VACUUM PUMP

• US 20110103934A1
• Filed: 07/14/2009
• Published: 05/05/2011
• Est. Priority Date: 07/14/2008
• Status: Active Grant

• Current Assignee: Edwards Japan Limited (Atlas Copco AB)
• Original Assignee: Edwards Japan Limited (Atlas Copco AB)
• Inventors: Ohtachi, Yoshinobu, Nabaka, Manabu, Maejima, Yasushi
• Granted Patent: US 8,690,525 B2
• Time in Patent Office: Days
• US Class Current: 415/118
• CPC Class Codes: F04D 19/042 Turbomolecular vacuum pumps
• CPC Class Codes: F04D 27/001 Testing thereof; Determination or simulation of flow characteristics; Stall or surge detection, e.g. condition monitoring
• CPC Class Codes: F04D 27/0292 Stop safety or alarm devices, e.g. stop-and-go control; Disposition of check-valves
• CPC Class Codes: F04D 29/661 especially adapted for elastic fluid pumps
• CPC Class Codes: F05D 2260/607 Preventing clogging or obstruction of flow paths by dirt, dust, or foreign particles

Abstract

Provided is a vacuum pump which can detect precisely physical contact between a rotor portion and a stator portion, and contact between the rotor portion and the stator portion that occurs as the amount of deposited solid product reaches the clearance between the rotor portion and the stator portion.

A vibration sensor is provided, taking advantage of a clearance, at the outer peripheral of a thread groove spacer. Contact between the rotor portion and the stator portion is decided, when a particular vibration during contact between the rotor portion and the stator portion exceeds a predetermined threshold value. The vibration sensor is mounted on the outer peripheral of the thread groove spacer at the end of the side of an exhaust port. The thread groove spacer is fixed on a casing via an elastic member (an O-ring) that have a vibration absorption (vibration damping) function of a cutoff frequency (fc1). A vibration signal outputted from the vibration sensor is converted into a digital vibration signal, and is inputted to a digital filter having a passing band of fc1 to fc2 [Hz]. If the vibration level of the vibration signal having passed through the digital filter exceeds a predetermined threshold value, it is detected that contact between the rotor portion and the stator portion has occurred in a turbo-molecular pump.

Claims

1. A vacuum pump, comprising:

a casing provided with an inlet port and an outlet port;

a stator portion provided inside the casing;

a rotor portion having a shaft rotatably supported inside the casing, and a rotor disposed on the shaft and provided with a gas transfer mechanism that transfers a gas from the inlet port to the outlet port, the rotor portion being arranged with a predetermined clearance between the rotor portion and the stator portion;

a motor rotating the shaft;

vibration detection means for detecting vibration; and

contact detection means for detecting an occurrence of contact between the stator portion and the rotor portion when, in the vibration detected by the vibration detection means, a specific vibration caused by contact between the stator portion and the rotor portion exceeds a predetermined threshold value.

2. The vacuum pump according to claim 1, wherein

the specific vibration is a vibration of at least one frequency from among:

a first frequency that denotes a natural frequency of a part configuring the stator portion;

a second frequency that denotes a natural frequency of a part configuring the rotor portion;

a third frequency that denotes a frequency that is a multiple of revolutions (frequency) of the rotor portion;

a fourth frequency that denotes a beat frequency of vibrations of the first through third frequencies; and

a fifth frequency, of a specific range, generated upon contact between the rotor portion and the stator portion.

3. The vacuum pump according to claim 1 or 2, wherein the vibration detection means is configured of a vibration sensor disposed in the stator portion, on a member that opposes the rotor portion.

4. The vacuum pump according to any one of claims 1 to 3, wherein the vibration detection means is configured of a plurality of vibration sensors disposed at different location of the stator portion, and detects the occurrence of contact between the stator portion and the rotor portion on the basis of differences in the vibrations detected by the vibration sensors.

5. The vacuum pump according to any one of claims 1 to 4, wherein the stator portion at which the vibration detection means is provided is fixed to the casing through an elastic member.

6. The vacuum pump according to claim 1 or 2, wherein the vibration detection means detects, as vibration, a change over time of a positional displacement of the rotor portion.

7. The vacuum pump according to claim 6, wherein the vibration detection means is configured of a contact-less displacement sensor that detects a displacement of the rotor portion.

8. The vacuum pump according to any one of claims 1 to 7, comprising alarm output means for emitting an alarm for urging execution of maintenance when the contact detection means detects occurrence of contact between the stator portion and the rotor portion.

9. A vacuum pump, comprising:

an casing provided with an inlet port and an outlet port;

a stator portion provided inside the casing;

a rotor portion having a shaft rotatably supported inside the casing, and a rotor disposed on the shaft and provided with a gas transfer mechanism that transfers a gas from the inlet port to the outlet port, the rotor portion being arranged with a predetermined clearance between the rotor portion and the stator portion;

a motor rotating the shaft;

an elastic member having a vibration damping characteristic, disposed between the casing and the stator portion;

vibration detection means disposed on the stator portion;

a filter to which an output of the vibration detection means is inputted, and having, as a pass band, a frequency band higher than a cutoff frequency of the vibration damping characteristic of the elastic member; and

contact detection means for detecting an occurrence of contact between the stator portion and the rotor portion when an output of the filter exceeds a predetermined threshold value.

10. The vacuum pump according to claim 9, which is a composite-type vacuum pump comprising a turbo-molecular pump section and a thread groove pump section, wherein

the vibration detection means is disposed on a thread groove spacer that forms an evacuation flow path of the thread groove pump section.

11. The vacuum pump according to claim 9 or 10, comprising sensitivity adjustment means, provided on or inside the casing, for adjusting the sensitivity of the vibration detection means.

12. The vacuum pump according to claim 9 or 10, comprising storage means, provided on or inside the casing, for storing a correction value of an output level of the vibration detection means.

13. The vacuum pump according to any one of claims 9 to 12, wherein the elastic member is formed of a material used for O-ring, or formed of an O-ring that is continuous in a circumferential direction.

14. The vacuum pump according to any one of claims 9 to 13, wherein the vibration detection means outputs a digital signal to which a vibration detection value is converted, and

the filter is configured of a digital filter.

15. The vacuum pump according to any one of claims 9 to 14, comprising alarm output means for emitting an alarm, or a contact notification signal, urging execution of maintenance when the contact detection means detects occurrence of contact between the stator portion and the rotor portion.