JPS5994521A - Manufacture of metallic torsion bar - Google Patents

Abstract

PURPOSE:To manufacture easily a metallic torsion bar in a short time and in high material yield, by reducing radially a desired part of a metallic bar-shaped blank material by heating and stretching it, and providing a desired end-part work to the material after heat-treating the reduced part by quenching. CONSTITUTION:One end 1d of a part to be formed into a torsion bar of a blank material 1 such as a round bar of spring steel is heated by a heating coil 6 connected to a source 8 of high-frequency induction heating, and then is heat- treated by jetting cold air from a cooling nozzle 7. Next, the material 1 is heated to a prescribed temperature and stretched in the direction of an arrow F2 to reduce it radially by a stretching device 5a, 5b, and the radially reduced part is quenched to form a small diametral part 1b, while moving the heating coil 6 and the cooling nozzle 7 in the direction of an arrow F1 by driving a moving device 14. Next, after heat-treating the other end part 1e in the same manner as that of the part 1d, an end-part work such as a serration work is provided to the non-reducing parts of both end parts 1a, 1c to obtain a torsion bar.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a metal torsion bar, such as a torsion bar for power steering of an automobile. In order to manufacture a product with such a large rate of change in cross-sectional area in the longitudinal direction, conventionally, a lathe or the like is used to cut a rod-shaped material 1 into the desired thickness and shape, as shown in FIG. There is. However, in this case, the machining time is long and the material loss due to turning is several tens of percent.
In addition, it requires tools that are expendable, such as a cutting tool, resulting in high costs.

Moreover, conventionally, after turning, both ends 1&, IQ, etc. are subjected to thermal refining treatment, and the small diameter portion 1b, which becomes the twisted portion, is subjected to complete heat treatment such as induction hardening treatment in order to improve its strength.

FIG. 2 shows an example of a conventional torsion bar manufacturing process, in which a turning process 2 is followed by various heat treatment processes 3, and then a final polishing process 4. In addition to these steps, it is necessary to perform end processing for attachment, such as serration processing, on both fiA parts za and ze.

As described above, conventional methods require many steps from material processing to heat treatment, resulting in poor productivity and high costs.

The present invention has been made based on the above circumstances, and its purpose is to create a metal torsion that can be machined in a short time without using conventional machining or turning, and that can be heat treated at the same time as the machining, thereby simplifying the process. The object of the present invention is to provide a method for manufacturing a bar. In other words, the present invention forms a small diameter portion that becomes a twisted portion of a torsion bar by heating a required portion of a metal rod-shaped material and reducing the diameter by applying a tensile force. At the same time, the reduced diameter portion of the page is rapidly cooled and subjected to heat treatment such as quenching and heat refining, and the non-reduced diameter portions located at both ends of the small diameter portion of the page are processed with serrations or other edge finishing for attachment. This is a method of manufacturing a metal torsion bar.

An embodiment of the present invention will be described below with reference to the drawings. First, the apparatus used in the method of the present invention will be schematically explained based on Figure 3. In the figure, numeral 1 is a rod-shaped material made of gold figurines, for example, a round rod made of ferrous metal such as spring steel. This material 1 may be either a solid material or a hollow material, and may be a regular length material or a continuous material.

A tensioning device 5a is provided in the middle of the material 1.

5b are provided spaced apart from each other in the length direction of the material 1. These tensioning devices 5a and 5b can be attached to and removed from the material 1, respectively, and can be moved in the length direction of the material 1 by a drive mechanism (not shown). These drive mechanisms, tension devices 5a, 5b, etc. constitute a tension device system.

Further, a heating coil 6 and a cooling nozzle 7 are provided at positions close to each other between the tension devices 5g and 5b. The heating coil 6 is connected to a high-frequency induction heating power source 8 to constitute a heating system, so that the entire circumference of the surface of the material 1 can be uniformly heated by high-frequency induction.

On the other hand, the cooling nozzle 7 is, for example, a cryogenic air generator 1.
Material 1 is made by blowing the low-temperature air generated in 0 onto material 1.
The amount of ejected air, etc. is adjusted by a flow rate control valve 11, so that the material Ik can be cooled at a desired cooling rate and temperature.
2 is a compressed air supply source such as a compressor, and these compressed air supply source 12, cooling nozzle 7, flow control valve 11,
The cooling system is composed of an ultra-low temperature air generator IO and the like. Note that instead of air, an inert gas or other gas pipe may be used for cooling.

Further, a non-contact thermometer 13, such as a radiation thermometer, is provided as a temperature measurement system for detecting the temperature of the material I.

A moving device 14 is provided for moving the thermometer 13, the heating tube 1/I/6, and the cooling nozzle 2 together in the length direction of the material 1.

The moving speed of the moving device 14, the cold air injection amount of the outlet flow rate control valve 11 of the high-frequency induction heating power source 8, the moving speed of the tensioning device 5a, etc. can be automatically controlled by a control device 15 using a computer. There is.

Next, a method of manufacturing a torsion bar using the above-mentioned apparatus will be explained.

First, after carrying the material 1 between the tensioning devices 5 & 5b, the material I
f: Sandwiched between tension devices 5a and 5b. Next, the moving device 14
0 to the heating start point of the material 1, that is, one end 1d of the part that will become the torsion bar.Then, the high-frequency induction heating power source 8 is operated and the heating coil 6 heats the material to a predetermined temperature.When the predetermined heating temperature is reached, the moving device 14 toward the other end 1e in the direction F shown in the figure, and
The cooling nozzle 7 is rapidly cooled by injecting cold air, and the end portion 1a is thermally refined to improve mechanical properties.

In this case, the moving device 1
4 and the amount of cold air injected by the flow rate control valve 11 are controlled, and the hardness of the product end 1a is tempered to about HRC 16 to 40, for example.

When the heating coil 6 reaches the part where the diameter of the material 1 is to be reduced, that is, the part that becomes the twisted part of the torsion bar, the heating coil 6 reaches the part where the diameter of the material 1 is to be reduced, that is, the part that becomes the twisted part of the torsion bar. The material 1 is heated to a predetermined heating temperature while changing the output and monitoring the heating temperature on the non-contact temperature side I3.

The heating temperature at this time is usually in the temperature range where the elongation is greatest (for iron-based metals, just below point A3, around 750° C.).

Then, the tensioning device 5a is driven to pull the material 1 as indicated by the arrow F in the figure.
The material 1 is stretched in two directions to cause the material 1 to make a constriction sound while being reduced in diameter without causing breakage, and the reduced diameter portion is rapidly cooled by a cooling nozzle 7 to successively perform heating, tension, and cooling.

At this time, the moving speed of the tensioning device 5a and the moving device 14 are controlled by the control device 15 as appropriate in accordance with the desired product shape. In addition, a predetermined thermal refining or quenching hardness can be obtained. As such, the amount of cold air injection is controlled by the flow rate control valve 11.

By the above-described heating and tensioning and rapid cooling, the small diameter portion 1b which becomes the twisted portion of the torsion bar is formed, and the interface of this small diameter portion 1b is simultaneously heat-treated. The hardness of the small diameter portion 1b after heat treatment is preferably HRC 16 to 60, but depending on the case, it may be hardened in the heat-treated state without being hardened, and cooling control may be performed according to the specifications of the product. After completing the processing and heat treatment of the small diameter portion 1b as described above, the output of the high-frequency induction heating power source 8 is changed and the heating and cooling are controlled in the same way as the one end 1& with 1cf removed from the other end. Thermal refining is performed by

The torsion bar product, which has been given the desired shape and heat-treated through the above series of operations, is cut into a predetermined product length, and further cut into both ends 1a.

In other words, the IC, that is, the non-reduced diameter part, is subjected to serration processing as shown in Figure 4, non-circular processing such as hexagonal cross section, etc., in short, end processing for attaching the torsion bar. Some general polishing is performed as necessary.

As is clear from the above explanation, according to the above method, even a torsion bar with a large rate of change in cross-sectional area in the longitudinal direction can be shaped into the desired shape in a short time by controlling the occurrence of constriction through rapid heating and tensioning of the material and local cooling. can be obtained.

As an example, the dimensions of a power steering torsion bar are: the outside diameter of the large diameter part is 9.861uIL, and the outside diameter of the small diameter part is 6.
．． 75m, the length of the small diameter part is 1QQNL, the area reduction rate is 53cm, and as other dimension examples, the outer diameter of the large diameter part is 10,31cm.
1Ll, outer diameter of small diameter part 4.7 to 1. J-diameter length is 7
5. Although the area reduction rate is 78.6% and the cross-sectional area change rate is short and large, according to the above method, the machining time is only about 30 seconds at maximum. Compared to the conventional turning process, which required an average of about 3 minutes to obtain a similar shape, the working time can be significantly reduced.

According to the method of this embodiment, there is almost no waste of material due to cutting compared to conventional turning processing, and the material yield can be improved from 70 to 80% in the past to nearly 100%.

Moreover, according to the method of this embodiment, as illustrated in FIG. 5, diameter reduction processing by high-frequency heating tensioning and heat treatment can be performed simultaneously in one step 1θ, so it is possible to perform heat treatment, especially for torsion bars for power steering. It is extremely effective in simplifying the process for products that have small diameter parts and large diameter parts where heat treatment methods such as induction hardening and heat treatment zone lengths vary.

Furthermore, according to the method of the above embodiment, pattern hardening by high-frequency induction heating is also possible as shown in FIGS. 6 and 7, and the strength of the spring material used under torsional stress can be effectively increased. Therefore, a high-strength torsion bar that can withstand practical use can be obtained using relatively easily available and inexpensive materials without using special high-quality materials.

In carrying out the method of the present invention, for example, as illustrated in FIG. The material 1 may be heated and stretched. That is, since the non-diameter-reduced portion is covered by the heat shielding member 16 and the heat generated by the heating coil 6 is suppressed, the temperature of the non-diameter-reduced portion can be suppressed to a much lower temperature than the portion scheduled for diameter reduction.

Therefore, it is possible to prevent problems such as part of the non-reduced diameter part being stretched and unnecessarily reduced in diameter during heating tensioning.
It is effective in obtaining the desired product shape. The heat shielding member 16 may be provided integrally with the gripping portions of the tension devices 5a and 5b, or may be provided as a separate heat shielding member 16.
It may also be applied to the material 1.

As described above, the present invention is designed to completely form the small diameter part that becomes the torsion part of the torsion bar by heating and stretching the material, and to perform the desired heat treatment by rapidly cooling the part after diameter reduction. The material yield is greatly improved compared to machining using conventional methods, and the time required for machining can be significantly shortened, and consumable tools such as bits and the like can hardly be used.

In addition, heat treatment can be performed at the same time as heating and tensile processing of small diameter parts, so even if the heat treatment area length and heat treatment method change in the length direction of the material, such as torsion bars, diameter reduction of small diameter parts can be performed. At the same time, the heat treatment can be carried out in a short time with a simple process, and the torsion bar can be manufactured with higher productivity and at lower cost than in the past.

[Brief explanation of drawings]

171 is a side view showing a torsion bar product before cutting both ends, FIG. 2 is a process explanatory diagram showing an outline of the conventional manufacturing process, and FIG. 3 is a schematic diagram of an apparatus for carrying out the entire method of the present invention. FIG. 4 is a side view of a torsion bar with serrations applied to the end, FIG. 5 is a process explanatory diagram showing an outline of an embodiment of the method of the present invention, FIG. The figure is a diagram showing the relationship between hardening hardness and distance from the surface in the same pattern hardening, and Figure 8 is a cross-sectional view showing an example of a heat shielding member.01...Material, 1g, Ic...
・Both ends, 1b...small diameter part and twisted part), 5a, 5b
... Tension device, 6... Heating coil, 2... Cooling nozzle, 16... Heat tracing section vane.

Claims (2)

[Claims] (1) By fully heating the required part of a metal rod-shaped material and reducing the diameter by applying tensile force, a small diameter part that will become the torsion part of the torsion bar is formed, and by rapidly cooling this diameter reduced part, the diameter is reduced. A method of manufacturing a metal torsion bar, which comprises heat-treating the surface, and further processing the ends of the non-reduced diameter portions located at both ends of the small diameter portion for attachment. (2) The metal torsion bar according to claim (1), characterized in that a heat shielding member is provided on the outer periphery of the non-diameter-reduced portion adjacent to the portion to be reduced in diameter, and the heating tension is performed. Manufacturing method 0