Motor and liquid conveyance device

Abstract

A water pump (1), which is an example of a motor, is provided with: a shaft (3); a cylinder (7) rotatably supported by the shaft (3); an impeller (6) fixed to the cylinder (7); a rotor (5) including a magnet (52) fixed to the impeller (6); a stator (4) surrounding the rotor (5); a coil (42) wound around the stator (4); a magnetic body (8) disposed with a predetermined gap with respect to the magnet (52) in the axial direction (X-axis direction); a first space (2s1) formed between the shaft (3) and the cylinder (7); and a second space (2s2) in which the rotor (5) is accommodated. The coil (42) faces the magnet (52) in the radial direction. The first space (2s1) and the second space (2s2) are spaces into which liquid enters. The cylinder (7) is movable in the axial direction with respect to the shaft (3), and in the axial direction, the magnet (52) is disposed between the magnetic body (8) and the impeller (6).

Description

Motor and liquid transport device

[0001] The present invention relates to a motor and a liquid transport device.

[0002] 2. Description of the Related Art A technique is known for providing a vibration-generating eccentric weight in a small air-operated vibration-generating motor (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2005-20980

[0004] However, the motor described in Patent Document 1, which uses a liquid, leaves room for improvement in terms of improving stability.

[0005] In one aspect, an object is to provide a motor that uses a liquid and that can improve stability.

[0006] In one aspect, the motor comprises a shaft, a cylinder rotatably supported on the shaft, an impeller fixed to the cylinder, a rotor including a magnet fixed to the impeller, a stator surrounding the rotor, a coil wound around the stator, a magnetic body arranged in the axial direction with a predetermined gap from the magnet, a first space between the shaft and the cylinder, a second space in which the rotor is housed, and a second space between the rotor and the stator, wherein the coil faces the magnet in the radial direction, the first space and the second space are spaces in which liquid is placed, the cylinder is movable in the axial direction relative to the shaft, and the magnet is arranged in the axial direction between the magnetic body and the impeller.

[0007] According to one aspect, stability can be improved in a motor that uses a liquid.

[0008] Fig. 1 is a perspective view of a water pump according to this embodiment, viewed from one axial side. Fig. 2 is a perspective view of the water pump shown in Fig. 1, viewed from the other axial side. Fig. 3 is a plan view of the water pump shown in Fig. 1. Fig. 4 is an exploded perspective view of the water pump shown in Fig. 1. Fig. 5 is a cross-sectional view of the water pump shown in Fig. 1. Fig. 6 is a cross-sectional view showing the flow of liquid when the water pump shown in Fig. 1 is operated. Fig. 7 is a diagram showing a simulation of pressure distribution in the internal space of the water pump shown in Fig. 1.

[0009] [Embodiment] A water pump (liquid transport device) as an embodiment of a motor according to the present invention will be described in detail below with reference to the drawings. Note that the dimensional relationships and ratios of elements in the drawings may differ from the actual situation. The dimensional relationships and ratios may also differ between the drawings.

[0010] For ease of explanation, the following description will use the mutually perpendicular X-axis, Y-axis, and Z-axis directions. The X-axis direction is, for example, the extension direction (axial direction) of the axis 3x of the shaft 3 included in the water pump 1. In addition, in the water pump 1 according to this embodiment, for example, the direction in which the liquid circulating inside is drawn in is the negative X-axis direction, and the direction in which the liquid is discharged is the positive Y-axis direction. Furthermore, in the water pump 1 according to this embodiment, the circumferential direction is the direction in which the rotor 5 rotates relative to the stator 4, and the radial direction is a direction that is included in a plane perpendicular to the axial direction, passes through the axis 3x of the shaft 3, and is perpendicular to the circumferential direction.

[0011] The configuration of a liquid transfer device (hereinafter referred to as water pump 1) according to this embodiment will be described with reference to FIGS. 1 to 5. FIG. 1 is a perspective view of the water pump 1 according to this embodiment, viewed from one axial side. FIG. 2 is a perspective view of the water pump 1 shown in FIG. 1, viewed from the other axial side. FIG. 3 is a plan view of the water pump 1 shown in FIG. 1. FIG. 4 is an exploded perspective view of the water pump 1 shown in FIG. 1. FIG. 5 is a cross-sectional view of the water pump 1 shown in FIG. 1. Note that in FIG. 4, the magnetic body 8 and the second case 22 are shown as separate entities for the sake of clarity, but in reality, the magnetic body 8 and the second case 22 are formed integrally, as described below. For ease of explanation, the third case 23 has been omitted from FIGS. 1 to 3 and 5.

[0012] As shown in FIG. 4, the water pump 1 of this embodiment includes a case 2, a shaft 3, a stator 4, a rotor 5, an impeller 6, and a cylinder 7 (see FIGS. 4 and 5).

[0013] The case 2 shown in Fig. 4 includes a first case 21, a second case 22, and a third case 23. Each of the cases 21, 22, and 23 is formed of, for example, synthetic resin. The first case 21 is disposed on the positive X-axis side in the axial direction of the case 2. The third case 23 is disposed on the negative X-axis side in the axial direction of the case 2. The second case 22 is disposed between the first case 21 and the third case 23 in the axial direction. Note that an O-ring may be provided between the first case 21 and the second case 22 in the X-axis direction, or an O-ring may be provided between the second case 22 and the third case 23 in the X-axis direction.

[0014] The case 2 has an internal space (space) 2s formed inside the case 2 by watertightly fastening the first case 21 to the second case 22 in the X-axis direction. In the water pump 1 according to this embodiment, a liquid circulates in the internal space 2s of the water pump 1. Here, the liquid may be, for example, a coolant. The internal space 2s may contain other liquids besides water. Examples of the other liquids include antifreeze such as propylene glycol or ethylene glycol, and anti-rust agents.

[0015] In other words, the water pump 1 accommodates the rotor 5 and the impeller 6 in an internal space 2s formed by the first case 21 and the second case 22, and circulates liquid inside the case 2.

[0016] The internal space 2s has a first space 2s1 between the shaft 3 and the cylinder 7 and a second space 2s2 in which the rotor 5 is housed (see FIG. 6). In other words, the case 2 has the first space 2s1 formed between the shaft 3 and the cylinder 7 and the second space 2s2 in which the rotor 5 is housed.

[0017] The first space 2s1 extends along the axial direction. The second space 2s2 includes a space 2s21 (hereinafter referred to as the "suction port side space") arranged on the suction port 21a side and a space 2s22 (hereinafter referred to as the "discharge port side space") arranged on the discharge port 21b side. The suction port side space 2s21 is arranged on the other axial side of the internal space 2s. The discharge port side space 2s22 extends along the axial direction.

[0018] In addition, the third case 23 is fixed to the second case 22 in a watertight manner in the X-axis direction, so that the stator 4 is disposed inside the case 2 .

[0019] The first case 21 shown in Figures 1 and 3 has an intake port 21a for drawing liquid into the internal space 2s of the water pump 1 and an outlet port 21b for discharging the liquid from the internal space 2s of the water pump 1. The water pump 1 according to this embodiment uses a liquid (coolant). The liquid circulating inside the water pump 1 is, for example, a liquid with a specific gravity heavier than water (e.g., propylene glycol or ethylene glycol). In other words, the density of the liquid used in the water pump 1 is greater than the density of air. Furthermore, the viscosity coefficient of the liquid used in the water pump 1 is greater than the viscosity coefficient of air.

[0020] As shown in FIG. 5 , the second case 22 includes a bottom wall 22a, an inner wall 22b, a top wall 22c, and an outer wall 22d. The second case 22 includes a first cup-shaped recess 22h1 formed by the bottom wall 22a and the inner wall 22b and opening toward the negative side of the X-axis (see FIG. 5 ). The second case 22 also includes a second cup-shaped recess 22h2 formed by the inner wall 22b, the top wall 22c, and the outer wall 22d and opening toward the positive side of the X-axis (see FIG. 5 ). The stator 4 is disposed in the second recess 22h2, and the rotor 5 is disposed in the first recess 22h1.

[0021] Bottom wall 22a is formed in a generally annular shape with a plane perpendicular to the X-axis direction. Inner wall 22b extends from the radially outer edge of bottom wall 22a about axis 3x toward the positive X-axis direction. Top wall 22c extends from the radially outer edge of inner wall 22b about axis 3x toward the negative X-axis direction. Outer wall 22d extends radially inward from axis 3x with a predetermined space between it and the radially outer edge of top wall 22c about axis 3x.

[0022] A through hole 2H is formed in bottom wall 22a, through which shaft 3 is inserted and fixed. Note that, in order to improve the watertightness of internal space 2s, a recess may be formed in bottom wall 22a instead of through hole 2H, supporting shaft 3 from the X-axis negative direction side. Furthermore, a thrust bearing may be provided in this recess.

[0023] A plurality of dynamic pressure grooves (not shown) are formed on the radially inner circumferential surface of the inner wall 22b, and are arranged, for example, at equal intervals in the circumferential direction of the axis 3x.

[0024] The shaft 3 is formed of, for example, a metal material in a cylindrical shape and extends, for example, in the X-axis direction.

[0025] The stator 4 is a part that generates a force for rotating the rotor 5. In the water pump 1 according to this embodiment, the stator 4 is disposed radially outward of the rotor 5. In other words, the stator 4 surrounds the rotor 5 from the radially outer side. The stator 4 includes a stator core 41, a plurality of coils 42, and an insulator 43.

[0026] The stator core 41 is made up of, for example, a plurality of magnetic members (an example of a magnetic body). The magnetic members are formed into a plate shape using metal such as silicon steel plate or soft magnetic steel plate such as electromagnetic steel plate, or amorphous metal. The stator core 41 is formed, for example, by stacking a plurality of such plate-shaped metal members in the X-axis direction. The stator core 41 is also disposed radially between the inner wall 22b and the outer wall 22d of the second case 22. In other words, the stator core 41 is disposed in the second recess 22h2 of the second case 22.

[0027] As shown in FIG. 4 , the stator core 41 includes a yoke 411 and a plurality of teeth 412. The yoke 411 is the main body of the stator core 41 and is configured in a cylindrical shape. The outer peripheral surface of the yoke 411 is fixed to the inner peripheral surface of the outer wall 22d. Meanwhile, each of the plurality of teeth 412 protrudes inward from the inner peripheral surface of the yoke 411 in the radial direction. Note that the radial ends of the teeth 412 may contact the inner wall 22b and be fixed to the inner wall 22b. In this case, the stator 4 can be stably fixed to the case 2.

[0028] The coils 42 are formed, for example, by winding a conductive wire having a conductive core around the teeth 412. Note that the coils 42 may also be configured such that a wound bobbin coil is fitted onto the teeth 412.

[0029] The insulator 43 is made of, for example, an insulating synthetic resin, and ensures insulation between the stator core 41 and the coil 42 .

[0030] The rotor 5 is a part that rotates relative to the stator 4. In the water pump 1 according to this embodiment, the rotor 5 is disposed radially inward of the stator 4. The rotor 5 includes, for example, a rotor core 51 made of a magnetic material and a magnet 52 that is a permanent magnet. The rotor 5 according to this embodiment is disposed in the second space 2s2.

[0031] The rotor core 51 according to this embodiment is fixed to, for example, an end portion 62 of the impeller 6. In other words, the rotor 5 is fixed to the impeller 6. That is, in the water pump 1 according to this embodiment, the rotor 5 is fixed to the impeller 6, and when the rotor 5 rotates in the circumferential direction relative to the stator 4, the impeller 6 rotates in the circumferential direction together with the rotation of the rotor 5. The rotor core 51 according to this embodiment is disposed on the negative side of the impeller 6 in the X-axis direction, and is formed in a cylindrical shape.

[0032] The magnet 52 is formed in a cylindrical shape. The inner peripheral surface of the magnet 52 is fixed to the outer peripheral surface of the rotor core 51. The magnet 52 is preferably a rare earth magnet such as a neodymium magnet, which has high magnetic properties. The magnet 52 may be formed integrally with the rotor core 51. In the rotor 5 according to this embodiment, the outer peripheral surface of the magnet 52 is an example of the outer surface of the rotor 5.

[0033] A magnetic gap is formed between the teeth 412 shown in Fig. 4 and the magnets 52 of the rotor 5. The stator 4 generates a magnetic field for rotating the magnets 52 of the rotor 5 by sequentially applying an externally supplied AC current to the coils 42 wound around each tooth 412. As a result, the magnets 52 of the rotor 5 rotate around the shaft 3 as the rotation axis due to the magnetic field generated by the coils 42. The stator 4 including the teeth 412 and the rotor 5 including the magnets 52 face each other in the radial direction via the inner wall 22b, thereby forming a magnetic cap.

[0034] The impeller 6 has a plurality of rotor blades 61 and an end portion 62. The rotor blades 61 are arranged on one axial side of the impeller 6 (the positive X-axis side), and the end portion 62 is arranged on the other axial side (the negative X-axis side).

[0035] The impeller 6 rotates together with the rotor 5 to draw in liquid through the intake port 21a and discharge the liquid through the exhaust port 21b. At this time, the rotor 5 and the impeller 6 disposed in the first recess 22h1 of the second case 22 come into contact with the liquid flowing inside the water pump 1 and are immersed in the liquid. On the other hand, the stator 4 disposed in the second recess 22h2 of the second case 22 is prevented from coming into contact with the liquid by the second case 22.

[0036] In the impeller 6 of this embodiment, the rotor blades 61 and the end portion 62 are integrally formed from, for example, a synthetic resin, etc. Alternatively, the rotor blades 61 and the end portion 62 of the impeller 6 may be formed separately and then the end portion 62 may be fixed to the rotor blades 61.

[0037] The cylinder 7 is formed in a cylindrical shape extending in the X-axis direction with its center at the axis 3x of the shaft 3. The outer peripheral surface of the cylinder 7 is fixed to the inner peripheral surface of the impeller 6.

[0038] Furthermore, the internal space 2s according to this embodiment has at least a first space 2s1 and a second space 2s2 through which the liquid (coolant) flows when the water pump 1 is in operation (see FIG. 6).

[0039] 6 is a gap formed between the inner circumferential surface 7 f of the cylinder 7 and the outer circumferential surface 3 f of the shaft 3 in the radial direction of the axis 3 x. The length of the first space 2 s 1 in the circumferential direction of the axis 3 x is, for example, 10 μm. The cylinder 7 according to this embodiment is a fluid bearing (slide bearing) in which a liquid is interposed between the inner circumferential surface 7 f of the cylinder 7 and the outer circumferential surface 3 f of the shaft 3 in the radial direction of the axis 3 x.

[0040] The second space 2s2 accommodates the rotor 5. The second space 2s2 includes an intake port-side space 2s21 and an exhaust port-side space 2s22. The intake port-side space 2s21 is formed between the rotor core 51 and the magnet 52 and the bottom wall 22a in the X-axis direction.

[0041] The outlet-side space 2s22 is formed between the inner circumferential surface of the second case 22 and the outer circumferential surface of the magnet 52 in the radial direction of the axis 3x. The outlet-side space 2s22 is an example of a space formed between the rotor 5 and the stator 4.

[0042] When the water pump 1 having such a configuration is operated, the liquid enters the internal space 2s from the intake port 21a, circulates inside the case 2, and is then discharged from the outlet port 21b.

[0043] The flow of liquid when the water pump 1 having the above configuration is in operation will now be described with reference to Figure 6. Figure 6 is a cross-sectional view showing the flow of liquid when the water pump 1 shown in Figure 1 is in operation.

[0044] Liquid drawn into the internal space 2s of the water pump 1 from the suction port 21a flows radially outward from the axis 3x of the shaft 3 due to the impeller 6 rotating in the circumferential direction about the axis 3x, and some of the liquid flows radially from the axis 3x into a first space 2s1 formed between the inner circumferential surface 7f of the cylinder 7 and the outer circumferential surface 3f of the shaft 3. In other words, the cylinder 7 according to this embodiment is a fluid bearing (slide bearing) that is supported on the shaft 3 in the radial direction via liquid.

[0045] In this case, the liquid that has flowed into the first space 2s1 flows in the negative direction of the X axis as indicated by arrow A1 in FIG. 6, and flows into the suction port side space 2s21.

[0046] Next, the liquid that has flowed into the suction port-side space 2s21 flows from the inside to the outside in the radial direction of the axis 3x, as indicated by arrow A2 in Figure 6, due to the rotating impeller 6. At this time, the liquid may flow not only in the direction of arrow A2, but also in other directions. Specifically, the liquid may circulate between the rotor core 51 and the bottom wall 22a in a vortex-like manner.

[0047] Next, as shown by arrow A3 in Figure 6, the liquid in the intake port side space 2s21 flows in the positive direction of the X-axis through the outlet port side space 2s22 formed between the second case 22 and the magnet 52 due to a dynamic pressure groove (not shown) facing in the positive direction of the X-axis, which is provided in the part of the inner wall 22b facing the magnet.

[0048] Thereafter, the pressure of the rotating impeller 6 causes the liquid to flow outward in the radial direction of the axis 3x, and is discharged from the discharge port 21b.

[0049] Furthermore, in the water pump 1 according to this embodiment, when a substance including liquid or gas (hereinafter referred to as "fluid") enters the internal space 2s, the pressure is low on one axial side (the positive X-axis side) of the impeller 6, which is a rotating body, and high on the other axial side (the negative X-axis side) of the impeller 6. The pressure inside the water pump 1 will now be specifically described with reference to FIG. 7 . FIG. 7 is a diagram showing a simulation of the pressure distribution in the internal space 2s of the water pump 1 shown in FIG. 1 . Note that, for convenience, FIG. 7 shows the pressure levels of the portions of the case 2 that come into contact with the fluid, rather than the pressure levels of the fluid itself.

[0050] On one axial side of the internal space 2s of the water pump 1, rotation of the impeller 6 causes fluid to flow radially outward relative to the axis 3x, resulting in lower pressure on the radially inner side (i.e., the portion where the impeller 6, which is a rotating body, is located). On the other hand, on the other axial side, there is less movement of liquid, resulting in less fluctuation in pressure. As a result, the pressure generated on one axial side of the impeller 6 is relatively smaller than the pressure generated on the other axial side of the impeller 6, and the impeller 6 is urged toward one axial side where the pressure is higher.

[0051] Furthermore, in the internal space 2s of the water pump 1 according to this embodiment, the rotor 5, impeller 6 and cylinder 7 are movable in the axial direction relative to the shaft 3. Therefore, when the impeller 6, which is a rotating body, moves from one side to the other side in the axial direction, the radially outer portion (outer peripheral edge) of the impeller 6 comes into contact with the inner peripheral edge of the first case 21, which can cause a deterioration in reliability and current consumption.

[0052] Therefore, in order to prevent the above problems from occurring, the water pump 1 according to this embodiment has the following configuration.

[0053] The water pump 1 further includes a magnetic body 8. The magnetic body 8 is made of a magnetic metal. More specifically, the magnetic body 8 is made of, for example, magnetic stainless steel (e.g., ferritic stainless steel such as SUS430 or martensitic stainless steel such as SUS410), or the magnetic metal is plated (for example, nickel plated on iron) to prevent rust from occurring.

[0054] The magnetic body 8 has an annular top view from one axial side and is formed in a disk shape with a relatively thin axial thickness. Furthermore, the magnetic body 8 has a through-hole 8H in the center through which the shaft 3 is inserted. The magnetic body 8 according to this embodiment is formed integrally with the resin second case 22 by, for example, insert molding. The magnetic body 8 is disposed, for example, in the suction port-side space 2s21 of the second space 2s2. In other words, the magnetic body 8 is disposed in the second space 2s2.

[0055] In the internal space 2s of the water pump 1, the magnet 52 of the rotor 5 and the magnetic body 8 are magnetically attracted to each other. In the water pump 1 according to this embodiment, the magnetic body 8, which is integrally formed with the second case 22, and the magnet 52 are attracted to each other, so that the rotor 5, impeller 6, and cylinder 7 on the non-stationary side move from one side to the other in the axial direction relative to the stationary case 2 and stator 4. This prevents the impeller 6 from floating up in the positive direction of the X axis due to a pressure difference.

[0056] In the water pump 1 according to this embodiment, the case 2, the shaft 3, the stator 4, and the magnetic body 8 are arranged on the fixed side, while the rotor 5, the impeller 6, and the cylinder 7 are arranged on the non-fixed side. In other words, the rotor 5, the impeller 6, and the cylinder 7 are movable in the axial direction relative to the case 2, the shaft 3, the stator 4, and the magnetic body 8.

[0057] As described above, the water pump 1 of this embodiment comprises the shaft 3, the cylinder 7 rotatably supported on the shaft 3, the impeller 6 fixed to the cylinder 7, the rotor 5 including the magnet 52 fixed to the impeller 6, the stator 4 surrounding the rotor 5, the coil 42 wound around the stator 4, the magnetic body 8 arranged in the axial direction (X-axis direction) with a predetermined gap from the magnet 52, a first space 2s1 between the shaft 3 and the cylinder 7, and a second space 2s2 in which the rotor 5 is accommodated, the coil 42 facing the magnet 52 in the radial direction, the first space 2s1 and the second space 2s2 being spaces into which liquid is placed, the cylinder 7 is movable in the axial direction relative to the shaft 3, and the magnet 52 is arranged in the axial direction between the magnetic body 8 and the impeller 6. As a result, in the water pump 1 in which the cylinder 7 is movable axially relative to the shaft 3, the magnetic force acting between the magnet 52 and the magnetic body 8 can prevent the impeller 6 from contacting the case 2 on one side of the axial direction (the positive X-axis side), thereby improving the stability of the water pump (motor) 1 that uses liquid.

[0058] Furthermore, in the water pump 1 according to this embodiment, the magnetic body 8 magnetically attracts the magnet 52 toward the magnetic body 8 in the axial direction (X-axis direction).

[0059] In the water pump 1 according to this embodiment, the magnetic body 8 is disposed in the second space 2s2.

[0060] In addition, the water pump 1, which is a liquid transport device according to this embodiment, comprises an internal space (space) 2s, a liquid (fluid) inside the internal space 2s, and an impeller 6 that transports the fluid, and a pressure difference occurs between one side and the other side of the impeller 6 in the axial direction, and the pressure generated on one side of the impeller 6 is smaller than the pressure generated on the other side of the impeller 6, and the impeller 6 is urged toward the other side in the axial direction where the pressure is higher.

[0061] The above description is based on an embodiment of the motor that is the water pump 1 according to the present invention, but it goes without saying that the present invention is not limited to the embodiment and various modifications are possible without departing from the spirit of the present invention. The present invention also includes configurations in which the components of the above-described embodiments are appropriately combined. Such modifications without departing from the spirit of the present invention are also included in the technical scope of the present invention, and this will be clear to those skilled in the art from the claims.

[0062] REFERENCE SIGNS LIST 1 Water pump (motor) 2s1 First space 2s2 Second space 3 Shaft 4 Stator 42 Coil 5 Rotor 52 Magnet 6 Impeller 7 Cylinder 8 Magnetic body

Claims

1. A motor comprising: a shaft; a cylinder rotatably supported on the shaft; an impeller fixed to the cylinder; a rotor including a magnet fixed to the impeller; a stator surrounding the rotor; a coil wound around the stator; a magnetic body arranged in the axial direction with a predetermined gap from the magnet; a first space between the shaft and the cylinder; and a second space in which the rotor is housed; wherein the coil faces the magnet in the radial direction; the first space and the second space are spaces in which liquid is filled; the cylinder is movable in the axial direction relative to the shaft; and the magnet is arranged in the axial direction between the magnetic body and the impeller.

2. The motor according to claim 1, wherein the magnetic body magnetically attracts the magnet toward the magnetic body in the axial direction.

3. The motor according to claim 1 or 2, wherein the magnetic body is disposed in the second space.

4. A liquid transport device comprising: a space; a fluid inside the space; and an impeller for transporting the fluid, wherein a pressure difference occurs between one axial side and the other axial side of the impeller, the pressure generated on one side of the impeller is smaller than the pressure generated on the other side of the impeller, and the impeller is urged towards the other axial side where the pressure is higher.

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