JPS6336386Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electromagnetic plunger for a player piano that has a simple structure and is capable of detecting the speed of a movable core during driving and controlling the thrust of the plunger.

Generally, this type of electromagnetic plunger used in player pianos has a coil bobbin 2 fitted and fixed to the outer circumferential surface of a brass guide pipe 1, and a coil wound around the outer circumferential surface of the coil bobbin 2, as shown in FIG. The solenoid coil 3 is formed into a cylindrical shape, for example, by the rotated solenoid, the movable iron core 4 passed through the guide pipe 1 with a small gap, and a magnetic material such as soft iron, and the solenoid coil 3 is housed inside. The yoke 5 and the like provide a magnetic path. When the solenoid coil 3 is excited by an electric signal obtained by reproducing a previously recorded electric signal, the movable iron core 4 is absorbed and raised by the action of the magnetic flux generated at this time.
Therefore, the key 6 is pushed up by the movable iron core 4 and operates as if the key had been pressed. The movable core 4 is normally elastically supported by a spring 7 and is locked at the initial position.

Here, when the relationship between the thrust of the electromagnetic plunger (the force that drives the movable core 4) and the stroke of the movable core 4 is shown in FIG. 2, the thrust decreases in a curve as the stroke increases, and this thrust - Stroke characteristics are, for example, coil current I ₁ → I ₂ → I ₃ ……
As the magnetic flux density is gradually lowered, the strength of the magnetic field decreases as the magnetic flux density decreases, resulting in a decrease.

However, this type of electromagnetic plunger is required to have thrust-stroke characteristics as flat as possible. In other words, in actual keystroke operation, in order to improve drive efficiency, it is desirable that the time when the string is struck by the hammer and the time when the maximum thrust is output approximately coincide; however, as the movable iron core 4 moves upward, the thrust increases. This means that in conventional plungers, the thrust force is not effectively and maximally utilized. As a result, the striking force of the hammer is weak, making it difficult to play soft notes, resulting in poor performance expression.

This idea was made in view of the above-mentioned points, and includes first and second coils arranged coaxially, and a first coil that is inserted through the center hole of both coils.
a movable member that pushes up the key by being moved upward by energization of the coil; and a magnetic fluctuation section provided on the movable member corresponding to the second coil, the magnetic fluctuation part When the movable member passes through the second coil part as the movable member moves upward, it generates an electromotive force in the coil, and this electromotive force is detected as a pulse signal, and the electromotive force is detected as a pulse signal. To provide an electromagnetic plunger for a self-playing piano, which generates a required thrust by controlling the current value of a first coil to increase so as to perform a good key-pressing operation.

This invention will be described in detail below based on embodiments shown in the drawings.

FIG. 3 is a longitudinal sectional view showing an embodiment of the electromagnetic plunger for a player piano according to this invention. Components in the figure that are the same as those in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted. A fixed yoke 10, a movable iron core 4 and a movable yoke 12 constituting a movable member 11 are arranged inside the coil bobbin 2. The upper end of the fixed yoke 10 is fitted and fixed in common with the upper open end of the inner hole 13 of the coil bobbin 2 and the hole 14 provided in the center of the upper surface of the yoke 5, and the lower end has an inverted truncated conical shape. The tapered portion 15 is formed by forming the taper portion 15 .

The movable core 4 is loosely inserted into the center hole 16 of the fixed yoke 10 with a small gap between them, and its upper and lower ends protrude above and below the yoke 5. A push-up button 17 made of rubber or the like is integrally attached to the upper protruding end of the movable core 4.
A buffer member 18 made of felt, rubber, or the like is disposed in the center of the upper surface of the button 17. An annular groove 19 having a substantially V-shaped cross section is formed in the lower surface of the push-up button 17, and the upper end of the spring 7 is inserted and held in this annular groove 19. The lower end of the spring 7 abuts against the upper surface of the yoke 5, thereby constantly urging the movable member 11 upward, causing the buffer member 18 to abut or approach the lower surface of the rear end of the key 6. In this case, the force of the spring 7 is set to an appropriate value within a range in which the key 6 is not pushed up by the movable member 11.

On the other hand, the movable yoke 12 is fitted and fixed on the outer circumferential surface of the approximately central portion of the movable iron core 4, and a tapered hole 20 is formed in the upper surface of the movable yoke 12 in correspondence with the tapered portion 15 of the fixed yoke 10. . A magnetic gap 21 is formed between the tapered hole 20 and the tapered portion 15.

A coil wound around the outer peripheral surface of the coil bobbin 2 constitutes a first coil 3 , and a second coil 23 and a magnetic yoke 33 coaxially wound around the bobbin 24 form a first coil 3 on the lower surface of the coil bobbin 2 . It is located in This second coil 23 is formed sufficiently thinner than the first coil 3, and the counter 25
It is connected to the. This counter 25 is connected to a control circuit 26 that controls the current, voltage, or power applied to the first coil 3.

A magnetic variation section 27 is provided on the outer peripheral surface of the lower end portion of the movable iron core 4 in correspondence with the second coil 23 . Each of the magnetic fluctuation parts 27 is formed into a disc shape with approximately the same outer diameter and thickness as the movable yoke 12, and includes a plurality of magnetic bodies 29a, which are fitted into the lower end of the movable iron core 4. 29b, 29
c, 29d and non-magnetic materials 30a, 30b, 30c,
30d. the magnetic body 29a,
29b, 29c, 29d and non-magnetic materials 30a, 30
b, 30c, and 30d are alternately stacked and in close contact with each other, and are prevented from falling off from the movable core 4 by a nut 31. The uppermost non-magnetic material 30a is normally located within the bobbin 24 and the second
It corresponds to the coil 23 of.

In this case, the magnetic variation part 27 is not limited to a magnetic material and a non-magnetic material. For example, as shown in FIG. 4, the lower end of the movable yoke 12 is extended, and a plurality of The annular grooves 35 may be formed at predetermined intervals, and these annular grooves 35 may be made into non-magnetic material equivalent portions, and the large diameter portions 36 between the annular grooves 35 may be made into a magnetic material-equivalent portion. In short, when the magnetic fluctuation unit 27 moves upward together with the movable iron core 4, it intermittently applies an electromotive force to the second coil 23 by electromagnetic induction or alternately applies two electromotive forces having different magnitudes. It suffices as long as it can be triggered multiple times.

In the electromagnetic plunger having such a configuration, a signal current _I0 is supplied to the first coil 3 via the control circuit 26, and when the coil 3 is excited, the movable yoke 12 is moved by the action of the magnetic flux generated in the magnetic gap 21. It is absorbed and lifted up. This rise of the movable yoke 12 means an upward movement of the movable member 11, so the buffer member 18 of the push-up button 17 pushes up the lower surface of the key 6, making it difficult to press the key 6 by hand. Operate as follows.

By the way, when the movable member 11 moves upward, the magnetically variable part 27 also rises together with it, so that the non-magnetic bodies 30a, 30b, 30c, 30d and the magnetic bodies 29a, 29b, 29c, 29d are connected to the second coil. Pass the 23rd part. Therefore, when the magnetic bodies 29a, 29b, 29c, and 29d pass through the second coil 23, an electromotive force is generated in the coil 23 due to the electromagnetic induction phenomenon, and this is transferred to the counter 2.
5 processes the waveform and detects it as a pulse signal. In this case, the number of pulse signals is the same as the number of magnetic bodies 29a, 29b... passing through the second coil 23,
The pulse interval becomes narrower as the passing speed of the magnetic material, in other words, the rising speed of the movable member 11 is faster. Therefore, the rising speed of the movable member 11 can be detected based on the pulse interval, and functions as a speed sensor. Further, this pulse signal is applied to the control circuit 26, and the signal current _I0 supplied to the first solenoid coil 3 is controlled moment by moment according to the pulse interval. This control gradually increases the solenoid current as the stroke of the movable member 11 increases, thereby preventing the thrust of the electromagnetic plunger from decreasing. That is, in Fig. 2, as the stroke increases, the solenoid current changes to I _o ... → I ₃ → I ₂
If you gradually increase the switch like →I ₁ ,
The thrust-stroke characteristic becomes nearly flat as shown by the dashed line 40, and the thrust force when the string is struck by the hammer can be maintained large. Therefore, a large impact force can be obtained, and if the impact force is large and spread out, weak sounds can be reproduced more faithfully.

As described above, the electromagnetic plunger for a player piano according to the invention includes a second coil disposed coaxially with the first coil, and a movable member disposed corresponding to the second coil. The electromotive force induced in the second coil by the magnetic variation part when the movable member is driven is detected as a pulse signal, and the electromotive force induced in the second coil is detected as a pulse signal according to the width of the interval between the pulse signals. Since the thrust force of the plunger is increased by increasing the current value of the coil, the striking force of the hammer can be increased. Therefore, the output range of the piano is expanded, and weak tones can be reproduced more faithfully, thereby enabling faithful playback performance. On the other hand, when trying to obtain the same thrust as a conventional plunger, the first coil can be made smaller. Furthermore, the structure is simple and assembly work is easy, and its practical effects are very great.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional electromagnetic plunger, FIG. 2 is a diagram showing thrust-stroke characteristics,
FIG. 3 is a longitudinal sectional view showing one embodiment of an electromagnetic plunger for a player piano according to this invention, and FIG. 4 is a front view of main parts showing another embodiment of this invention. 2... Coil bobbin, 3... First coil, 4
...Movable iron core, 6...Key, 10...Fixed yoke,
11...Movable member, 12...Movable yoke, 23...
...Second coil, 27...Magnetic fluctuation section.

Claims (1)

[Scope of utility model registration request] first and second coils arranged coaxially; a movable member that is inserted into the center holes of both coils and is moved upwardly when the first coil is energized to push up the key; and a magnetically variable part provided on the movable member corresponding to the coil, and the magnetically variable part is configured to cause a change in the inside of the coil when the movable member passes through the second coil part as the movable member moves upward. For a player piano, the electromotive force is detected as a pulse signal, and the current value of the first coil is controlled to increase in accordance with an increase in the interval between the pulse signals. Electromagnetic plunger.