JPH0355105Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Purpose of the Invention] (Field of Industrial Application) The present invention relates to a drive circuit for a movable magnet type instrument that displays measured quantities such as vehicle speed and engine rotational speed.

(Prior art) Moving magnet type instruments have traditionally been used to display measured quantities such as vehicle speed and engine rotational speed, and their drive circuits are driven by, for example, output from a rotational speed detection sensor connected to the axle. The pulse signal is processed and converted into two trapezoidal waveforms with a voltage and frequency corresponding to the frequency and a phase difference of 90 degrees from each other, and these trapezoidal waveforms are converted into electrical signals that change in an alternating current manner. Therefore, the coil of the movable magnet type meter is driven to cause the pointer to wave according to the amount to be measured. For example, this trapezoidal wave drive is disclosed in Japanese Patent Publication No. 62-20504.

(Problem to be solved by the invention) Trapezoidal wave driving as in the above-mentioned prior art approximately converts the frequency of a pulse signal, and the trapezoidal wave has no voltage change with respect to the phase angle on its upper and lower sides. Since it is constant, there is almost no change in the pointing angle of the pointer in this part, and the linearity of the pointing becomes poor, causing an error and causing a problem that accurate pointer display is not possible. In addition, this trapezoidal wave requires first converting the frequency and voltage of the pulse signal output by the sensor, and then converting this output voltage into a trapezoidal wave, which poses the problem of complicating the circuit.

The present invention was developed based on the above problem, and aims to provide a drive circuit for a movable magnet type instrument that can accurately display changes in a measured quantity and has a simple circuit configuration. That is.

[Structure of the idea]

(Means for solving the problem) The present invention includes a pair of coils arranged to intersect with each other at a certain angle, a sensor that outputs a signal whose frequency changes depending on the amount to be measured,
An oscillation circuit that outputs an AC voltage that has a constant period and changes depending on characteristics such as a sine wave or a cosine wave, and a trigger signal that is generated when a time corresponding to the frequency of the signal has elapsed after the reference voltage of this AC voltage is detected. and a signal processing circuit that supplies voltages at two points of the AC voltage having a phase difference of 90 degrees to each of the coils based on the output of the trigger signal.

(Function) The present invention detects changes in the measured quantity using a sensor as a change in frequency, detects this change in frequency as time, and detects the effective value of a sine wave alternating current voltage with a constant period after this time elapses. to each other
By capturing data at two points with a 90 degree phase difference and supplying them to each coil, the sine wave alternating current voltage follows the phase and its effective value constantly changes, making it possible to accurately display the deflection of the pointer.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. In Figure 1, at a constant angle to each other, e.g.
A pair of coils 1 arranged at an angle of 90 degrees,
A movable magnet 3 is rotatably disposed in the internal space of the movable magnet 3, and a movable magnet type instrument is constructed in which a pointer 5 is provided at the tip of a pointer shaft extending through the center of the movable magnet 3. Movable magnet 3 under magnetic field
rotates and the pointer 5 swings.

A sensor 6 is installed on the axle of the vehicle to detect a measured quantity such as vehicle speed, and outputs a pulse signal having a frequency proportional to the rotational speed of the axle. Reference numeral 7 denotes an oscillation circuit that outputs a sine wave alternating current voltage that changes with the characteristics of a sine wave with a constant period. 8 is a phase delay circuit that delays the phase of this sine wave AC voltage by 90 degrees and outputs a cosine wave AC voltage.
These sine wave AC voltage and cosine wave AC voltage are output to analog switch 9, respectively.

Reference numeral 10 denotes a trigger generation section which inputs the pulse signal and the sine wave AC voltage and outputs a trigger signal at a timing proportional to the frequency of the pulse signal, a zero cross circuit 11 which detects the zero cross point of the sine wave AC voltage, and a counter. a clock generator 12 that outputs a clock pulse of a predetermined frequency for the clock, an F/V converter 13 that converts the frequency of the pulse signal into a voltage, and an A/D that converts this voltage into a digital value.
It consists of a converter 14 and a preset counter 15 which uses this digital value corresponding to the frequency as a preset value, detects a zero cross point, counts this preset value using the clock pulse, and outputs a trigger signal. The output of this preset counter 15 is connected to an analog switch 9, and when a trigger signal is output, the analog switch 9 is closed, and the effective values of the sine wave AC voltage and cosine wave AC voltage at that time are sent to the capacitor C. Charge each. The charging current from the capacitor C is amplified by an amplifier 16 and supplied to the coils 1 and 2. Note that a signal processing circuit 17 is constituted by the analog switch 9, the phase delay circuit 8, the trigger generation section 10, the amplifier 16, and the like.

The operation of the present invention configured as described above will be explained next. The sensor 6 outputs a pulse signal with a frequency proportional to the vehicle speed. For example, if the vehicle speed is high, the frequency becomes high, and a large preset value is set in the preset counter 15. Oscillation circuit 7
As shown in FIG. 2, outputs a sine wave AC voltage with a constant period to one analog switch 9, and the phase delay circuit 8 outputs a cosine wave AC voltage whose phase is delayed by 90 degrees to the other analog switch 9. There is.
The preset counter 15 is reset at the zero cross point of the sine wave AC voltage and counts the clock signal, and when this count reaches the preset value, it outputs a trigger signal to close the analog switch 9. The capacitors C are charged with the effective values of both AC voltages at that time, and the charging currents are passed through the coils 1 and 2 to cause the pointer 5 to swing. In this case, since the preset value increases as the vehicle speed increases, the trigger signal is output at a time T proportional to the frequency of the pulse signal, and the effective values of both AC voltages are output. Therefore, in the case of high speed, the trigger signal is output when the phase has considerably advanced from the zero crossing point of the sine wave AC voltage, and from the effective value at that time, the deflection angle of the pointer 5 is, for example, as shown in Fig. 2B.
On the other hand, in the case of low speed, the trigger signal is output when the phase is not far ahead of the zero crossing point of the sine wave AC voltage, and the deflection angle of the pointer 5 is, for example, 45 degrees as shown in Figure 2C. . In addition, if the maximum deflection angle of the pointer 5 is set to 270 degrees and the maximum deflection angle is used to indicate the maximum vehicle speed, for example, 180 km/h, the vehicle speed should be 180 km/h at the position where the phase of the sine wave AC voltage is 270 degrees. The period of the sine wave alternating current voltage or clock pulse is set so that a preset value corresponding to the frequency of the pulse signal output at this time is set and the trigger signal is output.

In this way, the present invention uses a sine wave alternating current voltage whose effective value always changes according to the change in phase, and uses a sine wave AC voltage whose effective value always changes to follow the change in phase. In order to take in the effective value of the AC voltage at T and cause the current due to this voltage to flow through the coils 1 and 2 to make the pointer 5 swing,
Unlike conventional trapezoidal waves, there is no part where the voltage remains constant even if the phase changes, and voltage changes can be detected in any phase of the AC voltage, allowing accurate display with few errors. Further, there is no need to convert to a conventional trapezoidal wave, and this conversion circuit and the like are unnecessary, and the circuit configuration can be simplified.

FIG. 3 shows a second embodiment of the present invention, in which the trigger generator 10 uses a sensor 6 in an analog manner.
This shows something that detects the frequency of the pulse signal from. In this case, a charging/discharging circuit 20 consisting of a charging resistor R ₁ , a charging capacitor C, a discharging resistor R ₂ and an analog switch 19 is connected to the output of the F/V converter 13 via an analog switch 18 . It is connected to the inverting input terminal (-) of the comparator 21, and the voltage dividing points of the voltage dividing resistors _R3 and _R4 are connected to the non-inverting input terminal (+) of the comparator 21. Also,
The output of the zero cross detection circuit 11 is connected to analog switches 18 and 19 so that they can be switched reciprocally. When the zero cross point is detected, the analog switch 18 is closed, the analog switch 19 is opened, and the capacitor C is instantly charged with a voltage corresponding to the frequency of the pulse signal, and then the analog switch 18 is opened. The analog switch 19 is closed and the voltage on the capacitor C is discharged. At this time, the voltage charged in the capacitor C increases as the frequency of the pulse signal increases;
Since the discharge time becomes longer, the time during which the comparator 21 outputs the trigger signal after detecting the zero-crossing point changes, so that the same effect as in the embodiment described above can be achieved.

FIG. 4 shows a third embodiment of the present invention, in which a counter 22 is used instead of the phase delay circuit 8 to detect a 90 degree phase difference in a sine wave AC voltage. In this case, a sine wave AC voltage is output to two analog switches 9, and the first
When the preset counter 15 outputs the first trigger signal as shown in the embodiment, one analog switch 9 closes and the effective value of the sine wave AC voltage at that time is transferred to the capacitor C as shown in FIG. At the same time, the counter 22 is reset by the first trigger signal, counts the clock pulses, and outputs the second trigger signal at a timing with a 90 degree phase difference in the sine wave AC voltage, and the other analog switch 9 is charged. is closed and the capacitor C is charged with the effective value of the sine wave AC voltage at that time,
The pointer 5 is swung by the effective value of these sine wave AC voltages having a 90 degree phase difference.

FIG. 6 shows a fourth embodiment of the present invention, in which the trigger generating section 10 of the third embodiment detects the pulse signal from the sensor 6 in an analog manner. In this case, the same parts as in the second and third embodiments are given the same reference numerals. Comparator 21 outputs a first trigger signal, which is output to analog switches 23 and 24 to reciprocally close them. One analog switch 23 has its input side connected to the voltage dividing point of the voltage dividing resistors R ₅ and R ₆ , its output side connected to the charge/discharge circuit 25 , and a predetermined divided voltage is applied to the capacitor C via the resistor R ₇ . At the same time, the voltage discharged by the discharge resistor R ₈ is output to the inverting input terminal (-) of the comparator 26, and the non-inverting input terminal (+) is connected to the voltage dividing point of the voltage dividing resistors R ₉ and R ₁₀ . A second trigger signal is output from the connected comparator 26. In this case as well, the same actions and effects as described above can be achieved. Incidentally, although the above embodiment has been described in detail regarding vehicle speed, it can also be applied to measured quantities such as engine speed.

(Effects of the invention) As detailed above, according to the invention, a pair of coils are arranged to intersect with each other at a certain angle, and a signal whose frequency changes depending on the quantity to be measured is output. A sensor and an oscillator circuit that outputs an alternating current voltage that has a constant period and changes depending on characteristics such as a sine wave or a cosine wave, when a time corresponding to the frequency of the signal has elapsed after detecting the reference voltage of this alternating voltage. a trigger generating section that outputs a trigger signal, and a signal processing circuit that supplies voltages at two points having a phase difference of 90 degrees from each other in the AC voltage to the coils based on the output of the trigger signal. Accordingly, it is possible to provide a drive circuit for a movable magnet type instrument that can accurately display changes in the measured quantity and has a simple circuit configuration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the first embodiment of the present invention, Fig. 2 A is a waveform diagram of the main part, B and C are graphs showing the deflection of the pointer, and Fig. 3 shows the second embodiment. FIG. 4 is a block diagram showing the third embodiment, FIG. 5 is a waveform diagram of the main part, and FIG. 6 is a circuit diagram of the main part showing the fourth embodiment. 1, 2... Coil, 6... Sensor, 7... Oscillation circuit, 10... Trigger generation section, 17... Signal processing circuit.

Claims (1)

[Scope of utility model registration request] A pair of coils arranged to intersect each other at a certain angle, a sensor that outputs a signal whose frequency changes depending on the measured quantity, and a characteristic such as a sine wave or cosine wave with a certain period. an oscillator circuit that outputs an alternating current voltage that changes according to the frequency of the signal; a trigger generating section that outputs a trigger signal when a time corresponding to the frequency of the signal has elapsed after detecting a reference voltage of the alternating voltage; and a signal processing circuit that supplies voltages at two points having a phase difference of 90 degrees from each other in the alternating current voltage to the coils based on the AC voltage.