DE3020852A1 - LINEAR MOTOR - Google Patents

Description

Patent Attorneys D: ρ :. - i η g. Curt Wallach

. Dipl.-1-ng. Günther Koch

ρ 'Dipl.-Phys. Dr Tino Haibach

Dipl.-Ing. RainerEeIdKamp

D -8000 Munich 2 Kaufingerstraße 8 Telephone (0 89) 24 02 75 - Telex 5 29 513 wakai d

Date: June 2, 1989

Our reference: 16 388 - Κ

Applicant: Polaroid Corporation

Technology Square
Cambridge, Mass. 02139
United States

Title; Linear motor

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ORIGINAL INSPECTED

The invention relates to a linear motor, in particular as a shutter drive for photographic apparatus suitable is.

Dynamo-electric motors come in a wide variety of designs known. They all have a bobbin that carries one or more field coils. Within the coil former is an armature which has a core made of soft iron, as in US-PS 37 28 654 or the core may have multiple permanent magnets, as in US Pat. No. 3,022,400, 32 02 886 and 34 95 described. Finally, the armature can represent a combination of a soft iron core and a permanent magnet. By applying a direct voltage to the field coil, a magnetic field is generated, which in turn supplies a force to to drive the armature in a first direction until it is stopped. By reversing the polarity of the DC voltage the anchor is moved in the opposite direction until it strikes. A disadvantage of the patents mentioned motors described is that each output member only one stroke for each excitation and de-excitation of the field coil performs. This means that the armature does not return to the starting position when the field coil is de-energized.

One of the problems associated with returning the armature to its original position is the precise positioning of the armature relative to the field coil, thereby ensuring that the length of each stroke is substantially is equal to. A solution shows the US-PS 35 49 9I7, counteracting springs are used to center the armature and return it to its original position when the Field coil is de-energized. The US-PS 37 55 699 shows the use of a flexible membrane to the coil in the starting position to-

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traced back. Adjusting the return springs or the diaphragms to ensure that they are always the same and supply opposing forces, but leaves many from both a practical and an economic standpoint Wishes open.

The US-PS j58 60 J> 00 describes a control system with several permanent magnets made of samarium cobalt and two electromagnets for restoring a rotating shaft. The output of each solenoid is controlled by a circuit which includes a differential amplifier. In this connection, reference is also made to US Pat. No. 3,874,750, in which a thrust bearing system operating with a permanent magnet is used to move a rotatable shaft relative to a fixed component. However, none of these systems relate to an environment where a field coil is energized to axially displace an armature and thereby provide an output to drive a component, while when de-energized it is automatically returned to the home position.

The present invention relates to a dynamo-electric Motor and in particular a linear motor. According to a preferred embodiment of the invention, the Linear motor on a generally cylindrically shaped bobbin, which has two electric between its cheeks Field coils. The bobbin has a cylindrical channel which extends axially to the coils and a receives appropriately designed armature which is axially movable to and fro in the channel. The anchor preferably has a core made of magnetically permeable material, for example steel. The anchor is held by two permanent magnets completed, preferably made of one material

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rait; rare earth, for example consist of samarium cobalt. The magnets are axially connected to one another on the front side in such a way that poles of the same name of the magnets touch each other, while the two outer ends of the core also have the same polarity, but polarize opposite to the central pole are. Two cylinder covers are attached to the opposite ends of the spool carrier to cover the length of the stroke of the Limit anchor. Each end cap has a central opening dimensioned to allow a piston rod to protrude through it can projecting axially from each end of the armature. The end of each piston rod that secures the piston rod to the armature is, has a diameter that is larger than the diameter of the opening and the rest of the piston rod, so that the cylinder cover limit the movement of the armature along the channel via this piston rod connection head.

Two field coils are arranged side by side around the coil body, which are symmetrical relative to the steel core, when they are not aroused. Two washers are tightly attached to each end of the spool carrier over the cylinder head so determined that they essentially the poles at de: i enclose opposite ends of the anchor and on this aligned when the coils are not energized. Any washer ordered from a magnetically permeable material, for example steel.

The common poles of the permanent magnets are set at the axial ends of the steel core to create a zone of maximum magnet insulating flux density projecting radially outwardly from the central portion of the steel core, thereby creating an anchor which has practically three poles, i.e. common poles and one pole at the end of the armature at the same distance from the center. These poles are hereinafter referred to as

effective pole of the anchor.

When excited by a direct current, the first of the two field coils generates a magnetic field whose force exerts the armature one of the first positions of the steel bases the end poles of the same name of the armature are aligned, moved into a second position in which the movement of the armature is stopped by the enlarged portion on one of the piston rod heads abutting the cylinder cover. This movement or this stroke of the armature has a length which is less than half the distance between the North and south poles of the magnet, which is located at that end of the armature which is closest to the second position is. This ensures that the end pole of the magnet, closest to the second position is closer to the associated steel washer than the opposite one Pole of the magnet. If the flow of current is interrupted after the first field coil, then it causes a magnetic one Attraction between the end pole adjacent the second position and the associated steel washer causes a return of the Armature in the first position, with the effective end poles viieclerurn aligned with their corresponding steel washers are. The second field coil is used to move the armature from the first when excited by a direct current Position in a third position which is generally opposite the second position, the other effective end pole of the The anchor and the corresponding steel washer cooperate in a manner similar to the operation described above, is equivalent to. In this way, after the second field coil is de-energized, the armature is returned to the first position.

According to a modified embodiment of the invention, can the two steel washers by a single steel washer

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Be replaced washer, which is arranged in the plane of the maximum magnetic flux density. When the anchor has moved into the second or third position in this combination, then the effective, non-common pole lies of the armature closer to the steel washer than the two effective common poles of the magnet, making one larger magnetic attraction takes place therebetween, which returns the armature to the first position after the field coil is de-energized is.

According to a further exemplary embodiment, the linear motor consists of a coil carrier with a single field winding and a single steel washer at one end of the armature, with a cylinder cover and a Armature, which consists of a single permanent magnet, which is polarized in the direction of displacement and carries a piston rod, which protrudes to the outside on one side. The steel washer is aligned with one of the effective poles of the armature when the anchor is in the first position. The armature is moved to the second position when its field coil is excited. In this position is the effective pole of the armature, which was previously aligned with the steel washer was, even closer to the steel washer than the other effective pole. Accordingly, after de-energizing the field coil causes the greater magnetic attraction between the pre-aligned washer and the effective pole one Return of the armature to the first position.

It is accordingly an object of the invention to provide a linear motor which has improved means for return the armature to its starting position after de-energizing the field coil.

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The invention also aims to magnetically center the armature when the field coil is de-energized.

Another object of the invention is the use of the magnetic attraction force between a magnetically permeable material and a permanent magnet to return an armature to an initial position after a field coil has been switched off.

Exemplary embodiments of the invention are described below with reference to the drawing. In the drawing show:

1 shows a sectional view of a preferred embodiment of a linear motor designed according to the invention in the non-excited state;

FIG. 2 shows a section of the linear motor according to FIG. 1 with an armature position when the Field coils;

3 shows a sectional view of a modified embodiment of a linear motor in the de-energized state;

FIG. K shows a sectional view of the linear motor according to FIG. 3 in the excited state;

5 shows a section of a further embodiment of a linear motor designed according to the invention;

Fig. 6 is a diagram showing the relationship between Can recognize displacement and magnetic flux density in the armature.

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Figures 1 and 2 show a preferred embodiment of a linear motor 10, the outer housing of the Is not shown in the drawing because of clarity. The motor 10 has a cylindrically shaped bobbin 12 preferably made of non-conductive material, e.g. Delrin (this is a thermoplastic plastic, that of E.I. duPont de Nemours & Cq. will be produced). Of the Spool 12 has a plurality of annular cheeks 14, 16 and 18 as well as end sections 20 and 22 and a cylindrical one Channel 24 on.

A piston-shaped armature 26 is displaceable back and forth in the channel 24, which is designed as a cylinder bore. The armature 26 has a core 28, preferably made of steel, and two permanent magnets 30 and 32, which are preferably made of a material made of rare earths, for example samarium-cobalt. Each of the magnets 30 and 32 is fixed with a common pole, for example with the north pole N, on the end face of the steel core 28 in such a way that the south poles S. uer magnets form the opposite ends of the armature 26.

Two piston rods 34 and 36, preferably made of the plastic sold under the name “Delrin”, are fixed to the opposite ends of the armature 26. The piston rod 34 consists of the rod section 38 and a head part 40, the diameter of which is larger than that of the arm part 38. The piston rod 36 consists in the same way of a rod section 42 and a head part 44. The rod section 38 protrudes through an opening 46 of a cylinder cover 48, while the rod section 42 passes through an opening 50 of a cylinder cover 52. Each cylinder cover 48 is preferably made of a plastic material, for example ¹¹ De Ir in ".

Two field coils 54 and 56 are placed side by side the coil body 12 arranged such that the field coil 54 lies between the cheeks 14 and 16, and. the field coil 56 between the cheeks 16 and 18. Each coil 54 and 56 is provided with an electrical connection 58 or 6O in order to connect the field coils to a DC voltage source can. Each connection is designed with two wires, so that each coil can be excited separately.

There are two washers 62 and 64 made of magnetic-per- flawless material J For example, made of soft iron, to automatically return the armature 26 from the position shown in FIG. 2 to the position shown in FIG. 1 when the field coil 54 is de-excited. The washer 62 is pulled onto the end portion 20 so that they are effective on the left The south pole of the armature 26 surrounds it, and it is fixed by means of the cylinder cover 48. In the same way is the Washer 64 is drawn onto the end section 22 in such a way that it encloses the effective right south pole of the armature and is geared towards this. A determination is made jthrough the cylinder cover 52.

As mentioned, the north poles of magnets 30 and 52 are fixed on the axial end faces 66 and 68 of the steel core 28 set to create a zone of maximum magnetic flux density radially from the central portion of the steel core 28 protrudes outward, creating an anchor that actually has 5 poles, i.e. two south poles S and one single north pole, marked by the dash-dotted line 70 is marked. This is shown in FIG. 6 by curve 72 graphically illustrated. This curve represents the radial flow density of the armature 26 measured along its axis. The maximum fluid thickness is aligned with the effective North Pole 70 *

while the thief of magnets 30 and 32 is on one Reverse position, which is equidistant from the north and south poles of each magnet.

In one embodiment of a linear motor constructed in accordance with the invention, each magnet 30 and 32 is 3.175 mm in length and diameter and the steel core is 1.905 mm in length and 3.175 mm in diameter. The channel 24 has a diameter of 3.2512 mm and a length of 12.192 mm. The coil 12 has a maximum diameter of 9> 525 mm and a minimum diameter of 3.5052 mm at the point where the field coils 54 and 56 are wound around the coil former 12. This combination results in a maximum magnetic flux density of about 800 Gauss at the effective north poles of the armature 26, which are shown by the dash-dotted line JO .

In the switched-off state, the armature 26 of the linear motor 10 assumes the position shown in FIG. 1. The anchor 26 is off the position according to FIG. 1 (this is to be referred to as the "first position") into a second position, which is shown in FIG is illustrated by connecting the field coil 54 to a DC voltage source is connected. Accordingly, the armature moves a distance Y before its effective left south pole on the inner one Surface of the cylinder cover 48 abuts. In the linear motor according to the example mentioned, this distance is Y about 1.2065 mm. In this position, the effective south pole is still at one point on the left side of the anchor closer to steel washer 62 than the north pole N of the iMagnet 30. This is always true because the distance Y is less than 1/2 X, where X is the distance between adjacent poles of the xMagneten 30 is. When the current in the field coil 54 is switched off then creates the greater magnetic attraction between the effective south pole on the left side of the armature

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2.6 and the associated steel washer 62 a force which returns the armature 2.6 to its first position. This force is supported by the magnetic attraction that occurs between the other effective south pole of the armature 26 and the associated steel washer 64. With an engine thus constructed, each washer has an outer diameter of 9.525 mm and an inner diameter of 5.08 mm, and a thickness of 0.254 mm. The magnetic attraction between each washer and the associated effective pole can be increased or decreased by decreasing or increasing the diameter of the hole in each washer.

The armature 26 can be moved to the right, i.e. to a third position, by connecting the field coil 56 to a DC voltage source is created. This excitation causes the head portion 44 of the piston rod 36 to be on the inner surface of the cylinder cover 52 abuts after the armature has moved a distance Y. As soon as the field coil 56 is switched off is moved, the greater magnetic force between the effective south pole of the armature 26 and its associated Washer 64 is in comparison with the effective force between north pole N of magnet 32 and washer 64, the armature 26 back to its original position.

Reference is now made to FIGS. 3 and 4 of the drawing Referenced. A modified embodiment of a linear motor 10 ″ is shown here. The linear motor 10 ′ is essentially identical to the linear motor of Figures 1 and 2 with one important difference, i.e. the two steel washers 62 and 64 are replaced by a single steel washer 74 which is on the spool 12 'at that Position is arranged that was previously occupied by the cheek 16.

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The operation of the linear motor 10 'is essentially identical to that of the motor 10 with the difference that in this embodiment a greater magnetic force is effective between the effective north pole and the single steel washer which moves the armature 26 from the second or third position back into the first position moved. The excitation of the field coil 54 by a direct current causes the armature 26 to shift to the left over the distance Y into the second position, while the effective south pole on the left side of the armature 26 abuts the inner surface of the cylinder cover 48, as shown in FIG Fig. 4 is shown. However, the effective north pole 70 is closer to the steel washer 74 than any of the effective south poles of the anchor because the distance Y is less than half of X ', where X ^{1 is} the distance between the effective poles. Accordingly, when the field coil 5-4 is energized, the greater magnetic attraction between the effective north pole JO and the washer 74 provides the force required to return the armature 26 to its central position, ie, to the first position. Excitation of the field coil 56 causes the armature 26 to move to the right into its third position.

Reference is now made to FIG. 5 of the drawing, which represents a further embodiment of a linear motor, which is shown in a first position in which the excitation is switched off. The motor 100 has a cylindrical bobbin 102, the two annular cheeks 104 and 106, between which a field coil I08 is wound is. A cylindrically shaped end section 110, which has a cylinder bore, projects from one side of the cheek 104 which forms the extension of a cylindrical channel 114. One made of magnetically permeable material, for example

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Washer 116 made of soft iron is pulled onto the end section 110 and is there by a cylinder cover 118 held. The cylinder cover 118 has an opening 120 for the passage of part of a cylindrical one Shank 122 of a piston rod 124. The piston rod 124 has a head 126, the diameter of which is greater than the diameter of opening 120 and slightly smaller than the diameter of opening 112 and channel 114. The open The end of the channel 114 is closed off by a plate 128 which has an indented section I30. This one indented Section 130 is sufficiently far from the end of the motor armature removed in order to avoid contact with this when the armature is returned to the position shown in FIG which is to be referred to as the "first position". The bobbin 102, the cylinder cover 118 and the plate 128 and the piston rod 124 are preferably made of a thermoplastic material such as "DeIrin".

A cylindrically shaped armature piston I32 is inside the The cylinder bore formed by opening 112 and channel 114 is slidable. The armature ljJ2 consists of a permanent magnet, which is preferably consists of samarium cobalt, with its effective north pole N and its effective south pole S axially on the cylinder 114 are aligned. The effective south pole S of the armature is firmly connected to the head 126 of the piston rod 124. if the armature I32 is in its first position (Fig. 5), then the steel washer II6 lies in such a way that it encloses the south pole S of the armature 132 and is aligned with it is.

The field coil I08 is excited by the connection line I34 is connected to a DC voltage source. in the excited state, a magnetic field is generated, which a

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Force supplies to the armature I32 to the left as shown in FIG. 5 to move the distance Y. This distance Y is smaller than X / 2. After passing the distance, the anchor will be in the second position is stopped by a stop on the inner surface of the cylinder cover 118. When the anchor Ij52 in its second position is located, then the south pole S is even closer to the steel washer II6 than the effective north pole N, thereby exerting a greater magnetic attraction on the washer 116. If the Field coil I08 is switched off, then causes this greater magnetic attraction between the effective south pole S and the Washer II6 automatically returns the armature 132 to its first position. The indented section I30 the plate 128 allows the armature to briefly overshoot the first position without the armature Exposing I32 to damage. The anchor I32 is shown as that its effective south pole is aligned with the washer 116. However, it is also possible to use the pole reverse, as is the case with all known double magnet motors.

Numerous modifications can be made without departing from the scope of the invention. So it is, for example within the scope of the invention, the two field coils in the embodiment of FIGS. 1 to 4 by a single field coil replace, the direction of movement of the armature from the first position to the second position by a current flow through the field coil is effected in one direction, while the movement of the armature to the third position is effected by reversal of the current can be achieved.

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Claims (18)

patent claims- · ■ .. Linear motor with a coil carrier, which carries an electrical excitation winding and ^{defines an axially ^ '., Yerlauf ^ rijdien 1} cylindrical channel, with a piston armature axially displaceable in the channel, which is displaceable between a first and a second position,
- characterized in that the armature has a permanent magnet, the magnet axis of which runs in the direction of the channel, that when excited, the armature is transferred from the first position to the second position, that at least one piston rod at one end of the armature begins to transmit the driving force, that means are provided to limit the movement of the armature along the channel when the winding is excited, and that a ferromegnate body is arranged on the coil carrier, which when the armature is in the first position on one Magnet pole is aligned to automatically return the armature to the first position when the winding is de-energized. 2. Linear motor according to claim 1, characterized by the fact that the ferromagnetic body consists of a ring washer exists, through the center hole of which a section of the anchor can pass through. 030ÖS1 / Ü73S ORIGINAL INSPECTED 3. Linear motor according to claim 2, characterized, that the.vom anchor moves out of the The distance traveled from the first position to the second position is less than half the distance between the effective opposing poles of the armature. 4, linear motor according to claim 3 »characterized in that that the coil carrier and the limit stops for the armature are made of non-magnetic material. 5 »linear motor according to claim 3, characterized in that the piston armature has a second permanent magnet and has a core lying between the first and second permanent magnets, whereby poles of the same name of the magnets are directed against each other, so that an anchor is created, the pole of the same name at the axial ends and an effective pole of unlike polarity on one Have a point about halfway between the ends of the core, 6. Linear motor according to claim 5, characterized in that motion transmission members at both ends of the armature attack in the form of piston rods. 0300S1 / 073-S -ν 7. Linear motor according to claim 6, characterized in that that the coils can be excited in such a way that the armature from the first position to a third Position is transferable, the third Position lies in a direction which is opposite to the direction in which the anchor is transferred from the first position to the second position. 8. Linear motor according to claim 7, characterized in that the one effective pole of the armature is a magnetic pole which is about halfway between the opposite ends of the core, and that the disc is aligned with an effective pole when the armature is in the first position is. 9. Linear motor according to claim 8, characterized in that that a first and a second field coil are provided, wherein the first field coil is excitable to to transfer the armature from the first position to the second position while the second field coil is excitable to move the armature from the first position to the third position. 10. Linear motor according to claim 5 » characterized in that the permanent magnets consist of a material that has rare earths. Ö30051 / 073S 11. Linear motor according to claim 2,
characterized in that the distance traversed by the armature when moving from the first position to the second position is less than half the distance between the magnetic poles of the permanent magnet. 12. Linear motor according to claim 11,
characterized in that the coil carrier and the stop cylinder cover carried by it consist of non-ferromagnetic material. 13. Linear motor according to claim 11,
characterized in that the armature has a second magnet and a core which is arranged between the two magnets, with poles of the same name of the two magnets facing each other or at the opposite ends, and that an effective magnetic pole of opposite polarity halfway lies between the ends of the core. 14. Linear motor according to claim Ij5,
characterized in that the core carries a piston rod on each side in order to guide the drive movement of the armature to the outside. 630051 / 073S - γ -ζ. 15. Linear motor according to claim 14, characterized in that that the coils can be excited in such a way that the armature from the first position to a third Position is transferred which is opposite to the first position. 16. Linear motor according to claim I5, characterized in that that a second washer made of ferromagnetic Material is provided through which a portion of the anchor protrudes and moves through, when the armature is moved between the first and third positions, and that the discs on the Coil carrier arranged transversely to the armature and aligned on opposite ends of the armature are when the anchor is in the first position to automatically remove the anchor from the third position returned to the first position when the coil windings are de-energized. 17. Linear motor according to claim 16, characterized in that two field coils are provided, of which the the first is excitable to transfer the armature from the first position to the second position while the second coil is effective when energized to move the armature from the first position to the third position to convict. 18. Linear motor according to claim I3, characterized in that the permanent magnets are made of samarium cobalt. Ö3OO51 / 073S