JP2009293104A - Apparatus and method for tempering camshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for tempering with which a time needed to the tempering in terms of one piece can be shortened and the reduction of electrical energy needed to the tempering can be obtained. <P>SOLUTION: This apparatus is provided with; a coil (1) for tempering, which has a function for heating a camshaft (10) arranged in the inner part with an induction-heating by supplying the alternating current, and has the longitudinal directional size equal to or longer than the longitudinal directional size of the camshaft (10); an alternating current power source (2) for supplying the alternating current having a prescribed frequency to the coil (1) for tempering; a first fixture (3) which has a function for holding the one-end part (11) of the camshaft (10) and a function for rotation-driving while holding the one-end part (11) of the camshaft (10); and a second fixture (4) for rotatably supporting the other-end part (12) of the camshaft (10). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for heat-treating a camshaft for a vehicle engine. More particularly, the present invention relates to such a camshaft tempering apparatus and method.

In a heat treatment performed when manufacturing a camshaft for a vehicle engine, a batch processing method using a heating furnace is generally adopted as a tempering furnace. For example, 20 camshafts that have been quenched are accommodated in a bucket, and the 20 camshafts are tempered at once in a heating furnace.
In this case, the intermediate work in process is waiting before and after the electric furnace, and compared with the so-called single-flow process, the loss of the work-in-process waiting time is lost. Arise.

Further, in the tempering process in the heating furnace, for example, as shown in FIG. 14, in one cycle, the heating time (for example, 0.5 hours) until the furnace temperature reaches a predetermined temperature (for example, 150 ° C.) The temperature (150 ° C.) holding time (for example, 2 hours) and the air cooling time (for example, 1 hour) are set.
However, the energy consumed during the heating time does not contribute at all to the heat treatment of the camshaft, and there is a problem that the energy consumed during the heating time (for example, electric energy) is wasted.

As another conventional technique, for example, there is a technique for reducing the processing cost and ensuring the quality of the chamber portion by expanding the diameter of the shaft portion (see, for example, Patent Document 1).
However, the related art (Patent Document 1) does not solve the above-described problems of the prior art.
Japanese Patent Laid-Open No. 8-150853

  The present invention has been proposed in view of the above-described problems of the prior art, and provides a tempering apparatus and method that can shorten the time required for tempering for one line and reduce the electrical energy input to tempering. It is aimed.

  The tempering device (100) of the present invention has a function of heating the camshaft (10) accommodated therein by induction heating when AC is supplied, and has a longitudinal direction equal to or greater than the longitudinal dimension of the camshaft (10). A tempering coil (1) having dimensions, an AC power source (2) for supplying an AC current of a predetermined frequency (eg, 3 KHz) to the tempering coil (1), and one end (11) of the camshaft (10). The first jig (3) that functions to grip and to rotate and drive the one end (11) of the camshaft (10) and the other end (12) of the camshaft (10) are rotated. And a second jig (4) for supporting the second jig (4).

  In the present invention, the AC power source (2) includes a DC power source and a transmitter, and an AC current having a predetermined frequency (for example, 3 KHz) is generated for a predetermined time (for example, 20 seconds) in order to heat the camshaft (10). It preferably has a function of supplying (Claim 2).

  In the present invention, the AC power source (2) supplies an AC current of a predetermined frequency for a first predetermined time (T1: for example, 20 seconds) to heat the camshaft (10), and for a second predetermined time ( It is preferable to have a function of repeating a cycle of stopping the supply of alternating current only for t2 (for example, 10 seconds) a predetermined number of times (N: for example, 7 times).

  Furthermore, in the present invention, the tempering coil (1) is composed of a pair of substantially semicircular coils (1A, 1B), and each of the pair of coils (1A, 1B) includes the AC power source (2 ), And are arranged so as to be opposed to each other at intervals in the circumferential direction, and are arranged so as to accommodate the camshaft (10) radially inward (claims). 4).

  In the present invention, the first jig (3) preferably has a function of rotationally driving while the camshaft (10) is heated by the tempering coil (1). Item 5).

  In the tempering method of the present invention, the one end (11) of the camshaft (10) is gripped by the first jig (3) that rotationally drives, and the other end (12) of the camshaft (10) is Cam that is rotatably supported by a jig (4) and has a longitudinal dimension equal to or larger than the longitudinal dimension of the camshaft (10) and is connected to the tempering coil (1) connected to the AC power source (2). A step of accommodating the shaft (10), and a step of supplying an alternating current of a predetermined frequency (for example, 3 KHz) to the tempering coil (1) to heat the camshaft (10) by induction heating. In this step, an alternating current of a predetermined frequency (for example, 3 KHz) is supplied for a first predetermined time (t1: for example 20 seconds) to heat the camshaft (10), and a second predetermined time (t2: for example 10). If you stop supplying AC current for a second) Starts selling cycle, a predetermined number of times: is characterized by repeated for (N eg 7 times) (Claim 6).

  In the tempering method of the present invention, it is preferable to have a step of cooling the camshaft (10) with tap water.

According to the present invention having the above-described configuration, the camshaft (10) is heated by induction heating using the tempering coil (1) that supplies an alternating current of a predetermined frequency (for example, 3 kHz). The time required is shortened. Therefore, the camshaft production lead time can be shortened.
Further, according to the present invention, the “tempering” process can be performed for each camshaft (10) one by one, so that it is not necessary to perform the “tempering” process by a batch process using a heating furnace or the like. Therefore, in order to perform tempering, an intermediate mechanism in which the camshaft (10) stays immediately before the heating furnace or the like becomes unnecessary.

According to the present invention, the tempering coil (1) has a longitudinal dimension that is equal to or greater than the longitudinal dimension of the camshaft (10), so that the tempering coil (1) is placed in the longitudinal direction of the camshaft (10). The camshaft (10) can be tempered without moving to.
As a result, the structure for moving the tempering coil (1) in the longitudinal direction of the camshaft (10) becomes unnecessary, and the number of parts can be reduced.

  Here, the alternating current supplied to the tempering coil (1) has a predetermined frequency, for example, 3 kHz, and is lower than the frequency (for example, 10 kHz) of the alternating current used in the induction heating according to the prior art. Yes. Therefore, it heats from the surface to a deep area | region compared with a prior art, the whole base material is heated, and tempering is performed favorably.

  Further, according to the present invention, since heating is performed by the tempering coil (1), there is no energy consumption that does not contribute to heat treatment unlike the heating process in the case of heating in a heating furnace or the like, and energy is saved correspondingly. I can do it.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 and 2, a tempering apparatus 100 according to the illustrated embodiment includes a tempering coil 1, an AC power source (high frequency power source) 2, and a first jig (headstock) that holds a camshaft 10 that is a workpiece. 3, a second jig (tailstock) 4, and a power line L that connects the tempering coil 1 and the AC power source 2 in series.
The AC power source 2 includes a DC power source and a transmitter (not shown). Further, the camshaft 10 to be described in detail later includes a plurality of cams C and a plurality of journal portions J (see FIG. 6).

In FIG. 2, the tempering coil 1 is composed of a pair of substantially semicircular coils 1 </ b> A and 1 </ b> B, and the ends 1 </ b> Ae and 1 </ b> Be of the pair of coils 1 </ b> A and 1 </ b> B are connected via a power line L. Connected to power supply 2.
The pair of coils 1 </ b> A and 1 </ b> B are disposed to face each other with a gap in the circumferential direction, and accommodate the camshaft 10 radially inward.
As shown in FIG. 1, the total length of the tempering coil 1, that is, the vertical dimension of the coil 1 in FIG. 1 is set longer than the total length of the camshaft 10.

In FIG. 1, a first jig (head stock) 3 is configured to grip one end 11 of a camshaft and to rotationally drive the camshaft 10 while gripping.
The second jig (tailstock) 4 is configured to be able to rotatably support the camshaft 10 while gripping the other end 12 of the camshaft 10.

With reference to FIG. 3, the principle of tempering using an induction current by high frequency will be described.
In FIG. 3, a coil 1 is arranged around a work W, and the coil 1 is connected to a high frequency power source 2. When a current is passed from the high frequency power source 2 to the coil 1, a magnetic flux M is generated so as to penetrate the workpiece W. Here, since the electricity input from the high frequency power source 2 to the coil 1 is alternating current, the direction of the current flowing through the coil 1 periodically changes, and the direction of the magnetic flux M also changes periodically (alternating magnetic flux). As a result, an induced current E is generated on the surface of the workpiece W.
Joule heat is generated by the induced current E, and the work is tempered by the Joule heat.

The table below shows the tempering conditions, and FIG. 4 shows the relationship between the tempering heating temperature and time.
table

According to the above table, the frequency of the illustrated embodiment is 3 KHz, for example, and the output of the power supply 2 is 25 Kw.
In the illustrated embodiment, as shown in FIG. 4, after a heating time of 20 seconds (t1: first predetermined time) (time for supplying an alternating current to the coil 1), 10 seconds (t2: second predetermined time). Time) (state in which the heating temperature is kept constant), heating is performed again for 20 seconds, and heat radiation is performed for 10 seconds.
This pattern is repeated a total of 7 times. After the seventh cooling, the workpiece surface temperature is lowered to the temperature before the start of tempering (original temperature) in 30 seconds.

In the illustrated embodiment, the reason for setting the frequency of the AC power supply 2 to 3 KHz is as follows.
(1) Since the quenching depth is inversely proportional to the 1/2 power of the frequency, if the frequency is increased as when quenching (10 KHz), heat penetrates only to the skin of the workpiece. In order to level the internal structure of the workpiece, it is necessary to sufficiently transfer heat to the inside during tempering. Therefore, the frequency needs to be lower than at least the quenching frequency (10 KHz).
(2) At a relatively high frequency of 5 to 10 KHz, as described above, heat penetrates only to the workpiece surface. Therefore, when tempering is performed at a relatively high frequency of 5 to 10 KHz, the number of repetitions must be increased in order to sufficiently transfer heat to the inside of the workpiece.
(3) At a frequency of 2 KHz or less, the equipment generates large vibrations, causing environmental problems. In addition, the capital investment is increased because the control panel must have special specifications. Therefore, it is not preferable to perform tempering at a frequency of 2 KHz or less.
According to the above (1) to (3), in the illustrated embodiment, the frequency of the AC power supply when tempering is set to 3 KHz.

The number of repetitions is set to 7 because the workpiece to be tempered by the tempering apparatus 100 according to the illustrated embodiment is a camshaft of a medium-sized commercial vehicle engine, and the shape thereof is relatively complicated. For this reason, this is related to the fact that the temperature of the camshaft does not rise uniformly in a single heating. In other words, as shown in FIG. 4, by repeating heating / cooling seven times, the steep rise of temperature rise in the camshaft is reduced, and the appropriate thickness of the camshaft in the radial direction is reduced. It is possible to communicate sufficiently.
The heating / cooling time and the repetition number N of heating / cooling are not 7 for all workpieces, but depend on the total mass, total surface area, shape, and other conditions of the workpiece to be tempered. A different number of repetitions N is set.
Although illustration is omitted, in the embodiment, in order to lower the temperature of the work to the temperature before tempering in 30 seconds, the work heated by the tap water is cooled. It is also possible to cool the camshaft of a vehicle engine.

The tempering procedure in the illustrated embodiment is as follows.
Procedure 1: The camshaft 10 that is a workpiece is supported (chucked) by the first jig 3 and the second jig 4 of the tempering device 100, and is accommodated in the tempering coil 1 (inner area in the radial direction). .
Procedure 2: A cycle in which an alternating current is supplied to the coil 1, heated for 20 seconds, and allowed to cool for 10 seconds is repeated seven times. During this time, the workpiece 10 is rotated inside the tempering coil 1 at a rotation speed of 200 rpm by the first jig 3 which is a rotational drive source (see FIG. 5). The time required for the procedure 2 is, for example, 210 seconds.
Procedure 3: Cooling with cooling water (for example, tap water) so that the workpiece 10 is heated to room temperature in 30 seconds.
Procedure 4: The workpiece 10 is removed from the tempering apparatus 100.

Here, in the illustrated embodiment, the cycle of heating for 20 seconds and allowing to cool for 10 seconds is repeated seven times in the above-described procedure 2, but this number of repetitions (seven times in the illustrated embodiment) is small. (In the illustrated embodiment, if the number of repetitions is less than 6), the heating necessary for tempering is not performed, so that the effect of tempering may not be sufficiently obtained.
On the other hand, if the number of repetitions is large (8 or more times), the surface temperature of the camshaft 10 becomes too high, and the hardness of the surface of the camshaft 10 increased by the quenching process may be lowered.
In other words, the number of repetitions of the heating and heat dissipation cycle may be within a range in which a sufficient tempering effect can be obtained and the surface temperature of the workpiece does not become too high. In that sense, it is not limited to “7 times”.

The entire camshaft 10 is configured as shown in FIG. 6, and has a plurality of cams C (C1 to C12) and a plurality of journal portions (bearing corresponding portions) J (J1 to J7).
Here, in particular, the plurality of cams C (C1 to C12) have different directions of protruding portions.
Further, for example, in each of the plurality of cams C (C1 to C12), tempering is performed from the top Ct, the base Cb, and the right lift Clr (or the left lift Cll) of the cam C, as indicated by (5-1) in FIG. The distances δc1, δc3, and δc2 to the radially inner surface of the coil 1 for use are different. Similarly, the distances δj1 and δj2 from the surface of the journal J to the radially inner surface of the tempering coil 1 are also different.
Furthermore, the tempering coil 1 is not a complete ring.

Due to the reasons described above, in the state where the camshaft 10 is gripped by the first jig 3 and the second jig 4, the rotation center of the camshaft 10 may not match the curvature center of the tempering coil 1. is there.
Therefore, the amount of heat generated on the surfaces of the cam C and the journal J during induction heating is not equal in each part of the cam C and the journal J.

Here, as described with reference to (5-1) in FIG. 5, the distances δc1, δc2, and δc3 between the portions of the surface of the cam C and the radially inner surface of the tempering coil 1 are different. ing. Similarly, the distances δj1 and δj2 between the surface of the journal portion J and the radially inner surface of the tempering coil 1 are also strictly different.
Therefore, in the illustrated embodiment, as shown in the order of (5-1) → (5-2) → (5-3) → (5-4) → (5-1) in FIG. The camshaft 10 is rotated within the tempering coil 1. By rotating the camshaft 10 in the tempering coil 1, there is a large difference in the heat generated in each part Ct, Cb, Cll, Clr on the surface of the cam C or in each part of the journal part J. I am trying not to do it.

The tempering apparatus 100 of FIGS. 1 and 2 is configured to perform quenching in addition to tempering. When performing quenching, the heating temperature of the camshaft 10 by induction heating using the tempering coil 1 is raised to the transformation point or higher.
Here, since it is not necessary to deepen the curing depth in quenching, in the illustrated embodiment, when quenching is performed with the coil 1, the alternating current supplied (to the coil 1) is compared with the case of tempering. The current frequency is set high (for example, 10 kHz).

As shown in FIG. 6, the camshaft 10 has a shaft body S formed with a plurality of cams C (C1 to C12) and a plurality of journal portions J (J1 to J7) at predetermined intervals.
7 to 13 show the surface hardness of the journal portions J1 to J7 and the hardness of the surface of the cam C when the journal portion J and the cam C are tempered by the tempering apparatus 100 according to the illustrated embodiment. Shows experimental data in comparison with the hardness when tempering is performed by the prior art.
Hereinafter, such experimental data will be described with reference to FIGS.

FIG. 7 shows the surface hardness of each of the journal portions J1 to J7 when tempered in the illustrated embodiment as a table compared with the hardness when tempered according to the prior art (heated with an electric furnace). ing. FIG. 8 shows FIG. 7 replaced with a graph.
Here, in FIGS. 7 to 13, the Rockwell hardness _HRC is shown as the hardness. The shipping standard is 57 to 64H _RC .

7 and 8, except for the sixth journal portion J6, the hardness of the prior art is higher than the hardness in the illustrated embodiment.
However, since the Rockwell hardness when tempering is performed in the illustrated embodiment is sufficient for the allowable value 57H _RC in all the journals J1 to J7, the tempering according to the illustrated embodiment. It can be said that the processed camshaft has no problem as a heat-treated product.

FIG. 9 is a table comparing the surface hardness of the four locations of the No. 1 cam C1 when tempering is performed according to the illustrated embodiment and the hardness when tempering is performed by the conventional technique (heating with an electric furnace). Show.
In FIG. 10, the hardness is compared between the tempering according to the illustrated embodiment and the tempering according to the prior art, that is, the top Ct, the base Cb, the left lift Cll, and the right lift Clr are identified in the first cam C1. ing.
FIG. 11 shows the hardness shown in FIG. 9 (the hardness in the illustrated embodiment and the hardness in the prior art) in the form of a graph.

According to FIGS. 9 and 11, the hardness according to the prior art is higher than the hardness according to the illustrated embodiment at any location (top Ct, base Cb, left lift Cll, right lift Crl) of the cam C1. It has exceeded.
However, the Rockwell hardness according to the illustrated embodiment is sufficiently higher than the allowable value 57H _RC at any location of the cam C1. Therefore, the camshaft that has been tempered according to the illustrated embodiment has no problem as a heat-treated product.

FIG. 12 shows the surface hardness at four locations (top Ct, base Cb, left lift Cll, right lift Clr: see FIG. 10) of the No. 12 cam C12 when tempering is performed in the illustrated embodiment, and the prior art ( Compared with the hardness when tempering (heated in an electric furnace), it is shown in the form of a table.
FIG. 13 shows a comparison between the hardness when tempering is performed in the illustrated embodiment and the hardness when tempering according to the prior art is performed in the form of a graph, as in FIG. Yes.
According to FIGS. 12 and 13, the conventional technique is more than the hardness when tempering is performed in the illustrated embodiment at any location (top Ct, base Cb, left lift Cll, right lift Crl) of the cam C12. The hardness when tempering is exceeded. However, in the tempering according to the illustrated embodiment, the Rockwell hardness of the four locations of the cam C1 exceeds the allowable value 57H _RC , and the tempered camshaft according to the illustrated embodiment is a heat-treated product. There is no problem.

Although not shown, according to the applicant's experiment, the runout in the journal portions J1 to J7 of the tempered camshaft according to the illustrated embodiment is an allowable value of 0.1 mm (0.1 mm or less). Much smaller. This means that the compressive residual stress before heat treatment of the tempered camshaft according to the illustrated embodiment is reduced.
Moreover, since the runout in the journal portions J1 to J7 of the tempered camshaft according to the illustrated embodiment is equivalent to that in the case of performing the tempering of the prior art, there is no problem with “runout”. .

According to the illustrated embodiment having the above-described configuration, it is possible to perform continuous processing, so-called single-flow, from the conventional batch processing method, and to eliminate the work before and after the heat treatment.
In the illustrated embodiment, the time required for tempering can be significantly reduced from 10.5 minutes to 4 minutes in the prior art when compared in terms of one camshaft. Therefore, the electrical energy required for the tempering process can be greatly reduced.
In addition, since the generation of Joule heat due to induction current is directly used for heat treatment from the initial stage of heating, energy is directly used for heat treatment from the initial stage of heating, unlike the case of heating in a heating furnace.

  In the illustrated embodiment, the heating-to-cooling cycle is repeated seven times, so that a sufficient tempering effect can be obtained, and the surface temperature of the workpiece does not become too high. However, the number of repetitions of the cycle is not limited to “7 times”.

In addition to this, as a result of the experiment conducted by the applicant on the illustrated embodiment, the man-hour is 5 in the prior art, whereas in the illustrated embodiment, it is 4.5, and labor saving is 10%. It became possible.
The production lead time was reduced from 1.5 days of the prior art to 1.25 days, which was reduced by about 17%.

  It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.

The perspective view which shows embodiment of this invention. The block diagram which shows the XX cross section of FIG. The block diagram explaining the principle of tempering using the induced current. The characteristic view which shows the relationship between the tempering heating temperature and time in embodiment. The figure explaining rotation of the workpiece | work within the coil of embodiment of this invention. The side view of a cam shaft. The figure which shows the tempering hardness in embodiment of this invention and the tempering hardness of a prior art as a table | surface. The figure which shows the tempering hardness in embodiment of this invention of FIG. 7, and the tempering hardness of a prior art with a graph. The figure which shows the tempering hardness of 4 places of the 1st cam in embodiment of this invention as a table | surface compared with a prior art example. The cam sectional view for displaying four places which showed tempering hardness in Drawing 9. FIG. 10 is a diagram showing the tempering hardness at four positions of the No. 1 cam in the embodiment of the present invention in the same manner as FIG. 9, and is a graph expressed as a graph. The figure which shows the tempering hardness of 4 places of the 12th cam in embodiment of this invention as a table | surface compared with a prior art. FIG. 13 is a diagram showing the tempering hardness at four locations of the No. 12 cam in the embodiment of the present invention in comparison with the prior art, and is a graph expressed in the same manner as FIG. 12. The figure which shows the thermal cycle of the tempering in a prior art.

Explanation of symbols

1 ... Temperature coil 1
1A, 1B ... Pair of semicircular coils 2 ... AC power supply 3 ... First jig (headstock)
4 ... Second jig (tailstock)
DESCRIPTION OF SYMBOLS 10 ... Cam shaft 11 ... One end 12 of a cam shaft ... The other end 100 of a cam shaft ... Tempering device C ... Cam J ... Journal part

Claims (7)

  A tempering coil (1) having a function of heating the camshaft (10) housed therein by induction heating when supplied with an alternating current and having a longitudinal dimension equal to or greater than the longitudinal dimension of the camshaft (10); The AC power source (2) for supplying an alternating current of a predetermined frequency to the tempering coil (1), the function of gripping one end (11) of the camshaft (10), and the one end (11 of the camshaft (10)) ) And a second jig (4) for rotatably supporting the other end (12) of the camshaft (10). A tempering device for a camshaft (10), characterized in that:   The AC power source (2) includes a DC power source and a transmitter, and has a function of supplying an AC current having a predetermined frequency for a predetermined time (t1) in order to heat the camshaft (10). Camshaft tempering device.   The AC power supply (2) supplies an AC current of a predetermined frequency for a first predetermined time (t1) and stops supplying an AC current for a second predetermined time (t2) in order to heat the camshaft (10). The camshaft tempering apparatus according to any one of claims 1 and 2, wherein the camshaft tempering device has a function of repeating a cycle of performing a predetermined number of times (N).   The tempering coil (1) is composed of a pair of substantially semicircular coils (1A, 1B), and each of the pair of coils (1A, 1B) is connected to the AC power source (2). And are arranged so as to face each other at intervals in the circumferential direction, and arranged so as to accommodate the camshaft (10) radially inwardly. Camshaft tempering device.   The first jig (3) has a function of being driven to rotate while the camshaft (10) is heated by the tempering coil (1).   One end (11) of the camshaft (10) is gripped by the first jig (3) that rotationally drives, and the other end (12) of the camshaft (10) is rotated by the second jig (4). The camshaft (10) is accommodated inside the tempering coil (1) having a longitudinal dimension larger than the longitudinal dimension of the camshaft (10) and connected to the AC power source (2). And a step of supplying an alternating current of a predetermined frequency to the tempering coil (1) and heating the camshaft (10) by induction heating, and in the heating step, the camshaft (10) is heated. Therefore, a cycle in which an alternating current having a predetermined frequency is supplied only for a first predetermined time (t1) and the supply of the alternating current is stopped for a second predetermined time (t2) is repeated a predetermined number of times (N). How to temper the camshaft.   The method of tempering a camshaft according to claim 6, further comprising a step of cooling the camshaft with tap water.

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