DE102006038787A1 - Mirror drive for projection systems - Google Patents

Abstract

A magnetic drive uses only one permanent magnet and two voice coils to alternate a mirror relative to an idle state between two angular positions. A magnetic field component causes magnetic flux to act on the voice coils. An upper plate and a lower plate are held by a permanent magnet, so that each plate forms a magnetic pole. Current flow through the windings activates the voice coils, resulting in a magnetic field around the coils. As a result, the coils move up or down as dictated by current flow. A mirror holder includes a fixed periphery and movable arms connected to a torsion bar that spans the periphery. The arms are moved by the voice coils and twist the torsion bar. This also moves the mirror attached to the arms.

Description

The The present invention relates to an electromagnetic Drive to alternate a mirror between angular positions deflect. In particular, the invention relates to mirror drives for use in a projection system to provide a mirror between two angular positions that are inclined relative to the resting state, to move alternately, the drive being a simple combination used from permanent magnet and voice coils.

in the present context is the mirror between two positions moves to double the pixel density of a projected image. This happens through two alternating fields, each of which half Has pixel count of the overall picture. The fields will be conditioned by the movement of the mirror, slightly offset from each other. For example For example, one field may shift down relative to the other field have that half the pixel size corresponds. The human eye integrates the two consecutive images, to create a single overall picture.

While the needed Vibration amplitude is typically very small, come very close high accelerations, for example, 12G or more be.

The motors heretofore used in this type of application to realize such forces have included a variety of magnets and a variety of moving parts. The 1A and 1B show such a motor 1 according to the prior art, which is used to drive a mirror in a projector. The 1A shows an assembled component 1 and 1B shows the exploded view of the component 1A , In order to achieve the necessary forces for the drive of the mirror, two voice coils 4 , four permanent magnets 14 and five steel parts (four steel plates 12 and a base 16 ) needed.

As can be seen from the figures, so many expensive Components needed, whose Assembly is difficult and because of the complexity the danger include a malfunction.

It is therefore the need after an electromagnetic drive, which is just a simple Component that includes a permanent magnet and coils to form a surface between two closely spaced angular positions at high frequency to rotate.

A Object of the present invention is therefore to provide an electromagnetic Specify drive, which is a simple component, which is a permanent magnet and coils comprises a surface between two close to each other Rotate angular positions at high frequency to rotate. The drive especially for the rotation of a mirror between two angular positions relative be suitable for a resting state.

The solution the task is done by means of a simple combination of a permanent magnet and achieved voice coils.

According to the invention is a electromagnetic drive for alternating deflection of a mirror built between two angular positions with a fixed magnetic field component and with a mirror holder, with a movably mounted about an axis Part, wherein the magnetic field component comprises two magnetic poles and one magnetic pole of the magnetic field component has two openings and the other magnetic pole of the magnetic field component two Includes arms which are formed such that in each of the two openings one arm protrudes in each case, so that between an arm and the edge the opening, in which he protrudes, an air gap is present, the magnetic Flux of the magnetic field component from one magnetic pole to the other bridges; and the movably mounted part of the mirror holder comprises an arm, on which a mirror and on both sides of the axis each have a voice coil is arranged, wherein mirror holder and magnetic field component in such a way arranged to each other, that in each of the two openings each one of the voice coils at least partially protrudes and in each one voice coil one arm of the other magnetic Pols engages, allowing the magnetic flux through turns of the voice coils occurs.

Preferably the electromagnetic drive is characterized in that the magnetic field component a permanent magnet, a top plate and a lower plate, and the upper plate comprises the one pole of the magnetic field component and the lower plate forms the other Pol forms the magnetic field component.

Preferably is the movable storage of the movably mounted part over a Torsionsbalken realized on a periphery of the mirror holder.

peripherals, Torisionsbalken and arm of the mirror holder may be in one piece, preferably from a be made of cast aluminum alloy.

The following procedure is then used to switch the mirror between two angular positions: In a first step, one will read current in a suitable direction through the voice coil sen. Due to the force on a current carrying conductor, the coils will experience a force vertical to their windings and the magnetic flux passing through the coils, and the forces will add up to a torque on the arm of the movably mounted part of the mirror holder and a deflection of the mirror effect in an angular position. In a second step, the current direction and thus the torque are reversed, so that a deflection of the mirror is effected in a different angular position. In a third step, the first step and the second step are cyclically repeated.

there can the steps are repeated in such rapid succession that on the arm of the movably mounted part of the mirror holder accelerations of ≥ 12G occur.

voice coil are known. While she originally for speakers They are also used to design elements in different ways Moving components and thereby stepper motors or the like to replace. For example, they are used in hard disk drives, about the arms that carry the head over to swing the plate in or out again. The voice coils are activated by sending current through the windings will, causing vertical forces to be produced. A magnetic flux, through the magnet and two Caused by plates, crossed Air gaps. As a result, the voice coils move up or down, depending on the current direction.

Of the Permanent magnet according to the present invention comprises an upper surface, which forms a magnetic pole and a lower surface of the forms the other magnetic pole. The upper surface has openings to pick up the voice coils and has the bottom surface Poor those in the openings protrude from the voice coil. In this way is inventive with only one magnet has a high flux in the gaps around the two voice coil motors of the drive generated around.

In a preferred embodiment According to the present invention, the magnet comprises in addition to Permanent magnets only two parts of a ferromagnetic material such as stamped steel: a top plate and a bottom plate which are held together by the permanent magnet such that each of the plates forms a magnetic pole. The top plate has openings to pick up the voice coils and the bottom plate has arms which protrude into the interior of the voice coil. In this way will inventive with only one permanent magnet (for example, rare Erdenn) and two parts of a ferromagnetic material a high Flow in the columns around the two voice coil motors of the drive generated around.

One still needed Holder for The mirror includes a fixed periphery or outer edge as well movable arms mounted on a torsion bar, the over the periphery extends. The arms are moved by the voice coils. The mirror is attached from the opposite side of the voice coil and moves with the arms.

It Now follows a short description of the pictures.

1A (Prior Art) is an isometric view of a known device to drive a mirror. The component comprises two voice coils, four magnets and five steel parts

1B (Prior Art) is an exploded view of the known component 1A ,

2A Figure 11 is an exploded isometric view showing a mirror drive according to the present invention.

2 B is an isometric view of the mirror drive 2A in assembled form.

3 shows an exploded isometric view of the magnetic field component 2A and 2 B ,

4 is a section of an isometric view of the in 3B illustrated magnetic field component, in assembled form.

5 is a side view of the mirror drive of 2A and 2 B at rest.

6 is a side view of the mirror drive of 2A and 2 B in one of the angular positions.

7 is the section of an isometric side view of the mirror drive of 2A and 2 B , at rest.

8th is the section of an isometric side view of the mirror drive of 2A and 2 B , in one of the angular positions.

9 is an isometric side view showing the movable part of the mirror holder of the mirror drive of the 2A with more details shows.

The following is a more detailed explanation of the present invention, by way of example and with reference to FIG gures.

The Reference numerals that are used in the figures can be as follows assign to the parts:

1

component as per stand of the technique

4

voice coil

12

steel plate

14

magnets

16

Base

100

mirror

101

Housing of drive

102

engine component

104

voice coil

105

Magnetic field component

106

mirror Mounts

108

mirror

109

mirror lock

110

bending axis

112

Upper Plate of the magnetic field component

114

magnet

115

flow lines from the magnet

116

Lower Plate of the magnetic field component

118

poor the lower plate

120

openings for voice coils

122

portable Part of the mirror holder

123

torsion

124

poor of the moving part

125

periphery the mirror holder

2A is an exploded isometric view. the one mirror drive 100 according to the present invention. 2 B is an isometric view of the mirror drive 100 out 2A in assembled form.

A housing 101 forms the basis for the drive. The mirror lock 109 snaps into the mirror holder 106 and holds the mirror 108 on the holder 106 , The magnetic field component 105 (better represented in the 3 and 4 ) and the voice coils 104 make up the engine 102 of the drive. The mirror holder 106 includes a moving part 122 (better represented in 9 ), located on a torsion bar 123 rotates. The mirror 108 is with the moving part 122 connected to the mirror holder and moves with this.

The deflection of the mirror is typically very small, on the order of 30 to 60 arc seconds (0.007 to 0.015 degrees). This is similar to a bistable drive in which the mirror, apart from the rest position, occupies two staggered positions. Accordingly, the mirror is deflected by +/- 0.015 degrees from the rest position. This is best in the 5 - 8th shown. While the required oscillation amplitude is thus very small, very high accelerations are achieved, which may be 12G or more, for example.

The voice coils 104 comprise a wire of small cross-section, which is wound around a roll and which is designed so that the voice coils in the openings 120 fit. In one embodiment, the coils comprise about 80 turns of wire. In the embodiment according to the 2A and 2 B the dimensions of the coils are chosen as follows: 18 mm long × 4 mm wide by 3 mm high. The coils are operated in the example at 100 to 500 mA. (Power source not shown).

3 shows an exploded view of the magnetic field component 105 , Magnetic field component 105 includes a top plate 112 , only a permanent magnet 114 and a lower plate 116 , The permanent magnet 114 holds the two plates together and also delivers the river 115 like in the 4 shown. In one embodiment of the present invention, the permanent magnet is made of a rare earth material having dimensions of about 3 mm thick and 8 mm ^{2 in} size. The bottom plate 116 has arms 118 in the openings 120 the top plate 112 protrude, but an air gap for the voice coil 104 leave (see 2A and 2 B ). The plates 112 . 116 can be made from stamped ferromagnetic metal plates. No machined parts are needed.

The drive housing 101 holds the plates 112 . 116 in a precise spatial arrangement to each other by means provided on the housing elements on which the plates are aligned. This is necessary because the magnetic flux from one to the other plate contracts them. Based on the air gap, a pole is formed by the inner pole (arms 118 the lower plate) and the other pole is defined by the surface of the outer pole (edges of the openings 122 the top plate 112 ) educated. To simplify the discussion, the upper plate is referred to as north and the lower plate as south. However, the correspondingly different polarity would also work.

Note that in conjunction with a mirror that is moved away from the rest position in two angular positions, an engine constant of 0.1 to 0.2 degrees / A is advantageous. The design as it is in the 2A - 4 has such a capability. Other configurations, such as those on the top plate 112 is omitted, also lead to the movement of the mirror, although possibly with too small motor constants.

4 is a section of an isometric view of the magnetic field component 105 , in assembled Shape. Shown are also the river lines 115 caused by the magnet 114 , The top plate is one of the magnetic poles (North in this example) and the bottom plate 116 is the other pole (south). The river bridges the air gap between the arms 118 and the openings 120 and acts on the voice coils 104 , which are not shown for clarity. Will electrical current through the voice coil 104 sent, then they move the moving part 122 the mirror holder 106 that is around the torsion bar 123 rotates. When the relative current directions through the coils are properly selected, one side moves up and the other side down (see 6 - 9 ). If the current direction is reversed, the vibration coils move the mirror holder in the other direction.

5 is a side view of the mirror drive 100 at rest. The mirror lock 109 and the housing are not shown for clarity. The bending axis 110 is shown. 6 is a side view of the mirror drive 100 in one of the angular positions. Note that the deflection in this figure is exaggerated to better illustrate the situation. In the example of 6 electric current flows (for example) in one direction of the voice coil left hand and by the voice coil right hand in the opposite direction. The voice coils 104 thereby produce vertical forces that act on them and set them in motion. With the coils, the mirror holder attached to them is set in motion, either upwards (in the case of the right-hand coil) or downwards (in the case of the left-hand coil, relative to the columns in the magnet) 114 caused magnetic field.

7 is the section of an isometric side view of the mirror drive 100 at rest. 8th is the section of an isometric side view of the mirror drive of 2A and 2 B , in one of the angular positions as in 6 shown. Based on these figures, it can be seen that the voice coils 104 down into the openings 120 and around the arms 118 extend the lower plate. Therefore, the magnetic flux between the two plates is strongest where it passes through the voice coils 104 attacks.

9 is an isometric side view showing the moving part of the mirror holder 122 the mirror drive 106 with more details shows. The voice coils 104 are to the moving part 122 mounted and therefore move together. The torsion bar 123 twists when the coils apply torque to the arms 124 exercise. The ends of the torsion bar 123 are on the periphery 125 attached to the mirror holder. In contrast, the arms 124 where the mirror 108 is arranged, movable relative to the periphery.

Due to the design, the bend only becomes a single part 123 that twisted, reached. In a preferred embodiment, the torsion bar is 123 cast from an aluminum alloy (designated 380.0). This achieves a good balance between fabrication costs, strength and characteristics of the part. The cross section of the beam results in the example to 1.5 mm wide and 5.0 mm high. The beam comprises two parts, each 11 mm in length. Thus, the bar is 22 mm long and extends over the periphery 125 the mirror holder 106 ,

In The present description has always been of only one permanent magnet the speech. This is not meant to be limiting in that, for example definitely two or more permanent magnets connected in series can be and these form a closed total magnetic flux. Also Such combinations are intended to be within the scope of the present invention counted become. Preferably, however, actually becomes a single permanent magnet used.

Moreover was in the context of the present description mainly on lifted a mirror drive. The concept, however, can be applied to everything expand, which requires a deflection with fast frequency.

It should also be noted that it is at the openings 120 for the voice coils does not actually have to act holes. These can for example also be recesses and or slots.

Claims (6)

An electromagnetic drive for alternately deflecting a mirror between two angular positions, with a fixed magnetic field component and with a mirror holder with a movably mounted about an axis part, wherein the magnetic field component comprises two magnetic poles and one magnetic pole of the magnetic field component comprises two openings and the other magnetic Pol of the magnetic field component comprises two arms, which are designed such that in each of the two openings in each case an arm protrudes, so that between an arm and the boundary of the opening into which it protrudes, an air gap is present, the magnetic flux of the magnetic field component bridged from one magnetic pole to the other; and the movably mounted part of the mirror holder comprises an arm on which a mirror and on each side of the axis each have a Schwingspu le is arranged; wherein mirror holder and magnetic field component are arranged to each other such that in each of the two openings each one of the voice coils at least partially protrudes and in each of which a voice coil, an arm of the other magnetic pole engages, so that the magnetic flux passes through windings of the voice coil. Electromagnetic actuator according to claim 1, characterized characterized in that the magnetic field component is a permanent magnet, an upper plate and a lower plate; and the upper one Plate which forms one pole of the magnetic field component and the lower one Plate forms the other pole of the magnetic field component. Electromagnetic drive according to one of claims 1 or 2, characterized in that the movable mounting of the movable stored part about realized a torsion bar on a periphery of the mirror holder is. Electromagnetic actuator according to claim 3 characterized characterized in that the periphery, toris beam and arm of the mirror holder integrally, are preferably made of a cast aluminum alloy. Method for switching a mirror between two Angular positions by means of an electromagnetic drive according to claim 1, wherein in a first step current in a suitable direction can flow through the voice coils and so because of the force on a current-carrying conductor, the coils a force vertically to their windings and to the magnetic flux passing through the coils kicks, experienced and the forces to a torque on the arm of the movably mounted part of the mirror holder and a deflection of the mirror effect in an angular position; and in a second step the current directions and thus the torque reverses, leaving a Deflection of the mirror is effected in a different angular position; and in a third step, the first step and the second step be repeated cyclically. Method according to claim 5, characterized in that that the steps are repeated in such rapid succession that on the arm of the movably mounted part of the mirror holder accelerations of ≥ 12G occur.