JP5651874B2 - Operation method of vacuum pump - Google Patents

Description

  In the present invention, the two rotor shafts are respectively rotated in a non-contact state in the cylinder to generate a vacuum pressure so that the two oils are transmitted through a gear that is oil-lubricated by the power of the electric motor. The present invention relates to a vacuum pump operating method in which a rotation speed of a rotor can be controlled by controlling an inverter that adjusts a frequency of electric power supplied to the electric motor for a vacuum pump whose rotary shaft is driven synchronously.

  In the rotary vane pump, since there is a possibility that the function may be deteriorated due to defective popping out of the blade when the rotational speed is lowered, an operation method of controlling the vacuum output by controlling the rotational speed with an inverter is not adopted. For this reason, in this rotary vane pump, the vacuum pressure (output vacuum pressure) output from the vacuum pump is adjusted by a spring-type valve structure so that air is allowed to leak when the vacuum pressure exceeds the set vacuum pressure. A vacuum controller capable of inhaling air is used.

  According to this vacuum controller, it can be maintained at a constant vacuum pressure, and also functions as a safety valve for preventing the reaching operation (deadline operation). However, since this rotary vane pump is always operated in a state in which a constant rotational speed is maintained, it cannot be operated to save energy when the vacuum output may be small.

  On the other hand, the non-contact type vacuum pump with a structure in which the rotor in the cylinder is rotated in a non-contact state does not have the possibility of the above-mentioned deterioration in function, so that it is possible to perform a rotational speed control operation by an inverter. become. Examples of the non-contact type vacuum pump include a claw pump, a roots pump, and a screw pump.

  As a vacuum pump that is controlled by an inverter, for example, an actual intake pressure (output vacuum pressure) is detected at an intake port of a dry vacuum pump, and a set intake pressure (set vacuum pressure) is set by a vacuum exhaust capacity control device (controller). And the output frequency of the inverter, and hence the rotation speed of the pump, are controlled by using the deviation of the comparison (see Patent Document 1). According to this, when the vacuum chamber is evacuated by a pump, the automatic pressure adjustment valve (vacuum controller) is not required, and the actual intake pressure (output vacuum pressure) is used at a pressure higher than the ultimate pressure. In this case, an energy saving effect can be expected by lowering the rotational speed.

  However, in the case of a specification that does not install a vacuum chamber, when the rotation speed of the rotor in the non-contact type vacuum pump is a lower limit by inverter control, and the output vacuum pressure is a degree of vacuum higher than the set vacuum pressure, The inverter cannot be controlled to lower the output vacuum pressure. Unlike compressed air, it is difficult to store a vacuum pressure of up to 1 atm. Therefore, it is practically meaningless to install a vacuum chamber when the exhaust flow rate is above a certain level, and it is rare to install a vacuum chamber.

  In the inverter control, the lower limit is set for the rotation speed of the rotor of the vacuum pump for the following reason. If the rotational speed of the rotor exceeds the lower limit and becomes low speed, the oil may not be sufficiently lubricated by pumping up the oil stored in the gearbox, and the rotating shaft of the electric motor and the vacuum pump This is because the number of rotations of the cooling fan (impeller) fixed to the coupling connecting the rotor rotation shaft is also low, and cooling may not be sufficiently performed.

  Further, according to the present applicant, first, as a pneumatic device station, a pneumatic device for generating negative or positive air pressure such as a vacuum pump and a blower, and a plurality of pneumatic devices can be stored and stored in a closed space. And a blower that generates a cooling airflow that flows in one direction from the lower side to the upper side in the storage box so as to cool the storage box heated by the pneumatic device. (See Patent Document 2) has been proposed. According to this, a plurality of pneumatic devices can be housed centrally and soundproofed, and can be suitably cooled and managed centrally. However, in this pneumatic equipment station, energy saving by inverter control has not been studied.

  Further, as a prior art, a method of operating a deaeration device having a configuration in which a deaeration unit and a vacuum pump are connected via a vacuum suction line, and the liquid to be deaerated in the deaeration unit is vacuum deaerated by the vacuum pump. A vacuum pressure in the deaeration means or in the vacuum suction line is detected, the number of rotations of the vacuum pump is controlled based on the detected value, and the detected value reaches a preset lower limit pressure value. Then, while switching the said vacuum pump from high speed operation to low speed operation, what introduces predetermined air to the said vacuum suction line is proposed (refer patent document 3).

  In addition, as a prior art, a vacuum suction line communicating with a vacuum pump in a deaeration tower formed by connecting a supply line having a pressure feed pump for supplying degassed liquid and a discharge line having an exhaust pump for taking out degassed liquid In the vacuum degassing apparatus connected to the suction pump, a regenerative pump having a controller for controlling the number of revolutions is used as the discharge pump, a vacuum pressure gauge is provided in the degassing tower and an electromagnetic valve is provided in the vacuum suction line. A vacuum deaerator (see Patent Document 4) in which a line is connected and the vacuum pressure gauge and the electromagnetic valve are connected to a vacuum controller via the line has been proposed.

JP 05-231381 A (first page) JP 2007-127114 A (first page) JP-A-10-253005 (Claims, FIG. 1) JP 07-213805 (Claims, FIG. 1)

The problem to be solved regarding the operation method of the vacuum pump is that oil lubrication is performed by the power of the electric motor so that the rotor provided on each of the two rotating shafts rotates in a non-contact state in the cylinder to generate vacuum pressure. For a vacuum pump in which the two rotary shafts are driven synchronously via a gear, the lower limit of the rotational speed by inverter control of the rotor is set to one predetermined value, and a set vacuum pressure with a lower vacuum degree is set. In this case, outside air is introduced to lower the output vacuum pressure, which makes it difficult to perform better energy-saving operation.
SUMMARY OF THE INVENTION An object of the present invention is to provide a method of operating a vacuum pump that expands a control range by an inverter and can perform an energy saving operation even in a vacuum pressure region having a lower degree of vacuum.

The present invention has the following configuration in order to achieve the above object.
According to one aspect of the operation method of the vacuum pump according to the present invention, the power provided by the electric motor is used to generate the vacuum pressure by rotating the rotors respectively provided on the two rotating shafts in a non-contact state in the cylinder. For a vacuum pump in which the two rotary shafts are driven synchronously via a gear that is oil-lubricated, a vacuum that can control the rotational speed of the rotor by frequency control of an inverter that adjusts the frequency of electric power supplied to the electric motor. In the operation method of the pump, the output vacuum pressure is set to the set vacuum by comparing the output vacuum pressure in the flow path on the vacuum output side of the vacuum pump with a set vacuum pressure and adjusting the rotational speed of the rotor by the inverter. The lower limit by the control of the inverter over the rotation speed of the rotor is the first stage lower limit frequency and the first step. It is set to at least two stages with a lower limit frequency of the second stage that is lower than the lower limit frequency of one stage, and the lower limit by the control of the inverter is set from the start of the vacuum pump until the oil lubrication of the gear is stabilized. Is the lower limit frequency of the first stage, and after the oil lubrication of the gear of the vacuum pump is stabilized, the lower limit frequency of the second stage.

Further, according to one aspect of the operation method of the vacuum pump according to the present invention, the time from the start of the vacuum pump until the oil lubrication of the gear is stabilized is that a required time elapses and / or the temperature of the oil It can be characterized in that it is determined when becomes equal to or greater than a predetermined value.
Further, according to one aspect of the operation method of the vacuum pump according to the present invention, the rotation speed of the rotor is a lower limit controlled by the inverter, and the output vacuum pressure is higher than the set vacuum pressure. In the case, an opening is created so that outside air is sucked in a pressure regulating valve provided in a flow path on the vacuum output side of the vacuum pump, and the vacuum level of the output vacuum pressure is reduced to reduce the set vacuum pressure. It can be characterized by controlling to become.

Moreover, according to one form of the operating method of the vacuum pump which concerns on this invention, the said pressure control valve can be an electromagnetic on-off valve or an electromagnetic proportional control valve, It can be characterized by the above-mentioned.
Further, according to one aspect of the operation method of the vacuum pump according to the present invention, a plurality of the vacuum pumps are provided, and the inverter is adjusted so that the rotation speed is adjusted by the inverter for at least one of the vacuum pumps. It may be characterized in that a controller for controlling is used.

  According to the operation method of the vacuum pump according to the present invention, the control range by the inverter is expanded to the lower limit side, and there is a particularly advantageous effect that the energy saving operation can be performed even in the vacuum pressure region having a lower degree of vacuum.

It is a block diagram which shows the operating method of the vacuum pump which concerns on this invention, and the form example of a vacuum pump unit. It is a flowchart figure explaining the control method of the example of a form of FIG. (A) which shows the form example of the vacuum pump unit which concerns on this invention is a front view, (b) is a side view. It is a top view of the example of a form of FIG. It is the assembly perspective view which abbreviate | omitted the side panel of the example of FIG. It is sectional drawing which shows the example of the form of the vacuum pump which concerns on this invention. It is sectional drawing which shows the form example of the principal part of the vacuum pump which concerns on this invention. It is a perspective exploded view which shows the example of the principal part of the vacuum pump which concerns on this invention.

Hereinafter, the operation method of the vacuum pump and the embodiment of the vacuum pump unit according to the present invention will be described in detail based on the attached drawings (FIGS. 1 to 8).
The vacuum pump operating method and vacuum pump unit according to the present invention provide a vacuum output generated in the vacuum pump 10 having a structure in which the rotor in the cylinder is rotated in a non-contact state by the driving force of the electric motor 20. This is based on a function that can be controlled by the inverter 30 that can adjust the frequency of the power supplied to the inverter 20. Note that the cylinder forms a space where gas is sucked and exhausted, and the rotor is a rotating body that rotates about its axis, for example, a claw shape, a roots shape, a screw shape, or the like. Is mentioned.

  As shown in FIGS. 3 and 5 to 8, the vacuum pump 10 includes rotors 130 </ b> A and 130 </ b> B (see FIGS. 7 and 8) provided on two rotating shafts 131 and 132 (see FIGS. 7 and 8), respectively, and 3 (see FIGS. 3 and 8), and the vacuum is generated by rotating in a non-contact state within the above two through the oil lubricated gears 137 and 137 (see FIGS. 6 to 8) by the power of the electric motor 20. This is a non-contact type pump in which two rotating shafts are driven synchronously. Reference numeral 21 denotes a silencer, which is a part of a flow path of exhaust discharged from the cylinder 110 (see FIGS. 3, 5, and 6). Reference numeral 145 denotes a gear box (see FIGS. 3 and 6 to 8). As shown in FIG. 6, 15 is a pump coaxial air blowing mechanism, 15a is a cooling fan (impeller), which is fixed coaxially with the rotating shaft of the electric motor 20, and is arranged in the air blowing casing 15b. ing. The cooling fan 15 a of this embodiment is fixed to a coupling that connects the rotating shaft of the electric motor 20 and the rotating shaft 131 of one rotor 130 </ b> A of the vacuum pump 10. Here, the example of the form of the claw pump which is an example of the vacuum pump 10 which concerns on this invention is demonstrated easily based on FIG. Reference numeral 121 denotes an intake port, which opens on the side peripheral wall of the cylinder 110. An exhaust port 122 is open to one side plate 120 </ b> A that covers one end surface of the cylinder 110. The two rotors 130A and 130B are fixed to the free ends of the rotary shafts 131 and 132 supported in a cantilevered support state. And the bearing part 135 containing the bearings 134 and 134 which support each rotating shaft 131 and 132 is continuously provided in the outer side (opposite side of the cylinder 110) of the other side plate 120B which blocks the other end surface of the cylinder 110. It has been. In addition, two gears 137 and 137 are meshed in a gear box 145 outside the other side plate 120B, and the two rotors 130A and 130B are provided to rotate in the opposite directions at the same speed. Oil is sealed in the gear box 145, and oil is supplied to the gears 137 and 137, the bearings (bearings 133 and 134), and the oil seal 136 and lubricated by scraping by gear rotation. Examples of the non-contact type vacuum pump include a roots pump and a screw pump in addition to the claw pump.

  The inverter 30 is connected to a power source (not shown), is connected so as to be controlled by a controller 60 described later, and is connected so as to supply electric power whose frequency is adjusted to the electric motor 20. (See FIG. 1).

  According to this inverter 30, when the actually required vacuum output is smaller than the rated vacuum output, the number of rotations of the vacuum pump 10 (rotary pump) is reduced to appropriately adjust the vacuum pressure and the exhaust flow rate. be able to. According to this, energy consumption can be reduced because power consumption can be reduced, noise reduction can be achieved, longer life can be expected due to lower oil temperature and bearing temperature, and maintenance time can be extended. Can be expected.

  Reference numeral 40 denotes a vacuum pressure sensor, which is provided so as to measure the output vacuum pressure in the flow path 11 on the vacuum output side of the vacuum pump 10. As the vacuum pressure sensor 40, it is possible to appropriately perform control automation by using a sensor that can output measurement data (measurement pressure) by an electrical signal.

Reference numeral 50 denotes a pressure adjusting valve that operates to lower the degree of vacuum of the output vacuum pressure by generating an opening so that outside air is sucked in the flow path 11 on the vacuum output side of the vacuum pump 10.
As the pressure regulating valve 50, an electromagnetic opening / closing valve can be used. According to this, it becomes possible to automate the control for outputting a vacuum pressure with a low degree of vacuum at a low cost with a simple configuration. Further, an electromagnetic proportional control valve can be used as the pressure adjusting valve 50. According to this, it becomes possible to automate the control for outputting the vacuum pressure with a low degree of vacuum, and more precise control is possible.

  Reference numeral 60 denotes a controller, which compares the output vacuum pressure measured by the vacuum pressure sensor 40 with the set vacuum pressure, and adjusts the rotation speed of the rotor of the vacuum pump 10 by the inverter 30, thereby changing the output vacuum pressure to the set vacuum pressure. When the rotation speed of the rotor is the lower limit by the control of the inverter 30 and the output vacuum pressure is higher than the set vacuum pressure, the pressure adjusting valve 50 is operated to make the vacuum of the output vacuum pressure It is provided so as to control to a set vacuum pressure by decreasing the degree.

That is, according to the embodiment of the vacuum pump unit according to the above configuration, the pressure (output vacuum pressure) can be adjusted by the rotation speed control (inverter frequency control). . Thereby, the above-described effects such as energy saving can be realized.
In the low pressure range (the range of the output vacuum pressure when the required degree of vacuum is low), the pressure adjustment valve 50 is operated to adjust the pressure. According to this, in the vacuum pump unit, it is possible to adjust the pressure within a wider range of output vacuum pressure, and it is possible to meet a wide range of user needs.

  By the way, the lower limit of the frequency controlled by the inverter 30 can be set to 20 Hz, for example. The reason why the lower limit of the frequency is set in this way is that, with regard to oil lubrication of the vacuum pump 10, if the rotational speed is small, there is a possibility that the oil will be lifted up in the gearbox and there is a possibility that the lubricating oil will be insufficient. There is a possibility that the air volume for cooling by the cooling fan (impeller) 15a fixed to the rotating shaft of the pump 10 is reduced, and the vacuum pump may be overheated. For this reason, in the low pressure range which should be pressure-regulated below a lower limit frequency, pressure regulation by rotation speed control (inverter control) may not be performed appropriately. Therefore, in the low pressure range, the pressure adjustment valve 50 is operated to adjust the pressure in a state where air is leaked (a state where outside air is sucked). In the embodiment shown in FIG. 1, an electromagnetic on-off valve as the pressure regulating valve 50 is provided so as to perform an intermittent operation. Note that the vacuum pump 10 can be prevented from being overheated by a separate cooling fan device 90 as described later.

  And according to this invention, the lower limit by control of the inverter 30 concerning the rotation speed of the rotor is the lower limit frequency of the first stage and the lower limit frequency of the second stage that is lower than the lower limit frequency of the first stage. There are at least two stages. Then, the lower limit by the control of the inverter 30 is set as the lower limit frequency of the first stage from the start of the vacuum pump 10 until the oil lubrication of the gear is stabilized, and after the oil lubrication of the gear of the vacuum pump is stabilized It is controlled by the controller 60 so as to be the lower limit frequency of the second stage.

  When the lower limit of the rotational speed of the rotor is set in at least two stages, for example, the lower limit frequency of the first stage of the inverter 30 can be set to 20 Hz, and the lower limit frequency of the second stage can be set to 15 Hz. Further, the time from the start of the vacuum pump to the stabilization of the oil lubrication of the gear may be a timing determined when a required time elapses and / or when the oil temperature becomes a predetermined value or more. it can. For example, normally the oil temperature rises by about 50 ° C. relative to the ambient temperature and stabilizes in about 2 hours after the start of operation, so that 2 hours after the start of operation, the lower limit frequency of the first stage is reduced from the lower limit frequency of the first stage It can be time to shift to frequency. Since the oil temperature is stabilized and the oil viscosity is stabilized and the vacuum pump can be stably operated, the temperature may be used as a criterion. For example, a temperature sensor that directly or indirectly detects the oil temperature may be provided, and the lower limit rotational speed of the rotor may be changed based on the detection information.

In this way, the frequency control range by the inverter 30 is expanded on the lower limit side, and the lower limit rotational speed of the rotor is reduced, so that energy-saving operation can be performed in a vacuum pressure region with a lower degree of vacuum. Further, by lowering the lower limit rotational speed of the rotor, the use of the pressure regulating valve can be reduced in a vacuum pressure region having a lower degree of vacuum. In this way, by reducing the use of the pressure regulating valve, it is possible to save energy because no excess air is sucked.
Further, in the timer control in which a certain time is set so as to determine the stability of the oil temperature (oil temperature) based on the operation time, more precise control is difficult, but it can be configured at a lower cost. Further, more accurate control can be performed by determining the stability of the oil temperature based on the temperature of the temperature sensor. In the determination based on the temperature of the temperature sensor, it takes a certain time (for example, 2 hours) considering the safety factor according to the determination by time. However, depending on the operating conditions, the time until the determination can be shortened. It is possible to shift to energy saving operation by lowering the lower limit rotational speed with time. And when the minimum of the rotation speed of a rotor is set to three steps or more, more precise control can be performed.

  Reference numeral 70 denotes a safety valve, which generates an opening so that outside air is sucked when the output vacuum pressure is higher than the upper limit set vacuum pressure in the flow path 11 on the vacuum output side of the vacuum pump 10 to thereby output vacuum pressure. Operates to reduce the vacuum level.

  According to the safety valve 70, it is possible to prevent a cutoff operation by using a spring-type safety valve having the same structure as the vacuum controller as a safety device, assuming the worst case of a control system failure. Therefore, it is possible to prevent an overcurrent from occurring due to an increase in required torque due to the shut-off operation, and secure a safe operation.

As shown in FIGS. 3 to 5, reference numeral 80 denotes a storage box that stores the vacuum pump 10 and stores all components including electrical components such as the inverter 30 and the controller 60 in this embodiment. Thus, the vacuum pump unit is packaged. Moreover, according to this storage box 80, since the vacuum pump 10 is stored in a closed space and sound-insulated, it is a soundproof box.
In this embodiment, two vacuum pumps 10 are stored, but only one unit may be stored, or a plurality of three or more units may be stored.

As shown in FIGS. 3 and 4, reference numeral 90 denotes a cooling fan device, which is installed in the storage box 80 and is provided to cool the vacuum pump 10 by circulating cooling air. The cooling fan device 90 can be circulated by using outside air as cooling air and taking in the outside air and exhausting it as indicated by arrows in the figure. The inner space of the storage box 80 is a suitable passage (flow path) for cooling air (outside air). Reference numeral 91 denotes a cooling air exhaust port provided on the top plate surface of the storage box 80.
If a cooling device such as a water-cooled cooler is installed in the storage box 80, the cooling air can be circulated.

  As described above, the cooling pump device 90 can cool the vacuum pump 10, thereby further lowering the lower limit of the frequency controlled by the inverter 30 as described above, and further increasing the rotational speed (rotational speed) of the rotor of the vacuum pump 10. It is possible to reduce the speed and to eliminate the setting of the lower limit. That is, overheating of the vacuum pump 10 due to a decrease in the number of rotations of the cooling fan (impeller) fixed to the rotating shaft of the vacuum pump 10 as the frequency decreases is caused by the cooling fan device 90 installed separately. This is because it can be resolved. According to this, it becomes possible to eliminate the need for the pressure regulating valve 50 that operates in a low pressure region, and the device configuration can be simplified. It should be noted that oil lubrication can be dealt with by other well-known techniques, for example, using a grease-enclosed bearing.

  In addition, in the storage box 80 of this embodiment, at least one stage of the mounting table 81 on which the vacuum pump 10 is mounted is provided in the middle of the height direction. In this embodiment, a two-stage mounting table portion 81 is provided. And the mounting base part 81 has the opening part 82 so that the flow of cooling air may be permitted as shown in FIG.

  Thus, the plurality of vacuum pumps 10 can be suitably accommodated in a three-dimensional manner by the plurality of mounting table portions 81. Therefore, the installation space can be reduced. Further, since the mounting table 81 has the opening 82, the cooling air flows smoothly, and the inside of the storage box 80 can be suitably cooled. Moreover, ventilation resistance can be suppressed low and the burden of the air blower (cooling fan device 90) can be reduced.

Furthermore, the cooling fan device 90 according to the present embodiment is disposed at the upper part of the storage box 80 and is provided so that the cooling air flows upward from below (see FIGS. 3 and 4).
Since the cooling air is thus sucked from the lower side and discharged to the upper side, the one-way cooling air from the bottom to the top together with the rising air flow of the air heated by each vacuum pump 10. This flow can be suitably generated. That is, it is possible to efficiently blow air by matching the convection phenomenon with the air flow by the cooling fan device 90.

  The cooling fan device 90 can reliably obtain the above-described cooling effect by being operated at a constant speed. However, the cooling fan device 90 can be controlled in accordance with the operating state (the number of rotations) and the environment of the vacuum pump 10 or can be turned on. It is possible to further save energy by performing -OFF control.

  Further, in the present invention, a plurality of vacuum pumps 10 are provided, and at least one of the vacuum pumps 10 is provided so that the rotation speed can be adjusted by the inverter 30, and the controller 60 is connected to at least one inverter 30. It can be provided so that it can be controlled. In this embodiment, as shown in FIG. 1, two vacuum pumps 10, 10 are provided, and are connected to inverters 30, 30 and controlled by a controller 60.

Thus, the number control can be performed by providing the plurality of vacuum pumps 10 whose rotation speed is adjusted by the plurality of inverters 30.
For example, when the flow rate requested by the user is less than the rated amount of one vacuum pump 10, only one vacuum pump 10 needs to be operated, and the second and subsequent units are increased according to the increase in required vacuum output. The vacuum pump 10 may be operated.
It should be noted that the vacuum pump 10 that is operating in the unit control may be stopped when there is no air flow and the pressure is maintained. Also, when air flows and the pressure decreases, first, the number of rotations of the operating vacuum pump 10 is increased to increase the pressure, and if that is not sufficient, the next one vacuum pump 10 is controlled to start. do it.

In addition, by controlling the number of the plurality of vacuum pumps 10, if one vacuum pump 10 is abnormal and cannot be operated, the other vacuum pumps 10 may be operated, and the maintenance time of the plurality of units can be shifted. It becomes possible to complement each other.
In the case of a combination of one constant speed vacuum pump 10 and a vacuum pump 10 under inverter control, in the case of full operation of the constant speed vacuum pump 10 and operation at + α flow rate, the + α portion is the pressure at the lower limit of the inverter frequency. Since there is a possibility that the operation is performed with control by the regulating valve, there is a possibility that power is wasted. On the other hand, in the case of the configuration using only the vacuum pump 10 by inverter control, the above-described waste does not occur, which is advantageous for realizing energy saving.

Next, the operation method of the vacuum pump of this embodiment will be described based on the flowchart of FIG.
First, the set vacuum pressure value is input to the controller 60 by the user setting the pressure, and the operation switch (SW) is turned on.
Next, the output vacuum pressure (measured pressure) in the flow path on the vacuum output side of the vacuum pump 10 is compared with the set vacuum pressure (set pressure), PID control is started, and the inverter 30 controls the rotor of the vacuum pump 10. The measurement pressure is controlled to be the set pressure by adjusting the rotation speed.

In this control, in this embodiment, the lower limit of the motor frequency by the inverter 30 that determines the rotational speed of the rotor of the vacuum pump 10 is set to 20 Hz.
As a result of the PID control, when the measured pressure becomes equal to the set pressure, the motor frequency is determined and the pump operation is performed, and the operation is continued in the absence of disturbance.

When the measured pressure is not equal to the set pressure even by PID control (when the measured pressure is higher than the set pressure), the electromagnetic valve (pressure adjusting valve 50) is activated and the vacuum pump 10 is evacuated. An opening is generated so that outside air is sucked in the flow channel 11 on the output side, and the vacuum level of the output vacuum pressure (measurement pressure) is reduced to control the set pressure.
When the measured pressure exceeds the upper limit of the set pressure, the safety valve 70 is set to open by “safety valve operation”.

  As described above, the present invention has been described in various ways with preferred embodiments. However, the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention. That is.

DESCRIPTION OF SYMBOLS 10 Vacuum pump 11 Flow path on the vacuum output side 20 Electric motor 21 Silencer 30 Inverter 40 Vacuum pressure sensor 50 Pressure adjustment valve 60 Controller 70 Safety valve 80 Storage box 81 Mounting base part 82 Opening part 90 Cooling fan apparatus 110 Cylinder 130A Rotor 130B Rotor 131 Rotating shaft 132 Rotating shaft 137 Gear 145 Gearbox

Claims (5)

The two rotary shafts are synchronized via a gear that is oil-lubricated by the power of the electric motor so that the rotor provided on each of the two rotary shafts rotates in a non-contact state in the cylinder to generate vacuum pressure. In the operation method of the vacuum pump that can control the rotation speed of the rotor by frequency control of an inverter that adjusts the frequency of the electric power supplied to the electric motor for the driven vacuum pump,
The output vacuum pressure in the flow path on the vacuum output side of the vacuum pump is compared with the set vacuum pressure, and the rotation speed of the rotor is adjusted by the inverter so that the output vacuum pressure becomes the set vacuum pressure. And
The lower limit by the control of the inverter relating to the rotation speed of the rotor is set to at least two stages, that is, a first stage lower limit frequency and a second stage lower limit frequency that is lower than the first stage lower limit frequency. ,
The lower limit by the control of the inverter is the lower limit frequency of the first stage from the start of the vacuum pump until the oil lubrication of the gear is stabilized, and after the oil lubrication of the gear of the vacuum pump is stabilized A method for operating a vacuum pump, wherein the lower limit frequency of the second stage is set.   The time from the start of the vacuum pump to the stabilization of oil lubrication of the gear is determined by elapse of a required time and / or when the oil temperature becomes a predetermined value or more. The operation method of the vacuum pump of 1.   When the rotation speed of the rotor is a lower limit by the control of the inverter and the output vacuum pressure is higher than the set vacuum pressure, the rotor is provided in the flow path on the vacuum output side of the vacuum pump. The operation method of the vacuum pump according to claim 1 or 2, wherein an opening is generated so that outside air is sucked in the pressure adjusting valve, and the vacuum pressure of the output vacuum pressure is reduced to control to be the set vacuum pressure. . 4. The operation method of a vacuum pump according to claim 3 , wherein the pressure adjusting valve is an electromagnetic on-off valve or an electromagnetic proportional control valve.   5. The controller according to claim 1, wherein a plurality of the vacuum pumps are provided, and a controller that controls the inverter is used so that the rotation speed is adjusted by the inverter for at least one of the vacuum pumps. A method for operating the vacuum pump according to claim 1.

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