Patent Description:
In a rotating machine or the like under a special environment such as a vacuum pump, a magnetic bearing device for supporting a rotating body in a non-contact manner is often used as a bearing device (see <CIT>, for example). <CIT> discloses another prior art vacuum pump.

The magnetic bearing device is typically configured to support the load of the rotating body in a non-contact manner by attracting a target provided on the rotating body by means of a plurality of electromagnets provided around the rotating body. Therefore, in a case where the electromagnets do not attract the target of the rotating body with appropriate attracting force (magnetic force), bearing accuracy may be lowered.

<CIT> discloses a structure in which a rotating body shaft is attached to the center of a rotor having rotor blades, and an annular electromagnet is disposed outside the rotor shaft in a radial direction thereof, thereby levitating and supporting the rotor shaft using the annular electromagnet.

A schematic structure of the magnetic bearing device of the prior art is explained using <FIG> and <FIG>. <FIG> is a diagram showing a horizontal cross section of a magnetic bearing device <NUM>, viewed from above, in which a rotor shaft <NUM> is levitated and supported in the air by an annular electromagnet <NUM>. <FIG> is an enlarged view of a part of <FIG>.

The bearing device <NUM> illustrated in <FIG> and <FIG> has a structure in which the annular electromagnet <NUM> is disposed in a non-contact manner and concentrically with the rotor shaft <NUM> on the radially outer side of the rotor shaft <NUM>. The annular electromagnet <NUM> has a stator core <NUM> in an annular shape (referred to as "annular stator core <NUM>" hereinafter) and a plurality of coil portions <NUM> attached to an inner peripheral wall 103a of the annular stator core <NUM>. This bearing device <NUM> constitutes a magnetic bearing, and the rotor shaft <NUM> is configured to have only the degree of freedom of rotation around the axis.

The annular stator core <NUM> is provided with eight teeth 103b that protrude from the inner peripheral wall 103a toward a center O, with predetermined intervals in a circumferential direction, at a phase angle of, in the illustrated embodiment, 2α and <NUM>° - 2α. The cross-sectional shape of each tooth 103b is a rectangular shape. The coil portions <NUM> are attached to the teeth 103b respectively. Flat core bearing surfaces 103c for placing second flange portions <NUM> of bobbins <NUM> in close contact with the inner peripheral wall 103a are each provided in a base portion of each of the teeth 103b on which the respective coil portions <NUM> are mounted, that is, a part of the inner peripheral wall 103a of the annular stator core <NUM>,.

The coil portions <NUM> include, respectively, the bobbins <NUM> and coils <NUM> formed by winding coil wires 106a around respective outer peripheries of the bobbins <NUM> a predetermined number of times.

The bobbins <NUM> are each formed of an insulating material such as resin and each have a bobbin body <NUM>, a first flange portion <NUM>, and a second flange portion <NUM>.

The bobbin body <NUM> has a rectangular insertion hole <NUM> through which the corresponding tooth 103b can be inserted, and is a cylindrical body penetrating in in a front-rear direction and having a rectangular cross-sectional shape. The coil wire 106a of the coil <NUM> is wound around an outer peripheral surface of the bobbin body <NUM> the predetermined number of times.

The first flange portion <NUM> is a rectangular flange portion having a rectangular hollow shape when viewed from the front, i.e., having a hole in the center thereof, and is provided on one end surface of the bobbin body <NUM> located near the center O of the annular stator core <NUM> so as to project from the outer peripheral surface of the bobbin body <NUM> to the outside at a substantially right angle.

The second flange portion <NUM> is a rectangular flange portion having a rectangular hollow shape when viewed from the front, i.e., having a hole in the center thereof as with the first flange portion <NUM>, and is provided on an end surface of the bobbin body <NUM>, opposite to the first flange portion <NUM>, so as to project from the outer peripheral surface of the bobbin body <NUM> to the outside at a substantially right angle.

In each of the bobbins <NUM> formed as described above, after winding the coil wire 106a around the outer peripheral surface of the bobbin body <NUM> the predetermined number of times, the corresponding tooth 103b of the annular stator core <NUM> is inserted from the other end side of the bobbin body <NUM> provided with the second flange portion <NUM>, to mount the bobbin <NUM> onto the tooth 103b. Then, the second flange portion <NUM> of the bobbin <NUM> is placed in close contact with the core bearing surface 103c and fixed to the tooth 103b by a means which is not illustrated (e.g., by means of fitting, bonding, etc.). <FIG> shows the magnetic bearing device <NUM> in which the bobbins <NUM> having the coils <NUM> wound therearound are attached to the respective teeth 103b of the annular stator core <NUM> as described above.

The magnetic bearing device <NUM> illustrated in <FIG> has a structure in which the annular electromagnet <NUM> is disposed in a non-contact manner and concentrically with the rotor shaft <NUM> on the radially outer side of the rotor shaft <NUM>. The annular electromagnet <NUM> is a uniaxial electromagnet by using a pair of coil portions <NUM> illustrated in <FIG>. Four pairs of the uniaxial electromagnets are provided at a phase angle of <NUM> degrees, in which the rotor shaft <NUM> is attracted by the magnetic force generated by each of these electromagnets and supported in a non-contact manner.

In the annular electromagnet <NUM> illustrated in <FIG>, four electromagnets are arranged in pairs along an X axis and a Y axis, as well as in a + direction and a - direction (if necessary, these electromagnets arranged in pairs these pairs are referred to as "electromagnet +X," "electromagnet -X," "electromagnet +Y," and "electromagnet - Y").

According to the structure of the annular electromagnet <NUM>, as illustrated in <FIG>, in the bobbin <NUM> attached to each of the respective teeth 103b of a pair of electromagnets -Y1, -Y2, circumferential end surfaces 108a of the first flange portion <NUM> and circumferential end surfaces 108b of the second flange portion <NUM> are formed at right angles. Furthermore, the coil wire 106a of each of the coils <NUM> is wound from the first flange portion <NUM> to the second flange portion <NUM> of each bobbin <NUM> in such a manner that the cross-sectional shape of the bobbin <NUM> is a substantially rectangular shape. Specifically, rectangular winding is formed.

An attractive force F of each uniaxial electromagnet can be obtained by the following equation (<NUM>).

<MAT> where N is the number of turns of the coil wire 106a, i a current flowing through the coil wire 106a, R a magnetic resistance, S a magnetic pole area, u a magnetic permeability of an air gap, α a half angle, and k a constant.

From the equation (<NUM>), it is clear that the attractive force F of each uniaxial electromagnet (electromagnet +X, electromagnet -X, electromagnet +Y, electromagnet -Y) is proportional to the square of the number of turns of the coil wire 106a.

Therefore, it is important to improve the number of turns of the coil wire 106a wound around each bobbin <NUM>, in order to increase the attractive force F of each uniaxial electromagnet without changing the sizes of components other than the coil <NUM>.

However, regarding the bobbins <NUM> attached to the respective teeth 103b of the annular stator core <NUM> illustrated in <FIG> and <FIG>, an interval L6 between the first flange portions <NUM> of the bobbins <NUM> adjacent to each other is equivalent to an interval between outer edges 108c, as illustrated in <FIG>. The interval L6 between these adjacent bobbins <NUM> is required as an interval for preventing the bobbins <NUM> from interfering with each other during assembly. Thus, it is considered that a winding space of each coil <NUM> is limited and that improving the attractive force by increasing the number of turns of each coil wire 106a by using the bobbins <NUM> of the same size has already reached its limit.

Moreover, in the prior art, as a method for increasing the attractive force by increasing the number of turns of the coil wires 106a under the restriction of the coil winding space, for example, as illustrated in <FIG>, there have been known a structure in which the teeth 103b of the annular stator core <NUM> are sequentially offset from the center O to the outside by a dimension e and then the bobbin <NUM> that has the coil <NUM> wound therearound into a rectangular shape as planarly viewed is attached to each of the teeth 103b, and a structure illustrated in <FIG> in which the teeth 103b of the annular stator core <NUM> are sequentially offset from the center O to the outside by the dimension e and then the bobbin that has the coil wire 106a of the coil <NUM> wound therearound into a trapezoidal shape as planarly viewed is attached to each of the teeth. Unfortunately, these structures are not sufficient.

Therefore, a technical problem occurs for providing a vacuum pump, and a magnetic bearing device used for such a vacuum pump, and an annular electromagnet, the vacuum pump being capable of increasing the attractive force of electromagnets by increasing the number of turns of a coil wire wound around each bobbin, without changing the shape of the conventional annular stator core <NUM>, i.e., the size of the conventional annular stator core such as, as illustrated in <FIG> and <FIG>, for example, magnetic pole half angle α, thickness L1 of the coil <NUM>, coil width L2, plate thickness L3 of the first flange portion <NUM>, plate thickness L4 of the second flange portion <NUM>, distance between the outermost periphery of the coil <NUM> and the outermost ends of the flange portions <NUM>, <NUM> of each bobbin <NUM>, which is the amount of projection L5 of the flange portions <NUM>, <NUM> from the coil <NUM>, interval L6 between the bobbins <NUM>, interval L7 between the bobbins <NUM> and the core bearing surface end portions, and magnetic pole connecting thickness L8. An object of the present invention is to solve such a technical problem.

The present invention is proposed in order to achieve the foregoing object, and an invention according claim <NUM> is a vacuum pump having a magnetic bearing device that is disposed radially outside of a rotor shaft and rotatably holds the rotor shaft, wherein the magnetic bearing device has an annular stator core having, on an inner peripheral wall thereof, a plurality of teeth provided at predetermined intervals in a circumferential direction of the rotor shaft, and an annular electromagnet having a plurality of bobbins attached to the teeth respectively, the plurality of bobbins having coil wires wound around outer peripheries thereof, the bobbins each having a rectangular cylindrical bobbin body that has the coil wire wound around the outer periphery thereof and is attached to each of the teeth, a first flange portion provided on an end surface of the bobbin body so as to face the rotor shaft and formed into a rectangular hollow shape as viewed from the front, a second flange portion provided on an end surface of the bobbin body so as to be opposite to the first flange portion and formed into a rectangular hollow shape as viewed from the front, characterised in that the vacuum pump comprises a coil winding amount increasing means formed at least on the first flange portion and increasing the amount of winding of the coil wire wound around the bobbin body, wherein the coil winding amount increasing means comprises on circumferential end faces of the first flange portion, chamfers that are inclined inward from outer edges of the first flange portion in a direction of a plate thickness, and/or on the circumferential end faces of two first flange portions of each of the plurality of bobbins adjacent to each other, notches that accommodate parts of the plurality of adjacent bobbins adjacent to each other, such that the first flange portion of each of the plurality of bobbins adjacent to each other does not interfere with each other by the coil winding amount increasing means.

According to this configuration, since the coil winding amount increasing means for increasing the amount of winding of the coil wire wound around the bobbin body is provided at least on the first flange portion or the second flange portion, a vacuum pump can be realized in which the attractive force of the annular electromagnet is increased by increasing the number of turns of the coil wire wound around each bobbin, without changing the size of the annular stator core of the prior art, so that the vacuum pump can be operated while keeping the rotating rotor shaft stable.

As a first alternative of the invention, the coil winding amount increasing means has, on circumferential end faces of the first flange portion, chamfers that are inclined inward from outer edges of the first flange portion in the plate thickness direction.

According to this configuration, the distance between the inner edges of the first flange portions of the adjacent bobbins can be increased by providing the circumferential end surfaces of each of the first flange portions with chamfers that are inclined inward from the outer edges of each first flange portion in the plate thickness direction. Therefore, even when the adjacent bobbins that are arranged on the inner peripheral wall of the annular stator core face the center, the inner edges do not interfere with each other, keeping the distance between the outer edges of the first flange portions wide. Thus, even when the amount of projection of each first flange portion is increased so that the outer edges of the first flange portions of the adjacent bobbins come close to each other, the first flange portions of the adjacent bobbins do not interfere with each other during assembly. Consequently, the vacuum pump can be realized by increasing the distance between the circumferential end surfaces of the first flange portions of the bobbins (the amount of projection of the first flange portion) and increasing and the number of turns of the coil wires to enhance the attractive force of the annular electromagnet, which enables an operation of the vacuum pump while keeping the rotating rotor shaft stable.

As a second alternative of the invention, the coil winding amount increasing means has, on the circumferential end faces of at least the first flange portion of each of the plurality of bobbins adjacent to each other, notches that accommodate parts of the plurality of adjacent bobbins adjacent to each other.

According to this configuration, since the circumferential end surfaces of at least the first flange portions of the adjacent bobbins are provided with the notches for accommodating the parts of the adjacent bobbins, the first flange portions of the adjacent bobbins do not interfere with each other during assembly even when the amount of projection of the first flange portions of the adjacent bobbins is increased to shorten the distance between the inner edges of the first flange portions. Therefore, by increasing the amount of projection of the flange portions to bring the inner edges of the first flange portions of the adjacent bobbins closer to each other, the coil wire is wound as much as possible around each of the adjacent bobbins, to further enhance the attractive force of the annular electromagnet. Consequently, the vacuum pump can be operated while keeping the rotating rotor shaft more stable. Note that better results can be expected by providing these notches in both the first and second flange portions.

An invention according to claim <NUM> provides, in the configuration described in claim <NUM>, a vacuum pump in which the coil winding amount increasing means has, on circumferential end faces of the second flange portion, chamfers that are inclined inward from inner edges of the second flange portion in the plate thickness direction.

According to this configuration, the chamfers inclined inward from the inner edges dodge the curved shape of the inner peripheral wall of the annular stator core even if the amount of circumferential protrusion of the second flange portion of each bobbin is increased, that is, even if the distance between the circumferential end surfaces is increased. Therefore, the present invention can realize a vacuum pump in which the attractive force of the annular electromagnet is increased by increasing the amount of circumferential projection of the second flange portion of each bobbin and increasing the number of turns of the coil wire, so that the vacuum pump can be operated while keeping the rotating rotor shaft stable.

The present invention can achieve a vacuum pump capable of increasing the attractive force of electromagnets by increasing the number of turns of a coil wire wound around each bobbin without changing the shape of the annular stator core of the prior art.

In order to achieve the object of increasing the attractive force of electromagnets by increasing the number of turns of a coil wire wound around each bobbin, without changing the shape of the conventional annular stator core, the present invention achieved the object with a vacuum pump having a magnetic bearing device that is disposed radially outside of a rotor shaft and rotatably holds the rotor shaft, wherein the magnetic bearing device has an annular stator core having, on an inner peripheral wall thereof, a plurality of teeth provided at predetermined intervals in a circumferential direction of the rotor shaft, and an annular electromagnet having a plurality of bobbins attached to the teeth respectively, the plurality of bobbins having coil wires wound around outer peripheries thereof, the bobbins each having a rectangular cylindrical bobbin body that has the coil wire wound around the outer periphery thereof and is attached to each of the teeth, a first flange portion provided on an end surface of the bobbin body so as to face the rotor shaft and formed into a rectangular hallow shape as viewed from the front, a second flange portion provided on an end surface of the bobbin body so as to be opposite to the first flange portion and formed into a rectangular hallow shape as viewed from the front, and coil winding amount increasing means formed at least on the first flange portion or the second flange portion and increasing the amount of winding of the coil wire wound around the bobbin body.

The best mode for carrying out the present invention is now described hereinafter in detail with reference to the accompanying drawings. Note that in the following description, the same reference numerals are given to the same elements throughout the description of the embodiment. In the following description, expressions indicating directions such as up, down, left, and right are not absolute and are appropriate when the parts of a vacuum pump of the present invention are depicted, but when the positions of the parts are changed, the expressions should be interpreted according to such changes.

<FIG> is a diagram showing a schematic configuration of a vacuum pump <NUM> according to the present embodiment. Note that <FIG> shows a cross section of the vacuum pump <NUM> along an axial direction thereof. In this embodiment, a so-called composite blade type vacuum pump having a vacuum pump portion T and a thread groove pump portion S is described as an embodiment of the vacuum pump <NUM>. Note that the present embodiment may be applied to a pump having only the vacuum pump portion T or a pump in which a thread groove is provided on the rotating body side.

A casing <NUM> configuring a housing of the vacuum pump <NUM> has a cylindrical shape and constitutes the housing of the vacuum pump <NUM> together with a base <NUM> provided in a bottom portion of the casing <NUM>. A gas transfer mechanism, which is a structure bringing about exhaust functions of the vacuum pump <NUM>, is stored inside the housing of the vacuum pump <NUM>.

The gas transfer mechanism in the vacuum pump <NUM> includes the vacuum pump portion T provided on the inlet port <NUM> side and the thread groove pump portion S provided on the outlet port <NUM> side. The structure bringing about these exhaust functions is composed mainly of a rotating portion supported rotatably and a stator portion fixed to the casing <NUM>. Furthermore, a controller <NUM> for controlling the operation of the vacuum pump <NUM> is connected to the outside of the housing of the vacuum pump <NUM>.

The rotating portion is composed of a rotor shaft (shaft) <NUM> rotated by a motor portion <NUM> described hereinafter, and a rotor portion <NUM>.

The rotor shaft <NUM> is a rotating shaft of a cylindrical member. The rotor portion <NUM> is attached to an upper end of the rotor shaft <NUM> by a plurality of bolts <NUM>.

The rotor portion <NUM> is a rotating member disposed on the rotor shaft <NUM>. The rotor portion <NUM> includes rotor blades <NUM> provided on the inlet port <NUM> side (the vacuum pump portion T), a cylindrical member <NUM> provided on the outlet port <NUM> side (the thread groove pump portion S), and the like. Note that the rotor portion <NUM> is made of a metal such as stainless steel or an aluminum alloy.

The rotor blades <NUM> are configured by a plurality of blades extending radially from the rotor portion <NUM> at a predetermined angle from a plane perpendicular to an axis of the rotor shaft <NUM>. In the vacuum pump <NUM>, the rotor blades <NUM> are provided in a plurality of stages in the axial direction. The cylindrical member <NUM> is composed of a member, an outer peripheral surface of which has a cylindrical shape.

The motor portion <NUM> for rotating the rotor shaft <NUM> is provided in the middle of the rotor shaft <NUM> in the axial direction thereof. The present embodiment assumes that the motor portion <NUM> is configured by, for example, a DC brushless motor. A permanent magnet 15a is fixed to a part of the rotor shaft <NUM> that configures the motor portion <NUM>. The permanent magnet 15a is fixed in such a manner that, for example, the N pole and the S pole thereof are arranged <NUM> degrees apart around the rotor shaft <NUM>. Also, six electromagnets 15b, for example, are arranged <NUM> degrees apart around the permanent magnet 15a, with a predetermined gap (air gap) from the rotor shaft <NUM> in such a manner as to be symmetrical with respect to the axis of the rotor shaft <NUM> and to be opposed to one another. The permanent magnet 15a functions as a rotor portion (rotating portion) of the motor portion <NUM>, and the electromagnets 15b function as a stator portion (stationary portion) of the motor portion <NUM>.

The vacuum pump <NUM> has a sensor for detecting a rotation speed and a rotation angle (phase) of the rotor shaft <NUM>, and by means of this sensor, the controller <NUM> can detect the positions of the magnetic poles of the permanent magnet 15a fixed to the rotor shaft <NUM>.

On the basis of the detected positions of the magnetic poles, the controller <NUM> switches currents of the electromagnets 15b of the motor portion <NUM> successively, to generate a rotating magnetic field around the permanent magnet 15a of the rotor shaft <NUM>. The permanent magnet 15a fixed to the rotor shaft <NUM> follows this rotating magnetic field, thereby rotating the rotor shaft <NUM>.

On the inlet port <NUM> side and the outlet port <NUM> side of the motor portion <NUM> are, respectively, a radial magnetic bearing portion <NUM> and a radial magnetic bearing portion <NUM> that support the rotor shaft <NUM> in a radial direction, that is, support a load of the rotating portion in the radial direction.

Furthermore, a lower end of the rotor shaft <NUM> is provided with a thrust magnetic bearing portion <NUM> that supports the rotor shaft <NUM> in the axial direction (thrust direction), that is, supports the load of the rotating portion in the thrust direction.

The rotor shaft <NUM> (rotating portion) is supported by the radial magnetic bearing portions <NUM> and <NUM> in a non-contact manner in the radial direction (radial direction of the rotor shaft <NUM>), and is supported by the thrust magnetic bearing portion <NUM> in a non-contact manner in the thrust direction (axial direction of the rotor shaft <NUM>). These magnetic bearings constitute a so-called five-axis control type magnetic bearing, and the rotor shaft <NUM> only has a degree of freedom of rotation around the axis.

In the radial magnetic bearing portion <NUM>, for example, four electromagnets 21b are arranged <NUM> degrees apart around the rotor shaft <NUM> in such a manner as to face each other. These electromagnets 21b are arranged, with a gap (air gap) from the rotor shaft <NUM>. Note that this gap value takes into consideration the amount of vibration (swing amount) of the rotor shaft <NUM> in a steady state, the spatial distance between the rotor portion <NUM> and the stator portion (stationary portion), the performance of the radial magnetic bearing portion <NUM>, and the like. Also, a target 21a is formed on the rotor shaft <NUM> facing the electromagnets 21b. The target 21a is attracted by the magnetic force of the electromagnets 21b of the radial magnetic bearing portion <NUM>, whereby the rotor shaft <NUM> is supported in a non-contact manner in the radial direction. The target 21a functions as a rotor portion of the radial magnetic bearing portion <NUM>, and the electromagnets 21b function as stator portions of the radial magnetic bearing portion <NUM>.

The radial magnetic bearing portion <NUM>, too, has the same configuration as the radial magnetic bearing portion <NUM>. Specifically, a target 22a is attracted by the magnetic force of electromagnets 22b of the radial magnetic bearing portion <NUM>, whereby the rotor shaft <NUM> is supported in a non-contact manner in the radial direction.

The thrust magnetic bearing portion <NUM> causes the rotor shaft <NUM> to levitate in the axial direction via a disc-shaped metal armature <NUM> that is provided perpendicular to the rotor shaft <NUM>. In the thrust magnetic bearing portion <NUM>, for example, two electromagnets 23a, 23b are arranged so as to face each other via the armature <NUM>. These electromagnets 23a, 23b are arranged, with a gap from the armature <NUM>. Note that this gap value takes into consideration the amount of vibration of the rotor shaft <NUM> in a steady state, the spatial distance between the rotor portion <NUM> and the stator portion, the performance of the thrust magnetic bearing portion <NUM>, and the like. The armature <NUM> is attracted by the magnetic force of the electromagnets of the thrust magnetic bearing portion <NUM>, whereby the rotor shaft <NUM> is supported in a non-contact manner in the thrust direction (axial direction).

Moreover, displacement sensors <NUM>, <NUM> are formed in the vicinity of the radial magnetic bearing portions <NUM>, <NUM>, respectively, so that displacement of the rotor shaft <NUM> in the radial direction can be detected. In addition, a displacement sensor <NUM> is formed at the lower end of the rotor shaft <NUM>, so that displacement of the rotor shaft <NUM> in the axial direction can be detected.

The displacement sensors <NUM>, <NUM> are elements for detecting displacement of the rotor shaft <NUM> in the radial direction and, in the present embodiment, are configured by inductance-type sensors such as eddy current sensors having coils 25b, 26b. The coils 25b, 26b of the displacement sensors <NUM>, <NUM> are part of an oscillation circuit, not illustrated, which is formed in the controller installed outside the vacuum pump <NUM>. The displacement sensor <NUM> is configured to have a high-frequency current flow therein as the oscillation circuit oscillates, thereby generating a high-frequency magnetic field on the rotor shaft <NUM>. Then, the oscillation amplitude of the oscillation circuit changes when the distance between the displacement sensors <NUM>, <NUM> and the targets 25a, 26a changes, whereby the displacement of the rotor shaft <NUM> can be detected. The sensors for detecting displacement of the rotor shaft <NUM> are not limited to the foregoing sensors, and, for example, capacitive sensors or optical sensors may be used.

Also, once the displacement of the rotor shaft <NUM> in the radial direction is detected on the basis of signals from the displacement sensors <NUM>, <NUM>, the controller <NUM> adjusts the magnetic force of each of the electromagnets 21b, 22b of the radial magnetic bearing portions <NUM>, <NUM> to bring the rotor shaft <NUM> back to a predetermined position. In this manner, the controller <NUM> performs feedback control on the radial magnetic bearing portions <NUM>, <NUM> on the basis of the signals from the displacement sensors <NUM>, <NUM>. As a result, the rotor shaft <NUM> is magnetically levitated in the radial direction, via a predetermined air gap from the electromagnets 21b, 22b in the radial magnetic bearing portions <NUM>, <NUM>, and held in the air in a non-contact manner.

As with the displacement sensors <NUM>, <NUM>, the displacement sensor <NUM> is configured to have a coil 27b. The displacement sensor <NUM> detects displacement of the rotor shaft <NUM> in the thrust direction by detecting the distance between the coil 27b and a coil 27a that is provided on the rotor shaft <NUM> side so as to face the coil 27b. Once the displacement of the rotor shaft <NUM> in the thrust direction is detected on the basis of a signal from the displacement sensor <NUM>, the controller <NUM> adjusts the magnetic force of each of the electromagnets 23a 23b of the thrust magnetic bearing portion <NUM> to bring the rotor shaft <NUM> back to a predetermined position. In this manner, the controller <NUM> performs feedback control on the thrust magnetic bearing portion <NUM> on the basis of the signal from the displacement sensor <NUM>. As a result, the rotor shaft <NUM> is magnetically levitated in the thrust direction, via a predetermined air gap from each of the electromagnets 23a, 23b in the thrust magnetic bearing portion <NUM>, and held in the air in a non-contact manner.

Since the rotor shaft <NUM> is held by the radial magnetic bearing portions <NUM>, <NUM> in the radial direction and held by the thrust magnetic bearing portion <NUM> in the thrust direction as described above, the rotor shaft <NUM> can rotate about the axis.

The motor portion <NUM> and each of the magnetic bearing portions <NUM>, <NUM> of the present embodiment function as the annular electromagnets 21b according to the present invention that use the actions of electromagnet force.

Configurations of the magnetic bearing portions <NUM>, <NUM> are further described using <FIG> and <FIG>. Since the magnetic bearing portions <NUM>, <NUM> share the same configuration, the structure of the magnetic bearing portion <NUM> is mainly described. Therefore, although <FIG> and <FIG> each show the cross section of the part corresponding to line D-D of <FIG>, the illustration of the hatched sections is omitted in order to simplify the drawings.

In <FIG> and <FIG>, the magnetic bearing portion <NUM>, which is a magnetic bearing device, has a structure in which the electromagnets 21b, which are annular electromagnets (referred to as "annular electromagnets 21b" hereinafter), are arranged in a non-contact manner and concentrically with the rotor shaft <NUM> on the radially outer side of the rotor shaft <NUM>. The annular electromagnets 21b each have a stator core <NUM> in an annular shape (referred to as "annular stator core <NUM>" hereinafter) and a plurality of coil portions <NUM> attached to an inner peripheral wall 31a of the annular stator core <NUM>.

The annular stator core <NUM> is formed from a laminated silicon steel sheet and is provided with eight teeth 31b that protrude so as to project from an inner peripheral wall 31a toward a center O of the annular stator core <NUM> (which is also the center O of the rotor shaft <NUM>), with predetermined intervals in the circumferential direction, at a phase angle of, in the illustrated embodiment, 2α and <NUM>°-2α. The cross-sectional shape of each of the teeth 31b is a rectangular shape. The coil portions <NUM> are attached to the teeth 31b respectively. Flat core bearing surfaces 31c for placing second flange portions <NUM> of bobbins <NUM> in close contact with the inner peripheral wall 31a are provided at base portions of the respective teeth 31b on which the respective coil portions <NUM> are mounted, the base portions being part of the inner peripheral wall 31a of the annular stator core <NUM>.

The coil portions <NUM> include, respectively, the bobbins <NUM> and coils <NUM> formed by winding coil wires 34a around the outer peripheries of the bobbins <NUM> a predetermined number of times.

The bobbins <NUM> are each formed of an insulating material such as resin and each integrally have a bobbin body <NUM>, a first flange portion <NUM>, and a second flange portion <NUM>.

The bobbin body <NUM> is a cylindrical body having a rectangular cross section, which penetrates in a front-rear direction and has a rectangular insertion hole <NUM> through which the corresponding tooth 31b can be inserted. In other words, the bobbin body <NUM> is a rectangular cylindrical body (so-called square tube). The coil wire 34a of the coil <NUM> is wound around an outer peripheral surface of the bobbin body <NUM> the predetermined number of times.

The first flange portion <NUM> is a flat flange portion having a rectangular hollow shape when viewed from the front, i.e., having a hole in the center thereof, and is provided on one end surface of the bobbin body <NUM> located near the center O of the annular stator core <NUM> in such a manner as to protrude from the outer peripheral surface of the bobbin body <NUM> to the outside at a substantially right angle.

The second flange portion <NUM> is a flat flange portion having a rectangular hollow shape when viewed from the front, i.e., having a hole in the center thereof as with the first flange portion <NUM>, and is provided on an end surface of the bobbin body <NUM>, opposite to the first flange portion <NUM>, in such a manner as to protrude from the outer peripheral surface of the bobbin body <NUM> to the outside at a substantially right angle.

In each of the bobbins <NUM> formed as described above, after winding the coil wire 34a around the outer peripheral surface of the bobbin body <NUM> the predetermined number of times, the tooth 31b of the corresponding annular stator core <NUM> is inserted from the other end side of the bobbin body <NUM> that is provided with the second flange portion <NUM>, to mount the bobbin <NUM> onto the tooth 31b. Then, the second flange portion <NUM> of the bobbin <NUM> is placed in close contact with the core bearing surface 31c and fixed to the tooth 31b by a means which is not illustrated (e.g., by means of fitting, bonding, etc.). <FIG> shows the radial magnetic bearing device <NUM> in which the bobbins <NUM> are attached to the respective teeth 31b of the annular stator core <NUM> as described above. Each annular electromagnet 21b is a uniaxial electromagnet using a pair of coil portions <NUM> illustrated in <FIG>. Four pairs of the uniaxial electromagnets are provided at a phase angle of <NUM> degrees, in which the rotor shaft <NUM> is attracted by the magnetic force generated by each of these electromagnets and supported in a non-contact manner.

In the annular electromagnet 21b illustrated in <FIG> and <FIG>, four electromagnets are arranged in pairs along the X axis and the Y axis, as well as in the + direction and the - direction (if necessary, these electromagnets arranged in pairs are referred to as "electromagnet +X," "electromagnet -X," "electromagnet +Y," and "electromagnet -Y"). Since these electromagnets +X, -X, +Y, and -Y share the same structure, <FIG> only shows the electromagnet -Y. Thus, the configuration of the electromagnet -Y described below is applied to the electromagnets +X, -X, and +Y as well.

The electromagnet -Y of the embodiment illustrated in <FIG> is a uniaxial electromagnet configured by an electromagnet -Y1 and an electromagnet -Y2. In the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y1 and the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y2, circumferential end surfaces 36a of the first flange portion <NUM> and circumferential end surfaces 37a of the second flange portion <NUM> are chamfered into coil winding amount increasing means <NUM>. Note that the electromagnet -Y1 and the electromagnet -Y2 are symmetrical with respect to α angle and that the parts of the electromagnet -Y1 and the parts of the electromagnet -Y2 share the same structure. Therefore, in <FIG>, the detailed reference numerals corresponding to the description are given only to the electromagnet -Y1, but for the electromagnet -Y2, reference numerals are given generically and omitted accordingly.

Specifically, each end surface 36a of the first flange portion <NUM> is chamfered to have a width L9 so as to be inclined inward at a chamfer angle β from an outer edge 36b to an inner edge 36c in the direction of a plate thickness L3 of the first flange portion <NUM>. Here, β ≤ <NUM>° - 2α, L9 ≤ L3. This chamfering of each end surface 36a of the first flange portion <NUM> reduces a protrusion amount L61 of the inner edge 36c to effectively increase the interval L6 between the first flange portions <NUM>. In other words, the protrusion amount L61 contributes to increasing the interval between the bobbins <NUM>, that is, the amount of projection of the first flange portion <NUM>, and allows the first flange portion <NUM> to project to both sides in the circumferential direction, to contribute to increasing the number of turns of the coil wire 34a. This interval increase L6 between the bobbins <NUM> is obtained by the following equation (<NUM>).

Each end surface 37a of the second flange portion <NUM>, on the other hand, is chamfered to have a width L10 so as to be inclined inward at a chamfer angle γ from an inner edge 37c to an inner edge 37b in the direction of a plate thickness L4 of the second flange portion <NUM>. Here, L10 ≤ L4. This chamfering of each end surface 37a of the second flange portion <NUM> reduces a protrusion amount L71 of the inner edge 37c to effectively increase an interval L7 between an end portion of the corresponding core bearing surface 31c and the bobbin <NUM> (L7 + L71). In other words, as with the first flange portion <NUM>, the protrusion amount L71 contributes to increasing the amount of projection of the second flange portion <NUM>, and allows the second flange portion <NUM> to project to both sides in the circumferential direction, to contribute to increasing the number of turns of the coil wire 34a. The interval L71 between the end portion of the core bearing surface 31c and the bobbin <NUM> is obtained by the following equation (<NUM>).

A magnetic pole connecting thickness L81 between the bobbins <NUM> can also be increased. Specifically, when L8 represents a magnetic pole connecting thickness obtained by not chamfering each end surface 37a of the second flange portion <NUM> according to the illustrated embodiment, the magnetic pole connecting thickness L81 of the illustrated embodiment is expressed by the following equation (<NUM>), in which it is clear that the magnetic pole connecting thickness L81 according to the illustrated embodiment is greater than the magnetic pole connecting thickness L8 of the structure of the prior art.

Therefore, in the annular electromagnet 21b illustrated in <FIG> and <FIG>, because the circumferential end surfaces 36a of the first flange portion <NUM> are each chamfered at an angle from the outer edge 36b toward the inside in the plate thickness direction of the first flange portion <NUM>, the distance between the outer edges 36b of the first flange portions <NUM> of the adjacent bobbins <NUM> is increased, contributing to increasing the amount of projection of the first flange portions <NUM>.

As a result, as illustrated in <FIG>, for example, even when the amount of projection of the first flange portions <NUM> is increased so that the outer edges 36b of the first flange portions <NUM> of the adjacent bobbins <NUM> come close to each other, the first flange portions <NUM> of the adjacent bobbins <NUM> do not interfere with each other at the time of assembly. Therefore, increasing the amount of projection of the circumferential end surfaces 36a of the first flange portion <NUM> of the bobbin <NUM> can increase the number of turns of the coil wire 34a, thereby enhancing the attractive force of the annular electromagnet 21b. In other words, in a case where the amount of projection of the bobbins <NUM> illustrated in <FIG> is increased to narrow the interval L61, a thickness L11 of each coil <NUM> is expressed by the following equation (<NUM>), and the number of turns of the coil wire 34a can be made greater than the thickness L1 of the coil <NUM> when the interval L61 between the bobbins <NUM> illustrated in <FIG> is not narrowed.

Furthermore, since the circumferential end surfaces 37a of the second flange portion <NUM> are each chamfered at an angle from the inner edge 37c toward the inside in the direction of the plate thickness L4 of the second flange portion <NUM>, these inclined chamfered surfaces function as the coil winding amount increasing means <NUM> and dodge the curved shape (magnetic pole connecting part) of the inner peripheral wall 31a of the annular stator core <NUM>, resulting in an increase of the amount of projection between the circumferential end surfaces of the second flange portions <NUM> of the bobbins <NUM>. Therefore, the number of turns of each coil wire 34a can be increased and thereby the attractive force of the annular electromagnet 21b can be enhanced. Moreover, a magnetic pole connecting thickness L82 according to the present embodiment and the conventional magnetic pole thickness L8 of the prior art establish the chamfer angle γ so as to satisfy L82 ≥ L8.

Specifically, L71 ≥ L7 + L9 × tan2α/<NUM> tanγ ≤ L10/(L7 + L9 × tan 2α/<NUM>) are established, in which the number of turns of each coil wire 34a and the attractive force of the annular electromagnet 21b can be increased by increasing γ.

The bobbins <NUM> of the annular electromagnet 21b of the foregoing embodiment adopt the structure in which the circumferential end surfaces 36a of each of the first flange portions <NUM> and the circumferential end surfaces 37a of each of the second flange portions <NUM> of the electromagnets -Y1 and -Y2 are chamfered. However, chamfering does not need to be performed on the end surfaces of the both electromagnets but may be performed as in the following (a) to (c) or by combining them, as illustrated in <FIG> and <FIG>.

<FIG> each show a first modification of the annular stator core <NUM>. <FIG> and <FIG> correspond to the electromagnet -Y illustrated in <FIG> and <FIG> and omit the illustration of the hatched section for the purpose of simplification. Also, <FIG> show the bobbins <NUM> of the annular stator core <NUM> of <FIG> and <FIG>. <FIG> are a plan view taken along arrows A and B of <FIG>. In the following description, the same reference numerals are given to the parts corresponding to the annular stator core <NUM> illustrated in <FIG>, and redundant explanations are omitted accordingly. Thus, only the parts having different configurations are described. In addition, the electromagnet -Y1 and the electromagnet -Y2 illustrated in the first modification are symmetrical with respect to the α angle, and the parts of the electromagnet -Y1 and the parts of the electromagnet -Y2 share the same structure. Therefore, in <FIG> and <FIG>, the detailed reference numerals corresponding to the description are given only to the electromagnet -Y1, but for the electromagnet -Y2, reference numerals are given generically and omitted accordingly.

The electromagnet -Y illustrated in <FIG> and <FIG> is a uniaxial electromagnet having the electromagnet -Y1 and the electromagnet -Y2. In the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y1 and the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y2, as illustrated in <FIG>, a plurality of recess portions 40a that function as notches for accommodating portions 39a of these adjacent bobbins <NUM> are arranged as the coil winding amount increasing means, at a predetermined pitch along a vertical direction, on the circumferential end surfaces 36a of the respective first flange portions <NUM>.

The recess portion 40a on the right side and the left side of the first flange portion <NUM> of the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y1 are shifted by approximately <NUM> pitch in the vertical direction in relation to the recess portions 40a on the left side and right side of the first flange portion <NUM> of the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y2.

On the other hand, the circumferential end surfaces 37a of the second flange portions <NUM> of the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y1 and of the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y2, too, are provided with a plurality of recess portions 40b as notches which are arranged at approximately the same pitch as in the both circumferential end surfaces 36a of the first flange portions <NUM> and accommodate the portions 39b of the bobbins <NUM>, as indicated by the parenthesized reference numerals illustrated in <FIG>.

Note that a notch depth L15 of each of the recess portions 40a of the first flange portions <NUM> is equal to a notch depth L16 of each of the recess portions 40b (L15 = L16). Also, a width L20 of each of the recess portions 40a of the first flange portions <NUM> is equal to a width L24 of each of the recess portions 40b of the second flange portions <NUM> (L20 = L24), and a distance L21 between the recess portions 40a of each first flange portion <NUM> is equal to a distance L25 between the recess portions 40b of each second flange portion <NUM> (L21 = L25). Furthermore, the width L20 of each recess portion 40a in the first flange portions <NUM> and the width L24 of each recess portion 40b in the second flange portion <NUM> are configured to be greater than the distance L21 between the recess portions 40a of each first flange portion <NUM> and the distance L25 between the recess portions 40b of each second flange portion <NUM> (L20 > L21, L24 < L25).

Therefore, according to this structure, even when the amounts of projection of the first flange portion <NUM> and the second flange portion <NUM> are increased and thereby the bobbin <NUM> of the electromagnet -Y1 and the bobbin <NUM> of the electromagnet -Y2 are arranged close to each other, the portions 39b and 39a of the second flange portion <NUM> in the bobbin <NUM> of the electromagnet -Y2 are sequentially fitted in the recess portions 40a on the right hand side of the bobbin <NUM> of the electromagnet -Y1 and are dodged when the bobbin <NUM> of the electromagnet -Y1 and the bobbin <NUM> of the electromagnet -Y2 are attached to the respective teeth 31b. Consequently, the bobbins <NUM> adjacent to each other can be attached to the respective teeth 31b so as not to interfere with each other. In this case, increasing the amount of projection of the first flange portion <NUM> and the amount of projection of the second flange portion <NUM> in the bobbins <NUM> allows the coil wires 34a to be wound up to approximately <NUM>/<NUM> the notch depth L15 of the recess portions 40a. Therefore, the number of turns of the coil wires 34a can be increased and thereby the thickness L1 of the coils <NUM> can be increased. Specifically, when a thickness L12 of each coil <NUM> illustrated in <FIG> is L1 + L15/<NUM> > L1, with L15 being the notch depth of each first flange portion <NUM>, the coils <NUM> having a higher number of turns of the coil wires 34a can be obtained.

<FIG> each show a second modification of the annular stator core <NUM>. <FIG> and <FIG> correspond to the electromagnet -Y illustrated in <FIG> and <FIG> and omit the illustration of the hatched section for the purpose of simplification. Also, <FIG> each show the bobbins <NUM> of the annular stator core <NUM> of <FIG> and <FIG>. <FIG> are a plan view taken along arrows A and B of <FIG>. <FIG> is a schematic perspective view showing the bobbins <NUM> from the center of the annular stator core <NUM>. <FIG> is a schematic perspective view showing the bobbins <NUM> from the outer periphery side of the annular stator core <NUM>.

The second modification illustrated in <FIG> is a modification that is further developed by combining the embodiment illustrated in <FIG> and the first modification illustrated in <FIG>. Therefore, the same reference numerals are given to the parts corresponding to the annular stator core <NUM> illustrated in <FIG>, and redundant explanations are omitted accordingly. Thus, only the parts having different configurations are described. In addition, the electromagnet -Y1 and the electromagnet -Y2 illustrated in the second modification are symmetrical with respect to the α angle, and the parts of the electromagnet -Y1 and the parts of the electromagnet -Y2 share the same structure. Therefore, in <FIG> and <FIG>, the detailed reference numerals corresponding to the description are given only to the electromagnet -Y1, but for the electromagnet -Y2, reference numerals are given generically and omitted accordingly.

The electromagnet -Y illustrated in <FIG> and <FIG> is a uniaxial electromagnet having the electromagnet -Y1 and the electromagnet -Y2. In the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y1 and the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y2, as illustrated in <FIG>, circumferential end surfaces 36a, 36a1 of the first flange portion <NUM> and circumferential end surfaces 37a, 37a1 of the second flange portion <NUM> are chamfered to have widths L9, L91, L10, L17 that are inclined at chamfer angles β, β1, γ, γ1 and are provided with a plurality of recess portions 40a, 40b that function as notches for accommodating the portions 39a, 39b of these adjacent bobbins <NUM>. The chamfers and the recess portions 40a, 40b function as the coil winding amount increasing means <NUM>.

Therefore, in the annular electromagnet 21b illustrated in <FIG> and <FIG>, because the circumferential end surfaces 36a, 36a1 of the first flange portion <NUM> are chamfered so as to be inclined inward from outer edges 36b, 36b1 in the plate thickness direction of the first flange portion <NUM>, the distance between the inner edges 36c, 36c1 of the first flange portions <NUM> of the adjacent bobbins <NUM> can be increased, contributing to increasing the amount of projection of the first flange portions <NUM>. Note that <FIG> and <FIG> each show the bobbins <NUM> that are provided with the chamfers and recess portions 40a, 40b formed on the circumferential end surfaces 36a, 36a1, 37a of the first flange portions <NUM> and the second flange portions <NUM>. <FIG> is a schematic perspective view showing the bobbins from the center of the annular stator core <NUM>, and <FIG> is a schematic perspective view showing the bobbins from the outer periphery of the annular stator core <NUM>.

Therefore, in this modification as well, the interval L6 between the first flange portions <NUM> can be narrowed in such a manner that the amount of projection of the first flange portions <NUM> is increased so that the first flange portions <NUM> come close to each other, as illustrated in <FIG>, from the state in which the first flange portions <NUM> of the adjacent bobbins <NUM> are separated from each other as illustrated in <FIG>. Specifically, by increasing the amount of projection of the first flange portions <NUM> of the adjacent bobbins <NUM> so as to bring the outer edges 36b of the first flange portions <NUM> close to each other, the thickness of the coil wires 34a can be increased from L1 to L13, thereby making the number of turns of the coil wires 34a greater than the thickness L1 of the coil <NUM>.

Furthermore, since the circumferential end surfaces 37a of the second flange portion <NUM> are chamfered so as to be inclined inward from the inner edge 37c in the direction of the plate thickness L4 of the second flange portion <NUM>, this chamfering functions as the coil winding amount increasing means <NUM>, and these inclined chamfered surfaces dodge the curved shape (magnetic pole connecting part) of the inner peripheral wall 31a of the annular stator core <NUM>, increasing the amount of circumferential projection of the second flange portions <NUM> of the bobbins <NUM> and the number of turns of the coil wires 34a. Moreover, the chamfer angle γ is set so that the magnetic pole connecting thickness L83 becomes greater than the magnetic pole connecting thickness L8 of the prior art (L83 ≥ L8).

That is, L71 ≥ L7 + L15/<NUM>+ L9 × tan2α/<NUM> tanγ ≤ L10/(L7 + L15/<NUM> + L9 × tan2α/<NUM>) are satisfied, where the chamfer angle γ can be set at L83 ≥ L8.

In addition, since the recess portions 40b that function as the notches for accommodating the portions 39b of the bobbins <NUM> are provided in the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y1 and the bobbin <NUM> attached to the tooth 31b of the electromagnet -Y2, the first flange portions <NUM> of these adjacent bobbins <NUM> do not interfere with each other at the time of assembly. Accordingly, the distance between the circumferential end surfaces (the amount of projection) of the first flange portions <NUM> of the bobbins <NUM> can be increased, and, with the resultant coil winding amount increasing means <NUM>, the number of turns of the coil wires 34a can be increased and thereby the attractive force of the annular electromagnet 21b can be enhanced.

Claim 1:
A vacuum pump (<NUM>) comprising:
a magnetic bearing device (<NUM>,<NUM>) that is disposed radially outside of a rotor shaft (<NUM>) and rotatably holds the rotor shaft, wherein
the magnetic bearing device has an annular stator core (<NUM>) having, on an inner peripheral wall (31a) thereof, a plurality of teeth (31b) provided at predetermined intervals in a circumferential direction of the rotor shaft, and an annular electromagnet (21b,22b) having a plurality of bobbins (<NUM>) attached to the teeth respectively, the plurality of bobbins having coil wires (34a) wound around outer peripheries thereof,
the plurality of bobbins each having:
a rectangular cylindrical bobbin body (<NUM>) that has the coil wire wound around the outer periphery thereof and is attached to each of the teeth;
a first flange portion (<NUM>) having a plate thickness and being provided on an end surface of the bobbin body so as to face the rotor shaft and formed into a rectangular hollow shape as viewed from the front;
a second flange portion (<NUM>) having a plate thickness and being provided on an end surface of the bobbin body so as to be opposite to the first flange portion and formed into a rectangular hollow shape as viewed from the front;
characterised in that the vacuum pump (<NUM>) comprises:
coil winding amount increasing means formed at least on the first flange portion and increasing the amount of winding of the coil wire wound around the bobbin body, wherein the coil winding amount increasing means comprises:
on circumferential end faces of the first flange portion, chamfers (36a, 36a1) that are inclined inward from outer edges of the first flange portion in a direction of a plate thickness; and/or
on the circumferential end faces of two first flange portions of each of the plurality of bobbins adjacent to each other, notches (40a,40b) that accommodate parts of the plurality of adjacent bobbins adjacent to each other;
such that the first flange portion of each of the plurality of bobbins adjacent to each other does not interfere with each other by the coil winding amount increasing means.