JPH03211234A - Induction hardening method for crank shaft - Google Patents

Abstract

PURPOSE:To decrease the distortions of a crank shaft after hardening by subjecting the pins at the ends of the crank shaft to high-frequency heating and cooling and injecting a cooling liquid to the joint parts of journals while rotating the crank shaft around the shaft of rotation. CONSTITUTION:The crank shaft 100 alternately disposed with the journals 21 to 25 and the pins 11 to 14 via counter weights 31 to 38 is subjected to the induction hardening, by which hardened layers 11a continuous with the circular cylindrical part 112 of the pin 11 (likewise the pin 14) at the end and the round parts 113 and fillet parts 114 in succession thereto are formed. The journal 21 is previously hardened and thereafter, the above-mentioned end pin 11 is subjected to the high-frequency heating and is then cooled by injecting the cooling liquid for hardening from a cooling liquid jacket in the method for executing the above-mentioned round part hardening. The crank shaft 100 is rotated around the 103 of rotation and the cooling liquid l is injected shaftfrom the nozzle 41 to the joint part of the counter weight 31 and the journal 21 at the end during the above-mentioned heating and cooling. The distortions of the crank shaft after the hardening are decreased in this way and the need for tempering of the above-mentioned joint part is eliminated.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a method for induction hardening a crankshaft.

<Prior Art> Conventionally, only the journals at both ends of a crankshaft of a four-cylinder engine in which pins and journals are arranged alternately, and also only the pins at both ends, are sometimes R-hardened.

In this case, the journal is usually hardened after all the pins are hardened.

Note that heating and hardening to form a continuous hardened layer over the cylindrical portion of the pin or journal, the R portion following the cylindrical portion, and the fillet portion following the R portion are referred to as R heating and R quenching, respectively. Taking a pin as an example, the pin 11 of the crankshaft 100 has a cylindrical portion 112 and a cylindrical portion
12, and a fillet portion 114 that continues from the eight portions 113 and protrudes in a direction perpendicular to the cylindrical portion 112.

<Problems to be Solved by the Invention> However, when the crankshaft is hardened as described above, the distortion of the crankshaft after hardening is large. Depending on the wall thickness of the pin, heating conditions, etc., when the pin is R-heated, a minute area of the fillet part of the already hardened journal (the journal that has already been hardened by hardening the journal) may be tempered. There has been a demand for reducing the above-mentioned distortion and preventing tempering.

The present invention has been devised in view of the above circumstances, and has pins and journals arranged alternately. Only the journals at both ends, which are the hardened parts of the crankshaft, and the journals at both ends, which are also the hardened parts, are arranged alternately. When R-hardening the pin only, the distortion of the crankshaft after hardening is small, and
It is an object of the present invention to provide an induction hardening method that does not require tempering a minute area of a fillet portion of a journal that has already been hardened.

<Means for Solving the Problems> In order to solve the above problems, the crankshaft induction hardening method of the present invention provides a crankshaft induction hardening method in which journals and pins are alternately arranged via counterweights. a cylindrical part, and an R part following the cylindrical part,
In an induction hardening method that performs R hardening to form a continuous hardened layer across the R part and the fillet part perpendicular to the cylindrical part, a cooling liquid is injected onto the end pin after high frequency heating. And, while the heating and injection are being performed, the crankshaft is rotated around the rotation axis, and the coolant is injected to the portion where the counterweight in contact with the pin at the end joins with the journal.

After hardening the journal at the end, the crankshaft is rotated around the rotation axis while cooling fluid is injected to the part where the counterweight that contacts the pin at the end joins the journal. After high-frequency heating, coolant is injected into this pin.

<Example> Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a side view of a crankshaft for explaining this embodiment, and FIG. 2 is a partially enlarged view of FIG. 1.

Now, the case where the crankshaft 100 shown in FIG. 1 is subjected to induction hardening will be described. crankshaft 100
includes five journals 21 to 25, a flange 26 joined to the journal 25, and four pins 11 to 14,
It is equipped with eight counterweights 31 to 38. In this crankshaft 100, journals and pins are alternately arranged via counterweights. Both end surfaces of the crankshaft 100 are supported by center pins 101 and 102. Note that 103 is the rotation axis of the crankshaft 100.

As a hardened specification of the crankshaft 100, only the journals 21 and 25 at both ends and the pins 11 and 14 at both ends
Only the journals and pins are required to be R-hardened, and other journals and pins are specified not to be hardened. Note that the R hardening of the journals 21 and 25 is R hardening only on one side.

Hereinafter, a method of induction hardening this crankshaft 100 will be explained. First, the journals 21 and 25 are heated for a predetermined time by saddle-shaped semi-loop coils for induction hardening (not shown) placed on each journal, and then cooled by injecting a cooling liquid for hardening from a cooling liquid jacket (not shown). By doing so, the journals 21 and 25 are R-hardened. That is, the journal 21 is provided with a hardened layer 21a shown in FIG. 2, and the journal 25 is provided with a hardened layer (not shown) that is similar to the hardened layer 21a but has burnout in a portion of the journal 25 close to the flange 26. Form.

After that, the pins 11 and 14 are heated for a predetermined time by the semi-loop coils (not shown) placed on each pin, and then
The pins 11 and 14 are R-hardened by cooling them by injecting a hardening cooling liquid from a cooling liquid jacket (not shown). That is, a hardened layer 11a shown in FIG. 2 is formed on the pin 11, and a hardened layer (not shown) similar to the hardened layer 11a is formed on the pin 14. However, while the pins 11 and 14 are being heated and cooled, as shown in FIG. Coolant flows from the coolant nozzles 41 and 42, respectively, in the vicinity of the coolant! Inject. In addition, at the beginning, journals 21 and 2
When hardening the cooling liquid nozzle 41.4,
2 will be raised.

Heating the pins 11 and 14 performs so-called power reduction. In this power reduction, for example, as shown in Japanese Patent Application No. 62-333.084, the pin is
The power applied to the semi-loop coil is reduced only while the crankshaft 100 passes through a predetermined rotational angle section before and after top dead center, thereby forming a hardened layer of a desired depth around the entire circumference of the pin. can be formed. In addition,
The heating of journals 21 and 25 described above does not effect this power reduction.

Note that 111 is a groove formed in both end portions of the pin 11, and this groove is also provided in the other pins 12 to 14. Further, 211 is a groove formed on the counterweight 31 side of the journal 21, and is a groove formed on the counterweight 31 side of the journal 21.
The journals 22 to 2 are also provided in the same manner.
4, grooves similar to the grooves 211 are provided on both sides of the counterweight.

Next, the effects of this embodiment will be explained. Now pin 11.
The diameter and width of 14 are 30III11 and 17ma+ respectively.
and the diameter and width of journal 21.25 are each 4
The pin 11.14 and journal 21.25 of the crankshaft 100, which has a total length of 350 m and a half stroke equivalent to 35IIIS steel type 550C, are hardened using the above method. Heating of pins 11.14 for about 12 seconds at an average power of 70 to 80-80% per pin
0 to - for about 12 seconds), and then tempered after quenching to 1
12 of all journals for 1 hour at 80°C.
TIR (Total Indicat) in the direction of time
The result of measuring 0.15
~0.25aem. However, the 12 o'clock direction means that the crankshaft 100 is aligned with both center bins 101 and 102.
and hold the crankshaft 100 with the center pin 10.
Refers to the direction toward the top of the pin 11.14 shown in FIG. 1 when viewed from the 1 side. When the conventional hardening method is used and the same tempering is performed as above, the TIR is 0.30 in the 12 o'clock direction.
0.45 mn+, it can be seen that the distortion of the crankshaft 100 after hardening could be reduced by the method of this example.

In this way, distortion of the crankshaft after hardening can be reduced by heating and cooling the pins 11 and 14.
A cooling liquid is injected into the joint between the pin 11 and the journal 21 and between the pin 14 and the journal 25 to cool the counterweight 31 due to the heating of the pin 11.14.
．． 34, the crankshaft 10
It is thought that this contributed to the reduction of the overall distortion of 0.

Furthermore, since the cooling liquid is injected from the cooling liquid nozzles 41.42, during R-hardening of the pin 11.14, it is possible to prevent tempering of a minute range of the already hardened fillet portion of the journal 21.25.

Note that while the pins 11 and 14 are being hardened, not only the joints between the counterweight 31 and the journal 21 and the joints between the counterweight 38 and the journal 25 but also the joints between the counterweight 32 and the journal 22 and the counter Even when the cooling liquid is injected to the joint portion between the weight 37 and the journal 24, the same effect as in this embodiment can be obtained.

In this embodiment, the journals 21 and 25 are hardened at the same time,
Next, although the case where the pins 11 and 14 are hardened at the same time has been described, the journal 21 is hardened and then the journal 25 is hardened.
Alternatively, the pin 14 may be hardened after the pin 11 is hardened.

<Effects of the Invention> As explained above, the induction hardening method of the present invention is an induction hardening method in which the pins at the end of the crankshaft are R-hardened in which journals and pins are alternately arranged via counterweights. In the method, a cooling liquid is injected to the end pin after high-frequency heating, and while the heating and injection are being performed, the crankshaft is rotated around the rotation axis and the end pin is heated. The coolant is injected to the part where the counterweight in contact with the pin of the part joins with the journal.

Therefore, according to the induction hardening method of the present invention, the distortion of the crankshaft after hardening is reduced. Further, when the end pin is R-hardened, it is possible to prevent the minute range of the fillet portion of the journal that is in contact with the pin and has already been hardened from being tempered.

[Brief explanation of drawings]

FIG. 1 is a side view of a crankshaft for explaining this embodiment, and FIG. 2 is a partially enlarged sectional view of the crankshaft shown in FIG. 1. 11-14...pin, 21-25...journal,
31-38...Counterweight, 100...
・Crankshaft, 112 ... Cylindrical part, 11
3...R part, 114...fillet part, l...cooling liquid.

Claims (1)

[Claims] (1) A cylindrical portion of the pin at the end of the crankshaft where journals and pins are alternately arranged via a counterweight, an R portion following the cylindrical portion, and a fillet portion following the R portion and perpendicular to the cylindrical portion. In an induction hardening method that performs R hardening to form a continuous hardened layer over the entire area, a pin at an end is heated with high frequency and then a cooling liquid is injected onto the pin at the end, and while the heating and injection are being performed. rotates the crankshaft around the rotation axis, and
A method for induction hardening a crankshaft, comprising injecting a coolant to a portion where a counterweight in contact with a pin at the end joins with a journal.