JP4332666B2 - Reciprocating sealing device - Google Patents

Description

  The present invention relates to a sealing device for a mechanical element in which a liquid fluid such as oil is sealed inside a cylinder and a piston and a piston rod reciprocate as in a hydraulic cylinder, a damper, a front fork of a motorcycle, and the like.

  As shown in FIG. 9, mechanical elements in which a liquid fluid such as oil is sealed inside the cylinder and the piston and the piston rod reciprocate as in a hydraulic cylinder, a damper, a front fork of a motorcycle, and the like. The piston rod 103 is constituted. In this mechanical element, a guide bush 105 is fixed to the inner peripheral surface of the cylinder 101 in order to guide the axial movement of the piston rod 103. One end of the cylinder 101, the upper end as viewed in FIG. 9, is closed, and at the other end, a sealing element such as an oil seal 106 is inserted into an annular gap formed between the outer peripheral surface of the piston rod 103 and the inner peripheral surface of the cylinder 101. It is densely arranged. Thus, for example, in a front fork of a motorcycle, a gaseous fluid such as air is sealed at one end of the cylinder 101 as shown in FIG.

  In the mechanical element having the reciprocating member, the liquid fluid such as oil moves between the inner peripheral surface of the guide bush 105 and the outer peripheral surface of the piston rod 103 in accordance with the movement of the reciprocating member such as the piston rod. As a result, positive pressure and negative pressure are generated in the annular space between the guide bush 105 and the sealing element (seal) 106 as the piston rod 103 reciprocates. In the extension stroke of the piston rod 103 shown in FIG. 9A, positive pressure (p> 0) is generated in the annular space between the guide bush 105 and the sealing element (seal) 106, and FIG. In the contraction stroke of the piston rod 103 shown in FIG. 3, a negative pressure (p <0) is generated in the annular space between the guide bush 105 and the sealing element (seal) 106.

  The positive pressure / negative pressure in the annular space between the guide bush 105 and the sealing element (seal) 106 generated by the reciprocating motion of the piston rod 103 is a liquid fluid such as oil from the sealing element (seal) 106 due to the positive pressure. The outflow of air also causes inhalation of outside air due to negative pressure. In order to solve such problems as outflow of liquid fluid such as oil from the sealing element (seal) 106 and suction of outside air from the sealing element (seal) 106, the tightening force of the sealing element (seal) 106 is reduced. Although it has been increased, friction between the outer peripheral surface of the piston rod 103 and the sealing element (seal) 106 is increased, causing problems such as energy loss and hindering smooth operation of the mechanical element.

Further, in order to reduce the load on the O-ring (seal member) embedded in the groove formed in the circumferential direction of the piston rod (plunger) outer peripheral surface, the pressure surface end of the plunger and the O-ring (seal member) A fluid seal structure is disclosed in which a pressure accumulating volume portion is formed in the plunger barrel portion (see, for example, Patent Document 1).
JP-A-10-61528

However, when the fluid seal structure is used, the pressure in the space formed by the pressure surface end of the plunger and the fuel pressurization chamber shown in FIG. Although it is possible to relieve an excessive load on the O-ring (seal member) caused by pressure fluctuations several times, the guide bush 105 and the seal are sealed in the contraction stroke of the piston rod 103 shown in FIG. 9 attached to the present application. Inhalation of outside air due to negative pressure (p <0) in the space formed between the elements (seal) 106 cannot be suppressed.
The present invention reduces pressure fluctuations in the annular space between the guide bush and the sealing element (seal) due to the reciprocating motion of the piston rod in the reciprocating machine element, thereby reducing the liquid fluid such as oil sealing element (seal). The sealing device for reciprocating motion that can prevent the outside air from sucking out or sucking outside air from the sealing element (seal) and can reduce the frictional force between the outer peripheral surfaces of the piston rod in the sealing element (seal) to the lowest possible level. The purpose is to provide.

The present invention for solving the above problems is a reciprocating mechanical element having a cylinder, a piston, and a piston rod, in which a liquid fluid is enclosed and one end of the cylinder is closed, and at the other end, the piston rod outer peripheral surface and The liquid fluid sealing element is densely disposed in an annular gap between the inner peripheral surfaces of the cylinder, and a guide bush for guiding the piston rod at a predetermined interval in the axial direction of the piston rod with the sealing element. In the reciprocating machine element fixed to the inner wall surface of the cylinder, the liquid flowing into and out of the space consisting of the guide bush and the sealing element accompanying the reciprocating movement of the piston rod is provided outside the reciprocating machine element. The lower part of the accumulator, which is sealed in the upper space and filled with the liquid fluid in the lower part, is connected by a pipe line, and includes a guide bush and a sealing element. A reciprocating sealing device consisting configured to dampen a pressure variation in the space.

  According to the reciprocating sealing device of the present invention, liquid fluid can flow into and out of the space formed between the guide bush in the cylinder and the sealing element (seal) in accordance with the reciprocating motion of the piston rod with a simple configuration. The pressure fluctuation in the space consisting of the guide bush and sealing element can be suppressed within a small range, and it is possible to prevent the leakage of liquid fluid from the sealing element (seal) due to the pressure fluctuation and the suction of outside air. it can.

  The reciprocating sealing device of the present invention has a structure that allows liquid fluid to flow in and out (moving) into a space formed between a guide bush in a cylinder and a sealing element (seal) accompanying reciprocal movement of a piston rod. The pressure fluctuation in the space can be maintained within a small range. Thus, it is possible to effectively prevent leakage of liquid fluid from the sealing element (seal) due to pressure fluctuations and inhalation of outside air, and to reduce the pressure applied to the sealing element (seal) part. The number of sealing elements (seal) can be reduced, and the frictional force at the seal portion can be reduced. Further, by allowing the liquid fluid to flow in the guide bush, the frictional force between the guide bush inner peripheral surface and the piston rod outer peripheral surface can be reduced. Further, the movement of the liquid fluid on the inner peripheral surface of the guide bush facilitates the formation of an oil film on the inner peripheral surface of the guide bush and the outer peripheral surface of the piston rod, and also reduces friction. According to the sealing device for reciprocating motion of the present invention, the guide bush caused by the flow of liquid fluid into and out of the space formed between the guide bush in the cylinder and the sealing element (seal) accompanying the reciprocating motion of the piston rod, and The pressure fluctuation in the space composed of the sealing elements is about 1/10 that in the conventional reciprocating mechanical element shown in FIG.

  The present invention has a structure that allows liquid fluid to flow in and out (moving) into a space formed between a guide bush in a cylinder and a sealing element (seal) that accompanies the reciprocation of a piston rod. The pressure fluctuation in the space consisting of the guide bush and the sealing element due to the flow of liquid fluid into and out of the space formed between the guide bush and the sealing element (seal) in the cylinder due to the reciprocating movement of the rod is reduced, This is to prevent troubles such as leakage of liquid fluid from the reciprocating machine element and inhalation of outside air from the sealing element (seal).

  FIG. 1 shows a reciprocating sealing device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a cylinder whose upper end is closed as viewed in FIG. 2 is a piston, 3 is a piston rod, and 4 is a liquid fluid such as oil. A guide bush 5 functions to guide the reciprocating motion of the piston rod 3 in the axial direction, and is fixed to the inner peripheral surface of the cylinder 1. Thus, as the piston rod 3 reciprocates, the outer circumferential surface of the piston rod 3 slides with the inner circumferential surface of the guide bush 5. Reference numeral 6 denotes a sealing element such as an oil seal, which is disposed in an annular gap formed by the inner peripheral surface of the cylinder 1 and the outer peripheral surface of the piston rod 3 at the lower open end of the cylinder 1 as viewed in FIG. 1 It functions to seal leakage of the liquid fluid 4 inside.

7 is an accumulator. As shown in FIG. 1, an air chamber in which a gas such as air or nitrogen gas is sealed is formed at the upper portion thereof, and a lower liquid fluid such as oil 4 is
The fluid fluid such as oil 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 in the cylinder 1 is communicated via the flow path 72. 8 is a gaseous fluid such as air, which is sealed on the closed end side of the cylinder 1 and above the liquid fluid 4 as viewed in FIG.

The operation of the sealing device for reciprocating motion according to one embodiment of the present invention shown in FIG. 1 will be described.
In the mechanical element for reciprocating motion shown in FIG. 1, the piston rod 3 protrudes, and in the extending stroke shown in FIG. 9A, the liquid in the annular space formed by the guide bush 5 and the sealing element (seal) 6. The pressure of the fluid, for example oil 4, increases. Then, the liquid fluid 4 flows into the accumulator 7 through the flow path 72 and compresses the gas body in the air chamber 71 above the accumulator 7. In this way, the pressure increase of the liquid fluid 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 is absorbed.

  On the other hand, in the contraction stroke shown in FIG. 9B in which the piston rod 3 is stored in the cylinder 1, a liquid fluid such as oil in an annular space formed by the guide bush 5 and the sealing element (seal) 6. 4 pressure drops. Then, the gas body compressed in the air chamber 71 in the accumulator 7 expands, and the liquid fluid in the accumulator 7 such as oil 4 flows into the annular space formed by the guide bush 5 and the sealing element (seal) 6. It flows in through the path 72. In this way, the pressure drop and the negative pressure in the annular space formed by the guide bush 5 and the sealing element (seal) 6 are eliminated.

  In making the present invention, the inventors made a test apparatus in which an eccentric cam was rotated by a motor, a piston rod was linearly moved by a connecting rod and a linear guide, imitating a front fork of a motorcycle. In this test apparatus, the piston rod was reciprocated relatively by pushing a fork with wheels. At this time, the reaction force applied to the cylinder (fork) was detected with a strain gauge. Moreover, the pressure fluctuation of the liquid fluid, for example, oil 4, in the annular space formed by the guide bush 5 and the sealing element (seal) 6 was detected by a pressure sensor. Data were taken for eccentric cam rotation speeds of 4.2 and 120 rpm.

FIG. 2 shows the results when the reciprocating mechanical element shown in FIG. 9 is used, and the results when the eccentric cam rotation speed is 4.2 rpm. FIG. 3 shows the results when the eccentric cam rotation speed is 120 rpm. Show. In either case, the load (lateral load) in the direction perpendicular to the axis of the piston rod caused by the relative position fluctuation between the wheel and the front fork axis is
245N. As shown in FIG. 3, when the reciprocating mechanical element shown in FIG. 9 is used, an annular space formed by the guide bush 5 and the sealing element (seal) 6 when the rotational speed of the eccentric cam is 120 rpm. The pressure fluctuation (indicated by the dotted line) of the liquid fluid (oil) 4 in the figure fluctuates between +250 kPa and -80 kPa.

  1, the reaction force (frictional force) when the rotational speed of the eccentric cam is 4.2 rpm and the liquid state in the annular space formed by the guide bush 5 and the sealing element (seal) 6 are used. FIG. 4 shows the pressure fluctuation of the fluid (oil) 4 and FIG. 5 shows the case where the rotation speed of the eccentric cam is 120 rpm. As is clear from FIGS. 4 and 5, the pressure of the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 when the rotational speed of the eccentric cam is 4.2 rpm is as follows. It is stable at a level of 10 kPa. The pressure of the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 when the rotational speed of the eccentric cam is 120 rpm is stable between 0 kPa and +30 kPa. . Thus, according to the present invention, the pressure fluctuation of the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 is stably maintained at a very low level.

(Reference Example 1)
FIG. 6 shows a reciprocating sealing device as a reference example related to the present invention. In FIG. 6, the same reference numerals as in FIG. 1 are the same elements as in the first embodiment. In this reference example , as shown in FIG. 6, a groove 51 extending in the axial direction is formed on the outer peripheral surface of the guide bush 15. Thus, the liquid fluid (oil) 4 in the annular space formed by the guide bush 15 and the sealing element (seal) 6 is an axially extending groove formed on the outer peripheral surface of the guide bush 15. Via 51, the liquid fluid 4 communicates with the space formed by the guide bush 15 and the piston 2. Thereby, the pressure fluctuation of the liquid fluid (oil) 4 in the annular space formed by the guide bush 15 and the sealing element (seal) 6 due to the reciprocating motion of the piston rod 3 is reduced.

(Reference Example 2)
FIG. 7 shows a reciprocating sealing device as a reference example related to the present invention. 7, the same reference numerals as in FIG. 1 are the same elements as in the first embodiment. In this reference example , as shown in FIG. 7, the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6, and the space formed by the guide bush 5 and the piston 2. The liquid fluid 4 is configured to communicate with the liquid fluid conduit 73. Thereby, the pressure fluctuation of the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 due to the reciprocating motion of the piston rod 3 is reduced.

(Reference Example 3)
FIG. 8 shows a reciprocating sealing device as a reference example related to the present invention. 8, the same reference numerals as in FIG. 1 are the same elements as in the first embodiment. In this reference example , as shown in FIG. 8, the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 and the closed ends of the piston 2 and the cylinder 1 are used. The liquid fluid 4 in the space to be formed is configured to be in communication with the liquid fluid pipe 74. Thereby, the pressure fluctuation of the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 due to the reciprocating motion of the piston rod 3 is reduced.

(Reference Example 4)
An annular space formed by the guide bush 5 and the sealing element (seal) 6 is provided with a donut-like expansion / contraction element made of a flexible member in which a gas such as air or nitrogen gas is enclosed. . Thus, the pressure fluctuation of the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 due to the reciprocating motion of the piston rod 3 is changed to a gas such as air or nitrogen gas. It is absorbed by a donut-like expansion / contraction element made of a flexible member in which is encapsulated.

(Reference Example 5)
In an annular space formed by the guide bush 5 and the sealing element (seal) 6, an annular bellows in which a gas such as air or nitrogen gas is enclosed is disposed. Thus, the pressure fluctuation of the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 due to the reciprocating motion of the piston rod 3 is changed to a gas such as air or nitrogen gas. Is absorbed by the annular bellows in which is encapsulated.

(Reference Example 6)
In this reference example , on the side of the sealing element (seal) 6 that is in contact with the liquid fluid 4, a sponge-like body covered with a non-permeable membrane or a gas is enclosed in the non-permeable membrane. The elements are disposed adjacent to each other, and the pressure fluctuation of the liquid fluid (oil) 4 in the annular space formed by the guide bush 5 and the sealing element (seal) 6 due to the reciprocating movement of the piston rod 3 is reduced by the sealing. The element (seal) 6 is absorbed by a sponge-like body covered with a non-permeable membrane disposed on the side in contact with the liquid fluid 4 or an element in which a gas is sealed inside the non-permeable membrane.

1 is a longitudinal sectional view showing a reciprocating sealing device according to an embodiment of the present invention. Graph showing friction force and pressure fluctuation between guide bush and sealing element (seal) when piston reciprocating at 4.2 cycles / min using a conventional reciprocating sealing device Graph showing frictional force and pressure fluctuation between guide bush and sealing element (seal) when piston reciprocating motion is performed 120 cycles / min using a conventional sealing device for reciprocating motion The frictional force and the pressure fluctuation between the guide bush and the sealing element (seal) when the piston is reciprocated by 4.2 cycles / min using the reciprocating sealing device according to one embodiment of the present invention are shown. Graph The graph which shows the frictional force and the pressure fluctuation between a guide bush and a sealing element (seal) when a piston reciprocating motion is performed 120 cycles / min using the sealing device for reciprocating motion which concerns on one Example of this invention. The longitudinal cross-sectional view which shows the sealing device for reciprocating motion as a reference example relevant to this invention The longitudinal cross-sectional view which shows the sealing device for reciprocating motion as a reference example relevant to this invention The longitudinal cross-sectional view which shows the sealing device for reciprocating motion as a reference example relevant to this invention A longitudinal sectional view showing an example of a conventional reciprocating mechanical element

1 Cylinder 2 Piston 3 Piston Rod 4 Liquid Fluid 5 Guide Bush 6 Sealing Element (Seal)
7 Accumulator 8 Gaseous fluid 15 Guide bush 51 Groove 71 Air chamber 72 Channel 73 Liquid fluid conduit 74 Liquid fluid conduit 101 Cylinder 102 Piston 103 Piston rod 104 Liquid fluid 105 Guide bush 106 Sealing element (seal)
108 Gaseous fluid

Claims (1)

A reciprocating mechanical element having a cylinder, a piston, and a piston rod, in which liquid fluid is enclosed and one end of the cylinder is closed, and at the other end, the liquid is placed in an annular gap between the piston rod outer peripheral surface and the cylinder inner peripheral surface. A reciprocating machine in which a sealing element for fluid is closely arranged and a guide bush for guiding the piston rod at a predetermined interval in the axial direction of the piston rod is fixed to the inner wall surface of the cylinder In the element, a liquid fluid flowing into and out of the space consisting of the guide bush and the sealing element accompanying the reciprocating movement of the piston rod is provided outside the reciprocating mechanical element, the gas is enclosed in the upper space, and the liquid fluid is in the lower part. Connect the lower part of the accumulator filled with a pipe to suppress pressure fluctuations in the space consisting of the guide bush and sealing element. Configuration reciprocates sealing device comprising.

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