JP2012214164A - Rack-and-pinion steering gear unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure capable of making durability preferable by preventing the outer peripheral surface of a pressing block and the inner peripheral surface of a cylinder part from colliding with each other with great force.SOLUTION: A small-diameter step part 27 is formed on the entire perimeter of an end on the outer end opening side of the cylinder part 20, on the outer peripheral surface of the pressing block 21a. A buffer ring 28, which is made of a material greater in internal loss than a material constituting the pressing block 21a and a casing 10 and which has an outside diameter as large as/larger than an outside diameter of the pressing block 21a, is externally fitted to the small-diameter step part 27. Even when the pressing block 21a is swung and displaced in the cylinder part 20 along with power transmission, an outer peripheral edge of a leading end of the pressing block 21a and the inner peripheral surface of the cylinder part 20 are prevented from colliding with each other with the strong force.

Description

  The present invention relates to an improvement of a rack and pinion type steering gear unit that constitutes a steering device for giving a steering angle to a steering wheel of an automobile.

   A steering device including a rack and pinion type steering gear unit that uses a rack and pinion as a mechanism for converting a rotational motion input from a steering wheel into a linear motion for giving a steering angle is disclosed in, for example, Patent Documents 1 to 3. 5 and the like. In addition, the rack and pinion type steering gear unit can be configured to be small and light, and since it has high rigidity and a good steering feeling, it is actually widely used. 5 to 7 show a structure described in Patent Document 4 as an example of a steering apparatus incorporating such a rack and pinion type steering gear unit. In this steering device, the movement of the steering shaft 2 that rotates in accordance with the operation of the steering wheel 1 is transmitted to the pinion shaft 6 that is the input shaft of the steering gear unit 5 through the universal joints 3 and 3 and the intermediate shaft 4. To do. In addition, the up-down direction of the said FIGS. 6-7 does not necessarily correspond with the up-down direction in use condition. The vertical direction is appropriately selected depending on the state of assembly in the vehicle, and in general, the pinion shaft 6 is installed in an inclined state with respect to the vertical direction.

  In any case, the steering gear unit 5 is formed by meshing the pinion teeth 7 provided on a part of the pinion shaft 6 in the axial direction with the rack teeth 9 provided on the front surface of the rack shaft 8. Of these, the rack teeth 9 having a twist angle θ as schematically shown in FIG. 8 are used, and a helical gear having a similar twist angle is also used for the pinion teeth 7 correspondingly. ing. Each of the pinion shaft 6 and the rack shaft 8 is housed in a casing 10. The casing 10 includes a main storage portion 11 and a sub storage portion 12 each having a cylindrical shape. Of these, the main storage portion 11 is open at both ends. Moreover, this sub-accommodating part 12 is provided in a part of the main accommodating part 11, and one end is opened. The central axis of the main storage portion 11 and the central axis of the sub storage portion 12 are in a twisted positional relationship with each other. The rack shaft 8 is inserted through the main storage portion 11 of the rack shaft 8 so as to be axially displaceable, and both end portions protrude from the main storage portion 11. Also, a pair of rack guides (sliding bearings) 13 and 13 supported on both ends of the inner peripheral surface of the main storage portion 11 are brought into sliding contact with the outer peripheral surface of the rack shaft 8 so that the rack shaft 8 The main storage portion 11 can be displaced in the axial direction without rattling. And the base end part of the tie rods 15 and 15 is couple | bonded with the both ends of this rack shaft 8 via the spherical couplings 14 and 14, respectively. The tip portions of both tie rods 15 and 15 are respectively connected to the tip portions of knuckle arms (not shown) by pivots. The rack shaft 8 does not rotate around its central axis due to the engagement of the pinion teeth 7 and the rack teeth 9.

  The pinion shaft 6 supports the tip half of the pinion teeth 7 in the sub-accommodating portion 12 so that it can only rotate. For this purpose, the tip end portion of the pinion shaft 6 is supported by the radial needle bearing 16 at the back end portion of the auxiliary storage portion 12. Further, a radial load and a thrust load are supported by a single-row ball bearing 17 such as a deep groove type, a three-point contact type, or a four-point contact type at an intermediate portion of the pinion shaft 6 near the opening of the auxiliary storage portion 12. It supports as possible (rotates while preventing axial displacement). In order to support the ball bearing 17 at a predetermined position of the casing 10, a holding screw cylinder 18 is screwed to the casing 10, and an inner circumferential surface of the holding screw cylinder 18 and an outer circumferential surface of the pinion shaft 6 are arranged. The gap between them is closed by the seal ring 19.

  A cylinder portion 20 is provided on the opposite side of the auxiliary storage portion 12 with respect to the diameter direction of the main storage portion 11, and a pressing block 21 is fitted in the cylinder portion 20. An elastic member such as a spring 23 is provided between the cover 22 screwed into the opening of the cylinder portion 20 and the pressing block 21 to press the pressing block 21 toward the rack shaft 8. . As a result, the rack shaft 8 is elastically pressed toward the pinion shaft 6 to eliminate backlash of the meshing portion between the pinion teeth 7 and the rack teeth 9. Furthermore, the meshing state of the meshing portion is properly maintained regardless of the force in the direction away from the pinion shaft 6 applied to the rack shaft 8 with the transmission of power at the meshing portion between the teeth 7 and 9. I am trying to do it. Of the both end surfaces in the axial direction of the pressing block 21, the inner end surface on the side pressing the rack shaft 8 is a partially cylindrical concave surface according to the shape of the back surface of the rack shaft 8. On the other hand, the outer end surface of the pressing block 21 is formed with a recess 24 in the center portion to serve as a spring seat for contacting one end portion of the spring 23, and the weight of the pressing block 21 is reduced. I am trying.

  Further, a locking groove 25 is formed over the entire periphery of the outer peripheral surface of the pressing block 21 (a portion close to the rack shaft 8), and an elastic ring is formed in the locking groove 25. 26 is locked. The elastic ring 26 has a circular cross-sectional shape in a free state like an O-ring, and the outer diameter related to the cross-sectional shape is larger than the depth of the locking groove 25 in the free state. Such an elastic ring 26 is elastically compressed between the bottom surface of the locking groove 25 and the inner peripheral surface of the cylinder portion 20. And while preventing that the press block 21 rattles in this cylinder part 20, mud water etc. in the said casing 10 through the clearance gap between the internal peripheral surface of these cylinder parts 20, and the outer peripheral surface of the press block 21 Prevent foreign material from entering. Note that a minute gap is interposed between the outer peripheral surface of the pressing block 21 and the inner peripheral surface of the cylinder portion 20 to allow the pressing block 21 to be displaced in the axial direction.

  When a steering angle is given to the left and right front wheels by the steering device incorporating the steering gear unit 5 as described above, the pinion shaft 6 is rotated by operating the steering wheel 1. Then, the rack shaft 8 is displaced in the axial direction based on the meshing of the pinion teeth 7 and the rack teeth 9. Then, the tie rods 14 and 14 coupled to both ends of the rack shaft 8 are pushed and pulled to give a desired rudder angle to the front wheels.

  In the case of the conventional steering gear unit 5 as described above, the rotational direction of the pinion shaft 6 is reversed when the torsion angle θ is provided in the pinion teeth 7 and the rack teeth 9. The pressing block 21 is oscillated and displaced. And with this rocking displacement, the tip end portion (the end portion opposite to the engaging portion with the rack shaft 8) of the outer peripheral surface of the pressing block 21 and the inner peripheral surface of the cylinder portion 20 May collide vigorously, generating unpleasant vibrations and noises, or causing significant wear on both peripheral surfaces. The reason why such a problem occurs will be described with reference to FIGS.

  The central axis of the pressing block 21 and the central axis of the cylinder portion 20 do not transmit force between the pinion teeth 7 and the rack teeth 9 and no external force is applied to the pressing block 21. Then, as shown in FIG. 9A, they tend to almost coincide with each other. If the central axis of the pressing block 21 and the central axis of the cylinder part 20 are completely aligned, the outer peripheral surface of the pressing block 21 and the inner peripheral surface of the cylinder part 20 are all around. It will be in the state which opposes through a clearance gap. In an actual case, both the central axes are slightly inclined and the both peripheral surfaces often abut each other. However, the swing displacement of the pressing block 21 is shown in FIG. It is performed on the basis of the state shown in A). Further, in this reference state, the inner peripheral surface of the cylinder portion 20 and the outer peripheral edge of the elastic ring 26 are in light contact with each other over the entire periphery.

  On the other hand, as the pinion teeth 7 and the rack teeth 9 are provided with a torsion angle θ, the force between the pinion teeth 7 and the rack teeth 9 due to the rotation of the pinion shaft 6 is increased. At the time of transmission, a force in the axial direction of the pinion shaft 6 is applied to the rack shaft 8 as indicated by an arrow α in FIG. The direction of action of this force is reversed when the direction of rotation of the pinion shaft 6 is reversed. The rack shaft 8 has a long total length of about 400 to 800 mm and is supported by the rack guides 13 and 13 only in the vicinity of both end portions. 9) (flexible in the left-right direction), and in some cases it can be twisted, albeit slightly. Such elastic deformation of the rack shaft 8 is linked to the displacement of the portion of the rack teeth 9 meshing with the pinion teeth 7, and this displacement presses the rack shaft 8. This is connected to the displacement of the pressing block 21 in the arrow α direction. In accordance with this displacement, the pressing block 21 is oscillated and displaced corresponding to the displacement direction of the rack shaft 8 as shown exaggeratedly in FIG.

  As the rocking displacement occurs, the outer peripheral edge of the tip of the pressing block 21 and the inner peripheral surface of the cylinder 20 collide with each other, causing unpleasant vibration, noise, and wear. In particular, the outer peripheral edge portion of the front end portion of the pressing block 21 (the edge portion opposite to the rack shaft 8) has a short distance from the elastic ring 26, and the force is amplified by the lever principle, In addition to the collision part between the two peripheral surfaces, the surface pressure of this collision part increases. In this state, if the pressing block 21 is displaced in the axial direction, the wear on both peripheral surfaces tends to proceed.

JP-A-55-68472 JP-A-10-217985 JP 2007-186185 A JP 2009-184591 A JP 2009-190426 A

  In view of the circumstances as described above, the present invention can prevent the outer peripheral surface of the pressing block from colliding with the outer peripheral surface of the tip and the inner peripheral surface of the cylinder portion with high surface pressure. It was invented to realize a structure of a steering gear unit that can be improved.

The rack and pinion type steering gear unit according to the present invention includes a casing, a rack shaft, a pinion shaft, a pressing block, and an elastic member in the same manner as the conventionally known rack and pinion type steering gear unit. Prepare.
Of these, the casing includes a cylindrical main storage portion that is open at both ends, a cylindrical sub storage portion that is provided in a twisted positional relationship with respect to the main storage portion, and that is open at one end, and the main storage portion. And a cylinder portion provided in a direction orthogonal to the main storage portion in a state where the inside and outside of the chamber are communicated.
Further, the rack shaft is provided with rack teeth on the front surface, and is installed in the main housing portion of the casing so as to be capable of axial displacement.
In addition, the pinion shaft is configured such that pinion teeth formed on the front half portion in the axial direction mesh with the rack teeth, and the base half portion in the axial direction protrudes outward from the opening of the auxiliary storage portion of the casing. In this sub-accommodating portion, it is rotatably arranged.
The pressing block is fitted in the cylinder portion so as to be movable relative to the rack shaft.
The elastic member is, for example, a compression coil spring, and is provided between the pressing block and a lid fixed to the outer end opening of the cylinder portion. Then, the pressing block is pressed toward the back surface of the rack shaft.

In particular, in the rack and pinion type steering gear unit of the present invention, the outer end opening side of the outer peripheral surface of the pressing block is located at the end (outer peripheral edge of the tip end) of the cylinder portion. The small-diameter step part which the end surface side and the outer peripheral surface side opened is formed over the perimeter. That is, the outer diameter of the end of the pressing block in which the small diameter step is formed is made smaller than the outer diameter closer to the inner end than the small diameter step. Then, a buffer ring made of a material having an internal loss larger than that of the material constituting the pressing block and the casing and having an outer diameter equal to or larger than the outer diameter of the pressing block is externally fitted to the small diameter step portion. As a material constituting the buffer ring, a relatively soft material can be adopted among polymer materials such as elastomers such as rubber and vinyl or synthetic resins. Depending on the material of the casing provided with the cylinder part (for example, when the casing is made of a hard metal such as an iron-based alloy), a soft metal such as lead, an aluminum-based alloy, or a magnesium-based alloy is used. You can also do it. In short, any material can be employed as long as it has a material with a significantly larger internal loss (softer) than the material constituting the pressing block and the casing.
In the case of carrying out the present invention as described above, preferably, as in the invention described in claim 2, the buffer ring is externally fixed to the small diameter step portion by an interference fit.

According to the rack and pinion type steering gear unit of the present invention configured as described above, the outer peripheral edge of the front end of the pressing block and the inner peripheral surface of the cylinder can be prevented from colliding with force, and the durability is excellent. Can be.
That is, even when the pressing block is oscillated and displaced, the outer peripheral surface of the buffer block and the inner peripheral surface of the cylinder portion only collide with each other at the tip of the outer peripheral surface of the pressing block. The main part of the pressing block does not collide. Since the buffer ring is made of a material having a large internal loss, even if the outer peripheral surface of the buffer ring collides with the inner peripheral surface of the cylinder portion, the collision energy is a deformation of the material constituting the buffer ring. It is absorbed by (internal loss) and does not lead to the generation of large vibrations or abnormal noise. Further, no great impact is applied to the inner peripheral surface. As a result, in addition to suppressing the unpleasant vibration and noise as described above, the wear of the outer peripheral surface of the pressing block and the inner peripheral surface of the cylinder portion can be suppressed, and the durability of the rack and pinion type steering gear unit can be suppressed. Can be improved.
Furthermore, according to the structure of the invention described in claim 2, it is possible to prevent the buffer ring from dropping from the small diameter step portion of the pressing block during the assembly.

The fragmentary sectional view equivalent to the left part of FIG. 7 which shows the 1st example of embodiment of this invention. The X section enlarged view of FIG. FIG. 10 is a view similar to FIG. 9B, showing a state where the pressing block is oscillating and displaced. The figure similar to FIG. 2 which shows the 2nd example of embodiment of this invention. The partial cutting side view which shows an example of the steering device for motor vehicles incorporating the rack and pinion type steering gear unit. YY sectional drawing of FIG. The expanded ZZ sectional view of FIG. 7 is a schematic diagram showing the rack shaft taken out and viewed from above in FIG. The schematic diagram which shows the state to which a press block rock | fluctuates and displaces with the motive power transmission between a rack tooth and a pinion tooth in a neutral state (A) and an inclination state (B).

[First example of embodiment]
1 to 3 illustrate a first example of an embodiment of the present invention corresponding to claims 1 and 2. The feature of the present invention including this example is that the outer peripheral edge of the tip of the pressing block 21a and the inner peripheral surface of the cylinder portion 20 of the casing 10 collide vigorously regardless of the rocking displacement of the pressing block 21a. It is in the structure for preventing it. Since the structure and operation of the other parts are the same as those of the conventional structure shown in FIG. 7, the illustration and description of the equivalent parts are omitted or simplified, and the following description will focus on the characteristic parts of the present invention.

  In the rack and pinion type steering gear unit of the present example, the outer end surface of the front end portion (lower end portion in FIGS. 1 to 3) of the pressing block 21a, that is, the outer end opening of the cylinder portion 20 in this outer peripheral surface. A small-diameter stepped portion 27 is formed at the end on the side over the entire circumference. The small diameter step portion 27 is open on the end face side and the outer peripheral face side on the outer end opening side. A buffer ring 28 is externally fitted to the small diameter step portion 27. In the case of this example, the buffer ring 28 is made of a polymer material such as synthetic resin or rubber, and is externally fixed to the small diameter step portion 27 by an interference fit. The outer diameter of the buffer ring 28 is fitted to the small-diameter step portion 27, and the outer side of the pressing block 21a is closer to the inner end than the small-diameter step portion 27 (upper side in FIGS. 1 to 3). The diameter is secured.

  The pressing block 21a is made of a metal such as an iron alloy or an aluminum alloy, or a synthetic resin such as a polyamide resin or a polytetrafluoroethylene resin. In the case of metal, a low friction material such as synthetic resin or oil-impregnated metal is attached to the surface that is in sliding contact with the back surface of the rack shaft 8. In any case, the outer peripheral surface of the pressing block 21a is chamfered on the outer peripheral edge of the inner end portion, which is the end portion on the rack shaft 8 side, so that the pressing block 21a can be easily placed in the cylinder portion 20. So that it can be inserted. When the pressing block 21a is made of a synthetic resin, the synthetic resin constituting the buffer ring 28 is made of a material having a larger internal loss (softer) than the synthetic resin constituting the pressing block 21a. .

  As described above, in the case of the rack and pinion type steering gear unit of the present example, since the buffer ring 27 is externally supported at the tip of the pressing block 21a, the pinion shaft 6 and the rack shaft 8 are Even if the pressing block 21a swings and displaces with the transmission of power, the outer peripheral edge of the pressing block 21a does not collide with the inner peripheral surface of the cylinder portion 20a. The buffer ring 28 may collide with the inner peripheral surface. However, since the buffer ring 28 is made of a material having a large internal loss, the collision energy is consumed when the buffer ring 28 is deformed, and the collision part Vibration and noise generation can be suppressed. As a result, it is possible to prevent unpleasant vibration, noise, or significant wear as described above, regardless of the swing displacement of the pressing block 21a accompanying the power transmission.

  Further, in the case of the structure of this example, the buffer ring 28 is externally fitted to the small diameter step portion 27 by an interference fit. Can be prevented from falling off. That is, in the state where the assembly of the steering gear unit is completed, the buffer ring 28 is suppressed by the lid body 22 and does not come out of the small diameter step portion 27. Accordingly, in terms of function, the buffer ring 28 may be externally fitted to the small-diameter step portion 27 with a gap fit, but in that case, the buffer ring 28 is moved from the small-diameter step portion 27 in the course of assembly work. Is easy to drop off. On the other hand, in the case of this example, it is possible to prevent the buffer ring 28 from falling off and facilitate the assembling work.

[Second Example of Embodiment]
FIG. 4 also shows a second example of an embodiment of the present invention corresponding to claims 1 and 2. In the case of this example, a rubber O-ring is employed as the buffer member 28a that is fitted around the small-diameter step portion 27 of the pressing member 21a. In a state where the buffer member 28a is externally fitted to the small-diameter step portion 27 by an interference fit, the maximum diameter of the buffer member 28a is set to be equal to or larger than the outer diameter of the portion near the base end of the pressing member 21a. Therefore, when the pressing member 21a is oscillated and displaced, the maximum diameter portion of the buffer member 28a is moved to the inner periphery before the outer peripheral edge of the outer peripheral surface of the pressing member 21a collides with the inner peripheral surface of the cylinder portion 20. Abuts against the surface and suppresses vibration and noise at the abutment.
Since the configuration and operation of the other parts are the same as in the first example of the above-described embodiment, illustration and description regarding the equivalent parts are omitted.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Universal joint 4 Intermediate shaft 5 Steering gear unit 6 Pinion shaft 7 Pinion tooth 8 Rack shaft 9 Rack tooth 10 Casing 11 Main storage part 12 Sub-storage part 13 Rack guide 14 Spherical joint 15 Tie rod 16 Radial needle bearing 17 Ball bearing 18 Retaining screw cylinder 19 Seal ring 20 Cylinder part 21, 21a Press block 22 Lid body 23 Spring 24 Recess 25 Locking groove 26 Elastic ring 27 Small diameter step part 28, 28a Buffer ring

Claims (2)

  A cylindrical main storage portion with both ends open, a cylindrical sub storage portion provided in a twisted positional relationship with respect to the main storage portion, and one end open, and a state in which the inside and outside of the main storage portion are communicated And a casing having a cylinder portion provided in a direction orthogonal to the main storage portion, a rack shaft provided with rack teeth on the front surface and installed in the main storage portion of the casing so as to be axially displaceable, and a shaft The pinion teeth formed in the front half of the direction are meshed with the rack teeth and the base half in the axial direction protrudes outward from the opening of the secondary storage part of the casing and can be rotated in the secondary storage part. A pinion shaft disposed in the cylinder portion, a pressure block that is fitted in the cylinder portion so as to be movable relative to the rack shaft, and a lid body fixed to the pressure block and an outer end opening of the cylinder portion. Between In a rack and pinion type steering gear unit comprising an elastic member that presses the pressing block toward the back surface of the rack shaft, an end of the outer peripheral surface of the pressing block on the outer end opening side of the cylinder portion A small-diameter step portion having an opening on the end surface side and the outer peripheral surface side on the outer end opening side is formed on the entire periphery, and the small-diameter step portion has an inner portion than the material constituting the pressing block and the casing. A rack-and-pinion type steering gear unit characterized in that a shock-absorbing ring made of a material having a large loss and having an outer diameter equal to or larger than the outer diameter of the pressing block is externally fitted.   The rack-and-pinion type steering gear unit according to claim 1, wherein the buffer ring is externally fixed to the small-diameter step portion by an interference fit.

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