JP2003311364A - Shaft for power steering sensor, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor shaft manufacturing method for reducing the possibility of breakage of a punch and a die without increasing a forming load, and performing the forming at low cost, with high accuracy and by the same process. <P>SOLUTION: Flow in the radial direction, i.e., radius expansion (upset) is caused in a material with a punch 52 in the vicinity of the upper end of a small diameter part d1, and the expanded material is allowed to bite an inwardly projecting bar 542 of a stock hole 541. The material advanced into a drawing hole 232 is formed into a small diameter part D2 of a sensor shaft, and the expanded material is formed into a large diameter part D1 and a stop groove G1 of the sensor shaft. The tip shape of the punch 52 is transferred to a blind hole H. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a sensor shaft used mainly in a sensor section of an electric power steering system of an automobile.

[0002]

2. Description of the Related Art In an electric power steering system, the rotation of a steering wheel operated by a driver is transmitted to one end of a torsion bar, and the rotation of the steering wheel is detected by the torsion of the torsion bar. The other end of the torsion bar is connected to the sensor shaft. The rotation of the sensor shaft or another shaft mechanically coupled thereto is further connected to a mechanism for turning the front wheels.

The sensor shaft, the other shaft, or the front wheel side is structured to additionally transmit the rotational force of the assist motor. The torsion of the torsion bar is always detected, and the assist motor is controlled so as to rotate in the direction in which the torsion of the torsion bar is canceled. This allows the driver to operate the steering wheel with very light force. A detailed description of the structure and operation of the electric power steering apparatus itself is omitted because it is not necessary for explaining the manufacturing method of the present invention.

The sensor shaft has a non-uniform sectional shape in the axial direction. Conventionally, when manufacturing such a deformed part, generally, a machining method has been mainly used. The manufacturing process is roughly as follows. First, a cylindrical round bar is cut into a required length. The outer diameter of the cut bar is turned. The irregular shape blind hole and the cylindrical outer peripheral groove are processed by milling or the like. After that, heat treatment is performed on a portion requiring hardness.

However, when the machining method is used, the processing time becomes very long. An expensive machine such as a machining center must be used as the processing machine. Cutting tool life is short. The surface roughness after cutting is poor. Since heat treatment must be performed after machining, the cost becomes high. Various problems such as occur.

On the other hand, when a part having such an irregular blind hole is to be manufactured by plastic working (cold forging), a punch having an irregular convex ridge on a cylindrical material is used. It is necessary to push in to perform molding.

Generally, when forming a modified blind hole having a depth of about 10 mm, it is general to set the cross-section reduction rate to about 45%. This is for the following reason. When the difference between the maximum diameter of the odd-shaped blind hole and the outer diameter of that portion is small, setting the outer dimension of the material before forging to a dimension close to the outer diameter of the product increases the cross-section reduction rate during molding. The cross-section reduction rate is almost proportional to the forming load, and as a result, the forming load becomes too high, which may damage the punch and / or the die.

In consideration of formability, tool life, etc., when a large area reduction rate is involved, it is realistic to adopt the plastic working method (cold forging method) for such a product. Not done.

Further, if the outer diameter of the material is increased to reduce the molding load and the reduction rate of the cross-section is reduced, it is not economical because many parts must be removed by subsequent cutting.

Further, when the outer peripheral groove along the axial direction is formed in the cylindrical portion, the above-mentioned problem occurs in machining, and
When trying to perform blind hole forming and outer peripheral groove forming in the same process by plastic working, if the cross-section reduction rate during processing is set to a value suitable for blind hole forming, in many cases the material outer diameter will be the product outer diameter. As a result, the peripheral groove must be formed deeper than necessary, resulting in a large load on the die. On the contrary, if the cross-section reduction rate is suitable for forming the outer peripheral groove, the outer diameter of the material will be close to the outer diameter of the product.
The cross-section reduction rate when focusing on blind hole forming becomes large, and as a result, there is a high possibility that the punch will be overloaded and damaged. Therefore, each of them is molded in a separate process.

In the case of separate processes, the accuracy of the shape of the irregular blind hole and the coaxiality of the inner and outer diameters due to the deviation of the posture during conveyance of the work, the deformation of the irregular blind hole shape due to the separation of the molding process, the phase shift, etc. New problems such as the accuracy of the phase of the inner and outer diameters will occur, and a satisfactory product cannot be obtained. Further, when the outer peripheral groove is only halfway in the axial direction, there is a problem that it cannot be processed by a normal extrusion molding method.

[0012]

SUMMARY OF THE INVENTION In view of the above problems in manufacturing, the present invention reduces the risk of punch and die damage without increasing the molding load, and also has low cost, high accuracy, and the same process. It is an object of the present invention to provide a method for manufacturing a sensor shaft that can perform this molding.

[0013]

The above-mentioned problems can be solved by the following means. That is, the solution means of the first invention is a manufacturing method in which a sensor shaft is molded from one material by cold forging, and the material is connected to the large-diameter cylindrical material part and the large-diameter cylindrical material part. It is made of a stepped round bar with a small diameter cylindrical material part whose outer diameter is smaller than the diameter, and a large diameter first material hole and a drawing die with a drawing hole connected to it, and the same diameter as the above first material hole. An upper die having a second material hole which is a concentric second material hole and in which a plurality of ridges along the axial direction of the second material hole are formed toward the inside,
Using a punch having a modified cross section at the tip, inserting the large-diameter cylindrical material portion of the material into the first material hole, and pressing the punch with the drawing die and the upper die in close contact with each other. Thus, the small-diameter cylindrical material portion of the material is upset in the radial direction, and the large-diameter cylindrical material portion is caused to flow into the throttle hole, whereby the large-diameter portion of the sensor shaft and the axial groove on the outer periphery thereof and the end surface thereof. The method of manufacturing a shaft for a sensor of a power steering, comprising forming a blind hole and a small-diameter portion having a different shape.

According to a second aspect of the present invention, in the method of manufacturing a sensor shaft according to the first aspect of the invention, a small diameter of the sensor shaft is provided by giving the throttle hole a complementary shape corresponding to a pinion. A pinion is molded in the portion, which is a method of manufacturing a shaft for a power steering sensor.

According to a third aspect of the present invention, in the method for manufacturing a sensor shaft according to the first or second aspect of the invention, a further deformed portion is extendedly formed at the tip of the punch. A torsion bar hole is formed by the deformed portion, which is a method for manufacturing a sensor shaft for a power steering.

A fourth aspect of the invention is to provide a stepped round bar material having a large-diameter cylindrical material part and a small-diameter cylindrical material part connected to the large-diameter cylindrical material part and having an outer diameter smaller than this. And a drawing die having a large diameter first material hole and a drawing hole connected to the first material hole, and a second material hole having the same diameter and concentricity as the first material hole, and in the axial direction of the second material hole. A large-diameter cylindrical material portion of the material is used as the first material by using an upper die having a second material hole in which a plurality of ridges are formed inward and a punch having a modified cross section at the tip. Inserted in a hole, in a state where the drawing die and the upper die are in close contact with each other, by pushing the punch, the small diameter cylindrical material part of the material is set up in the radial direction, and the large diameter cylindrical material part is By making it flow in the throttle hole, the large diameter part and its outer circumference can be axially moved. And profile of the blind hole in the end face, and the small diameter portion is a sensor shaft of the power steering, characterized in that it has been formed.

According to a fifth aspect of the invention, in the sensor shaft according to the fourth aspect, the pinion is provided in the small diameter portion of the sensor shaft by providing the throttle hole with a complementary shape corresponding to the pinion. Is a molded shaft for a power steering sensor.

According to a sixth aspect of the present invention, in the sensor shaft according to the fourth or fifth aspect of the invention, the bottom portion of the irregular blind hole is further formed by another irregular portion extended from the tip of the punch. A shaft for a power steering sensor, characterized in that a torsion bar hole is formed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view for explaining the shapes of the sensor shaft and its material. Figure 1A
Shows an example of the shape of the material W used in the present invention,
1B and 1C show examples of different types of sensor shafts SS1 and SS2 processed according to the present invention. FIG. 2 is a top view showing a shape of a sensor shaft (FIG. 1B) having a blind groove, as viewed from above the end portion.

The sensor shaft has a large-diameter portion D1 and a small-diameter portion D2, and the end of the large-diameter portion has a coaxial bottomed hole H.
A (blind hole) is bored, and a plurality of ridge portions R along the axial direction are formed inward on the inner surface of the cylinder of the bottomed hole. The ridge portion R functions as a stopper for preventing an excessive twist in the torsion bar. Although not shown in FIG. 1, a torsion bar hole HT (shown by a dotted line in FIG. 2) is formed in the bottom portion for inserting and crimping the end portion of the torsion bar. The torsion bar hole HT can be formed by drilling, but as will be shown later, according to the present invention, the torsion bar hole HT can be plastically formed simultaneously with the bottomed hole H.

On the outer side of the large diameter portion D1, a plurality of grooves G are provided along the axial direction in order to mount the torsion detecting cylindrical member of the torsion bar at an angle. As shown in FIG. 1B, this groove is a blind groove G that terminates halfway.
There is a case of 1 and a case of a through groove G2 passing through the entire length of the large diameter portion as shown in FIG. In any case, the mutual phases of these grooves G1 and G2 and the convex streak portion R of the bottomed hole H are designed to have a predetermined relationship.

FIG. 3 is a sectional view of the die set 1 for carrying out the manufacturing method of the present invention. The die set 1 is composed of two parts, a lower die set 2 and an upper die set 5. FIG. 4 is a perspective view of the lower die set 2, and is a diagram when the material W is loaded in the lower die set 2. Note that these show examples of sensor shafts having a blind groove G2.

The lower die set 2 comprises a lower plate 21, a die holder 22, and a drawing die 23. The cylindrical die holder 22 is attached to the lower plate 21, and the cylindrical spacer 24 and the plate 2 are provided in the holes thereof.
5, the cylindrical spacer 26, and the drawing die 23 are housed in order from the bottom.

The drawing die 23 is clamped and fixed to the die holder 22 by a drawing die tightening plate 27. The knockout pin 28 is provided so as to penetrate the spacer 24 and the plate 25, and can be pushed up from below.

The drawing die 23 is provided with a large-diameter material hole 231 and a drawing hole 232 connected thereunder. The counter punch 29 penetrates the spacer 26 and extends into the drawing hole 232 of the drawing die 23.
By pushing up 8, the counter punch 29 is pushed up.

The upper die set 5 includes an upper plate 51, a punch 52, an intermediate plate 53, and an upper die 54. The punch 52 whose tip is directed downward is the punch holder 55.
Is fixed to the upper plate 51.

The intermediate plate 53 is supported by a guide post 57 fixed to the upper plate 51, and is vertically movable with respect to the upper plate 51. Below the intermediate plate 53, an upper die 54 and an upper die clamping plate 58 for clamping and fixing the upper die 54 are provided. The gas cushion 59 functions to press the upper die 54 toward the drawing die 23 with a strong force via the intermediate plate 53 when the upper plate 51 descends. The spring 56 functions to return the intermediate plate 53 to the initial position when the upper plate 51 rises after the processing is completed.

The upper die 54 has a material hole 541 having the same diameter and the same diameter as the material hole 231 of the drawing die 23. At the time of processing, the tip of the punch 52 moves inside the material hole 541 to pressurize the material W contained in the lower material hole 231 to cause plastic flow.

A plurality of inward projections 542 are formed inwardly in the material hole 541. Further, a plurality of outwardly projecting ridges 521 are formed on the tip of the punch 52 toward the outside. Inward ridge 54 of material hole 541
2 has a shape complementary to the cross section of the blind groove G1 (FIGS. 1 and 2) of the sensor shaft SS1. Further, the shape between the outward protruding ridge 521 at the tip of the punch 52 and the adjacent outward protruding ridge 521 is made to correspond to the complementary shape of the protruding ridge R (FIGS. 1 and 2) of the sensor shaft SS1. ing.

The operation is as follows. 5 to 9 are explanatory views showing the process of cold forging (plastic working) according to the present embodiment. Here, the material W is the drawing die 23,
It is shown that the upper die 54 and the punch 52 deform.

The lower die set 2 is previously fixed at a predetermined position on a table of a press machine (not shown). As shown in the perspective view of FIG. 4, the material W is loaded into the material hole 231 (lower die set 2) of the drawing die 23. At this time,
The large diameter portion d2 of the material W is housed in the material hole 231.
The small diameter portion d1 is in a state of protruding from the upper portion of the drawing die 23.

The press machine is driven, and the upper die set 5 starts descending. As shown in FIG. 5, the small diameter portion d1 of the material W enters the material hole 541 of the upper die 54. The outer diameter of the small diameter portion d1 is preliminarily machined to a size that does not interfere with the inward protruding ridges 542 formed in the material hole 541 of the upper die 54. Therefore, the material W does not change at this point.

Eventually, as shown in FIG. 6, the upper die lower surface 5
43 and the upper surface of the drawing die 233 come into close contact with each other, and the upper die 54
Stops descending. At this time, the material hole 54 of the upper die 54
Since 1 and the material hole 231 of the drawing die 23 have the same diameter and concentricity, they form a continuous cylindrical surface. The upper die set 5 continues to descend while compressing the gas cushion 59 and the spring 56.
Therefore, the two surfaces (543, 233) are pressed against each other with a very strong force.

The upper die set 5 and the punch 52 fixed to the upper die set 5 continue to descend, and the tip of the punch 52 comes into contact with the material W to start plastically deforming the material W. FIG. 7 shows an initial state in which the material W is deformed. Material W
The large-diameter portion d2 is deformed together with the small-diameter portion d1. In the vicinity of the upper end of the small diameter portion d1, the punch 52 starts to flow in the material in the radial direction, that is, the diameter is expanded, and a part of the expanded diameter bites into the inward convex ridge 542. Note that this is not the only expansion (upset) that occurs, and at the same time, the material also flows upward.

Further, as the punch 52 continues to descend, the material of the material W continues to expand in the material hole 541 as it flows into the throttle hole 232 as shown in FIGS. In this way, the entire area of the inward ridge 542 is filled with the material. When the press machine stops descending, as shown in FIG. 9, each portion of the material that has entered the throttle hole 232 is formed into the small diameter portion D2 of the sensor shaft shown in FIG. Is formed in the large diameter portion D1 of the sensor shaft, and the blind groove G1 of the large diameter portion D1 is also formed by this. Through the above process, the punch 52
Is transferred to the material to form the bottomed hole H, the ridge R, and the bottom of the sensor shaft.

Then, the upper die set 5 is raised to the initial position. The counter punch 29 is pushed up by the knockout pin 28 when it is in the middle of rising or when it reaches the rising end, and the material that has become the sensor shaft is pushed upward by this pushing up and can be taken out. The material W taken out has a shape as shown in FIG. 1B.

The groove G is a blind groove G1 as described above.
In the case of (FIG. 1B), it is necessary to provide the end of the blind groove G1 (the end of the inward projection 542) on the side of the upper die 54, which catches the finished material from the die (die). You can easily pull it out.

The sensor shaft SS2 having the groove G through the groove G2 (FIG. 1C) can be molded by the same method. In this case, since there is no end like the blind groove G1, the inward convex ridge 542 is also provided in the material hole 231 on the drawing die 23 side so as to be continuous with the upper die 54. The completed material W can be extracted from the material hole 231 without being caught.

The sensor shaft used in the steering device may be integrated with a pinion (helical tooth) (in this case, called a pinion shaft). FIG. 10 shows an example of such a sensor shaft SS3 with a pinion. FIG. 10A is a top view of the sensor shaft SS3 viewed from the axial direction, and FIG. 10B is a side view thereof. Since this pinion P section is not twisted so much,
The pinion P can be simultaneously formed in the small diameter portion D2 by the method of the present invention. In this case, the throttle hole 232 is provided with a complementary shape corresponding to the pinion P. Material hole 23
Since the material flowing from 1 flows along the complementary shape, the small diameter portion D2 is formed as the pinion P. When the material is withdrawn after completion, it is lifted by the counter punch 29 to rotate and rise, and the material can be withdrawn without difficulty.

It is also possible to simultaneously form a torsion bar hole HT (shown by a dotted line in FIG. 2) at the bottom. in this case,
If a complementary shape portion corresponding to the torsion bar hole HT is extended and provided at the tip of the punch 52 and such a punch 52 is used, there is no particular problem. The torsion bar hole HT is shown in Fig. 2.
The shape does not have to be circular as shown by the dotted line, and can be any shape as long as the axial cross section does not change depending on the axial direction.

As shown in the above embodiment, the material W is provided with the small diameter portion d1 in advance, and the small diameter portion d1 is expanded by upsetting, so that the cross-section reduction rate is small. Therefore, product cracking and tool damage rarely occur. If the small diameter portion d1 of the material W is made too small, the large diameter portion d1
Since the step with 2 becomes a fold and remains on the surface after molding, it is preferable to limit the difference in diameter to about 8 to 12%. Further, the depth of the bottomed hole H is preferably set so as to be about half of the prescribed depth when the upsetting is completed.

Further, since upsetting is performed, it is possible to form a large number of axial grooves at arbitrary positions in the outer peripheral portion of the cylinder at the same time as forming the odd-shaped hole. It is possible to secure the accuracy of the quantity. The groove formed at this time may be either a through groove or a blind groove.

Further, since it is not necessary to make the outer diameter of the material larger than necessary in order to reduce the processing load, the outer diameter of the product after molding can be made close to the product shape, and the material and the cutting after molding can be performed. The time required for processing can be saved. No special heat treatment is required due to work hardening due to plastic working even in the part that comes into contact with the mating component that requires hardness as product performance.

[0044]

According to the present invention, when the irregular blind hole and the outer circumferential axial groove of the sensor shaft are formed, the two-stage cylindrical round bar material is used to perform upsetting and extrusion in the front-rear direction. A blind hole (bottomed hole) and a blind groove or through groove on the outer circumference can be formed at the same time. As a result, it is possible to mass-produce the high-precision sensor shaft at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining the shapes of a sensor shaft and its material. A shows an example of the shape of the material W used in the present invention, and B and C show examples of different types of sensor shafts SS1 and SS2.

FIG. 2 is a sensor shaft having a blind groove (FIG.
It is a top view which shows the shape when B) is seen from an edge upper part.

FIG. 3 is a die set 1 for carrying out the manufacturing method of the present invention.
FIG.

FIG. 4 is a perspective view of the lower die set 2 when a material W is loaded.

FIG. 5 is an explanatory diagram showing a process of cold forging (plastic working) according to the present embodiment.

FIG. 6 is an explanatory diagram showing a process of cold forging (plastic working) according to the present embodiment.

FIG. 7 is an explanatory diagram showing a process of cold forging (plastic working) of the present embodiment.

FIG. 8 is an explanatory diagram showing a process of cold forging (plastic working) according to the present embodiment.

FIG. 9 is an explanatory diagram showing a process of cold forging (plastic working) according to the present embodiment.

FIG. 10 is an explanatory diagram showing an example of a sensor shaft SS3 with a pinion.

[Explanation of symbols]

1 die set 2 Lower die set 21 Lower plate 22 Dice holder 23 Aperture dies 231 material hole 232 aperture 233 Top surface of the aperture die 24 spacer 25 plates 26 Spacer 27 Tightening plate 28 Knockout pin 29 Counter punch 5 Upper die set 51 Upper plate 52 punch 521 outward ridge 53 Intermediate plate 54 upper die 541 material hole 542 inward ridge 543 Upper die bottom surface 55 punch holder 56 spring 57 Guide post 58 Tightening plate 59 gas cushion D1 large diameter part (sensor shaft) D2 small diameter part (sensor shaft) d1 small diameter part (material) d2 Large diameter part (material) G groove G1 blind groove G2 through groove H Bottomed hole (blind hole) HT torsion bar hole P pinion R ridge Shaft for SS1, SS2, SS3 sensors W material

Claims (6)

[Claims] 1. A manufacturing method for forming a sensor shaft by cold forging from one material, comprising a large diameter cylindrical material part and a small diameter having an outer diameter smaller than that connected to the large diameter cylindrical material part. It is a stepped round bar material with a cylindrical material part, with a large diameter first material hole and a drawing die with a drawing hole connected to it, and a second material hole of the same diameter and concentric as the first material hole. There is used an upper die having a second material hole in which a plurality of ridges along the axial direction of the second material hole are formed inward, and a punch having a modified cross section at the tip. Insert the large diameter cylindrical material part of the material into the first material hole,
With the drawing die and the upper die in close contact with each other,
By pushing in the punch, the small-diameter cylindrical material part of the material is set up in the radial direction, and the large-diameter cylindrical material part is caused to flow into the throttle hole. A method of manufacturing a shaft for a sensor of a power steering, comprising forming a directional groove, an irregular blind hole in an end surface thereof, and a small diameter portion. 2. The method of manufacturing a sensor shaft according to claim 1, wherein the throttle hole is provided with a complementary shape corresponding to the pinion, so that the pinion is formed in the small diameter portion of the sensor shaft. A method for manufacturing a shaft for a power steering sensor, comprising: 3. The method of manufacturing a sensor shaft according to claim 1 or 2, wherein a further deformed portion is extendedly formed at the tip of the punch, and the torsion bar hole is formed by the deformed portion. A method for manufacturing a shaft for a sensor of a power steering, wherein the shaft is molded. 4. A stepped round bar material comprising a large-diameter cylindrical material part and a small-diameter cylindrical material part connected to the large-diameter cylindrical material part and having a smaller outer diameter than the large-diameter cylindrical material part. A drawing die having a hole and a drawing hole connected to the hole, and a second material hole having the same diameter and concentricity as the first material hole, and a plurality of ridges along the axial direction of the second material hole are provided inside. Using an upper die having a second material hole formed toward the side and a punch having a modified cross-section at the tip, insert a large-diameter cylindrical material part of the material into the first material hole,
With the drawing die and the upper die in close contact with each other,
By pushing in the punch, the small-diameter cylindrical material part of the material is set up in the radial direction, and the large-diameter cylindrical material part is caused to flow into the throttle hole, whereby the large-diameter part and the axial groove on the outer periphery thereof and the A shaft for a sensor of a power steering, which has a shape of a blind hole having a deformed end surface and a small diameter portion. 5. The sensor shaft according to claim 4, wherein a pinion is formed in the small diameter portion of the sensor shaft by giving the throttle hole a complementary shape corresponding to the pinion. A shaft for a power steering sensor, which is characterized by that. 6. The shaft for a sensor according to claim 4 or 5, wherein a torsion bar hole is further formed at the bottom of the irregular blind hole by another irregular portion extended from the tip of the punch. A shaft for a power steering sensor, which is characterized by being a thing.