JPH03189043A - Manufacture of torsion bar for power steering device - Google Patents

Abstract

PURPOSE:To simplify the working process and to reduce the working manhour by reducing a range to be worked of round bar steel to the finish diameter by cold working. CONSTITUTION:In a swaging machine, by drawing round bar steel 3, while stretching it in the left direction shown in the figure, an input axis side end part initial state A1 is formed. While further stretching it in the same direction, a torsion part initial state M1 is formed. Subsequently, by executing the drawing while stretching the steel 3 in the left direction, a torsion part second stage M2 is formed. Next, while repeating a pushing-in operation and a stretching operation of the steel 3 against the working machine, a torsion part M is fin ished. In the end, by executing the drawing, while pushing the steel into the working machine, an input axis side connecting end part A is finished. In the same way, by executing the drawing, while stretching the steel 3, an output axis side connecting end part B is finished.

Description

Detailed Description of the Invention The present invention relates to a method of manufacturing a torsion bar for a power steering device, and more particularly, to a method of manufacturing a torsion bar from a round steel bar.

[Prior Art] Traditionally, in power steering systems for vehicles, rotary valves are manufactured by interposing a torsion bar between a power shaft and an output shaft, and slidingly fitting a valve sleeve around the outer periphery of the input shaft. It is known that the formation of

The torsion bar used here is an important component that determines the properties of the companion power steering system, and requires sufficient strength and durability.

Due to these requirements for strength and durability, the twisted part of the torsion bar must have a certain hardness and surface roughness, and it also needs to be integrally formed with a special shape that is thin in the center and thick at both ends. The manufacturing method takes the following steps: First, a round steel bar is cut over a predetermined range to form a twisted part in the center, then heat treated to ensure a predetermined hardness, and then The manufacturing method used was to polish the cut portion to ensure a predetermined surface roughness.

[Problem to be solved by the invention] However, cutting requires an extremely large number of man-hours, and heat treatment and polishing also require a considerable number of man-hours, so this conventional manufacturing method requires a large number of steps and processing man-hours. There is the problem of high costs. Therefore, if you try to at least reduce the number of processes, for example, eliminate the polishing process,
The accuracy of the cutting process had to be increased according to the required surface roughness, which resulted in an increase in man-hours.Also, if a steel material with low hardness was used to make the cutting process easier, the lack of strength became significant. There was a problem in that the heat treatment process became complicated accordingly.

A method for manufacturing a torsion bar for a power steering device according to the present invention (1) Aiming to solve the above-mentioned problems, satisfy durability, reduce the number of processing steps and reduce the number of processing steps, and at the same time simplify the final tempering. The aim is also to achieve this goal.

Composition [Means for Solving the Problem] A method for manufacturing a torsion bar for a power steering device according to the present invention (by connecting an input shaft and an output shaft of a power steering device, In the method for manufacturing a torsion bar for a power steering device, the torsion bar for a power steering device is formed from a round steel bar, the torsion bar having a small-diameter twisted portion adjusted to have a surface roughness as described above, and large-diameter connecting ends at both ends of the twisted portion. The round steel bar has a diameter greater than or equal to the finished diameter of the connection end before processing, and the round shape is determined based on the amount of steel in the part determined from the finished length and finished diameter of the twisted portion and the diameter before processing. The method is characterized in that the dimensions of the round steel bar to be machined are determined, and the range of the round steel bar to be machined is narrowed down to the finished diameter by cold working.

[Function] In the method for manufacturing a torsion bar for a power steering device of the present invention (by cold working a round steel bar having a diameter larger than the finished diameter of the connection end of the front torsion bar, a predetermined finished length and A twisted part with a finished diameter is formed. Since this process is based on cold drawing, the surface of the twisted part is processed smoothly and the hardness of the part increases due to work hardening. As a result, Parts with special shapes can be easily processed, the requirements for surface roughness can be met, and the final thermal refining can be simplified due to the increase in hardness.

[Example] Next, embodiments embodying the present invention will be described in detail.

In this example (as shown in FIG. 1 above), the diameter dM=5.
Foreman length LM = 69.5 strokes (parallel length LMP = 62
．． 2 mm) twisted part M and diameter dA = 8.58 ring
A torsion bar 1 having an input shaft side connecting end A with a length LA = 38.0 mm and an output shaft side connecting end B with a diameter dB = 9.51 and a ring length LB = 23.0 mm is made of structural carbon. Steel SCM435. Special alloy steel (non-tempered steel) and spring steel 5U
A round steel bar manufactured by swaging a round steel bar made of P9 (Yo). From the finished dimensions of the torsion bar and the gripping allowance during processing, the diameter dO is as shown in Figure 2 (A). :9.7-length LO=201°5rrITl.

This round steel bar material is set in a swaging machine, and
As shown in Figures (B) to (E), the cold drawing process is performed in four stages, and the swaging machine is equipped with a die made of RTWC alloy and an adjustment member for adjusting the interval between the dies. By operating this adjusting member according to the cutting program, it is possible to change the die interval and continuously perform drawing to different diameters.

The four-stage processing process will be explained.

[First stage: Fig. 1 (B)] First, the die interval of the swaging machine is determined by the processing diameter d A
! = 8-8 mm, and then process the first position (corresponding to the starting position of the input shaft side connection end A) x 1 at a predetermined distance from the chuck side end 3a of the round steel bar 3. Insert it so that it is located in the die part of the machine. Next, the round steel bar 3 is drawn to the second position x 2 while being pulled to the left in the figure at a predetermined speed so that the diameter dA1=8. 8rrgn
After machining, an initial state A1 of the input shaft side end with length LA1=35, 5 mm is formed.

Furthermore, the die interval was adjusted to the machining diameter dM1=8. After adjusting the spacing to correspond to 3mm, pull in the same direction and process the embossment up to the 3rd position x 3 to make the diameter dM1 = 8. Length 1M1 = 30 on 3 sides. 5rrrn twisted part initial state Ml
form.

[Second stage: Fig. 1 (C)] Next, the second position x 2 is adjusted to the die position, and the die interval is set to machining diameter dM2 = 6. After adjusting the spacing to correspond to 8rrrn, the round steel bar 3 is drawn to the third position x 3 while pulling it toward the left in the figure, and the diameter dM2=6.
A second stage M2 of twisted portion is formed with a length of 8 mm and a length of 1M2:=44.2rrrn.

[Third stage: Figure 1 (D)] Next, the die spacing is adjusted to the machining diameter dM = 5. After adjusting the spacing to correspond to 3nn+, the round steel bar 3 is repeatedly pushed and pulled against the processing machine and drawn within the range of 2nd position x 3 to 3rd position x 3 to obtain a diameter dM.
: = 5.3nvn, length LM = 69, Finish the twisted part M of 5rrrn.

Fourth step: Figure 1 (E) Finally, after aligning the second position x 2 of the round steel bar 3 with the die and adjusting the die interval to the interval corresponding to the machining diameter dA = 8°58rrrn, While pushing the round steel bar 3 into the processing machine, the round steel bar 3 is processed to the first position x 1 to finish the input shaft side connecting end A having a diameter dA = 8.58 nvn and a length LA = 38.0 rm+.

Similarly, after aligning the third position x 2 of the round steel bar 3 with the die and adjusting the die interval to the interval corresponding to the machining diameter dB = 9.51■, the round steel bar 3 is placed on the processing machine. While pulling it, make a pattern to the 4th position x 4 and make the diameter dB.
Finish the output shaft side connection end B with =9.51mm and length LB =23.0rITrl.

In this example, the above four-step process was executed in a required time of 1 minute and 44 seconds according to a pre-installed cannibal program.

Regarding the torsion bar 1 manufactured in this way, the hardness of the twisted part M and the input shaft side connection end A, and the blank hardness were measured. rl inner position P2.1/4
Regarding the diameter position P3 and center position P4, the surface position P5 and center position P6 of the input shaft side connection end A, and the surface position P7 and center position P8 of the part that was not drawn for blank hardness. Tests were conducted. However, some samples have not yet been measured.

The measurement results are shown in Table 1.

Table 1 Here, sample N11l, 4 is structural carbon steel SCM4
Sample N112.35 (HRC20) was used without heat refining. 3 is also structural carbon steel SCM43
5 is heat-treated and tempered to a soft HRCI5 Rockwell hardness and a slightly hard Rockwell hardness 1-IRC29. Similarly, sample N
et5. 6F Shows the measurement results for non-heat-refined special alloy steel and spring steel 5UP9, which was subjected to material heat-refining, respectively.

For each sample, a significant increase in hardness was confirmed at the twisted part M. In particular, sample Nα6 exceeded 1. The hardness at the center position P4 of the twisted part M increased to Vickers hardness HV354. This value is the Rockwell hardness. When converted to , it is approximately H
It becomes RC37. Also, in sample Nα3, the Vickers hardness is HV at the 0.05rrrn internal position P2 of the twisted portion M.
350, that is, the hardness was approximately HRC37, similar to sample floor 6.

Sample NQ5. No. 6 almost satisfies the hardness conditions required for a torsion bar for a power steering device. Also,
For other materials, the hardness condition can be satisfied by further applying some heat refining, and it is also possible to eliminate heat refining by further limiting the usage conditions.

In addition, when the blank hardness was HRC20 or higher (Friend), the Rockwell hardness value increased by about 5 to 7 due to swaging.

Furthermore, for sample floor 2, the hardness of the torsion part increased significantly due to swaging to about HRC31 in Rockwell hardness conversion, and the rate of increase was the largest.
This sample level 2 (the hardness of the material itself has been lowered through heat refining, and the result is that the softness of the round steel bar makes it easier to process, and the amount and rate of increase in hardness is large. became.

Regarding the spring steel 5UP9, three similar pieces were further manufactured and the surface roughness of the twisted portion was measured.

Surface roughness (maximum height Rmax = 1.4~2.2
μm, center average roughness Ra = 0.2 μm, which satisfies the conditions required for a torsion bar as it is.

As explained above, according to this example, a satisfactory surface roughness can be obtained as is, and a satisfactory hardness can be obtained with simple heat treatment. At N113.6 (HRC29 or higher), the surface roughness and hardness are both satisfactory.As a result, there is no need for a polishing process, and thermal refining can be simplified and, in some cases, omitted. We were able to significantly reduce the number of man-hours required to process the torsion bar.In addition, since the swaging process is applied, processing is easier than cutting, and from this point of view we were also able to reduce the number of man-hours. In the past, three processes had to be performed, from the cutting machine to the heat refining device and then to the polishing machine, which required many man-hours such as attaching and removing materials, making the work complicated. According to this embodiment, the number of steps can be reduced, and the processing is completed in a step of - especially at the sample level of 3°6, which is extremely simple.

Further, since work hardening can be expected, a soft material that is easy to process can be used as the material, and the patterning process itself can be made simple.

Furthermore, since torsion bars can be manufactured without removing material from the raw material, yields are significantly improved.

In addition, in this example, torsion bars were manufactured for three types of steel materials, and for approximately four types of blank hardness conditions, and the results of measuring the hardness etc. were shown.
Not limited to these, various other steel materials can be used.

Although the present invention has been described in detail above, the present invention is not limited thereto, and various embodiments can be adopted without departing from the gist thereof.

For example (not limited to swaging), it is also possible to apply processing methods in the form of prestige, such as cold drawing accompanied by work hardening.

In addition, various diameters can be selected as long as the diameter of the round steel bar material is larger than the largest diameter part and within the capabilities of the processing equipment.

As explained above, according to the present invention, it is possible to easily manufacture a torsion bar having a torsion portion adjusted to the surface roughness required for the durability of a power steering device, and to reduce the number of processing steps. Significant savings can be made.

In addition, since the round steel bar material is cold-worked, the hardness of the twisted portion increases due to work hardening, and the refining to the hardness required from the viewpoint of strength can be simplified.

Furthermore, since this work hardening can be expected, the blank hardness of the round steel bar material that is the raw material can be kept small, and the cold working itself can be simplified.

In this way, the application of cold drawing (in the manufacture of torsion bars for power steering systems, where surface roughness is required for surface durability, it has a particularly large effect and effect, and simplifies the processing process. It is possible to reduce the number of processing steps significantly.

[Brief Description of the Drawings] Figure 1 is an explanatory diagram showing the shape and hardness measurement position of the torsion bar manufactured in the example after swaging, and Figure 2 (
A) to (E) are explanatory diagrams showing the four stages of processing states. 1... Torsion bar 3... Round steel bar M...
Twisted part A: Output shaft side connection end Meter: Input shaft side connection end

Claims (1)

[Scope of Claims] 1. A twisted portion with a small diameter that connects the input shaft and output shaft of a power steering device and is adjusted to a surface roughness required for the durability of the power steering device, and both ends of the twisted portion. In the method for manufacturing a torsion bar for a power steering device, the torsion bar is formed from a round steel bar, the round steel bar having a diameter larger than the finished diameter of the connecting end before processing. Then, the range to be processed of the round steel bar is determined based on the amount of steel in the part determined from the finished length and finished diameter of the twisted part and the diameter before processing, and the range to be processed of the round steel bar is determined. A method for manufacturing a torsion bar for a power steering device, characterized in that the torsion bar is narrowed to the finished diameter by cold working.