JPH06193708A - Manufacture of cam shaft - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a cam shaft which can correspond to shortening both a cam shaft diameter and a cam piece width without using a heating furnace requiring a great deal of equipment cost. CONSTITUTION:A soldering material is arranged on a cam piece 11 tack-welded to a shaft 10. High-frequency heating with a relatively low frequency is applied to the cam piece 11 for a relatively long period, thereby soldering the cam piece 11 to the shaft 10. Next, high frequency heating with a relatively high frequency is applied to the cam piece 11, which was soldered in advance, for hardening, and immediately after this, the affected part is quenched with cooling water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a cam piece on a shaft,
The present invention relates to an improvement in a method for manufacturing a camshaft by fitting a fitting member such as a journal.

[0002]

2. Description of the Related Art A known camshaft manufacturing method in which a cam piece manufactured separately from a shaft is fitted to a shaft and integrally joined thereto is described. A cam piece is fitted into the shaft and placed in a heating furnace, and the cam piece and the shaft are diffusion-bonded. Alternatively, they are integrally fixed by brazing. A camshaft manufacturing method that does not use a heating furnace is to form concavo-convex parts to prevent rotation in the shaft hole of the cam piece, and press the cam piece into an enlarged part such as a knurl that has been preformed on the outer circumference of the shaft to mechanically connect the cam piece. It has been proposed to integrally fix the shaft and the shaft (Japanese Patent Laid-Open No. 63-297707). The cam shaft thus integrally fixed is quenched to give the cam piece the necessary surface hardness.

[0003]

In the method using the heating furnace, not only the equipment cost is high, but also the entire shaft is passed through the furnace, so that the shaft may be bent. In recent years, a camshaft for an internal combustion engine is required to have a smaller shaft diameter and a smaller cam piece width, but a camshaft manufactured by a mechanical joining method requires a smaller diameter shaft and a smaller cam piece, resulting in a smaller joining area. There is a possibility that the bonding strength cannot be maintained.

The present invention has been made to solve these problems, and an object thereof is to integrally fix a shaft and a fitting member such as a cam piece or a journal without using a heating furnace. It is possible to provide a method for manufacturing a camshaft that can maintain a necessary joining strength even if the diameter of the shaft is reduced and the width of the cam piece is reduced.

[0005]

In order to achieve the above-mentioned object, the means adopted by the present invention is that a fitting member such as a cam piece or a journal temporarily fixed to a shaft is heated by a high frequency heating of a relatively low frequency for a relatively long time. The purpose is to braze the shaft and then quench the surface of the cam piece or the like by high-frequency heating at a relatively high frequency for a relatively short time. It is desirable that the high frequency heating frequency for brazing is about 5 KHz, the high frequency heating time is about 30 seconds, the high frequency heating frequency for quenching is about 200 KHz, and the high frequency heating time is about 1 second. The high frequency heating coil is divided into one for brazing and one for quenching, or the same high frequency heating coil is used for both brazing and quenching by using an inverter. The brazing high-frequency heating coil and the quenching high-frequency heating coil are installed side by side in the same facility, or separated into separate facilities. When the equipment is the same, it is desirable that the camshaft or the high frequency heating coil be movable in the axial direction. Since water is cooled immediately after quenching, it is desirable to use a cooling water jet type coil for quenching.

[0006]

In the brazing of the fitting member such as the cam piece or the journal to the shaft by the high frequency heating, the strain due to the local heating exceeds the allowable limit, and it takes a lot of trouble to correct it. As a result of repeating many trials, the inventor of the present application has found that if the frequency of high frequency heating is relatively low and the heating time is relatively long, the strain associated with high frequency heating can be suppressed within an allowable limit. .

As shown in the example of the cam piece in FIG. 1, when high frequency heating of a relatively low frequency of 5 KHz is applied to the cam piece temporarily fixed to the shaft for 30 seconds, the brazing portion of the cam piece and the shaft is deeply heated to 620 ° C. Since the temperature of 700 ° C. is maintained for 10 seconds or more, the brazing material penetrates the entire joint surface, and strong brazing is performed. Then, apply a high frequency heating of a relatively high frequency of 200 KHz to the same cam piece.
When it is applied for a second, and immediately thereafter, cooling water is sprayed to quench it, only the shallow portion of the peripheral surface of the cam piece reaches a high temperature of 800 ° C. or higher for quenching. Immediately after that, since the peripheral surface of the cam piece is rapidly cooled, there is no possibility that the quenched portion is tempered. Further, since this rapid heating is for a short time, there is no fear of affecting the brazing material at the brazing portion. Since this method does not use a heating furnace, the equipment cost is low, and even if the shaft has a small diameter and the cam piece has a small width, brazing is required, so that the necessary joining strength can be secured.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of the present invention will be described based on the embodiments shown in the drawings. As shown in FIG. 2, the cam piece 11 is temporarily fixed to a predetermined position on the shaft 10 in advance. This temporary fixing is a knurling or spiraling process that expands the outer diameter of the shaft on which the cam piece is attached, and the cam piece is press-fitted or screwed, but pin fixing, spot welding, adhesive bonding, etc. The cam piece may be temporarily fixed to the shaft by the above method. An annular groove 12 is formed on the inner circumference of the side surface of the cam piece 11, and a brazing material 13 is fitted into the groove.

A cam piece 11 temporarily fixed to the shaft 10 is arranged coaxially with the brazing heating coil 14 in the same cross section, and a high frequency power having a frequency of 5 KHz is applied to the brazing heating coil 30.
Apply for seconds. As shown in the left half of FIG. 1, the joint portion between the shaft and the cam piece rises in temperature with application of high-frequency power to reach a brazable temperature of 620 ° C. to 700 ° C., and after maintaining this temperature for 10 seconds or more, Cool down. Since the heating of the brazing heating coil 14 takes a relatively long time, the temperature rise is deep and reaches the joint between the shaft and the cam piece. As a result, the brazing material is melted, and the brazing material is turned around the entire joint portion between the shaft and the cam piece, and the cam piece and the shaft are firmly brazed.

As shown in FIG. 3, the quenching heating coil 15 is installed at a position adjacent to the brazing heating coil in the axial direction of the shaft. The quenching heating coil 15 is a cooling water jet type connected to a cooling water source via a valve 16, and can jet cooling water from a jet hole 17 to a work. After brazing, as shown in FIGS. 3 and 4, the shaft 10 or the heating coils 14, 15 are arranged so that the brazed cam piece 11 is located coaxially with the quenching heating coil 15 and in the same cross section.
Move in the axial direction. Then, high frequency power of 200 KHz is applied to the heating coil 15 for quenching for 1 second, and then the valve 16 is opened to put cooling water on the circumferential surface of the cam piece 11.
Spray for 3 seconds. At this time, as shown in the right half of FIG.
The peripheral surface of the cam piece 11 rapidly rises to a quenchable temperature range of 800 ° C. or higher, but is rapidly cooled by the injection of cooling water immediately after that and drops to room temperature.

Thus, the peripheral surface of the cam piece 11 is adjusted to a predetermined hardness by quenching the peripheral surface of the cam piece 11 by rapid heating and then rapidly cooling it before tempering. Since the heating by the quenching heating coil 15 is extremely short, the temperature rise is limited to the shallow portion of the peripheral surface of the cam piece 11 and does not reach the joint surface of the cam piece and the shaft. There is no risk of melting.

Although the embodiment has shown one set of brazing and quenching heating coils for one cam piece, the equipment has one set of heating for each cam piece and journal of one cam shaft. Place the coil. or,
In the embodiment, the brazing and quenching heating coils are provided as one set, but the brazing and quenching may be separate facilities, and the brazing heating coil and the quenching heating coil may be separated. Further, when the frequency of the high frequency power can be modulated through an inverter or the like, the same high frequency heating coil can be used for brazing and quenching.

[0013]

As described above, according to the manufacturing method of the present invention, fitting members such as cam pieces and journals are brazed to the shaft, and then the peripheral surface of the cam piece is quenched, which is different from the conventional brazing method. In contrast, since the heating furnace is not used, the facility cost is low and it is possible to reduce the cost, and compared with the conventional manufacturing method of mechanically joining the cam piece and the shaft without using the heating furnace. Even if the diameter of the shaft is reduced and the width of the cam piece is reduced, the joint strength between the cam piece and the shaft can be sufficiently increased, so it is also suitable for camshafts for internal combustion engines that require a reduction in the diameter of the shaft and a reduction in the width of the cam piece. There is an excellent effect of doing.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between brazing and quenching time and temperature in one embodiment of the present invention,

FIG. 2 is a sectional view showing a camshaft and a high-frequency heating coil during brazing,

FIG. 3 is a sectional view showing a camshaft and a high frequency heating coil during quenching,

FIG. 4 is a sectional view showing a camshaft and a high-frequency heating coil during cooling water injection,

[Explanation of symbols]

10: Shaft, 11: Cam piece, 12: Groove, 13: Brazing material,
14: Heating coil (for brazing), 15: Heating coil (for hardening), 16: Valve, 17: Injection hole

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area F01L 1/04 J 6965-3G

Claims (2)

[Claims] 1. A fitting member such as a cam piece having a brazing material fitted to a shaft in advance is brazed by high-frequency heating of a relatively low frequency for a relatively long time, and the brazed cam piece has a relatively high frequency. 2. The method for manufacturing a camshaft, which comprises subjecting the cam piece to rapid quenching by high-frequency heating for a relatively short period of time, and then immediately cooling the cam piece. 2. The brazing is performed by applying high frequency heating at a frequency of about 5 KHz for about 30 seconds, and quenching at a high frequency of about 200 KHz for about 1 second. Method for manufacturing camshaft.