KR101677078B1

KR101677078B1 - Worm wheel boss making method for steering unit

Info

Publication number: KR101677078B1
Application number: KR1020150078480A
Authority: KR
Inventors: 박태섭
Original assignee: 광성강관공업 주식회사
Priority date: 2015-06-03
Filing date: 2015-06-03
Publication date: 2016-11-17

Abstract

The present invention relates to a manufacturing method of worm wheel bosses for a steering unit and, more specifically, to a method for manufacturing worm wheels forming a steering unit. The method comprises the steps of: preparing a billet or pipe components which are materials to manufacture a wheel boss which is the core of the worm wheel; firstly processing the external circumference roughly and the internal circumference of the wheel boss at the same time by inputting the prepared billet or pipe components into a drawer; secondly processing the outer circumference by re-drawing after the first processing process is completed; and polishing the surface to form the surface of tooth on the outer circumference of the wheel boss by final drawing after the secondary processing is completed.

Description

TECHNICAL FIELD [0001] The present invention relates to a worm wheel boss for a steering apparatus,

The present invention relates to a method of manufacturing a worm wheel boss for a steering apparatus, and more particularly, to a method of manufacturing a worm wheel boss for a steering apparatus that secures a tooth strength and an adhesion force equal to or greater than those without hoisting.

Recent developments of vehicle steering systems have been research and development in pursuit of safety along with safety such as steering stability and smooth and comfortable steering.

In accordance with the development trend, a variety of power assisted steering devices such as a hydraulic type or an electric type have been developed as a method for improving the steering feeling of a driver. Because of the advantage that the electric type is lighter, the energy consumption is less and the fuel efficiency is improved, The use of auxiliary steering devices is increasing.

The electric power assist steering system provides a light and comfortable steering condition at low speeds by assisting the steering torque of the driver by driving the motor in the electronic control device according to the driving condition of the vehicle sensed by the vehicle speed sensor and the steering torque sensor, It provides a heavy and stable steering condition during operation and provides a steering performance that enables the driver to maintain an optimum steering feeling by coping with sudden emergency situations so as to enable rapid steering operation.

Prior art related to such a steering apparatus is disclosed in Korean Patent No. 0241710 (November 11, 1999), Korean Patent No. 0695440 (2007.03.08), Publication No. 2005-0090364 (September 13, 2005) 0082765 (September 12, 2008) and Published Patent Application No. 2014-0060109 (May 19, 2014).

1, the steering device composed of the worm 10 and the worm wheel 20 is used to adjust the traveling direction when operating the steering wheel of a vehicle or the like.

At this time, because the worm wheel 20 is directly processed with metal, the wheel boss 22 is processed into a metal at present due to cost and productivity problems, The worm gear 24 having a tooth profile is injected and integrated by a plastic injection molding method to reduce the cost and increase the productivity.

In this case, the wheel boss 22 and the worm gear 24 integrally molded on the outer circumferential surface of the wheel boss 22 should not slip from each other. If the slip occurs, the steering is not performed and the steering failure causes a serious accident.

Therefore, in the prior art, the outer circumferential surface of the wheel boss 22 is subjected to hoisting before injecting the worm gear 24.

That is, the billet is cut to a proper length and chamfered at both ends, and then the inner diameter and outer diameter are processed. In particular, when the outer diameter is large, the worm gear 24 injected by the hobbing process should not slip.

However, this method has a serious problem that the material is wasted so much, the machining time is long due to the hobbing, and the slip occurs due to the failure when the hobbing is wrong. Particularly, NC machining is required for forming the inner diameter, and hobbing machining requires a very large amount of cost because there is a dedicated equipment.

Alternatively, the billet may be cut to an appropriate length, chamfered and then subjected to cold extrusion to process the inner and outer diameters into predetermined dimensions, and the outer peripheral surface may also be subjected to hoisting processing.

However, this method is also difficult to lower the manufacturing cost because the material has a large loss and an excessive mold cost is entered.

Further, as shown in Fig. 2, machining of the grooved surface 26 is required to be performed by press-fitting with a high-pressure hydraulic or hob-shaped punch made of hard steel, so that a long working time is required. , The defect rate is very high, which is a very important problem that leads to poor steering, and therefore improvement is required.

The present invention has been made in view of the above-mentioned problems in the prior art, and it is an object of the present invention to provide a worm wheel which can easily and quickly produce a large amount of worm wheels without hobbing, The present invention provides a method of manufacturing a worm wheel boss for a steering apparatus that increases the strength of the steering wheel and increases the strength of the steering wheel, thereby achieving a safe steering without a steering failure of the steering apparatus.

The present invention provides a method for manufacturing a worm wheel and a worm wheel constituting a steering apparatus, the method comprising: Preparing a billet or a pipe assembly as a material for manufacturing a wheel boss which is a core of the worm wheel; A primary machining step of forming the inner diameter of the wheel boss by injecting the prepared billet or pipe assembly into a drawer and shaping the outer diameter into a rough shape; A second machining step of once again machining the outer diameter once the first machining is completed; And a finishing step of finishing the second machining to form a predetermined tooth surface on the outer circumferential surface of the wheel boss upon completion of the secondary machining.

At this time, the primary processing step only processes up to 50% of the finished product; The secondary processing step only processes up to 75% of the finished product; The finishing step is also characterized by processing up to 100% of the final product.

In addition, the primary, secondary, and finishing steps are sequentially processed in succession to enhance the treatment efficiency.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to secure equal strength and adhesive force equal to or greater than those without hoisting.

In addition, there is an advantage that manufacturing is easy, processing is easy, and manufacturing cost is reduced.

FIG. 1 is a block diagram of a steering device including a general worm and a warm wheel.
2 is an exemplary view showing a manufacturing example of a warm wheel boss according to the prior art.
3 is an exemplary view of a worm wheel boss for a steering apparatus according to the present invention.
4 is a view showing an example of a manufacturing method of a worm wheel boss for a steering apparatus according to the present invention.
5 is a graph showing a result of tooth strength test of a conventional warm wheel boss.
FIG. 6 is a graph showing the tooth strength test results of the worm wheel boss according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Before describing the present invention, the following specific structural or functional descriptions are merely illustrative for the purpose of describing an embodiment according to the concept of the present invention, and embodiments according to the concept of the present invention may be embodied in various forms, And should not be construed as limited to the embodiments described herein.

In addition, since the embodiments according to the concept of the present invention can make various changes and have various forms, specific embodiments are illustrated in the drawings and described in detail herein. However, it should be understood that the embodiments according to the concept of the present invention are not intended to limit the present invention to specific modes of operation, but include all modifications, equivalents and alternatives falling within the spirit and scope of the present invention.

3, the worm wheel boss for a steering apparatus according to the present invention includes a boss main body 100 having an inner diameter and a tooth surface 200 formed along an outer peripheral surface of the boss main body 100. As shown in Fig.

That is, in the past, the tooth surface 200 was not a tooth surface 200, but in the present invention, the tooth surface 200 was differentiated from the conventional tooth surface 200, and the processability was improved.

However, the tooth surface 200 may vary slightly depending on the type of the vehicle, but the following conditions must be satisfied.

This is for the purpose of eliminating the slip property with the worm gear 24 (see FIG. 1) projected to the tooth surface 200, and if the tooth surface is out of the range described below, sufficient tooth strength, that is, torsional strength can not be ensured This is because the slip occurs and the steering failure is caused.

In addition, the boss main body 100 is formed by bending a billet in the longitudinal direction to form an inner diameter, and the primary processed body having an inner diameter is processed into a shape of Cold Drawn to simultaneously form the tooth surface 200 do.

This process has the advantage that it is not necessary to separately process the inner diameter, thereby reducing time and cost.

Further, since the tooth surface 200 is formed not of the freezing surface, it is not necessary to provide a separate hobbing facility, and no defective machining occurs. However, it may be a matter of securing a tooth strength equal to or greater than that of the tooth surface 200 formed of the tooth surface.

The present inventors have repeatedly carried out numerous studies and experiments due to such troubles, and as a result, it has been confirmed that a tooth strength equal to or higher than that of a frozen surface can be secured under certain conditions.

The condition of the tooth surface 200 is as follows.

As shown in FIG. 3, the pitch P of the tooth surface 200 should satisfy 4 1 mm.

If the pitch P is out of the range, the tooth strength is decreased and slip occurs.

The bone angle Ra of the tooth surface 200 should be maintained within a range of 70 占 N.

At this time, N is 40 °, and if it deviates from the range of the tread angle (Ra), the tread is generated and the tooth strength is decreased to cause slip.

Also, the curvature R of the tooth surface 200 should be maintained at 0.6 M, where M is 0.4. If the curvature R deviates from the tooth surface 200 in this case, Causing steering failure.

In addition, the knurling depth Nd of the tooth surface 200 should be maintained at 1 ± 0.05 mm. If the knurling depth is out of the range, the tooth strength is weak and slip occurs.

Here, since the above condition can not be solved by one drawing, it is possible to complete the elaborate dental surface 200 condition by successively drawing in a cold condition continuously in accordance with a predetermined condition.

Now, a manufacturing method according to the present invention will be described.

The present invention is produced by cold drawing.

Generally, the cold drawing method is not widely used for forming a tooth surface as in the present invention. This is because the tooth profile can not be precisely processed and the desired mechanical strength can not be secured without the accumulated technology of the die and drawing.

Therefore, most cold drawing methods are applied when making straight tube without shape.

However, in the present invention, a new attempt has been made to completely overturn such a concept, and as a result of the test after completion of the final product, the tooth strength (torsional strength) equal to or higher than that of the existing hobbing type can be secured.

That is, in the cold drawing method according to the present invention, as in the example of FIG. 4, a step of preparing a coarse product or a billet in which a coil is made into a pipe is first performed.

When the billet or pipe assembly is prepared, a primary machining step is performed in which the inner diameter of the wheel boss is machined and the outer diameter is machined by being inserted into the drawing machine.

The primary machining step is a step of molding an inner diameter of a specific shape and an outer diameter to be preliminarily prepared so as to have the above-mentioned tooth surface, and is a step of drawing to about 50% of the final product.

At this time, the configuration of the 50% flange surface of the final product, that is, the pitch, the bone angle, the knurling depth, the curvature, and the like are not precisely processed.

After the primary drawing of about 50% through the primary working step is completed, a secondary working step of finishing the outer diameter of the tooth surface to 75% of the finished product is carried out again.

Thereafter, when the secondary processing is completed, a finishing step of finely finishing the tooth surface up to 100% of the finished product is performed.

Here, the primary, secondary, and finishing steps must be sequentially processed in order to increase the processing efficiency by preventing the process from being interrupted.

Particularly, since the inner diameter machining is performed simultaneously with the first drawing, the conventional NC machining is not necessary, so the process can be saved, the cost can be reduced, and a separate hobbing facility can be omitted, .

In addition, in the case of optimizing the rough specifications to be inputted to reduce the drawing process, it is of course possible to form the final product by drawing three times in one drawing.

As a result of testing that the finished worm wheel boss is useful when the worm wheel is used as a wheel through such processing, it was sufficiently useful as shown in Figs. 5 and 6.

For example, Figs. 5 and 6 show results of testing the tooth strength (torsional strength) of each of the conventional wobbling type worm wheel and the tooth type worm wheel of the present invention by three samples each.

As shown in the graph, it can be seen that the tooth strength peak of the tooth type of the present invention exceeds the maximum of 600 N · m, compared with the conventional hobbing type.

On the other hand, in the case of the hobbing type, it can be confirmed that it is less than 600 Nm.

As a result of testing each of them without performing averaging of three, it was confirmed that all three of them resulted in such results. As a result, it was confirmed that the tooth type worm wheel of the present invention had better tooth strength than the conventional hobbing type Therefore, it is considered that the existing hobbing type can be replaced.

In addition, it is a matter of course that the molding step can be completed by the first machining when selecting the optimum shape of the billet or the coarse product.

100: Boss main body 200: Tooth

Claims

Preparing a worm and a worm wheel constituting a steering device, and preparing a billet or a pipe assembly as a material for manufacturing a wheel boss which is a core of the worm wheel when manufacturing the worm wheel; A primary machining step of forming the inner diameter of the wheel boss by injecting the prepared billet or pipe assembly into a drawer and shaping the outer diameter into a rough shape; A secondary machining step of once again machining the outer diameter once the primary shape forming is completed; And a finishing step of finishing the second machining to form a tooth surface defined on the outer circumferential surface of the wheel boss when the second machining is completed, the method comprising the steps of:
Said primary processing step molding to 50% of the final product; The secondary processing step forms only up to 75% of the finished product; The finishing step is performed until 100% of the final product,
The tooth surface formed through the above-described finishing step is processed to have a pitch of 3-5 mm, a bone angle of 30-110 °, a curvature of 0.2-1.0, and a knurling depth of 0.95-1.05 mm, thereby securing tooth strength and preventing slip occurrence Of the worm wheel boss for a steering system.

delete