JP2535563Y2 - Indicators for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an indicating instrument for a vehicle using a servo mechanism using a potentiometer.

[Conventional technology]

Conventionally, as this kind of indicating instrument, there is an indicating instrument shown in FIG. 2 applied to a tachograph for displaying or recording the speed and the number of revolutions of a vehicle. In the figure, a battery as a power supply
The V _B, the ignition key switch SW ₁ of the tachograph
And tachograph A is connected via a fuse FU _1. Tachograph A is an ignition key switch SW ₁
And a power supply circuit 4 connected to the battery V _B through the fuse FU _1, power supply circuit 4 is a stabilized voltage F / V converter circuit 1, to one input comprises a differential amplifier circuit F / The output voltage of the V conversion circuit 1 is supplied to a comparison circuit 2 to which the output voltage is input.
The output of the comparison circuit 2 is connected to a DC motor M, and the motor M is connected to a speed and rotation speed indicating mechanism and a recording mechanism (not shown).

A potentiometer 3 that outputs a voltage corresponding to the rotational position is coupled to the motor M, and the output voltage of the potentiometer 3 is input to the other input of the comparison circuit 2. The F / V conversion circuit 1 converts a speed signal or a rotation speed signal, which is a pulse signal having a frequency corresponding to the speed or the rotation speed, into a DC voltage and inputs the DC voltage to one input of the comparison circuit 2.

FIG. 3 shows a specific example of the power supply circuit 4, in which a diode D ₁ ,
Transistor Q _1, a conventional stabilized power supply circuit configured from such a Zener diode ZD ₁ and the smoothing capacitor C _1. The clock 6 is connected directly to the battery V _B through the fuse FU ₂ is in the tachograph A.

In the above configuration, the ignition key switch SW
_{When 1} is turned on, the operating voltage is supplied from the power supply circuit 4 to the F / V conversion circuit 1, the comparison circuit 2, and the potentiometer 3, and the operation state is established. The F / V8 conversion circuit 1 outputs a DC voltage having a magnitude inversely proportional to the frequency of the signal when a speed signal or a rotation speed signal whose frequency increases in accordance with the speed and the rotation speed is input to the input thereof. This is input to the comparison circuit 2. For example, in the case of a vehicle speed signal, when the vehicle is stopped, the frequency of the vehicle speed signal is 0, and at this time, the F / V conversion circuit 1 outputs the maximum DC voltage. The comparison circuit 2 compares the output voltage from the potentiometer 3 with the DC voltage from the F / V conversion circuit 1. When the former voltage is large, the DC motor M is rotated in one direction, and when the latter voltage is large, A drive voltage is supplied to the DC motor M so as to rotate in the reverse direction.

On the other hand, since the potentiometer 3 outputs a voltage corresponding to the rotational position of the DC motor M, the DC motor M rotates to a position where the two voltages match and no drive voltage is output from the comparison circuit 2. Therefore, the rotation position of the DC motor M corresponds to the speed signal and the rotation speed signal, whereby the speed and rotation speed indicating mechanism and the recording mechanism indicate and record the vehicle speed and the engine rotation speed.

In the indicating instrument configured as described above with reference to FIG.
When turning off the ignition key switch SW _1, come wraps around the discharge current of this through an ignition key switch SW ₁ charges the power accumulated in the capacitor of the other device (not shown) is supplied to the power supply circuit 4. For this reason, the output voltage of the power supply circuit 4 does not immediately drop, but rather decreases over time. During the fall of the output voltage of the power supply circuit 4, the output voltage from the potentiometer 3 is reduced by the F / V conversion circuit 1 In some cases, the DC voltage may be lower than the DC voltage of the pointer, and the pointer may be moved in a direction opposite to the zero position.

Therefore, directly connected power circuit 4 to the power supply, the power supply to the power supply circuit 4 so as to control the on and off the ignition key switch SW _1, immediately output voltage of the power supply circuit 4 by an ignition key switch SW ₁ off It is conceivable to lower it.

However, such a case, when the ignition key switch SW ₁ because of the many et when the speed signal or speed signal is sufficiently large is turned off, indicated mechanism and /
Alternatively, the rotation of the DC motor M is stopped in a state where the recording mechanism does not completely return to the zero point position, and a zero point floating state occurs.

In order to prevent the zero point from floating when the switch is turned off during the indicating operation, an indicating instrument having a circuit configuration shown in FIG. 4 has been proposed.

That is, in the Figure 4, the power supply circuit 4 is connected directly to the battery V _B through the fuse FU ₂ with clock 6. Ignition key switch SW ₁ and fuse F
Through U ₁ is connected a delay circuit 5 to the battery V _B, by the delay circuit 5 of the ignition key switch SW ₁ on,
When turned off, the operation of the power supply circuit 4 is controlled.

FIG. 5 is a circuit diagram showing a specific example of the power supply circuit 4 and the delay circuit 5, in which the delay circuit 5 includes a diode D ₂ ,
The time constant circuit includes resistors R ₁ and R ₂ , a capacitor C ₂ , transistors Q ₂ and Q _3, and a resistor R _3. The time constant circuit includes a diode D ₂ , a fuse FU _2, and an ignition key switch SW ₁ . is connected to the battery V _B via its output is connected to the base of the transistor Q _2. Collector and the diode D ₁ and the transistors of the transistor Q ₂
Between the collector connection point Q ₁ is the resistance R ₃ is connected, the collector of the transistor Q ₂ is connected to the base of the transistor Q _3. The collector of the transistor Q ₃ are connected to the base of the transistor Q _1.

In the above configuration, the ignition key switch SW
When you turn on _1, of the transistor Q ₂ base voltage v
(T) Stand up. When the base voltage v (t) reaches the predetermined voltage, the transistor Q ₂ is turned on, the transistor Q ₃ is turned off. This base bias is applied to the transistor to Q ₁ power supply circuit 4, which tachograph A drive voltage from the power supply circuit 4 to the F / V converter circuit 1 and the comparison circuit 2 is supplied by turning on is in an operating state. Base voltage V of the transistor Q ₂ in the operating state (steady state) V _d1 : terminal voltage of diode D ₁ V _d2 : terminal voltage of diode D ₂ h _fe2 : h _fe of transistor Q ₂ .

On the other hand, turning off the ignition key switch SW ₁ from ON, the transistor Q ₂ of the base voltage v (t) is Fall. Therefore, when the base voltage v (t) falls to a predetermined voltage transistor Q ₂ is turned off, the transistor
Q ₃ is turned on, the transistor Q ₁ is turned off. As a result, the drive voltage from the power supply circuit 4 to the F / V conversion circuit 1, the comparison circuit 2, and the potentiometer 3 stops.

The ignition key switch SW ₁ is turned off transistor Q ₂ is turned off from as described above, the transistor Q ₁ is provided with a delay time to turn off the ignition key switch SW ₁ from the power supply circuit 4 is also turned off Power supply is continued for the delay time.
The drive voltage for driving the DC motor M in the zero point direction can be reliably output. Accordingly, at the time of off the ignition key switch SW _1, DC motor M is returned to the zero point position by the driving voltage.

[Problems to be solved by the invention]

However, in any of the conventional indicating instruments described above,
When the battery voltage becomes to continuously turned on and off by the Zener diode ZD ₁ and are greatly varies the like when the engine is started, the power supply circuit 4 conducts the transistor Q ₁ is no longer carried out steadily the stably constant Voltage cannot be supplied.

When the voltage supplied by the power supply circuit 4 fluctuates in this manner,
The output voltage of the FV conversion circuit 1 and the output voltage of the potentiometer 3 also change. However, since the two output voltages change in different ways, a voltage is generated at the output of the comparison circuit 2, and the motor M is driven to rotate. Therefore, in the case of the vehicle speed indicating instrument, there is a problem that the hands are swung and the movement becomes unstable even though the vehicle is stopped.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and in a vehicle indicating instrument using a servomechanism using a potentiometer, the movement of the hands does not become unstable even if the battery voltage drops and fluctuates greatly. It is an object of the present invention to provide an indicator for a vehicle which has been improved.

[Means for solving the problem]

In order to solve the above problems, a vehicle indicating instrument made according to the present invention is connected to an indicating mechanism, and is driven forward and reverse according to a driving voltage to drive the indicating mechanism, and a frequency corresponding to a predetermined measurement amount. F / that inputs a pulse signal and outputs a voltage of a magnitude corresponding to the frequency of the input pulse signal.
A V conversion circuit, a potentiometer coupled to the motor and outputting a voltage corresponding to a rotation angle position of the motor,
The voltage output by the F / V conversion circuit is applied to one input terminal,
A voltage output from the potentiometer is input to the other input terminal, and a comparison circuit that outputs a drive voltage for driving the motor to rotate forward and reverse so that the voltages input to both input terminals match, and an ignition switch is turned on. A power supply circuit that supplies a constant voltage stabilized from a vehicle-mounted battery using a constant voltage element to the F / V conversion circuit, the comparison circuit, and the potentiometer as an operating voltage. In the indicating instrument for a vehicle provided, when the ignition switch is on,
When the voltage of the battery is stabilized by the constant voltage element of the power supply circuit and a constant voltage cannot be supplied to the F / V conversion circuit, the comparison circuit, and the potentiometer, the voltage of the battery is a predetermined voltage value. A voltage drop detecting means for detecting that the battery voltage has dropped below, and a voltage drop detecting means for detecting that the voltage of the battery has fallen below a predetermined voltage value when the ignition switch is turned on. And a power supply cutoff unit that cuts off voltage supply from the power supply circuit to the F / V conversion circuit, the comparison circuit, and the potentiometer.

[Action]

In the above configuration, even if the ignition switch is turned on, the battery voltage is so low that the constant voltage stabilized by the constant voltage element of the power supply circuit cannot be supplied to the F / V conversion circuit, the comparison circuit, and the potentiometer. When the voltage drop detecting means detects that the voltage has dropped below a predetermined voltage value, during this detection, the power supply cutoff means supplies the voltage from the power supply circuit to the F / V conversion circuit, the comparison circuit, and the potentiometer. Since the cutoff is performed, the power supply circuit does not supply an unstable voltage to the F / V conversion circuit, the comparison circuit, and the potentiometer based on the battery voltage that has dropped below the predetermined voltage value.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a vehicle indicating instrument according to the present invention. In FIG. 1, the same parts as those of the circuit described above with reference to FIG. Detailed description is omitted.

In FIG. 1, 7 is a low voltage monitoring circuit as a voltage drop detecting means for detecting that the voltage of the power supply falls below a predetermined voltage value, and the circuit is dividing by resistors R ₁₁ and R ₁₂ Battery the voltage Vb - having an input, a resistor R ₁₃ is a Zener diode ZD ₂ voltage comparator 7a constituted by a comparator reference voltage Vr generated are input to the + input by. Voltage comparator 7a, when the reference voltage Vr is higher than the partial pressure battery voltage Vb, that is, when the battery voltage has dropped, and outputs an H-level signal at its output, which divides by resistors R ₁₄ and R ₁₅ is applied to the base of the transistor Q _4, turn on the transistor Q _4.

Transistor Q ₄ are being connected between the base and the ground of the transistor Q ₃ of the delay circuit 5, drop to the ground the base potential of the transistor Q ₃ by the on. Transistor Q ₃ is turned off by this, the on-bias is not applied to the transistor Q ₁ transistor Q ₁ is in the non-conductive state, so that the voltage supplied from the power supply circuit 4 is cut off.

The holding, when the reference voltage Vr is lower than the partial pressure battery voltage Vb, that is, when the battery voltage is normal voltage, since the output of the voltage comparator 6a is output L level signal, the transistor Q ₄ are in the OFF state Then, the power supply circuit 4 normally supplies a voltage.

The relationship between the reference voltage Vr and the divided battery voltage Vb, so that the battery voltage is greater in the reference voltage Vr than the divided battery voltage Vb, even when the zener diode ZD ₁ is sufficiently higher than the OFF If the battery voltage drops, the power supply from the power supply circuit 4 is surely cut off, and the voltage is intermittently supplied due to the fluctuation of the battery voltage, and the operation is performed. Instability is prevented.

〔effect〕

As described above, according to the present invention, when the voltage of the battery drops below a predetermined voltage value while the ignition switch is on, the power supply circuit cuts off the voltage supply and the F / V conversion circuit, The supply of the operating voltage to the comparison circuit and the potentiometer is stopped, and the F / V conversion circuit is stopped.
Since the operation of the comparison circuit and the potentiometer is stopped immediately before the battery voltage drops below the predetermined voltage value, the operation of the pointer mechanism coupled to the motor, which is operated by the drive voltage output by the comparison circuit, is also stopped. Is done.

Therefore, the F / V conversion circuit, the comparison circuit, and the potentiometer are prevented from being operated at an unstable voltage, and when the ignition switch is turned on and the engine is started, the battery voltage is reduced. , The unstable movement of the pointer of the pointer mechanism can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an indicating instrument according to the present invention, FIG. 2 is a circuit diagram showing an example of a conventional indicating instrument, and FIG. 3 is a circuit showing a specific example of a power supply circuit in FIG. FIG. 4 is a circuit diagram showing another example of the conventional indicating instrument, and FIG. 5 is a circuit diagram showing a circuit configuration of a main part of the indicating instrument of FIG. A ... tachograph, V _B ... battery, SW ₁ ... ignition switch, M ... DC motor, 1 ... F / V conversion circuit, 2 ... comparison circuit, 3 ... potentiometer, 4 ... power supply circuit, 5 ... delay circuit, 7 ... Low Voltage monitoring circuit (voltage drop detection means), Q ₃ …
Transistor (power supply cutoff means).

Claims (1)

(57) [Scope of request for utility model registration] A motor coupled to an indicating mechanism and driven forward and reverse in accordance with a driving voltage to drive the indicating mechanism, a pulse signal having a frequency corresponding to a predetermined measurement amount is input, and a pulse signal of the input pulse signal is input. Output voltage of magnitude corresponding to frequency
An F / V conversion circuit, a potentiometer coupled to the motor and outputting a voltage corresponding to the rotation angle position of the motor, and a voltage output by the F / V conversion circuit output to one input terminal by the potentiometer. A voltage is input to the other input terminals, and a comparison circuit that outputs a drive voltage for driving the motor to rotate forward and reverse so that the voltages input to both input terminals match, and when an ignition switch is on, An indicating instrument for a vehicle, comprising: a power supply circuit that supplies a constant voltage stabilized from a vehicle-mounted battery using a constant voltage element to the F / V conversion circuit, the comparison circuit, and the potentiometer as an operating voltage. In the above, when the ignition switch is turned on, the voltage of the battery is stabilized by the constant voltage element of the power supply circuit so that the F / V So that a constant voltage cannot be supplied to the conversion circuit, the comparison circuit and the potentiometer,
Voltage drop detecting means for detecting that the voltage of the battery has dropped to a predetermined voltage value or less, and when the ignition switch is turned on, it is determined that the voltage of the battery has dropped to a predetermined voltage value or less. An instruction for a vehicle, comprising: a power supply cutoff unit that cuts off a voltage supply from the power supply circuit to the F / V conversion circuit, the comparison circuit, and the potentiometer while the voltage drop detection unit is detecting. Instrument.