JPH0451098A - Key driving device of keyboard musical instrument - Google Patents

Abstract

PURPOSE:To reduce the weight of a movable part by positioning the tip of a fixed yoke in the movable yoke of a plunger and decreasing the movable yoke in the equivalent of confronting area with the fixed yoke gradually to the inside of a solenoid coil in the axial direction. CONSTITUTION:The plunger 24 is composed of a shaft 25 nearly coaxial with the solenoid coil 22 and the cylindrical movable yoke 26 fixed on the shaft 25, the fixed yoke 23 is extended to the inner peripheral part of the solenoid coil 22, and its tip is positioned in the movable yoke 26 of the plunger 24. The movable yoke 26 is so shaped as to decrease gradually in the equivalent of the confronting area with the fixed yoke 23 toward the inside of the solenoid 22 in the axial direction. Consequently, the initial thrust is made large, variation in thrust to the stroke of the plunger is made smooth, and the majority of the weight part of the solenoid is distributed to the side of the fixed yoke 23 to reduce the weight of the plunger 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a key drive device that electrically swings the keys of a keyboard instrument such as a player piano or an electronic piano.

[Prior Art] A DC solenoid is used in a conventional key driving device of this type, and a structure shown in FIG. 4 is known as an example.

The twist/id l shown in this figure is an anechoic solenoid, and is provided to cover a cylindrical coil 3 wound around a bobbin 2 and the fill 3, and has coils 3 at both ends.
The fixed yoke 4 has a cylindrical portion 4a positioned coaxially with the center hole 3a of the bobbin 2, and the plunger 5 is slidably disposed within the bobbin 2.

Then, by applying a voltage to the coil 3 to generate a magnetic field, the plunger 5 is attracted and slid in the axial direction of the coil 3 as shown by the arrow in the figure, and by this sliding operation, A key 6 disposed above the solenoid 1 is pushed up and swung.

By the way, in a key drive device using such a solenoid 1, the thrust is small at the beginning of suction by the plunger 5, and as the stroke becomes thicker (enters the inside of the coil 3), the thrust increases. Since it has a characteristic of increasing rapidly, even when the input power is kept constant, the thrust changes greatly depending on the stroke, making it difficult to control when driving the key 6.

Accordingly, a proposal has been made for a threaded nose 10 having a configuration as shown in FIG.

The tube 10 has a cylindrical portion 11a formed at one end of the fixed yoke 11 extending toward the inside of the coil 12, and the thickness of the peripheral wall of the cylindrical portion 11a is set to the inside of the coil 12 in the axial direction. One end of the plunger 13 (-i-, 075 part in the figure), which is formed so as to become gradually thinner as it goes to the bottom, and is slidably inserted into the inside of the fill 12, or within its sliding range. , it is configured to be positioned so as to overlap with the cylindrical portion 11a.

With this configuration, even at the start position of the stroke of the plunger 13, an amount equivalent to the opposing area is ensured between the cylindrical portion 11a and the plunger 13, and the initial thrust is increased, thereby, It becomes possible to smooth the thrust force characteristics with respect to the stroke of the plunger 13.

[Problems to be Solved by the Invention] However, even with the above-mentioned conventional technology, the following problems still remain to be solved.

In other words, both of the plungers 5 and 13 are formed into true cylinders (this is a measure taken to avoid magnetic saturation), and for this reason, the weight of the plungers 5 and 13 is large. However, it is disadvantageous in terms of responsiveness.

This point also greatly affects the fidelity when reproducing trills and half-touch performances on keyboard instruments.

Therefore, in the past, it has been desired to deal with such problems, and the present invention aims to solve the problems that remain in the conventional art.

[Means for Solving the Problems] The present invention aims to provide a key drive device for a keyboard instrument that can effectively solve the above-mentioned problems. The key driving device includes a solenoid coil, a fixed yoke containing the solenoid coil, and a plunger that slidably engages with the helical/four-way coil, and the plunger engages with the solenoid coil. It is composed of a substantially concentric shaft and a cylindrical movable yoke fixed to the shaft. The movable yoke of the plunger has a shape in which an area equivalent to the area facing the fixed yoke gradually decreases toward the inside of the thread-made coil in the axial direction.

[Function] The key drive device for a keyboard instrument of the present invention always makes the tip of the fixed yoke and a part of the movable yoke face each other within the sliding range of the movable yoke to ensure a facing area equivalent M. This increases the initial thrust and smoothes the change in thrust with respect to the stroke of the plunger.

Furthermore, by configuring the movable part by a shaft and a movable yoke fixed to the shaft, most of the weight of the solenoid is distributed to the fixed yoke, thereby reducing the weight of the plunger.

Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The key driving device 20 of the present embodiment shown in FIGS. 1 and 2 is arranged opposite to each other under each of a plurality of keys 21 of a keyboard instrument, and is provided with a solenoid coil 22 and a fixing device containing the solenoid coil 22. The plunger 24 is provided with a yoke 23 and a plunger 24 that is slidably fitted into the solenoid coil 22.
2 and a cylindrical movable yoke 26 fixed to the shaft 25.
is extended to the inner circumferential portion of the solenoid coil 22, and its tip is located inside the movable yoke 26 of the plunger 24, and is connected to the plunger 24.
The movable yoke 26 has a general configuration in which the equivalent area of the opposing area with the fixed yoke 23 gradually decreases toward the inside of the solenoid coil 22 in the axial direction.

Next, to explain these details, the solenoid coil 22 is wound around a bobbin 27 having a through hole 27a in the center in a direction surrounding the through hole 27a.

The fixed yoke 23 is an outer yoke L (a
and a cylindrical inner yoke 23b connected to the outer yoke 23a and inserted into the through hole 27a of the bobbin 27.

Further, bearing members 28 are fixed to both ends of the inner yoke 23b, and the shaft 25 of the plunger 24 inserted into the inner yoke 23b is slidably supported by these bearing members 28.

Further, the shaft 25 projects outward from the fixed yoke 23 and is swingably connected to the lower part of the key 21.

The movable yoke 26 fixed to the shaft 25 has a first
As shown in the drawings and FIG. 2, it is formed into a cylindrical shape whose upper end (the upper end in the drawing) is closed and whose lower end is open.

In this embodiment, the peripheral wall portion 26a of the movable yoke 26 is formed to become gradually thinner toward its open end.

In addition, in a non-operating state where no voltage is applied to the solenoid coil 22, the tip of the inner yoke 23b is located within the open end of the movable yoke 26, and the inner yoke 23b is at a position where they face each other in the radial direction. held in a relationship.

Thus, the key drive device 20 of this embodiment configured as described above generates a magnetic field by applying a voltage to the solenoid coil 22, and the magnetic force causes the movable yoke 26 to move as shown by the arrow in FIG. By suctioning toward the inner yoke 23b, the plunger 24 is slid, and the key 21 to which the shaft 25 of the plunger 24 is connected is
Pull down to swing the key 21.

When the key 21 is swung in this manner, since the movable yoke 26 and the inner yoke 23b are opposed to each other in the non-operating state as described above, magnetic flux passes between them in the opposed portion. As a result, a magnetic circuit is formed, whereby an attractive force effectively acts on the plunger 24 even in the initial stage of startup, and the movable yoke 26
The suction force gradually increases as the inner yoke 23b approaches the inner yoke 23b.

On the other hand, the suction force F is expressed by the following equation.

F − (10'/8 π)・Bg”・SHowever,
Bg: Gap magnetic flux density S: Opposing area between the inner yoke 23b and the movable yoke 26 As can be understood from this equation, if the shape of the movable yoke 26 of the plunger 24 is set so that the value of BglS is constant, the plunger It is possible to smooth out changes in suction force with respect to 24 strokes.

In this embodiment, this is the movable yoke 2.
This is realized by making the peripheral wall portion 26a of No. 6 gradually thinner toward the inner yoke 23b.

When the plunger 24 slides like this, the plunger 24 is composed of a small diameter shaft 25 and a cylindrical movable yoke 26 fixed to the shaft 25, and most of the weight is the fixed part. Since it is concentrated on the fixed yoke 23 side, the weight of the movable parts is significantly reduced. Therefore, the responsiveness when the plunger 24 slides is improved.

Furthermore, as described above, smooth suction force characteristics can be obtained with respect to the stroke of the plunger 24, which facilitates its control.

Due to these synergistic effects, when the operation of the keys 21 is servo-controlled, fine control becomes possible, and it becomes possible to reproduce a performance that is closer to a human performance.

In particular, in keyboard instruments that do not have an action mechanism and directly drive the /1 mark, the weight of the /1 mark is 6 to 1.
Since the plunger 24 is lightweight, weighing only a few grams, reducing the weight of the plunger 24 described above has a great effect.

In addition, since fine control of the driving of the keys 21 is possible, for example, when applied to control the keyboard of an a-ply piano, it is possible to achieve a touch similar to that of a grand piano.

Furthermore, when applied to the keyboard of an electronic musical instrument, it is possible to achieve a touch similar to that of an acoustic piano by using the thrust of the key drive device 20 as a reaction force during key operation. Become.

Furthermore, FIG. 3 shows another embodiment of the present invention, in which an inner yoke 23b is attached to the peripheral wall portion 30a of the movable yoke 30.
A generally fan-shaped protrusion 31 is formed that tapers gradually as it approaches .Other than that, the structure is the same as that of the embodiment shown in FIGS. 1 and 2.

With such a configuration, it is also possible to obtain a characteristic in which the suction force is smoothed by adjusting the amount corresponding to the area facing the inner yoke 23b in the above-described relationship.

[Effects of the Invention] As described above, the key driving device for a keyboard instrument according to the present invention is a key driving device that is arranged opposite to a key of a keyboard instrument and swings the key, and includes a solenoid coil. a fixed yoke containing the solenoid coil; and a plunger slidably fitted to the solenoid coil;
The plunger includes a shaft substantially concentric with the solenoid coil and a cylindrical movable yoke fixed to the shaft, and the fixed yoke extends to the inner circumference of the solenoid coil, and the tip thereof is , is located inside a movable yoke of the plunger, and the movable yoke of the plunger has a shape in which an equivalent area facing the fixed yoke gradually decreases toward the inside of the solenoid coil in the axial direction. It is characterized by the following excellent effects.

By constructing the plunger with a shaft and a cylindrical movable yoke fixed to the shaft, the main part of the weight is concentrated on the fixed yoke side, which is the fixed part, and the weight of the movable part can be reduced. and its responsiveness can be improved.

Further, the tip of the fixed yoke is located inside the movable yoke of the plunger, and the movable yoke of the plunger is gradually moved as the area equivalent to the area facing the fixed yoke moves toward the inside of the solenoid coil in the axial direction. By having a decreasing shape, it is possible to increase the suction force at the initial stage of sliding of the plunger and obtain smooth suction force characteristics with respect to the stroke of the plunger.
The operation of the plunger can be easily controlled.

These synergistic effects enable fine control when servo-controlling the key operation, making it possible to realize a performance that is more similar to a human performance.

[Brief explanation of the drawing]

In the drawings, FIGS. 1 and 2 show one embodiment of the present invention, in which FIG. 1 is a longitudinal cross-sectional view, FIG. 2 is a partially cut away external perspective view of the movable yoke, and FIG. FIG. 4 is a longitudinal section showing an example of a conventional key drive device, and FIG. 5 is a longitudinal section showing still another conventional example. 20...Key drive device, 21...Key,
22...Solenoid coil, 23...Fixed yoke, 24...Plunger, 25...
...Axis, 26...Movable yoke.

Claims (1)

[Scope of Claims] A key drive device that is disposed opposite to a key of a keyboard instrument and swings the key, the device comprising: a solenoid coil; a fixed yoke containing the solenoid coil; and a fixed yoke that is slidable on the solenoid coil. a plunger that fits into the solenoid coil; the plunger includes a shaft substantially concentric with the solenoid coil; and a cylindrical movable yoke fixed to the shaft; and the fixed yoke includes an inner periphery of the solenoid coil. the movable yoke of the plunger has an area equivalent to that of the fixed yoke,
A key drive device for a keyboard instrument, characterized in that the solenoid coil has a shape that gradually decreases toward the inside in the axial direction.