JPS6253000B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a permanent magnet and a pole bar having four windings, the axis of the pole bar being arranged at the apex of a square in a plane perpendicular thereto, and near the end of the pole bar. a soft iron member driven by a regenerating needle is movably supported about a center point on the central axis of the transducer device;
The present invention relates to an electromagnetic transducer for converting a mechanically recorded acoustic signal into an alternating current voltage, for example for reproducing a stereo signal recorded on a plate-shaped record carrier.

Such known transducer devices have a magnetically conductive iron jacket of high quality, and one end of the iron jacket is provided with a generally plate-shaped permanent magnet. The other end of the soft-magnetic iron jacket is a section of a soft-iron member, generally in the form of a small soft-iron tube, driven by the regeneration needle, formed with an air gap relative to the pole rod. . The soft iron tube is magnetized to or near saturation to minimize signal distortion. A winding on the pole bar is used to convert the magnetic flux, which varies in response to the recorded acoustic signal, into a proportional voltage. A transducer device constructed in this way is advantageous because the dynamic mass of the movable device consisting of the needle with needle support and the soft iron tubular body is low. However, the above-mentioned known devices have the disadvantage of being relatively expensive, since the construction of the known device requires a large number of individual parts, which makes assembly of the device expensive.

A further disadvantage is that the soft iron tube of the needle support must be magnetically saturated in order to minimize distortion. This requirement limits the minimum mass of the permanent magnet, making it difficult to integrate permanent magnets of that size into conventional configurations. Also, in the part of the soft iron part which is driven by the regenerating needle through the needle support, relatively little stray magnetic flux occurs between the pole rod and the soft iron jacket, so that the soft iron part is generally constructed as a small tube. It has the disadvantage that it cannot be magnetically saturated as required, and that it becomes difficult to reduce strain depending on the saturation state. In order to achieve the required sensitivity with the known device, it is necessary to wind the pole bar with a winding having a large number of turns. The disadvantage is that this increases the inherent inductance of the windings and that, if such a pickup is connected to an amplifier via a cable with a relatively large capacity, resonance peaks in the audible range and thus unacceptable acoustic disturbances occur. has.

Also, a transducer is known in which a small tube made of soft iron is provided inside an annular magnet magnetized in the axial direction. Such devices require a pole plate that supports the pole bar and directs magnetic flux from the permanent magnet to the pole bar. In such a structure, since the soft iron member is provided at the front end of the magnetic pole bar, it is possible to actually magnetically saturate the soft iron small tube, but an additional member to guide the magnetic flux is required. This complicates the structure of the known device. Axial magnetization of the permanent magnet has the same effect as if it were placed at the end of the pole bar, so it is possible to pre-magnetize the pole bar to a significant extent without compensation for the DC magnetic field. can. Also, since the size of the permanent magnet remains limited, it is necessary to provide the pole bar with a winding having a large number of turns in order to obtain sufficient sensitivity. The drawbacks to this have already been explained.

The object of the invention is to provide an electromagnetic transducer of the type mentioned at the outset which avoids the disadvantages of the known transducers mentioned above and which consists of a minimum number of components.
According to the invention, this object is achieved by forming the permanent magnet in the form of a short tube or consisting of a rod-shaped section of a short tube and magnetizing it in the radial direction, so that the four pole bars are arranged with respect to the central axis of the transducer arrangement. symmetrically and parallelly, passing through the space at least partially surrounded by the permanent magnets, and moving the movable soft iron member by means of a regeneration needle directly into one of the tubular permanent magnets near the end of the pole bar.
This is achieved by arranging the two ends in relation to the magnetic circuit.

In the device according to the invention, the DC magnetic flux is compensated by providing the pole bar inside the tubular permanent magnet or its rod-shaped part, so that the soft iron member, which is generally formed as a small tube, is placed near the front end of the pole bar. This is very advantageous because magnetization can be achieved up to the saturation region. As already mentioned, magnetization up to this saturation region is extremely difficult with known devices. That is because in that case a permanent magnet is provided at one end of the pole bar, whether directly or indirectly, in order to generate sufficient magnetic flux for the magnetization of the soft iron member at the other end of the pole bar. This is because a sufficiently large magnetic flux density is required. Also, the pole bars of the known device should be thicker than those of the present invention, since otherwise the pole bars would go into saturation before reaching the desired flux density in the movable soft iron member. Furthermore, by forming the permanent magnet or part of the permanent magnet in the form of a short tube in the present invention, a greater magnetic flux density can be obtained than with the relatively small magnet blocks of conventional devices. Based on this, an electromagnetic transducer constructed according to the invention can increase sensitivity and reduce distortion compared to known devices. This is because a large magnetic flux effect is then obtained only if the stray magnetic flux through the pole rods is small. If the permanent magnet is constructed as a short tube or in combination with rod-shaped sections of radially magnetized short tubes and the device according to the invention is constructed accordingly, the lines of magnetic force will be concentrated in the area of the movable soft iron member, and the conventional This is very advantageous since it is possible to magnetically saturate the soft iron component with a smaller magnet mass than would otherwise be the case. Since the transducer according to the invention has a high sensitivity, the number of turns of the pole bar winding is relatively small. The low inherent inductance of the windings therefore makes it possible to advantageously provide relatively long cable capacitances between the converter and the amplifier. It should also be noted that permanent magnets in the form of short tubes can be made of ferrimagnetic material, which is very inexpensive compared to other magnet materials and can be formed into any shape. In order to considerably reduce the manufacturing costs and to avoid the rather expensive radial magnetization of the tubular element, the aforementioned tubular permanent magnet can be replaced by a number of preferably identically shaped rod-shaped sections, and the said rod-shaped sections can be It can be formed as individual parts and arranged parallel to the axis in a jacket in the form of a cylinder or a short tube with a square cross section.

It is also advantageous that such individual parts can be magnetized much more easily and better than ferromagnetic parts in the form of short tubes. Furthermore, due to the good magnetization properties of the individual components, the magnetic field strength increases, so that a greater sensitivity can be achieved. When the individual parts are shaped into tube segments,
After the individual parts have been magnetized, they can be assembled into a tubular permanent magnet, in which case the individual parts can be interconnected, for example, by gluing. However, modern magnet materials generate large magnetic field strengths and have large coercive forces, so that it is not necessary to form permanent magnets as closed cylindrical tubes. It is possible, for example, for the permanent magnets to be formed by individual rod-shaped, longitudinally individual parts with a square cross-section and arranged parallel to one another along the geometry of the cylinder envelope and parallel to the axis. Due to the remarkable properties of modern magnet materials, only four rod-shaped permanent magnets need be provided, since the gaps between the individual rods can be relatively large. As long as the vertical axes of the bar magnets and the magnetic pole rods are parallel, the four bar magnets provided corresponding to each magnetic pole rod can be placed at arbitrary positions with respect to the corresponding magnetic pole rods. can be provided. By configuring the converter in this way,
A large amount of space is provided for the spatial arrangement of the individual parts. If the individual parts are designed as tube segments, it is sufficient to provide two opposing parts, each corresponding to a pair of opposing pole bars, in order to generate the required magnetic field.

The invention will now be explained with reference to illustrated embodiments.

In the embodiment of the invention shown in cross section in FIG. 1, 1 comprises a needle support which is movably supported in an elastic bearing member 2 and which supports at its free end a soft iron member 4 in the form of a small tube. show. The small tube body 3 is provided near the end of the magnetic pole bar 4 having the winding 6 . Four pole bars 4 are provided, only two of which are shown in FIG. The pole bars 4 are arranged parallel to each other and symmetrically with respect to the longitudinal axis of the permanent magnets, inside a space enclosed by radially magnetized permanent magnets 5.

FIG. 2 shows the course of the magnetic field lines in a cross section of the embodiment shown in FIG. It can be seen that in the case of the transducer according to the invention, no magnetic flux guiding parts other than the pole rods are required. It can be seen from FIG. 3 that the DC flux distribution is practically equal to zero at the center of the pole bar and has a maximum value at each end. Such an effect is obtained by magnetizing the permanent magnet 5 in the radial direction. It can be seen that in the device of the present invention, the small tube body 3 is reliably magnetized to the saturation region. Also, in this case, the things shown in Figures 1 and 2 are considerably enlarged compared to the actual ones.
And in reality, the space bridged by magnetic flux is very small.
It should be noted that it is on the order of 0.1 mm.

The embodiment shown in FIG. 4 has, in addition to the pole rod 4 with the magnetic coil 3', permanent magnets 5 formed from four individual mutually identical tube segments. Four such individual parts can be glued together at the contact surfaces or embedded in a plastic part.
It is easy to see that the device for magnetizing individual members can be constructed much more simply than the device required for tubular members. Here, the dimensions of the electromagnetic transducer that reproduces the signal from the plate-shaped record carrier are very small, so
In order to limit the degree of magnetization, care should be taken that the magnetizing device does not exceed a predetermined maximum value of magnitude. This disadvantage is avoided in the present invention by disassembling the permanent magnet 5 into individual parts. This is because in that case the rod-shaped part or similar part does not have the size limitations mentioned above with respect to the magnetizing device. Rather, the magnetization device is constructed in such a way that a large number of individual parts can be magnetized simultaneously, which can be considered as essentially two-dimensional parts.
This is difficult, for example, in the case of a three-dimensional member such as a short tube.

FIG. 5 shows an embodiment in which the permanent magnets 5 are composed entirely of bar magnets arranged parallel to the axis of the magnetic pole bar 4 so as to form a cylindrical surface. The spaces between the individual rods with a rectangular cross section can be filled with plastic material. It is also possible to use a single plastic member housing the rod.

Modern magnetic materials have very high energy densities, which can reach values of 26 MGOe, which in itself reduces the number of individual parts that make up a permanent magnet to 4, as shown in Figures 6 and 7. can be reduced to In the embodiment of FIG. 6, the permanent magnet 5 has four mutually opposed individual parts, each corresponding to a pole bar 4. In the embodiment of FIG. As long as the axes of the individual members are parallel to the axis of the magnetic pole rod and thus parallel to the axis of the transducer, each rod-shaped individual member can have any position relative to the corresponding magnetic pole, for example the position shown in FIG. It can be made to have.

It is also possible, for example, to provide only two individual parts, as shown in FIG. The two individual parts constituting the permanent magnet 5 advantageously have the form of tube segments, but if appropriate they can also be formed in the form of a flat iron. Corresponding to each individual member there is provided a set of adjacent magnetic pole bars 4 arranged opposite to each other. In all embodiments according to the invention, as already explained briefly with reference to FIG. Alternatively, the pole bar 4 and the individual parts of the permanent magnet 5 can be embedded in thermoplastic plastic, in which case one end of the pole bar and the magnet arrangement is inserted into the plastic and then the magnetic coil is inserted. can be installed. In addition, whether the individual parts are tube segments or flat iron, by enclosing the individual parts with plastic, a short tube with a closed surface is again formed and the tube is inserted into the cavity of the short tube. A magnetic pole bar can be accommodated.

A simple plastic member may be used to hold the pole bar in the position shown. However, the non-movable parts of the device according to the invention can simply be fixed by injection molding with plastic. The natural oscillations of the pole rod, which can occur if only one end is mounted, for example by latching it to the pole plate, are thereby completely suppressed, so that the transducer according to the invention has a good frequency response. It is advantageous in this respect. Also, since the transducer according to the invention is assembled from only a small number of components, it is inexpensive to produce compared to the production costs of conventional electromagnetic transducers.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the device according to the present invention, FIG. 2 is a diagram showing the course of magnetic lines of force of a magnetic field, and FIG.
4 is a schematic perspective view of an embodiment of a device with permanent magnets assembled with tube segments according to the invention; FIG. 6 is a schematic perspective view showing an embodiment of a device having permanent magnets made of individual bar-shaped members according to the present invention, FIG. 6 is a schematic front view of an embodiment of a device having four bar magnets according to the present invention, and FIG. A schematic front view showing an embodiment of the device with four bar magnets arranged differently than in FIG. 6, FIG. 8 having individual parts in the form of two opposed tube segments according to the invention; 1 is a schematic perspective view of an embodiment of the device, each with the direction of the magnetic field indicated by a chain line with an arrow; FIG. DESCRIPTION OF SYMBOLS 1... Needle support body, 2... Supporting member, 3... Small tube body, 4
...Magnetic pole bar, 5...Permanent magnet, 6...Winding wire, 3'...Magnetic coil.

Claims (1)

[Scope of Claims] 1. A permanent magnet and a magnetic pole bar having four windings, the axis of the magnetic pole bar being arranged at the apex of a square in a plane perpendicular thereto, and near the end of the magnetic pole bar. In an electromagnetic transducer for converting a mechanically recorded acoustic signal into an alternating voltage, the soft iron member driven by a scanning needle is movably supported around a central point on the central axis of the transducer device. , the permanent magnet 5 has the shape of a short tube or is constituted by a rod-like section of said short tube and is radially magnetized, the four pole bars 4 being symmetrical and parallel to the central axis of the transducer device. , penetrates the space at least partially surrounded by the permanent magnet 5, and directs the movable soft iron member 3 by the regeneration needle 1 near the end of the magnetic pole bar 4 directly to the magnetism of one end of the permanent magnet 5. An electromagnetic transducer characterized by being arranged in relation to a circuit. 2. The transducer according to claim 1, wherein the rod-shaped portion of the permanent magnet is formed as a tube segment. 3. The transducer according to claim 1, wherein the rod-shaped portion of the permanent magnet has a rectangular cross section. 4. The converter according to claim 3, wherein only four rod-shaped permanent magnet portions are provided, each of which is provided close to one of the four magnetic pole bars. 5. The conversion according to claim 2, in which there are only two tube segments arranged opposite to each other as permanent magnets, each tube segment being provided corresponding to a pair of opposing magnetic pole bars 4. vessel.