JP2005049239A - Lighting device of meter for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device of meter for vehicles which can light remaining luminescent diode even when some of luminescent diode wires fail. <P>SOLUTION: In the lighting device of meters for a vehicle provided with a plurality of light emitting diodes 5 connected in series, a Zener diode 4 having a Zener voltage Vc larger than the normal direction voltage Vf of the light emitting diode 5 is provided in a drive circuit 14b by connecting in parallel to the light emitting diode 5 with inverse polarity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an illumination device for a vehicle instrument, and is suitable for application to an illumination device for a vehicle instrument using a light emitting diode as an illumination light source, for example.

  2. Description of the Related Art Some lighting devices for vehicular instruments use a light emitting diode (LED) as an illumination light source to illuminate a plurality of LEDs in series.

  In the prior art, it is possible to keep current consumption low by connecting a plurality of LEDs in series, but if any one of these LEDs is disconnected due to a failure or the like, all the LEDs connected in series are turned off. There is a problem. For example, when this type of illumination device is used for illumination of a speed display device or the like, which is one of vehicular instruments, the visibility of the speed display at night or the like decreases. In some cases, it becomes difficult for a driver who is a viewer to maintain a good running state of the vehicle.

  The present invention has been made in view of such circumstances, and its object is to provide an illumination device for a vehicle instrument that can cause the remaining light emitting diodes to emit light even if any of the light emitting diodes is disconnected. Is to provide.

  Another object of the present invention is to provide an illumination device for a vehicle instrument that can cause the remaining light emitting diodes to emit light even if any one of the light emitting diodes is disconnected, and can keep current consumption in a normal state low. It is in.

  According to claim 1 of the present invention, in a lighting device for a vehicle instrument comprising a plurality of light emitting diodes connected in series and a drive circuit capable of turning on and off the light emitting diodes, the drive circuit has a polarity reversed. And a Zener diode connected in parallel to the light emitting diode and having a Zener voltage larger than the forward voltage of the light emitting diode.

  According to this, for example, a Zener diode that is connected in parallel to the light emitting diode opposite to the pole of the light emitting diode to which a driving voltage such as a power supply voltage is applied and that has a Zener voltage that is larger than the forward voltage of the light emitting diode is used. Therefore, when the light emitting diode is in a normal state, a current flows only through the light emitting diodes connected in series. On the other hand, even if any one of the plurality of light emitting diodes connected in series is disconnected due to a failure or the like, a current flows around the Zener diode connected in parallel to the disconnected light emitting diode. Therefore, the remaining light emitting diodes other than the disconnected light emitting diode can emit light.

  According to claim 2 of the present invention, the plurality of light emitting diodes are divided into at least two sets, and the light emitting diodes constituting the set are connected in parallel by one Zener diode.

  According to this, it is not necessary to prepare Zener diodes by the number of light-emitting diodes connected in series, and it can be provided at a low cost as a measure for preventing all extinction due to disconnection. For example, when a display panel such as a dial of a vehicle instrument is illuminated using a light emitting diode, the dial part illuminated by the group including the disconnected light emitting diode is dimmer than the surroundings. It is possible to ensure the visibility of display information displayed on the dial portion.

  According to claim 3 of the present invention, the Zener voltage of the Zener diode is formed to be larger than the sum of the forward voltages in the light emitting diodes constituting the set.

  According to this, when any of the light emitting diodes constituting the set is disconnected by setting the Zener voltage a little larger than the total value of the forward voltages of the light emitting diodes constituting the set in which the Zener diodes are connected in parallel, for example. Only current bypasses this set of light emitting diodes and flows through the other set of light emitting diodes.

  According to claim 4 of the present invention, the light emitting diode includes a plurality of light emitting diodes and a display panel made of a translucent material, and the light emitting diode irradiates the display panel with light on a surface opposite to a surface to be visually recognized. It is suitable for application to a vehicular instrument that can be arranged.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a lighting device for a vehicle instrument according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a circuit diagram showing a light emitting diode driving circuit according to this embodiment. FIG. 2 is a cross-sectional view of an example vehicle instrument to which the vehicle instrument illumination device of the present embodiment is applied. FIG. 3 is a partial front view of the vehicle instrument shown in FIG. 2 as viewed from the viewing direction. FIG. 4 is a schematic diagram showing an electric circuit configuration of the vehicle meter shown in FIG.

  As shown in FIGS. 2 and 3, a vehicle meter (hereinafter referred to as a combination meter) 1 is composed of a plurality of meters, and is arranged at a position that can be seen by a driver in front of a driver seat of a vehicle such as an automobile. In addition, a display panel (hereinafter referred to as a dial) 2 for displaying various information and making the driver visually recognize the information is provided. The dial 2 is a speedometer that displays the speed of the vehicle in the combination meter 1.

  The dial 2 is made of a translucent material such as transparent polycarbonate and is formed in a flat plate shape. As shown in FIGS. 2 and 3, a pointer 8 is disposed on the surface (viewing surface) side of the dial 2 at a substantially central portion of the dial 2. The pointer 8 is fixed to a shaft 71 that passes through a through hole provided in the dial 2.

  A design portion 3 is provided on the surface of the dial 2 by printing or the like. As shown in FIG. 3, the design portion 3 includes a scale portion 31 including a plurality of scales 31a and a plurality of numbers 31b. The plurality of scales 31a and the numbers 31b are arranged in a substantially arc shape with the shaft 71 as the center, as shown in FIG.

  In addition, the design part 3 which has the scale part 31 may be arrange | positioned in the back surface of the dial 2, and the design part 3 may be formed by arrange | positioning the pixel for right eyes and the pixel for left eyes which are not illustrated alternately. In this case, a three-dimensional effect sheet such as a parallax sheet for using the viewer's left-right parallax is provided on the surface of the dial 2 by sticking or the like.

  Further, as shown in FIG. 2, a plurality of (for example, 5 in this embodiment) light emitting diodes 5 are arranged on the back side of the dial 2. As shown in FIG. 2, the light emitting diode 5 is mounted on a printed circuit board 6 that is also arranged on the back side of the dial 2. The plurality of light-emitting diodes 5 transmit and illuminate the dial 2.

  Further, on the back side of the dial 2, a movement 7 as a rotating inner unit is arranged. The movement 7 is mounted and fixed on the printed circuit board 6, and the shaft 71, that is, the pointer 8 is rotated along the scale portion 31 arranged in the arc shape by an angle corresponding to an electric signal from the outside. This electric signal is a signal related to the vehicle speed detected by the speed sensor 15 (see FIG. 4). Note that the pointer 8 guides light from an external light source (not shown) to the inside thereof, so that the pointer 8 itself is lit and displayed.

  As shown in FIG. 2, the light-emitting diode 5, the movement 7, and a control device 14 that controls these are mounted on the printed circuit board 6. Specifically, as in the electric circuit configuration shown in FIG. 4, the control device 14 includes a drive circuit 14b that drives the light-emitting diode 5 to emit light and can be turned off, a drive circuit 14c that drives the movement 7 to rotate, and a microcomputer. 14a. The microcomputer 14 a receives an electrical signal from the vehicle speed sensor 15. The microcomputer 14a performs a vehicle speed calculation process based on the detection output of the vehicle speed sensor 15 to control the drive circuit 14c, thereby rotating the movement 7 to an angle corresponding to a predetermined vehicle speed. Further, the microcomputer 14a controls the lighting and extinction of the light-emitting diode 5 by controlling the driving current 14 or the duty of the driving circuit 14b in response to a lighting / extinguishing request from the outside or the like (for example, setting of a lighting switch by the driver). Or the brightness as a light source when it is turned on is controlled. The microcomputer 14a is operated by being supplied with power from the battery 13 when the ignition switch 12 of the vehicle is turned on.

  Note that the dial 2, the light emitting diode 5, the control device 14, the printed circuit board 6, and the like are housed and held in a case 9, as shown in FIG. Further, a transparent cover 11 is mounted on the dial 2 on the right side in FIG. 2 via a resin facing plate 10. The facing plate 10 arranges the appearance of the combination meter 1. The transparent cover 11 is formed of a transparent thin plate-like polycarbonate or the like, and maintains the airtightness or the like of the combination meter 1 well.

  Here, in the electric circuit configuration of the combination meter 1 shown in FIG. 3, a light emitting diode driving circuit related to the lighting and extinguishing control of the light emitting diode 5 will be described with reference to FIG. As shown in FIG. 1, the light-emitting diode driving circuit has a plurality (five in this embodiment) of light-emitting diodes 5 connected in series. Specifically, five light emitting diodes 5a, 5b, 5c, 5d, and 5e are connected in the order shown in FIG. These light emitting diodes 5a, 5b, 5c, 5d, and 5e are arranged so as to illuminate the scale portion 31 of the dial 2, for example, as shown in FIG. A battery voltage 13 is connected in the forward direction to the light emitting diode 5a on one end side of the light emitting diodes 5a, 5b, 5c, 5d, and 5e connected in series. A driving circuit 14b is connected to the light emitting diode 5e on the other end side, and power is supplied from the battery 13 to control a current flowing through the light emitting diodes 5a, 5b, 5c, 5d, and 5e.

  Zener diodes 4 are connected to both ends of the light emitting diodes 5a, 5b, 5c, 5d, and 5e. Specifically, the same number of Zener diodes 4a, 4b, 4c, 4d and 4e as the number of light emitting diodes are connected in parallel to the light emitting diodes 5a, 5b, 5c, 5d and 5e, respectively. Note that one light-emitting diode 5a and one zener diode 4a are used as one set to form a parallel connection circuit unit of five sets of light-emitting diodes and zener diodes. Here, the light-emitting diode 5, the Zener diode 4, and the drive circuit 14b constitute a light-emitting diode drive circuit.

  Hereinafter, for simplicity of explanation, a parallel connection circuit portion of the light emitting diode 5a and the Zener diode 4a, which is one of the five sets, will be described. Since the other four sets are configured in the same manner, description thereof is omitted.

  Furthermore, in this embodiment, as shown in FIG. 1, the Zener diode 4a is disposed with the pole opposite to that of the light emitting diode 5a, and is set to a Zener voltage higher than the forward voltage of the light emitting diode 5a. The Zener voltage is preferably set to be slightly higher than the forward voltage. As a range of the voltage difference to be higher than the forward voltage of the light emitting diode 5a, the lower limit of the voltage difference is an abnormal voltage or an abnormal current generated when the combination meter 1 or an electromagnetic driving device such as a solenoid valve mounted on the vehicle is operated. Even if a higher voltage than usual is applied to the light-emitting diode 5a due to the influence of the above, the voltage difference is set to a level that is not lower than the actual forward voltage. The upper limit of the voltage difference is set to be equal to or less than a voltage difference that allows a detour current to flow through the Zener diode 4a when a light-emitting diode, which will be described later, is disconnected. For example, when the forward voltage of the light emitting diode 5a is expressed as Vf and the Zener voltage of the Zener diode 4a is expressed as Vc, the Zener diode 4a is set to a Zener voltage Vc that is relatively slightly larger than the forward voltage Vf, and the forward voltage A zener voltage Vc that is relatively close to Vf is set.

  Here, the light emitting diode drive circuit having the light emitting diodes 5a, 5b, 5c, 5d, and 5e and the Zener diodes 4a, 4b, 4c, 4d, and 4e constitutes an illumination device for a vehicle meter.

  The operation of the illumination device for a vehicle instrument having the above-described configuration will be described with reference to FIGS. When the ignition switch 12 of the vehicle is turned on, power is supplied from the battery 13 and the microphone computer 14a is activated. When the microphone computer 14a receives the turn-on / off request, the microphone computer 14a controls the drive circuit 14b. Under the control of the microphone computer 14a, the drive circuit 14b controls the lighting and extinction of the five light emitting diodes 5a, 5b, 5c, 5d, and 5e, or the brightness of the light emitting diodes when the light emitting diodes are lit. Adjust the size etc. to make it variable. The light emitting diodes 5a, 5b, 5c, 5d, and 5e transmit and illuminate the scale portion 31 and the like of the dial 2 so that the speed indicated by the relationship between the pointer 8 and the scale portion 31 rotated according to the signal to the vehicle speed sensor 15. Visibility that the driver sees the display information is improved.

  Here, when the light emitting diodes 5a, 5b, 5c, 5d, and 5e are in a normal normal state without disconnection such as a failure, the relationship between the forward voltage Vf of the light emitting diode 5a and the Zener voltage Vc of the Zener diode 4a. Does not flow through the Zener diode 4a because Vf <Vc. Therefore, when all the light-emitting diodes are in a normal state, as shown in FIG. On the other hand, when any one of the light emitting diodes 5a, 5b, 5c, 5d, and 5e (in this embodiment, for example, 5c shown in FIG. 1) is in an abnormal state that is disconnected due to a failure or the like, the light emitting diode 5c In the Zener diode 4c, the relationship between the forward voltage Vf of the light emitting diode 5c and the Zener voltage Vc of the Zener diode 4c becomes Vf> Vc due to the disconnection of the light emitting diode 5c. As a result, a current flows through the Zener diode 4c, bypassing the disconnected light emitting diode 5c. Therefore, when the light-emitting diode 5c is in an abnormal state in which the light-emitting diode 5c is disconnected, as shown in FIG. 1, a current flows along a path indicated by an arrow B indicated by a broken line, and the remaining light-emitting diodes 5a, 5b, 5d, and 5e emit light.

  Next, functions and effects of the present embodiment will be described. (1) Zener diodes 4a and 4b in which the poles of the light emitting diodes 5a, 5b, 5c, 5d and 5e connected in series are reversed in the light emitting diode driving circuit. 4c, 4d, and 4e are connected in parallel. Moreover, since the predetermined Zener voltage Vc larger than the forward voltage Vf of the light emitting diodes 5a, 5b, 5c, 5d, and 5e is set, the light emitting diodes 5a, 5b, 5c, 5d, and 5e are all in a normal state. The current flows only in the light emitting diodes connected in series. On the other hand, even if any one of these light emitting diodes 5a, 5b, 5c, 5d, and 5e is disconnected due to a failure or the like, the current bypasses the Zener diode 4c connected in parallel to the disconnected light emitting diode 5c. Flowing. Therefore, the remaining light emitting diodes 5a, 5b, 5d, and 5e other than the disconnected light emitting diode 5c can emit light.

  (2) Even if any one of the light emitting diodes 5a, 5b, 5c, 5d, and 5e that illuminate the dial 2 is disconnected, the dial portion that the disconnected light emitting diode 5c illuminates is compared with the surroundings. Although it becomes dimmed, the dial portion is illuminated by the remaining light emitting diodes 5a, 5b, 5d, and 5e. Therefore, the visibility of display information displayed by the dial 2 and the pointer 8 can be ensured.

  (3) In the above description of the present embodiment, it is assumed that any one of the light emitting diodes connected in series is disconnected as an abnormal state related to the light emitting diode, but the light emitting diodes 5a, 5b, 5c, 5d, 5e Even if one of them (for example, two of 5c and 5d), a current flows through the Zener diodes 4c and 4d bypassing the disconnected light-emitting diodes 5c and 5d, so that the remaining normal light-emitting diodes 5a and 5b, 5e can emit light.

(Second Embodiment)
Hereinafter, other embodiments to which the present invention is applied will be described. In the following embodiments, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and description thereof will not be repeated.

  In the second embodiment, as shown in FIG. 5, the plurality of light emitting diodes 5a, 5b, 5c, 5d, and 5e are divided into at least two sets (in this embodiment, three sets shown in FIG. 5). Are configured to be connected in parallel by one Zener diode. FIG. 5 is a circuit diagram showing a light emitting diode driving circuit according to this embodiment. Specifically, as shown in FIG. 5, there are three sets of two light emitting diodes 5a and 5b, two light emitting diodes 5c and 5d, and one light emitting diode 5e.

  Hereinafter, for convenience of description, the relationship between the two light emitting diodes 5a and 5b and the Zener diode 4a will be described.

  The relationship between the light emitting diodes and the Zener diodes constituting the set is such that the Zener voltage of the Zener diode 4a is set larger than the total value of the forward voltages of the two light emitting diodes 5a and 5b. When the forward voltage of each of the light emitting diodes 5a and 5b is expressed as Vf and the Zener voltage of the Zener diode 4a is expressed as Vc, 2 × Vf <Vc is set. Thus, when in a normal state, current does not flow through the Zener diodes 4a, 4b, and 4c connected in parallel corresponding to the three sets, but current flows only through the light emitting diodes 5a, 5b, 5c, 5d, and 5e. If any one of the light emitting diodes 5c is disconnected, a current flows through the Zener diode 4b bypassing the pair including the light emitting diodes 5c, that is, the two light emitting diodes 5c and 5d, and therefore the remaining normal light emitting diodes 5a, 5b, 5e can emit light.

  (1) Thereby, as a measure for preventing all the light emitting diodes 5a, 5b, 5c, 5d, and 5e from being extinguished due to disconnection, the Zener diodes are provided by the number of light emitting diodes 5a, 5b, 5c, 5d, and 5e connected in series Since it is not necessary to prepare, an illumination device for a vehicle instrument can be provided at low cost.

  (2) Even if any one of the light emitting diodes 5a, 5b, 5c, 5d, and 5e that illuminate the dial 2 is disconnected, the dial portion that the group including the disconnected light emitting diode 5c illuminates is around However, since the dial portion is illuminated by another set of light emitting diodes 5a, 5b, and 5e, the visibility of display information displayed by the dial 2 and the pointer 8 can be ensured. it can.

(Other embodiments)
When the plurality of light emitting diodes 5a, 5b, 5c, 5d, and 5e are divided into at least two groups, the vehicle speed display frequency is low in the range in which the vehicle speed is displayed on the display panel 2 and the pointer 8 of the vehicle instrument 1. In the range portion (for example, 100 km / h or more), the number of the light emitting diodes 5 constituting the set may be set to be larger than that in the high range portion. As a result, when any of the light-emitting diodes 5a, 5b, 5c, 5d, and 5e is disconnected, it is prevented from being completely turned off, and is displayed on the dial 2 and the pointer 8 while suppressing the cost increase due to the addition of a Zener diode. The visibility of the display information can be efficiently ensured.

  In the present embodiment described above, when a disconnection occurs in any of the light emitting diodes, a current is passed through the Zener diode connected in parallel to the disconnected light emitting diode or the light emitting diode that constitutes the set including the disconnected light emitting diode. Therefore, the current does not flow through the Zener diode in a normal state, so that the characteristics of the light emitting diodes connected in series that keep the current consumption low are not impaired.

1 is a circuit diagram showing a light emitting diode drive circuit according to a first embodiment of the present invention. It is sectional drawing of the vehicle meter of one Example to which the illuminating device of the vehicle meter of 1st Embodiment is applied. It is the partial front view which looked at the vehicle instrument shown in FIG. 2 from the visual recognition direction. It is a schematic diagram which shows the electric circuit structure of the meter for vehicles shown in FIG. It is a circuit diagram which shows the light emitting diode drive circuit concerning 2nd Embodiment.

Explanation of symbols

1 Combination meter (vehicle instrument)
2 Dial (Display board)
3 Design part 31 Scale part 4 (4a, 4b, 4c, 4d, 4e) Zener diode 5 (5a, 5b, 5c, 5d, 5e) Light-emitting diode 6 Printed circuit board 7 Movement (rotation inner machine)
8 Pointer 12 Ignition switch 13 Battery 14 Controller 14b Drive circuit

Claims (4)

In a lighting device for a vehicle instrument comprising a plurality of light emitting diodes connected in series and a drive circuit capable of turning on and off the light emitting diodes,
The drive circuit includes a zener diode having a zener voltage greater than the forward voltage of the light emitting diode, with the poles reversed and connected in parallel to the light emitting diode. apparatus. Dividing the plurality of light emitting diodes into at least two sets;
The lighting device for a vehicle instrument according to claim 1, wherein the light emitting diodes constituting the set are connected in parallel by one Zener diode. The lighting device for a vehicle meter according to claim 2, wherein a Zener voltage of the Zener diode is formed to be larger than a total of forward voltages in the light emitting diodes constituting the set. A plurality of light emitting diodes according to any one of claims 1 to 3,
A display panel made of a translucent material,
The said light emitting diode is arrange | positioned so that light can be irradiated to the said display panel on the surface opposite to the surface of the said display panel to be visually recognized.

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