JP6634266B2 - Rack bar and steering device - Google Patents

Description

  The present invention relates to a rack bar and a steering device.

  Various vibrations, such as vibrations caused by unevenness of a road surface, vibrations caused by braking imbalance and rotation imbalance of wheels, and the like, act on a rack bar incorporated in a steering device of a vehicle such as an automobile. The vibration acting on the rack bar is transmitted to the driver via the steering shaft connected to the pinion meshing with the rack teeth and the steering wheel connected to the steering shaft, and causes discomfort to the driver. Further, noise is generated due to the vibration of the rack bar, and the quietness of the vehicle is impaired. In recent years, hybrid vehicles using an internal combustion engine and an electric motor as power sources have become widespread, and electric vehicles using only an electric motor as a power source have been developed. In these quiet vehicles, noise is particularly noticeable. There is a tendency.

  In the rack bar described in Patent Literature 1, the weight is housed in the housing hole inside the rack bar, and the weight vibrates relatively to the rack bar, so that the weight and the inner peripheral surface of the housing hole are moved. Sliding friction and collision occur, and vibration of the rack bar is attenuated by energy loss due to sliding friction and collision.

  In the rack bars described in Patent Literature 2 and Patent Literature 3, a shaft portion provided in the axial direction of a tooth portion on which rack teeth are formed is formed of a carbon fiber reinforced resin material. The vibration of the rack bar is damped by the vibration damping characteristics of the material.

JP 2002-161969 A JP 2013-75533A JP 2015-127187 A

  In the rack bar described in Patent Literature 1, sliding friction and collision between the weight and the rack bar may be a new noise source, and the quietness of the vehicle may be impaired. In addition, since the carbon fiber reinforced resin material itself is relatively expensive and takes a long time to form, a shaft forming the outer shape of the rack bar, such as the rack bar described in Patent Literature 2 or Patent Literature 3, is used. When the portion is formed of a carbon fiber reinforced resin material, there is a concern about an increase in cost.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a rack bar and a steering device capable of suppressing a vibration and improving a driver's steering feeling and quietness of a vehicle.

A rack bar according to one embodiment of the present invention includes a tooth portion formed with a plurality of rack teeth, and a shaft portion provided adjacent to the tooth portion in the axial direction, and a hollow portion is formed in at least a part of the axial direction. A rack bar in which a tubular damping material is inserted along the axis inside the hollow portion, and a ventilation path that penetrates through the inside of the shaft portion in the axial direction to flow air. The hollow portion is provided at least in the shaft portion, the ventilation path is passed through the inside of the hollow portion, the inside of the hollow portion provided with the vibration damping material, A space is left to connect both ends of the air passage.

  The steering device of one embodiment of the present invention incorporates the rack bar.

  ADVANTAGE OF THE INVENTION According to this invention, the rack bar and steering apparatus which can aim at the driver's steering feeling and the quietness of a vehicle by suppressing vibration can be provided.

It is a front view of an example of a steering device for explaining an embodiment of the present invention. FIG. 2 is a sectional view of a rack bar incorporated in the steering device of FIG. 1. 2 is a sectional view of a modification of the rack bar. 2 is a sectional view of another modification of the rack bar. 2 is a sectional view of another modification of the rack bar. It is a front view of an example of a steering device for explaining an embodiment of the present invention. It is sectional drawing of the rack bar integrated in the steering device of FIG. It is sectional drawing of the modification of the rack bar of FIG. It is sectional drawing of another modification of the rack bar of FIG. It is sectional drawing of another example of the rack bar for describing embodiment of this invention. It is sectional drawing of another example of the rack bar for describing embodiment of this invention.

  FIG. 1 shows an example of a steering device for describing an embodiment of the present invention.

  The steering device 1 shown in FIG. 1 includes a substantially cylindrical rack housing 2 and a rack bar 10 housed in the rack housing 2.

  Tie rods 3 are connected to both ends of a rack bar 10 protruding from openings at both ends in the axial direction of the rack housing 2 via joints 4, and the periphery of the joint 4 extends over the rack housing 2 and the tie rods 3. It is covered by a boot 5 to cover.

  A steering gear box 6 is provided at one axial end of the rack housing 2. The steering gear box 6 houses a steering pinion (not shown) formed on an input shaft 7 connected to a steering shaft. The steering gear box 6 is provided with a motor 8 of an assist mechanism, and the driving force of the motor 8 is transmitted to a steering pinion.

  The rack bar 10 has a tooth portion 11 on which rack teeth meshing with the steering pinion are formed, and a shaft portion 12 provided adjacent to the tooth portion 11 in the axial direction. The shaft portion 12 is supported by a slide bearing (not shown) so as to be movable in the axial direction.

  The steering pinion of the input shaft 7 is rotated by the rotation operation of the steering wheel, and the rack bar 10 meshing with the steering pinion is moved in the axial direction by the teeth 11. The driving force of the motor 8 of the assist mechanism, which is controlled in accordance with the steering force of the steering wheel, is transmitted to the rack bar 10 via the steering pinion, and assists the movement of the rack bar 10 by turning the steering wheel. . The movement of the rack bar 10 turns the steering wheel of the vehicle via the tie rods 3 and the steering mechanism to which the tie rods 3 are connected.

  FIG. 2 shows the configuration of the rack bar 10.

  The rack bar 10 is formed of a single solid bar having a circular cross section formed of a metal material such as carbon steel such as JIS-S45C. A toothed portion 11 is provided on one end side of the rack bar 10 in the axial direction, and a shaft portion 12 slidably supported by a slide bearing is provided on the other end side. Screw holes 13 to which the joints 4 are fastened are provided at both ends.

  The plurality of rack teeth formed on the tooth portions 11 of the rack bar 10 made of a bar are formed by, for example, cutting or forging.

  Further, the rack bar 10 has a hollow portion 15 in at least a part in the axial direction. In the illustrated example, a hole 14 extending in the axial direction over substantially the entire length of the shaft portion 12 is formed from the screw hole 13 on the shaft portion 12 side, and the entire shaft portion 12 is a hollow portion 15. The hole 14 is formed by a cutting process using a gun drill, for example.

  The hole 14 may extend in the axial direction from the screw hole 13 on the shaft portion 12 and extend to the tooth portion 11, and may extend from the screw hole 13 on the tooth portion 11 side to substantially the entire length of the tooth portion 11. It may extend in the axial direction, and may further extend to the shaft portion 12.

  A damping material 16 is fixed inside the hollow portion 15.

  The material of the damping material 16 is not limited as long as it has damping properties. However, from the viewpoint of reducing the weight of the rack bar 10, the specific gravity is smaller than that of a metal material such as steel constituting the rack bar 10. Materials are preferable, for example, rubber-based materials such as NBR (nitrile rubber) and HNBR (hydrogenated nitrile rubber), and resin-based materials such as CFRP (carbon fiber reinforced resin) and CFRTP (carbon fiber reinforced thermoplastic resin) are preferable. Can be used.

  In the illustrated example, the material of the damping material 16 is the rubber-based material described above, and the damping material 16 is formed by adding a foaming agent to raw rubber and foaming the inside of the hollow portion 15. According to the foam molding, the vibration damping material 16 can be filled in the hollow portion 15, and the vibration damping material 16 can be easily fixed in a state of being in close contact with the inner surface of the hollow portion 15.

  Note that the vibration damping material 16 only needs to be fixed to at least a part of the hollow portion 15 in close contact with the inner surface of the hollow portion 15. For example, the damping material 16 may be formed in a sheet shape and adhered to the inner surface of the hollow portion 15, and the damping material 16 may be formed in a columnar or tubular shape and pressed into the hollow portion 15, 16 may be formed into a granular shape, and a large number of vibration damping materials 16 may be packed in the hollow portion 15 and sealed inside the hollow portion 15 by the joint 4 or the like.

  The vibration acting on the rack bar 10 is attenuated by the vibration damping characteristics of the damping material 16. Thus, transmission of the vibration acting on the rack bar 10 to the driver via the steering shaft and the steering wheel can be suppressed, and the steering feeling can be improved.

  Further, since the vibration acting on the rack bar 10 is attenuated by the damping material 16, noise caused by the vibration of the rack bar is suppressed, and the quietness of the vehicle can be improved. Since the damping material 16 is fixed inside the hollow portion 15, the damping material 16 does not relatively vibrate and become a new noise source.

  Further, the rack bar 10 is not limited to vibration transmitted from wheels such as vibration caused by unevenness of a road surface, but also includes, for example, vibration generated in a power source such as an internal combustion engine or an electric motor mounted on a vehicle. Vibration transmitted from the vehicle through the frame also acts, and these vibrations are also attenuated by the vibration damping material 16, so that the rack bar 10 also contributes to vibration damping of the entire vehicle.

  Although the above-described rack bar 10 has been described as being made of a single solid bar, it may be made of a single hollow tube as in the example shown in FIG.

  The rack teeth of the tooth portion 11 of the rack bar made of a tubular material are formed, for example, as follows. First, a flat tooth forming surface is preliminarily formed in a portion (hereinafter, referred to as a tooth forming portion) which is to be a tooth portion in a part of the tube material in the longitudinal direction. The tooth forming surface is formed by, for example, pressing using a molding die to crush the tooth forming portion of the tube material.

  Next, the tube is placed in a molding die including a tooth mold pressed against the tooth forming surface and surrounding the tooth forming portion of the tube over the entire circumference, and the core is inserted through the tube. The flesh of the tube material forming the tooth forming surface is squeezed from the inside by the inserted metal core and bites into the tooth mold pressed against the tooth forming surface. A plurality of rack teeth corresponding to the tooth form are formed on the pipe by gradually increasing the thickness of the inserted metal core and repeating ironing.

  In the rack bar shown in FIG. 3 made of a tubular material, the tooth portion 11 and the shaft portion 12 are entirely formed as a continuous hollow portion 15 by utilizing the shape of the tubular material, which is a material, and a vibration damping material 16 is provided inside the hollow portion 15. Has been fixed. As described above, in the rack bar made of a tubular material, the hollow portion 15 can be provided by utilizing the shape of the material, and the installation of the vibration damping material 16 is easy.

  In addition, as in the example shown in FIG. 4, the tooth portion 11 may be made of a solid rod material, and the shaft portion 12 may be made of a tube material, and as in the example shown in FIG. The shaft portion 12 may be made of a solid bar material, and may be made of a tube material. The hollow bar and the tube are joined by, for example, friction welding by being rotated with their end faces abutting each other.

  When a solid bar and a tube are joined to form a rack bar, the damping material 16 may be provided only in the tube as shown in the illustrated example, or a hole may be formed in the solid bar. May be provided, and the damping material 16 may be provided only on the solid bar, or the damping material 16 may be provided on both the pipe and the solid bar.

  FIG. 6 shows another example of the steering device for describing the embodiment of the present invention.

  A steering device 101 shown in FIG. 6 is a dual pinion type steering device. A steering pinion (not shown) formed on an input shaft 107 connected to a steering shaft is provided at one axial end of a rack housing 102. ) Is provided, and an auxiliary gear box 109 for storing an auxiliary pinion (not shown) driven by a motor 108 of an assist mechanism is provided at the other axial end of the rack housing 102. Is provided.

  The rack bar 110 has a first tooth portion 111 formed with rack teeth meshing with the steering pinion, a second tooth portion 112 formed with rack teeth meshing with the auxiliary pinion, and a first tooth portion 111 and a second tooth portion 112. And a shaft portion 113 interposed in the axial direction. The shaft portion 113 is supported by a slide bearing (not shown) movably in the axial direction.

  FIG. 7 shows a configuration of the rack bar 110.

  The rack bar 110 is made of a single solid bar having a circular cross section. A first tooth 111 is provided at one end of the rack bar 110 in the axial direction, and a second tooth 112 is provided at the other end of the rack bar 110. The first tooth 111, the second tooth 112 A shaft portion 113 is provided therebetween, and screw holes 114 for fastening the joint 104 (see FIG. 6) are provided at both ends in the axial direction. A predetermined rotation angle difference is set between the first tooth portion 111 and the second tooth portion 112 around the central axis in accordance with the positional relationship between the steering shaft and the assist mechanism in the vehicle.

  Further, the rack bar 110 has a hollow portion 116 in at least a part in the axial direction. In the illustrated example, a hole 115 extending in the axial direction over substantially the entire length of the first tooth portion 111 and the shaft portion 113 is formed from the screw hole 114 on the first tooth portion 111 side, and the first tooth portion 111 and the shaft are formed. The entire part 113 is a continuous hollow part 116. In addition, the hole 115 may stop at the first tooth portion 111 or may extend to the second tooth portion 112. The hole 115 may extend from the screw hole 114 on the second tooth portion 112 side.

  The damping material 117 is fixed inside the hollow portion 116. The vibration acting on the rack bar 110 is attenuated by the vibration damping characteristics of the damping material 117. Accordingly, it is possible to suppress the vibration acting on the rack bar 110 from being transmitted to the driver via the steering shaft and the steering wheel, and to improve the steering feeling. Further, since the damping member 117 is fixed inside the hollow portion 116, the damping member 117 does not relatively vibrate and becomes a new noise source. Thereby, the quietness of the vehicle can be improved.

  Although the above-described rack bar 110 has been described as being made of a single solid bar, the first tooth portion 111 and the shaft portion 113 are made of one tube as shown in FIG. The two-tooth portion 112 may be made of a solid bar, and the two members may be joined by friction welding. In this case, typically, a rack tooth of the first tooth portion 111 is formed in advance on the tube material on which the first tooth portion 111 is provided, and after the two materials are joined, a solid tooth is formed as the second tooth portion 112. The rack teeth of the second tooth portion 112 are formed at a predetermined portion of the bar, that is, a portion where a predetermined rotation angle difference is provided between the bar portion and the first tooth portion 111.

  Note that the first tooth 111 and the shaft 113 may be made of one solid bar, the second tooth 112 may be made of a tube, and the second tooth 112 and the shaft 113 may be made of one rod. Or a solid rod.

  When the solid bar and the tube are joined to form a rack bar, the damping material 117 may be provided only on the tube as shown in the illustrated example, or the solid bar may be provided. A hole may be formed in the material, and the vibration damping material 117 may be provided only on the solid bar material, or the vibration damping material 117 may be provided on both the pipe material and the solid bar material.

  As shown in FIG. 9, the first tooth portion 111 and the second tooth portion 112 are each made of a tube material, and the shaft portion 113 is a solid member different from the first tooth portion 111 and the second tooth portion 112 as a joint member. It is also possible to form a rack bar by joining these members by friction welding. In this case, the tube material serving as the first tooth portion 111 and the tube material serving as the second tooth portion 112 can be fixed, and the solid bar material serving as the shaft portion 113 can be rotated to perform friction welding. The rack teeth of the first tooth portion 111 are formed in advance on the tube material that is the first tooth portion 111, and the rack teeth of the second tooth portion 112 are formed in advance on the tube material that is the second tooth portion 112. The rotation angle difference between the tooth 111 and the second tooth 112 can be set with high accuracy.

  When the solid bar and the tube are joined to form a rack bar, the damping material 117 may be provided only on the tube as shown in the illustrated example, or the solid bar may be provided. A hole may be formed in the material, and the vibration damping material 117 may be provided only on the solid bar material, or the vibration damping material 117 may be provided on both the pipe material and the solid bar material.

  In the steering device 101 and the rack bar 110 described above, the driving force of the motor 108 of the assist mechanism is transmitted to the rack bar 110 by engagement of the auxiliary pinion and the rack teeth of the second tooth portion 112, but is transmitted by the ball screw. In this case, a thread groove of a ball screw is formed in the rack bar 110 instead of the rack teeth of the second tooth portion 112. The sliding noise when the ball nut slides in the thread groove can also be suppressed by the damping material 117.

  FIG. 10 shows a configuration of another example of a rack bar for describing the embodiment of the present invention.

  The rack bar shown in FIG. 10 is different from the rack bar 10 shown in FIG. 2 in that an air passage 17 that penetrates the inside of the shaft portion 12 in the axial direction and allows air to flow is further provided.

  The ventilation path 17 is passed through the inside of the shaft portion 113, and is provided at a ventilation hole 17 a provided at an end of the shaft portion 12 on the tooth 11 side and at an end of the shaft portion 12 on the screw hole 13 side. Including the vent hole 17b.

  The ventilation holes 17a and 17b are formed to be open on the outer peripheral surface of the rack bar 10, are separated by the shaft portion 12 and a slide bearing that supports the shaft portion 12, and are surrounded by the boot 5 (see FIG. 1). To the left and right enclosed spaces.

  The damping material 16 is formed in a tubular shape and is inserted into the shaft portion 12 as the hollow portion 15, and the inside of the shaft portion 12 communicates with the ventilation holes 17 a and 17 b at both ends of the ventilation path 17. An air gap is left along the central axis of the tubular damping material 16. Therefore, the flow of air through the ventilation path 17 between the left and right sealed spaces surrounded by the boots 5 is maintained.

  When the rack bar 10 is moved, air flows from one of the left and right sealed spaces surrounded by the boot 5 from one of the spaces where the rack bar 10 protrudes to the other space via the ventilation path 17. Thereby, it is possible to suppress that the air is compressed in one space where the rack bar 10 protrudes, and that the movement of the rack bar 10 is hindered as a reaction, and the steering feeling can be improved.

  Note that the vibration damping material 16 may be formed into a granular shape, and a large number of the vibration damping materials 16 may be packed inside the shaft portion 12. In this case, a gap is left between the granular vibration damping materials 16. By connecting these gaps, a gap for communicating the ventilation holes 17 a and 17 b at both ends of the ventilation path 17 is left inside the shaft portion 12.

  The configuration of the ventilation path 17 described above is also applicable to the rack bar 110 incorporated in the dual pinion type steering device 101 shown in FIGS. 6 and 7, and the rack bar shown in FIG. 11 is shown in FIG. The rack bar 110 is further provided with an air passage 118 that penetrates the inside of the shaft portion 113 in the axial direction and allows air to flow.

  The ventilation passage 118 is passed through the interior of the first tooth portion 111 and the shaft portion 113 which are formed as a continuous hollow portion 116, and has a ventilation hole 118 a provided at an end of the first tooth portion 111, and a shaft portion. 113 includes a vent hole 118b provided at the end of the second tooth portion 112 side.

  The ventilation holes 118a and 118b are formed to be open on the outer peripheral surface of the rack bar 110, are separated by the shaft 113 and a slide bearing supporting the shaft 113, and are surrounded by the boot 105 (see FIG. 6). To the left and right enclosed spaces.

  The vibration damping material 117 is formed in a tubular shape, and is fitted into the first tooth portion 111 and the shaft portion 113 which are the hollow portions 116. A gap for communicating the ventilation holes 118a and 118b, which are both ends, is left along the central axis of the tubular damping material 117. Therefore, the circulation of the air through the ventilation path 118 between the left and right sealed spaces surrounded by the boots 105 is maintained.

  Also in this example, when the rack bar 110 is moved, air flows from the one space where the rack bar 110 projects out of the left and right sealed spaces surrounded by the boots 105 to the other space via the air passage 118. Flowed. Thereby, it is possible to suppress that the air is compressed in one space where the rack bar 110 protrudes, and that the movement of the rack bar 110 is hindered as a reaction, and the steering feeling can be improved.

  In addition, the vibration damping material 117 may be formed into a granular shape, and a large number of the vibration damping materials 117 may be packed inside the first tooth portion 111 and the shaft portion 113. Air gaps are left between the air gaps, and the air gaps connecting the air holes 118 a and 118 b at both ends of the air passage 118 are left inside the first tooth portion 111 and the shaft portion 113.

  The present invention has been described above by taking the rack bars 10 and 110 incorporated in the electric power steering devices 1 and 101 using the motors 8 and 108 as an example. The present invention is also applicable to a rack bar incorporated in a power steering device.

DESCRIPTION OF SYMBOLS 1 Steering device 2 Rack housing 3 Tie rod 4 Joint 5 Boot 6 Steering gear box 7 Input shaft 8 Motor 10 Rack bar 11 Teeth 12 Shaft 13 Screw hole 14 Hole 15 Hollow 16 Damping material 17 Ventilation passages 17a, 17b Ventilation holes 101 Steering device 102 Rack housing 104 Joint 105 Boot 106 Steering gear box 107 Input shaft 108 Motor 109 Auxiliary gear box 110 Rack bar 111 First tooth portion 112 Second tooth portion 113 Shaft portion 114 Screw hole 115 Hole 116 Hollow portion 117 Vibration suppression Material 118 Ventilation passage 118a, 118b Vent

Claims (4)

A vibration damper having a tooth portion formed with a plurality of rack teeth and a shaft portion provided adjacent to the tooth portion in the axial direction, having a hollow portion in at least a part in the axial direction, and having a tubular shape. A rack bar in which a material is inserted inside the hollow portion along an axis ,
An air passage that pierces the inside of the shaft portion in the axial direction and allows air to flow therethrough,
The hollow portion is provided at least in the shaft portion,
The air passage is passed through the inside of the hollow portion,
A rack bar in which a void for communicating both ends of the ventilation path is left inside the hollow portion provided with the vibration damping material. The rack bar according to claim 1, wherein
At least partially made of tubing,
A rack bar, wherein the vibration damping material is fixed inside the pipe material. The rack bar according to claim 1, wherein
At least partially made of solid bars,
A hole extending in the axial direction from one end is formed in the bar,
A rack bar, wherein the damping material is fixed inside the hole. A steering device incorporating the rack bar according to claim 1.

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