JPH07294286A - Driver for instrument - Google Patents

Abstract

PURPOSE:To provide a driver for instrument in which the influence of a chattering signal can be suppressed when the chattering signal is generated in a pulse signal to cause an error in the measurement of period and thereby vibration of a pointer is prevented. CONSTITUTION:A period measuring section 2 measures the period by detecting the state of an object and the edge of a pulse signal having a corresponding period. A drive section 6 outputs a drive signal corresponding to a measurement at the period measuring section 2. An instrument 7 displays the state of object corresponding to the drive signal. A mask section 8 inhibits provision of a pulse signal to the period measuring section 2 until a measurement of predetermined value is obtained every time when the edge of pulse signal is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device of an instrument for detecting an object to be measured such as a vehicle running speed and an engine speed and displaying the state of the object.

[0002]

2. Description of the Related Art In general, the means for displaying an object to be measured by means of a meter is provided with a sensor for generating a pulse signal having a period corresponding to the state of the object to be measured at a predetermined position of a vehicle and detecting the pulse signal from the sensor. Then, a pointer (analog) display or digital display is provided. As one means for detecting the state of the object to be measured from the pulse signal, a method of measuring the period of the pulse signal is known (for example, JP-A-2-51065 and JP-A-4-12276). this is,
The one cycle of the input pulse signal from the measured object is measured with the short period reference pulse signal, and the fact that the reciprocal of this count number (measured value) is proportional to the state of the measured object is used. By performing a predetermined input process and a drive process, the state of the measured object, that is, the traveling speed and the engine speed are displayed on a predetermined instrument.

If the sensor is composed of a magnet that rotates according to the state of the object to be measured and a reed switch that repeatedly turns on and off according to changes in the ambient magnetic field due to the rotation of the magnet, the reed switch is , That on
It creates a bounce time when the contacts make and break when off. As a result, chattering occurs in the pulse signal, and an error is included in the cycle measurement, which causes needle deflection when displaying with a pointer.

As a countermeasure against this, it is possible to add an error prevention circuit such as an external low-pass filter or a one-shot monostable multivibrator to absorb and remove the chattering signal.

[0005]

In such a measure, since an external error prevention circuit is added, the cost is increased and the structure is enlarged, and the characteristics of the low-pass filter and the monostable multivibrator are set to predetermined values. There is a large variation in the precision of the resistors and capacitors used for this purpose, and there is the problem that separate adjustment is required.

In particular, when a chattering signal is absorbed by a low-pass filter composed of a resistor and a capacitor, a low-pass filter having a large time constant and having a sufficient margin must be used as a preventive measure against temperature changes. To increase the size. In addition, if the time constant is large, there is a problem that it is not possible to cope with a pulse signal having a high frequency.

[0007]

In order to solve the above-mentioned problems, the present invention provides a cycle measuring section for detecting the edge of a pulse signal having a cycle corresponding to the state of an object to be measured and performing the cycle measurement, and the cycle measuring section. A drive unit that outputs a drive signal according to the measurement value of the unit, and a meter that displays the state according to the drive signal of the drive unit, at least one of the rising edge or the falling edge of the pulse signal. A mask unit is provided for suppressing the input of the pulse signal to the period measuring unit until the measured value reaches a predetermined value for each detection.

Further, the cycle measuring section has a cycle counter for counting the pulse signals, and the mask section is
The cycle counter section has a determination section that determines whether or not the measured value is larger than a predetermined value, and when the measured value is smaller than the predetermined value, inhibits the pulse signal from being input to the cycle measurement section. It has an input suppression unit.

[0009]

Even when the chattering signal is generated in the pulse signal and the period measurement includes an error, the mask portion can suppress the influence of the chattering signal. Can be suppressed.

In particular, the structure is simplified by forming the mask section so as to suppress the influence of the chattering signal by using the cycle counter in the cycle measuring section.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in FIGS. 1 to 3 in which an instrument for displaying the engine speed of a vehicle is applied.

FIG. 1 is a schematic block diagram showing the configuration of the above-mentioned embodiment. Reference numeral 1 is an input terminal for receiving an input pulse signal having a cycle corresponding to the engine speed, and 2 is a pulse signal entering the input terminal 1. For example, a rising edge is detected and counted at regular time intervals, and the count number (measured value) is, for example, 8
The period measuring unit 3 which outputs a bit digital signal, the deflection angle converting unit 3 which determines a pointer deflection angle of a meter, which will be described later, according to the output of the period measuring unit 2 and outputs it as a digital signal, 4 is the deflection angle converting unit 3. The responsiveness adjuster 5 adjusts the responsiveness according to the output so that the responsiveness becomes slower when the engine is at low speed and becomes faster when the engine is at high speed than when the engine is at low speed. The converter 6 generates data of a sine wave (or cosine wave) signal corresponding to the digital signal from the deflection angle converter 3 which has passed through, and 6 which are electrically connected to each other and wound around a measuring instrument 7.
This is a drive unit that outputs a sine wave signal and a cosine wave signal to the two sets of coils 71 and 72 having a phase difference of 100 degrees based on an instruction from the conversion unit 5.

In the instrument 7, the magnetic field changes in response to the signals applied to the coils 71 and 72, and the coils 71 and 7 respond accordingly.
The magnet 73 located inside 2 rotates, and the engine speed is displayed by the deflection angle of the pointer 74 fixed to the tip of the pointer shaft inserted through the rotation center of the magnet 73.

Reference numeral 8 is a masking section for suppressing the input of the pulse signal to the period measuring section 2 until the measured value reaches a predetermined value every time at least one of the rising edge and the falling edge of the pulse signal is detected. Then, the influence of the chattering signal is suppressed by using the period counter described later in the period measuring unit 2.

Next, a detailed description will be given with reference to the block diagram of the main part of FIG. 2 and the time chart of the pulse signal of FIG. In the period measurement of the pulse signal, the time t from the rising edge to the next rising edge is sequentially measured. t1 and t2 are times during which the mask section 8 suppresses the input of the pulse signal to the period measuring section 2, and the occurrence time (bounce time) of the chattering signal occurring at the rise and fall of the pulse signal is confirmed in advance. , It is set to be a little longer than this time. Then, by providing a permission flag for inhibiting the detection of the rising edge at this time, the influence (error occurrence) by the chattering signal is prevented, and while the permission flag is "high level (H)", the pulse signal The input is permitted, and the input of the pulse signal is suppressed during the "low level (L)".

Specifically, as shown in FIG. 2, the pulse signal input to the terminal 1 enters the input suppressing section (for example, AND circuit) 81 of the mask section 8. Since the initial value of the permission flag unit 82 is “H”, the pulse signal remains as it is in the period measuring unit 2.
Is sent to the rising edge detecting section 21 and the rising edge (a in FIG. 3) is detected, a start signal is sent to the cycle counter section 22 and the cycle measuring section 2 starts the cycle measurement. At that time, the permission flag unit 82 is reset via the OR circuit unit 83, and the output of the permission flag unit 82 becomes “L”. Therefore, after that, the input suppression unit 81 suppresses the input of the pulse signal.

Then, when the judgment section 84 for judging whether the measured value of the cycle counter section 22 is larger than the predetermined value t1 or not, when the measured value exceeds the predetermined value t1, it is judged that the bounce time has elapsed. Then, “H” is set in the permission flag unit 82 via the OR circuit unit 85. After that, the input suppression unit 81 permits the input of the pulse signal.
Here, when the falling edge detection unit 86 detects the falling edge (b in FIG. 3) of the pulse signal, the measured value of the cycle counter unit 22 at that time, that is, the measured value between the edge a and the edge b is stored in the memory. In addition to temporarily storing it in the unit 87, the permission flag unit 82 is reset via the OR circuit unit 83.

Then, the difference between the measured value of the cycle counter section 22 and the stored value of the memory section 87, that is, the measured value from the edge b, is judged by the judging section 89 for judging whether the difference is larger than a predetermined value t2. When it is determined that the value t2 is exceeded, it is determined that the bounce time has elapsed, and the permission flag unit 82 is set to "H".
Set to. Here, when the rising edge detector 21 detects the rising edge (c in FIG. 3) of the next pulse signal,
The cycle counter unit 22 outputs the measured value, that is, the measured value between the edge a and the edge c to the swing angle conversion unit 3.

With such a structure, the chattering signal of the pulse signal can be suppressed by the mask section 8, the error in the cycle measurement by the cycle measuring section 2 can be suppressed, and the indicator 74 of the instrument 7 displays the error. It is possible to prevent the shake of the needle when doing.

Moreover, the added mask portion 8 does not require adjustment as compared with the conventional external low-pass filter, is small in size, and can follow high frequencies.

4 and 5 show another embodiment of the present invention, in which the same parts as those of the above-mentioned embodiment are designated by the same reference numerals and detailed description thereof will be omitted. FIG. 4 is a block diagram of a main part, and FIG. 5 is a time chart of a pulse signal. The difference from the above embodiment is that there is no chattering signal at the rising edge of the pulse signal. This is because the bounce time of the reed switch is generally different between on-time and off-time, so the rising edge (a, c in FIG. 5), which is the shorter bounce time, is attached to an external low-pass filter (not shown). ), The chattering signal is absorbed.

In this embodiment, the period measurement of the pulse signal in the period measuring unit 2 is performed from the falling edge (b of FIG. 5) of the pulse signal to the next falling edge (d of FIG. 5) and the predetermined value is obtained. The input of the pulse signal is suppressed only during t2.

Also in such a configuration, the masking section 8 can suppress the chattering signal of the pulse signal, the cycle measuring section 2 can suppress the error in the cycle measurement, and the measuring instrument 7 (see FIG. 1). ) Pointer 74 (Fig. 1
It has the same operation as that of the above-described embodiment, such as the prevention of the needle runout of the reference).

In this embodiment, an external low-pass filter is used as a countermeasure against the shorter bounce time.
The shorter bounce time is because the time constant does not need to be so large even if a low-pass filter is used, and the fact that the mask unit 8 can be simplified is effective in the overall configuration.

In addition, in each of the above-mentioned embodiments, the invention is applied to the instrument for displaying the engine speed, but the invention is not limited to this and can be applied to other instruments such as an instrument for displaying the traveling speed.

[0026]

According to the present invention, a cycle measuring section for detecting the edge of a pulse signal having a cycle corresponding to the state of an object to be measured and performing cycle measurement, and a drive signal according to the measured value of the cycle measuring section are output. And a meter that displays the state according to a drive signal of the drive unit, and the measured value becomes a predetermined value each time at least one of the rising edge and the falling edge of the pulse signal is detected. Up to a period, a mask unit is provided for suppressing the input of the pulse signal to the period measuring unit, and even if the period measurement includes an error due to a chattering signal generated in the pulse signal, The part can suppress the influence of chattering signals,
When displaying with a pointer, needle shake can be suppressed, and an instrument having good displayability can be realized.

Further, the cycle measuring section has a cycle counter for counting the pulse signals, and the mask section is
The cycle counter section has a determination section that determines whether or not the measured value is larger than a predetermined value, and when the measured value is smaller than the predetermined value, inhibits the pulse signal from being input to the cycle measurement section. The structure is simplified by having the input suppression unit.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of the embodiment.

FIG. 3 is a time chart of a pulse signal according to the above embodiment.

FIG. 4 is a block diagram of a main part of another embodiment of the present invention.

FIG. 5 is a time chart of a pulse signal according to the above embodiment.

[Explanation of symbols]

 1 Input Terminal 2 Cycle Measurement Section 3 Swing Angle Conversion Section 4 Responsiveness Adjustment Section 5 Conversion Section 6 Drive Section 7 Meter 8 Mask Section 22 Cycle Counter Section 84,89 Judgment Section

Claims (2)

[Claims] 1. A cycle measuring section for detecting a edge of a pulse signal having a cycle corresponding to a state of an object to be measured to perform cycle measurement, and a driving section for outputting a drive signal according to a measured value of the cycle measuring section. , A meter for displaying the state according to the drive signal of the drive unit, until the measured value reaches a predetermined value at each detection of at least one of the rising edge and the falling edge of the pulse signal, A device for driving a measuring instrument, comprising a mask section for suppressing the input of the pulse signal to the cycle measuring section. 2. The cycle measuring section has a cycle counter for counting the pulse signals, and the mask section has a judging section for judging whether or not a measured value of the cycle counter section is larger than a predetermined value. However, when the measured value is smaller than the predetermined value, the input measuring section has an input suppressing section for suppressing the input of the pulse signal to the period measuring section.
The driving device for the measuring instrument according to.