JPS6015175Y2 - Rotating magnetic field type instrument - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a rotating magnetic field type instrument with a large indicating torque.

When a rotating magnetic field type instrument is used, for example, as a speedometer or a tachometer for a vehicle, it has conventionally been driven by an alternating current rectangular wave signal.

FIG. 1 shows the configuration of a conventional rotating magnetic field type instrument.

Reference numeral 1 denotes a pointer shaft having a pointer 6, and a conductive cup-shaped rotor 3 is fixed to the end thereof.

Reference numeral 2 denotes a spiral spring as a zero return means for applying a zero return torque to the pointer shaft 1.

A first coil 4 and a second coil 5 are wound around the rotor 3 without contacting each other.

The first coil 4 and the second coil 5 are located perpendicular to each other.

Each of these coils 4 and 5 is provided with a rectangular wave signal supply circuit. ', 8' to 9 mutually as shown in Figure 2.
AC rectangular wave voltage signals A and B having different phases by 0 degrees are supplied.

By the way, in this case, since each coil 4, 5 becomes an L load, the current flowing through each coil 4, 5 due to the time constants T□, T2 and T1', T2' determined by its inductance and impedance is Figure 3 shows B/
This shows a transient phenomenon such as .

The resulting composite magnetic field of the coils 4 and 5 rotates when the current flowing through each coil changes, that is, during a transient phenomenon.

The composite magnetic field rotates stepwise, causing eddy currents in the rotor 3 and causing the pointer 6 to indicate the input signal frequency.

However, in the case of this rectangular wave drive, the magnitude of the composite magnetic field and the rotation speed have a great influence on the magnitude of the generated torque.

In particular, the rotational speed is determined by the time constant T1.
A submolecule determined by and consisting of T2, T1', and T2'.

It does not change depending on the input signal frequency.

Therefore, this is used to obtain an instruction approximately proportional to the input signal frequency, but if the rotation speed of the composite magnetic field is slow, the generated torque will decrease, and conversely, if it is too fast, eddy current will occur in the rotor 3. This makes it difficult for this to occur, and on the contrary, the generated torque decreases.

Therefore, it is necessary to select the rotational speed of the composite magnetic field to an appropriate value, and usually the time constant of the transient phenomenon is Tl '''Tl
' = set to approximately 2 to 3 ms.

Therefore, the winding specifications of each coil 4, 5 are limited, and in this case, T'> T2- TI'>T2'
Therefore, the time constant T2. The rotational speed of the composite magnetic field due to T2' is too fast, so it hardly contributes to the generated torque, and has the disadvantage that the generated torque is small.

This idea was made to eliminate the above-mentioned drawbacks. By driving each coil with a trapezoidal wave whose time constant does not change depending on the input signal frequency, the generated torque is large and the winding of the coil is reduced. The purpose is to provide a rotating magnetic field type instrument that has flexibility in wire specifications.

Hereinafter, one embodiment of this invention will be described in detail with reference to FIGS. 4 to 6.

Figure 4 shows the configuration of an embodiment of this invention.
Each section 1 to 6 has exactly the same structure corresponding to each section shown in FIG. 1 above.

That is, 1 is a pointer shaft, 2 is a thinly wound spring, 3 is a rotor, 4 and 5 are first and second coils, and 6 is a pointer.

On the other hand, 7 and 8 are trapezoidal voltage signal supply circuits, which supply trapezoidal voltage signals as shown by C and D in FIG. 5 to the respective coils 4 and 5.

Signals C and D have a phase difference of 90 degrees from each other.

In the waveforms of these signals, the time constants of the rising edge (including the falling edge on the negative polarity side) and the falling edge do not change depending on the input signal frequency, but are constant (2 to 31113
) is set.

When these signals C and D are supplied to each coil 4.5, each coil 4 and 5 receives C',
As shown by D', the time constant T3. T4 and 'r3',
A signal with a waveform having a current changing portion of 'r4' flows.

In this case, the composite magnetic field is set when the current flowing through each coil changes as in the case of rectangular wave driving, that is, when the time constant T3. T
, and T3', T,'.

This step rotation of the composite magnetic field generates eddy current in the rotor 3, and the pointer 6 indicates the input signal frequency.

Time constant T3 of current changing section. T, and T3', T,'
does not change within the range defined by the input signal frequency (the input signal frequency range in which the trapezoidal wave does not become a triangular wave), so an instruction approximately proportional to the input signal frequency can be obtained.

When driven with such a trapezoidal voltage signal, the time constant T3. T3' is approximately equal to the larger of the time constant determined by the inductance and impedance of each coil 4.5 and the time constant of the trapezoidal wave, and the time constant T, T4' at the time of the fall of the current changing section is the trapezoidal wave. It is almost equal to the time constant of

Therefore, since torque is generated even at the time of falling, the generated torque is significantly larger than that in the case of conventional rectangular wave drive.

Furthermore, since the rotational speed of the composite magnetic field can be determined by the time constant T of the trapezoidal wave of the drive signal, freedom in winding specifications for each coil is increased.

As described above, this invention is equipped with a trapezoidal wave supply circuit and is driven by a trapezoidal wave whose time constant does not change even when the input signal frequency changes, so the generated torque is large and the winding of each coil can be freely controlled. You can get something of high quality.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a conventional rotating magnetic field type instrument;
Fig. 2 is a waveform diagram of the drive signal, Fig. 3 is a waveform diagram of the current flowing through each coil in that case, Fig. 4 is a block diagram of an embodiment of this invention, and Fig. 5 is a diagram of the drive signal. FIG. 6 is a waveform diagram of the current flowing through each coil in that case. 1... Pointer shaft, 2... Spiral blade, 3
...Rotor, 4...First coil, 5
...Second coil, 6...Pointer, 7,
8...Trapezoidal wave supply circuit.

Claims (1)

[Scope of utility model registration request] A pointer shaft 1, a conductive rotor 3 fixed to the pointer shaft 1, and a plurality of coils 4 arranged close to the rotor.
5, a zero return means 2 for applying zero return torque to the rotor 3, and a trapezoidal wave signal supply circuit 7 for supplying trapezoidal wave voltage signals having different phases to the plurality of coils 4 and 5, respectively. , 8 is a rotating magnetic field type instrument.