JPH1125375A - Monitoring device for dc motor and monitoring method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitoring device of a DC motor and a monitoring method for the same that detects deterioration of brushes of the DC motor and that gives an alarm indicative of adverse effects such as a rotation stop or the like of the electric caused by brush wear before the motor stop. SOLUTION: This device detects a point in which a current changes at the time when brushes 7c and 7d, which are in sliding contact with a commutator segment 2 of an armature 1 of a DC motor, are simultaneously in sliding contact with communicator segments 8 (8a, 8b, 8c...) the commutator segment 2 is adjacent to. A time period for this current change varies because a contact points becomes longer from a point contact to circular arc contact by a wear of sliding surfaces of brushes 7c and 7d. Thus, accumulated time periods for the current change is compared to a ratio of a time period for current change per unit revolution of the armature, so as to determine a wear limitation of brushes 7c and 7d of the DC electric 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording / reproducing apparatus,
The present invention relates to a monitoring device and a monitoring method for a DC motor used in a carrier recording / reproducing device and the like. The present invention relates to a monitoring device for a DC motor and a monitoring method for performing a warning or display when worn out.

[0002]

2. Description of the Related Art Conventionally, when a brush contacting a commutator of a DC motor gradually wears and is worn to near its limit, it becomes inoperable. In order to avoid the problem of damaging the commutator, for example, in Japanese Patent Application Laid-Open No. Hei 1-311848, when the brush contacting the commutator wears to a predetermined position, the contact length of the brush in the rotational direction of the commutator is changed. For this purpose, there is disclosed a brush having a wide portion formed on an upper portion of the brush.

That is, as shown in FIG. 8, a commutator (commutator) 2 fitted to a rotating shaft (5) of an armature (amateur) 1 of a DC motor includes a plurality of commutator pieces (segments) as shown in FIG. 3, 3 'is formed in a cylindrical shape with insulators 4, 4' interposed therebetween. The brush 7 is configured to be slid in the circumferential direction of the commutator 2 via the ridge.

The above-mentioned brush 7 formed of carbon or the like has a wide portion 7b in the rotation direction CW of the commutator 2 on the side (upper side) in which the connection line (pigtail) 6 is embedded. Is in sliding contact with the commutator 2 at the width sandwiching portion 7a, and the contact area is small. However, after the brush 7 is worn by L in the height direction due to use, the brush 7 contacts the wide portion 7b of the brush 7 and the contact area is small. As the load current I increases, the characteristic curve of the load current I versus the output torque T of the DC motor moves in parallel so that the load current I increases, and the characteristic curve of the load current I versus the rotation speed N has a gradient such that the load current I decreases. To change.

Therefore, such a change is detected and the brush 7 is detected.
It is configured to detect the abrasion state of the.

Further, Japanese Patent Application Laid-Open No. 6-141513 discloses a monitoring device which monitors the wear amount of the brush 7 as a parameter based on the current or the rotation speed supplied from the armature 1 to the brush 7. .

That is, the above-mentioned Japanese Patent Laid-Open Publication No. Hei 6-141513 is configured as shown in FIG. In FIG. 9, a voltage is applied to the armature 1 of the DC motor from the battery 12 via one brush 7, and the other brush 7 is connected to the drain of a field effect transistor (MOS-Tr) 13,
A current detector 14 is connected between the source of the Tr 13 and the ground, and a detection output 14a of the current detector 14 such as a resistor is connected to a microcomputer (hereinafter referred to as a CPU) via an analog-digital (A / D) converter 15. It is supplied to 16 input ports. Further, a voltage detector 17 such as a bridge circuit is connected in parallel with the armature 1, and a detection output 17 a of the voltage detector 17 is supplied to an input port of the CPU 16 via an A / D converter 18. On the other hand, the CPU 16 reads the detection values of the current detector 14 or the voltage detector 17 and calculates the number of revolutions based on these detection values.
The wear amount per unit time is accumulated based on the current data versus the wear amount characteristic data and the rotation speed versus the wear amount characteristic data stored in the memory such as the OM.

The CPU 16 issues a warning signal when the accumulated amount of wear of the brush 7 exceeds a predetermined limit value,
And so on. 23 is a CPU 16
Is a reset button for clearing the accumulated value of
Reference numeral 21 denotes an analog converter for converting output data from an output port 16a of the CPU 16 through a digital-analog (D / A) converter 19, and a modulator 20 such as a pulse width modulation (PWM).
The MOS is driven by the drive circuit 21 through the pulse modulated by
The gate of Tr13 is controlled.

[0009]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 1-31 is disclosed.
In the device disclosed in Japanese Patent No. 1848, in order to detect a change in the contact area between the brush and the commutator, the brush is specially shaped to detect a change in rotation speed with respect to load current or a change in rotation torque with respect to load current. And the detection is difficult, and a special brush 7 must be prepared.

Further, in the monitoring apparatus disclosed in Japanese Patent Application Laid-Open No. 6-141513, a wear amount calculation corresponding to an armature current is performed by detecting an armature current, and a rotation corresponding to a rotation is detected by detecting an armature voltage. Since the wear amount is calculated and the wear limit is determined by cumulatively adding these two wear amounts, there is a problem that a large-scale CPU and memory are required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the problem to be solved by the present invention is that brushes sliding on a commutator of an armature are worn out and are adjacent to each other. As the length of contact with the commutator piece increases, the point where the current flowing during the predetermined rotation of the armature is detected is detected, and the time of this current is accumulated to determine the wear amount of the brush. Since the monitoring device and the monitoring method for the DC motor thus formed are used, an extremely simple configuration that can accurately determine the abrasion state of the brush can be obtained.

[0012]

As shown in FIG. 1, an apparatus for monitoring a DC motor according to the present invention has a commutator 2 in an armature 1 and a brush in contact with the commutator 2. In the monitoring device of the DC motor 10 driven via 7c and 7d, the monitoring device includes a plurality of commutator pieces 8, 8 # and an insulator 4 disposed between the commutator pieces 8 and 8. When the brushes 7c and 7d are opposed to each other by bridging the insulator 4 between the adjacent commutator pieces 8 and 8, the brushes 7c and 7d
Detecting means 14 for detecting a current or a voltage when one contacts one commutator piece 8, and based on the output of this detecting means 14, brushes 7 c and 7 d are placed between adjacent commutator pieces 8 and 8.
The control means 31 counts and calculates the time in which the armature 1 contacts, and compares the count calculation time with the time determined within the fixed rotation time of the armature 1.
It comprises.

As shown in FIGS. 1 and 2, the method of monitoring a DC motor according to the present invention has a commutator 2 in an armature 1 and brushes 7c and 7d in contact with the commutator 2. In the method of monitoring the DC motor 10 driven through the brushes, when the commutator 2 rotates, the brushes 7c and 7d simultaneously contact between adjacent commutator pieces 8 and 8 of the commutator 2, and The current or the voltage when the contacts 7c and 7d come into contact with one commutator piece 8 is detected (ST ₂ ). Based on this detection signal, the brushes 7c and 7d make the adjacent commutator pieces 8 and 8 of the commutator 2 adjacent to each other.
Are counted and calculated (ST ₃ , ST ₄ ) based on the control means 31, and the ratio of the armature 1 to the fixed rotation time is compared with a predetermined ratio (ST ₅ ). An alarm or display (ST ₆ ) is performed when the ratio with respect to the constant rotation time exceeds a predetermined ratio.

According to the DC motor monitoring device and the monitoring method of the present invention, the life of the brush of the DC motor can be accurately predicted, so that the maintenance of the DC motor can be performed before the DC motor is damaged. Reliability can be improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a DC motor monitoring apparatus and a monitoring method according to the present invention will be described with reference to FIGS. Note that the same reference numerals are given to portions corresponding to the conventional configuration, and redundant description is omitted. Before describing the specific configuration of the present invention in detail with reference to FIGS. 1 and 2, the principle of the present invention will be described in detail with reference to FIGS.

3A and 3B, the commutator 2 of the armature 1 of the DC motor insulates the three-pole commutator pieces 8a, 8b, 8c from each other with insulators 4, 4, 4, such as mica. Drive coils 9a, 9b, 9c are delta-connected to the commutator pieces 8a, 8b, 8c. The armature 1 is assumed to be rotating clockwise CW.

In the commutator 2 of FIG. 3A, the pair of brushes 7c and 7d are in contact with only one commutator piece 8c and 8b. In the case of the commutator 2 in FIG. 3B, one of the brushes 7c and 7d is in contact with only the commutator piece 8a, while the other brush 7c is in contact with the two commutator pieces 8b and 8d.
It touches between c.

[0018] Now, the drive coils 9a, 9b, respectively Z ₁ impedance 9c, When Z _2, Z _3, the equivalent circuit between the brush 7c and 7d in FIG. 3A is represented in Figure 4A, the impedance Z ₃ and Z ₁ of the impedance Z ₂ to the series circuit are connected in parallel, each of the drive coils 9a, 9b, 9c in order to obtain a uniform driving force as a direct current motor, as far as possible uniformly wound in which the drive coils 9a, 9b , 9c can be regarded as Z ₁ = Z ₂ = Z ₃ = Z, and the equivalent circuit of FIG. 4A can be represented as shown in FIG. 4B. That is, impedance Z and impedance 2
A parallel circuit of Z is formed between the pair of brushes 7c and 7d.

Therefore, the supply voltage applied to the DC motor is V
DC motor current I flowing between brushes 7c and 7d
_{In 1, the} current shown at 11 a in FIG. 5 flows, and I ₁ = 3/2
× V / Z.

On the other hand, as shown in FIG. 3B, an equivalent circuit when one brush 7c straddles two commutator pieces 8b and 8c and the other brush 7d contacts one commutator piece 8a is shown in FIG. 4C. Can be expressed as a combined impedance of Z ₃ = Z and Z ₁ = Z in parallel, so that the DC motor current I ₂ flowing between the brushes 7c and 7d flows as indicated by 11b in FIG. ₂ = 2 × V / Z, and I ₁ <I ₂
Next, the current I ₂ will flow a current of up 25% compared to the current I _1.

FIG. 6A shows a state in which the current I ₂ flows within a certain unit time during which the armature 1 of the DC motor makes one rotation.
This occurs when the brush 7c or 7d contacts two adjacent commutator pieces 8b and 8c across the insulator 4 as shown in FIG.
Therefore, the armature 1 of the three-pole structure of Figure 3A and B are a current I ₂ in period T ₁ one revolution generated by six points between time T ₂ as shown in FIG.

In a state where the brushes 7c and 7d are not used and are not worn, as shown in FIG.
And the contact surface of the brush 7c with 8c is formed as a straight line 7e,
Contact commutator segments 8b and 8c are made point contact, the time T ₂ of the current I ₂ flowing through the initial DC motor when driven becomes a very short time.

On the other hand, when the brushes 7c and 7d are worn out, the contact surfaces of the brushes 7c and 7d with the commutator pieces 8a, 8b and 8c of the commutator 2 become arcuate 7f as shown in FIG. 6B. The contact state of 7d and 7d is changed from point contact at the time of initial movement to arc contact. As a result, 'T ₂ than the time the initial current I ₂ flows through the T _2'> T ₂ next time the current I ₂ flowing through T _2, it becomes longer. The unit time T ₁
The length of the accumulated T ₂ ′ becomes longer, and the time T ₁ during which the current I ₁ flows becomes shorter.

Accordingly, the ratio of the sum of the time T ₂ ′ during which the current I ₂ flows to the time T ₁ of one rotation of the armature of the DC motor, for example, is measured and compared with a predetermined value, thereby making the brush 7
It becomes possible to easily determine the wear limit due to the life deterioration of c and 7d.

According to the present invention, there is provided a DC motor monitoring apparatus and method for monitoring the wear limit of a brush based on the above-described principle and generating a warning display or warning when the life of the brush has deteriorated. An example of a specific configuration will be described with reference to FIGS. 1, 2, and 7. FIG.

FIG. 1 shows a system diagram of the present invention. A commutator 2 fitted to a rotating shaft 5 of an armature 1 of a DC motor includes a plurality of commutator pieces 8a, 8b, 8c, and a plurality of commutator pieces. And the insulator 4 interposed between the commutator pieces 8a, 8b, 8c} are formed in an arc shape, one end of one of the brushes 7c is supplied with a supply voltage V from a voltage source, and the other is a brush 7d. Are grounded via a resistor R constituting the armature current detector 14.

A voltage change across the resistor R of the armature current detector 14 is detected and amplified by a DC amplifier 24 connected to the connection point between the other brush 7d and the resistor R.

The output terminal of the DC amplifier 24 is connected to a DC blocking capacitor 25. The DC component is blocked by the capacitor 25 and supplied to the buffer amplifier 26. The output terminal of the buffer amplifier 26 outputs only the AC component. .

The AC output voltage of the buffer amplifier 26 is, as shown in FIG. 7, within one rotation period T ₁ of the armature 1, as shown in FIG.
And it outputs the 6 rounds of pulsed AC component 27 of the pulse time T ₂ are the polar structure of the DC motor.

The output terminal of the buffer amplifier 26 is a differential amplifier 28
While the non-inverting terminal T ₁ of the through resistor 29 connected to the other of the inverting terminal T ₂ of the differential amplifier 28, the contact point between the resistor 29 and the other inverting terminal T ₂ to the capacitor 30 and the ground Connecting. The resistor 29 and the capacitor 30 constitute reference average level setting means, and supply the average level to the differential amplifier 28.

The output terminal of the differential amplifier 28 has an AC component 27
The pulse of the difference output between the pulse and the average level (threshold) is shown in FIG.
Is output as a pulse similar to the above, and supplied to the input port 32 of the CPU 31.

The output port 33 of the CPU 31 is connected to the alarm means 3
When the CPU 31 determines that the brush 7c or 7d has reached the wear limit, the CPU 31 outputs a warning signal and issues a notification to the warning means 34, or blinks a warning indicator light.

The CPU 31 easily determines the wear limit of the brushes 7c and 7d by software according to the flowchart shown in FIG.

Hereinafter, the operation of the CPU 31 will be described with reference to FIG. In the flow diagram of FIG. 2, reset the CPU31 of cumulative operations of the first step ST ₁ the last is performed.

[0035] The second step ST ₂ the CPU31 follows performs determination of whether the armature current I ₁ and I ₂ is detected, when the current I ₁ and I ₂ is not detected in the first step ST ₁ head However, if the currents I ₁ and I ₂ are detected, the process proceeds to the third step ST ₃ .

The third step ST ₃ 1 rotation time of the armature 1 of the DC motor in, or cumulative operation time T ₂ of the pulse width of the measurement and the current I ₂ of the predetermined unit time T ₁ is performed.

In the next fourth step ST ₄ , the calculation of the ratio of the constant unit time T ₁ to the total calculated value of the time T ₂ measured in the third step ST ₃ , d = T ₂ , is calculated / T ₂ .

[0038] of the fifth step ST ₅ in β = T ₂ total /
The initial set value of T ₁ is stored in a memory such as a RAM of the CPU 31 and compared with the α value calculated in the third step ST ₃ .
That is, it is determined whether β ≦ α. In this case, the value of β is a value at which the brush 7c and / or 7d reaches the wear limit.

[0039] The fifth step ST does not satisfy the conditions of the beta ≦ alpha at ₅ "NO" if the is returned to the first step ST ₁ head "YES" in case when the sixth alarm proceeds to step ST ₆ means 34 , An alarm signal is output to emit a warning sound, or an indicator lamp or the like is blinked to notify that the brushes 7c and 7d have reached the limit life.

According to the present invention, it is not necessary to form a wide portion on the brush, and further, it is not necessary to store the characteristic data of the current versus the amount of wear and the characteristic data of the number of rotations versus the amount of wear in the memory of the CPU. Accumulates time T ₂ of the pulse-like pulse width of the current I ₂ flowing when in contact with both the commutator piece brush is adjacent in a unit rotation time of the child, and computation time, dividing, such as in a unit rotation time Since only the comparison with the wear limit value is performed, the scale of the CPU is small, and the wear state of the brush can be accurately known with a simple configuration. Therefore, according to the DC motor having the monitoring device of the present invention, the limit life of the brush can be accurately predicted, maintenance can be performed in advance, and the reliability of the device can be improved.

In the above configuration, the resistor is used as the armature current detector, and the voltage drop of the resistor is detected. However, the voltage or the like may be directly detected, and the detection method is limited to this embodiment. Instead, it is apparent that the hardware configuration such as the counting circuit and the dividing circuit can be realized without using a CPU or the like.

[0042]

According to the DC motor monitoring apparatus and the monitoring method of the present invention, the life limit due to the brush wear of the DC motor is constantly monitored during operation, and a warning is issued in a predetermined wear state. It is possible to prevent sudden stoppage of the motor or damage to the commutator etc. with advance maintenance,
Of course, the reliability of equipment using a DC motor can be improved with a very simple configuration.

[Brief description of the drawings]

FIG. 1 is a system diagram of a DC motor monitoring apparatus according to the present invention.

FIG. 2 is a flowchart of a microcomputer used in the DC motor monitoring device of the present invention.

FIG. 3 is a diagram illustrating the principle of a monitoring device for a DC motor according to the present invention.

FIG. 4 is an equivalent circuit diagram of FIG.

FIG. 5 is a current waveform diagram between brushes of the monitoring device for a DC motor according to the present invention.

FIG. 6 is an explanatory diagram of a worn state of a brush of the monitoring device for a DC motor according to the present invention.

FIG. 7 is an output voltage waveform diagram of a buffer amplifier used in the DC motor monitoring device of the present invention.

FIG. 8 is a configuration diagram of a brush used for a conventional DC motor.

FIG. 9 is a circuit diagram of a conventional brush wear limit monitoring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Armature 2 Commutator 7, 7c, 7d Brush 8, 8a, 8b, 8c Commutator piece 9a, 9b, 9c Drive coil 14 Armature current detector 31 CPU 34 Alarm means

Claims (4)

[Claims] 1. A monitoring device for a DC motor having an armature having a commutator and driven through a brush in contact with the commutator, wherein a plurality of commutator pieces are disposed between the commutator pieces. When the brush is in contact with the commutator formed of the formed insulator, the brush is in contact with one commutator between the adjacent commutator pieces by bridging the insulator. Detection means for detecting the current or voltage at the time of the detection, based on the output of the detection means, counts and calculates the time in which the brush is in contact between the adjacent commutator pieces, within a certain rotation time of the armature. A monitoring device for a DC motor, comprising: control means for comparing the time determined in (1) with the counting operation time. 2. The detecting means comprises a resistor for converting the armature current into a voltage, and a differential amplifying means for extracting an AC component of a voltage across the resistor and comparing the AC component with a predetermined reference value. The monitoring device for a DC motor according to claim 1, wherein: 3. The control means comprises a microcomputer, compares the unit time of rotation of the armature with comparison reference data stored in advance in a storage means, and issues an alarm or display when a predetermined comparison reference value is exceeded. 3. The DC motor monitoring device according to claim 1, wherein the monitoring is performed. 4. A monitoring method for a DC motor having a commutator in an armature and driven via a brush in contact with the commutator, wherein the commutators are adjacent to each other when the commutators are rotating. A current or voltage is detected when the brush contacts the commutator pieces at the same time and when the brush contacts one commutator piece. Based on the detection output, the brush is positioned adjacent to the commutator. The time of simultaneous contact with the matching commutator pieces is counted and calculated based on the control means, and an alarm or a display is performed when the ratio of the armature to the fixed rotation time exceeds a predetermined ratio. DC motor monitoring method.