Linear motor

Abstract

This linear motor comprises: a field system; an armature (50) that is provided with a plurality of coils (13) and an armature core (15) having a core back (11) and a plurality of teeth (12), that is disposed to face the field system, and that moves in a movement direction that is relative to the field system; and a top plate disposed on the side opposite to the teeth (12) with the core back (11) therebetween. Auxiliary teeth (14) formed from a magnetic body and disposed at a distance from the armature core (15) are provided to at least one end of the armature core (15). The length (La) of the auxiliary teeth (14) in the Z direction is longer than the length (Lb) of the armature core (15) in the Z direction.

Description

Linear motor

[0001] The present disclosure relates to a linear motor.

[0002] A linear motor, which is a direct-acting electric motor, includes a field magnet and an armature arranged facing the field magnet and movable relative to the field magnet. The armature has a core back, a plurality of teeth extending from the core back toward the field magnet and aligned in the direction of movement of the armature relative to the field magnet, and a plurality of coils attached to the plurality of teeth, and includes an armature module group including the core back, teeth, and coils, and moves linearly relative to the field magnet.

[0003] In Patent Document 1, auxiliary cores made of magnetic material are provided on both sides of the armature in the direction of movement, sandwiching the armature, and the armature core and auxiliary core are separated to leave a certain gap W between the core and auxiliary core, preventing the salient poles at both ends of the core from forming a magnetic circuit and reducing the impact on cogging countermeasures that increase the magnetic flux of the salient poles at both ends of the core. The auxiliary cores and armature are fixed to the table with screws.

[0004] International Publication No. 2009 / 035050

[0005] However, because the screw holes in the table have play, when screws are inserted into the screw holes in the table to fasten the auxiliary core and armature to the table, installation variation occurs, where the auxiliary core and armature are misaligned in the direction of armature movement. For this reason, in Patent Document 1, variation occurs in the gap W, which should be constant, and the cogging thrust cannot be reduced as intended.

[0006] The present disclosure has been made in view of the above, and has an object to provide a linear motor that can suppress variations in cogging thrust caused by variations in the placement of auxiliary teeth.

[0007] To solve the above-mentioned problems and achieve the object, the linear motor of the present disclosure includes: a field magnet, a core back, an armature core having a plurality of teeth extending in a first direction from the core back toward the field magnet and arranged in a second direction perpendicular to the first direction; a plurality of coils wound around the plurality of teeth; an armature disposed facing the field magnet and moving in the second direction relative to the field magnet; and a plate member disposed on the opposite side of the core back from the teeth. Auxiliary teeth made of a magnetic material and disposed spaced apart from the armature core are provided on at least one side of the armature core in the second direction. A first length, which is the length of the auxiliary teeth in a third direction perpendicular to the first and second directions, is longer than a second length, which is the length of the armature core in the third direction.

[0008] The linear motor of the present disclosure has the effect of suppressing variations in cogging thrust caused by variations in the placement of auxiliary teeth.

[0009] 1 is a perspective view showing the configuration of a linear motor according to a first embodiment; 2 is a perspective view showing the configuration of an armature of a linear motor according to a first embodiment; 3 is a cross-sectional view showing the configuration of a linear motor according to a second embodiment; 4 is a cross-sectional view showing the configuration of an auxiliary tooth of a linear motor according to a third embodiment; 5 is a cross-sectional view showing the configuration of an armature of a motor according to a fourth embodiment; 6 is a cross-sectional view showing the configuration of a linear motor according to a fifth embodiment;

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A linear motor according to an embodiment will be described in detail below with reference to the drawings.

[0011] First Embodiment. Figure 1 is a perspective view showing the configuration of a linear motor 100 according to a first embodiment. Hereinafter, the linear motor may also be simply referred to as a motor. In the following explanation, the horizontal plane is defined as the XZ plane, the Y direction is defined as the direction parallel to the vertical direction, and a case will be explained in which an armature 50 serving as a mover moves in the X direction. Hereinafter, the X direction, which is the second direction, may be referred to as the relative movement direction, the Y direction, which is the first direction, as the tooth extension direction, and the Z direction, which is the third direction perpendicular to the X and Y directions, as the stack thickness direction.

[0012] The linear motor 100 is placed on a stand 60 provided for industrial machinery or the like. The linear motor 100 includes a field 20 as a stator extending in the X direction, an armature 50 disposed opposite the field 20 and moving in the X direction relative to the field 20, and a top plate 40.

[0013] A top plate 40 serving as a plate member is placed on the armature 50, and a workpiece W or the like is placed on the upper surface of the top plate 40. The top plate 40 is placed on the opposite side of the core back 11 (described later) from the teeth 12 (described later). When the linear motor 100 operates, the armature 50 moves along the X direction. As a result, the top plate 40 fixed on the armature 50 moves along the X direction, and the workpiece W moves along the X direction.

[0014] Field 20 has a plurality of permanent magnets (not shown), with S-pole permanent magnets and N-pole permanent magnets alternately spaced apart in the X direction. Field 20 may be configured such that the plurality of permanent magnets are attached to mounting seats (not shown) on the surface of a stator core (not shown), or may be configured such that the plurality of permanent magnets are embedded inside the stator core.

[0015] FIG. 2 is a perspective view showing the configuration of an armature 50 of a linear motor 100 according to the first embodiment. The armature 50 has an armature core 15, a plurality of coils 13 attached to the armature core 15, and auxiliary teeth 14. Regarding the coils 13, lead wires are shown at the locations where they are disposed, but the coils 13 themselves are not shown. The armature core 15 has a core back 11 extending in the direction of travel of the armature 50, and a plurality of teeth 12 extending from the core back 11 toward the field 20. The armature module 16 has the armature core 15 and a plurality of coils 13. The auxiliary teeth 14 are disposed adjacent to the core back 11 at both ends of the core back 11. However, although not clearly shown in FIG. 2 , the auxiliary teeth 14 and the core back 11 are not in contact with each other but are spaced apart. That is, a small gap (not shown) is formed between the auxiliary teeth 14 and the core back 11. The armature core 15 and the auxiliary teeth 14 are formed, for example, from a laminate of thick electromagnetic steel sheets.

[0016] In Fig. 2, the armature core 15 has six teeth 12. The six teeth 12 are aligned in the direction of travel of the armature 50. The tip of each tooth 12 on the field 20 side is straight. The slot in which the coil 13 is arranged is a portion adjacent to the tooth 12 in the direction of travel of the armature 50. Adjacent teeth 12 form a slot. A coil 13 is wound around each tooth 12.

[0017] 2 , in the field 20, five of the multiple permanent magnets aligned in the direction of travel of the armature 50 face six teeth 12. That is, in the field 20, the number of magnetic poles in the range facing the six teeth 12 in the direction of travel of the armature 50 is five.

[0018] The auxiliary teeth 14 are made of magnetic material and are attached to the top plate 40 or the core back 11 of the armature core 15. The auxiliary teeth 14 are attached to the end face or bottom face of the top plate 40 in the X direction. Alternatively, the auxiliary teeth 14 are attached to the end face of the core back 11 in the X direction. The auxiliary teeth 14 are fastened by screws, for example. In this case, the auxiliary teeth 14 and the armature core 15 are spaced apart, as described above. Furthermore, the auxiliary teeth 14 and the top plate 40 do not necessarily have to be in contact with each other.

[0019] An armature module group may be configured by connecting multiple armature modules 16 in the direction of relative movement. FIG. 3 is a cross-sectional view showing the configuration of a linear motor 100 according to the first embodiment. In FIG. 3, the armature 50 is configured as an armature module group in which multiple armature modules 16 are arranged. Coils 13 are not shown in FIG. 3. In FIG. 3, the armature core 15 has five teeth 12. When an armature module group is configured, the auxiliary teeth 14 are arranged at both ends of the connected armature module group. The auxiliary teeth 14 are spaced apart from the armature core 15. The field 20 includes a stator core 21 and multiple permanent magnets 22 whose south and north poles are alternately arranged in the X direction. In the case of FIG. 3, four of the multiple permanent magnets 22 arranged in the direction of travel of the armature 50 face the five teeth 12.

[0020] In the first embodiment, the lamination direction length La, which is the length of the auxiliary teeth 14 in the Z direction, is longer than the lamination direction length Lb, which is the length of the armature core 15 in the Z direction. The lamination direction length La corresponds to a first length, and the lamination direction length Lb corresponds to a second length. In other words, both ends of the auxiliary teeth 14 in the Z direction protrude in the Z direction from the ends of the armature core 15 in the Z direction. In the armature 50, by configuring the lamination direction length La of the auxiliary teeth 14 to be longer than the lamination direction length Lb of the armature core 15, it is possible to suppress variations in cogging thrust depending on the installation state of the auxiliary teeth 14.

[0021] Furthermore, by configuring the lamination-direction length La of the auxiliary teeth 14 to be longer than the lamination-direction length Lb of the armature core 15, it is possible to suppress a decrease in induced voltage due to the end effect. Furthermore, when drilling screw holes in the auxiliary teeth 14 by machining, it is possible to suppress a local increase in magnetic flux density, and it is possible to suppress an increase in variation in cogging thrust.

[0022] In the first embodiment, the number of slots in the armature 50 is six or five, and the number of magnetic poles in the field 20 is five or four, but the number of slots may be other than six or five, and the number of magnetic poles may be other than five or four.

[0023] Furthermore, in embodiment 1, the auxiliary teeth 14 are arranged at both ends of a single armature module 16, or at both ends of an armature module group made up of multiple armature modules 16, but the auxiliary teeth 14 may also be arranged at one end of a single armature module 16, or at one end of an armature module group.

[0024] Furthermore, the tip of each of the plurality of teeth 12 on the side of the field magnet 20 is not limited to being straight. The tip of each tooth 12 on the side of the field magnet 20 may have a protrusion or a depression facing the direction of travel.

[0025] Thus, according to embodiment 1, the auxiliary teeth 14 and the armature core 15 are spaced apart, and the auxiliary teeth 14 having a thickness-wise length La longer than the thickness-wise length Lb of the armature core 15 are arranged at at least one end of the armature core 15, thereby suppressing variations in cogging thrust depending on the installation state of the auxiliary teeth 14.

[0026] Second Embodiment Fig. 4 is a cross-sectional view showing the configuration of a linear motor 102 according to a second embodiment. In Fig. 4, the linear motor 102 is cut along the XY plane. The linear motor 102 includes an armature 51, a field 20, and a top plate (not shown).

[0027] Similar to the first embodiment, the field 20 includes a stator core 21 and a plurality of permanent magnets 22 in which south poles and north poles are alternately arranged in the X direction. In the field 20, the plurality of permanent magnets 22 may be configured so as to be attached to a mounting seat (not shown) on the surface of the stator core 21, or the plurality of permanent magnets 22 may be configured so as to be embedded inside the stator core 21.

[0028] Similar to the first embodiment, the armature 51 of the second embodiment includes the core back 11, a plurality of teeth 12, and a coil 13. The coil 13 includes coils 13a, 13b, 13c, 13d, 13e, and 13f. The armature 51 of the second embodiment includes teeth 12 whose number is not an integer multiple of the number of phases of the motor. For example, the linear motor 102 of the second embodiment has three phases, and the armature 51 of the second embodiment includes five teeth.

[0029] In the second embodiment, four of the multiple permanent magnets 22 aligned in the direction of travel of the armature 51 face five teeth 12. In other words, the number of magnetic poles in the range facing the five teeth 12 in the direction of travel of the armature 51 is four. Coils 13a, 13b, 13e, and 13f are wound around different teeth 12. Central coils 13c and 13d are wound around the same central tooth 12. Coils 13a to 13f have two or more types of winding numbers. With this configuration, the three-phase induced voltages required for three-phase drive of the linear motor 102 are balanced.

[0030] In the armature 51, similar to the first embodiment, the auxiliary teeth 14 and the armature core 15 are spaced apart, and the lamination length La, which is the length of the auxiliary teeth 14 in the Z direction, is longer than the lamination length Lb, which is the length of the armature core 15 in the Z direction. This suppresses a decrease in induced voltage due to the end effect. Furthermore, it also suppresses a decrease in inductance, thereby balancing the induced voltage and inductance of the three phases. Therefore, thrust ripples caused by imbalance between the three phases can be suppressed. Furthermore, the lamination length La of the auxiliary teeth 14 can be used as a single parameter, which increases the flexibility in the number of turns, thereby increasing the space factor of the coil 13 and suppressing heat generation. Furthermore, when drilling screw holes in the auxiliary teeth 14 by machining, it is possible to suppress a local increase in magnetic flux density and suppress an increase in the variation in cogging thrust.

[0031] In the second embodiment, the number of slots in the armature 51 is five, and the number of magnetic poles in the field 20 facing the five teeth 12 is four, but the above-described effect can also be obtained when the number of slots is other than five and the number of magnetic poles is other than four.

[0032] Furthermore, in the configuration shown in Figure 4, auxiliary teeth 14 are arranged at both ends of a single armature module that includes an armature core 15 and multiple coils 13a to 13f, but the configuration may also be such that auxiliary teeth 14 are arranged at both ends of an armature module group that is made up of multiple armature modules.

[0033] Furthermore, the tip of each of the plurality of teeth 12 on the side of the field magnet 20 is not limited to being straight. The tip of each tooth 12 on the side of the field magnet 20 may have a protrusion or a depression facing the direction of travel.

[0034] Thus, according to the second embodiment, the stacking direction length La, which is the length in the Z direction of the auxiliary teeth 14, is longer than the stacking direction length Lb, which is the length in the Z direction of the armature core 15, the armature 51 has teeth 12 whose number is not an integer multiple of the number of phases, and the coils 13a to 13f wound around the teeth 12 have at least two different numbers of turns. Therefore, in addition to the effects of the first embodiment, it is possible to adjust the induced voltage and inductance at the ends of the armature 51 in the direction of relative movement.

[0035] Third Embodiment Fig. 5 is a cross-sectional view showing the configuration of an auxiliary tooth 14 of a linear motor according to a third embodiment. Fig. 5 shows the auxiliary tooth 14 cut along the YZ plane. The third embodiment is applicable to the first or second embodiment.

[0036] In the third embodiment, the auxiliary teeth 14 have a two-stage configuration in the Y direction, and the Z-direction length La of the upper stage portion 14a that contacts the top plate 40 is longer than the Z-direction length Lb of the lower stage portion 14b. The Z-direction length Lb of the lower stage portion 14b is equal to the Z-direction length Lb of the armature core 15. The lower stage portion 14b corresponds to a first portion that includes an end portion on the field 20 side. The upper stage portion 14a corresponds to a second portion that includes an end portion on the opposite side from the field 20 side.

[0037] In the upper step portion 14a of the auxiliary tooth 14, a portion 14a1 protruding in the Z direction from the lower step portion 14b is provided with a screw hole 14c for fixing the auxiliary tooth 14 to the top plate 40 with a screw 70. When attaching the auxiliary tooth 14 to the outer surface of the armature core 15, a screw hole for fixing the auxiliary tooth 14 to the armature core 15 with a screw 70 is also provided in the protruding portion 14a1.

[0038] According to the third embodiment, the auxiliary teeth 14 have a two-stage structure, which makes it possible to suppress a local increase in magnetic flux density when drilling screw holes in the auxiliary teeth 14 by machining, thereby suppressing an increase in variation in cogging thrust. In addition, the two-stage structure is adopted and the length Lb of the lower stage 14b in the Z direction is made equal to the length Lb of the armature core 15 in the Z direction, which makes it possible to reduce the volume and weight of the auxiliary teeth 14 compared to the structure shown in the first embodiment. Furthermore, the magnetic attraction force acting on the auxiliary teeth 14 in the Y direction can be reduced.

[0039] Fourth Embodiment Fig. 6 is a cross-sectional view showing the configuration of an armature 52 of an electric motor according to a fourth embodiment. Fig. 6 cuts the armature 52 along the XZ plane. The fourth embodiment is applicable to the first or second embodiment.

[0040] The armature 52 has an armature core 15 and auxiliary teeth 14 arranged at both ends of the armature core 15. The auxiliary teeth 14 have central portions 14d and end portions 14e arranged at both ends in the Z direction, and the lamination-direction length La of the auxiliary teeth 14 is longer than the lamination-direction length Lb of the armature core 15. The central portions 14d have the same length in the Z direction as the armature core 15 and face the armature core 15 across a gap 30. The end portions 14e protrude from the central portion 14d in the Z direction and are offset from the central portion 14d in a direction approaching the armature core 15 in the X direction. The end portions 14e of the auxiliary teeth 14 may contact the armature core 15. The central portions 14d correspond to a third portion facing the X-direction end portions of the armature core 15. The end portions 14e correspond to a fourth portion.

[0041] In addition, auxiliary teeth 14 having central portions 14d and end portions 14e may be arranged at least at one end of the armature module group in the X direction.

[0042] As described above, according to the fourth embodiment, the end portion 14e protrudes in the Z direction from the central portion 14d and is offset from the central portion 14d in the X direction toward the armature core 15, thereby reducing variations in cogging thrust due to the installation state. Also, reduction of induced voltage due to the end effect can be suppressed.

[0043] Fifth Embodiment Fig. 7 is a cross-sectional view showing the configuration of a linear motor 103 according to a fifth embodiment. Fig. 7 shows the linear motor 103 cut along the XY plane. The linear motor 103 includes an armature 53 and a field 20. The field 20 includes a stator core 21 and a permanent magnet 22. The armature 53 includes an armature core 15 having a core back 11 and a plurality of teeth 12, a plurality of coils 13, and auxiliary teeth 14. The auxiliary teeth 14 and the armature core 15 are spaced apart, and the lamination direction length La, which is the length of the auxiliary teeth 14 in the Z direction, is longer than the lamination direction length Lb, which is the length of the armature core 15 in the Z direction.

[0044] In the fifth embodiment, the auxiliary teeth 14 are not made of laminated electromagnetic steel sheets, but are made of blocks of carbon steel or other materials, which are different from the material of the armature core 15. This configuration improves the mechanical strength when drilling screw holes by machining the auxiliary teeth 14. Furthermore, because a laminated electromagnetic steel sheet is not used, material costs can be reduced.

[0045] When auxiliary teeth 14 are made of block material, the magnetic flux cannot be separated in the Z direction, which causes the problem of increased eddy current loss compared to electromagnetic steel sheets. For this reason, in armature 53, distance a between field magnet 20 and auxiliary teeth 14 is made larger than distance b between armature 53 and field magnet 20. This reduces eddy current loss generated in auxiliary teeth 14, suppresses an increase in magnetic flux density, and suppresses an increase in iron loss.

[0046] Additionally, in the armature 53, the ratio of the length c of the armature core 15 in the X direction to the total width d of the auxiliary teeth 14 in the X direction is set to 4 or more, as shown in the following formula (1): c / d=c / (d1+d2)≧4 (1)

[0047] FIG. 8 is a diagram showing the relationship between loss and the value c / d in the linear motor 103 according to the fifth embodiment. In FIG. 8, the horizontal axis represents the value c / d, and the vertical axis represents the loss [pu] (Per Unit Method). The loss is the sum of iron loss and copper loss. As shown in FIG. 8, when the value c / d is 4 or more, the loss does not decrease from 1.0. Because the value c / d is 4 or more, the opposing area between the auxiliary teeth 14 and the field magnet 20 can be reduced, and the loss, which is the sum of the eddy current loss and copper loss of the auxiliary teeth 14, can be reduced.

[0048] FIG. 9 is a cross-sectional view showing the configuration of an auxiliary tooth 14 used in a linear motor 103 according to a fifth embodiment. In FIG. 9 , the auxiliary tooth 14 is cut along the XY plane. In the auxiliary tooth 14 shown in FIG. 9 , the X-direction length f of the lower surface of the auxiliary tooth 14 is shorter than the X-direction length e of the upper surface of the auxiliary tooth 14. For example, the upper surface of the auxiliary tooth 14 abuts against the top plate 40. The lower surface of the auxiliary tooth 14 faces the field 20. In FIG. 9 , the auxiliary tooth 14 has a two-tiered configuration, with an upper and lower tier, and the tip portion extending to the lower surface is tapered. However, this configuration is not limited to this, and any shape may be used as long as the relationship e>f is satisfied. This configuration reduces the opposing area between the auxiliary tooth 14 and the field 20, thereby suppressing an increase in magnetic flux density and iron loss.

[0049] Thus, according to the fifth embodiment, the auxiliary teeth 14 are made of block material, which improves mechanical strength and reduces material costs. Furthermore, since the relationship c / (d1 + d2) ≥ 4 is satisfied, loss can be reduced even when the auxiliary teeth 14 are made of block material. Furthermore, since the auxiliary teeth 14 satisfy the relationship e > f, an increase in iron loss can be reduced even when the auxiliary teeth 14 are made of block material.

[0050] In the fifth embodiment, the number of slots in the armature 53 is six, and the number of magnetic poles in the field 20 is five, but the number of slots and the number of magnetic poles may be other than six and other than five. In the fifth embodiment, the auxiliary teeth 14 are arranged at both ends of a single armature module, but the auxiliary teeth 14 may be arranged at both ends of an armature module group. The auxiliary teeth 14 may be arranged at one end of a single armature module, or at one end of an armature module group. In the fifth embodiment, the tip of each of the multiple teeth 12 on the field 20 side is not limited to being straight. The tip of the tooth 12 on the field 20 side may have a protrusion or recess facing the traveling direction.

[0051] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies, or embodiments may be combined with each other, and some of the configurations may be omitted or modified within the scope of the gist of the present disclosure.

[0052] 11 Core back, 12 Teeth, 13, 13a, 13b, 13c, 13d, 13e, 13f Coil, 14 Auxiliary teeth, 14a Upper portion, 14a1 Protruding portion, 14b Lower portion, 14c Screw hole, 14d Central portion, 14e End portion, 15 Armature core, 16 Armature module, 20 Field magnet, 21 Stator core, 22 Permanent magnet, 30 Air gap, 40 Top plate, 50, 51, 52, 53 Armature, 60 Frame, 70 Screw, 100, 102, 103 Linear motor, La, Lb Stacking thickness direction length, W Workpiece.

Claims

1. A stator core including a field magnet, a core back, and a plurality of teeth extending from the core back toward the field magnet in a first direction and arranged in a second direction perpendicular to the first direction, a plurality of coils wound around the plurality of teeth, an armature disposed to face the field magnet and move in the second direction with respect to the field magnet, and a plate member disposed on the side opposite to the teeth with the core back interposed therebetween, wherein auxiliary teeth made of a magnetic material are provided at least on one side of the stator core in the second direction and spaced apart from the stator core, and a first length, which is a length of the auxiliary teeth in a third direction perpendicular to the first direction and the second direction, is longer than a second length, which is a length of the stator core in the third direction. A linear motor characterized by this.

2. The linear motor according to claim 1, wherein the auxiliary teeth are fixed to the plate member or the stator core.

3. The linear motor according to claim 1 or 2, wherein the stator core has a number of teeth that is not an integer multiple of the number of phases, and the coils have at least two types of winding turns.

4. The linear motor according to any one of claims 1 to 3, wherein the auxiliary teeth have the second length along the third direction, and include a first portion including an end portion on the field magnet side in the first direction, and a second portion having the first length along the third direction and including an end portion on the side opposite to the field magnet side in the first direction.

5. The linear motor according to claim 4, wherein the second portion has a screw hole for fixing the plate member or the stator core.

6. The linear motor according to any one of claims 1 to 3, wherein the auxiliary teeth have the second length along the third direction, and include a third portion facing an end portion of the stator core in the second direction, and a fourth portion protruding in the third direction from both end portions of the third portion in the third direction and arranged to be displaced in the second direction with respect to the third portion.

7. The linear motor according to any one of claims 1 to 6, wherein the auxiliary teeth are a block material and are made of a material different from that of the stator core.

8. The linear motor according to claim 7, wherein the distance between the auxiliary teeth and the field magnet is longer than the distance between the stator core and the field magnet.

9. The ratio of the length of the armature core in the second direction to the total value of the lengths of the auxiliary teeth in the second direction is 4 or more. The linear motor according to claim 7 or 8, characterized in that.

10. The auxiliary teeth are characterized in that the length along the second direction at the end on the field side in the first direction is smaller than the length along the second direction at the end on the side opposite to the field side in the first direction. The linear motor according to any one of claims 7 to 9.

11. The armature is an armature module group having a plurality of armature modules arranged in the second direction. Each of the armature modules has the core back, the armature core, and a plurality of coils. The auxiliary teeth are arranged at at least one of both ends of the armature module group. The linear motor according to any one of claims 1 to 10, characterized in that.

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