motor

Abstract

The present invention provides a motor capable of reducing vibration. The motor (100) includes: a shaft (1); a pair of bearings (41, 42); a sleeve (7) that houses 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), facing the magnet (21); and an elastic member (5) disposed between the pair of bearings (41, 42), where D is the outer diameter [m] of the elastic member (5), d is the wire diameter φ [m] of the elastic member (5), γ is the unit volume weight [kg / m3] of the material of the elastic member (5), S is the no-load rotational speed [rpm] of the shaft (1), and g is the acceleration due to gravity.

Description

Technical Field

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

[0002] In the past, there is known a motor having a bearing portion, which is composed of a pair of bearings, a spring (elastic component) arranged 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 (for example, refer to patent document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-145897 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In the above-mentioned motor, sometimes a large vibration occurs due to the wide range of the motor's operating speed. If a large vibration occurs in the motor, the load on the bearing increases, which may sometimes affect the durability of the motor or make the pressure applied to the bearing by the spring insufficient.

[0008] Therefore, the present invention has been made in view of the above background, and provides a motor capable of reducing vibration as an example of the problem.

[0009] Solutions for solving problems

[0010] The above object is achieved by the following present invention. That is, as one embodiment of the motor of the present invention, it has:

[0011] axis;

[0012] a pair of bearings fixed to the shaft;

[0013] a sleeve accommodating the pair of bearings;

[0014] a magnet, fixed directly or indirectly to any one of the shaft and the sleeve;

[0015] a coil fixed directly or indirectly to the other of the shaft and the sleeve, and facing the magnet; and

[0016] an elastic member disposed between the pair of bearings,

[0017] The elastic member satisfies the following (Formula 1).

[0018] (Formula 1)

[0019]

[0020] The above formula (1) is respectively expressed as follows: D represents the outer diameter of the elastic member [m], d represents the wire diameter of the elastic member [m], γ represents the unit volume weight of the material of the elastic member [kg / m 3 ], S represents the no-load speed of the shaft [rev / min.], and g represents the acceleration due to gravity.

[0021] As the above-mentioned one aspect of the motor of the present invention, it is possible to satisfy the following (Formula 1a) instead of satisfying the above-mentioned (Formula 1).

[0022] (Formula 1a)

[0023] S<1.42×10 4 ×d / D 2

[0024] The above formula 1a is respectively expressed as follows: D represents the outer diameter of the elastic member [m], d represents the wire diameter of the elastic member [m], S represents the no-load speed of the shaft [rev / min.].

[0025] In addition, as the above-mentioned one aspect of the motor of the present invention, it is preferable that the following (Formula 1b) is satisfied instead of satisfying the above-mentioned (Formula 1).

[0026] (Formula 1b)

[0027] S<0.71×10 4 ×d / D 2

[0028] The above formula 2a is respectively expressed as follows: D represents the outer diameter of the elastic member [m], d represents the wire diameter of the elastic member [m], S represents the no-load speed of the shaft [rev / min.].

[0029] Another embodiment of the motor of the present invention comprises:

[0030] axis;

[0031] a pair of bearings fixed to the shaft;

[0032] a sleeve accommodating the pair of bearings;

[0033] a magnet fixed to either the shaft or the sleeve;

[0034] a coil fixed to the other of the shaft and the sleeve and facing the magnet; and

[0035] an elastic member disposed between the pair of bearings,

[0036] The elastic member satisfies the following (Formula 2).

[0037] (Formula 2)

[0038]

[0039] The above formula 2 is respectively expressed as follows: D represents the outer diameter of the elastic member [m], d6 represents the wire diameter of the elastic member [m], γ represents the unit volume weight of the material of the elastic member [kg / m 3 ], S represents the no-load speed of the shaft [rev / min.], and g represents the acceleration due to gravity.

[0040] As the above-mentioned one aspect of the motor of the present invention, it is possible to satisfy the following (Formula 2a) instead of satisfying the above-mentioned (Formula 2).

[0041] (Formula 2a)

[0042] S>4.20×10 4 ×d / D 2

[0043] The above formula 2a is respectively expressed as follows: D represents the outer diameter of the elastic member [m], d represents the wire diameter of the elastic member [m], S represents the no-load speed of the shaft [rev / min.].

[0044] In addition, as the above-mentioned another aspect of the motor of the present invention, it is preferable that the following (Formula 2b) is satisfied instead of satisfying the above (Formula 2).

[0045] (Formula 2b)

[0046] S>10.78×10 4 ×d / D 2

[0047] The above formula (2b) is respectively expressed as follows: D represents the outer diameter of the elastic member [m], d represents the wire diameter of the elastic member [m], S represents the no-load speed of the shaft [rev / min.]. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a cross-sectional view of an inner rotor type motor as an example embodiment of the present invention.

[0049] Figure 2 It is a cross-sectional view of an outer rotor type motor according to another embodiment as an example of the present invention.

[0050] Figure 3 This is an enlarged view in which only a spring (elastic member) used in the motor of the embodiment is extracted and enlarged.

[0051] Figure 4 It is a graph showing the results of verifying the generation conditions of the vibration modes of the natural vibrations of the spring (elastic component) in the implementation mode, and is a graph in which the orders of the vibration modes of the generated natural vibrations are marked on the horizontal axis and the vibration frequencies (Hz) of each natural vibration are marked on the vertical axis.

[0052] Figure 5 It is represented by a diagonal grid. Figure 4 A graph of the area in the graph of that satisfies (Formula 1a) in the present invention under a specific condition X.

[0053] Figure 6 It is represented by a diagonal grid. Figure 4 A graph of the area in the graph of that satisfies (Formula 2a) in the present invention under a specific condition X. DETAILED DESCRIPTION

[0054] Hereinafter, a motor according to an embodiment of the present invention will be described with reference to the drawings.

[0055] The motor according to the embodiment of the present invention is Figure 1 The inner rotor type motor and Figure 2 Any type of outer rotor type motor mentioned in the above may be used. Figure 1 is a cross-sectional view of an inner rotor type motor 100 according to an embodiment of the present invention. Figure 2 It is a cross-sectional view of an outer rotor type motor 200 according to another embodiment of the present invention.

[0056] It should be noted that in the description of this embodiment, when it is mentioned above or below, it means Figure 1 or Figure 2 The up-down relationship in the direction of gravity is not necessarily the same as the up-down relationship in the direction of gravity. In addition, in the description of this embodiment, when it is said to be left or right, it means Figure 1 or Figure 2 The left-right relationship in .

[0057] First, the inner rotor type motor 100 will be described.

[0058] like Figure 1As shown, the motor 100 is constructed to include: a shaft 1; a pair of bearings 41, 42 fixed to the shaft 1; a sleeve 7, accommodating the pair of bearings 41, 42; a spring (elastic member) 5, arranged 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 opposite to the magnet 21; and a housing 6, accommodating or fixing the stator 3 and the sleeve 7 inside and supporting them.

[0059] The shaft 1 is located at the center of the motor 100 when viewed from above, and extends in the up-down direction. The shaft 1 is formed of, for example, aluminum for the purpose of reducing 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 below, when the term "circumferential direction" is used, it means the circumferential direction of a circle centered on the rotation axis of the shaft 1.

[0060] The housing 6 is composed of a small diameter portion 61 at the top, a large diameter portion 62 at the bottom, and a bottom plate 63 that closes the opening on the large diameter portion 62 side (the bottom side) (wherein a circular opening 64 is provided at a position opposite to the lower end of the shaft 1). The housing 6 is made of, for example, a resin material or a metal material. In the internal space of the housing 6, it is needless to say that the rotor including the magnet 21 and the rotor yoke and the stator 3 including the coil 32 are accommodated, and most of the components of the other motor 100 are also accommodated.

[0061] It should be noted that the housing 6 can be formed by, for example, integrally molding a cup-shaped member consisting of a small diameter portion 61, a large diameter portion 62, and a bottom plate 63, or by molding the small diameter portion 61, the large diameter portion 62, and the bottom plate 63 separately and bonding the two together by a known method. For example, in order to dissipate heat in the internal space of the motor 100, the bottom plate 63 can be further opened with holes or formed with a mesh or other material having openings. In addition, the housing can be originally without a bottom plate 63 and with an opening at the bottom.

[0062] A rotor is fixed to the lower side of the shaft 1 in the housing 6. The rotor is composed of a rotor yoke (not shown) fixed to the shaft 1 and a magnet 21 attached to the outer periphery of the rotor yoke.

[0063] The rotor yoke is formed of a magnetic material, but may be formed of a non-magnetic material such as aluminum if there is no problem in terms of characteristics.

[0064] On the other hand, magnet 21 is mounted on the outer peripheral surface of the rotor yoke so as to face stator coil 3 described below. Magnet 21 has an annular or cylindrical shape, and regions magnetized to N poles and regions magnetized to S poles are alternately arranged at a certain period along the circumferential direction.

[0065] The stator 3 surrounding the magnet 21 includes a stator core (only the teeth 34 are shown) and a coil 32 .

[0066] The stator core is a laminate of silicon steel plates and includes an annular portion (core) not shown arranged coaxially with the shaft 1 and a plurality of teeth 34 extending from the annular portion toward the magnet 21. The stator 3 is held from the outside of the annular portion by a housing 6 described in detail later.

[0067] The coil 32 is wound around each tooth portion 34 and is indirectly fixed to the sleeve 7 through the tooth portion 34 and the housing 6. The stator core and the coil 32 are insulated by an insulating material (insulator, not shown) formed of an insulator. It should be noted that an insulating film may be applied to the surface of the stator core to insulate the coil 32 instead of the insulating material.

[0068] In the motor 100 of this embodiment, due to the magnetic field generated by applying a controlled current to the coil 32, an attraction or repulsion effect is exerted between the coil 32 and the magnet 21 to apply a rotational force to the magnet 21, thereby causing the shaft 1 to which the magnet 21 is indirectly fixed via the rotor yoke to rotate.

[0069] The shaft 1 is fixed in a state of being embedded in the bearings 41 and 42. The bearings 41 and 42 are arranged at a certain interval on the upper side of the shaft 1 opposite to the side where the rotor is fixed. The second bearing 42 is located near the lower side where the rotor is fixed. In addition, the first bearing 41 is located on the upper end side.

[0070] The bearings 41 and 42 are so-called ball bearings, which are 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 rotation 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 hard metals such as iron, ceramics, etc. according to their functions. The shaft 1 is fixed to the inner rings 41b and 42b and can rotate freely relative to the outer rings 41a and 42a.

[0071] The bearings 41 and 42 are accommodated in the sleeve 7. The sleeve 7 is a member having a cylindrical (particularly cylindrical) shape, and is formed of, for example, plastic or metal. There are no bumps on the outer circumferential surface of the sleeve 7, but a locking groove (not shown) is provided on the inner circumferential 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. In addition to the locking structure described in this embodiment, they can also be fixed by, for example, fixing with an adhesive, and any fixing method can be used.

[0072] A spring (elastic member) 5 is provided between the pair of bearings 41 and 42. In a compressed state, both ends of the spring 5 abut against the outer rings 41a and 42a, and 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 an appropriate condition. The conditions of the spring 5 will be described in detail later.

[0073] In the present embodiment, a cylindrical member is formed by the shaft 1, the sleeve 7, the spring 5, the first bearing 41 and the second bearing 42. The cylindrical member in which the sleeve 7, the spring 5, the first bearing 41 and the second bearing 42 are pre-installed on the shaft 1 is set as one component, thereby facilitating the assembly operation during manufacturing. In addition, for example, when the bearings 41 and 42 are damaged, the cylindrical member can be replaced together, so the replacement operation is easy, and the repair can be performed by easy operation, which also contributes to low cost.

[0074] In addition, it is relatively easy to adjust the rotational balance in the state of the barrel member, which is a stage where the number of parts is small. Therefore, by pre-adjusting the rotational balance in the state of the barrel member, the operation of rotational balance during or after manufacturing or repairing the motor can be omitted or completed by a simple operation, which can simplify the operation of manufacturing or repairing. Therefore, even in this point, it may contribute to cost reduction.

[0075] In particular, in the case of a cylindrical member including the rotor 1, the cylindrical member can be easily assembled as a subassembly, and as a result, centering of the components in the cylindrical member during assembly is easy, so that the motor 100 can be easily manufactured.

[0076] The sleeve 7 is supported so that its outer peripheral surface is fixed to the inner peripheral surface of the small diameter portion 61 of the housing 6. Therefore, the shaft 1 is supported rotatably relative to the housing 6, and the rotational force of the motor 100 can be extracted from the shaft 1.

[0077] Next, the outer rotor type motor 200 will be described.

[0078] It should be noted that components having the same structure and function as the motor 100 of the above-described embodiment are denoted by the same reference numerals as those of the motor 100 , and thus detailed description thereof will be omitted.

[0079] like Figure 2 As shown, the motor 200 is constructed to include: a shaft 1; a pair of bearings 41, 42 fixed to the shaft 1; a sleeve 7, accommodating the pair of bearings 41, 42; a spring (elastic component) 5, arranged between the pair of bearings 41, 42; a magnet 22, indirectly fixed to the shaft 1 through a rotor yoke 23; and a stator 3', including a coil 33 opposite to the magnet 22.

[0080] The shaft 1 is located at the center of the motor 200 as viewed from above and extends in the up-down direction. The center of the disc 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 disc-shaped disc portion 23a and a cylindrical portion 23b connected to the outer periphery of the disc portion 23a and extending downward.

[0081] The rotor yoke 23 is formed of a magnetic body, but may be formed of a non-magnetic body such as aluminum or plastic if there is no problem in terms of characteristics.

[0082] The rotor 2 is composed of a rotor yoke 23 fixed to the shaft 1 and a magnet 22 mounted on the inner periphery of a cylindrical portion 23b of the rotor yoke 23. The rotor 2 rotates with the rotation of the shaft 1, with the center of the disk portion 23a of the rotor yoke 23 fixed to the shaft 1.

[0083] The magnets 22 are disposed so as to face each other so as to surround a coil 33 of a stator 3' described below. In the magnets 22, regions magnetized to N poles and regions magnetized to S poles are alternately provided at a constant period along the circumferential direction.

[0084] The stator 3 ′ surrounded by the magnet 22 includes a stator core and a coil 33 , which are partially not shown.

[0085] The stator core is a laminate of silicon steel plates and includes an annular portion (core) disposed coaxially with the shaft 1 and a plurality of teeth 35 extending outward from the annular portion toward the magnet 22. In the stator 3', the inner circumference of the annular portion 31 is fixed to the outer circumference of the sleeve 7.

[0086] The coil 33 is wound around each tooth portion 35 and is indirectly fixed to the sleeve 7 through the base 31. The stator core and the coil 33 are insulated by an insulating material (not shown) formed by an insulator. It should be noted that an insulating film can be applied to the surface of the stator core to insulate the coil 33 instead of the insulating material. In addition, the base 31 is formed of a magnetic body, but if there is no problem in the characteristics, the base 31 can be formed of a non-magnetic body such as aluminum, plastic, or the base 31 may not exist.

[0087] In the motor 200 of this embodiment, due to the magnetic field generated by applying a controlled current to the coil 33, an attraction or repulsion effect is exerted between the coil 33 and the magnet 22 to apply a rotational force to the magnet 22, thereby causing the shaft 1 to which the magnet 22 is indirectly fixed via the rotor yoke 23 to rotate.

[0088] The shaft 1 is fixed in a state of being embedded in the bearings 41 and 42. The bearings 41 and 42 are arranged at a certain interval on the lower side of the shaft 1 opposite to the side where the disc portion 23a of the rotor 2 is fixed. The first bearing 41 is located on the upper side close to the disc portion 23a to which the rotor 2 is fixed. In addition, the second bearing 42 is located on the lower end side. The bearings 41 and 42 are accommodated in the sleeve 7.

[0089] A spring (elastic member) 5 is disposed between the pair of bearings 41 and 42 to apply preload to the bearings 41 and 42. In this embodiment, the vibration of the motor 200 can be suppressed by adjusting the spring 5 to an appropriate condition. The conditions of the spring 5 will be described in detail later.

[0090] The sleeve 7 is supported so that its outer peripheral surface is fixed to the inner peripheral surface of the annular portion 31 of the stator. Therefore, the shaft 1 is supported rotatably relative to the stator, and the rotational force of the motor 200 can be extracted from the shaft 1.

[0091] Conditions suitable for the spring (elastic member) 5 used in the motor 100 and the motor 200 of these embodiments will be described.

[0092] Figure 3 This is an enlarged view in which only the spring 5 used in the motor 100 or the motor 200 of the above-described embodiment is extracted and enlarged.

[0093] The condition suitable for the spring 5 is to satisfy at least one of the following two formulas.

[0094] (Formula 1)

[0095]

[0096] (Formula 2)

[0097]

[0098] A more appropriate condition for the spring 5 is to satisfy any one or more of the following four formulas.

[0099] (Formula 1a)

[0100] S<1.42×10 4 ×d / D 2

[0101] (Formula 1b)

[0102] S<0.71×10 4 ×d / D 2

[0103] (Formula 2a)

[0104] S>4.20×10 4 ×d / D 2

[0105] (Formula 2b)

[0106] S>10.78×10 4 ×d / D 2

[0107] They are respectively expressed as follows: In the above formulas, D represents the outer diameter of the spring 5 [m], and d represents the wire diameter of the elastic member [m], S represents the no-load speed of the shaft [rpm] (hereinafter, the unit may be abbreviated as "rpm"), and γ represents the unit volume weight of the material of the elastic member [kg / m 3 ], g is the acceleration due to gravity. In particular, for D and d, Figure 3 The corresponding parts are shown in , and are common to all the formulas shown below.

[0108] When a coil spring such as the spring 5 receives an external impact, the 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 the shock wave to reciprocate once along the wire of the spring 5 is called a surge time.

[0109] When the coil spring 5 is vibrated, if the period of the vibration is equal to the impact time T or the period of the vibration is 1 / 2 or 1 / 3 of the impact time T, a resonance phenomenon called surging occurs.

[0110] The impact time T can be calculated by the following (Formula 3).

[0111] (Formula 3)

[0112] T=2πND / a

[0113] In the above (Formula 3), the impact velocity a refers to the velocity when the shock wave moves along the wire of the spring 5. This is also common to all the equations shown below.

[0114] In addition, the impact velocity a can be calculated by the following (Formula 4).

[0115] (Formula 4)

[0116]

[0117] In the above (Formula 4), c represents the spring index of the spring 5, G represents the lateral 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.

[0118] If set to Then, the impact velocity a is expressed by the following (Formula 5).

[0119] (Formula 5)

[0120]

[0121] (Spring index c)=D / d. Generally, D is about 5 to 20 times larger than d. Therefore, it can be approximated as shown in the following (Formula 6).

[0122] (Formula 6)

[0123]

[0124] From this, the following (Formula 7) is derived.

[0125] (Formula 7)

[0126] (1 / a)≒(1 / k)×(D / d)

[0127] According to this (Formula 7) and the above (Formula 3), the impact time T is expressed by the following (Formula 8).

[0128] (Formula 8)

[0129]

[0130] As described above, the impact time T is the time it takes for the spring 5 to reciprocate once due to vibration caused by the wave, and the impact frequency fs thereof can be calculated by (1 / T) as described above.

[0131] The inventors prepared three types of springs with 4, 6, and 8 turns (effective turns N), and verified the generation of vibration modes of the natural vibrations of these springs by simulation. The results are shown in Figure 4 Graph of the curve.

[0132] It should be noted that Figure 4 This is a graph in which the order of the vibration mode of the generated natural vibration is plotted on the horizontal axis and the vibration frequency (Hz) of each natural vibration is plotted on the vertical axis. Figure 4In the figure, the curve graph with black circles ● and dashed lines is the result of the spring with effective number of turns N=4, the curve graph with black squares ■ and solid lines is the result of the spring with effective number of turns N=6, and the curve graph with black triangles ▲ and single-point dashed lines is the result of the spring with effective number of turns N=8.

[0133] In addition, by Figure 3 It is known that the spring 5 used in the above 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 embodiment is also used. Therefore, in the description related to this simulation, the reference numeral 5 may not be added but simply described as "spring".

[0134] The conditions of this simulation are as follows.

[0135] D = 12.9 mm

[0136] 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 the wire will shrink to the same position when the same load is applied, the wire diameter d is set to be larger when the number of turns is large)

[0137] ·Load※:8N

[0138] ※from Figure 3 The load when an impact is applied horizontally to the spring 5 from the left side.

[0139] Through this verification, it was found that: Figure 4 As can be seen from the curve graph, the vibration mode of the natural vibration of the spring will occur until the number of times is the same as the effective number of turns N of the spring.

[0140] In addition, it was found that the order of the vibration mode and the vibration frequency (Hz) of the natural vibration showed a roughly proportional relationship when the order was small, but for each spring, when the order exceeded 2 / 3 of the maximum order of the vibration mode, the vibration order and the natural vibration number were no longer proportional.

[0141] It should be noted that in Figure 4 In each graph, an asterisk is marked on the point which is 2 / 3 of the maximum order vibration mode.

[0142] It was found that in the non-proportional, large-order vibration mode, the vibration frequency (Hz) of the natural vibration occurs in a narrow frequency range (refer to Figure 4 The area enclosed by the ellipses in each curve graph).

[0143] The inventors of the present invention have discovered that when the basic frequency of the motor's rotation (= the number of revolutions per second) is higher than the impact frequency of a specific spring (satisfying the condition of (Formula 1a)) or when the basic frequency of the motor's rotation (= the number of revolutions per second) is lower than the impact frequency of a specific spring (satisfying the condition of (Formula 2a)), resonance will not occur between the motor and the spring and vibration can be suppressed.

[0144] First, the conditions for satisfying (Formula 1a) will be described.

[0145] When the basic frequency of the motor is set to fm and the impact frequency of the spring is set to fs, the following (Formula 9) can express that the basic frequency of the motor fm is less than 2 / 3 of the maximum order vibration mode equivalent to the order mode times (= number of turns) of the impact frequency fs of the spring.

[0146] (Formula 9)

[0147] fm<2 / 3×N×fs

[0148] If the above (Formula 9) is rearranged, it becomes

[0149] fm<2 / 3×N×(1 / T)

[0150] fm<2 / 3×N×(k×d / 2πND 2 ),

[0151] The following (Formula 10) is derived.

[0152] (Formula 10)

[0153] fm <k×d / (3π×D 2 )

[0154] The maximum rotation speed of the motor is the no-load rotation speed S. Therefore, if it is assumed that there is no problem as long as it is used at a speed lower than the no-load rotation speed S, the above (Formula 10) can be converted into the following (Formula 11) according to fm=S / 60.

[0155] (Formula 11)

[0156] S<20kd / πD 2

[0157] In (Formula 5), ​​in order to simplify the formula, However, if we substitute into the above formula (Formula 11) This is as shown in the following (Formula 1) which is a condition suitable for the spring.

[0158] (Formula 1)

[0159]

[0160] In general spring materials (spring steel), G = 7850N / mm 2 =8.0×10 9 kgf / m 2 And γ=7850kg / m 3 , therefore, if it is applied to (Formula 1), it becomes as shown below (Formula 12).

[0161] (Formula 12)

[0162] S<(20×0.22×10 4 / π)×d / D 2

[0163] When this (Formula 12) is rearranged, the following (Formula 1a) is derived as a condition suitable for the spring.

[0164] (Formula 1a)

[0165] S<1.42×10 4 ×d / D 2

[0166] That is, by designing the motor so as to satisfy the above (Formula 1a), resonance of the spring caused by the rotation of the motor can be avoided, and vibration of the motor can be reduced.

[0167] For example, if we take the case where the effective number of coils of the spring is N = 6, then due to the wire diameter d = 1 mm and the outer diameter D = 12.9 mm (hereinafter, this condition is referred to as "specific condition X"), the above (Formula 1a) is calculated as the following (Formula 1a-1) to find the preferred range of the no-load speed S (rpm).

[0168] (Formula 1a-1)

[0169] S<1.42×10 4 ×1×10 -3 / (12.9×10 -3 ) 2 ≒85300

[0170] That is, under the specific condition X, it is sufficient to design the no-load speed to be less than 85300rpm. Figure 4 The motor is used at the point marked with a hollow asterisk in the solid line graph of the effective number of turns N = 6. This will use the motor in the following area: the area on the lower side that avoids the area with a narrow vibration frequency range (the range surrounded by the ellipse around 1400Hz to 1600Hz) where the natural vibration of many orders (fourth mode to sixth mode) is generated. The area that satisfies the above (Formula 1a) under the specific condition X is Figure 5The area of ​​the oblique grid in the curve graph. It should be noted that Figure 5 It is represented by a diagonal grid. Figure 4 A graph of the area in the graph of that satisfies the above (Formula 1a) under a specific condition X.

[0171] If the no-load speed is set in a manner that forms a region where natural vibrations of many order modes are generated, the natural vibrations that resonate with the vibrations generated by the rotation of the motor are likely to increase, and the vibrations may be amplified. However, the vibrations can be reduced by using the motor in a region avoiding this region.

[0172] As for the specific condition X, the example is when the effective number of coils N of the spring is 6. When the effective number of coils N is 4, the conditions of wire diameter d = 0.9 mm and outer diameter D = 12.9 mm are satisfied (Formula 1a). Figure 4 The vibration frequency (Hz) of the point marked with a black asterisk in the curve of the wavy line with the effective number of turns N = 4 is the motor used. In addition, when the effective number of turns N = 8, the conditions of wire diameter d = 1.1 mm and outer diameter D = 12.9 mm satisfy (Formula 1a), and thus, in the case of less than Figure 4 The motor is used at the point marked with a shaded asterisk in the one-dot chain line graph with the effective number of turns N=8.

[0173] It should be noted that in the above description, for the sake of convenience, an example is described in which the above (Formula 1a) is satisfied by using the no-load speed S within a prescribed range when a spring with a fixed outer diameter D and a wire diameter d is used. However, the motor can be designed in a manner that satisfies the above (Formula 1a) by appropriately selecting the outer diameter D and the wire diameter d of the spring in comparison with the no-load speed S required by the motor, or the motor can be designed in a manner that satisfies the above (Formula 1a) by appropriately combining and selecting all conditions in comparison with the no-load speed S required by the motor.

[0174] In order to 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 is twice the fundamental frequency fm, it is expected to satisfy the following (Formula 13) where the left side of the above (Formula 10) is set to "2fm".

[0175] (Formula 13)

[0176] 2fm <k×d / (3π×D 2 )

[0177] If this (Formula 13) is rearranged in the same manner as the above-mentioned (Formula 10), the following (Formula 1b) is derived as a more appropriate condition.

[0178] (Formula 1b)

[0179] S<0.71×10 4 ×d / D 2

[0180] That is, by designing the motor in a manner that satisfies the above (Formula 1b), not only the resonance of the spring caused by the fundamental frequency of the motor but also the resonance of the spring caused by the second harmonic component can be avoided, and the vibration of the motor can be further reduced.

[0181] Next, the conditions for satisfying (Formula 2) are described.

[0182] If the following (Formula 14) or (Formula 14a) is satisfied, in which the fundamental frequency fm of the motor is greater than the vibration mode of the maximum order corresponding to the order mode times n (i.e., the same as the number N of effective turns) of the impact frequency fs of the spring (=1 / T), then the resonance between the motor and the spring can be considered to be avoided.

[0183] (Formula 14)

[0184] fm>n×fs

[0185] (Formula 14a)

[0186] fm>N×(1 / T)

[0187] Furthermore, if (Formula 8) is used to rearrange (Formula 14a), the following (Formula 14b) to (Formula 14c) are obtained.

[0188] (Formula 14b)

[0189] fm>N×(k×d / 2πND 2 )

[0190] (Formula 14c)

[0191] fm>k×d / (2π×D 2 )

[0192] The practical speed of the motor is generally 1 / 2 of the no-load speed S, so fm = 1 / 2 × S / 60. Therefore, if it is assumed that there is no problem as long as it is used at 1 / 2 or more of the no-load speed S, the above (Formula 14c) can be converted into the following (Formula 15).

[0193] (Formula 15)

[0194] S>60kd / πD 2

[0195] In (Formula 5), ​​in order to simplify the formula, However, if we substitute into the above formula (Formula 15) This is as shown in the following (Formula 2) which is a condition suitable for the spring.

[0196] (Formula 2)

[0197]

[0198] If the G in the general spring material (spring steel) is 7850N / mm 2 =8.0×10 9 kgf / m 2 and γ=7850kg / m 3 Applicable to (Formula 2), it is as shown below (Formula 16).

[0199] (Formula 16)

[0200] S>(60×0.22×10 4 / π)×d / D 2

[0201] When this (Formula 16) is rearranged, the following (Formula 2a) is derived as a condition suitable for the spring.

[0202] (Formula 2a)

[0203] S>4.20×10 4 ×d / D 2

[0204] That is, by designing the motor so as to satisfy the above (Formula 2a), resonance of the spring caused by the rotation of the motor can be avoided, and vibration of the motor can be reduced.

[0205] For example, taking the above-mentioned specific condition X when the effective number of spring turns N=6 as an example, the above (Formula 2a) is calculated as the following (Formula 2a-1) to find the preferred range of the no-load speed S (rpm).

[0206] (Formula 2a-1)

[0207] S>4.20×10 4 ×1×10 -3 / (12.9×10 -3 ) 2 ≒250000

[0208] That is, under the specific condition X, it is sufficient to design the no-load speed to exceed 250,000 rpm. Figure 4The motor is used at the vibration frequency (Hz) of the sixth mode (maximum mode) of the solid line curve with the effective number of turns N = 6. This will use the motor in the following area: the area on the upper side that avoids the highest frequency (about 1600Hz) among the vibration frequencies that produce natural vibrations. The area that satisfies the above (Formula 2a) under specific conditions X is Figure 6 The area of ​​the oblique grid in the curve graph. It should be noted that Figure 6 It is represented by a diagonal grid. Figure 4 A curve graph of the area in the curve graph that satisfies the above (Formula 2a) under a specific condition X.

[0209] If the no-load speed is set in a region where natural vibration of any order mode occurs, the vibration generated by the rotation of the motor may resonate with the natural vibration of any order mode and amplify the vibration. However, the vibration can be reduced by using the motor in a region avoiding this region.

[0210] Regarding the specific condition X, the example is when the number of effective coils N of the spring is 6. When the number of effective coils N is 4, the conditions of wire diameter d = 0.9 mm and outer diameter D = 12.9 mm are satisfied (Formula 2a). Thus, the spring exceeds Figure 4 The motor is used to obtain the vibration frequency (Hz) of the fourth mode (maximum mode) of the wave line curve with the effective number of turns N = 4. In addition, when the effective number of turns N = 8, the conditions of wire diameter d = 1.1 mm and outer diameter D = 12.9 mm are satisfied (Formula 2a), thus, exceeding Figure 4 The motor is used at the vibration frequency (Hz) of the point in the octal mode (maximum order mode) of the single-dot chain line graph with the effective number of turns N=8.

[0211] It should be noted that in the above description, for the sake of convenience, an example is described in which the above (Formula 2a) is satisfied by using the no-load speed S within a prescribed range when a spring with a fixed outer diameter D and a wire diameter d is used. However, the motor can be designed in a manner that satisfies the above (Formula 2a) by appropriately selecting the outer diameter D and the wire diameter d of the spring in comparison with the no-load speed S required by the motor, or the motor can be designed in a manner that satisfies the above (Formula 2a) by appropriately combining and selecting all conditions in comparison with the no-load speed S required by the motor.

[0212] In order to prevent resonance of the periodic component of the motor bearing (bearing) (referring to the periodic component of the vibration caused 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 is generally equivalent to 0.39 times the fundamental frequency, it is expected to satisfy the following (Formula 17) in which the left side of the above (Formula 14c) is set to "0.39fm".

[0213] (Formula 17)

[0214] 0.39fm>k×d / (2π×D 2 )

[0215] If this (Formula 17) is rearranged in the same manner as the above (Formula 14c), the following (Formula 2b) is derived as a more appropriate condition.

[0216] (Formula 2b)

[0217] S>10.78×10 4 ×d / D 2

[0218] That is, by designing the motor in a manner that satisfies the above (Formula 2b), not only the resonance with respect to the fundamental frequency of the motor can be avoided, but also the resonance with respect to the bearing periodic component can be avoided, and the vibration of the motor can be further reduced.

[0219] The motor of the present invention has been described above by taking a preferred embodiment as an example, but the motor of the present invention is not limited to the structure of the above embodiment. For example, in the motor of the above embodiment, two schemes are given 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, but the present invention can also be applied 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.

[0220] Furthermore, the fixing of the magnet or the coil to any one of the shaft and the sleeve may be direct rather than indirect.

[0221] The effective number N of turns of the spring (elastic member) used is 6 in the above embodiment and 4, 6 and 8 in the simulation, but it is not limited thereto and may be 9 or more or an odd number.

[0222] It should be noted that in the aforementioned verification by simulation, a general spring material (spring steel) was used as the material of the spring (elastic member), and the formula was calculated using the transverse elastic coefficient G and unit volume weight γ of the spring material, but 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 no matter what the material is, the conditions are not greatly different, so in the present invention, springs (elastic members) of other materials can also be applied.

[0223] In addition, those skilled in the art can make appropriate changes to the motor of the present invention based on the prior known knowledge. As long as the structure of the present invention is still possessed through the relevant changes, it is obviously included in the scope of the present invention.

[0224] Description of Reference Numerals

[0225] 1: shaft; 2: rotor; 21, 22: magnet; 23: rotor yoke; 23a: disk portion; 23b: cylinder portion; 3: stator; 31: annular portion; 32, 33: coil; 34, 35: tooth portion; 41: first bearing; 42: second bearing; 41a, 42a: outer ring; 41b, 42b: inner ring; 41c, 42c: ball; 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, comprising: axis; a pair of bearings, the pair of bearings being fixed to the shaft; a sleeve accommodating the pair of bearings; a magnet, the magnet being fixed directly or indirectly to any one of the shaft and the sleeve; a coil, the coil being fixed directly or indirectly to the other of the shaft and the sleeve and facing the magnet; and an elastic member disposed between the pair of bearings, The elastic member satisfies the following formula 1: The above formula 1 is respectively expressed as follows: D represents the value of the outer diameter of the elastic member in m, d represents the wire diameter of the elastic member The value in m is used as the unit, and γ represents the unit volume weight of the material of the elastic member in kg / m 3 The value is expressed in units of rpm, S is the value of the no-load speed of the shaft expressed in revolutions per minute, and g is the value of the acceleration due to gravity expressed in m / s 2 The value is in kgf / m2, G represents the transverse elastic coefficient of the material of the elastic member. 2 The value of the unit.

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

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

4. A motor, comprising: axis; a pair of bearings, the pair of bearings being fixed to the shaft; a sleeve accommodating 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 and facing the magnet; and an elastic member disposed between the pair of bearings, The elastic member satisfies the following formula 2: The above formula 2 is respectively expressed as follows: D represents the value of the outer diameter of the elastic member in m, d represents the wire diameter of the elastic member The value in m is used as the unit, and γ represents the unit volume weight of the material of the elastic member in kg / m 3 The value is expressed in units of rpm, S is the value of the no-load speed of the shaft expressed in revolutions per minute, and g is the value of the acceleration due to gravity expressed in m / s 2 The value is in kgf / m2, G represents the transverse elastic coefficient of the material of the elastic member. 2 The value of the unit.

5. The motor according to claim 4, wherein: The elastic member satisfies the following formula 2a, S>4.20×10 4 ×d / D 2 The above formula 2a is respectively expressed as follows: D represents the value of the outer diameter of the elastic member in m, d represents the wire diameter of the elastic member The value is in m, and S represents the value of the no-load speed of the shaft in rpm.

6. The motor according to claim 4, wherein: The elastic member satisfies the following formula 2b, S>10.78×10 4 ×d / D 2 The above formula 2b is respectively expressed as follows: D represents the value of the outer diameter of the elastic member in m, d represents the wire diameter of the elastic member The value is in m, and S represents the value of the no-load speed of the shaft in rpm.

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