JP2009120027A - Hydraulic power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid oil film break of a resin bush due to rise of oil temperature of a cylinder tube in a hydraulic power steering system. <P>SOLUTION: This power steering system 10 is constituted by inserting a rack shaft 15 in an oil chamber which the cylinder tube 14 of a power cylinder 13 forms and fitting a metal bush 33 and the resin bush 34 having an inside diameter smaller than that of the metal bush 33 adjacent to the metal bush 33 in a bearing part provided on an end part of the cylinder tube 14 and supporting the rack shaft 15, and a grease basin 35 facing an outer periphery of the rack shaft 15 is provided on the end part of the cylinder tube 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydraulic power steering apparatus.

In the electric power steering apparatus, as described in Patent Document 1, a rack having a rack shaft fitted to a bearing portion in a gear box and a metal bush arranged adjacent to the metal bush and smaller than the metal bush (tightening). Some are supported by a resin bush having an inner diameter. According to this, the backlash (fine vibration) of the rack shaft resulting from the clearance between the rack shaft and the metal bush is absorbed by the resin bush, so that no abnormal noise is generated. In addition, since a heavy load on the rack shaft can be received by the metal bush, there is no problem in the operation of the rack shaft. Furthermore, in order to eliminate the backlash of the rack shaft, it is not necessary to specially improve the accuracy of the metal bush or the rack shaft, and these accuracy can be made appropriate.
JP2000-72005

  In the hydraulic power steering apparatus, the rack shaft is fitted into an oil chamber formed by the cylinder tube of the power cylinder, and the rack shaft bearing provided at the end of the cylinder tube is used for the electric power steering apparatus described in Patent Document 1. If this bearing structure is applied, there is a concern that the oil temperature rising in the oil chamber of the cylinder tube is transmitted to the resin bush via the rack shaft, and as a result, the oil film of the resin bush is cut. This oil film breakage causes wear of the resin bush and generation of sliding noise.

  An object of the present invention is to provide an oil film of a resin bush due to an increase in oil temperature of a cylinder tube when a resin bush having a tightening margin is fitted to a bearing portion of a rack shaft provided at an end of the cylinder tube in a hydraulic power steering device. It is to avoid cutting.

  According to the first aspect of the present invention, a rack shaft is fitted into an oil chamber formed by a cylinder tube of a power cylinder, and a metal bush and a metal bush are provided at a bearing portion provided at an end of the cylinder tube and supporting the rack shaft. In a hydraulic power steering apparatus in which a resin bush having an inner diameter smaller than that of the metal bush is fitted adjacently, a grease reservoir that faces the outer periphery of the rack shaft is provided at the end of the cylinder tube.

  According to a second aspect of the present invention, in the first aspect of the present invention, the grease reservoir is arranged in the axial direction of the end portion of the cylinder tube, closer to the oil chamber than the metal bush and the resin bush. is there.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the bearing portion and the grease reservoir are coupled to a cylinder tube and provided at a cylinder end constituting an end portion of the cylinder tube. .

(Claim 1)
(a) In the hydraulic power steering device, the grease in the grease reservoir is always passed through the outer periphery of the rack shaft under the condition that a resin bush having a tightening margin is fitted to the bearing portion of the rack shaft provided at the end of the cylinder tube. It is supplied to the resin bush to ensure the lubricity of the resin bush. Thereby, even if the oil temperature which rose in the oil chamber in the cylinder tube is transmitted to the resin bush through the rack shaft, the oil film of the resin bush is not cut.

(Claim 2)
(b) The grease reservoir is disposed closer to the oil chamber than the metal bush and the resin bush in the axial direction of the end of the cylinder tube. Accordingly, in order to allow the rubber boot to extend and contract by being supplied and exhausted between the end of the cylinder tube and the end of the rack shaft and covering the rack shaft, it is close to the end of the hollow rack shaft. Even if the drilled air hole approaches the metal bush and the resin bush at the stroke end where the rubber boot of the rack shaft is contracted most, the oil reservoir holds the metal bush and the resin bush between the air hole. The grease in the grease reservoir does not block the air holes.

(Claim 3)
(c) A rack shaft bearing and a grease reservoir are coupled to the cylinder tube and provided at the cylinder end constituting the end of the cylinder tube. Therefore, it is possible to improve the assembling property of the metal bush and the resin bush to the bearing portion and the grease filling property to the grease reservoir.

  FIG. 1 is an overall view showing a hydraulic power steering device, FIG. 2 is an enlarged view of a main part of FIG. 1, FIG. 3 is a schematic view showing a rack shaft and a cylinder end, and FIG. 4 is a schematic view showing a rack shaft bearing structure. .

  The hydraulic power steering apparatus 10 in FIG. 1 has a gear box 11. The gear box 11 includes a gear housing 12 and a cylinder tube 14 of the power cylinder 13. One end of the cylinder tube 14 is press-fitted and fixed to the outer periphery of the cylindrical mounting portion 12 </ b> A of the gear housing 12.

  The hydraulic power steering apparatus 10 has a hollow rack shaft 15 slidably fitted in oil chambers 17A and 17B formed by the gear housing 12 and the cylinder tube 14 of the gear box 11, and the cylinder tube 14 is mounted on the rack shaft 15. The piston 16 that is slidably fitted is fixed. The power cylinder 13 divides the oil chambers 17A and 17B of the cylinder tube 14 into a first chamber 17A and a second chamber 17B by a piston 16. The first chamber 17A is loaded on one end side of the cylinder tube 14 and sealed with an oil seal 18A that is in sliding contact with the outer periphery of the rack shaft 15, and the second chamber 17B is loaded on the other end side of the cylinder tube 14 and mounted on the rack shaft 15. It is sealed by an oil seal 18B that is in sliding contact with the outer periphery of the oil.

  In the hydraulic power steering apparatus 10, a valve body 21 of a control valve 20 is fixed to a gear housing 12. The control valve 20 pivotally supports an input shaft 22 that rotates in conjunction with the steering wheel on the valve body 21, and includes a circular rotor (not shown) integrated with the input shaft 22 and a torsion bar 22 </ b> A fixed to the input shaft 22. A circular sleeve (not shown) fixed together with a pinion (not shown) at the tip is coaxially arranged so as to be relatively displaceable by elastic torsional deformation of the torsion bar 22A according to the steering torque applied to the steering wheel. The pump-side supply flow path and the tank-side return flow path are switched and connected to the first and second supply / discharge flow paths 19A and 19B connected to the first chamber 17A and the second chamber 17B, respectively, according to the steering operation. A pinion (not shown) fixed to the sleeve (not shown) is engaged with the rack teeth of the rack shaft 15.

  As shown in FIG. 2, the hydraulic power steering apparatus 10 includes a cylinder tube 14 of a power cylinder 13 made of a thin steel pipe, and an iron cylinder end 30 is screwed onto a threaded portion on the inner periphery of the other end of the cylinder tube 14. Fix it. A shoulder surface 31 provided at an intermediate portion in the axial direction of the cylinder end 30 abuts against an end surface of the cylinder tube 14. One end of the rack shaft 15 is supported inside the gear housing 12 by a rack guide (not shown) provided on the back side of the meshing portion with the pinion shaft, and the other end of the rack shaft 15 is a bearing on the inner periphery of the cylinder end 30. It is supported by a metal bush 33 and a resin bush 34 fitted to the portion 32. The resin bushing 34 is disposed adjacent to the anti-oil chamber 17B side of the metal bush 33, has an inner diameter smaller than that of the metal bush 33, and supports the rack shaft 15 with a tight fit. In the cylinder tube 14, an oil seal 18 </ b> A that is loaded on one end side of the cylinder tube 14 and seals the first chamber 17 </ b> A is backed up by a backup ring 12 </ b> B provided between the end face of the cylindrical mounting portion 12 </ b> A of the gear housing 12. The oil seal 18B that is loaded on the other end side of the cylinder tube 14 and seals the second chamber 17B is backed up by the end face of the cylinder end 30.

  The hydraulic power steering apparatus 10 projects both ends of the rack shaft 15 to the left and right of the gear box 11, and screwes and fixes the male thread portions of the left and right rack ends 40 to the inner periphery of these ends. The left and right tie rods 41 are connected to each other, and the wheels are connected to the tie rods 41 so that the left and right wheels can be steered. At one end side of the gear box 11, both end portions of the rubber boot 42 </ b> A are fastened to and spanned from the end portion of the gear housing 12 and one of the tie rods 41 (end portion of the rack shaft 15), and project from the gear box 11. One end of the rack shaft 15 to be covered is covered. On the other end side of the gear box 11, both end portions of the rubber boot 42 </ b> B are fastened to and spanned from the end portion of the cylinder end 30 and the other tie rod 41 (end portion of the rack shaft 15). The other end of the protruding rack shaft 15 is covered. Air holes 15 </ b> A penetrating into and out of the hollow portion of the rack shaft 15 are formed in the vicinity of both ends of the rack shaft 15 protruding from the gear box 11. As a result, when the rack shaft 15 strokes left and right and the one rubber boot 42A and the other rubber boot 42B expand and contract with each other, the air in the rubber boot 42A and the air in the rubber boot 42B are removed from the air hole 15A and the hollow portion of the rack shaft 15. The rubber boots 42A and 42B are allowed to expand and contract.

  The hydraulic power steering device 10 controls the supply and discharge of pressure oil to and from the first chamber 17A and the second chamber 17B of the power cylinder 13 by the above-described operation of the control valve interlocked with the steering operation. The tie rod 41 is driven to assist the steering force of the steering wheel by the driver.

  At this time, in the hydraulic power steering device 10, as described above, the bearing portion 32 for the rack shaft 15 provided in the cylinder end 30 is disposed on the metal bush 33 and the anti-oil chamber 17 </ b> B side of the metal bush 33. A resin bushing 34 that is disposed adjacently and has a smaller inner diameter than the metal bushing 33 is fitted. As a result, the backlash (microvibration) of the rack shaft 15 due to the clearance between the rack shaft 15 and the metal bush 33 is absorbed by the resin bush 34, so that no abnormal noise is generated. Further, since the heavy load of the rack shaft 15 can be received by the metal bush 33, the rack shaft 15 is not hindered in operation. Furthermore, in order to eliminate the backlash of the rack shaft 15, it is not necessary to specially improve the accuracy of the metal bush 33 and the rack shaft 15, and these accuracy can be made appropriate.

  However, in the hydraulic power steering device 10, in order to avoid the oil film of the resin bush 34 being cut off due to an increase in the oil temperature of the cylinder tube 14, as shown in FIGS. 2, 3, and 4, In addition, a grease reservoir 35 facing the outer periphery of the rack shaft 15 is provided, and the grease reservoir 35 is filled with grease G (FIG. 4).

  As shown in FIG. 4A, the grease reservoir 35 is disposed closer to the oil chamber 17B (oil seal 18B) than the metal bush 33 and the resin bush 34 in the axial direction of the cylinder end 30. The grease reservoir 35 is formed by an annular groove provided in the inner periphery of an intermediate portion closer to the oil chamber 17B (oil seal 18B) than the metal bush 33 and the resin bush 34 in the axial direction of the cylinder end 30.

  In this embodiment, a grease reservoir 35, a metal bush 33, and a resin bush 34 are arranged in this order from the oil chamber 17B side in the axial direction of the cylinder end 30, and the grease reservoir 35 and the metal bush 33 are adjacent to each other without a gap. However, the grease reservoir 35, the resin bush 34, and the metal bush 33 may be disposed in this order from the oil chamber 17B side in the axial direction of the cylinder end 30. In this case, the grease reservoir 35 and the resin bush 34 are adjacent to each other without a gap. Also good.

  Therefore, as shown in FIG. 3, the hydraulic power steering apparatus 10 fills the grease reservoir 35 of the cylinder end 30 assembled with the metal bush 33 and the resin bush 34 with the grease G, and attaches the rack shaft 15 to the inner periphery of the cylinder end 30. The cylinder end 30 is fixed to the cylinder tube 14 by screwing.

  When the backup ring 30A for the oil seal 18B is provided on the end face of the cylinder end 30 near the oil chamber 17B, the grease reservoir 35 is provided on the end face of the cylinder end 30 near the oil chamber 17B, as shown in FIG. May be formed by an annular hole provided at the opening end of the inner periphery that is open to the oil chamber 17B (oil seal 18B) from the metal bush 33 and the resin bush 34. In FIG. 4B, a grease reservoir 35, a metal bush 33, and a resin bush 34 are arranged in this order from the oil chamber 17B side in the axial direction of the cylinder end 30, and the grease reservoir 35 and the metal bush 33 are adjacent to each other without a gap. However, the grease reservoir 35, the resin bush 34, and the metal bush 33 may be disposed in this order from the oil chamber 17B side in the axial direction of the cylinder end 30. In this case, the grease reservoir 35 and the resin bush 34 are adjacent to each other without a gap. Also good.

  Further, as shown in FIG. 4C, the grease reservoir 35 may be formed by an annular groove provided on the inner periphery of an intermediate portion sandwiched between the metal bush 33 and the resin bush 34 in the axial direction of the cylinder end 30. In FIG. 4C, the metal bush 33, the grease reservoir 35, and the resin bush 34 are arranged in this order from the oil chamber 17B side in the axial direction of the cylinder end 30, but from the oil chamber 17B side in the axial direction of the cylinder end 30. A resin bush 34, a grease reservoir 35, and a metal bush 33 may be arranged in this order.

According to the present embodiment, the following operational effects can be obtained.
(a) In the hydraulic power steering apparatus 10, the grease G in the grease reservoir 35 is racked in a state in which a resin bush 34 having a tightening margin is fitted to the bearing portion 32 of the rack shaft 15 provided at the end of the cylinder tube 14. It is always supplied to the resin bush 34 via the outer periphery of the shaft 15 to ensure the lubricity of the resin bush 34. As a result, even if the oil temperature rising in the oil chambers 17A and 17B in the cylinder tube 14 is transmitted to the resin bush 34 via the rack shaft 15, the oil film of the resin bush 34 is not cut.

  (b) The grease reservoir 35 is disposed closer to the oil chamber 17B than the metal bush 33 and the resin bush 34 in the axial direction of the end of the cylinder tube 14. Therefore, in order to allow expansion and contraction of the rubber boots 42A and 42B by supplying and discharging air in the rubber boots 42A and 42B that are spanned between the end of the cylinder tube 14 and the end of the rack shaft 15 and cover the rack shaft 15. Even if the air hole 15A drilled near the end of the hollow rack shaft 15 approaches the metal bush 33 and the resin bush 34 at the stroke end where the rubber boots 42A and 42B of the rack shaft 15 are contracted most, the grease reservoir 35 Is on the side of the oil chamber 17B that sandwiches the metal bush 33 and the resin bush 34 between the air hole 15A and the grease G of the grease reservoir 35 does not block the air hole 15A.

  (c) The bearing portion 32 of the rack shaft 15 and the grease reservoir 35 are coupled to the cylinder tube 14 and provided at the cylinder end 30 constituting the end portion of the cylinder tube 14. Therefore, the assembling property of the metal bush 33 and the resin bush 34 to the bearing portion 32 and the filling property of the grease G to the grease reservoir 35 can be improved.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration of the present invention is not limited to these embodiments, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, the bearing portion and grease reservoir of the rack shaft of the present invention may be provided at the end of the cylinder tube itself.

FIG. 1 is an overall view showing a hydraulic power steering apparatus. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is a schematic diagram showing a rack shaft and a cylinder end. FIG. 4 is a schematic diagram showing the bearing structure of the rack shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydraulic power steering apparatus 13 Power cylinder 14 Cylinder tube 15 Rack shaft 17A, 17B Oil chamber 30 Cylinder end 32 Bearing part 33 Metal bush 34 Resin bush 35 Grease pool

Claims (3)

The rack shaft is inserted into the oil chamber formed by the cylinder tube of the power cylinder, and the metal bush and the metal bush adjacent to the metal bush are installed in the bearing portion provided at the end of the cylinder tube to support the rack shaft. In a hydraulic power steering device in which a resin bush having a small inner diameter is fitted,
A hydraulic power steering device, wherein a grease reservoir is provided at an end of the cylinder tube so as to face an outer periphery of a rack shaft.   2. The hydraulic power steering apparatus according to claim 1, wherein the grease reservoir is disposed closer to the oil chamber than the metal bush and the resin bush in the axial direction of the end portion of the cylinder tube.   The hydraulic power steering device according to claim 1 or 2, wherein the bearing portion and the grease reservoir are coupled to a cylinder tube and provided at a cylinder end constituting an end portion of the cylinder tube.

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