JPS5892956A - Speed display device - Google Patents

Abstract

PURPOSE:To provide a device which performs a reliable display of a speed during a running even if a key switch is brought to OFF, by a method wherein, in a speed display device for electrically displaying a speed of a vehicle, after a power supply switch is shifted to opening from closing, and a running of a vehicle is detected by means of an output signal from a speed sensor to keep a feeding to the speed display device in case the vehicle is in a running condition. CONSTITUTION:If a key switch 2 is closed, electricity is fed to a speed display device 10, and a constant-voltage circuit 4 outputs driving circuit 7. The speed computing circuit 6 computes a speed after counting an output signal from a speed sensor 5 at each unit time, and outputs it to the display driving circuit 7 to drive a display element 8. If a key switch 2 is closed, in case a speed signal from the speed sensor 5 is generated, a feeding needs to continue. If the speed computing circuit 6 detects a speed signal from the speed sensor 5 and decides that a vehicle is during running, with a switch activated, electricity is fed to the speed display device 10 from a power source 1 through a switch 3, and thereby, even if the key switch is opened, a feeding continues to perform a display.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed display device that electronically displays the speed of a vehicle.

With conventional mechanical speed needles, even when the key switch is off, the pointer operates normally as long as the vehicle is running, allowing the driver to accurately recognize the speed. For example, if the key switch is turned off while driving downhill, the speed needle will also operate. However, in the case of a device that displays speed electronically, when the key switch is turned off, the power supply to the device is stopped, and if the vehicle is running at this time, the display disappears, which poses a problem for driving. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a speed display signal that can accurately display the speed while the vehicle is running even when the key switch is off.

Embodiments of the present invention will be described below based on the drawings.

The figure is an electrical circuit diagram showing an embodiment of the present invention. In the figure, C11) is a power supply, (2) is a key switch that supplies power to the speed display device a1, and C3) is a key switch that supplies power to the speed display device a1, and C3) displays the speed by the output signal from the speed display device rm even when the key switch (2) is open. A switch for supplying power to the device Q1, (4) a static voltage circuit that makes the voltage supplied to the speed display device constant, (5) a speed sensor that detects the running speed of the vehicle, (
6) a speed calculation circuit that receives the output signal of the speed sensor (6) and converts it into a speed display signal; (7) a display drive circuit that receives the output signal of the speed calculation circuit and converts it into a display element drive signal; (8) is a display element such as a fluorescent display tube, a liquid crystal dual light emitting diode, etc., which is turned on or off in response to the output signal of the display drive circuit.

Next, the operation of the embodiment of the present invention will be explained based on the drawings. Normally, when the key switch (1) is closed, the speed display device 1Q
Power is supplied to I. The constant voltage circuit (4) outputs a desired constant voltage and supplies power to the speed calculation display circuit (6) or the display drive circuit (7). The speed calculation circuit (6), for example, counts the output signal from the speed sensor (6) for each unit time, processes the speed calculation, and converts it into decimal data or 7-segment data for display, and then outputs the signal to the display drive circuit (7). Output to. When the output signal from the speed calculation circuit (6) is decimal data, the display drive circuit (7) decodes it into 7 segments and drives the display element (8).

In addition, if the output signal from the speed calculation circuit (6) has already been 7-segment decoded, the key switch (2) is closed by converting it into a signal suitable for the display element (8) and driving it by 1° or more. When the speed is reached, the normal speed will be displayed. However, when the key switch (2) is opened, the display disappears because there is no power supply. However, if the speed display disappears when the key switch (2) is opened while the car is running, it is a safety problem. Therefore, when the variable key switch (2) is closed, if there is a speed signal from the speed sensor (6), it is necessary to continue power supply. In Fig. 1, the speed calculation circuit (6) detects the speed signal from the speed sensor (6) and
When it is determined that the vehicle is running, the switch (3) is activated and power is supplied from the power source (1) to the speed display device OO via the switch (3). Therefore, even if the key switch (2) is opened, power supply continues and the speed is displayed. After that, when the speed signal from the speed sensor (6) stops and the speed calculation circuit (6) detects that the vehicle has stopped, the switch (3) is deactivated, power supply is stopped, and the display disappears.

As is clear from the above, according to the present invention, even if the key switch (2) is opened while the vehicle is running, the speed display is performed normally, and this is considered to be a good sign for safe driving.

and

[Brief explanation of the drawing]

The figure is an electrical circuit diagram showing an embodiment of the present invention. For the same reason, (l) is the power supply, (2) is the key switch,
(3) is a switch, (4) is a constant voltage circuit, (6) is a speed sensor, (6) is a speed calculation circuit, (7) is a display drive circuit, and (8) is a display element. Agent Shin Kuzuno −

Claims (1)

[Claims] A speed sensor that detects the running speed of a vehicle, a speed calculation circuit that receives a signal from the vehicle speed sensor and converts it into a speed display signal, and a display drive circuit that receives the output signal of the speed calculation circuit and converts it into a display element drive signal. , and a display element that responds to the output signal of the display drive circuit, after the power supply switch to the speed display device transitions from closed to open, the output signal from the speed sensor causes the vehicle to A speed display device comprising means for detecting running of a vehicle and maintaining power supply to the speed display device when the vehicle is in a running state.