| Method of controlling the stopping operation of vacuum pump and device therefor -> Monitor Keywords |
|
|
  Method of controlling the stopping operation of vacuum pump and device thereforUSPTO Application #: 20080063536Title: Method of controlling the stopping operation of vacuum pump and device therefor Abstract: A method for controlling the operation of a vacuum pump when stopping the gas transferring operation thereof, the vacuum pump having a housing in which a pump chamber is formed and a gas transferring body which is rotatably disposed in the pump chamber for transferring gas, the method comprises the steps of reducing rotational speed of the gas transferring body to a first preset speed below a second preset speed that is lower than a normal speed of the gas transferring body during normal gas transferring operation of the vacuum pump, maintaining the speed of the gas transferring body below the second preset speed, and stopping the rotation of the gas transferring body when the temperature of the housing reaches a predetermined temperature which is lower than that of the housing during the normal gas transferring operation of the vacuum pump. (end of abstract) Agent: Morgan & Finnegan, L.L.P. - New York, NY, US Inventors: Ryosuke Koshizaka, Shinya Yamamoto, Yoshiaki Fujiwara, Kentaro Ishihara, Osamu Uchiyama USPTO Applicaton #: 20080063536 - Class: 417032000 (USPTO) Related Patent Categories: Pumps, Condition Responsive Control Of Pump Drive Motor, Responsive To Pump Or Pump Fluid Temperature The Patent Description & Claims data below is from USPTO Patent Application 20080063536. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to a method of controlling the stopping operation of a vacuum pump which transfers gas by moving a gas transferring body in a pump chamber and also to a device for practicing the method. [0002] A vacuum pump is used to discharge gas for use in semiconductor manufacturing processes from a process chamber and to create a vacuum environment in the process chamber. As the vacuum pump, a positive displacement vacuum pump is known which has roots type or screw type pump rotors as a gas transferring body. Generally, the displacement vacuum pump has a pair of pump rotors which is disposed in the pump chamber of a pump casing and a motor which drives the pump rotors to rotate. [0003] Narrow clearances are formed between the pair of the pump rotors and between each rotor and the inner surface of the casing such that the pair of pump rotors rotates without contact with the casing, and the paired pump rotors are rotated synchronously in opposite directions. Such rotation of the pump rotors, causes gas in the pump casing to be transferred from the suction side to the discharge side of the casing, and then to flow out of the process chamber which is connected a suction port. [0004] Gas used in semiconductor manufacturing processes may sometimes contain an element which is solidified during being transferred (hereinafter, such solidified element is referred to as "solid products"). Because the vacuum pump generates heat of compression during transferring of the gas, the vacuum pump in operation, or specifically the casing and the pump rotors of the vacuum pump, becomes relative high in temperature. While the vacuum pump maintains a high temperature, the casing and the pump rotors are thermally expanded. Thus, the clearance between the pump rotor and the inner surface of the pump chamber facing the pump rotor becomes wider and, therefore, solid products tend to get into the clearance and accumulate therein. [0005] When the operation of the vacuum pump is stopped, the vacuum pump becomes gradually lower in temperature and the thermally-expanded casing and pump rotors contract, so that the clearance is narrowed, so that, the solid products accumulated in the clearance are held between the pump rotors and the inner surface of the pump chamber. When the vacuum pump is restarted, the pump rotors may be prevented from rotating by the solid products held between the pump rotors and the inner surface of the pump chamber and cannot be rotated by starting torque of a motor. If the vacuum pump cannot be restarted by the staring torque of the motor, a tool is engaged with a rotary shaft of the vacuum pump and then a torque is applied to the rotary shaft by manually rotating the pump rotors with the tool, thus removing the solid products from the clearance and making the vacuum pump ready for restarting. [0006] Unexamined Japanese Patent Publication No. 2004-138047 discloses a method of starting a vacuum pump which enables the solid products to be removed without manual operation and the vacuum pump to be restarted. According to the method disclosed in the above publication, when restarting the vacuum pump having therein solid products, a torque is applied from the motor to the pump rotors for rotation in normal direction. Thereafter, the torque applied to the pump rotors becomes zero and again a torque is applied to the pump rotors for rotation in forward direction. Thus, torque is applied to the solid products accumulated between the pump rotor and the inner surface of the pump chamber. As a result, the solid products become brittle and are broken, so that they are removed from the clearance and, therefore, the vacuum pump can be started without manual operation. [0007] According to the vacuum pump starting method disclosed in the above publication, the vacuum pump is started from a state that the solid products are held between the pump rotors and the inner surface of the pump chamber. Thus, solid products need to be removed from the clearance by application of a force of the pump rotors before it becomes possible for the vacuum pump to transfer the gas. If solid products are held tightly or a large amount of solid products is held between the pump rotors and the inner surface of the pump chamber, the pump rotors need to be rotated for many times for application of force that is enough to break the solid products, with the result that the time for prior operation of the vacuum pump before actual gas transferring will be lengthened. According to the starting method disclosed in the above publication, the vacuum pump requires a relatively long time before gas transferring becomes possible after the vacuum pump has been started. [0008] The present invention, which is made in view of the above problems, is directed to a method and an apparatus of controlling the stopping operation of the vacuum pump. The method and apparatus of controlling the stopping operation of the vacuum pump according to the present invention prevents the vacuum pump from stopping in a state that solid products are held between the inner surface of the pump chamber and the gas transferring body and permits the vacuum pump to be restarted rapidly for transferring of gas. SUMMARY OF THE INVENTION [0009] In accordance with the present invention, a method for controlling the operation of a vacuum pump when stopping the gas transferring operation thereof, the vacuum pump having a housing in which a pump chamber is formed and a gas transferring body which is rotatably disposed in the pump chamber for transferring gas, the method comprises the steps of reducing rotational speed of the gas transferring body to a first preset speed below a second preset speed that is lower than a normal speed of the gas transferring body during normal gas transferring operation of the vacuum pump, maintaining the speed of the gas transferring body below the second preset speed, and stopping the rotation of the gas transferring body when the temperature of the housing reaches a predetermined temperature which is lower than that of the housing during the normal gas transferring operation of the vacuum pump. [0010] In accordance with the present invention, a device is used for controlling the operation of a vacuum pump when stopping the gas transferring operation thereof. The vacuum pump has a housing in which a pump chamber is formed and a gas transferring body rotatably provided in the pump chamber for transferring gas. The device includes means for controlling the stopping operation of the vacuum pump and detection means for detecting the temperature of the housing and generating a detection signal when the temperature of the housing reaches a predetermined temperature. The predetermined temperature is lower than a temperature of the housing during normal operation of the vacuum pump when gas is transferred by the gas transferring body. The controlling means is operable to reduce rotating speed of the gas transferring body to a speed below a second preset speed that is lower than a normal speed of the gas transferring body during normal gas transferring operation of the vacuum pump in response to a pump-stop command signal for stopping the gas transferring body. The controlling means is also operable to stop the rotation of the gas transferring body in response to the detection signal from the detection means. [0011] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0012] The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: [0013] FIG. 1 is a plan cross-sectional view of a roots pump of a first embodiment according to the present invention; [0014] FIG. 2(a) is a cross-sectional view taken along the line A-A in FIG. 1; [0015] FIG. 2(b) is a cross-sectional view taken along the line B-B in FIG. 1; [0016] FIG. 2(c) is a cross-sectional view taken along the line C-C in FIG. 1; [0017] FIG. 3 is a graph showing change of rotation speeds of rotor and change of temperature of a rotor housing according to the first embodiment of method of controlling the stopping operation of the vacuum pump; and [0018] FIG. 4 is a graph showing change of rotation speeds of rotor and change of temperature of a rotor housing according to a second embodiment of method of controlling the stopping operation of the vacuum pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0019] The following will describe the first preferred embodiment of a method and apparatus of controlling the stopping operation of a roots pump as a vacuum [0020] pump which transfers gas in a semiconductor manufacturing equipment with reference to FIGS. 1 through 3. The front and the rear of the roots pump in the following description are indicated by the double-headed arrow Y in FIG. 1. Continue reading... Full patent description for Method of controlling the stopping operation of vacuum pump and device therefor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of controlling the stopping operation of vacuum pump and device therefor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Method of controlling the stopping operation of vacuum pump and device therefor or other areas of interest. ### Previous Patent Application: Pump controller system and method Next Patent Application: Speed-related control mechanism for a pump and control method Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Method of controlling the stopping operation of vacuum pump and device therefor patent info. IP-related news and info Results in 1.04222 seconds Other interesting Feshpatents.com categories: Novartis , Pfizer , Philips , Polaroid , Procter & Gamble , |
||
