Turbo molecular pump with variable side inlet position for reverse flow leak detection

Abstract

A turbo molecular pump (14) having a variable intermediate gas inlet for a reverse flow leak detector (10) with a gas detector (12), the turbo molecular pump comprising a pump housing (16), an internal structure contained in the pump housing, the invention relates to a pump for a motor vehicle, comprising a pump housing (16) having an internal structure with a pump stator (28) and a pump rotor, a gas inlet (18) leading to the internal structure through the pump housing (16), a gas outlet (20) leading out of the internal structure through the pump housing (16), and at least one intermediate gas inlet (22) leading to the internal structure through the pump housing (16) between the gas inlet (18) and the gas outlet (20), the gas inlet (18) is connected to the gas detector (12), and the intermediate gas inlet (22) is connected to a test connection (24) of a test sample to be tested or to a test chamber containing the test sample, characterized in that the pump housing (16) has an elongated slot (30) extending in a longitudinal direction of the pump housing (16), the intermediate gas inlet (22) may be partially covered by at least one cover movable relative to the elongated slot (30) such that an uncovered portion of the elongated slot (30) forms the intermediate gas inlet (22), the position and / or opening cross-section of the intermediate gas inlet being changed by moving the cover.

Description

[0001] The present invention relates to a turbomolecular pump having a variable side inlet position for use in a reverse flow leak detector comprising a gas detector and a turbomolecular pump for reverse flow leak detection.

[0002] In a reverse flow leak detector, it is known to connect the gas inlet of the turbomolecular pump to a gas detector (e.g., a mass spectrometer) and the gas outlet of the turbomolecular pump to the gas inlet of a fore-vacuum pump, while the intermediate gas inlet of the turbomolecular pump is connected to a test connector of a test sample to be tested or a test chamber containing the test sample. When a suitable vacuum pressure is reached inside the gas detector, gas from the test sample or test chamber is then allowed to enter the turbomolecular pump via the intermediate gas inlet and from there enters the gas detector in a direction countercurrent to the main flow direction in the turbomolecular pump.

[0003] Conventionally, valves are used to allow the pumping gas to enter the turbomolecular pump at different intermediate gas inlets or at different positions, depending on the prevailing inlet pressure of the turbomolecular pump, such that fewer compression stages of the turbomolecular pump to the mass spectrometer remain or have to pass at a lower pressure. Each inlet point is characterized by different criteria such as compression, sensitivity, and pumping speed, or for example gas flow rate, heat generation, temperature sensitivity, etc.

[0004] Since the pressure varies continuously when a sample is pumped out with a turbomolecular pump, the selected intermediate gas inlet point is rarely optimal but rather a compromise for the actual task. The compromise is that, on the one hand, when the pressure at the inlet of the leak detector is still high, the position of the intermediate gas inlet on a multi-stage turbomolecular pump having several rotor stages between the inlet and the gas detector must be selected such that the total pressure in the gas detector can be kept low enough. On the other hand, there should be as few rotor stages as possible between the inlet and the gas detector such that the path of the test gas molecules in the direction opposite to the pumping direction remains as short as possible, thus enabling high sensitivity. The aim is to measure the partial pressure of the test gas (usually helium or hydrogen) in the permitted gas at the highest sensitivity at the pumping speed in order to obtain the best detection limit and the fastest response time. The valves used throttle the available pumping speed at the intermediate gas inlet of the turbomolecular pump by their conductivity.

[0005] In this context, the present invention is based on the object of providing an improved reverse flow leak detector comprising a gas detector and a turbomolecular pump, wherein the position and / or the opening cross-section of the intermediate gas inlet used can be varied.

[0006] The turbomolecular pump according to the invention is defined by the features of claim 1.

[0007] A turbomolecular pump includes a pump housing and structures accommodated in the pump housing, in particular a pump rotor and a pump stator. The turbomolecular pump preferably has a plurality of pumping stages, where each pumping stage can be formed by a corresponding rotor stage. A gas inlet leads through the pump housing to the internal structures. A gas outlet leads through the pump housing from the internal structures. Between the gas inlet and the gas outlet, at least one intermediate gas inlet is provided, which leads through the pump housing to the internal structures. The gas inlet is connected to a gas detector, and the intermediate gas inlet is connected to a test connection of a test sample to be tested or to a test chamber accommodating the test sample.

[0008] A special feature of the invention is that the pump housing has an elongated slot extending in the longitudinal direction of the pump housing, and the internal structures have a plurality of inlet openings leading to the elongated slot, where each pumping stage can be assigned its own inlet opening, and in the internal structures, each stage of the turbomolecular pump has a static inlet opening (hereinafter referred to as a stator opening) leading to the elongated slot.

[0009] At least one cover is provided between the pump housing and the internal structures, the cover being configured to cover the inlet openings from the elongated slot and to expose only one inlet opening at a time, such that only one of the inlet openings is directly connected to the elongated slot in a gas-conducting manner. The cover is movable relative to the elongated slot and the internal structures and is configured to change the position and / or the opening cross-section of the intermediate gas inlet by moving the cover. The intermediate gas inlet is a gas-conducting connection between the pump housing and the internal structures. By moving the cover, the position of the intermediate gas inlet can be changed, in particular to establish a gas-conducting connection to a specific pump stage. For this purpose, the internal structures can be provided with a plurality of stator openings, where each stator opening is assigned to a pump stage. The cover can be used to create a gas-conducting connection between the elongated slot and one of the stator openings. It is also possible or alternatively to change the opening cross-section of the intermediate gas inlet by moving the cover.

[0010] By moving the cover relative to the pump housing, the dimensions and / or the position of the intermediate gas inlet can be adapted to basic criteria, such as compression, sensitivity, pumping speed, etc., without having to use a plurality of intermediate gas inlets with different positions and / or dimensions, from which a suitable one would have to be selected in each case. In addition, no switching valves are required to change the position and / or the dimensions of the intermediate gas inlet.

[0011] The cover can be cylindrically arranged as a cover cylinder and is rotatable relative to the pump housing and the internal structure of the pump housing. In particular, the cover cylinder can be arranged inside the pump housing. Here, the cover cylinder can have a plurality of cover openings arranged offset in the longitudinal direction and / or transversely to the longitudinal axis, such that when the cover cylinder rotates relative to the pump housing, the position and / or size of the overlap between the cover openings and the elongated slots changes. This allows changing the position and / or cross-section of the intermediate gas inlet. The overlap between the cover openings and the elongated slots forms the opening of the intermediate gas inlet. The cover openings can be arranged along a line arranged inclined relative to the elongated slots and preferably extending at least partially around the cover cylinder in a spiral pattern.

[0012] If the cover cylinder has a plurality of cover openings arranged in a spiral pattern around the cover cylinder, by rotating the cover cylinder relative to the elongated slots, respectively, one cover opening can be aligned with one of the stator openings, thereby forming the intermediate gas inlet. By rotating the cover cylinder relative to the pump housing, the position of the intermediate gas inlet along the elongated slots and / or the opening cross-section of the intermediate gas inlet can be changed.

[0013] The internal structure having the pump stator can have at least one stator opening that forms the intermediate gas inlet. In particular, a number of stator openings can be provided along a line extending in the longitudinal direction of the internal structure. By rotating the cover cylinder relative to the internal structure, one or more of the cover openings can overlap with one or more of the stator openings. On the one hand, this allows changing the opening cross-section of the intermediate gas inlet. On the other hand, the position of the intermediate gas inlet can be changed along the longitudinal axes of the cover cylinder and the internal structure.

[0014] The cover and the internal structure or the pump stator are advantageously cylindrical, where the cover forms a cover cylinder that is rotatable and is sufficiently sealed relative to the pump housing and relative to the pump stator in the sense of the present invention.

[0015] Below, exemplary embodiments of the present invention are explained in more detail with reference to the accompanying drawings. The drawings show:

[0016] Figure 1 A block diagram is shown, and

[0017] Figure 2 A schematic diagram of a turbomolecular pump is shown.

[0018] The countercurrent leak detector 10 according to the present invention includes a gas detector 12 in the form of a mass spectrometer and a turbomolecular pump 14. The turbomolecular pump 14 includes a pump housing 16 having a gas inlet 18, a gas outlet 20, and an intermediate gas inlet 22 arranged between the gas inlet 18 and the gas outlet 20. As Figure 1As shown, the gas inlet 18 is connected to the gas detector 12 via a gas conduction path, while the intermediate gas inlet 22 is connected to the test connector 24 via a separate gas conduction path. The test sample to be tested and / or the test chamber containing the test sample to be tested can be connected to the test connector 24. The gas outlet 20 is adapted to be connected to a pre-vacuum pump, which is not shown in the figure and generates the required pre-vacuum pressure at the outlet region of the turbomolecular pump 14.

[0019] Figure 2 The turbomolecular pump 14 is shown in a schematic perspective view and has a cover cylinder 26 arranged in the turbomolecular pump, an internal structure arranged in the cover cylinder 26, a pump stator 28, and a pump rotor arranged in the pump stator 28. The pump rotor consists of a number of rotor stages, and each rotor stage forms a pumping stage of the multi-stage turbomolecular pump 14. Each of these pumping stages is assigned a stator opening 34 in the pump stator 28.

[0020] The pump housing 16 is provided with an elongated slot 30, which forms an opening in the wall of the pump housing 16. The first cover cylinder 26 is sealingly guided in the pump housing 16 in such a way that its outer shell surface contacts the edge of the elongated slot 30 in a sufficiently airtight manner (e.g., using a seal or via a sufficiently low conductivity). The cover cylinder 26 is provided with a plurality of cover openings 32 arranged along a helical line around a part of the outer shell surface, and each cover opening 32 forms an opening in the outer shell surface. The helical line along which the plurality of cover openings 32 are arranged extends Figure 2 from the upper left to the lower right.

[0021] The pump stator 28 is sealingly guided within the shroud cylinder 26 such that the outer shell surface of the pump stator 28 sealingly contacts the inner surface in the edge region of the shroud opening 32, for example, using a seal or a sealing ring. Similar to the shroud cylinder 26, the pump stator 28 is provided with a plurality of stator openings 34, the size and shape of which correspond to the shroud openings 32, and the stator openings 34 are arranged on its shell surface along a straight line extending parallel to the central longitudinal axis of the pump stator 28. Each stator opening 34 penetrates the shell surface of the pump stator 28, thereby forming an opening in the pump stator 28. Each of these openings is assigned as an inlet to one of the pumping stages.

[0022] Accordingly, the stator openings 34 are arranged along a straight line parallel to the longitudinal axis, while the plurality of cover openings are arranged along a helix. By rotating the cover cylinder 26 relative to the pump stator 28, one or more adjacent cover openings 32 then overlap one or more adjacent stator openings 34, thereby creating an opening 36 for the intermediate gas inlet 22 and changing its size and shape in the region of the elongated slot 30. The pump stator is oriented relative to the pump housing 16 such that the stator openings 34 are arranged within the elongated slot 30 to provide a passage through the pump housing 16, the cover cylinder 26, and the pump stator 28 into the interior of the pump stator by overlapping with the cover openings 34.

[0023] Gas from the test connection 24 passes through the opening 36 into the interior of the turbo molecular pump 14, i.e., into the interior of the pump stator 28. From there, under suitable pressure conditions, the gas passes through the gas inlet 18 into the gas detector 12, where it is detected.

[0024] By rotating the cover cylinder 26 relative to the pump stator 28 and relative to the pump housing 16, the position of the opening 36 is changed along the elongated slot 30 and the size of the opening 36 is changed, i.e., the cross-section of the opening 36.

[0025] This makes it easy to change the position of the intermediate gas inlet 22 in the longitudinal direction of the pump housing 16, thereby increasing or decreasing the distance between the intermediate gas inlet 22 and the gas inlet 18 as required. The size of the opening cross-section of the opening 36 can also be changed accordingly to increase or decrease the gas flow rate as required.

[0026] The movement and rotational position of the cover cylinder 26 and the pump stator 28 can be controlled manually or electronically.

Claims

1. A turbomolecular pump (14) having a variable intermediate gas inlet for a countercurrent leak detector (10) with a gas detector (12), the turbomolecular pump comprising: a pump housing (16), an internal structure contained in the pump housing, the internal structure having a pump stator (28) and a pump rotor, a gas inlet (18) that passes through the pump housing (16) to the internal structure, a gas outlet (20) that passes from the internal structure through the pump housing (16), and at least one intermediate gas inlet (22) that passes through the pump housing (16) between the gas inlet (18) and the gas outlet (20) to the internal structure, wherein the gas inlet (18) is adapted to be connected to a test connection (24) of a test sample to be tested and the intermediate gas inlet (22) and the gas detector (12) or to a test chamber containing the test sample, characterized in that the pump housing (16) has an elongated slot (30) that extends along the longitudinal direction of the pump housing (16) and can be partially covered by at least one cover, the at least one cover being movable relative to the elongated slot (30) such that the uncovered portion of the elongated slot (30) forms the intermediate gas inlet (22), and the position and / or the opening cross-section of the intermediate gas inlet is changed by moving the cover.

2. The turbo molecular pump (14) according to claim 1, characterized in that, The cover is arranged as a cylindrical cover cylinder (26), and the cover is rotatable relative to the pump housing (16) and the internal structure within the pump housing (16).

3. The turbo molecular pump (14) according to claim 1 or 2, characterized in that, The cover has a plurality of cover openings (32) that are arranged offset in the longitudinal direction and / or transversely to the longitudinal direction.

4. The turbo molecular pump (14) according to claim 3, characterized in that, The plurality of cover openings (32) are arranged along a line that is arranged inclined relative to the elongated slot (30) and preferably extends at least partially in a spiral manner around the cover cylinder (26).

5. The turbomolecular pump (14) according to any one of the preceding claims, characterized in that, The pump stator has at least one stator opening (34) that forms the intermediate gas inlet (22).

6. The turbo molecular pump (14) according to the preceding claim, characterized in that, A plurality of stator openings (34) are provided along a line extending in the longitudinal direction of the pump stator (28).

7. The turbo molecular pump (14) according to any one of the preceding claims, characterized in that, The cover and the pump stator (28) are of cylindrical shape, and the cover forms a cover cylinder (26) that is rotatably and sealingly arranged relative to the pump housing (16) and relative to the pump stator (28).

8. The turbo molecular pump (14) according to claim 7, characterized in that, The cover cylinder (26) has a plurality of cover openings (32) that are distributed spirally around the cover cylinder (26) such that by rotating the cover cylinder (26) within the elongated slot (30), a respective one of the cover openings can be aligned with one of the stator openings (34), and thus the intermediate gas inlet (22) is formed.

9. The turbo molecular pump (14) according to claim 8, characterized in that, The position of the intermediate gas inlet (22) along the elongated groove (30) and / or the opening cross-section of the intermediate gas inlet (22) can be changed by rotating the cover cylinder (26) relative to the pump housing (16).

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