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Operation control device and method of vacuum pumpsOperation control device and method of vacuum pumps description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080063534, Operation control device and method of vacuum pumps. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]The present invention relates to an operation-control device and an operation-control method of vacuum pumps such as a scroll pump, a vane pump and the like, especially to a case where plural set of vacuum pumps are provided. [0003]2. Description of the Related Art [0004]In conventional operation-control methods for vacuum pumps such as a scroll pump, a vane pump and the like, a frequency control by an inverter is introduced and the speed of an AC motor which drives a vacuum pump is controlled by using a signal of a pressure-sensor detecting a pressure of gas inside a vacuum tank to be depressurized. As for a pump load control by means of an inverter, a prior art, for instance, such as JP-A-H9-4591/1997 (hereafter, referred to as a patent document 1) has been known. [0005]As shown in FIG. 5, in the patent document 1 is illustrated a control-step constitution, wherein the speed of an AC motor 04, which drives a vacuum blower (vacuum pump) 03 connected to a vacuum tank 01, is controlled by a frequency converter (inverter) 05, and the speed is increased when the operation differential pressure of the pump decreases and demand power goes down, while the speed is decreased when the operation differential pressure of the pump increases and demand power goes up; so that the input power poured into the motor driving the pump is kept constant. Further, the pressure P inside the vacuum tank 01 is detected for the estimation of vacuum condition. [0006]In the conventional operation-control approaches for the vacuum pump as shown in the patent document 1, a pressure (vacuum) sensor is used for estimating the vacuum condition, since the vacuum condition in the tank 01 is detected as pressure P. In case when dust and/or water droplets in the tank or the vacuum facility room adhere to the probe of the sensor, it is afraid that the signals are not accurate and unexpected failure may happen. Thus, special sensors of a dust-free type and/or a waterproof type are required in order to prevent the invasion of dust and/or water droplet. Consequently, there arises a problem of cost increase as to equipment and/or facility. [0007]Furthermore, a speed control inverter always accompanies electronic noise which causes undesirable problems to the surrounding electrical/electric equipment if it is nearby the inverter. [0008]On the other hand, in case where a constant vacuum condition is needed, for instance, in case where a highly depressurized vacuum condition is required in a vacuum chamber of semiconductor production devices, plural sets of vacuum pumps are provided. And even when one of the pumps is out of service due to failure or maintenance and exhaust ability is lessened, the remaining pumps hold the predetermined required vacuum condition. [0009]However, driving plural sets of pumps results in an increase of power consumption and maintenance costs. Furthermore, providing plural pumps may increase failure frequency of the pumps, maintenance frequency of the pumps along with affiliated facility and man-hours for repairing. SUMMARY OF THE INVENTION [0010]In view of the above-stated background, the present invention is aiming at: eliminating the difficulties in such a case of introduction of vacuum sensors and/or inverter speed control; realizing the operation of plural vacuum pumps wherein the increase of facility costs is restrained, the maintenance frequency is reduced and the man-hour of repair work is lessened; and providing an operation control device and an operation control method which are compatible with the just-stated aims. [0011]In order to resolve the problems mentioned above, the present invention provides an operation control device of plural vacuum pumps for depressurizing a gas inside at least one tank and/or vacuum facility room and so on, including: a current detecting means which detects a current flowing in a motor that drives the vacuum pumps; and a control means which reduces the number of the vacuum pumps actually under operation, while judging whether a target vacuum or substantially vacuum condition is reached, based on a situation that a current value detected by the current detection means converges within a predetermined range. [0012]According to the present invention, the current flowing in the motor is detected, and it is judged that a target vacuum or substantially target vacuum condition is realized when the current value converges within a predetermined range. Therefore, it is not necessary to provide with vacuum sensors for pressure detection of a vacuum tank as conventionally used, so that equipment costs can be restrained and a remarkable cost effectiveness can be obtained, especially in case where special sensors of a dust-free type and/or a waterproof type are required, depending on the service condition as to a vacuum tank or a vacuum facility room. [0013]Since the gas to be exhausted is reduced when a target vacuum or substantially target vacuum condition is realized, it is possible to hold the vacuum condition or to reach the target vacuum condition without operation of an unnecessary pump. Therefore, it becomes possible to decrease the number of plural working vacuum pumps, to reduce the amount of power consumption as a result and to prolong maintenance intervals by stopping the operation of an unnecessary pump. In the control for operation and start/stop of the pumps, speed control equipment such as inverters and the like is not provided. Therefore, undesirable effect due to inverters on surrounding equipment is avoidable. [0014]According to another constitution of the present invention, the control means of the operation control device further includes a vacuum-degree-estimation means to judge that a threshold criterion value is reached when a current value of the motor under watch reaches the predetermined range, the threshold criterion value being predetermined in advance of a target-vacuum value and to conclude that said target-vacuum value is reached in case when the current value stays within the predetermined range for a predetermined span of time after the threshold criterion value is reached; in which when the vacuum-degree-estimation means concludes that the threshold criterion value or the target-vacuum value within the predetermined range is reached, the number of the pumps under operation is reduced. [0015]The another constitution of the above mentioned makes it possible to decrease the number of plural working vacuum pumps and to reduce the amount of power consumption as a result, because the target vacuum can be reached without large current after the depressurized pressure reaches the threshold criterion value. In addition, it is made possible that the number of pumps and the amount of power consumption are reduced after surely estimating that the target vacuum (negative pressure) is reached when the detected current stays for a predetermined span of time in the predetermined range. [0016]According to another aspect of the present invention, the target-vacuum value within the predetermined range is reset at a lower value as the operation hours of the vacuum pumps are prolonged. [0017]By the above constitution, more accurate judgment on a vacuum-degree-completion is carried out, while the operation hours are taken into consideration. Here, the consideration is given in such a manner that the aforementioned predetermined current range, whereby the threshold-criterion value is regarded as reached, is lowered in connection with operation hours. In addition, the reason of this lowering is that a load demand for the vacuum pumps decreases gradually in proportion to the accumulated operation hours because of a running-in effect as to rotating and/or sliding wear-elements. [0018]Another aspect of the present invention is characterized in that the operation control device includes a pump operation control means, which designates one of the plural pumps as a pump under watch, stops at least one of the pumps other than the pump under watch when the vacuum-degree-estimation means concludes, based on a current value of the motor driving the pump under watch, that the threshold criterion value or the target-vacuum value within the predetermined range is reached and shifts the pump under watch evenly one by one among the whole pumps. [0019]According to a method of the present invention of controlling plural vacuum pumps, the method includes the steps of designating a pump under watch, stopping the pumps other than the pump under watch and shifting the pump under watch one by one among the whole pumps; thereby such operation manner can be evaded that a specific pump is always working, the other pumps are kept under suspension, and the operation unevenness among the plural pumps is incurred as a result. Therefore, plural pumps are evenly employed and maintenance work for each pump is equalized. Thus, the increase in efficiency of maintenance work can be promoted. [0020]Another constitution of the present invention is characterized in that, in a case where any one of the vacuum pumps is unable or difficult to be operated, the operation of the pump unable or difficult to be operated is skipped and the other next pump is designated as a pump under watch. [0021]The above constitution makes it possible to prevent operation unevenness among the plural sets of the vacuum pumps, since plural pumps are evenly employed and the operation hours of each pump are equalized. [0022]Another constitution of the present invention relates to an operation control method for plural vacuum pumps for depressurizing a gas inside at least one tank and/or chamber including the steps of: detecting a current flowing in a motor that drives the vacuum pumps; and reducing the number of the vacuum pumps actually under operation, while judging whether a target vacuum and/or substantially vacuum condition is reached, based on the situation that a current value detected by the current detection means converges within a predetermined range. Continue reading about Operation control device and method of vacuum pumps... Full patent description for Operation control device and method of vacuum pumps Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Operation control device and method of vacuum pumps 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 Operation control device and method of vacuum pumps or other areas of interest. ### Previous Patent Application: Turbine blade for a gas turbine engine Next Patent Application: Pressure compensated pump Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Operation control device and method of vacuum pumps patent info. 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