JP4532783B2 - Magnetic bearing excitation circuit and turbo molecular pump device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic bearing excitation circuit and a turbo molecular pump device, and in particular, a magnetic bearing excitation circuit and a turbo molecular pump device that can both reduce the size of the entire device, reduce costs, and improve reliability by simplifying the circuit configuration. About.
[0002]
[Prior art]
Magnetic bearings are used in rotating equipment such as turbomolecular pumps used in semiconductor manufacturing processes. A conventional magnetic bearing excitation circuit will be described based on a configuration example of a magnetic bearing of a turbo molecular pump.
[0003]
FIG. 10 shows a cross-sectional view of a turbo molecular pump as a configuration example of the magnetic bearing.
10, the turbo molecular pump includes a rotating body 103 including a plurality of rotating blades 101a, 101b, 101c,... By turbine blades for exhausting gas.
[0004]
In order to support the rotating body 103, a magnetic bearing is configured by disposing an upper radial electromagnet 105a, a lower radial electromagnet 107a, and an axial electromagnet 109a. Further, an upper radial direction sensor 105b, a lower radial direction sensor 107b, and an axial direction sensor 109b are provided.
[0005]
The upper radial direction electromagnet 105a and the lower radial direction electromagnet 107a are composed of four electromagnets by the electromagnet windings configured as shown in FIG. These four electromagnets are arranged so as to face each other, and constitute a biaxial magnetic bearing in the X-axis direction and the Y-axis direction.
[0006]
Specifically, one electromagnet is formed by arranging electromagnet windings 111 and 111 wound around two adjacent core convex portions as a pair and having opposite polarities. This electromagnet constitutes one pair with the electromagnets 113 and 113 of the core convex portions facing each other with the rotating body 103 interposed therebetween, and each attracts the rotating body 103 in the positive or negative direction of the X axis.
[0007]
Further, in the Y-axis direction orthogonal to the X-axis, the two electromagnet windings 115 and 115 and the two electromagnet windings 117 and 117 facing the same are also opposed in the Y-axis direction as described above. One pair is configured as an electromagnet.
[0008]
The axial direction electromagnets 109a and 109a are configured as one pair by two electromagnet windings 121 and 123 sandwiching the armature 103a of the rotating body 103 as shown in FIG. The two electromagnets 109a and 109a formed by the electromagnet windings 121 and 123 act to attract the armature 103a in the positive or negative direction of the rotation axis.
[0009]
Further, the upper radial direction sensor 105b and the lower radial direction sensor 107b are composed of four sensing coils arranged on the XY2 axes corresponding to the electromagnets 105a and 107a, and detect the radial displacement of the rotating body 103. The axial direction sensor 109b detects the axial displacement of the rotating body 103. These sensors are configured to send respective detection signals to a magnetic bearing control device (not shown).
[0010]
Based on these sensor detection signals, the magnetic bearing control device individually applies the attraction force of a total of ten electromagnets constituting the upper radial electromagnet 105a, the lower radial electromagnet 107a, and the axial electromagnets 109a and 109a by PID control or the like. By adjusting, the rotating body 103 is configured to support magnetic levitation.
[0011]
Next, a magnetic bearing excitation circuit for exciting and driving the electromagnets of the magnetic bearing configured as described above will be described. FIG. 13 shows a conventional magnetic bearing excitation circuit when the current flowing in the electromagnet winding is controlled by a switching method.
[0012]
In FIG. 13, an electromagnet winding 111 constituting one electromagnet is connected to a power source 133 at both ends thereof via transistors 131 and 131, respectively. Similarly, diodes 135 and 135 for current regeneration are connected to the power source 133. It is interposed between. Gates of both transistors 131 and 131 are provided with gate drive circuits 131a and 131a, respectively, and are connected to a current control circuit 137. In addition, a current detection circuit 139 is interposed in the electromagnet winding 111 and is connected to the current control circuit 137.
[0013]
The current control circuit 137 determines the pulse width by comparing the current command with the value detected by the current detection circuit 139, and sends the pulse width to the gate drive circuit 131a. The gate driving circuit 131a adjusts the excitation of the electromagnet winding 111 by adjusting the electromagnet winding current via the transistor 131.
[0014]
Thus, since the magnetic bearing excitation circuit requires two transistors 131 and 131 per electromagnet, it requires four transistors per one axis by two electromagnets. Therefore, in the excitation circuit of the magnetic bearing device having the five-axis configuration, a large number of members constituting the total number of transistors 131 and the gate driving circuit 131a attached to each of the transistors 131 are required.
[0015]
As another configuration example of the magnetic bearing excitation circuit, FIG. 14 shows an example in which two electromagnets facing on one axis are collectively controlled. 14, two electromagnet windings 111 and 113 are connected in series, and a bridge circuit is constituted by four transistors 131. A current detection circuit 139 is interposed in the electromagnet windings 111 and 113 connected in series, and is connected to the current control circuit 137. The two electromagnets formed by the two electromagnet windings 111 and 113 are accompanied by a magnet (not shown) that generates a bias magnetic field, and the attractive force is adjusted in the positive direction or the negative direction by changing the magnetic flux density of the biased magnetic field. To do.
[0016]
Also in this configuration example, a large number of members such as four transistors 131 per axis and four gate driving circuits 131a attached thereto are required.
[0017]
[Problems to be solved by the invention]
However, the magnetic bearing control device in which the excitation circuit having a large number of transistors and the like is incorporated has a problem that the cost is high due to the number of components. Further, since a large number of transistors are required, there are problems that the failure rate is high and miniaturization is difficult.
[0018]
In particular, since the turbo molecular pump is used in a semiconductor manufacturing apparatus or the like, it is often installed in a clean room. Since the construction cost per unit floor area is high in a clean room, there is an increasing demand for miniaturization by integrating the pump body and control unit for the turbo molecular pump device used there, but it requires a complicated excitation circuit Therefore, an integrated structure in which a control circuit is incorporated in the pump body has not been realized.
[0019]
As described above, the magnetic bearing excitation circuit in the turbo molecular pump device is strongly required to be downsized as a whole including the magnetic bearing control device, and the number of components can be reduced from the viewpoint of the component cost and reliability of the control device. I was waiting.
[0020]
The present invention has been made in view of the above-described conventional problems, and a magnetic bearing excitation circuit and a turbo molecular pump device that can both reduce the size of the entire device, reduce costs, and improve reliability by simplifying the circuit configuration. The purpose is to provide.
[0021]
[Means for Solving the Problems]
Therefore, the present invention (Claim 1) includes a switching means for controlling connection / disconnection of a current received from a power supply, a first electromagnet winding controlled to be excited by the switching means, and a transformer coupling with the first electromagnet winding. It is, and, a second electromagnet windings to be excited by the induced current is interposed a regeneration means for directing a current in the regenerative direction, one of the first electromagnet winding or the second electromagnet winding Meanwhile And a current control means for instructing the switching means to receive a detection signal from the current detection means so that the current of the electromagnet winding becomes a command current. To do.
[0022]
The first electromagnet winding provided with the switching means is excited in correspondence with the energization operation of the switching means. When the switching means stops energization, power is induced in the regeneration direction in the second electromagnet winding coupled to the transformer. With this regenerative power, the second electromagnet winding is excited continuously with the excitation of the first electromagnet winding. In this repetition, the current control means receives the electromagnet winding current detection signal from the current detection means, and adjusts the switching means so that the electromagnet winding current becomes the command current.
[0023]
In this way, the first electromagnet winding and the second electromagnet winding are transformer-coupled, the switching means is connected to one of them to supply power, and the regenerative means is connected to the other to regenerate power. By configuring, the first electromagnet winding and the second electromagnet winding can be alternately excited by one switching means.
Therefore, the magnetic bearing excitation circuit can be simplified by a single switching means such as a transistor.
[0026]
Furthermore, the present invention (Claim 2 ) is characterized in that at least one of the switching means and the regeneration means is provided with a surge absorbing means.
[0027]
By providing the surge absorbing means, an excessive voltage applied to the electronic component is relieved, so that the excitation circuit can be stably operated and the durability of the control device can be improved.
[0028]
Further, in the turbo molecular pump device of the present invention (claim 3 ), the rotor blades are excited by the magnetic bearing excitation circuit and the excitation of the first electromagnet winding or the second electromagnet winding by the magnetic bearing excitation circuit. And a turbo molecular pump supported by levitation.
[0029]
By simplifying the magnetic bearing excitation circuit, the entire turbo molecular pump control device including the magnetic bearing excitation circuit can be made compact.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. A magnetic bearing excitation circuit according to an embodiment of the present invention is shown in FIG. Note that the same elements as those in FIG. 13 are denoted by the same reference numerals and description thereof is omitted.
[0031]
In FIG. 1, two electromagnet windings 1a and 1b are constituted by transformer coupling by dividing one electromagnet of a magnetic bearing into two.
The transistor 131 and the electromagnet winding 1a are connected in series to the power supply 133. The conduction of the transistor 131 excites the electromagnet winding 1a. The transistor 131 includes a gate drive circuit 131a. The gate drive circuit 131a is connected to a current control circuit 137 that receives a current command.
[0032]
The electromagnet winding 1a is provided with a current detection circuit 139 for current detection. The current detection circuit 139 is connected to the current control circuit 137 for sending the current detection signal.
The electromagnet winding 1b is transformer-coupled to the electromagnet winding 1a, and a diode 135 for regenerating current is interposed in series on the power supply side.
[0033]
Next, the operation of the magnetic bearing excitation circuit of the present invention will be described.
The current control circuit 137 calculates the difference between the detected value of the current detection circuit 139 and the command value in order to perform excitation control of the electromagnet winding 1a, creates a switching pulse signal based on the difference, and sends it to the gate drive circuit 131a. Send it out. The switching pulse signal is a PWM pulse signal generated from the current command, the current detection value of the current detection circuit 139, and the carrier wave.
[0034]
When this switching pulse signal is sent to the gate drive circuit 131a, the gate drive circuit 131a sends the gate drive signal to the gate of the transistor 131. The transistor 131 repeats ON / OFF according to this gate drive signal.
[0035]
When this transistor 131 conducts, power is supplied from the power supply 133, and the electromagnet winding 1a is excited. When the transistor 131 is cut off, an induced current i2 is generated in the regenerative direction in the electromagnet winding 1b that is transformer-coupled to the electromagnet winding 1a, and the electromagnet winding 1b is excited by the induced current i2.
[0036]
The current control circuit 137 adjusts the pulse width of the switching pulse signal based on the detection value of the current detection circuit 139 so that the electromagnet winding current i1 matches the current command. With this switching pulse signal, the currents i1 and i2 flowing through the electromagnet winding can be controlled by the switching method.
[0037]
Next, the magnetic characteristics of the electromagnet winding will be described. FIG. 2 shows the relationship between the current of the electromagnetic winding and the magnetic flux density.
In FIG. 2, the electromagnet winding 1a is excited by the current i1 when the transistor 131 receiving the switching pulse signal conducts.
[0038]
The electromagnet winding 1b is excited by a current i2 in the regeneration direction induced by the transformer-coupled electromagnet winding 1a. Therefore, the electromagnet winding 1a and the electromagnet winding 1b are alternately excited, and the electromagnet winding 1a and the electromagnet winding 1b are driven in a time-sharing manner so that the magnetic flux density B flowing through the core is integrated continuously. Is possible.
[0039]
The waveform of the current i1 is determined by the number of turns N1 of the electromagnet winding 1a, and the waveform of the current i2 is determined by the number of turns N2 of the electromagnet winding 1b. Therefore, the electromagnet characteristics can be appropriately set by these both windings.
[0040]
As described above, in the magnetic bearing excitation circuit of the present invention, the electromagnet constituted by the electromagnet winding 1a and the electromagnet winding 1b is integrally driven by the power supply by the single transistor 131 and the subsequent regeneration. Therefore, the number of necessary parts is halved compared with the conventional excitation circuit. Similarly, the number of parts including the gate drive circuit 131a and the corresponding current control circuit 137 can be halved.
[0041]
When the transistor 131 is disconnected, the electromagnet winding 1b that is transformer-coupled with the electromagnet winding 1a is excited by the current in the regenerative direction by the diode 135, so that the power consumption in the semiconductor is halved. Furthermore, since heat generation is reduced accordingly, the heat sink capacities of the transistor 131 and the diode 135 can be reduced by half.
[0042]
Therefore, the magnetic bearing excitation circuit of the present invention makes it possible to reduce the cost associated with the reduction in the number of parts, improve the reliability, and reduce the size of the magnetic bearing control device. As a result, the magnetic bearing control device can be integrated with the rotating device main body such as a turbo molecular pump.
[0043]
Next, a specific configuration aspect of the electromagnet winding of the radial direction electromagnet in the present invention will be described. FIG. 3 shows a cross-sectional view of the electromagnet winding of the radial electromagnet in the present invention.
In FIG. 3, two electromagnet windings that are transformer-coupled are provided on each core convex portion of the electromagnet core 11. Adjacent core protrusions 13 and 13 are paired and one transformer-coupled electromagnet windings 13a and 13a are arranged and connected in opposite polarities, and the other electromagnet windings 13b and 13b are arranged and connected in opposite polarities. . The core convex parts 13 and 13 form a two-part electromagnet composed of two transformer-coupled electromagnet windings 13a and 13b.
[0044]
Similarly to the electromagnet having the two-divided configuration related to the core convex portions 13 and 13, the electromagnet having the two-divided configuration is formed for the core convex portions 15 and 15 facing each other with the rotating body 103 interposed therebetween. The two electromagnets formed to face each other constitute a pair, and each acts an attractive force in the positive or negative direction of the rotating body 103 in the X-axis direction.
[0045]
The core convex portions 17 and 17 and the core convex portions 19 and 19 that face each other in the orthogonal direction are configured in the same manner to form one pair, each of which is a positive direction or a negative direction in the Y-axis direction of the rotating body 103. Acts on the suction force.
[0046]
Therefore, a two-axis radial magnetic bearing in the X-axis direction and the Y-axis direction can be configured by the two electromagnet windings that are transformer-coupled to the electromagnet core 11.
[0047]
Next, a specific configuration aspect of the electromagnet winding of the axial direction electromagnet in the present invention will be described. FIG. 4 shows a longitudinal sectional view of the electromagnet winding of the axial direction electromagnet.
In FIG. 4, the two electromagnet cores 21 and 23 are disposed opposite to each other in a circumferential shape with the armature 103 a of the rotating body 103 interposed therebetween. By arranging and connecting the electromagnet windings 21a and 21b that are transformer-coupled with respect to the upper electromagnet core 21, an electromagnet having a two-part configuration is formed. Similarly for the lower electromagnet core 23, the electromagnets 23a and 23b, which are transformer-coupled, are arranged and connected to form a two-part electromagnet.
[0048]
The electromagnets of the two-part configuration formed on each of the upper side and the lower side constitute one pair. The upper and lower electromagnets can constitute an axial magnetic bearing that attracts the armature 103a in the positive or negative direction of the axis.
[0049]
Next, a specific configuration of the current detection circuit 139 will be described. FIG. 5A shows a configuration example of a current detection circuit using a current detection resistor, and FIG. 5B shows a configuration example of a current detection circuit using a Hall sensor type current sensor. Note that the same elements as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
[0050]
In FIG. 5A, a current detection circuit can be configured by a current detection resistor 31 provided at the source of the transistor 131 and a voltage detector 31a for extracting the voltage drop.
[0051]
In FIG. 5B, the current detection circuit can be configured by passing the source connection line of the transistor 131 through the hole of the Hall sensor type current sensor 33. In either case, it is possible to detect the current i1 of the electromagnet winding 1a with a minimum component configuration.
[0052]
Next, another current detection method of the magnetic bearing excitation circuit will be described. FIG. 6 shows another current detection circuit configuration of the current detection circuit. Note that the same elements as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
In FIG. 6, the current detection circuit 41 is configured to collectively detect the currents i1 and i2 of the electromagnet winding 1a and the electromagnet winding 1b. Therefore, the exciting current of the electromagnet can be detected continuously. As described above, it is possible to control the regenerative current while securing a simple configuration based on collective detection, so that excitation control with high accuracy is possible.
[0053]
FIG. 7 shows a first specific example of the current detection circuit configuration in this case. Note that the same elements as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
In FIG. 7, a differential voltage detector 47 is connected in series with the electromagnet winding 1a and the electromagnet winding 1b through current detection resistors 43 and 45 to extract respective voltage drops.
[0054]
In this case, since the current i2 of the electromagnet winding 1b is in the opposite direction to the current i1 of the electromagnet winding 1a, it is configured to be input to the inverting input side of the differential voltage detector 47. This voltage detector 47 enables detection processing with a simple configuration for the two systems of currents i1 and i2 including the opposite directions. In addition, since the regenerative current can be controlled, highly accurate excitation control can be performed.
[0055]
Next, FIG. 8A shows a second specific example of the current detection circuit configuration, and FIG. 8B shows how the Hall sensor type current sensor is used. Note that the same elements as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
In FIG. 8A, the current detection circuit can be configured by passing the connection lines of the electromagnet winding 1a and the electromagnet winding 1b through the holes of the hall sensor type current sensor 33.
[0056]
However, since the current i2 of the electromagnet winding 1b is in the reverse direction to the current i1 of the electromagnet winding 1a, the connection line of the electromagnet winding 1b is input in the reverse direction. That is, as shown in FIG. 8 (b), by inputting so that the directions of the currents i1 and i2 of the connection lines of the electromagnet winding 1a and the electromagnet winding 1b are aligned, two systems including the reverse direction as described above. The currents i1 and i2 can be detected with a simple configuration and the regenerative current can be controlled.
[0057]
Next, a surge processing configuration example of the magnetic bearing excitation circuit of the present invention will be described. A configuration example of surge processing of the magnetic bearing excitation circuit is shown in FIG. Note that the same elements as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
In FIG. 9, a surge absorption circuit in which a resistor 51 and a capacitor 53 are connected in series is connected in parallel with each of a transistor 131 and a diode 135.
[0058]
These surge absorption circuits alleviate an excessive spike voltage generated when the transistor 131 is disconnected. Therefore, since the transistor 131 and the diode 135 can be protected from an excessive voltage, a stable operation of the control device is possible.
[0059]
The transistor 131 in the magnetic bearing excitation circuit of the present invention is not limited to the FET, and general switching devices such as thyristors can be widely applied.
[0060]
【The invention's effect】
As described above, according to the present invention, the first electromagnet winding and the second electromagnet winding are transformer-coupled, switching means is connected to one of them to supply power, and regenerative means is connected to the other. Therefore, the first electromagnet winding and the second electromagnet winding can be alternately excited by one switching means.
Therefore, the magnetic bearing excitation circuit of the present invention makes it possible to reduce the cost associated with the reduction in the number of parts, improve the reliability, and reduce the size of the magnetic bearing control device.
[Brief description of the drawings]
1 is a magnetic bearing excitation circuit of the present invention. FIG. 2 is a characteristic diagram of a magnetic bearing excitation circuit of the present invention. FIG. 3 is a cross-sectional view of an electromagnetic winding of a radial direction electromagnet in the present invention. FIG. 5 is a configuration example (a) of a current detection circuit and a usage mode (b) of a Hall sensor type current sensor in the present invention.
6 is another current detection circuit configuration example according to the present invention. FIG. 7 is a first specific example of the current detection circuit configuration according to the present invention. FIG. 8 is a second specific example (a of the current detection circuit configuration according to the present invention. ) And usage mode of Hall sensor type current sensor (b)
9 is a configuration example of surge processing of a magnetic bearing excitation circuit according to the present invention. FIG. 10 is a cross-sectional view of a turbo molecular pump. FIG. 11 is a cross-sectional view of a conventional radial magnetic bearing. [Fig. 13] Conventional magnetic bearing excitation circuit [Fig. 14] Other conventional magnetic bearing excitation circuit [Explanation of symbols]
1a, 1b Electromagnetic winding 31, 43, 45 Current detection resistor (current detection means)
31a Voltage detector (current detection means)
33, 41, 139 Current detection circuit (current detection means)
47 Differential voltage detector (current detection means)
51 Resistor (Surge absorbing means)
53 Battery (Surge absorption means)
131 transistor (switching means)
131a Gate drive circuit (switching means)
135 Diode (regenerative means)
137 Current control circuit (current control means)

Claims (3)

Switching means for controlling connection / disconnection of the current received from the power source;
A first electromagnet winding that is excited and controlled by the switching means;
A second electromagnet winding which is transformer-coupled to the first electromagnet winding and is excited by an induced current through a regenerative means for guiding a current in a regenerative direction;
Current detection means for detecting the current of either the first electromagnet winding or the second electromagnet winding, and the current of the electromagnet winding becomes a command current upon receiving a detection signal from the current detection means A magnetic bearing excitation circuit comprising: current control means for commanding the switching means. Said switching means and magnetic bearing exciting circuit of claim 1 Symbol mounting characterized by comprising a surge absorption means to at least one of said regeneration means. The rotor blade is levitated and supported by the magnetic bearing excitation circuit according to any one of claims 1 to 2 and excitation of the first electromagnet winding or the second electromagnet winding by the magnetic bearing excitation circuit. A turbomolecular pump device comprising a turbomolecular pump.

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