JPH0813898A - Door closure for sliding door - Google Patents

Abstract

PURPOSE:To prevent the quick movement of a sliding door. CONSTITUTION:A piston 12 having a check valve 14 in the through-hole 13 of a head section 12a and a rack 15 in a side section 12b is fitted slidably to a cylinder 1. The piston is energized toward a compression chamber 16a by springs 17, 18 attached on the spring chamber 16b side in a contracted warmer, the shaft 22 of a pinion 21 engaged with the rack 15 is borne rotatably to a cylinder wall, and the compression chamber and the spring chamber are communicated by oil paths 19, 20 in the cylinder wall. The door closure is provided droopingly while the compression chamber side is directed to an upper section, and the other end of an opening-closing arm, in which one end is fixed onto a pinion shaft 22, is fitted slidably to sliding fittings fastened along the edge of a sliding door. One end P2 of the oil path 20 is opened to a section just above the surface of a working fluid in the compression chamber at a working maximum temperature, and an air chamber 3 is mounted while being communicated with the compression chamber 16a in the upper section of the opening. An air relief valve 10 receiving the buoyancy of the working fluid and being closed is installed so as to partition the air chamber 3 and the compression chamber 16a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertically installed door closer for a sliding door used for opening and closing a sliding door at a connecting portion of a vehicle.

[0002]

2. Description of the Related Art Conventionally, a door closer of this type is known, for example, as shown in FIG. This door closer has a cylinder 11 and a bottomed cylindrical shape, and has a check valve 14 for blocking the inflow of hydraulic oil in a through hole 13 at the center of a head 12a corresponding to the bottom, and a rack 15 on a side 12b. And a piston 12 slidably fitted in an oil chamber 16 in the cylinder 11 and another oil chamber (spring chamber) 16b partitioned by the piston 12
(Compression chamber) Spring 1 compressed to urge to the end of 16a
7, 18 and the first and second oil passages 19 and 20 provided in the wall of the cylinder 11 so that the compression chamber 16a communicates with the spring chamber 16b, and the rack 15 and the shaft 22. The pinion 21 is rotatably supported on the cylinder wall and accommodated in the cylinder 11.

As shown in FIG. 2B, the first oil passage 19 extends from the first port P ₁ near the center of the compression chamber 16a to the axial passage 19a, the clearance around the pinion 21, and the axial direction. It communicates with the spring chamber 16b through the rear portion of the extending annular groove 23 on the outer circumference of the piston and the through hole 24 in the piston radial direction, and the end portion is located in the vicinity of the first port P ₁ and the head portion is the front end surface of the cylinder 11. It has the 1st speed control valve 25 screwed together. Further, as shown in FIG. 2A, the second oil passage 20 extends from the second port P ₂ at the end of the compression chamber 16a to the axial passage 20a, the front portion of the annular groove 23, and the penetrating passage. It has a second speed adjusting valve 26 which communicates with the spring chamber 16b through the hole 24, has its end located at the intermediate step of the axial passage 20a, and has its head screwed onto the front end surface of the cylinder 11. As shown in FIG. 3, the door closer 31 described in FIG.
One end of the opening / closing arm 32 is fixed to the pinion shaft 22 projecting outside the door closer 31 on the floor at the corner between the side wall 37 and the side wall 37. A roller pivotally attached to the other end of the sliding door 33 is slidably fitted to a sliding metal fitting 34 fixed along the vertical edge of the sliding door 33. Then, the sliding door 33 is moved to the right and left along the floor by the turning motion of the opening / closing arm 32 indicated by the chain double-dashed line to open / close the opening 35 to the connecting portion.

The swing movement of the opening / closing arm 32 is performed by the door closer 31 as follows. When the user grasps the handle and moves the sliding door 33 to the right in FIG. 3 to open it, as the roller slides upward along the sliding metal fitting 34 of the sliding door 33, the opening / closing arm 32 has a double-dot chain line. It turns like this. The pivot of the opening / closing arm 32 causes the shaft 22 to rotate.
2A, the pinion 21 rotates in the direction of the arrow in FIG. 2A, and the piston 12 meshing with the pinion 21 returns toward the spring chamber 16b while compressing the springs 17 and 18 from the top dead center shown in FIG. Move. Then, the hydraulic oil in the spring chamber 16b pushes up the check valve 14 of the piston head 12a while pushing up the through hole 1
When the piston 12 passes through 3 and flows into the compression chamber 16a and the sliding door 33 is fully opened, the piston 12 reaches the bottom dead center shown in FIG.
Next, when the user releases the handle of the sliding door 33, the piston 12 moves forward toward the compression chamber 16a as the compressed springs 17 and 18 are restored, and the rack 15 of the piston 12 moves.
The pinion 21 that meshes with the shaft rotates in the direction of the arrow in FIG. 2 (B) to move the opening / closing arm 32 downward through the shaft 22 (see FIG. 3).
The sliding door 33 is closed to the left in FIG. 3 through the sliding fitting 34.

During the forward movement of the piston 12, the piston head 1
Since the check valve 14a of 2a is closed, the hydraulic oil in the compression chamber 16a is first opened in the first half stroke of the forward movement of the first port P.
Flows into the spring chamber 16b via the first oil passage 19 of the flow path resistance smaller from _1, the motion in the piston 12 is relatively high first speed, it followed open at the forward movement late stroke second port P
₂ flows into the spring chamber 16b through the second oil passage 20 having a large flow resistance, the movement of the piston 12 slows down to the second speed, and finally reaches the top dead center of FIG. 2 (A). Stop,
The sliding door 33 is fully closed.

[0006]

The operating temperature of the door closer 31 is, for example, -20 ° C to + 50 ° C.
The expansion coefficient of the hydraulic oil is determined by the cylinder 1
Since it is considerably larger than that of aluminum, which is the material of No. 1, the oil chamber 16 is filled with a volume of air equal to the apparent expansion volume of the hydraulic oil in the cylinder 11 corresponding to the operating temperature range. Therefore, the piston 12 is shown in FIG.
At the bottom dead center shown in, the oil level of the hydraulic oil in the cylinder 11 vertically installed with the compression chamber 16a up reaches the second port P ₂ at the upper end at an operating maximum temperature of 50 ° C. in one example. ,
At the normal temperature of use of 20 ° C., for example, it is at the position shown by the chain double-dashed line in the figure, and there is an air layer above it.

However, due to the presence of this air layer, the above-mentioned conventional vertically installed door closer has the following problems. That is, when the piston 12 starts to move from the bottom dead center shown in FIG. 2B toward the compression chamber 16a by the force of the springs 17 and 18, and the sliding door 33 in the fully opened state starts to close, the compression chamber 16
Since the second oil passage 20 connected to the second port P ₂ at the upper end of a is closed by the side surface of the piston head 12a, the air in the air layer, which is much more easily compressed than the hydraulic oil, is compressed and the volume rapidly increases. And the piston 12 rapidly moves forward. afterwards,
The hydraulic oil in the compression chamber 16a is compressed and flows into the spring chamber 16b through the first oil passage 19, so that the piston 12
Moves at the above-mentioned first speed, which is slower than the rapid movement. However, when the opening size of the sliding door 33 is small, the piston 1
2 starts to move forward from the intermediate position between Fig. 2 (A) and (B), the piston reaches near the top dead center of Fig. 2 (A) at the time when the compression of the air layer due to the rapid movement is completed. Therefore, the sliding door 33 collides with the door stop at the speed of the rapid forward movement which is faster than the first speed and is closed.

Such a rapid movement when the opening size of the sliding door is small does not adapt to the user's feeling that the closing end should be late, and there is a problem that the user feels uncomfortable and dangerous. In addition, with the recent increase in the quality of buildings and vehicles, the vertically installed door closer, which does not require space and is easy to clean the floor, is not only for buildings but also for connecting parts of vehicles and
Furthermore, although it is being applied to the doors of toilets and changing rooms, the rapid movement described above also deteriorates the high-class image. Therefore, an object of the present invention is to provide the compression chamber end of the cylinder with
An object of the present invention is to provide a door closer for a sliding door, which is provided with an air chamber that eliminates the initial compression of an air layer so that the sliding door does not move rapidly even when the opening size is small, has an excellent aesthetics, and can be installed vertically in a small space.

[0009]

In order to achieve the above object, a sliding door closer of the present invention has a check valve for preventing the inflow of hydraulic oil in a through hole of a head, and a check valve is provided in a side portion or a body. A piston having a rack is slidably fitted in an oil chamber in the cylinder, and a spring for urging the piston to one oil chamber end is compressed in the other oil chamber partitioned by this piston, and a cylinder wall An oil passage that connects one of the oil chambers to the other of the oil chambers is provided therein, while the pinion shaft that meshes with the rack is rotatably supported by the cylinder wall, with the one oil chamber facing up. For a sliding door, which consists of a vertically installed door closer and an opening and closing arm whose one end is fixed to the pinion shaft of this door closer and whose other end is slidably fitted to a sliding metal fitting fixed along the edge of the sliding door. In the door closer, the oil passage is One end opens directly above the operating oil surface of the one oil chamber of the vertically extending cylinder at the maximum operating temperature, and an air chamber is provided above the opening and connected to the one oil chamber in the cylinder. And an air relief valve that is provided so as to partition the air chamber from one of the oil chambers and that is closed by receiving the buoyancy of the hydraulic oil.

The air relief valve is provided with a circular partition plate and a center of the partition plate such that the one oil chamber side forms a large diameter valve chamber and the air chamber side forms a small diameter valve seat. And a spherical valve body loosely fitted in the valve chamber so as to be seated on the valve seat when immersed in hydraulic oil. Further, the volume of the air chamber can be made substantially equal to the expansion volume of the hydraulic oil in the cylinder corresponding to the operating temperature range.

[0011]

[Function] When the user fully opens the sliding door, the other end of the opening / closing arm slides along the sliding metal member fixed to the edge of the sliding door, and the pinion returns through the shaft fixed to one end of the opening / closing arm. The piston in the cylinder rotates backward from the top dead center toward the other oil chamber and reaches the bottom dead center via the rack meshing with the piston. Next, when the user releases his / her hand from the sliding door, the piston receives a force from the spring that tries to restore, and moves forward toward one of the oil chambers with the check valve in the through hole of the head closed. To do. At this time, the upper end of the one oil chamber, which is the top of the vertically installed cylinder, is an air layer to absorb the expansion of the hydraulic oil.
The air in the air layer, which is more easily compressed than the hydraulic oil in one of the oil chambers, is first compressed by the forward movement of the piston. However, the top of one of the oil chambers is partitioned by an air relief valve, and since this valve is open in the air without receiving the buoyancy of the hydraulic oil, the air in the above air layer is compressed before it is compressed. Through the air relief valve into the upper air chamber. Therefore, within a very short time from the start of the forward movement of the piston, all the air at the upper end of one oil chamber moves to the air chamber, the oil surface of the hydraulic oil reaches the opening at the upper end of the oil chamber and the air relief valve, and the air escapes. The valve is closed by the buoyancy of hydraulic oil,
The hydraulic oil that has been prevented from flowing into the air chamber flows into the other oil chamber from the opening through the oil passage in the cylinder wall.

That is, by providing the air chamber partitioned by the air relief valve above one of the oil chambers, the compression of the air layer as in the conventional case at the beginning of the piston forward stroke is eliminated, so that the rapid forward movement of the piston is also possible. The piston is gone
Controlled at a predetermined speed determined by the spring constant of the above springs and the flow path resistance of the oil passage, etc., and moved forward to the top dead center. Thus, the sliding door is closed at a controlled predetermined speed without being closed rapidly. The air that has flowed into the air chamber again flows into one of the oil chambers through the air relief valve that opens when the oil level drops when the piston starts returning. The above operation can be said even when the sliding door is opened to the half-opened state and the piston returns to the middle of the top dead center and the bottom dead center.
Since there is no rapid closing motion when the sliding door has a small opening dimension, the user does not feel a sense of discomfort or danger in operation.

The air relief valve is provided with a circular partition plate, and at the center of the partition plate, the one oil chamber side forms a large-diameter valve chamber and the air chamber side forms a small-diameter valve seat. With a through hole and a spherical valve element that is loosely fitted into the valve chamber so as to be seated on the valve seat when immersed in hydraulic oil, the oil level rises at the start of forward movement of the piston, When the valve element loosely fitted in the valve chamber is submerged in the hydraulic oil, the valve element receives buoyancy and floats and sits on the valve seat, preventing the hydraulic oil from flowing into the air chamber, and returning the piston. The movement lowers the oil level to move the valve body away from the valve seat, causing air to flow from the air chamber into one of the oil chambers.
The air relief valve having such a structure can be fitted into the tip of the end cover of the cylinder whose internal space is an air chamber and the like, and can be incorporated in the cylinder, which simplifies the structure and is convenient for maintenance and inspection.

Further, if the volume of the air chamber is made substantially equal to the expansion volume of the working oil in the cylinder corresponding to the operating temperature range, the air layer at the upper end of one of the oil chambers is totally collected immediately after the forward movement of the piston is started. To move the oil surface of the hydraulic oil to the opening at the upper end of the oil chamber and the air relief valve, reliably eliminating the compression of the air layer at the start of piston forward movement and the rapid forward movement of the piston, The sliding door can be reliably closed at a controlled and predetermined speed.

[0015]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a vertical cross-sectional view showing an example of a sliding door closer of the present invention. This sliding door closer is described in FIG. 2 except that the structure on one oil chamber (compression chamber) side of the cylinder is different. Since it has the same structure as the conventional door closer and is arranged and connected to the sliding door in the same manner as in FIG. 3,
The same members are given the same numbers and their explanations are omitted. A bottomed cylindrical head cap 2 having an outer peripheral thread is liquid-tightly attached to an end surface of the vertically extending cylinder 1 on the side of the compression chamber 16a. A circular partition plate 4 is provided in an annular groove at the end of the cylindrical wall of the head cap 2, and a central part of the partition plate 4 is provided with a large diameter valve chamber 7 in the lower portion and a small diameter valve seat 6 in the upper portion. Through hole 5, a resin-made spherical valve body 8 loosely fitted in the valve chamber 7 so as to be seated on the valve seat 6 when immersed in hydraulic oil, and the valve body 8 is prevented from falling off. An air escape valve 10 including a holding claw 9 is liquid-tightly fitted via a packing 30 attached to the outer periphery of the partition plate 4.

Due to the air release valve 10, the inside of the head cap 2 forms an air chamber 3 separated from the compression chamber 16a in the cylinder 1, and the volume of this air chamber 3 is, for example, -20 ° C to + 50 ° C. When the piston 12 is at the bottom dead center at the normal operating temperature (20 ° C.), the oil level of the hydraulic oil (FIG. 1) is approximately equal to the apparent expansion volume of the operating oil that takes into account the expansion of the cylinder 1 corresponding to the operating temperature range. It is a little larger than the volume of the air layer above (see the chain double-dashed line). Further, the volume of the air chamber is about 15% of the volume of all working oil in the cylinder 1.

The sliding door closer having the above structure operates as follows. When the user of the vehicle grasps the handle and fully opens the sliding door 33 shown in FIG. 3 to the right in the figure, the opening / closing arm 32 whose tip slides along the sliding metal fitting 34 fixed to the vertical edge of the sliding door 33 is , Pivots upward as indicated by the chain double-dashed line, and moves the pinion 2 through the shaft 22 fixed to the base end of the opening / closing arm 32.
1 rotates in the direction opposite to the arrow in FIG. 1, and through a rack 15 that meshes with the piston 1, the piston 12 in the cylinder 1 compresses the springs 17 and 18 from the top dead center of the upper end while compressing the springs 1 and 18.
6b, the hydraulic oil in the spring chamber 16b flows into the compression chamber 16a through the through hole 13 while pushing up the check valve 14 of the piston head 12a, and when the sliding door 33 is fully opened, the piston 12 Reaches the bottom dead center shown in FIG. next,
When the user releases his / her hand from the sliding door 33, the piston 12 receives the force from the springs 17 and 18 which are going to be restored, and the piston 12 receives the force.
With the check valve 14 of the through hole 13 of 2a closed, the spring chamber 1
Go upwards toward 6b. At this time, the upper end of the compression chamber 16a, which is the top of the vertically extending cylinder 1, is an air layer above the two-dot chain line in FIG. 1 to absorb the expansion of the hydraulic oil. The air in the air layer, which is much more easily compressed than the hydraulic oil, is first compressed by the forward movement of the piston.

However, the upper end of the compression chamber 16a is partitioned by the air escape valve 10, and the valve body 8 of this valve is in the air and rests on the holding claw 9 without receiving the buoyancy of the hydraulic oil. The layer air passes through the side of the valve body 8 while the compression is hardly progressing, passes through the valve seat 6 and flows into the upper air chamber 3 larger than the volume of the air layer. Therefore,
Immediately after starting the forward movement of the piston, all the air in the compression chamber 16a moves to the air chamber 3, and the oil surface of the hydraulic oil reaches the second port P _{2 at} the upper end of the compression chamber 16a and the valve body 8 of the air relief valve 10. , The valve body 8 floats and sits on the valve seat 6 to close the through hole 5. The hydraulic oil that has been blocked from flowing into the air chamber 3
At this point, it flows into the spring chamber 16b through the first oil passage 19 from the first port P ₁ opened, and the piston 12 moves forward at the predetermined first speed set by the first speed adjusting valve 25. . When the first port P ₁ is closed by the forward movement of the piston, the second oil passage 2 from the second port P ₂ is replaced with this.
0 opens, the hydraulic oil in the compression chamber 16a flows into the spring chamber 16b via the second oil passage 20, and the piston 12 moves forward at a predetermined second speed set by the second speed adjusting valve 26.
Finally, when the sliding door 33 is fully closed, the piston 12 is at top dead center.
(See FIG. 2 (A)) and reaches a stop. The air that has flowed into the air chamber 3 passes through the through hole 5 opened by the valve body 8 which is separated from the valve seat 6 due to the decrease in the oil level when the piston 12 starts to return due to the subsequent opening of the sliding door, and then the compression chamber again. It flows into 16a.

Thus, by providing the air chamber 3 partitioned by the air relief valve 10 above the compression chamber 16a at the top of the vertically installed cylinder 1, the piston 12 moves forward (up).
Since there is no compression of the air layer in the early stage of the stroke, the rapid forward movement of the piston 12 also disappears, and the piston 1
2 is controlled to the first and second speeds determined by the spring force of the springs 17 and 18 and the set values of the first and second speed adjusting valves 25 and 26, and moves forward to the top dead center, and the forward movement of the rack. Motion pinion 21
Rotation in the direction of the arrow in FIG. 1, the opening / closing arm 32 shown in FIG.
Of the sliding door 33 through the sliding metal fitting 34 by turning downwards.
Closes at a controlled predetermined speed without closing rapidly. The above operation is performed when the sliding door 33 is opened to the half-opened state and the piston 12 is moved back to the midpoint between the top dead center and the bottom dead center (see FIGS. 2A and 2B), and the piston is accompanied by the sliding movement of the sliding door. As for the forward movement, the quick closing operation when the opening size of the sliding door 33 is small is also eliminated, so that the user does not feel uncomfortable and dangerous in operation, and the high-grade image using this door closer is deteriorated. Nothing.

In the above embodiment, the air relief valve 10 is loosely fitted in the circular partition plate 4, the through hole 5 having the small diameter valve seat 6 and the large diameter valve chamber 7 at the center thereof, and the valve chamber 7. And a spherical valve body 8 made of resin, and the air release valve 10 is
Since the inner space is fitted to the tip of the head cap 2 forming the air chamber 3 and screwed into the upper end of the cylinder 1 in a liquid-tight manner, the structure is simplified and convenient for maintenance and inspection. . Further, since the volume of the air chamber 3 is set to be substantially equal to the expansion volume of the hydraulic oil in the cylinder 1 corresponding to the operating temperature range, the air in the compression chamber 16a immediately after the forward movement (raising) of the piston 12 is started. All the layers can be moved to the air chamber 3, and the oil surface of the hydraulic oil can reach the second port P ₂ at the upper end and the valve body 8, and the compression of the air layer at the start of the piston forward movement and the rapid forward movement of the piston With certainty, the sliding door 33 can be reliably closed at a controlled predetermined speed.
Further, in the above embodiment, the first and second oil passages 19 and 20 are provided, and the speed adjusting valves 25 and 26 thereof can be adjusted from the upper end surface of the cylinder 1. Therefore, the closing speed of the sliding door 33 can be adjusted. There is an advantage that the speed can be controlled in two steps and the fine adjustment of both speeds can be easily performed.

The air relief valve of the present invention is not limited to the one of the embodiment, and it is sufficient if it is closed by receiving the buoyancy of the hydraulic oil, and the air chamber of the present invention is the head of the embodiment. The volume is not limited to the cap type, and the volume thereof may not be equal to the expansion volume of the hydraulic oil corresponding to the operating temperature range. Further, in the above-mentioned embodiment, the pinion is rotated by the rack provided on the outer peripheral surface of the piston, but the present invention is also applied to one in which the rack is provided on the inner peripheral surface of the piston and the pinion is rotated by this rack. it can. Further, the door closer of the present invention can be applied to general sliding doors as well as the sliding door of the embodiment as long as it is vertically installed with the compression chamber facing upward. Even in such a case, needless to say, as long as the air chamber and the air relief valve according to the first aspect are provided, the rapid closing of the sliding door due to the air layer compression at the initial stage of the closing is prevented.

[0022]

As is apparent from the above description, the sliding door closer of the present invention has a check valve in the through hole of the head,
A piston having a rack on the side or inside the body is slidably fitted in the cylinder, and the pinion shaft that meshes with the rack is urged by a spring compressed toward the spring chamber to urge the piston toward the compression chamber. A door closer, which is rotatably supported on the cylinder wall and connects the compression chamber and the spring chamber with each other through an oil passage in the cylinder wall, is vertically installed with the compression chamber side facing up, and one end is fixed to the pinion shaft. The other end of the arm is slidably fitted to a sliding fitting fixed along the edge of the sliding door, and one end of the oil passage is opened directly above the hydraulic oil surface of the compression chamber at the maximum operating temperature. , An air chamber is provided above the opening so as to be connected to the compression chamber, and an air relief valve that closes by receiving the buoyancy of the hydraulic oil is provided so as to partition the air chamber from the compression chamber. Rise) Above the compression chamber within an extremely short time from the start It is possible to move all the air in the air chamber to the air chamber, and to eliminate the rapid forward movement of the piston due to the compression of the air layer as in the past, and to control the closing movement of the sliding door at a predetermined speed even when the opening size is small. Therefore, the present invention can be widely applied to high-class buildings, vehicles, etc. while enhancing the image with a compact structure and smooth operation without giving the user a feeling of strangeness or danger in operation.

Further, the air relief valve is provided with a circular partition plate,
The structure is simple if it consists of a through hole consisting of a small diameter valve seat and a large diameter valve chamber at the center and a spherical valve body that is loosely fitted in the valve chamber and sits on the valve seat when immersed in hydraulic oil. And maintain,
It is convenient for inspection. Furthermore, if the volume of the air chamber is made approximately equal to the expansion volume of the hydraulic oil in the cylinder corresponding to the operating temperature range, all the air in the compression chamber will be transferred to the air chamber immediately after the start of the forward movement of the piston. The oil surface of can be made to reach the opening of the oil passage at the upper end, the rapid forward movement of the piston due to the compression of the air layer can be reliably eliminated, and the sliding door can be reliably controlled to the predetermined speed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a door closer for a sliding door according to the present invention.

FIG. 2 is a vertical cross-sectional view of a conventional sliding door closer with a sliding door fully closed and a fully opened state.

FIG. 3 is a front view showing a connected state of the sliding door closer to the sliding door.

[Explanation of symbols]

1 ... Cylinder, 2 ... Head cap, 3 ... Air chamber, 4 ...
Partition plate, 5 ... through hole, 6 ... valve seat, 7 ... valve chamber, 8 ... valve body,
9 ... Holding claw, 10 ... Air escape valve, 12 ... Piston, 1
2a ... Head, 12b ... Side, 13 ... Through hole, 14 ... Check valve, 15 ... Rack, 16 ... Oil chamber, 16a ... Compression chamber, 16b
... Spring chamber, 17, 18 ... Spring, 19 ... First oil passage, 20
... 2nd oil passage, 21 ... Pinion, 22 ... Shaft, 23 ... Annular groove, 24 ... Radial through hole, 30 ... Packing, 32 ... Opening / closing arm, 33 ... Sliding door, 34 ... Sliding metal fitting.

Claims (3)

[Claims] 1. A piston having a check valve for blocking the inflow of hydraulic oil in a through hole of a head portion, and a piston having a rack on a side portion or a body is slidably fitted in an oil chamber in a cylinder, A spring for urging the piston to the end of one of the oil chambers is compressed in the other oil chamber partitioned by the piston, and an oil passage for communicating the one oil chamber with the other oil chamber is provided in the cylinder wall. On the other hand, a pinion shaft that meshes with the rack is rotatably supported by the cylinder wall, and one end is fixed to the door closer that is vertically installed with the one oil chamber facing upward, and the pinion shaft of the door closer. A door closer for a sliding door, the other end of which is slidably fitted to a sliding metal member fixed along the edge of the sliding door, wherein the oil passage is formed in a vertically extending cylinder at the maximum operating temperature. One of the oil chambers directly One end of the oil chamber is opened, and an air chamber that is connected to the one oil chamber and is provided in the cylinder above the opening, and is provided so as to partition the air chamber and the one oil chamber. A door closer for a sliding door, comprising an air relief valve that receives and closes. 2. The air relief valve comprises a circular partition plate,
At the center of this partition plate, there is a through hole provided so that the one oil chamber side forms a large diameter valve chamber and the air chamber side forms a small diameter valve seat, and the above-mentioned valve seat when immersed in hydraulic oil. The door closer for a sliding door according to claim 1, comprising a spherical valve body that is loosely fitted into the valve chamber so as to be seated. 3. The door closer for a sliding door according to claim 1, wherein the air chamber has a volume substantially equal to the expansion volume of the hydraulic oil in the cylinder corresponding to the operating temperature range.