JPH0378461A - Linear motor - Google Patents

Abstract

PURPOSE:To improve the efficiency without complicating the circuitry by providing input terminals at two joints of each coil for each phase in addition to three-phase input terminals and switching the conducting section of each phase coil in response to an output signal from a position detecting sensor arranged on a fixed section. CONSTITUTION:When a movable section 1 is at the left end, a movable section position detector a(32) is turned OFF. Three-phase outputs U, V, W are connected, respectively, with U1 and V3, V1 and W3, W1 and U3. Current flows through section I but does not flow through section I'. A linear scale 30 detects the position of the movable section 1, and a commutation circuit 31 performs three-phase commutation based on the detected position. When the movable section 1 comes to position A, shown by a dot line, the movable section position detector a(32) is turned OFF. A switching circuit 33 switches the joints of three- phase outputs U, V, W. Three-phase outputs U, V, W are connected, respectively, with U1 and U2, V1 and V2, W1 and W2. Consequently, current flows through section II but does not flow through section II'.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application] The present invention relates to a linear motor, and particularly to a MM (movable magnet) type linear motor that directly drives a precision positioning table or the like.

[Prior Art] The present inventors disclosed in Japanese Patent Application No. 63-225357 that it is possible to simplify the logic circuit and the drive circuit, and further reduce the number of lead wires connecting the logic circuit, the drive circuit, and each coil. proposed a linear motor. FIG. 10A is a structural diagram showing the main front structure of the movable part and fixed part of the above-mentioned proposed linear motor, FIG. 10B is a side view of FIG. 10A, and FIG. 10C is a diagram of FIG. 10A. FIG. 3 is a wiring diagram at a fixed part of the linear motor shown in FIG. Referring to FIG. 10A, the linear motor is composed of a movable part 1 and a fixed part 2, and the movable part 1 is composed of a yoke 11 and a permanent magnet 12. The movable part 1 is arranged so as to actually move in the left-right direction in FIG. 10A by means of a guide (not shown) via the fixed part 2 and a certain air gap 3.

Further, a table (not shown) is attached to the movable part 1. The fixed part 2 is composed of a core 21 and a core 22. This coil 22 has three phases: U+I], V phase, and W phase.
The phase coils are arranged in order. In the example shown in FIG. 10A, the ■ phase and the W phase are energized, and the direction of the current is the first. If it is as shown in the OA diagram, the movable part 1 will generate thrust to the left and move forward. In addition, the fixed part 2
The coil 22 is ul r vI from the left end of FIG. 10A.
r IA/11 u2 + v2+ W2+
””I S+ vI S+ WIS
Let j ul G+■I 6 + wI 6. These coils ul, V++ WI+ ”'1JI6+
"IG+" 16 is connected as shown in FIG. 10C. That is, U-phase coils u1 to u16,
■ Phase coils V, ~V1G and W-phase coils W, ~w1
In both cases, all coils are electrically connected in series.

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

v and W are each connected to a drive circuit. This drive circuit controls the currents applied to the terminals U, V, and W, causing the movable part 1 to travel.

[Issue 8 to be solved by the invention] As mentioned above, in the proposed linear motor, it is only necessary to control the current applied to the three terminals U, V, and W.
Control circuit configuration can be simplified. However, since it is an energization method in which current is passed through all the coils of each energized phase, current also flows in parts that do not contribute to moving the movable part 1, resulting in poor efficiency. Moreover, the longer the stroke of the motor, the more the efficiency decreases, so there is also the disadvantage that it cannot be applied to a linear motor with a long stroke. Therefore, instead of the full energization method, a method can be considered in which terminals are provided for each of the coils of each phase, for example, U, ~ulfi, and only the necessary coils are energized. However, in this case, although the efficiency is good, a large number of lead wires and a large number of power elements are required, creating a new problem of complicating the circuit.

The present invention was made to solve the above problems, and an object of the present invention is to provide a linear motor that can improve efficiency without complicating the circuit.

[Means for solving the volatile problem] The invention according to the first to third claims includes a movable part provided with a permanent magnet and a core having a rectangular cross section, and a conductor is wound around the outer periphery of the core to excite the core. A fixed part in which a coil is formed, a position detection part provided in the fixed part to detect the position of the movable part, and a position detection part provided in the fixed part to detect that the movable part is in a predetermined area. The excitation coil has three phases, and the coil of each phase is wound around the outer circumference of the core for each convex pole, and the coil of each phase is entirely electrically connected to each phase. are connected in series, the coils of each phase connected in series are Δ-connected, and input terminals are provided at the connection point of each phase and two of the connection points of each coil of each phase,
This is a linear motor that switches the current-carrying section of the coil of each phase in response to a detection signal output from a region detection section.

In the invention according to the second claim, the position of the first input terminal among the two input terminals provided in the coils of each phase connected in series is such that the number of poles of the movable part is A and the number of poles of the fixed part is A. When B is an even number, the position of the second input terminal is (A+B)/2 or (A+B+2)/2 from one end of the coil of each phase.
From the other end of the coil of each phase (A+B)/2 or (A+8
+2)/2.

In the invention according to claim 3, the position of the first input terminal among the two input terminals provided in the coils of each phase connected in series is such that the number of poles of the movable part is A and the number of poles of the fixed part is A. When B is an odd number, (A+B+1)/2 from one end of the coil of each phase
The position of the second input terminal is configured to be (A+B+1)/2 from the other end of the coil of each phase.

[Operation] In the invention according to the first claim, in addition to the three-phase input terminals, input terminals are provided at two of the connection points of each coil of each phase,
The energizing section of each phase coil is switched in response to the output signal of the position detection sensor provided on the fixed part, so the control circuit and drive circuit can be simplified, and the The number of lead wires can be reduced and efficiency can be improved. In the inventions according to the second and third claims, since the interval between the intermediate terminals is set longer than the length of the fixed part, the overlapping energized section is longer than the length of the fixed part, and the thrust when switching the energized section is Fluctuations in speed and changes in speed can be prevented.

[Embodiment of the Invention] Fig. 1A is a structural diagram showing the main front structure of a movable part and a fixed part of a linear motor showing an embodiment of the present invention, and Fig. 1B is a side view of Fig. 1A. FIG. 2 is a wiring diagram of the fixed part. Referring to FIGS. 1A and 1B, the linear motor is comprised of a movable part 1 and a fixed part 2, and the movable part 1 is comprised of a yoke 11 and a permanent magnet 12.

The movable part 1 is disposed so as to be freely movable in the left-right direction in FIG. 1A via a fixed part 2 and a fixed air gap 3 by a guide (not shown). In addition, the movable part 1
A table (not shown) is attached to the .

On the other hand, the fixed part 2 is constituted by a core 21 and a coil 22, and is fixed to a mounting member (not shown) to form a -axis sliding table.

To explain more specifically, the yoke 11 of the movable part 1 is made of a magnetic material so as to form a magnetic circuit of the permanent magnet 12,
A cross-sectional area that will not be saturated by the magnetic flux of the permanent magnet 12 is required. A predetermined number of permanent magnets 12 are arranged on the yoke 11 at equal intervals. In the example shown in FIG. 1A, it is a four-blade type in which four permanent magnets 12 are arranged, and the polarity of each magnet is such that N pole and S pole appear alternately. The core 21 of the fixing part 2 is formed so that its cross section is square as shown in FIG. 1B. A conductor is wound around the outer periphery of the core 21 to form a coil 22 .

A three-phase system is employed in which three coils, for example, u, vl, and w, are provided per length of one pole of the permanent magnet 12. The method of connecting these coils is as shown in Figure 2.
The U-phase coils 'I+u2+u3+ to +u8 are all connected in series in sequence. Connect in the same way for the ■phase and W phase. Furthermore, the connected three-phase coils are connected in a delta connection, and the connection wires are connected to terminals U, V, and V, respectively.
.

W is provided.

Furthermore, U-phase coils u2 and u3r uG and U.

Terminals U2 and U are provided at the connection points of , respectively. Similarly,
For the ■phase and W phase, terminal V2. V3. W2, W, are provided. The positions where these terminals are provided are the length of four poles between U2 and U. This length is the same as the number of poles of the movable part 1.

FIG. 3 is a structural diagram showing another embodiment of the present invention in which the length of the fixed part 2 is three times the length of the movable part 1, and FIG. FIG. 3 is a wiring diagram of the embodiment. Referring to FIGS. 3 and 4, in this example as well, the distance between U2 and U is provided so as to correspond to the length of four poles.

This coil has 12 poles, whereas the coil shown in FIG. 1A has 8 poles.

FIG. 5 is a block diagram showing a linear motor drive circuit applied to the present invention. Referring to FIG. 5, this drive circuit drives the linear motor as a permanent magnet synchronous three-phase AC motor. The drive circuit includes a linear scale 30 that is directly connected to the linear motor to detect the position of the movable part 1, and a linear scale 30 that is adapted to the position of the movable part 1 based on the position detected by the linear scale 3o.
A commutation circuit 31 for producing a phase alternating current, a moving part position detector 32 for obtaining a moving part position signal of the linear motor, and a terminal for supplying three-phase alternating current in response to the moving part position signal are switched. It includes a switching circuit 33 for switching the energization section of the motor, and a connection terminal 35 for connecting the three-phase alternating current generated by the current circuit 31 to the linear motor 34 and the switching circuit 32.

6 and 7 are structural diagrams showing the arrangement of the position detector.

Next, with reference to FIGS. 5, 6, and 7,
The operation will be explained. In FIG. 6, when the movable part 1 is at the left end, the movable part position detector a is OFF.

At this time, the switching circuit is in the state shown in FIG. That is, the U phase of the three-phase power supply is connected to U, and V,
The (2) phase is connected to vl and Wl, and the W phase is connected to Wl and U, respectively.

In this case, the fixed part coil u, u2 u3 u4u
5 u6 VI V2 VI VI VI
Current flows through V6 WI W2 W3 W4 W5 W6. In other words, current flows in the section I shown in FIG. 6, but no current flows in the section I. Due to the current flowing in the section of the workpiece, the movable part 1 receives force and moves to the left. When the movable part 1 moves, the linear scale 30 detects its position.

Based on the detected position, the commutation circuit 31 performs three-phase commutation according to the position of the movable part 1, and three-phase alternating current suitable for the position of the movable part 1 is generated. In this way, the movable part]
continues to move to the right.

When the movable part 1 comes to the position A indicated by the dotted line in FIG. 6, the movable part position detector a is turned on. Moving part position detector a is ON
Then, the switching circuit changes U and V.

The connection points of the three phases of W are switched. That is, the three-phase output U is connected to the terminals U, U2, and U2. V is connected to terminals v1 and V2, and W is connected to terminals W and W2. In this case, the coils u3u4 u5 u6 u7 u6 VI V of the fixed part 2
I VI V6 V7 V6 W3 W4 W
5 W6 W7 Current flows through W6. In other words, the 6th
Current flows in the section marked ■ in the figure, and no current flows in the section marked ■'. This H until the movable part 1 reaches the left end in Fig. 6.
Current will flow in the section.

FIG. 7 is a layout diagram of the movable part position detector when the length of the fixed part 2 is three times the length of the movable part 1. Referring to FIG. 7, movable part position detectors are further added at intervals slightly shorter than the length of movable part 1 to form movable part position detectors a and b.
The switching circuit is controlled by both signals. Similarly, if the length of the fixed part 2 is three times or more the length of the movable part, the length of the movable part 1
It is sufficient to add movable part position detectors at intervals slightly shorter than the length of .

FIG. 8 shows intermediate terminals U2 and U3 + v2 and v.

FIG. 3 is a schematic diagram of a linear motor in which the distance between W2 and W is set equal to the number of poles of the movable part plus two poles. This linear motor is realized when the fixed part has an even number of poles,
When the number of poles of the movable part is A and the number of poles of the fixed part is B, the lengths of the energized sections 1 and 2 are (A+B+2)/2. In this case, the energized section! Since the overlapping energized sections of and ■ are longer than the length of the movable part by two poles, the installation position of the movable part position detector does not have to be set so strictly, and thrust fluctuations and speed changes when switching the energized section can be easily avoided. No inconvenience will occur.

FIG. 9 is a schematic diagram of a linear motor in which the interval between intermediate terminals is set to the number of poles of the movable part 1 plus one pole. This linear motor is realized when the number of poles of the fixed part is an odd number, and if the number of poles of the movable part is A and the number of poles of the fixed part is B, the lengths of the energized sections I and ■ are (A+B+1)/2 becomes. In this case as well, the same effect as shown in FIG. 8 can be obtained because the overlapping current-carrying sections I and (2) are longer than the length of the movable part by one pole.

As described above, in this embodiment, by providing a switching circuit for switching the energized section and a movable part position detector, the control circuit can be simplified and the number of lead wires can be reduced. This allows the winding resistance to be reduced. As a result, the voltage drop due to the winding resistance can be reduced, and the speed and efficiency of the linear motor can be improved. Note that this embodiment is most suitable for a linear motor whose stroke is twice or more the length of the movable part.

[Effects of the Invention] As described above, according to the invention according to the first claim, the number of lead wires for connecting each coil and the drive circuit can be reduced, and the drive circuit can also be simplified, so that the circuit can be simplified. Efficiency can be improved without increasing complexity. Furthermore, the second
According to the invention described in the claims and the third claim, it is possible to prevent fluctuations in thrust force and changes in speed when switching between energized sections.

[Brief explanation of drawings]

Fig. 1A is a structural diagram showing the main front structure of the movable part and fixed part of a linear motor according to an embodiment of the present invention, Fig. 1B is a side view of Fig. 1A, and Fig. 2 is shown in Fig. 1A. A wiring diagram of the fixed part of the linear motor, FIG. 3 is a structural diagram showing another embodiment of the present invention, FIG. 4 is a wiring diagram of another embodiment shown in FIG. 3, and FIG. 5 is a diagram of the present invention. Figures 6 and 7 are layout diagrams showing the arrangement of position detectors, and Figure 8 shows the distance between intermediate terminals based on the number of poles of the movable part. Figure 9 is a schematic diagram of a linear motor when the length is equal to +2 poles, and Figure 9 is a schematic diagram of a linear motor when the interval between intermediate terminals is equal to the number of poles of the movable part + 1 pole. 10B is a side view of the linear motor shown in FIG. 10A, and FIG. 10C is a side view of the linear motor shown in FIG. 10A. FIG. 3 is a wiring diagram of the fixed portion of the linear motor shown in the figure. In the figure, 1 is a movable part, 2 is a fixed part, 11 is a yoke,
12 is a permanent magnet, 21 is a core, and 22 is a coil. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 15

Claims (3)

[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; a position detection section for detecting the position of the excitation coil; and an area detection section provided on the fixed section that detects that the movable section is in a predetermined area and outputs a detection signal, is three-phase, and the coils of each phase are wound around the outer periphery of the core for each pole, and the coils of each phase are all electrically connected in series for each phase, and the coils of each phase are electrically connected in series for each phase. The coils are Δ-connected, and input terminals are provided at two points of the connection point of each phase and the connection point of each coil of each phase, and in response to a detection signal output from the area detection section,
A linear motor characterized in that the current-carrying sections of the coils of each phase are switched. (2) 2 provided in the coils of each phase connected in series.
The position of the first input terminal among the two input terminals is (A+B)/2 or (A+B+2) from one end of the coil of each phase when the number of poles of the movable part is A and the number of poles of the fixed part is an even number B. )
/2, and the position of the second input terminal is (A+B)/2 or (A+B+2)/2 from the other end of the coil of each phase. . (3) 2 provided in the coils of each phase connected in series.
The position of the first input terminal among the two input terminals is (A+B+1)/2 from one end of the coil of each phase, assuming that the number of poles of the movable part is A and the number of poles of the fixed part is an odd number B. The position of the input terminal 2 is from the other end of the coil of each phase (A+B+1)
2. The linear motor according to claim 1, wherein: /2.