JP2719817B2 - Digital tachometer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital tachometer that measures the number of rotations of various rotating bodies such as motors and gears and digitally displays the values.

<Prior Art> A conventional digital tachometer has, for example, a configuration shown in FIG.

In the figure, a is a rotation detector such as a rotary encoder that outputs a rotation pulse corresponding to a rotation speed of a rotating body (not shown) such as a motor, and b is a rotation pulse counter that counts rotation pulses from the rotation detector a. , C is a rotation speed calculation unit for calculating the rotation speed per unit time based on the count value of the rotation pulse counter b, d is a display made of LEDs or the like for displaying the calculation result of the rotation speed calculation unit c, e is A timer for regulating the count time of the rotation pulse counter b, and f is an AND gate for inputting both the output of the timer e and the rotation pulse.

In digital tachometers the above configuration, the rotation detector a, as shown in FIG. 5, the rotation pulse P ₀ corresponding to the rotation speed of the rotating body is output. The rotation pulse P ₀ is counted by the rotation pulse counter b. On the other hand, timer e
Is a high-level pulse having a reference time T ₀ (which is set to, for example, 1.0 sec in consideration of the display update time) triggered by the input of one rotation pulse passing through the AND gate f. Output a signal. The output of the timer e is applied to one inverting input terminal of the AND gate f. The other input terminal of the AND gate f is supplied with a rotation pulse from the rotation detector a. Therefore, after the output of the timer e has timed out and becomes low level, when the first rotation pulse is applied, this rotation pulse passes through the AND gate f. Then, the timer e the rotational pulse as the display change pulse P ₁
While given by the set the timer e, the display change pulse P ₁ is given respectively to the rotational speed calculating section c and the rotation pulse counter b. In response, the rotation pulse counter b is reset, while the rotation speed calculation unit c
The count value of the rotation pulse counter b is captured. Therefore, in the rotation speed calculating section c, the timer e is provided with the display change pulse.
The period T from the setting of P ₁ to the rising timing of the first rotation pulse after the elapse of the reference time T ₀
At (= T ₀ + Tαsec), the count value counted by the rotation pulse counter b is fetched. Then, the rotation speed calculation unit c calculates the rotation speed N per unit time by the following equation based on the count value.

N (rpm) = 60 × (n / A) / T (1) where T is the count time of the rotation pulse counter b,
n is a count value counted during the count time T, A
Is the number of pulses per rotation of the rotating body output from the rotation detector a.

Then, the calculation result of the rotation speed calculation unit c is given to the display d at the next stage. In this case, the rotation speed calculation unit c may, until the operation result is updated by the display update pulse P ₁ is maintains the output content. Thus, the display content of the display d is updated in a time-division manner every count time T (= T ₀ + Tαsec).

<Problem to be Solved by the Invention> As described above, after the reference time T ₀ has elapsed, the rotation speed calculation unit c waits for the next rising timing of the rotation pulse, and then resets the count value of the rotation pulse counter b. The reason for taking in is that the calculation result is inaccurate unless the count value is taken as an integer and the time T between the count values is not measured in the calculation of the rotational speed based on the equation (1).

However, those having such a configuration have the following problems.

That is, when an AC servomotor used in a machine tool or the like is program-controlled, the motor may be suddenly decelerated or suddenly stopped. In such a case, the next rotation pulse after a reference time T ₀ Do not input for a long time, or not at all input next rotation pulse. Then, the display change pulse P ₁ from the AND gate f along with this is not output, the rotation speed calculation unit c can not computing the revolution speed takes in the count value of the rotation pulse counter b. For this reason, the display content of the display device d is not updated for a long time. As a result, a problem arises in that the high-speed rotation speed remains displayed on the display d even though the motor has actually stopped.

In order to improve this, in the related art, the presence or absence of a rotation pulse is detected, and the rotation pulse is supplied for a predetermined time (for example, 6 seconds).
If the input is not continued during the period, the display d
Is set to "0". However, even in this case, the high-speed rotation speed is displayed for a period of time until the display content becomes "0", so that responsiveness is lacking. In addition, it is not natural that the display rapidly changes to "0" from the point where the high-speed rotation is displayed.

Further, in the prior art, as shown in FIG. 6, a constant attenuation curve S is set in advance, and when a rotation pulse is not continuously input for a predetermined time (for example, for 0.25 sec), this attenuation curve S is set. In some cases, the display content of the number of revolutions is sequentially changed along a curve S. However, as long as this damping curve S is followed, there is no consideration at all at what rate the actual number of revolutions will decrease. Until later, it does not become almost "0", and as a result, there is a disadvantage that the responsiveness of the digital display is still lacking.

The present invention has been made in view of such circumstances, and when the rotating object to be measured is suddenly decelerated and suddenly stopped and the rotation pulse is not input for a predetermined time, the actual rotation speed is reduced. Predict the rate at which the speed will decrease, and calculate the number of revolutions based on the prediction, so that the display content is sequentially updated in accordance with the change in the number of revolutions, and the true It is an object of the present invention to be able to display a content similar to a number change.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a rotation detector that outputs a rotation pulse corresponding to the rotation speed of a rotating body,
A rotation pulse counter that counts rotation pulses from the rotation detector, a rotation number calculator that calculates the number of rotations per unit time based on the count value of the rotation pulse counter, and a calculation result of the rotation number calculator. The following configuration is adopted in a digital tachometer having a display for displaying.

That is, in the digital tachometer of the present invention, a rotation pulse detection unit that detects the presence or absence of a rotation pulse from the rotation detector and outputs a rotation pulse stop detection signal after a lapse of a predetermined time from the stop of the rotation pulse, In response to the rotation pulse stop detection signal from the rotation pulse detection unit, the rotation number immediately before the stop of the rotation pulse obtained by the rotation number calculation unit is input, and based on this rotation number and a preset reference rotation number. A predictive gradient determining unit that determines a predictive gradient of a decrease in the rotational speed, and a predictive calculating unit that calculates the rotational speed according to a rotational speed decrease curve having the predictive gradient determined by the predictive gradient determining unit.

<Operation> According to the above configuration, if the rotation pulse is not output from the rotation detector for a predetermined time due to the sudden stop of the rotating body, this is detected by the rotation pulse detection unit, and the rotation pulse stop detection signal is output. You. In response to the rotation pulse stop detection signal, the predicted gradient determination unit inputs the rotation number immediately before the stop of the rotation pulse obtained by the rotation number calculation unit,
Based on the rotation speed and a preset reference rotation speed, a predicted gradient of the rotation speed decrease is determined. Since the value of the prediction gradient is given to the prediction calculation unit, the prediction calculation unit calculates the rotation speed at every elapse of a predetermined time according to the rotation speed decrease curve having the prediction gradient. Then, the calculation result of the prediction calculation unit is output to the display.

In this way, the prediction gradient determination unit and the prediction calculation unit predict how much the actual rotational speed will decrease,
Since the rotational speed is calculated based on the prediction, the display contents are sequentially updated in a manner following the change in the actual rotational speed.

<Embodiment> FIG. 1 is a block diagram showing a configuration of a digital tachometer according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an entire digital tachometer, and 2 denotes a rotation detector which outputs a rotation pulse corresponding to a rotation speed of a rotating body (not shown) such as a motor, a gear, a pulley, and is, for example, a rotary encoder. , Magnetic sensors, photoelectric switches, and the like. Reference numeral 4 denotes a rotation pulse counter that counts rotation pulses from the rotation detector 2, 6 denotes a rotation speed calculation unit that calculates the rotation speed per unit time based on the count value of the rotation pulse counter 4, and 8 denotes a rotation speed calculation unit 6. Display the calculation result of
An indicator made of an LED or the like, 10 is a timer for regulating the count time T (1.0 sec in this example) of the rotation pulse counter 4, and 12 is both the output of the timer 10 and the rotation pulse from the rotation detector 2. These are AND gates for inputting, and their configurations are the same as in the conventional example.

14 detects the presence or absence of a rotation pulse from the rotation detector 2,
A predetermined time after the rotation pulse stops (0.25se in this example)
c) A rotation pulse detection unit that outputs a rotation pulse stop detection signal after a lapse of time. Reference numeral 16 denotes a reference rotation speed register unit in which a reference rotation speed (240 rpm in this example) is set in advance. This reference rotation speed is determined in consideration of the number of pulses per unit time that can be detected by the rotation detector 2. For example, if 0.25 sec is the minimum detection time as one pulse per rotation, the minimum rotation that can be measured is The number is (1 pulse / 0.25 sec) × 60 = 240 rpm. Reference numeral 18 denotes the number of rotations immediately before the stop of the rotation pulse obtained by the rotation number calculator 6 in response to the rotation pulse stop detection signal from the rotation pulse detector 14, and this rotation number and the reference rotation number register 16 A prediction gradient determining unit that determines a predicted gradient of a decrease in the rotational speed based on the reference rotational speed of the engine; It is an operation unit.

Next, regarding the digital tachometer 1 having the above configuration,
The control operation when the rotating body such as the motor is suddenly stopped will be described with reference to the flowchart shown in FIG.

When the rotating body is suddenly stopped, no rotation pulse is output from the rotation detector 2. The rotation pulse detector 14 outputs a rotation pulse stop detection signal when the rotation pulse is not input for a predetermined time (0.25 sec in this example). The rotation pulse stop detection signal is provided to the rotation speed calculation unit 6, the reference rotation speed register unit 16, and the prediction calculation unit 20, respectively.

In response to the rotation pulse stop detection signal, data of the reference rotation speed M (240 rpm in this example) is read from the reference rotation speed register unit 16 and supplied to the prediction gradient determination unit 18 and the prediction calculation unit 20, respectively. . Further, the number of revolutions L (hereinafter, referred to as the immediately preceding number of revolutions) L obtained immediately before the stop of the rotation pulse is read from the number of revolutions calculating section 6 and sent to the prediction gradient determining section 18 and the predicting computation section 20, respectively.

Upon receiving the rotation pulse stop detection signal from the rotation pulse detection unit 14, the prediction calculation unit 20
The immediately preceding rotation speed L is compared with the reference rotation speed M (step). If the immediately preceding rotation speed L is larger than the reference rotation speed M, the prediction gradient K is set to 1 and M / K is calculated. The calculation result M is output as display data D. Therefore,
First, the data of the reference rotation speed M (= 240 rpm) given by the reference rotation speed register unit 16 is directly output from the prediction calculation unit 20, and is supplied to the display 8. Thus, the reference rotation speed (240 rpm) is displayed on the display 8 0.25 sec after the stop of the rotation pulse (step). The display data D is fed back to the prediction calculation unit 20 and input again (step).

On the other hand, when both the immediately preceding rotation speed L and the reference rotation speed M are input (step), the predicted gradient determining unit 18 determines the predicted gradient K of the reduced rotation speed based on both data as shown in FIG. = L / M is determined (step). In this case, the gradient K
Increases as the immediately preceding rotational speed L increases. This is because the time (0.25 sec) for gradient determination K is constant.
The reason why no pulse is input during that time is that it can be considered that the larger the immediately preceding rotation number L, the faster the speed is reduced. Then, the data of the prediction gradient K is sent to the prediction calculation unit 20. In the step, if the immediately preceding rotation speed L is already smaller than the reference rotation speed M, the following prediction calculation is not performed.

Next, when both data of the reference rotation speed M and the prediction gradient K are input, the prediction calculation unit 20 changes the rotation speed according to the rotation speed decreasing curve having the prediction gradient K for a certain period of time as shown in FIG. It is calculated every 0.25 seconds in this example. That is, the prediction calculation unit 20 first calculates D (= M) / K from both data of the reference rotation speed M and the prediction gradient K, and calculates this as the display data D.
(Step). Then, the display data D is compared with the minimum rotation speed MIN at which the calculation is terminated (step). If the display data D is larger than the minimum rotation speed MIN, the display data D is output to the display 8 (step). The display data D is fed back to the prediction calculation unit 20 and input (step). Subsequently, the prediction operation unit 20 executes Steps 1 to 2 again after 0.25 seconds. In this case, the prediction calculation unit 20 keeps the output content until the next calculation result is obtained. Therefore, the display content of the display 8 is updated every 0.25 seconds.

Then, in the step, when the display data D becomes smaller than the minimum rotation speed MIN of the operation termination, the prediction calculation unit 20 forcibly sets the display data D to 0,
This is output to the display 8 ().

Therefore, for example, when the immediately preceding rotation speed is 1000 rpm and the minimum operation rotation speed MIN is 5 rpm, the display content of the display 8 is 240 rpm after 0.25 sec, 58 rpm after 0.5 sec, and 0.
It becomes 14 rpm after 75 sec and 0 rpm after 1.0 sec.

As described above, when the rotating body to be measured is rapidly decelerated and suddenly stopped, and the rotation pulse is not input for a predetermined time, the actual rotation speed is determined by the prediction gradient determination unit 18 and the prediction calculation unit 20. Since it is predicted whether the vehicle will decelerate at a rate of about a degree, and the rotation speed is calculated based on the prediction, the display contents are sequentially updated in a manner following the change in the actual rotation speed.

<Effect of the Invention> According to the present invention, even when the rotating body is suddenly stopped, the display contents are sequentially updated in a manner following the change in the number of rotations. Therefore, excellent effects such as the fact that the content approximate to the true change in the number of revolutions is displayed in real time are exhibited.

[Brief description of the drawings]

1 to 3 relate to an embodiment of the present invention. FIG. 1 is a block diagram showing the configuration of a digital tachometer of the present invention.
FIG. 3 is a flowchart for explaining the operation of the digital tachometer of FIG. 1, and FIG. 3 is an explanatory diagram of a prediction calculation of a decrease in the number of revolutions. 4 to 6 relate to a conventional example, FIG. 4 is a block diagram of a digital tachometer, FIG. 5 is a time chart of a rotation pulse obtained by a rotation detector, and FIG. 6 is an explanatory diagram of a decay curve. is there. 1 ... digital tachometer, 2 ... rotation detector, 4 ... rotation pulse counter, 6 ... rotation speed calculator, 8 ... display
14 ... Rotation pulse detector, 18 ... Predicted gradient determiner, 20 ...
... Prediction calculation unit.

Claims (1)

(57) [Claims] 1. A rotation detector for outputting a rotation pulse corresponding to the rotation speed of a rotating body, a rotation pulse counter for counting rotation pulses from the rotation detector, and a unit based on a count value of the rotation pulse counter. In a digital tachometer including a rotation speed calculation unit that calculates the rotation speed per time, and a display that displays the calculation result of the rotation speed calculation unit, detecting the presence or absence of a rotation pulse from the rotation detector, A rotation pulse detection unit that outputs a rotation pulse stop detection signal after a predetermined time has elapsed after the rotation pulse stops, and a rotation pulse calculation unit that is obtained in response to the rotation pulse stop detection signal from the rotation pulse detection unit. A rotation speed immediately before the stop of the rotation pulse, and a prediction gradient determination unit that determines a prediction gradient of the rotation speed decrease based on the rotation speed and a preset reference rotation speed, Digital tachometer, characterized in that it comprises a prediction calculation section for calculating the rotational speed as the rotational speed decreases curve with a prediction slope determined by the prediction gradient determination unit.