Motor

Abstract

The invention provides a motor capable of reducing vibration. A motor (100) is provided with: a shaft (1); a pair of bearings (41, 42); a sleeve (7) accommodating the pair of bearings (41, 42); a magnet (21) fixed to either the shaft (1) or the sleeve (7); a coil (32) fixed to the other of the shaft (1) and the sleeve (7) and facing the magnet (21); and an elastic member (5) disposed between the pair of bearings (41, 42) and satisfying # imgabs0 # D is the outer diameter [m] of the elastic member (5), d is the wire diameter of the elastic member (5) # imgabs1 # gamma is the weight per unit volume [kg / m3] of the material of the elastic member (5), S is the no-load rotation speed [revolution / min] of the shaft (1), and g is the gravitational acceleration.

Description

This application is a divisional application of the patent application with the application number 202180033552.0, the filing date of June 7, 2021, and the invention title of "Motor". Technical Field

[0001] The present invention relates to a motor. Background Art

[0002] Conventionally, a motor having a bearing portion is known, the bearing portion being composed of a pair of bearings, a spring (elastic member) disposed between the pair of bearings and applying preload to the outer rings of the two bearings, and a sleeve that holds the outer rings of the pair of bearings (see, for example, Patent Document 1). Prior Art Documents Patent Documents

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-145897 Summary of the Invention Problems to be Solved by the Invention

[0004] In the motor as described above, a phenomenon sometimes occurs in which large vibrations are caused due to a wide rotational speed range of the motor during use. If large vibrations occur in the motor, the load on the bearings becomes large, which may affect the durability of the motor or make it insufficient to apply the pressure achieved by the spring to the bearings.

[0005] Therefore, the present invention has been completed in view of the above background, and an example of the problem is to provide a motor capable of reducing vibrations. Solutions to the Problems

[0006] The above object is achieved by the following present invention. That is, as one aspect of the motor of the present invention, it has: A shaft; A pair of bearings fixed to the shaft; A sleeve that houses the pair of bearings; A magnet directly or indirectly fixed to either the shaft or the sleeve; A coil directly or indirectly fixed to the other of the shaft and the sleeve, facing the magnet; and An elastic member disposed between the pair of bearings, The elastic member satisfies the following (Formula 1).

[0007] (Formula 1) In the above (Formula 1), they respectively represent the following: D represents the outer diameter [m] of the elastic member, and d represents the wire diameter of the elastic member γ represents the unit volume weight of the material of the elastic member [kg / m 3 , S represents the no-load rotational speed of the shaft [rpm], and g represents the acceleration due to gravity.

[0008] As one aspect of the motor of the present invention, it can be set to satisfy the following (Formula 1a) instead of satisfying the above (Formula 1). (Formula 1a) S < 1.42×10 4 ×d / D 2 In the above (Formula 1a), they respectively represent the following: D represents the outer diameter of the elastic member [m], and d represents the wire diameter of the elastic member S represents the no-load rotational speed of the shaft [rpm].

[0009] In addition, as one aspect of the motor of the present invention, preferably, it satisfies the following (Formula 1b) instead of satisfying the above (Formula 1). (Formula 1b) S < 0.71×10 4 ×d / D 2 In the above (Formula 2a), they respectively represent the following: D represents the outer diameter of the elastic member [m], and d represents the wire diameter of the elastic member S represents the no-load rotational speed of the shaft [rpm].

[0010] As another aspect of the motor of the present invention, it has: A shaft; A pair of bearings fixed to the shaft; A sleeve that houses the pair of bearings; A magnet fixed to either the shaft or the sleeve; A coil fixed to the other of the shaft and the sleeve, facing the magnet; and An elastic member disposed between the pair of bearings, The elastic member satisfies the following (Formula 2).

[0011] (Formula 2) In the above (Formula 2), they respectively represent the following: D represents the outer diameter of the elastic member [m], and d6 represents the wire diameter of the elastic member γ represents the unit volume weight of the material of the elastic member [kg / m 3 , S represents the no-load rotational speed of the shaft [rpm], and g represents the acceleration due to gravity.

[0012] As one aspect of the motor of the present invention, it can be set to satisfy the following (Formula 2a) instead of satisfying the above (Formula 2). (Formula 2a) S > 4.20×10 4 ×d / D 2 In the above (Formula 2a), they are respectively represented as follows: D represents the outer diameter [m] of the elastic member, and d represents the wire diameter of the elastic member S represents the no-load rotational speed [rpm] of the shaft.

[0013] In addition, as another aspect of the motor of the present invention, preferably, it satisfies the following (Formula 2b) instead of satisfying the above (Formula 2). (Formula 2b) S > 10.78×10 4 ×d / D 2 In the above (Formula 2b), they are respectively represented as follows: D represents the outer diameter [m] of the elastic member, and d represents the wire diameter of the elastic member S represents the no-load rotational speed [rpm] of the shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a cross-sectional view of an inner-rotor type motor according to an embodiment which is an example of the present invention. Figure 2 is a cross-sectional view of an outer-rotor type motor according to another embodiment which is an example of the present invention. Figure 3 is an enlarged view showing only the spring (elastic member) used in the motor of the embodiment and enlarged. Figure 4 is a graph showing the result of verifying the generation state of the vibration mode of the natural vibration of the spring (elastic member) in the embodiment, and is a graph in which the number of times of the vibration mode of the generated natural vibration is marked on the horizontal axis and the vibration frequency (Hz) of each natural vibration is marked on the vertical axis. Figure 5 is represented by diagonal hatching in Figure 4 the graph of the area that satisfies (Formula 1a) in the present invention under a specific condition X. Figure 6 is represented by diagonal hatching in Figure 4 the graph of the area that satisfies (Formula 2a) in the present invention under a specific condition X. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the motor according to the embodiment of the present invention will be described with reference to the drawings. The motor according to an embodiment of the present invention is Figure 1 either the inner rotor type motor exemplified in Figure 2 or the outer rotor type motor exemplified in Figure 1 This is a cross-sectional view of the inner rotor type motor 100 according to an embodiment of the present invention, Figure 2 and this is a cross-sectional view of the outer rotor type motor 200 according to another embodiment of the present invention.

[0016] It should be noted that in the description of this embodiment, when referring to above or below, it means the Figure 1 or Figure 2 up and down relationship in Figure 1 or Figure 2 and is not necessarily the same as the up and down relationship in the direction of gravity. In addition, in the description of this embodiment, when referring to left or right, it means the

[0017] left and right relationship in First, the inner rotor type motor 100 will be described. Figure 1 As shown in

[0018] the motor 100 is configured to include: a shaft 1; a pair of bearings 41, 42 fixed to the shaft 1; a sleeve 7 that houses the pair of bearings 41, 42; a spring (elastic member) 5 disposed between the pair of bearings 41, 42; a magnet 21 indirectly fixed to the shaft 1 through a rotor yoke (not shown); a stator 3 including a coil 32 opposed to the magnet 21; and a housing 6 that houses or fixes the stator 3 and the sleeve 7 inside and supports them.

[0019] The shaft 1 is located at the center of the motor 100 as viewed from above and extends in the up and down direction. The shaft 1 is made of, for example, aluminum for light weight. The shaft 1 is located inside the housing 6 except for the upper end portion, and the upper end portion protrudes upward from the housing 6 so that the rotational driving force of the motor 100 can be extracted externally. It should be noted that in this embodiment and the embodiments described later, when referring to the "circumferential direction", it means the circumferential direction of a circle centered on the rotation axis of the shaft 1.

[0020] It should be noted that the housing 6 can be formed, for example, by integrally molding a cup-shaped member composed of a small-diameter portion 61, a large-diameter portion 62, and a bottom plate 63, or by separately molding the small-diameter portion 61, the large-diameter portion 62, and the bottom plate 63 and bonding the two by a known method. For the heat dissipation of the internal space of the motor 100, for example, holes can be further formed in the bottom plate 63 or the bottom plate 63 can be formed of a material with openings such as a mesh. In addition, it can also be a housing without a bottom plate 63 originally and with an open lower part.

[0021] Inside the housing 6, a rotor is fixed below the shaft 1. The rotor is composed of a rotor yoke (not shown) fixed to the shaft 1 and magnets 21 assembled on the outer periphery of the rotor yoke. The rotor yoke is formed of a magnetic material, but can also be formed of a non-magnetic material such as aluminum if there are no problems in terms of characteristics.

[0022] On the other hand, the magnets 21 are assembled on the outer peripheral surface of the rotor yoke so as to face the coils 3 of the stator described below. The magnets 21 have an annular or cylindrical shape, and regions magnetized as N poles and regions magnetized as S poles are alternately arranged along the circumferential direction at a certain period.

[0023] The stator 3 surrounding the magnets 21 includes a stator core with only the tooth portions 34 shown and coils 32. The stator core is a laminate such as a silicon steel sheet, and is composed of an annular portion (core) (not shown) arranged coaxially with the shaft 1 and a plurality of tooth portions 34 extending from the annular portion toward the magnets 21. The stator 3 is held from the outside of the annular portion by the housing 6 which will be described in detail later.

[0024] The coils 32 are wound around the respective tooth portions 34 and are indirectly fixed to the sleeve 7 through the tooth portions 34 and the housing 6. The stator core and the coils 32 are insulated by an insulating material (insulator, not shown) formed of an insulator. It should be noted that an insulating film can also be coated on the surface of the stator core to insulate it from the coils 32 instead of the insulating material.

[0025] In the motor 100 of the present embodiment, due to the magnetic field generated by applying a controlled current to the coils 32, an attracting or repelling action acts between the coils 32 and the magnets 21 to apply a rotational force to the magnets 21, so that the shaft 1 to which the magnets 21 are indirectly fixed through the rotor yoke rotates together.

[0026] The shaft 1 is fixed in a state of being inserted into the bearings 41 and 42. The bearings 41 and 42 are assembled on the upper side of the shaft 1 on the opposite side of the side where the rotor is fixed, with the first bearing 41 and the second bearing 42 arranged at a certain interval. The second bearing 42 is located closer to the lower side where the rotor is fixed. In addition, the first bearing 41 is located on the upper end side.

[0027] The bearings 41 and 42 are so-called ball bearings composed of outer rings 41a and 42a, inner rings 41b and 42b, and balls (bearing balls) 41c and 42c sandwiched between the outer rings 41a and 42a and the inner rings 41b and 42b. Since the balls 41c and 42c roll between the outer rings 41a and 42a and the inner rings 41b and 42b, the rotational resistance of the inner rings 41b and 42b to the outer rings 41a and 42a is greatly reduced. The bearings 41 and 42 are formed of components such as hard metals such as iron and ceramics according to their functions. The shaft 1 is fixed to the inner rings 41b and 42b and is rotatable relative to the outer rings 41a and 42a.

[0028] The bearings 41 and 42 are accommodated in the sleeve 7. The sleeve 7 is a member having a cylindrical shape (particularly a cylindrical shape) and is formed of, for example, plastic or metal. There are no irregularities on the outer peripheral surface of the sleeve 7, but a locking groove (not shown) is provided on the inner peripheral surface of the sleeve 7 to lock and position the outer rings 41a and 42a of the bearings 41 and 42. It should be noted that the outer rings 41a and 42a of the bearings 41 and 42 only need to be fixed to the sleeve 7, and in addition to the locking structure described in this embodiment, they can also be fixed by, for example, fixing using an adhesive, and can be fixed by any fixing method.

[0029] A spring (elastic member) 5 is disposed between the pair of bearings 41 and 42. In the compressed state, both ends of the spring 5 abut against the outer rings 41a and 42a, and a preload is applied to the bearings 41 and 42. In this embodiment, the vibration of the motor 100 can be suppressed by adjusting the spring 5 to appropriate conditions. The conditions of the spring 5 will be described in detail later.

[0030] In this embodiment, a cylindrical member is constituted by the shaft 1, the sleeve 7, the spring 5, the first bearing 41, and the second bearing 42. By setting the cylindrical member in a state where the sleeve 7, the spring 5, the first bearing 41, and the second bearing 42 are pre-installed on the shaft 1 as one component, the assembly operation becomes easy during manufacturing. In addition, for example, when the bearings 41 and 42 are damaged, it is only necessary to replace the cylindrical member together, so the replacement operation is easy, the repair can be performed through an easy operation, and it also contributes to cost reduction.

[0031] In addition, it is relatively easy to adjust the rotational balance in the state of the cylindrical member at the stage where the number of components is small. Therefore, by pre-adjusting the rotational balance in the state of the cylindrical member, the operation of rotational balance during or after manufacturing or repairing the motor can be omitted or completed through a simple operation, and the manufacturing or repairing operation can be simplified. Therefore, even in this regard, it may contribute to cost reduction.

[0032] In particular, in the case of a cylindrical member including the rotor 1, it is easy to assemble the cylindrical member as a subassembly. As a result, centering during the assembly of each member in the cylindrical member is easy, and thus, the motor 100 can be easily manufactured.

[0033] The sleeve 7 is supported in such a manner that its outer peripheral surface is fixed to the inner peripheral surface of the small-diameter portion 61 of the housing 6. Accordingly, the shaft 1 is supported so as to be rotatable relative to the housing 6, and the rotational force of the motor 100 can be extracted from the shaft 1.

[0034] Next, an outer-rotor type motor 200 will be described. It should be noted that members having the same structure and function as those of the motor 100 in the above-described embodiment are denoted by the same reference numerals as those of the motor 100, and thus, detailed description thereof is omitted. As Figure 2 shown, the motor 200 is configured to include: a shaft 1; a pair of bearings 41 and 42 fixed to the shaft 1; a sleeve 7 that houses the pair of bearings 41 and 42; a spring (elastic member) 5 disposed between the pair of bearings 41 and 42; a magnet 22 indirectly fixed to the shaft 1 through a rotor yoke 23; and a stator 3' including a coil 33 opposed to the magnet 22.

[0035] The shaft 1 is located at the center of the motor 200 as viewed from above and extends in the vertical direction. The center of the disk portion 23a of the rotor yoke 23 is fixed to the upper side of the shaft 1. The rotor yoke 23 is composed of a disk-shaped disk portion 23a and a cylindrical portion 23b connected to the outer periphery of the disk portion 23a and extending downward. The rotor yoke 23 is formed of a magnetic material, but may also be formed of a non-magnetic material such as aluminum or plastic if there are no problems with the characteristics.

[0036] The rotor 2 is composed of the rotor yoke 23 fixed to the shaft 1 and the magnet 22 fitted to the inner periphery of the cylindrical portion 23b of the rotor yoke 23. The rotor 2 with the center of the disk portion 23a of the rotor yoke 23 fixed to the shaft 1 rotates integrally with the rotation of the shaft 1.

[0037] The magnets 22 are arranged to oppose each other so as to surround the coil 33 of the stator 3' described below. In the magnets 22, regions magnetized as N poles and regions magnetized as S poles are alternately provided along the circumferential direction at a certain period. The stator 3' surrounded by the magnets 22 includes a stator core (partially not shown) and a coil 33.

[0038] The stator core is a laminate such as a silicon steel sheet, and is composed of an annular portion (core) arranged coaxially with the shaft 1 and a plurality of tooth portions 35 extending outward from the annular portion toward the magnet 22. For the stator 3', the inner peripheral surface of the annular portion 31 is fixed to the outer peripheral surface of the sleeve 7.

[0039] The coil 33 is wound around each tooth portion 35 and is indirectly fixed to the sleeve 7 via the base portion 31. The stator core and the coil 33 are insulated by an insulating material (not shown) formed of an insulator. It should be noted that an insulating film may be coated on the surface of the stator core to insulate it from the coil 33 instead of the insulating material. In addition, the base portion 31 is formed of a magnetic material, but if there is no problem in characteristics, the base portion 31 may be formed of a non-magnetic material such as aluminum or plastic, or the base portion 31 may not exist.

[0040] In the motor 200 of the present embodiment, due to the magnetic field generated by applying a controlled current to the coil 33, an attracting or repelling action acts between the coil 33 and the magnet 22 to apply a rotational force to the magnet 22, so that the shaft 1 indirectly fixed with the magnet 22 through the rotor yoke 23 rotates integrally.

[0041] The shaft 1 is fixed in a state of being inserted into the bearings 41 and 42. The bearings 41 and 42 are assembled to the lower side of the opposite side of the shaft 1 where the disk portion 23a of the rotor 2 is fixed, with the first bearing 41 and the second bearing 42 arranged at a certain interval. The first bearing 41 is located above the disk portion 23a where the rotor 2 is fixed. In addition, the second bearing 42 is located at the lower end side. The bearings 41 and 42 are accommodated in the sleeve 7.

[0042] A spring (elastic member) 5 is provided between the pair of bearings 41 and 42 to apply a preload to the bearings 41 and 42. In the present embodiment, the vibration of the motor 200 can also be suppressed by adjusting the spring 5 to appropriate conditions. The conditions of the spring 5 will be described in detail later.

[0043] The sleeve 7 is supported in such a way that its outer peripheral surface is fixed to the inner peripheral surface of the circular ring portion 31 of the stator. Therefore, the shaft 1 is supported to be rotatable relative to the stator, and the rotational force of the motor 200 can be extracted from the shaft 1.

[0044] The conditions of the spring (elastic member) 5 suitable for use in the motors 100 and 200 of these embodiments will be described. Figure 3 It is an enlarged view in which only the spring 5 used in the motors 100 and 200 of the above embodiments is drawn out and enlarged.

[0045] The conditions suitable for the spring 5 are to satisfy at least one of the following two formulas.

[0046] (Formula 1)

[0047] (Formula 2)

[0048] More appropriate conditions for the spring 5 are to satisfy any one or more of the four formulas shown below. (Formula 1a) S < 1.42×10 4 ×d / D 2 (Formula 1b) S < 0.71×10 4 ×d / D 2 (Formula 2a) S > 4.20×10 4 ×d / D 2 (Formula 2b) S > 10.78×10 4 ×d / D 2

[0049] They are respectively expressed as follows: D in each of the above formulas represents the outer diameter [m] of the spring 5, and d represents the wire diameter of the elastic member. S represents the no-load rotational speed [revolutions / min.] of the shaft (hereinafter, the unit may sometimes be abbreviated as “rpm”), γ represents the unit volume weight [kg / m 3 of the material of the elastic member, and g represents the acceleration due to gravity. In particular, for D and d, their corresponding parts are shown in Figure 3 and are also common to all the formulas shown below.

[0050] For a helical spring such as the spring 5, when it is subjected to an impact from the outside, torsion is transmitted as a shock wave along the wire of the spring 5. This shock wave is called a surge wave, and the time T for this shock wave to reciprocate once along the wire of the spring 5 is called the shock time.

[0051] When the helical spring-shaped spring 5 is vibrated, when the period of this vibration is equal to the shock time T or the period of the vibration is in a relationship such as 1 / 2 or 1 / 3 of the shock time T, a resonance phenomenon called surging occurs. This shock time T can be calculated by the following (Formula 3).

[0052] (Formula 3) T = 2πND / a

[0053] In the above (Formula 3), the shock velocity a refers to the velocity when the shock wave moves along the wire of the spring 5. It is also common to all the formulas shown below. In addition, the shock velocity a can be calculated by the following (Formula 4).

[0054] (Formula 4)

[0055] In the above (Formula 4), they are respectively expressed as follows: c represents the spring index of the spring 5, G represents the transverse elastic coefficient of the material of the spring 5, γ represents the unit volume weight of the material of the spring 5, and g represents the acceleration due to gravity.

[0056] If it is set as then the impact velocity a is expressed by the following (Formula 5).

[0057] (Formula 5)

[0058] (Spring index c) = D / d. Usually, D is about 5 to 20 times larger than d. Therefore, it can be approximated as shown in the following (Formula 6).

[0059] (Formula 6)

[0060] From this, the following (Formula 7) is derived.

[0061] (Formula 7) (1 / a) ≒ (1 / k) × (D / d)

[0062] According to this (Formula 7) and the above (Formula 3), the impact time T is expressed by the following (Formula 8).

[0063] (Formula 8)

[0064] As described above, the impact time T is the time for the spring 5 to reciprocate once due to the vibration caused by the fluctuation, and its impact frequency fs can be calculated by (1 / T) as described above.

[0065] The present inventor prepared three kinds of springs with the number of turns (effective number of turns N) being 4, 6, and 8, and verified the generation status of the vibration modes of the natural vibrations of these springs through simulation. The results are shown in Figure 4 the curve graph of.

[0066] It should be noted that Figure 4 is a curve graph in which the number of times of the vibration mode of the generated natural vibration is marked on the horizontal axis, and the vibration frequency (Hz) of each natural vibration is marked on the vertical axis. In Figure 4 , the curve graph with black circles ● and dotted lines is the result of the spring with the effective number of turns N = 4, the curve graph with black squares ■ and solid lines is the result of the spring with the effective number of turns N = 6, and the curve graph with black triangles ▲ and single-dot dash lines is the result of the spring with the effective number of turns N = 8.

[0067] In addition, from Figure 3It can be seen that the spring 5 used in the above-described embodiment has an effective number of turns N = 6. That is, in this simulation, a spring different from the spring 5 used in the above-described embodiment was also used. Therefore, in the description related to this simulation, sometimes the reference numeral 5 is not marked and it is only described as "spring".

[0068] The conditions of this simulation are as follows. ·D = 12.9 mm ·d: 0.9 mm when the effective number of turns N = 4, 1 mm when the effective number of turns N = 6, and 1.1 mm when the effective number of turns N = 8 (since it is assumed that when the same load is applied, it will contract to the same position, so the wire diameter d is set thicker as the number of turns increases) · Load ※: 8 N ※ The load when an impact is applied horizontally from the left to the spring 5 in Figure 3 .

[0069] Through this verification, it was found that: as can be seen from the Figure 4 graph, the vibration mode of the natural vibration of the spring occurs up to the same number of times as the effective number of turns N of the spring. In addition, it was found that: the number of vibration modes and the vibration frequency (Hz) of the natural vibration roughly show a proportional relationship at small numbers of times, but for each spring, when the number of times exceeds 2 / 3 of the maximum number of vibration modes, the number of vibrations and the natural vibration number no longer show a proportional relationship.

[0070] It should be noted that in Figure 4 , an asterisk is marked at the point of 2 / 3 of the vibration mode as the maximum number of times in each graph. It was found that: in the vibration mode with a large number of times in the non-proportional relationship, the vibration frequency (Hz) of the natural vibration occurs in a relatively narrow frequency range (refer to the area surrounded by the ellipse in each graph of Figure 4 ).

[0071] The present inventor has found that when the basic frequency of the motor rotation (= number of revolutions per second) is higher than the impact frequency of a specific spring (satisfying the condition of (Equation 1a)) or when the basic frequency of the motor rotation (= number of revolutions per second) is lower than the impact frequency of a specific spring (satisfying the condition of (Equation 2a)), resonance does not occur between the motor and the spring, and vibration can be suppressed.

[0072] First, the condition satisfying (Equation 1a) will be described. When the basic frequency of the motor is set to fm and the impact frequency of the spring is set to fs, the basic frequency fm of the motor can be expressed by the following (Equation 9) as being less than or equal to 2 / 3 of the maximum number of vibration modes that is the equivalent number of times mode ( = number of turns times) of the impact frequency fs of the spring.

[0073] (Formula 9) fm < 2 / 3 × N × fs If the above (Formula 9) is rearranged, it becomes fm < 2 / 3 × N × (1 / T) fm < 2 / 3 × N × (k × d / 2πND 2 ) Derive the following (Formula 10).

[0074] (Formula 10) fm < k × d / (3π × D 2 )

[0075] The maximum rotational speed of the motor is the no-load rotational speed S. Therefore, if it is assumed that there is no problem as long as it is used at a speed less than the no-load rotational speed S, then according to fm = S / 60, the above (Formula 10) can be converted into the following (Formula 11).

[0076] (Formula 11) S < 20kd / πD 2

[0077] In (Formula 5), in order to simplify the formula, it is set as However, if a more accurate formula is to be used and substituted into the above (Formula 11) Then it is as shown in the following (Formula 1), which is the condition suitable for the spring.

[0078] (Formula 1)

[0079] In general spring materials (spring steel), G = 7850 N / mm 2 = 8.0 × 10 9 kgf / m 2 And γ = 7850 kg / m 3 , therefore, if it is applied to (Formula 1), it is as shown in the following (Formula 12).

[0080] (Formula 12) S < (20 × 0.22 × 10 4 / π) × d / D 2

[0081] If the (Formula 12) is rearranged, then the following (Formula 1a), which is the condition suitable for the spring, is derived.

[0082] (Formula 1a) S < 1.42 × 10 4 × d / D 2

[0083] That is, by designing the motor in such a way that the above (Formula 1a) is satisfied, resonance of the spring caused by the rotation of the motor can be avoided, and vibration of the motor can be reduced. For example, if the case where the effective number of turns N of the spring is 6 is taken as an example, then due to the wire diameter d = 1 mm and the outer diameter D = 12.9 mm (hereinafter, this condition will be referred to as "specific condition X"), the above (Formula 1a) is calculated as the following (Formula 1a-1), and the preferable range of the no-load rotational speed S (rpm) is obtained.

[0084] (Formula 1a-1) S < 1.42×10 4 ×1×10 -3 / (12.9×10 -3 ) 2 ≒85300

[0085] That is, under the specific condition X, it is only necessary to design the condition that the no-load rotational speed is less than 85300 rpm. Since this condition is set, therefore, in the graph of the solid line of the effective number of turns N = 6 in < Figure 4 , the motor is used at the point marked with an open asterisk. The motor will be used in the following area: the area that avoids the narrow range of vibration frequencies (the range surrounded by the ellipse around 1400 Hz to 1600 Hz) where the natural vibration of a large number of times (the fourth mode to the sixth mode) is generated on the lower side. The area that satisfies the above (Formula 1a) under the specific condition X is the Figure 5 area of the slant grid in the graph of < Figure 5 . It should be noted that Figure 4 is the graph that represents the area that satisfies the above (Formula 1a) under the specific condition X in the graph of <

[0086] If the no-load rotational speed is set in such a way that it becomes the area of the natural vibration of a large number of times of the mode, the natural vibration that resonates with the vibration generated by the rotation of the motor is likely to increase, and the vibration may be amplified. However, by using the motor in the area that avoids this area, the vibration can be reduced.

[0087] Regarding the specific condition X, it is an example in the case where the effective number of turns N of the spring is 6. In the case where the effective number of turns N is 4, (Formula 1a) is satisfied with the conditions of the wire diameter d = 0.9 mm and the outer diameter D = 12.9 mm. Thus, the motor is used at the vibration frequency (Hz) of the point marked with a black asterisk in the wavy line graph of the effective number of turns N = 4 in < Figure 4 . In addition, in the case where the effective number of turns N is 8, (Formula 1a) is satisfied with the conditions of the wire diameter d = 1.1 mm and the outer diameter D = 12.9 mm. Thus, the motor is used at the point marked with a shaded asterisk in the single dotted line graph of the effective number of turns N = 8 in < Figure 4 .

[0088] It should be noted that in the above description, for the sake of convenience, an example has been described in which, in the case of using a spring with a fixed outer diameter D and wire diameter d, the no-load speed S is used within a specified range to satisfy the above (Formula 1a). However, the motor can also be designed in such a way that the outer diameter D and wire diameter d of the spring are appropriately selected in accordance with the required no-load speed S of the motor to satisfy the above (Formula 1a), or the motor can be designed in such a way that all conditions are appropriately combined and selected in accordance with the required no-load speed S of the motor to satisfy the above (Formula 1a).

[0089] In order to also prevent resonance of the second harmonic component of the motor, it is required to set the speed lower than the no-load speed S3 obtained by the above (Formula 1a). That is, since the second harmonic component of the motor means twice the fundamental frequency fm, it is desirable to satisfy the following (Formula 13) in which the left side of the above (Formula 10) is set to "2fm".

[0090] (Formula 13) 2fm < k × d / (3π × D 2 )

[0091] If the above (Formula 13) is arranged in the same way as the above (Formula 10), the following (Formula 1b) is derived as a more appropriate condition.

[0092] (Formula 1b) S < 0.71 × 10 4 × d / D 2

[0093] That is, by designing the motor in such a way as to satisfy the above (Formula 1b), not only can resonance of the spring caused by the fundamental frequency of the motor be avoided, but also resonance of the spring caused by the second harmonic component can be avoided, and the vibration of the motor can be further reduced.

[0094] Next, the conditions for satisfying (Formula 2) will be described. If the following (Formula 14) or (Formula 14a) is satisfied, which represents that the fundamental frequency fm of the motor expressed by the formula is greater than the vibration mode of the maximum number of times n (i.e., the same as the number N of active turns) of the equivalent multiple of the impact frequency fs (= 1 / T) of the spring, it can be considered that resonance between the motor and the spring can be avoided.

[0095] (Formula 14) fm > n × fs

[0096] (Formula 14a) fm > N × (1 / T)

[0097] Moreover, if (Equation 8) is used to reorganize this (Equation 14a), it will be as follows in (Equation 14b) to (Equation 14c).

[0098] (Equation 14b) fm > N×(k×d / 2πND 2 )

[0099] (Equation 14c) fm > k×d / (2π×D 2 )

[0100] The practical rotational speed of the motor is generally 1 / 2 of the no-load rotational speed S. Therefore, fm = 1 / 2×S / 60. Thus, if it is assumed that there is no problem as long as it is used at 1 / 2 or more of the no-load rotational speed S, the above (Equation 14c) can be converted into the following (Equation 15).

[0101] (Equation 15) S > 60kd / πD 2

[0102] In (Equation 5), in order to simplify the formula, it is set as However, if a more accurate formula is to be adopted and substituted into the above (Equation 15) then it is as shown in the following (Equation 2) which is the condition suitable for the spring.

[0103] (Equation 2)

[0104] If G = 7850 N / mm 2 = 8.0×10 9 kgf / m 2 and γ = 7850 kg / m 3 are applied to (Equation 2), it will be as shown in the following (Equation 16).

[0105] (Equation 16) S > (60×0.22×10 4 / π)×d / D 2

[0106] If this (Equation 16) is reorganized, the following (Equation 2a) which is the condition suitable for the spring is derived.

[0107] (Equation 2a) S > 4.20×10 4 ×d / D 2

[0108] That is, by designing the motor in a manner that satisfies the above (Equation 2a), resonance of the spring caused by the rotation of the motor can be avoided, and the vibration of the motor can be reduced. For example, if the aforementioned specific condition X in the case where the effective number of turns N of the spring is 6 is taken as an example, then the above (Equation 2a) is calculated as the following (Equation 2a-1), and the preferred range of the no-load rotational speed S (rpm) is obtained.

[0109] (Equation 2a-1) S > 4.20×10 4 ×1×10 -3 / (12.9×10 -3 ) 2 ≒250000

[0110] That is, under the specific condition X, it is only necessary to design the condition that the no-load rotational speed exceeds 250000 rpm. Since this condition is set, the motor is used at a vibration frequency (Hz) exceeding the points of the sixth mode (maximum order mode) of the solid line graph of the effective number of turns N = 6 in Figure 4 . This uses the motor in the following region: the region above that avoids the highest frequency (around 1600 Hz) within the vibration frequencies that generate natural vibrations. The region that satisfies the above (Equation 2a) under the specific condition X is Figure 6 the hatched grid region in the graph of Figure 6 . It should be noted that Figure 4 is a graph that uses hatched grid to represent the region that satisfies the above (Equation 2a) under the specific condition X in the graph of

[0111] If the no-load rotational speed is set in the region that generates the natural vibration of any order mode, it may cause the vibration generated by the rotation of the motor to resonate with the natural vibration of any order mode and amplify the vibration. However, by using the motor in the region that avoids this region, the vibration can be reduced.

[0112] Regarding the specific condition X, it is an example in the case where the effective number of turns N of the spring is 6. In the case where the effective number of turns N = 4, (Equation 2a) is satisfied with the wire diameter d = 0.9 mm and the outer diameter D = 12.9 mm. Thus, the motor is used at a vibration frequency (Hz) exceeding the points of the fourth mode (maximum order mode) of the wavy line graph of the effective number of turns N = 4 in Figure 4 . In addition, in the case where the effective number of turns N = 8, (Equation 2a) is satisfied with the wire diameter d = 1.1 mm and the outer diameter D = 12.9 mm. Thus, the motor is used at a vibration frequency (Hz) exceeding the points of the eighth mode (maximum order mode) of the single dotted line graph of the effective number of turns N = 8 in Figure 4 .

[0113] It should be noted that in the above description, for the sake of convenience, an example has been described in which, in the case of a spring with a fixed outer diameter D and wire diameter d, the no-load speed S is used within a specified range to satisfy the above (Formula 2a). However, the motor can also be designed in such a way that the outer diameter D and wire diameter d of the spring are appropriately selected in accordance with the required no-load speed S of the motor to satisfy the above (Formula 2a), or the motor can be designed in such a way that all conditions are appropriately combined and selected in accordance with the required no-load speed S of the motor to satisfy the above (Formula 2a).

[0114] In order to also prevent resonance of the periodic component of the motor's bearing (bearing, the periodic component refers to the component of the vibration generated by the balls in the ball bearing), it is required to set the speed higher than the no-load speed S obtained by the above (Formula 2a). That is, since the bearing periodic component generally corresponds to 0.39 times the fundamental frequency, it is desirable to satisfy the following (Formula 17) in which the left side of the above (Formula 14c) is set to "0.39fm".

[0115] (Formula 17) 0.39fm > k × d / (2π × D 2 )

[0116] If the (Formula 17) is arranged in the same way as the above (Formula 14c), the following (Formula 2b) is derived as a more appropriate condition.

[0117] (Formula 2b) S > 10.78 × 10 4 × d / D 2

[0118] That is, by designing the motor in such a way as to satisfy the above (Formula 2b), not only can resonance with respect to the fundamental frequency of the motor be avoided, but also resonance with respect to the bearing periodic component can be avoided, and the vibration of the motor can be further reduced.

[0119] As described above, preferred embodiments of the motor of the present invention have been described, but the motor of the present invention is not limited to the structure of the above embodiments. For example, in the motor of the above embodiments, two schemes in which the magnet is indirectly fixed to the shaft to form the rotor and the coil is indirectly fixed to the sleeve to form the stator are given. However, the present invention is also applicable to a motor in which the coil is indirectly fixed to the shaft to form the rotor and the magnet is indirectly fixed to the sleeve to form the stator.

[0120] In addition, the fixing of either the shaft or the sleeve to the magnet or the coil may not be indirect fixing but direct fixing. As the effective number of turns N of the spring (elastic member) used, 6 was only cited in the above embodiment, and 4, 6, and 8 were only cited in the simulation for explanation, but it is not limited thereto. For example, it can be 9 or more, or an odd number.

[0121] It should be noted that in the above verification implemented by simulation, a general spring material (spring steel) was used as the material of the spring (elastic member), and the formula was calculated using conditions such as the transverse elastic modulus G and the unit volume weight γ of the spring material. However, the material of the spring (elastic member) is not limited to general spring steel. Considering the characteristics required of the spring (elastic member), it can be considered that regardless of the material, the conditions do not differ greatly. Therefore, in the present invention, springs (elastic members) of other materials can also be applied as they are.

[0122] In addition, those skilled in the art can appropriately modify the motor of the present invention according to the knowledge known in the past. As long as the relevant modifications still have the structure of the present invention, they are clearly included in the scope of the present invention. Explanation of reference numerals

[0123] 1: shaft; 2: rotor; 21, 22: magnets; 23: rotor yoke; 23a: disc portion; 23b: cylindrical portion; 3: stator; 31: ring portion; 32, 33: coils; 34, 35: tooth portions; 41: first bearing; 42: second bearing; 41a, 42a: outer rings; 41b, 42b: inner rings; 41c, 42c: balls; 5: spring (elastic member); 6: housing; 61: small-diameter portion; 62: large-diameter portion; 63: bottom plate; 64: opening; 7: sleeve; 100: motor; 200: motor.

Claims

1. A motor, the motor having: A shaft; A pair of bearings fixed to the shaft; A sleeve that houses the pair of bearings; A magnet directly or indirectly fixed to either the shaft or the sleeve; A coil directly or indirectly fixed to the other of the shaft and the sleeve, opposed to the magnet; and An elastic member disposed between the pair of bearings, The elastic member satisfies the following formula 1, In the above formula (1), they are respectively represented as follows: D represents the value of the outer diameter of the elastic member in meters, d represents the wire diameter of the elastic member in meters, γ represents the unit volume weight of the material of the elastic member in kg / m 3 in meters, S represents the no-load rotational speed of the shaft in revolutions per minute, g represents the acceleration due to gravity in m / s 2 in meters, G represents the transverse elastic coefficient of the material of the elastic member in kgf / m 2 in meters.

2. The motor according to claim 1, wherein The elastic member satisfies the following formula 1a, S < 1.42×10 4 × d / D 2 In the above formula 1a, they are respectively expressed as follows: D represents the value of the outer diameter of the elastic member in meters, and d represents the wire diameter of the elastic member in meters, and S represents the value of the no-load rotational speed of the shaft in revolutions per minute.

3. The motor according to claim 1, wherein The elastic member satisfies the following formula 1b, S < 0.71×10 4 ×d / D 2 In the above formula 1b, they are respectively expressed as follows: D represents the value of the outer diameter of the elastic member in meters, and d represents the wire diameter of the elastic member. The value in meters, and S represents the value of the no-load rotational speed of the shaft in revolutions per minute.

4. A motor, the motor having: A shaft; A pair of bearings fixed to the shaft; A sleeve that houses the pair of bearings; A magnet fixed to either the shaft or the sleeve; A coil fixed to the other of the shaft and the sleeve, opposed to the magnet; And An elastic member disposed between the pair of bearings, The elastic member satisfies the following formula 2, In the above formula (2), they are respectively represented as follows: D represents the value when the outer diameter of the elastic member is in meters, and d represents the wire diameter of the elastic member The value when in meters, γ represents the unit volume weight of the material of the elastic member in kg / m 3 The value when in units, S represents the no-load rotational speed of the shaft in revolutions per minute, and g represents the acceleration due to gravity in m / s 2 The value when in units, G represents the transverse elastic coefficient of the material of the elastic member in kgf / m 2 The value when in units.

5. The motor according to claim 4, wherein The elastic member satisfies the following formula 2a, S > 4.20×10 4 × d / D 2 In the above formula 2a, they are respectively represented as follows: D represents the value of the outer diameter of the elastic member in meters, and d represents the wire diameter of the elastic member. The value in meters, and S represents the value of the no-load speed of the shaft in revolutions per minute.

6. The motor according to claim 4, wherein The elastic member satisfies the following formula 2b, S > 10.78×10 4 ×d / D 2 In the above formula 2b, they are respectively represented as follows: D represents the value of the outer diameter of the elastic member in meters, and d represents the wire diameter of the elastic member in meters, and S represents the value of the no-load speed of the shaft in revolutions per minute.

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