JP2512377Y2 - Breaking mechanism of rotating body - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake mechanism for a rotating body which reliably brakes a motor for driving a load mechanism section or a rotating body connected to a rotating shaft of the load mechanism section.

[0002]

2. Description of the Related Art Although various mechanisms are adopted as a brake mechanism for braking a motor for driving a load mechanism section or a rotating body connected to a rotating shaft of the load mechanism section, a rotating body used for an electronic device or the like is braked. A simple structure is often used in the brake mechanism.

As a brake mechanism for braking the rotating body, for example, a well-known block brake mechanism 100 as shown in FIG. 5 or a well-known band brake mechanism not shown is adopted.

In the block brake mechanism 100, a brake lever 103 having a friction member 102 made of rubber or the like attached at one end 103a to an outer peripheral portion 101a of a brake wheel 101 connected to a rotation shaft of a motor (not shown) or a load mechanism portion (not shown). Is rotatably supported by the shaft 104. In addition, the other end portion 1 via the one end portion 103a and the shaft 104
Solenod 105 is connected to 03b and Solenod 1
Compression spring 106 fitted in the pole 105a of No. 05
Thus, one end 103a side of the brake lever 103 can come into contact with the outer peripheral portion 101a of the brake wheel 101. With the above configuration, the block brake mechanism 1
00 is a structure capable of braking the rotation of the brake wheel 101. The brake of the brake wheel 101 may be released by suctioning the solenoid 105.

[0005]

The block brake mechanism 100 shown in FIG. 5 has a simple structure for stopping the rotation of the brake wheel 101, but when the inertia force of the load mechanism is small. Good braking can be obtained, but there is a problem that the rotation of the brake wheel 101 cannot be stopped easily when the inertial force of the load mechanism is large.

Further, in a band brake mechanism (not shown), it is difficult for the friction member adhered to a steel band or the like to evenly contact the rotating body, resulting in one-sided contact, which makes braking of the rotating body less likely and wear of the friction member. There is a problem that it is not uniform.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a brake wheel connected to a motor for driving a load mechanism or a rotating shaft of the load mechanism, and an outer periphery of the brake wheel. First and second brakes that are provided so as to face each other and have one end that contacts and separates from the outer peripheral portion of the brake wheel and the other end that is connected to this one end via a shaft. A lever, a solenoid having a pole that moves linearly during a suction operation or a non-suction operation, a connecting member whose one end is rotatably connected to the tip of the pole of the solenoid, and a connecting member connected to the other end of the connecting member. An abutting member movably connected to each other, the abutting member having substantially tapered first and second abutting portions with which the other end portions of the first and second brake levers abut and face each other. And the second brake The other end portion of the bar of the contact member 1
And a spring for urging the connecting member and the abutting member in a balanced manner to urge the abutting member to abut the second abutting portion. When the pole is sucked or non-sucked,
By the movement of the pawl, the connecting member and the abutting member move in the moving direction of the pawl while rotating, and the first and second abutting portions of the abutting member abut. And one end of the first and second brake levers is brought into contact with and separated from an outer peripheral portion of the brake wheel in accordance with a contact state of the other end of the second brake lever. It provides a body braking mechanism.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a brake mechanism for a rotating body according to the present invention will be described below with reference to FIGS.
> And << 2nd Example >> in order.

<< First Embodiment >> FIG. 1 is an overall perspective view showing a load mechanism section adopting a brake mechanism for a rotating body according to a first embodiment of the present invention, and FIG. 2 is related to the present invention. It is the perspective view which expanded and showed the brake mechanism of the rotary body of 1st Example. Furthermore, as shown in FIG.
FIG. 6B is a diagram for explaining the operation of the brake mechanism for the rotating body of the first embodiment according to the present invention.

In the brake mechanism of the rotating body of the first embodiment, a pair of brake levers arranged to face each other when the solenoid is attracted (when energized) is brought into contact with the brake wheel serving as a rotating body to rotate the brake wheel. It is configured to reliably brake.

Referring to FIG. 1, a load mechanism section 1 employing a brake mechanism for a rotating body according to a first embodiment of the present invention comprises a load mechanism section 1 and a motor 2 serving as a drive source for the load mechanism section 1.
And a brake mechanism section 20 for braking the rotation of the motor 2.
It is roughly composed of and.

Here, the load mechanism unit 1 will be briefly described before describing the brake mechanism unit 20 which is the main part of the present invention. That is, in the configuration of the load mechanism section 1, the worm 3 fixed to the shaft 2a of the motor 2 is replaced by the worm wheel 4
Further, the worm wheel 4 is fixed to one end of the shaft 5, and the timing pulley 6 is fixed to the other end of the shaft 5, so that the worm wheel 4 and the timing pulley 6 connect the shaft 5 to each other. It is possible to rotate integrally via the. A timing belt 8 is provided between the timing pulley 7 and the timing pulley 6 arranged below.
And the timing belt 8 is connected to the connecting portion 9a of the transport base 9. Further, a long shaft 10 vertically installed is fitted to the sliding portion 9b of the transport base 9. Further, another guide member for guiding the transport base 9 along the shaft 10 is provided at the right end of the transport base 9, but the illustration thereof is omitted. The operation of the load mechanism unit 1 is such that when the motor 2 is rotated, the transport base 9 passes through the constituent members 3 to 8 along the shaft 10 in the vertical direction (arrows A ₁ , A).
It is movable in ₂ directions).

Next, the brake mechanism 2 which is the main part of the present invention
The configuration of 0 will be described with reference to FIGS. 1 and 2.

In the construction of the brake mechanism portion 20 of the present invention, a brake wheel (rotating body) 21 which is a part of the constituent members of the brake mechanism portion 20 is connected to the shaft 3a of the worm 3 on the side opposite to the motor 2. Has been done. The outer peripheral portion 21a of the brake wheel 21 is formed in the shape of an uneven knurl or a spur gear.

FIG. 2 is an enlarged view of the components of the brake mechanism section 20 shown in FIG. 1. In FIG. 2, the outside of the outer peripheral portion 21a of the brake wheel 21 faces each other. And second formed substantially symmetrically
Brake levers 22 and 23 (hereinafter, brake lever 2
2 and 23) are supported so as to be independently rotatable about axes 24 and 25. The brake levers 22 and 23 are formed in a substantially symmetrical "dogleg" shape, and one end 22 of the brake levers 22 and 23 is formed.
a and 23a can be brought into contact with and separated from the outer peripheral portion 21a of the brake wheel 21, and the other ends 22b and 23b, which are connected to the one ends 22a and 23a through the shafts 24 and 25, have their tips rounded to be described later. The first substantially tapered shape of the contact member 29
The second contact portions 29a, 29b or the contact portions 27a, 27b of the connecting member 27 can be brought into contact with each other.

Further, the outer peripheral portion 21 of the brake wheel 21
Outside of a, the brake lever 22 and the brake lever 23
A solenoid 26 is provided centering on a dividing line L that divides the distance between and. This is the solenoid 26 iron pole 26a is fitted freely linearly move substantially along arrow B _1, B ₂ direction dividing line L, moreover the tip portion of the pole 26a is opposed to the outer peripheral portion 21a of the brake wheel 21 ing. When the solenoid 26 is arranged in this manner, the tip of the pole 26a of the solenoid 26 is located at the brake lever 22.
Is located near the other end 22b of the brake lever 23 and the other end 23b of the brake lever 23. The moving direction of the pole 26a of the solenoid 26 is linearly moved in the horizontal direction here, but the present invention is not limited to this, and it is also possible to dispose so as to be linearly moved in an appropriate direction. Depending on the position of the solenoid 26, the brake lever 2
It goes without saying that the positions where the Nos. 2 and 23 are arranged are also determined.

Further, one end of a connecting member 27 having linear contact portions 27a and 27b is rotatably connected to the tip of the pole 26a of the solenoid 26 via a pin 28. The linear contact portions 27a and 27b are divided by the dividing line L.
Is formed in a substantially symmetrical shape with respect to the contact portion 2
The width between 7a and the contact portion 27b is formed to have a narrow width dimension H ₁ . Therefore, the connecting member 27 is formed of a plate material or a round bar material satisfying the above conditions.

An abutting member 29 having first and second abutting portions 29a and 29b, which are substantially tapered, is provided on the other end of the connecting member 27, which is opposite to the one end, via a pin 30. Are rotatably connected. The contact portions 29a, 29
b is formed in a substantially symmetrical shape with respect to the dividing line L,
Further, the width between the contact portions 29a and 29b on the pin 30 side is formed to be substantially equal to the narrow width H ₁ of the connecting member 27, and the width between the contact portions 29a and 29b on the brake wheel 21 side is the pin 30.
It is formed in a nearly tapered shape that gradually increases from the side width,
At the end, it is formed with a wide width H ₂ . Therefore, the contact member 29 is formed of a plate material or a conical rod material that satisfies the above conditions.

The other end 22b of the brake lever 22
A single tension spring 31 is stretched between the side and the other end 23b side of the brake lever 23. This tension spring 31 is used for the other end 22 of the brake levers 22 and 23.
b and 23b are contact parts 29 of the contact member 29 which are substantially tapered
a, 29b or the contact portions 27a, 27b of the connecting member 27 are always urged. That is, the brake lever 22 moves the shaft 24 by the urging force of the tension spring 31.
Is urged clockwise around the
3 is biased counterclockwise about the shaft 25. Further, the urging force of the tension spring 31 urges the rotatable connecting member 27 and the rotatable contact member 29 so as to keep the balance of the rotatable movement. Further, the urging force of the tension spring 31 causes the solenoid 2 to move when the solenoid 26 is not attracting.
Action to draw the 6 poles 26a in the arrow _{B 2} direction to go. The other ends 22b and 23b of the brake levers 22 and 23 do not need to use the single tension spring 31.
It is also possible to provide separate springs for each of them, but it goes without saying that a single tension spring 31 can easily balance the biasing force, and the number of parts can be small.

The operation of the brake mechanism section 20 of the first embodiment constructed as above will be described with reference to FIGS. 3 (A) and 3 (B).

[0021] 3 (A) is a diagram showing the non-suction operation state of the solenoid 26, the solenoid 26 is Setsuden, and in a state in which the pawl 26a of the solenoid 26 is pulled out in the arrow B ₂ direction is there. Further, the brake wheel 21 is in a state of being rotated clockwise or counterclockwise by the motor 2 (FIG. 1). That is, in this state, the pawl 26a of the solenoid 26 is pulled out in the arrow _{B 2} direction, the connecting member 27 and the abutting member 29
Also moves in the direction of arrow B ₂ . The urging force of the tension spring 31 causes the brake lever 22 to rotate in the clockwise direction (arrow C ₁ direction) about the shaft 24, while the brake lever 23 rotates in the counterclockwise direction (arrow D ₂ direction) about the shaft 25. ), The other ends 22b and 23b of the brake levers 22 and 23 come into contact with the contact portions 27a and 27b of the narrow width H ₁ of the connecting member 27, and the brake levers 22 and 23 are rotated.
Is restricted from rotating further. On the other hand, the one ends 22a and 23a of the brake levers 22 and 23 are completely separated from the outer peripheral portion 21a of the brake wheel 21. As a result, the brake wheel 21 is rotatable. The contact portions 27a and 27b of the connecting member 27
Not necessarily the other end 22 of the brake levers 22 and 23.
It is not necessary to bring the b and 23b into contact with each other. For example, the rotation restriction of the brake levers 22 and 23 may be restricted by another stopper member (not shown), and the original function of the connecting member 27 is to make contact with the pole 26a of the solenoid 26. The purpose is to rotatably connect the contact member 29.

Next, when the motor 2 shown in FIG. 1 is turned off from the state shown in FIG. 3A, the brake wheel 21 still tries to continue rotating due to the inertial force of the load mechanism section 1 (FIG. 1). At this time, the solenoid 26 is energized and the pole 2
6a is suctioned in the direction of arrow B ₁ . This state is shown in FIG. 3B as a suction operation state of the solenoid 26. That is, the pole 26a of the solenoid 26 is indicated by the arrow B.
_When moving in _one direction, the connecting member 27 and the contact member 29 also move in the direction of arrow B ₁ accordingly. Then, the other ends 22b and 23b of the brake levers 22 and 23 are wide while coming into contact with the tapered contact portions 29a and 29b of the contact member 29 from the contact portions 27a and 27b having the narrow width H ₁ of the connecting member 27. The width H ₂ shifts. Along with this operation, the brake lever 22 moves the tension spring 31 around the shaft 24.
The brake lever 23 rotates counterclockwise (direction of arrow C ₂ ) against the urging force of the tension spring 31, and the brake lever 23 rotates clockwise about the shaft 25 (direction of arrow D ₁ ) against the urging force of the tension spring 31. Since the brake levers 22 and 23 are pivoted to one side, one end portions 22a and 23a of the brake levers 22 and 23 are attached to the outer peripheral portion 21
It abuts on a uniformly, without hitting one side, which will be described later. As a result, the rotation of the brake wheel 21 that continues to rotate due to the inertial force of the load mechanism unit 1 (FIG. 1) is stopped. At this time, as described above, the outer peripheral portion 2 of the brake wheel 21 is
The brake lever 2 has a concave and convex shape.
Brake wheel 2 and one end 22a, 23a of 2, 23
1 has a large friction coefficient in the abutting relationship with the outer peripheral portion 21a,
The brake wheel 21 can be stopped more reliably. It should be noted that one end 22a of the brake levers 22 and 23,
A friction member such as rubber may be attached to 23a.

The reason why the one ends 22a and 23a of the brake levers 22 and 23 can be evenly contacted with the outer peripheral portion 21a of the brake wheel 21 will now be described. As described above, the connecting member 27 is rotatably connected to the pole 26a of the solenoid 26, and the contact member 29 connected to the connecting member 27 is also rotatable. 2 degrees of freedom in the direction of movement
It becomes a link mechanism. By the suction operation of the solenoid 26 described above, for example, one end 22a of the brake lever 22 abuts on the outer peripheral portion 21a of the brake wheel 21, the rotation posture of the brake lever 22 is determined here, and the other end 22b is further determined. Also comes into contact with the tapered contact portion 29a of the contact member 29. On the other hand, one end 23 a of the brake lever 23 is attached to the outer peripheral portion 2 of the brake wheel 21.
The rotation posture of the brake lever 23 is also determined by abutting on 1a. At this time, the connecting member 27 is rotated so that the other end portion 23b of the brake lever 23 can come into contact with the tapered contact portion 29b of the contact member 29 by the urging force of the tension spring 31, and the contact member 29 also rotates. Further, the urging force of the tension spring 31 urges the connecting member 27 and the abutting member 29 to a proper position while keeping balance, and at the same time, the other ends 22b and 23b of the brake levers 22 and 23 are simultaneously.
Is in contact with the contact portions 29a and 29b of the contact member 29. In this way, the other end 2 of the brake levers 22 and 23
Even if 2b and 23b contact the contact portions 29a and 29b of the contact member 29, the one end portion 22 of the brake levers 22 and 23
The a and 23a can be evenly contacted with the outer peripheral portion 21a of the brake wheel 21 without hitting one side. As a result, the rotation of the brake wheel 21 can be surely stopped, and further, the motor 2 (FIG. 1) and the load mechanism unit 1 (FIG. 1) can be surely stopped, and the reliability of the brake mechanism unit 20 is significantly improved. You can get the benefits.

The brake mechanism section 20 of the first embodiment described in detail above can be attached to any rotating shaft in the load mechanism section 1 as shown in FIG. Obviously, it may be attached directly to 2a or any attachment method may be used. Further, the brake mechanism portion 20 of the first embodiment is configured to brake the rotation of the brake wheel 21 by the brake levers 22 and 23 when the solenoid 26 is attracted (when energized). The solenoid 26 is turned off, and the braking of the load mechanism unit 1 (FIG. 1) is maintained by the braking action when the worm 3 and the worm wheel 4 shown in FIG. 1 are engaged. Therefore, during braking, the braking action of the brake mechanism 20 of the first embodiment and the braking action of the worm 3 and the worm wheel 4 function simultaneously, which makes it more reliable when the inertia force of the load mechanism section 1 is large. Braking is performed.

<< Second Embodiment >> FIGS. 4A to 4C are configuration diagrams showing a brake mechanism for a rotating body according to a second embodiment of the present invention.

In the brake mechanism of the rotating body according to the second embodiment, a pair of brake levers arranged to face each other when the solenoid is not attracted (when the solenoid is turned off) is brought into contact with the brake wheel to reliably brake the rotation of the brake wheel. It is configured to do. Further, in the second embodiment, a part of the constituent members is modified without changing the technical idea that the rotating body brake mechanism 20 of the first embodiment can be uniformly abutted without being hit against one side. Explained. The same components as those of the first embodiment are designated by the same reference numerals, and the description of the same components will be omitted.

In the brake mechanism section 40 of the second embodiment shown in FIG. 4A, the structure of the pole 26b of the solenoid 26 is different from that of the brake mechanism 20 of the first embodiment, and the suction operation of the pole 26b is performed. The direction is completely opposite. That is, the pole 26b of the solenoid 26
Is always urged in the arrow E ₁ direction during the non-suction operation (when the power is turned off), and is drawn out in the arrow E ₂ direction during the suction operation (when the power is supplied). Then, in order to perform the non-suction operation and the suction operation of the solenoid 26 as described above, the rear end portion of the pole 26b of the solenoid 26 projects rearward,
A compression spring 41 is fitted into the rear end of the pole 26b, and an E washer 42 is fitted after the compression spring 41. Therefore, when the solenoid 26 is not attracted (when the solenoid is off), the pole 26b moves in the arrow E ₁ direction, so that the connecting member 27 and the contact member 29 also move in the arrow E ₁ direction. Then, the brake levers 22 and 23
The other end portions 22b and 23b of the brake lever 2 are always in contact with the wide width portions of the tapered contact portions 29a and 29b of the contact member 29, while the brake lever 2 is the same as that described in the first embodiment.
Brake wheel 2 is provided at one end 22a, 23a of 2, 23.
The outer peripheral portion 21a of No. 1 is always abutted uniformly without hitting. Further, when the solenoid 26 is sucked and the pole 26b is pulled out in the direction of the arrow E ₂ , the one end portions 22a and 23a of the brake levers 22 and 23 are separated from the outer peripheral portion 21a of the brake wheel 21 in the first embodiment. Since the operation is the same as that described above, the description thereof is omitted here. As a result, the effect of the brake mechanism unit 40 of the second embodiment is the same as that of the brake mechanism unit 20 of the first embodiment, and the solenoid 26 is energized even when the load mechanism 1 (FIG. 1) is not operating. It has the advantage of being able to reliably brake without

Next, in the brake mechanism portion 50 of the modified example of the second embodiment shown in FIG. 4B, the attaching direction of the contact member 51 is completely opposite to that of the brake mechanism portion 20 of the first embodiment. it is, compression spring 52 and E washer 53 as pole 26c of the solenoid 26 is always urged in the arrow F ₂ direction when the non-suction operation (during switching electricity) is fitted to the pole 26c. In addition, since the pole 26c moves in the arrow F ₂ direction when the solenoid 26 is not attracting (when the power is cut off), the connecting member 27 and the contact member 51 also move in the arrow F ₂ direction. The other ends 22b and 23b of the brake levers 22 and 23 are always in contact with the wide width portions of the tapered contact portions 51a and 51b of the contact member 51.
Therefore, like the brake mechanism section 40 of the second embodiment,
The one ends 22a and 23a of the brake levers 22 and 23 are always in uniform contact with the outer peripheral portion 21a of the brake wheel 21 without any one-sided contact. Furthermore, since the pole 26a moves in the direction of the arrow F ₁ during the suction operation (when energized) of the solenoid 26, the other ends 22 of the brake levers 22 and 23 are
b and 23b move while abutting in the narrow width direction of the first and second tapered abutting portions 51a and 51b of the abutting member 51, while the one ends 22a and 22a of the brake levers 22 and 23 move.
23a is separated from the outer peripheral portion 21a of the brake wheel 21. As a result, the effects of the brake mechanism 50 of the modified example of the second embodiment are similar to those of the brake mechanism unit 40 of the second embodiment, and there is an advantage that the commercially available solenoid 26 can be applied as it is. .

Further, in the brake mechanism portion 60 of the modified example of the second embodiment shown in FIG. 4C, the direction opposite to the urging direction of the brake levers 22 and 23 in the brake mechanism portion 50 of FIG. 4B. Is urged to. That is, the tension springs 61 and 62 are stretched around the other ends 22b and 23b of the brake levers 22 and 23 as shown in the drawing, and the brake lever 22 rotates counterclockwise about the shaft 24 when the solenoid 26 is not attracting. On the other hand, the brake lever 23 is biased to rotate clockwise about the shaft 25. Accordingly, the contact member 63 has first and second tapered contact portions 63a and 63b formed inside. The operation of the brake mechanism unit 60 will not be described in detail here.

As described above in detail, in the rotating body brake mechanism according to the present invention, the connecting member rotatably connected to the pole of the solenoid and the tapered contact member rotatably connected to the connecting member are provided. When the solenoid is attracted or not attracted, the other ends of the brake levers that face each other are brought into contact with the tapered abutment member, so that one end of the brake lever hits the outer periphery a of the brake wheel. Since it is configured so as to be able to abut uniformly without doing so, it is possible to configure an appropriate form without changing the basic configuration.

[0031]

According to the brake mechanism for a rotating body according to the present invention described in detail above, a connecting member rotatably connected to a solenoid pole and a tapered contact member rotatably connected to the connecting member. Is provided, and the other end of the brake lever facing each other is brought into contact with the tapered contact member during the suction operation or the non-suction operation of the solenoid, so that one end of the brake lever is attached to the outer peripheral portion a of the brake wheel. Since the contact can be made evenly without hitting, the brake wheel, the motor, and the load mechanism can be reliably stopped. This has the advantage that the reliability of the braking mechanism during braking is significantly improved, and for example, it becomes possible to reliably brake the load mechanism having a large inertial force.
The range of applications can be expanded.

[Brief description of drawings]

FIG. 1 is an overall perspective view showing a load mechanism section adopting a brake mechanism for a rotating body according to a first embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a brake mechanism for a rotating body according to a first embodiment of the present invention.

3A and 3B are views for explaining the operation of the brake mechanism of the rotating body of the first embodiment according to the present invention.

4A to 4C are configuration diagrams showing a brake mechanism for a rotating body according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a conventional brake mechanism for a rotating body.

[Explanation of symbols]

1 ... load mechanism part, 2 ... motor, 20 ... brake mechanism part,
21 ... Brake wheel (rotating body), 22 ... 1st brake lever, 22a ... One end part, 22b ... Other end part, 23 ...
Second brake lever, 23a ... One end, 23b ... Other end, 24 ... Shaft, 25 ... Shaft, 26 ... Solenoid, 26a,
26b, 26c ... Pole, 27 ... Connecting member, 29 ... Abutting member, 29a, 29b ... First and second abutting portions, 31 ...
Tensile springs, 40 ... Brake mechanism section, 50 ... Brake mechanism section, 51 ... Abutting member, 51a, 51b ... First and second abutment sections, 60 ... Brake mechanism section, 63 ... Abutting member, 63a, 63b ... 1st and 2nd contact part, L ... Dividing line.

Claims (1)

(57) [Scope of utility model registration request] 1. A brake wheel connected to a motor for driving a load mechanism or a rotating shaft of the load mechanism, and a brake wheel provided on the outer peripheral portion of the brake wheel so as to face each other, and contacted with and separated from the outer peripheral portion of the brake wheel. Solenoid having first and second brake levers that rotate with one end and one end that is connected to this one end via a shaft, and a pole that linearly moves during a suction operation or a non-suction operation When,
A connecting member whose one end is rotatably connected to the tip of the pole of the solenoid, and the other end of the connecting member is rotatably connected, and the other ends of the first and second brake levers are connected to each other. An abutting member having substantially tapered first and second abutting portions facing each other and abutting, and the other end portions of the first and second brake levers are connected to the first and second abutting members. And a spring for biasing the rotatable connecting member and the abutting member while keeping the balance in a balanced manner. When a suction operation or a non-suction operation is performed, the connecting member and the contact member move in the moving direction of the pole while rotating, and the first and second contact members of the contact member move. The first and second contact parts that contact the contact parts of the Depending on the contact state of the other end of Kireba, the first and second rotating body of the brake mechanism, one end portion of the brake lever, characterized in that it has toward and away from construction on the outer peripheral portion of the brake wheel.