JP2004286682A - Indicating device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure light-emitting operation of a light-emitting diode in a case a battery voltage lowers, even when using a white color or a blue color light-emitting diode as a light-emitting diode. <P>SOLUTION: An indicating device for a vehicle includes light-emitting diodes 101, 102 displaying a measuring instrument for a vehicle, and a measurement instrument displaying circuit 100 that light-emits the light-emitting diodes 101, 102 when tuning an ignition switch 2 of the vehicle to ON, and light-reduces the light-emitting diodes 101, 102 when turning a lighting switch 3 lighting an illuminating lamp 4 to ON. The measuring instrument displaying circuit 100 serially connects a switching means 110 which turns ON in case the lighting switch 3 is ON and turns OFF in case the lighting switch 3 is ON, when the ignition switch 2 is ON, between the ignition switch 2 and the light-emitting diodes 101, 102. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle display device suitable for use in, for example, a vehicle instrument of a type that constantly illuminates while driving a vehicle.
[0002]
[Prior art]
Today, there are various types of vehicular instruments that constantly illuminate while driving a vehicle, and for example, a vehicular display device as shown in FIG. 3 is known. This display device includes a vehicle-mounted battery 1, an ignition switch 2, an illumination switch 3, an illumination lamp 4, an instrument display circuit 100, light emitting diodes 101 and 102, backflow prevention diodes 103, 104, 105, a resistor 106, and a dimming resistor 107. It is composed of
[0003]
For illumination, white or blue light emitting diodes are used as the light emitting diodes 101 and 102, and the voltage drop VF of the light emitting diodes is larger than that of a red light emitting diode or the like. The voltage drop VF of the red light emitting diode is about 2 V, and the voltage drop of white or blue is 2 to 4 V.
[0004]
Further, a display control circuit for displaying an operation state of an air conditioner on a vehicle instrument as shown in FIG. 4 is known from Patent Document 1, for example. When the operation switch 5 of the air conditioner is turned on, the transistor 6 is turned on when the lighting switch 3 of the lighting lamp 4 is off, and a current flows from the battery 1 to the light emitting diode 9 via the transistor 6 and the backflow preventing diode 7, On the other hand, when the illumination switch 3 is turned off, the transistor 6 is turned off, and a current flows from the battery 1 to the light emitting diode 9 via the dimming resistor 8.
[0005]
[Patent Document 1]
Japanese Patent No. 2807847 [0006]
[Problems to be solved by the invention]
As described above, even when the lighting switch is OFF, such as in the daytime, the light emitting diode is made to emit light to display the meter, while when the lighting switch is ON, such as at night, the light is dimmed so as not to be dazzling and displayed on the meter.
[0007]
However, in the case of a display device using two or more white or blue light-emitting diodes as the light-emitting diodes 101, 102, or 9, the battery voltage VB of the battery 1 may be increased due to an excessive electric load or the like when the lighting switch is turned off, such as during daytime. For example, when the voltage drops to 10 V or less, there is a possibility that the light emitting diodes 101, 102, or 9 are turned off due to the backflow prevention diodes 105, 7 being connected in series in the current supply path of the light emitting diodes 101, 102, or 9. was there.
[0008]
The present invention has been made in view of the above points, and provides a vehicle display device capable of securing a light emitting operation of a light emitting diode when a battery voltage drops even when a white or blue light emitting diode is used as a light emitting diode. The purpose is to do.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the technical means described in claims 1 to 5 is adopted.
[0010]
According to the first aspect of the present invention, there is provided a light emitting diode for displaying an instrument for a vehicle, and when the ignition switch of the vehicle is turned on, the light emitting diode is made to emit light, and when the lighting switch for lighting the lighting of the vehicle is turned on, A vehicle display device having an instrument display circuit for dimming a light emitting diode,
The instrument display circuit is characterized in that, when the ignition switch is ON, a switch means for turning ON when the illumination switch is OFF and OFF when the illumination switch is ON is connected in series between the ignition switch and the light emitting diode. .
[0011]
Thus, even when a white or blue light emitting diode is used as the light emitting diode, it is possible to ensure the light emitting operation of the light emitting diode when the battery voltage drops.
[0012]
According to the second aspect of the present invention, the backflow prevention diode and the dimming resistor are connected between the connection point between the illumination switch and the illumination lamp and the light emitting diode, so that the illumination switch can be turned on and off. An energization path for energizing the light emitting diode can be divided between when the device is turned off, and the current value to the light emitting diode can be adjusted independently.
[0013]
According to the third aspect of the present invention, the switch means has a PNP transistor, and its base electrode is connected to the ground side via the illuminating lamp, so that the operation of the transistor is controlled in accordance with the operation of the illuminating lamp. Can be realized with a simple configuration.
[0014]
According to the invention of claim 4, a plurality of light emitting diodes are connected in series, and according to the invention of claim 5, the light emitting diode is one of a white light emitting diode and a blue light emitting diode, Alternatively, it is configured as a combination, so that it is possible to respond to the lighting requirements of the vehicle instrument.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is an overall circuit diagram showing a display device for a vehicle, and FIG. 2 is a characteristic diagram showing a relationship between a battery voltage VB and a current i flowing through a light emitting diode.
[0017]
In the case of the 12V type, the vehicle-mounted battery 1 normally generates 13 to 15 V during operation of the vehicle due to the relationship with the charging voltage of the vehicle-mounted generator (not shown). It comprises an ignition switch 2 operated by a driver, an illumination switch 3 for turning on and off a night illumination lamp 4, and an instrument display circuit 100.
[0018]
In the instrument display circuit 100, the light emitting diodes 101 and 102 are, for example, a plurality of serially connected white or blue light emitting diodes for displaying or illuminating a vehicle instrument provided on an instrument panel in front of a driver's seat, or both colors. Combination of These are the backflow preventing diodes 103 and 104, the PNP transistor 110 and the resistors 111 and 112 that constitute the switch means.
[0019]
The current adjustment resistor 113 adjusts the current (that is, luminance) flowing through the light emitting diodes 101 and 102 to obtain a predetermined instrument illuminance when the ignition switch 2 is turned off and the illumination switch 3 is turned off in the daytime or the like. Resistance. The backflow preventing diode 103, the switch means, and the current adjusting resistor 113 constitute a daytime energizing circuit for the light emitting diodes 101 and 102.
[0020]
The dimming resistor 114 is a resistor for reducing the current flowing through the light emitting diodes 101 and 102 in order to prevent glare when the illumination switch 3 is ON regardless of whether the ignition switch 2 is ON or OFF. The backflow prevention diode 104 and the dimming resistor 114 constitute a nighttime energizing circuit for the light emitting diodes 101 and 102.
[0021]
By connecting the daytime energizing circuit and the nighttime energizing circuit in parallel to the light emitting diodes 101 and 102 in this manner, light emission luminance according to daytime and nighttime can be obtained using the resistors 113 and 114. The current value can be adjusted quickly.
[0022]
In addition, these light emitting diodes 101 and 102 may be a negative type liquid crystal display instrument (display type in which the display plate is opaque and characters and numerals are transparent parts and light is transmitted from the back surface), and characters and numerals are displayed on the smoke display plate. Are used for illumination of a display instrument that emits light, and a white or blue light emitting diode is employed, and the voltage drop VF (about 2 to 4 V) of the light emitting diode is larger than that of a red light emitting diode or the like (about 2 V).
[0023]
The operation of the above configuration will be described. First, when the driver uses the vehicle, the ignition switch 2 is turned on. At that time, in the daytime, when the lighting switch 3 is OFF, the battery 1 is connected to the ignition switch 2, the diode 103, the emitter-base of the transistor 110, the resistor 112, and the lighting lamp 4. The base current flows, and the transistor 110 turns on.
Here, when the illuminating lamp 4 is turned off, the cooling / heating resistance value of the filament is nearly zero, so that a sufficient base current can flow. Thus, by passing a current through the daytime energizing circuit, the light emitting diodes 101 and 102 can emit light and be displayed on an instrument.
[0024]
On the other hand, when the lighting switch 3 is ON, such as at night, the base electrode side of the transistor 110 becomes the battery voltage VB, so that no base current flows and the transistor 110 is turned off. On the other hand, the light emitted from the battery 1 through the lighting switch 3, the diode 104, and the dimming resistor 114 (nighttime energizing circuit) is supplied to the light emitting diodes 101 and 102 so that the light emitting diodes 101 and 102 are dimmed from daytime. It can emit light and be displayed on an instrument.
[0025]
Here, when the lighting switch 3 is turned off in the daytime, the battery voltage VB has dropped to 10 V due to the occurrence of an excessive electric load in the vehicle exceeding the power generation capability while the light emitting diodes 101 and 102 emit light. Even in this case, in this circuit, the voltage drop due to the diodes 103, 101, and 102 and the transistor 110 in the current path is suppressed to be lower than that of the conventional circuit shown in FIG. 3, so that the battery voltage VB decreases by at least that much. Even in this case, it is possible to secure energization to the light emitting diodes 101 and 102.
[0026]
By the way, if the voltage drop of the light emitting diodes 101 and 102 is 4 V, the voltage drop of the diodes 103 and 105 is 1 V, and the voltage drop of the transistor 110 is 0.1 V or less, according to the circuit of the present embodiment, the lighting switch 3 in the daytime is turned off. In some cases, the minimum operating voltage when the battery voltage is low is expressed by Equation 1.
[0027]
(Equation 1)
Minimum operating voltage = 1V + 0.1V or less + 4V + 4V + α <10V
Here, α is the voltage drop of the resistor 113.
[0028]
Further, the relationship between the battery voltage VB and the light emitting diode current i is shown by the characteristic B in FIG. 2, and the minimum operating voltage is lower by one diode (1 V) than the characteristic A of the conventional circuit shown in FIG.
[0029]
On the other hand, according to the conventional circuit shown in FIG. 3, when the lighting switch 3 is turned off in the daytime, the minimum operating voltage when the battery voltage drops is expressed by the following equation (2).
[0030]
(Equation 2)
Minimum operating voltage = 1V + 4V + 4V ++ 1V + β> 10V
Here, β is a voltage drop of the resistor 106 and the illumination lamp 4.
[0031]
When the lighting switch 3 is ON at night, the minimum operating voltage when the battery voltage drops is 10 V or less, which is the same as in the present embodiment and the conventional circuit shown in FIG. 3, and the battery voltage VB drops to 10 V. Also, the light emitting diodes 101 and 102 can emit light to be displayed on an instrument.
[0032]
According to the above embodiment, the PNP transistor 110 is used as the switch means. However, an NPN transistor or another switch element may be used as long as the switch has a small voltage drop.
[Brief description of the drawings]
FIG. 1 is an overall circuit diagram illustrating an embodiment of a vehicle display device.
FIG. 2 is a characteristic diagram illustrating a relationship between a battery voltage and a current flowing through a light emitting diode.
FIG. 3 is an overall circuit diagram illustrating an example of a conventional display device.
FIG. 4 is an overall circuit diagram illustrating an example of a conventional display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Battery 2 Ignition switch 3 Lighting switch 4 Lighting lamp 100 Instrument display circuit 101, 102 Light emitting diode 103, 104 Backflow prevention diode 110 PNP transistor (switch means)
113 Current adjustment resistor 114 Dimming resistor

Claims (5)

An instrument having a light emitting diode for displaying an instrument for a vehicle, wherein the light emitting diode emits light when an ignition switch of the vehicle is turned on, and the light emitting diode is dimmed when an illumination switch for lighting an illumination light of the vehicle is turned on. In a vehicle display device having a display circuit,
The instrument display circuit is configured such that when the ignition switch is ON, a switch unit that turns ON when the illumination switch is OFF and OFF when the illumination switch is ON is connected in series between the ignition switch and the light emitting diode. A display device for a vehicle, comprising: 2. The vehicle display device according to claim 1, wherein a backflow prevention diode and a dimming resistor are connected between a connection point between the illumination switch and the illumination lamp and the light emitting diode. 2. The vehicle display device according to claim 1, wherein said switch means has a PNP transistor, and a base electrode thereof is connected to a ground side via said illuminating lamp. The vehicle display device according to claim 1, wherein a plurality of the light emitting diodes are connected in series. The display device for a vehicle according to claim 4, wherein the light emitting diode is configured by one or a combination of a white light emitting diode and a blue light emitting diode.

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