Magnetically controlled transmission and artificial heart using the same

Abstract

The magnetic flux path is adjusted in the motors that control the flow rates of the left and right heart pumps of an artificial heart so that the negative spring is suppressed. [Solution] The magnetically controlled transmission includes an input shaft that transmits the rotation of a motor to a first impeller, an output shaft that transmits the rotation of the input shaft to a second impeller supported by a magnetic bearing, an MR fluid interposed in the fitting portion between the input shaft and the output shaft, and a transmission means that controls the rotational speed transmitted from the input shaft to the output shaft by changing the viscosity of the MR fluid by flowing a magnetic flux through the MR fluid, wherein the transmission means includes a magnetic flux adjustment means that reduces the radial magnetic flux of the output shaft and increases the axial magnetic flux of the output shaft.

Description

[Technical Field]

[0001] The present invention relates to a magnetically controlled transmission that controls the rotation speed using MR fluid, and an artificial heart that controls blood flow balance using the magnetically controlled transmission. [Background Art]

[0002] Artificial hearts are used as one of the solutions to the problem of organ donor shortage in the treatment of patients with severe heart failure. Artificial hearts include ventricular assist devices that connect in parallel with the native heart to bypass blood for the purpose of bridging until heart transplantation or functional recovery of the native heart, and total artificial hearts that replace all functions of the heart after excision of the native heart.

[0003] In a total artificial heart, for example, one actuator simultaneously drives two left and right turbo pumps to rotate an impeller, which is a type of vane wheel, to pump blood. By employing a non-contact, wear-free magnetically levitated motor in the actuator, blood cell components are less prone to damage. A magnetically levitated motor is a motor equipped with a magnetic bearing that supports the impeller by magnetic levitation.

[0004] As described in Patent Document 1, an invention of a rotating device using a high-precision axial-type magnetically levitated rotary motor is disclosed, which is formed by combining magnetic circuits required for 5-degree-of-freedom magnetic levitation control (3 position axes in radial direction and axial direction, 2 tilt axes around radial axes) and rotation control, so that stable rotation without risk of shaft runout can be maintained even during high-speed rotation.

[0005] In the invention described in Patent Document 1, miniaturization and high blood compatibility are achieved by magnetic bearings, but since the left ventricular turbo pump and the right ventricular turbo pump operate at the same rotation speed, the flow rates of both the left ventricular turbo pump and the right ventricular turbo pump increase and decrease simultaneously.

[0006] In a real heart, the systemic and pulmonary circulations are balanced by adjusting the output of the left and right ventricular systems. For example, if blood accumulates in the lungs, the heart increases the output of the left ventricular system and decreases the output of the right ventricular system to correct the blood imbalance. In a total heart replacement, independent flow control of the left and right heart pumps is also necessary to balance blood volume.

[0007] Furthermore, because the left heart, which pumps blood into the aorta, typically needs to produce a larger output than the right heart, which pumps blood into the pulmonary artery, the left and right heart pumps have different pump designs, including the pump casing, impeller, and volute (fluid passage).

[0008] Therefore, as described in Patent Document 2, the invention of a magnetically controlled transmission is disclosed that balances blood flow by controlling the rotational speeds of the left heart pump and the right heart pump in an artificial heart, and furthermore, controls the rotational speeds of the impellers of the left heart pump and the right heart pump with a single motor, thereby making it compact and achieving blood flow balance.

[0009] This magnetically controlled transmission incorporates a magnetically controlled transmission using MR fluid or similar into the magnetically levitated impellers for two turbopumps, which are driven by a single magnetic levitation motor. This allows for independent control of the rotational speed and flow rate of the two turbopumps. Applying this to an artificial heart enables a compact design and independent flow rate control for the left and right heart pumps, thus avoiding pulmonary congestion and other complications. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Patent No. 3808811 [Patent Document 2] International Publication No. 2024 / 090290 [Overview of the project] [Problems that the invention aims to solve]

[0011] In the invention described in Patent Document 2, an MR fluid is interposed between an input shaft that rotates due to motor drive and an output shaft that receives rotational force from the input shaft. By changing the viscosity of the MR fluid using a magnetic field, the rotational speed (speed ratio) of the output shaft is also changed. However, if the magnetic flux generated by a permanent magnet or electromagnet flows in the radial direction of the shaft, the magnetic force acts as a negative spring and affects the magnetic levitation function.

[0012] Therefore, the present invention aims to adjust the magnetic flux path in a motor that controls the flow rate of the left heart pump and right heart pump of an artificial heart so that the negative spring is suppressed. [Means for solving the problem]

[0013] To solve the above problems, the magnetically controlled transmission of the present invention comprises an input shaft that transmits the rotation of a motor to a first impeller, an output shaft that transmits the rotation of the input shaft to a second impeller supported by a magnetic bearing, an MR fluid interposed in the fitting portion between the input shaft and the output shaft, and a transmission means that controls the rotational speed transmitted from the input shaft to the output shaft by changing the viscosity of the MR fluid by flowing a magnetic flux through the MR fluid, wherein the transmission means includes a magnetic flux adjustment means that reduces the radial magnetic flux of the output shaft and increases the axial magnetic flux of the output shaft.

[0014] Furthermore, in the magnetically controlled transmission, the transmission means is characterized in that an external magnet is positioned outside the MR fluid, and the magnetic flux adjustment means is characterized in that an internal magnet is positioned inside the MR fluid such that a magnetic flux is generated whose path is opposite to the magnetic flux of the external magnet, and the magnetic flux is adjusted so that it is axial at the position of the MR fluid.

[0015] Further, the artificial heart provided with the magnetically controlled transmission comprises a left heart pump connected to the input shaft or the output shaft, and a right heart pump connected to the output shaft or the input shaft, wherein the flow rates of the left heart pump and the right heart pump are independently controlled by varying the viscosity of the MR fluid. Effects of the Invention

[0016] According to the present invention, in a magnetically levitated motor for controlling the flow rates of a left heart pump and a right heart pump of an artificial heart, by reducing magnetic flux generated in the radial direction of a shaft and increasing magnetic flux generated in the axial direction of the shaft, a negative spring is suppressed, and the speed shifting performance from an input shaft to an output shaft via an MR fluid can be maintained. Brief Description of the Drawings

[0017] [Figure 1] It is an overview view showing an artificial heart using the magnetically controlled transmission according to the present invention. [Figure 2] It is a longitudinal sectional view showing an artificial heart using the magnetically controlled transmission according to the present invention. [Figure 3] It is a view showing the structure of the magnetically controlled transmission according to the present invention. [Figure 4] It is a graph showing experimental results of the magnetically controlled transmission according to the present invention. [Figure 5] It is a view showing magnetic field generating means of the magnetically controlled transmission according to the present invention. [Figure 6] It is a view showing a case where rotation speed is controlled using axial displacement in the magnetically controlled transmission according to the present invention. [Figure 7] It is a view showing magnetic flux that varies according to axial displacement of the magnetically controlled transmission according to the present invention. [Figure 8] It is a view showing a case where rotation speed is controlled using magnetic flux generated by a magnetically levitated motor in the magnetically controlled transmission according to the present invention. [Figure 9] It is a view showing an arrangement example of permanent magnets in magnetic field generating means of the magnetically controlled transmission according to the present invention. [Figure 10]It is a diagram showing a case where the magnetic flux generated by the magnetic field generating means of the magnetically controlled transmission according to the present invention is in the radial direction. [Figure 11] It is a diagram showing a case where the magnetic flux generated by the magnetic field generating means of the magnetically controlled transmission according to the present invention is adjusted in the axial direction. [Figure 12] It is a graph showing the shift performance test results and magnetic flux density analysis results of the magnetic flux generated by the magnetic field generating means of the magnetically controlled transmission according to the present invention. [Figure 13] It is a graph comparing the effects of magnetic flux generated by the magnetic field generating means of the magnetically controlled transmission according to the present invention. MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted. EXAMPLES

[0019] First, an artificial heart using the magnetically controlled transmission according to the present invention will be described. FIG. 1 is a general view showing an artificial heart using the magnetically controlled transmission. FIG. 2 is a longitudinal sectional view showing an artificial heart using the magnetically controlled transmission. In the present configuration, the left heart is arranged on the lower side and the right heart is arranged on the upper side, and power is transmitted from the left heart side to the right heart side, but the arrangement and the driving side may be reversed.

[0020] As shown in FIG. 1(a), the artificial heart 100 draws blood sucked from the pulmonary circulation into the left atrium into the left heart pump 300 through the inflow port 310, and discharges blood pumped out from the left ventricle from the discharge port 320 to the aorta for systemic circulation, and simultaneously draws blood sucked from the systemic circulation into the right atrium into the right heart pump 200 through the inflow port 210, and discharges blood pumped out from the right ventricle from the discharge port 220 to the pulmonary artery for pulmonary circulation.

[0021] As shown in Figure 1(b), in the left heart pump 300, the impeller 330 is rotated by the rotating shaft 500 to send blood from the inlet 310 to the outlet 320, and in the right heart pump 200, the impeller 230 is rotated by the rotating shaft 500 to send blood from the inlet 210 to the outlet 220. The rotating shaft 500 is rotated by a motor and its speed can be changed by a magnetically controlled transmission 400. The impellers 230 and 330 are impeller-shaped rotating bodies.

[0022] As shown in Figure 2, the rotating shaft 500 is formed by axially connecting an input shaft 510 and an output shaft 520 with an MR fluid 540 interposed between them, and the rotational speed of each is controlled by a magnetically controlled transmission 400.

[0023] In the artificial heart 100, the output shaft 520 is connected to the right heart pump 200, and the input shaft 510 is connected to the left heart pump 300. In the magnetic control transmission 400, the viscosity of the MR fluid 540 is varied by the magnetic field generating means 600, and the flow rates of the right heart pump 200 and the left heart pump 300 are controlled independently.

[0024] The input shaft 510 transmits the rotation of a single motor 420 to the impeller 330 of the left heart pump 300. The output shaft 520 receives the rotation of the input shaft 510, depending on the viscosity of the MR fluid 540, and transmits it to the impeller 230 of the right heart pump 200.

[0025] Furthermore, in order to increase the flow rate from the left heart pump 300 compared to the flow rate from the right heart pump 200, it is necessary to design the pumps with different shapes, such as the pump casing, impeller, and volute (fluid passage), for the left and right heart pumps. Specifically, this could involve changing the pump casing dimensions, impeller diameter, impeller blade shape and dimensions, and volute shape.

[0026] Furthermore, the right heart pump 200 is a turbopump in which the impeller 230 is supported by magnetic levitation using a magnetic bearing 410, but the magnetic support method may be different. The combination of input / output shafts and left / right pumps may also be reversed.

[0027] One end of the input shaft 510 is concave, and one end of the output shaft 520 is convex, and the MR fluid 540 is interposed in the fitting portion 530 between the input shaft 510 and the output shaft 520. The MR fluid 540 is a magnetorheological fluid in which ferromagnetic fine particles are dispersed in a medium, and its viscosity changes when a magnetic field is applied. When the magnetic field is weak, it becomes a liquid state with low viscosity, and when the magnetic field is strong, it becomes a semi-solid state with high viscosity. Alternatively, the end shape of the input shaft 510 may be convex and the end shape of the output shaft 520 may be concave.

[0028] Figure 3 shows the structure of a magnetically controlled transmission. Figure 4 is a graph showing the experimental results of the magnetically controlled transmission. The mating portion 530 of the input shaft 510 and the output shaft 520 has MR fluid 540 in between, allowing the output shaft 520 to rotate independently of the input shaft 510.

[0029] As shown in Figure 3(a), the magnetically controlled transmission 400 has a magnetic field generating means 600 which consists of a coil 610 and a yoke 620 arranged around the input shaft 510 and the output shaft 520. A magnetic field is generated by passing an electric current through the coil 610, and the yoke 620 guides the magnetic flux 630 to the region through which it is to be passed. For example, the electromagnet may be arranged with its magnetic poles aligned radially with respect to the rotating shaft 500, or with its magnetic poles aligned axially.

[0030] As shown in Figure 3(b), when the magnetic field generating means 600 passes magnetic flux 630 through the MR fluid 540 in the fitting portion 530, the viscosity of the MR fluid 540 increases. When the MR fluid 540 becomes less able to flow, the output shaft 520 rotates together with the input shaft 510, and the rotational speed increases. When the magnetic flux 630 decreases and the MR fluid 540 becomes easier to flow, the output shaft 520 rotates with a lag behind the input shaft 510, and the rotational speed decreases.

[0031] The viscosity of the MR fluid 540 is changed by altering the strength of the magnetic field applied to the MR fluid 540 and the way the magnetic flux 630 passes through it. Accordingly, the rotational speeds of the input shaft 510, which is rotated by power transmitted from the motor 420, and the output shaft 520, which is rotated by power transmitted from the input shaft 510 through the MR fluid 540, also change relatively.

[0032] Figure 4(a) shows the result of controlling the rotational speed of the output shaft 520 by changing the current value while fixing the position of the electromagnet in the magnetically controlled transmission 400, when the input shaft 510 is rotated by a motor 420 at 2000 rpm.

[0033] When the current value is low, the generated magnetic field is weak, and the viscosity of the MR fluid 540 is also low, so the rotational speed of the output shaft 520 is lower than that of the motor 420. When the current value is increased, the generated magnetic field becomes stronger, and the viscosity of the MR fluid 540 also increases, so the rotational speed of the output shaft 520 rises to about the same level as that of the motor 420.

[0034] Figure 4(b) shows the result of controlling the rotational speed of the output shaft 520 by changing the position of the electromagnet while keeping the current value constant in the magnetically controlled transmission 400 when the input shaft 510 is rotated by a motor 420 at 2000 rpm.

[0035] When the electromagnet is displaced axially and brought closer to the MR fluid 540, the influence of the magnetic field becomes stronger and the viscosity of the MR fluid 540 increases, so the rotational speed of the output shaft 520 rises to about the same as the rotational speed of the motor 420. When the electromagnet is moved away from the MR fluid 540, the influence of the magnetic field weakens and the viscosity of the MR fluid 540 decreases, so the rotational speed of the output shaft 520 becomes less than the rotational speed of the motor 420.

[0036] Figure 5 shows the means for generating the magnetic field of a magnetically controlled transmission. It illustrates an example in which the viscosity of the MR fluid 540 is increased by flowing a control magnetic flux 650 through the MR fluid 540 using an electromagnet, thereby increasing the rotational speed of the output shaft 520.

[0037] As shown in Figure 5(a), when coils 610 are arranged on all four sides around the output shaft 520, the coils 610 may be wound in a multi-pole type manner to generate the current-controlled magnetic flux 650, for example, from the horizontal direction towards the center and then outwards in a vertical direction. Alternatively, as shown in Figure 5(b), the coils 610 may be wound in a homopolar type manner to generate the current-controlled magnetic flux 650, for example, from all four sides towards the center. Note that for both the multi-pole and homopolar types, there are many variations in the arrangement of the coils, i.e., the way the magnetic flux is generated.

[0038] In this case, the multi-pole type, as shown in Figure 5(a), is one in which the magnetic flux distribution generated on the shaft surface by electromagnets, etc., consists of two or more poles, namely north and south poles. Adopting a multi-pole type has the advantage of allowing the electromagnets to be configured in the radial plane, thus reducing the axial height of the device. However, axial rotation causes changes in magnetic poles within the shaft, making it prone to eddy current losses.

[0039] Furthermore, in the homopolar type, as shown in Figure 5(b), the magnetic flux distribution generated on the axial surface by electromagnets, etc., consists of either one north pole or one south pole. In order to form an efficient magnetic circuit, the homopolar type requires the formation of a magnetic circuit that rotates the magnetic flux in the axial direction. If two locations are provided in the axial direction for generating the north pole and the south pole respectively, eddy current losses due to axial rotation can be reduced, but the device becomes taller in the axial direction. Depending on the three-dimensional design of the magnetic circuit, the routing of the magnetic flux (the path through which the magnetic flux flows) can vary widely.

[0040] As shown in Figure 5(c), permanent magnets 640 may be placed on all four sides around the output shaft 520 to generate bias magnetic flux 660 from the magnets, for example, so that it exits vertically from the side toward the center. Alternatively, as shown in Figure 5(d), the bias magnetic flux 660 from the magnets may be generated so that it exits from all four sides toward the center. The routing of the bias magnetic flux 660 (the path through which the magnetic flux flows) also changes depending on where the permanent magnets 640 are placed, and together with the routing of the electromagnet magnetic flux, there are a wide variety of methods for forming the magnetic circuit.

[0041] Furthermore, to increase or decrease the viscosity of the MR fluid 540, a control magnetic flux 650 is applied by current in the same direction as the bias magnetic flux 660 from the magnet. To decrease the viscosity of the MR fluid 540, a control magnetic flux 650 is applied by current in the opposite direction to the bias magnetic flux 660 from the magnet. The control magnetic flux 650 and bias magnetic flux 660 can be generated using permanent magnets or electromagnets, and there are many ways to generate the magnetic flux.

[0042] Figure 6 shows a case where rotational speed is controlled using axial displacement in a magnetically controlled transmission. Figure 7 shows the magnetic flux that fluctuates according to the axial displacement of the magnetically controlled transmission.

[0043] As shown in Figure 6, in the artificial heart 100a, the rotating shaft 500 is structured to be axially displaceable relative to the right heart pump 200 and the left heart pump 300. The input shaft 510, which is rotated by the motor 420, is magnetically supported radially by magnetic bearings 410 and 410a. The impeller 330 of the left heart pump 300 is directly rotated by the input shaft 510. The rotation of the input shaft 510 is transmitted to the output shaft 520 via a magnetically controlled transmission 400 using MR fluid 540, which rotates the impeller 230 of the right heart pump 200. Alternatively, the impeller 230 of the right heart pump 200 may be directly rotated by the input shaft 510, and the impeller 330 of the left heart pump 300 may be rotated by the output shaft 520 via the magnetically controlled transmission 400.

[0044] By using the input pressure difference between the right heart pump 200 and the left heart pump 300 to move the impellers 230 and 330 in the axial direction, passive control of the rotational speed (creating a rotational difference between the impellers 230 and 330) becomes possible. While the concave input shaft 510 is used as the main shaft and the convex output shaft 520 as the secondary shaft, the convex shaft could also be used as the main shaft and the concave shaft as the secondary shaft.

[0045] As shown in Figure 7(a), permanent magnets 640 are placed around the MR fluid 540 to generate a constant magnetic field, and a control magnetic flux 650a is flowed through the MR fluid 540 under this constant magnetic field. The constant magnetic field may also be generated by an electromagnet.

[0046] When the input shaft 510 and output shaft 520 are displaced axially, for example, by moving them upward or downward, the magnetic flux region 670 decreases, reducing the control magnetic flux 650a flowing through the MR fluid 540 and lowering the viscosity of the MR fluid 540.

[0047] As shown in Figure 7(b), if a projection 550 is provided on the circumferential surface of the input shaft 510 or output shaft 520, and the projection 550 comes into contact with the yoke 620 due to the axial displacement of the rotating shaft 500, it becomes a section through which the control magnetic flux 650a can easily pass. It is also possible to vary the magnetic flux density by utilizing the change in magnetic path resistance. Leakage flux or other methods may also be used.

[0048] Alternatively, the axial displacement of the input and output shafts 510 and 520 may be generated using the pressure difference between the left and right pumps 200 and 300, and the rotational speed may be changed by increasing or decreasing the magnetic flux applied to the magnetically controlled transmission 400 in a passive control manner. Alternatively, the pressure at the inlet 210 of the right heart pump 200 and the inlet 310 of the left heart pump 300 may be measured, and the input shaft 510 and output shaft 520 may be moved axially by a separate mechanism according to the input pressure difference to control the rotational speed of the input shaft 510 and output shaft.

[0049] Figure 8 shows a case in which the rotational speed is controlled using the magnetic flux generated by a magnetic levitation motor in a magnetically controlled transmission. The viscosity of the MR fluid may also be varied by utilizing the magnetic flux generated by the magnetic bearing 410 or the motor 420.

[0050] As shown in Figure 8(a), in the artificial heart 100b, the right heart pump 200 and the left heart pump 300 are similar and are magnetic levitation motors using magnetic bearings 410, and the viscosity of the MR fluid 540 is controlled by the magnetic flux generated therein. The shape of the magnetic control transmission 400a is disc-shaped, and increasing the magnetic flux of the coils of the magnetic bearing 410 increases the rotational speed. The magnetic control transmission 400a may be installed on the right heart side or the left heart side. If the magnetic control transmission 400a is installed on the motor side, opposite to the figure, increasing the magnetic flux of the motor 420 increases the rotational speed of the impeller on the motor side. The magnetic control transmission 400a may be installed on both the magnetic bearing side and the motor side.

[0051] As shown in Figure 8(b), the artificial heart 100c levitates the impellers 230 and 330 by controlling the magnetic force radially using magnetic bearings 410 and 410a, rather than controlling the magnetic force in the bearing direction. The magnetic control transmission 400b and the rotating shaft 500 are incorporated into the body that makes up the impellers 230 and 330, and the viscosity of the MR fluid 540 is varied by controlling the magnetic flux applied to the magnetic control transmission 400b by changing the control magnetic flux of the magnetic bearings 410 and 410a and the motor control magnetic flux. The magnetic control transmission 400b can utilize only the magnetic flux of the magnetic bearing, only the magnetic flux of the motor, or the magnetic flux of both the magnetic bearing and the motor.

[0052] By utilizing the magnetic bearings 410 and motor 420 used in the magnetic levitation motor, it becomes unnecessary to separately install electromagnets or permanent magnets 640 as magnetic field generating means 600, thus avoiding structural complexity. [Examples]

[0053] The arrangement of electromagnets and permanent magnets in the magnetically controlled transmission of the present invention will be described. Figure 9 shows an example of the arrangement of permanent magnets in the magnetic field generating means of the magnetically controlled transmission when an electromagnet coil that generates the control magnetic flux is arranged around the transmission as a single coil. As explained in Figure 5, the magnetic flux may be generated by permanent magnets or by electromagnets, and there are many methods for generating the magnetic flux.

[0054] Possible arrangements for the permanent magnets include embedding the permanent magnet 640 within the yoke 620 as shown in Figure 9(a), and arranging the permanent magnet 640 on the surface of the yoke 620 as shown in Figure 9(b). The yoke 620 can also take the form of a U-shaped claw pole as shown in Figures 9(a) and (b), or a case shape that covers the coil 610 as shown in Figure 9(c).

[0055] According to the present invention, by incorporating a magnetically controlled transmission using MR fluid or the like into the magnetically levitated impellers for two turbopumps driven by a single magnetic levitation motor, the rotational speed and flow rate of the two turbopumps can be controlled independently. Applying this to an artificial heart makes it possible to create a compact device with independent flow rate control for the left and right heart pumps, thus avoiding pulmonary congestion and other problems. [Examples]

[0056] The magnetic flux generated by the magnetic field generating means of the magnetic control transmission of the present invention will be described. Figure 10 shows the case where the magnetic flux generated by the magnetic field generating means is in the radial direction. Figure 11 shows the case where the magnetic flux generated by the magnetic field generating means is adjusted in the axial direction. Figure 12 is a graph showing the results of the transmission performance test and magnetic flux density analysis of the magnetic flux generated by the magnetic field generating means. Figure 13 is a graph comparing the effects of the magnetic flux generated by the magnetic field generating means.

[0057] As shown in Figure 10, the magnetically controlled transmission 400 includes an input shaft 510 that transmits the rotation of the motor 420 to the impeller 330, an output shaft 520 that transmits the rotation of the input shaft 510 to the impeller 230 supported by the magnetic bearing 410, and an MR fluid 540 interposed in the fitting portion 530 between the input shaft 510 and the output shaft 520.

[0058] The magnetically controlled transmission 400 further includes a transmission mechanism that controls the rotational speed transmitted from the input shaft 510 to the output shaft 520 by varying the viscosity of the MR fluid 540 by flowing magnetic fluxes such as control magnetic flux 650 and bias magnetic flux 660 into the MR fluid 540 using a magnetic field generating means 600. The magnetic field generating means 600 can be a coil 610 or a permanent magnet 640.

[0059] As shown in Figure 10(a), when no current is applied to the coil 610, the viscosity of the MR fluid 540 is high due to the bias magnetic flux 660, and the rotation of the input shaft 510 is directly transmitted to the output shaft 520, resulting in synchronous rotation.

[0060] As shown in Figure 10(b), when current is applied to the coil 610, a control magnetic flux 650 is generated, which reduces the viscosity of the MR fluid 540. As a result, the output shaft 520 slides, causing its rotational speed to decrease compared to that of the input shaft 510.

[0061] At this time, both the control magnetic flux 650 and the bias magnetic flux 660 are generated radially along the input shaft 510 and the output shaft 520, traversing the MR fluid 540 in the mating portion 530, and thus act as a negative spring against the magnetic levitation of the impellers 230 and 330.

[0062] As shown in Figure 11, the gear shifting means in the magnetically controlled transmission 400a includes a magnetic flux adjustment means that reduces the magnetic flux generated in the radial direction of the input shaft 510a and the output shaft 520a, and increases the magnetic flux in the axial direction of the input shaft 510a and the output shaft 520a.

[0063] In the gear shifting mechanism, for example, external magnets (a permanent magnet 640a for generating a bias magnetic flux 660a, and a coil 610a for generating a control magnetic flux 650a using an electromagnet) are arranged outside the MR fluid 540a.

[0064] The magnetic flux adjustment means then positions the internal magnet (permanent magnet 700 placed inside the output shaft 520a) so that a magnetic flux is generated inside the MR fluid 540a that is opposite to the magnetic flux of the external magnet, and adjusts the magnetic flux concentration point at the position of the MR fluid 540a so that it is axial.

[0065] The adjustment magnetic flux 710 generated by the internal magnet should adjust the control magnetic flux 650a and bias magnetic flux 660a from the external magnet, as well as the adjustment magnetic flux 710, to axial magnetic fluxes in the input shaft 510a and output shaft 520a so that they traverse the MR fluid 540a.

[0066] Furthermore, the method of generating and adjusting the adjustment flux 710 can be changed to match the state of the already installed bias flux 660a and control flux 650a. For example, if the bias flux is generated by a permanent magnet inside the output shaft 520a, the adjustment flux 710 may be generated by a permanent magnet or coil outside the output shaft 520a.

[0067] Furthermore, by changing the material of the input shaft 510a and the output shaft 520a, the bias magnetic flux 660a and the control magnetic flux 650a may be made to be axial magnetic fluxes that traverse the MR fluid 540a.

[0068] As shown in Figure 12(a), when the radial magnetic flux is reduced and the axial magnetic flux is increased, when the input shaft rotation speed is 2000 rpm, the output shaft rotation speed is approximately 2000 rpm with a coil current of 0A, and with a coil current of 1A, the rotation speed of the output shaft decreases to approximately 1750 rpm due to the change in the viscosity of the MR fluid, demonstrating that sufficient speed variation is achieved for artificial hearts.

[0069] As shown in Figure 12(b), in the magnetically controlled transmission 400, the radial magnetic flux density is large and the axial magnetic flux density is considerably small, and the degree to which the radial magnetic flux density needs to be increased in order to change speed is also large. In the magnetically controlled transmission 400a, the axial magnetic flux density is larger than the radial magnetic flux density, so it is not necessary to significantly increase the radial magnetic flux density in order to change speed.

[0070] As shown in Figure 13, assuming an input / output shaft displacement of -0.2 to 0.2 mm, the radial magnetic force of the magnetically controlled transmission 400 was 1.40 N / mm, whereas the radial magnetic force of the magnetically controlled transmission 400 was 0.25 N / mm. By reducing the radial magnetic flux, the radial magnetic force is significantly reduced, and the influence of the negative spring on magnetic levitation is also reduced.

[0071] According to the present invention, in a magnetic levitation motor that controls the flow rate of the left heart pump and right heart pump of an artificial heart, by reducing the magnetic flux generated in the radial direction of the shaft and increasing the magnetic flux generated in the axial direction of the shaft, it is possible to suppress negative springs and maintain the speed change performance from the input shaft to the output shaft via MR fluid.

[0072] The embodiments of the present invention have been described above, but the invention is not limited thereto. For example, the positions of the input shaft and output shaft may be swapped, the installation locations of the magnetically controlled transmissions may be swapped, or multiple magnetically controlled transmissions may be installed. Furthermore, the arrangement of the left heart pump and right heart pump may be swapped. Various magnetic levitation methods and magnetically controlled transmission control methods can be employed. This invention can be applied not only to total replacement artificial hearts, but also to ventricular assist devices and industrial pumps for rotational speed control. [Explanation of symbols]

[0073] 100: Artificial heart 200: Right heart pump 210:Inlet 220:Discharge port 230: Impeller 300: Left ventricular pump 310:Inlet 320:Discharge port 330: Impeller 400: Magnetically controlled transmission 400a: Magnetically controlled transmission 410: Magnetic bearing 420: Motor 500: Rotation axis 510: Input shaft 510a: Input shaft 520: Output shaft 520a: Output shaft 530: Fitting part 540:MR fluid 540a:MR fluid 550: Protrusion 600: Magnetic field generation means 610: Coil 610a: Coil 620: York 630: Magnetic flux 640: Permanent magnet 640a: Permanent magnet 650: Controlled magnetic flux 650a: Controlled magnetic flux 660: Bias magnetic flux 660a: Bias magnetic flux 670: Magnetic flux region 700: Permanent magnet 710: Adjusted magnetic flux

Claims

1. An input shaft that transmits the rotation of the motor to the first impeller, An output shaft that transmits the rotation of the input shaft to a second impeller supported by a magnetic bearing, An MR fluid interposed in the fitting portion between the input shaft and the output shaft, The system includes a speed control means that controls the rotational speed transmitted from the input shaft to the output shaft by changing the viscosity of the MR fluid by passing a magnetic flux through the MR fluid, The gear shifting means includes a magnetic flux adjustment means that reduces the radial magnetic flux of the output shaft and increases the axial magnetic flux of the output shaft. A magnetically controlled transmission characterized by the following features.

2. The aforementioned gear shifting means has an external magnet positioned outside the MR fluid, The magnetic flux adjusting means arranges the internal magnets so that a magnetic flux is generated inside the MR fluid such that the magnetic flux of the external magnets and the path of the internal magnets are opposite, and adjusts the magnetic flux so that it is axial at the position of the MR fluid. The magnetically controlled transmission according to feature 1.

3. An artificial heart comprising a magnetically controlled transmission according to claim 1 or 2, A left heart pump connected to the input shaft or the output shaft, It comprises a right heart pump connected to the output shaft or the input shaft, By varying the viscosity of the MR fluid, the flow rates of the left heart pump and the right heart pump are controlled independently. An artificial heart characterized by the following features.

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