high-frequency induction heating method according to the present invention will be described. Example (1) Workpiece: 4-cylinder crankshaft (a) Material: S37C (b) Pin part diameter Pin part diameter; 45 mm Pin part width; 20 mm (2) High frequency induction heating conditions (A) Each pin part P ₂ , P ₃ (a) Frequency: 20 kHz (b) Output: 68 kW (W ₃ ), 46 kW (W ₄ ) (c) Heating time: 16 sec (H ₂ ) (d) Rotation speed: 30 rpm (B) Each pin P _1, P ₄ (a) frequency: 20 kHz (b) _{output: 72kW (W 1), 51kW} (W 2) (c) heating _{time: 14sec (H 1) (d} ) rotation speed: 30 rpm (e) start of heating Delay time: 2 sec (H ₀ ) (3) Cooling conditions (a) Coolant: Yukon quenchant A (8%) (b) Liquid temperature: 30 ° C. (c) Flow rate: 100 l / min for each pin section (e) Cooling time: 20 sec

After all the pins P _{1 to} P ₄ have been hardened by fillet R under the above processing conditions, the journals J _{1 to} J ₅
The fillet R hardening (however, the journal portion J _1, J ₅ is single fillet R hardening) shows the amount of flexure and bending direction of the center of the journal portion J ₃ of the crankshaft 1 when subjected to in Table 2 below .

[0028]

[Table 2]

The amount of bending of the crankshaft 1 is
Support the crankshaft 1 at the center of both ends,
The outer diameter of the center of the journal portion J ₃ was determined by the difference between the maximum value and the minimum value with a dial gauge. Direction of bend, the pin portion P ₁ 12 times, is the direction when the value in the dial gauge viewed sites displaying a maximum value from the side of the journal portion J _1, was measured in 1 hour units.

In the conventional induction hardening method in which all the pin portions P _{1 to} P ₄ are simultaneously subjected to high-frequency induction heating and cooled, the value of the amount of bending after all the pin portions are hardened is a reference value (TIR).
And the bending direction of the crankshaft is at 6 o'clock.
Further, a bend toward 6:00 was added.

On the other hand, according to the induction hardening method according to the embodiment of the present invention, the value of the bending amount after hardening all the pin portions is within the reference value, and the bending direction is 12
It was time direction. If all journals are quenched after quenching of all pins, a bend always occurs at 6:00 due to the history of forging of the crankshaft, etc. It will be smaller than the amount of bending after entering. That is, the amount of bending after quenching of all pins is small, and the direction of bending is opposite to the direction that occurs after quenching of all journals. And the level was not at a level that would cause a problem in polishing in a later step.

Regarding the heating time for high-frequency induction heating of the _four pin portions P _{1 to} P ₄ , the heating time H ₂ of the _two pin portions P ₂ and P ₃ located inside is reduced by the two heating times H ₂ located at both ends. It has been experimentally confirmed that the above-mentioned effects can be obtained remarkably when the heating time of the pin portions P ₁ and P ₄ is set to be longer than the heating time H ₁ by 2 sec (H ₀ ≧ 2 sec).

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment.
Various modifications are possible based on the technical concept of the present invention. For example, in the above-described embodiment, the four-cylinder crankshaft 1 is a hardened body (work), but the present invention is a multi-cylinder crankshaft other than the four-cylinder crankshaft 1 (for example, an eight-cylinder crankshaft). Is also applicable to induction hardening.

[0034]

As described above, according to the present invention, among a plurality of pins arranged at intervals along the center axis direction of a crankshaft (for example, a four-cylinder crankshaft),
The heating start timing of a plurality of pin portions (for example, two pin portions) located between the two pin portions located at both ends in the central axis direction is located at both ends in the central axis direction. Since the heating start timing for the two pin portions is set earlier and the heating end timing for all the pin portions is set at the same time, thereby reducing the distortion in the pin portions, all the pin portions are hardened. In addition to reducing the distortion of all the pin portions afterward, the direction of bending of the crankshaft can be made opposite to the direction of the bending that occurs when the journal portion is hardened after the hardening of the pin portion. The amount of bending of the crankshaft after quenching can be reduced. Then, since the amount of bending of the crankshaft and the pin portion is reduced, a crankshaft having a good completed dimension can be provided as a product without causing trouble such as unpolished portion in the polishing process in a later step.

[Brief description of the drawings]

FIG. 1 is a side view showing an induction hardening device used for performing an induction hardening method for a crankshaft according to an embodiment of the present invention.

FIG. 2 is a front view showing an arrangement relationship between a half-open saddle-type high-frequency induction heating coil and a crankshaft.

FIG. 3 is a view for explaining an induction hardening method for a crankshaft according to one embodiment of the present invention,
FIG. 3A is a graph showing heating conditions when heating two pin portions on both ends in the central axis direction (longitudinal direction) of the crankshaft, and FIG. It is a graph which shows the heating conditions at the time of heating two pin parts.

FIG. 4 is a front view of a four-cylinder crankshaft.

FIG. 5 is a diagram conceptually showing a quench hardened layer formed on a pin portion and a journal portion of the above-described four-cylinder crankshaft.

FIG. 6 is a view for explaining a bent state of the four-cylinder crankshaft when the pin part of the four-cylinder crankshaft is heated, and FIG. 6 (a) shows a case where only two pin parts at both ends are heated. FIG. 6B is a view showing a bent state of the four-cylinder crankshaft, and FIG. 6B is a view showing a bent state of the four-cylinder crankshaft when only two inner pin portions are heated.

FIG. 7 is an enlarged front view of a main part of a pin portion of a four-cylinder crankshaft.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 14 Four-cylinder crankshaft 3a, 4a Column part 3b, 4b R part 3c, 3c Fillet part (thrust part) 20 Half-open saddle-type high-frequency induction heating coil 21 High-frequency quenching device H ₀ delay time H ₁ heating time H ₂ heating time J ₁ through J ₅ journal portions P ₁ to P ₄ pin portion

Claims (5)

[Claims] 1. A semi-open saddle-type high-frequency induction heating coil is mounted on a cylindrical peripheral surface of a cylindrical portion of a pin portion of a multi-cylinder crankshaft, and the multi-cylinder crankshaft is rotated about its central axis. While causing the high-frequency induction heating coil to follow the cylindrical peripheral surface of the cylindrical portion, the cylindrical portion, the fillet R portion following the cylindrical portion, and the fillet portion following the fillet R portion are each subjected to high-frequency induction heating. Then, in a method of cooling the pin portion and then quenching the surface of the pin portion with a fillet R, a plurality of pin portions arranged at intervals along the center axis direction of the multi-cylinder crankshaft. The heating start timing of the plurality of pin portions located between the two pin portions located at both ends in the central axis direction is set to two pins located at both ends in the central axis direction. A high-frequency quenching method for a crankshaft, characterized in that the heating start timing of all the pin portions is set earlier than the heating start timing of the portion, and the heating end timing of all the pin portions is set at the same time, thereby reducing distortion in the pin portions. 2. A half-open saddle-type high-frequency induction heating coil is mounted on a cylindrical peripheral surface of a cylindrical portion of a pin portion of a four-cylinder crankshaft, and the four-cylinder crankshaft is rotated about its central axis. While causing the high-frequency induction heating coil to follow the cylindrical peripheral surface of the cylindrical portion, the cylindrical portion, the fillet R portion following the cylindrical portion, and the fillet portion following the fillet R portion are each subjected to high-frequency induction heating. Then, in the method of cooling the pin portion and then quenching the surface of the pin portion with a fillet R, the four pin portions disposed at intervals along the center axis direction of the four-cylinder crankshaft. Of these, the time when the high frequency induction heating of the two inner pin portions is started is earlier than the time when the high frequency induction heating of the two outer pin portions is started, and the four pins are started. The induction hardening method for a four-cylinder crankshaft, characterized in that the high-frequency induction heating of the section is finished at the same time, thereby reducing distortion in the pin section. 3. The high-frequency induction heating coil when supplying power to the high-frequency induction heating coil for high-frequency induction heating of the pin portion, wherein the high-frequency induction heating coil faces a top side portion of the pin portion. The power supplied to the high-frequency induction heating coil when the high-frequency induction heating coil is opposed to the bottom side portion of the pin portion is set to be smaller than the power supplied to the high-frequency induction heating coil. Induction hardening method for the described crankshaft. 4. A heating time for heating the four pin portions by high-frequency induction heating, wherein a heating time of the two inner pin portions is set to be longer than a heating time of the two outer pin portions by 2 sec or more. The induction hardening method for a crankshaft according to any one of claims 2 to 3, characterized in that: 5. The four pins corresponding to the four pins, respectively.
5. The four pin portions are subjected to high-frequency induction heating and cooled at the same station by using two semi-open saddle-type high-frequency heating coils.
Induction hardening method for a crankshaft according to any one of the above.