JPH0146336B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display control device for a taximeter.

[Conventional technology]

With the recent development of electronic technology, most taximeters have been implemented electronically from the viewpoint of basic advantages such as high accuracy, high reliability, and long life, as well as ease of changing the fare system. It has come to be widely used, especially for price displays and tariff displays. That is, a display is performed by converting and amplifying an electronically processed digital signal and lighting up an electronic display element such as a known light emitting diode or fluorescent display.

By the way, in the case of a lighting display, when the outside world is bright such as during the day, the brightness of the taximeter display must be increased considerably in order to be able to read the display. When the outside world is dark, such as at night, the light from the display element preferentially enters the driver's field of vision, obstructing the driver's field of view of the outside world such as the road, and making it difficult to see, which is dangerous for driving. This effect is particularly large when a display element with high luminance is used. On the other hand, if the brightness is set to a level that does not interfere with driving at night, the display status will be almost impossible to read during the day, causing trouble with customers.

Therefore, conventionally, as seen in Japanese Utility Model Application No. 56-27769, the supply voltage to the display element is switched according to the on/off of a small light switch for the electrical load, and the display element is lit in two stages: bright or dark. As a result, there has been created a taximeter display control device that brightens the display when the outside world is bright, and darkens the display when the outside world is dark, thereby eliminating problems in driving and taximeter operation.

On the other hand, buttons for empty vehicle, actual vehicle, premium, payment, tariff, etc. were generally lit whenever the ignition switch was turned on.

[Problem that the invention seeks to solve]

In the conventional display control device described above, the light was dimmed only by turning on the small light switch, so it was up to the driver to operate the small light switch on rainy days, cloudy days, at dusk, or in dim light such as inside a tunnel. If you are left to your senses and operate the small light switch at the wrong time relative to the brightness of the outside world, the brightness of the display will be inappropriate for the brightness of the outside world.

In addition, in this known device, one step of dimming is forced when the small light switch is turned on, and the brightness is maintained unless the small light switch is turned off next time, so various changes in brightness at night (e.g. Appropriate brightness cannot be obtained even in bright places at night, such as in downtown areas, and good visibility cannot necessarily be obtained. The same thing can be said about the daytime, and appropriate brightness could not be obtained even with various brightness changes during the daytime.

Furthermore, this conventional device has only one type of dimming pattern, and although its dimming function is poor, it requires wiring work to incorporate a small light switch when installing the meter, and it also requires a small This requires an additional wire for the light switch signal input, which has the disadvantage of making wiring work difficult and adding more wires to devices that have a wide variety of wires.

In addition, since the operation parts such as tariff buttons are always lit, the temperature inside the device increases due to the heat generated by the light emitting element, the brightness of the light emitting element deteriorates and the lifespan is shortened, and the reliability of the device decreases due to increased power consumption and wasted energy. Each had their own drawbacks in terms of consumption.

[Means for solving problems]

The present invention has been made in view of the problems of the conventional ones mentioned above.
To provide a taximeter display control device that automatically performs stepless dimming of the taximeter display and operation section illumination at night and in dim light, and improves visibility, operability, reliability, and product price. A display control device designed for this purpose includes a brightness detection means that generates a signal with a level corresponding to the surrounding brightness, and a comparison between the level of the signal from the brightness detection means and a reference level. and an operation section illumination on/off circuit that turns on and off the operation section illumination section according to the comparison result, and a dimming circuit that changes the brightness of the tariff display section according to the level of the signal from the brightness detection means. It is characterized by having the following.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a display control device according to the present invention, and FIG. 2 is a perspective view showing an example of a front panel of a taximeter that displays information using the display control device of FIG.

First, the front panel of a taximeter will be explained with reference to Fig. 2.In the center of the panel, for example, a fluorescent display for fare, total (vehicle fare), and tariff display section 1 is provided. A large number of tariff buttons 3 are provided at the top and bottom as operation sections. The part of the display section 1 adjacent to the tariff button 3 is marked with a letter 4 indicating the type of tariff button, and the upper and lower edges of the tariff button 3 (black portions in the figure) are provided with a light-emitting diode, for example. An operation unit illumination unit 2 is provided.

The display section 1 is automatically dimmed according to the surrounding brightness by the circuit shown in FIG.
The circuit shown in the figure automatically turns the light on and off.

To explain further by returning to Figure 1, in the figure, a resistor is connected in series between the power supply V _D and ground.
A dimming timing setting section 10 is constituted by R ₁ and R ₂ , and a photocell 11 is connected in parallel with the resistor R ₁ of the dimming timing setting section 10 . The resistance value of the photocell 11 changes depending on the change in the amount of light received, and a voltage corresponding to the amount of light received is generated at the connection point a with the voltage level set by the dimming timing setting section 10 as a reference.

The connection point a is connected to the inverting input of the first comparator 12 via a resistor R ₃ and to the inverting input of the second comparator 13 via a resistor R ₄ .

The non-inverting input of the first comparator 12 has resistors R ₅ and R ₆ connected in series between the power supply V _D and ground.
The resistance R ₅ of the reference voltage setting section 14 is composed of
The connection point b between _R6 is connected, and the resistor _R7 is connected between it and the output c. The resistor R ₇ constitutes a hysteresis setting section 15 together with the resistor R ₆ . The output c of the first comparator 12 is connected to a driver section 16 consisting of transistors Q ₁ and Q ₂ . The driver section 16 drives the operation section illumination section 2 described above with reference to FIG. 2 to turn on. The operation section illumination section 2 illuminates the operation section 3 and the characters 4 by lighting the operation section illumination section 2 .

The non-inverting input of the second comparator 13 is connected to an oscillation frequency setting section ₁ consisting of a capacitor C1.
The output d of a multivibrator 18 that sends out a triangular wave having a frequency set by 7 is connected. The output e of the second comparator 13 is a resistor
A transistor that is connected to the power supply _VD through _R8 and pulled up, and also constitutes the inverter 19.
Connected to the base of _Q3 .

The multivibrator 18 sends out a rectangular wave having the same frequency as the triangular wave of the output d to another output f, and the output f is connected to the base of the transistor Q ₃ of the inverter 19 via the light-off prevention circuit 20. . The light-off prevention circuit 20 includes a capacitor C ₂ and a resistor.
A differentiating circuit 20a consisting of _R10 , and the differentiating circuit 2
The transistor Q ₄ has its base connected to the output f via 0a, and the collector of the transistor Q ₄ is connected to the base of the transistor Q ₃ of the inverter 19.

The collector of the transistor Q ₃ which is the output g of the inverter 19 is connected to the power supply V _D via a resistor R ₁₁ and pulled up, and the output g is connected to the drive input of the driver section 21 . The driver 21 drives the fare, cumulative total (pick-up fee), and tariff display unit 1 described above with reference to FIG. 2 based on control signals from the control unit 22 that calculates taximeter fares, is displayed.

The first comparator 12, reference voltage setting section 14, hysteresis setting section 15, and driver 16 constitute an operation section illumination on/off circuit, and the second comparator 13, oscillation frequency setting section 17, multivibrator 18, and inverter 19. The light-off prevention circuit 20 constitutes a dimming circuit, and in both of these circuits, the voltage at point a, which is changed by the photocell 11 according to the amount of light received by the photocell 11, is utilized.

In the above configuration, the operation will be described below with reference to FIG. 3 showing waveforms of each part.

First, the latter dimming circuit will be explained.

The multivibrator 18 is the oscillation frequency setting section 1
It oscillates at the frequency set by the capacitor _C1 of 7, and outputs a rectangular wave (Fig. 3A) at the output f and output d.
A triangular wave (Fig. 3B) is output respectively. The above triangular wave has the voltage level at point a (a ₁ to a ₄ in FIG. 3B) determined according to the amount of light received by the photocell 11 and the second
are compared in the comparator 13. The second comparator 13 is a rectangular wave whose level is H level for a period when the level of the triangular wave is higher than the voltage level (Fig. 3C).
Output. This rectangular wave has a high duty (C, a 3 in FIG. ₃ ) when the amount of light received by the photocell 11 is small, that is, when the surroundings are dark, and a low duty (C, a 3 in FIG. 3) when the amount of light received by the photocell 11 is large, that is, when the surroundings are bright. a ₂ ), but if the surroundings are noticeably bright and the voltage level determined by the photocell 11 is higher than the upper limit voltage level of the triangular wave (FIG. 3B, a ₁ ), the output e of the second comparator 13 will always be On the other hand, when the surroundings are noticeably dark and the voltage level determined by the photocell 11 is lower than the lower limit voltage level of the triangular wave (Fig. 3, a ₄ ), the output e of the second comparator 13 is always at the H level. becomes.

The above light-off prevention circuit 20 is a multivibrator 1
In response to the rise of the rectangular wave (Fig. 3A) sent to the output f of 8, the transistor Q ₄ is turned on for a narrow fixed time period with a time constant C ₂ R ₁₀ determined by the capacitor C ₂ and the resistor R ₁₀ . Then, the output e of the second comparator 13 is set to the L level for a certain period of time regardless of the input to the second comparator 13 (FIG. 3D). Therefore, even if the surroundings are dark and the output e of the second comparator 13 is always at H level, at least the transistor
During the on period of Q ₄ , the level of the output e is L, turning off the transistor Q ₃ during this period, and turning off the inverter 1.
In order to make the output g of 9 H level (Fig. 3 E),
It is guaranteed that the display unit 1 is lit at the lowest brightness. Note that the output e of the second comparator 13 and the output of the lights-out prevention circuit 20 are connected to a wired NOR, so that when either of the two outputs becomes L level, the input of the inverter 19 becomes L level. ing. Note that for the voltage levels a ₂ and a ₃ caused by the photocell 11, the output g of the inverter 19 becomes H level as shown by g ₂ and g ₃ in FIG. lights up.

Next, the operation unit illumination on/off circuit will be explained.

The reference voltage level set by the reference voltage setting section 14 and the voltage level determined by the photocell 11 are compared in the first comparator 12, and the surroundings are bright and the voltage level by the photocell 11 is higher than the reference voltage level. Sometimes, the output c of the first comparator 12 is at L level during that period, and the driver section 16 does not drive the illumination section 2.

On the other hand, when the surroundings are dark, the output c of the first comparator 12 becomes H level, the driver section 16 is turned on, and the operation lighting section 2 is turned on.
The operation unit 3 and the characters 4 are illuminated.

Note that the hysteresis setting section 15 changes the voltage of the output b of the reference voltage setting section 14 when the output C of the first comparator 12 is at H level and when it is at L level.
When the output of 2 shifts from L to H level, and when the output of H
Hysteresis is provided in the trigger timing when transitioning from the low level to the low level. That is,
When the voltage level generated by the photocell 11 transitions from H to L level and becomes lower than the reference voltage level determined by the reference voltage setting section 14, the output c of the first comparator 12 changes from L to H level, which is applied to the reference voltage setting section 14. They will be returned. For this reason,
The reference voltage level is raised by the voltage level set by the hysteresis setting section 15, and the comparison level is revised upward. Therefore, when the voltage level generated by the photocell 11 shifts from L to H level and becomes higher than the new corrected reference level, the output c of the first comparator 12 changes from H to L level, and the reference voltage level returns to the level before correction. Return to By providing hysteresis as described above, even if the voltage level of the photocell 11 fluctuates around the reference voltage level, flickering of the illumination can be prevented.

In summary, in a bright place during the day, the duty of the dimming circuit is 100%, and the charge/cumulative/tariff display section 1 shows the maximum brightness. At this time, the operation unit illumination unit 2 is turned off. Then the outside world became dark,
When the voltage level of the photocell 11 crosses the voltage level of the triangular wave, the dimming circuit starts dimming the light. Further, when the voltage level generated by the photocell 11 falls below the reference voltage level, the illumination unit 2 is turned on. Next, when the outside world becomes even darker, the dimming circuit further intensifies the dimming, and when it is completely dark, the brightness reaches the minimum brightness set by the lights-out prevention circuit 20. The form of brightness change from the brightness at the start of dimming to the lowest brightness is stepless.
Since an infinite number of dimming patterns can be obtained, this automatic dimming circuit can always maintain the brightness of the outside world and the brightness of the display section 1 in the best condition.

〔Effect of the invention〕

As explained above, according to the present invention, the brightness of the display section is automatically changed and the illumination of the operation section is turned on and off according to changes in the surrounding brightness, so that the following can be done. Various effects can be obtained.

(1) Ignoring all driver operations such as turning on the small light switch, and ignoring the timing that is left to the driver's sense to turn on the small light switch, the brightness of the outside world is moderate enough to start dimming. It is now possible to automatically sense the light and dim the light automatically at the ideal time.

(2) Appropriate brightness can always be obtained even with various changes in brightness at night, and good visibility can now be obtained.

(3) Appropriate brightness can always be obtained even with various changes in brightness during the day, and good visibility can now be obtained.

(4) Ignoring any operations by the driver such as turning off the small light switch, or the timing that is left to the driver's sense to turn off the small light switch, the brightness of the outside world is moderate enough to cancel dimming. It now automatically senses the darkness and automatically cancels dimming at the ideal time.

(5) No increase in wiring work or equipment wiring for small light switches.

(6) The light control function has an infinite number of light control patterns, and the light control function has become extremely rich.

(7) The control unit lights on/off circuit senses the brightness of the outside world and turns on the light only when necessary.
Temperature rise inside the device, deterioration of light emitting elements, and power consumption were suppressed to the necessary minimum, ensuring device reliability and energy savings.

(8) By having both a dimming control and an on/off circuit for the control section illumination, it is possible to find unprecedented commercial value in taximeters, and for drivers and customers, it is easier to use than ever before. It has become a taxi meter that can be easily read.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is a perspective view showing the front panel of a taximeter to which the present invention is applied, and FIG. 3 is a waveform diagram of each part for explaining the operation of a part of the circuit of FIG. 1. 1...Fee/cumulative (pick-up fee) tariff display section,
2...Operation unit illumination unit, 11...Photocell, 12...
...first comparator, 13...second comparator, 18...multivibrator.

Claims (1)

[Claims] 1 A brightness detection means that generates a signal with a level corresponding to the surrounding brightness, and the level of the signal from the brightness detection means is compared with a reference level, and depending on the comparison result, the control unit illumination section is turned on or off. 1. A display control device for a taximeter, comprising: an operation section illumination on/off circuit that performs the above operations; and a dimming circuit that changes the brightness of a tariff display section according to the level of a signal from the brightness detection means.