JPH04310870A - Meter driving apparatus - Google Patents

Abstract

PURPOSE:To perform accurate display and to enhance response when the frequency of an input pulse signal becomes extremely small. CONSTITUTION:A meter driving apparatus is equipped with a calculation means 34 calculating the cycle of a pulse signal and an indication means 36 emitting a command so as to perform the meter display corresponding to the reciprocal of the time elapsed after the pulse signal of the previous time is inputted in such a case that no pulse signal is inputted even when the time corresponding to the cycle of the pulse signal of the previous time calculated by the calculation means 34 is elapsed. The time corresponding to the cycle of the pulse signal of the previous time is calculated by the calculation means 34. When no pulse signal is inputted even when the time corresponding to the cycle of the pulse signal of the previous time calculated by the calculation means 34 is elapsed, the reciprocal of the elapsed time from the input of the pulse signal of the previous time is calculated by the indication means 36 to emit a command so as to lower meter display on the basis of the calculation result.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a meter drive device, and more particularly to a meter drive device for driving a cross-coil meter that provides a desired angular orientation using a magnetic field generated by energizing two mutually orthogonal coils.

0002

[Prior Art] Conventionally, a cross coil meter has been used in which a current is passed through two excitation coils orthogonal to each other to generate a magnetic field, and this magnetic field applies torque to a rotatable magnet to indicate a desired angular orientation. is known, and this cross coil meter is used in speedometers, tachometers, etc. of automobiles.

FIGS. 5 and 6 show schematic configuration diagrams of this cross coil meter.

The two excitation coils LS and LC arranged orthogonally to each other generate a magnetic field in a desired angular direction by being supplied with a pulse current according to an input amount such as speed, and are rotatable. The supported permanent magnet M receives torque from the magnetic field generated by the two excitation coils LS and LC.

Then, as shown in FIG. 6, the indicator needle fixed to the permanent magnet M is moved to a reference position indicating a predetermined position on the meter indicator board on which the physical quantity to be measured (speed in FIG. 6) is displayed. It moves by θ from , and indicates an instruction value according to the input amount.

[0006] A meter drive device that drives a cross coil meter used in a speedometer or tachometer of an automobile generally receives a pulse signal whose frequency changes depending on an input amount, for example, speed, and also uses a reference clock generating means. The generated reference clock signal is input, one cycle of the pulse signal is counted by the pulses of this reference clock signal, and the frequency is calculated.

[0007] Then, a current corresponding to the calculated frequency is subjected to pulse width modulation (PWM) and is caused to flow through the two excitation coils LS and LC arranged orthogonally to each other.

At this time, if the frequency of the pulse signal is sufficiently high, the frequency is calculated by counting the number of pulses of the input pulse signal during a predetermined period, but if the frequency of the pulse signal becomes low, the frequency of the input pulse signal is The period is measured and its reciprocal is calculated and displayed.

[0009]

In the conventional meter driving device, when the frequency of the pulse signal is sufficiently high, the number of pulses of the input pulse signal during a predetermined period is counted and displayed. On the other hand, when the frequency of the pulse signal is low, the period of the input pulse signal is measured, and its reciprocal is calculated and displayed. Therefore, the period of the input pulse signal is measured,
Until the reciprocal is calculated and displayed, the previous display value will be displayed as is. Therefore, as shown by the solid line in FIG. 7, each time a pulse signal is input, it becomes step-like.
If the frequency of the input pulse signal deviates from the true speed value (broken line) and the frequency of the input pulse signal becomes very small, the display change will be delayed, and if the frequency of the input pulse signal becomes "0", the previous display value will remain displayed and will not change. was there.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a meter drive device that can provide accurate display and improve responsiveness when the frequency of an input pulse signal becomes extremely low. It's about doing.

[0011]

[Means for Solving the Problems] In order to achieve the above object, the meter driving device of the present invention includes a calculation means for calculating the period of a pulse signal, and a period corresponding to the previous pulse signal calculated by the calculation means. If the pulse signal is not input even after a period of time has elapsed, the apparatus is provided with an instruction means for calculating the reciprocal of the elapsed time since the previous pulse signal was input and instructing to lower the meter display based on the calculation result. .

0012

[Operation] The meter driving device of the present invention has the above-described configuration, in which the calculation means calculates the period of the previous pulse signal, and the time corresponding to the period of the previous pulse signal calculated by the calculation means is calculated. If the pulse signal is not input even after the elapse of time, the instruction means instructs the meter to display the reciprocal of the elapsed time since the previous pulse signal was input.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the meter driving device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the configuration of this embodiment.

The meter driving device has a binary counter 10 to which a pulse signal is input, and a reference clock generator 12 that generates a reference clock signal is connected to the binary counter 10. The number of pulses of the reference clock signal within one period, that is, from one rising or falling edge of the input pulse signal to the next rising edge or falling edge, is counted.

A latch 14 is connected to the binary counter 10 for storing the period of the pulse signal counted by the binary counter 10.

Further, a CPU 16 as a calculation means is connected to the latch 14, and a RAM 18 for storing data and the like and a ROM 20 for storing programs, coefficients, etc. are connected to the CPU 16.

The CPU 16 also includes a PWM modulator 22 that modulates the output signal output from the CPU 16 with two pulse widths, sin and cos, and a steering logic 24.
, a timer 30 , and a pulse input flag 32 are connected to the PWM modulator 22 and steering logic 24 , and the excitation coil LS of the cross coil meter 26 is connected to the PWM modulator 22 and steering logic 24 .
, LC is connected thereto.

[0019]The steering logic 24 then
The sign of sin and cos in the two modulations of sin and cos performed by the WM modulator 22 is determined. For example, the first quadrant of the meter is set as sin positive and cos positive, and the second quadrant is set as sin positive. , cos negative, etc. to determine the quadrant (see FIG. 2).

[0020] Furthermore, the reference clock generator 12
16 and PWM modulator 22, and is connected to CP
The operation timing of U16 and PWM modulator 22 is determined based on a reference clock.

[0021]Then, the CPU 16 uses the calculation means 34 for calculating the period of the pulse signal, and if the pulse signal is not input even after a period of time corresponding to the period of the previous pulse signal calculated by the calculation means 34 has elapsed, the CPU 16 calculates the period of the pulse signal. An instruction means 36 is provided for instructing a meter to display a value corresponding to the reciprocal of the elapsed time since the pulse signal was input.

Next, the operation of this embodiment will be explained.

When a pulse signal is input to the binary counter 10, the binary counter 10 counts the time from the rising edge or falling edge of the input pulse signal to the next rising edge or falling edge, that is, the number of pulses of the reference clock signal within one cycle. Then, the period Tc of the pulse signal counted by the binary counter 10 is stored in the latch 14.

[0024] The CPU 16 executes step S every 20 msec.
1) Perform the following processing.

The presence or absence of pulse input between the previous processing and the current processing is determined (step S2). If there is a pulse input, reset the pulse no-input time T, which is the time from the last pulse input to the previous processing (step S
3), the period T of the pulse signal stored in the latch 14;
The output value Fout (=1/Tc) is calculated from c (step S4), and this Fout is stored in the CPU 16 as Fa.

On the other hand, if it is determined in step S2 that there is no pulse input, the time obtained by adding 20 msec to the previous pulse no-input time T is set as a new time (step S5).
), calculate the frequency F (=1/T) corresponding to this T (
Step S6), the frequencies Fa and F at the time of the last pulse input are compared (Step S7). If F is greater than or equal to Fa, the output value Fout is calculated as Fout = Fa (step S8), and if F is less than Fa, the output value Fout is calculated as Fout = Fa (step S8).
Calculate out as Fout = F (step S
9).

The meter display is updated using Fout calculated as above as a new display value (step S
10).

The CPU calculates the meter deflection angle θ according to the instruction value Fout, further calculates the coil currents sin θ and cos θ corresponding to the deflection angle θ, and writes these values into the register of the PWM modulator 22. The PWM modulator outputs a PWM pulse with a width of this value. Then, a current corresponding to the meter deflection angle θ is caused to flow through the two excitation coils LS and LC arranged orthogonally to each other by the driver 28, and the meter is displayed. The resulting display value decreases along a 1/T curve until a pulse is input, as shown in FIG.

At this time, the steering logic 24
The signs of sin and cos in the two modulations of sin and cos performed by the WM modulator 22 are determined. for example,
The quadrants are determined by determining that the first quadrant of the meter is sine positive and cosine positive, and the second quadrant is sine positive and cosine negative.

[0030]

[Effects of the Invention] As explained above, the meter driving device of the present invention calculates the period of the previous pulse signal by the calculation means, and waits for the elapse of time corresponding to the period of the previous pulse signal calculated by the calculation means. If the pulse signal is not input even after
Since the instruction means is configured to instruct the meter to display a value corresponding to the reciprocal of the elapsed time since the previous pulse signal was input, the display can be quickly changed if the frequency of the input pulse signal becomes extremely low. It is possible to lower the response time and improve responsiveness, and it is also possible to perform more accurate display than in the conventional example.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a meter driving device according to the present invention.

FIG. 2 is a diagram showing the positive and negative signs in the steering logic according to the embodiment of the present invention.

FIG. 3 is a flow chart diagram showing the operation of the present invention.

FIG. 4 is a diagram showing the operation of the present invention.

FIG. 5 is a diagram showing a conventional excitation coil.

FIG. 6 is a diagram showing a conventional cross coil meter.

FIG. 7 is a diagram showing a conventional operation.

[Explanation of symbols]

10 Binary counter 12 Reference clock generator 16 CPU 22 PWM modulator 26 Cross coil meter 34 Calculation means 36. Instruction means

Claims (1)

[Claims] Claim 1: A meter driving device that calculates a frequency from the period of an input pulse signal and inputs it to a meter, comprising: a calculating means for calculating the period of the pulse signal, and a period of the previous pulse signal calculated by the calculating means. The apparatus is characterized by comprising an instruction means for instructing a meter to display a value corresponding to the reciprocal of the elapsed time since the previous pulse signal was input, if the pulse signal is not input even after a corresponding period of time has elapsed. meter drive device.