Linear synchronous motor and linear motor actuator

Abstract

Linear synchronous motor comprising: a first element (4) in which N-poles and S-poles are arranged linearly alternately to generate a magnetic field, a second element (5) which is opposite to the first element (4) at a distance therefrom and which, when alternating currents of a plurality of phases flow, generates a traveling magnetic field in an arrangement direction of the magnetic poles to exert a thrust on the first element (4), wherein: the second element (5) comprises a core element (50) in which teeth (52) are arranged, the number of which is an integer multiple and more than twice a number of phases of the alternating currents, and a coil (51) wound around the teeth (52) of the core element (50) and through which the alternating current of any one of the phases flows; and where: the alternating current is a three-phase alternating current consisting of a u-phase, a v-phase and a w-phase, wherein the u-phase flows through the coil (51) wound around the tooth (52) at one end of the core element (50), the w-phase flows through the coil (51) wound around the tooth (52) at another end of the core element (50), and distal ends of the teeth (52) around which the v-phase coil (51) is wound are spaced further from the first element (4) than distal ends of the teeth (52) around which the u-phase and w-phase coils (51) are wound.

Description

Technical area

[0001] The present invention relates to a linear motor used as a driving device of a linear guide section of a general conveyor or a machine tool for applying, for example, a thrust force or a braking force to a movable body that is linearly guided, and more particularly, to an improvement of a linear synchronous motor that allows an alternating current to flow through a coil wound around a core member and utilizes, as the thrust force, a magnetic attraction force generated between the core member and a magnet. Technical background

[0002] In a general conveyor or a machine tool, as a means for reciprocating and linearly moving a movable body such as a table, a so-called linear motor actuator is known, in which a linear motor is used as a thrust generating source. As a more general linear motor actuator, one is known in which the movable body is supported on a stationary portion such as a bed or a column using a pair of linear guides so as to be reciprocally movable, and a stator and a movable member constituting the linear motor are mounted on the stationary portion and the movable body, respectively, in such a manner as to oppose each other (JP H10-290560 A or the like). JP H07-88039 A also discloses such a linear motor, wherein teeth on each end side protrude from a recess on a central tooth.

[0003] That is, while the linear guide rails are arranged on the stationary section, and the stator of the linear motor is mounted thereon parallel to the linear rails, the sliders of the linear guides and a drive member of the linear motor are mounted on the movable body, and the sliders on the movable body side are mounted in the guide rail. Thus, the movable body is supported so that it can reciprocate on the stationary section, and the stator on the stationary section side and the drive member on the movable body side are opposite each other.

[0004] There are various types of linear motors, each differing in its drive system. A representative example is the so-called linear synchronous motor, in which alternating currents of a plurality of phases flow through a coil to be used (JP 2003-70226 A, JP H08-205514 A, and the like). The linear synchronous motor includes a stator magnet with N-poles and S-poles arranged linearly alternately to generate a magnetic field, and a driving member that generates a traveling magnetic field along an arrangement direction of the magnetic poles of the stator magnet due to the flow of alternating current. A magnetic attraction force and a magnetic repulsion force are generated between the traveling magnetic field generated by the driving member and the magnetic field generated by the stator magnet, respectively. Thus, a thrust force is generated, by which the driving member and the stator magnet move relatively.

[0005] There are two types of drive elements, which either contain a core element made of ferromagnetic material such as iron or not. The former type is advantageous in terms of the amount of thrust to be generated. Teeth, the number of which is an integer multiple of the number of phases of the alternating current, are provided on the core element so that they face the stator magnet. The coil is wound around these teeth. When current is supplied to the coil, each of the teeth becomes an electromagnet, and the magnetic attraction or repulsion force is generated between the coil and the respective magnetic poles, which each form the stator magnet. For example, a three-phase alternating current consists of three alternating currents consisting of a u-phase, a v-phase, and a w-phase, which have a phase difference of 120° from each other.Accordingly, if alternating currents with a phase difference of 120° to each other are allowed to flow sequentially through the coil around a row of teeth, with the u-phase at one end of the core element, the v-phase at the next tooth, and the w-phase at the tooth adjacent to the next tooth, a phenomenon occurs that makes the magnetic field appear to move from the tooth located at the end of the core element to the tooth located at the other end. This is the aforementioned traveling magnetic field. Due to the interaction between the traveling magnetic field and the stator magnet, the thrust force acts between the drive member and the stator magnet. Patent document 1: JP H10- 290 560 A Patent document 2: JP 2003- 70 226 A Patent Document 3: JP H08-205 514 A Disclosure of the invention Problems to be solved by the invention

[0006] The strength of the magnetic attraction force acting between the teeth of the core element and the magnetic poles of the stator magnet varies depending on the densities of the magnetic fluxes flowing through the teeth. The higher the magnetic flux density, the stronger the magnetic attraction force. Therefore, if the densities of the magnetic fluxes flowing through the teeth of the core element are equal, a uniform thrust force must be generated when alternating currents of the u-phase, v-phase, and w-phase, which differ in phase, flow through a row of teeth.

[0007] However, as for the two teeth located at both ends of the core element, only one side of each of the teeth is adjacent to another tooth, and not both sides of it are adjacent to other teeth, so the densities of the magnetic fluxes flowing through these two teeth are generally lower than the densities of the other magnetic fluxes flowing through the other teeth.Therefore, if, of the u-phase, the v-phase, and the w-phase constituting the three-phase alternating current, the u-phase can correspond to the tooth at one end of the core element and the w-phase can correspond to the tooth at the other end of the core element, there is a problem that when the thrust force is generated by allowing the three-phase alternating current to flow through the coil wound around the teeth in the manner described above, the thrust force generated by the v-phase alternating current is slightly stronger than the thrust force generated by the u-phase and w-phase alternating currents, so that periodic fluctuation of the thrust force occurs.

[0008] Furthermore, since the density of magnetic flux flowing through the two teeth located at both ends of the core member is lower than that of the magnetic flux flowing through the other teeth, when the core member, which is made of ferromagnetic material, is moved relative to the stator magnet, a cogging torque fluctuates locally. This also leads to a problem in that the thrust force between the drive member and the stator magnet fluctuates.

[0009] Conventionally, to counteract the above-mentioned problem of thrust force fluctuation, the pitch of the teeth is changed, or the thickness or width of the teeth is changed. However, the above-mentioned countermeasures result in a reduction in the groove space (the space between two adjacent teeth) for accommodating the coil, etc. There is also a problem that a significant reduction in thrust force often occurs due to the reduction in the number of turns of the spiral. Means to solve the problems

[0010] The present invention has been made in view of the problems discussed above. An object of the present invention is to provide a linear synchronous motor in which, when alternating currents of a plurality of phases flow through a coil of a driving member, thrust forces generated by the alternating currents of each phase are balanced, so that fluctuation in thrust force can be minimized.

[0011] A linear synchronous motor according to claim 1 achieves the above-mentioned object. A linear synchronous motor of the present disclosure includes: a first element including N-poles and S-poles arranged linearly alternately to generate a magnetic field; and a second element opposite the first element at a distance therefrom, which, when alternating currents of a plurality of phases flow, generates a traveling magnetic field in an arrangement direction of the magnetic poles to exert a thrust force on the first element. Furthermore, the second element includes a core element in which teeth are arranged, the number of which is an integer multiple of a number of phases of the alternating currents, and a coil wound around the teeth of the core element, through which the alternating current of any one of the phases flows.Of the plurality of teeth provided on the core member, at least one of the teeth corresponding to the phases of the alternating currents flowing through the coil wound around the teeth has a distal end at both ends of the core member that projects further toward the first member than distal ends of the remaining teeth.

[0012] The invention is implemented using a three-phase alternating current (u-phase, v-phase, and w-phase). Thus, the u-phase alternating current flows through the coil wound around the tooth at one end of the core element, and the w-phase alternating current flows through the coil wound around the tooth at the other end. In this case, the distal ends of the teeth around which the v-phase coil is wound are farther away from the first element than the distal ends of the teeth around which the u-phase and w-phase coils are wound, and the distal ends of the teeth around which the u-phase and w-phase coils are wound protrude farther toward the first element than the distal ends of the teeth around which the v-phase coil is wound.

[0013] With this structure, if one or more teeth corresponding to the u-phase, one or more teeth corresponding to the v-phase, and one or more teeth corresponding to the w-phase are assumed to form groups, the magnetic flux densities of the groups can be balanced. Accordingly, the fluctuation in the thrust force when the alternating current flows can be minimized. Furthermore, it is also possible to suppress local fluctuation in the cogging torque that occurs when the second member to which the core member is attached is moved relative to the first member. Given this, the fluctuation in the thrust force can also be minimized.

[0014] Furthermore, the first element can be the stator or the drive member. If the first element is the stator, the second element is the drive member. Alternatively, if the first element is the drive member, the second element is the stator. Of course, the second element includes a coil for generating the traveling magnetic field. Accordingly, if the second element is the stator, the core element and coil elements must be present over a travel range of the first element, which is the stator, making assembly of the second element labor-intensive. Therefore, to facilitate assembly of the second element, the first element is preferably the stator. Short description of the drawings Fig. 1 is a perspective view showing a linear motor actuator according to a first embodiment of the present invention, to which a linear synchronous motor of the present invention is applied. Fig. 2 is a vertical sectional view of the Fig. 8 along a direction perpendicular to a longitudinal direction of a guide rail. Fig. 3 is a sectional plan view showing the ball orbits of the Fig. 1 shows the linear motor actuator. Fig. 4 is a plan view showing a spacer band used for the Fig. 1 shown linear motor actuator is used. Fig. 5 is a side view showing the spacer band for which the Fig. 1 shown linear motor actuator is used. Fig. 6 is a vertical sectional view of a drive member and stator elements of the Fig. 1 shown linear motor actuator along the longitudinal direction of the guide rail. Fig. 7 is a view showing only one state of magnetic fluxes ϕ flowing through teeth of a core element. Fig. 8 is a plan view showing another example of an arrangement mode of the stator magnets on the track rail. Fig. 9 is a schematic view showing a linear motor actuator according to another embodiment using the linear synchronous motor of the present invention. Description of the symbols 1 guide rail, 2 movable bodies, 3 table structures, 3a, 3b runners, 3c common upper plate, 4 stator magnet, 5 drive link, 10 stationary floor, 11 side wall section, 30 storage section, 31 upper plate section, 50 core element, 51 coil, 52 teeth. Best mode for carrying out the invention

[0015] Hereinafter, a linear synchronous motor of the present invention will be described in detail with reference to the accompanying drawings.

[0016] Fig. 1 shows an example of a linear motor actuator to which the linear synchronous motor of the present invention is mounted. The linear motor actuator includes a guide rail 1 formed in a channel-like configuration, a table body 3 to which a movable body to be controlled is mounted and which can be moved along the guide rail 1, stator magnets 4 arranged on the guide rail 1, and a drive member 5 mounted on the table body 3, which, together with the stator magnets 4, forms the linear synchronous motor. By magnetizing a coil of the drive member 5 mounted on the table body 3, the table body 3 can be slid along the guide rail 1 and stopped at a predetermined position.

[0017] The track rail 1 includes a stationary floor 10 attached to a stationary portion such as a bed with a screw (not shown), and a pair of side wall portions 11 and 11 extending upright from the stationary floor 10. A space enclosed by the stationary floor 10 and the side wall portions 11 is a guide path 12 of a concave groove shape. The table body 3 reciprocates on the guide path 12. Furthermore, in each of the inner surfaces of the side wall portions 11 facing the guide path 12, two ball rolling grooves 13 are formed on an upper and a lower surface. The ball rolling grooves 13 are formed in a longitudinal direction of the track rail 1.

[0018] Furthermore, the table body 3 includes a pair of sliders 3a and 3b arranged in the guide part of the guide rail and movable back and forth along the guide path, and a common upper plate 3c connecting the sliders 3a and 3b at a predetermined distance. The common upper plate 3c is formed in a substantially rectangular shape with long sides coinciding with the longitudinal direction of the guide rail 1. Sliders 3a and 3b, respectively, arranged on the guide path 12 of the guide rail 1 are fixed to both end portions in the longitudinal direction, and the common upper plate 3c itself is attached to the sliders 3a and 3b so as to be positioned outside the guide path 12 of the guide rail 1. Furthermore, the drive member 5 is provided between the pair of sliders 3a and 3b, which are fixed to the common upper plate 3c.The drive member 5 is suspended from the common upper plate 3c and positioned on the guide path 12 of the guide rail 1.

[0019] Fig. 2 is a sectional view of the track rail 1 and the slider 3a, 3b. The slider 3a, 3b is formed in a substantially rectangular shape and arranged on the guide path 12 of the track rail 1. At least a part of the sliders 3a, 3b protrudes outward from the guide path 12 of the track rail 1. An upper surface of the slider 3a, 3b, which is arranged above an upper end of the side wall portion 11 of the track rail 1, is provided with a mounting surface 33. The slider 3a, 3b includes endless tracks in which balls 6 circulate, in two rows each on the right and left sides, i.e., a total of four rows. The endless tracks respectively correspond to the ball rolling grooves 13 formed in the side wall portions 11 of the track rail 1.

[0020] Fig. 3 is a plan view showing the endless ball tracks of the slider. The slider 3a, 3b includes a bearing raceway 34 made of a metal block and a pair of end caps 35 made of synthetic resin, which are fixed to both the front and rear end surfaces of the bearing raceway 34 with respect to a moving direction of the sliders 3. Each of the endless tracks includes a load rolling groove 36 formed on an outer surface of the bearing raceway 34, a ball return hole 37 formed in the bearing raceway 34 so as to be parallel to the load rolling groove 36, and U-shaped direction reversing paths 38 formed in the end caps 35. The large number of balls 6 roll between the ball rolling groove 13, the raceway 1, and the load rolling groove 36 of the bearing raceway while a load is applied to them.Further, the balls 6, which have passed through the load rolling groove 36, enter the direction reversal path 38 on one end cap 35 and are unloaded. Then, they roll in the ball return hole 37 in a no-load state, and continue to roll in the direction reversal path 38 on the other end cap 35, thus re-entering the load rolling groove 36 of the bearing raceway 34. It should be noted that when the balls 6 roll in the ball return hole 37 in the no-load state, an inner peripheral surface of the ball return hole 37 and the balls 6 come into contact with each other, generating noise. Accordingly, the inner peripheral surface of the ball return hole 37 is coated with a synthetic resin.

[0021] The balls 6 are arranged at predetermined intervals in a flexible spacer band 7, which is made of synthetic resin and in Fig. 4 and Fig. 5. The balls 7 are installed together with the spacer belt 7 in each of the endless tracks of the sliders 3a and 3b. The spacer belt 7 includes spacer portions 70 so that the adjacent balls are spaced from each other and the balls 6 are prevented from coming into contact with each other while rotating in the endless track. Furthermore, a ball 6 receiving hole is formed between the pair of front and rear spacer portions 70, in which the ball 6 is received. As a result, no contact noise is generated between the balls in the endless track even when the sliders 3a and 3b are moved at high speed on the guide path 12 of the track rail 1.Accordingly, the generation of noise due to the rapid movement of the sliders 3a and 3b can be prevented, and serpentine movement of the balls 6 in the endless track is prevented, so that smooth movement of the sliders 3a and 3b with respect to the guide rail 1 and thus smooth movement of the table body 3 is ensured.

[0022] The sliders 3a and 3b constructed as described above are arranged in the guide path 12 of the track 1 by being sandwiched between the pair of side walls 11 and 11 of the track 1 with the balls 6 therebetween. The balls 6 roll in the ball rolling grooves 13 of the track rail 11, thus allowing free reciprocating movement in the longitudinal direction of the track rail 1. In this case, the track rail 1 is formed in the channel-like shape surrounding the guide path, so that it is extremely rigid. Furthermore, the table body 3 is guided by the pair of sliders 3a and 3b and thus also has high rigidity with respect to the track rail 1. The table body 3 can be moved along the track rail 1 with high accuracy.

[0023] The following describes the stator magnets and the drive element that form the linear synchronous motor.

[0024] The stator magnets 4 are, as in Fig. 1, are arranged on the stationary floor 10 of the track rail 1 and face the guide path 12 on which the sliders 3a and 3b reciprocate. That is, the stationary floor 10 serves as a yoke of the stator magnet 4. Each of the stator magnets 4 is made of a permanent magnet. N poles and S poles are alternately arranged at a predetermined interval in the longitudinal direction of the track rail 1. The stator magnets 4 must be arranged parallel to the moving direction of the sliders 3a and 3b on the guide path 12 of the track rail 1. A concave groove 14 is formed on the stationary floor 10 of the track rail 1, parallel to the ball rolling grooves 13. The magnetic field magnets 4 are fixed to the track rail 1 so as to fit into the concave groove 14.

[0025] Fig. 6 is a vertical sectional view further showing a positional relationship between the drive member 5 attached to the table body and the stator magnets 4 in the longitudinal direction of the guide rail 1. The drive member 5 includes a core member 50 fixed to the common upper plate 3c with screws 39, and a coil 51 wound around the core member 50. The core member 50 is formed with a plurality of slots at a predetermined pitch in the longitudinal direction of the guide rail 1 and is formed in a comb-like shape as a whole. The armature core 50 is provided with twelve teeth 52 having slots formed on the front and back surfaces thereof. The coil 51 is wound around the twelve teeth 52 of the core member 50 so as to fill the slots. Around the twelve teeth 52, the coil 51 is wound for three phases, which include (u1, u2, u3, u4), (v1, v2, v3, v4), and w1, w2, w3, w4).A three-phase alternating current of a u-phase, a v-phase, and a w-phase flows through the three-phase coil 51, thus magnetizing the coil 51. This generates an attractive magnetic force and a repulsive magnetic force between the drive member 5 and the stator magnet 4. Accordingly, a thrust force or a braking force can be exerted on the table body 3 to which the drive member 5 is attached in the longitudinal direction of the track 1. Note that the teeth 52 are formed with a uniform width and thickness.

[0026] A current applied to the coil 51 wound for the three phases is determined based on a detection signal of a position detecting device 8 mounted on the outside of the raceway 1 (see Fig. 2). A linear scale 80 is attached to the outer surface of the side wall portion 11 of the guide rail 1, on which conductor patterns are repeatedly marked at a predetermined pitch. An encoder 81 is mounted on the common upper plate 3c of the table body 3, which optically reads the conductor patterns of the linear scale 80. When a current position and a current speed of the sliders 3 are detected based on an output signal of the encoder 81, a control unit for controlling a variable frequency source changes a frequency of the three-phase alternating current depending on a difference between a target position and the current position and a difference between a target speed and the current speed, while allowing an alternating current to be supplied to the coil 51 of each of the phases.

[0027] Of the twelve teeth 52 present on the core element 50, as shown in Fig. As shown in Figure 6, the four teeth around which the v-phase coil is wound (hereinafter referred to as "v-phase teeth") are slightly shorter than the teeth around which the u-phase coil and the w-phase coil are wound (hereinafter referred to as "u-phase teeth" and "w-phase teeth", respectively). The v-phase teeth are spaced farther from the stator magnets than the u-phase teeth and the w-phase teeth. Conversely, the u-phase teeth and the w-phase teeth protrude farther toward the stator magnets 4 than the v-phase teeth.

[0028] The reason why only the v-phase teeth of the core element 50 are slightly shorter is that, in view of a difference between the densities of magnetic fluxes flowing through the teeth, densities of magnetic fluxes flowing through the teeth should be substantially balanced between a group of the u-phase teeth, a group of the b-phase teeth, and a group of the w-phase teeth, each of which includes four teeth. Fig. 7 is a view showing, with only arrows, a state of magnetic fluxes φ flowing through the teeth 52 of the core member 50. For convenience of description, it is assumed that, not according to the present invention, the number of u-phase teeth, v-phase teeth, and w-phase teeth is each two, that is, six teeth are formed on the core member. Except for two teeth (u1 and w2) arranged at both ends of the core member 50, each of the other four teeth (v1, w1, u2, and v2) has other teeth on both adjacent sides. Accordingly, for example, the magnetic flux Φ flowing through the w1-phase tooth can flow through the v1-phase tooth and the u2-phase tooth on both adjacent sides thereof.However, the u1-phase tooth is only adjacent to the v1-phase tooth, so the magnetic flux φ flowing through the u1-phase tooth flows through the v1-phase tooth, but it is difficult to flow through a region shown by a broken line in the figure. The same applies to the w2-phase tooth. That is, of the six teeth provided on the core element 50, the number of magnetic fluxes φ flowing through the two teeth (v1 and w1) located at both ends is smaller than the remaining four teeth (v1, w1, u2, and v2).

[0029] Thus, a comparison between a case where the coil wound around the two u-phase teeth (u1 and u2) is magnetized and a case where the coil wound around the two v-phase teeth (v1 and v2) is magnetized reveals that the magnetic attraction force generated with respect to the stator magnets 4 is larger in the latter case. The same is true when comparing a case where the coil wound around the two w-phase teeth (w1 and w2) is magnetized and a case where the coil wound around the two v-phase teeth (v1 and v2) is magnetized. This results in fluctuation of the thrust generated by the drive member based on one period of the v-phase, i.e., ripple.

[0030] Furthermore, even in a state where no current is supplied to the coil, since the core member 50 is a ferromagnetic body, the magnetic attraction force is exerted between each of the teeth provided on the core member 50 and the stator magnet 4. When the core member 50 is moved in an arrangement direction of the stator magnets 4, a change in the magnetic attraction force occurs due to a correlation between an arrangement pitch of the stator magnets 4 and an arrangement pitch of the teeth of the core member 50, that is, a so-called cogging torque. A comparison between all the u-phase teeth (u1 and u2) and all the w-phase teeth (w1 and w2) reveals that the same number of magnetic fluxes flow through them. However, the larger number of magnetic fluxes flow through the v-phase teeth (v1 and v2) than through the u-phase teeth (u1 and u2) and the w-phase teeth (w1 and w2).Accordingly, the cogging torque also causes changes due to the presence of the v-phase teeth. Therefore, the thrust force of the drive element 5 also fluctuates periodically due to the change in cogging torque.

[0031] However, if the v-phase teeth, through which the magnetic fluxes ϕ flow easily, are farther away from the stator magnets 4 than the u-phase and w-phase teeth, it becomes correspondingly more difficult for the magnetic fluxes ϕ to flow through the v-phase teeth. When the teeth of each phase are considered as a group, the number of magnetic fluxes ϕ flowing through the u-phase teeth (u1 and u2), the v-phase teeth (v1 and v2), and the w-phase teeth (w1 and w2) can be substantially equalized. This can minimize the fluctuation of the thrust force and the fluctuation of the cogging torque based on the v-phase period.

[0032] For example, if Fig. 7, the number of magnetic fluxes flowing through each of the two teeth (u1 and u2) arranged at both ends of the core element 50 is represented by ϕ1, and the number of magnetic fluxes flowing through each of the four teeth (v1, w1, u2, and v2) is represented by ϕ0. As can be seen from the above-mentioned description, a relationship of ϕ1<ϕ0 is established. Accordingly, the total number of magnetic fluxes flowing through the u-phase teeth (u1 and u2) is represented by ϕ0+ϕ1, and the total number of magnetic fluxes flowing through the w-phase teeth (v1 and v2) is also represented by ϕ0<ϕ1. However, the total number of magnetic fluxes flowing through the v-phase teeth (v1 and v2) is represented by ϕ1+ϕ0 (>ϕ0+ϕ1).In this case, if the v-phase teeth are spaced farther from the stator magnets than the u-phase and w-phase teeth, in order to regulate the number of magnetic fluxes flowing through each of the v-phase teeth to ϕ2 (ϕ0>ϕ2>ϕ1), the total number of magnetic fluxes flowing through the v-phase teeth (v1 and v2) is ϕ2+ϕ2. At least a relationship ϕ1+ϕ0>ϕ1+ϕ2 is established, and by regulating a difference between a length of the v-phase teeth and a length of the u-phase and w-phase teeth, it is possible to establish a relationship ϕ2+ϕ2 ≈ ϕ0<ϕ1.When such a length of the v-phase teeth is determined, the total number of magnetic fluxes flowing through the u-phase teeth (u1 and u2), the total number of magnetic fluxes flowing through the w-phase teeth (v1 and v2), and the total number of magnetic fluxes flowing through the v-phase teeth (v1 and v2) are substantially equalized, so that it becomes possible to suppress the fluctuation of the thrust force and the fluctuation of the cogging torque based on the period of the v-phase.

[0033] The number of magnetic fluxes flowing through each of the teeth of the core element 50 is affected by the width and thickness, a distal end shape, slot intervals, or the like of the teeth. Accordingly, it is necessary to empirically determine the length of the v-phase teeth (v1 and v2) through testing. When all the u-phase, v-phase, and w-phase teeth are formed under the same conditions, it is necessary that at least the v-phase teeth be spaced farther from the stator magnets 4 than the u-phase and w-phase teeth. That is, the u-phase and w-phase teeth must be arranged closer to the stator magnets 4 than the v-phase teeth.

[0034] In a case where the v-phase teeth are shorter than the u-phase and w-phase teeth, or the u-phase and w-phase teeth are longer than the v-phase teeth, it is not necessary to perform adjustment on each tooth belonging to each phase. As described above, if the total number of magnetic fluxes flowing through the teeth of each phase is substantially the same, the fluctuation of the thrust force based on the v-phase period can be suppressed. For example, if only a certain v-phase tooth is made shorter and only certain u-phase and w-phase teeth are made longer, it is possible to adjust the total number of magnetic fluxes.

[0035] It should be noted that Fig. 7 illustrates a case in which the six teeth are formed on the core member 50, but it is also possible to imagine a case in which the twelve teeth 52 are formed, as shown in Fig. 6. When the v-phase teeth are spaced farther from the stator magnets 40 than the u-phase and w-phase teeth, the fluctuation of the thrust force and the fluctuation of the cogging torque based on the period of the v-phase can be suppressed.

[0036] Furthermore, the above description includes an example in which three-phase alternating current flows through the coil. However, the present invention can be flexibly applied not only to the linear motor that uses three-phase alternating current, but also to one in which alternating currents of a plurality of phases (x1, x2, ..., x n) can be used. In this case, the core element of the drive element contains teeth whose number is an integer multiple of the number n of phases of the alternating current. If the phases of the corresponding alternating currents of the two teeth located at both ends of the core element are represented by x1 and xn, then distal ends of the teeth corresponding to the other phases (x s , x3, ..., x n-1) are spaced farther from the stator magnets than distal ends of the aforementioned two teeth. This makes it possible to suppress the fluctuation of the thrust force and the fluctuation of the cogging torque. It should be noted that as the number of phases of the alternating current increases, the length difference of the teeth decreases. This is because it is assumed that as the total number of teeth present on the core member increases, an effect of the two teeth arranged at the two ends of the core member applied to the total number of magnetic fluxes is reduced.

[0037] Fig. 8 shows another example of an arrangement of stator magnets 4 on the stationary base 10 of the guide rail 1. In the Fig. 1, the N-poles and the S-poles of the stator magnets 4 are simply arranged alternately in the longitudinal direction of the guide rail 1. A boundary between the N-poles and the S-poles is parallel to the width direction of the guide rail 1 (right-left direction of a plane in Fig. 2). In the Fig. However, in the example shown in Fig. 8, the N poles and the S poles of the stator magnets 4 are formed in parallelograms, and the boundary between the N poles and the S poles is inclined with respect to the width direction of the track rail 1. That is, when the teeth 52 of the core member advance in the longitudinal direction of the track rail 1, magnetic poles of the stator magnets 4 facing the teeth 52 change from the N poles to the S poles or the S poles to the N poles, not suddenly but gradually. In this way, when the boundary of each of the magnetic poles is inclined with respect to the width direction of the track rail 1, the fluctuation of the magnetic attraction force due to the correlation between the arrangement pitches of the stator magnets 4 and the arrangement pitches of the teeth of the core member 50, that is, the fluctuation of the cogging torque, can be reduced, thereby making it possible to reduce the ripple of the thrust force of the drive member 5.

[0038] The linear motor actuator used in Fig. As shown in Figure 1, the drive member of the linear synchronous motor is mounted on the guide path provided on the channel-shaped track rail between the pair of reciprocating sliders 3a and 3b. However, a use mode of the linear motor according to the present invention is not limited to this. Fig. 9 shows a linear motor actuator in another mode, which is constructed using the linear synchronous motor of the present invention. The linear motor actuator includes a floor 106 attached to a stationary portion 107, such as a bed of a mechanical device, a linear guide 104 having two shafts arranged parallel to each other on the floor 106, a movable table 103 provided on the floor via the linear guide 104 therebetween, and a linear synchronous motor 100 provided between the floor 106 and the movable table 103. The linear guide 104 includes guide rails 108 fixed to the floor 106 and sliders 105 fixed to the movable table 103 and capable of reciprocating movement on the guide rails 108.The linear synchronous motor 100 includes a drive member 101 and stator magnets 102, wherein the stator magnets are arranged on the floor 106 in a moving direction of the movable table 103, and the drive member 101 is suspended from the movable table 103 so as to maintain a predetermined distance from the stator magnet 102. A structure of the drive member 101 is completely the same as that shown in FIG. Fig. 6 shown drive element 5.

[0039] Also in the linear motor actuator having this structure, by adjusting the lengths of the teeth of the core member of the drive member 101 in the above-described manner of the present invention, fluctuation of the thrust force and fluctuation of the cogging torque based on the period of the v-phase of the alternating current can be reduced to a minimum.

Claims

[1] Linear synchronous motor comprising: a first element (4) in which N-poles and S-poles are arranged linearly alternately to generate a magnetic field, a second element (5) which is opposite to the first element (4) at a distance therefrom and which, when alternating currents of a plurality of phases flow, generates a traveling magnetic field in an arrangement direction of the magnetic poles to exert a thrust on the first element (4), wherein: the second element (5) comprises a core element (50) in which teeth (52) are arranged, the number of which is an integer multiple and more than twice a number of phases of the alternating currents, and a coil (51) wound around the teeth (52) of the core element (50) and through which the alternating current of any one of the phases flows; and where: the alternating current is a three-phase alternating current consisting of a u-phase, a v-phase and a w-phase, wherein the u-phase flows through the coil (51) wound around the tooth (52) at one end of the core element (50), the w-phase flows through the coil (51) wound around the tooth (52) at another end of the core element (50), and distal ends of the teeth (52) around which the v-phase coil (51) is wound are spaced further from the first element (4) than distal ends of the teeth (52) around which the u-phase and w-phase coils (51) are wound. [2] Linear motor actuator comprising: a guide rail (1) with a stator magnet (4) in which N-poles and S-poles are arranged alternately in a longitudinal direction; rotors (3a and 3b) which move back and forth on the guide rail (1). can be moved, and a drive member (5) which is attached to the runners (3a and 3b) in such a way that a distance from the stator magnet (4) of the guide rail (1) is maintained, and which, when alternating currents of a plurality of phases flow, generates a traveling magnetic field in the longitudinal direction of the guide rail (1) to exert a thrust force on the guide rail (1), wherein: the drive member (5) comprises a core element (50) in which teeth (52) are arranged, the number of which is an integer multiple and more than twice a number of phases of the alternating currents, and a coil (51) wound around the teeth (52) of the core element (50) and through which the alternating current of any one of the phases flows; and where: the alternating current is a three-phase alternating current consisting of a u-phase, a v-phase and a w-phase, wherein the u-phase flows through the coil (51) wound around the tooth (52) at one end of the core element (50), the w-phase flows through the coil (51) wound around the tooth (52) at another end of the core element (50), and distal ends of the teeth (52) around which the v-phase coil (51) is wound are spaced further from the first element (4) than distal ends of the teeth (52) around which the u-phase and w-phase coils (51) are wound. [3] A linear motor actuator according to claim 2, wherein each of the magnetic poles constituting the stator magnet (4) is arranged at an inclination with respect to the longitudinal direction of the track rail (1).

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