JP2007001531A - Telescopic shaft for vehicle steering - Google Patents

Abstract

Disclosed is a telescopic shaft for steering of a vehicle that has less influence on the steering feeling and can transmit torque more smoothly during rotation.
Torque transmission grooves 27 and 28 extending in the axial direction of a male shaft 21 and a female shaft 22 that are spline-fitted with each other are formed on the outer peripheral surface of the male shaft 21 and the inner peripheral surface of the female shaft 22 and the torque transmission groove 27 is formed. , 28 is a steering telescopic shaft of a vehicle in which a torque transmission pin 29 that is engaged between the male shaft 21 and the female shaft 22 is disposed, and the outer peripheral surface of the torque transmission pin 29 and / or the grooves of the torque transmission grooves 27, 28. A solid lubricant film 30 made of a solid lubricant was formed on the surface with an area ratio of 75% or more so as to reduce the sliding resistance of the sliding portions of the torque transmission grooves 27 and 28 and the torque transmission pin 29.
[Selection] Figure 3

Description

  The present invention relates to a telescopic shaft used for steering a vehicle such as an automobile.

In general, as shown in FIG. 5, the steering mechanism of an automobile includes a steering wheel 11, a steering shaft 12, a steering column 13, and the like. The steering shaft 12 includes an upper steering shaft portion 121 and a lower steering shaft portion 122. ing.
The upper steering shaft portion 121 and the lower steering shaft portion 122 are composed of telescopic shafts that can be expanded and contracted in the axial direction. Absorption of undesired vibrations in the steering wheel 11 by absorbing axial displacements that occur when the vehicle is traveling by the telescopic shafts. I try not to communicate.

As such a telescopic shaft for steering, for example, the one described in Patent Document 1 below is known, and this telescopic shaft for steering is between a male shaft and a female shaft that are spline-fitted with each other. Although the built-in ball can reduce the sliding resistance in the axial direction, there is a problem that torque cannot be transmitted during rotation.
Therefore, in order to enable transmission of torque, a torque transmission groove extending in the axial direction of the male shaft and the female shaft is formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft, and is engaged with the torque transmission groove. The thing which has arrange | positioned the torque transmission pin between the male shaft and the female shaft is proposed (refer patent document 2).
JP 2001-50293 A JP 2004-130928 A

In the telescopic shaft for steering described in Patent Document 2, both torque transmission and sliding in the axial direction during rotation are improved. However, in a vehicle with low engine vibration such as a so-called luxury car or electric car, Therefore, further improvement is desired.
The present invention has been made paying attention to such problems, and provides a telescopic shaft for steering of a vehicle that has less influence on steering feeling and can transmit torque more smoothly during rotation. It is intended to do.

  In order to achieve the above object, the invention according to claim 1 is characterized in that torque transmission grooves extending in the axial direction of the male shaft and the female shaft that are spline-fitted with each other are formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft. In a telescopic shaft for steering of a vehicle in which a torque transmission pin that is formed and engages with the torque transmission groove is disposed between the male shaft and the female shaft, an outer peripheral surface of the torque transmission pin and / or the torque transmission groove A solid lubricating film made of a solid lubricant is formed on the groove surface of each with an area ratio of 75% or more.

According to a second aspect of the present invention, in the telescopic shaft for steering of the vehicle according to the first aspect, the thickness of the solid lubricating film is 0.1 μm or more and 8.0 μm or less.
According to a third aspect of the present invention, in the telescopic shaft for steering of a vehicle according to the first or second aspect, the outer peripheral surface of the torque transmission pin and / or the groove surface of the torque transmission groove has a depth of 0.1 to 5.0 μm. The present invention is characterized in that fine dimples having the above are formed.

According to a fourth aspect of the present invention, in the telescopic shaft for steering of a vehicle according to any one of the first to third aspects, the center line average roughness of the outer peripheral surface of the torque transmission pin and / or the groove surface of the torque transmission groove. Is within the range of 0.1 to 1.6 μmRa.
According to a fifth aspect of the present invention, in the vehicle telescopic shaft according to any one of the first to fourth aspects, solid lubricant powder is applied to the outer peripheral surface of the torque transmission pin and / or the groove surface of the torque transmission groove. The solid lubricant film is formed by shot peening.

  According to the telescopic shaft for steering of a vehicle according to the first aspect of the present invention, the torque transmission pin and the torque transmission are compared with those in which the solid lubricant film is not formed on the outer peripheral surface of the torque transmission pin and / or the groove surface of the torque transmission groove. The sliding resistance of the sliding part with the groove can be reduced. Further, the seizure resistance of the torque transmission pin can be improved as compared with the solid lubricant film having an area ratio of less than 75%. Therefore, when the rotational torque is transmitted from the male shaft to the female shaft or from the female shaft to the male shaft via the torque transmission pin, the sliding resistance of the sliding portion between the torque transmission pin and the torque transmission groove can be reduced.

According to the telescopic shaft for steering of a vehicle according to the invention of claim 2, a solid lubricating film having sufficient strength can be obtained while maintaining good lubricity, and the sliding of the solid lubricating film with wear powder being suppressed. The sliding resistance of the part can be reduced.
According to the telescopic shaft for steering of a vehicle according to the invention of claim 3, the adhesion strength between the solid lubricant film and the base material is improved by the anchor effect, and the sliding resistance of the sliding portion can be kept low for a long period.

According to the telescopic shaft for steering of a vehicle according to the invention of claim 4, the sliding resistance of the sliding portion can be further reduced and the durability of the torque transmission pin is not impaired.
According to the telescopic shaft for steering of a vehicle according to the invention of claim 5, since the solid lubricating film that is firmly adhered to the base material is formed, lubrication with the solid lubricant is performed over a long period of time, and grease lubrication is used in combination. However, the sliding resistance of the sliding portion can be further reduced and the durability of the torque transmission pin is not impaired.

Hereinafter, a telescopic shaft for steering of a vehicle according to the present invention will be described with reference to the drawings.
1 to 3 are views showing an embodiment of a telescopic shaft for steering according to the present invention. 1 and 2, reference numeral 20 denotes a steering telescopic shaft. The steering telescopic shaft 20 includes a male shaft 21 and a female shaft 22 that are spline-fitted with each other.
The male shaft 21 has a circular cross section in the radial direction, and three ball rolling grooves 23 are formed on the outer peripheral surface of the male shaft 21 at intervals of 120 degrees in the circumferential direction of the male shaft 21. The three torque transmission grooves 27 extending in the axial direction of the male shaft 21 are formed at intervals of 120 degrees in the circumferential direction of the male shaft 21.

On the other hand, the female shaft 22 has a cylindrical cross section in the radial direction, and three ball rolling grooves 24 having a circular arc cross section are formed on the inner peripheral surface of the female shaft 22 in the circumferential direction of the female shaft 22. Are formed along the axial direction of the female shaft 22 and three torque transmission grooves 28 extending in the axial direction of the female shaft 22 are formed at 120 ° intervals in the circumferential direction of the female shaft 22. Yes.
The ball rolling grooves 23 and 24 are opposed to each other, and in order to reduce the sliding resistance in the axial direction of the male shaft 21 and the female shaft 22 between the ball rolling grooves 23 and 24, a plurality of the rolling balls are provided. A ball 25 is interposed so as to freely roll.

The ball rolling groove 23 has a substantially trapezoidal cross section. In each ball rolling groove 23, the ball 25 is pressed against the groove surface of the ball rolling groove 24 to prevent rattling of the ball 25. A plate spring 26 as a member is provided.
The torque transmission grooves 27 and 28 have an arc shape in cross section perpendicular to the longitudinal direction. Further, the torque transmission grooves 27 and 28 are opposed to each other, and between these torque transmission grooves 27 and 28, the torque in the circumferential direction is transmitted from the male shaft 21 to the female shaft 22 or from the female shaft 22 to the male shaft 21. In addition, a torque transmission pin 29 is incorporated.

The torque transmission pin 29 has a circular cross section perpendicular to the longitudinal direction thereof, and a solid lubricating film 30 (see FIG. 3) made of a solid lubricant is 75% or more on the outer peripheral surface of the torque transmission pin 29. It is formed by area ratio.
Here, the reason why the solid lubricant film 30 is formed on the outer peripheral surface of the torque transmission pin 29 with an area ratio of 75% or more will be described.

  The present inventors conducted the following experiment in order to reduce the sliding resistance generated at the sliding portion between the torque transmission grooves 27 and 28 and the torque transmission pin 29. First, the average roughness of the outer peripheral surface of the torque transmission pin before the solid lubricant film was formed was measured. Next, tin powder (or molybdenum disulfide powder with an average particle diameter of 3 μm) having an average particle diameter of 45 μm as defined in JISR6001 is sprayed onto the outer peripheral surface of the torque transmission pin (pin weight: 1 to 6 kg) by a shot peening device, A solid lubricant film was formed on the outer peripheral surface of the torque transmission pin. Then, after measuring the area ratio and average film thickness of the solid lubricant film, a seizure durability test and a sliding resistance test of the torque transmission pin were performed. The results are shown in Table 1.

The shot peening was performed under the conditions of the injection pressure: 19.6 to 88.2 N / cm ² and the injection time: 10 to 20 min. In addition, the area ratio of the solid lubricant film was measured by observing the outer peripheral surface of the torque transmission pin on which the solid lubricant film was formed with an EPMA (Electron Probe Microanalyzer) (magnification × 2000, 30 fields of view). Is magnified 1000 times, it is assumed that the solid lubricant film is formed in a region where the element characteristic X-ray intensity before the solid lubricant film is formed is 10 times or more. The average value of the area ratio of the lubricating coating was determined.

  In order to protect the solid lubricating film, the average film thickness of the solid lubricating film is such that first, the surface of the torque transmission pin is coated with a compound obtained by dissolving polyamideimide, which is a thermosetting resin, in pyrrolidone, and then the ambient temperature of 175 ° C. The torque transmission pin was allowed to stand for 2 hours to cure the surface layer. Next, the torque transmission pin is cut and embedded in an epoxy resin, and the cut surface is mirror-finished by buffing, and then the torque transmission pin is placed in a 3% picral solution for the purpose of roughening the mirror-finished cut surface. Soaked for 5 seconds. Thereafter, a nano-order chromium coating layer was formed on the cut surface of the torque transmission pin by sputtering, and the surface was observed with an electron microscope (magnification × 5000, 30 fields of view).

  In the electron microscope observation, we tried to check the film thickness of the solid lubricant film clearly by using different secondary electron beam images and reflected electron beam images depending on the type of solid lubricant. More specifically, it is confirmed that the coated surface is crossed in the horizontal direction for each field of view, and is divided into six in the vertical direction, and an average value of these five points is obtained, and the film per field is determined. The thickness was set to an average thickness in 30 fields of view.

  The seizure durability test of the torque transmission pin was performed by a block-on-ring test method (a test method in which a block is pressed against a rotating ring with a predetermined load and the rotating ring is rotated at a predetermined speed). In the sliding resistance test, the joint angle was fixed at 30 °, rotational torque was input to the steering mechanism, and the force required to slide the torque transmission pin in the axial direction of the male shaft and female shaft was measured.

Sample No. shown in Table 1 No. 1-25 For the samples 6 to 10, 13 to 15, 21, 22, 24, and 25, after forming fine dimples with a depth of 0.2 to 6 μm on the outer peripheral surface of the torque transmission pin, the solid lubricant film is torque transmitted. It was formed on the outer peripheral surface of the pin. The dimples are formed by a shot peening apparatus, and a steel ball, SiC, SiO ₂ , Al ₂ O ₃ , glass beads or the like having an average particle diameter of 45 μm as defined in JIS R6001 can be used as a shot material.

Regarding the depth of the dimple, the dimple formed on the outer peripheral surface of the torque transmission pin was observed with a three-dimensional date contact surface shape measuring machine (magnification × 5000, 30 fields of view), and the obtained image was converted into a cross-sectional profile. And five places of the cross section in the X direction and the cross section in the Y direction were measured, and the results were obtained as average values.
As apparent from the test results shown in Table 1, by forming a solid lubricant film made of a solid lubricant on the outer peripheral surface of the torque transmission pin, a solid lubricant film is not formed on the outer peripheral surface of the torque transmission pin ( For example, it can be seen that the sliding resistance of the sliding portion between the torque transmission groove and the torque transmission pin is reduced as compared with Sample Nos. 16 and 18).

Further, by setting the area ratio of the solid lubricant film to the outer peripheral surface of the torque transmission pin to 75% or more, the area ratio is less than 75% (for example, samples No. 19, 20, 21, 22). It can be seen that the seizure durability of the torque transmission pin, that is, the durability is improved.
Therefore, as in the embodiment shown in Table 1, by forming a solid lubricant film made of a solid lubricant on the outer peripheral surface of the torque transmission pin with an area ratio of 75% or more, the male shaft is connected via the torque transmission pin. When the rotational torque is transmitted from the female shaft or the female shaft to the male shaft, the sliding resistance of the sliding portion between the torque transmission pin and the torque transmission groove can be reduced and the durability of the torque transmission pin can be increased.

In addition, by setting the average film thickness of the solid lubricant film to 0.1 μm or more and 8.0 μm or less, torque transmission can be achieved as compared with those having an average film thickness exceeding 8.0 μm (for example, Sample Nos. 23 and 24). The sliding resistance of the sliding part between the pin and the torque transmission groove can be reduced and the durability of the torque transmission pin can be improved.
Further, by forming fine dimples having a depth of 0.1 to 5.0 μm on the outer peripheral surface of the torque transmission pin, the outer periphery of the torque transmission pin does not have dimples (for example, sample No. 17) and In comparison, the durability of the torque transmission pin can be improved. Furthermore, the sliding resistance of the sliding portion between the torque transmission pin and the torque transmission groove can be reduced as compared with a dimple whose depth exceeds 5.0 μm (for example, sample No. 25).

Further, by forming the solid lubricating film by shot peening, the durability of the torque transmission pin can be improved as compared with the solid lubricating film formed by spray coating (for example, sample No. 17).
In the examples shown in Table 1, a hardness test was performed using a micro hardness tester after a solid lubricant shot. As a result, the hardness at a depth of 2 to 15 μm has a gradient from the surface of the base material covered with the solid lubricant film, and the highest hardness of the gradient is 5 to 20% compared to the base material hardness before processing. It was confirmed that the degree increased.

In the embodiment described above, the case where the solid lubricant film made of the solid lubricant is formed on the outer peripheral surface of the torque transmission pin is exemplified, but the present invention is not limited to this. For example, as shown in FIG. 30 may be formed on the groove surfaces of the torque transmission grooves 27 and 28, or a solid lubricating film may be formed on both the torque transmission pin and the torque transmission groove.
In the above-described embodiment, the case where the present invention is applied to the hybrid telescopic shaft is illustrated. However, the present invention is not limited to this. can do.

In the examples shown in Table 1, the case where tin or molybdenum disulfide is used as the solid lubricant is exemplified. For example, polyethylene, fluororesin, nylon, polyacetal, polyolefin, polyester, metal soap, MoS ₂ , WS ₂ BN, graphite, calcium fluoride, barium fluoride, tin alloy, copper alloy, pure iron, pure copper, pure chromium, or the like may be used as the solid lubricant.

  In the examples shown in Table 1, the dimples are formed by shot peening. However, the dimples may be formed by a barrel method, and the dimples are formed by using both the barrel method and the shot peening method. May be. With respect to the barrel, various media and additives can be blended to perform rough processing for providing large irregularities on the surface and finishing processing for adjusting the roughness of the plateau portion.

It is an axial sectional view of a telescopic shaft for steering according to an embodiment of the present invention. It is II-II sectional drawing of FIG. FIG. 3 is an enlarged detail view of a part A shown in FIG. 2. It is sectional drawing which shows the principal part of the expansion-contraction shaft for steering which concerns on other embodiment of this invention. It is a figure which shows schematic structure of the steering mechanism of a motor vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Steering wheel 12 Steering shaft 121 Upper steering shaft part 122 Lower steering shaft part 13 Steering column 20 Telescopic shaft for steering 21 Male shaft 22 Female shaft 23, 24 Ball rolling groove 25 Ball 27, 28 Torque transmission groove 29 Torque transmission pin 30 Solid lubricant coating

Claims (5)

Torque transmission grooves extending in the axial direction of the male shaft and female shaft that are spline-fitted with each other are formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft, and the torque transmission pin that engages with the torque transmission groove is In a telescopic shaft for steering a vehicle disposed between a male shaft and the female shaft,
A telescopic shaft for steering of a vehicle, wherein a solid lubricant film made of a solid lubricant is formed at an area ratio of 75% or more on an outer peripheral surface of the torque transmission pin and / or a groove surface of the torque transmission groove.   The telescopic shaft for steering a vehicle according to claim 1, wherein the solid lubricating film has a thickness of 0.1 µm or more and 8.0 µm or less.   3. A telescopic shaft for steering a vehicle according to claim 1, wherein fine dimples having a depth of 0.1 to 5.0 [mu] m are formed on an outer peripheral surface of the torque transmission pin and / or a groove surface of the torque transmission groove. A telescopic shaft for steering a vehicle.   The telescopic shaft for steering of a vehicle according to any one of claims 1 to 3, wherein the center line average roughness of the outer peripheral surface of the torque transmission pin and / or the groove surface of the torque transmission groove is 0.1 to 1. A telescopic shaft for steering a vehicle characterized by being in a range of 6 μmRa.   The telescopic shaft for steering of a vehicle according to any one of claims 1 to 4, wherein the solid lubricant powder is shot peened on an outer peripheral surface of the torque transmission pin and / or a groove surface of the torque transmission groove. A telescopic shaft for steering a vehicle, wherein a lubricating coating is formed.

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