JPH02168845A - Linear motor - Google Patents

Abstract

PURPOSE:To increase the rigidity of core and to reduce deformation of core by arranging at least one foot at the intermediate section of core at fixed section then securing the core at least three points including the opposite ends to a fixing base. CONSTITUTION:Opposite ends of a core 21 are secured through spacers 4 to a fixing base 3 to provide an empty section Y wound with no coil 22 in the central section of the core 21, then a foot 5 is fixed with a screw 6 and further secured through a screw 7 to a base 3.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a linear motor, and in particular, a movable part and a fixed part in which an excitation coil is formed by winding a conductor around the outer periphery of the core, and a fixed part provided in the fixed part. The present invention relates to a linear motor equipped with a position detection section for detecting the position of a movable section.

[Prior Art] In Japanese Patent Application No. 63-225357, the present inventors proposed a linear motor having a structure in which a conductor is wound around the outer periphery of a rectangular stator core to form a coil. This proposed linear motor has the advantage that the core can be designed to be thin by making the permanent magnets multipolar, making it possible to convert the entire system into a compact I-type motor.

FIG. 8 is a diagram showing a movable part and a fixed part of the above-mentioned proposed linear motor, in particular, FIG. 8(a) shows a front view, and FIG. 8(b) shows a side view.

In FIG. 8, the fixed part 2 is composed of a core 21 and a coil 22 wound around the outer periphery of the core 21. Movable part 1
is movable in the left-right direction by a linear guide (not shown), and is composed of a permanent magnet 11 and a yoke 12. The magnetic circuit is a permanent magnet]] - Air gap 5 -
Core 21 - Air gap 5 - Permanent magnet 11 → Yoke 12
→Permanent magnet] It is formed by a loop of 1. Therefore, an attractive force is always generated between the core 21 and the permanent magnet 11 via the air gap 5. The magnitude of this attractive force reaches several tens of kgf in an example where a strong rare earth magnet is used as a permanent magnet.

[Problem to be solved by the invention] By the way, since the core 2 of the fixed part 2 shown in FIG. 11, the core 21
is pulled upward, and the core 2] is deformed into an arched shape. This amount of deformation becomes maximum at the midpoint of the core 2 when the movable portion 1 is located in the middle of the entire length of the core 2. In this way, by deforming the core 2 into an arcuate shape, the magnitude of the thrust changes depending on the position of the movable part, and the permanent magnet 1]
In some cases, a problem may occur where the coil 22 comes into contact with the coil 22. Therefore, at the time of design, it was necessary to calculate the amount of deflection of the core 21 from the magnitude of the suction force and the cross-sectional shape and length of the core 21, and to determine the thickness of the air gap 5.

Therefore, the main object of the present invention is to provide a linear motor that can improve the rigidity of the core and reduce the amount of core deformation caused by the attractive force of the permanent magnets.

Another object of the present invention is to provide a linear motor that can minimize the reduction in thrust due to the reduction in the number of conductors when at least one leg is attached to the intermediate portion of the core. .

[Means for Solving the Problem] The invention according to the first claim includes a movable part provided with a permanent magnet and a core having a rectangular cross section, and an excitation coil is formed by winding a conductor around the outer periphery of the core. A linear motor comprising a fixed part and a position detecting part provided on the fixed part for detecting the position of the movable part, the linear motor including at least one leg provided in the middle of a core of the fixed part, and at least one leg provided at both ends of the core. It is designed to be fixed to the mounting base in at least three places including.

In the invention according to the second claim, the mounting interval of at least one leg is an even number of pole lengths of at least four poles, and the number of legs included per length of the movable part is in the entire moving range of the movable part. The length of the six coils on both poles on both sides where the legs are provided is shortened by u/6 (u is the width of the legs), and the movable part is placed at the left or right end. Once in position, the three coils at the left or right end pole of the fixed part are each shortened by 6/6, and a blank space is provided at the left or right end where no coil is wound by 1/2 length. configured.

In the invention according to the third claim, the mounting interval of the legs is at least 2.
The poles are even-numbered pole lengths and are arranged so that the number of legs included per length of the movable part is an integer of 1 or more in the entire movement range of the movable part, and on one side where the legs are provided. When the lengths of the three coils of the pole are each shortened by fl/3 (Q is the width of the leg) and the movable part is located at the right end, if the left end of the movable part touches the leg, the right end of the fixed part The lengths of the three pole coils are each shortened by gun/3.

In the fourth aspect of the invention, the excitation coil has three phases, the coils of each phase are electrically connected in series for each phase over the entire length, and one end of the coil of each phase connected in series is short-circuited. , and a drive signal is input to the other end.

[Function] The invention according to the first claim is provided with at least one leg in the middle part of the core, and the core is fixed to the mounting base, so that the rigidity of the core is improved and the core is fixed by the attraction force of the permanent magnet. The amount of deformation can be reduced.

In the inventions according to the second and third claims, the reduction in the number of conductors due to the attachment of the legs is taken into consideration, so that the reduction in thrust force can be minimized.

In the fourth aspect of the invention, the coils of each phase are electrically connected in series for each phase, one end of which is short-circuited, and a drive signal is input to the other end. can be simplified, and the number of lead wires connecting each coil and the drive circuit can be reduced.

[Embodiment of the invention] Fig. 1 is a diagram showing a movable part and a fixed part of an embodiment of the invention, in particular, Fig. 1(a) shows a front view, and Fig. 1(b) shows a front view. A side view is shown. The embodiment shown in FIG.
A blank part Y in which the coil 22 is not wound is provided in the center of the core 21, and the legs 5 are attached to this part with screws 6, and further tightened to the mounting base 3 with screws 7. Thereby, the rigidity of the core 21 is improved, and the amount of deformation of the core 21 due to the attractive force of the permanent magnet 11 can be reduced.

As mentioned above, by providing the leg 5 in the center of the core 21 and attaching it to the mounting base 3, the amount of deformation of the core 21 can be reduced, but by providing the blank portion Y, the number of turns of the coil 22 is reduced, Thrust is reduced. Therefore, an embodiment that can reduce such a decrease in thrust will be described below.

FIG. 2A is a front view showing a movable part and a fixed part without legs for comparison with each embodiment of the present invention, and FIG.
FIG. B, FIG. 2C, FIG. 2E, and FIG. 2F are front views of the fixing portion in each embodiment of the present invention, and FIG. 2D is a front view of the fixing portion for explaining the effects of the embodiment of the present invention. It is a diagram.

First, FIG. 2B shows the fixed part 2 when one leg 5 is provided for the entire length (stroke direction) of the movable part 1. A blank portion is also provided at the left end of 2 where the coil is not wound by the length of hair/2. As a result, the length of the coil 22 per length of the movable part 1 becomes shorter than that in the example shown in FIG. 2A.

That is, one pole adjacent to leg 5 (coil uB).

VB, w8 and coil ug, Vg, Wg)
shorten it by /2, and further shorten it by one pole on the left end of Figure 2B (
Coil LJ+ + ``+ + '''+) is adapted to shorten the length by 1/2.

In other words, as shown in Figure 2B, the length of one pole in eight poles is τ
In this case, if each coil is marked with a symbol as shown in Figure 2B, the location where the length of one pole is shortened by 0/2 is u8.
n7+V8n? +w8n7 and u8n
+ va n + W8 n (n 11+ 2゛'
).

In the example shown in FIG. 2C, the rigidity of the core 21 is further improved by providing legs 5 at 1/2 of the length of the movable part 1. In the example shown in FIG. 2C, u4n 3+ v4n 3W4o-a and u4n
+4n+w4n pole length ■ will be shortened by 0/2.

As described above, as shown in FIGS. 2B and 2C, the rigidity of the core 21 is improved by providing at least one leg 5 in the middle of the core 21 and fixing it to a highly rigid mounting base. In addition, by providing the legs 5, the coil 22
However, according to this embodiment, the decrease in thrust can be minimized.

Here, the explanation will be given using more specific numerical values as an example. leg 5
The permanent magnet 1] provided in the movable part shown in Fig. 2A which is not provided with 8 poles, and the length τ of 1 pole is 25 m.
Let it be m. In this system, two phases (e.g. coil VI + V2 + v3 + V4'' and ~W
l, W2, w3. w4 °゛) When a constant current continues to flow, the magnitude of the thrust generated in the movable part 1 is sinusoidal, as shown by the solid line in Figure 3, if the magnetic flux distribution is sinusoidal. Become.

FIG. 3 is a diagram for explaining the magnitude of thrust according to this embodiment. In FIG. 3, A indicates only one direction, which is the magnitude of the total thrust, and indicates the maximum value of the magnitude as 1. Further, a indicates the thrust generated by the magnetic flux and current of one pole (for example, coils v1 and wl). Therefore, there is the relationship A=gXa, and the maximum value of a is 0°125.

Here, the same applies to the embodiments of the present invention.]1 When considering the magnitude of the force, in FIG. 2B, the width of the leg 5 is assumed to be 8 mm. In this case, coil U.

The length of one pole of the group Vl, Wl and the group [6, VB, W6 is 21. It becomes mm. In this case, the length of the coils for the other six poles remains unchanged at 25 mm. therefore,
Compared to the example shown in FIG. 2A, the number of turns of the coil contributing to thrust generation is (21,X2+25X6)/25x8=0.
96, the reduction in the number of conductors is 96%, that is, the number of conductors is reduced by 4%, and the thrust force is also reduced by 4% for the same current value.

However, the length of one pole of the permanent magnet 11 is different from the length of one pole of the coil uI + v+ + Vl + w+
Since there is a phase shift between uB, VB, and W8, the total thrust further decreases. bl in Figure 3
and b2 are coils ul, Vl, Wl and coils UB, VB
, shows the magnitude of the thrust generated by the W8 group. In both cases, the maximum value is the number of conductors or 21/25 = 0
．． 84 (84%), so 0,1,25x
0.84=0.105.

Other coils u2, v2, w2-1J7,
For the six poles of V7 and w7, the thrust shown in a is generated.

When these are combined, the result is shown in B, and the maximum value is approximately 0.95, which means that the thrust reduction due to phase shift is approximately 0.
．． It becomes 01-.

In addition, in the example shown in FIG. 2C, by providing the leg 5 with a width of 3 mm in the middle, the number of conductors is reduced by 8% to 0.92 compared to the example shown in FIG. 2A, but the phase difference The maximum value of the total thrust including the shift is about 09905, and the decrease in thrust due to the phase shift is about 0.015.

For these embodiments, the example shown in FIG.
The decrease in coils due to the provision of
1, Vl, Wl-uB, VB, and W8. In the example shown in this Figure 2D,
The total number of conductors was set to 0. as in the embodiment shown in FIG. 2B.
96, but the length of one pole of the coil 22 is all τ-
Q, /8 = 24 mm, and the length of one pole of the permanent magnet 1 is 25 mm.] 3 Since this is different, the phases of the thrust generated for each of the six poles are all different.

FIG. 4 is a diagram showing the magnitude of thrust in the example shown in FIG. 2D. The thrusts generated for each of the six poles in the example shown in FIG. 2D are C4c2...C8 in order from the left in FIG. 2D.

The maximum value of each of them is 0°125X24/25=0.
It becomes 12. All the thrusts become like C, the maximum value is about 0.92, and the decrease in thrust due to phase shift is 0.92. It becomes 04. In the example shown in FIG. 2D, if the magnitude of the thrust is calculated in the same manner when the legs 5 are added, it is approximately 0.88, and the decrease in thrust due to the phase shift is also 0.04. This is a considerably larger value than 0.01 in the embodiment shown in FIG. 2B and 0.01.5 in the embodiment shown in FIG. 2C.

In addition, the coil 22 is placed at the left end of the fixed part 2 by the length of /2.
The reason for providing a blank part where the magnetic flux is not wound is to ensure that the number of conductors interlinked with the magnetic flux emitted from the permanent magnet 11 is the same no matter where the movable part 1 is located. Therefore, for example, if the position of the leg 5 is as in this embodiment,
If it is between W6 and u7 instead of between w8 and u9, there is no need to provide the above-mentioned blank space at the left end of the fixed part 2.

In addition, in order to achieve the feature of minimizing the reduction in thrust force as in this embodiment, the mounting interval of the legs 5 should be an even number of pole lengths of at least 4 pole lengths, and the position of the movable part 1 should be adjusted. Even if the movable part 1 moves, the number of legs included in the length of the movable part 1 must be arranged so that it is an integer of at least one.

Next, a second embodiment of the present invention will be described with reference to FIGS. 2E and 2F. The example shown in Figure 2E is
This is an example in which one leg 5 is provided at the length interval of the movable part 1, and the second
The example shown in Figure F is an example in which a leg 5 is further provided in the middle.

Here, regarding FIGS. 2E and 2F, the above-mentioned
In the same manner as in the examples, explanation will be given using specific numerical values.

In FIG. 2E, coils uB, VB.

Only the pole of the w8 group was shortened by 8 mm, which is the width of the leg 5, to 17 mm. The reduction in the number of conductors is 4%, as in the first embodiment, so if the thrust when the legs 5 are not provided is 1, it becomes 0.96. Coil L to this
There is a reduction in thrust because the phase of the 18, VB, and WB groups is different from the other seven groups. Taking these into consideration, the maximum value of thrust is calculated to be approximately 0.945.

The reduction in thrust due to the phase shift is approximately 0.015.

On the other hand, in the example shown in FIG. 2F in which one more leg 5 is provided, the thrust force decreases by 8% due to the decrease in the number of conductors, and the magnitude of the thrust force becomes 0.92. Further, the maximum value of the thrust including the phase shift is about 0.915, and the decrease in thrust due to the phase shift is about 0.05. These methods also apply to 2D
This method is more effective than the example shown in the figure.

FIG. 5 is a wiring diagram of the coil in this embodiment, FIG. 6 is a block diagram of the logic circuit, and FIG. 7 is an electric circuit diagram of the drive circuit.

Next, a method for driving the coil 22 will be explained.

Coil u1. v11W1~u8~. V8. W8~ is the 5th
Connected as shown. That is, coil u1
．． u21 u3~u8N and % vll V2V5~V
8~, WI, W2, W3~W8~ (so all the coils are electrically connected in series.

And the polarity is coil uI + u3 ~ u7 ~ (odd number)
, v2. ■4~v8~ (even numbered), w++w3~w7
~ (odd numbered) are assumed to have the same polarity, and the others are assumed to have opposite polarity. Then, the coil U, ~u8~ forms a U phase, and ■1
~V8~ forms a V phase, and W1~w8~ forms a W phase, forming three phases.

The right end of the three-phase coil described above is used as terminals U, V, and W, and the other end is a so-called Y-connection system in which all three phases are short-circuited at a neutral point N.

Although this wiring is somewhat complicated, it is also possible to use the Δ wiring method. In any case, the terminal coming out of the linear motor (
There are three lead wires.

The drive section 41 is composed of power transistors Tr1 to Tr6 and a power source E, as shown in FIG. The collectors of the transistors Tr and Tr2 are connected in series, and the connection point thereof is connected to the terminal U. The collectors of the transistors Tra and Tr4 are connected in series,
The connection point is connected to terminal V. transistor Tr,
and Tr6 have their respective collectors connected in series, and the connection point thereof is connected to the terminal W.

On the other hand, as shown in FIG. 2B, three position detectors a, b, and c are provided at three locations with an interval of 2/3 poles. Further, although not shown, position detectors a', b'c' are provided at an interval corresponding to the length of the movable portion 1. however,
The stroke of the movable part 1 is the same as the length of the movable part 1,
Moreover, if the position detector is one that can obtain an output at the S pole of the permanent magnet 11, when the movable part 1 moves to the right end, the right end permanent magnet is the N pole, so the position detectors b' and C'
can be made unnecessary.

As shown in FIG. 6, each detection signal of the position detectors a and a' is given to a logic circuit 32 via an OR gate 31, and each detection signal of position detectors S and c is directly given to a logic circuit 32.
given to 2. Based on each detection signal, the logic circuit 32 outputs a signal e-j for making the power transistors Tr to Tr6 conductive. Note that the logic circuit 32 is given a signal d instructing the left and right movement direction of the movable portion 1.

As described above, by electrically configuring, the position of the movable part 1 is detected by the position detectors a, a', b, and c, and the logic circuit 32 controls each of the power transistors Tr, to Tr6 of the drive circuit 41. The movable part can be moved by making the coil 22 conductive and passing current through the coil 22 to generate an effective thrust.

[Effects of the Invention] As described above, according to the invention claimed in claim 1, at least one leg is provided in the middle part of the core to fix the core to the mounting base, so the rigidity of the core is improved. However, the amount of deformation of the core due to the attractive force of the permanent magnet can be reduced. Moreover, the heat generated by the copper loss of the coil is radiated from the core through the legs and through the mounting base, so the heat radiation characteristics can be improved compared to the case where the legs are not provided.

According to the inventions according to the second and third claims, since the reduction in the number of conductors due to the attachment of the legs is taken into consideration, the reduction in thrust force can be minimized.

According to the fourth aspect of the invention, by considering the coil connections, the logic circuit and the drive circuit can be simplified and the number of lead wires can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a movable part and a fixed part of an embodiment of the present invention. FIG. 2A is a front view showing a movable part and a fixed part of a conventional linear motor. 2B, 2C, 2E and 2F are front views of the fixing part in each embodiment of the present invention, and FIG. 2D is a front view of the fixing part for explaining the effects of the embodiment of the present invention. It is. FIG. 3 is a diagram for explaining the magnitude of thrust in the first embodiment of the present invention. FIG. 4 is a diagram for explaining the magnitude of thrust in the embodiment shown in FIG. 2D. FIG. 5 is a wiring diagram of a coil in an embodiment of the present invention. FIG. 6 is a block diagram of the logic circuit. FIG. 7 is an electrical circuit diagram showing the drive circuit. FIG. 8 is a diagram showing a movable part and a fixed part of a linear motor which is a prior art of the present invention. In the figure, 1 is a movable part, 2 is a fixed part, 5 is a leg part, 11
is a permanent magnet,] 2 is a yoke, 21 is a core, 22 is a coil, 32 is a logic circuit, and 41 is a drive circuit. Patent applicant NCH N Toyo Bearing Figure 4 Figure 7

Claims (4)

[Claims] (1) a movable part provided with a permanent magnet; a fixed part including a core with a rectangular cross section and an excitation coil formed by winding a conductor around the core; In a linear motor equipped with a position detection unit for detecting the position of the fixed unit, the fixed unit includes at least one leg provided in the middle of the core, and is fixed to the mounting base at at least three locations including both ends of the core. A linear motor characterized by: (2) The mounting interval of the at least one leg is an even pole length of at least four poles, and the number of legs included per length of the movable part is one or more in the entire movement range of the movable part. The lengths of the six coils of the poles on both sides where the legs are provided are each shortened by l/6 (l is the width of the legs), and the movable part is placed at the left end or the right end. When positioned, each of the three coils at the left or right end of the fixed part is shortened by 1/6, and the length is 1/2 at the left or right end.
2. The linear motor according to claim 1, further comprising a blank portion in which no coil is wound for a length of . (3) The mounting interval of the legs is an even pole length of at least two poles, and the number of legs included per length of the movable part is an integer of 1 or more in the entire movement range of the movable part. When the lengths of the three coils of the one pole arranged as shown in FIG. 2. The linear motor according to claim 1, wherein when the left end of the movable part rests on the leg, the lengths of the three coils at the right end of the fixed part are each shortened by 1/3. (4) The excitation coil is three-phase, and the coils of each phase are electrically connected in series over the entire length, one end of the series-connected coil of each phase is short-circuited, and the other end is connected electrically in series. Claim 2, characterized in that a drive signal is input.
Linear motor described in item 3 or item 3.