JPH08247194A - Gas stay - Google Patents

Abstract

PURPOSE: To achieve prevention of generation of wllision sound in full-opening and decrease of impact, and also to prevent a slam when a gas stay is applied to a back door, by decreasing the extending speed of the gas stay just before the complete extension. CONSTITUTION: Orifice holes 4a are formed on a piston 4, a valve body 7 for opening and closing the orifice holes 4a is provided, and a guide groove 11 to be engaged with an engaging protrusion of the valve body 7, and for turning the valve body 7 with the stroke of the piston 4 is provided on a cylinder tube 1. The engaging protrusion is guided by an extending side guide part 11b deformed in the circumferential direction in the extending stroke, and the opening areas of the orifice holes 4a are decreased just before the complete extension of a gas stay GS, and damping force is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas stay suitable for use as a balancer for an automobile back door.

[0002]

2. Description of the Related Art Conventionally, a balancer for the weight of a door is set in a flip-up type back door of an automobile to optimize the operating force. As this balancer, a torsion bar and a gas stay are known. . As such a gas stay, for example, the one described in Vol. 13 of Automotive Engineering (published on April 20, 1980 by Sankaido Co., Ltd.), page 157 is known.

In this conventional gas stay, a piston that defines the inside of the cylinder tube into an upper chamber and a lower chamber is provided at the tip of a piston rod that is capable of moving in and out of the cylinder tube. In addition to being filled with gas and oil, a stopper is provided which restricts the stroke in the extension direction when the piston rod is fully extended. Then, while the base end of the cylinder tube is attached to the vehicle body,
The tip of the piston rod is attached to the back door,
The gas stay expands and contracts as the back door opens and closes. That is, when the back door is fully closed, the gas stay is shortened to increase the internal gas pressure, and the gas pressure of the gas stay acts in the direction against the moment on which the weight of the back door acts.

FIG. 7 shows the opening / closing speed characteristic corresponding to the opening degree of the back door, and the characteristic of the above-mentioned prior art is shown by a dotted line a in the figure. The range indicated by in this figure is the range in which the back door closes by its own weight because the center of gravity of the back door is located behind the point of action of the gas reaction force of the gas stay. It is located in the vicinity of the action point of the gas reaction force of the gas stay, and is the range where the weight of the back door and the gas stay reaction force are balanced. In the figure, the range indicated by is that the center of gravity of the back door is greater than the gas force action point of the gas stay. Even if it moves forward, the back door will jump up. As shown by the dotted line a in this figure, the opening and closing speed of the back door suddenly increases as it approaches the fully open position.

[0005]

In the conventional gas stay described above, the opening and closing speed of the back door suddenly increases as the back door approaches the fully open position.
When the back door is fully opened (when the gas stay is fully extended), the piston collides with the stopper at the maximum speed, which causes a loud collision noise, and the impact of this collision is large, resulting in poor durability. There is a problem of doing. Further, as described above, when the piston collides with the stopper at a high speed, there is a problem that the reaction force of the collision causes the so-called “fluttering” in which the back door swings up and down.

Further, in order to prevent the collision noise, it is conceivable to provide an elastic body such as a rubber bush on the stopper, but in this case, the action of the elastic force causes a problem that the above "fluttering" is further enhanced. .

The present invention has been made by paying attention to the above-mentioned conventional problems, and when it is applied to a back door so that the extension speed of the gas stay is reduced immediately before it is fully extended,
Preventing collision noise at full opening and reducing impact,
Furthermore, it aims at providing the gas stay which can prevent "fluttering."

[0008]

In order to achieve the above-mentioned object, in the present invention, a piston tube is inserted from one end so that the piston rod can advance and retreat, and a cylinder tube filled with a fluid containing gas, and the inside of the cylinder tube. Is slidably defined by an upper chamber on the side where the piston rod moves in and out and a lower chamber on the opposite side, and a piston connected to the tip of the piston rod In a gas stay equipped with a stopper that restricts the stroke in the extension direction of the piston when fully extended to the piston, a through hole that communicates the upper chamber and the lower chamber is formed in the piston, and the piston includes the piston A valve that is formed so that the opening area of the through hole can be changed by rotating around a central axis in the same direction as the axis of the A guide groove is formed on the inner circumference of the cylinder tube to determine the rotation angle of the valve body with respect to the cylinder tube by engaging with the engagement projection. And a pressure-side guide portion extending in such a manner that the engagement protrusion can be guided in the axial direction of the cylinder tube, and the pressure-side guide portion is arranged in parallel with the pressure-side guide portion and can engage with the engagement protrusion in the circumferential direction. Along with this, the extension side guide portion extending so that the engagement projection can be guided in the cylinder tube axial direction, the extension stroke direction end portion of this extension side guide portion and the extension stroke direction end portion of the compression side guide portion are connected. A stretch-cut connecting portion that extends in the circumferential direction, and a shrink-cut connecting portion that extends in the circumferential direction by connecting the pressure-stroke direction end portion of the stretch-side guide portion and the pressure-stroke direction end portion of the pressure-side guide portion. Is formed in a circumferential shape by the While the opening area of the through hole is minimized immediately before fully extended, in the contracted state, the fluid is formed in a shape displaced in the circumferential direction so as to have a predetermined opening area in which the through hole can be smoothly moved. The portion is formed in a shape that maintains the through hole to have a size equal to or larger than the predetermined opening area, and the valve body is provided with a spring for urging the valve body to rotate. At a position near the connecting portion, there is a cam surface that comes into contact with a part of the valve element and converts the movement of the valve element in the piston stroke direction into a rotation in a direction opposite to the biasing direction of the spring of the valve element. The configuration is provided.

According to the second aspect of the invention, one of the piston rod and the cylinder tube is connected to the flip-up type back door, and the other is connected to the vehicle body.

[0010]

In the gas stay of the present invention, in the extension stroke from the fully compressed state, the engaging projection of the valve element moves along the extension side guide portion of the guide groove and is displaced in the circumferential direction of the extension side guide portion. At, the engagement protrusion is guided in the circumferential direction to rotate the valve element, which changes the opening area of the through hole.
That is, the opening area of the through-hole is a predetermined opening area that allows fluid to flow smoothly in the contracted state, but becomes the minimum just before fully extended. Therefore, in the initial stage of the extension stroke, a smooth stroke was performed without the damping force being generated in the through hole, but immediately before the full extension, smooth flow was hindered and the damping force was generated.

Therefore, the stroke speed of the piston at the time of full extension is reduced, and the impact when the stroke of the piston is restricted by the stopper at the time of full extension becomes small.

When the gas stay is fully extended in this way, the engaging projection is arranged at the end of the extension side guide portion in the extension stroke direction and at the connection position with the extension extension connection portion extending in the circumferential direction. To be done. Therefore, the valve body can be rotated, and is rotated in the circumferential direction by the urging force of the spring or the turning force generated by the contact with the cam surface, so that the engagement protrusion reaches the end of the compression side guide portion in the extension stroke direction. Moving. In addition,
By this rotation of the valve element, the opening area of the through hole becomes equal to or larger than the predetermined opening area having a small flow resistance.

Next, when the pressure stroke is performed from this fully extended state, the through hole has a predetermined opening area or more,
A smooth stroke is made without the generation of a damping force, and at this time, the engagement protrusion moves on the pressure side guide portion.

When the gas stay is in the fully compressed state, the engagement projection of the valve body is located at the end of the pressure side guide portion in the pressure stroke direction and at the position where the circumferentially extended contraction connection portion is connected. When the valve body is reached, the valve body can rotate and the valve body rotates due to the turning force generated by the contact with the cam surface or the urging force of the spring, and the engaging projection contracts and moves through the connecting portion to the extension side. It moves to the end of the guide section in the pressure stroke direction.

In this way, the engaging projections shrink and move in the connecting portion to move from the end of the pressure side guide portion in the pressure stroke direction to the end of the extension side guide portion in the pressure stroke direction. In doing so, the engaging protrusion moves along the extension side guide portion to obtain the above-described operation.

Therefore, in the gas stay used as the balancer of the flip-up type back door, the damping force is generated in the gas stay immediately before the full opening of the back door, the opening speed becomes slow, and the full opening is restricted. As the impact becomes smaller, the reaction force becomes smaller and the backdoor fluttering is suppressed.

[0017]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a perspective view showing an automobile to which the gas stay GS according to the embodiment of the present invention is applied as a back door balancer. As shown in the figure, the rear door of the automobile is pivoted up and down to open and close the back door BD. Is provided. And
The gas stay GS of the embodiment has the back door BD at one end.
And the other end is connected to the vehicle body so that the spring force by the gas pressure acts in the direction to open the back door BD.

FIG. 1 is a cross-sectional view showing a gas stay GS of an embodiment, which defines a cylinder tube 1 filled with gas as in the prior art, and the inside of the cylinder tube 1 is divided into an upper chamber 2 and a lower chamber 3. Piston 4 which is provided slidably in the cylinder tube 1 in the axial direction, and a piston rod which has a base end coupled to the piston 4 and is inserted in and out from a guide 1c provided at the upper end of the cylinder tube 1. 5
And a stopper 6 that regulates the movement of the piston 4 in the direction in which the piston rod 5 retracts from the cylinder tube 1 at a predetermined position to regulate the maximum extension of the gas stay GS. A mounting bracket 1b for connecting to the vehicle body is integrally provided at the lower end of the cylinder tube 1,
A mounting bracket 5b for fixing to the back door BD is integrally provided on the upper end of the piston rod 5. Further, as described above, the cylinder 1 and the piston rod 5 are connected to the vehicle body and the back door BD, respectively.
There is no turning around.

The piston 4 has a plurality of orifice holes (through holes) 4a for communicating the upper chamber 2 and the lower chamber 3 with each other.
Is formed so that the orifice hole 4a
A thin plate-shaped valve body 7 that opens and closes is attached to the lower surface of the piston 4 so as to be rotatable around the tip shaft portion 5a of the piston rod 5. That is, as shown in FIG. 3, a total of four orifice holes 4a are formed in the piston 4 at positions equidistant from the shaft center at an angle of 90 degrees. On the other hand, the valve body 7 is formed in a disk shape, and on the same circumference as the orifice hole 4a, arc-shaped opening / closing holes 7a, 7 overlapping the circumference.
b, 7c, 7d are formed. These opening / closing holes 7a
2 to 7d are formed with two holes 7a and 7c having a long circumferential length and two holes 7b and 7d having a shorter length than that. Therefore, as shown in the figure, the opening area of the orifice hole 4a is changed by the rotation of the valve body 7 with respect to the piston 4, and the all opening / closing holes 7a to 7d are vertically overlapped with all the orifice holes 4a. [(A) in the figure
(B) It will be described later that there are two types of fully open states], and conversely a fully closed state in which none of the opening / closing holes 7a to 7d overlaps the orifice hole 4a [(d) in the figure]. The opening area of the orifice hole 4a can be changed according to the overlapping state of the opening / closing holes 7a to 7d and the orifice hole 4a. It should be noted that (c) in the drawing shows a half-open state in which only the two orifice holes 4a overlap the opening / closing holes 7a, 7c.

Further, as shown in FIG. 4, the valve body 7 has one engaging projection 7e projecting outwardly on the outer periphery and one cam projection 7f projecting downward. Has been formed.

One end of the valve body 7 is engaged with the valve body 7, while the other end is engaged with the tip end shaft portion 5a of the piston rod 5 so that the valve body 7 is fully opened (see FIG. 3). A spring 8 is provided (see FIG. 1) that urges it to rotate in the counterclockwise direction (see FIG. 1), and a stopper (not shown in the figure is omitted) that restricts further rotation by the urging force of the spring 8 in this fully opened state. However, it can be easily configured with protrusions and grooves).

The engagement projection 7e of the valve body 7 is engaged with the guide groove 11 inside the cylinder tube 1.
That is, as shown in FIG. 1, the cylinder tube 1 is double formed within the stroke range of the piston 4, and the guide groove 11 is formed in the thin inner cylinder 1a provided inside the cylinder tube 1. ing.

As shown in the explanatory view of FIG. 5, the guide groove 11 is formed in the axial direction to open and close the back door BD between the fully closed state and the fully opened state of FIG.
Of the compression side guide portion 11a and the extension side guide portion 11b having a length in the axial direction equal to the stroke amount, and the extension cut connection portion 11c and the guide portions 11a and 11b for connecting the upper ends of these guide portions 11a and 11b. It is formed in a circumferential shape by the shrinkage cut connecting portion 11d that connects the lower ends. Then, the contraction connecting portion 11d is
As shown, from the compression side guide portion 11a to the extension side guide portion 11
It is inclined so as to be displaced downward as it goes to b. That is, the guide groove 11 serves to rotate the valve body 7 by guiding the engaging protrusion 7e and displacing it in the circumferential direction during the stroke of the piston 4, and the pressure side guide portion 11a should be displaced in the circumferential direction. Instead of being formed in a straight line in the axial direction and the engaging projection 7e moves on the pressure side guide portion 11a, the valve body 7 is kept in the fully opened state of FIG. 3 (a). In addition, the extension side guide portion 11b has a first displacement portion 11e and a second displacement portion 11f that are displaced in the circumferential direction at two locations on the way, and between the compression cut connection portion 11d and the first displacement portion 11e, When the engaging projection 7e is arranged at this position, the valve body is in the fully open state of FIG. 3B, and the half-open guide is provided between the first displacement portion 11e and the second displacement portion 11f. When the engaging projection 7e is located at this position in the portion 11h, the valve body is in the half-opened state of FIG.
Between the displacement portion 11f and the fully extended connection portion 11c is the fully closed guide portion 11j, and when the engagement protrusion 7e is arranged at this position, the valve body is in the fully closed state of FIG. 3 (d). The urging force of the spring 8 acts on the valve body 7 in a direction to move the engagement protrusion 7e to the right in FIG. Further, an upper left inclined surface 11k in the drawing is formed on the upper side of the contraction connecting portion 11d.

As shown in FIG. 1, a cam surface 9a is provided at the lower edge position of the compression cut connection portion 11d.
The cam surface 9a is formed on the upper surface of the cam member 9 shown in the perspective view of FIG. 6, and is arranged at a position where the cam projection 7f comes into contact with the cam member 9 when it is fully compressed. The cam projection 7f comes into contact with the compression stroke direction. Therefore, the spring 8 is inclined in a direction in which a turning force is generated in a direction opposite to the biasing direction. The cam member 9 is crimped to the lower end of the inner cylinder 1a.

Next, the operation of the embodiment will be described.

A) When the back door is open When the back door BD is fully closed, the gas stay GS is in the fully cut state, and the engagement protrusion 7e of the valve body 7 is shown in FIG. It is located at the left end of the center, and the valve body 7 is in the fully open state in FIG. 3 (b). Since the piston rod 5 has entered the cylinder tube 1 most, the gas pressure in the cylinder tube 1 is the maximum pressure.

When the opening of the back door BD is started from this state, the gas pressure of the gas stay GS acts in the extending direction to urge the back door BD in the opening direction to assist the opening operation.

FIG. 7 is an opening / closing speed characteristic diagram showing the relationship between the opening degree of the back door BD and the opening / closing speed of the back door BD. The opening degree of the back door BD at the initial stage of the opening operation is within the range shown in FIG. Then, the center of gravity of the back door BD is located rearward from the mounting position of the gas stay GS, and is a range where the back door BD closes by its own weight when the opening operation is stopped. Is located at the fully open guide portion 11g of the extension side guide portion 11b of the guide groove 11 and fully opens the orifice hole 4a. Therefore, when the fluid in the upper chamber 2 flows into the lower chamber 3 as the volume of the upper chamber 2 is reduced due to the stroke of the piston 4, no damping force is generated in the orifice hole 4a, and this opening operation is performed smoothly. Is made.

Next, in the range of FIG. 7 where the opening degree of the back door BD is larger than the above, the center of gravity of the back door BD approaches the mounting position of the gas stay GS and the back door B is moved.
This is a range in which the weight of D and the spring force due to the gas pressure of the gas stay GS are balanced, and at this time as well, the engagement protrusion 7e of the valve body 7
Is located at the fully open guide portion 11g of the extension side guide portion 11b of the guide groove 11 and fully opens the orifice hole 4a.

Next, in the range of FIG. 7 where the opening degree of the back door BD is further increased, the center of gravity of the back door BD is closer to the mounting position of the gas stay GS, and the back door BD can be flipped up. In the conventional range, the opening / closing speed is rapidly increased as shown by the dotted line in FIG. When the back door BD is opened up to this range, the engaging projection 7e of the valve body 7 first exceeds the first displacement portion 11e of the extension side guide portion 11b of the guide groove 11 and the half-open guide portion 11e.
After reaching h, the orifice hole 4a becomes a half open state [Fig.
(C)], the flow resistance of the fluid between the upper chamber 2 and the lower chamber 3 is increased, and a damping force is generated. Therefore, this damping force suppresses an increase in the opening / closing speed as compared with the conventional case as shown in FIG. 7, and the opening / closing speed hardly increases.

Further, in the range of FIG. 7, the engagement projection 7e of the valve body 7 reaches the fully closed guide portion 11j of the extension side guide portion 11b of the guide groove 11 and the orifice hole 4a is in the fully closed state [FIG. (D)], between the upper chamber 2 and the lower chamber 3, including the guide groove 11, the outer circumference of the piston 4 and the cylinder tube 1
The fluid can flow only between the inner circumference of the (inner cylinder 1a) and the maximum damping force is generated. Therefore, as shown in FIG. 7, conventionally, the opening / closing speed was extremely high in the vicinity of full opening of the back door BD. On the contrary, in the present embodiment, the opening / closing speed is decreased in the vicinity of full opening.

Accordingly, when the back door BD is fully opened, the speed at which the piston 4 collides with the stopper 6 is low, a large collision noise is not generated unlike the conventional case, and the orifice hole 4 is not generated.
The backdoor BD does not "flutter" due to the large damping force obtained by fully closing a.

When the back door BD is in the fully opened state, the gas stay GS is in the fully extended state, and the engagement protrusion 7e of the valve body 7 is at the upper end of the extension side guide portion 11b, that is, the fully extended connection portion 11c. 5, the engagement in the arrow direction is disengaged, and as a result, the valve body 7 moves to the right end in FIG. 5 of the connecting portion 11c as the engagement projection 7e is fully extended by the biasing force of the spring 8. The rotation of the orifice hole 4a brings the orifice hole 4a into the fully opened state shown in FIG. 3 (a).

B) When the back door is closed When the back door BD is closed from the fully open position, the engagement projection 7e of the valve body 7 moves the pressure side guide portion 11a, and the fully opened state of the orifice hole 4a is maintained. Therefore, in the gas stay GS, a damping force is not generated, and the back door BD is smoothly closed and rotated.

When the back door BD is in the fully closed state, the gas stay GS is in the fully compressed state, and the engagement projection 7e of the valve body 7 is the lower end of the pressure side guide portion 11a shown in FIG. 5, that is, the fully compressed connection. The portion 11d reaches the right end in the figure, and the cam projection 7f is further pressed against the cam surface 9a, and the inclination of the cam surface 9a causes the cam protrusion 7f to move to the left in FIG. 5, that is, in the direction opposite to the biasing direction of the spring 8. As a result, the valve body 7 is rotated and the engagement projection 7e is moved to the extension side guide portion 11
The lower end position of b is reached. The rotation of the valve body 7 causes the orifice hole 4a to be fully opened as shown in FIG. 3 (b).

In this way, when the back door BD is fully closed, the cam projection 7f moves from the lower end of the pressure side guide portion 11a to the lower end of the extension side guide portion 11b due to the inclination of the cam surface 9a, so that the next time the back door BD is opened. In the above, the engaging projection 7e moves the extension side guide portion 11b upward without moving the compression side guide portion 11a upward, and the above-described operation is obtained. Further, since the inclined surface 11k is formed,
It does not return to the pressure side guide portion 11a at the beginning of the extension stroke.

As described above, in the gas stay GS of this embodiment, the orifice hole 4a is formed in the piston 4 and the valve body 7 is provided, and the inner cylinder 1a of the cylinder tube 1 is provided with this valve body. 7 is provided with a guide groove 11 that engages with the engagement protrusion 7e of the piston 7 to rotate the valve body 7 according to the stroke of the piston 4, and the orifice hole is provided when the back door BD is fully opened, that is, near the fully extended position of the gas stay GS. Four
Since a is closed by the valve body 7 to generate a damping force, the opening / closing speed of the back door BD immediately before the full opening can be reduced, whereby the collision noise generated when the piston 4 collides with the stopper 6 is generated. Can be suppressed,
Moreover, it is possible to obtain an effect that it is possible to prevent the "fluttering" of the back door BD due to the reaction force of the collision.

Further, as described above, the gas stay GS is constituted so that the orifice hole 4a is closed immediately before the expansion stroke is completed during the expansion stroke.
Since the orifice hole 4a is kept in the fully opened state without changing the opening degree as described above, the operation force for closing the back door BD does not become heavy, and the effect that it can be closed smoothly can be obtained. .

Although the embodiment has been described above, the specific configuration is not limited to this embodiment, and the present invention includes a design change and the like without departing from the scope of the invention.

For example, in the embodiment, the cam member 9 having the cam surface 9a is provided, and the cam projection 7f of the valve body 7 has the cam surface 9a.
However, the position of the cam surface and the member for contacting the cam surface are not limited to this, and the cam surface is formed in the guide groove and the cam surface is engaged with the cam surface. You may comprise so that a compound protrusion may contact | abut. Further, the cam surface is not formed on the side of the contraction connecting portion 11d as in the embodiment, but the cam surface on the upper right side is formed on the fully extending connecting portion 11c, that is, the rotational force in the right direction of FIG. 5 is formed by the extension stroke. However, in this case, the rotational biasing direction of the valve element by the spring is set opposite to that of the embodiment.

In the embodiment, an example in which four orifice holes are formed as the through holes has been shown, but the number and shape thereof are not limited to those of the embodiment. The cross-sectional shape is the shape of the opening / closing holes 7a to 7d of the embodiment. Even if the shape of the opening / closing hole is the shape of the orifice hole, the same effect as that of the embodiment can be obtained.

In the embodiment, the cylinder tube 1 and the piston rod 5 are respectively connected to the vehicle body and the back door BD so that the piston 4 does not rotate with respect to the cylinder tube 1. Between the guide 1c of the tube 1 and the piston rod 5, for example,
The piston 4 is provided with a structure for restricting the rotation of the protrusion and the groove.
May be prevented from rotating.

Further, in the embodiment, the example in which the back door is applied to the BD balancer is shown, but the applicable range is not limited to this.

[0045]

As described above, in the gas stay according to the first aspect of the present invention, the piston is provided with the valve body for opening and closing the through hole, and the cylinder tube is provided with the valve body. Providing a guide groove that engages with the engagement protrusion and rotates the valve body according to the stroke of the piston,
During the extension stroke, the extension side guide part, which is displaced in the circumferential direction, guides the engaging protrusion to reduce the opening area of the through hole immediately before the extension of the gas stay so that the damping force is generated. It is possible to reduce the speed, and thereby, it is possible to obtain the effect of suppressing the collision noise generated when the stroke of the piston is restricted by the stopper, and it is possible to suppress the impact at this time and improve the durability. The effect is obtained. Further, even though the damping force is generated in the extension stroke as described above, in the pressure stroke from the fully extended state of the gas stay, the pressure side guide different from the extension side guide portion that guides the engaging protrusion during the extension stroke. Since it is configured so as to pass through the portion and maintain the opening area of the through hole larger than a predetermined value, there is an effect that the pressure stroke can be smoothly performed without generating a large damping force during the pressure stroke.

Further, in the gas stay according to the second aspect, when the back door is opened, the opening area of the through hole becomes small immediately before the full opening of the back door and a damping force is generated to reduce the opening speed of the back door. It is possible to obtain an effect that the collision noise at the time is reduced and the backdoor fluttering can be prevented. When the back door is closed, since the damping force is not generated as described above, the operation force for closing the back door does not become heavy, and the effect that the back door can be closed smoothly is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a gas stay according to an embodiment of the present invention.

FIG. 2 is a perspective view of an automobile to which the gas stay of the embodiment is applied.

FIG. 3 is an operation explanatory view showing the operation of the valve body.

FIG. 4 is a perspective view of a valve body.

FIG. 5 is an enlarged view showing a guide groove.

FIG. 6 is a perspective view of a cam member.

FIG. 7 is an opening / closing speed characteristic diagram of backdoors of the embodiment and the prior art.

[Explanation of symbols]

 GS Gas stay 1 Cylinder tube 2 Upper chamber 3 Lower chamber 4 Piston 4a Orifice hole (through hole) 5 Piston rod 6 Stopper 7 Valve body 8 Spring 9a Cam surface 11 Guide groove 11a Pressure side guide part 11b Extension side guide part 11c Extension cut connection part 11d Shrink cut connection

Claims (2)

[Claims] 1. A cylinder tube in which a piston rod is inserted from one end so as to be able to move forward and backward, and a fluid containing gas is filled therein, an upper chamber on the side where the piston rod moves in and out of the cylinder tube, and a lower portion on the opposite side. A piston connected to the tip of the piston rod, which is slidably defined to define a chamber, and restricts the stroke of the piston in the extension direction when the piston rod is fully retracted from the cylinder tube. In a gas stay including a stopper, a through hole that communicates the upper chamber and the lower chamber is formed in the piston, and the piston rotates about a central axis in the same direction as the axial center of the piston. A valve body is provided, which is formed so that the opening area of the through hole can be changed, and an engaging projection is provided on the outer periphery of the valve body. A guide groove is formed which engages with the engaging projection and determines the rotation angle of the valve body with respect to the cylinder tube. The guide groove is engageable with the engaging projection in the circumferential direction, and the engaging projection is provided on the cylinder tube. A pressure side guide portion extending so as to be able to be guided in the axial direction, and a pressure side guide portion that is arranged in parallel and is engageable with the engaging protrusion in the circumferential direction, and the engaging protrusion is extendable so as to be able to guide in the cylinder tube axial direction. The extending side guide portion that is present, the extension stroke direction end portion of the extension side guide portion and the extension stroke direction end portion of the compression side guide portion, and the extension cut connection portion that extends in the circumferential direction, and It is formed in a circumferential shape by a compression cut connecting portion that extends in the circumferential direction by connecting the pressure stroke direction end portion of the extension side guide portion and the pressure stroke direction end portion of the pressure side guide portion, and the extension side guide portion is Immediately before fully extending, minimize the opening area of the through hole On the other hand, in the contracted state, the fluid is formed in a shape that is displaced in the circumferential direction so as to have a predetermined opening area that allows the through hole to move smoothly, and the pressure side guide portion keeps the through hole at or above the predetermined opening area. The valve body is provided with a spring that urges the valve body to rotate, and a part of the valve body is provided at a position near the extension cutout connection part or the compression cutout connection part. A gas stay characterized in that a cam surface is provided, which abuts and converts the movement of the valve element in the piston stroke direction into a rotation in a direction opposite to the biasing direction of the spring of the valve element. 2. The gas stay according to claim 1, wherein one of the piston rod and the cylinder tube is connected to a flip-up type back door, and the other is connected to a vehicle body.