JPH10272962A - Rotary shaft supporting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary shaft supporting structure that is able to install a rotary shaft simply by merely thrusting it into a bearing part along a guide groove part, and to surely support this rotary shaft receiving a load from the limited direction. SOLUTION: This rotary shaft supporting structure consists of a bracket 4 with a bearing part and a rocking lever 2 having two cylindrical parts 3a and 3b to be fitted in two bearing part 5a and 5b, and a thin wall part 6 is installed in a tip side of the cylindrical part on one side and a stepped part 3c is formed there, while the bracket 4 is made up so as to widen an interval between both sidewall parts 4a and 4b, and further two guide grooves 7a and 7b slidingly guiding the thin wall part 6 and the cylindrical parts 3a, 3b, respectively are continuously formed in these bearing parts 5a and 5b, and then the thin wall part 6 and these cylindrical parts 3a and 3b are inserted into the guide grooves 7a and 7b, as making them be slidingly guided, and each of these cylindrical parts 2a and 3b is fitted in these bearing parts 5a and 5b as widening an interval between both sidewall parts 4a and 4b at the sides of the stepped part 3c of the cylindrical parts 3a and 3b and the rocking lever 2 which is ratably supported.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a route bus operated by a single person, for example, in order to prevent danger, in a state where an entrance door is open, an accelerator pedal is fixed, and even if the accelerator pedal is depressed, The present invention relates to a rotating shaft support structure such as a swing lever of an accelerator interlock device that prevents an accelerator pedal from being depressed.

[0002]

2. Description of the Related Art In a one-man route bus, etc., since the entrance is at the center or rear of the vehicle, it is difficult to confirm the open / closed state of the door. If the driver depresses the accelerator pedal to start the vehicle with the door closed incompletely, there is a risk that passengers may be in danger.

In order to prevent this danger, if the door is not completely closed, the accelerator pedal is mechanically fixed so that the accelerator pedal cannot be depressed even if depressed. Equipment is provided. This accelerator interlock device is used to prevent a taxi from starting when the door is not completely closed, and to prevent various work vehicles from starting during work. Instead, a similar locking device is used for the clutch pedal.

[0004] Various modifications have been made to the accelerator pedal lock device. One of them is a structure of an accelerator pedal lock device developed by the present inventors, as shown in FIG.
As shown in FIG. 13 and 14 are views of the accelerator pedal 1 as viewed from the side. The lock lever 24 has a rotation shaft 24c fitted to a bracket 22 provided in front of the accelerator pedal 1.
And a roller 25 is provided at one end. A shaft 26a of an air cylinder 26 is in contact with the other end of the lock lever 24. The air cylinder 26 is connected to an air tank 29 via an electromagnetic valve 27 which opens and closes in synchronization with a door open / close switch. Connected.

According to the accelerator pedal lock device,
When the door is closed, the solenoid valve 27 releases the compressed air of the air cylinder 26 into the atmosphere as shown in FIG. 13, so that the shaft 26a of the air cylinder 26 is retracted by the internal return spring. State. When the shaft 26a is retracted, the lock lever 24 is also locked.
13 is returned by an unillustrated helix-shaped return spring or the like attached around a rotating shaft 24c that constantly biases the rotating shaft 24 downward, hits the stopper 23 or the floor 10 and returns to the unlocked position U shown in FIG. Therefore, the accelerator pedal 1 can be depressed, and normal operation with the accelerator pedal 1 becomes possible.

[0006] When the door is in the open state, FIG.
As shown in FIG. 4, the solenoid valve 27
Makes the air tank 29 and the air cylinder 26 communicate with each other, and the compressed air in the air tank 29 is
26, the shaft 26a of the air cylinder 26 is pushed out, and the end of the lock lever 24 is pushed down until it hits the stopper 23, and at the same time, the roller 25 on the opposite side is pushed up to make contact with the accelerator pedal 1. To lock.

At this time, even if the accelerator pedal 1 and the roller 25 come into contact with each other, a large operating force is used as the air cylinder 26 and the roller 25 provided at the tip of the lock lever 24 rotates. The lock lever 24 can be brought to a predetermined lock position. When the accelerator pedal 1 is depressed during this lock, the pushing force of the roller 25 at the tip of the lock lever 24, that is, the air cylinder 26
The depressing force of the shaft 26a opposes this depressing force, thereby preventing the accelerator pedal 1 from being depressed. At this time, only a substantially downward force acts on the rotating shaft 24c.

In this manner, by linking the operation of the solenoid valve 27 with the opening / closing switch of the door, during normal operation with the door closed, the accelerator pedal 1 is depressed with a predetermined stroke S as shown in FIG. When the door is opened and the interlock is effective, the accelerator pedal 1 can be fixed by the lock lever 24 as shown in FIG. 14 so that the accelerator pedal 1 cannot be depressed.

As shown in the enlarged view of FIGS. 9 (a) and 9 (b), the support portion of the rotation shaft 24c of the lock lever 24 is provided with a bolt 35 and a nut 37 on a bracket 35, and a spacer bush 38.
, The lock lever 24 having the lever bush 39 is fitted. The lock lever 24 includes an input lever 24 a pressed by an actuator 26 and an accelerator pedal 1.
And an output lever 24b for fixing the
When the input lever 24a is pressed, the lock lever 24 is
By rotating around 36, the output lever 24b is moved to a position where the accelerator pedal 1 is fixed, and the accelerator pedal 1 is locked.

[0010]

However, in these accelerator pedal lock devices, it is necessary to press the input lever 24a to move the output lever 24b of the lock lever 24 as shown in FIG. However, there is a problem that the structure for supporting the rotating shaft is complicated, even if the rotation can be performed.

For this reason, as shown in FIG. 10, a bracket 45 constituting a bearing portion is divided into a rotating shaft supporting structure for rotating the lock lever 24 by a rotation input of a motor or the like, so that the rotating shaft can be rotated in one direction. The bracket 45a is set on the bracket 45a, and then the other bracket 45b is mounted. As shown in FIG. 11, the rotating shaft 24c is inserted between the brackets 55, and then both ends are rotatably locked.
As shown in Fig. 2, a structure is adopted in which the output lever 24b is retrofitted with a screw 56 or the like. However, each of them has a complicated structure, and it is difficult to adjust the alignment of the shaft center. In addition, there is a problem that the cost is increased.

In Japanese Utility Model Laid-Open No. 6-60950,
A shaft part with an oval cross section is integrally formed, and a notch is provided from the bracket end to the bearing part that can fit the short diameter side of the shaft part into the bracket,
There has been proposed a synthetic resin pedal support structure for an automobile that can be easily assembled by inserting a shaft into a bearing portion from this notch.

However, in this structure, the contact surface between the rotating shaft portion and the bearing portion on the bracket side is small because the rotating shaft is not oval and not perfectly circular, so that the contact surface during rotation is small. And the rotation of the accelerator pedal cannot be performed smoothly. In addition, when the accelerator pedal is supported by a small contact surface when supporting the depressing force of the accelerator pedal, there is a problem that failure or breakage easily occurs.

In addition, if a force is applied in the direction opposite to the direction of insertion of the rotating shaft, there is a problem that the rotating shaft can easily fall off even with a small force, and there is a surface lacking in reliability. An object of the present invention is to provide a rotating shaft support structure that can be easily mounted simply by pushing a rotating shaft into a bearing along a guide groove, and that can reliably support a rotating shaft that receives a load from a limited direction. It is in.

[0015]

According to the present invention, there is provided a rotating shaft support structure comprising: a bracket having first and second bearing portions opposed to first and second side wall portions facing each other;
A swinging lever having first and second cylindrical portions on both sides inserted and supported by the bearing portion, and a step portion is formed at a tip end side of the first cylindrical portion by a thin portion thinner than the diameter of the cylindrical portion. ,
The bracket is formed so as to elastically expand between the distal end sides of the side wall portions. The first side wall portion has a first guide groove portion for inserting and guiding the thin portion, and the terminal portion has the first guide groove portion. Forming the first bearing portion into which one cylindrical portion is fitted;
The side wall portion is formed with a second guide groove portion for guiding the insertion of the second columnar portion, and the second bearing portion for fitting the second columnar portion at the end. Is a side portion of the swing lever and a step portion of the first cylindrical portion,
The space between the insertion sides of the side wall portions is elastically expanded, and the first
When the cylindrical portion is fitted into the first bearing portion, the space between the side wall portions is restored, and the swing lever is pivotally supported.

Alternatively, the bracket includes a bracket provided with bearing portions opposed to the side wall portions facing each other, and a swing lever having a cylindrical portion on both sides fitted and pivotally supported by the bearing portion. A step portion is formed by a thin portion thinner than the diameter of the column, and the bracket is formed so as to elastically expand between the distal end sides of the side wall portions,
The side wall portion is formed with a guide groove portion for guiding the insertion of the thin portion, and the bearing portion for fitting the cylindrical portion at the end,
At the time of inserting and assembling the swing lever, at the end surface of the step portion of the cylindrical portion inserted into the guide portion, the space between the insertion sides of the side wall portions is elastically expanded, and the cylindrical portion is When fitted into the bearing portion, the space between the side walls is restored,
The swing lever is configured to pivot.

Further, at least one of the swing lever and the bracket is provided with a pressing portion for pressing the other abutting portion to resiliently expand the space between the side wall portions, so that it can be used at the time of assembly. , Facilitating expansion between the side walls.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a rotating shaft support structure according to an embodiment of the present invention has first and second side walls 4a and 4b facing a bracket 4, respectively.
First and second cylindrical portions 3a and 3b, which are rotating shafts protruding from both sides of the swing lever 2, are pivotally supported by the first and second bearing portions 5a and 5b. I do.

Then, as shown in FIG.
A thin portion 6 having a thickness t smaller than the diameter d of the column is provided at the tip end of one of the first column portions 3a that pivotally supports the step portion 3c. The step portion 3c is formed by, for example, a thin portion 6 having a first cylindrical portion 3a of a rotating shaft extending therefrom, and a half of the extended cylindrical portion being cut off to form a half-moon cross section. Since the cross-sectional shape of the thin portion 6 may be a cross-sectional shape having a thickness smaller than that of the cylindrical portion, it may be a two-sided cut or a knob shape as shown in FIGS.

Since the notched surface 6a of the thin portion 6 can be used as a cam surface, a rotation input can be given by pressing the cam surface with an actuator (not shown). Further, a rotating shaft such as a motor can be engaged with the thin portion 6 to directly receive a rotation input. The swing lever 2 is, as shown in FIG.
A tapered pressing portion 2d is provided at a portion connecting the tip side surface 2c to the side surface 2b of the cylindrical portion 3b.
And the side surface 2b is configured such that the step amount e is substantially equal to the protrusion amount E of the cylindrical portion of the first cylindrical portion 3a.
The width A between the step 3c of the cylindrical portion 3a and the tip side surface 2c
Is formed substantially equal to the inner dimension C of the bracket side walls 4a, 4b shown in FIG. In addition, the width B between the side surfaces 2a and 2b is formed slightly smaller than the inner dimension C of the brackets 4a and 4b to facilitate the rotation of the swing lever 2.

As shown in FIG. 3, the bracket 4 includes first and second side walls 4a and 4b and a connecting portion 4 for supporting them.
The first and second side walls 4a, 4b are made of synthetic resin or the like so that the side on which the swing lever 2 is inserted on the opposite side to the bracket connecting portion 4c is elastically expanded and the tip side is opened. Molding. The thin portion 6 provided on the first cylindrical portion 3a
The first side wall portion 4 is inserted into the first bearing portion 5a to guide it.
the thickness t of the thin portion 6 from the end of the first bearing portion 5a to the first bearing portion 5a
A first guide groove 7a having a width T substantially the same as that of the first guide groove 7a is provided. Also,
With respect to the second cylindrical portion 3b on the opposite side, the bracket side wall portion 4
A second guide groove portion 7b having a width D substantially equal to the diameter d of the second cylindrical portion 5b extending from the end of the second bearing portion 5b to the second bearing portion 5b is provided.

When the bracket 4 is formed of a highly rigid metal or the like, at least one of the first and second side walls 4a and 4b is configured to be movable. This movable second side wall 4b
Is, for example, as illustrated in FIG.
And the second side wall portion 4b are rotatable about a rotation shaft 4e provided at an intersection thereof, and are returned by a return spring 9 connecting the side wall portions 4a and 4b, and are brought into a restored position by a stopper 4f. .

Alternatively, as illustrated in FIG. 8 (b), the second side wall 4b can be moved in parallel by engaging with the guide 4g, and the first and second side walls 4a, 4b are connected by the return spring 9. To apply the restoring force, and the first and second
A stopper 4f is provided so as to keep the interval between the side wall portions 4a and 4b at a regular interval between the bearing portions. Then, as shown in FIG. 1B, the first and second cylindrical portions 3a and 3b of the swing lever 2 are assembled with the first and second bracket side walls 4a and 4b.
The swing lever 2 is turned around the first and second cylindrical portions 3a and 3b so as to be parallel to the second bearing portions 5a and 5b, and provided on the first cylindrical portion 3a of the swing lever 2. The thin portion 6 is placed in a position where it can be inserted into the first guide groove 7a formed in the first side wall 4a.

Next, while maintaining this posture, FIG.
As shown in FIG. 5, the thin portion 6 is inserted into the first guide groove 7a, and the tip side surface 2c of the swing lever 2 is attached to the bracket side wall portion 4.
Push along the inner surface of b. At this time, the first cylindrical part 3
The width A between the step portion 3c and the front end side surface 2c is the side wall portion 4.
Since the inner dimension C substantially coincides with the inside dimension C of the first and second side walls 4a, the step 3c advances along the inner surface of the first side wall 4a.

Further, the second cylindrical portion 3b is connected to the second guide groove 7
4b, the tapered pressing portion 2d of the swing lever 2 comes into contact with the second side wall portion 4b, exerts a wedge effect, and as shown in FIG. 4B, the pressing portion 2d.
4A and 4B expands and pushes the gap between the first and second side walls 4a and 4b by the step amount e, and the side surface 2b of the swing lever 2 hits the inner side surface of the bracket side wall 4b, as shown in FIG. Become. Further, the space between the bracket side wall portions 4a and 4b is further expanded to reach the state shown in FIG. 4D, and the thin portion 6 and the first and second columnar portions 3a and 3b are substantially composed of the first and second bearing portions. 5a, 5
Proceed to just before position b. In this state, still the first,
The second side walls 4a and 4b are in an expanded state.

By further pushing the first and second cylindrical portions 3a,
3b to the first and second bearings 5a and 5b,
When fitted, the first and second side walls 4a and 4b return from the expanded elastically deformed state to the original state, and return to the state of FIG. 4E, that is, the state of FIG. The attachment ends.
At this time, the swing lever width B is equal to the first and second side wall portions 4a and 4b.
Since it is slightly smaller than the inner dimension C of the swing lever 2, the swing lever 2 can rotate smoothly while preventing the tilt of the swing lever 2.

In this state, the first and second bearing portions 5a, 5
Since the first and second columnar portions 3a and 3b having a cylindrical shape are fitted to the portion b, the column does not come off easily even if a force is applied from any direction. However, since the second guide groove 7b is provided on the side of the second bearing portion 5b, it is weak when a force in this direction is received, and the direction of the load received by the second cylindrical portion 3b is roughly as shown in FIG.
Is limited to the direction from the range of F shown to the first and second bearing portions 5a and 5b, but when the swing lever 2 is used as the lock lever 24, it is sufficient if the load within 180 degrees can be supported. And the first and second guide groove side 7a,
It is easy to set so as not to be pushed back to 7b.

In addition, since the bracket side walls 4a and 4b are integrally formed via the connecting portion 4c, the axial center of the cylindrical portions 3a and 3b, ie, the axis of the rotating shaft, does not deviate during mounting. Further, in the above description, the step portion 3c is replaced with the first cylindrical portion 3
a, but as shown in FIG. 7, a step 3c is provided on both the first and second cylindrical portions 3a and 3b, and the first and second bearing portions 5a having a contact surface of a semicircle or more are provided. , 5b.

In the structure shown in FIG. 7, instead of the tapered pressing portion 2d provided on the swinging lever 2, a tapered pressing portion 4d is provided on the bracket 4 side, and the first and second cylindrical portions are provided. When fitting 3a, 3b to the 1st, 2nd bearing parts 5a, 5b, it is made to expand and deform between the 1st, 2nd side wall parts 4a, 4b. The shape of these pressing parts 2d and 4d may be a convex cylindrical shape or a convex spherical shape.
Any shape can be used as long as the first and second side walls 4a and 4b can be expanded.

According to the above-described rotating shaft support structure, the first and second cylindrical portions 3a and 3b are connected to the first and second guide groove portions 7 respectively.
a, 7b and can be easily mounted simply by pushing them into the first and second bearing portions 5a, 5b, and the first and second cylindrical portions 3a, 3b, that is, the pivots can be easily pivoted without complicated adjustment. Can support. Further, since the thin portion 6 is provided on the tip end side of the first cylindrical portion 3a, the reciprocating motion of the air cylinder can be input by using the notched surface 6b of the thin portion 6 as a cam surface.
Further, since the rotational force can be directly transmitted to the thin portion 6, the swing lever 2 can be rotated by a rotational motion such as a step motor.

The step 3c is connected to one of the first cylindrical portions 3a.
In the case where the bracket is provided only on the side, the space between the first and second side walls 4a and 4b of the bracket may be expanded by the amount of the protrusion of one of the first columnar portions 3a, so that the mounting is facilitated. When the stepped portion 3c is provided on both the first and second columnar portions 3a and 3b as shown in FIG. 7, the first and second columnar portions 3a and 3b on both sides are resistant to forces from all directions. And can be supported so that it does not fall out,
The first and second cylindrical portions 3a and 3b, that is, the rotating shaft can be reliably supported.

In addition, at least one of the swing lever 2 or the first and second side walls 4a and 4b of the bracket 4
By forming pressing portions 2d, 4d that expand between the first and second side wall portions 4a, 4b by pressing the other contact portion, the first and second side wall portions 4a, 4a at the time of assembly are formed. 4b can be easily expanded.

[0033]

According to the rotary shaft support structure of the present invention described above, the swing lever can be easily mounted on the bracket simply by inserting the rotary shaft portion into the guide groove and pushing it into the bearing portion, which is troublesome. The rotating shaft can be reliably pivoted without adjusting the axis. In addition, since it has a simple structure, it can be manufactured at low cost, and since it is easy to mount, the timing of assembling can be freely selected and the process can be simplified.

If the notched surface of the thin portion of the rotating shaft portion is used as a cam surface, reciprocating motion by an air cylinder or the like can be input. Therefore, various driving sources can be used as inputs. In addition, by forming at least one of the side wall portions of the swing lever or the bracket with a pressing portion that elastically expands between the side wall portions by pressing the other abutting portion that abuts on the swing lever or the bracket. In addition, the opening between the side wall portions at the time of assembling can be facilitated, and the structure can be easily assembled.

[Brief description of the drawings]

FIG. 1 is a rotary shaft supporting structure according to a first embodiment of the present invention, in which (a) is a perspective view after assembly and (b) is a perspective view before assembly.

FIGS. 2A and 2B are structural views of a swing lever according to the first embodiment of the present invention, wherein FIG. 2A is a plan view, FIG. 2B is a side view, and FIG. FIG.

FIGS. 3A and 3B are structural views of a bracket according to the first embodiment of the present invention, wherein FIG. 3A is a plan view, FIG. 3B is a side view, and FIG. It is.

FIG. 4 is a plan view showing the assembly of the rotating shaft support structure of the present invention, and the assembly proceeds in the order of (a), (b), (c), (d) and (e).

FIG. 5 is a partial perspective view of a rocking lever showing a thin-walled portion having two faces cut.

FIG. 6 is a partial perspective view of a swing lever showing a thin portion having a knob shape.

FIG. 7 is a perspective view of a rotary shaft supporting structure according to a second embodiment of the present invention before being assembled.

FIGS. 8A and 8B are perspective views of a bracket having a movable side wall, wherein FIG. 8A shows a rotatable bracket and FIG. 8B shows a parallel movable bracket.

FIG. 9 is a structural diagram of a rotary shaft support structure of the prior art;
(A) is sectional drawing which shows the support structure of a rotating shaft, (b)
Is a ZZ sectional view.

FIG. 10 is a cross-sectional view of another prior art rotating shaft support structure.

FIG. 11 is a cross-sectional view of another prior art rotating shaft support structure.

FIG. 12 is a cross-sectional view of another prior art rotating shaft support structure.

FIG. 13 is a side view of a prior art accelerator pedal lock device at the time of unlocking.

FIG. 14 is a side view of a prior art accelerator pedal lock device when locked.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Accelerator pedal 2 ... Swing rocking lever 2a, 2b ... Side surface 2c ... Tip side surface 2d, 4d ... Press part 3a, 3b ... Cylindrical part (rotating shaft) 3c ... End surface 4 ... Bracket 4a, 4b ...
Side wall portion 4c Connecting portion 5a, 5b Bearing portion 6 Thin portion 7a, 7b Guide groove portion

Continuing from the front page (72) Inventor Akio Saito 3-25-1, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Kawasaki Plant of Isuzu Motor Co., Ltd. (72) Inventor Masanobu Morino 3- 25-1, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture No. Isuzu Motors Corporation Kawasaki Plant (72) Inventor Toru Okubo 3-25-1, Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Isuzu Motors Corporation Kawasaki Plant (72) Inventor Shuji Wakisaka 8 Fujisawa City, Fujisawa City, Kanagawa Prefecture Isuzu Motors Co., Ltd. Fujisawa Plant (72) Inventor Tsuguo Fujita 8th floor of Tsurana, Fujisawa City, Kanagawa Prefecture Isuzu Motors Co., Ltd. Fujisawa Plant (72) Inventor Michiyo Tokumoto 3-25-1, Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Isuzu Motors Corporation Kawasaki Plant (72) Inventor Kazuyuki Kuroda 3-25-1, Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Isuzu Motors Corporation Kawasaki Plant (72) Inventor Takehisa Iwamoto Kamizayabe, Totsuka-ku, Yokohama, Kanagawa Prefecture Town character Fujii 320 Hashimoto Forming Industry Co., Ltd.

Claims (3)

[Claims] 1. A bracket provided with first and second bearing portions facing first and second side wall portions facing each other, and first and second brackets fitted and pivotally supported by the first and second bearing portions. A swing lever having a cylindrical portion on both sides, a stepped portion formed by a thin portion thinner than the diameter of the cylinder at the distal end of the first cylindrical portion, and the bracket is provided at the distal end of the both side walls. The first side wall portion is formed with a first guide groove portion for inserting and guiding the thin portion, and the first bearing portion for fitting the first columnar portion at the end is formed on the first side wall portion. Forming
The second side wall portion is formed with a second guide groove for inserting and guiding the second columnar portion, and the second bearing portion for fitting the second columnar portion at a terminal end. In this case, the side portion of the swing lever and the step portion of the first cylindrical portion elastically expand between the insertion sides of the both side wall portions,
A rotating shaft support structure for pivotally supporting the swing lever when the first cylindrical portion is fitted into the first bearing portion, with the two side walls being in a restored state. 2. A bracket provided with bearings opposed to side walls facing each other, and a swinging lever having a cylindrical portion on both sides fitted and supported by the bearing, the tip of the cylindrical portion. A step portion is formed by a thin portion thinner than the diameter of the cylinder, the bracket is formed so as to elastically expand between the tip sides of the side wall portions, and the thin wall portion is formed on the side wall portion. A guide groove portion for guiding the insertion, and a bearing portion for fitting the cylindrical portion at the end, and an end face of a step portion of the cylindrical portion inserted into the guide portion when the swing lever is inserted and assembled. Then, the space between the insertion sides of the side wall portions is elastically expanded, and when the column portion is fitted into the bearing portion, the space between the both side wall portions is restored, and the swing lever is pivotally supported. Rotating shaft support structure. 3. A pressing portion formed on at least one of the swing lever and the bracket to resiliently expand the space between the side walls by pressing the other contact portion. Rotary shaft support structure.