Patent Description:
The damping stopper is used as a rack end stopper for an end of a steering rack provided in a steering gear of a vehicle, for example. As illustrated in <FIG>, the rack end stopper compresses and deforms an elastic body <NUM> containing a rubber material between a rack housing <NUM> and a rack <NUM> axially facing each other and axially displaced relative to each other.

A damping stopper <NUM> damps a shock when the rack <NUM> collides with the rack housing <NUM> when a steering wheel is vigorously turned to a full lock in a hydraulically/electrically assisted steering rack, for example.

The damping of the shock by the damping stopper <NUM> is performed by absorbing the kinetic energy by the weight and the speed of a movable object (rack <NUM>) by the displacement and the reaction force of the damping stopper <NUM> (elastic body <NUM>). As illustrated in a graph of <FIG>, the absorbable energy amount is defined by the size of an area S illustrated by a diagram obtained by the displacement amount and the reaction force of the damping stopper <NUM>.

Therefore, in order to increase the absorbable energy amount, it is common to enlarge the area S by increasing the displacement amount of the damping stopper <NUM> or increasing the reaction force (Rigidity = Spring constant).

<CIT> discloses a damping stopper comprising: an elastic body formed into an annular shape, configured to be provided between two members which are configured to be axially displaced relative to each other, and, when an interval between the two members decreases in a state where the elastic body is provided between the two members, configured to be axially compressed by the two members and expand radially outward; and a metal attachment ring presenting an L-shaped cross section and bonded to one axial end and the inner peripheral surface of the elastic body.

<CIT> and <CIT> each disclose a damping stopper comprising: an elastic body formed into an annular shape, configured to be provided between two members which are configured to be axially displaced relative to each other, and, when an interval between the two members decreases in a state where the elastic body is provided between the two members, configured to be axially compressed by the two members and expand radially outward; and a resistance member attached to an outer periphery of the elastic body in one axial region of the elastic body and suppressing expansion of the elastic body in the one region.

The above-described technique has room for improvement in the following points.

The damping stopper <NUM> requires a proper distortion in order to obtain a high reaction force like a nonlinear region as the characteristic of a common elastic material. In this point, the above-described structure requires an increase in the stopper size in order to satisfy a request function. However, a design space is limited due to the relationship with peripheral components, and thus the size increase is not easy.

As a solution technique for the above-described problem, it is considered to obtain a high reaction force by filling, with the elastic body <NUM> which is deformed by an input, a clearance c between a mating component (housing <NUM>) and the stopper <NUM>.

However, according to this technique, the reaction force sharply rises when the elastic body <NUM> reaches a filled state, and therefore efficient energy absorption cannot be performed. As a result, the absorbable energy amount cannot be increased.

It is an object of the disclosure to provide a damping stopper capable of increasing the absorbable energy amount.

A damping stopper as disclosed in claim <NUM>.

According to the disclosure, a resistance force by the second member is generated in an expansion process of the elastic body, and thus the absorbable energy amount can be increased.

A damping stopper <NUM> of this embodiment is an example of a rack end stopper of a steering rack provided in a steering gear of a vehicle. As illustrated in <FIG> or <FIG>, the damping stopper <NUM> is interposed between a rack housing <NUM> and a rack <NUM> as two members axially facing each other and axially displaced relative to each other.

The rack housing <NUM> has an end surface <NUM> having a planar shape perpendicular to the axis. On the outer periphery of the end surface <NUM>, a level difference <NUM> is provided. On the inner peripheral surface of the level difference <NUM>, a side wall <NUM> is provided. The rack <NUM> has an end surface <NUM> axially facing the end surface <NUM> of the rack housing <NUM>. On the inner periphery of the end surface <NUM>, a level difference <NUM> is provided. On the outer peripheral surface of the level difference <NUM>, a side wall <NUM> is provided. Therefore, an annular mounting space <NUM>, four sides of which are surrounded by the end surface <NUM> and the side wall <NUM> of the rack housing <NUM> and the end surface <NUM> and the side wall <NUM> of the rack <NUM>, is provided. The damping stopper <NUM> forms an annular shape as a whole and mounted in the mounting space <NUM>.

A first embodiment is described based on <FIG>.

As illustrated in <FIG>, the damping stopper <NUM> has an elastic body <NUM> axially compressed between the end surface <NUM> of the rack housing <NUM> and the end surface <NUM> of the rack <NUM>.

The elastic body <NUM> is formed into an annular shape by a predetermined rubber material. To one axial end (upper side in the figure, the rack <NUM> side) and the inner peripheral surface, a metal attachment ring <NUM> presenting an L-shaped cross section is bonded (vulcanized and bonded). As illustrated in <FIG>, when the rack <NUM> is displaced in the direction of approaching the rack housing <NUM> (direction indicated by an arrow D) so that the interval between the end surfaces <NUM> and <NUM> decreases, the elastic body <NUM> is axially compressed by the rack housing <NUM> and the rack <NUM> and expands radially outward.

In the implementation of the disclosure, a metal attachment ring (not illustrated) may be bonded also to the other axial end (lower side in the figure, the rack housing <NUM> side) of the elastic body <NUM>.

The damping stopper <NUM> has a second member <NUM> attached to one axial part of the outer periphery in the elastic body <NUM> and restricting the expansion of the elastic body <NUM> in the one axial part. More specifically, the second member <NUM> is attached to the outer periphery of the elastic body <NUM> in one axial region of the elastic body <NUM> and suppresses the expansion of the elastic body <NUM> in the one region.

The second member <NUM> is a ring body having rigidity such that the second member <NUM> does not contact the side wall <NUM> when the elastic body <NUM> expanding radially outward contacts the side wall <NUM>. The ring body is formed of metal as an example and formed of resin as another example. The ring body has a shape in which the dimension in a direction orthogonal to the axis is larger than the axial dimension and is assembled to an annular mounting groove <NUM> provided in the elastic body <NUM>. The mounting groove <NUM> is a groove provided beforehand in the outer peripheral surface of the elastic body <NUM>.

The mounting groove <NUM> is formed at a position where the elastic body <NUM> is divided into a portion <NUM> of a length L<NUM> and a portion <NUM> of a length L<NUM>. Therefore, the ring body configuring the second member <NUM> is attached to a position where the elastic body <NUM> is divided into the portion <NUM> of the length L<NUM> having a long axial length and the portion <NUM> of the length L<NUM> having a short axial length. It is needless to say that the axial length does not have an absolutely long-and-short relationship and has a relatively long-and-short relationship between the portions <NUM> and <NUM>. Due to the structure, the ring body has an interleaf-like shape sandwiched between the portion of the length L<NUM> having a long axial length and the portion of the length L<NUM> having a short axial length of the elastic body <NUM>.

As another embodiment, in order to facilitate the assembling work to the mounting groove <NUM>, the annular second member <NUM> may be provided with a cut portion or the like in one place on the circumference. Moreover, the second member <NUM> may be buried in the elastic body <NUM> by carrying out insert molding in the vulcanization molding of the elastic body <NUM> by a mold. Considering the function or the like thereof, the second member <NUM> is also referred to as a resistance member or also referred to as an elastic body clamping member.

The outer diameter of the second member <NUM> is formed to be larger than the outer diameter of the elastic body <NUM>. Therefore, the second member <NUM> is projected radially outward from the outer peripheral surface of the elastic body <NUM>.

The outer diameter of the second member <NUM> is formed to be smaller than the inner diameter of the side wall <NUM> of the rack housing <NUM>. Therefore, a radial clearance c<NUM> is formed between the second member <NUM> and the side wall <NUM>. However, the second member <NUM> does not expand, and therefore it may be also structured so that the outer diameter of the second member <NUM> is set to be equal to the inner diameter of the side wall <NUM> so that the second member <NUM> is brought into contact with the side wall <NUM>.

The outer diameter of the elastic body <NUM> is formed to be smaller than the inner diameter of the side wall <NUM> of the rack housing <NUM>, and therefore radial clearances c<NUM> are formed between the elastic body <NUM> and the side wall <NUM>.

In the damping stopper <NUM> of this embodiment, when the rack <NUM> is displaced in the direction of approaching the rack housing <NUM> (arrow D) so that the interval between the end surfaces <NUM> and <NUM> decreases, the elastic body <NUM> is axially compressed between the rack housing <NUM> and the rack <NUM> and expands radially outward corresponding to the compression. The second member <NUM> is attached to one axial part of the outer periphery of the elastic body <NUM>, and therefore acts as a resistance element to the expansion of the elastic body <NUM>. As a result, the radially outward expansion of the elastic body <NUM> is restricted in the one axial part.

As described above, the elastic body <NUM> is divided into the portion <NUM> of the length L<NUM> having a long axial length and the portion <NUM> of the length L<NUM> having a short axial length. The elastic body <NUM> expands in both the portions <NUM> and <NUM>.

When the portion <NUM> of the length L<NUM> having a long axial length and the portion <NUM> of the length L<NUM> having a short axial length are compared, the portion <NUM> of the length L<NUM> has a surface area larger than that of the portion <NUM> of the length L<NUM> and more greatly extends radially outward than the portion <NUM> of the length L<NUM>. As a result, the portion <NUM> of the length L<NUM> contacts the side wall <NUM> earlier than the portion <NUM> of the length L<NUM> as illustrated in <FIG>. Then, a situation is realized in which the portion <NUM> of the length L<NUM> does not yet contact the side wall <NUM> even when expanding in a state where the portion <NUM> of the length L<NUM> expands and contacts the side wall <NUM>.

Accordingly, the rise (increase) of the reaction force after the contact becomes slow as illustrated in a graph of <FIG>. Therefore, the displacement amount until the allowable reaction force is reached increases, and thus efficient energy absorption is enabled and the absorbable energy amount can be increased.

In the graph of <FIG>, Comparative Example illustrates a damping stopper of a conventional structure not having the second member <NUM> and the reaction force sharply rises after contact in Comparative Example, and therefore the displacement amount is small. A point E indicates the timing when the elastic body <NUM> contacts the side wall <NUM>.

A second embodiment is described based on <FIG> and <FIG>. The same portions as those of the first embodiment are designated by the same reference numerals and a description thereof is omitted.

As illustrated in <FIG>, a damping stopper <NUM> has an elastic body <NUM> axially compressed between an end surface <NUM> of a rack housing <NUM> and an end surface <NUM> of a rack <NUM>.

The elastic body <NUM> is formed into an annular shape by a predetermined rubber material. To one axial end (upper side in the figure, the rack <NUM> side) and the inner peripheral surface, a metal attachment ring <NUM> presenting an L-shaped cross section is bonded (vulcanized and bonded). When the rack <NUM> is displaced in the direction of approaching the rack housing <NUM> so that the interval between the end surfaces <NUM> and <NUM> decreases, the elastic body <NUM> is axially compressed by the rack housing <NUM> and the rack <NUM> and expands radially outward.

The damping stopper <NUM> has a second member <NUM> attached to one axial part of the outer periphery of the elastic body <NUM> and restricting the expansion of the elastic body <NUM> in the one axial part. More specifically, the second member <NUM> is attached to the outer periphery of the elastic body <NUM> in one axial region of the elastic body <NUM> and suppresses the expansion of the elastic body <NUM> in the one region.

The second member <NUM> is a ring body having elasticity such that the second member <NUM> expands radially outward when pressed by the elastic body <NUM> expanding radially outward and rigidity higher than that of the elastic body <NUM> such that the second member <NUM> contacts a side wall <NUM> earlier than the elastic body <NUM>. The ring body having such a characteristic has rigidity higher than that of the elastic body <NUM> by being formed of a material different from that of the elastic body <NUM>. As an example, the second member <NUM> is formed of urethane.

As another embodiment, in order to facilitate the assembling work to a mounting groove <NUM>, the ring body configuring the second member <NUM> may be provided with a cut portion in one place on the circumference. Alternatively, the ring body may be divided into two parts on the circumference to have a halved structure. Considering the function or the like thereof, the second member <NUM> is also referred to as a resistance member or also referred to as an elastic body clamping member.

The outer diameter of the second member <NUM> is formed to be smaller than the inner diameter of the side wall <NUM> of the rack housing <NUM>. Therefore, a radial clearance c<NUM> is formed between the second member <NUM> and the side wall <NUM>.

The outer diameter of the elastic body <NUM> is formed to be smaller than the inner diameter of the side wall <NUM> of the rack housing <NUM>. Therefore, radial clearances c<NUM> are formed between the elastic body <NUM> and the side wall part <NUM>.

In the damping stopper <NUM> of this embodiment, when the rack <NUM> is displaced in the direction of approaching the rack housing <NUM> so that the interval between the end surfaces <NUM> and <NUM> decreases, the elastic body <NUM> is axially compressed between the rack housing <NUM> and the rack <NUM> and expands radially outward corresponding to the compression. The second member <NUM> is attached to one axial part of the outer periphery of the elastic body <NUM>, and therefore acts as a resistance element to the expansion. As a result, the radially outward expansion of the elastic body <NUM> is restricted in the one axial part.

When the elastic body <NUM> continuously expands in response to a load accompanying the displacement of the rack <NUM>, the pressure by the expansion presses the second member <NUM> radially outward and expands the second member <NUM> radially outward (diameter enlarging deformation) to bring the second member <NUM> into contact with the side wall <NUM>. In order to expand the second member <NUM> radially outward to bring the second member <NUM> into contact with the side wall <NUM>, a large load is required. Therefore, the rigidity of the entire damping stopper <NUM> is increased, so that a high reaction force as compared with that in the case where the elastic body <NUM> is used alone is generated.

Thereafter, when the rack <NUM> is displaced in the direction of further approaching the rack housing <NUM> in the state where the second member <NUM> contacts the side wall <NUM>, the second member <NUM> slides against the side wall <NUM>, so that sliding resistance is generated between the second member <NUM> and the side wall <NUM>. The rigidity is increased by the sliding resistance, so that a higher reaction force is generated.

As illustrated in a graph of <FIG>, according to the damping stopper <NUM> of this embodiment, a sharp rise (increase) of the reaction force is already started at the timing (point F) when the second member <NUM> contacts the side wall <NUM>. Thus, efficient energy absorption is enabled and the absorbable energy amount can be increased.

Claim 1:
A damping stopper (<NUM>) comprising:
an elastic body (<NUM>) formed into an annular shape, configured to be provided between two members (<NUM>, <NUM>) which are configured to be axially displaced relative to each other, and, when an interval between the two members decreases in a state where the elastic body is provided between the two members, configured to be axially compressed by the two members and expand radially outward; and
a metal attachment ring (<NUM>) presenting an L-shaped cross section and bonded to one axial end and the inner peripheral surface of the elastic body,
characterized by:
a resistance member (<NUM>) attached to an outer periphery of the elastic body in one axial region of the elastic body and suppressing expansion of the elastic body in the one region,
wherein
the elastic body is configured to, when the interval between the two members decreases in the state where the elastic body is provided between the two members, expand while receiving resistance by the resistance member to thereby contact a side wall provided in one member of the two members, and
the resistance member is a ring body having rigidity such that the resistance member does not contact the side wall when the elastic body expanding radially outward contacts the side wall,
the ring body being attached to a position where the elastic body is divided into a portion (<NUM>) having a long axial length (L<NUM>) and a portion (<NUM>) having a short axial length (L<NUM>).