JPH0256252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an illumination device that controls the lighting of illumination lamps for vehicle instruments according to ambient temperature to adjust the temperature inside the instrument housing.

Generally, the instruments installed in a vehicle are illuminated and displayed using night illumination lamps, but these illumination lamps are placed inside the instrument housing, which is sealed to prevent the intrusion of dust, etc. There is a problem in that the heat generated by the lamp causes high temperatures in the instrument housing, especially around the lamp.

Particularly in tropical areas, when the outside temperature rises, the heat from the lamp causes the area around the lamp to reach a high temperature of nearly 100 degrees Celsius, which may cause the synthetic resin holding the lamp to melt or deform, or damage other electronic circuits. If the temperature exceeds the allowable temperature, it may affect operation.

In order to solve these problems, conventional
A device with a temperature adjustment lamp added, as in Japanese Patent No. 30539, has been proposed. In this system, a plurality of lamps are arranged corresponding to one meter in the meter housing, and the temperature inside the housing is controlled by turning on or off the temperature adjustment lamp according to changes in temperature. However, as in the above method, lighting the display section with multiple lamps and turning off the temperature adjustment lamp when the temperature is high also reduces the brightness of the main instruments such as the speedometer, so constant monitoring is required. There is a problem that the necessary instruments are very difficult to see at night, and if the lights are set to be relatively bright when the lights are off, they are too bright when they are all on, and they are arranged in multiple directions. Some of the multiple lamps are lit,
When the lights are turned off, the illumination and reflection are different, resulting in uneven illumination of the instruments, which makes it difficult for the driver to see, and there are problems such as a lack of driving safety. In addition, since a dedicated temperature adjustment lamp will be added, the number of lamps will significantly increase compared to the number required for original lighting, and the housing itself will have to be enlarged, requiring design changes to the lighting mechanism itself and parts. As the number of points increases, it becomes extremely expensive.

By the way, instruments should be divided into main instruments such as speedometers that need to be constantly monitored while driving, and auxiliary instruments such as tachometers, thermometers, trip meters, etc. that provide auxiliary information that does not need to be constantly monitored. Lighting lamps are installed on each of the main and auxiliary instruments, and when the night light switch is turned on, they are turned on at the same time to illuminate each instrument. However, since it is not necessary to constantly check the auxiliary instruments while driving, and the driver does not always look at them, it is okay to dim or turn off the auxiliary instruments.

The present invention has been made with attention to the above points, and it provides an illumination lamp for auxiliary instruments that maintains the illuminance of the main instruments, which is necessary for safe driving, almost constant without making any changes to the general lighting mechanism. An object of the present invention is to provide a lighting device for a vehicle instrument that regulates the temperature inside the housing and prevents overheating inside the housing by controlling the illuminance of the housing according to the temperature.

An embodiment of the present invention will be described in detail below based on the accompanying drawings.

FIG. 1 is a front view of an instrument panel that displays various instruments. 1 is a speedometer as a main instrument, and auxiliary instruments include a fuel gauge 2, a temperature gauge 3, a tachometer 4, etc.

FIG. 2 is a partial sectional view of the instrument panel. 5
A main lamp 6 illuminates a speedometer 1 as a main instrument, and a sub lamp 6 illuminates a fuel gauge 2, a thermometer 3, a tachometer 4, etc. as auxiliary instruments. Note that an alarm display section having a transparent light guide plate for graphical illumination can be included as auxiliary instruments, for example, as in Utility Model Application Publication No. 54-32447, but in this case, a transparent light guide plate covering the front surface of the alarm display section may be included. The sub-lamp placed opposite the light-receiving surface can also be used as a lamp for other instruments. In addition, the instruments include not only pointer-type instruments but also electronic instruments equipped with light-receiving elements such as liquid crystal display panels.

Figure 3 shows the above main lamp 5 and sub lamp 6.
1 is a block diagram of a lighting device for vehicle instruments according to the present invention, which drives a vehicle. In the figure, power Vcc from the vehicle battery is supplied to a main lamp 5 and a lighting control circuit 7, which will be described later, via a lighting switch SW which is turned on and off by the driver. The output voltage Vout of the lighting control circuit 7 is then supplied to the sub-lamp 6. This lighting control circuit 7 is an application of a well-known constant voltage circuit, and includes control transistors Tf1,
It is composed of a detection and amplification transistor Tr2, a reference voltage generation diode D1, a resistor R1, and a thermistor 8 which is a temperature detection element connected in parallel to output voltage dividing resistors R2, R3, and R2. As the temperature of this thermistor 8 increases, its resistance value Rt decreases. Then, the lighting control circuit 7 dims or increases the brightness of the sub-lamp 6 by changing the resistance value of the thermistor 8. Note that Vz is the voltage between the terminals of the diode D1.

FIG. 4 shows another embodiment of the lighting control circuit 7, which turns off the sub-lamp 6 when the temperature inside the instrument housing rises and exceeds a predetermined value. In the figure, numeral 9 denotes a well-known constant voltage circuit comprised of a control transistor Tr3, a resistor R4, and a reference voltage generating diode D2. Also, the connection point between the thermistor 10 and the resistor R5 is the comparator 11.
The connecting point of the reference voltage setting resistors R6 and R7 is connected to the + terminal of the comparator 11, and the resistors R6 and R7 are set to correspond to the starting temperature of the operation to turn off the sub-lamp 6. There is. Further, the output terminal of the comparator 11 is connected to the base of the transistor Tr3 in the constant voltage circuit 9.

The operation of the present invention configured as described above will be explained.

First, in FIG. 3, the battery power Vcc is supplied to the main lamp 5 by turning on the lighting switch SW manually by the driver, and the main instruments such as the speedometer 1 are illuminated with a constant illuminance. or,
This power supply Vcc is supplied to the sub-lamp 6 via the lighting control circuit 7, but at this time, the output voltage Vout of the lighting control circuit 7, which is the supply voltage of the sub-lamp 6, is determined by the parallel resistance of the resistor R2 and thermistor resistor Rt, and the resistor R.
Vout≒R2Rt/R2+Rt+R3/R3Vz - (1) for a constant voltage Vz.

Therefore, if the resistances R2 and R3 are constant, the output voltage
Vout varies depending on the thermistor resistance Rt. In other words, as the temperature inside the instrument housing increases, the thermistor resistance Rt decreases and the output voltage Vout decreases. Accordingly, the light of the sub-lamp 6 is dimmed, the temperature rise in the housing due to lamp heat is suppressed, and deformation of the synthetic resin and malfunction of electronic circuits etc. due to overheating can be prevented. On the other hand, when the temperature is low, the resistance Rt of the thermistor increases, and the output voltage Vout increases. Then, the sub-lamp 6 increases the brightness, and the temperature inside the housing rises due to lamp heat, making it possible to prevent malfunctions of electronic circuits and the like due to low temperatures. When a liquid crystal display board is used as a meter, the internal temperature of the meter can be maintained at the normal operating level of the liquid crystal due to the heat generation effect caused by the brightness of the sub-lamp 6 at low temperatures, making it possible to function more effectively.

In this way, only the sub-lamp 6 dims or increases in brightness, but the illuminance of the main lamp 5 remains constant, so the illuminance of the main instruments that require constant monitoring while driving does not become dim or dazzling like in the past. This allows you to maintain safe driving. In addition, there is no disadvantage that, unlike in the prior art, some of the plurality of lamps arranged in multiple directions go out, causing uneven illumination of the instruments and making it difficult for the driver to see them. Furthermore, it is possible to adjust the temperature using only the lighting lamps that are involved in the original lighting, without adding a dedicated lamp for temperature adjustment, and there is an advantage that there is no need to make major design changes to the conventional lighting mechanism.

Next, in FIG. 4, the battery power Vcc is supplied to the main lamp 5 by turning on the lighting switch SW manually by the driver, and the speedometer 1 as the main instrument is illuminated with a constant illuminance. The power supply Vcc is the output voltage via the lighting control circuit 7.
It is supplied to the sub-lamp 6 as Vout. On this occasion,
The output voltage Vout is determined by whether the transistor Tr3 is turned on or off. In other words, the resistance R for setting the reference voltage
The comparator 11 compares the partial pressure V1 of 6 and R7 with the partial pressure V2 of the thermistor resistor Rt and resistor R5.
outputs "H", the transistor Tr3 turns on, the output voltage Vout becomes a predetermined voltage, and the sub-lamp 6 lights up. On the other hand, when the temperature inside the housing rises and exceeds a predetermined range, the thermistor resistance Rt decreases, so that the partial pressure V1<V2. The comparator 11 is a transistor in order to output "L".
Tr3 is turned off, the output voltage Vout becomes zero, and the sub-lamp 6 is turned off. In this way, when the temperature inside the housing becomes high and exceeds a predetermined value, the sub-lamp 6 is turned off, no lamp heat is generated, and the temperature inside the housing is suppressed. Note that since the main lamp 5 is always lit at a constant level, the main instruments maintain a constant level of illumination, so there is no problem with safe driving.

Although one embodiment of the present invention has been described in detail above, it goes without saying that various modifications are included within the scope of the invention.

For example, as a very simple lighting control circuit, a temperature switch 12 (thermal reed switch or bimetallic switch) that opens and closes at a predetermined temperature as shown in FIG. 5 may be used.

Furthermore, an oscillation circuit whose duty changes depending on the temperature may be used as the lighting control circuit for the sub-lamp.

In each of the embodiments, the speedometer has been explained as the main instrument, but if necessary, a fuel gauge etc. may be classified as the main instrument and illuminated with a constant illuminance, and lighting lamps for auxiliary instruments may also be used. It is also possible to adopt a configuration in which an arbitrary number of lamps are selectively controlled according to the number of lamps and the environment in which they are used, without controlling all the lamps.

As detailed above, according to the present invention, the illuminance of the main instruments necessary for driving is kept constant, and the illuminance of auxiliary instruments that do not need to be constantly viewed while driving is output controlled based on the sensitive state of the temperature detection element etc. By configuring the lighting control circuit to adjust the temperature inside the instrument housing by dimming, increasing, or extinguishing the light, the location of the lighting lamps and the number of lamps that are involved in the original instrument lighting are almost completely changed. We provide a lighting system suitable for safe driving that can prevent damage to synthetic resins and electronic circuits due to overheating, prevent malfunction of electronic circuits due to low temperatures, and maintain constant illumination of main instruments. can.

[Brief explanation of drawings]

FIG. 1 is a front view of a conventional instrument panel, FIG. 2 is a partial sectional view of the same panel, FIG. 3 is a block diagram showing one embodiment of the present invention, and FIGS. FIG. 2 is a block diagram showing an embodiment of the invention. 1... Speedometer, 2... Fuel gauge, 5... Main lamp,
6...Sub lamp, 7...Lighting control circuit, 8, 10...
Thermistor, 11... comparator.

Claims (1)

[Scope of Claims] 1. In a lighting system for vehicle instruments that detects the temperature inside a vehicle instrument housing and controls lighting of lighting lamps in the housing according to changes in temperature, main instruments that require constant monitoring are provided. An illumination lamp, an auxiliary instrument illumination lamp that displays auxiliary information, and a lighting control circuit that controls the illuminance of at least one of the auxiliary instrument illumination lamps in response to temperature changes within the housing. Characteristic lighting system for vehicle instruments. 2. The lighting device for vehicle instruments according to claim 1, wherein the illumination lamp of the auxiliary instruments is dimmed in the lighting control circuit as the temperature inside the housing increases. 3. The lighting device for vehicle instruments according to claim 1, wherein the lighting control circuit turns off the illumination lamps of the auxiliary instruments as the temperature inside the housing increases.