JPH0339242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for rotationally driving the pointer of a moving coil type, moving magnet type, rotating magnetic field type, etc. meter, such as a speedometer or engine tachometer in a vehicle, to an appropriate position on a scale plate. This invention relates to a meter drive device.

Conventionally, in an electric speedometer using a moving coil ammeter, as shown in FIG. It is not equal to the scale between "10" and "20" in FIG. For this reason, there is a drawback that speed cannot be displayed in the low speed range or accuracy is not achieved. This is due to the structure of the movable film ammeter that is the display section. As shown in Fig. 2, the moving coil type ammeter has a permanent magnet 10.
An air gap is provided between the two yokes 102, 103 to create an equal magnetic field, and a moving coil 104 is disposed between the two yokes 102, 103. 10
4, a current is applied to the movable coil 104.
The force acting on the movable coil 104 is controlled by the spring 105, and the movable coil 104 is rotated to an angle proportional to the current flowing through the movable coil 104.
Pointer 1 through shaft 106 fixed to 04
07 can be rotated. and,
The relationship between the deflection angle θ of the pointer 107 and the current value flowing through the moving coil 104 is as follows: deflection angle θ, proportionality constant K ₁ ,
If the current is i, it is expressed as θ=K ₁ i, which is linear as shown by the solid line in FIG. However, when the deflection angle of the pointer 107 is around θ=0°, the moving coil 104 and the pointer 107 are unbalanced, and furthermore, due to the friction of the bearing, even if the current flowing into the moving coil 104 is 0, the pointer 107 does not necessarily move around θ=0°. Instead of pointing, it stops near it. For this reason, the pointer 107 is raised in advance by the stopper 108 to the point θ=θ ₀ (this is called raising to zero) to eliminate the failure of the pointer 107 to return to zero due to the above-mentioned friction or the like. The drive circuit is expressed by the equation i=K ₂ f, where f is the input signal frequency, i is the circuit output current, and K ₂ is the proportionality constant, and has a linear characteristic as shown by the solid line in FIG. Therefore, the pointer 107 always remains pointing at the "0" scale for the coil input current from θ=0° to θ=θ ₀ and does not indicate the speed in the low speed range.

Therefore, as a device that improves the shortcomings of the above-mentioned device, a spring 1 in a meter (ammeter) is proposed.
By shifting the fixed position of 05 by θ = θ ₀ so that the indication is in the decreasing direction (minus), the characteristics are as shown by the broken line in Figure 3, and the current i from the output circuit is linearly proportional to the input signal frequency f. At the same time, the pointer 107 is swayed by the deflection angle θ (=K ₁ i−θ ₀ ), and θ=θ ₀ is completely unrelated to the input signal frequency f.
By supplying the ammeter with a current i ₀ that causes the pointer to swing by the compensation circuit, a current i (=K ₂ f + i ₀ ) shown by the two-dot chain line in FIG. There is one in which the angle θ is set to θ=K ₃ f as shown in FIG. 6, and the scale of the ammeter is set as shown in FIG.

However, even with such a device, when the vehicle is stopped with the key switch turned on, such as when the vehicle is temporarily stopped at an intersection, the apparent balance between the driving force from i ₀ and the force of the spring 105 is Because it only returns to the upper "0" scale position, due to the inherent characteristics of an ammeter such as friction on the bearing,
There is a problem in that the pointer 107 does not necessarily point to θ=0, but stops near that point, resulting in a poor return.

The present invention prohibits the supply of current i ₀ by the compensation circuit when the speed of the vehicle exceeds a predetermined value, so that the pointer can return to below the "0" scale, and also allows the pointer to return to below the "0" scale. It is an object of the present invention to provide a vehicle meter drive device that eliminates the above-mentioned problem by forcibly preventing the meter from going below the "0" scale.

A first embodiment of the present invention will be described in detail below with reference to the electrical wiring diagram shown in FIG. In FIG. 7, 1 is a battery, 2 is a key switch, 3 is a vehicle speed sensor that generates vehicle speed pulses, 4 is an ammeter with characteristics as shown in the broken line in FIG. 3, and 5 is a vehicle speed pulse that receives vehicle speed pulses from vehicle speed sensor 3. 6 is a differential capacitor for triggering, 7 is a trigger circuit for triggering monostable multivibrator 8, and 9 is a regulator for stabilizing the operation of each circuit from voltage fluctuations of battery 1. Voltage power supply section, 10 is ammeter 4 using the signal from monostable multivibrator 8.
11 is an ammeter 4 that supplies a constant current to
This is a constant current circuit that serves as a compensation circuit that supplies a constant current to the 12 is a determination circuit that determines whether or not a vehicle speed pulse is generated from the vehicle speed sensor 3; an integrating circuit 12a that integrates the vehicle speed pulse from the vehicle speed sensor 3 and converts it into a DC signal;
Comparator 12b for comparing with reference value near Km/h
The transistor 12c is turned on by a signal from the comparator 12b when no vehicle speed pulse is generated from the vehicle speed sensor 3, and stops the operation of the constant current circuit 11. In addition,
The above components 3, 5, 6, 7, 8, and 10 constitute an output circuit. Further, the stopper 108 is provided at a position that defines the pointer 107 at the zero scale position in FIG.

The operation of the above configuration will be explained.

Now, when the key switch 2 is turned on and the vehicle is not running, the vehicle speed sensor 3 will not generate a vehicle speed pulse, and the monostable multivibrator 8 will not operate.
The constant current circuit 10 driven by the monostable multivibrator 8 also does not operate, and the determination circuit 12 also determines that there is no vehicle speed pulse and stops the operation of the constant current circuit 11. Therefore, the current generated by the vehicle speed pulse from the vehicle speed sensor 3 and the constant current from the constant current circuit 11 do not flow through the ammeter 4. Therefore, due to the characteristics of the ammeter 4, the pointer 1 tends to swing to -θ ₀ in FIG.
07 is stopped.

Next, when the vehicle starts running from this state and a vehicle speed pulse is emitted from the vehicle speed sensor 3, the determination circuit 1
2, it is determined that there is a vehicle speed pulse, the constant current circuit 11 is activated, and the constant current 10 is first supplied to the ammeter 4 by the constant current circuit 11, so a driving force corresponding to i ₀ acts, and θ ₀ minutes. I can only feel it. In addition, in the components 5, 6, 7, 8, and 10 that constitute the output circuit,
A monostable multivibrator 8 is triggered for each vehicle speed pulse through a waveform shaping circuit 5, a trigger differential capacitor 6, and a trigger circuit 7.
A pulse with a constant time width is generated, and a constant current pulse with a constant time width is further generated by the constant current circuit 10 and supplied to the ammeter 4. Therefore, the constant current circuit 10
Through this, a current linearly proportional to the signal frequency f of the vehicle speed sensor 3 where i=K ₂ f is supplied to the ammeter 4 as shown by the solid line in FIG. Since the characteristics of the ammeter 4 itself are as shown by the broken line in Fig. 3,
The combination of this characteristic and the constant current supply by the constant current circuits 10 and 11 results in a deflection angle θ = K ₃ f, resulting in a speedometer with a characteristic that indicates completely linearly from the low speed range to the high speed range as shown in Figure 6. .

Next, the necessity of the determination circuit 12 will be explained.

If the key switch 2 is stopped while the vehicle is running at a certain speed (when the vehicle speed is below a predetermined value), if the determination circuit 12 is not present and the constant current circuit 11 continues to pass a current of i ₀ , the pointer 107 does not try to return to the -θ ₀ position from the running state display position, but returns to the 0 position, but the moving coil type meter From the property of , the guideline 107 is θ=0
It does not point to the point and stops near it, resulting in a failure to return to zero. Therefore, when the vehicle stops, the determination circuit 12 cuts off the i ₀ of the constant current circuit 11, causing the pointer 107 to return to the -θ ₀ position,
The action of this and the stopper 108 ensures a return to zero.

Next, a second embodiment shown in FIG. 8 will be described. The second embodiment differs from the first embodiment in that it is applied to an engine tachometer and that potential fluctuations at the charge lamp terminal are used as a method for determining the presence or absence of a signal.

In FIG. 8, 31 is an ignition system that serves as a signal source for the engine tachometer. Ignition coil 3
A signal line is connected to the negative terminal of 11 to detect intermittent signals caused by ignition. 51 is a waveform shaping circuit for converting the signal into a complete rectangular wave.
81 is a monostable multivibrator using a flip-flop circuit 81a (set by a signal from the waveform shaping circuit 51, its output Q becomes high level and the timer circuit 81b is discharged, which becomes the reference value of the comparator 81c). Flip-flop circuit 8
generate pulses until 1a is reset), 11
Reference numeral 1 denotes a constant current circuit serving as a compensation circuit that supplies a constant current to the ammeter 4. 121 is a part used to determine whether or not the engine is rotating, 13 is a charge lamp, and 14 is a regulator. Reference numeral 122 is a determination circuit that determines whether or not the engine is rotating based on the signal at the L terminal of the regulator 14, and stops the operation of the constant current circuit 111 when the engine is not rotating.

The operation of the above configuration will be explained.

Now, when the key switch 2 is turned on and the engine is stopped, the ignition system 31 does not operate and no signal is generated, so the monostable multivibrator 81,
Constant current circuit 10 does not operate.

Moreover, at the L terminal of the regulator 14,
When the engine is stopped, it is at ground potential.
The charge lamp 13 is in a lit state. Afterwards,
The transistor 122a of the constant current circuit 122 is turned on, and the constant current circuit 111 has stopped its constant current supply operation. Therefore, no current from the signal from the ignition system 31 and no constant current from the constant current circuit 111 flows through the ammeter 4, and the pointer stops at the zero scale position due to the action of a stopper (not shown).

Next, when the engine starts from this state and enters the rotating state, at the L terminal of the regulator 14,
Since the alternator starts generating electricity, the L terminal becomes almost the battery voltage, and the charge lamp 13 turns off. Therefore, the transistor 122a of the constant current circuit 122 is reversed from on to off, and the constant current circuit 111 supplies the constant current i ₀ to the ammeter 4. Therefore, the combination characteristic of the constant current circuit 10 and the constant current circuit 111 is a deflection angle K ₃ f as shown in FIG. 6, and the direction is completely linear from the low speed range to the high speed range.

In the above embodiment, a moving coil type meter was described, but the present invention is not limited to a square coil type, and may be applied to a type of meter that controls torque with a spring, such as a moving magnet type, a rotating magnetic field type, etc. .

As described above, in the present invention, the scale on the scale plate can be scaled at equal intervals from the zero scale position, and at the same time, when the speed of the vehicle is below a predetermined value (when the vehicle is stopped), the pointer is reliably set to the zero scale. This has an excellent effect in that it is possible to provide a useful vehicle meter drive device that can return up to

[Brief explanation of the drawing]

Figure 1 is a front view of the display section of a conventional speedometer, Figure 2 is a structural diagram of a moving coil type meter, and Figure 3 is a characteristic diagram showing the relationship between the current value for driving the meter and the deflection angle of the pointer. , Fig. 4 is a characteristic diagram showing the relationship between the frequency of the output signal depending on the vehicle speed and the current value for driving the meter, Fig. 5 is a front view of the speedometer display section, and Fig. 6 is a characteristic diagram showing the relationship between the frequency of the output signal depending on the vehicle speed and the current value for driving the meter. A characteristic diagram showing the relationship with the deflection angle of the pointer, FIG. 7 is an electrical wiring diagram showing the first embodiment of the meter drive circuit according to the present invention, and FIG. 8 shows the second embodiment of the meter drive circuit according to the present invention. It is an electrical wiring diagram. 3, 5, 6, 7, 8, 10...Vehicle speed sensor, waveform shaping circuit, capacitor, trigger circuit, monostable multivibrator, constant current circuit, 12...judgment circuit, 100...scale plate that constitutes the output circuit , 10
7...guideline, 108...stoppa.

Claims (1)

[Scope of Claims] 1. An output circuit that electrically detects the state of a display target item that is displaced in an increasing direction from a stopped state, and generates an output signal for driving a vehicle meter based on the detected signal; The state of the display target item is displayed by the output signal from the output circuit at the position of the pointer on the scale plate, where the stop state is the zero scale position and the scale is graduated according to the displacement in the increasing direction. On the other hand, there is a meter having a characteristic in which the rotation range of the pointer is shifted in parallel in a decreasing direction by a predetermined rotation range from the rotation range on the scale plate, and a predetermined signal is sent to the meter regardless of changes in the output signal. a compensation circuit for compensating for rotational characteristics of the meter by rotating the pointer in the increasing direction by the predetermined rotation range; a stopper defined in the above; vehicle speed detection means for detecting whether the speed of the vehicle is below a predetermined value; A vehicle meter drive device comprising: a determination circuit that prohibits the supply of a signal to the meter;