JP4338800B2 - Air cylinder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air cylinder.
[0002]
[Prior art]
Air cylinders are conventionally used in various mechanical devices for various purposes. When the air cylinder is used, even if the piston position fluctuates, it is devised to give a substantially constant load or a load with a very small fluctuation range to the controlled device. However, in reality, the air cylinder is structurally accompanied by fluctuations in the internal pressure of the cylinder due to fluctuations in the position of the piston, so the actual situation is that the load applied to the controlled device via the piston rod varies. For this reason, conventionally, an air tank is simply provided in a system including an air cylinder as a configuration for controlling fluctuation of the cylinder internal pressure to be substantially constant or within a very small range.
[0003]
[Problems to be solved by the invention]
However, when the air tank is provided, air leaks mainly from between the piston and the cylinder, so that the cylinder internal pressure needs to be constant. As a means for this, generally, an air compressor is used in combination to supply compressed air. However, a new power source is required by using this air compressor together. Therefore, the apparatus is complicated as a whole, and the cost is increased.
[0004]
The present invention has been made in view of the above problems, and enables a simple structure that does not require the use of an air compressor. In addition, even if the piston moves within a predetermined stroke range, the fluctuation of the cylinder internal pressure is substantially reduced. An object of the present invention is to provide an air cylinder that can be kept to a minimum and that can reduce the manufacturing cost.
[0005]
[Means for Solving the Problems]
In order to achieve the object of the present invention, an air cylinder of the present invention corresponding to claim 1 (hereinafter referred to as invention 1) includes a cylinder body, a piston that reciprocates in the cylinder body, and a piston connected to the piston. The cylinder body has an atmospheric pressure in the space only when the piston is stationary at a position where the volume in the space surrounded by the cylinder and the piston is maximized. In the state where the piston slides, the inside of the space is shielded from the outside air , and the space and the outside are not affected by the sliding of the piston. A cylinder part provided with a connecting hole capable of communicating; an air tank formed of a non-extensible and airtight material and having a space sufficiently larger than the cylinder volume inside; An air cylinder provided with a connecting portion for connecting the two spaces through the connecting hole, and a partition wall is provided in the air tank for partitioning into a space that can communicate with the outside and a closed space. The closed space is characterized by a pressure higher than atmospheric pressure.
[0006]
The connecting hole may be provided in the bottom portion that is the lowest point of the cylinder body, but is preferably provided in the side wall of the cylinder body slightly before this lowest point. Moreover, as a partition structure, it is good also as a structure which accommodated the structure which has closed spaces, such as a balloon, in an air tank, or it is good also as a structure which provided the partition which partitions the space in an air tank into two.
[0009]
The operation of the invention 1 will be described below by taking the corresponding embodiment as an example . FIG. 3 is a diagram for explaining the operation of the embodiment according to the configuration of the invention 1, and the operation will be described below with reference to this drawing.
[0010]
First, when the piston is stationary at a position where the volume in the space surrounded by the cylinder main body and the piston is maximized, the air is opened to the vent hole and the atmosphere. The cylinder internal pressure P) is equal to the atmospheric pressure (P ₀ ), and then the cylinder internal pressure P increases as the piston is pushed down. When this cylinder internal pressure P reaches the sealed gas pressure (P ₁ ) in the air tank, the inside of the cylinder and the air tank communicate with each other, the air tank works so that the cylinder internal pressure P does not increase, and even if the piston stroke proceeds, a certain stroke , The cylinder internal pressure P is maintained at a substantially constant pressure. In the configuration in which the connection hole is provided on the side wall of the cylinder body slightly before the lowest point, when the piston passes through the connection hole, the space in the cylinder is disconnected from the air tank, and the cylinder internal pressure P increases rapidly. Thereby, the collision with a piston and a cylinder bottom part is avoided.
[0011]
Further, the length of the piston stroke for keeping the cylinder internal pressure P at a constant pressure can be adjusted by controlling the size and pressure of a closed space that does not communicate with the outside provided in the air tank. For example, when it is desired to lengthen the stroke, the closed space is enlarged or the pressure in the space is further increased.
[0013]
In accordance with the principle described above, the invention 1 has a direction opposite to the moving direction when the piston moves in the direction of increasing the cylinder internal pressure, and the same direction as the returning direction when the piston returns to its initial position. An extremely small and almost constant load can be generated.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
FIG. 1 is a cross-sectional view showing an embodiment of the invention 1, and shows a state where a piston is in an initial position.
[0016]
The air cylinder of the present embodiment is configured by a cylinder portion 10, an air tank portion 30, and a connecting portion 20 that connects them. The cylinder portion 10 includes a cylinder body 1, a piston 2 that reciprocates within the cylinder body 1, and a piston rod 3 that is coupled to the piston 2. The cylinder body 1 is provided with a vent hole 4, and the position thereof is only when the piston 2 is stationary at a position where the volume in the space 11 surrounded by the cylinder body 1 and the piston 2 is maximized. It has a configuration set in a place that communicates with the outside air. Further, the cylinder body 1 is always provided with a connection hole 5 through which the space 11 can communicate with the outside regardless of sliding of the piston 2, and is provided in a side wall portion slightly above the bottom of the cylinder body 1. ing. On the other hand, the air tank portion 30 is formed of a material having non-extensible and airtight properties, and is constituted by an air tank 31 having a space inside and a balloon 32 having a closed space in the air tank 31. The balloon 32 is formed of an airtight material, and a gas having higher atmospheric pressure or a volatile liquid having a low boiling point such as ether is sealed in the closed space. In this embodiment, vinyl is used for the balloon 32. The air tank 31 and the cylinder body 1 are connected by a pipe line 21, and one end of the pipe line 21 is connected to the connection hole 5.
[0017]
The balloon internal pressure is preferably about 1.2 to 1.5 atm. When the balloon internal pressure is 1.2 atmospheres, the piston 2 advances through the cylinder body 1 by about 1/5 stroke. When the balloon internal pressure is 1.5 atmospheres, the piston 2 moves through the cylinder body 1 Air tanks start to work when they have advanced about 3 strokes. These numerical values are obtained by the equation [1], where adiabatic compression is assumed, P is the cylinder internal pressure, V is the volume of the cylinder internal space, and c is the gas constant (≈1.6).
[0018]
PV ^c = const. (Constant) ... [1]
In the present embodiment having the above-described configuration, as shown in FIG. 3, when the volume of the space in the cylinder body 1 is maximum, the space in the cylinder body 1 is equal to the atmospheric pressure. Pushed down, the cylinder pressure rises as shown in (1). When the cylinder pressure exceeds the gas pressure enclosed in the air tank 31, that is, at the point (2), the cylinder body 1 and the air tank 31 communicate with each other so that the cylinder pressure does not increase. Work like (3). Further, when the piston 2 passes through the connection hole 5 and is pushed down, the space 11 in the cylinder body 1 and the air tank 31 are separated, and the cylinder internal pressure rapidly rises as shown in (4). Thereby, the collision between the piston 2 and the bottom of the cylinder body 1 is avoided.
[0019]
Thus, the cylinder internal pressure can be kept constant during the predetermined stroke of the piston 2.
[0020]
In the above embodiment, the air tank portion 30 has a double structure of the air tank 31 and the balloon 32. However, as shown in FIG. 2, the air tank portion 30 includes two airtight diaphragms 33 in the air tank 31. It can also be set as the structure which partitions off into the spaces 35 and 36 and connects the space 31 with the air cylinder main body 1 via the pipe line 21. FIG. In this case, a gas higher than atmospheric pressure or a volatile liquid is sealed in the space 36. Also in this embodiment, the same operation as the previous embodiment is achieved.
[0023]
In this embodiment, a structure in which one cylinder is connected to one air tank is shown. However, the present invention is not limited to this, and a structure (not shown) in which a plurality of cylinders are connected to one air tank may be used. it can.
[0025]
【The invention's effect】
As described above, according to the air cylinder of the first aspect of the present invention, in the configuration in which the cylinder portion and the air tank portion are connected via the connecting portion, the air tank portion is formed of an airtight material, and a space is formed inside. Since the air tank has a partition wall for partitioning into a space that can communicate with the outside and a closed space in the air tank, and the closed space is configured to have a pressure higher than the atmospheric pressure, Thus, it is not necessary to install an air compressor so that gas does not leak from the piston. Thus, a simple structure can be made and the manufacturing costs are reduced. Furthermore, even if the piston moves within a predetermined stroke range, fluctuations in the cylinder internal pressure can be maintained to a minimum.
[0026]
Further, according to the air cylinder of the second aspect of the present invention, a deformable container having airtightness is provided in the cylinder body, and it has non-extensibility and airtightness communicating with the space in the container via a pipeline. Since an air tank formed of a material and having a space inside is provided and the space in the air tank is set to a pressure higher than the atmospheric pressure, a simple structure can be realized and the manufacturing cost can be reduced as in the first aspect. . Further, even if the piston moves within a predetermined stroke range, the same effect can be obtained in that the fluctuation of the cylinder internal pressure is substantially kept to a minimum. Furthermore, the configuration of the invention 2 is advantageous in that a configuration in which a plurality of air cylinders are connected to a single air tank is possible, and the range of usage forms can be expanded.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an embodiment of the present invention. FIG. 2 is a block diagram of another embodiment of the present invention. FIG. 3 is for explaining the operation of the embodiment shown in FIGS. Figure [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Air cylinder part 20 Connection part 30 Air tank part 1 Cylinder main body 2 Piston 3 Piston rod 4 Ventilation hole 5 Connection hole 31 Air tank 32 Balloon 33 Diaphragm

Claims (1)

  A cylinder body, a piston that reciprocates in the cylinder body, and a piston rod connected to the piston, the cylinder body having a volume in a space surrounded by the cylinder and the piston. The air vent is opened to the outside air so that the inside of the space is at atmospheric pressure only when it is stationary at a position where the air pressure reaches the maximum. When the piston slides, the inside of the space is cut off from the outside air. The cylinder portion is provided with a connection hole that allows the space and the outside to communicate with each other regardless of sliding of the piston, and is formed of a non-extensible and airtight material, An air cylinder comprising an air tank having a sufficiently large space compared to a cylinder volume, and a connection part for connecting the two spaces through the connection hole, Air cylinder, the partition wall is provided for partitioning into a space which is closed to the external communicable with space, the closed space is characterized in that it is higher than atmospheric pressure.

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