JP3011701B1 - Door closing device - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To control the speed at the time of closing a door, but do not have a structure to overcome the friction with a member to close the door, and to completely close the door by frictional force of the member. May not be possible. SOLUTION: A cam surface to which a tip roller 14 abuts is formed on a cam member 10 which rotates along with the rotation of an opening / closing shaft member 74, and the cam surface is formed on a circumferential side corresponding to an open state of a door 70. Since the formed arcuate surface 10a and the stepped surface 10b for releasing the elastic force of the third spring 33 are provided, when the door 70 is opened, the tip roller 14 contacts the arcuate surface 10a and the third spring 33 The elastic force does not increase, and the door 70 can be completely opened with a small force.
Is rotated to move the tip roller 14 from the arc surface 10a to the stepped surface 10b, whereby the elastic force of the third spring 33 is released, and the closing force is added to the elastic force of the first spring 22 and the second spring 31. Be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a door closing device for automatically closing an opened door by supporting a door of a building at a lower portion or the like, such as a floor hinge.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 13, a floor hinge 7 is used as an example of a door closing device used to be embedded in a floor surface 71 to support a lower portion of a door 70 of a building.
There are two.

The structure of the floor hinge 72 is shown in a sectional view of FIG. In the figure, one of the floor hinge bodies 73 embedded in the floor surface 71 has an upper part on the floor hinge body 7.
An opening and closing shaft member 74 protruding from the third and supporting the lower part of the door 70 is rotatably mounted, and a cam member 76 which rotates around a support shaft member 75 with the rotation of the opening and closing shaft member 74.
Is provided.

A partition 77 is provided on the other side of the floor hinge body 73.
Cylinder chambers 7 arranged side by side by being partitioned by
The cylinder device 83 having the pistons 8 and 79 is disposed in one cylinder chamber 78 of the cylinder device 83.
A rod 81 to which the rod 81 is attached is slidably inserted into the partition wall 82, and a protruding portion of the rod 81 from the partition wall 82 is connected to one side of the cam member 76, and the partition wall 82
In addition, a sliding rod member 84 which is inserted into the other cylinder chamber 79 so as to be able to freely move back and forth is arranged side by side with the rod 81. 76 is connected to the other side, and one cylinder chamber 7
8, a first spring 86 that urges the piston 80 in the direction in which the door 70 closes is provided inside, and the other cylinder chamber 79 urges the sliding rod member 84 in the direction in which the door 70 closes. A second spring 87 is provided.

A first valve hole 89 through which a hydraulic oil 88 passes is formed in the center of the piston 80. A spherical valve element 90 is provided in the first valve hole 89, and the partition wall 77 is provided.
Is formed with a second valve hole 91 for communicating the two cylinder chambers 78 and 79 with each other. In the second valve hole 91, a control valve 92 for adjusting the amount of hydraulic oil 88 passed is provided. ing.

According to this configuration, when the door 70 is opened, the opening / closing shaft member 74 rotates in the clockwise direction A1 in the drawing, and the cam member 76 rotates in the counterclockwise direction A2 in the drawing.
The rotation of the cam member 76 in the direction A2 causes the piston 80 to be pulled in the arrow direction B1 in the drawing against the elasticity of the first spring 86, and the rotation of the cam member 76 causes the pressing member 85 to rotate. As a result, the sliding rod member 84 is pushed in the arrow direction C1 in the drawing against the elasticity of the second spring 87.

At this time, the hydraulic oil 88 in the cylinder chamber 78
When the valve element 90 opens the first valve hole 89, the rod 81 passes through the first valve hole 89 from the rod 81 side, and the arrow D in the drawing
As shown in FIG.

When the door 70 is closed, the piston 8 is closed.
0 is returned in the arrow direction B2 in the figure by the elastic force of the first spring 86, and the sliding rod member 84 is returned in the arrow direction C2 in the figure by the elastic force of the second spring 87.
From the piston 80 side of one cylinder chamber 78, the control valve 9
While passing through the second valve hole 91 in the direction indicated by the arrow D2 in FIG.

The flow rate of the hydraulic oil 88 is adjusted by the adjusting valve 92, so that the closing speed of the door 70 is adjusted.

[0010]

In recent years, in order to secure airtightness and sound insulation, another member (airtight) is applied to the edge of the opening 70A of the wall, and when the door 70 is closed, this member and the door are closed. In some cases, a structure is used in which the outer peripheral portion 70 is in close contact with the outer peripheral portion.

However, in the case of the above-mentioned conventional floor hinge 72, although the speed at which the door 70 closes can be adjusted, it does not have a structure that overcomes the friction with the member and closes the door 70. When the member is provided, the door 70 may not be able to be completely closed due to the frictional force. In order to overcome the friction with the member and close the door 70, it is necessary to set the strength of the first spring 86 or the second spring 87 to be strong. However, if the strength of the first spring 86 or the second spring 87 is set strong, a large force is required when opening the door 70.

The relationship between the door opening / closing force: F and the door opening / closing angle: ° in such a floor hinge 72 is as shown by a graph shown by a dashed line in FIG. From this graph, it can be seen that the door 70 that has begun to open by the force of P1 is closed by the force of P2 due to the friction of the components inside the floor hinge.

Therefore, an object of the present invention is to provide a door closing device that can solve the above-mentioned problems.

[0014]

An object of the present invention is to provide an opening / closing shaft member serving as an opening / closing center of a door that opens / closes with respect to an opening provided in a building, and a pivoting operation of the opening / closing shaft member. A rotating member that rotates about one support shaft, a piston that moves in the hydraulic oil chamber with a rotating operation of the rotating member by opening and closing of the door, and a plurality of members for urging the piston in the closing direction of the door. A spring member, and a passage hole formed at a predetermined position of the piston and the hydraulic oil chamber and through which hydraulic oil for adjusting a closing force while resisting the elastic force of these spring members passes, wherein the door is provided. When the door is to be closed from the middle of the closing, a closing force increasing means for applying a larger closing force to the door than during the closing is provided. Together with the power that rotates around the first support shaft. A member having an abutting portion having a base end rotatably supported around a second support shaft and a distal end abutting on a cam surface of a cam member; A spring for biasing around a second support shaft in a direction in which the first support shaft is axially centered on the cam surface on a circumferential side corresponding to an open state of the door. A surface is formed, and a stepped surface is formed on the circumferential side corresponding to the closed state of the door of the cam surface, the step surface being formed continuously with the arc surface to release the elastic force of the boosting spring.

According to the above configuration, when the door is to be closed with respect to the opening, the contact portion of the arm member shifts from the circular arc surface formed on the circumferential side corresponding to the closed state of the door. Since the elastic force of the boosting spring is released, the closing force of the door is increased, and the door is securely closed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A door closing device according to an embodiment of the present invention will be described below with reference to a floor hinge 72 shown in FIGS. FIG. 13 is shared with the description of the conventional technique.

The floor hinge 7 according to the embodiment of the present invention
As shown in FIG. 13, reference numeral 2 is used to be embedded in a floor surface 71 to support a lower portion of a door 70 that opens and closes an opening 70A provided in a building.

As shown in FIG. 1, a floor hinge body 73 is provided.
The interior is partitioned by a partition wall 1 into a storage chamber 2 on one side and a cylinder chamber 3 on the other side.
The first hydraulic oil chamber 17 and the second hydraulic oil chamber 1 are formed by the first partition 15 and the second partition 16 formed on the sides a, 73b and 73c.
8 and a third hydraulic oil chamber 19 are formed.

A door 70 is mounted in the storage chamber 2, and an opening / closing shaft member 74 in the vertical axis direction, which is the center of opening and closing, is rotatably supported, and is disposed adjacent to the opening / closing shaft member 74 to open and close. Sector gear 5 meshing with gear portion 4 of shaft member 74
Is rotatably supported by the floor hinge body 73 via the first support shaft 6, and a cam member 10 described later is integrally formed on one side of the sector gear 5.
Are also rotatably supported by the floor hinge body 73 via the first support shaft 6.

On one side of the sector gear 5 on the partition wall 1 side,
A base roller is rotatably mounted around a pivot shaft 7b and a rotatable roller 7 is rotatably mounted on a distal end thereof via a pin 8a.
The first arm member 7 to which a is attached is arranged.

A contact roller 11, which moves from the corner of the first arm member 7 to the side surface and contacts the cam member 10, is rotatably mounted on a support shaft 11a.

A first sliding hole 1a, a second sliding hole 1b, and a third sliding hole 1c are formed in the partition wall 1 in parallel with each other. A first rod 20 in which a piston 21 that slides in the oil chamber 17 is rotatably mounted around a pin 8f is slidably fitted.
Is protruded into the storage chamber 2 from the first sliding hole 1a, and the pin 8e attached to the base end of the first rod 20 and the pin 8a on the sector gear 5 side are connected by a connecting member. 9. Between the partition wall 1 and the piston 21, the door 70 is closed in the closing direction (the direction in which the sectoral gear 5 pulls the first rod 20 so that the opening / closing shaft member 74 rotates clockwise A in the counterclockwise direction B). A biasing first spring 22 is interposed, and a floor hinge 73 is provided at the center of the piston 21.
A passage hole 24 is formed to allow the working oil 23 filled therein to pass from the first spring 22 side, that is, from the left chamber to the right chamber, and a spherical valve body 25 passes through the passage hole 24. It is fitted to the peripheral surface of the hole 24 so as to be detachable and seatable.

A reciprocating hole 36 for allowing the hydraulic oil 23 to pass between the first hydraulic oil chamber 17 and the cylinder chamber 3 is formed in the first partition 15 over substantially the same length as the first partition 15. At the end of the reciprocating hole 36, adjusting holes 37a and 37b for allowing the hydraulic oil 23 to pass between the first operating oil chamber 17 and the reciprocating hole 36 are formed, and the adjusting holes 37a and 37b are formed.
Hydraulic oil amount adjusting valves 38 and 39 are screwed vertically.

A second rod 29 is slidably fitted in the second sliding hole 1b, and a base end of the second rod 29 projects into the storage chamber 2 from the second sliding hole 1b. A spring seat member 28 is formed on the distal end side of the second rod 29 so as to be detachable and seatable on the partition wall 1. A door 70 is provided in the second hydraulic oil chamber 18 between the lid member 73 b and the spring seat member 28. A second spring 31 biasing in the closing direction is provided, and a base end of the second rod 29 is
The second spring 31 is pressed against the rotating roller 7a by the elastic force.

On the other side of the sector gear 5 on the partition wall 1 side,
A second arm member 26 having a base end rotatably mounted around the second support shaft 12 and a tip end roller 14 rotatably provided via a pin 13 at the other end is disposed.
In the middle of the second arm member 26, a pressed roller 27 is rotatably mounted on a pin 27a.

The third rod 30 is slidably fitted in the third sliding hole 1c, and the base end of the third rod 30 is brought into contact with the pressed roller 27, and A spring seat member 32 is formed on the front end side of the partition wall 1 so as to be detachable from the partition wall 1, and a door is provided via the second arm member 26 to the third hydraulic oil chamber 19 between the lid member 73 c and the spring seat member 32. A third spring (power boosting spring) 33 for urging the valve 70 in the closing direction;
The third rod 30 is pressed against the pressed roller 27 by the elastic force of the third spring 33.

The cam member 10 has a cam surface with which the tip roller 14 contacts, and is formed on the circumferential surface corresponding to the open state of the door 70 with the first support shaft 6 as the axis. An arcuate surface 10a and a stepped surface 10b formed on the circumferential side corresponding to the closed state of the door 70 and formed continuously with the arcuate surface 10a to release the elastic force of the third spring 33 are formed. The angle between the tangent of the step and the stepped surface 10b can be variously set depending on the case. In the case of the present embodiment, the stepped surface 10b closes the door 70 as shown in FIG. In the state, the first rod 20, the second rod 29, and the third rod 30 are continuous with the arc surface 10 a so as to be in a plane perpendicular to the left-right directions C and D (substantially parallel to the partition wall 1). It is provided.

The door 70 is provided with a closing force increasing means 34 for applying a closing force larger than that during the closing, and the closing force increasing means 34 includes the cam member 10, the arm member 26, and the third rod 30. And a third spring 33.

Next, the operation of the embodiment of the present invention will be described. First, FIG. 1 is a partially cutaway plan view when the door 70 starts to open from a closed state. When the door 70 starts to open manually, the opening / closing shaft member 74 starts rotating in the clockwise direction A.

FIG. 2 is a plan view showing a state where the door is opened by, for example, 5 °. When the opening / closing shaft member 74 rotates clockwise A as described above, the cam member 10 rotates together with the sector gear 5 in the counterclockwise direction B around the first support shaft 6, and the first arm member 7 rotates counterclockwise. B, the second arm member 26 rotates clockwise A, and the third spring 33 is compressed.

As the sector gear 5 rotates, the first rod 2
Zero is moved in the left direction C against the elasticity of the first spring 22, and the first spring 22 is compressed. At this time, the hydraulic oil 23
Flows from the left chamber of the first hydraulic oil chamber 17 through the passage hole 24 of the piston 21 to the right chamber side. In addition, the contact roller 10 moves with the rotation of the sector gear 5 and the first arm member 7
Pivots in the counterclockwise direction B about the swing shaft 7b to press the second rod 29 rightward D, and the second spring 31 is compressed.
Further, the cam member 10 rotates in the counterclockwise direction B, the tip roller 14 is pressed by the stepped surface 10b, the second arm member 26 rotates in the clockwise direction A, and the pressed roller 27 is rotated.
Accordingly, the third rod 30 is pressed in the right direction D, and the third spring 33 is compressed. At this time, the tip roller 14 is still in contact with the stepped surface 10b.

FIG. 3 is a plan view showing, for example, a state in which the door 70 is opened to 30 °, the sector gear 5 and the cam member 10 further rotate counterclockwise B, and the second arm member 26 further rotates clockwise. A, and the leading end roller 14 is moved to the stepped surface 1
0b rides on the arc surface 10a, whereby the third spring 33 is greatly compressed.

FIG. 4 is a plan view showing a state in which, for example, the door 70 is opened up to 90 °. With the rotation of the sector gear 5, the first rod 20 is further pulled in the left direction C, and the first spring 22 is moved. It is further compressed, and the adjusting holes 37a and 37b are opened.
Further, with the rotation of the sector gear 5, the second rod 29 is further pressed in the right direction D, and the second spring 31 is further compressed. The leading end roller 14 completely rides on the arcuate surface 10a.
In the state where the third spring 33 rides on a, the third spring 33 is not further compressed. Therefore, when the door 70 is further opened from 30 °, the third spring 33 does not compress or expand, and therefore, the increase or decrease in the force due to the elastic force of the third spring 33 does not act when the door 70 is opened.

FIG. 5 is a plan view showing a state in which, for example, the door 70 is opened up to 180 °. Similar to the case shown in FIG. C, the first spring 22 is further compressed, and the respective adjustment holes 37a and 37b are opened. Further, with the rotation of the sector gear 5, the second rod 29 further moves rightward D
And the second spring 31 is further compressed. Then, the leading end roller 14 rides on the arc surface 10a,
In this way, when the front end roller 14 rides on the arc surface 10a, the third spring 33 is not compressed.
Open the door 70 further from 90 ° (eg, up to 180 °)
At this time, the third spring 33 has neither compression nor extension, and therefore, the increase or decrease in the force due to the elastic force of the third spring 33 does not act when the door 70 is opened.

FIG. 6 is a plan view showing a state in which the door 70 starts to be closed from a state opened to 180 °. When the door 70 is manually started to be closed, the opening / closing shaft member 74 rotates counterclockwise B. Start. When the opening / closing shaft member 74 rotates in the counterclockwise direction B, the cam member 10 rotates in the clockwise direction A together with the sector gear 5, and the first rod 20 is compressed with the rotation of the sector gear 5. The first spring 22 is pulled in the right direction D by the elasticity of the first spring 22 and starts moving.

At this time, the hydraulic oil 23 is supplied to the first hydraulic oil chamber 17.
Move from the right chamber to the left chamber, but the valve body 25 is seated on the peripheral surface of the passage hole 24 and the movement is stopped, and the hydraulic oil 23 in the right chamber of the first hydraulic oil chamber 17 is supplied to each adjustment hole. It moves from 37a, 37b to the left chamber of the first hydraulic oil chamber 17 through the reciprocating hole 36. At this time, the flow rate of the hydraulic oil 23 causes the door 7
The speed at which 0 closes is adjusted.

Further, the second rod 2 is moved by the second spring 31.
9 is pressed in the left direction C, the second rod 29
As a result, the first arm member 7 is urged clockwise A around the swing shaft 7 b, so that the door 70 starts the closing operation by the combined force of the first spring 22 and the second spring 31.

FIG. 7 shows a state in which the door 70 is closed to 90 °, the first spring 22 and the second spring 31 are extended by the rotation of the cam member 10 and the first arm member 7, and the door 70 is closed. Although it is urged in the direction, the tip roller 14 is still on the arc surface 10a, and the third spring 33 is in a state where the extension is reserved. Since the adjusting holes 37a and 37b are still open, the hydraulic oil 23 in the right chamber flows from the adjusting holes 37a and 37b to the left chamber.

FIG. 8 shows a state in which the door 70 is closed to 30 °, the adjustment hole 37 a is closed by the piston 21,
The hydraulic oil 23 is supplied only from the adjustment hole 37b to the first hydraulic oil chamber 17.
, And the speed at which the door 70 closes is slow.
The second arm member 26 is urged counterclockwise B around the second support shaft 12 via the third rod 30 by the elastic force of the third spring 33 until the door 70 closes at 30 °. That is, while the tip roller 14 is in contact with the arc surface 10a, the increase or decrease of the force due to the elastic force of the third spring 33 is
It has no effect when closing 0.

FIG. 9 shows a state in which the door 70 is closed to 5 °. While the door 70 closes from 30 ° to 5 °, the sector gear 5
And the cam member 10 further rotates in the clockwise direction A, and the leading end roller 14 moves from the arc surface 10a to the step surface 10b. Then, when the leading end roller 14 moves from the arc surface 10 a to the stepped surface 10 b, the second arm member 26 largely rotates counterclockwise B around the second support shaft 12, and the elastic force of the third spring 33. Is opened, and this is added to the elastic force of the first spring 22 and the second spring 31, and a closing force larger than the force when the door 70 is closed from 30 ° to 5 ° acts on the door 70, and FIG.
As shown at 0, the door 70 is closed.

FIG. 12 shows the opening force of the door 70 in the conventional door closing device and the door closing device according to the embodiment of the present invention, where the horizontal axis represents the opening angle of the door 70 and the vertical axis represents the opening / closing force of the door 70. This is a comparison of the force required by human power when opening the door 70) and the closing force of the door 70 (the force by which the door 70 naturally closes).
From this graph, it can be seen that in the door closing device according to the embodiment of the present invention, for example, the closing force until the door 70 is completely closed from 30 ° is increased.

As described above, according to the embodiment of the present invention, the cam member 1 which rotates in accordance with the rotation of the opening / closing shaft member 74.
0, a cam surface with which the leading end roller 14 abuts is formed. On the cam surface, a circular arc surface 10a formed on the circumferential side corresponding to the open state of the door 70 with the first support shaft 6 as an axis, and a door 70 A stepped surface 10b formed continuously with the circular arc surface 10a on the circumferential side corresponding to the closed state to release the elastic force of the third spring 33
Therefore, when the door 70 is opened, the elasticity of the third spring 33 does not increase due to the tip roller 14 abutting against the arc surface 10a and rolling, so that the third spring 33 is provided. Even with a small force, the door 70 can be completely opened,
When closing the door 70, the elastic force of the third spring 33 is released by the cam member 10 rotating and the tip roller 14 moving from the arc surface 10a to the step surface 10b, and the first spring 22 is closed.
And the elastic force of the second spring 31 to increase the closing force. Therefore, even if another member (air tight) is applied to the edge of the opening 70A of the wall to maintain airtightness. The door 70 can be reliably closed by overcoming the frictional force with the member.

In order to increase the closing force when the door 70 is closed, a configuration in which the flow of the hydraulic oil 23 is controlled may be considered. In this case, the flow path for the flow of the hydraulic oil 23 is processed. It may be difficult and costly,
In the case of the embodiment of the present invention, since the closing force is increased by changing the shape of the cam surface of the cam member 10, the processing of the door closing device is easy and the cost is reduced.

[0044]

As is apparent from the above description, the present invention is directed to a rotating member which rotates around a first support shaft in accordance with a rotating operation of an opening / closing shaft member serving as a door opening / closing center; And a plurality of spring members for urging a plurality of pistons moving in the hydraulic oil chamber in the closing direction of the door with the turning operation of the turning member by the turning member, and the door is closed with respect to the opening during the closing of the door. At this time, a closing force increasing means for applying a greater closing force to the door during the closing is provided by a cam member which rotates around the first support shaft together with the rotating member, and a base end which is formed by the second end. An arm member rotatably supported around the two support shafts and having an abutting portion having a distal end portion abutting on the cam surface of the cam member; and Consisting of a spring for biasing around the support shaft, corresponding to the open state of the door on the cam surface An arc surface having the first support shaft as the axis is formed on the circumferential side, and the cam surface is formed continuously with the arc surface on the circumferential side corresponding to the closed state of the door, and the elasticity of the spring for boosting is formed. Since the stepped surface for releasing the force is formed, when the door is closed, the arm member rotates around the second support shaft as the cam member rotates around the first support shaft. When the contact portion of the spring shifts from the arc surface to the stepped surface, the elastic force of the boosting spring is released, and the arm member strongly rotates the cam member around the first support shaft through the contact portion, For example, even in a door structure in which another member is provided on the opening edge of the wall in order to ensure airtightness and sound insulation, the door can be reliably closed against the frictional force between the member and the door. it can.

[Brief description of the drawings]

FIG. 1 is a partially broken plan view of a floor hinge showing an embodiment of the present invention in a state where a door starts to open from a closed state.

FIG. 2 is a partially broken plan view showing a state where a door is opened by 5 °.

FIG. 3 is a partially broken plan view showing a state where the door is opened by 30 °.

FIG. 4 is a partially cutaway plan view showing a state where the door is opened by 90 °.

FIG. 5 is a partially cutaway plan view showing a state where the door is opened by 180 °.

FIG. 6 is a partially broken plan view when the door starts to be closed from a state where it is opened by 180 °.

FIG. 7 is a partially broken plan view showing a state in which the door is closed to 90 °.

FIG. 8 is a partially broken plan view showing a state where the door is closed to 30 °.

FIG. 9 is a partially broken plan view showing a state where the door is closed to 5 °.

FIG. 10 is a partially broken plan view showing a state where the door is completely closed.

FIG. 11 is a partially cutaway front view of the floor hinge showing the embodiment of the present invention.

FIG. 12 is a graph in which the horizontal axis represents the door opening angle and the vertical axis represents the door opening / closing force.

FIG. 13 is a partially cutaway front view showing a use state of a floor hinge.

FIG. 14 is a partially broken plan view showing a configuration of a conventional floor hinge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Partition wall 2 Storage chamber 3 Cylinder chamber 5 Sector gear 6 First support shaft 7 First arm member 7a Rotating roller 10 Cam member 10a Arc surface 10b Stepped surface 12 Second support shaft 15 First partition 16 Second partition 17 First hydraulic oil chamber 18 Second hydraulic oil chamber 19 Third hydraulic oil chamber 20 First rod 21 Piston 22 First spring 23 Hydraulic oil 26 Second arm member 27 Pressed roller 29 Second rod 30 Third rod 31 Second Spring 33 Third spring (spring for increasing force) 34 Closing force increasing means 70 Door 72 Floor hinge 73 Floor hinge body 74 Opening / closing shaft member A Clockwise B Counterclockwise

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Ishii 1-3-17 Katase Kaigan, Fujisawa-shi, Kanagawa 304 Diamond Square Katase Enoshima 304 (58) Field surveyed (Int.Cl. ⁷ , DB name) E05F 3 / 04-3/22

Claims (1)

(57) [Claims] An opening / closing shaft member serving as an opening / closing center of a door that opens / closes with respect to an opening provided in a building; and a rotating member that rotates around a first support shaft in accordance with a rotating operation of the opening / closing shaft member. A piston that moves in the hydraulic oil chamber in accordance with the turning operation of the turning member by opening and closing the door, a plurality of spring members for urging the piston in the closing direction of the door, the piston and the operating oil chamber And a passage hole through which hydraulic oil for adjusting the closing force while resisting the elastic force of these spring members passes through, and wherein the door is opened from the middle of its closing. A closing force increasing means for applying a closing force to the door which is larger than the closing force when the door is to be closed, and the closing force increasing means is provided with the first support together with the rotating member. The cam member that rotates around the axis and the base end is the second support shaft An arm member rotatably supported around and having an abutting portion having a distal end portion abutting on the cam surface of the cam member, and an arm member having the abutting portion rotating around the second support shaft in a direction in which the abutting portion abuts the cam surface; Of the cam surface, an arc surface having the first support shaft as an axis is formed on a circumferential side corresponding to an open state of the door, and the cam surface includes: A door closing device, wherein a stepped surface is formed on a circumferential side corresponding to a closed state of the door, the stepped surface being formed continuously with the arc surface to release the elastic force of the boosting spring.