Vehicular steering device

A vehicular steering device includes a turning shaft, a housing storing therein the turning shaft, a stopper provided at a shaft end of the turning shaft, and an annular elastic body. An opening of the housing is formed in a U-shaped cross-sectional shape and in an annular shape opened toward the stopper by an external cylinder portion and an internal cylinder portion. The elastic body includes a first elastic portion and a second elastic portion. The first elastic portion is supported by an inner circumferential surface of the external cylinder portion and the bottom surface, and is provided with a first clearance from an outer circumferential surface of the internal cylinder portion. The second elastic portion extends toward the stopper from the first elastic portion, and is provided with a second clearance larger than the first clearance from the inner circumferential surface of the external cylinder portion.

TECHNICAL FIELD

The present disclosure relates to a vehicular steering device that includes a stopper provided at a shaft end of a turning shaft (e.g., a rack shaft), and an elastic body that attenuates a collision with the stopper.

BACKGROUND ART

In vehicular steering devices that are commonly utilized, there is a so-called rack-and-pinion type steering device that converts a rotation motion from a steering wheel into an axial motion of a rack shaft (a turning shaft) by rack and pinion. The rack shaft is stored in a housing so as to be movable in a vehicle widthwise direction. A stopper (a rack end) is provided at a shaft end of the rack shaft. When the stopper slackly abuts an elastic body (a buffer member) provided at an end of the housing, the movement of the rack shaft and that of the stopper are restricted. This kind of vehicular steering device is disclosed in, for example, Patent Document 1.

The elastic body (the buffer member) of the vehicular steering device disclosed in Patent Document 1 includes a low-spring-rate portion and a high-spring-rate portion, and is integrally molded by a single kind of elastic material. The low-spring-rate portion and the high-spring-rate portion are each in an annular shape around the rack shaft, and are arranged in line in the vehicle widthwise direction. The low-spring-rate portion protrudes toward the stopper from the tip surface of the high-spring-rate portion. The width of the low-spring-rate portion in the radial direction is smaller than the width of the high-spring-rate portion in the radial direction. The pressure receiving area of the low-spring-rate portion is smaller than the pressure receiving area of the high-spring-rate portion. Hence, the spring rate of the low-spring-rate portion is smaller than the spring rate of the high-spring-rate portion. The low-spring-rate portion is compressed and deformed in preference to the high-spring-rate portion. When the elastic body receives small abutment load by a normal steering operation, the low-spring-rate portion is deformed and absorbs such load. When the elastic body receives large shock load, the low-spring-rate portion and the high-spring-rate portion are deformed, and absorb such load. Accordingly, the load that the steering device receives can be attenuated.

CITATION LIST

Patent Literatures

SUMMARY OF INVENTION

Technical Problem

The elastic body disclosed in Patent Document 1 employs a structure in which the low-spring-rate portion and the high-spring-rate portion are arranged side by side in a line in the vehicle widthwise direction. Accordingly, the characteristics of the compression and deformation amount of the elastic body relative to compression load applied to the elastic body from the stopper, i.e., load absorbing characteristics are two-stage characteristics. In recent years, there is a demand to further enhance the steering feeling of a vehicular steering device. In order to do so, it is preferable that the elastic body should have further fine load absorbing characteristics.

An objective of the present disclosure is to provide a vehicular steering device that includes an elastic body that has further fine load absorbing characteristics.

Solution to Problem

Upon keen research and development, the inventor of the present disclosure achieved a technical knowledge such that, by designing a clearance as appropriate between the housing and the elastic body, it becomes possible to provide an elastic body that has further fine load absorbing characteristics. The present disclosure has been accomplished in view of such a technical knowledge.

The present disclosure will be described below.

According to an embodiment of the present disclosure, there is provided a vehicular steering device that includes:

a turning shaft movable in a vehicle widthwise direction;

a stopper provided at an end of the turning shaft;

a housing which is extended in the vehicle widthwise direction so as to be able to store the turning shaft therein, has an opening at an end in the vehicle widthwise direction formed in a U-shaped cross-sectional shape and in an annular shape so as to be opened toward the stopper by an external cylinder portion located outwardly in a radial direction, an internal cylinder portion located inwardly in the radial direction, and an annular and flat bottom surface that closes a space between one end of the external cylinder portion and one end of the internal cylinder portion, and has a length from the bottom surface to an open end of the internal cylinder portion shorter than a length from the bottom surface to the open end of the external cylinder portion; and

an elastic body through which the turning shaft passes so as to be movable in the vehicle widthwise direction, and which is formed of an annular integral molding component with elasticity that includes:an annular first elastic portion having a same length as the length from the bottom surface to the open end of the internal cylinder portion, being fitted in the opening, having a whole surface supported by an inner circumferential surface of the external cylinder portion and the bottom surface, and being provided with a first clearance across a whole circumference from the outer circumferential surfaces of the internal cylinder portion; andan annular second elastic portion extending toward the stopper from the first elastic portion and being provided with a second clearance across the whole circumference from the inner circumferential surface of the external cylinder portion, the second clearance being larger than the first clearance.

Advantageous Effects of Invention

According to the present disclosure, a vehicular steering device is provided which includes an elastic body that has further fine load absorbing characteristics.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described below with reference to the figures. Note that the embodiments illustrated in the figures are merely examples of the present disclosure, and the present disclosure is not limited to such embodiments. In the following description, the right side and the left side mean the right side and the left side with reference to a person getting on a vehicle, and the front side and the rear side mean the front side and the rear side with reference to the travelling direction of the vehicle.

First Embodiment

A vehicular steering device10according to a first embodiment will be described with reference toFIG.1toFIG.8.

As illustrated inFIG.1, the vehicular steering device10includes a steering system20from a steering wheel21of a vehicle to wheels29and29(turn wheels29and29) thereof, an auxiliary torque mechanism40that adds auxiliary torque to the steering system20, and right and left attenuator devices50and50at the right and left sides (respective sides in the vehicle widthwise direction), respectively.

The steering system20includes the steering wheel21, a steering shaft22coupled to the steering wheel21, an input shaft24coupled to the steering shaft22by a universal joint23, a turning shaft26coupled to the input shaft24by a first transmission mechanism25, and the right and left (respective sides in the vehicle widthwise direction) wheels29and29coupled to the respective ends of the turning shaft26through respective ball joints27and27, respective tie rods28A and28A, and respective knuckles28B and28B.

The first transmission mechanism25includes, for example, a rack-and-pinion mechanism. The turning shaft26is movable in the vehicle widthwise direction within a through-hole31of the housing30. Respective ends of the turning shaft26protrude from respective ends of the housing30in the vehicle widthwise direction. The ball joints27and27are provided at respective ends of the turning shaft26in the lengthwise direction.

The housing30is extended in the vehicle widthwise direction so as to be able to store the turning shaft26therein, and is provided with the through-hole31passing completely through in the vehicle widthwise direction, and openings32and32located at respective ends in the vehicle widthwise direction. These openings32and32are each a hole in a circular shape with a bottom and each of which is concentric to the corresponding through-hole31, and which has a larger diameter than that of the through-hole31.

According to the steering system20, when a driver turns the steering wheel21, the right and left wheels29and29can be steered through the first transmission mechanism25, the turning shaft26, and the right and let tie rods28A and28A with steering torque.

The auxiliary torque mechanism40includes a steering torque sensor41, a control unit42, an electric motor43, and a second transmission mechanism44. The steering torque sensor41detects steering torque of the steering system20applied to the steering wheel21. The control unit42generates control signals based on torque detection signals from the steering torque sensor41. The electric motor43generates motor torque (auxiliary torque) in accordance with the above-described steering torque based on the control signals from the control unit42. The second transmission mechanism44transmits the auxiliary torque generated by the electric motor43to the above-described turning shaft26, and includes, for example, a belt transmission mechanism45and a ball screw46.

According to this vehicular steering device10, the wheels29and29can be turned through the turning shaft26by combination torque obtained by adding the auxiliary torque of the electric motor43to the driver's steering torque.

The vehicular steering device10includes the right and left (respective sides in the vehicle widthwise direction) attenuator devices50and50as described above. Collision load generated when the turning shaft26moves up to respective stroke ends can be attenuated by the right and left attenuator devices50and50. The left attenuator device50will be described below on the behalf of such devices.

As illustrated inFIG.2, the attenuator device50includes a stopper51and an elastic body52.

The stopper51is provided at a shaft end26a(an end26a) of the turning shaft26exposed from the housing30, and includes, for example, a holder27a(also referred to as a joint housing27a) of the ball joint27. The holder27acan move forward or retract relative to the opening32of the housing30. An end surface51aof the stopper51is a flat surface orthogonal to the turning shaft26, and faces the opening32of the housing30.

As illustrated inFIG.2andFIG.3, the opening32located at the end of the housing30in the vehicle widthwise direction is formed in an annular shape with a U-shaped cross section opened toward the stopper51by an external cylinder portion33(a first cylinder portion33) located outwardly in the radial direction, an internal cylinder portion34(a second cylinder portion34) located inwardly in the radial direction, and an annular bottom surface35(the bottom surface35of the opening32) that closes a space between one end of the external cylinder portion33and one end of the internal cylinder portion34.

The respective shapes of an inner circumferential surface33aof the external cylinder portion33and of an outer circumferential surface34aof the internal cylinder portion34are each a true circular shape that is concentric to each other. The outer circumferential surface34aof the internal cylinder portion34is a tapered surface tapered toward an open end34bof the internal cylinder portion34from the bottom surface35. The outer circumferential surface34aof the internal cylinder portion34will be also referred to as a “tapered surface34aof the internal cylinder portion34”. An angle θ (a tapered angle θ) of the tapered surface34aof the internal cylinder portion34is set as appropriate. The bottom surface35is a flat surface orthogonal to the turning shaft26, and faces the end surface51aof the stopper51. A length L1from the bottom surface35to the open end34b(an opened end surface34b) of the internal cylinder portion34is shorter than a length L2from the bottom surface35to an open end33b(an opened end surface33b) of the external cylinder portion33.

As illustrated inFIG.3andFIG.4, The shape of an edge (a corner) between the inner circumferential surface33aof the external cylinder portion33and of the bottom surface35is in a circular arc shape. The shape of an edge (a corner) between the outer circumferential surface34aof the internal cylinder portion34and the bottom surface35is in a circular arc shape. The shape of an edge (a corner) between the outer circumferential surface34aof the internal cylinder portion34and the open end34bof the internal cylinder portion34is in a circular arc shape.

The elastic body52is an annular member which is provided in the opening32of the housing30, and through which the turning shaft26is inserted so as to be movable in the vehicle widthwise direction. The elastic body52includes an integrally molded component with elasticity which is formed of an annular first elastic portion60and an annular second elastic portion70. The elastic body52is formed of, for example, an elastic material, such as a urethane resin or a rubber.

The first elastic portion60has the length L1that is equal to the length L1from the bottom surface35of the opening32to the open end34bof the internal cylinder portion34, and is fitted in the opening32. A whole outer circumferential surface61of the first elastic portion60is supported by the inner circumferential surface33aof the external cylinder portion33. Relative to a diameter D1of the inner circumferential surface33aof the external cylinder portion33, a diameter d1of the outer circumferential surface61of the first elastic portion60is designed so as to be the same or slightly larger. A whole bottom surface62of the first elastic portion60is supported by the bottom surface35of the opening32.

A first clearance81is provided across the whole circumference between the outer circumferential surface34aof the internal cylinder portion34and the inner circumferential surface63of the first elastic portion60. A size δ1of the first clearance81is designed with the elastic deformation amount of the whole elastic body52when compression load acts on the elastic body52from the stopper51being taken into consideration. It is preferable that the size δ1of the first clearance81should be constant (uniform).

An inner circumferential surface63of the first elastic portion60is a tapered surface along the outer circumferential surface34aof the internal cylinder portion34. That is, the inner circumferential surface63of the first elastic portion60is a tapered surface tapered from the bottom surface62of the first elastic portion60toward a tip64thereof. The inner circumferential surface63of the first elastic portion60may be also referred to as “the tapered surface63of the first elastic portion60” below. A straight line Lx extended along the tapered surface63of the first elastic portion60will be defined as “an extended line Lx of the tapered surface63”. In the first elastic portion60, an edge (a corner) between the outer circumferential surface61and the bottom surface62and an edge (a corner) between the bottom surface62and the inner circumferential surface63are chamfered, respectively.

The second elastic portion70continuously extends toward the stopper51from the tip64of the first elastic portion60. A second clearance82is provided across the whole circumference between an outer circumferential surface71of the second elastic portion70and the inner circumferential surface33aof the external cylinder portion33. A size δ2of the second clearance82is designed with the elastic deformation amount of the whole elastic body52when compression load acts on the elastic body52from the stopper51being taken into consideration, and is larger than the size δ1of the first clearance81.

This will be described in more detail. A diameter d2at the tip71aof the outer circumferential surface71of the second elastic portion70is smaller than the diameter d1at the outer circumferential surface61of the first elastic portion60. The outer circumferential surface71is a tapered surface that is tapered toward the tip71aof the outer circumferential surface71of the second elastic portion70from the tip61aof the outer circumferential surface61of the first elastic portion60. Moreover, the contour of the outer circumferential surface71is in a curved shape as a whole from a base end71b(the tip64of the first elastic portion60) up to the tip71a.

It is preferable that the outer circumferential surface71of the second elastic portion70should include an annular first groove72indicated by a fictitious outline inFIG.4. The first groove72is concaved in a curved shape across the whole circumference from the tip61aof the outer circumferential surface61of the first elastic portion60toward a tip surface73of the second elastic portion70.

The inner circumferential surface74of the second elastic portion70is a tapered surface along the extended line Lx of the tapered surface63of the first elastic portion60(the outer circumferential surface34aof the internal cylinder portion34). It is preferable that the tip74aof the inner circumferential surface74of the second elastic portion70should be aligned with an intersection Px between the tip surface73of the second elastic portion70and the extended line Lx. A diameter d4at the intersection Px (the tip74aof the inner circumferential surface74) is larger than a diameter D2at the inner circumferential surface34cof the internal cylinder portion34. The length of the second elastic portion70is L3.

The inner circumferential surface74of the second elastic portion70includes an annular second groove75concaved across the whole circumference. The second groove75is concaved in a curved shape across the whole circumference from the tip63aof the inner circumferential surface63of the first elastic portion60toward the tip surface73of the second elastic portion70.

A boundary76between the inner circumferential surface63of the first elastic portion60and the inner circumferential surface74of the second elastic portion70is a surface in a circular arc shape across the whole circumference.

It is preferable that an annular and tabular plate90(a collar90) should be provided at, at least a portion that contacts the stopper51in the tip surface73of the second elastic portion70. The plate90is formed of a metal. The plate90is integrated with the second elastic portion70by, for example, integral molding, welding, or bonding. An outer circumferential surface91of the plate90is exposed from the second elastic portion70. An outer diameter d5at the plate90is the same as the diameter d2at the tip71aof the outer circumferential surface71of the second elastic portion70. A pore diameter d6of the plate90is smaller than a diameter d4of the tip74a(the intersection Px) of the inner circumferential surface74of the second elastic portion70, and is the same as the diameter D2of the inner circumferential surface34cof the internal cylinder portion34. The thickness of the plate90is Tp.

The stopper51(seeFIG.3) abuts the tip surface73of the second elastic portion70through the plate90. The plate90can uniformly distribute compression load acting on the second elastic portion70from the stopper51to the tip surface73of the second elastic portion70. In addition, the tip surface73of the second elastic portion70is protected against the exterior since covered by the plate90.

Next, the characteristics of the elastic body52will be described with reference toFIG.3andFIG.5toFIG.8.

As indicated by a fictitious outline inFIG.3, the stopper51is located at a position apart from the elastic body52. At this time, the value of depressing force fc when the end surface51aof the stopper51depresses the tip surface73of the second elastic portion70through the plate90by t, i.e., the compression load fc is 0 (fc=0). The value of a compression amount St of the elastic body52is 0 (St=0).

Subsequently, when the end surface51aof the stopper51depresses the tip surface73of the second elastic portion70through the plate90, the compression load fc acts on the tip surface73of the second elastic portion70from the end surface51aof the stopper51. Upon receiving the compression load fc, the elastic body52starts compressing.

The outer circumferential surface61of the first elastic portion60and the bottom surface62thereof are wholly supported by the inner circumferential surface33aof the external cylinder portion33and by the bottom surface35of the opening32. Conversely, the first clearance81is provided at the internal side in the radial direction relative to the inner circumferential surface63of the first elastic portion60. The second clearance82is provided at the external side in the radial direction relative to the outer circumferential surface71of the second elastic portion70. Hence, the elastic body52starts compressing and deforming as a whole, and the inner circumferential surface63of the first elastic portion60starts elastically deforming toward the internal side in the radial direction, and the outer circumferential surface71of the second elastic portion70starts elastically deforming toward the external side in the radial direction. In accordance with such events, the compression amount St of the elastic body52relative to the compression load fc gradually increases.

As the compression load fc increases, the first clearance81and the second clearance82decrease. The size δ1of the first clearance81is smaller than the size δ2of the second clearance82. Hence, the whole elastic body52is continuously compressed and deformed, and the inner circumferential surface63of the first elastic portion60contacts the outer circumferential surface34aof the internal cylinder portion34, and is supported (seeFIG.5). The value of the compression load fc at this time is fc1, and the value of the compression amount St of the elastic body52is St1. A compression range A1 for the value of the compression amount St of the elastic body52from 0 to fc1 will be referred to as “a first compression range A1”.

Within the first compression range A1, the elastic body52shows first load characteristics (low-spring-rate characteristics) in which the ratio of the compression load fc per a unit amount of the compression amount St deforming in the axial direction of the turning shaft26gradually increases. That is, within the first compression range A1, since there are the first clearance81and the second clearance82, the elastic body52is likely to elastically deform. The first load characteristics A1, i.e., the range of the first compression range is defined by, in particular, the size δ1of the first clearance81.

As the compression load fc further increases, the second clearance82further decreases. Hence, the whole elastic body52is continuously compressed and deformed, and the outer circumferential surface71of the second elastic portion70contacts the inner circumferential surface33aof the external cylinder portion33, and is supported (seeFIG.6). The value of the compression load fc at this time is fc2, and the value of the compression amount St of the elastic body52is St2. A compression range A2 for the value of the compression amount St of the elastic body52from fc1 to fc2 will be referred to as “a second compression range A2”.

Within the second compression range A2, the elastic body52tends to show second load characteristics (intermediate-spring-rate characteristics) in which the ratio of the compression load fc per a unit amount of the compression amount St deforming in the axial direction of the turning shaft26increases in comparison with the first load characteristics. The second load characteristics, i.e., the range of the second compression range A2 is defined by, in particular, the size δ2of the second clearance82.

As the compression load fc further increases, the inner circumferential surface74of the second elastic portion70expands toward the internal side in the radial direction, and a part of the second elastic portion70expands toward the stopper51from the second clearance82(seeFIG.7). That is, the compression and deformation of the elastic body52reach an uppermost limit. The value of the compression load fc at this time is fc3, and the value of the compression amount St of the elastic body52is St3. A compression range A3 for the value of the compression amount St of the elastic body52from fc2 to fc3 will be referred to as “a third compression range A3”.

Within the third compression range A3, the elastic body52tends to show third load characteristics (high-spring-rate characteristics) in which the ratio of the compression load fc per a unit amount of the compression amount St changing in the axial direction of the turning shaft26keenly increases in comparison with the second load characteristics.

The characteristics regarding the compression load fc and the compression amount St as described above will be summarized inFIG.8.FIG.8is a characteristics diagram representing the characteristics of the compression amount St relative to the compression load fc with the vertical axis representing the compression load fc input to the elastic body52and the horizontal axis representing the compression amount St of the elastic body52. According to the characteristic curve shown in the characteristics diagram, the following becomes apparent.

Within the first compression range A1, since an effect due to the first clearance81and to the second clearance82acts, the elastic body52is likely to deform. Within the second compression range A2, since the effect due to the first clearance81does not act but the effect due to the second clearance82only acts, the elastic body52is not likely to deform in comparison with the case of the first compression range A1. Within the third compression range A3, since the effect due to the first clearance81and to the second clearance82does not act, the elastic body52keenly becomes difficult to deform in comparison with the case of the second compression range A2. As described above, by designing the size δ1of the first clearance81and the size δ2of the second clearance82as appropriate, the respective compression ranges A1 to A3 can be set optimally.

Next, the actions of the attenuator device50will be described with reference toFIG.3andFIG.5toFIG.8.

As indicated by a fictitious outline inFIG.3, the stopper51is located at a position apart from the elastic body52. Subsequently, the turning shaft26moves in the vehicle widthwise center direction by a so-called normal steering operation originating from the turning of the steering wheel21(seeFIG.1) and/or the drive by the electric motor43. When the turning shaft26moves to the movable limit (the stroke end) in the vehicle widthwise center direction, the end surface51aof the stopper51loosely abuts the tip surface73of the second elastic portion70through the plate90. At this time, abutment load due to the normal steering operation is input to the tip surface73of the second elastic portion70from the end surface51aof the stopper51. Consequently, the elastic body52absorbs the abutment load (the compression load) due to the normal steering operation by elastic deformation. Subsequently, when the turning shaft26moves outwardly in the vehicle widthwise direction, the end surface51aof the stopper51becomes apart from the plate90. Consequently, the elastic body52returns to the original position by the own elasticity.

Moreover, as indicated by a fictitious outline inFIG.3, when the stopper51is apart from the elastic body52, and when, for example, the wheel31(seeFIG.1) goes over the curbstone of a road, large shock load in the axial direction acts from the wheel31to the stopper51. Consequently, the end surface51aof the stopper51abuts the tip surface73of the second elastic portion70through the plate90. The shock load at this time is greater than the abutment load due to the normal steering operation. The shock load is input to the tip surface73of the second elastic portion70from the end surface51aof the stopper51. In this case, as illustrated inFIG.5toFIG.7, the elastic body52largely deforms and absorbs the shock load. Consequently, the shock load which is to be received by the steering device10can be reduced.

The above description can be summarized as follows.

As illustrated inFIG.1toFIG.4, the vehicular steering device10includes:

the turning shaft26movable in the vehicle widthwise direction;

the stopper51provided at the end26aof the turning shaft26;

the housing30which is extended in the vehicle widthwise direction so as to be able to store the turning shaft26therein, has the opening32at the end in the vehicle widthwise direction formed in a U-shaped cross-sectional shape and in an annular shape so as to be opened toward the stopper51by the external cylinder portion33located outwardly in the radial direction, the internal cylinder portion34located inwardly in the radial direction, and the annular and flat bottom surface35that closes a space between one end of the external cylinder portion33and one end of the internal cylinder portion34, and has the length L1from the bottom surface35to the open end34bof the internal cylinder portion34shorter than the length L2from the bottom surface35to the open end33bof the external cylinder portion33; and

the elastic body52through which the turning shaft26is inserted so as to be movable in the vehicle widthwise direction, and which is formed of an annular integral molding component with elasticity including; the annular first elastic portion60having the same length L1as the length L1from the bottom surface35to the open end34bof the internal cylinder portion34, being fitted in the opening32, having the whole surface supported by the inner circumferential surface33aof the external cylinder portion33and the bottom surface35, and being provided with the first clearance81from the outer circumferential surface34aof the internal cylinder portion34across the whole circumference; and the annular second elastic portion70extending toward the stopper51from the first elastic portion60and being provided with the second clearance82from the inner circumferential surface33aof the external cylinder portion33across the whole circumference, the second clearance being larger than the first clearance.

As described above, the first elastic portion60has the elastic deformation restricted by the inner circumferential surface33aof the external cylinder portion33and by the bottom surface35of the opening32, but has the first clearance81from the outer circumferential surfaces34aof the internal cylinder portion34, and thus the elastic deformation inwardly in the radial direction is permitted to some extent. The elastic deformation of the second elastic portion70outwardly in the radial direction is permitted to some extent by the second clearance82from the inner circumferential surfaces33aof the external cylinder portion33. Accordingly, the load characteristics (the spring-rate characteristics) of the elastic body52can be optimized by designing the size δ1of the first clearance81and the size δ2of the second clearance82as appropriate. Therefore, the vehicular steering device10can be provided which includes the elastic body52with further fine load absorbing characteristics.

Moreover, as illustrated inFIG.3andFIG.4, the outer circumferential surface71of the second elastic portion70includes the annular first groove72that is concaved across the whole circumference. This further facilitates the elastic deformation of the second elastic portion70.

Furthermore, as illustrated inFIG.3andFIG.4, the outer circumferential surface34aof the internal cylinder portion34is the tapered surface34atapered toward the open end34bof the internal cylinder portion34from the bottom surface35, and

the size δ1of the first clearance81between the outer circumferential surface34aof the internal cylinder portion34and the inner circumferential surface63of the first elastic portion60is constant.

Accordingly, the load acting on the outer circumferential surface34aof the internal cylinder portion34from the inner circumferential surface63of the first elastic portion60can be attenuated.

Still further, as illustrated inFIG.3andFIG.4, the inner circumferential surface74of the second elastic portion70is a tapered surface along the extended line Lx of the tapered surface63of the first elastic portion60, and includes the annular second groove82concaved across the whole circumference. This further facilitates the elastic deformation of the second elastic portion70.

Yet still further, as illustrated inFIG.3andFIG.4, the annular plate90is provided at, at least the portion that contacts the stopper51in the tip surface73of the second elastic portion70. Accordingly, the compression load can be uniformly input to the tip surface73of the second elastic portion70. The compression load can be efficiently absorbed by the elastic body52.

In other words, as illustrated inFIG.1toFIG.3, the vehicular steering device10includes:

the turning shaft26movable in the vehicle widthwise direction;

the stopper51provided at the end26aof the turning shaft26;

the housing30which is extended in the vehicle widthwise direction so as to be able to store the turning shaft26therein, has the opening32at the end in the vehicle widthwise direction formed in a U-shaped cross-sectional shape and in an annular shape so as to be opened toward the stopper51by the external cylinder portion33located outwardly in the radial direction, the internal cylinder portion34located inwardly in the radial direction, and the annular and flat bottom surface35that closes a space between one end of the external cylinder portion33and one end of the internal cylinder portion34, and has the length L1from the bottom surface35to the open end34bof the internal cylinder portion34shorter than the length L2from the bottom surface35to the open end33bof the external cylinder portion33; and

the elastic body52through which the turning shaft26is inserted so as to be movable in the vehicle widthwise direction, and which is formed of an annular integral molding component with elasticity including; the annular first elastic portion60having the same length L1as the length L1from the bottom surface35to the open end34bof the internal cylinder portion34, being fitted in the opening32, having the whole surface supported by the inner circumferential surface33aof the external cylinder portion33and the bottom surface35, and being provided with the first clearance81from the outer circumferential surfaces34aof the internal cylinder portion34across the whole circumference; and the annular second elastic portion70extending toward the stopper51from the first elastic portion60and being provided with the second clearance82from the above-described inner circumferential surfaces33aof the above-described external cylinder portion33across the whole circumference, the second clearance being larger than the first clearance.

The outer circumferential surface71of the second elastic portion70includes the annular first groove72that is concaved in a curved shape across the whole circumference from the tip61aof the outer circumferential surface61of the first elastic portion60toward the tip surface73of the second elastic portion70.

The outer circumferential surface34aof the internal cylinder portion34is a tapered surface tapered toward the open end34bof the internal cylinder portion34from the bottom surface35, and an edge with the open end34bof the internal cylinder portion34is a surface formed in a circular arc shape.

The size δ1of the first clearance81between the outer circumferential surface34aof the internal cylinder portion34and the inner circumferential surface63of the first elastic portion60is constant.

The inner circumferential surface74of the second elastic portion70is a tapered surface along the extended line Lx of the tapered surface63of the first elastic portion60, and includes the annular second groove82concaved across the whole circumference.

The boundary76between the inner circumferential surface63of the first elastic portion60and the inner circumferential surface74of the second elastic portion70is a surface in a circular arc shape across the whole surface.

The annular plate90is provided at, at least the portion that contacts the stopper51in the tip surface73of the second elastic portion70.

Next, with reference toFIG.9, a vehicular steering device10A according to a second embodiment will be described.

Second Embodiment

FIG.9illustrates a cross-sectional structure of an elastic body52A which is provided in the opening32of the housing30of the vehicular steering device10A according to the second embodiment, and which is illustrated in corresponding ways toFIG.3.

The vehicular steering device10A illustrated inFIG.9has features such that the following two structures are changed, and the other basic structure is common to the above-described vehicular steering device10illustrated inFIG.1toFIG.7. The common component to that of the above-described vehicular steering device10will be denoted by the same reference numeral, and the detailed description thereof will be omitted.

The first changed part is that the outer circumferential surface34aof the internal cylinder portion34of the first embodiment illustrated inFIG.3is changed to an outer circumferential surface34Aa of an internal cylinder portion34A illustrated inFIG.9. The outer circumferential surface34Aa of the second embodiment is not a tapered surface but a straight surface in parallel with the inner circumferential surface33aof the external cylinder portion33.

The second changed part is that the elastic body52of the first embodiment illustrated inFIG.3is changed to an elastic body52A. According to the elastic body52A of the second embodiment, an inner circumferential surface63A of the first elastic portion60is a straight surface in parallel with the outer circumferential surface34Aa of the internal cylinder portion34A. Like the first embodiment, the first clearance81with the size δ1is provided between the outer circumferential surface34Aa of the internal cylinder portion34A and the inner circumferential surface63A of the first elastic portion60. An inner circumferential surface74A of the second elastic portion70according to the second embodiment is a straight surface along the inner circumferential surface63A of the first elastic portion60, and does not include the second groove75of the first embodiment (seeFIG.3).

Next, with reference toFIG.10, a vehicular steering device10B according to a third embodiment will be described.

Third Embodiment

FIG.10illustrates a cross-sectional structure of an elastic body52B which is provided in the opening32of the housing30of the vehicular steering device10B according to the third embodiment, and which is illustrated in corresponding ways toFIG.3.

The vehicular steering device10B illustrated inFIG.10has a feature such that the elastic body52of the first embodiment illustrated inFIG.3is changed to the elastic body52B, and the other basic structure is common to the above-described vehicular steering device10illustrated inFIG.1toFIG.7. The common component to that of the above-described vehicular steering device10will be denoted by the same reference numeral, and the detailed description thereof will be omitted.

The elastic body52B of the third embodiment does not include the first groove72of the first embodiment (seeFIG.3) in the outer circumferential surface71of the second elastic portion70. Moreover, according to the elastic body52B of the third embodiment, an inner circumferential surface74B of the second elastic portion70is a straight surface in parallel with the outer circumferential surface71of the second elastic portion70, and does not include the second groove75of the first embodiment (seeFIG.3).

Next, with reference toFIG.11toFIG.15, a vehicular steering device10C according to a fourth embodiment will be described.

Fourth Embodiment

FIG.11illustrates a cross-sectional structure of an elastic body52C which is provided in the opening32of the housing30of the vehicular steering device10C according to the fourth embodiment, and which is illustrated in corresponding ways toFIG.3.FIG.12illustrates a structure in which the opening32of the housing30and the elastic body52C both illustrated inFIG.11are disassembled, and which illustrates in corresponding ways toFIG.4.

The vehicular steering device10C illustrated inFIG.11andFIG.12has a feature such that the elastic body52of the first embodiment illustrated inFIG.3toFIG.4is changed to the elastic body52C, and the other basic structure is common to the above-described vehicular steering device10illustrated inFIG.1toFIG.7. The common component to that of the above-described vehicular steering device10will be denoted by the same reference numeral, and the detailed description thereof will be omitted.

According to the elastic body52C of the fourth embodiment, the second elastic portion70includes an annular extended portion77extended (expanded) toward the stopper51from the tip surface73. The shape of the extended portion77is in a true circular shape concentric to the second elastic portion70. An outer circumferential surface91of the plate90is embedded in the extended portion77. The plate90is integrated with the tip surface73of the second elastic portion70and the extended portion77thereof by, for example, integral molding, welding or bonding.

As described above, the outer circumferential surface91of the plate90is embedded in the extended portion77. Hence, the plate90is integrated with the tip surface73of the second elastic portion70and also the extended portion77. Accordingly, a peeling of the plate90relative to the tip surface73of the second elastic portion70can be further surely suppressed.

A diameter d2C at the tip71aof the outer circumferential surface71of the second elastic portion70is larger than an outer diameter d5of the plate90. Moreover, the diameter d2C at the tip71aof the outer circumferential surface71is larger than the diameter d2at the tip71aof the first embodiment illustrated inFIG.3toFIG.4(d2C>d2=d5).

The second clearance82is provided between the outer circumferential surface71of the second elastic portion70and the inner circumferential surface33aof the external cylinder portion33across the whole circumference. A size δ2C of the second clearance82is designed with the elastic deformation amount of the whole elastic body52when compression load acts on the elastic body52from the stopper51being taken into consideration, and is larger than the size δ1of the first clearance81. Moreover, the size δ2C of the second clearance82may be designed so as to be smaller than the size δ2of the second clearance82according to the first embodiment illustrated inFIG.3andFIG.4(δ2C<δ2).

This will be described in more details. The diameter d2C at the tip71aof the outer circumferential surface71of the second elastic portion70is smaller than the diameter d1at the outer circumferential surface61of the first elastic portion60. The outer circumferential surface71of the second elastic portion70includes the annular first groove72. The first groove72is concaved in a curved shape across the whole circumference toward the tip surface73of the second elastic portion70from the tip61aof the outer circumferential surface61of the first elastic portion60. A diameter d3(seeFIG.12) of the most concaved portion of the first groove72is smaller than the diameter d2C at the tip71aof the outer circumferential surface71of the second elastic portion70.

As described above, the outer circumferential surface71of the second elastic portion70includes the annular first groove72concaved across the whole circumference. This further facilitates the elastic deformation of the second elastic portion70.

Next, with reference toFIG.11,FIG.13toFIG.15, the characteristics of the elastic body52C will be described. Note that since the characteristics of the elastic body52C are the same as the characteristics of the elastic body52of the first embodiment illustrated inFIG.3,FIG.5toFIG.8, only a summary will be described.

As illustrated inFIG.11, when the end surface51aof the stopper51depresses the tip surface73of the second elastic portion70through the plate90, the compression load fc (unillustrated) acts on the tip surface73of the second elastic portion70from the end surface51aof the stopper51. As the compression load fc increases, the first clearance81and the second clearance82are reduced. The elastic body52is continuously compressed and deformed as a whole, and the inner circumferential surface63of the first elastic portion60contacts the outer circumferential surface34aof the internal cylinder portion34, and is supported (seeFIG.13). In the state illustrated inFIG.13, like the first embodiment inFIG.5, the first load characteristics (the low-spring-rate characteristics) are exerted.

As the compression load fc further increases, the second clearance82are further reduced. Hence, the elastic body52is continuously compressed and deformed as a whole, and the outer circumferential surface71of the second elastic portion70contacts the inner circumferential surface33aof the external cylinder portion33, and is supported (seeFIG.14). In the state illustrated inFIG.14, like the first embodiment inFIG.6, there is a tendency that the second load characteristics (the intermediate-spring-rate characteristics) are exerted.

As the compression load fc further increases, the inner circumferential surface74of the second elastic portion70are expanded inwardly in the radial direction, and the extended portion77of the second elastic portion70expands toward the stopper51(seeFIG.15). That is, the compressive deformation of the elastic body52reaches the limit. In the state illustrated inFIG.15, like the first embodiment inFIG.7, there is a tendency that the third load characteristics (the high-spring-rate characteristics) are exerted.

The vehicular steering device10C according to the fourth embodiment accomplishes the same actions and advantageous effects as those of the vehicular steering device10according to the first embodiment illustrated inFIG.1toFIG.8.

Note that the vehicular steering devices10,10A,10B and10C according to the present disclosure are not limited to the embodiments as far as the actions and the advantageous effects of the present disclosure are accomplished.

For example, according to the present disclosure, the vehicular steering devices10,10A,10B and10C may employ a structure that includes only the steering system20, and may be a so-called manually operated type steering device that does not include the auxiliary torque mechanism40.

Moreover, the vehicular steering devices10,10A,10B and10C may be a so-called steer-by-wire type steering device which mechanically separates the steering wheel21and the turning shaft26, causes a turn actuator (unillustrated) to generate turn force in accordance with the steered amount of the steering wheel21, and transmits the turn force to the turning shaft26.

Moreover, the vehicular steering devices10,10A,10B and10C may employ a structure in which equal to or greater than two of those are arbitrary combined as appropriate.

INDUSTRIAL APPLICABILITY

The vehicular steering devices10,10A,10B and10C according to the present disclosure are suitably to be loaded on a vehicle.

REFERENCE SIGNS LIST

10,10A,10B,10C Vehicular steering device26Turning shaft26aShaft end (end) of turning shaft30Housing32Opening33External cylinder portion (first cylinder portion)33aInner circumferential surface of external cylinder portion33bOpen end of external cylinder portion (opened end surfaceof external cylinder portion)34Internal cylinder portion (second cylinder portion)34aOuter circumferential surface of internal cylinder portion(tapered surface of internal cylinder portion)34bOpen end of internal cylinder portion (opened end surfaceof internal cylinder portion)34cInner circumferential surface of internal cylinder portion50Attenuator device51Stopper52,52A,52B Elastic body60First elastic portion61Outer circumferential surface of first elastic portion61aTip of outer circumferential surface of first elastic portion62Bottom surface of first elastic portion63Inner circumferential surface (tapered surface) of firstelastic portion63aTip of inner circumferential surface of first elastic portion64Tip of first elastic portion70Second elastic portion71Outer circumferential surface of second elastic portion72First groove73Tip surface of second elastic portion74Inner circumferential surface of second elastic portion74aTip of inner circumferential surface of second elasticportion75Second groove77Extended portion81First clearance82Second clearance90PlateL1Length from bottom surface to open end of internalcylinder portionL2Length from bottom surface to open end of externalcylinder portionδ1Size of first clearanceδ2, δ2C Size of second clearance