Flow rate switching mechanism and mass spectroscope

Abstract

To provide a flow rate switching mechanism which can be realized at a low cost and can be easily controlled.SOLUTION: A flow rate switching mechanism comprises: a first channel narrowing part 200 including a first housing which has a passage that penetrates the inside thereof and in which the passage has a narrow part having a smaller cross-sectional area than a cross-sectional area of the passage on one end at a position apart from the one end, a capillary 230 which has an internal passage having a smaller cross-sectional area than the narrow part, and a sealing support member which supports the capillary in the passage and seals a gap between the outer peripheral surface of the capillary and the inner peripheral surface of the passage; a second channel narrowing part 300 including a second housing in a same shape as the first housing and not including the capillary and the sealing support member; and a three-way valve 150 including an exit end 153, a first inlet end 151 connected to the other end of the passage of the first channel narrowing part and a second inlet end 152 connected to the other end of the passage of the second channel narrowing part, and which can switch between a state where the exit end is connected to the first inlet end and a state where the exit end is connected to the second inlet end.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a flow rate switching mechanism for switching the flow rate of a gas flowing through a pipe, and a mass spectrometer equipped with the same. [Background technology]

[0002] 2. Description of the Related Art In an apparatus equipped with a vacuum chamber, such as a mass spectrometer, a plurality of vacuum pumps with different operable pressures may be used to evacuate the vacuum chamber (see, for example, Patent Document 1, etc.).

[0003] A mass spectrometer equipped with such a plurality of vacuum pumps will be described with reference to FIG. 7. This mass spectrometer includes an ionization section 10 that generates ions from a sample, an analysis section 20 that mass separates and detects the generated ions, and an exhaust section 30 that exhausts the internal space of the analysis section 20. The analysis section 20 includes a first vacuum chamber 21, a second vacuum chamber 22, and a third vacuum chamber 23 in order from the side closer to the ionization section 10, and has a multi-stage differential exhaust system configuration in which the degree of vacuum is increased stepwise in this order. The exhaust section 30 includes a first pump 31 that is a turbo molecular pump and a second pump 32 that is a rotary pump. An intake port 33 of the second pump 32 is connected to the first vacuum chamber 21 via a first pipe 34, and an exhaust port 35 of the second pump 32 is open to the atmosphere. In addition, one of the two intake ports 36 and 37 provided in the first pump 31 is directly connected to the second vacuum chamber 22, and the other intake port 37 is directly connected to the third vacuum chamber 23. Further, the exhaust port 38 of the first pump 31 is connected midway through the first pipe 34 via a second pipe 39 .

[0004] In such a configuration, the second pump 32 serves to evacuate the first vacuum chamber 21 to a desired vacuum level and maintain the vacuum level, and also serves as a roughing pump that evacuates the second vacuum chamber 22 and the third vacuum chamber 23 to a pressure at which the first pump 31 can operate, and also serves as an auxiliary pump that maintains the back pressure of the first pump 31 by discharging air sent out from the first pump 31. In order to sufficiently exhaust a gas with a small molecular weight (light gas) such as hydrogen by the first pump 31, it is necessary to introduce a gas with a large molecular weight between the first pump 31 and the second pump 32. For this reason, the exhaust unit 30 is provided with an air supply unit 40 for feeding a small amount of air into the second piping 39. However, during standby when mass analysis is not being performed (i.e., the first pump 31 and the second pump 32 are operating but ions are not being introduced into the analysis section 20), the pressure in the second pipe 39 is lower than during analysis when mass analysis is being performed, which may cause the noise generated by the second pump 32 to increase and oil to flow back from the second pump 32 into the first pipe 34. To prevent this, the flow rate of air introduced from the air supply section 40 into the second pipe 39 during standby must be made larger than the flow rate during analysis. For this reason, the air supply section 40 is provided with two types of flow path restrictors 44, 47 with different inner diameters, and the flow rate of air introduced into the second pipe 39 can be changed by switching between the flow path restrictors 44, 47 used during standby and during analysis.

[0005] Specifically, the air supply unit 40 is provided with a first flow path 41 including a first valve 43, a first flow path throttle unit 44, and a first air filter 45, and a second flow path 42 including a second valve 46, a second flow path throttle unit 47, and a second air filter 48, which are arranged in parallel. When the first valve 43 is opened and the second valve 46 is closed, the air that has passed through the first flow path 41 flows into the second pipe 39 (first state), and conversely, when the first valve 43 is closed and the second valve 46 is opened, the air that has passed through the second flow path 42 flows into the second pipe 39 (second state). Each of the first flow path throttle unit 44 and the second flow path throttle unit 47 includes a capillary (not shown) made of a quartz tube or the like, and the flow rate of the air that has flowed into each of the flow path throttle units 44, 47 is restricted by passing through the capillary. Since the capillary included in the second flow path narrowing section 47 has a smaller inner diameter than the capillary included in the first flow path narrowing section 44, by controlling the opening and closing of the first valve 43 and the second valve 46 so that the above-mentioned first state is reached during standby and the above-mentioned second state is reached during analysis, the flow rate of air introduced from the air supply section 40 into the second flow path 42 can be made relatively large during standby and relatively small during analysis. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-091988 A (

[0020] , Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above configuration requires a large number of parts to switch the flow rate, which increases manufacturing costs and makes control complicated.

[0008] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a flow rate switching mechanism that can be realized at low cost and is easy to control, and a mass spectrometer equipped with the same. [Means for solving the problem]

[0009] The flow rate switching mechanism according to the present invention, which has been developed to solve the above problems, comprises: a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrow portion at a position spaced from one end of the first housing, the narrow portion having a cross-sectional area smaller than the cross-sectional area of ​​the passage at the one end; a capillary having an internal passage having a cross-sectional area smaller than the cross-sectional area of ​​the narrow portion; and a sealing support member supporting the capillary within the passage and sealing between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; A second flow path restricting portion having a second housing having the same shape as the first housing and not having a capillary or a sealing support member; a three-way valve having an outlet end, a first inlet end connected to the other end of the passage of the first flow path throttle section, and a second inlet end connected to the other end of the passage of the second flow path throttle section, and configured to be selectively switched between a first state in which the outlet end and the first inlet end are connected and a second state in which the outlet end and the second inlet end are connected; It has the following.

[0010] The flow rate switching mechanism according to the present invention comprises: a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrow portion at a position spaced from one end of the first housing, the narrow portion having a cross-sectional area smaller than the cross-sectional area of ​​the passage at the one end; a capillary having an internal passage having a cross-sectional area smaller than the cross-sectional area of ​​the narrow portion; and a sealing support member supporting the capillary within the passage and sealing between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; A second flow path restricting portion having a second housing having the same shape as the first housing and not having a capillary or a sealing support member; a three-way valve having an inlet end, a first outlet end connected to the one end of the passage of the first flow path throttle section, and a second outlet end connected to one end of the passage of the second flow path throttle section, and configured to be selectively switched between a first state in which the inlet end and the first outlet end are connected and a second state in which the inlet end and the second outlet end are connected; a branch pipe having an outlet port, a first inlet port connected to the other end of the passage of the first flow path throttle section, and a second inlet port connected to the other end of the passage of the second flow path throttle section; The present invention may also have the following structure.

[0011] In order to solve the above problems, the mass spectrometer according to the present invention is A vacuum chamber; a first pump having an inlet and an outlet, the inlet connected to the vacuum chamber; a second pump having an intake port and an exhaust port, the exhaust port being open to the atmosphere; a connection pipe connecting the exhaust port of the first pump and the intake port of the second pump; an air supply pipe having one end connected to the middle of the connection pipe and supplying air to the connection pipe; a flow rate switching mechanism that switches the flow rate of air introduced from the air supply pipe to the connection pipe; A control unit; having The flow rate switching mechanism is a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrow portion at a position spaced from one end of the first housing, the narrow portion having a cross-sectional area smaller than the cross-sectional area of ​​the passage at the one end; a capillary having an internal passage having a cross-sectional area smaller than the cross-sectional area of ​​the narrow portion; and a sealing support member supporting the capillary within the passage and sealing between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; A second flow path restricting portion having a second housing having the same shape as the first housing and not having a capillary or a sealing support member; a three-way valve having an outlet end connected to the other end of the air supply pipe, a first inlet end connected to the other end of the passage of the first flow path throttle section, and a second inlet end connected to the other end of the passage of the second flow path throttle section, and configured to be able to selectively switch between a first state in which the outlet end and the first inlet end are connected and a second state in which the outlet end and the second inlet end are connected; and The control unit controls the three-way valve so that the three-way valve is in the first state when mass analysis is being performed, and is in the second state during standby when the first pump and the second pump are operating and mass analysis is not being performed.

[0012] The mass spectrometer according to the present invention comprises: A vacuum chamber; a first pump having an inlet and an outlet, the inlet connected to the vacuum chamber; a second pump having an intake port and an exhaust port, the exhaust port being open to the atmosphere; a connection pipe connecting the exhaust port of the first pump and the intake port of the second pump; an air supply pipe having one end connected to the middle of the connection pipe and supplying air to the connection pipe; a flow rate switching mechanism that switches the flow rate of air introduced from the air supply pipe to the connection pipe; A control unit; having The flow rate switching mechanism is a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrow portion at a position spaced from one end of the first housing, the narrow portion having a cross-sectional area smaller than the cross-sectional area of ​​the passage at the one end; a capillary having an internal passage having a cross-sectional area smaller than the cross-sectional area of ​​the narrow portion; and a sealing support member supporting the capillary within the passage and sealing between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; A second flow path restricting portion having a second housing having the same shape as the first housing and not having a capillary or a sealing support member; a three-way valve having an inlet end, a first outlet end connected to the one end of the passage of the first flow path throttle section, and a second outlet end connected to one end of the passage of the second flow path throttle section, and configured to be selectively switched between a first state in which the inlet end and the first outlet end are connected and a second state in which the inlet end and the second outlet end are connected; a branch pipe having an outlet port connected to the other end of the air supply pipe, a first inlet port connected to the other end of the passage of the first flow path throttle section, and a second inlet port connected to the other end of the passage of the second flow path throttle section; and The control unit may control the three-way valve so that the three-way valve is in the first state when mass analysis is being performed, and is in the second state during standby when the first pump and the second pump are operating and mass analysis is not being performed. Effect of the Invention

[0013] According to the flow rate switching mechanism or mass spectrometer of the present invention, the flow rate can be switched at low cost, and the control of the flow rate switching can be easily performed. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a mass spectrometer according to an embodiment of the present invention; [Diagram 2] FIG. 4 is a diagram showing an example of a specific configuration of an air supply unit in the embodiment. [Diagram 3] FIG. 4 is a cross-sectional view showing the configuration of a second flow path throttle portion in this embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing the configuration of a first flow path throttle portion in this embodiment. [Diagram 5] 4 is a flowchart showing the operation of the mass spectrometer according to the embodiment. [Figure 6] FIG. 4 is a schematic diagram showing a schematic configuration of a mass spectrometer according to another embodiment of the present invention. [Figure 7] FIG. 1 is a schematic diagram showing a schematic configuration of a conventional mass spectrometer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram showing the general configuration of a mass spectrometer according to this embodiment. This mass spectrometer includes an ionization unit 110 that generates ions from a sample using inductively coupled plasma, an analysis unit 120 that mass separates and detects the generated ions, an exhaust unit 130 that exhausts the internal space of the analysis unit 120, and a control unit 181 that controls the operation of each of the above units.

[0016] The ionization section 110 includes an ionization chamber 111 at approximately atmospheric pressure, and a plasma torch 112 disposed within the ionization chamber 111. The plasma torch 112 includes a sample tube for passing a liquid sample atomized by a nebulizer gas, a plasma gas tube formed on the outer periphery of the sample tube, a cooling gas tube formed on the outer periphery of the plasma gas tube, and a high-frequency induction coil wound around the tip of the cooling gas tube (all not shown). An autosampler 113 for introducing a liquid sample into the plasma torch 112 is provided at the inlet end of the sample tube of the plasma torch 112. When a high-frequency current is applied to the high-frequency induction coil while a plasma generating gas such as argon gas is passed through the plasma gas tube, plasma is generated at the tip of the plasma torch 112. When a sample is introduced from the sample tube in this state, the compounds in the sample are ionized in the high-temperature plasma, and the generated ions are guided to the analysis section 120.

[0017] The analysis section 120 includes a first vacuum chamber 121, a second vacuum chamber 122, and a third vacuum chamber 123 in order from the side closest to the ionization chamber 111, and has a configuration of a multi-stage differential pumping system in which the degree of vacuum is increased stepwise in this order. Here, the analysis section 120 is configured with three vacuum chambers, but the number of partitioned vacuum chambers can be changed as appropriate. The first vacuum chamber 121 functions as an interface for sending ions supplied from the ionization chamber 111 to the subsequent stage and discharging solvent gas and the like. A roughly conical sampling cone is provided on the wall surface on the inlet side of the first vacuum chamber 121, and ions are introduced into the first vacuum chamber 121 through a small ion passage hole formed at the top of the sampling cone. The second vacuum chamber 122 is provided with an ion lens 124 for converging the flight trajectory of the ions, and a collision cell 125 for removing interfering ions such as polyatomic ions by colliding with an inert gas such as helium gas. In the third vacuum chamber 123, a quadrupole mass filter 126 that separates ions based on mass (strictly speaking, m / z) and a detector 127 that detects the mass-separated sample are disposed. The first vacuum chamber 121 and the second vacuum chamber 122, and the second vacuum chamber 122 and the third vacuum chamber 123 are communicated with each other through small ion passage holes. Note that, although the mass separation of ions is performed by the quadrupole mass filter 126 here, the mass separation may be performed by a mechanism other than the quadrupole mass filter.

[0018] The exhaust unit 130 includes a turbomolecular pump 131 (corresponding to the first pump in the present invention) and a rotary pump 132 (corresponding to the second pump in the present invention). The turbomolecular pump 131 includes two intake ports 136 and 137 and one exhaust port 138, and the rotary pump 132 includes one intake port 133 and one exhaust port 135. The intake port 133 of the rotary pump 132 is connected to the first vacuum chamber 121 via a first pipe 134, and the exhaust port 135 of the same pump is open to the atmosphere. Of the two intake ports 136 and 137 of the turbomolecular pump 131, one intake port 136 is directly connected to the second vacuum chamber 122, and the other intake port 137 is directly connected to the third vacuum chamber 123. In addition, the exhaust port 138 of the turbo molecular pump 131 is connected to the middle of the first pipe 134 via the second pipe 139 (the area downstream of the middle of the first pipe 134 and the second pipe 139 correspond to the connecting pipe in the present invention). In this embodiment, the rotary pump 132 plays a role of evacuating the first vacuum chamber 121 to a target vacuum level and maintaining the vacuum level, and also plays a role of a roughing pump that evacuates the second vacuum chamber 122 and the third vacuum chamber 123 to a predetermined pressure that can be evacuated by the turbo molecular pump 131, and a role of an auxiliary pump that maintains the back pressure of the turbo molecular pump 131 by discharging air sent from the turbo molecular pump 131. On the other hand, the turbo molecular pump 131 plays a role of evacuating the second vacuum chamber 122 and the third vacuum chamber 123, which have been evacuated to the predetermined pressure by the rotary pump 132, to a target vacuum level and maintaining the vacuum level.

[0019] As described above, in order to exhaust light gas such as hydrogen sufficiently by the turbo molecular pump 131, it is necessary to introduce a gas with a large molecular weight between the turbo molecular pump 131 and the rotary pump 132. For this reason, the exhaust unit 130 is provided with an air supply unit 140 for feeding a small amount of air into the second pipe 139. Furthermore, as described above, it is necessary to make the flow rate of air introduced into the second pipe 139 relatively large when the mass spectrometer is on standby and to make the flow rate relatively small when analysis is being performed. Therefore, the air supply unit 140 is configured to be able to switch the flow rate of air flowing into the second pipe 139 between the standby state and the analysis state. The air supply unit 140 will be described in detail below.

[0020] An example of a specific configuration of the air supply unit 140 in this embodiment is shown in Fig. 2. The air supply unit 140 includes a first flow path throttle unit 200, a second flow path throttle unit 300, a three-way valve 150, a branch pipe 160, and an air filter 170, all of which are configured to allow gas to flow therethrough (however, the air filter 170 is not shown in Fig. 2). Among these, the first flow path throttle unit 200, the second flow path throttle unit 300, and the three-way valve 150 correspond to the flow rate switching mechanism in the present invention. The three-way valve 150 is an electromagnetic valve or an electric valve having two inlet ends (hereinafter referred to as a first inlet end 151 and a second inlet end 152) and one outlet end 153, and is configured to be able to selectively switch between a first state in which the first inlet end 151 and the outlet end 153 are connected, and a second state in which the second inlet end 152 and the outlet end 153 are connected. The branch pipe 160 has three opening ends (hereinafter referred to as a first opening end 161, a second opening end 162, and a third opening end 163). The first flow path throttle section 200 has one inlet end 201 and one outlet end 202, and similarly the second flow path throttle section 300 has one inlet end 301 and one outlet end 302. The outlet end 153 of the three-way valve 150 is connected to the middle of the second pipe 139 via a third pipe 141 (corresponding to the air supply pipe in the present invention). The third opening end 163 of the branch pipe 160 is open to the atmosphere via a fourth pipe 142, and an air filter 170 is disposed in the middle of the fourth pipe 142. An inlet end 201 of the first flow path throttle section 200 is connected to a first opening end 161 of the branch pipe 160 via a fifth pipe 143, and an outlet end 202 of the first flow path throttle section 200 is directly connected to a first inlet end 151 of the three-way valve 150. An inlet end 301 of the second flow path throttle section 300 is connected to a second opening end 162 of the branch pipe 160 via a sixth pipe 144, and an outlet end 302 of the second flow path throttle section 300 is directly connected to a second inlet end 152 of the three-way valve 150. The first flow path throttle section 200 and the fifth pipe 143 are connected to each other via a first joint 145, and the second flow path throttle section 300 and the sixth pipe 144 are connected to each other via a second joint 146.

[0021] The first flow path throttle section 200 and the second flow path throttle section 300 are both portions that restrict the flow rate of air flowing into the second pipe 139 by narrowing the cross-sectional area of ​​the flow path through which the air flows. Here, the second flow path throttle section 300, which has a simpler configuration, will be described first with reference to FIG. 3. The end portion located on the right side of the figure is the inlet end 301 of the second flow path throttle section 300, and the end portion located on the left side of the figure is the outlet end 302 of the second flow path throttle section 300. The second flow path throttle section 300 has a housing 310 having a cross-sectional shape as shown in FIG. 3. The housing 310 is typically made of metal, but is not limited thereto, and may be made of hard plastic, ceramics, or the like. The housing 310 has a substantially cylindrical main body section 311 and a substantially cylindrical protruding section 312 that protrudes from the end face of the main body section 311 on the side opposite to the inlet end 301 and has a smaller outer diameter than the main body section 311. The protrusion 312 is a portion that is screwed into the second inlet end 152 of the three-way valve 150, and has a screw thread 313 formed on its outer circumferential surface.

[0022] A passage 320 for air circulation is formed inside the housing 310 so as to penetrate the housing 310, and the passage 320 opens at an end face on the inlet end 301 side of the main body 311 and an end face on the outlet end 302 side of the protruding portion 312. The passage 320 includes a large diameter portion 321 located at an end on the inlet end 301 side of the housing 310, a small diameter portion 327 (corresponding to the narrow portion in the present invention) located at an end on the outlet end 302 side, and a reduced diameter portion 329 located between the large diameter portion 321 and the small diameter portion 327. The reduced diameter portion 329 includes a first tapered portion 322, a first intermediate portion 323, a second tapered portion 324, a second intermediate portion 325, and a third tapered portion 326. The first tapered portion 322, the first intermediate portion 323, the second tapered portion 324, the second intermediate portion 325, and the third tapered portion 326 are provided in this order from the large diameter portion 321 side toward the small diameter portion 327 side, and the first intermediate portion 323 has an inner diameter smaller than the inner diameter of the large diameter portion 321, and the second intermediate portion 325 has an inner diameter smaller than the inner diameter of the first intermediate portion 323 and larger than the inner diameter of the small diameter portion 327. The first tapered portion 322 has a tapered inner peripheral shape whose diameter gradually decreases from the large diameter portion 321 side toward the first intermediate portion 323 side, and the second tapered portion 324 has a tapered inner peripheral shape whose diameter gradually decreases from the first intermediate portion 323 side toward the second intermediate portion 325 side. The third tapered portion 326 has a tapered inner peripheral shape whose diameter gradually decreases from the second intermediate portion 325 side toward the small diameter portion 327 side. However, the reduction section 329 in the present invention is not necessarily limited to the above configuration as long as it is configured so that the cross-sectional area is reduced stepwise or continuously from the large diameter section 321 side to the small diameter section 327 side. The region on the inlet end 301 side of the large diameter section 321 is a portion into which the end of the second joint 146 is screwed, and a screw thread 328 is formed on the inner circumferential surface of the region. In this embodiment, the large diameter section 321 and the small diameter section 327 both have a circular cross-sectional shape, and the inner diameters of the large diameter section 321 and the small diameter section 327 are 5 mm to 10 mm and 0.3 mm to 1 mm, respectively, but are not limited thereto. In order to ensure the mechanical strength required for connection to the second inlet end 152 of the three-way valve 150, the wall surface of the protrusion 312 needs to have a certain degree of thickness.

[0023] Next, the configuration of the first flow path narrowing section 200 will be described with reference to FIG. 4. In FIG. 4, the components corresponding to those shown in FIG. 3 are denoted by reference characters having the same last two digits. As shown in FIG. 4, the first flow path narrowing section 200 includes a housing 210, a capillary 230 arranged coaxially with the passage 220 in the housing 210, and a sealing support member 240 that holds the capillary 230 and fixes it in the passage 320. The shape, dimensions, and material of the housing 210 are the same as those of the housing 310 of the second flow path narrowing section 300, and therefore the description thereof will be omitted here. The capillary 230 is a thin tube having an inner diameter smaller than the inner diameter of the small diameter section 227 of the housing 210. The inner diameter of the capillary 230 is preferably, for example, about 0.05 mm to 0.5 mm. The outer diameter of the capillary 230 is not particularly limited, and may be smaller or larger than the inner diameter of the small diameter section 227. The length of the capillary may be shorter than the entire length of the passage 220, and is preferably, for example, about 1 / 3 to 2 / 3 of the length of the passage. In FIG. 4, the tip of the capillary 230 (the end located on the outlet end 202 side) is located at the second intermediate portion 225, but the tip of the capillary 230 may be located at, for example, the third tapered portion 226 or the small diameter portion 227. The capillary 230 is typically made of quartz, but is not limited thereto, and may be made of, for example, glass, hard resin, ceramics, metal, or the like. The sealing support member 240 is a cylindrical member made of a material having rubber elasticity, for example, natural rubber, or synthetic rubber such as silicone rubber or urethane rubber, and a capillary insertion hole (not shown) for inserting the capillary 230 is formed at the axial center of the member. The outer diameter of the sealing support member 240 is slightly larger than the inner diameter of the first intermediate portion 223 of the housing 210, and with the capillary 230 inserted into the capillary insertion hole, the sealing support member 240 is advanced into the passage 220 from the opening on the inlet end 201 side and press-fitted into the first intermediate portion 223, thereby holding the capillary 230 in the passage 220. Furthermore, at this time, the gap between the outer periphery of the capillary 230 and the inner periphery of the passage 220 is airtightly sealed by the sealing support member 240.Furthermore, the protrusion 212 of the first flow path restricting portion 200 is screwed into the first inlet end 151 of the three-way valve 150, and the end of the first fitting 145 is screwed into the area of ​​the large diameter portion 221 of the first flow path restricting portion 200 on the inlet end 201 side.

[0024] The cross-sectional area of ​​the small diameter portion 227, 327 of the housing 210, 310 is sufficiently smaller than the cross-sectional area of ​​the air flow path in other areas included in the air supply unit 140 (i.e., the third pipe 141, the fourth pipe 142, the fifth pipe 143, the sixth pipe 144, the three-way valve 150, the air filter 170, the branch pipe 160, the first joint 145, and the second joint 146). In addition, the small diameter portion 227, 327 has a circular cross-sectional shape, and its diameter is larger than the inner diameter of the capillary 230. Therefore, the flow rate of the air flowing from the air supply unit 140 to the second pipe 139 depends on the inner diameter of the capillary 230 in the first flow path throttle portion 200 or the inner diameter of the small diameter portion 327 in the second flow path throttle portion 300, and the flow rate is larger when the three-way valve 150 is in the second state than when it is in the first state.

[0025] The actual entity of the control unit 181 is a computer such as a personal computer, and a CPU included in the computer executes a predetermined program to perform analysis of a sample using the mass spectrometer according to this embodiment. An input unit 182 including a keyboard, a mouse, or the like for inputting instructions from an operator is connected to the computer. For simplification, only the control lines connecting the control unit 181 to the three-way valve 150 or the autosampler 113 are shown in FIG. 1, but the operations of the turbo molecular pump 131 and the rotary pump 132, as well as the operations of the ionization unit 110 and the analysis unit 120 are also controlled by the control unit 181.

[0026] Next, a characteristic operation of the mass spectrometer according to this embodiment will be described with reference to the flowchart of FIG.

[0027] In addition, in a standby state before the start of analysis, the first vacuum chamber 121, the second vacuum chamber 122, and the third vacuum chamber 123 are in a state in which they have been evacuated to a target vacuum level by the rotary pump 132 and the turbo molecular pump 131, respectively. Furthermore, at this time, the three-way valve 150 of the air supply unit 140 is in the above-mentioned second state, and the air that flows into the fourth pipe 142 of the air supply unit 140 and passes through the air filter 170 passes through the second flow path throttle unit 300, and then flows into the second pipe 139 via the three-way valve 150 and the third pipe 141.

[0028] In the above state, when an instruction to start analysis is given by an operator or a preset automatic analysis program (step 1), a liquid sample is introduced into the sample tube of the plasma torch 112 by the autosampler 113 under the control of the control unit 181 (step 2), and further, under the control of the control unit 181, the three-way valve 150 of the air supply unit 140 is switched to the above-mentioned first state (step 3). As a result, the air that has flowed into the fourth pipe 142 of the air supply unit 140 and passed through the air filter 170 passes through the first flow path throttle unit 200, and then flows into the second pipe 139 via the three-way valve 150 and the third pipe 141. Note that steps 2 and 3 may be performed in the reverse order, or may be performed simultaneously.

[0029] The sample introduced into the sample tube in step 2 is ionized in plasma torch 112, and the ions are introduced into analysis section 120 for analysis. Thereafter, when control section 181 determines that the analysis of the sample is complete (i.e., when step 4 is Yes), three-way valve 150 is switched back to the second state under the control of control section 181 (step 5). Whether or not the analysis of the sample is complete can be determined, for example, based on the magnitude of the detection signal from detector 127, or based on whether a predetermined time has passed since the introduction of the sample by autosampler 113.

[0030] Thereafter, the control unit 181 judges whether or not introduction into the ionization unit 110 and analysis in the analysis unit 120 have been completed for all of the one or more samples set in advance (step 6). If there are samples that have not yet been analyzed, the control unit 181 returns to step 2 and repeats steps 3 to 6 above, and ends the series of processes when it is judged that analysis of all samples has been completed (i.e., when step 6 becomes Yes).

[0031] In this way, in the mass spectrometer according to this embodiment, by switching the three-way valve 150 to the first state during analysis and to the second state during standby, the flow rate of air supplied from the air supply unit 140 to the second pipe 139 can be made relatively small during analysis and relatively large during standby. Furthermore, by using the same configuration of housings 210, 310 for the first flow path restricting unit 200 and the second flow path restricting unit 300 and configuring the flow rate restricting effect to differ depending on the presence or absence of the capillary 230, it is possible to reduce manufacturing costs by standardizing parts.

[0032] In the mass spectrometer according to this embodiment, as described above, the first flow path narrowing section 200 is configured to hold the capillary 230 inside the housing 210, and the end of the housing 210 is connected to the members (the three-way valve 150 and the joint 145) constituting the front and rear flow paths. This allows the function of narrowing the flow rate of air supplied from the air supply unit 140 to the second flow path 139 to a level required for analysis and the function of connecting the first flow path narrowing section 200 to the front and rear flow paths to be realized by different parts (i.e., the capillary 230 and the housing 210). Therefore, in the mass spectrometer according to this embodiment, it is not necessary to directly connect the capillary 230 to members such as the three-way valve 150 or the joint 145, and it is not necessary to process a deep hole with a very small inner diameter required for the capillary 230 in the housing 210 configured to be directly connectable to the members. This makes it easier to manufacture the first flow path narrowing section 200, and further reduces the manufacturing cost.

[0033] Furthermore, in the mass spectrometer according to this embodiment, either the first flow path throttle section 200 or the second flow path throttle section 300 can be selectively used to restrict the flow rate by switching one three-way valve 150, thereby simplifying the control related to the switching of the flow rate. Also, by providing one air filter 170 for the two flow path throttle sections 200, 300, the number of parts can be reduced and it is also possible to easily manage the replacement frequency of the air filter 170, which is a consumable item.

[0034] Although the embodiment of the present invention has been described above with specific examples, the present invention is not limited to the above-mentioned embodiment, and appropriate modifications are permitted within the scope of the present invention. For example, the mass spectrometer according to the present invention is not limited to the one that ionizes a sample by inductively coupled plasma as described above, but may be any type of mass spectrometer. Furthermore, the flow rate switching mechanism according to the present invention is not limited to a mass spectrometer, but may be applied to any device that includes a vacuum chamber, a first pump that evacuates the vacuum chamber, and a second pump that exhausts the gas sent from the first pump. The first pump and the second pump in the present invention are not limited to the turbomolecular pump and the rotary pump as described above, but may be any type of pump.

[0035] The sealing support member in the present invention is not limited to the sealing support member 240 in the above embodiment, which has both the function of supporting the capillary 230 in the passage 220 and the function of sealing between the outer periphery of the capillary 230 and the inner periphery of the passage 220, but may be, for example, a combination of a support member arranged in the passage 220, which is a block or ferrule made of metal or resin having a hole through which the capillary 230 is inserted, and a seal member such as an O-ring that seals between the outer periphery of the support member and the inner periphery of the passage 220. In this case, the support member may be fixed in the passage by the seal member, or may be fixed in the passage 220 by a screw or the like that is inserted radially from the outer periphery of the housing 210.

[0036] In the above embodiment, the branch pipe 160 is disposed upstream of the air flow in the air supply unit 140 and the three-way valve 150 is disposed downstream, but the three-way valve 150 may be disposed upstream and the branch pipe 160 downstream. An example of such a mass spectrometer is shown in FIG. 6. In this figure, components that are the same as or correspond to those shown in FIG. 1 are given reference numerals with the same last two digits and their explanations are omitted as appropriate. In addition, the first flow path restricting section 500 and the second flow path restricting section 600 in this example have the same configuration as the first flow path restricting section 200 and the second flow path restricting section 300 in the above embodiment, respectively, and therefore detailed explanations are omitted. 6, the three-way valve 450 is a solenoid valve or motor-operated valve having one inlet end and two outlet ends (hereinafter referred to as a first outlet end and a second outlet end), the inlet end being connected to a fourth pipe 442, the first outlet end being connected to an inlet end of a first flow path throttle section 500 via a fifth pipe 443, and the second outlet end being connected to an inlet end of a second flow path throttle section 600 via a sixth pipe 444. The branch pipe 460 has three opening ends, one of which (corresponding to a first inlet port in the present invention) is connected to an outlet end of the first flow path throttle section 500, another opening end (corresponding to a second inlet port in the present invention) is connected to an outlet end of the second flow path throttle section 600, and the remaining opening end (corresponding to an outlet port in the present invention) is connected to a third pipe 441 (corresponding to an air supply pipe in the present invention). The three-way valve 450 is configured to be capable of alternatively switching between a first state in which the inlet end and the first outlet end are connected, and a second state in which the inlet end and the second outlet end are connected. By switching the three-way valve 450 to the first state when performing analysis and to the second state when on standby, the flow rate of air supplied from the air supply unit 440 to the second piping 439 can be made relatively small when performing analysis and relatively large when on standby.

[0037] [Aspects] It will be apparent to those skilled in the art that the above-described exemplary embodiments are illustrative of the following aspects.

[0038] (Item 1) A mass spectrometer according to one aspect of the present invention comprises: A vacuum chamber; a first pump having an inlet and an outlet, the inlet connected to the vacuum chamber; a second pump having an intake port and an exhaust port, the exhaust port being open to the atmosphere; a connection pipe connecting the exhaust port of the first pump and the intake port of the second pump; an air supply pipe having one end connected to the middle of the connection pipe and supplying air to the connection pipe; a flow rate switching mechanism that switches the flow rate of air introduced from the air supply pipe to the connection pipe; A control unit; having The flow rate switching mechanism is a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrow portion at a position spaced from one end of the first housing, the narrow portion having a cross-sectional area smaller than the cross-sectional area of ​​the passage at the one end; a capillary having an internal passage having a cross-sectional area smaller than the cross-sectional area of ​​the narrow portion; and a sealing support member supporting the capillary within the passage and sealing between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; A second flow path restricting portion having a second housing having the same shape as the first housing and not having a capillary or a sealing support member; a three-way valve having an outlet end connected to the other end of the air supply pipe, a first inlet end connected to the other end of the passage of the first flow path throttle section, and a second inlet end connected to the other end of the passage of the second flow path throttle section, and configured to be able to selectively switch between a first state in which the outlet end and the first inlet end are connected and a second state in which the outlet end and the second inlet end are connected; and The control unit controls the three-way valve so that the three-way valve is in the first state when mass analysis is being performed, and is in the second state during standby when the first pump and the second pump are operating and mass analysis is not being performed.

[0039] (2) A mass spectrometer according to another aspect of the present invention comprises: A vacuum chamber; a first pump having an inlet and an outlet, the inlet connected to the vacuum chamber; a second pump having an intake port and an exhaust port, the exhaust port being open to the atmosphere; a connection pipe connecting the exhaust port of the first pump and the intake port of the second pump; an air supply pipe having one end connected to the middle of the connection pipe and supplying air to the connection pipe; a flow rate switching mechanism that switches the flow rate of air introduced from the air supply pipe to the connection pipe; A control unit; having The flow rate switching mechanism is a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrow portion at a position spaced from one end of the first housing, the narrow portion having a cross-sectional area smaller than the cross-sectional area of ​​the passage at the one end; a capillary having an internal passage having a cross-sectional area smaller than the cross-sectional area of ​​the narrow portion; and a sealing support member supporting the capillary within the passage and sealing between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; A second flow path restricting portion having a second housing having the same shape as the first housing and not having a capillary or a sealing support member; a three-way valve having an inlet end, a first outlet end connected to the one end of the passage of the first flow path throttle section, and a second outlet end connected to one end of the passage of the second flow path throttle section, and configured to be selectively switched between a first state in which the inlet end and the first outlet end are connected and a second state in which the inlet end and the second outlet end are connected; a branch pipe having an outlet port connected to the other end of the air supply pipe, a first inlet port connected to the other end of the passage of the first flow path throttle section, and a second inlet port connected to the other end of the passage of the second flow path throttle section; and The control unit controls the three-way valve so that the three-way valve is in the first state when mass analysis is being performed, and is in the second state during standby when the first pump and the second pump are operating and mass analysis is not being performed.

[0040] According to the mass spectrometer of paragraph 1 or 2, the flow rate of air supplied to the connection pipe via the air supply pipe can be made relatively small when mass analysis is being performed and relatively large when in standby. Also, by using the same housing for the first flow path throttle section and the second flow path throttle section and configuring the flow rate restriction effect to differ depending on the presence or absence of a capillary, it is possible to standardize parts and reduce manufacturing costs. Furthermore, by switching one three-way valve, either the first flow path throttle section or the second flow path throttle section can be selectively used to restrict the flow rate, which simplifies control related to flow rate switching.

[0041] (3) The mass spectrometer according to the third paragraph is a mass spectrometer according to the first or second paragraph, The sealing support member is made of a material having rubber elasticity and has a through hole through which the capillary is inserted, and is press-fitted into the passage.

[0042] According to the mass spectrometer according to the third aspect, the structure of the sealing support member can be simplified, thereby further reducing the manufacturing cost.

[0043] (Item 4) A flow rate switching mechanism according to one aspect of the present invention comprises: a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrow portion at a position spaced from one end of the first housing, the narrow portion having a cross-sectional area smaller than the cross-sectional area of ​​the passage at the one end; a capillary having an internal passage having a cross-sectional area smaller than the cross-sectional area of ​​the narrow portion; and a sealing support member supporting the capillary within the passage and sealing between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; A second flow path restricting portion having a second housing having the same shape as the first housing and not having a capillary or a sealing support member; a three-way valve having an outlet end, a first inlet end connected to the other end of the passage of the first flow path throttle section, and a second inlet end connected to the other end of the passage of the second flow path throttle section, and configured to be selectively switched between a first state in which the outlet end and the first inlet end are connected and a second state in which the outlet end and the second inlet end are connected; It has the following characteristics.

[0044] (5) A flow rate switching mechanism according to another aspect of the present invention comprises: a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrow portion at a position spaced from one end of the first housing, the narrow portion having a cross-sectional area smaller than the cross-sectional area of ​​the passage at the one end; a capillary having an internal passage having a cross-sectional area smaller than the cross-sectional area of ​​the narrow portion; and a sealing support member supporting the capillary within the passage and sealing between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; A second flow path restricting portion having a second housing having the same shape as the first housing and not having a capillary or a sealing support member; a three-way valve having an inlet end, a first outlet end connected to the one end of the passage of the first flow path throttle section, and a second outlet end connected to one end of the passage of the second flow path throttle section, and configured to be selectively switched between a first state in which the inlet end and the first outlet end are connected and a second state in which the inlet end and the second outlet end are connected; a branch pipe having an outlet port, a first inlet port connected to the other end of the passage of the first flow path throttle section, and a second inlet port connected to the other end of the passage of the second flow path throttle section; It has the following characteristics.

[0045] According to the flow rate switching mechanism of paragraph 4 or 5, by switching one three-way valve, either the first flow path throttle section or the second flow path throttle section can be selectively used to restrict the flow rate, so that the control related to the flow rate switching can be simplified. Also, by using the same housing for the first flow path throttle section and the second flow path throttle section and configuring the flow rate restriction effect to differ depending on the presence or absence of a capillary, it is possible to reduce manufacturing costs by standardizing parts.

[0046] (Clause 6) The flow rate switching mechanism according to clause 6 is a flow rate switching mechanism according to clause 4 or 5, The sealing support member is made of a material having rubber elasticity and has a through hole through which the capillary is inserted, and is press-fitted into the passage.

[0047] According to the flow rate switching mechanism according to the sixth aspect, the structure of the sealing support member can be simplified, and the manufacturing costs can be further reduced. [Explanation of symbols]

[0048] 110...Ionization section 120…Analysis Department 121...1st vacuum chamber 122…Second vacuum chamber 123…Third vacuum chamber 130…Exhaust section 131...Turbo molecular pump 132...Rotary pump 134…First pipe 139…Second piping 140...Air supply section 141…Third pipe 150…Three-way valve 160…Branch pipe 170…Air filter 200…First flow passage restriction section 210…Housing 220…Aisle 227...Small diameter section 230…Capillary 240...Sealing support member 300…Second flow passage restriction section 310…Housing 320…Aisle 327...Small diameter section 181...Control unit 182...Input section

Claims

1. a vacuum chamber; a first pump having an inlet and an outlet, the inlet connected to the vacuum chamber; a second pump having an intake port and an exhaust port, the exhaust port being open to the atmosphere; a connecting pipe connecting the exhaust port of the first pump and the intake port of the second pump; an air supply pipe having one end connected to the middle of the connecting pipe and supplying air to the connecting pipe; a flow rate switching mechanism for switching the flow rate of air introduced from the air supply pipe to the connection pipe; A control unit; and The flow rate switching mechanism a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrowed portion at a position spaced from one end thereof, the narrowed portion having a cross-sectional area smaller than the cross-sectional area of the passage at the one end; and a capillary held within the passage, having an internal passage having a cross-sectional area smaller than the cross-sectional area of the narrowed portion, the outer peripheral surface of which is airtightly sealed against the inner peripheral surface of the passage; a second flow path restricting portion having a second housing having the same shape as the first housing and not having the capillary; a three-way valve having an outlet end connected to the other end of the air supply pipe, a first inlet end connected to the other end of the passage of the first flow path throttle section, and a second inlet end connected to the other end of the passage of the second flow path throttle section, and configured to be switchable between a first state in which the outlet end and the first inlet end are connected and a second state in which the outlet end and the second inlet end are connected; and The control unit controls the three-way valve so that the three-way valve is in the first state when mass analysis is being performed, and is in the second state when the first pump and the second pump are operating and mass analysis is not being performed.

2. a vacuum chamber; a first pump having an inlet and an outlet, the inlet connected to the vacuum chamber; a second pump having an intake port and an exhaust port, the exhaust port being open to the atmosphere; a connecting pipe connecting the exhaust port of the first pump and the intake port of the second pump; an air supply pipe having one end connected to the middle of the connecting pipe and supplying air to the connecting pipe; a flow rate switching mechanism for switching the flow rate of air introduced from the air supply pipe to the connection pipe; A control unit; and The flow rate switching mechanism a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrowed portion at a position spaced from one end thereof, the narrowed portion having a cross-sectional area smaller than the cross-sectional area of the passage at the one end; and a capillary held within the passage, having an internal passage having a cross-sectional area smaller than the cross-sectional area of the narrowed portion, the outer peripheral surface of which is airtightly sealed against the inner peripheral surface of the passage; a second flow path restricting portion having a second housing having the same shape as the first housing and not having the capillary; a three-way valve having an inlet end, a first outlet end connected to one end of the passage of the first flow path throttle section, and a second outlet end connected to one end of the passage of the second flow path throttle section, and configured to be switchable between a first state in which the inlet end and the first outlet end are connected and a second state in which the inlet end and the second outlet end are connected; a branch pipe having an outlet port connected to the other end of the air supply pipe, a first inlet port connected to the other end of the passage of the first flow path throttle section, and a second inlet port connected to the other end of the passage of the second flow path throttle section; and The control unit controls the three-way valve so that the three-way valve is in the first state when mass analysis is being performed, and is in the second state when the first pump and the second pump are operating and mass analysis is not being performed.

3. Furthermore, a sealing support member that supports the capillary in the passage of the first flow path throttle portion and seals between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; and 3. The mass spectrometer according to claim 1, wherein the sealing support member is made of a rubber-elastic material and has a through-hole through which the capillary is inserted, and is press-fitted into the passage.

4. a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrowed portion at a position spaced from one end thereof, the narrowed portion having a cross-sectional area smaller than the cross-sectional area of the passage at the one end; and a capillary held within the passage, having an internal passage having a cross-sectional area smaller than the cross-sectional area of the narrowed portion, the outer peripheral surface of which is airtightly sealed against the inner peripheral surface of the passage; a second flow path restricting portion having a second housing having the same shape as the first housing and not having the capillary; a three-way valve having an outlet end, a first inlet end connected to the other end of the passage of the first flow path throttle section, and a second inlet end connected to the other end of the passage of the second flow path throttle section, and configured to be switchable between a first state in which the outlet end and the first inlet end are connected and a second state in which the outlet end and the second inlet end are connected; A flow rate switching mechanism having a

5. a first flow path restricting section including: a first housing having a passage penetrating therethrough, the passage having a narrowed portion at a position spaced from one end thereof, the narrowed portion having a cross-sectional area smaller than the cross-sectional area of the passage at the one end; and a capillary held within the passage, having an internal passage having a cross-sectional area smaller than the cross-sectional area of the narrowed portion, the outer peripheral surface of which is airtightly sealed against the inner peripheral surface of the passage; a second flow path restricting portion having a second housing having the same shape as the first housing and not having the capillary; a three-way valve having an inlet end, a first outlet end connected to one end of the passage of the first flow path throttle section, and a second outlet end connected to one end of the passage of the second flow path throttle section, and configured to be switchable between a first state in which the inlet end and the first outlet end are connected and a second state in which the inlet end and the second outlet end are connected; a branch pipe having an outlet port, a first inlet port connected to the other end of the passage of the first flow path throttle section, and a second inlet port connected to the other end of the passage of the second flow path throttle section; A flow rate switching mechanism having a

6. Furthermore, a sealing support member that supports the capillary in the passage of the first flow path throttle portion and seals between an outer peripheral surface of the capillary and an inner peripheral surface of the passage; and 6. The flow rate switching mechanism according to claim 4, wherein the sealing support member is made of a material having rubber elasticity and has a through hole through which the capillary is inserted, and is press-fitted into the passage.

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