JP2007321868A - Telescopic shaft and telescopic shaft for steering vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce noise in a telescopic shaft. <P>SOLUTION: An intermediate shaft 5 as the telescopic shaft comprises an inner shaft 12 and a cylindrical outer shaft 13 that are fitted in such a state that they are slidable in an axial direction X1 and they can transmit torque to each other. Balls 14 as rolling elements are mounted in a row between corresponding axial grooves 15, 16 of the inner shaft 12 and the outer shaft 13. The adjacent balls 14 are capable of being contact with each other. The outer shaft 13 is resiliently increased in diameter. Pre-loads are applied to the balls 14 by a resilient restoring force of the outer shaft 13. Grease 23 fills a gap between the axial grooves 15, 16. The consistency of the grease 23 is equal to or less than 250 in the JIS standard or the kinetic viscosity of the base oil of the grease 23 is 20 to 5,500 mm<SP>2</SP>/sec. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a telescopic shaft and a telescopic shaft for vehicle steering using the same.

  The above-mentioned telescopic shaft is used as, for example, an automobile steering shaft. The telescopic shaft is used as an intermediate shaft that connects, for example, a steering shaft of an automobile and a steering mechanism such as a rack and pinion mechanism. In this case, the telescopic function is used for adjusting the length of the intermediate shaft for absorbing the relative displacement between the steering gear and the column when the vehicle is traveling, or for adjusting the length of the intermediate shaft during assembly.

In this type of telescopic shaft, a telescopic shaft has been proposed in which a plurality of rollable balls are interposed between corresponding axial grooves of the inner shaft and the cylindrical outer shaft, and both shafts are fitted. (For example, patent document 1).
JP 2001-50293 A

Some types of telescopic shafts of this type do not have a cage for the ball. In such a type of telescopic shaft, a slip occurs between the ball and the axial groove when the inner shaft and the outer shaft move relative to each other in the axial direction with the rolling of the ball in the axial groove. Adjacent balls collide with each other, generating abnormal noise and causing noise.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a telescopic shaft and a telescopic shaft for vehicle steering that generate less noise.

In order to achieve the above-described object, the present invention provides an inner shaft and a cylindrical outer shaft that are fitted to each other so as to be relatively movable in the axial direction and capable of transmitting torque, and an outer peripheral surface of the inner shaft and an inner peripheral surface of the outer shaft. Are formed between each of the axial grooves facing each other and the axial grooves facing each other, and can be in contact with each other in rows arranged in the axial direction and transmit torque between the inner shaft and the outer shaft. A plurality of possible rolling elements and grease interposed between the rolling elements that can contact each other, and the grease has a consistency of 250 or less in accordance with JIS standards, or the movement of the base oil contained in the grease. Provided is a telescopic shaft in which at least one of a viscosity of 20 mm ² / sec or more and 5500 mm ² / sec or less is achieved.

  In the present invention, a grease having a low consistency or a high viscosity base oil that is interposed between adjacent balls when adjacent balls are close to each other due to vibrations applied to the balls or slip generated on the balls. The grease containing the water acts as a cushioning material, and the collision speed and collision energy of adjacent balls can be significantly reduced. As a result, noise can be significantly reduced.

  It is sufficient that the grease is interposed between adjacent balls. Therefore, the grease may be applied to the surface of the rolling element, or may be filled between the axial grooves facing each other. Good. In the former case, even if a small amount of grease is used, there is an advantage that the grease can surely contribute to preventing the occurrence of collision noise. In the latter case, a sufficient amount of grease can be used to prevent collision noise over a long period of time. There is an advantage that generation can be prevented. Note that grease may be applied to the surface of the rolling element, and the grease may be filled between the axial grooves facing each other.

  If a solid lubricant is blended in the grease, the friction coefficient of contact can be lowered even between the balls and the raceway or under extreme pressure contact between the balls. As a result, the difference between the load received by the rolling ball and the load received by the sliding ball can be reduced, thereby suppressing the ball stick phenomenon that causes the balls to collide with each other. As a result, noise reduction can be achieved effectively.

In particular, when the solid lubricant contains molybdenum disulfide, there is an advantage that lubrication under extreme pressure is good and wear can be suppressed.
The present invention is preferably applied to a vehicle steering device that transmits the steering torque of the steering member using the telescopic shaft.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus in which a telescopic shaft according to an embodiment of the present invention is applied to an intermediate shaft. The vehicle steering apparatus 1 includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, an intermediate shaft 5 as a telescopic shaft connected to the steering shaft 3 via a universal joint 4, and an intermediate shaft 5 A rack as a steered shaft extending in the width direction of the automobile, having a pinion shaft 7 connected to the vehicle through a universal joint 6 and rack teeth 8a meshing with pinion teeth 7a provided in the vicinity of the end of the pinion shaft 7 Bar 8. A steering mechanism 50 is provided by a rack and pinion mechanism by the pinion shaft 7 and the rack bar 8.

In the present embodiment, the description will be made in the case where the telescopic shaft is applied to the intermediate shaft 5, but the telescopic shaft of the present invention is applied to the steering shaft 3, and the telescopic adjustment function and the impact absorbing function are applied to the steering shaft 3. May be fulfilled.
The rack bar 8 is supported in a housing 9 fixed to the vehicle body so as to be capable of linear reciprocation through a plurality of bearings (not shown). Both ends of the rack bar 8 protrude to both sides of the housing 9, and tie rods 10A are coupled to the respective ends. Each tie rod 10A is connected to a corresponding steering wheel 11 via a corresponding knuckle arm 10B.

The intermediate shaft 5 is slidable along an axial direction X1 between an inner shaft 12 as an upper shaft and a cylindrical outer shaft 13 as a lower shaft via a ball 14 (rolling element) as a torque transmission element. And is fitted so that torque can be transmitted.
Next, the intermediate shaft 5 will be described in detail with reference to FIG. 2 which is a cross-sectional view of the intermediate shaft 5 and FIG. 3 which is a cross-sectional view taken along line III-III in FIG.

As shown in FIGS. 2 and 3, at least a pair of axial grooves 15 and 16 extending along the axial direction X <b> 1 are formed on the outer periphery 12 a of the inner shaft 12 and the inner periphery 13 a of the outer shaft 13.
The axial groove 15 and the axial groove 16 that are paired with each other are opposed to each other in the radial direction of the shafts 12 and 13, and the torque transmission is performed between the axial groove 15 and the axial groove 16 that are paired with each other. Balls 14 that provide rolling elements as elements are interposed. A track for the ball 14 is directly formed on the inner surface of each axial groove 15, 16.

As shown in FIG. 2, the balls 14 are arranged in a line in the axial direction of both shafts 12 and 13. Although a predetermined interval is provided between each ball 14 and each adjacent ball 14, the adjacent balls 14 may come into contact with each other because the cage is not used. That is, the adjacent balls 14 can contact each other.
A protrusion 17 is formed on the inner periphery 13 a of the end 131 of the cylindrical outer shaft 13 corresponding to the position of the axial groove 16 of the outer shaft 13. The protrusion 17 is formed by plastically deforming the inner periphery 13a of the outer shaft 13 at the same time when the recess 18 is formed on the outer periphery 13b of the outer shaft 13 by pressure. Further, a projection 19 is formed on the outer periphery 12 a of the end 121 of the inner shaft 12 corresponding to the axial groove 15 of the inner shaft 12. The protrusion 19 is formed by plastically deforming the outer periphery 12a of the inner shaft 12 when the concave portion 20 is formed by pressurizing the end surface 122 of the inner shaft 12.

The inner shaft 12 may have a rectangular cross section as shown in FIG. On the outer periphery 12 a of the inner shaft 12, restricting portions 31 and 32 made of a pair of flat surfaces are provided on both sides sandwiching the axial groove 15 in the circumferential direction. The inner periphery 13a of the outer shaft 13 is provided with restricting portions 33 and 34 made of a pair of flat surfaces on both sides of the axial groove 16 in the circumferential direction.
The outer periphery 13 b of the outer shaft 13 has a bulging portion 13 c corresponding to the axial groove 16 and bulging in a mountain shape radially outward. Further, the outer shaft 13 forms a pair of bent portions 35 and 36 corresponding to the respective restricting portions 33 and 34, and the outer shaft 13 is elastically deformable in the radial direction. The bent portion 35 is disposed at the proximal end of the bulging portion 13c.

The outer shaft 13 is elastically expanded in a state in which the ball 14 is interposed between the axial grooves 15 and 16 that are paired with each other. The elastic restoring force of the outer shaft 13 causes the ball 14 to have a diameter of the outer shaft 13. The ball 14 is urged inward in the direction, and as a result, the ball 14 is elastically held between the inner shaft 12 and the outer shaft 13.
When no transmission torque is applied between the inner shaft 12 and the outer shaft 13 or when a transmission torque of a predetermined value or less is applied, the inner shaft 12 and the outer shaft are The shafts 13 are elastically connected to each other in the circumferential direction. At this time, the restricting portion 31 and the restricting portion 31 are not in contact with each other, and the restricting portion 32 and the restricting portion 34 are not in contact with each other, and therefore, the resistance of the relative movement of the inner shaft 12 and the outer shaft 13 in the axial direction. Is to be reduced.

  Further, when the transmission torque between the inner shaft 12 and the outer shaft 13 exceeds a predetermined value, the inner shaft 12 and the outer shaft 13 are rotated relative to each other by a minute amount with the deflection of the outer shaft 13, thereby causing the inner shaft 12 and the outer shaft 13 to rotate. Depending on the direction of relative rotation of the shaft 13, either the restricting portion 31 and the restricting portion 33 abut on each other or the restricting portion 32 and the restricting portion 34 abut on each other is achieved. 12 and the outer shaft 13 are rigidly connected.

A feature of this embodiment is that, as shown in FIG. 4, grease 23 satisfying a predetermined condition is filled between the axial grooves 15 and 16 of the inner shaft 12 and the outer shaft 13 facing each other. In the point. The predetermined condition is at least one of a grease consistency of 250 or less according to JIS standard (JIS K 2200) and a kinematic viscosity of the base oil contained in the grease 23 being 20 mm ² / sec or more. Has been achieved.

If either one of the grease consistency is 250 or less according to JIS standards, or the kinematic viscosity of the base oil contained in the grease 23 is 20 mm ² / sec or more, the ball 14 is When adjacent balls 14 come close to each other due to the influence of vibration received and slips generated on the balls 14, as schematically shown in FIG. 4, the grease 23 interposed between the adjacent balls 14 acts as a cushioning material, The collision speed and collision energy of adjacent balls 14 can be significantly reduced. As a result, noise can be significantly reduced.

Note that when the intermediate shaft 5 is contracted when assembled to the vehicle, if the sliding load of the inner shaft 12 and the outer shaft 13 becomes excessively large, it becomes difficult to assemble the base oil contained in the grease 23 to prevent this. The kinematic viscosity is preferably 5500 mm ² / sec or less. Further, the consistency of the grease 23 is preferably 100 or more according to JIS standard (JIS K 2200).

As the base oil of the grease 23, for example, mineral oil or synthetic oil can be used. As the synthetic oil, for example, silicone oil, ester oil, and olefin oil can be used. As the thickener, various metal soap groups, nonmetal soap groups, and composite groups can be used, and it is particularly preferable to use a lithium soap group.
It is sufficient that the grease 23 is interposed between the adjacent balls 14. Therefore, for example, as shown in FIG. 5, the grease 23 is applied to the surface of the ball 14 in advance before the intermediate shaft 5 is assembled. Alternatively, it may be filled between the axial grooves 15 and 16 facing each other. In the former case, even if a small amount of grease 23 is used, there is an advantage that the grease 23 can be surely contributed to preventing the occurrence of collision noise. There is an advantage that it is possible to prevent the occurrence of a collision sound. Alternatively, the grease 23 may be applied to the surface of the rolling element, and the grease 23 may be filled between the axial grooves 15 and 16 facing each other.

  If a solid lubricant is blended in the grease 23, the friction coefficient of contact is lowered even between the balls 14 and the raceways of the axial grooves 15, 16 or even under extreme pressure contact between the balls 14. Can do. As a result, the difference between the load received by the rolling ball 14 and the load received by the sliding ball 14 can be reduced, thereby suppressing the stick phenomenon of the balls 14 that causes the balls 14 to collide with each other. As a result, noise reduction can be achieved effectively.

As the solid lubricant, molybdenum disulfide, graphite, and PTFE can be used. In particular, when the solid lubricant contains molybdenum disulfide, there is an advantage that lubrication under extreme pressure is good.
Further, although the track is directly formed in the axial groove 15 of the inner shaft, as shown in FIG. 6, an elastic member 24 having a hook shape is disposed in the axial groove 15, and the ball 14 is preloaded by the elastic member 24. You may make it provide.

  Further, the telescopic shaft of the present invention can be applied to the steering shaft 3, and in this case, it is preferable when the steering shaft 3 performs a telescopic adjustment function and an impact absorbing function.

The telescopic shafts of Examples and Comparative Examples having the specifications shown in Table 1 below were prepared.
<Each specification of Examples 1-10 and Comparative Examples 1-4 and its test results>

上記の各実施例および各比較例について、下記の試験条件にて騒音測定試験および伸縮荷重測定試験を実施したところ、上記の表１に示す試験結果を得た。
＜試験条件＞
１）騒音測定試験
図７に示すような試験装置を用いた。すなわち、各実施例および各比較例のそれぞれの伸縮自在シャフト４０を、実車での中間軸の取付角度に相当する角度で傾斜させた状態で、アッパーシャフトとしての内軸１２を固定し、ロワーシャフトとしての外軸１３を加振台５０の加振ロッド５１に取り付け、外軸１３の下端を上下方向に、下記の条件にて加振した。また、伸縮自在シャフト４０から発生する音を、集音マイクロフォン５２で電気信号に変換し、増幅器５３で適当な信号レベルまで増幅した後、データ収集・解析装置５４で騒音値を測定した。騒音レベルが基準値（５５デシベル）以下であれば良であり、基準値（５５デシベル）を超えると不良である。

About each said Example and each comparative example, when the noise measurement test and the expansion-contraction load measurement test were implemented on the following test conditions, the test result shown in said Table 1 was obtained.
<Test conditions>
1) Noise measurement test A test apparatus as shown in FIG. 7 was used. That is, the inner shaft 12 as the upper shaft is fixed while the retractable shaft 40 of each example and each comparative example is inclined at an angle corresponding to the mounting angle of the intermediate shaft in the actual vehicle, and the lower shaft The outer shaft 13 was attached to the vibration rod 51 of the vibration table 50, and the lower end of the outer shaft 13 was vibrated in the vertical direction under the following conditions. The sound generated from the telescopic shaft 40 was converted into an electrical signal by the sound collecting microphone 52 and amplified to an appropriate signal level by the amplifier 53, and then the noise value was measured by the data collecting / analyzing device 54. It is good if the noise level is below the reference value (55 dB), and bad if it exceeds the reference value (55 dB).

Excitation frequency: 20Hz
Excitation amplitude: ± 2mm
Test temperature: 80 ° C
2) Stretching load measurement test The sliding load (N) when the inner shaft 12 and the outer shaft 13 were slid relative to each other was measured in a state where the respective telescopic shafts of the examples and the comparative examples were supported horizontally. . However, the test temperature was −40 ° C. The slide load is good if it is less than or equal to the reference value (40N), and it is bad if it exceeds the reference value (40N).

As a result of the noise measurement test, data shown in FIG. 8 was obtained. As shown in FIG. 8, each of Examples 3 to 10 and Comparative Examples 2 to 4 in which the kinematic viscosity of the base oil is 20 mm ² / sec or more has a good noise level (55 dB or less) and the noise is low. Low proved.
Moreover, since the results of the noise measurement tests of Examples 1 and 2 are good, even if the kinematic viscosity of the base oil is less than 20 mm ² / sec, the grease consistency is 250 or less in JIS standards. It was found that the noise level can be lowered.

Further, from the results of the noise measurement tests of Examples 4, 5, 7 to 10 and Comparative Example 2, the kinematic viscosity of the base oil is 20 mm ² / sec or more even if the grease consistency exceeds 250 according to JIS standards. If so, it was found that the noise level could be lowered.
Further, from the results of the noise measurement tests of Examples 3 and 6, it was found that both the kinematic viscosity of the grease base oil was 20 mm ² / sec or more and the consistency of the grease was 250 or less according to JIS standards. When achieved, the noise level was found to be good (less than 55 dB).

Further, from the result of the noise measurement test of Comparative Example 1, it was found that when the kinematic viscosity of the base oil was less than 20 mm ² / sec and the consistency of the grease exceeded 250 in the JIS standard, the noise level was 58 decibels. And found to be defective (greater than 55 dB).
From the above results, if at least one of the kinematic viscosity of the grease base oil is 20 mm ² / sec or more or the grease consistency is 250 or less according to the JIS standard is achieved, the noise level is reduced. It was found that the value could be made below the reference value (55 dB).

Moreover, since the result of the expansion / contraction load measurement test of Comparative Example 2 was unsatisfactory, it was found that the upper limit value of the kinematic viscosity of the grease base oil was preferably 5500 mm ² / sec. That is, in Comparative Example 2 in which the kinematic viscosity of the base oil exceeds 5500 mm ² / sec, the noise level is a preferable level, but there is a problem that the slide load becomes excessively large when expanding and contracting and the workability is poor.

  Further, from the results of the expansion / contraction load measurement test of Comparative Examples 3 and 4, it was found that the lower limit value of the consistency of the grease was preferably set to 100. That is, in Comparative Example 4 in which the consistency of grease is 70 in the JIS standard, the noise level is a preferable level, but the slide load when expanding and contracting exceeds the reference value (40N) and the workability is poor. There is a bug.

1 is a schematic configuration diagram of a vehicle steering apparatus in which a telescopic shaft according to an embodiment of the present invention is applied to an intermediate shaft. It is sectional drawing of an intermediate shaft. It is sectional drawing which follows the III-III line of FIG. It is the schematic diagram which expanded the principal part of FIG. It is a typical sectional view of a ball of another embodiment of the present invention. It is a schematic sectional drawing of the intermediate shaft of another embodiment of this invention. It is the schematic of the test apparatus of a noise measurement test. It is a graph of the noise level measurement result with respect to the kinematic viscosity and the consistency of the grease of an Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 2 ... Steering member, 3 ... Steering shaft, 5 ... Intermediate shaft (expandable shaft), 12 ... Inner shaft, 13 ... Outer shaft, 14 ... Ball (rolling element), 15, 16 ... Shaft Directional groove, 23 ... Grease

Claims (6)

An inner shaft and a cylindrical outer shaft fitted together so as to be relatively movable in the axial direction and capable of transmitting torque to each other;
The axial grooves formed on the outer peripheral surface of the inner shaft and the inner peripheral surface of the outer shaft and facing each other, and interposed between the axial grooves facing each other, can be in contact with each other in a row aligned in the axial direction. A plurality of rolling elements that are capable of transmitting torque between the inner shaft and the outer shaft;
A grease interposed between the rolling elements that can contact each other,
Or consistency of the grease is 250 or less in JIS standard, or the kinematic viscosity of the base oil contained in the grease, 20 mm ² / sec ～5500Mm least one or in the range of ² / sec is achieved Stretchable shaft characterized by   2. The telescopic shaft according to claim 1, wherein the grease is applied to the surface of the rolling element.   3. The telescopic shaft according to claim 1, wherein the grease is filled between the axial grooves facing each other.   4. A telescopic shaft according to claim 1, wherein a solid lubricant is blended in the grease.   5. A telescopic shaft according to claim 4, wherein the solid lubricant includes molybdenum disulfide.   A telescopic shaft for steering a vehicle, wherein the telescopic shaft according to any one of claims 1 to 5 is used to transmit a steering torque of a steering member.

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