JP2010138901A - Device having vacuum pump and operation method of vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum pump having a lengthened effective service life with a simple structure, and a simple operation method of the vacuum pump for lengthening the effective service life. <P>SOLUTION: This device has the vacuum pump 10 including at least one pump stage 12 and a motor 14 for driving the pump stage and a current-carrying device 21. For reducing abrasion of a part of the pump stage, the device has a measuring device 24 for determining an electric operation variable. This invention also relates to an operation method of the vacuum pump 10 having the motor 14. Here, the invention proposes to measure electric power consumption of the motor and to reduce a rotating speed of the motor when the electric power consumption is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus including the vacuum pump according to the superordinate concept of claim 1 and a method for operating the vacuum pump according to the superordinate concept of claim 7.

  Vacuum pumps are indispensable today in many industrial processes. Its applications range from freeze-drying to leak detection as well as lamp manufacturing and vacuum tube manufacturing, but these are just a few examples. The processes utilized in these applications today have increasingly shorter cycle times, which increases the vacuum pump load. For this reason, there is an increasing desire to use a dry compression vacuum pump, that is, a vacuum pump in which no lubricant is present in the pump chamber. However, since contact seals must often be used in these conditions, the seals are subject to high wear. Means for reducing wear are known, ie German Offenlegungsschrift 102006012532 proposes to support the seal with a guide element. However, there is a desire to achieve a sufficient improvement in useful life.

German Patent Publication No. 102006012532

  Accordingly, an object of the present invention is to provide a vacuum pump having a simple structure and an extended useful life. It is a further object of the present invention to provide a simple method of operating a vacuum pump that extends the useful life.

  This problem is solved by a vacuum pump having the features of claim 1 and a method having the features of claim 7. Dependent claims 2-6 and 8 provide advantageous modifications of the invention.

  The measuring device for determining the electric operating variables of the motor of the vacuum pump makes it possible to operate the motor so that the wear of the pump stage is significantly reduced. The method according to the invention as claimed in claim 7 has the advantage that, with simple measurements and simple criteria, it is possible to lead to an operation in which wear at reduced rotational speed is reduced.

  This method is advantageously improved by being below the power threshold being selected as a criterion for reducing the rotational speed. This simplifies the necessary control devices.

  The modification of providing a connection between the measuring device and the energizing device simplifies the circuit and allows automatic switching to an operating state with less wear.

  Another variant proposes to provide at least two pump stages, in which case the motor drives at least two of these pump stages simultaneously. This device is particularly advantageous because there is a simple and unambiguous criterion for switching to an operating state with less wear. For example, pressure switch positioning problems are avoided. In multi-stage vacuum pumps, many different pressure levels occur at various positions of the pump, so it is unclear which pressure measurement provides a meaningful value for determining switching.

  When the motor is configured as a brushless DC motor, the motor generates sufficient torque even at low rotational speeds, so that the reduction in wear is particularly significant. That is, a particularly low rotational speed can be formed without impairing the pump action.

  One variant proposes that the at least one pump stage is configured to compress towards the atmosphere in dry operation. In this case, the advantage of reducing wear is particularly remarkable.

  The last variant proposes that the at least one pump stage has a reciprocating piston moving in the sliding liner and a seal between the sliding liner and the reciprocating piston. In this case, the seal can be significantly worn, but a significant reduction in wear is achieved because the vacuum pump can be operated at low rotational speeds without losing hermeticity.

  The invention will be described in detail by way of examples and the advantages thereof should be emphasized.

FIG. 1 shows a schematic view of an apparatus according to the invention with a vacuum pump. FIG. 2 shows a cross-sectional view along the axis of a two-stage reciprocating piston vacuum pump. FIG. 3 shows a cross-sectional view of the two-stage reciprocating piston vacuum pump perpendicular to the axis along the line II ′ of FIG. FIG. 4 shows a schematic diagram of a circuit provided in the driving device of the reciprocating piston vacuum pump.

  First, the present invention is shown schematically in FIG.

  The vacuum pump 10 includes a pump stage 12 and a motor 14. The motor drives the pump stage. A driving device 20 is provided alongside the vacuum pump. The drive device may be an independent device, but may also be present in the housing portion of the vacuum pump. The drive device includes an energization device 21, and the energization device is coupled to a vacuum pump motor via an energization line 22. The energization device generates a current and a voltage, which causes the motor to be moved and in particular rotated. The current and voltage are supplied to the motor via the energization line.

  A measurement line 26 is provided and connects the energization line 22 with the measurement device 24. The measuring device is configured to determine an electrical variable, which is transmitted via an energization line. This electrical variable may be current or voltage. Preferably, the power consumption of the motor is determined by the measuring device via measurement of the electrical variable. The measuring device and the energizing device are connected via the connection 27. By this connection, the energization amount of the motor is changed to a signal of the measuring device. This change is made as a function of the measured energization amount. In particular, as soon as the measuring device determines a low power consumption by the motor, the rotational speed of the motor generated by energization is reduced.

  The pump stage is preferably configured to dry and compress, for example as a membrane pump, a piston pump or a reciprocating piston pump, because in this case a reduction in rotational speed leads to a particularly significant reduction in wear Because.

  With reference to FIGS. 2 and 3, the invention will be described by means of a reciprocating piston vacuum pump.

  The reciprocating piston vacuum pump 210 has a shaft 250 rotatably supported by a bearing 253, for example, a rolling bearing, in a housing 240 thereof. The shaft is rotated by a motor 214, and the motor is formed by an electric coil 251 on the stator side and a permanent magnet 252 on the shaft side. The motor is formed as a brushless DC motor. A crank disc 254 is coupled to the shaft, and the crank disc has a crank pivot 255. A connecting rod 256 is rotatably supported on the crank pivot.

  The cylinder 241 that is hermetically coupled to the housing has a cylindrical hollow chamber, and a sliding liner 245 is fitted in the cylindrical hollow chamber. Within this sliding liner, a piston 246 coupled to and driven by the connecting rod 256 reciprocates between two reversal points.

  At the first reversal point, the piston releases the inlet opening, which forms a gas inlet connection with the gas inlet 243. At the second reversal point, the piston lifts the valve lid 249 from the valve seat so that gas is exhausted from the pump chamber 248 surrounded by the piston, valve lid and sliding liner. Next, the gas leaves the pump stage via the gas outlet 244 provided in the cylinder cover 242 and reaches the discharge pipe 280.

  A seal 247 is fixed to the piston, the seal is in sliding contact with the sliding liner and thus seals the gap between the sliding liner and the piston. Due to the sliding contact and the absence of a lubricant such as oil, the seal is subjected to high stresses and correspondingly wears significantly.

  The reciprocating piston vacuum pump has a drive device 220, and an energization device 221 and a power measurement unit 224 are provided in the drive device. The energization device is electrically connected to the electric coil by an energization line 222. The energizing device generates a current and a voltage in the coil, and the coil rotates the shaft. The energizing device is formed such that the rotational speed of the shaft can be set within a wide rotational speed range. Advantageously, the rotational speed range includes a range from stopping and several revolutions per second up to 60 revolutions per second. The power measurement unit is configured such that the power consumed by the motor is determined by measuring electrical variables. Measurement takes place via measurement line 226. The rotational speed is set as a function of the measured power consumption. In particular, when the power consumption is reduced, the rotation speed is set to a low value. The reduction in motor power consumption represents a small amount of compression work to be performed in the pump stage, in particular a small amount of gas to be compressed. When the amount of gas is small, even if the rotational speed is low and therefore the number of strokes of the piston is low, it is sufficient to maintain a high vacuum at the gas inlet. A low number of strokes is equivalent to essentially less seal wear since the seal will rub against the sliding liner less per unit time. It is advantageous to easily switch the rotation speed from the upper limit value of the normal condition to a lower protection rotation speed value when the power consumption threshold is dropped.

  In FIG. 3, the reciprocating piston vacuum pump is shown in a cross-sectional view along the line II ′ marked in FIG. Correspondingly, the first pump stage connecting rod 256, sliding liner 245, piston 246 and cylinder 241 are shown. Similarly, the seal 247, cylinder cover 242 and valve lid 249 already described in FIG. 2 are also shown.

  A second cylinder 261 having a second cylinder cover 262 is similarly coupled to the reciprocating piston vacuum pump housing 240 and forms its second pump stage. A second sliding liner 265 is provided in the cylinder, and the second piston 266 reciprocates in the second sliding liner. The second piston is coupled to and driven by the second connecting rod 257. For this purpose, the connecting rod is rotatably supported on the crank pivot 255, which is provided on the crank disc 254. The crank disk is rotated by shaft 250. The gas discharged from the first pump stage passes through the discharge pipe and reaches the second stage gas inlet 281. After compression by the second piston, the second piston pushes up the second valve lid 269 and discharges gas from the pump outlet 282 toward the atmosphere. The piston of the second pump stage is also provided with a seal 267 that contacts the sliding liner, and the seal is subject to wear according to the same principle as the seal 247 of the first pump stage. Similarly, wear is reduced if the rotational speed is reduced by the above method.

  Finally, FIG. 4 schematically shows the principle diagram of the electric circuit of the driving device 220. The voltage supply unit 431 is detachably connected to the power supply network 430. This power supply network is, for example, a 230V AC power supply or an industrial power supply. The voltage supply generates a voltage for the intermediate circuit 432 and an operating voltage for the electronic device of this circuit. Therefore, the voltage supply unit is coupled to the power measurement unit 224 and the transmitter 433 of the energization device via the supply circuit 440. The energization device has a final stage 434. In this final stage, an upper power transistor 435 and a lower power transistor 436 are arranged in pairs. The power transistor converts the intermediate circuit voltage into a phase voltage, which is then applied to the motor 214 coil via the motor phase 437. The switching operation of the power transistors 435 and 436 is performed by a transmitter. The transmitter shuts off or opens the power transistor so that the motor is rotated by energization of the motor phase. In this case, the transmitter can generate the switching operation of the power transistor for a large number of rotation speeds. It is formed as follows.

  The power measurement unit is coupled to the motor phase via measurement line 226 and measures the current and voltage generated in the motor phase. A connection 227 is formed between the power measurement unit and the transmitter. If the power measurement unit determines that the power consumption by the motor is reduced, the transmitter causes the power transistor to be activated and thus energized in the motor phase so that the rotational speed of the motor takes a lower value. It is advantageous to easily switch the rotation speed from the upper limit value of the normal condition to a lower protection rotation speed value when the power consumption threshold is dropped.

10, 210 Vacuum pump 12, 212 Pump stage 14, 214 Motor 20, 220 Drive device 21, 221 Current supply device 22, 222 Current supply line 24, 224 Measurement device (power measurement unit)
26, 226 Measurement line 27, 227 Connection 240 Housing 241, 261 Cylinder 242, 262 Cylinder cover 243 Gas inlet 244 Gas outlet 245, 265 Sliding liner 246, 266 Reciprocating piston 247, 267 Seal 248 Pump chamber 249, 269 Valve Lid 250 Shaft 251 Electric coil 252 Permanent magnet 253 Bearing 254 Crank disk 255 Crank pivot 256, 257 Connecting rod 280 Discharge pipe 281 Second stage gas inlet 282 Pump outlet 430 Power supply network 431 Voltage supply unit 432 Intermediate circuit 433 Transmitter 434 Final stage 435, 436 Power transistor 437 Motor phase 440 Supply circuit

Claims (8)

In an apparatus comprising a vacuum pump (10; 210) comprising at least one pump stage (12; 212) and a motor (14; 214) for driving said pump stage, and an energizing device (21; 221),
A device with a vacuum pump, characterized in that the device comprises a measuring device (24; 224) for determining the electric operating variables of the motor. Device according to claim 1, characterized in that the device has a connection (27; 227) between the measuring device (24; 224) and the energization device (21; 221). The apparatus according to claim 1 or 2, characterized in that the vacuum pump (10; 210) comprises at least two pump stages and the motor (214) drives at least two of the pump stages simultaneously. 4. A device according to claim 1, wherein the motor is formed as a brushless DC motor. 5. The device according to claim 1, wherein the at least one pump stage (12; 212) is configured to compress towards the atmosphere in dry operation. At least one pump stage (12) has a reciprocating piston (246; 266) moving in a sliding liner (245; 265) and a seal (247;) between the sliding liner and the reciprocating piston. 267) according to any one of the preceding claims. In a method of operating a vacuum pump (10; 210) with a motor (14; 214),
A method of operating a vacuum pump, wherein the power consumption of the motor is measured and the rotational speed of the motor is reduced when the power consumption is reduced. The method according to claim 7, wherein the rotation speed is reduced when a power consumption threshold is dropped.

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