JP3473438B2 - Speed measuring device and its abnormality monitoring circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a circuit for monitoring a rotational speed of a rotating body such as a generator or an abnormality of a measuring device of a moving body such as a machine tool. It is about. 2. Description of the Related Art In a generator or other rotating machine or a moving body, a detector for detecting the rotating speed or speed of the generator,
A conversion circuit for converting this detection signal (both are referred to as a speed measuring device) is widely used. Hereinafter, a description will be given of a rotating machine as an example, but the same applies to a moving body. Since the speed signal of the rotation speed is often used for feedback control of the speed of the rotating machine, an abnormality in its detection is extremely significant and dangerous, so a circuit that monitors the operation of the rotation speed measurement device has conventionally been used. Various proposals have been made. FIG. 9 is a configuration diagram showing a conventional rotation speed measuring device similar to that disclosed in Japanese Patent Publication No. 7-69196 and an abnormality monitoring circuit for monitoring the device for abnormalities. In the figure, reference numeral 1 denotes a rotating body whose rotation speed is to be detected, such as a gear made of a ferromagnetic material for measuring a running speed of a vehicle. Reference numeral 2 denotes a rotational speed detector (also referred to as a detector) that detects a change in magnetic flux density due to gear displacement by using an electromagnetic pickup type sensor having an inductance (L) component, and detects, for example, an AC frequency or a pulse train proportional to the rotational speed. Is what happens. Reference numeral 3 denotes a signal processing circuit for calculating (converting to an analog signal or a digital signal) an output from the rotation speed detector 2 and outputting a speed signal 60. The signal processing circuit 3 includes a current application circuit 6 including switching means S for supplying / cutting a DC current to the detector 2 and a comparator 4 having a noise filter 13.
1 and a threshold value setting means 44 for processing the signal from the detector 2 according to the level of the threshold value, and monitoring the output of the detector signal conversion circuit 4 The signal processing circuit 3 includes an abnormality determination processing circuit 5 that determines whether the operating state of the entire signal processing circuit 3 is correct or not. The switching means S and the detector 2 are configured such that when the current supply to the detector 2 is stopped by the switching means S, a reverse voltage that generates a voltage having a polarity opposite to that at the time of the current supply due to the action of the inductance component of the detector 2. It constitutes a generating circuit. Next, the operation will be described. During the detection of the rotation speed, the AC or pulse signal output from the rotation speed detector 2 passes through the noise filter 13 and then is output from the comparator 4.
Formatted as 1. The shaped pulse signal is represented by f (not shown).
The signal is converted into a voltage signal proportional to the rotation speed by a / v conversion circuit (at the time of analog processing), or is converted into numerical data corresponding to the rotation speed by a counter circuit (at the time of digital processing) not shown. Since the rotation speed detector 2 has a large inductance (L), when a DC current is supplied from the current application circuit 6 to the inductance (L) component, and then the current is cut off, the polarity is inverted at both ends of the inductance. It has the property of generating a voltage. Therefore, when the rotation speed is not detected or when the rotation speed is detected, the operation is temporarily stopped, the power supply is once connected by the switching means S of the current application circuit 6, and then the power supply is cut off. At this time, if the output value of the comparator 41 is inverted (if the signal generated at both ends of the coil of the detector 2 exceeds a preset threshold value for validity determination), the abnormality determination processing circuit 5 determines that the abnormality is normal. If the polarity is not reversed when the current is cut off by the switching means S, it is determined that an abnormality has occurred (disconnection of the coil or wiring, short circuit, or malfunction of the comparator). After determining that the rotation speed is normal, the rotation speed is detected again. Naturally, the rotation speed cannot be detected during this determination. Since the detector signal conversion circuit 4 can be constituted by a computer, a controller, or the like, these other methods are collectively called detector signal processing means. The abnormality monitoring circuit of the conventional speed measuring apparatus is constituted as described above. The detector signal processing means performs the speed detection processing and the detector and signal processing means. Since the time when the abnormality of the circuit is determined is differently used in time (batch processing), the speed measurement and the abnormality determination process cannot be performed simultaneously. Therefore, the abnormality determination process is always performed. There was a problem that I could not do things. Also, since it is not always possible to determine the abnormality,
There has been a problem that it may take a long time from the occurrence of the abnormality to the detection of the abnormality. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is possible to simultaneously determine the abnormality of the detector and the signal processing circuit while measuring the speed, that is, always monitor the abnormality. It is an object of the present invention to obtain a speed measuring device and an abnormality monitoring circuit thereof. It is another object of the present invention to provide an abnormality monitoring circuit in which the time from occurrence of an abnormality to detection is short. An abnormality monitoring circuit for a speed measuring apparatus according to the present invention comprises: a detector having a coil for generating an AC frequency signal or a pulse train signal by moving a moving body; speed and a speed calculation means for converting the signal to an analog or digital speed signal
An abnormality monitoring circuit that monitors an abnormality of the measuring device, comprising: acceleration calculating means for calculating an acceleration signal from the speed signal output by the speed measuring device; and comparing the acceleration signal with a predetermined maximum acceleration of the moving body. possess an acceleration abnormality determination means for, the maximum acceleration is the movement of the movable body
It is a function of the speed of the body . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a moving body speed measuring apparatus and an abnormality monitoring circuit according to a first embodiment of the present invention will be described with reference to the drawings. The mechanical device to which the present invention is applied is not limited to a rotating body but is intended for a moving body in general. However, for convenience of explanation, the embodiment will be described by measuring the rotating speed of the rotating body as an example. FIG. 1 is a configuration diagram of a rotation speed measuring device and its abnormality monitoring circuit. Reference numeral 1 denotes a rotating body whose rotation speed is to be detected, such as a gear made of a ferromagnetic material for measuring a running speed of a vehicle. It is. Reference numeral 2 denotes a rotation speed detector (speed detector) that detects a change in magnetic flux density due to gear displacement using an electromagnetic pickup type sensor having an inductance (L) component, and for example, an AC frequency or a pulse train that changes according to the rotation speed. Is caused. Reference numeral 41 denotes a comparator for shaping the waveform of the AC frequency or pulse train signal from the detector 2. Reference numeral 42 denotes a rotational speed calculating circuit for analog or digitally processing the shaped signal output from the comparator 41 and outputting a speed signal 60. (Rotation speed calculation means). Reference numeral 9 denotes a rotation speed measurement device (speed measurement device) including the rotation speed detector 2, a comparator 41, and a rotation speed calculation circuit. However, the comparator 41 is necessary for ensuring the operation of the rotation speed calculation circuit 42 and obtaining a stable signal output up to a low speed, and is not always necessary depending on the specification of the rotation speed range to be measured. Reference numeral 50 denotes an abnormality monitoring circuit, which performs time differentiation processing on the speed signal 60 (same as the output of the rotation speed calculation circuit 42) of the rotation speed measuring device 9 to reduce the rotation acceleration (hereinafter referred to as acceleration in the present invention). A rotation acceleration calculation circuit 51 (acceleration calculation means) for calculating the acceleration signal (including speed) and an acceleration abnormality determination circuit 52 (acceleration abnormality determination means) for determining whether or not the acceleration signal is correct. Reference numeral 61 denotes an abnormality notification signal output from the acceleration abnormality determination circuit 52. The acceleration abnormality determination circuit 52 is a comparison circuit that determines whether the absolute value of the acceleration signal is within a predetermined range (Amax). Next, the operation will be described. The rotating body 1 rotates, and an alternating current or a pulse signal having a frequency proportional to the rotation speed is output from the rotation speed detector 2. The comparator 42 shapes the pulse waveform into a more complete pulse waveform (the pulse peak value does not fluctuate with the rotation speed). The rotation speed calculation circuit 42 counts the number of pulses per unit time, calculates the rotation speed of the rotating body 1 and outputs it as an analog voltage signal (or digital data signal) 60. The rotation acceleration calculation circuit 51 calculates the absolute value A of acceleration (including the deceleration as described above), which is a change in the speed signal per unit time. By the way, the maximum value Amax of the acceleration (deceleration) of all the rotating machines (the same applies to the moving machines) can be known in advance by the weight, the maximum power of the driving device, the torque applied from the outside, and the like. Speed signal 6
When 0 is output, one of the detector 2, the signal line of the detector 2, the comparator 41, and the rotation speed calculation circuit 42, that is, any one of the components of the rotation speed measurement device 9 is disconnected, short-circuited, failed, or the like. In most cases, since the absolute value A of the acceleration signal exceeds Amax, the acceleration abnormality determination circuit 52 can determine the abnormality of the rotation speed measuring device 9. The rotation speed measuring device 9 and its abnormality monitoring circuit 50 shown in FIG. 1 can determine whether the rotation speed measuring device 9 including the rotation speed detector 2 is normal or abnormal while measuring the rotation speed. it can. In addition, since the monitoring is always performed while the speed signal 60 is being output, the detection is not delayed when an abnormality occurs. Embodiment 2 FIG. In the description of FIG. 1 of the first embodiment, the predetermined upper limit value Amax of the acceleration does not necessarily have to be a constant value. FIG. 2 shows an example of the maximum acceleration in a normal state of the rotating machine. In the range of forward rotation + N and reverse rotation -N,
It indicates the maximum acceleration and the maximum deceleration. Generally, the acceleration / deceleration increases as the speed decreases. FIG. 3 shows a circuit configuration for operating the acceleration abnormality determination means 52 using such a curve as Amax. However, FIG. 3 shows only a part, and parts not shown are the same as those in FIG. In FIG. 3, reference numeral 40 denotes a function Amax shown in FIG.
Since this type of circuit technology is well known, a detailed description thereof will be omitted. By making the maximum acceleration more accurately matched to the actual machine by the function generating circuit 40,
Normal / abnormal discrimination can be performed more accurately. Embodiment 3 FIG. FIG. 4 shows the configuration of another method for monitoring the acceleration / deceleration, and FIG. 5 is a time chart for explaining the operation of FIG. In the figure, reference numeral 54 denotes a time interval tn (period) of each pulse of the output pulse train of the comparator 41
Is a cycle time change calculation circuit that constantly measures the acceleration and deceleration from the change in the time interval. This operation is shown in FIG.
This will be described in more detail. FIG.
, And the instantaneous rotation speed at the moment when each pulse is output is represented by N1, N2,... Nn (of course, N cannot be measured at that moment). The time interval between each pulse is represented by t1, t2,... Tn shown in the figure. At this time, between n and t, tn ≒ 1 / N, on the assumption that the physical distance between one pulse generation position and the next pulse generation position is the same for all pulses.
The relationship n is established. The acceleration at the moment when the rotation speed changes from N (n-1) to N (n) is acceleration = {(N (n) -N (n-1))} / (tn).
By transforming this, acceleration = {t (n-1)-t (n)} / {(t (n) ² · t (n-1)} That is, if the pulse time interval is measured, the acceleration can be calculated. The cycle time change calculation circuit 54 executes the calculation of the above equation for each pulse, and can calculate the instantaneous acceleration for each pulse, and the acceleration abnormality determination circuit 52 constantly monitors this acceleration and compares it with Amax. In the above description, the time between each pulse is measured, but it is obvious that the measurement may be performed every two pulses or every ten pulses depending on the capability of the computer used. According to the method, the acceleration is measured without passing through the rotation speed calculation circuit 42. Therefore, the abnormality of the rotation speed calculation circuit 42 cannot be detected. The effect of speeding up is obtained. The embodiment 4. Figure 6 is a diagram showing a rotational speed measuring device and the abnormality detecting circuit of the fourth embodiment of the present invention. 1 rotator in FIG, 2 is the rotational speed detector, 9
Is a rotation speed measuring device, and 59 is an abnormality monitoring circuit. FIG.
The same reference numerals denote the same or similar components, and a detailed description thereof will be omitted. The rotation speed measuring device 9 includes a DC cut filter 43 for cutting a DC component from a signal of the detector 2.
(A capacitor c1 and a resistor R2). An abnormality monitoring circuit 59 detects a current application circuit 6 including a resistor R1 connected to a detector disconnection detection power supply Vf, a constant current diode 16 connected to the resistor R1, and an output of the current application circuit 6. A current monitoring circuit 7 having a photocoupler 71 applied to a coil of the photocoupler 2 and comprising an output of the photocoupler 71 and a pull-up resistor R3 connected to a power supply Vp; A detector disconnection determination circuit 55 (detector disconnection determination means) that outputs an abnormality notification signal 61 if there is an abnormality upon monitoring. The operation of FIG. 6 will be described with reference to FIG. FIG. 7 shows the waveforms at points a and b in the rotation measuring device 9 of FIG. 6, the waveform at point c of the abnormality monitoring circuit 59, and the waveform at the output of the DC filter 43. FIG. The voltage waveform at point a in FIG. 6 and b in FIG.
7C shows the output waveform of the comparator 41 at the point, and FIG. 7C shows the output waveform of the current monitoring circuit 7 at the point c. The filter waveform is the output waveform of the DC filter 43. The rotation speed of the rotating body 1 causes the rotation speed detector 2 to output the detector output shown in FIG. 7A. The detector 2 is always supplied with a weak DC current from the current application circuit 6,
This direct current is superimposed on the output of the detector 2,
The DC component is cut by the filter 43 (differentiated and the phase advances by 90 degrees) and input to the comparator 41. b
The voltage at the point becomes the maximum value of the output of the comparator 41 when the voltage after the DC filter 43 exceeds zero, and becomes the minimum value when it falls below zero. Although not shown, the comparator 41
Is desirably provided with a threshold setting means. The rotation speed calculation circuit 42 calculates the rotation speed by counting the number of comparator output pulses per unit time. The voltage at the point c is a monitoring voltage Vw (see FIG. 5) in which the output voltage of the detector 2 is determined by the voltage Vf of the power supply for detecting detector disconnection and the drop voltage of the resistor R1, the constant current diode 16, the photocoupler 71 and the like. 7a), the current of the photocoupler 71 becomes a sufficient level to turn on the photocoupler 71, and the voltage at the point c becomes the ground level. When the detector output voltage exceeds the voltage Vw, the photocoupler 71 turns off, and the voltage at the point c becomes the pull-up voltage Vp.
Becomes In the case where the detector 2 is of an electromagnetic pickup type having a configuration as shown in the figure, the output voltage decreases as the rotation speed of the rotating body 1 decreases. Maintain the ground level. If the detector 2 is disconnected at time T in FIG. 7, the current applying circuit 6 charges the capacitor c1 of the DC filter 43, and when the voltage at point a rises and reaches Vw, the photocoupler 71 Is turned off, and the voltage at the point c rises to the pull-up voltage. The waveform at the output point b of the comparator 41 becomes maximum immediately after the time T, but soon the comparator 4
Since there is no input to 1, the level is corresponding to this. (In general, it is unclear whether the output of the comparator becomes high or low due to the influence of temperature drift or the like for an input whose level is close to the input level at which the output is inverted.) 55 indicates that the detector 2 is normal while the voltage at the point c is a pulse wave that minimizes and maximizes the ground level and the pull-up voltage Vp.
If the time to reach the p level is longer than the preset time, it is determined that the wire is broken. Here, the predetermined time is a time slightly longer than the longest time in which the voltage at the point c is held at the pull-up level by the output of the detector 2 at the slowest rotational speed. Since the voltage at the point c is at the ground level during the rotation stop, no erroneous alarm is issued. Then, even if the rotation is stopped, it can be detected if a disconnection occurs. As described above, the abnormality determination circuit 59 shown in FIG. 6 includes the current application circuit 6 which constantly supplies a current to the detector 2, the current monitoring circuit 7 which monitors the current, and the detector disconnection determination circuit 55.
Is provided, the measurement of the rotational speed and the determination of the detector abnormality can be executed simultaneously, and the abnormality of the detector can be monitored regardless of the magnitude of the rotational speed, so that the reliability is high. In addition,
The constant current diode 16 can be replaced with a resistor, a constant current control circuit, or a choke coil, and the photocoupler 71 can be replaced with a known current detection circuit. Embodiment 5 FIG. FIG. 8 shows a case where the acceleration of the signal in the first embodiment (FIG. 1) is monitored, and a case where the acceleration in the fourth embodiment is used.
The monitoring of the direct current flowing to the detector shown in FIG. 6 was performed at the same time. 6 can be monitored irrespective of the speed level at that time, but it is necessary to wait for a predetermined time before determining that the wire is broken. On the other hand, in the case of FIG. 1, if the acceleration signal deviates from the range of FIG. 2, it can be immediately determined that there is an abnormality. In this respect, each has advantages and disadvantages, but by providing both as shown in FIG. 8, it is possible to cover these disadvantages. In the above description, the target machine is a rotating body, and the speed is the rotation speed. However, for example, a linear motion pulse obtained from a ground gear such as a rack gear of a machine tool or a linear motor car is used. It is obvious that the present invention can be applied to a device for measuring a linear velocity based on the above. In this case, the rotation speed detector 2 described in each embodiment is a speed detector, the rotation speed measurement device 9 is a speed measurement device, the rotation speed calculation circuit 42 is a speed calculation circuit (speed calculation means), and the rotation acceleration calculation circuit 51. Is appropriately read as an acceleration calculation circuit (acceleration calculation means). Also,
It is clear that all the hardwired circuits shown in the embodiments described above can be replaced with intelligent systems using computers and controllers. [0037] [0038] [Effect of the Invention] Since the abnormality monitoring circuit monitors the acceleration of the speed signal output to the invention, can also monitor an abnormality in the rotational speed calculating means well anomaly detector The effect is obtained. Further, in monitoring the acceleration, the maximum acceleration to be compared is treated as a function of the speed, so that the abnormality can be monitored accurately. [0040]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a rotation measuring device and an abnormality monitoring circuit thereof according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating an operation of a function generating circuit according to a second embodiment. FIG. 3 is a configuration diagram of an abnormality monitoring circuit according to a second embodiment. FIG. 4 is a configuration diagram of an abnormality monitoring circuit according to a third embodiment; FIG. 5 is a timing chart illustrating the operation of FIG. FIG. 6 is a configuration diagram of a rotation speed measuring device and an abnormality monitoring circuit thereof according to a fourth embodiment. FIG. 7 is a timing chart illustrating the operation of FIG. FIG. 8 is a configuration diagram of a rotation speed measuring device and an abnormality monitoring circuit thereof according to a fifth embodiment. FIG. 9 is a configuration diagram of a conventional rotation speed measuring device and an abnormality monitoring circuit thereof. [Description of Signs] 1 rotating body, 2 rotating speed detector (speed detector), 6 current applying circuit (current applying means),
7 current monitoring circuit (current monitoring means), 9 rotation speed measuring device, 16 constant current diode, 40 function generation circuit, 41 comparator, 42 rotation speed calculation circuit (speed calculation means), 43 DC filter, 5
0 abnormality monitoring circuit, 51 rotation acceleration calculation circuit (acceleration calculation means), 52 acceleration abnormality determination circuit (acceleration abnormality determination means), 54 cycle time change calculation circuit (cycle time change calculation means), 55 detector disconnection determination circuit (detection) Disconnection determining means), 60 speed signal, 61
Error notification signal, 71 photocoupler

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seigo Kadota 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (56) References JP-A-5-133962 (JP, A) JP-A Heisei 7-306216 (JP, A) JP-A-4-58110 (JP, A) JP-A-4-203969 (JP, A) JP-A-10-206460 (JP, A) JP-A-11-83895 (JP, A A) JP-A-5-172836 (JP, A) JP-A-59-38659 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 3/42 G01P 3/48-3 / 481 G01P 21/02

Claims (1)

(57) converting the Patent Claims 1. A detector having a coil for generating a result AC frequency signal or pulse train signal to the movement of the movable body, the AC or a pulse train signal to an analog or digital speed signal Speed measuring device having speed calculating means
An abnormality monitoring circuit that monitors an abnormality of the acceleration measuring means for calculating an acceleration signal from the velocity signal output by the velocity measuring device; and an acceleration for comparing the acceleration signal with a predetermined maximum acceleration of the moving body. possess the abnormality judgment means, the maximum acceleration of the moving body function der velocity of the moving body
An abnormality monitoring circuit characterized by: