JPS58208668A - Digital speed display device for automobile - Google Patents

Abstract

PURPOSE:To automatically display vehicle speed corrected according to the actual vehicle speed by calculating a corrected value based on output of a correction value computing circuit for calculating an arithmetic constant reading a state of a vehicle speed correction switch group. CONSTITUTION:A data holding circuit 5 holds a sensor pulse signal I from a sensor for detecting revolutions of a wheel or the like as data for one hour and a main arithmetic circuit 7 computes a correct vehicle speed using outputs of the data holding circuit 5 and a correction value computing circuit 6 as data. Various correction commands are applied with a vehicle speed correction switch block S1 while arithmetic constants such as correction value and rate are preset for the correction value computing circuit 6 thereby enabling the indication of the vehicle speed automatically corrected. Thus, the vehicle speed can be corrected according to the actual vehicle speed only by switch operation only if the setting of a correct speed data is done with a testing base or the like for correction value from the type of vehicles, tire, the weight of vehicles or the like.

Description

[Detailed Description of the Invention] This invention is capable of displaying up to decimal digits greater than or equal to the number of digits on the display, and also automatically corrects and displays the displayed vehicle speed to the actual vehicle speed using a vehicle speed correction switch. This invention relates to a digital speed display device for automobiles.

Generally, in a car speedometer that displays an electronic digital display, the output of a speed sensor 1 that detects, for example, the number of rotations of a wheel is sent to an arithmetic circuit 2, as shown in Figure 1.
The vehicle speed is converted to speed by , and the display circuit 3 is driven by the output, so that the vehicle speed is displayed on the 7-segment, 2-digit display 4.

Such a conventional weight-type digital display speedometer cannot always accurately display the speed due to differences in tire diameter and vehicle type. Therefore, a single speed display device can only accurately display speeds for vehicles with specific tire diameters, specific vehicle types, and specific weights. For this reason, the conventional method was to calculate the information accuracy rate from the displayed value and the actual value, input that value into the Kansho Isoshi, and display the corrected value. It was necessary to take the time and effort to calculate.

In addition, a display (a 7-segment display with four or more digits) is required to display the decimal places, and the display circuit is complicated.

This invention was made in view of the above points, and its purpose is to read the state of the vehicle speed correction switch group when converting data obtained from a speed sensor into vehicle speed using an arithmetic circuit. An object of the present invention is to provide a digital speed display device for an automobile that calculates a corrected numerical value based on the output of a correction value calculation circuit that calculates a calculation constant, and displays the vehicle speed converted from a speed sensor signal on a sleeve correction display. .

Another object of the present invention is to determine which mode to display using a switch to display vehicle speed, integer, or decimal, and to also display decimals using a display with a small number of digits. The purpose of the present invention is to provide a digital speed display device for automobiles that can be used in vehicles.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

In FIG. 2, 5 is a data block waiting circuit, and 6 is a data providing circuit that temporarily holds as data a sensor pulse signal ■ from a sensor ((9) not shown) that detects the rotation speed of wheels, etc. A correction value calculation circuit reads signals from the vehicle speed correction switch group S1 and outputs calculation constants, and a main calculation circuit 8 uses the outputs of the 7-tri data holding circuit 5 and the correction value calculation circuit 6 as data to calculate the correct vehicle speed. 9 is an integer part data circuit that outputs only the integer part of the input from the main arithmetic circuit 7; 9 is a decimal part data circuit that outputs the lower digit value including the decimal part of the input from the main arithmetic circuit 7; lO is a selector switch S that switches between integer mode and decimal mode.
The integer/decimal number judgment circuit judges the mode of the command from 2, and its output controls the data transmitter 11 to display the data input from the integer part data 8 and the decimal part data circuit 9 as an integer mode or a decimal number mode. The output is output to the device driver 12, and this output drives the display device 13. Based on the above configuration, the operation when displaying in integer mode and decimal mode will be explained with reference to FIG. If a 7-segment, 3-digit display is used as the display 13, the actual vehicle speed is 119.8 km/h and the display is, for example, 120°5.
In the case of Km/h, the uncorrected display shows 120 Km/h in integer display mode as in (a), and 20.5 Km/h in decimal display mode (as in bl).(c
l, (d) Fi vehicle speed correction switch group S] to display the actual vehicle speed of 119.8 & I/h. In decimal display mode (like CI, it shows 19.8 Kya/Fl; Deke゛ (119km like di
/h. Therefore, to correct the display speed, in the above example, the display is 19.8 Km/h in decimal mode.
If the vehicle speed is corrected using the vehicle speed correction switch group S1 and then switched to the @ number mode again, the normal speed can be displayed. In this case, f'J is 119 Km/h8.Furthermore, the correction value calculation circuit 6 may be set in advance to calculate the correction amount in each case, such as accurate speed data, using a test vehicle or the like.

That is, let the speed of the car be V, and the sensor pulse signal I
If the waveform is such that two pulses are generated for one rotation of the wheel, then when the wheel rotates 684 times during 1 hour of driving, I
Ktn running results in 1368 pulses. Here, if the pulse period of sensor pulse signal 1 is T, then v=/'r
becomes.

Here, it is a constant determined by KFi tires, vehicle type, etc. Therefore, by reading the state of the vehicle speed correction switch group S1, the value of the constant is changed, and the accurate speed is calculated to, for example, one digit after the decimal point. The display value is transferred to the display device driver 12 by the data transmitting unit 11, and the display value is transferred to the display device driver 12 by the display device I3.
It can be displayed like this.

In the above, the data holding circuit 5, the correction value calculation circuit 6,
Main arithmetic circuit 7, integer part data circuit 8, decimal part data circuit 9, integer decimal judgment circuit 10. A CPU as shown in FIG.
(Central processing unit) 14 is used, sensor pulses, vehicle speed correction switch group, integer, and decimal changeover switches are used as inputs, ROM (read-on memory) 15 is used as program memory, and the same as above is used as an output device. By using the display driver 16, display 17, etc., functions can be easily and relatively inexpensively diversified.

As described above, this invention enables various correction commands to be issued by a group of vehicle speed correction switches, and sets calculation constants such as correction amounts and correction factors in advance in a correction value calculation circuit.
As a result, it is possible to automatically correct and display nine vehicle speeds, so once accurate speed data is set on a test stand etc. by the amount of correction based on the car type, tires, car weight, etc., the actual speed can be displayed by simply operating a switch. Can be quickly corrected,
The method for correcting the speed # display becomes very simple, and correction can be made in many cases.

In addition, the display means can be switched between integer mode and decimal mode by operating a switch, and for example, a 3-digit display can display the lower four digits including the decimal point if necessary. You can see large digit numbers including the decimal point on the display, allowing you to know more accurate speeds.Furthermore, by using a microcomputer to create the circuit, it can be realized relatively easily and at low cost with an off-the-shelf microcomputer. is possible.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional digital speedometer for automobiles.
FIG. 2 is a block diagram of one practical example according to the present invention, FIG. 4 is a block circuit of another implementation V]. 5.-...r... Data holding circuit 6...
......Correction value calculation circuit 7...
...Main calculation circuit 8...Integer part data circuit 9...Decimal part data circuit lO... Integer/decimal number judgment circuit 11...
...Data transmitter 12...Display driver 18...
····display

Claims (1)

[Claims] A data holding circuit that holds wheel rotation speed data, a group of vehicle speed correction switches that command correction of vehicle speed display, and a correction value calculation circuit that reads the state of the group of vehicle speed correction switches and changes a calculation constant for calculating vehicle speed. a main arithmetic circuit that calculates an actual vehicle speed using the outputs of the data holding circuit and the correction value arithmetic circuit as input data and outputs the result; and an integer part data circuit that holds only the integer part of the output of the main arithmetic circuit. and a decimal part data circuit that holds the number of lower digits including the decimal part, and an integer, decimal number that commands whether the integer display mode that displays only integers or the decimal display mode that displays the number of lower digits including the decimal number. Input the respective outputs of a changeover switch, an integer/decimal judgment circuit for determining each of the display modes commanded by the integer/decimal changeover switch, the integer part data circuit, the decimal part data circuit, and the integer/decimal number judgment circuit. a data transmitter that transfers a signal of an integer display mode or a decimal display mode to a display device according to the phalanx of each mode, and a display device that is driven by the output of the display device, By operating the vehicle speed correction switch group, the displayed speed is automatically corrected to the actual vehicle speed, and by operating the integer/decimal selector switch, the vehicle speed can be displayed only in the integer part, or the F digit including the decimal can be displayed. A digital vehicle speed display device for a moving vehicle, characterized in that it is configured to display a numerical value of the vehicle speed to the decimal point.