JP5764337B2 - Manufacturing method and molding apparatus for sealing member - Google Patents

Description

  The present invention relates to a seal member used in a piston vacuum pump (reciprocating pump) that transports gas by reciprocating movement of a piston in a cylinder, and more specifically, a seal member mounted on a piston that slides in a cylinder. The present invention relates to a manufacturing method and a molding apparatus suitable for the manufacturing method.

  The piston vacuum pump is a volume transfer type dry vacuum pump that includes a cylinder and a piston that can move inside the cylinder, and alternately performs intake and exhaust by reciprocation of the piston in the cylinder.

  This type of vacuum pump is required to have a sealing property between the inner surface of the cylinder and the peripheral surface of the piston. For example, Patent Document 1 below discloses a vacuum pump including a cup packing having an auxiliary seal portion extending in a direction away from an intake / exhaust chamber formed by a cylinder and a piston. The auxiliary seal portion is integrally formed in a flange shape at the edge of the cup packing.

JP 2003-328937 A

  In recent years, piston vacuum pumps are required to improve the sealing performance between the cylinder and the piston and to improve the durability of the vacuum pump. However, the seal portion of the piston that slides on the inner surface of the cylinder is worn over time according to the operation time of the pump, and the sealing performance tends to decrease as the wear amount increases. As a result, the exhaust performance is reduced and the life of the pump is shortened.

  In view of the circumstances as described above, an object of the present invention is to provide a manufacturing method and a molding apparatus of a sealing member capable of improving the durability of the pump while maintaining the sealing performance between the cylinder and the piston. It is in.

In order to achieve the above object, a manufacturing method of a sealing member according to an aspect of the present invention is provided with a circular flat surface portion and an annular seal formed on a peripheral edge of the flat surface portion, which are attached to a piston that reciprocates in a cylinder. A first member having a first cylindrical portion having a first inner diameter and a first bottom portion formed at one end of the first cylindrical portion. Mounting a circular resin sheet having a first outer diameter larger than the first inner diameter on the tool.
A second jig having a second cylindrical portion having a second outer diameter smaller than the first inner diameter and a second bottom surface portion formed at one end of the second cylindrical portion; Attached to the first jig.
The sheet member is clamped at a predetermined pressure by the first bottom surface portion and the second bottom surface portion, and the first jig and the second jig are heated to a predetermined temperature. The flat portion is formed between the first bottom surface portion and the second bottom surface portion, and the seal portion is formed between the first cylindrical portion and the second cylindrical portion.

The shaping | molding apparatus which concerns on one form of this invention comprises the metal 1st jig | tool, the metal 2nd jig | tool, and the clamping mechanism.
The first jig includes a first cylindrical portion having a first end portion and formed with a first inner diameter, and a first bottom surface portion formed at the first end portion, A circular resin sheet having a first outer diameter larger than the first inner diameter is mounted.
The second jig includes a second cylindrical portion having a second end portion and a second outer diameter smaller than the first inner diameter, and the second end portion. And a second bottom surface portion. The second jig holds the resin sheet between the first bottom surface portion and the second bottom surface portion, and the peripheral edge of the resin sheet between the first cylindrical portion and the second cylindrical portion. Pinch.
The tightening mechanism tightens the first jig and the second jig in a direction in which the first bottom surface portion and the second bottom surface portion are close to each other.

It is a schematic sectional drawing which shows the structure of the vacuum pump provided with the piston with which the sealing member which concerns on one Embodiment of this invention was mounted | worn. It is an enlarged view which shows the said piston and its peripheral structure. It is a schematic diagram explaining operation | movement of the said piston. It is a disassembled perspective view of the shaping | molding apparatus which shape | molds the said sealing member. It is a schematic sectional drawing of the said shaping | molding apparatus. It is a schematic sectional drawing explaining the process of taking out a sealing member from the said shaping | molding apparatus. It is one experimental result which shows the abrasion loss of each seal member when a vacuum pump is comprised using the some seal member produced by making molding conditions different. It is one experimental result which shows the power consumption of the said vacuum pump when a vacuum pump is comprised using the some sealing member produced by making shaping | molding conditions different. It is one experimental result which shows the relationship between the molding temperature of the said sealing member, and the amount of wear. It is one experimental result which shows the relationship between the molding temperature of the said sealing member, and the power consumption of a vacuum pump. It is one experimental result which shows the relationship between the molding temperature of the said sealing member, and the temperature rise amount of a vacuum pump.

A manufacturing method of a seal member according to an embodiment of the present invention is a seal member that is attached to a piston that reciprocates in a cylinder, and that has a circular flat surface portion and an annular seal portion formed on the periphery of the flat surface portion. A first jig having a first cylindrical portion having a first inner diameter and a first bottom surface portion formed at one end of the first cylindrical portion; Mounting a circular resin sheet having a first outer diameter larger than the inner diameter.
A second jig having a second cylindrical portion having a second outer diameter smaller than the first inner diameter and a second bottom surface portion formed at one end of the second cylindrical portion; Attached to the first jig.
The sheet member is clamped at a predetermined pressure by the first bottom surface portion and the second bottom surface portion, and the first jig and the second jig are heated to a predetermined temperature. The flat portion is formed between the first bottom surface portion and the second bottom surface portion, and the seal portion is formed between the first cylindrical portion and the second cylindrical portion.

  The resin sheet is sandwiched between a first jig and a second jig at a predetermined pressure, and further heated to a predetermined temperature, whereby a flat portion and an annular seal portion formed on the periphery thereof are provided. Is formed. According to the manufacturing method, since the sealing member is molded while being heated, it is possible to adjust the elastic force toward the outside of the diameter of the sealing portion. That is, by heat-molding the seal member, it is possible to reduce the elastic force toward the outside of the diameter of the seal portion as compared to the case of molding without heating.

  Therefore, when the seal member is used by being attached to the piston of the dry vacuum pump, the seal portion of the seal member can be pressed against the inner surface of the cylinder with an appropriate elastic force, and the seal portion is unnecessary. Wear is suppressed. Thereby, the durability of the pump can be improved while the sealing performance between the cylinder and the piston is maintained. Moreover, since the favorable sealing performance of a seal part can be maintained, the power consumption of a pump can be reduced.

  The said predetermined temperature is not specifically limited, It sets suitably according to the magnitude | size of a sealing member, the required sealing characteristic, and durability. As the heating temperature is lower, the elastic force toward the outside of the seal portion tends to increase, and as the heating temperature is higher, the elastic force tends to decrease. In one embodiment, the predetermined temperature is, for example, 160 ° C. or higher and 250 ° C. or lower.

  The constituent material of the resin sheet is not particularly limited, and is composed of, for example, a polytetrafluoroethylene sheet.

A molding apparatus according to an embodiment of the present invention is a molding apparatus that molds a circular resin sheet, and includes a first metal jig, a second metal jig, and a tightening mechanism. To do.
The first jig includes a first cylindrical portion having a first end portion and formed with a first inner diameter, and a first bottom surface portion formed at the first end portion, A circular resin sheet having a first outer diameter larger than the first inner diameter is mounted.
The second jig includes a second cylindrical portion having a second end portion and a second outer diameter smaller than the first inner diameter, and the second end portion. And a second bottom surface portion. The second jig holds the resin sheet between the first bottom surface portion and the second bottom surface portion, and the peripheral edge of the resin sheet between the first cylindrical portion and the second cylindrical portion. Pinch.
The tightening mechanism tightens the first jig and the second jig in a direction in which the first bottom surface portion and the second bottom surface portion are close to each other.

  The resin sheet has an outer diameter larger than the first inner diameter. The first jig and the second jig clamp the resin sheet with a predetermined pressure. Moreover, since both the first jig and the second jig are made of metal, the heat supplied from the outside is efficiently transmitted to the resin sheet. Therefore, according to the molding apparatus, since the heat treatment of the resin sheet can be performed in a state in which the resin sheet is pressed into a predetermined shape, the sealing member having the seal portion in which the elastic force toward the outer diameter is appropriately adjusted is provided. Can be molded.

  The molding apparatus may further include a heating mechanism that heats the first jig and the second jig. The heating mechanism may be provided in at least one of the first jig and the second jig, or may be configured separately from these jigs.

The first jig may further include a first fitting portion that is provided at the center of the first cylindrical portion and can be fitted into the center hole of the resin sheet. On the other hand, the second jig may further include a second fitting portion that is provided at the center of the second cylindrical portion and can be fitted to the first fitting portion.
Thereby, a sealing part can be uniformly formed in the peripheral part of a resin sheet. In addition, the resin sheet and the second jig can be accurately positioned with respect to the first jig.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of a vacuum pump to which a sealing member according to an embodiment of the present invention is applied. In the present embodiment, a swing piston type dry vacuum pump will be described as an example of the vacuum pump.

[Schematic configuration of vacuum pump]
As shown in the figure, the vacuum pump 1 includes a motor 2, a shaft 3, a connecting rod 4, a piston 5, a cylinder 6, an intake chamber 7 and an exhaust chamber 8. The connecting rod 4, piston 5, cylinder 6, intake chamber 7 and exhaust chamber 8 constitute a “cylinder”, and the vacuum pump 1 has two cylinders. FIG. 2 is an enlarged view of the cylinder. The number of cylinders is not limited to two, but may be one or three or more.

  In the vacuum pump 1, a connecting rod 4 is connected to a shaft 3 connected to a motor 2, and a piston 5 is connected to the connecting rod 4. The piston 5 is accommodated in the cylinder 6. The cylinder 6 is provided with an intake chamber 7 and an exhaust chamber 8 adjacent to each other. Of the above configuration, the shaft 3, the connecting rod 4, the piston 5, and the cylinder 6 are accommodated in the housing 9.

  The motor 2 generates rotational power and rotates the shaft 3 around the axis. The motor 2 is a general motor, for example, a DC brushless motor.

  The shaft 3 extends linearly from the motor 2 into the housing 9 and is rotatably supported by the housing 9 via a bearing 10.

  One end of the connecting rod 4 is connected to the shaft 3 by the eccentric shaft 12 and the bearing 11, and the other end is connected to the piston 5. The connecting rod 4 and the eccentric shaft 12 convert the rotational motion of the shaft 3 into a reciprocating (oscillating) motion.

  The piston 5 reciprocates in the cylinder 6 by the connecting rod 4 to perform intake and exhaust. The vacuum pump 1 includes a seal member 50 that seals between the piston 5 and the cylinder 6. The seal member 50 is attached to the piston 5. The piston 5 includes a piston main body 51 and a fixture 52.

  The piston main body 51 is integrally formed at the distal end portion of the connecting rod 4. The fixture 52 is attached to the piston main body 51 and fixes the seal member 50. The seal member 50 is sandwiched between the piston body 51 and the fixture 52. The seal member 50 is a circular resin sheet, and in the present embodiment, the seal member 50 is made of a fluororesin such as polytetrafluoroethylene.

  The seal member 50 constitutes a cup packing having a flat portion 50a sandwiched between the piston main body 51 and the fixture 52 and a seal portion 50b formed on the periphery of the flat portion 50a. The seal portion 50 b extends from the peripheral surface portion of the flat surface portion 50 a to the connecting rod 4 side, and is interposed between the inner surface of the cylinder 6 and the peripheral surface of the piston 5. The seal portion 50 b functions to seal between the piston 5 and the cylinder 6 when the piston 5 reciprocates in the cylinder 6.

  The cylinder 6 is a cylindrical chamber having an inner diameter close to the outer diameter of the piston 5, and is configured so that the piston 5 can be inserted and inserted. The cylinder 6 is provided with an intake valve 13 and an exhaust valve 14, and these valves open and close according to the reciprocating motion of the piston 5.

  The intake chamber 7 communicates with the cylinder 6 via an intake valve 13, and an intake pipe 15 is connected to the intake chamber 7. The intake pipe 15 is connected to an exhaust target such as a chamber.

  The exhaust chamber 8 communicates with the cylinder 6 via an exhaust valve 14, and an exhaust pipe 16 is connected to the exhaust chamber 8. The exhaust pipe 16 is connected to the atmosphere or exhaust equipment.

  FIG. 2 is a view of the cylinder as viewed from a direction parallel to the shaft 3, but the orientation of the intake chamber 7 and the exhaust chamber 8 is shown differently from FIG. 1 for convenience of explanation.

[Operation of vacuum pump]
Next, the operation of the vacuum pump 1 will be described. Here, one cylinder of the vacuum pump 1 will be described, but the operation is the same for the other cylinders. FIG. 3 is a schematic diagram showing the swinging motion of the piston 5. The piston 5 is driven in the order of FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D, and the state returns to the state shown in FIG.

  In FIG. 3A, the piston 5 is at the top dead center. In this state, the piston 5 is close to the bottom of the cylinder 6. When the shaft 3 rotates, the connecting rod 4 descends while tilting via the eccentric shaft 12 and the bearing 11 as shown in FIG. 3B, and the piston 5 leaves the cylinder 6. At this time, since the volume between the cylinder 6 and the piston 5 increases, the exhaust target gas flows into the cylinder 6 from the intake chamber 7 and the intake pipe 15 communicating with the cylinder 6 via the intake valve 13.

  When the shaft 3 further rotates, the piston 5 reaches the bottom dead center as shown in FIG. At this time, exhaust target gas exists in the cylinder 6. When the shaft 3 further rotates, as shown in FIG. 3 (d), the connecting rod 4 rises while tilting via the eccentric shaft 12 and the bearing 11. At this time, since the volume between the cylinder 6 and the piston 5 decreases, the exhaust target gas in the cylinder is discharged from the exhaust chamber 16 and the exhaust pipe 16 communicating with the exhaust valve 14 through the exhaust valve 14. As described above, the rotation of the shaft 3 causes the piston 5 to be repeatedly raised and lowered (oscillating motion) with an inclination, and the gas in the chamber (not shown) is exhausted.

  Here, as shown in FIG. 3, in the swinging motion of the piston 5, the seal portion 50 b of the seal member 50 always abuts against the inner wall of the cylinder 6 and seals between the cylinder 6 and the piston 5. For this reason, wear of the seal part 50b becomes a problem in long-term use.

  In general, the greater the elastic force of the seal part, the higher the sealing performance. However, if the elastic force of the seal part is excessively large, the amount of wear of the seal part that moves relative to the cylinder unnecessarily increases. The durability of is reduced. In addition, since the sealing performance is lowered, the ultimate vacuum is lowered, and the power consumption of the pump is further increased. Therefore, the decrease in sealing performance necessitates replacement of the sealing member, resulting in a decrease in the durability of the pump.

  In the present embodiment, the durability of the pump is improved while maintaining the sealing performance by adjusting the elastic force of the sealing portion to an appropriate size that provides the desired sealing performance. Hereinafter, a method for manufacturing the seal member 50 will be described.

[Seal member forming device]
FIG. 4 is an exploded perspective view showing a configuration of a molding apparatus used for manufacturing the seal member 50. FIG. 5 is a sectional view of the molding apparatus in an assembled state. First, the molding apparatus 100 will be described.

  The forming apparatus 100 includes a first jig 110, a second jig 120, and a fastening tool 130. The molding apparatus 100 accommodates the resin sheet 50S between the first jig 110 and the second jig 120, and fastens the jigs 110 and 120 to each other by the fastening tool 130 to heat the resin sheet 50S. Thus, the resin sheet 50S is formed.

  The first jig 110 is made of a cylindrical member made of metal such as stainless steel or aluminum alloy. The first jig 110 has a first cylindrical portion 111 and a first bottom surface portion 112 formed at the lower end of the first cylindrical portion 111.

  The first cylindrical portion 111 is formed with an inner diameter (first inner diameter) smaller than the outer diameter (first outer diameter) of the resin sheet 50 </ b> S, and the size of the inner diameter is that of the flat portion 50 a of the seal member 50. The size (diameter) is set. Therefore, when the resin sheet 50S is mounted on the first jig 110, the peripheral portion of the resin sheet 50S is accommodated inside the first cylindrical portion 111 in a state of being bent by approximately 90 degrees as shown in FIG. It will be.

  The first jig 110 further includes a first fitting portion 113. The first fitting portion 113 is formed at the center of the first bottom surface portion 112 and has a columnar shape concentric with the first cylindrical portion 111. The first fitting portion 113 can be fitted with a center hole 50c formed at the center of the resin sheet 50S, and the outer diameter thereof is set to be approximately the same as the inner diameter of the center hole 50c. . Thereby, the resin sheet 50 </ b> S can be assembled with high accuracy to the first jig 110.

  The second jig 120 is composed of a cylindrical member made of metal such as stainless steel or aluminum alloy. The second jig 120 includes a second cylindrical portion 121, a second bottom surface portion 122 formed at the lower end of the second cylindrical portion 121, and a second shape formed at the center of the second bottom surface portion 122. And a fitting portion 123. As shown in FIG. 5, the second jig 120 is assembled to the first jig 110 such that the second bottom surface portion 122 faces the first bottom surface portion 112.

  The second cylindrical portion 121 is formed with an outer diameter (second outer diameter) smaller than the inner diameter of the first cylindrical portion 111, and the outer diameter is equal to or smaller than the inner diameter of the seal portion 50 b of the seal member 50. Is set to the size of Therefore, when the second jig 120 is attached to the first jig 110 to which the resin sheet 50S is attached, the peripheral portion of the resin sheet 50S is connected to the first cylindrical portion 111 and the second cylindrical portion as shown in FIG. It is accommodated between the cylindrical part 121.

  The second fitting portion 123 is provided at the center of the second bottom surface portion 122 and is configured by a recess that can be fitted to the first fitting portion 113. That is, the second fitting portion 123 is fitted to the first fitting portion 113 when the first jig 110 and the second jig 120 are assembled. As a result, the second jig 120 can be assembled to the first jig 110 with high accuracy. In addition, in order to accurately position the second jig 120 with respect to the first jig 110, an annular space having a certain size is formed between the first cylindrical portion 111 and the second cylindrical portion 121. Can be formed.

  The fastening tool 130 is composed of parts such as bolts and screws, and is attached to the center portions of the first jig 110 and the second jig 120, respectively. Here, the first jig 110 is formed with an attachment hole 114 that is screwed with the shaft 131 of the fastening tool 130 at the center of the first fitting part 113, and the second jig 120 has a second hole. An insertion hole 124 through which the shaft portion 131 is inserted is formed at the center of the fitting portion 123. As a result, the first and second jigs 110 and 120 are fastened to each other by the fastening tool 130 and fastened in a direction in which the first bottom surface portion 112 and the second bottom surface portion 122 are close to each other. The fastening tool 130, the attachment hole 114, and the insertion hole 124 constitute a fastening mechanism that fastens the first and second jigs 110 and 120 to each other.

  The first and second bottom surface portions 112 and 122 are formed in parallel to each other, and sandwich the resin sheet 50 </ b> S when the first and second jigs 110 and 120 are tightened by the tightening tool 130. The clamping pressure of the resin sheet 50 </ b> S by the first and second bottom surface portions 112 and 122 is adjusted by the tightening torque by the tightening tool 130.

[Method of forming sealing member]
Then, the manufacturing method of the sealing member 50 using the shaping | molding apparatus 100 comprised as mentioned above is demonstrated.

  First, a resin sheet 50S serving as a prototype of the seal member 50 is prepared. The resin sheet 50S is typically punched out into an annular shape as shown in FIG. The size (outer diameter) of the resin sheet 50S is appropriately set according to the size of the applied piston, and is, for example, 93 mm in diameter. The thickness of the resin sheet 50S is not particularly limited, and is 1.0 mm, for example. The hole diameter of the center hole 50 c is not particularly limited, and is determined by the configuration of the piston 5.

  Subsequently, as shown in FIGS. 4 and 5, the resin sheet 50 </ b> S is sandwiched between the first jig 110 and the second jig 120, and the resin sheet 50 </ b> S is heated while being pressed to a predetermined temperature. Is made.

  As a procedure, first, the resin sheet 50 </ b> S is mounted on the first jig 110. At this time, the positioning accuracy of the resin sheet 50S with respect to the first jig 110 is secured by the fitting action of the center hole 50c of the resin sheet 50S and the first fitting portion 113. Therefore, as the difference between the outer diameter of the first fitting portion 113 and the hole diameter of the central hole 50c of the resin sheet 50S is smaller, higher positioning accuracy is obtained.

  Further, since the inner diameter of the first cylindrical portion 111 is smaller than the outer diameter of the resin sheet 50 </ b> S, the peripheral edge portion of the resin sheet 50 </ b> S contacts the inner surface of the first cylindrical portion 111.

  After the resin sheet 50 </ b> S is attached to the first jig 110, the second jig 120 is assembled to the first jig 110. At this time, the positioning accuracy of the second jig 120 with respect to the first jig 110 is ensured by the fitting action of the first fitting part 113 and the second fitting part 123. Also in this case, as the difference between the outer diameter of the first fitting portion 113 and the inner diameter of the second fitting portion 123 is smaller, higher positioning accuracy is obtained.

  After the second jig 120 is assembled to the first jig 110, both the jigs 110 and 120 are tightened by the tightening tool 130. At this time, as shown in FIG. 5, a region other than the peripheral portion of the resin sheet 50 </ b> S is sandwiched between the first bottom surface portion 112 and the second bottom surface portion 122, thereby ensuring a predetermined flatness. .

  On the other hand, as shown in FIG. 5, the peripheral edge of the resin sheet 50 </ b> S enters an annular gap between the first cylindrical portion 111 and the second cylindrical portion 121, and the pressing action of the second bottom surface portion 122. Thus, the sheet is folded in a direction perpendicular to the first bottom surface portion 112.

  Here, the width of the gap between the first cylindrical portion 111 and the second cylindrical portion 121 is set to a value larger than the thickness of the peripheral edge portion of the resin sheet 50S. Thereby, the peripheral part of resin sheet 50S can be turned back smoothly and uniformly over the whole region. Further, as the width of the gap increases, the elastic force toward the radially outward side of the seal portion 50b of the manufactured seal member 50 tends to increase.

  The tightening force of the second jig 120 with respect to the first jig 110 requires at least a pressure that allows the resin sheet 50 </ b> S to be in close contact with the first bottom surface portion 112. Thereby, the peripheral part of the resin sheet 50S can be appropriately folded back in the vertical direction. In this case, the resin sheet 50 </ b> S may generate a predetermined compressive force between the first bottom surface portion 112 and the second bottom surface portion 122. As a result, the peripheral edge of the resin sheet 50S can be smoothly folded back in the vertical direction. The predetermined compressive force is not particularly limited, and is, for example, 1 MPa, and is 13 N · m in this embodiment when converted to the tightening torque of the fastener 130.

  The molding apparatus 100 clamped together by the clamp 130 is heated to a predetermined temperature. As a result, the resin sheet 50S is formed into a seal member 50 having a flat surface portion 50a and a seal portion 50b (FIG. 5).

  The molding apparatus 100 is heated inside an oven set to a predetermined temperature, for example. In addition to this, a heating source such as a heater may be incorporated in at least one of the first jig 110 and the second jig 120. Since each of the first and second jigs 110 and 120 is made of metal, heat can be efficiently transferred to the resin sheet 50S.

  The predetermined temperature is not particularly limited, and is the material, size, and thickness of the resin sheet 50S, for example, 160 ° C. or higher and 250 ° C. or lower. The holding time of the predetermined temperature is not particularly limited, and is 40 minutes, for example.

  The flat surface portion 50 a of the seal member 50 is formed between the first bottom surface portion 112 and the second bottom surface portion 122 by receiving the compression action by the fastening tool 130 and the heating action. On the other hand, the seal portion 50 b is formed between the first cylindrical portion 111 and the second cylindrical portion 121 by receiving the compression action and the heating action. In particular, the internal stress of the seal member 50 is alleviated by the heat treatment, and the seal portion 50b bent with respect to the flat portion 50a can be stably formed.

  After holding the heat treatment of the resin sheet 50S for a predetermined time, the molding apparatus 100 is cooled. The cooling method is not particularly limited, and natural cooling or forced cooling may be used. After cooling, the molding apparatus 100 is separated into a first jig 110 and a second jig 120, and the sealing member 50 (resin sheet 50S) is taken out from the first jig 110.

  FIG. 6 is a cross-sectional view illustrating a method for taking out the seal member 50 from the first jig 110. In the present embodiment, a take-out jig 200 as shown in FIG. 6 is used. The take-out jig 200 includes a main body 201 and a plurality of pins 202 provided on one surface of the main body 201. A plurality of holes into which the pins 202 are inserted are formed in the first bottom surface portion 112 in advance, and the main body 201 is attached to the first jig 110 by inserting the pins 202 into the holes. Is attached. The seal member 50 on the first bottom surface portion 112 is pushed upward in FIG. 6 by the pin 202 and is taken out from the first jig 110.

  As described above, the seal member 50 in which the seal portion 50b is formed annularly at the peripheral portion of the flat portion 50a is manufactured. According to the present embodiment, since the seal member 50 is molded while being heated, it is possible to adjust the elastic force toward the radially outward direction on the seal portion 50b.

  That is, by heat-molding the seal member 50, it is possible to reduce the elastic force toward the outside of the diameter of the seal portion as compared to the case of molding without heating. Therefore, when the seal member 50 is used by being attached to the piston 5 of the vacuum pump 1, the seal portion 50b of the seal member 50 can be brought into pressure contact with the inner surface of the cylinder 6 with an appropriate elastic force. Unnecessary wear of 50b is suppressed. Thereby, the durability of the pump can be improved while maintaining the sealing performance between the cylinder 6 and the piston 5.

  The molding temperature is not particularly limited, and is appropriately set according to the material and shape factors such as the material, size and thickness of the seal member 50 as well as the product specific factors such as required seal characteristics and durability. Is done. As the molding temperature is lower, the elastic force toward the outside of the diameter of the seal portion 50b tends to increase, and as the molding temperature is higher, the elastic force tends to decrease.

  The inventor makes a plurality of samples of the seal member 50 by varying the inner diameter of the first cylindrical portion 111, the outer diameter of the second cylindrical portion 121, and the molding temperature, and actually attaches them to the piston 5. The pump was driven and the power consumption of the pump was measured for each sample. Further, after the pump was driven for 1 hour, the wear amount of the seal portion 50b was measured for each sample.

  A polytetrafluoroethylene sheet having a diameter of 93 mm and a thickness of 1.0 mm was used as the resin sheet 50 </ b> S serving as a prototype of the seal member 50. The holding time at the molding temperature was 40 minutes, followed by cooling over 20 minutes. As the vacuum pump, an oscillating piston type dry vacuum pump manufactured by ULVAC Kiko Co., Ltd. was used.

  Table 1 shows the conditions of the inner diameter of the first cylindrical portion 111, the outer diameter of the second cylindrical portion 121, and the molding temperature used for producing each sample. Moreover, the measured value of the abrasion amount of each sample and the power consumption of a pump is shown in FIG.7 and FIG.8, respectively.

  Regarding sample 5, the amount of wear of the seal portion 50b was the largest among the samples, and the ultimate pressure was also high. The reason for this is considered to be that since the molding temperature was relatively low at 130 ° C., the elastic restoring force of the seal portion 50b was maintained high, and the elastic force against the cylinder 6 was the highest among the samples.

  For samples 1 to 4, 6 and 7, the main pump performances such as ultimate vacuum and power consumption were almost the same, although the amount of wear varied. From the evaluation results of these samples, it was confirmed that the amount of wear of the seal portion 50b is smaller as the molding temperature is higher. Moreover, since the favorable sealing performance of a seal part can be maintained, the power consumption of a pump can be reduced.

  Here, the same pump characteristics can be obtained even when the inner diameter of the first cylindrical portion 111 and the outer diameter of the second cylindrical portion 121 are different between the samples, such as Samples 1, 3, 6 and 7, for example. It was confirmed. From this, it is considered that the sealing performance of the seal member has a strong dependence on the molding temperature and does not strongly depend on the diameter of the molding jig.

  Next, a plurality of seal members 50 were produced in a molding temperature range of 160 ° C. to 250 ° C. using the jigs used for producing Sample 7. Then, for each sample, the pump characteristics including the ultimate pressure, the discharge flow rate when the atmosphere was released (no load), the power consumption, the temperature rise of the pump casing, and the wear amount of the seal portion were evaluated. The results are shown in Table 2. Further, FIG. 9, FIG. 10 and FIG. 11 show the relationship between the molding temperature and the amount of wear of the seal portion, the power consumption of the pump, and the amount of temperature rise, respectively.

  As shown in Table 2 and FIGS. 9 to 11, it is recognized that the wear amount of the seal portion, the power consumption of the pump, and the temperature increase amount all decrease as the molding temperature increases. This is presumably because the higher the molding temperature, the more the internal stress of the seal member 50 is relaxed, and the seal part 50b bent with respect to the flat part 50a can be formed stably. That is, as the molding temperature is higher, the shape maintaining property of the seal portion 50b is improved, and the outer diameter of the seal portion after the piston is mounted is reduced. As a result, the elastic force of the seal portion is reduced, and the sliding friction force acting on the seal portion is reduced, so that wear can be suppressed. Regarding the sealing property, since the power consumption is reduced as the molding temperature is increased, it is recognized that a stable sealing property between the cylinder 6 and the piston 5 is ensured.

As described above, by setting the molding temperature of the seal member to 160 ° C. or more and 250 ° C. or less, it is possible to suppress wear of the seal portion while maintaining stable sealing performance, and to reduce power consumption of the pump. It becomes.
Further, although the upper limit of the molding temperature is 250 ° C., it can be appropriately set according to the thermal stability of the material constituting the seal member, the intended sealability, and the like.

  The embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

  For example, in the above embodiment, the manufacturing method and the molding apparatus of the seal member applied to the piston for the oscillating piston type dry vacuum pump have been described as an example. The present invention can also be applied to manufacture of a seal member applied to a vacuum pump.

  In the above embodiment, the fitting portions 113 and 123 of the first and second jigs 110 and 120 are both formed in a cylindrical or columnar shape. Instead, they have a fitting relationship with each other. Other geometric shapes such as a polygonal column shape may be used. Moreover, these fitting parts may be abbreviate | omitted as needed.

  Furthermore, although the fastening tool 130 is used as a fastening mechanism for fastening the first and second jigs 110 and 120, other members such as a clamp may be used instead.

DESCRIPTION OF SYMBOLS 1 ... Vacuum pump 5 ... Piston 50 ... Sealing member 50a ... Flat surface part 50b ... Sealing part 50S ... Resin sheet 100 ... Molding apparatus 110 ... 1st jig | tool 111 ... 1st cylindrical part 112 ... 1st bottom face part 113 ... 1st fitting part 120 ... 2nd jig 121 ... 2nd cylindrical part 122 ... 2nd bottom face part 123 ... 2nd fitting part 130 ... Fastening tool

Claims (3)

A manufacturing method of a seal member attached to a piston that reciprocates in a cylinder, and having a circular plane portion and an annular seal portion formed on the periphery of the plane portion,
A first jig having a first cylindrical portion having a first inner diameter and a first bottom surface portion formed at one end of the first cylindrical portion has a first larger than the first inner diameter. A circular resin sheet composed of a polytetrafluoroethylene sheet having an outer diameter of
It has a smaller second outer diameter than said first inner diameter, is set to a value larger than said first inner diameter and said second thickness of the peripheral portion of the distance between the outer diameter of said circular resin sheet Attaching a second jig having a second cylindrical portion and a second bottom surface portion formed at one end of the second cylindrical portion to the first jig;
Wherein the resin sheet nipped at a predetermined pressure, for heating said first jig and the second jig 160 ° C. or higher 250 ° C. or less by said first bottom and the second bottom portion Thus, the planar portion is formed between the first bottom surface portion and the second bottom surface portion, and the seal portion is formed between the first cylindrical portion and the second cylindrical portion. Manufacturing method of sealing member. A first cylindrical portion having a first end portion and formed with a first inner diameter; and a first bottom surface portion formed at the first end portion, wherein the first cylindrical portion is larger than the first inner diameter. A metal first jig to which a circular resin sheet having a first outer diameter is attached;
A second cylindrical portion having a second end portion and having a second outer diameter smaller than the first inner diameter; and a second bottom surface portion formed at the second end portion. The resin sheet is sandwiched between the first bottom surface portion and the second bottom surface portion, and the periphery of the resin sheet is sandwiched between the first cylindrical portion and the second cylindrical portion. 2 jigs,
A tightening mechanism for tightening the first jig and the second jig in a direction in which the first bottom surface portion and the second bottom surface portion are close to each other ;
A heating mechanism for heating the first jig and the second jig to 160 ° C. or more and 250 ° C. or less ;
A molding apparatus in which a width of a gap between the first cylindrical portion and the second cylindrical portion is set to a value larger than a thickness of a peripheral edge portion of the circular resin sheet . The molding apparatus according to claim 2 ,
The first jig further includes a first fitting portion that is provided at the center of the first cylindrical portion and can be fitted into a center hole of the resin sheet,
The second jig further includes a second fitting portion that is provided at the center of the second cylindrical portion and can be fitted into the first fitting portion.

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