Switchgear Buffers

Abstract

To provide a buffer for an electrical switchgear that does not need to enhance the rigidity of the housing of an operating device as compared with the prior art, and can perform a high-speed operation in an early stage of a breaking operation and perform damping and stopping in a final stage of the breaking operation.SOLUTION: A buffer for an electrical switchgear includes a cylinder 10 having a bottom surface, a piston 20 which is freely slidably retracted in a cylinder 10 and connected to an opening / closing shaft of the electrical switchgear, a liquid chamber 50 which is defined between the bottom surface and the top surface 23 of the piston 20 and filled with liquid, and counterforce generating means for generating a counterforce that counteracts the internal pressure which the piston 20 receives from the liquid chamber 50 when the piston slides to the bottom surface 24 side of the cylinder 10. The counterforce when the piston 20 in the cylinder 10 is located to be nearer to the bottom side than a predetermined position is smaller than the counterforce when the piston 20 is located on the side opposite to the bottom surface 24 with respect to the predetermined position.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a shock absorber for a switchgear. [Background technology]

[0002] Electric power systems such as substations and power plants are typically equipped with power switchgear. Here, the term "electric power switchgear" refers to a device that turns on and off electric power, such as a circuit breaker or disconnecting switch.

[0003] Patent Document 1 discloses an operating device for a switching device that uses the driving force of a spring to separate or connect the contacts of the switching device. The operating device includes a breaking spring that is primarily used to separate the contacts and a closing spring that is primarily used to connect the contacts. The operating device also includes a camshaft supported by multiple bearing devices, a cam provided on the camshaft, and a main lever with which the cam comes into contact.

[0004] The driving force of the closing spring rotates the cam shaft, which in turn rotates the cam. The main lever comes into contact with the outer circumferential surface of the cam, so that the main lever also moves as the cam rotates. A breaking spring link is connected to the main lever, and a breaking spring is provided on the breaking spring link.

[0005] The main lever is mounted on one side of the opening / closing shaft, and the contact lever is mounted on the other side of the opening / closing shaft. The contact lever is connected by a pin to a contact link, which is a component of a link mechanism connected to the contacts. These mechanisms transmit the driving force of the closing spring to the breaking spring and the contacts of the switching device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-283691 Summary of the Invention

Problems to be Solved by the Invention

[0007] In the operating device of the opening / closing device according to Patent Document 1, at the end stage of the cutoff operation for separating contacts, an oil damper as a shock absorber constantly connected to the opening / closing shaft is provided to attenuate and stop the movement of the mechanism having the main lever. High-speed operation is essential from the initial stage to the middle stage of the cutoff operation. At this time, however, the oil damper becomes a load and hinders high-speed operation. Therefore, in order to achieve high-speed operation from the initial stage to the middle stage of the cutoff operation, it is necessary to increase the rigidity of the cutoff spring so as to cancel the load from the oil damper. Further, as the rigidity of the cutoff spring is increased, when the cutoff spring is displaced by a predetermined displacement amount, it is necessary to increase the force acting on the cutoff spring. Since the force acting from the input spring is transmitted to the cutoff spring by the above mechanism, in order to increase the force acting on the cutoff spring, it is necessary to increase the force generated by the input spring. Therefore, similar to the cutoff spring, it is necessary to increase the rigidity of the input spring. That is, in order to achieve high-speed operation from the initial stage to the middle stage of the cutoff operation, it is necessary to increase the forces generated by both the input spring and the cutoff spring. Subsequently, in order to counteract both forces, it is necessary to increase the rigidity of the housing of the operating device, particularly the housing in which the cutoff spring and the input spring are stored.

[0008] Therefore, as an alternative method, it is conceivable to adopt a structure in which the opening / closing shaft and the oil damper are not constantly connected and are separated from each other. Specifically, from the initial stage to the middle stage of the cutoff operation, the opening / closing lever connected to the opening / closing shaft moves without receiving resistance toward the oil damper, and when entering the end stage of the cutoff operation, the opening / closing lever and the oil damper collide. Thereafter, throughout the end stage of the cutoff operation, the opening / closing lever continues to move while receiving the load from the oil damper. On the other hand, during the input operation, the opening / closing shaft moves in the direction opposite to that during the cutoff operation, that is, in the direction away from the oil damper. As described above, both the opening / closing shaft and the oil damper have a separated structure, and during this input operation, since the opening / closing shaft does not receive the load from the oil damper, the input speed becomes excessively high. For this reason, there is a possibility of failure in locking the opening / closing shaft in the link mechanism during the input operation.

[0009] The present invention aims to provide a shock absorber for an opening / closing device that can operate at high speed in the initial stage of the cutoff operation, with the operating speed decaying and eventually stopping in the final stage of the cutoff operation, without the need to increase the rigidity of the housing of the operating device compared to the prior art.

Means for Solving the Problems

[0010] A shock absorber for an opening / closing device according to an aspect of the present invention is a shock absorber for an opening / closing device, comprising a cylinder having a bottom surface, a piston slidably stored in the cylinder and connected to an opening / closing shaft of the opening / closing device, a liquid chamber defined between the bottom surface and the top surface of the piston and filled with liquid, and a counterforce generating means for generating a counterforce against the internal pressure received by the piston from the liquid chamber when the piston slides toward the bottom surface side of the cylinder. The counterforce when the position of the piston in the cylinder is on the bottom surface side of a predetermined position is smaller than the counterforce when the position of the piston is on the side opposite to the bottom surface of the predetermined position.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view of a shock absorber 1 according to an embodiment of the present invention. [Figure 2] It is an explanatory diagram of the force acting on the shock absorber 1 according to an embodiment of the present invention in the initial stage during the cutoff operation. [Figure 3] It is an explanatory diagram of the force acting on the shock absorber 1 according to an embodiment of the present invention in the final stage during the cutoff operation. [Figure 4] It is an explanatory diagram of the distance to the limit of the movable range of the contact point and the time-dependent change of the force acting on the opening / closing shaft in each of an oil damper as the prior art and the shock absorber 1 according to an embodiment of the present invention. [Figure 5] It is an explanatory diagram of the force acting on the shock absorber 1 according to an embodiment of the present invention in the initial stage during the insertion operation. [Figure 6] It is an explanatory diagram of the force acting on the shock absorber 1 according to an embodiment of the present invention in the final stage during the insertion operation. [Figure 7] 10 is a diagram showing the relationship between the spring stroke and the closing spring force and the breaking spring force in the prior art and the present invention. FIG. [Figure 8] 1 is a cross-sectional view of a shock absorber 1A according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] A shock absorber according to an embodiment will be described below with reference to the drawings. Note that in each drawing, the dimensions and scale of each part are appropriately different from those of the actual parts. Furthermore, the embodiments described below are preferred specific examples, and therefore various technically preferable limitations are applied, but the scope of the present disclosure is not limited to these forms unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0013] 1. First embodiment Hereinafter, a shock absorber 1 according to a first embodiment will be described with reference to FIGS.

[0014] 1.1 Configuration of the first embodiment FIG. 1 is a cross-sectional view of a shock absorber 1 according to a first embodiment. The shock absorber 1 is a device for cushioning the opening and closing shaft of a switchgear. The switchgear is used in an electric power system in an electric power facility such as a substation or a power plant, and controls the on / off of electric power. The shock absorber 1 includes a cylinder 10, a piston 20, a coil spring 30, a spring support 40, a liquid chamber 50, and an air chamber 60. The shock absorber 1 is installed in oil O stored in an oil tank 2. As shown in FIG. 1, the piston 20 is slidably housed in the cylinder 10.

[0015] The cylinder 10 has a bottom surface portion 11, a side surface portion 12, and a top surface portion 13. The top surface portion 13 is the end of the cylinder 10 opposite the bottom surface portion 11, i.e., the end on the opening / closing axis side. The cylinder 10 is preferably cylindrical with an axis connecting the center of the bottom surface portion 11 and the center of the top surface portion 13 as its central axis. However, the shape of the cylinder 10 according to this embodiment is not limited to a cylindrical shape. For example, the cylinder 10 may be a rectangular tube with the above-mentioned axis as its central axis.

[0016] The piston 20 has a top portion 21 and a shaft portion 22. The top portion 21 also has a top surface 23 that faces the bottom surface 11 of the cylinder 10, a bottom surface 24 on the opposite side of the top portion 21 from the top surface 23, and a side portion 25 that contacts the side surface 12 of the cylinder 10. The side portion 25 protrudes from the bottom surface 24 toward the shaft portion 22, thereby forming a space between the bottom surface 24 and the shaft portion 22.

[0017] A shaft portion 22 of the piston 20 is connected to an opening / closing shaft of the switchgear. During a power-off operation to cut off power in the switchgear, the piston 20 is pushed into the cylinder 10. On the other hand, during a power-on operation to turn on power in the switchgear, the piston 20 is pulled out of the cylinder 10.

[0018] In the following description, the Z axis is assumed. The Z axis is common to all the drawings exemplified in the following description. As exemplified in FIG. 1, one direction along the Z axis as viewed from an arbitrary point is referred to as the Z1 direction, and the direction opposite to the Z1 direction is referred to as the Z2 direction. The Z axis direction is a direction that includes both the Z1 direction and the Z2 direction.

[0019] In addition, in the Z-axis direction, the direction toward the top surface portion 13 side as viewed from the bottom surface portion 11 of the cylinder 10 is defined as the Z1 direction, and the direction toward the bottom surface portion 11 side is defined as the Z2 direction. That is, during a shutoff operation, the piston 20 slides in the Z2 direction. On the other hand, during a closing operation, the piston 20 slides in the Z1 direction. Furthermore, the top portion 21 of the piston 20 is located in the Z2 direction relative to the shaft portion 22.

[0020] An inlet / outlet hole 14 for oil O is provided in the bottom surface 11 of the cylinder 10. In addition, inlet / outlet holes 15A to 15C for oil O are arranged in this order in the Z2 direction in the side surface 12 of the cylinder 10. When the piston 20 moves in the Z1 direction, the oil O passes through the inlet / outlet holes 14 and 15A to 15C, thereby filling a liquid chamber 50 defined between the bottom surface 11 of the cylinder 10 and the top surface 23 of the piston 20. When the piston 20 moves in the Z2 direction, the oil O passes through the inlet / outlet holes 14 and 15A to 15C, thereby being discharged from the liquid chamber 50 to the outside of the cylinder 10. Note that the liquid filling the liquid chamber 50 is not limited to oil O, and any liquid may be used.

[0021] Because the inlet / outlet hole 14 is provided in the bottom surface 11 of the cylinder 10, even if the top 21 of the piston 20 moves close to the bottom surface 11 of the cylinder 10, the oil O remaining in the liquid chamber 50 is discharged to the outside of the cylinder 10 through the inlet / outlet hole 14. Therefore, the piston 20 can move in the Z2 direction relative to the cylinder 10 until the top 21 and the bottom surface 11 are almost in contact with each other.

[0022] Furthermore, the area of the inlet / outlet hole 15A is larger than the area of the inlet / outlet hole 15B, which is larger than the area of the inlet / outlet hole 15B. Specifically, the diameter of the inlet / outlet hole 15A is larger than the diameter of the inlet / outlet hole 15B, which is larger than the diameter of the inlet / outlet hole 15C. That is, the flow path resistance of the inlet / outlet hole 15C is larger than the flow path resistance of the inlet / outlet hole 15B, which is larger than the flow path resistance of the inlet / outlet hole 15B. Therefore, as the piston 20 moves in the Z2 direction, the piston 20 receives a greater internal pressure from the oil O in the liquid chamber 50. Therefore, a greater damping effect on the shutoff operation can be obtained at the end of the shutoff operation. Here, the "damping effect" refers to a decrease in the movement speed of the piston 20 in the Z2 direction during the shutoff operation.

[0023] In this specification, the inlet / outlet hole 15B may be referred to as the "first hole", and the inlet / outlet hole 15A may be referred to as the "second hole". On the other hand, the inlet / outlet hole 15C may be referred to as the "first hole", the inlet / outlet hole 15B may be referred to as the "second hole", and the inlet / outlet hole 15A may be referred to as the "third hole".

[0024] Furthermore, the distance between the inlet / outlet hole 15A and the inlet / outlet hole 15B is larger than the distance between the inlet / outlet hole 15B and the inlet / outlet hole 15C. Therefore, at the end stage of the blocking operation, it is possible to accelerate the attenuation effect on the blocking operation. The specific content of the "end stage" of the blocking operation will be described later.

[0025] In addition, air vent holes 16A and 16B are provided in the top surface portion 13 of the cylinder 10. When the piston 20 moves in the Z2 direction, air passes through the air vent holes 16A and 16B, filling the air chamber 60 defined between the top portion 21 and the shaft portion 22 of the piston 20 and the top surface portion 13 of the cylinder 10. When the piston 20 moves in the Z1 direction, air is discharged from the air chamber 60 to the outside of the cylinder 10 through the air vent holes 16A and 16B. Note that the air chamber 60 is not limited to being filled with air, and may be any gas or liquid.

[0026] The coil spring 30 is stored in the air chamber 60. The coil spring 30 expands and contracts in the Z-axis direction. The coil spring 30 is supported by the spring support 40. The spring support 40 includes a first portion 41 fixed to the top surface portion 13 of the cylinder 10 and a second portion 42 that slides in the Z-axis direction with respect to the first portion 41. The first portion 41 is a cylindrical member. The shaft portion 22 of the piston 20 moves in the Z-axis direction while being in contact with the inner peripheral surface of the first portion 41. The second portion 42 is a cylindrical member having a larger diameter than the first portion 41 and surrounds the first portion 41. The first end E1 of the coil spring 30 is fixed to the top surface portion 13. The second end E2 of the coil spring 30 is fixed to the second portion 42. More specifically, a flange portion 46 that projects outward from the outer peripheral surface is formed at the end portion of the second portion 42 in the Z2 direction. The coil spring 30 is supported between the flange portion 46 and the top surface portion 13. Note that the second end E2 is the end portion of the coil spring 30 on the side opposite to the first end E1. Thereby, the coil spring 30 expands and contracts in the Z-axis direction in accordance with the sliding of the second portion 42 with respect to the first portion 41.

[0027] Note that the inner peripheral surface of the side surface portion 12 of the cylinder 10 and the outer peripheral surface of the side portion 25 of the piston 20 are in a sealed state so that the oil O does not leak from the liquid chamber 50 to the air chamber 60.

[0028] Further, a first protrusion 44 is provided at the end of the first portion 41 in the Z2 direction. The first protrusion 44 is an annular portion with a predetermined width that projects outward from the outer peripheral surface of the first portion 41 over the entire circumference. Also, a second protrusion 45 is provided at the end of the second portion 42 in the Z1 direction. The second protrusion 45 is an annular portion with a predetermined width that indents inward from the inner peripheral surface of the first portion 41 over the entire circumference. The outer diameter of the first protrusion 44 is larger than the inner diameter of the second protrusion 45. Therefore, when the spring support 40 extends to a predetermined length, the first protrusion 44 and the second protrusion 45 engage with each other. Due to this engagement, the spring support 40 only extends to a predetermined length. That is, the second portion 42 of the spring support 40 can only move to a predetermined position in the Z2 direction. As described above, since the first end E1 of the coil spring 30 is fixed to the top surface portion 13 and the second end E2 is fixed to the second portion 42, the coil spring 30 only extends to a predetermined length in a state where the first protrusion 44 and the second protrusion 45 are engaged with each other.

[0029] In addition, in the present embodiment, the second portion 42 of the spring support 40 is separated and independent from the top portion 21 of the piston 20. Also, in a state where the first protrusion 44 and the second protrusion 45 are engaged, it is preferable that the coil spring 30 is in a compressed state. However, for example, in this state, the coil spring 30 may be in a natural length state.

[0030] Next, with reference to FIGS. 2 to 4, the force acting on the shock absorber 1 during the cutoff operation will be described. FIG. 2 is an explanatory diagram of the force acting on the shock absorber 1 at the beginning of the cutoff operation. FIG. 3 is an explanatory diagram of the force acting on the shock absorber 1 at the end of the cutoff operation. FIG. 4 is an explanatory diagram of the change over time of the distance to the limit of the movable range of the contact point and the force acting on the opening and closing shaft in each of the oil damper as a prior art and the shock absorber 1 according to the present embodiment.

[0031] Here, the "beginning stage" during the cutoff operation means the stage in which the piston 20 moves from the end point where the piston 20 is farthest from the bottom surface portion 11 of the cylinder body 10 to the middle of the movable range toward the bottom surface portion 11 within the movable range of the piston 20. The "middle of the movable range" refers to the position where the extension of the spring support 40 stops and the contact between the second portion 42 of the spring support 40 and the top portion 21 of the piston 20 is released. On the other hand, the "end stage" during the cutoff operation means the stage in which the piston 20 moves from the middle of the movable range, where the contact between the second portion 42 of the spring support 40 and the top portion 21 of the piston 20 is released, to the position where it contacts the bottom surface portion 11 of the cylinder body 10.

[0032] As shown in FIG. 2, during the cutoff operation, the piston 20 moves in the Z2 direction by receiving the cutoff spring force B of the cutoff spring connected to the opening / closing shaft of the opening / closing device from the opening / closing shaft in the Z2 direction. Further, as the piston 20 moves in the Z2 direction, the piston 20 receives the reaction force I due to the internal pressure from the oil O filling the liquid chamber 50 in the Z1 direction. Note that the magnitude of this reaction force I is proportional to the square of the moving speed of the piston 20 and inversely proportional to the square of the total opening area of the oil inlet / outlet holes 14 and 15A to 15C. This reaction force I due to the internal pressure acts in the direction of suppressing the cutoff speed. Here, the "cutoff speed" refers to the moving speed at which the piston 20 moves in the Z2 direction during the cutoff operation.

[0033] In the beginning stage during the cutoff operation, the first protrusion 44 and the second protrusion 45 of the spring support 40 are not engaged, and the spring support 40 has not fully extended. The coil spring 30 supported by the spring support 40 is in a compressed state, and the second portion 42 of the spring support 40 to which the second end E2 of the coil spring 30 is fixed is in contact with the bottom surface 24 of the top portion 21 of the piston 20. For this reason, the spring force F generated by the compression of the coil spring 30 acts on the piston 20 in the Z2 direction. Note that in the beginning stage during the cutoff operation, as the liquid chamber 50 shrinks due to the movement of the piston 20, the oil O in the liquid chamber 50 is discharged outside the cylinder body 10 through the oil inlet / outlet holes 14 and 15A to 15C.

[0034] By applying the spring force F of the coil spring 30 to the piston 20, it is possible to reduce the cutoff spring force B required to move the piston 20 at an appropriate speed. Further, the driving force during the cutoff operation burdens the force for moving the piston 20 during the cutoff operation not only with the cutoff spring force B but also with both the cutoff spring force B and the spring force F of the coil spring 30. For this reason, the strength required for the housing that supports the cutoff spring in the opening / closing device is reduced.

[0035] As shown in FIG. 3, when the first protrusion 44 and the second protrusion 45 of the spring support 40 engage with each other and the spring support 40 stops extending, the cutoff operation transitions to the final stage. Although the coil spring 30 supported by the spring support 40 is in a compressed state, the contact between the second portion 42 of the spring support 40 to which the second end E2 of the coil spring 30 is fixed and the bottom surface 24 of the top portion 21 of the piston 20 is eliminated. For this reason, the spring force F generated by the coil spring 30 does not act on the piston 20. That is, when the position of the piston 20 in the cylinder 10 is on the bottom surface portion 11 side from the position where the spring support 40 stops extending, the value of the spring force F as the resistance force against the reaction force I due to the internal pressure becomes zero.

[0036] Further, as the piston 20 moves in the Z2 direction, the inlet / outlet holes 15A, 15B, and 15C provided in the side surface portion 12 of the cylinder 10 are closed in this order by the piston 20. Also, as described above, the hole areas of the inlet / outlet holes 15A, 15B, and 15C become smaller in this order. Furthermore, the distance between the inlet / outlet hole 15C and the inlet / outlet hole 15B is smaller than the distance between the inlet / outlet hole 15B and the inlet / outlet hole 15A. As a result, a gradually increasing resistance is applied to the discharge of the oil O from the liquid chamber 50. For this reason, at the final stage of the cutoff operation, the reaction force I due to the internal pressure that the piston 20 receives from the oil O filling the liquid chamber 50 becomes larger compared to the initial stage of the cutoff operation and becomes even larger as the piston 20 moves in the Z2 direction.

[0037] As described above, when the spring support 40 stops extending, the action of the spring force F generated by the coil spring 30 on the piston 20 stops. Also, the reaction force I of the piston 20 due to the internal pressure received from the oil O becomes greater as the piston 20 moves in the Z2 direction. For this reason, the speed of the piston 20 decreases acceleratively, and finally, the piston 20 contacts the bottom surface portion 11 and stops.

[0038] For example, as disclosed in the above Patent Document 1, an oil damper piston as a shock absorber according to the prior art is constantly connected to an opening and closing shaft. Also, the piston 20 of the shock absorber 1 according to the present embodiment is connected to the opening and closing shaft of the opening and closing device. During the cutoff operation, as the opening and closing shaft of the opening and closing device rotates, the contact connected to the opening and closing shaft moves. The contact is connected to the opening and closing shaft via a contact lever and a contact link. In the example shown in FIG. 4, as the cutoff operation progresses, the contact moves to the limit of the movable range. When the shock absorber 1 according to the present embodiment is used, in the initial stage of the cutoff operation, the piston 20 is urged in the Z2 direction by the spring force F of the compressed coil spring 30, so that the piston 20 can be moved at a sufficient speed. For this reason, the shock absorber 1 according to the present embodiment can operate at high speed in the initial stage during the cutoff operation. Therefore, as shown in the graph of FIG. 4, compared with the case of using a conventional oil damper, the contact starts to approach the limit of the movable range from an earlier stage. That is, when the shock absorber 1 according to the present embodiment is used, the moving speed of the contact becomes faster compared with the case of using a conventional oil damper.

[0039] Also, in the oil damper according to the prior art and the liquid chamber 50 provided in the shock absorber 1 according to the present embodiment, a reaction force against the piston is generated that is proportional to the square of the moving speed of the piston and inversely proportional to the square of the opening area of the oil inlet and outlet holes. Therefore, when using the oil damper according to the prior art, as shown in FIG. 4, a reaction force due to the internal pressure of the oil damper is generated from the beginning of the cutoff operation, and the reaction force rapidly increases at the end of the cutoff operation. On the other hand, in the example shown in FIG. 4, when using the shock absorber 1 according to the present embodiment, at the beginning of the cutoff operation, the reaction force I due to the internal pressure of the liquid chamber 50 is reduced by the spring force F of the preloaded coil spring 30, enabling high-speed operation. On the other hand, after a predetermined time has elapsed since the two contacts are opened, that is, after the contact connected to the opening and closing shaft has separated from the fixed contact facing the contact, and after the spring support 40 and the bottom surface 24 of the piston 20 are separated, the force acting on the opening and closing shaft, that is, the reaction force I against the piston 20, rapidly increases at the end of the cutoff operation.

[0040] Next, with reference to FIGS. 5 and 6, the force acting on the shock absorber 1 during the insertion operation will be described. FIG. 5 is an explanatory diagram of the force acting on the shock absorber 1 at the beginning of the insertion operation. FIG. 6 is an explanatory diagram of the force acting on the shock absorber 1 at the end of the insertion operation.

[0041] Here, the "beginning" of the insertion operation refers to the stage where the piston 20 moves from the position in contact with the bottom surface portion 11 of the cylinder 10 to the middle of the movable range toward the end point farthest from the bottom surface portion 11 of the cylinder 10. This "middle of the movable range" refers to the position where the second portion 42 of the spring support 40 and the top portion 21 of the piston 20 come into contact and the contraction of the spring support 40 begins. On the other hand, the "end" of the insertion operation refers to the stage where the piston 20 moves from the middle of the movable range, the position where the contact between the second portion 42 of the spring support 40 and the top portion 21 of the piston 20 starts, to the end point farthest from the bottom surface portion 11 of the cylinder 10.

[0042] As shown in Fig. 5, during the insertion operation, the piston 20 receives a force D, which is the difference between the insertion spring force and the cutoff spring force connected to the opening / closing shaft of the opening / closing device, in the Z1 direction from the opening / closing shaft of the opening / closing device, and thus moves in the Z1 direction. Further, as the piston 20 moves in the Z1 direction, the piston 20 receives a reaction force I due to the internal pressure from the oil O filling the liquid chamber 50 in the Z2 direction. This reaction force I due to the internal pressure acts in a direction to suppress the insertion speed. Here, the "insertion speed" refers to the speed at which the piston 20 moves in the Z1 direction during the insertion operation.

[0043] In the initial stage of the insertion operation, the first protrusion 44 and the second protrusion 45 of the spring support 40 are engaged, and the spring support 40 is in a state where its elongation has stopped. Although the coil spring 30 supported by the spring support 40 is in a compressed state, the second part 42 of the spring support 40 to which the second end E2 of the coil spring 30 is fixed and the bottom surface 24 of the top portion 21 of the piston 20 are not in contact. Therefore, the spring force F generated by the coil spring 30 does not act on the piston 20. In addition, in the initial stage of the insertion operation, due to the expansion of the liquid chamber 50 accompanying the movement of the piston 20, the oil O flows into the liquid chamber 50 from outside the cylinder 10 through the inlet / outlet holes 14 and 15C.

[0044] As shown in FIG. 6, at the end of the charging operation, as the piston 20 moves in the Z1 direction, the bottom surface 24 comes into contact with the second portion 42 of the spring support 40. Further, as the piston 20 moves in the Z1 direction, the engagement between the first protrusion 44 and the second protrusion 45 is released, and due to the reaction force from the piston 20, the second portion 42 moves in the Z1 direction relative to the first portion 41 against the biasing force in the Z2 direction by the coil spring 30. The first protrusion 44 and the second protrusion 45 of the spring support 40 are not engaged, and the spring support 40 has not fully extended. The coil spring 30 supported by the spring support 40 is in a compressed state, and the second portion 42 of the spring support 40 to which the second end E2 of the coil spring 30 is fixed is in contact with the bottom surface 24 of the top portion 21 of the piston 20. Therefore, the spring force F generated by the compression of the coil spring 30 acts on the piston 20 in the Z2 direction. At the end of the charging operation, oil O flows into the liquid chamber 50 from outside the cylinder 10 through the inlet / outlet holes 14 and 15A - 15C.

[0045] Also, as the piston 20 moves in the Z1 direction, the inlet / outlet holes 15C, 15B, and 15A provided in the side surface portion 12 of the cylinder 10 are opened in this order by the piston 20. Also, as described above, the hole areas of the inlet / outlet holes 15C, 15B, and 15A increase in this order. Further, the distance between the inlet / outlet hole 15A and the inlet / outlet hole 15B is larger than the distance between the inlet / outlet hole 15B and the inlet / outlet hole 15C.

[0046] At the end of the charging operation, the action of the spring force F generated by the coil spring 30 on the piston 20 begins. Also, this spring force F increases as the coil spring 30 is compressed. Due to this spring force F, the charging speed is rapidly decelerated, creating a time margin for locking the opening / closing shaft in the link mechanism such as the shut-off latch, and it becomes possible to prevent the failure of locking.

[0047] FIG. 7 is a diagram showing the relationship between the spring length, the input spring force, and the cut-off spring force when using an oil damper according to the prior art and when using the shock absorber 1 according to the present embodiment. In the left diagram of FIG. 7, the change in the spring force of the cut-off spring and the input spring from compression to extension when using an oil damper according to the prior art is shown. On the other hand, in the right diagram of FIG. 7, the change in the cut-off spring force from compression to extension when the coil spring 30 acts as a cut-off spring in the shock absorber 1 according to the present embodiment, and the change in the input spring force from compression to extension when acting as a counteraction to the input spring are shown.

[0048] Also, in both diagrams, the acting force required for an ideal cut-off operation considering the counteraction to the reaction force of the prior art oil damper is shown. As described above, in the initial stage of the cut-off operation, it operates at high speed, while in the final stage of the cut-off operation, the speed of the piston decreases, and finally, it is ideal to stop. Therefore, in FIG. 7, the graph of the acting force from the ideal cut-off spring to the piston has a stepped shape such that the acting force is low when the cut-off spring is in the extended state and high when it is in the compressed state to counteract the reaction force I due to the internal pressure of the liquid chamber 50.

[0049] The spring force of the cut-off spring designed considering the reaction force of the prior art oil damper changes with a constant slope as shown in the left diagram of FIG. 7, and in order to achieve a high-speed cut-off, it does not take a value greater than the value shown by the stepped line as the ideal acting force. Therefore, it becomes a straight line passing through point A in the left diagram. For this reason, the cut-off spring force in the hatched area in the left diagram of FIG. 7 becomes excessive.

[0050] On the other hand, when using the shock absorber 1 according to the present embodiment, since the coil spring 30 assists the cut-off spring force in the hatched area in the right diagram of FIG. 7, the cut-off spring force can be a line that matches the lower step of the stepped line indicating the ideal acting force.

[0051] 7, when the shock absorber 1 according to this embodiment is used, the reaction force I due to the internal pressure of the liquid chamber 50 during the closing operation is smaller than that of the conventional technology, but it is still necessary to compress the coil spring 30. Therefore, when the shock absorber 1 according to this embodiment is used, the straight line drawn by the spring force of the coil spring 30 as the closing spring has the same slope as the spring force of the closing spring designed in consideration of the reaction force of the oil damper of the conventional technology.

[0052] 1.2 Effects of the First Embodiment The shock absorber 1 according to this embodiment includes a cylinder 10 having a bottom surface 11, and a piston 20 slidably housed in the cylinder 10 and connected to an opening / closing shaft of an opening / closing device. The shock absorber 1 also includes a fluid chamber 50 defined between the bottom surface 11 and a top surface 23 of the piston 20 and filled with oil O. The shock absorber 1 also includes a coil spring 30 that generates a spring force F that counteracts the internal pressure that the piston 20 receives from the fluid chamber 50 when the piston 20 slides toward the bottom surface 11 of the cylinder 10. Here, the spring force F is an example of a "counterforce" that counteracts the internal pressure, and the coil spring 30 is an example of a "counterforce generating means" that generates the "counterforce." The counterforce generated when the piston 20 in the cylinder 10 is closer to the bottom surface 11 than a predetermined position is smaller than the counterforce generated when the piston 20 is closer to the top surface 13 than the predetermined position.

[0053] The piston 20, which is connected to the opening / closing shaft, is constantly subjected to internal pressure from the fluid chamber 50, while also being subjected to a counter force against the internal pressure. This counter force varies depending on the position of the piston 20. Specifically, the counter force when the piston 20 is closer to the bottom surface 11 of the cylinder 10 than the predetermined position is smaller than the counter force when the piston 20 is closer to the top surface 13 of the cylinder 10 than the predetermined position. This allows the piston 20 to operate at high speed in the early stage of its movable range, when it moves from the end point farthest from the bottom surface 11 of the cylinder 10 to the predetermined position toward the bottom surface 11. On the other hand, the piston 20 can stop damping in the final stage, when it moves from the middle of its movable range to a position where it contacts the bottom surface 11 of the cylinder 10.

[0054] Also, when the position of the piston 20 in the cylinder 10 is on the bottom surface portion 11 side rather than the predetermined position, the reaction force becomes zero.

[0055] According to this configuration, while the cutoff operation is in the final stage, it is always possible to make the force acting on the piston 20 only the internal pressure from the liquid chamber 50. Thereby, it becomes possible to obtain a higher damping effect against the cutoff operation.

[0056] Further, in the present embodiment, as the reaction force generating means, a coil spring 30 stored in the space between the bottom surface 24 of the piston 20 and the top surface portion 13 in the cylinder 10 and expanding and contracting in the sliding direction of the piston 20 is used.

[0057] According to this configuration, it becomes possible to realize the reaction force generating means with a smaller number of parts as compared with the case where the reaction force generating means is realized using other methods.

[0058] Further, in the present embodiment, the shock absorber 1 further includes a spring support 40 that extends in the expansion and contraction direction of the coil spring 30 and supports the coil spring 30 while extending in accordance with the sliding of the piston 20. The spring support 40 includes a first portion 41 fixed to the cylinder 10 and a second portion 42 that slides with respect to the first portion 41. Also, the first end of the coil spring 30 is fixed to the top surface portion 13, the second end of the coil spring 30 is fixed to the second portion 42, and first protrusions 44 and second protrusions 45 that engage with each other are provided on each of the first portion 41 and the second portion 42.

[0059] According to this configuration, the movement of the coil spring 30 is guided by the spring support 40. This prevents the coil spring 30 from bending in a direction intersecting the longitudinal direction of the piston 20, and consequently prevents the magnitude of the counter force generated by the coil spring 30 from differing from that assumed at the time of design. Furthermore, by providing the first protrusion 44 and the second protrusion 45 on the spring support 40, the spring support 40 extends only to a predetermined position, and it becomes possible to eliminate the counter force when the position of the piston 20 in the cylinder 10 is closer to the bottom surface 11 than the predetermined position.

[0060] Furthermore, when the piston 20 slides toward the bottom surface 11 of the cylinder 10, the spring support 40 and the coil spring 30 extend until the position of the piston 20 reaches a predetermined position, and when the position of the piston 20 passes the predetermined position, the spring support 40 and the coil spring 30 stop extending.

[0061] According to this configuration, when the piston 20 passes a predetermined position, the extension of the spring support 40 stops, and the piston 20 and the cylinder 10 are separated. As a result, the spring force F, which reduces the reaction force I due to the internal pressure from the liquid chamber 50 that the piston 20 has been receiving, is no longer transmitted to the piston 20, and only the reaction force I due to the internal pressure from the liquid chamber 50 acts on the piston 20. As a result, a damping effect is generated against the blocking operation at the end of the blocking operation.

[0062] Furthermore, when the spring support 40 stops expanding, the coil spring 30 is in a compressed state.

[0063] According to this configuration, when the spring support 40 is fully extended, the coil spring 30 is in a compressed state, so that during the insertion operation, the insertion speed can be suddenly decelerated by the collision between the piston 20 and the fully extended spring support 40.

[0064] Further, a first inlet / outlet hole 15C and a second inlet / outlet hole 15B through which oil O enters and exits the liquid chamber 50 are provided at different positions in the axial direction of the cylinder 10 on the side surface of the cylinder 10. Further, when the piston 20 is in the first position, the first inlet / outlet hole 15C and the second inlet / outlet hole 15B are opened, and when the piston 20 is in the second position, the first inlet / outlet hole 15C is opened and the second inlet / outlet hole 15B is blocked by the piston 20. Further, the area of the first inlet / outlet hole 15C is smaller than the area of the second inlet / outlet hole 15B.

[0065] According to this configuration, the flow path resistance of the first inlet / outlet hole 15C is larger than the flow path resistance of the second inlet / outlet hole 15B. Therefore, when the first inlet / outlet hole 15C is opened and the second inlet / outlet hole 15B is blocked, compared with the case where both the first inlet / outlet hole 15C and the second inlet / outlet hole 15B are opened, the piston 20 will receive a significantly larger internal pressure. Therefore, at the end of the cutoff operation, it is possible to obtain a greater damping effect on the cutoff operation.

[0066] Further, a first inlet / outlet hole 15C, a second inlet / outlet hole 15B, and a third inlet / outlet hole 15A through which oil O enters and exits the liquid chamber 50 may be provided at different positions in the axial direction of the cylinder 10 on the side surface of the cylinder 10. Further, when the piston 20 is in the first position, the first inlet / outlet hole 15C, the second inlet / outlet hole 15B, and the third inlet / outlet hole 15A may be opened. When the piston 20 is in the second position, the first inlet / outlet hole 15C and the second inlet / outlet hole 15B may be opened, and the third inlet / outlet hole 15A may be blocked by the piston 20. When the piston 20 is in the third position, the first inlet / outlet hole 15C may be opened, and the second inlet / outlet hole 15B and the third inlet / outlet hole 15A may be blocked by the piston 20. Further, the distance between the first inlet / outlet hole 15C and the second inlet / outlet hole 15B may be smaller than the distance between the second inlet / outlet hole 15B and the third inlet / outlet hole 15A.

[0067] According to this configuration, at the end of the cutoff operation, it is possible to accelerate the increase of the damping effect on the cutoff operation.

[0068] 2. Second Embodiment Hereinafter, with reference to FIG. 8, the shock absorber 1A according to the second embodiment will be described. For the sake of simplicity of explanation hereinafter, the same reference numerals are used for the same components in the shock absorber 1A according to the second embodiment and the shock absorber 1 according to the first embodiment, and the description of their functions is basically omitted. Also, mainly, the differences between the shock absorber 1A according to the second embodiment and the shock absorber 1 according to the first embodiment will be described.

[0069] 2.1 Configuration of the Second Embodiment FIG. 8 is a cross-sectional view of the shock absorber 1A according to the second embodiment. Different from the shock absorber 1, the shock absorber 1A includes a spring support 40A instead of the spring support 40. The spring support 40A includes a first portion 41A and a second portion 42A. The first portion 41A is a cylindrical member. The shaft portion 22 of the piston 20 moves in the Z-axis direction while being in contact with the inner peripheral surface of the first portion 41A. The second portion 42A is a cylindrical member having a larger diameter than the first portion 41A and surrounds the first portion 41A. At the end portion in the Z2 direction of the second portion 42A, a flange portion 46A that projects outward from the outer peripheral surface is formed. The flange portion 46A of the second portion 42A is connected to the top portion 21 of the piston 20 at the bottom surface 24. Thereby, the second portion 42A slides inside the cylinder 10 together with the top portion 21 of the piston 20.

[0070] Further, the first portion 41A includes a first protrusion 44A. The second portion 42A includes a second protrusion 45A. In the example shown in FIG. 8, the first protrusion 44A and the second protrusion 45A are engaged in a state where the top portion 21 of the piston 20 is in contact with the bottom surface portion 11 of the cylinder 10. However, the embodiments of the present invention are not limited to this. Until the top portion 21 of the piston 20 reaches the position in contact with the bottom surface portion 11 of the cylinder 10, the second portion 42A may slide together with the top portion 21 of the piston 20. For example, the first portion 41A may not include the first protrusion 44A and the second portion 42A may not include the second protrusion 45A.

[0071] Also, in the present embodiment, the first end E1 of the coil spring 30 is fixed to the top surface portion 13. On the other hand, unlike the first embodiment, the second end E2 of the coil spring 30 is not fixed to the second portion 42 and has a structure separated from each other. In the shock absorber 1 according to the first embodiment, when the piston 20 moves to a predetermined position, the first protrusion 44 and the second protrusion 45 engage with each other, and the extension of the spring support 40 stops. As a result, the second portion 42 of the spring support 40 and the top portion 21 of the piston 20 are separated, and the spring force F of the coil spring 30 does not act on the piston 20. On the other hand, in the present embodiment, when the piston 20 moves to a predetermined position, the coil spring 30 becomes the natural length, and the contact between the second end E2 of the coil spring 30 and the second portion 42 is eliminated, so that the spring force F of the coil spring 30 does not act on the piston 20.

[0072] 2.2 Effects Exhibited by the Second Embodiment In the shock absorber 1A according to the present embodiment, the flange portion 46A of the spring support 40 is connected to the piston 20.

[0073] In a configuration where the piston 20 and the spring support 40 are separated, the piston 20 and the spring support 40 collide during the insertion operation. When the configuration is such that the piston 20 and the spring support 40 collide, it is necessary to increase the rigidity of the piston 20 and the spring support 40 as compared with a configuration where they do not collide. On the other hand, in the configuration of the present invention, since the piston 20 and the spring support 40A are connected, the impact can be suppressed. Therefore, there is no need to increase the rigidity of the piston 20 and the spring support 40 as compared with a configuration where the piston 20 and the spring support 40 collide.

[0074] Further, the coil spring 30 becomes the natural length when the position of the piston 20 in the cylinder 10 reaches a predetermined position.

[0075] According to this configuration, when the coil spring 30 returns to its natural length, the spring force F that counteracts the reaction force I from the internal pressure in the liquid chamber 50 received by the piston 20 no longer acts on the piston 20, and only the internal pressure from the liquid chamber 50 acts on the piston 20. As a result, at the end stage of the cutoff operation, a damping effect on the cutoff operation will occur.

[0076] 4. Modifications The present disclosure is not limited to the embodiments illustrated above. Specific modification modes are exemplified below.

[0077] 4.1 Modification 1 In the above embodiment, the reaction force that counteracts the internal pressure received by the piston 20 from the liquid chamber 50 was generated by the coil spring 30. However, the reaction force generating means in the embodiments of the present invention is not limited to the coil spring 30. For example, instead of the coil spring 30, a reaction force may be generated by supplying an electric current whose magnitude changes depending on the position of the piston 20 to electromagnetic means. For example, an actuator using a solenoid (coil) is exemplified as the electromagnetic means. Specifically, the electromagnetic force generated by supplying an electric current to the coil may act on the piston formed of a magnetic material as a reaction force. Alternatively, for example, by supplying compressed air to the air chamber 60 with a pump or the like, a reaction force may be generated.

[0078] By using electromagnetic means or means using pneumatic pressure as the reaction force generating means, it is possible to reduce the risk of material deterioration due to metal fatigue that occurs when using a spring.

[0079] As understood from the above examples, "reaction force" means the force that opposes the internal pressure received by the piston from the liquid chamber during the process of the cylinder approaching the bottom surface, and is a comprehensive concept including various forces such as electromagnetic force or pneumatic pressure in addition to the spring force F. Further, "reaction force generating means" is an arbitrary mechanism that generates the "reaction force" described above, and the mechanism or specific configuration for generating the reaction force is not a concern.

[0080] 4.2 Modification 2 In the above-described embodiment, the sliding direction of the piston 20 is the Z-axis direction, and the oil level S of the oil O is a plane parallel to the Z-axis. However, the relationship between the sliding direction of the piston 20 and the oil level S in the embodiment of the present invention is not limited to this. For example, the sliding direction of the piston 20 and the plane including the oil level S of the oil O may intersect each other.

[0081] 4.3 Modification 3 In the above-described embodiment, the spring support 40 or 40A has a two-stage structure including the first part 41 or 41A and the second part 42 or 42A. However, the structure of the spring support 40 or 40A in the embodiment of the present invention is not limited to the two-stage structure. For example, the spring support 40 or 40A may have a three-stage or more structure having three or more components.

Description of Reference Numerals

[0082] 1, 1A... shock absorber, 2... oil tank, 10... cylinder, 11... bottom surface portion, 12... side surface portion, 13... top surface portion, 14... bottom surface portion, 15, 15A, 15B, 15C... inlet / outlet holes, 16A, 16B... air vent holes, 20... piston, 21... top portion, 22... shaft portion, 23... top surface, 24... bottom surface, 25... side portion, 30... coil spring, 40, 40A... spring supports, 41, 41A... first parts, 42, 42A... second parts, 44, 44A... first protrusions, 45, 45A... second protrusions, 46... flange portion,

Claims

1. A shock absorber for an opening / closing device, comprising: a cylinder having a bottom surface; a piston that is slidably housed in the cylinder and is connected to an opening / closing shaft of the opening / closing device; a liquid chamber defined between the bottom surface and the top surface of the piston and filled with a liquid; counter-force generating means for generating a counter-force that resists the internal pressure received by the piston from the liquid chamber when the piston slides toward the bottom surface side of the cylinder; wherein the counter-force when the position of the piston in the cylinder is on the bottom surface side of a predetermined position is smaller than the counter-force when the position of the piston is on the side opposite to the bottom surface of the predetermined position; the counter-force generating means is a spring housed in a space between the bottom of the piston and the top surface portion of the cylinder and expanding and contracting in the sliding direction of the piston, and is a shock absorber for an opening / closing device.

2. The shock absorber according to claim 1, wherein the counter-force when the position of the piston in the cylinder is on the bottom surface side of a predetermined position is zero.

3. further comprising a spring support that extends in the expansion and contraction direction of the spring and supports the spring while elongating in accordance with the sliding of the piston, wherein the spring support includes a first portion fixed to the cylinder and a second portion that slides with respect to the first portion, a first end of the spring is fixed to the top surface portion, a second end of the spring is fixed to the second portion, and engaging portions that engage with each other are provided on each of the first portion and the second portion. The shock absorber according to claim 1.

4. The shock absorber according to claim 3, wherein when the piston slides toward the bottom surface side of the cylinder, the spring support and the spring elongate until the position of the piston reaches the predetermined position, and when the position of the piston passes the predetermined position, the elongation of the spring support and the spring stops.

5. The shock absorber according to claim 4, wherein the spring is in a compressed state when the elongation of the spring support stops.

6. The shock absorber according to claim 3, wherein an end surface of the spring support on the bottom surface side of the cylinder is connected to the piston.

7. The shock absorber according to any one of claims 1, 3, 4, and 6, wherein the spring has a natural length when the position of the piston in the cylinder reaches the predetermined position.

8. a first hole and a second hole through which the liquid enters and exits the liquid chamber are provided at different positions in the axial direction of the cylinder on a side surface of the cylinder. When the piston is in the first position, the first hole and the second hole are opened. When the piston is in the second position, the first hole is opened and the second hole is blocked by the piston. The area of the first hole is smaller than the area of the second hole. The shock absorber according to any one of claims 1 to 7.

9. The first hole, the second hole, and the third hole through which the liquid enters and exits from the liquid chamber are provided at different positions in the axial direction of the cylinder on the side surface of the cylinder. When the piston is in the first position, the first hole, the second hole, and the third hole are opened. When the piston is in the second position, the first hole and the second hole are opened, and the third hole is blocked by the piston. When the piston is in the third position, the first hole is opened, and the second hole and the third hole are blocked by the piston. The distance between the first hole and the second hole is smaller than the distance between the second hole and the third hole. The shock absorber according to any one of claims 1 to 7.

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