JP5215717B2 - Rack bar and steering device - Google Patents

Description

  The present invention relates to a rack bar used in a rack and pinion gear used in a power steering apparatus of an automobile and the like, and a steering apparatus in which the rack bar is incorporated, and particularly relates to an apparatus capable of improving measurement accuracy during manufacturing.

  A steering device for steering a vehicle includes a pinion gear on the steering shaft side and a rack bar in which a rack is formed on the tie rod side connecting the left and right wheels. The rotational steering force is converted into a lateral force on the left and right by a gear box and transmitted to the wheel, and the turning force around the kingpin is applied to the wheel (see, for example, Patent Document 1).

  Note that the steering gear ratio (steering wheel rotation angle / tire cutting angle) of the steering device depends on a specific stroke characteristic determined by the interval and shape of the tooth portion L of the rack bar (for example, see Patent Document 2). For example, as shown in FIG. 12, by setting the specific stroke lower than the pinion rotation angle near the center of the rack bar stroke, the change in the tire turning angle is reduced near the center of the steering wheel when traveling straight. Prevents wandering. At this time, the specific stroke characteristic is generally a VGR region that gradually changes near the center of the stroke.

On the other hand, when the rack bar is manufactured, as shown in FIG. 13, whether or not the tooth portion L has the designed dimension is measured by placing the pin Q on the tooth portion and checking the overpin size. ing.
JP 2007-253190 A JP-A-6-72344

  The rack bar described above has the following problems. That is, when measuring the overpin dimension, the side surface of the tooth portion L having the VGR region in the vicinity of the central portion of the stroke described above is formed on the curved surface S, and is stable even when the pin Q is placed on the tooth portion. Is difficult. For this reason, there existed a problem that the dimension measurement of a tooth part could not be performed correctly.

  Therefore, the present invention can measure the overpin dimensions with high accuracy even when the specific stroke characteristics in the vicinity of the center of the stroke are made smaller than both ends of the stroke, and can stabilize the steering performance during straight travel. An object of the present invention is to provide a rack bar and a steering device that can be used.

  In order to solve the above problems and achieve the object, the rack bar and the steering device of the present invention are configured as follows.

A rack bar meshed with a pinion gear, comprising: a shaft portion; and a rack tooth forming portion provided on the shaft portion, wherein a plurality of tooth portions meshing with the pinion gear are arranged side by side along the axial direction. The tooth portion of the tooth forming portion is formed such that the ratio between the rotation angle of the pinion gear and the movement distance of the shaft portion is different at both ends in the axial direction with respect to the center portion, and is constant in a predetermined region sandwiching the center portion The predetermined region is formed as a value, the central portion is the bottom of the valley between the tooth portion and the tooth portion, the rotation angle is 0 °, α ° = 360 ° / (number of pinion teeth), and the pinion number of teeth eight following time-.alpha. ° or more alpha ° or less, in the range of -45 ° to 45 ° when the pinion tooth number is more than nine, teeth which are adjacent Oite to the central portion, Each side facing across the trough divides the adjacent teeth in half Characterized in that it is a plane which forms the same angle with respect to that virtual plane.

A steering shaft coupled to a steering member, a pinion shaft coupled to the steering shaft and having a pinion gear at a tip thereof, and a rack bar meshed with the pinion gear, the rack bar including a shaft portion A rack tooth forming portion provided on the shaft portion and meshing with the pinion gear and arranged in parallel along the axial direction, and the tooth portion of the rack tooth forming portion has a rotation angle of the pinion gear. And the movement distance of the shaft portion are formed differently at both ends in the axial direction with respect to the central portion, and are formed at a constant value in a predetermined region sandwiching the central portion, and the predetermined region is the central portion Is the bottom of the valley between the teeth and the teeth, the rotation angle is 0 °, α ° = 360 ° / (number of pinion teeth), and when the number of pinion teeth is 8 or less, −α ° or more α ° or less, pinion teeth A range of numbers is less than 45 ° -45 ° or more when the above nine, teeth which are adjacent Oite to the central portion, each side of opposite sides of the valley, between teeth which the adjacent It is the plane which makes the same angle with respect to the virtual surface divided | segmented into half, It is characterized by the above-mentioned.

  According to the present invention, even when the specific stroke characteristic near the center of the stroke is made smaller than both end sides of the stroke, it is possible to measure the overpin dimensions with high accuracy and to stabilize the steering performance during straight traveling. Can be made.

  FIG. 1 is a perspective view showing a steering apparatus 10 incorporating a rack bar 20 according to an embodiment of the present invention, FIG. 2 is a plan view showing the rack bar 20, and FIG. 3 shows a specific stroke characteristic of the rack bar 20. FIG. 4 is an explanatory diagram schematically showing a main part of the rack bar 20.

  The steering device 10 includes a steering shaft 12 connected to a steering wheel (steering member) 11, a pinion shaft 13 having a pinion gear 13a at the tip thereof, and a rack bar engaged with the pinion gear 13a. 20. The rack bar 20 is further connected to the front wheels WR and WL via tie rods 30 and 30.

  The rack bar 20 is provided with a shaft portion 21 formed from a solid or hollow round bar, a rack tooth forming portion 22 provided at the center of the shaft portion 21, and provided at both ends of the shaft portion 21. The rod part 23 which has an outer diameter different from the outer diameter of the part 22 is provided.

  In the rack tooth forming portion 22, a plurality of tooth portions 22 a that mesh with the pinion gear 13 a are arranged in parallel along the axial direction C. As shown in FIG. 3, the tooth portions 22a are arranged at intervals having a predetermined specific stroke characteristic.

  The specific stroke characteristics are formed such that both end sides of the stroke are larger than the stroke center K. In particular, when the stroke center K is the bottom of the valley between the tooth portion 22a and the tooth portion 22a and the rotation angle of the pinion shaft 13 is 0 °, the predetermined region between −45 ° and 45 ° is constant (CGR region). It is said. The range of the predetermined region is determined by the number of teeth of the pinion gear 13a (the number of pinion teeth). For example, when the number of pinion teeth is 8, 360 ° / 8, which is 45 °.

  Thus, when the number of pinion teeth is 8, α ° is set to 360 ° / 8 sheets = 45 °. However, since the number of pinion teeth is normally about 5 to 12, the range of the predetermined region is −45. The angle is not limited to not less than 45 ° and not more than 45 °. Specifically, when the number of pinion teeth is 8 or less, it is preferably −α ° or more and α ° or less, and when it is 9 or more, it is preferably in the range of −45 ° or more and 45 ° or less with a margin.

  Therefore, as shown in FIG. 4, the side surface E of the tooth portion 22a in the vicinity of the stroke center portion K is flat. On the other hand, when overpin dimension measurement is performed, the cylindrical pin Q is placed in a valley between adjacent tooth portions 22a. At this time, since the outer peripheral surface of the pin Q comes into contact with the side surface E of the tooth portion 22a, it can be placed stably. Therefore, the overpin dimension measurement can be performed with high accuracy.

  On the other hand, since the specific stroke characteristic is constant in the region of the stroke center K (CGR region), the turning angle of the steering wheel and the turning angle of the front wheels WR and WL are in a constant relationship, and the steering performance during straight traveling is stable. You can make it feel uncomfortable.

  5-7 is a figure which shows an example of the manufacturing process of the rack bar 20 mentioned above. FIG. 5 is a side view showing the cored bar 110, and FIG. 6 is a cross-sectional view of the main part showing a hollow rack bar manufacturing apparatus 200 in which the cored bar 110 is used. In FIG. 7, P indicates an iron pipe (hollow material). Further, 110A in FIG. 8 indicates a core bar having the same configuration as the core bar 110. The pipe P is used as the rack bar 20 described above.

  The cored bar 110 includes a semicircular bar 111. The bar 111 includes a distal end portion 112 positioned on the distal end side in the press-fitting direction that is first inserted into the pipe P, and a proximal end portion 113 connected to the driving device.

  The bar 111 has a flat upper surface as a whole, but is formed with a flat portion 111 a in which three protrusions 121, 122, and 123 are integrally provided along the axial direction of the bar 111. On the other hand, the bar 111 is in close contact with the inner peripheral surface of the pipe P on the back side opposite to the flat portion 111a, and maintains the close contact with the inner peripheral surface of the pipe P during the forging process. A linear movement in the axial direction is possible. Moreover, it has the largest cross-sectional area smaller than the minimum cross-sectional area of the hollow part of the pipe P. That is, as will be described later, the pipe P is formed in such a size that it can move smoothly even after the upper surface is flattened and the flat portion Pa is formed. When the pipe P is used as a hollow rack bar, the back side of the bar 111 opposite to the protrusions 121 to 123 corresponds to a sliding surface with a guide member for guiding from the outer peripheral surface side. The outer peripheral pressing surface 114 is formed over a range Q (120 to 150 ° centering on the axis).

  Each of the protrusions 121 to 123 is formed with a gently tapered guide surface so that a smooth movement of the cored bar 110 can be obtained regardless of the flow resistance at the time of molding.

  Next, the structure of the hollow rack bar manufacturing apparatus 200 using this core metal 110 will be described. The hollow rack bar manufacturing apparatus 200 includes a lower mold 210 and an upper mold 220 that hold an iron pipe P. The hollow rack bar manufacturing apparatus 200 presses the metal core 110 into the internal cavities of the pipes P held by the lower mold 210 and the upper mold 220 to stretch the meat of the pipe P from the inner diameter side toward the tooth mold 230 described later. It is an apparatus for producing a hollow rack bar 20 by letting it out.

  The lower mold 210 includes a semicircular inner peripheral surface 211 in the cross section, and the pipe P is placed on the semicircular inner peripheral surface 211. The upper die 220 is detachably provided with a tooth die 230 whose upper inner surface is spaced in the length direction over a predetermined length, and the tooth die is placed at a predetermined length on the upper surface of the pipe P by transfer forging. A rack can be formed according to the unevenness of 230.

  The pipe P is forged using the hollow rack bar manufacturing apparatus 200 and the core bars 110 and 110A configured as described above.

  A pipe P is prepared in advance by using another mold and flattening the central part into a central concave shape. The pipe P is held between the upper mold 220 and the lower mold 210, and the flat portion Pa of the pipe P is brought into contact with the tooth mold 230.

  In this state, press-fitting of the core metal 110 into the pipe P is started. The core metal 110 is introduced into the hollow portion of the pipe P from the tip 112 thereof. Then, the first protrusion 121 acts on the inner surface of the flat portion Pa of the pipe P via the tapered guide surface, and the meat of the pipe P is projected toward the tooth profile of the tooth mold 230. Then, by continuing the press-fitting of the core metal 110, the overhanging of the meat by the protrusions 122 and 123 is sequentially received, and the press-forging is performed. Next, the metal core 110 is moved in the backward direction. Subsequently, press forging is alternately performed by press-fitting the core metal 110A. At this time, since the outer peripheral pressing surface 114 is formed on the cores 110 and 110A, an R shape is formed on the lower surface of the pipe P.

  In addition, after that, press-forging is performed in the same manner using the cored bar 110 in which the protruding amount of the protruding portion is slightly increased. Thereafter, the final processing is completed by repeating predetermined processes while changing the size of the core metal 110 little by little in the same manner. Finally, the height of the metal core 110 completes the transfer forging of the rack in which the meat of the pipe P is sufficiently extended corresponding to the unevenness of the tooth mold 230 by the metal core press-fitting.

  8-11 is a figure which shows another example of the manufacturing process of the rack bar. FIG. 8 is a side view showing a short-type metal core 110B which is one of the metal core sets, and FIGS. 9 to 11 are views showing a hollow rack bar manufacturing apparatus 300 using the metal core set. 9 shows a state where the core metal is clamped around the mold and the core metal holder, FIG. 10 shows a state where the core metal is delivered around the mold and the core metal holder, and FIG. 11 shows press-fitting of the core metal around the mold and the core metal holder. Is shown in a completed state. 11, the same functional parts as those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The length of the bar 111 of the core metal 110B is as short as half or less of the length of the tooth part of the tooth mold 313 described later.

  The hollow rack bar manufacturing apparatus 300 includes a metal mold 310, a metal core holder 320 that stores a set of a plurality of metal cores 110B, a first metal core push bar 330, a second metal core push bar 340, a metal core guide 350, and the like. It has.

  The mold 310 includes a lower mold 311 and an upper mold 312 that hold the iron pipe material P. The lower mold 311 includes a semicircular inner peripheral surface 311a in the cross section, and the pipe material P is placed on the semicircular inner peripheral surface 311a. The upper die 312 is detachably provided with a tooth die 313 whose inner surface on the upper side is spaced in the length direction over a predetermined length, and a tooth is placed on a portion of the predetermined length on the upper surface of the pipe material P by transfer forging. A rack can be formed according to the unevenness of the mold 313.

  The core metal holder 320 is disposed only on one side of the mold 310, for example, on the right side of the mold 310 in FIGS. As shown in FIGS. 9 to 11, the cored bar holder 320 has a plurality of holding holes 321. These holding holes 321 pass through the cored bar holder 320 in the direction in which the pipe material P extends, and the cored bar 110B is individually accommodated therein. The accommodated core metal 110B is held in a proper posture with respect to the mold 310 and by a leaf spring or the like (not shown) so as not to fall off carelessly. Each core metal 110 </ b> B supported by the core metal holder 320 is positioned on the side where the first core metal push bar 330 is inserted and removed from the mold 310.

  The cored bar holder 320 is moved by a holder driving unit (not shown). Each time this driving is performed, one of the plurality of holding holes 321 is sequentially selected and opposed to one end of the pipe material P that is joined together. Therefore, the cored bar 110B supported by the cored bar holder 320 can be taken in and out of the pipe material P sequentially. For this purpose, the metal core holder 320 is moved by a fixed pitch in the vertical direction (vertical direction) in FIGS. However, instead of this, it may be moved in the horizontal direction (the front and back direction of the paper on which FIGS. 9 to 11 are drawn). Alternatively, the cored bar holder 320 can be rotatably provided and rotated by a predetermined angle by the holder driving unit.

  The tip end side of the first cored bar 330 is formed so as to be detachable with respect to the pipe material P held by the mold 310. In that case, it inserts in the pipe material P hold | maintained at the metal mold | die 310 with the core metal 110B. In addition, the code | symbol 360 in FIGS. 9-11 has shown the tubular push rod guide.

  The tip end side of the second cored bar 340 is formed to be detachable with respect to the pipe material P held by the mold 310.

  As shown in FIGS. 9 to 11, the core bar guide 350 is disposed between the mold 310 and the core bar holder 320 and close to the mold 310. The core bar guide 350 is made of metal or the like and has a through hole 351 that penetrates in the thickness direction. The through hole 351 communicates with a hollow portion of the pipe material P held by the mold 310.

  Next, a procedure for manufacturing a hollow rack bar using the hollow rack bar manufacturing apparatus 300 having the above configuration will be described. The set pipe material P is arranged in the mold 310, and the other end side of the pipe material P protrudes from the mold 310. Further, the mold is clamped between the lower mold 311 and the upper mold 312 and the tooth mold 313 is brought into contact with the flat portion Pa.

  Before or after this setting operation, the cored bar holder 320 is operated to hold one of the plurality of cored bars 110B accommodated in the state facing the through hole 351 of the cored bar guide 350. At the same time, the tip end of the first metal core push bar 330 is engaged with the right end of the metal core 110B facing the through hole 351.

  Next, the second metal core push rod 340 is inserted into the pipe material P, and the tip of the second metal core push rod 340 is inserted through the through hole 351 of the pipe material P and the metal core guide 350, and this through hole 351 is inserted. It comes in contact with the left end of the metal core 110B in the metal core holder 320 facing the. Therefore, the metal core 110B in the through hole 351 is sandwiched between the first metal core push bar 330 and the second metal core push bar 340 that are in contact with both ends from both ends in the axial direction.

  Thereafter, the first cored bar 330 passes through the holding hole 321 of the cored bar holder 320 and the through hole 351 of the cored bar guide 350, and the pipe material P held in the mold 310 as shown in FIG. Inserted into.

  At this time, the metal core 110B is pressed by the first metal core push bar 330 and press-fitted into the pipe member P while being held between the first metal core push bar 330 and the second metal core push bar 340. Is done. By this press-fitting, press-fitting forging is performed in response to overhanging of the meat by the protrusions 121 to 123 of the core metal 110B. The press-fitting of the cored bar 110B is completed in a state where the cored bar 110B cannot be removed from the flat portion Pa as shown in FIG.

  Next, the first cored bar 330 is pulled back. At this time, the second cored bar pusher 340 is moved toward the cored bar holder 320. As a result, the core metal 110B is pressed by the second core metal push bar 340 while being held between the first core metal push bar 330 and the second core metal push bar 340 in contact with both ends of the core bar 110B. Then, it is pushed back into the metal core holder 320 through the pipe material P and the through hole 351 of the metal core guide 350. Also in this case, press forging is performed in response to the overhanging of the meat by the protrusions 121 to 123 of the core metal 110B.

  Thereafter, the metal core holder 320 is moved so that the metal core 110B having the next largest protrusion amount and the holding hole 321 in which the metal core 110B is accommodated are opposed to the opening of the pipe material P through the through hole 351 of the metal core guide 350. .

  Then, after the core bar 110B to be used next is clamped, the core bar 110B is similarly held between the first core bar push bar 330 and the second core bar push bar 340. Then, it is pressed by the first cored bar 330 and press-fitted into the pipe material P and reciprocated once. By sequentially repeating these procedures, the hollow rack bar 20 having the rack corresponding to the tooth mold 313 of the mold 310 on the pipe material P is manufactured.

  Finally, after returning the last used metal core 110B to the metal core holder 320, the second metal core push rod 340 is pulled out from the pipe material P, and then the mold 310 is opened.

  As described above, in the rack bar 20 according to the embodiment of the present invention, in order to improve the straight running stability, even when the specific stroke characteristics in the vicinity of the stroke center K are made smaller than both end sides of the stroke, It is possible to measure the overpin dimensions with high accuracy, and to stabilize the steering performance when traveling straight.

The present invention is not limited to the above embodiment. For example, the stroke center K described above is in the range of −45 ° to 45 °, but may be in the range of −55 ° to 55 ° when the condition of α = 360 ° / number of pinion teeth is satisfied. Of course, various modifications can be made without departing from the scope of the present invention.
Hereinafter, the invention described in the scope of claims of the present application will be appended.
[1] The rack bar meshed with the pinion gear includes a shaft portion, and a rack tooth forming portion provided on the shaft portion, and a plurality of tooth portions meshing with the pinion gear arranged in parallel along the axial direction. The tooth portion of the rack tooth forming portion is formed such that the ratio between the rotation angle of the pinion gear and the moving distance of the shaft portion is different at both ends in the axial direction with respect to the center portion, and sandwiches the center portion. A rack bar that is formed to have a constant value in a region.
[2] In the predetermined region, the central portion is the bottom of the valley between the tooth portion and the tooth portion, the rotation angle is 0 °, α ° = 360 ° / (number of pinion teeth), and the number of pinion teeth The rack bar as set forth in [1], wherein the rack bar is in a range of −α ° to α ° when the number of teeth is 8 or less, and −45 ° to 45 ° when the number of pinion teeth is 9 or more.
[3] A steering shaft coupled to the steering member, a pinion shaft coupled to the steering shaft and having a pinion gear at a tip, and a rack bar meshed with the pinion gear, the rack bar comprising: A shaft portion and a rack tooth forming portion provided on the shaft portion and meshing with the pinion gear are arranged in parallel along the axial direction. The tooth portion of the rack tooth forming portion is a pinion gear. The ratio between the rotation angle of the shaft portion and the movement distance of the shaft portion is formed such that both end sides in the axial direction are different from the center portion, and a constant value is formed in a predetermined region sandwiching the center portion. Steering device.

1 is a perspective view showing a steering apparatus in which a rack bar according to an embodiment of the present invention is incorporated. The top view which shows the same rack bar. Explanatory drawing which shows the specific stroke characteristic of the rack bar. Explanatory drawing which shows the principal part of the rack bar typically. The side view which shows the principal part of the metal core which concerns on an example of the manufacturing process of the rack bar. Sectional drawing which shows the hollow rack bar manufacturing apparatus with which a concentric metal bar is applied. Sectional drawing which shows the hollow rack bar of the state by which the concentric metal was inserted. The side view which shows the principal part of the metal core which concerns on another example of the manufacturing process of the rack bar. It is a figure which shows the hollow rack bar manufacturing apparatus using the same metal core, Comprising: Sectional drawing which shows a metal mold | die and the metal core holder periphery in the state by which the metal core was clamped. Sectional drawing which shows the metal mold | die of the said hollow rack bar manufacturing apparatus, and a metal core holder periphery in a metal core delivery state. Sectional drawing which shows the metal mold | die of the same hollow rack bar manufacturing apparatus, and the core metal holder periphery in the state which press-fit of the metal core was completed. Explanatory drawing which shows the specific stroke characteristic of the conventional rack bar. Explanatory drawing which shows the principal part of the rack bar typically.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Steering device, 11 ... Handle (steering member), 13 ... Pinion shaft, 13a ... Pinion gear, 20 ... Rack bar, 21 ... Shaft part, 22 ... Rack tooth formation part, 22a ... Tooth part, 23 ... Rod part.

Claims (2)

In the rack bar meshed with the pinion gear,
The shaft,
A rack tooth forming portion provided on the shaft portion and having a plurality of tooth portions meshing with the pinion gear arranged in parallel along the axial direction,
The tooth portion of the rack tooth forming portion is formed with a ratio between the rotation angle of the pinion gear and the moving distance of the shaft portion, the both ends in the axial direction being different from the center portion, and a predetermined region sandwiching the center portion At a constant value,
The predetermined region has the central portion as the bottom of the valley between the tooth portion and the tooth portion, the rotation angle is 0 °, α ° = 360 ° / (number of pinion teeth), and the number of pinion teeth is eight. -Α ° or more and α ° or less in the following cases, and the range of −45 ° or more and 45 ° or less when the number of pinion teeth is 9 or more ,
The teeth adjacent to each other Oite to the central portion, each side of opposite sides of the valley is the plane formed by the same angle to the imaginary plane that divides in half between teeth of the adjacent A featured rack bar. A steering shaft coupled to the steering member;
A pinion shaft connected to the steering shaft and having a pinion gear at the tip,
A rack bar meshed with the pinion gear,
The rack bar includes a shaft portion,
A rack tooth forming portion provided on the shaft portion and having a plurality of tooth portions meshing with the pinion gear arranged in parallel along the axial direction,
The tooth portion of the rack tooth forming portion is formed with a ratio between the rotation angle of the pinion gear and the moving distance of the shaft portion, the both ends in the axial direction being different from the center portion, and a predetermined region sandwiching the center portion At a constant value,
The predetermined region has the central portion as the bottom of the valley between the tooth portion and the tooth portion, the rotation angle is 0 °, α ° = 360 ° / (number of pinion teeth), and the number of pinion teeth is eight. -Α ° or more and α ° or less in the following cases, and the range of −45 ° or more and 45 ° or less when the number of pinion teeth is 9 or more ,
The teeth adjacent to each other Oite to the central portion, each side of opposite sides of the valley is the plane formed by the same angle to the imaginary plane that divides in half between teeth of the adjacent Steering device characterized.

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