JP2513213Y2 - Airframe opening / closing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a device body such as a copying machine, a printer, or a facsimile, and the device body is divided into upper and lower parts. Relates to an opening / closing device for an apparatus body which is opened and closed with one end as a fulcrum.

[Prior art and its problems]

The body of a copying machine, printer, facsimile, etc. is generally divided into upper and lower parts so that the upper body can be opened and closed with one end as a fulcrum with respect to the lower body.
Then, the upper body is opened and closed in accordance with maintenance and inspection of the equipment or operation of the equipment.

Conventionally, as a device having a function of opening and closing the upper body, there is, for example, one shown in FIG.

FIG. 5 shows an example of a printer as an image forming apparatus having an opening / closing function. The printer body 1 is divided into a lower body 2 and an upper body 3, and an upper body 3 is provided.
Is provided so as to be openable around the fulcrum shaft 4 at one end as shown by a two-dot chain line in the figure.

Therefore, operations such as maintenance of the internal structure for image formation and paper jam processing are facilitated by opening the upper machine body 3.

In the case of the printer body 1, most of the functional components are housed on the lower body 2 side, and the upper body 3 is accommodated.
An image forming head 5 is provided on the side of the image forming drum 6 on the lower machine body 2 side by closing the upper machine body 3 as shown by the solid line in the figure.
It is arranged so that it may face.

However, as shown in the above-mentioned conventional example, the opening angle of the upper body 3 is generally set to be smaller than 90 °, and the center of gravity of the upper body 3 when opened is set to a position for biasing the closing by its own weight. There is a risk.

Therefore, in the above-mentioned conventional example, in consideration of maintenance of, for example, a member mainly composed of the image forming drum 6 among the component members densely arranged on the lower machine body 2 side, the upper machine body 3 is opened. The operability was extremely poor due to lack of items.

When a rotary oil damper is used to open and close the upper body 3, the fulcrum shaft 4, which is the center of the opening and closing operation, is provided at the end of the printer body 1.
Therefore, there is a problem that it is difficult to perform maintenance such as paper jam treatment or toner (developer) replenishment.

On the other hand, by using the one-way mechanism of the rotary oil damper described above, the upper body 3 when opened is opened.
Can be opened smoothly, and good operability that the upper body 3 is slowly closed when closed is obtained.

However, when the rotary damper is applied to a conventional example having a fulcrum shaft 4 as shown in FIG. 5, for example, it is difficult to set the opening angle of the upper body 3 to be larger than 90 °. Therefore, in order to further increase the opening angle of the upper body 3 by using the rotary one-way damper, for example, a configuration as shown in FIG. 6 can be considered.

FIG. 6 shows an upper body 10 that can be opened and closed via a fulcrum shaft 9 on the lower body 8 of the same main body 7 as the printer shown in FIG. Aircraft
This is the case where the rotary damper 12 provided on the 10 side is engaged.

However, in such a configuration, the extending portion 13 for providing the rotary damper 12 is required on the side of the upper machine body 10, and the structure is complicated. Further, there has been a problem that the assembling property of the structure is poor as the structure becomes complicated, which is not preferable.

Further, the rotary oil damper resists the movement of the upper body 3 or the upper body 10 when it rotates counterclockwise in the drawing, and conversely when the upper body opens, that is, in the clockwise direction in the drawing. There is almost no resistance when rotating. At that point, in the state where the center of gravity of the upper body passes through the dead point just above the fulcrum shaft that pivotally supports the upper body and the lower body in the process of opening the upper body, and the upper body is opened to the fully opened state, The weight of the upper body acts as a force for urging the upper body in the opening direction. Therefore, as described above, since the rotary oil damper hardly resists the movement of the upper body in the opening direction, when the upper body is lifted vigorously, the stopper at the open position is added without any shock absorption. I will end up. Therefore, there is a problem that the stopper portion is easily broken.

On the contrary to the above, when the upper body is closed, the weight from the open position until the upper body reaches the dead point has to be increased, and the rotary oil damper acts on the rotary motion. There is a problem that the operation of closing the lid, that is, the operation of closing the upper body is extremely heavy because of giving resistance.

As described above, in the case of using the damper mechanism in the opening / closing device having the conventional shell type structure, there is a problem in both the case of opening and the case of closing.

[Purpose of device]

In view of the above-mentioned conventional problems, the present invention has a structure in which a rotary one-way damper for relaxing the closing speed is used in the upper body of the device body, and an arc centered on a fulcrum shaft meshes with the rotary gear of the one-way damper. The structure is simple and the operability of opening and closing is improved by comprising a gear part formed along the upper part and a rotating member that follows the opening and closing of the upper body and rotates around the fulcrum shaft. It is an object of the present invention to provide a device opening / closing device for a device body, which is excellent in cost reduction.

[Key points of device]

In order to achieve the above object, the present invention is a body opening / closing device in which a body is divided into an upper body and a lower body, and an upper body can be opened and closed with respect to a lower body by using one end as a fulcrum. With respect to the fulcrum, an arcuate gear portion formed outwardly or inwardly along the arc is engaged with the gear portion directly or via a transmission gear to interlock with the opening / closing operation of the upper body. One-way having a rotating gear that can move along the gear portion to revolve and can rotate and a rotation speed control unit that increases rotation resistance in a predetermined rotation direction corresponding to a closing operation of the upper body of the rotating gear. In a body opening / closing device including a damper mechanism, the second posture being rotatably provided around the fulcrum and rotating in a first posture with respect to the lower body and from the first posture in an opening direction of the upper body. Rotation that can take And a biasing member that biases the rotating member in the closing direction of the upper body to hold the rotating member in the first posture position, and the gear portion is provided on the rotating member. With the one-way damper mechanism is provided in the upper body, or the gear portion is provided in the upper body and the one-way damper mechanism is provided in the rotating member, in the upper body and the rotating member, When moments about the fulcrum due to the weight of the upper body are centered at a first opening angle of the upper body that balances in the opening direction and the closing direction of the upper body, they are engaged with each other, and In association with the opening operation of the upper body up to the second opening angle exceeding the opening angle of 1, the rotating member resists the urging force of the urging member to move from the first posture to the second posture direction. An engaging member that rotates During the closing operation of the upper body from the second opening angle to the first opening angle, the rotating member moves from the second posture to the first posture direction based on the urging force of the urging member. It is characterized in that the rotation speed control means is made inoperative by rotating the rotation gear to the non-rotation state.

〔Example〕

 Hereinafter, the present invention will be described with reference to illustrated embodiments.

<First Embodiment> FIG. 1 (a) shows a first embodiment of the present invention, and is a schematic side view of a device main body showing a state in which an upper body is opened from a first angular position to a maximum second angular position. FIG. 1 (b) is an explanatory view of the action of the center of gravity when the upper body is at the second angular position,
FIG. 2 (a) is a configuration diagram of the opening / closing device when the upper body is closed, and FIG. 2 (b) is the opening / closing device shown in FIG. 2 (a) in which the upper body is opened to the first angular position. FIG. 2 (c) is an operation explanatory view showing a state in which
It is an operation explanatory view showing the state opened to the angular position.

1 (a) to 2 (c), a device body 14 such as a printer is vertically divided into a lower body 15 and an upper body 16, and one lower end of the upper body 16 is a lower body 15. The frame 15a is rotatably supported via a fulcrum shaft 17 so that the upper body 16 can be opened to a first angular position (I) and a second angular position (II). The first angular position (II) indicates the state of the upper body 16 when the line Y passing through the fulcrum shaft 17 and the center of gravity G of the upper body 16 coincide with each other vertically above the lower body 15. , The above second
The angular position (II) shows a state in which it is wide open at 90 ° or more.

In FIG. 1B, the upper body 16 is pivotally supported on the lower body 15 by a fulcrum shaft 17. The upper body 16 is in the second angular position (II), in which the center of gravity G is at an angle θ with respect to the line Y and at a distance 1 from the fulcrum shaft 17. Assuming that the weight of the body 16 is w, the upper body 16 has a rotating ability of l · w · sin θ with respect to the fulcrum shaft 17.

In the above, a damper mounting frame 18 is fixedly located at the fulcrum shaft 17 portion on the upper body 16 side, and a rotary one-way oil damper (hereinafter referred to as one-way damper section) 19 and this one-way damper 18 are fixed to the frame 18. Damper part 19
The rotary gear 19a and the transmission gear 20 meshing with the rotary gear 19a are attached. The transmission gear 20 is a double gear consisting of a large-diameter gear 20a and a small-diameter gear 20b, and a rotary gear 19a of the one-way damper section 19
Is engaged with the large-diameter gear 20a.

The frame 18 is located near the fulcrum shaft 17 and further
The projecting portion 18a and the second projecting portion 18b are provided laterally (toward the front in the drawing), and the first projecting portion 18a abuts on a rotating member 21 described later when the upper body 16 is opened, and the second projecting portion 18b is formed. Is also a stopper on the lower fuselage 15 side when the upper fuselage 16 is opened.
Contact 15b.

The rotating member 21 can rotate about a fulcrum shaft 17, and a gear portion 21a formed along an arc centered on the fulcrum shaft 17.
Is integrally provided, and this gear portion 21a is the transmission gear 20.
It meshes with the small diameter gear 20b. Then, the rotating member 21
One end of the spring member 22 is hooked on the
21 is biased so as to be able to rotate counterclockwise in the figure. In the case of this embodiment, the spring member 22 is locked at its other end on the frame 15a side of the lower machine body 15 by using a spiral spring, and the spring member 22 is, for example, a torsion spring as a fulcrum shaft.
It may be provided via 17 so that the rotating member 21 can be biased in the same direction as described above.

Further, the rotating member 21 is provided with a stopper 21b at one end, and the stopper 15b is opposed to the stopper 15c.
The rotation member 21 is held in place by being received by. The stopper 15c is provided on the frame 15a side of the lower body 15.

The rotating member 21 is further formed with an arcuate slit 21c centered on the fulcrum shaft 17 at a position corresponding to the first protrusion 18a, and the slit 21c is formed by one end 21c ₁ and the other end 21c _2. The first protrusion 18a projects into the slit 21c.

Next, the operation will be described with reference to FIGS. 1 and 2A to 2C.

The switchgear configured as described above is in the state shown in FIG. 2 (a) when the body 16 is closed, and when the upper body 16 is manually opened in the direction of arrow a,
In the process in which the upper body 16 is opened to the first angular position (I), as shown in FIG. 2 (b), with respect to the rotating member 21 that is pulled in the counterclockwise direction by the spring member 22, The transmission gear 20 rotates while meshing with a gear portion 21a formed along an arc centered on the fulcrum shaft 17, and the rotation of the transmission gear 20 causes the rotation gear 19 of the one-way damper portion 19 to rotate.
a is rotated in the direction of arrow b shown.

In this case, since the one-way damper part 19 is configured to be free without a damper action when the rotary gear 19a rotates in the direction of arrow b, the upper body 16 is smooth until the first angular position (I) is reached. It can be opened to Also, the rotating member 21
Is not operating, the upper body 16 operates in the completely free state from the closed state to the first angular position (I).

On the other hand, when the machine body 16 reaches the first angular position (I), the first projecting portion 18a and the second projecting portion 18b provided on the upper machine body 16 side also move at the same time, and the first projecting portion 18a It moves in the slit 21c of the rotating member 21 and moves to the other end 21c _{2 of the} slit 21c.
Abut. Next, when the upper body 16 is further opened from the first angular position (I) toward the second angular position (II),
The first angular position (I) hereinafter are simultaneously rotated in the same direction against the urging of the rotating member 21 the spring member 22 by the contact between the first projecting portion 18a and the other end 21c _2.

Therefore, in this state, the transmission gear 20 and the rotary gear 19a stop rotating as the rotary member 21 rotates, and the second protrusion 18b on the upper machine body 16 side then stops on the lower machine body 15 side stopper 15b.
And the opening of the upper body 16 is stopped. This state becomes the state shown by the second angular position (II) and is shown in FIG. 2 (c).
The state shown in FIG. In this state, the spring member 22 is in the maximum tension state, and the upper body 16 is in the maximum open state when stopped at the second angular position (II).
It is set to 0 °. Therefore, the above-mentioned airframe 16 is the second
Opening to the angular position (II) means that the lower body
The operability of taking in and out of the process unit etc. on the 15 side and the maintenance will be good.

The second angular position (II) of the upper fuselage 16 to be opened
Can be set to an appropriate open position by selecting the contact position of the second protrusion 18b and the stopper 15b.

Further, when the upper body 16 is opened to the second angular position (II), the center of gravity G of the upper body 16 moves to the outside (right side in the drawing) of the fulcrum shaft 17, so that the angle in FIG. θ is the maximum, and therefore the rotation ability is also the maximum, but the spring member 22
Also, since the tension is also tense, the impact due to the collision of the stopper 15b and the second protrusion 18b is softened.

 Next, the closing of the upper body 16 will be described.

In this case, the upper body 16 remaining at the second angular position (II) is manually rotated slightly in the closing direction opposite to the above from the state as it is to pass the first angular position (I). When returned to the vicinity and the center of gravity G of the upper body 16 overlaps the line Y (Fig. 1 (b)) and reaches the dead point,
The stopper 21b contacts the stopper 15c. When the center of gravity G is slightly tilted in the closing direction from the dead point, this state becomes the second
In the same state as shown in FIG. 7B, the rotating member 21 returns to the old position by the elastic bias of the spring member 22, and the first protrusion 18a on the upper body 16 side passes through the slit 21c. Therefore, when the machine body 16 rotates in the closing direction by its own weight,
The transmission gear 20 meshing with the gear portion 21a of the rotating member 21 is rotated.

When the transmission gear 20 rotates, the rotation gear 19a of the one-way damper portion 19 rotates clockwise in the figure via the transmission gear 20, and the upper body 16 is automatically closed by the weight of the upper body 16. Then, the one-way damper part 19 in this case acts as a rotary oil damper only when it rotates in this direction, and the upper body 16 is buffered and closed.

In the above, the operator may pressurize the upper body 16 in the closing direction against the action of the one-way damper 19 in order to accelerate the closing of the upper body 16. Even in this case, the upper body 16 is kept buffered by the damper action. The upper body 16 after closing is maintained in a closed state by a lock mechanism (not shown), and when the lock mechanism is released along with the opening, the open end side of the upper body 16 is slightly moved by a spring mechanism (not shown). It is designed to be lifted.

In the above, in this embodiment, the gear portion 21 of the rotating member 21
The rotation is transmitted to the one-way damper section 19 via the transmission gear 20 between the a and the rotation gear 19a of the one-way damper section 19, but this is for adjusting the rotation amount of the one-way damper section 19. The gear 20 may be omitted and the rotary gear 19a of the one-way damper part 19 may be directly meshed with the gear part 21a of the rotary member 21.

Next, such a case will be described as a second embodiment of the present invention.

<Second Embodiment> FIGS. 3 (a) to (c) show a second embodiment of the present invention, and FIG. 3 (a) is a block diagram of an opening / closing device when the upper body is closed, FIG. 3 (b) is an operation explanatory view showing a state in which the upper body is opened to the first angular position in the switchgear shown in FIG. 3 (a), and FIG. It is an operation explanatory view showing the state opened to the 2 angle position.

The same members as those described in the first embodiment are designated by the same reference numerals, and the duplicated description will be omitted.

In FIGS. 3A to 3C, a gear member 24 having an arc-shaped internal gear portion 24a centered on the fulcrum shaft 17 is provided on a frame 18 provided on the upper body 16 with a screw 23.
The rotation member 25 is provided on the inner diameter side of the gear member 24 so as to be rotatable about the fulcrum shaft 17 as an axis. The rotary member 25 has an arcuate slit 25a centered on the fulcrum shaft 17, and the slit 25a.
One end 25a ₁ and the other end 25a ₂ of the slit are provided.
The first projection 18a provided on the frame 18 is engaged with the frame 25a.

Further, the rotating member 25 is biased counterclockwise in the figure by the elasticity of the spring member 22, and the rotating member 25 is in the biasing direction when a stopper 25b provided on the rotating member 25 abuts a facing stopper 15c. Is prevented from rotating.

A one-way damper part 26 by a rotary oil damper is further attached to the rotating member 25, and a rotary gear 26a of the one-way damper part 26 meshes with the internal gear part 24a. Then, the meshing of the both gears corresponds to the upper end of the internal gear portion 24a as shown in the figure when the upper body 16 is closed.

In the above, when the upper body 16 is rotated in the opening direction (the direction of arrow a) as shown in FIG. 3B, the internal gear portion that rotates together with the upper body 16 about the fulcrum shaft 17 is formed.
The one-way damper portion 26, which remains in a fixed position by being pulled by the spring member 22, is freed from the rotation of the rotary gear 26a by the 24a. Then, the first moving in the slit 25a
The protrusion 18a contacts the other end 25a _{2 of the} slit 25a when the upper body 16 is opened to the first angular position (I).

Therefore, when the upper body 16 moves open from the state shown in FIG. 3 (b) to the state shown in FIG. 3 (c) (the second angular position (II)), the first protrusion is accompanied by the opening movement of the upper body 16 Since the portion 18a simultaneously rotates the rotating member 25 in the same direction against the elasticity of the spring member 22, the rotating gear 26a moves non-rotatably with the internal gear portion 24a in this process. Then, the center of gravity of the upper machine body 16 moves to the right of the fulcrum shaft 17 in the drawing, and the second protrusion 18b contacts the stopper 15b, whereby the open state of the second angular position (II) is maintained.

 Next, the closing of the upper body 16 will be described.

In this case, when the upper body 16 is returned from the state shown in FIG. 3 (c) to the state shown in FIG. 3 (b) by tracing the state opposite to the case of the above open state, the upper body 16 is closed and rotated by its own weight. Aircraft 16 is first
If the angular position (I) is exceeded, the first protrusion 18a and the rotating member 25
And the stopper 25b comes into contact with the stopper 15c,
Rotation gear 26a of one-way damper unit 26 that stays in place
Is rotated counterclockwise in the drawing by the internal gear portion 24a.

Then, the one-way damper part is rotated by the rotation in the above direction.
26 generates a damper action, and automatically damps the closed rotation of the upper body 16.

The engagement between the first protrusion 18a and the rotating member 21 shown in the first embodiment, and the first protrusion 18 shown in the second embodiment.
The engagement between the a and the rotating member 25 has been described as the engagement relationship in which the first protrusion 18a abuts each member in the slit 21a or the slit 25a, but the above-mentioned engagement relationship is the slit 21a. Alternatively, the engagement may be performed without using 25a.

Further, if the one-way damper parts 19 and 26 that operate by opening and closing the upper machine body 16 are also configured to use the rotating members 21 and 25 that follow intermittent rotation by the opening and closing operation of the upper machine body 16, the rotating members 21, The shape of 25 is not limited to the shape shown.

FIG. 4 is a sectional view of the one-way damper section shown in the first and second embodiments. The above-mentioned one-way damper parts 19 and 26 have the same structure, and FIG. 4 explains the case of the first embodiment using a small diameter gear.

The one-way damper part 19 includes a cylindrical container body 27 and a lid 28.
Are fitted via O-rings 29, and mounting portions 27a are projectingly provided at three locations on the container body 27 so that they can be fixed to the supporting member (damper frame 18) with screws 30. .

The container body 27 has a fixed shaft-shaped boss 31 at the center of the inside, and the movable body 32 is rotatably supported by the boss 31. Silicon grease 33 is provided in the space between the movable body 32 and the container body 27. Is enclosed. A boss-shaped shaft portion 34 is also provided at the center of the movable body 32, and a rotary body 35 having a rotary shaft 35a is coaxially mounted on the shaft portion 34. The rotary gear 19a is press-fitted into 35a.

In the above, a pair of collars 36 and 37 are formed in the outer peripheral portions of the rotating body 35 and the movable body 32, which form the same surface.
Are attached to face each other, and the collars 36 and 37 are respectively integrated with the rotating body 35 and the movable body 32 by using a key (not shown). Further, the collars 36, 37 have the same outer peripheral surface, and the one-way spring 38 is fitted on the outer peripheral surfaces. And this one way spring 38
The rotational force is transmitted to the movable body 32 depending on the winding direction of the rotating body 35, and so-called coupling and disconnection of the rotating body 35 and the movable body 32 are performed.

Therefore, the rotation of the rotating body 35 is free at the time of release, but the movable body 32 is rotated together with the rotating body 35 at the time of connection, and the grease when the relative movement between the movable body 32 and the container body 27 is performed.
The damper function works by viscous resistance of 33.

Therefore, the damper function works when the rotating body 35 rotates clockwise in the first embodiment and when the rotating body 35 rotates counterclockwise in the second embodiment.

In both the first and second embodiments of the present invention described above, the center of gravity of the upper body can be greatly opened beyond the dead point during the opening operation. Since the inertia of the upper mechanism is absorbed by the spring member and absorbs the shock applied to the restraining member such as the stopper, the center of gravity of the upper body should be close to the dead point in consideration of the installation location of the device body. It can also be applied to a device body having a small opening angle.

[Effect of device]

As described above in detail, according to the present invention, in the opening and closing using the rotary one-way damper, the fulcrum shaft is provided at the end of the upper body that divides and opens the body of the body. By configuring the one-way damper part to rotate via the rotating member that follows the opening / closing operation, the opening angle of the upper fuselage can be easily obtained to 90 ° or more with a simple structure. , Maintenance such as replacement of consumables and parts for the lower machine can be performed safely without danger.

Further, according to the present invention, the spring member for biasing the operation habit to the upper body via the rotating member acts in the closing direction only on the latter half during the opening operation stroke of the upper body, and in the fully opened state. Since it has the strongest action, it is possible to reduce the impact on members such as stoppers that prevent the upper body from opening when fully opened. Therefore, when the upper body is opened, members such as the stopper can be prevented from being damaged by the impact of the opening operation of the upper body.

Further, according to the present invention, during the closing operation process of the upper body,
In the first half, that is, when the center of gravity is in a position where it acts to open more than the dead point, the one-way damper does not act at all and only the spring habit due to the biasing of the spring member acts in the direction to close the upper body, so it is extremely operation Is light and the one-way damper starts to operate when the center of gravity of the upper fuselage exceeds the dead point due to the closing operation, and the closing operation due to the own weight of the upper fuselage is performed gently. When the operation is performed, the operation can be performed extremely lightly and smoothly.

[Brief description of drawings]

FIG. 1 (a) shows a first embodiment of the present invention, and is a schematic side view of a device body showing a state in which an upper body is opened from a first angular position to a maximum second angular position, FIG. b) is an explanatory view of the action of the center of gravity when the upper body is at the second angular position; FIG. 2 (a) is a configuration diagram of the opening / closing device when the upper body is closed in the first embodiment; 2B is an operation explanatory view showing a state in which the upper body is opened to the first angular position in the switchgear shown in FIG. 2A, and FIG. 2C is the same upper body as the second body. FIG. 3 (a) is an operation explanatory view showing a state of being opened to an angular position, FIG. 3 (a) shows a second embodiment, a configuration diagram of the opening / closing device when the upper body is closed, and FIG. 3 (b). An operation explanatory view showing a state in which the upper body is opened to the first angular position in the switchgear shown in FIG. 3 (a), and FIG. 3 (c). Is an operation explanatory view showing a state in which the upper machine body is opened to the second angular position, FIG. 4 is a sectional view of the rotary one-way oil damper part shown in the embodiment of the present invention, and FIG. FIG. 6 is a schematic side view showing a conventional example of a printer having an opening / closing function, and FIG. 6 is a schematic side view showing a conventional example of an opening / closing device. 14 …… Main body, 15 …… Lower body, 15a …… Frame, 1
5b …… Stopper, 15c …… Stopper, 16 …… Upper body, 1
7 …… fulcrum shaft, 18 …… frame, 18a …… first protrusion, 18
b …… Second protrusion, 19 …… One-way damper, 19a ……
Rotating gear, 20 …… Transmission gear, 20a …… Large diameter gear, 20b ……
Small diameter gear, 21 …… Rotating member, 21a …… Gear part, 21b …… Stopper, 22 …… Spring member, 23 …… Damper cover, 24 ……
Gear member, 24a ... Internal gear section, 25 ... Rotating member, 25a ... Slit, 25b ... Stopper, 26 ... One-way damper section, 26a ... Rotary gear, I ... First angular position, II ... … Second angular position.

Claims (1)

(57) [Scope of utility model registration request] 1. A body opening / closing device in which a body is divided into an upper body and a lower body, and an upper body can be opened and closed with respect to a lower body by using one end as a fulcrum, and the outer body extends outward along an arc centered on the fulcrum. Alternatively, an inwardly formed arc-shaped gear portion is engaged with the gear portion directly or via a transmission gear to allow the gear portion to revolve with respect to the fulcrum in conjunction with the opening / closing operation of the upper body. A body provided with a rotating gear movable along the axis of rotation and a one-way damper mechanism having a rotation speed control means for increasing rotation resistance in a predetermined rotation direction corresponding to the closing operation of the upper body of the rotating gear. In the opening / closing device, a rotating member that is rotatable about the fulcrum and that can take a first posture with respect to the lower body and a second posture that is rotated from the first posture in the opening direction of the upper body. And the rotating member An urging member for urging the rotating member in the closing direction of the upper body to hold it in the first posture position, the gear portion is provided on the rotating member, and the one-way damper mechanism is provided on the upper part. The one-way damper mechanism may be disposed on the upper body or the gear portion may be disposed on the upper body, and the one-way damper mechanism may be disposed on the rotating member, and the fulcrum of the upper body and the rotating member due to its own weight. A second moment which is engaged with each other at a time point when a moment centering on the first airframe is opened to a first opening angle of the upper airframe that is balanced in a direction of opening and a direction of closing the upper airframe, An engaging member for rotating the rotating member from the first posture to the second posture direction in opposition to the urging force of the urging member in conjunction with the opening operation of the upper body up to the opening angle. Providing the second opening angle To the first opening angle during the closing operation of the upper body, the rotating member rotates from the second posture to the first posture direction based on the urging force of the urging member to rotate the rotating gear. The machine body opening / closing device is characterized in that the rotation speed control means is made inoperative by the non-rotation of the machine.