JP2012026759A - Illuminator of instrument for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device for a vehicular instrument that can reduce fluctuations in load even when measurement values are displayed by a number of light sources.
SOLUTION: A plurality of light emitting diodes 2 that emit light by power supply from a power supply circuit 1, display means P that expresses a measured value by the number of lighting of the light emitting diodes 2, and the measured value based on information from a vehicle. And a control means 3 for generating a control signal for switching on / off of each light emitting diode 2, and the control means 3 generates a control signal by adjusting the brightness of each light emitting diode 2 by pulse width modulation control. Then, the light emitting diode 2 is driven so that the pulse rising timing of the control signal is shifted by a predetermined time between the light sources.
[Selection] Figure 1

Description

  The present invention relates to an illumination device for a vehicle instrument that includes a large number of light sources and expresses a measured value by the number of lighting of the light sources.

  A vehicle meter is provided as a display device for informing the vehicle user of the state of the vehicle and the state of the in-vehicle device, preventing danger during traveling, and ensuring safety. The vehicle meter displays a measurement value that changes every moment, such as a speedometer that displays the traveling speed of the vehicle, a tachometer that displays the engine speed, and a fuel gauge that displays the remaining amount of fuel.

  In these vehicular instruments, the display format includes characters with scales of the measured values (quantities) around the pointer that rotates according to the measured values such as vehicle speed, engine speed, and remaining fuel. A so-called analog type is generally used in which a plate is arranged, and a measurement value is displayed by contrast reading according to the scale position indicated by the pointer. In addition to analog display formats for vehicle instruments, for example, display values such as liquid crystal display panels, fluorescent display tubes, or display panels using organic EL can be used to directly display measured values such as vehicle speed. A digital system such as a numerical display for displaying the engine speed, a remaining fuel amount, etc. in a zone or bar graph by a number of segments arranged in parallel is also adopted.

  In the digital display format described above, a display device such as a liquid crystal display panel or a fluorescent display tube may be used. However, a light emitting diode (light source) is used, and each segment in which the light emitting diode is arranged is selectively used. The measured value such as the vehicle speed is displayed as a number or a bar graph or the like by causing it to emit light, which is disclosed in, for example, Patent Document 1.

  Also, in vehicle meters, the voltage applied to the light emitting diode is controlled using a control circuit, pulse generation circuit, switching circuit, etc., and the light emission brightness of the light emitting diode is adjusted by changing the duty ratio of the pulse. For example, Patent Document 2 discloses that the brightness of a segment can be adjusted.

JP-A-10-26541 Japanese Utility Model Publication No. 5-55407

  However, when there are a large number of light emitting diodes that illuminate the segments and the segments, even if the light emission luminance is low, by turning on these lights at once, many light emitting diodes are switched on / off instantaneously. Since a large total load is generated, a power supply circuit that allows this is necessary. In addition, depending on the timing of the on / off switching pulse, the state in which there is almost no load and the state in which there is a large load change abruptly. There has been a problem of placing a heavy burden on the power supply circuit. In addition, when the power supply to the light emitting diodes by the power supply circuit is not in time, there is a possibility that the display may be affected, for example, the segments may flicker.

  Accordingly, an object of the present invention is to provide an illumination device for a vehicle instrument that can reduce fluctuations in load even when displaying measurement values with a large number of light sources, focusing on the above-described problems.

  The illumination device for a vehicle meter according to the present invention includes a plurality of light sources that emit light when power is supplied from a power supply circuit, display means that expresses measurement values based on the number of lighting of the light sources, and the measurement values based on information from the vehicle. And a control means for generating a control signal for switching on and off of each light source, and the control means generates a control signal obtained by adjusting the luminance of each light source by pulse width modulation control, The light source is driven so that the pulse rising timing of the control signal is shifted by a predetermined time between the light sources.

  The display means includes a light guide that outputs transmitted light from each of the light sources, and a display plate formed with a scale corresponding to the light guide.

  The illumination device for a vehicle meter according to the present invention can reduce load fluctuations even when the measurement values are displayed by a large number of light sources.

The figure which shows the electrical structure in embodiment of this invention. The figure which shows the example of a display of the meter for vehicles in embodiment same as the above. The figure which shows a part of vehicle meter in embodiment same as the above in a cross section. The figure which shows the wave form diagram in embodiment same as the above. The figure which shows the conventional waveform diagram.

  Hereinafter, embodiments in which the present invention is applied to a vehicle instrument will be described with reference to the accompanying drawings.

  FIG. 1 shows an electrical configuration of a vehicle meter according to the present invention, in which a power supply circuit 1, a light emitting diode (light source) 2, a control means 3, and a drive circuit 4 are mounted on a single circuit board. Have been provided.

  The power supply circuit 1 is a circuit to which a DC-DC converter can be applied, and a voltage required for the light emitting diode 2 is generated and supplied by stepping down a power supply such as an in-vehicle battery. In this case, the voltage of the in-vehicle battery (usually 12 to 14 V) is stepped down to a power supply voltage (for example, 5 V) for operating electronic components such as the light emitting diode 2 and the control means 3 through a circuit such as surge cut. is doing. As an application of a vehicle meter, a power supply circuit 1 that can tolerate power consumption of a maximum load (for example, a load when the light emitting diode 2 is fully lit) is applied.

  The light emitting diode 2 emits light when supplied with power from the power supply circuit 1 and is connected in parallel to the power supply circuit 1 and is provided to face each segment S on the display surface of the vehicle instrument shown in FIG. . In this case, 20 light emitting diodes 2 are provided corresponding to the segment S for displaying the engine speed in a bar graph, and further, light emitting diodes for transmitted illumination of other indicators D1 to D3 are also used. However, details of the latter light-emitting diode are omitted.

  Further, as shown in FIG. 3, the light emitting diodes 2 are provided in a row on the circuit board B on the back surface side (the surface opposite to the display side) of the display means P composed of the display plate P1 and the light guide P2. The light guide P2 is provided through the display plate P1 to form the shape of the segment S, and the opposite end surface on the display side (end surface on the circuit board B side) receives the irradiation light from the light emitting diode 2, The other end face emits light so that the vehicle user can visually recognize the lighting state. On the display board P1, scales, numerical values, units, etc. corresponding to each segment S are printed. In this case, the light-emitting diode 2 is provided for each segment serving as each element of the bar graph display, and is configured to be turned on / off according to driving by the drive circuit 4. The number of lights and the scale are associated with each other. The measured value is expressed.

  The control means 3 is provided with a storage unit such as a ROM and a RAM (not shown) used for storing a predetermined program and various data, a storage area at the time of calculation, a CPU for performing arithmetic processing according to the predetermined program, an input / output interface, and the like A microcomputer can be applied.

  The control means 3 is connected to the drive circuit 4 and the like, and generates and outputs a control signal for controlling each component based on the predetermined program. The control means 3 inputs detection signals of various on-vehicle sensors outside the instrument as vehicle information (for example, information such as vehicle speed, engine speed, remaining fuel amount) via the connector C of the circuit board B or a dedicated cable, for example. Then, a control signal for urging the display output of the measured value or the like based on the vehicle information is generated, and the vehicle is driven by the drive circuit 4 or other display (liquid crystal display panel D1, warning light D2, indicator D3, etc.). Control to display and output information.

  The control means 3 is configured to output a control signal composed of a pulse signal to the drive circuit 4, and adjusts the light emission luminance of the light emitting diode 2 by the duty ratio in one cycle of the pulse signal. . So-called pulse width modulation control is performed.

  The drive circuit 4 can be a switching circuit made of a transistor and is wired so that the light emitting diode 2 can be switched on / off based on a control signal from the control means 3. In this case, the drive circuit 4 is provided in the number of parallel connection of the light emitting diodes 2 with respect to the power supply circuit 1, and each of them is connected in parallel with the control means 3 so that different control signals can be inputted.

  Next, pulse width modulation control by the control means will be described with reference to FIG.

  The control means 3 outputs a control signal (pulse signal) having the same cycle at different timings for each drive circuit 4. In this case, a control signal whose pulse rising timing is shifted by a predetermined time Δt (for example, 20 msec) is sequentially output to each drive circuit 4. The control means 3 can delay the timing of the control signal by a predetermined time Δt every predetermined program period based on a dedicated delay counter or a reference clock. Further, the predetermined time Δt is set to be slightly smaller than the pulse period of the control signal, and the vehicle user cannot recognize the time difference, and thus does not affect the recognition of the measured value.

  On the other hand, the drive circuit 4 is driven to turn on / off the light emitting diode 2 in accordance with a control signal from the control means 3, and each waveform as shown in FIG. 4 is generated. In FIG. 4, the driving circuits (a to h) are driven so that eight light emitting diodes among the driving circuits (at) corresponding to the twenty light emitting diodes are lit with a predetermined luminance. The light-emitting diode 2 has a waveform related to the drive circuit (it) so that (it) is turned off (the drive circuits j to t are the same as those of the drive circuit i and are not shown). According to these waveforms, the total sum of the drive currents of the light emitting diodes 2 can be smaller than that of the conventional example shown in FIG. In addition, since the fluctuation of the sum of the drive currents can be reduced, the power supply circuit 1 that supplies the drive current can supply power to each light emitting diode 2 with high responsiveness in response to a small load fluctuation.

  Such a lighting device for a vehicle meter includes a plurality of light emitting diodes 2 that emit light when power is supplied from a power supply circuit 1, display means P that expresses a measured value by the number of lighting of the light emitting diodes 2, and information from the vehicle. And a control means 3 for obtaining a control signal for switching on / off of each light emitting diode 2 and obtaining the measurement value based on the measured value, and the control means 3 adjusts the luminance of each light emitting diode 2 by pulse width modulation control. The light emitting diode 2 is driven so that the pulse rising timing of the control signal is shifted by a predetermined time between the light emitting diodes 2.

  Accordingly, even when the measurement values are displayed by a large number of light emitting diodes 2, fluctuations in the load can be reduced. Therefore, the power supply circuit 1 can be operated with good responsiveness and flickering by the light emitting diodes 2 can be prevented. In addition, by reducing the power consumption, a power circuit with a small allowable amount can be applied. Therefore, the circuit configuration is relatively small and uses a power circuit that generates little heat. Therefore, space is saved in mounting on the circuit board B, and a simple illuminating device is provided for the heat dissipation structure. Moreover, since the switching timing of the drive circuit 2 can be distributed, the possibility of noise generation can be suppressed.

  Further, the display means P includes a light guide P2 that outputs the transmitted light from each light emitting diode 2, and a display plate P1 that has a scale corresponding to the light guide P2, thereby providing a large number of displays. Even when the measured value is displayed using the light emitting diode 2, the burden on the power supply circuit can be reduced and the above-described effects can be obtained.

  Although the present invention has been described by way of example in the configuration of the above-described embodiment, the present invention is not limited to this, and various other configurations can be used without departing from the spirit of the present invention. Of course, it is possible to improve the design and change the design.

  For example, in the above-described embodiment, a display form in which segments having the same shape are provided on one straight line as shown in FIG. 2 is shown, but the display may be bent at a predetermined angle or provided on a curved line. May be. Also, the segment shape may have a different shape or area depending on the size of the measurement value.

  Further, in the above-described embodiment, as shown in FIG. 4, each light emitting diode is driven with a waveform having the same cycle and the same duty ratio, but the rising edge of the pulse of the control signal is shifted by a predetermined time. If so, the same effects as those of the above-described embodiment can be obtained. For example, the same period is preferable for driving each light emitting diode, but the duty ratio may be individually changed. For example, it is conceivable to control and drive so that the light emission luminance increases as the measured value increases. .

  In addition to the configuration of the above-described embodiment, it is possible to adjust the light emission luminance of the light emitting diode using an illuminance sensor or a manual switch in consideration of changes in outside light such as daytime, nighttime, and inside / outside of a tunnel. It can also be configured. Note that the measurement value can be expressed with light emission luminance suitable for the vehicle user by automatically or manually adjusting the duty ratio of the control signal by the control means in accordance with the external light. Further, even when these light adjustments are performed, illumination can be performed without flickering.

  Further, as shown in FIG. 1, the light emitting diode 2 is connected in parallel. For example, a part of the light emitting diodes are connected in series to form a block, and each block is shifted at a predetermined time. Drive control may be performed, and the same effect as the above-described embodiment can be obtained.

  The present invention relates to an illumination device for a vehicle instrument using a number of light sources such as light-emitting diodes, and can be applied, for example, as an illumination device for an instrument mounted on a moving body including an automobile, a motorcycle, an agricultural machine, or a construction machine. .

1 Power supply circuit 2 Light emitting diode (light source)
3 Control means 4 Drive circuit P Display means P1 Display plate P2 Light guide

Claims (2)

A plurality of light sources that emit light by power supply from a power supply circuit;
Display means for expressing a measured value by the number of lighting of the light source;
A control means for obtaining the measurement value based on information from a vehicle and emitting a control signal for switching on and off of each light source;
The control means generates a control signal obtained by adjusting the luminance of each light source by pulse width modulation control, and drives the light source so that the pulse rising timing of the control signal is shifted by a predetermined time between the light sources. An illumination device for an instrument for a vehicle.   2. The display unit according to claim 1, further comprising: a light guide that outputs transmitted light from each of the light sources; and a display plate that is formed with a scale corresponding to the light guide. A lighting device for a vehicle instrument as described.

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