Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2001-11-02
2003-12-09
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
C318S135000
Reexamination Certificate
active
06661125
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a linear motor, more particularly relates to a linear motor able to use a stacked member comprised of a plurality of magnetic sheets stacked together as a stator (platen).
BACKGROUND ART
Explaining the principle of a Sawyer linear motor, as shown in
FIG. 12
, it is comprised of a platen (stator)
10
comprised of a magnetic thick plate on whose surface is repeatedly formed platen dots D at a spatial period of the dot pitch P and a movable member (traveling member)
20
comprised of a permanent magnet M for generating a bias magnetic flux, first and second yokes Y
1
(Y
2
) bonded to the magnetic pole surface to be arranged in parallel to the direction of advance and provided with first and second branched magnetic path legs A and A′ (B and B′), series-connected first and second A-phase excitation coils CA and CA′ wound around the first and second branched magnetic path legs A and A′ of the first yoke Y
1
, series-connected first and second B-phase excitation coils CB and CB′ wound around the first and second branched magnetic path legs B and B′ of the second yoke Y
2
, and two pole teeth (projecting poles) KA and KA′ (KB and KB′) formed at each of the bottom ends of the first and second branched magnetic path legs A and A′(B and B′) and arranged in the direction of advance at intervals of ½ of the dot pitch P. Here, each branched magnetic path leg may be formed with only one pole tooth, but in the event of several, the spatial phase held with respect to the closest dots of the platen dots D is the same. Further, the interval between the first branched magnetic path leg A (B) and second branched magnetic path leg A′(B′) is set so that the spatial phases with respect to the closest dots are shifted in the direction of advance by exactly P/2. Further, the interval between the second branched magnetic path leg A′ and the first branched magnetic path leg B is set so that the spatial phases with respect to the closest dots are shifted in the direction of advance by exactly P/4.
The movable member
20
has a pressurized air ejection port and floats slightly above the surface of the platen
10
by blown pressurized air. As shown in
FIG. 12A
, if a B-phase current of the illustrated polarity is flown through only the terminals of the first and second &bgr;-phase excitation coils CB and CB′ of the second yoke Y
2
, not only the bias magnetic flux due to the permanent magnet M, but also the alternating magnetic flux due to the second excitation coil CB′ are superposed and strengthened to generate a concentrated magnetic flux portion a in the air gap between the pole teeth KB′ of the second branched magnetic path leg B′ and the closest dots D
1
and D
2
and strongly magnetically draw the pole teeth KB′ to the closest dots D
1
and D
2
. Also, an alternating magnetic flux is applied to the pole teeth CB of the first branched magnetic path leg B in a direction canceling out the bias magnetic flux, so an extinguished magnetic flux portion b is formed. On the other hand, the magnetic flux comprised of the concentrated magnetic flux from the second branched magnetic path leg B′ of the second yoke Y
2
branched via the inside of the platen
10
passes through the first and second branched magnetic path legs A and A′ of the first yoke Y
1
, but the pole teeth KA of the fist branched magnetic path leg A are delayed in the direction of advance by exactly P/4 with respect to the closest dots D
15
and D
14
. Therefore, the closest dots D
15
and D
14
pull the pole teeth KA in the direction of advance by one branched magnetic flux and the pole teeth KA′ of the second branched magnetic path leg A′ proceed in the direction of advance by exactly P/4 with respect to the closest dots D
10
and D
9
due to the other branched magnetic flex Accordingly, the closest dots D
10
and D
9
pull the pole teeth KA′ in a direction opposite to the direction of advance. Therefore, the thrust in the direction of advance and the pullback force in the reverse direction match each other perfectly and the first yoke Y
1
as a whole is balanced. That is, a thrust branched magnetic flux portion d is generated in the air gap between the pole teeth KA of the first branched magnetic path leg A and the closest dots D
15
and D
14
, while a pullback force branched magnetic flux portion c is generated in the air gap between the pole teeth KA′ of the second branched magnetic path leg A′ and the closest dots D
10
and D
9
, so the first yoke Y
1
itself becomes a stable point of the magnetic attraction potential.
Next, as shown in
FIG. 12B
, if an A-phase current of the illustrated polarity is supplied to only the terminals of the first and second A-phase excitation coils CA and CA′ of the first yoke Y
1
, the air gap between the pole teeth KA of the first branched magnetic path leg A and the closest dots D
15
and D
14
switches from what had been the thrust branched magnetic flux portion d immediately before to the concentrated magnetic flux portion a comprised of the bias magnetic flux plus the alternating magnetic flux from the second excitation coil CA superposed, while the pole teeth KA′ of the second branched magnetic path leg A′ switch from the pullback branched magnetic flux portion c to the extinguished magnetic flux portion b, so the closest dots D
15
and D
14
strongly magnetically draw the pole teeth KA and advancing thrust occurs at the movable member
20
. On the other hand, a branched magnetic flux to form the concentrated magnetic flux at the first branched magnetic path leg A of the first yoke Y
1
through the inside of the platen
10
passes through the first and second branched magnetic path legs B and B′ of the second yoke Y
2
. The pole teeth KB of the first branched magnetic path leg B switch from the extinguished magnetic flux portion b to the thrust branched magnetic flux portion d, while the pole teeth KB′ of the second branched magnetic path leg B′ switch from the concentrated magnetic flux portion a to the pullback branched magnetic flux portion c. Therefore, due to the switching of the two-phase current, the movable member
20
advances by exactly P/4, if including the excitation patterns of
FIGS. 12C and 12D
, with a two-phase current, there are four excitation patterns of the excitation coils, so by one round of the excitation patterns, the movable member
20
advances four times and proceeds by exactly one pitch worth of distance. In the process of the switching of the two-phase current, a thrust force is generated at the pole teeth moving from the thrust branched magnetic flux portion d to the concentrated magnetic flux portion a.
To realize a planar linear motor having a movable member which moves planarly in the Y-axis and Y-axial direction using such a Sawyer linear motor, for example, as seen in Japanese Unexamined Patent Publication (Kokai) No. 9-261944, as shown in FIG.
13
and
FIG. 14
, there are provided a platen
10
formed on the platen surface with square-top platen dots D arranged in a matrix and a composite movable member comprised of X-axis movable members
20
X having stripe-shaped projecting pole teeth KA and KA′ (KB and KB′) parallel to the Y-axis and able to move in only the X-axial direction and Y-axis movable members
20
Y having stripe-shaped projecting pole teeth KA and KA′ (KB and KB′) parallel to the X-axis and able to move in only the Y-axial direction—all connected by a support plate
30
in an in-planar perpendicular relationship.
Further, to reduce the vibration or pulsation of the movable members
20
X (
20
Y) during the advance, as shown in
FIG. 15
, the yokes Y
1
and Y
2
may be given three branched magnetic path legs, the mutually independent phase excitation coils CU, CV, and CW (CU′, CV′, and CW′) wound around the branched magnetic path legs U, V, and W (U′, V′, a
Itoh Masato
Takeuchi Katsuhiko
Taknaka Kimihiko
Armstrong Westerman & Hattori, LLP.
Jones Judson H.
Ramirez Nestor
Shinano Electronics Co., Ltd.
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