JP2007131088A - Telescopic shaft for vehicle steering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To preclude certainly the generation of dints at the raceway surface of an axial groove in slide contact with a torque transmitting member, and to preclude effectively damage caused by an increase in sliding resistance, friction, etc. caused by dints. <P>SOLUTION: A telescopic shaft for a vehicle steering constituted so that a male shaft 1 and a female shaft 2 are fitted to each other in such a way so as to be capable of transmitting torque and to make relative movement in the axial direction is configured such that a slider 7b is fitted between axially stretching grooves 3b and 5b formed at the peripheral surface of the male shaft 1 and the inside surface of the female shaft 2, a resilient piece 9 is interposed between one of the male shaft side and the female shaft side of the axially stretching grooves and the slider 7b for preloading the slider to the other of the male shaft side and the female shaft side, and that torque transmitting members 7a and 7c are arranged in positions with respect to the circumferential direction different from the position in the circumferential direction where the resilient piece is installed, in which at least either of the male 1 and the female shafts 2 is subjected to heat treatment to generate at least such hardness as to preclude the generation of dints owing to the slide contact of the slider in the axially directed groove. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a telescopic shaft for vehicle steering that is incorporated in a steering shaft of a vehicle and has a male shaft and a female shaft that are non-rotatably and slidably fitted.

  The telescopic shaft of the steering mechanism portion of the automobile is required to absorb the axial displacement generated when the automobile travels and to transmit the displacement and vibration on the steering wheel. Further, in order to obtain an optimum position for the driver to drive the automobile, a function of moving the position of the steering wheel in the axial direction and adjusting the position is required. In any of these cases, the telescopic shaft is required to reduce the rattling noise, reduce the rattling on the steering wheel, and reduce the sliding resistance during the sliding operation in the axial direction. .

For this reason, in Patent Document 1, a cylindrical body composed of needle rollers as a plurality of sets of torque transmission members between a plurality of sets of axial grooves formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft. Is fitted. As a result, when the steering torque transmitted from the steering wheel is small, it is possible to prevent rattling between the male shaft and the female shaft. Thus, torque can be transmitted in a highly rigid state. Furthermore, in order to prevent rattling of the needle roller in the rotational direction (circumferential direction), a plastic cage shape is provided. Therefore, the position of the needle roller in the rotational direction can be adjusted with the plastic member, and the accuracy error between the male shaft and the female shaft can be absorbed by the elastic deformation of the plastic.
European Patent Application No. 1078843

However, in the conventional example described in Patent Document 1, a plurality of needles as torque transmission members are provided between a plurality of sets of axial grooves formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft. Since a cylindrical body made of a roller is fitted, there is a risk that this cylindrical body may come into sliding contact with the raceway surface of the axial groove to generate an indentation, and the raceway surface due to an increase in sliding resistance or friction due to the indentation produced. There is an unresolved problem that damage occurs.
Accordingly, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and reliably prevents the generation of indentations that may occur on the surface of the raceway surface of the axial groove that is in sliding contact with the torque transmission member. An object of the present invention is to provide a telescopic shaft for vehicle steering that can effectively prevent an increase in sliding resistance due to indentations and damage due to friction or the like.

  In order to achieve the above object, a telescopic shaft for vehicle steering according to claim 1 is incorporated in a steering shaft of a vehicle, and a vehicle steering device in which a male shaft and a female shaft are fitted so as to be able to transmit torque and move relative to each other in the axial direction. In the telescopic shaft, a sliding body is fitted between axial grooves formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft, and one of the male shaft side and the female shaft side in the axial groove An elastic body is interposed between the sliding body and the torque transmission member disposed at a circumferential position different from the circumferential position where the elastic body is disposed, and the male shaft outer circumferential surface and the female shaft At least one of the peripheral surfaces is subjected to a heat treatment that is hard enough to prevent generation of indentation due to sliding contact of the sliding body in at least the axial groove.

  Further, the telescopic shaft for vehicle steering according to claim 2 is the invention according to claim 1, wherein the elastic body exerts a preload action when the transmitted steering torque is less than a predetermined value, and exhibits low rigidity characteristics. A torque transmitting member disposed at a circumferential position different from the elastic body is engaged with the axial groove in the circumferential direction when the steering torque is equal to or greater than a predetermined value, and exhibits high rigidity characteristics. The torsional rigidity characteristic is obtained.

  Further, the telescopic shaft for vehicle steering according to claim 3 is incorporated in a steering shaft of a vehicle, and the telescopic shaft for vehicle steering is fitted with a male shaft and a female shaft so that torque can be transmitted and relatively moved in the axial direction. Between the outer circumferential surface of the male shaft and the axial groove formed on the inner circumferential surface of the female shaft, a rolling element that rolls in the axial relative movement of the two shafts is provided via an elastic body for preload. And forming a torque transmitting member between the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft, enabling relative movement in the axial direction between the two and restricting movement in the rotational direction, At least one of the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft is subjected to a heat treatment that is hard enough to prevent indentation due to sliding contact of the torque transmission member in the axial groove.

  Furthermore, the telescopic shaft for vehicle steering according to claim 4 is the invention according to claim 3, wherein the elastic body exerts a preload action when the transmitted steering torque is less than a predetermined value and exhibits low rigidity characteristics. The torque transmission member is configured to obtain a two-stage torsional rigidity characteristic by engaging the axial groove in the circumferential direction when the steering torque is equal to or greater than a predetermined value and exhibiting a high rigidity characteristic. It is characterized by that.

Still further, the telescopic shaft for vehicle steering according to a fifth aspect is characterized in that, in the invention according to the third or fourth aspect, the torque transmitting member is constituted by one of a serration and a spline.
A telescopic shaft for vehicle steering according to a sixth aspect is the invention according to the third or fourth aspect, wherein the torque transmitting member is formed of a cylindrical body.

Furthermore, the telescopic shaft for vehicle steering according to a seventh aspect is the invention according to any one of the first to sixth aspects, wherein the heat treatment is a gas soft nitriding treatment, and at least the hardness of the sliding contact surface of the axial groove. Is characterized by being HV400 or more.
Furthermore, the telescopic shaft for vehicle steering according to claim 8 is characterized in that, in any one of claims 1 to 7, the elastic body is configured by a leaf spring.

  According to the present invention, since the sliding contact surface with the sliding body, the rolling element, or the torque transmission member that transmits at least one of the torque between the male shaft and the female shaft is subjected to heat treatment that is hard enough to prevent indentation. In addition, when the sliding body or torque member is in sliding contact, it is possible to reliably prevent the occurrence of indentation and to effectively prevent the sliding body or torque transmission member from being damaged due to an increase in sliding resistance or friction due to the indentation. In addition, it is possible to reliably prevent backlash in the rotational direction by the elastic body and transmit torque in a highly rigid state.

In addition, by heat-treating only one of the male shaft and the female shaft, it is possible to provide a high-performance vehicle steering telescopic shaft while suppressing cost, and by applying a leaf spring as an elastic member, Durability can be improved while eliminating backlash.
Furthermore, by applying gas soft nitriding as a heat treatment to make the hardness of the sliding surface of the axial groove at least HV400, it is possible to reliably prevent the occurrence of indentations on the sliding surface of the axial groove. it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Overall configuration of vehicle steering shaft)
FIG. 1 is a side view showing an embodiment in which a vehicle steering telescopic shaft according to the present invention is applied to a steering mechanism of an automobile.
In FIG. 1, an upper steering shaft portion 120 (including a steering column 103 and a steering shaft 104 rotatably supported by the steering column 103 is attached to a member 100 on the vehicle body side via an upper bracket 101 and a lower bracket 102. ), A steering wheel 105 attached to the upper end of the steering shaft 104, a lower steering shaft portion 107 connected to the lower end of the steering shaft 104 via a universal joint 106, and a steering shaft joint 108 to the lower steering shaft portion 107. A pinion shaft 109 connected to the pinion shaft, a steering rack shaft 112 connected to the pinion shaft 109, and the steering rack shaft 112 to support the other frame 110 of the vehicle body. Steering mechanism from a fixed steering rack support member 113 via 111 is formed.

  Here, the upper steering shaft portion 120 and the lower steering shaft portion 107 use the vehicle steering telescopic shaft (hereinafter simply referred to as the telescopic shaft) according to the embodiment of the present invention. The lower steering shaft portion 107 is formed by fitting a male shaft and a female shaft. The lower steering shaft portion 107 absorbs axial displacement that occurs when the vehicle travels, and a steering wheel. The performance which does not transmit the displacement and vibration on 105 is required.

In such performance, the vehicle body has a sub-frame structure, and the member 100 for fixing the upper part of the steering mechanism and the frame 110 to which the steering rack supporting member 113 is fixed are separated, and the steering rack supporting member 113 is This is required in the case of a structure that is fastened and fixed to the frame 110 via an elastic body 111 such as rubber.
As another case, when the steering shaft joint 108 is fastened to the pinion shaft 109, the operator may need to have a telescopic function to temporarily retract the telescopic shaft and then engage the pinion shaft 109 for fastening. is there.

  In addition, the upper steering shaft portion 120 at the upper part of the steering mechanism is also fitted with a male shaft and a female shaft, and such an upper steering shaft portion 120 is optimal for a driver to drive an automobile. In order to obtain a correct position, the function of moving the position of the steering wheel 105 in the axial direction and adjusting the position is required. Therefore, the function of expanding and contracting in the axial direction is required. In all the cases described above, it is possible to reduce the rattling noise of the fitting portion on the telescopic shaft, to reduce the backlash on the steering wheel 105, and to reduce the sliding resistance when sliding in the axial direction. Required.

(First embodiment)
FIG. 2 is a longitudinal sectional view of the telescopic shaft for vehicle steering with a cardan shaft joint according to the first embodiment of the present invention. FIG. 3 is an exploded perspective view of the telescopic shaft for vehicle steering shown in FIG. FIG. 4 is a perspective view taken along line AA in FIG.
As shown in FIG. 2, the telescopic shaft for vehicle steering (hereinafter simply referred to as the telescopic shaft) includes a male shaft 1 and a female shaft 2 that are non-rotatable and slidably fitted to each other.
The male shaft 1 is connected to the yoke 21 of the cardan shaft joint 20 on the steering wheel side, and the female shaft 2 is connected to the yoke 23 of the cardan shaft joint 22 on the steering gear side.

As shown in FIG. 3, three axial grooves 3 a to 3 c are formed on the outer peripheral surface of the male shaft 1 so as to extend substantially in a circular arc shape with a cross section equally distributed at 120 ° intervals in the circumferential direction. . Correspondingly, axial grooves 5a to 5c that are paired with the axial grooves 3a to 3c having a substantially arc-shaped cross section equally distributed at intervals of 120 degrees in the circumferential direction also extend on the inner peripheral surface of the female shaft 2. Is formed.
In each pair, needle rollers 7a to 7c are slidably fitted between substantially arc-shaped axial grooves 3a to 3c of the male shaft 1 and substantially arc-shaped axial grooves 5a to 5c of the female shaft 2. Has been.

  A corrugated leaf spring 9 for preloading is interposed between one of the needle rollers 7a to 7c, for example, the needle roller 7b and the axial groove 5b of the female shaft 2. When the steering torque is not transmitted, the leaf spring 9 preloads the needle roller 7b against the male shaft 1 to the extent that it does not rattle. On the other hand, when the steering torque is transmitted, the leaf spring 9 is elastically deformed to move the needle roller 7b between the male shaft 1. It works to restrain in the circumferential direction. As shown in FIG. 4, the plate spring 9 has concave locking portions 9 c formed at both ends thereof, which are locked to the step portions 5 d on both sides of the axial groove 5 b of the female shaft 2. When the steering torque is transmitted, the entire leaf spring 9 is mounted so as not to move in the circumferential direction. Here, the needle roller 7b corresponds to the sliding body, and the needle rollers 7a and 7c disposed at different positions in the circumferential direction with respect to the needle roller 7b correspond to the torque transmission member.

  By fitting a stopper 11 having a concave cross section into the end of the female shaft 2, the needle rollers 7a to 7c are formed between the inwardly projecting protrusions 12 formed at the inner ends of the axial grooves 5a to 5c. It is fixed in the axial direction in a sandwiched manner. Here, the stopper 11 includes a short cylindrical portion 11a fitted to the outer peripheral surface of the end portion of the female shaft 2, and an end plate portion 11b extending inward from one end of the cylindrical portion 11a. As shown, a semicircular convex portion 11c that engages with the axial grooves 3a to 3c of the male shaft 1 of the end plate portion 11b is formed.

The male shaft 1 is hardened by gas soft nitriding treatment as heat treatment so that the hardness of the sliding contact surfaces of at least the axial grooves 3a to 3c contacting the needle rollers 7a to 7c is HV400 or more. Here, the gas soft nitriding treatment is performed by adding 30 to 50% of NH ₃ gas in a carburizing gas or nitrogen gas atmosphere such as a rapid heating type metamorphic gas or a pyrolysis gas of an organic solvent, and a temperature range of 550 to 600 ° C. And for 1 to 5 hours, and nitrogen and carbon are simultaneously penetrated and diffused to produce carbonitrides on the surface. The surface hardness can be HV400 to 700.
According to this gas soft nitriding treatment, it can be applied to low-grade steel, and the processing time is 90 to 150 minutes, which is much shorter than the normal gas nitriding treatment time 25 to 100 hours, and mass production is possible at low cost. It becomes.

  Thus, when the surface hardness of the axial grooves 3a to 3c of the male shaft 1 is set to HV400 or more, the needle rollers 7a to 7c are moved in the axial direction of the male shaft 1 when the male shaft 1 and the female shaft 2 are moved relative to each other. When the grooves 3a to 3c are slid, it is possible to reliably prevent the occurrence of indentation, and the generation of the indentation increases the sliding resistance of the needle rollers 7a to 7c, or the needle rollers 7a to 7c It can be reliably prevented from being damaged by friction or the like due to the indentation. Incidentally, if the surface hardness of the axial grooves 3a to 3c of the male shaft 1 is less than HV400, when the needle rollers 7a to 7c come into sliding contact, indentations are generated in the axial grooves 3a to 3c due to long-term use. The generated indentation increases the sliding resistance of the needle rollers 7a to 7c, and the needle rollers 7a to 7c are damaged by the friction caused by the indentation, so that a good relative movement between the male shaft 1 and the female shaft 2 is achieved. It cannot be secured.

Next, the operation of the first embodiment will be described.
In the telescopic shaft having the above-described configuration, when the steering torque is not transmitted to the steering wheel 105 described above from the driver, the needle roller 7b is not loosened with respect to the male shaft 1 by the leaf spring 9 when the steering torque is not transmitted. Since the preload is applied, rattling between the male shaft 1 and the female shaft 2 can be surely prevented, and the male shaft 1 and the female shaft 2 can be connected with a stable sliding load without rattling. Can slide in the direction. At this time, the needle rollers 7 a to 7 c are fixed to the female shaft 2 by the stopper 11 and the protrusion 12, so that the needle rollers 7 a to 7 c are in sliding contact with the inner peripheral surfaces of the axial grooves 3 a to 3 c of the male shaft 1. Although the sliding of these axial grooves 3a to 3c is set to HV400 or more, when the needle rollers 7a to 7c slide, the needle rollers 7a to 7c are moved to the axial groove 3a. It is possible to surely prevent intrusion into ˜3c, and to reliably prevent generation of indentation.

  Thus, since it can prevent reliably that an indentation is formed in the sliding contact surface which the needle rollers 7a-7c slidably contact, the sliding resistance of the needle rollers 7a-7c by the indentation formed like the prior art example Can be reliably prevented from affecting the expansion / contraction operation of the expansion / contraction shaft and the needle rollers 7a to 7c being damaged by friction due to indentations.

  On the other hand, when steering torque is transmitted to the steering wheel 105 from the driver, the needle rollers 7a to 7c interposed between the male shaft 1 and the female shaft 2 transmit torque as shown in FIG. To play a role. For example, when torque is input from the male shaft 1, since the preload of the leaf spring 9 is applied to the needle roller 7b in the initial stage, the male shaft 1 moves toward the needle rollers 7a and 7c via the needle roller 7b. When the needle rollers 7a and 7c are pressed against the axial grooves 3a and 3c of the female shaft 2, there is no backlash between the male shaft 1 and the female shaft 2, and the leaf spring 9 is torqued. Torque is transmitted by generating a reaction force against.

At this time, the torque transmission load between the male shaft 1, the leaf spring 9 and the female shaft 2 is balanced with the torque transmission load between the male shaft 1, the needle rollers 7 a to 7 c and the female shaft 2. Is made.
When the steering torque further increases, as shown in FIG. 4, the spring action of the leaf spring 9 is lost, the needle rollers 7a to 7c receive a strong reaction force, and the needle rollers 7a to 7c mainly generate torque. Tell axis 2.

Therefore, the play in the rotational direction of the male shaft 1 and the female shaft 2 can be reliably prevented, and torque can be transmitted in a highly rigid state.
Further, when the steering torque is less than a predetermined value, the preload leaf spring 9 performs a preload action and exhibits a low rigidity characteristic, while when the steering torque is equal to or higher than the predetermined value, each of the needle rollers 7a to 7c has a pair of shafts. By engaging the directional grooves 3a to 3c and 5a to 5c in the circumferential direction, high rigidity characteristics are exhibited.

That is, when the steering torque is less than a predetermined value, the leaf spring 9 buffers and reduces unpleasant noise and vibration transmitted from the engine room by a preloading action, while the steering torque increases and exceeds the predetermined value. Since the rollers 7a to 7c can be engaged with the pair of axial grooves 3a to 3c and 5a to 5c in the circumferential direction to transmit the steering torque, a sharp steering feeling can be obtained.
Therefore, since the torque transmission and sliding mechanism also serves as a buffer mechanism, the telescopic shaft having a two-stage torsional rigidity characteristic is provided while the space is effectively used, the number of parts is reduced, and the manufacturing cost is reduced. be able to.

  Moreover, since the hardness of the axial grooves 3a to 3c of the male shaft 1 with which the needle rollers 7a to 7c are slidably contacted is set to HV400 or higher by gas soft nitriding, when the needle rollers 7a to 7c are slidably contacted, The inclinations of the shaft 1 and the female shaft 2 are different, and it is possible to reliably prevent the impression grooves from being generated in the axial grooves 3a to 3c by the stick slip of the needle rollers 7a to 7c, and the needle rollers 7a to 7c due to the generation of the impression marks. It is possible to reliably prevent the needle rollers 7a to 7c from being damaged due to an increase in the sliding resistance and the friction of the indentation. Furthermore, since only one leaf spring 9 is required, the number of parts can be reduced and the cost can be reduced.

  In the first embodiment, the case where the leaf spring 9 as the elastic body is interposed between the axial groove 5a of the female shaft 2 and the needle roller 7b as the sliding body has been described. However, the present invention is not limited to this. The leaf spring 9 may be interposed between the other axial groove 5a or 5c and the needle roller 7a or 7c, and any one of the needle rollers 7i (i = ac). ) And the axial groove 3i of the male shaft 1 may be interposed, and the number of needle rollers as sliding bodies and needle rollers as torque transmission members may be arbitrarily set. be able to.

  Moreover, although the said 1st Embodiment demonstrated the case where the needle rollers 7a-7c were hold | maintained to the axial direction grooves 5a-5c of the female shaft 2, it is not limited to this, The axial direction of the male shaft 1 The needle rollers 7a to 7c may be held in the grooves 3a to 3c. In this case, surface hardening heat treatment such as gas soft nitriding treatment is performed on the female shaft 2 in which the needle rollers 7a to 7c are in sliding contact. Furthermore, surface hardening heat treatment such as gas soft nitriding treatment may be performed on both the male shaft 1 and the female shaft 2. The surface hardening heat treatment in this case is not limited to the case where the entire male shaft 1 is subjected to the surface hardening heat treatment, but only the axial groove 3b slidably in contact with the needle roller 7b as the sliding body of the male shaft 1 or the axial groove 3b. Only the axial grooves 3a and 3c that are in sliding contact with the needle rollers 7a and 7c serving as torque transmission members of the male shaft 1 or a peripheral portion including the axial grooves 3a and 3c is partially subjected to surface hardening heat treatment. Similarly, the surface hardening heat treatment of the female shaft 2 is not limited to the case where the whole female shaft 2 is subjected to the surface hardening heat treatment, but only the axial groove 5b that is in sliding contact with the needle roller 7b or the periphery including the axial groove 5b. Or only the axial grooves 5a and 5c that are in sliding contact with the needle rollers 7a and 7c, or the peripheral portion including the axial grooves 5a and 5c is partially subjected to surface hardening heat treatment. It may be.

(Second Embodiment)
FIG. 5 is a longitudinal sectional view of a telescopic shaft for vehicle steering with a cardan shaft joint according to a second embodiment of the present invention, and FIG. 6 is an exploded perspective view of the telescopic shaft for vehicle steering shown in FIG. 7 is a cross-sectional view taken along line BB in FIG.
In the second embodiment, the leaf spring 9 in the first embodiment described above is omitted, and the axial grooves 3a to 3c of the male shaft 1 with which the needle rollers 7a to 7c as torque transmitting members are engaged. And the axial grooves 4a to 4c of the male shaft 1 and the axial grooves of the female shaft 2 which are paired at a central position between the grooves adjacent to each other in the circumferential direction of the axial grooves 5a to 5c of the female shaft 2 at intervals of 120 degrees. 6a to 6c are formed to extend, and between these pairs of axial grooves 4a to 4c and 6a to 6c, the axial grooves 6a to 6c of the female shaft 2 are provided as rolling elements via leaf springs 10a to 10c. 2 except that a plurality of balls connected in series are arranged in series, and corresponding parts to FIGS. 2 to 4 are the same as those in the first embodiment described above. Are denoted by the same reference numerals, and detailed description thereof is omitted. Also in this second embodiment, the male shaft 1 is subjected to gas soft nitriding treatment so that at least the axial grooves 3a to 3c and 4a to 4c have a surface hardness of HV400 or more, and the needle is moved when the male shaft 1 and the female shaft 2 are relatively moved. The hardness is such that no indentation is generated by the rollers 7a to 7c and the ball rows 8a to 8c.

  In the telescopic shaft configured as described above, when the steering torque is not transmitted, the ball trains 8a to 8c and the needle rollers 7a to 7c are used for "rolling" and "sliding", respectively, and by the leaf springs 10a to 10c, Since the ball trains 8a to 8c are preloaded to the extent that there is no backlash with respect to the male shaft 1, backlash between the male shaft 1 and the female shaft 2 can be reliably prevented, and the male shaft 1 The female shaft 2 can slide in the axial direction with a stable sliding load without rattling.

  At the time of steering torque transmission, as shown in FIG. 7, needle rollers 7 a to 7 c interposed between the male shaft 1 and the female shaft 2 serve as main torque transmission. For example, when a steering torque is input from the male shaft 1, the leaf springs 10 a to 10 c are preloaded in the initial stage, so there is no backlash, and the leaf springs 10 a to 10 c generate a reaction force against the torque. Steering torque is transmitted. At this time, the torque transmission load between the male shaft 1, the ball trains 8a to 8c, the leaf springs 10a to 10c, and the female shaft 2 is balanced with the torque transmission load between the male shaft 1, the needle rollers 7a to 7c, and the female shaft 2. In this state, the entire steering torque is transmitted.

  When the steering torque further increases, as shown in FIG. 7, the clearance in the rotational direction between the male shaft 1, the needle rollers 7a to 7c, and the female shaft 2 is as follows: male shaft 1, ball rows 8a to 8c, plate Since the clearance between the spring 10a and the female shaft 2 is set to be small, the needle rollers 7a to 7c receive a reaction force stronger than the ball rows 8a to 8c, and the needle rollers 7a to 7c are mainly used. The steering torque is transmitted to the female shaft 2. Therefore, it is possible to reliably prevent backlash in the rotational direction of the male shaft 1 and the female shaft 2, and to transmit the steering torque in a highly rigid state.

Further, when the steering torque is less than a predetermined value, each of the leaf springs 10a to 10c for preload performs a preload action and exhibits a low rigidity characteristic. On the other hand, when the steering torque is equal to or greater than a predetermined value, each of the needle rollers 7a to 7c Engage the pair of axial grooves 3a to 3c and 5a to 5c in the circumferential direction to exhibit high rigidity characteristics.
That is, when the steering torque is less than a predetermined value, the leaf springs 10a to 10c reduce and reduce unpleasant noise and vibration transmitted from the engine room by the preload action, while the steering torque increases and exceeds a predetermined value. Since the needle rollers 7a to 7c can be engaged with the pair of axial grooves 3a to 3c and 5a to 5c in the circumferential direction to transmit the steering torque, a sharp steering feeling can be obtained.

  Accordingly, since the torque transmission / sliding mechanism also serves as a buffer mechanism, it is possible to provide a telescopic shaft having two-stage torsional rigidity characteristics while effectively using space, reducing the number of parts, and reducing manufacturing costs. Can do. In addition, in the second embodiment, since the ball trains 8a to 8c are provided in addition to the first embodiment, the sliding resistance is increased even if preload is applied by the leaf springs 10a to 10c. The sliding resistance can be reduced compared to the case where the preload is applied to the needle roller 7a as in the first embodiment.

  Further, since the male shaft 1 is subjected to gas soft nitriding treatment and the surface hardness is set to HV400 or more as in the first embodiment, when the male shaft 1 and the female shaft 2 move relative to each other, Since the shaft 1 and the female shaft 2 have different inclinations, it is possible to reliably prevent indentations from being generated in the axial grooves 3a to 3c of the male shaft 1 due to stick slips by the needle rollers 7a to 7c. It is possible to reliably prevent the needle rollers 7a to 7c from being damaged due to an increase in the sliding resistance of the rollers 7a to 7c, friction due to the generated indentation, or the like.

  In the second embodiment as well, the leaf springs 10a to 10c are replaced with the ball rows 8a to 8c instead of being interposed between the ball rows 8a to 8c and the axial grooves 6a to 6c of the female shaft 2. 8c may be interposed between the axial grooves 4a to 4c of the male shaft 1, and in this case, the female shaft 2 is subjected to a gas soft nitriding treatment so that at least the axial grooves 5a to 5c and What is necessary is just to make it the surface height of 6a-6c become HV400 or more, and you may make it perform gas soft nitriding processing to both the male shaft 1 and the female shaft 2. FIG.

  In the second embodiment, the case where the needle rollers 7a to 7c and the ball rows 8a to 8c are held in the axial grooves 5a to 5c and 6a to 6c of the female shaft 2 has been described. However, the present invention is not limited thereto. The needle rollers 7a to 7c and the ball rows 8a to 8c may be held in the axial grooves 3a to 3c and 4a to 4c of the male shaft 1 instead. In this case, the needle rollers 7a to 7c A surface hardening heat treatment such as gas soft nitriding treatment may be performed on the female shaft 2 in sliding contact with each other, and further, a surface hardening heat treatment such as gas soft nitriding treatment is performed on both the male shaft 1 and the female shaft 2. Also good. The surface hardening heat treatment in this case is not limited to the case where the entire male shaft 1 is subjected to the surface hardening heat treatment, but only the axial grooves 3a to 3c that are in sliding contact with the needle roller 7b as the torque transmission member of the male shaft 1 or the axial grooves 3a. Surface hardening partially in the peripheral part including -3c, or in the peripheral part including only the axial grooves 4a-4c in rolling contact with the ball trains 8a-8c as rolling elements of the male shaft 1, or in the peripheral part including the axial grooves 4a-4c Similarly, the case where the female shaft 2 is subjected to surface hardening heat treatment is not limited to the case where the entire female shaft 2 is subjected to surface hardening heat treatment, but only the axial grooves 5a to 5c which are in sliding contact with the needle rollers 7a to 7c. Alternatively, surface hardening heat treatment is partially applied to the peripheral portion including the axial grooves 5a to 5c, or only the peripheral grooves including the axial grooves 6a to 6c or the peripheral portions including the axial grooves 6a to 6c. It may be so.

Furthermore, in the said 2nd Embodiment, although the case where the torque transmission member comprised by the needle rollers 7a-7c and the rolling element comprised by the ball row | line | columns 8a-8c were each provided 3 each was demonstrated, The number of torque transmission members and rolling elements is not limited, and any number of sets can be provided.
Furthermore, in the second embodiment, the case where the ball trains 8a to 8c are applied as rolling elements has been described. However, the present invention is not limited to this, and the rolling is performed in the axial direction of the male shaft 1 and the female shaft 2. A roller row in which a plurality of moving rollers are arranged can also be applied.

(Third embodiment)
8 is a longitudinal sectional view of a telescopic shaft for vehicle steering according to a third embodiment of the present invention, FIG. 9 is a sectional view taken along the line CC of FIG. 8, and FIG. 10 is a perspective view showing a leaf spring. It is.
In the third embodiment, the needle rollers 7a to 7c as torque transmitting members in the second embodiment described above, the axial grooves 3a to 3c of the male shaft 1 and the axial grooves 5a of the female shaft 2 are housed therein. 5c are omitted, and instead of these, serrations 30a to 30c are formed as torque transmission members, and leaf springs interposed between the ball rows 8a to 8c and the axial grooves 6a to 6c of the female shaft 2 are formed. 10a to 10c are omitted, and in place of them, the leaf springs 33a to 33c are interposed between the axial grooves 4a to 4c of the male shaft 1 and the ball rows 8a to 8c. The configuration is the same as that of

  Here, as shown in FIGS. 8 and 9, the male shaft 1 is formed in a hollow pipe shape, and axial grooves 4 a to 4 c for receiving the ball rows 8 a to 8 c are formed, and these axial grooves are formed. Serration shaft portions 31a to 31c are respectively formed in the central portions in the circumferential direction between adjacent grooves 4a to 4c. Each of the serration shaft portions 31a to 31c has two strip-shaped trapezoidal protrusions 31d formed at a predetermined distance in the circumferential direction, as is apparent from FIG. Here, each of the axial grooves 4a to 4c has a tapered lateral side plate portion 4d that becomes narrower in width as it goes inward from the outer peripheral surface, and an inner peripheral side of the tapered side plate portion 4d. It is comprised by the bottom plate part 4e which connects.

  On the other hand, the female shaft 2 is formed with Gothic arc-shaped axial grooves 6a to 6c which are opposed to the axial grooves 4a to 4c of the male shaft 1 and are paired therewith, and these axial grooves 6a to 6c. Serration groove portions 32a to 32c that engage with the serration shaft portions 31a to 31c are formed at the circumferential center between the adjacent grooves. The serration shaft portions 31a to 31c and the serration groove portions 32a to 32c constitute serrations 30a to 30c serving as torque transmission members. Here, the serration shaft portions 31a to 31c and the serration groove portions 32a to 32c are opposed to each other in the circumferential direction with a minute gap.

  Further, leaf springs 33a to 33c as elastic bodies are interposed between the ball rows 8a to 8c and the axial grooves 4a to 4c of the male shaft 1, and the ball rows 8a to 8c and the leaf springs 33a to 33c are shown in FIG. As shown in FIG. 4, a convex stopper 34 fitted to the end of the male shaft 1 and an outwardly projecting step 35 formed at the rear ends of the axial grooves 4a to 4c of the male shaft 1. Is retained.

  Here, as shown in FIGS. 9 and 10, each of the leaf springs 33a to 33c has a ball side contact portion 33d that comes into contact with the balls of the ball rows 8a to 8c at two points, and the ball side contact portion 33d. A groove surface side contact portion 33e that contacts the tapered side surface plate portion 4d of the axial grooves 4a to 4c of the male shaft 1, and the ball side contact portion 33d and the groove surface. It has a biasing portion 33f that elastically biases the side contact portion 33e in a direction away from each other, and a bottom portion 33g that contacts the bottom surface plate portion 4e of the axial grooves 4a to 4c. Here, the urging portion 33f has a substantially U-shaped bent shape that is bent in a substantially arc shape, and the bent side urging portion 33f causes the ball side contact portion 33d and the groove surface side contact portion 33e to be bent. Can be elastically biased so as to be separated from each other.

  Then, at least one of the outer peripheral surface of the male shaft 1 and the inner peripheral surface of the female shaft 2 is moved between the serration shaft portions 31a to 31c and the serration groove portions 32a to 32c during the relative movement of the male shaft 1 and the female shaft 2. Gas soft nitriding treatment is performed to prevent generation of indentation, and the surface hardness of at least one of the serration shaft portions 31a to 31c and the serration groove portions 32a to 32c is set to HV400 or more.

  Also in the third embodiment, any one of the serration shaft portions 31a to 31c and the serration groove portions 32a to 32c constituting the serration serving as a torque transmission member is subjected to gas soft nitriding treatment to have a surface hardness of HV400 or more. Therefore, when the male shaft 1 and the female shaft 2 are relatively moved, the male shaft 1 and the female shaft 2 have different inclinations, and stick slip occurs between the serration shaft portions 31a to 31c and the serration groove portions 32a to 32c. Therefore, it is possible to reliably prevent generation of indentation, and serration shaft portions 31a to 31c or serration groove portions 32a to 32c due to an increase in sliding resistance in the serrations 30a to 30c due to the generation of the indentation, friction due to the indentation, or the like. Can be reliably prevented.

On the other hand, the leaf springs 33a to 33c can sufficiently bend the ball side contact portion 33d via the biasing portion 33f, and can ensure a sufficient amount of bending.
Further, in addition to the ball rows 8a to 8c, the serration shaft portions 31a to 31c and the serration groove portions 32a to 32c are provided with serrations 30a to 30c. Therefore, when the steering torque is transmitted, the serration shaft portions 31a to 31c and the serration groove portion are provided. 32a to 32c come into contact before the plate springs 33a to 33c are subjected to a problem load (stress), and the serrations 30a to 30c mainly transmit torque, so the ball trains 8a to 8c and the plate spring 33a. ˜33c is not subjected to an excessive load (stress).

  As described above, the leaf springs 33a to 33c can secure a sufficient amount of bending, and an excessive load (stress) is not applied to the balls of the ball rows 8a to 8c and the leaf springs 33a to 33c. Therefore, the stress generated in the ball trains 8a to 8c and the leaf springs 33a to 33c at the time of transmission of the steering torque can be relieved, so that no high stress is generated and the “sag” is caused by permanent deformation. And can maintain preload performance over a long period of time.

  Moreover, in 3rd Embodiment, both the taper side surface board part 4d and the bottom face board part 4e are comprised in the axial direction groove | channels 4a-4c of the male shaft 1 by the plane. The center lines of the axial grooves 4a to 4c are directed toward the center point of the male shaft 1, and the tapered side face plate portion 4d has a wedge shape that is a right and left object from the center of the axial grooves 4a to 4c. The wedge angle (contact angle) is preferably 40 to 70 degrees with respect to the centers of the axial grooves 4a to 4c. As a result, the leaf springs 33a to 33c are firmly fixed to the wedge surfaces of the axial grooves 4a to 4c, so that when the steering torque is applied, the entire leaf springs 33a to 33c are unlikely to cause a side slip. In addition, it is possible to prevent excessive hysteresis from occurring.

In the third embodiment, the case where the leaf springs 33a to 33c are provided on the male shaft 1 side has been described. However, the present invention is not limited to this and can be provided on the female shaft 1 side.
In the third embodiment, at least one of the outer peripheral surface of the male shaft 1 and the inner peripheral surface of the female shaft 2 is moved to the serration shaft portions 31a to 31c at the time of relative movement between the male shaft 1 and the female shaft 2. Although the case where the gas soft nitriding treatment for preventing the generation of indentation was performed between the serration groove portions 32a to 32c has been described, the present invention is not limited to this, and at least the serration shaft portions 31a to 31c or the serration groove portions 32a to 32c. Or a part thereof may be partially subjected to surface hardening heat treatment such as gas soft nitriding, and only the axial grooves 6a to 6c of the female shaft 2 to which the ball rows 8a to 8c are in rolling contact or the A surface hardening heat treatment may be partially applied to the peripheral portion including the axial grooves 6a to 6c.

Further, in the third embodiment, the case where the serration portions 30a to 30c are applied as the torque transmitting members has been described. However, the present invention is not limited to this, and instead of the serration portions 30a to 30c, a spline groove portion and a spline shaft are used. You may make it provide the spline part comprised by a part.
Furthermore, in the third embodiment, the case where three sets of rolling elements constituted by the ball rows 8a to 8c and three torque transmission members constituted by the serration portions 30a to 30c are provided, respectively. However, the number of rolling elements and the number of torque transmission members can be arbitrarily set.
Furthermore, in the third embodiment, the case where the ball trains 8a to 8c are applied as rolling elements has been described. However, the present invention is not limited to this, and the rolling is performed in the axial direction of the male shaft 1 and the female shaft 2. A roller row in which a plurality of moving rollers are arranged can also be applied.

(Fourth embodiment)
FIG. 11 is a longitudinal section of a telescopic shaft for vehicle steering according to the fourth embodiment of the present invention. FIG. 12 is an enlarged cross-sectional view of the main part.
In the fourth embodiment, a difference in inclination generated between the male shaft 1 and the female shaft 2 is suppressed.
That is, in the fourth embodiment, as shown in FIG. 11, in the configuration of FIG. 5 in the second embodiment described above, the leaf springs 10a to 10c have the same configuration as that of the third embodiment. To 33c, inserted between the ball rows 8a to 8c and the axial grooves 4a to 4c of the male shaft 1, and further, the open end of the female shaft 2 on the cardan shaft joint 20 side on the steering wheel side In addition, in order to suppress the inclination between the male shaft 1 and the female shaft 2, a relatively wide tilt stopper 41 is formed in the axial direction in sliding contact with the outer peripheral surface of the male shaft 1. The configuration is the same as that of the second embodiment, and the same reference numerals are given to the corresponding parts to those in FIG.

  Here, as shown in FIG. 12, the anti-tilt portion 41 includes a relatively wide flange 42 that is integrally formed at the open end of the female shaft 2 so as to protrude inward, and an inner periphery of the flange 42. Surrounded by sliding contact protrusions 43a and 43b formed so as to be in sliding contact with the outer peripheral surface of the male shaft 1 which is formed protruding at both ends in the axial direction on the surface, and these sliding contact protrusions 43a and 43b And a grease reservoir 44 for collecting grease.

  A seal portion 45 is formed outside the anti-tilt portion 41. The seal portion 45 includes a cylindrical portion 47 fitted to a small diameter portion 46 formed on the outer peripheral surface of the open end portion of the female shaft 2, and a flange 42 of the anti-tilt portion 41 inward from one end of the cylindrical portion 47. And a seal member 49 slidably in contact with the outer peripheral surface of the male shaft 1 mounted on the inner peripheral surface of the flange portion 48. The seal member 49 is formed of an elastic body such as rubber or elastomer.

  In the fourth embodiment, when the steering torque is not applied when the steering torque is not applied, the ball trains 33a to 33c apply preloads to the ball trains 8a to 8c so that the ball trains 8a to 8c have the axis of the female shaft 2. Since the slidably contacting projections 43a and 43b of the anti-tilt portion 41 formed on the open end of the female shaft 2 are in sliding contact with the outer circumferential surface of the male shaft 1, the slidably contacting projections 43a and 43b are surely brought into contact with the directional grooves 6a to 6c. The shaft 2 is held at two points of the ball row 8a to 8c and the tilt preventing portion 41 with respect to the male shaft 1, so that the central axes of the male shaft 1 and the female shaft 2 are aligned with each other. It is possible to reliably prevent the center axis from being inclined. In addition, a grease reservoir 44 is formed between the sliding contact projections 43a and 43b. By storing grease in the grease reservoir 44, the grease oozes out into the sliding contact projections 43a and 43b, thereby causing the sliding. The frictional resistance at the contact protrusions 43a and 43b can be reduced.

For this reason, when the male shaft 1 and the female shaft 2 are relatively moved when the steering torque is not transmitted, the stick rollers are not generated by the needle rollers 7a to 7c held by the male shaft 1, and the axial direction of the female shaft 2 is not caused. Generation of indentations in the grooves 5a to 5c can be reliably prevented.
In the fourth embodiment, as described above, the tilt preventing portion 41 prevents the tilt between the male shaft 1 and the female shaft 2 and prevents the stick rollers 7a to 7c from generating a stick slip. Therefore, although it is not necessary to perform gas soft nitriding on the male shaft 1 and the female shaft 2, it is possible to prevent the occurrence of indentation more reliably by performing gas soft nitriding on at least the female shaft 2. it can.

  In the fourth embodiment, the case where the tilt preventing portion 41 is integrally formed at the tip of the female shaft 2 has been described. However, the present invention is not limited to this, and as shown in FIG. An annular body 51 having the same cross-sectional shape as that of the anti-tilt portion 41 may be fitted on the inner peripheral surface of the distal end side, and in this case, an internal fitting position of the annular body 51 can be freely selected. Therefore, as shown in FIG. 13, the seal member 49 is axially attached to the outer peripheral surface of the male shaft 1 by fitting a gap between the front end side surface of the annular body 51 and the front end of the female shaft 2. It is possible to configure so as to be in sliding contact with each other at two locations, and the dust seal effect can be improved.

Furthermore, as shown in FIG. 14, the tilt preventing portion 41 may be integrally formed on the inner peripheral surface of the cylindrical portion 47 forming the seal portion 45. In this case, the seal member 49 is prevented from tilting. What is necessary is just to comprise so that it may mount | wear to the inner peripheral surface side of the part 41, and may slidably contact with the outer peripheral surface of the male shaft 1 on the outer side of the inclination prevention part 41.
Moreover, in 4th Embodiment, although the case where the torque transmission member was comprised with the needle rollers 7a-7c and ball row | line | columns 8a-8c was demonstrated, it is not limited to this, 3rd Embodiment As described above, the ball trains 8a to 8c and the serrations 30a to 30c constitute a torque transmission member, the needle rollers 7a to 7c alone constitute a torque transmission member, and further the serration or spline alone constitutes a torque transmission member. You may make it do.

1 is a schematic side view of a steering mechanism part of an automobile to which a telescopic shaft for vehicle steering according to an embodiment of the present invention is applied. It is a longitudinal cross-sectional view of the expansion-contraction shaft for vehicle steering with a cardan shaft coupling which concerns on 1st Embodiment of this invention. FIG. 3 is an exploded perspective view of the vehicle steering telescopic shaft shown in FIG. 2. FIG. 3 is a transverse sectional view taken along line AA in FIG. 2. It is a longitudinal cross-sectional view of the telescopic shaft for vehicle steering which concerns on 2nd Embodiment of this invention. FIG. 6 is an exploded perspective view of the vehicle steering telescopic shaft shown in FIG. 5. FIG. 6 is a cross-sectional view taken along line BB in FIG. 5. It is a longitudinal cross-sectional view of the telescopic shaft for vehicle steering which concerns on 3rd Embodiment of this invention. FIG. 9 is a cross-sectional view taken along line CC in FIG. 8. It is a perspective view of the leaf | plate spring which can be applied to 3rd Embodiment. It is a longitudinal cross-sectional view of the telescopic shaft for vehicle steering which concerns on 4th Embodiment of this invention. It is an expanded sectional view of the principal part of FIG. It is an expanded sectional view of the principal part similar to FIG. 12 which shows the modification of 4th Embodiment. It is an expanded sectional view of the same principal part as FIG. 12 which shows the other modification in 4th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Male shaft, 2 ... Female shaft, 3a-3c ... Axial groove, 4a-4c ... Axial groove, 5a-5c ... Axial groove, 6a-6c ... Axial groove, 7a-7c ... Needle roller, 8a ˜8c, ball train, 9, leaf spring, 10 a to 10 c, leaf spring, 11, stopper, 12, protrusion, 20, cardan shaft joint, 21, yoke, 22, cardan shaft joint, 23, yoke, 33 a to 33 c,. Leaf spring, 41 ... Anti-tilt part, 45 ... Seal part, 100 ... Member, 101 ... Upper bracket, 102 ... Lower bracket, 103 ... Steering column, 104 ... Steering shaft, 105 ... Steering wheel, 106 ... Universal joint, 107 ... Lower steering shaft part 108 ... steering shaft joint 109 ... pinion shaft 110 ... frame 111 ... elastic body 112 ... steer Ring rack shaft, 113 ... steering tic support portion, 120 ... upper steering shaft portion

Claims (8)

In a telescopic shaft for vehicle steering that is incorporated in a steering shaft of a vehicle and fitted so that a male shaft and a female shaft can transmit torque and can move relative to each other in the axial direction.
A sliding body is fitted between the axial grooves formed on the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft,
An elastic body is interposed between one of the male shaft side and the female shaft side in the axial groove and the sliding body,
A torque transmitting member is disposed at a circumferential position different from the circumferential position at which the elastic body is disposed;
Vehicle steering characterized in that at least one of the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft is subjected to a heat treatment that is hard to prevent indentation due to sliding contact of the sliding body in at least the axial groove. Telescopic shaft.   The elastic body exerts a preload action when the transmitted steering torque is less than a predetermined value and exhibits low rigidity characteristics, and the torque transmission member disposed at a circumferential position different from the elastic body is the steering torque 2. The structure according to claim 1, wherein when the angle is greater than or equal to a predetermined value, the axial groove is engaged in the circumferential direction to exhibit a high rigidity characteristic and to obtain a two-stage torsional rigidity characteristic. Telescopic shaft for vehicle steering. In a telescopic shaft for vehicle steering that is incorporated in a steering shaft of a vehicle and fitted so that a male shaft and a female shaft can transmit torque and can move relative to each other in the axial direction.
A rolling element that rolls in the axial relative movement of the two shafts via an elastic body for preload between the axial grooves formed in the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft. Intervening,
Between the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft, a torque transmission member that enables relative movement in the axial direction between the two and restricts movement in the rotational direction is formed.
A vehicle steering system characterized in that at least one of the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft is subjected to a heat treatment that is hard to prevent indentation due to sliding contact of the torque transmitting member in the axial groove. Telescopic shaft.   The elastic body exerts a preload action when the transmitted steering torque is less than a predetermined value and exhibits a low rigidity characteristic, and the torque transmitting member is circumferentially inserted into the axial groove when the steering torque is a predetermined value or more. The telescopic shaft for vehicle steering according to claim 3, wherein the telescopic shaft for vehicle steering according to claim 3 is configured to exhibit a high rigidity characteristic by engaging with the torsion, and to obtain a two-stage torsional rigidity characteristic.   5. The telescopic shaft for vehicle steering according to claim 3, wherein the torque transmission member is configured by one of a serration and a spline.   The telescopic shaft for vehicle steering according to claim 3 or 4, wherein the torque transmitting member is formed of a cylindrical body.   The expansion and contraction for vehicle steering according to any one of claims 1 to 6, wherein the heat treatment is gas soft nitriding, and at least a hardness of a sliding contact surface of the axial groove is HV400 or more. axis.   The telescopic shaft for vehicle steering according to any one of claims 1 to 7, wherein the elastic body is configured by a leaf spring.

Images