Stiffness gain mechanism for magnetic suspension bearing, magnetic suspension bearing, and blood pump

The present disclosure relates to a stiffness enhancing mechanism for a magnetic suspension bearing, a magnetic suspension bearing including the stiffness enhancing mechanism, and a blood pump. The magnetic suspension bearing comprises a stator with stator teeth and a rotor disposed within the stator. The stiffness enhancing mechanism comprises: a rotor permanent magnet, a stator permanent magnet, and an axial driving body. The rotor permanent magnet and the rotor of the magnetic suspension bearing form a rotor assembly, which has an asymmetric structure with respect to the main plane (P) of the rotor. The stiffness enhancing mechanism is configured such that the stator permanent magnet generates a radial attractive force to the rotor permanent magnet, and the axial driving body generates an axial repulsive force to the rotor permanent magnet, wherein the magnitude of the axial repulsive force is variable with a change of an axial distance between the axial driving body and the rotor permanent magnet. The stiffness enhancing mechanism can increase the torsional stiffness of the rotor of the magnetic suspension bearing and facilitate the miniaturization of the magnetic suspension bearing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the 371 U.S. national phase of PCT international patent application number PCT/CN2020/073208, filed Jan. 20, 2020, which claims priority to Chinese patent application number 201910113382.1, filed on Feb. 14, 2019. The disclosure of each aforementioned application is incorporated by reference herein in its entirety. Specifically, PCT international patent application number PCT/CN2020/073208 is incorporated by reference herein in its entirety. And, Chinese patent application number 201910113382.1 is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to the field of medical instruments. More specifically, the present disclosure relates to a stiffness enhancing mechanism for a magnetic suspension bearing, a magnetic suspension bearing including the stiffness enhancing mechanism, and a blood pump.

BACKGROUND ART

In the case where a heart loses its blood pumping function (such as arrested heart surgery, acute cardiogenic shock, etc.), a blood pump may be used to replace the heart to assist in maintaining the blood circulation of human body. The blood pump may be an implantable blood pump that is implantable into a patient's body to maintain the blood circulation of human body temporarily or permanently, or an extracorporeal blood pump that is usable outside the human body.

It is advantageous to use a magnetic suspension bearing in the blood pump. The magnetic suspension bearing, which functions with magnetic force, typically includes a rotor that is rotatable about a specific axis of rotation, and a magnetic force providing mechanism that provides magnetic force to suspend the rotor. According to the difference in the magnetic force providing mechanism, the magnetic suspension bearing may be classified as an active magnetic suspension bearing or a passive magnetic suspension bearing, wherein the magnetic force providing mechanism of the active magnetic suspension bearing may be an electromagnet, whereas the magnetic force providing mechanism of the passive magnetic suspension bearing may be a permanent magnet or a ferromagnetic material. The active magnetic suspension bearing usually further includes a displacement sensor, and a controller that controls magnitude of current through the electromagnet based on a signal from the displacement sensor to regulate the suspension electromagnetic force. In operation, locations of the rotor that relate to active magnetic suspension degrees of freedom are firstly provided to the controller by the displacement sensor, and then the controller provides a specific current to the electromagnet via a corresponding control algorithm (PID, PI, PD control, etc.) to generate a controlled suspension electromagnetic force. The passive magnetic suspension bearing generates attractive force or repulsive force based on interactions between two or more permanent magnets or between a permanent magnet and a ferromagnetic material to suspend the rotor at a balanced position.

Compared with a traditional bearing like a mechanical bearing, the rotor of the magnetic suspension bearing has no physical contact with other components (such as the magnetic force providing mechanism, etc.), and the rotor may be spaced apart from other components by a large gap, rendering significant advantageous of the magnetic suspension bearing. On one hand, mechanical wear of respective components of the magnetic suspension bearing can be eliminated due to the absence of physical contact; on the other hand, the large gap allows a fluid flowing through the gap to suffer less shear stress, which, in the case where the fluid is blood, can help to reduce damages to the blood cells and accordingly can improve blood compatibility.

FIG.1is a schematic view of an active magnetic suspension bearing10. The active magnetic suspension bearing10includes: a rotor101that is rotatable about an axis of rotation A; an electromagnet102that provides electromagnetic force to suspend the rotor101, wherein a gap or an airgap G1is present between the rotor101and the electromagnet102; a displacement sensor103for detecting the displacement of the rotor101relative to the electromagnet102; and a controller104, which controls magnitude of current through the electromagnet102based on signals from the displacement sensor103to regulate the suspension electromagnetic force.

In the active magnetic suspension bearing10shown inFIG.1, the electromagnet102provides radial electromagnetic force (i.e., the electromagnetic force in an X-Y plane) to the rotor101to ensure that the rotor101is stably suspended in the radial direction. However, the active magnetic suspension bearing10shown inFIG.1is prone to generating torsional movement about an X-axis or a Y-axis. In other words, the active magnetic suspension bearing10shown inFIG.1has a degree of freedom of torsion (that is, the degree of freedom of rotation with the X-axis or Y-axis as the axis of rotation), and alternatively speaking, the active magnetic suspension bearing10shown inFIG.1has a low torsional stiffness, which is undesirable. It is desirable that the magnetic suspension bearing has a torsional stiffness as high as possible so that the magnetic suspension bearing has no or rare torsional movement.

In order to solve above mentioned problem, a known method is to combine multiple layers of permanent magnets and ferromagnetic materials to form a sandwich-like structure, so that multiple parallel push and pull forces are formed on a plane perpendicular to the axis of rotation A (i.e., the X-Y plane shown inFIG.1) to thereby increase the torsional stiffness and improve the torsional stability. However, such sandwich structure has some drawbacks. On one hand, the strength of a permanent magnet is proportional to its volume: the larger the volume, the higher the strength of the permanent magnet; on the other hand, the smaller the volume of the permanent magnet, the more obvious the magnetization marginal effect of the permanent magnet. That is to say, the magnetic field intensity generated by a permanent magnet formed of a plurality of small permanent magnets is not equal to but less than the magnetic field intensity generated by a single permanent magnet of the same volume. Therefore, when above-mentioned sandwich structure formed of a plurality of permanent magnets is used, in order to reach a desired magnetic field intensity as that generated by a single permanent magnet, it needs to increase the volume of each small permanent magnet, which may necessarily lead to an increase in the total volume of the magnetic suspension bearing, thus limiting its scope of application. In many current applications, there are usually strict limitations for the volume of the rotor, and it is generally desired that the rotor can be miniaturized. For example, in the application in the blood pump, the gap or airgap in the magnetic suspension bearing is generally shared with a secondary flow path of the blood pump. When the blood flows in a secondary flow path narrower than a main flow path, it may suffer shear stress for a long period, thus causing damage to blood cells. Therefore, miniaturizing the rotor so as to shorten the length of the secondary flow path as much as possible is very important for the blood compatibility of the blood pump. In this kind of application, the miniaturization of the rotor is an important optimization target; however, the sandwich structure runs counter to this target.

Therefore, there is a demand to further modify the current magnetic suspension bearings.

CONTENT OF THE INVENTION

The above-mentioned problems and other problems will be overcome and additional advantages are to be achieved by exemplary embodiments of the present disclosure.

According to a first aspect of exemplary embodiments of the present disclosure, a stiffness enhancing mechanism for a magnetic suspension bearing is provided. The magnetic suspension bearing may include a stator and a rotor disposed within the stator, wherein the stator includes stator teeth. The stiffness enhancing mechanism may comprise: a rotor permanent magnet arranged on a side of the rotor with the rotor permanent magnet being parallel to a main plane of the rotor and abutting against the rotor, wherein the main plane of the rotor is a symmetrical plane of the rotor in a radial direction; a stator permanent magnet arranged on a side of the stator teeth of the stator with the stator permanent magnet being parallel to the main plane of the rotor and abutting against the stator teeth of the stator, wherein the side where the stator permanent magnet is located is the same as the side where the rotor permanent magnet is located, and the stator permanent magnet is spaced apart from the rotor permanent magnet by a certain distance in the radial direction; and an axial driving body arranged to face the rotor permanent magnet and be spaced apart from the rotor permanent magnet by a certain distance in an axial direction. The rotor permanent magnet and the rotor form a rotor assembly, which has an asymmetric structure with respect to the main plane of the rotor. The stiffness enhancing mechanism is configured such that the stator permanent magnet generates a radial attractive force to the rotor permanent magnet, and the axial driving body generates an axial repulsive force to the rotor permanent magnet, wherein the magnitude of the axial repulsive force is variable with a change of an axial distance between the axial driving body and the rotor permanent magnet.

According to an exemplary embodiment of the present disclosure, each of the rotor permanent magnet and the stator permanent magnet may have a mono-magnetization direction.

According to an exemplary embodiment of the present disclosure, the rotor permanent magnet and/or the stator permanent magnet may have an axial magnetization direction.

According to an exemplary embodiment of the present disclosure, the rotor permanent magnet and/or the stator permanent magnet may have a radial magnetization direction.

According to an exemplary embodiment of the present disclosure, each of the rotor permanent magnet and the stator permanent magnet may be of an integral structure in a circular shape.

According to an exemplary embodiment of the present disclosure, the rotor permanent magnet and/or the stator permanent magnet may be composed of a plurality of discrete permanent magnets spaced apart from each other in a circumferential direction.

According to an exemplary embodiment of the present disclosure, the axial driving body may be configured to be stationary.

According to an exemplary embodiment of the present disclosure, the axial driving body may be a permanent magnet.

According to an exemplary embodiment of the present disclosure, the axial driving body may be a permanent magnet having an integral structure in a circular shape.

According to an exemplary embodiment of the present disclosure, the axial driving body may be composed of a plurality of discrete permanent magnets spaced apart from each other in a circumferential direction.

According to an exemplary embodiment of the present disclosure, the axial driving body may be an electromagnet or an air coil.

According to an exemplary embodiment of the present disclosure, the axial driving body may be composed of a plurality of electromagnets or air coils spaced apart from each other in a circumferential direction.

According to an exemplary embodiment of the present disclosure, the stiffness enhancing mechanism may further include a controller or a control circuit, which can separately vary magnitude of current flowing through each electromagnet or air coil and accordingly can separately change the magnitude of the axial repulsive force generated by the corresponding one or more electromagnets or air coils to the rotor permanent magnet.

According to an exemplary embodiment of the present disclosure, when a torsional movement about the radial direction occurs to the rotor, the controller or the control circuit of the stiffness enhancing mechanism reduces the current flowing through one or more electromagnets or air coils corresponding to an end of the rotor away from the axial driving body and meanwhile increases the current flowing through one or more electromagnets or air coils corresponding to the other end of the rotor close to the axial driving body.

According to an exemplary embodiment of the present disclosure, the controller or control circuit of the stiffness enhancing mechanism is also capable of separately changing direction of current flowing through each electromagnet or air coil. When a torsional movement about the radial direction occurs to the rotor, the controller or control circuit of the stiffness enhancing mechanism changes the direction of current flowing through one or more electromagnets or air coils corresponding to an end of the rotor away from the axial driving body, so as to change the axial repulsive force generated by the one or more electromagnets or air coils to the rotor permanent magnet into an axial attractive force.

According to a second aspect of exemplary embodiments of the present disclosure, there is provided a magnetic suspension bearing, which includes the stiffness enhancing mechanism according to the exemplary embodiments of the present disclosure.

According to an exemplary embodiment of the present disclosure, the stator of the magnetic suspension bearing may comprise a plurality of stator teeth spaced apart from each other in a circumferential direction, and each of the stator teeth is provided with a magnetic suspension coil for suspending the rotor of the magnetic suspension bearing and controlling the movement of the rotor in the radial direction.

According to an exemplary embodiment of the present disclosure, each of the stator teeth may include a horizontal portion and a vertical portion to assume an inverted “L” shape, wherein the horizontal portion of each stator tooth and the rotor are located at substantially same heights with a gap existing between the horizontal portion of the stator tooth and the rotor, the magnetic suspension coil is wound on the vertical portion of the stator tooth, and a magnetic flux generated by the magnetic suspension coil is capable of passing through the horizontal portion of the stator tooth, through the gap between the horizontal portion of the stator tooth and the rotor, and through the rotor.

According to an exemplary embodiment of the present disclosure, each of the stator teeth may extend from a stator body towards the center in the radial direction to assume a linear shape, wherein each stator tooth and the rotor are located at substantially same heights with a gap existing between the stator tooth and the rotor, the magnetic suspension coil is wound on the stator tooth, and the magnetic flux generated by the magnetic suspension coil is capable of passing through the stator tooth, through the gap between the stator tooth and the rotor, and through the rotor.

According to an exemplary embodiment of the present disclosure, the magnetic suspension bearing may further comprise a displacement sensor and a controller, wherein the displacement sensor is used to measure a displacement of the rotor in the radial direction and send a displacement signal to the controller of the magnetic suspension bearing, and the controller of the magnetic suspension bearing separately changes magnitude and/or direction of current flowing through corresponding one or more magnetic suspension coils based on the displacement signal to thereby control movement of the rotor in the radial direction.

According to an exemplary embodiment of the present disclosure, the stator permanent magnet of the stiffness enhancing mechanism may be abutted against a surface of the stator.

According to an exemplary embodiment of the present disclosure, the magnetic suspension bearing may further comprise a support structure for supporting the axial driving body of the stiffness enhancing mechanism.

According to an exemplary embodiment of the present disclosure, the support structure may be a part of the stator of the magnetic suspension bearing.

According to an exemplary embodiment of the present disclosure, the support structure may be a part of a rotor driver of the magnetic suspension bearing.

According to an exemplary embodiment of the present disclosure, the support structure may be a part of a housing of the magnetic suspension bearing.

According to an exemplary embodiment of the present disclosure, the support structure may also be used to abut the stator permanent magnet of the stiffness enhancing mechanism against a surface of the stator.

According to an exemplary embodiment of the present disclosure, the rotor of the magnetic suspension bearing may be in the shape of a disc.

According to an exemplary embodiment of the present disclosure, an inner peripheral surface of the stator permanent magnet may be aligned with an inner peripheral surface of the stator tooth of the magnetic suspension bearing.

According to an exemplary embodiment of the present disclosure, an outer peripheral surface of the rotor permanent magnet may be aligned with an outer peripheral surface of the rotor of the magnetic suspension bearing.

According to an exemplary embodiment of the present disclosure, the stator teeth may be made of magnetically conductive materials.

According to an exemplary embodiment of the present disclosure, the stator teeth may be made of ferromagnetic materials.

According to an exemplary embodiment of the present disclosure, the rotor may be made of magnetically conductive materials.

According to an exemplary embodiment of the present disclosure, the rotor may be made of ferromagnetic materials.

According to a third aspect of exemplary embodiments of the present disclosure, there is provided a blood pump, which includes the stiffness enhancing mechanism according to the exemplary embodiments of the present disclosure.

According to a fourth aspect of exemplary embodiments of the present disclosure, there is provided a blood pump, which includes the magnetic suspension bearing according to the exemplary embodiments of the present disclosure.

The additional and/or other aspects and advantages of the present disclosure will be set forth in the following description, or may be obvious from the following description or can be learned through the practice of the present invention. The various technical features of the present disclosure can be combined arbitrarily as long as they do not contradict each other.

In the drawings, respective reference signs indicate respective components. The examples described herein are used to illustrate exemplary aspects of the present invention, and these examples should not be construed as limiting the scope of the present disclosure in any way.

DETAILED EMBODIMENTS

The present disclosure will be described below with reference to the drawings, in which several embodiments of the present disclosure are shown. It should be understood, however, that the present invention may be implemented in many different ways, and is not limited to the embodiments described below. In fact, the embodiments described hereinafter are intended to make a more complete disclosure of the present disclosure and to adequately explain the scope of the present invention to a person skilled in the art. It should also be understood that, the embodiments disclosed herein can be combined in various ways to provide many additional embodiments.

For the purpose of description, the terms “upper”, “lower”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “transverse”, “perpendicular” and their derivatives are all related to the orientation in the drawings of the present disclosure. However, it should be understood that the present disclosure may adopt various alternative modifications, unless otherwise clearly indicated.

The singular forms “a/an” and “the” as used in the specification, unless clearly indicated, all contain the plural forms. The words “comprising”, “containing” and “including” used in the specification indicate the presence of the claimed features, but do not preclude the presence of one or more additional features. The wording “and/or” as used in the specification includes any and all combinations of one or more of the relevant items listed.

In the specification, when an element is referred to as being “on”, “attached” to, “connected” to, “coupled” with, “contacting” another element, and so on, it can be directly on, attached to, connected to, coupled with or contacting the other element, or intervening elements may also be present. In contrast, when an element is referred to as being “directly on”, “directly attached” to, “directly connected” to, “directly coupled” with or “directly contacting” another element, there are no intervening elements present. In the specification, references to a feature that is disposed “adjacent” another feature may have portions that overlap, overlie or underlie the adjacent feature.

Referring toFIGS.2and3, a magnetic suspension bearing20according to an embodiment of the present disclosure is shown. The magnetic suspension bearing20includes a stator21and a rotor22disposed within the stator. The rotor22may be in the shape of a disc and is rotatable about an axis of rotation A. Ideally, the stator21and the rotor22are coaxial. The stator21includes a circular stator body210and a plurality of stator teeth211disposed on the stator body210in a circumferential direction. The stator teeth211and the rotor22are both made of magnetically conductive materials, such as ferromagnetic materials. In the embodiment shown inFIGS.2and3, the stator tooth211includes a vertical portion and a horizontal portion that are perpendicular to each other to assume an inverted “L” shape. The horizontal portion of the stator tooth211and the rotor22may be of the same thickness and may be located at a same height in an ideal situation with a gap or an airgap G existing between the horizontal portion of the stator tooth211and the rotor22. Specifically, the horizontal portion of the stator tooth211includes an upper surface2111, a lower surface2112, and an arc-shaped inner peripheral surface2113; the rotor22includes an upper surface221, a lower surface222, and a circumferential outer peripheral surface223. Ideally, the upper surfaces2111of the horizontal portions of the stator teeth211are aligned with the upper surface221of the rotor22, the lower surfaces2112of the horizontal portions of the stator teeth211are aligned with the lower surface222of the rotor22, and the inner peripheral surfaces2113of the horizontal portions of the stator teeth211are spaced apart from the outer peripheral surface223of the rotor22by an equal gap or airgap G. In addition, magnetic suspension coils212are wound on the vertical portions of the stator teeth211to provide a radial electromagnetic force (attractive force or repulsive force) to the rotor22, so as to suspend the rotor22. Specifically, once being excited by current, the magnetic suspension coils212can generate an electromagnetic field on the stator teeth211. By permeation of the magnetic field through the stator teeth211and the rotor22, a radial electromagnetic force (attractive force or repulsive force) can be generated between the stator teeth211and the rotor22to suspend the rotor22in a radial plane (the X-Y plane inFIGS.2and3).

In the embodiment shown inFIGS.2and3, the stator21includes four stator teeth211, each of which is provided with a magnetic suspension coil212. The four stator teeth211are evenly distributed in the circumferential direction, and thus can be divided into two pairs of stator teeth, with the two stator teeth in each pair of stator teeth being arranged opposite to each other in the radial direction. For example, one pair of stator teeth211may be disposed oppositely along the X-axis, and the other pair of stator teeth211may be disposed oppositely along the Y-axis. More pairs of stator teeth (such as three or four pairs of stator teeth) may also be provided as required without departing from the present disclosure.

According to specific conditions, the magnetic suspension coils212on each pair of stator teeth211can generate electromagnetic forces in same directions or in opposite directions on the rotor22. For example, in an ideal condition of the rotor being stably suspended, the magnetic suspension coils212on each pair of stator teeth211may generate electromagnetic forces in opposite directions on the rotor22, so that the rotor22can be stably suspended in the radial plane without radial displacement along the X-axis or Y-axis. In some cases, for example, when the rotor22is radially offset away from a central balanced position due to vibration of the magnetic suspension bearing20under the action of external forces, in order to enable the rotor22to return to the central balanced position more quickly, the magnetic suspension coils212on each pair of stator teeth211may generate electromagnetic forces in a same direction on the rotor22, and the direction of the resultant force of these electromagnetic forces is opposite to the direction in which the rotor is radially offset, thereby helping the rotor22to quickly return to the central balanced position. In this case, the magnitude and/or the direction of the electromagnetic forces generated by corresponding one or more magnetic suspension coils212can be changed by separately regulating the magnitude and/or the direction of current flowing through said magnetic suspension coils212, such that the rotor22can move oppositely in the radial direction by the generated so-called “push-pull” effect to quickly return to the central balanced position where it can be stably suspended. In the embodiment shown inFIGS.2and3, the magnetic suspension coils212on one pair of stator teeth211can control displacement of the rotor22along the X-axis, and the magnetic suspension coils212on the other pair of stator teeth211can control displacement of the rotor22along the Y-axis, thereby capable of regulating the location of the rotor22relative to the stator21in the radial plane.

The aforesaid regulation is fulfilled by means of a displacement sensor and a controller. The displacement sensor is used to detect the displacement of the rotor22relative to the stator21and send a signal to the controller. The controller is connected to the magnetic suspension coils212through wires. After receiving a signal from the displacement sensor, the controller separately varies the magnitude and/or the direction of current flowing through corresponding one or more magnetic suspension coils212as required, so as to change the magnitude and direction of the resultant force of the radial forces generated between the stator21and the rotor22, such that the rotor can move in a desired direction to achieve regulation of location of the rotor22relative to the stator21in the radial plane.

As described above, although the magnetic suspension coils212arranged in pairs can suspend the rotor22in the radial plane, and the location of the rotor22relative to the stator21in the radial plane can be regulated by using a controller to change the magnitude and the direction of the current flowing through the magnetic suspension coil212(that is, the degree of freedom of movement of the rotor22along the X-axis and Y-axis is controllable), the degree of freedom of torsion of the rotor22cannot be effectively controlled merely by these magnetic suspension coils212(i.e. the rotation of the rotor22about the X-axis and the Y-axis cannot be effectively controlled).

In order to solve the problem about torsional stiffness of the magnetic suspension bearing and to reduce the volume of the rotor, especially the height of the rotor associated with the secondary flow path as much as possible, the present disclosure proposes a technical solution of adding a stiffness enhancing mechanism23(shown by the dashed box inFIG.3) to the magnetic suspension bearing. The stiffness enhancing mechanism23not only significantly increases the torsional stiffness of the rotor of the magnetic suspension bearing (that is, making torsional movement of the rotor less occur), but also eliminates the defects of the prior art structures such as the sandwich structure and significantly reduces the volume of the rotor of the magnetic suspension bearing and the height of the rotor associated with the secondary flow path.

The specific structure and working principle of the stiffness enhancing mechanism23according to the present disclosure will be described in detail with reference toFIGS.3to5, whereinFIG.3shows the arrangement of the stiffness enhancing mechanism23according to the present disclosure in the magnetic suspension bearing in a cross-sectional view,FIG.4more clearly shows the specific structure of the stiffness enhancing mechanism23according to the present disclosure in a partial perspective view and shows the magnetization directions of components of the stiffness enhancing mechanism23in a schematic view, andFIG.5shows a different embodiment of an axial driving body233of the stiffness enhancing mechanism23.

Referring first toFIGS.3and4, the stiffness enhancing mechanism23according to the present disclosure includes: a rotor permanent magnet231arranged on a side of the rotor22with the rotor permanent magnet being parallel to a main plane P of the rotor22and abutting against the rotor22, wherein the main plane P of the rotor is a symmetrical plane of the rotor22in the radial direction; a stator permanent magnet232arranged on a side of the stator tooth211of the stator21with the stator permanent magnet being parallel to the main plane P of the rotor22and abutting against the stator tooth211of the stator21, wherein the side where the stator permanent magnet232is located is the same as the side where the rotor permanent magnet231is located, and the stator permanent magnet232and the rotor permanent magnet231are spaced apart from each other by a certain distance in the radial direction (in the inverted “L”-shaped stator teeth shown inFIGS.3and4, the stator permanent magnet232is disposed underneath the horizontal portion of the stator tooth211with the stator permanent magnet being parallel to the main plane P of the rotor and abutting against the horizontal portion of the stator tooth211); and an axial driving body233arranged to face the rotor permanent magnet231and to be spaced apart from the rotor permanent magnet231by a certain distance H in the axial direction (in the embodiment shown inFIGS.3and4, the axial driving body233is also parallel to the main plane P of the rotor). In the stiffness enhancing mechanism according to the present disclosure, the rotor permanent magnet231and the rotor22form a rotor assembly, which has an asymmetric structure with respect to the main plane P of the rotor22. Further, the stiffness enhancing mechanism according to the present disclosure is configured such that the stator permanent magnet232generates a radial attractive force to the rotor permanent magnet231, and the axial driving body233generates an axial repulsive force to the rotor permanent magnet231, wherein the magnitude of the axial repulsive force is variable with the change of the axial distance between the axial driving body233and the rotor permanent magnet231. The torsional stiffness of the rotor22is enhanced through the combined action of the radial attractive force and the axial repulsive force, with its specific principle being described in detail below.

In the embodiment shown inFIGS.3and4, the rotor permanent magnet231and the stator permanent magnet232are both of an integral structure in circular shape, and both have rectangular cross sections. The rotor permanent magnet231may abut against a lower surface222of the rotor22and the outer peripheral surface2311of the rotor permanent magnet231may be aligned with the outer peripheral surface223of the rotor22. The stator permanent magnet232may abut against a lower surface2112of the horizontal portion of the stator tooth211and the inner peripheral surface2321of the stator permanent magnet232may be aligned with the inner peripheral surface2113of the horizontal portion of the stator tooth211. In this way, the rotor permanent magnet231and the stator permanent magnet232are spaced apart from each other by a same distance as the distance G between the stator21and the rotor22. However, the present disclosure is not limited to this, and the distance at which the rotor permanent magnet231and the stator permanent magnet232are spaced apart from each other may also be different from the distance G at which the stator21and the rotor22are spaced apart. In addition, the rotor permanent magnet231and the stator permanent magnet232may be of the same thickness. However, the present disclosure is not limited to this, and the rotor permanent magnet231and the stator permanent magnet232may also be of different thicknesses.

The rotor permanent magnet231may be fixed to the lower surface222of the rotor22in various suitable ways. As mentioned above, the rotor assembly formed by the rotor permanent magnet231and the rotor22has an asymmetric structure with respect to the main plane P of the rotor22(that is, the rotor permanent magnet231is located only on one side of the main plane P of the rotor22), which is an important difference from the prior art sandwich structure. The permanent magnets in the prior art structure such as the sandwich structure are usually in symmetrical arrangement relative to the rotor, which necessarily requires at least two permanent magnets to be disposed on both sides of the rotor. Due to the magnetization marginal effect of the permanent magnet as mentioned above, the magnetic field intensity generated by two separate permanent magnets is less than the magnetic field intensity generated by a single permanent magnet of the same volume. Therefore, in case of two permanent magnets being separately disposed, in order to reach a desired magnetic field intensity as that generated by a single permanent magnet, the height or volume of the two permanent magnets must be increased, which is contrary to the current mainstream of seeking miniaturization of the magnetic suspension bearing. The rotor permanent magnet231according to the present disclosure is arranged on one side of the rotor22, and the asymmetric structure formed in this way not only can achieve the same function as the symmetrical structure, but also can reduce the volume of the rotor and the height of the rotor associated with the secondary flow path by adopting a rotor permanent magnet in small volume and height. When such a magnetic suspension bearing is applied to, for example, a blood pump, it can significantly reduce the damage to, for example, blood cells, thereby increasing the blood compatibility.

The axial driving body233is located directly below the rotor permanent magnet231in the axial direction. Preferably, the axial driving body233may be disposed directly below the rotor permanent magnet231in a stationary manner. Compared with the way in which the axial driving body233is movable, the stationary arrangement of the axial driving body can reduce, to some extent, the adverse effects caused by misalignment of the axial driving body233with the rotor permanent magnets231due to movement of the axial driving body. However, the present disclosure is not limited to this. The axial driving body233may also have a certain degree of freedom, for example, it may also rotate about the axis of rotation A.

In an embodiment according to the present disclosure, the axial driving body233may be in the form of a ring-shaped permanent magnet (as shown inFIGS.3to4). The axial driving body233in the form of a ring-shaped permanent magnet may have the same width as that of the rotor permanent magnet231and may be completely aligned with the rotor permanent magnet231in width. However, the present disclosure is not limited to this, and the axial driving body233in the form of a ring-shaped permanent magnet may also have a different width from that of the rotor permanent magnet231. The axial driving body233in the form of a ring-shaped permanent magnet forms in space a magnetic field repelling the rotor permanent magnet231, thereby generating a passive axial repulsive force (i.e., upward thrust force) to the rotor permanent magnet231. On one hand, when the rotor assembly formed by the rotor permanent magnet231and the rotor22is horizontally suspended in the radial plane without torsional movement about the X-axis or Y-axis, the passive axial repulsive force tends to push the rotor assembly upward; meanwhile, the rotor assembly undergoes an action of radial attractive force generated by the magnetic suspension coil212on the stator21and the stator permanent magnet232, which radial attractive force has a downward pulling force component to resist the passive axial repulsive force generated by the axial driving body233, such that the rotor assembly is maintained at a desired position in space and can be avoided from colliding with the bottom of the magnetic suspension bearing. On the other hand, when the rotor assembly is tilted in the radial plane and thus has a torsional movement about the X-axis or Y-axis, one end of the rotor permanent magnet231will move away from the axial driving body233during which the passive axial repulsive force generated by the axial driving body233to this end of the rotor permanent magnet231will be reduced, and the other end of the rotor permanent magnet231will approach the axial driving body233during which the passive axial repulsive force generated by the axial driving body233to this end of the rotor permanent magnet231will be increased. As the passive axial repulsive forces applied by the axial driving body233to the two ends of the rotor permanent magnet231are not equal, a net torque about the X axis or the Y axis is generated on the rotor permanent magnet231. The net torque is opposite to the torsion direction of the rotor assembly, thereby resisting the torsion of the rotor assembly and returning the rotor assembly to the radial plane. In other words, in the process that different portions of the rotor assembly move up and down due to the torsional movement of the rotor assembly, the axial driving body233generates passive axial repulsive forces of different magnitudes according to the distances from the different portions of the rotor assembly. These passive axial repulsive forces of different magnitudes produce a net torque against torsion of the rotor assembly on the rotor permanent magnet231and the rotor assembly. This net torque, together with the radial attractive force generated by the stator, acts on the rotor assembly to make the rotor assembly return to and stably suspended in the radial plane. This increases the torsional stiffness of the rotor assembly as a whole, i.e. producing an effect of stiffness enhancing. It is to be noted that this regulation process of the stiffness enhancing mechanism23is a dynamic balancing process.

In another embodiment according to the present disclosure, the axial driving body may be in the form of an electromagnet or an air coil233′ (as shown inFIG.5). In the embodiment where the electromagnet or air coil233′ is used as the axial driving body, the axial driving body may include multiple electromagnets or air coils (only one electromagnet or air coil is shown inFIG.5), preferably multiple electromagnets or air coils in pairs. These electromagnets or air coils may be disposed directly below the rotor permanent magnet231at a distance, preferably at an even distance, from each other in the circumferential direction. The axial driving body in the form of an electromagnet or an air coil233′ is actively controllable, that is, the magnitude and the direction of the current flowing through each electromagnet or air coil can be separately changed by a controller or a control circuit. In this way, if required, the controller or control circuit may be used to change the magnitude and the direction of the current flowing through any corresponding one or more electromagnets or air coils so as to change the magnitude or nature of the electromagnetic force generated by the corresponding one or more electromagnets or air coils (that is, capable of changing the magnitude of the axial repulsive force generated by the axial driving body, and capable of changing the initial axial repulsive force generated by the axial driving body into an axial attractive force), thereby increasing the torsional stiffness of the rotor assembly.

Specifically, when the rotor assembly formed by the rotor permanent magnets231and the rotor22has one end close to the axial driving body and its opposite end away from the axial driving body due to torsional movement (that is, rotating about the X-axis or Y-axis), the magnitude and/or the direction of the current flowing through the electromagnets or air coils corresponding to the two ends can be changed, so that the corresponding electromagnets or air coils together generate a net torque against the torsion of the rotor assembly to return the rotor assembly to the radial plane. In particular, it is possible to only change the magnitude of the current flowing through the electromagnets or air coils corresponding to the two ends, for example, increase the current flowing through the electromagnet or air coil close to the rotor assembly to generate a greater thrust force to the rotor assembly, and meanwhile reduce the current flowing through the electromagnet or air coil far away from the rotor assembly to generate a smaller thrust force to the rotor assembly, thereby forming a greater net torque on the rotor assembly to quickly return the rotor assembly to the radial plane. It is also possible to change only the direction of current flowing through the electromagnet or air coil corresponding to one of the two ends, for example, to keep the direction of the current flowing through the electromagnet or air coil close to the rotor assembly unchanged so that an axial repulsion (thrust) force is continued to be generated to the rotor assembly, and to change the direction of the current flowing through the electromagnet or air coil away from the rotor assembly so that an axial attractive force is generated to the rotor assembly. By this way of pushing at one end and attracting at the other end, a greater net torque is formed on the rotor assembly to enable the rotor assembly to quickly return to the radial plane. It is also possible to combine the previous two regulations methods by simultaneously changing the magnitude and the direction of the current flowing through the electromagnets or air coils corresponding to the two ends to obtain a greater net torque, so that the rotor assembly can return to the radial plane more quickly.

Compared with the use of permanent magnets as the axial driving body, the use of electromagnets or air coils233′ as the axial driving body can increase the torsional stiffness of the rotor assembly more significantly and enable the rotor assembly to be suspended more stably. However, in the case of using the electromagnet or air coil as the axial driving body, the electromagnet or air coil requires a large volume and a complicated control circuit. Therefore, if it is required to miniaturize the entire magnetic suspension bearing, the use of the permanent magnets as the axial driving body will be a better choice; but if it is only required to miniaturize the rotor itself (for example, the magnetic suspension bearing is configured as a component placed outside the human body), the use of an actively controllable electromagnet or air coil will be the better choice.

FIGS.4and5also show the magnetization directions of the rotor permanent magnet231and the stator permanent magnet232, in which mono-magnetization directions are shown. Specifically, the rotor permanent magnet231and the stator permanent magnet232shown inFIGS.4and5have axially-magnetized mono-magnetization directions. However, the present disclosure is not limited to this. As long as a radial attractive force required by the present disclosure can be generated between the rotor permanent magnet231and the stator permanent magnet232, the rotor permanent magnet231and the stator permanent magnet232may have any other forms of mono-magnetization directions (such as radially-magnetized or other suitable forms of mono-magnetization directions), and the rotor permanent magnet231and the stator permanent magnet232may have mono-magnetization directions in different magnetization directions (for example, the rotor permanent magnet231has an axial magnetization direction while the stator permanent magnet232has a radial magnetization direction, etc.). In addition, the rotor permanent magnet231and the stator permanent magnet232may also have non-single magnetization directions, such as tapered magnetization directions or other known or unknown non-single magnetization directions, as long as a radial attractive force can be generated between the rotor permanent magnet231and the stator permanent magnet232.

Returning toFIG.3, the magnetic suspension bearing20further includes a support structure24, which may be used to support the axial driving body233of the stiffness enhancing mechanism23. In the embodiment shown inFIG.3, the support structure24is used to support the stator21, the stator permanent magnet232, and the axial driving body233at the same time. In this exemplary embodiment, a central portion of the support structure24includes a boss, which includes a circular flange241and a cavity242surrounded by the circular flange. The circular flange241is used to support the stator permanent magnet232and abut the stator permanent magnet232against the lower surface2112of the horizontal portion of the stator teeth211. The axial driving body233is placed on the bottom of the cavity242of the boss. Preferably, the axial driving body233is placed on the bottom of the cavity242of the boss in a stationary manner.

The support structure24may be a part of the stator21. However, the present disclosure is not limited to this. The support structure24may be a part of a housing of the magnetic suspension bearing20, or a part of other suitable components of the magnetic suspension bearing20, such as a part of a rotor driver (for example, a driving motor) of the magnetic suspension bearing20.

Refer next toFIGS.6and7, which are a perspective view and a cross-sectional view of the magnetic suspension bearing20′ according to another embodiment of the present disclosure respectively. The magnetic suspension bearing20′ shown inFIGS.6and7has a similar structure to the magnetic suspension bearing20shown inFIGS.2and3, only with differences in the stator teeth and the support structure. Therefore, for the sake of simplicity, only the different parts will be described with the same components being omitted.

In the embodiment shown inFIGS.6and7, the stator21′ includes a circular stator body210′ and four linearly-shaped stator teeth211′. The four linearly-shaped stator teeth211′ are evenly disposed along the circumferential direction, and extend from the stator body210′ toward a center of the stator along the radial direction. Each linearly-shaped stator tooth211′ may have a uniform width (as shown inFIGS.6and7), but it may also have a non-uniform width, for example, the stator tooth211′ may have a tapered width, or the like.

Likewise, the rotor22′ may be in the shape of a disc, and there is a gap or airgap G′ between the stator teeth211′ and the rotor22′. The stator teeth211′ and the rotor22′ may be of the same thickness, and are ideally located at a same height. In other words, ideally, upper surfaces2111′ of the stator teeth211′ are aligned with an upper surface221′ of the rotor22′, lower surfaces2112′ of the stator teeth211′ are aligned with a lower surface222′ of the rotor22′, and inner peripheral surfaces2113′ of the stator teeth211are spaced apart from an outer peripheral surface223′ of the rotor22′ by an equal gap or airgap G′.

The stiffness enhancing mechanism of the magnetic suspension bearing20′ shown inFIGS.6and7is the same in structure and arrangement as the stiffness enhancing mechanism of the magnetic suspension bearing20shown inFIGS.2and3, which will not be repeated here. The magnetic suspension bearing20′ also includes a support structure24′, which is also used to support the stator, the stator permanent magnet, and the axial driving body. Different from the structure shown inFIG.3, the support structure24′ shown inFIG.7has a stepped shape, with its height gradually decreasing from the outer periphery to the center, thereby forming a cavity in the center. The outermost step of the support structure24′ is used to support the stator body210′, the intermediate step is used to support the stator permanent magnets and abut the stator permanents magnet against the lower surface2112′ of the stator teeth211′, and the axial driving body is placed on the bottom of the cavity in the center of the support structure24′.

Likewise, the support structure24′ may be a part of the stator21′. However, the present disclosure is not limited to this. The support structure24′ may also be a part of a housing of the magnetic suspension bearing20′, or a part of other suitable components of the magnetic suspension bearing20′, such as a part of a rotor driver (for example, a driving motor) of the magnetic suspension bearing20′.

Although the exemplary embodiments of the present disclosure have been described above with reference toFIGS.1to7, those skilled in the art should understand that the present disclosure is not limited to the specific structure that has been disclosed. Multiple changes and modifications may be made to the exemplary embodiments without substantively departing from the spirit and scope of the present invention. Accordingly, all the changes and modifications are encompassed within the protection scope of the present invention as defined by the claims.

For example, the magnetization directions of the rotor permanent magnet, the stator permanent magnet, and the axial driving body shown inFIG.4are just an example. Any permanent magnet magnetization directions that can generate a radial attractive force between the rotor and the stator and an axial repulsive force between the rotor and the axial driving body all conform to the principle of the present invention.

For another example, in the magnetic suspension bearings shown inFIGS.2-3and6-7, the rotor permanent magnet, the stator permanent magnet, and the axial driving body that is configured by a permanent magnet are all shown as an integral structure in a circular shape. However, the present invention is not limited to this. One or all of the rotor permanent magnet, the stator permanent magnet, and the axial driving body may be composed of a plurality of discrete permanent magnets spaced apart in the circumferential direction, as long as the desired stiffness enhancing effect can be reached. The plurality of the discrete permanent magnets may be arc-shaped. The use of a plurality of spaced-apart discrete permanent magnets can, for example, reduce the total mass of the permanent magnets to some extent, which is advantageous in applications where a higher requirement of the total mass is needed. However, when the plurality of spaced-apart discrete permanent magnets are used as the rotor permanent magnet, the stator permanent magnet or the axial driving body, uneven magnetic force may be generated in the circumferential direction due to discontinuity of the discrete permanent magnets in the circumferential direction. This may cause vibration of the rotor, and accordingly may affect the suspension stability of the rotor to some extent.

For another example, in the magnetic suspension bearings shown inFIGS.2-3and6-7, the support structure is shown to simultaneously support the stator, the stator permanent magnet, and the axial driving body. However, the present disclosure is not limited to this. The support structure is mainly used to support the axial driving body, and the stator and the stator permanent magnet may be supported by other suitable components. Further, in the magnetic suspension bearings shown inFIGS.2-3and6-7, the support structure is shown as an integral structure. However, the present disclosure is not limited to this, and the support structure may be assembled from multiple components.

The present disclosure is defined by the appended claims, and equivalents of these claims are also included in the scope of the present disclosure.