JPS6141455Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a gas spring, particularly a gas spring whose reaction force changes in two stages.

Gas springs used in automobile back door opening/closing assist devices have traditionally had one end sealed and a removable piston rod that extends sealingly through the other end of a cylinder filled with working gas. This type of gas spring utilizes the gas reaction force generated corresponding to the volume that enters the cylinder, and as is well known in the past, this type of gas spring
The gas reaction force generated corresponding to the penetrating volume of the piston rod changes only approximately linearly, and the gas reaction force is the smallest when the piston rod is fully extended. Therefore, when this is applied to a back door opening/closing assist device, the opening assist force is the smallest when the back door is open, and when the gas pressure decreases due to a drop in outside air temperature, etc. There was a problem of not being able to obtain support forces.

The present invention was developed in view of these conventional problems, and it stabilizes the assisting force in the open state by changing the gas reaction force in two stages and increasing the gas pressure at the maximum extension near the maximum extension stroke. To provide a gas spring with a low gas pressure that can easily open and close a door at other strokes.

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

FIG. 1 is a cross-sectional view of a main part of a gas spring.
In the figure, 1 is a cylinder with one end sealed, 2 is a piston rod that extends through the other end of the cylinder 1 in a sealed manner and can be inserted and removed, and 3 is a piston assembly that is attached to one end of the piston rod and divides the inside of the cylinder 1 into two chambers, _{C1 and C2} . This piston assembly 3 is made up of a cylindrical sleeve 4 that is in sliding contact with the outer periphery of the piston rod 2 and has a flange 4a at one end,
A stopper 5 is engaged with the end of the piston rod 2, and the flange 4 of the stopper 5 and the sleeve 4
a) and a) that is in sliding contact with the outer periphery of the sleeve 4 and the inner periphery of the cylinder 1 via a seal ring 7, and that is in communication with the chambers _C1 and _C2 .
a piston 8 having an end of the communicating hole 8a which is connected to the chamber _C2 sealed near the outer periphery of the check plate 6; a stopper ring 11 fitted to the end of the sleeve 4 opposite to the flange 4a;
The stopper 5 is made up of a retainer 9 whose position is restricted by the stopper ring 11, and a spring 10 which is interposed between the retainer 9 and the piston 8 and biases the piston 8 toward the flange 4a.
It is selected to be smaller than the diameter a.

On the other hand, the tip of the piston rod 2 is provided with a small diametrical hole 2a whose one end opens on the outer periphery, and a ball 13 is held in the small hole 2a. It is biased and engaged with the annular groove 4b on the inner circumference of the sleeve 4.

Moreover, the small hole 2 is provided on the end surface of the piston rod 2.
A communicating hole 2b is provided here to introduce the gas pressure of the chamber _C2 , and in addition to the spring 12, the gas pressure of the chamber _C2 normally controls the ball 1.
3 engages with the annular groove 4b to prevent the sleeve 4 from moving upward.

Next, the operation of the gas spring configured as described above will be explained.

When the gas spring is at its most extended position and the back door is to be closed, the piston rod 2 descends together with the piston assembly 3, and at this time the check plate 6 receives pressure from the chamber _C2 and closes the communication hole 8a. Since the chamber is closed, the pressure in chamber _C2 becomes even higher.

In this way, the pressure in chamber C ₂ becomes A as shown in Figure 2.
When the point is reached, the piston 8 is moved upward against the repulsive force of the spring 10, and the piston 8
is separated from the check plate 6, the gas in the chamber _C2 moves to the chamber _C1 between them and through the communication hole 8a, and the gas pressure in the chamber _C2 decreases to point B in FIG. Then, the elastic force of the spring 10 becomes effective again, the piston 8 descends, the communication hole 8a is sealed again by the check plate 6, and as the piston rod 2 continues to descend, the pressure in the chamber _C2 rises again. . In this way, the gas pressure, that is, the reaction force exhibits a zigzag curve characteristic as shown in FIG. 3, and a large reaction force acts on the piston 8.

On the other hand, the piston 8 further penetrates into the cylinder 1, and the lower end of the piston 8 is inserted into the annular projection 1a of the cylinder 1.
When this happens, the piston 8 and the sleeve 4 stop moving downward integrally with the piston rod 2, and only the piston rod 2 moves downward, and the check plate 6 opens the communication hole 8a and the ball in the small hole 2a. 13 is pushed into the small hole 2a against the elastic force of the spring 12, and the sleeve 4
The engagement with the annular groove 4b is released.

Such a state is shown at point C in FIG. 2. If the piston rod 2 is further penetrated from this point on, the rod reaction force becomes only the pressure increase corresponding to the volume of penetration of the piston rod 2, and the pressure characteristics change to point D in FIG. leading to.

Next, the case where the piston rod 2 rises will be described. At this time, a pressure drop corresponding to the retracted volume of the piston rod 2 occurs, and the rod reaction force decreases along D'-E in FIG. 2 due to the downwardly acting frictional force. During the withdrawal of the piston rod 2, the piston 8 returns to the position of the check plate 6, but since the check plate 6 is configured to bend downward with a small pressure, the piston 8 returns to the position of the check plate 6.
Almost no pressure rise occurs in C ₁ , and the gas flows through the communication hole 8.
It flows into chamber _C2 through a with almost no resistance, and the rod reaction force returns almost linearly to point E in FIG. In this way, the two-stage switching characteristic of obtaining a gas reaction force sufficiently large for a predetermined stroke from the maximum extension position of the piston rod 2 and reducing the gas reaction force within a shorter stroke allows the gas reaction force to be reduced at the maximum extension position. It is possible to increase the reaction force, prevent the back door from falling at the most open position, and make it easier to open and close the door at other positions.

In addition, in the embodiment, the spring 1
0 can be a disc spring in addition to a coil spring.

As described above in detail, the present invention includes a cylinder whose one end is sealed and filled with working gas, a removable piston rod that extends sealingly through the other end of the cylinder, and a sleeve fitted into the end of the piston rod so as to be slidable in the axial direction; a holding member that holds the sleeve from sliding in the axial direction with a predetermined pressure; a piston that slides in a sealing manner and separates the inside of the cylinder into two upper and lower chambers;
A check plate that is attached to the end of the piston rod and can close the side facing the lower chamber of the communication hole provided in the piston, a spring that biases the piston toward the check plate, and a retainer that locks the spring to the sleeve. , is provided with a locking protrusion that protrudes into the cylinder and restricts the downward position of the piston, and when the piston rod is retracted from the vicinity of the most extended position, the piston rod is retracted according to the gas pressure in the lower chamber and the elastic force of the spring. The communication hole is opened and closed by a check plate to obtain high gas pressure, and when the retracting operation is performed from a predetermined retracting position, the retention by the holding member is released and the piston is raised together with the sleeve, and during subsequent retracting operations, the piston is prevented from entering. By obtaining a gas pressure corresponding to the volume and making the rod reaction force a two-stage characteristic,
When this gas spring is applied to a back door opening/closing assist device, it has the practical advantage of stabilizing the back door in its most open state, and making opening and closing operations smooth and easy in other states. can get.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main parts of the gas spring of the present invention, and FIG. 2 is a gas reaction force characteristic diagram of this gas spring. 1... Cylinder, 1a... Locking protrusion, 2... Piston rod, 4... Sleeve, 6... Check plate, 8... Piston, 8a... Communication hole, 9
... Retainer, 10 ... Spring, 13 ... Ball (holding member), C ₁ , C ₂ ... Upper and lower two chambers.

Claims (1)

[Scope of utility model registration request] A cylinder whose one end is sealed and filled with working gas, a removable piston rod that extends sealingly through the other end of the cylinder, and a sleeve that is fitted into the end of the piston rod so as to be slidable in the axial direction. and a holding member that holds the sleeve from sliding in the axial direction at a predetermined pressure; a piston separated from the chamber; a check plate attached to the end of the piston rod to close the side of the communication hole provided in the piston facing the lower chamber; and a spring biasing the piston toward the check plate. A gas spring comprising: a retainer that locks one end of the spring to the sleeve; and a locking protrusion that projects inside the cylinder and restricts the downward position of the piston.