JP5496926B2 - Rack bar and manufacturing method thereof - Google Patents

Description

  The present invention relates to a rack bar used in a steering apparatus for an automobile and a manufacturing method thereof.

  Conventionally, as this kind of rack bar, a round bar (columnar) material formed by cutting rack teeth by cutting has been used.

  However, in such a rack bar, if the tooth width is increased in order to increase the strength of the rack teeth, the material inevitably becomes larger and heavier. As a result, the fuel consumption of the automobile deteriorates, the amount of greenhouse gas emissions such as carbon dioxide increases, and the steering operation feeling deteriorates.

  Therefore, in recent years, a hollow rack bar in which rack teeth are formed on a cylindrical material has been proposed (see, for example, Patent Document 1).

JP 2006-224822 A

  However, in such a hollow rack bar, after a part of the cylindrical bar body (arc cross-section part) is plastically processed into a flat shape, rack teeth are formed at the part. Therefore, the rack teeth can only have a tooth width equal to or less than the length of the chord in which the reference circle (outer diameter circle) of the bar body is cut by the pitch plane. As a result, there is a problem that the root stress of the pinion shaft that meshes with the rack bar increases, and the durability of the pinion teeth decreases.

  In view of such circumstances, it is a first object of the present invention to provide a rack bar capable of reducing the weight and increasing the durability of pinion teeth. In addition, a second object of the present invention is to provide a method for manufacturing a rack bar capable of ensuring the thickness and width of the rack teeth in such a rack bar.

  In order to achieve this object, the present inventor has adopted a cylindrical material as a bar body in order to reduce the weight of the rack bar, and to increase the durability of the pinion teeth by increasing the tooth width of the rack teeth. Prior to forming the rack teeth on the top of the bar, the present invention was completed by paying attention to plastically deforming this part into a flat plate shape inflating outside the reference circle (outer diameter circle) of the bar body. It was.

That is, the invention according to claim 1 is used in a steering apparatus for an automobile, and has a cylindrical bar body having an outer diameter corresponding to a predetermined reference circle, and rack teeth formed along a pitch plane. The rack tooth has a tooth width that is a rack bar whose reference circle is wider than the length of a chord cut by the pitch plane, and a lower portion of a cylindrical material is supported by a lower mold, and the material In the state where the upper part of the material is supported by the upper die formed with a punch insertion opening having a width equal to or larger than the outer diameter of the material, and further, a mandrel is inserted into the hollow part of the material and is in contact with the lower part of the material. Instead of the corrugated plate forming punch, a corrugated plate forming step of plastically deforming the upper portion of the material into a corrugated plate shape by inserting a plate shaped punch into the punch insertion port and pressing the upper portion of the material. Flat plate forming punch A plate-shaped deformation step of plastically deforming the upper portion of the material into a flat plate shape by inserting it into the punch insertion slot and pressing the upper portion of the material; and a tooth forming step of forming rack teeth on the upper portion of the material. The rack bar is manufactured by the manufacturing method including .

  The invention according to claim 2 is characterized in that, in addition to the configuration according to claim 1, the tooth width of the rack tooth coincides with the outer diameter of the bar body.

  On the other hand, in the invention according to claim 3, the lower part of the cylindrical material is supported by the lower mold, and the upper part of the material is formed by an upper mold in which a punch insertion opening having a width larger than the outer diameter of the material is formed. In a state where a mandrel is inserted into the hollow portion of the material and is in contact with the lower portion of the material, a corrugated plate-shaped molding punch is inserted into the punch insertion port and the upper portion of the material is pressed. A corrugated plate deformation step of plastically deforming the upper part of the material into a corrugated plate, and a flat plate forming punch instead of the corrugated plate forming punch is inserted into the punch insertion port to press the upper part of the material Thus, the manufacturing method of the rack bar includes a flat plate deformation process in which the upper portion of the material is plastically deformed into a flat plate shape, and a tooth formation step of forming rack teeth on the upper portion of the material.

  Moreover, in addition to the structure of Claim 3, the invention of Claim 4 has the press surface in which the several convex part was formed as the said corrugated plate-shaped shaping | molding punch in the said corrugated plate-shaped deformation | transformation process. Is used, and a plurality of concave portions are formed on the upper portion of the material to be plastically deformed into a corrugated plate shape.

  Moreover, in addition to the structure of Claim 3 or 4, in invention of Claim 5, when the upper part of the said material is plastically deformed to flat form in the said flat deformation process, the thickness of the upper part of the said raw material Is made thicker than the thickness of the lower part of the material.

  According to a sixth aspect of the present invention, in addition to the configuration according to any of the third to fifth aspects, in the tooth forming step, a tooth forming punch is inserted into the punch insertion opening instead of the flat plate forming punch. Then, by pressing the upper part of the material, rack teeth are formed on the upper part of the material.

  In addition to the configuration according to any one of claims 3 to 6, the invention according to claim 7 is characterized in that the mandrel has a kamaboko-shaped reaction force portion that opposes a portion of the material forming the rack teeth. And a curved lower surface having a radius of curvature substantially equal to half of the inner diameter of the material, and a flat upper surface having a width slightly narrower than the inner diameter of the material.

According to the invention relating to the rack bar of the present invention, since the whole is hollow, the weight of the rack bar can be reduced as compared with the conventional product having a solid shape (round bar shape). In addition, since the tooth width of the rack teeth is wider than the length of the chord cut by the pitch plane of the bar body, the tooth root stress of the pinion shaft that meshes with this rack bar is reduced, and the durability of the pinion teeth is increased. be able to. In addition, when manufacturing this rack bar, since the upper part of the material is plastically deformed into a corrugated plate shape and then plastically deformed into a flat plate shape, rack teeth are formed at this portion. It is possible to ensure the thickness and tooth width of the tooth.

  According to the invention relating to the rack bar manufacturing method of the present invention, when the rack bar is manufactured, the upper portion of the material is plastically deformed into a corrugated plate shape and then plastically deformed into a flat plate shape, and then the rack bar is attached to this portion. Since the teeth are formed, the thickness and width of the rack teeth can be secured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a vehicle steering apparatus according to Embodiment 1 of the present invention. FIG. 3 is a perspective view showing a meshed state between a rack bar and a pinion shaft of the steering device according to the first embodiment. It is a figure which shows the rack bar which concerns on the same Embodiment 1, Comprising: (a) is a front view, (b) is a D arrow line view of (a), (c) is an expansion by the EE line of (a). It is sectional drawing. It is a figure which shows the raw material preparation process in the manufacturing method of the rack bar which concerns on the same Embodiment 1, Comprising: (a) is sectional drawing of a raw material, (b) is sectional drawing by the AA line of (a). It is sectional drawing of the raw material which shows the tooth | gear formation part formation process in the manufacturing method of the rack bar which concerns on the same Embodiment 1. FIG. It is detail drawing of the tooth | gear formation part formation process shown in FIG. 5, Comprising: (a) is sectional drawing of a raw material, (b) is sectional drawing by the BB line of (a) in a corrugated plate-shaped deformation | transformation process, (c). These are sectional drawings by the BB line of (a) in a flat deformation process. It is an expanded sectional view of the raw material shown in FIG. 6, Comprising: (a) is a figure corresponding to FIG.6 (b), (b) is a figure corresponding to FIG.6 (c). It is a figure which shows the tooth | gear formation process in the manufacturing method of the rack bar which concerns on the same Embodiment 1, Comprising: (a) is sectional drawing at the time of forming a rack tooth in a tooth | gear formation part, (b) is a 1st tooth formation process. Sectional drawing by CC line of (a) in (a), (c) is sectional drawing by CC line of (a) in a 2nd tooth formation process. It is a figure which shows the tooth | gear formation process in the manufacturing method of the rack bar which concerns on Embodiment 2 of this invention.

Embodiments of the present invention will be described below.
Embodiment 1 of the Invention

  1 to 8 show a first embodiment of the present invention.

  As shown in FIG. 1, the automobile steering apparatus 1 includes an intermediate shaft 3 that transmits an operation force (forward / reverse rotational force) of the steering wheel 2, and a pinion shaft 5 is coupled to the intermediate shaft 3. And is supported rotatably. As shown in FIG. 2, the rack bar 6 is connected to the pinion shaft 5 so that the forward / reverse rotational motion of the pinion shaft 5 can be converted into the reciprocating motion of the rack bar 6. As shown in FIG. 1, tie rods 7 for steering the front wheels 8 are connected to both ends of the rack bar 6.

  The pinion shaft 5 has pinion teeth 5a as shown in FIG.

  Further, as shown in FIG. 3, the rack bar 6 has a D-shaped cylindrical tooth forming portion 10, and cylindrical bar bodies 11 are provided on both sides of the tooth forming portion 10, respectively. It is provided integrally in a form communicating with. Rack teeth 12 are formed in the tooth forming portion 10, and the rack teeth 12 mesh with the pinion teeth 5 a of the pinion shaft 5 as shown in FIG. 2.

  As shown in FIG. 3C, the rack teeth 12 have a tooth width L1 that is wider than the length L2 of the chord in which the reference circle SC of the bar body 11 is cut by the pitch plane PP. Here, the reference circle SC is a virtual circle corresponding to the outer diameter of the bar body 11. The pitch plane PP is a virtual plane in which the rack teeth 12 of the rack bar 6 mesh with the pinion teeth 5a of the pinion shaft 5.

  Thus, since the rack bar 6 is entirely hollow, the rack bar 6 can be reduced in weight compared to a solid (round bar-shaped) conventional product. In addition, the tooth width L1 of the rack tooth 12 is wider than the length L2 of the chord cut by the pitch plane PP of the reference circle SC of the bar body 11, so that the root stress of the pinion shaft 5 meshing with the rack bar 6 is reduced. The durability of the pinion teeth 5a can be increased.

  Moreover, when manufacturing such a rack bar 6, it follows the following procedure.

  First, in the material preparation step, a cylindrical material 13 is prepared as shown in FIG.

  When the cylindrical material 13 is thus prepared, the process proceeds to the tooth forming part forming step, and the D-shaped cylindrical tooth forming part 10 is formed on the material 13 in two stages as shown in FIG. For this purpose, as described in detail below, first, the upper portion 13a of the material 13 is plastically deformed into a corrugated plate shape in a corrugated plate deformation process, and then the upper portion 13a of the material 13 is plasticized into a flat plate shape in a flat plate deformation process. Deform.

  That is, in the corrugated plate deformation process, as shown in FIGS. 6A and 6B, the cylindrical material 13 is placed in the groove 15 a on the upper surface of the lower mold 15. Since the groove 15 a has a semicircular cross section that substantially matches the lower portion 13 b of the material 13, the outer peripheral surface of the lower portion 13 b of the material 13 is supported by the lower mold 15.

  Next, the upper mold 16 is placed on the upper side of the material 13. The upper die 16 has a frame shape in which a punch insertion port 16a having a width equal to the outer diameter of the material 13 is formed so as to penetrate vertically.

  Further, as shown in FIG. 6A, a pair of asymmetric cores 17 and 18 are inserted into the hollow portion 13 c of the material 13 from the left and right ends of the material 13. One mandrel 17 is formed with a kamaboko-shaped reaction force portion 17a and an annular step portion 17b. As shown in FIG. 7, the reaction force portion 17 a includes a curved lower surface 17 c having a radius of curvature substantially equal to half of the inner diameter of the material 13 (diameter of the hollow portion 13 c), and the material 13. And a flat upper surface 17d having a width slightly narrower than the inner diameter. The other mandrel 18 is formed with an annular step 18b. When these cores 17 and 18 are inserted from both left and right ends of the material 13, the inner peripheral surface of the lower part 13 b of the material 13 comes into contact with the lower surface 17 c of the reaction force part 17 a of the core 17, and a pair of The mandrels 17 and 18 are brought into contact with each other in the vicinity of the end portion of the tooth forming portion 10, and the step portions 17b and 18b of the mandrel 17 and 18 sandwich the material 13 from the left and right sides.

  Thereafter, as shown in FIGS. 6A and 6B, the corrugated plate-shaped forming punch 20 is inserted into the punch insertion opening 16 a of the upper mold 16 and the upper portion 13 a of the material 13 is strongly pressed downward. As shown in FIG. 7 (a), a pressing surface 20a in which two protruding portions 20b are provided downward is formed at the lower portion of the corrugated plate forming punch 20.

  Then, as shown in FIGS. 6B and 7A, the upper portion 13a of the material 13 is plastically deformed into a corrugated plate shape having two recesses 13d.

  At this time, since the punch insertion opening 16a of the upper die 16 has a width equal to the outer diameter of the material 13, as described above, the upper portion 13a of the material 13 swells outside the reference circle SC of the bar body 11. It is plastically deformed into a flat plate shape. Further, since the pair of mandrels 17 and 18 inserted into the hollow portion 13c of the material 13 are attached to each other in the vicinity of the end portion of the tooth forming portion 10, that is, the portion not near the center portion of the tooth forming portion 10, this plasticity The deformation can be performed uniformly along the length direction of the material 13. In addition, since the material 13 is sandwiched from the left and right sides by the step portions 17b and 18b of the cores 17 and 18, it is possible to restrain the movement of the material 13 in the length direction and plastically deform an appropriate part. Furthermore, as described above, the lower surface 13b of the material 13 is supported by the lower mold 15 and at the same time the inner peripheral surface is in contact with the lower surface 17c of the reaction force portion 17a of the mandrel 17. Therefore, the material of the upper part 13a of the raw material 13 does not move to the lower part 13b with this plastic deformation.

  In the flat plate deformation step, after the corrugated plate forming punch 20 is extracted from the upper die 16, the flat plate forming punch 21 is inserted into the punch insertion opening of the upper die 16 as shown in FIGS. It inserts in 16a and strongly presses the upper part 13a of the raw material 13 downward. As shown in FIG. 7B, a flat pressing surface 21a is formed below the flat plate forming punch 21. As shown in FIG. In addition, originally, the cross-sectional view in the corrugated plate deformation step and the cross-sectional view in the flat plate deformation step should be shown in two separate drawings, both of which are the corrugated plate forming punch 20 and the flat plate forming punch 21. These two drawings are simply shown in one drawing (FIG. 6A) for convenience.

  Then, as shown in FIGS. 6C and 7B, the upper portion 13a of the material 13 is plastically deformed into a flat plate shape.

  At this time, similarly to the corrugated plate deformation process, the pair of mandrels 17 and 18 inserted into the hollow portion 13c of the material 13 is not near the end of the tooth forming portion 10, that is, near the center of the tooth forming portion 10. Therefore, this plastic deformation can be carried out uniformly along the length direction of the material 13. In addition, since the material 13 is sandwiched from the left and right sides by the step portions 17b and 18b of the cores 17 and 18, it is possible to restrain the movement of the material 13 in the length direction and plastically deform an appropriate part. Further, the lower portion 13b of the material 13 is supported by the lower mold 15 and at the same time the inner peripheral surface is kept in contact with the lower surface 17c of the reaction force portion 17a of the mandrel 17. The material of the upper part 13a of the raw material 13 does not move to the lower part 13b with the deformation. Therefore, as shown in FIG. 7B, the pressing force of the flat plate forming punch 21 is set so that the upper portion 13a of the raw material 13 is plastically deformed into a flat plate shape at a position slightly above the center of curvature O of the lower portion 13b of the raw material 13. By adjusting appropriately, it becomes possible to make thickness t1 of flat upper part 13a thicker than thickness t2 of lower part 13b. Therefore, a material for forming the rack teeth 12 can be ensured in a tooth forming process described later.

  As a result, as shown in FIG. 5, the tooth forming portion 10 having a D-shaped cross-section cylindrical shape is formed on the material 13.

  In this way, the tooth forming portion 10 is formed on the material 13 and the cylindrical bar body 11 is formed at a portion other than the tooth forming portion 10.

  When the tooth forming portion 10 and the bar main body 11 are thus formed on the material 13, the process proceeds to the tooth forming process, and as shown in FIG. 8, two types of tooth forming punches (first tooth forming punch 22 and second tooth forming) are formed. Using the punch 23), the rack teeth 12 are formed on the tooth forming portion 10 in two stages. In FIG. 8A, illustration of the lower die 15, the upper die 16, and the cores 17 and 18 is omitted.

  For this purpose, first, in the first tooth forming step, the flat plate forming punch 21 is extracted from the upper die 16, and then the first tooth forming punch 22 is inserted into the punch insertion port 16a of the upper die 16 as shown in FIG. By inserting the tooth forming portion 10 and pressing the tooth forming portion 10 downward strongly, peaks and valleys having a height and a depth of about half of the desired height are formed. Subsequently, after the first tooth forming punch 22 is extracted from the upper die 16 in the second tooth forming step, the second tooth forming punch 23 is inserted into the punch insertion port 16a of the upper die 16 as shown in FIG. Then, the tooth forming part 10 is strongly pressed downward to form peaks and valleys having a desired height and depth.

  Then, as shown in FIG. 8A, rack teeth 12 are formed on the tooth forming portion 10.

  At this time, since the tooth forming portion 10 has a width approximately equal to the diameter of the bar body 11, the rack teeth 12 having a sufficient tooth width L1 can be formed. Therefore, the root stress of the pinion shaft 5 meshing with the rack bar 6 can be reduced, and the durability of the pinion teeth 5a can be increased. In addition, as described above, since the material for forming the rack teeth 12 on the flat upper portion 13a of the material 13 is secured in the immediately preceding corrugated plate deformation step, the rack teeth 12 are formed with a sufficient thickness. Can be formed. Further, since the pair of mandrels 17 and 18 inserted into the hollow portion 13c of the material 13 are attached to each other in the vicinity of the end portion of the tooth forming portion 10, that is, the portion not near the center portion of the tooth forming portion 10, this rack The teeth 12 can be formed uniformly along the length direction of the material 13. In addition, since the material 13 is sandwiched from the left and right sides by the step portions 17b and 18b of the cores 17 and 18, the rack teeth 12 can be formed at appropriate portions by restraining the movement of the material 13 in the length direction. it can.

  Thus, when the rack teeth 12 are formed on the upper portion 13a of the material 13, the process proceeds to a mandrel detachment process, and the mandrels 17 and 18 are detached from the hollow portion 13c of the material 13 and separated.

  Here, the production of the rack bar 6 is completed, and the rack bar 6 is completed.

As described above, when the rack bar 6 is manufactured, the predetermined lower die 15, upper die 16, core bars 17 and 18, corrugated plate-shaped forming punch 20, flat plate-shaped forming punch 21, first tooth forming punch 22, and second Using the tooth forming punch 23, the upper portion 13a of the material 13 was plastically deformed into a corrugated plate shape and then plastically deformed into a flat plate shape, and then the rack teeth 12 were formed at this portion. As a result, it is possible to ensure the thickness and tooth width of the rack teeth 12.
[Embodiment 2 of the Invention]

  FIG. 9 shows a second embodiment of the present invention.

  In the second embodiment, instead of forging the rack teeth 12 using the tooth forming punches 22 and 23 in the tooth forming step, two kinds of large and small transfer rollers 25 are provided on the tooth forming portion 10 as shown in FIG. The configuration is the same as that of the first embodiment except that the rack teeth 12 are formed by rolling. In addition, about the member same as Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

At this time, it is not always necessary to use two kinds of transfer rollers 25, and the rack teeth 12 can be rolled by only one kind of transfer roller 25.
[Other Embodiments of the Invention]

  In the first and second embodiments, the case where the width of the punch insertion opening 16a of the upper die 16 is equal to the outer diameter of the material 13 has been described. However, the upper die 16 having a punch insertion opening 16a having a width wider than the outer diameter of the material 13 can be substituted.

  Moreover, Embodiment 1 and 2 mentioned above demonstrated the case where the corrugated plate-shaped shaping | molding punch 20 which has the press surface 20a in which the two convex parts 20b were formed was used. However, the number of protrusions 20b is not limited to two, and any number of protrusions 20b may be used.

  The present invention can be widely applied to various devices and devices such as a steering device for automobiles.

DESCRIPTION OF SYMBOLS 1 ... Steering device 2 ... Steering wheel 3 ... Intermediate shaft 5 ... Pinion shaft 5a ... Pinion tooth 6 ... Rack bar 7 ... Tie rod 8 ... Front wheel 10 ... Tooth formation part 11 ... Bar main body 12 ...... Rack teeth 13 …… Material 13a …… Upper 13b …… Lower 13c …… Hollow 13d …… Recess 15 …… Lower mold 15a …… Groove 16 …… Upper mold 16a …… Punch insertion slot 17, 18 …… Mandrel 17a ... Reaction force part 17b, 18b ... Step part 17c ... Bottom face 17d ... Top face 20 ... Corrugated plate forming punch 20a ... Pressing surface 20b ... Convex part 21 ... Flat plate forming punch 21a ... ... Pressing surface 22 …… First tooth forming punch 23 …… Second tooth forming punch 25 …… Transfer roller L1 …… Rack tooth width L2 …… String length PP …… Pitch plane SC …… Reference circle t1 ...... Thickness at the top of the material t2 …… Thickness at the bottom of the material

Claims (7)

A cylindrical bar body that is used in a steering device for an automobile and has an outer diameter corresponding to a predetermined reference circle, and rack teeth formed along a pitch plane, and the tooth width of the rack teeth is: A rack bar whose reference circle is wider than the length of the string cut by the pitch plane ;
The lower part of the cylindrical material is supported by the lower mold, the upper part of the material is supported by the upper mold in which a punch insertion opening having a width equal to or larger than the outer diameter of the material is formed, and the hollow part of the material is further supported. With the mandrel inserted and in contact with the lower part of the material, a corrugated plate-shaped forming punch is inserted into the punch insertion port and the upper part of the material is pressed to plasticize the upper part of the material into a corrugated plate shape. A corrugated plate-shaped deformation process to be deformed;
A flat plate-shaped deformation step of plastically deforming the upper portion of the material into a flat plate shape by inserting a flat plate-shaped forming punch into the punch insertion port instead of the corrugated plate-shaped forming punch, and pressing the upper portion of the material.
A tooth forming step of forming rack teeth on the top of the material;
A rack bar manufactured by a manufacturing method including:   The rack bar according to claim 1, wherein a tooth width of the rack tooth coincides with an outer diameter of the bar main body. The lower part of the cylindrical material is supported by the lower mold, the upper part of the material is supported by the upper mold in which a punch insertion opening having a width equal to or larger than the outer diameter of the material is formed, and the hollow part of the material is further supported. With the mandrel inserted and in contact with the lower part of the material, a corrugated plate-shaped forming punch is inserted into the punch insertion port and the upper part of the material is pressed to plasticize the upper part of the material into a corrugated plate shape. A corrugated plate-shaped deformation process to be deformed;
A flat plate-shaped deformation step of plastically deforming the upper portion of the material into a flat plate shape by inserting a flat plate-shaped forming punch into the punch insertion port instead of the corrugated plate-shaped forming punch, and pressing the upper portion of the material.
And a tooth forming step of forming rack teeth on the upper portion of the material.   In the corrugated plate deformation step, by using a corrugated plate forming punch having a pressing surface on which a plurality of convex portions are formed, a plurality of concave portions are formed on the top of the material to form a corrugated plate shape. The method of manufacturing a rack bar according to claim 3, wherein the rack bar is plastically deformed.   5. The thickness of the upper part of the material is made thicker than the thickness of the lower part of the material when the upper part of the material is plastically deformed into a flat plate shape in the flat plate deformation step. Rack bar manufacturing method.   In the tooth forming step, a rack tooth is formed on the upper portion of the material by inserting a tooth forming punch into the punch insertion opening instead of the flat plate forming punch and pressing the upper portion of the material. The method for manufacturing a rack bar according to any one of claims 3 to 5.   The mandrel has a curved bottom surface in which the reaction force portion facing the portion forming the rack teeth of the material has a kamaboko shape and has a radius of curvature substantially equal to half of the inner diameter of the material, and the inner diameter of the material The method of manufacturing a rack bar according to any one of claims 3 to 6, further comprising a flat upper surface having a slightly narrower width.

Images