Vacuum pump, deaeration device, and liquid chromatograph

Abstract

The present invention comprises: a pump head (4) having a pump chamber forming surface (11) that forms an inner surface of a pump chamber (16); a diaphragm (6) provided to cover the pump chamber forming surface (11) of the pump head (4) and form the pump chamber (16) between the diaphragm (6) and the pump chamber forming surface (11); a rod (8) provided on the opposite side of the diaphragm (6) from the pump chamber forming surface (11) such that a tip of the rod (8) faces the pump chamber forming surface (11), and moving in the axial direction to change the distance between the tip and the pump chamber forming surface (11); and a pressing member (10) attached to the tip of the rod (8) in a state in which the diaphragm (6) is held between the pressing member (10) and the tip of the rod (8). The diaphragm (6) has a shape following the pump chamber forming surface (11) when the rod (8) is at top dead center, closest to the pump chamber forming surface.

Description

Vacuum pump, degassing device, and liquid chromatograph

[0001] The present invention relates to a vacuum pump, a degassing device, and a liquid chromatograph.

[0002] In a high-performance liquid chromatograph (hereinafter referred to as HPLC), a degassing device for removing dissolved oxygen and bubbles contained in the mobile phase fed by a liquid feed pump is provided. The degassing device is an apparatus in which a gas-permeable tube that allows gas to pass through and does not allow liquid to pass through is provided in a vacuum chamber, and by reducing the pressure in the vacuum chamber with a vacuum pump, gas components are extracted from the liquid flowing in the gas-permeable tube and discharged to the outside of the vacuum chamber (see Patent Document 1).

[0003] A diaphragm-type vacuum pump is often used as the vacuum pump of the degassing device for HPLC. The diaphragm-type vacuum pump is provided with a diaphragm so as to cover the pump chamber forming surface provided on the pump head, and a pump chamber is formed between the pump chamber forming surface and the diaphragm. The diaphragm is held at the tip of a rod, and when the rod is driven in the axial direction, the volume of the pump chamber changes, and gas is inhaled into and discharged from the pump chamber.

[0004] Japanese Patent No. 6991592

[0005] In order to improve the degassing performance of the degassing device, it is necessary to increase the degree of vacuum of the vacuum pump. In order to increase the degree of vacuum of the vacuum pump, it is preferable to make the internal volume of the pump chamber (this is referred to as the compression volume) as small as possible when the rod reaches the top dead center and discharges all the gas in the pump chamber.

[0006] To reduce the compression capacity of a vacuum pump, it is common practice to operate the vacuum pump during installation to reduce the pressure inside the pump chamber and use the pressure difference between the inside and outside of the pump chamber to deform the diaphragm, thus performing aging. However, if the diaphragm has a certain thickness, the viscoelasticity of the diaphragm material causes the diaphragm to return to its original shape when the vacuum pump is stopped, requiring aging to be performed again before the next use. Therefore, it is conceivable to form the diaphragm from a material that is easily deformable or to reduce the thickness of the diaphragm. However, since the gaseous components extracted from the mobile phase of an HPLC by a degassing device include vaporized organic solvents, it is not possible to use rubber or other materials that do not have chemical resistance as the diaphragm material, and it is necessary to use a diaphragm made of fluororesin such as PTFE (polytetrafluoroethylene). Furthermore, reducing the thickness of the diaphragm reduces durability and makes it more prone to wrinkles, making it difficult to stabilize the diaphragm's shape.

[0007] Furthermore, a thicker diaphragm presents the problem of requiring a long aging period to sufficiently reduce the compression capacity. Therefore, one might consider reducing the rod stroke to decrease the amount of diaphragm deformation required to reduce the compression capacity. However, reducing the rod stroke also reduces the internal volume of the pump chamber when the rod reaches bottom dead center, making it impossible to increase the compression ratio and ultimately preventing an increase in the vacuum level.

[0008] This invention was made in view of the above problems, and aims to achieve a high degree of vacuum without requiring long-term aging of the vacuum pump.

[0009] The vacuum pump according to the present invention comprises: a pump head having a pump chamber forming surface that forms the inner surface of a pump chamber; a diaphragm provided so as to cover the pump chamber forming surface of the pump head and to form a pump chamber between itself and the pump chamber forming surface; a rod provided on the opposite side of the diaphragm from the pump chamber forming surface, with its tip facing the pump chamber forming surface, and which moves axially to change the distance between its tip and the pump chamber forming surface; and a retaining member attached to the tip of the rod with the diaphragm sandwiched between it and the tip of the rod, wherein the diaphragm has a shape that conforms to the pump chamber forming surface when the rod is at its top dead center, closest to the pump chamber forming surface.

[0010] The degassing apparatus according to the present invention comprises a degassing channel made of a gas-permeable tube that allows gas to pass through but not liquid, a vacuum chamber that houses the degassing channel inside, and a vacuum pump according to the present invention connected to the vacuum chamber for reducing the pressure inside the vacuum chamber, and performs degassing of the mobile phase flowing in the degassing channel.

[0011] The liquid chromatograph according to the present invention comprises: a liquid delivery pump for delivering a mobile phase; a degassing device according to the present invention for degassing the mobile phase delivered by the liquid delivery pump; an autosampler fluidly connected downstream of the liquid delivery pump for injecting a sample into the mobile phase; a separation column fluidly connected downstream of the autosampler for separating a plurality of components in the sample injected into the mobile phase by the autosampler from each other; and a detector fluidly connected downstream of the separation column for detecting each component separated by the separation column.

[0012] The manufacturing method according to the present invention is a method for manufacturing the diaphragm of the vacuum pump according to the present invention as described above, and includes the steps of: preparing an upper mold; preparing a lower mold; preparing a material for forming the diaphragm; sandwiching the material between the upper mold and the lower mold; and applying heat to the material sandwiched between the upper mold and the lower mold to thermoform the material into a predetermined shape of the diaphragm and obtain the diaphragm, wherein the predetermined shape is a shape that follows the pump chamber forming surface when the rod is at the top dead center.

[0013] According to the vacuum pump of the present invention, since the rod is shaped to conform to the pump chamber forming surface when it is at top dead center, the internal volume of the pump chamber formed by the pump chamber forming surface and the diaphragm becomes smaller when the rod reaches top dead center. As a result, a high vacuum level can be achieved without requiring long-term aging.

[0014] The degassing device according to the present invention is configured to reduce the pressure inside the vacuum chamber using the vacuum pump according to the present invention described above. This eliminates the need for long-term aging of the vacuum pump, while achieving a high degree of vacuum in the pump chamber of the vacuum pump, thereby providing high degassing performance.

[0015] According to the liquid chromatograph of the present invention, since the degassing device described above is used as the degassing device for degassing the mobile phase, the degassing of the mobile phase is performed efficiently, and problems such as fluctuations in the flow rate of the mobile phase, fluctuations in the baseline of the detector signal, and a decrease in detection sensitivity caused by gaseous components contained in the mobile phase are suppressed.

[0016] According to the diaphragm manufacturing method of the present invention, a diaphragm is formed by heating and thermoforming a material for forming a diaphragm while it is sandwiched between two molds, thereby forming a diaphragm that has a shape along the pump chamber forming surface when the rod of the vacuum pump is at its top dead center, closest to the pump chamber forming surface of the pump head. Therefore, by using a diaphragm formed by this manufacturing method in a vacuum pump, a vacuum pump with a high degree of vacuum can be obtained.

[0017] This is a cross-sectional view of the vicinity of the pump head showing an embodiment of a vacuum pump, with the rod at its top dead center. This is a cross-sectional view of the vicinity of the pump head showing the rod at its bottom dead center in the same embodiment. This is an exploded cross-sectional view of the same embodiment. This is a diagram showing the first half of the procedure in an embodiment of a diaphragm manufacturing method. This is a diagram showing the second half of the procedure in the same embodiment. This is a schematic configuration diagram showing an embodiment of a degassing device and a liquid chromatograph.

[0018] The vacuum pump, degassing device, and liquid chromatograph according to the present invention will be described below with reference to the drawings.

[0019] Figures 1 and 2 show cross-sectional views of the vicinity of the pump head 4 of the vacuum pump 1. Figure 1 shows the rod 8 at its top dead center, and Figure 2 shows the rod 8 at its bottom dead center.

[0020] The vacuum pump 1 comprises a housing 2, a pump head 4, a diaphragm 6, a rod 8, and a retaining member 10.

[0021] The pump head 4 is attached to the housing 2 by bolts (not shown). The pump head 4 has a recessed pump chamber forming surface 11 on the side facing the housing 2. The diaphragm 6 is made of a fluororesin such as PTFE. The diaphragm 6 is positioned to cover the pump chamber forming surface 11 of the pump head 6, and its peripheral edge is sandwiched between the housing 2 and the pump head 4, holding it inside the vacuum pump 1. A pump chamber 16 is formed between the pump chamber forming surface 11 and the diaphragm 6.

[0022] The rod 8 is positioned on the opposite side of the pump chamber forming surface 11 from the diaphragm 6, with its tip facing the pump chamber forming surface 11 side (upward in the figure) of the pump head 4. The rod 8 is reciprocated axially (vertically) by a drive mechanism (not shown) such as a cam mechanism provided in the housing 2, so as to change the distance between its tip and the pump chamber forming surface 11.

[0023] The retaining member 10 is fixed to the tip of the rod 8 by a fixing member such as a bolt. The retaining member 10 is positioned to contact or come close to the pump chamber forming surface 11 when the rod 8 reaches the top dead center, which is the closest point to the pump chamber forming surface 11 of the pump head 4. The surface of the retaining member 10 facing the pump chamber forming surface 11 has a shape corresponding to the portion of the pump chamber forming surface 11 facing the retaining member 10, and is designed so that the gap between the retaining member 10 and the pump chamber forming surface 11 disappears or becomes smaller when the rod 8 reaches the top dead center.

[0024] The diaphragm 6 is held at the tip of the rod 8 by being sandwiched between the tip of the rod 8 and the fixing member 10 at its central portion, and changes the internal volume of the pump chamber 16 formed between the diaphragm and the pump chamber forming surface 11 as the rod 8 moves in the axial direction.

[0025] The pump head 4 is provided with a fluid inlet (not shown in the figure) for drawing fluid into the pump chamber 16 from outside the vacuum pump 1, and a fluid outlet (not shown in the figure) for discharging fluid from the pump chamber 16 to the outside of the vacuum pump 1. The fluid inlet and fluid outlet, respectively, are connected to the pump chamber 16 formed between the pump chamber forming surface 11 and the diaphragm 6 via an inlet check valve 12 and an outlet check valve 14 provided inside the pump head 4. The inlet check valve 12 opens during the suction operation when the rod 8 moves from top dead center to bottom dead center to increase the internal volume of the pump chamber 16, and closes during the discharge operation when the rod 8 moves from bottom dead center to top dead center to decrease the internal volume of the pump chamber 16. The outlet check valve 14 closes during the suction operation and opens during the discharge operation.

[0026] Here, as shown in Figure 3, the diaphragm 6, before being incorporated into the vacuum pump 1, has an inner circumferential flange 20 located in the center, a diaphragm body portion 22 connected to the inner circumferential flange 20 and surrounding the outer circumference of the inner circumferential flange 20, and an outer circumferential flange 24 connected to the diaphragm body portion 22 and surrounding the outer circumference of the diaphragm body portion 22. The inner circumferential flange 20 is the portion sandwiched between the tip of the rod 8 and the retaining member 10, and the outer circumferential flange 24 is the portion sandwiched between the housing 2 and the pump head 4. A through hole 26 is provided in the center of the inner circumferential flange 20. The through hole 26 is for allowing the threaded portion 10a of the retaining member 10 to pass through, which is fitted into the threaded hole 8a on the tip surface of the rod 8 when the retaining member 10 is attached to the tip of the rod 8. The shape of the diaphragm 6 is designed so that when the rod 8 reaches its top dead center, the outer circumference 22a of the diaphragm body 22 is substantially parallel to the pump chamber forming surface 11. Preferably, the diaphragm 6 is formed such that when the rod reaches its top dead center, the distance between the outer circumference 22a of the diaphragm body 22 and the pump chamber forming surface 11 is 1 mm or less.

[0027] By having the shape described above before the diaphragm 6 is incorporated into the vacuum pump 1, the internal volume (compression capacity) of the pump chamber 16 between the diaphragm 6 and the pump chamber forming surface 11 can be brought as close to zero as possible when the rod 8 reaches top dead center, thereby enabling a high vacuum level for the vacuum pump 1.

[0028] Because the diaphragm 6 has the shape described above from the beginning, there is no need to perform aging to reduce the compression capacity, and the viscoelasticity of the diaphragm 6 material prevents the curved portion of the diaphragm 6 from returning to its straight shape. Therefore, the diaphragm 6 can be formed by thermoforming a thick sheet of PTFE or the like, resulting in a highly durable diaphragm 6. In addition, since the diaphragm 6 is shaped by thermoforming so that the compression capacity becomes almost zero when the rod 8 reaches top dead center, the stroke of the rod 8 can be increased to achieve a high compression ratio.

[0029] When the diaphragm 6 is formed from a PTFE sheet with a diameter of 30 to 40 mm, for example, the thickness can be 0.1 mm or more (for example, about 0.2 to 0.4 mm). If a PTFE sheet of such thickness is used as a diaphragm in a flat plate shape, it requires a long aging period to reduce the compression capacity, and due to the viscoelasticity of PTFE, it may return to its original shape when the compression pump is not running, potentially requiring further aging. On the other hand, if the PTFE sheet is pre-shaped as described above to form the diaphragm 6, aging is unnecessary, and the shape does not return to its original state due to the viscoelasticity of PTFE, allowing for a small compression capacity to be achieved over a long period of time.

[0030] A diaphragm 6 having the shape described above can be obtained using thermoforming. An example of a method for manufacturing the diaphragm 6 will be described with reference to Figures 4 and 5.

[0031] As shown in Figure 4(A), a PTFE sheet 30, an upper mold 32, and a lower mold 34 are prepared, which are the materials for forming the diaphragm 6. A through hole 31 is provided in the center of the PTFE sheet 30. The through hole 31 will form a through hole 26 when it becomes the diaphragm 6. The opposing surfaces of the molds 32 and 34 are provided with irregularities for forming the inner circumferential flange 20, the diaphragm body portion 22, and the outer circumferential flange 24 of the diaphragm 6. In addition, a projection 35 having the same outer diameter as the inner diameter of the through hole 31 is provided on the mold surface of the lower mold 34 (upper surface in the figure), and a recess 33 is provided on the mold surface of the upper mold 32 (lower surface in the figure) at a position corresponding to the projection 35 of the lower mold 34 into which the projection 35 is fitted.

[0032] Next, as shown in Figure 4(B), the PTFE sheet 30 is set on the lower mold 34. At this time, the projection 35 of the lower mold 34 is passed through the through hole 31 of the PTFE sheet 30, thereby positioning the PTFE sheet 30 relative to the lower mold 34.

[0033] Subsequently, as shown in Figure 5(C), the mold surface of the upper mold 32 is superimposed on the mold surface of the lower mold 34 so that the projection 35 of the lower mold 34 fits into the recess 33 of the upper mold 32, the PTFE sheet 30 is sandwiched between the two molds 32 and 34, and the PTFE sheet 30 is heated by heating either or both of the molds 32 and 34, thereby thermoforming the PTFE sheet 30. This results in a diaphragm 6 having an inner flange 20, a diaphragm body 22, and an outer flange 24, as shown in Figure 5(D).

[0034] Furthermore, the diaphragm 6 is not limited to one obtained by the thermoforming method described above, but may also be manufactured by resin molding.

[0035] Next, a liquid chromatograph 100 equipped with a degassing device 104 using the vacuum pump 1 described above will be explained with reference to Figure 6.

[0036] The liquid chromatograph 100 comprises a liquid delivery pump 102, a degasser 104, an autosampler 106, a separation column 108, and a detector 110. The liquid delivery pump 102 delivers the mobile phase to the separation column 108. The degasser 104 is located upstream of the liquid delivery pump 102 and degasss the mobile phase. The autosampler 106 is fluid-connected downstream of the liquid delivery pump 102 and injects the sample into the mobile phase. The separation column 108 is fluid-connected downstream of the liquid delivery pump 102 and separates the multiple components contained in the sample injected into the mobile phase by the autosampler 106. The detector 110 is fluid-connected downstream of the separation column 108 and detects each of the multiple components separated from each other by the separation column 108.

[0037] The degassing device 104 comprises a degassing channel 112 made of a gas-permeable tube that allows gas to pass through but not liquid, a vacuum chamber 114 that houses the degassing channel 112, and a vacuum pump 1 that reduces the pressure inside the vacuum chamber 114 by discharging gas from the vacuum chamber 114 to the outside. The vacuum pump 1 has the structure of the above embodiment and achieves a compression capacity that is very close to zero and a high compression ratio without requiring aging during installation. As a result, the pressure inside the pressure chamber 114 can be reduced with high efficiency. Because the pressure inside the pressure chamber 114 is reduced with high efficiency, gaseous components can be extracted with high efficiency from the mobile phase flowing through the degassing channel 112. As a result, the degassing device 104 can achieve high degassing performance.

[0038] The embodiments described above are merely examples of the vacuum pump, degassing device, and liquid chromatograph according to the present invention. Embodiments of the vacuum pump, degassing device, and liquid chromatograph according to the present invention are as follows.

[0039] One embodiment of the vacuum pump according to the present invention comprises: a pump head having a pump chamber forming surface that forms the inner surface of a pump chamber; a diaphragm provided so as to cover the pump chamber forming surface of the pump head and to form a pump chamber between itself and the pump chamber forming surface; a rod provided on the opposite side of the diaphragm from the pump chamber forming surface, with its tip facing the pump chamber forming surface, and which moves axially to change the distance between its tip and the pump chamber forming surface; and a retaining member attached to the tip of the rod with the diaphragm sandwiched between it and the tip of the rod, wherein the diaphragm has a shape that conforms to the pump chamber forming surface when the rod is at its top dead center, closest to the pump chamber forming surface.

[0040] In the first aspect of the above-described embodiment of the vacuum pump, it further includes a housing, and the diaphragm has: an outer peripheral flange sandwiched between the housing and the pump head; an inner peripheral flange sandwiched between the rod and the pressing member; and a diaphragm main body portion connected to the outer peripheral flange and the inner peripheral flange. The diaphragm is formed such that in a state where the rod is at the top dead center, the shape of the outer peripheral portion of the diaphragm main body portion is substantially parallel to the shape of the pump chamber forming surface.

[0041] In the above first aspect, in a state where the rod is at the top dead center, the distance between the outer peripheral portion of the diaphragm main body portion and the pump chamber forming surface can be 1 mm or less.

[0042] In the second aspect of the above-described embodiment of the vacuum pump, the thickness of the diaphragm is not less than 0.1 mm. This second aspect can be combined with the above first aspect.

[0043] In the third aspect of the above-described embodiment of the vacuum pump, the material of the diaphragm is polytetrafluoroethylene. This third aspect can be combined with the above first aspect and / or the second aspect.

[0044] In the fourth aspect of the above-described embodiment of the vacuum pump, the diaphragm is thermoformed so as to have a shape along the pump chamber forming surface in a state where the rod is at the top dead center closest to the pump chamber forming surface. This fourth aspect can be combined with the above first aspect, the second aspect, and / or the third aspect.

[0045] An embodiment of the degassing device according to the present invention includes a degassing flow path composed of a gas-permeable tube that allows gas to pass through but not liquid, a vacuum chamber that houses the degassing flow path inside, and the above-described vacuum pump connected to the vacuum chamber to decompress the inside of the vacuum chamber, and performs degassing of the mobile phase flowing through the degassing flow path.

[0046] One embodiment of the liquid chromatograph according to the present invention includes a liquid delivery pump for delivering a mobile phase, the above-described degassing device for degassing the mobile phase delivered by the liquid delivery pump, an autosampler fluid-connected downstream of the liquid delivery pump for injecting a sample into the mobile phase, a separation column fluid-connected downstream of the autosampler for separating a plurality of components in the sample injected into the mobile phase by the autosampler from each other, and a detector fluid-connected downstream of the separation column for detecting each component separated by the separation column.

[0047] One embodiment of the manufacturing method according to the present invention is a method for manufacturing the diaphragm included in one embodiment of the above-described vacuum pump, including a step of preparing an upper mold, a step of preparing a lower mold, a step of preparing a material for forming the diaphragm, a step of sandwiching the material between the upper mold and the lower mold, and a step of thermoforming the material into a predetermined shape of the diaphragm by applying heat to the material sandwiched between the upper mold and the lower mold to obtain the diaphragm, wherein the predetermined shape is a shape along the pump chamber forming surface in a state where the rod is at the top dead center.

[0048] In the above embodiment of the manufacturing method, the material may be a sheet made of polytetrafluoroethylene.

[0049] Furthermore, another embodiment of the manufacturing method according to the present invention is a method for manufacturing the diaphragm provided in the vacuum pump of the first aspect of the above-described embodiment, comprising the steps of: preparing an upper mold; preparing a lower mold; preparing a material for forming the diaphragm; sandwiching the material between the upper mold and the lower mold; and applying heat to the material sandwiched between the upper mold and the lower mold to thermoform the material into a predetermined shape of the diaphragm, thereby obtaining the diaphragm, wherein the predetermined shape has an outer peripheral flange sandwiched between the housing and the pump head, an inner peripheral flange sandwiched between the rod and the retaining member, and a diaphragm body connected to the outer peripheral flange and the inner peripheral flange, and the shape of the outer peripheral portion of the diaphragm body is substantially parallel to the shape of the pump chamber forming surface when the rod is at the top dead center.

[0050] In the other embodiments described above, the material may be a sheet made of polytetrafluoroethylene.

[0051] 1 Vacuum pump 2 Housing 4 Pump head 6 Diaphragm 8 Rod 8a Screw hole 10 Retaining member 10a Screw part 11 Pump chamber forming surface 12 Inlet check valve 14 Outlet check valve 16 Pump chamber 20 Inner flange 22 Diaphragm body 22a Outer circumference of diaphragm body 24 Outer flange 26, 31 Through hole 30 Material (PTFE sheet) 32 Upper mold 33 Recess 34 Lower mold 35 Projection 100 Liquid chromatograph 102 Liquid transfer pump 104 Degassing device 106 Autosampler 108 Separation column 110 Detector 112 Degassing channel 114 Vacuum chamber

Claims

1. A vacuum pump comprising: a pump head having a pump chamber forming surface that forms the inner surface of a pump chamber; a diaphragm provided so as to cover the pump chamber forming surface of the pump head and to form a pump chamber between itself and the pump chamber forming surface; a rod provided on the opposite side of the diaphragm from the pump chamber forming surface, with its tip facing the pump chamber forming surface, and which moves axially to change the distance between its tip and the pump chamber forming surface; and a retaining member attached to the tip of the rod with the diaphragm sandwiched between it and the tip of the rod, wherein the diaphragm has a shape that conforms to the pump chamber forming surface when the rod is at its top dead center, closest to the pump chamber forming surface.

2. The vacuum pump according to claim 1, further comprising a housing, wherein the diaphragm has an outer peripheral flange sandwiched between the housing and the pump head, an inner peripheral flange sandwiched between the rod and the retaining member, and a diaphragm body connected to the outer peripheral flange and the inner peripheral flange, wherein the diaphragm is formed such that, when the rod is at the top dead center, the shape of the outer peripheral portion of the diaphragm body is substantially parallel to the shape of the pump chamber forming surface.

3. The vacuum pump according to claim 2, wherein, when the rod is at the top dead center, the distance between the outer circumference of the diaphragm body and the pump chamber forming surface is 1 mm or less.

4. The vacuum pump according to claim 1, wherein the thickness of the diaphragm is 0.1 mm or more.

5. The vacuum pump according to claim 1, wherein the material of the diaphragm is polytetrafluoroethylene.

6. The vacuum pump according to claim 1, wherein the diaphragm is thermoformed to conform to the shape of the pump chamber forming surface when the rod is at its top dead center, closest to the pump chamber forming surface.

7. A degassing apparatus comprising: a degassing channel made of a gas-permeable tube that allows gas to pass through but not liquid; a vacuum chamber housing the degassing channel inside; and a vacuum pump according to claim 1 connected to the vacuum chamber for reducing the pressure inside the vacuum chamber, wherein the apparatus degasses a mobile phase flowing through the degassing channel.

8. A liquid chromatograph comprising: a liquid delivery pump for delivering a mobile phase; a degassing device according to claim 4 for degassing the mobile phase delivered by the liquid delivery pump; an autosampler fluidly connected downstream of the liquid delivery pump for injecting a sample into the mobile phase; a separation column fluidly connected downstream of the autosampler for separating a plurality of components in the sample injected into the mobile phase by the autosampler from each other; and a detector fluidly connected downstream of the separation column for detecting each component separated by the separation column.

9. A method for manufacturing the diaphragm of a vacuum pump according to claim 1, comprising the steps of: preparing an upper mold; preparing a lower mold; preparing a material for forming the diaphragm; sandwiching the material between the upper mold and the lower mold; and applying heat to the material sandwiched between the upper mold and the lower mold to thermoform the material into a predetermined shape of the diaphragm, thereby obtaining the diaphragm, wherein the predetermined shape is a shape that follows the pump chamber forming surface when the rod is at the top dead center.

10. The manufacturing method according to claim 9, wherein the material is a sheet made of polytetrafluoroethylene.

11. A method for manufacturing the diaphragm of a vacuum pump according to claim 2, comprising the steps of: preparing an upper mold; preparing a lower mold; preparing a material for forming the diaphragm; sandwiching the material between the upper mold and the lower mold; and applying heat to the material sandwiched between the upper mold and the lower mold to thermoform the material into a predetermined shape of the diaphragm, thereby obtaining the diaphragm, wherein the predetermined shape comprises an outer peripheral flange sandwiched between the housing and the pump head, an inner peripheral flange sandwiched between the rod and the retaining member, and a diaphragm body connected to the outer peripheral flange and the inner peripheral flange, wherein, when the rod is at the top dead center, the shape of the outer peripheral portion of the diaphragm body is substantially parallel to the shape of the pump chamber forming surface.

12. The manufacturing method according to claim 11, wherein the material is a sheet made of polytetrafluoroethylene.

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