JP5188088B2 - Failure prediction devices such as reducers - Google Patents

Description

  The present invention relates to a device for predicting a failure in a rolling bearing or a reduction gear, and more particularly, to a failure prediction device for a reduction gear or the like that detects an iron powder contained in grease of a bearing or a reduction gear online to predict a failure due to wear.

For example, a large number of robots are used in production lines for flow work in the automobile industry and the like. If these robots fail, the impact on production is significant.
A lot of rolling bearings and speed reducers are used in the robot. If these parts break down, the robot stops moving, which has a great influence on the production line.
Needless to say, the field in which the failure of the bearing and the reduction gear causes serious damage is not limited to the robot.

  In order to prevent such serious damage, it is desirable to perform preventive maintenance that finds parts that are likely to fail and repairs them before they fail. Abnormalities in the bearings and the speed reducer can be detected online by vibrations and abnormalities in the current of the motor connected to them. However, when an abnormality occurs in vibration or current, the speed reducer or the like is already on the verge of failure and is not sufficient as an index used for preventive maintenance.

  In rolling bearings and reduction gears, rolling parts are worn according to the operation time and become mixed with grease for lubrication. Many of these parts fail due to abnormal wear, and when abnormal wear occurs, a large amount of iron powder is mixed in the grease, so a method has been developed to predict the abnormality by measuring the amount of iron powder in the grease. . The amount of iron powder in the grease gradually increases as the wear progresses, but it can be detected as an abnormal increase in iron powder long before the speed reducer or the like enters a failure state. Therefore, if the grease iron powder concentration is used, preventive maintenance can be performed with a sufficient time margin.

  A grease iron powder concentration meter and ferrography can be used for such purposes. In ferrography, iron powder in lubricating oil sampled from a speed reducer, etc., can be collected in a state in which the iron powder is sorted in order of size by flowing it over a glass plate tilted over a magnet after being dissolved in a solvent. Therefore, the amount of wear and the state of wear are diagnosed by analyzing the collected iron powder.

In addition, as shown in FIG. 8, when the container containing the lubricating oil sampled is inserted into one of the two excitation coils having the same configuration connected in reverse, the grease iron powder concentration meter outputs the difference output between the two excitation coils. This is a so-called magnetic balance type electromagnetic induction type densitometer that utilizes the principle that an induction output according to the iron concentration in the container is obtained in the detection coil to be detected.
These instruments sample lubricant oil and measure it offline, which is inconvenient for use in maintenance management, and an apparatus capable of online measurement is desired.

  Patent Literature 1 discloses a magnetic balance type electromagnetic induction type sensor developed for rolling bearings and used on-line. In the disclosed grease iron powder content detection sensor, a pair of exciting coils is provided with a stylus, and one stylus is inserted into the grease through an axial through hole provided in a seal member of a rolling bearing. And use it. Since the stylus inserted into the grease forms a magnetic circuit containing iron powder, and the other stylus forms a magnetic circuit in the air, the sensing coil has an unbalanced electromotive force according to the concentration of iron powder. Occur. This electromotive force is amplified and used as a detection signal.

Because of the demand for magnetic balance, the seal member through which the stylus penetrates must have the same permeability as air, such as synthetic resin, so the objects that can be measured are limited, such as those with an iron-based housing such as a reducer Not suitable for.
JP 2003-269470 A

  The problem to be solved by the present invention is to provide an on-line failure prediction device for detecting a grease iron powder content by incorporating a sensor in a rolling bearing or a speed reducer and for predicting the failure.

  The failure prediction apparatus of the present invention includes a sensor coil part, an excitation circuit, and a measurement circuit that are formed by meriding an excitation coil and a detection coil so that mutual inductance in the air becomes zero, and the sensor coil part is a component to be measured. It has one through-hole through which grease flows when immersed in the lubricating grease inside, and the excitation coil is connected to the excitation circuit to supply high-frequency current. The induction current of the detection coil is the iron powder in the through-hole. The iron powder concentration in the grease is measured by a measurement circuit based on the change in relation to the quantity, and the failure prediction of the part to be measured is made based on the result.

  Since the mutual inductance is close to zero in the air or in pure grease having a relative permeability close to 1, no current is generated in the detection coil even when the excitation coil is excited at a high frequency. However, the sensor coil part is immersed in the lubricating grease in the measurement target part, and the lubricating grease flows through the through-holes that penetrate the excitation coil and the detection coil. When the iron powder concentration increases, the magnetic flux is biased in the portion with the through hole, the magnetic balance is lost, and mutual inductance appears, and an induction current is generated in the detection coil. Since this induced current is related to the amount of iron powder, the amount of wear can be estimated from the measurement result.

Since the reduction gear and the like are known from the technical knowledge accumulated so far, the relationship between the wear state and the life can be estimated from the iron powder concentration.
Therefore, when a reduction gear that has deteriorated due to wear is found, preventive early repairs can be performed to prevent sudden failures during operation and to extend the life of the reduction gear.

  The sensor coil unit of the failure prediction apparatus according to the first embodiment of the present invention includes a first coil group including a first winding coil and a second winding coil, and a third winding surrounding the pair of winding coils. A second coil group including wire coils is provided. The first winding coil and the second winding coil are congruent and connected in series so that current flows in opposite directions, and the first winding coil has a through-hole through which grease flows, while the second winding The wire coil is mekra and does not have a passage through which grease flows. The first coil group and the second coil group are protected by applying an insulating coating while leaving the through hole. One of the first coil group and the second coil group is connected to the excitation circuit as an excitation coil, and the other is connected to the measurement circuit as a detection coil.

The insulating coating is formed using a material having a relative magnetic permeability close to 1 that is equivalent to grease. Moreover, it is preferable that the coating on the detection coil side is sufficiently thick so that grease containing iron powder does not affect the detection coil.
The sensor coil part is installed so as to be immersed in the grease in the rolling bearing or the speed reducer.
Further, the first coil group having two winding coils may be used on the excitation side, or the third winding coil surrounding the two winding coils may be used on the excitation side.
The winding coil can be formed on a printed board by printing.

The sensor coil section composed of the first coil group consisting of the first winding coil and the second winding coil and the second coil group consisting of the third winding coil is used for lubricating grease inside the rolling bearing and reducer. Installed to immerse.
Lubricating grease flows into the through hole of the first winding coil, and iron contained in the grease affects the mutual inductance between the first winding coil and the third winding coil. On the other hand, even if the second winding coil is immersed in lubricating grease, the core material penetrating the coil does not change, so that there is no significant change in the mutual inductance with the third winding.

  Since the direction of the current flowing through the first winding coil and the second winding coil is reversed, the total mutual inductance in the third winding coil is the first winding coil and the second winding coil. Due to the mutual inductance difference. Therefore, the mutual inductance of the third winding coil is a value of the mutual inductance of the first winding coil with reference to the mutual inductance in the second winding coil, and is a value determined substantially corresponding to the iron content contained in the grease. It becomes.

Therefore, when the first coil group is connected to the excitation circuit, the second coil group is connected to the measurement circuit, and a high-frequency current is passed in series from the excitation circuit to the first winding coil and the second winding coil, An electromotive force corresponding to the amount of iron powder is generated in the third winding coil, and an output signal representing the concentration of iron powder contained in the grease in the device can be obtained from the measurement circuit.
A high-frequency current is passed through the third winding coil, and the difference in electromotive force induced between the first winding coil and the second winding coil is observed by the electromotive force between the terminals of the first coil group. Can also achieve the same result.

  When the winding coil is formed on the printed circuit board using the printed circuit technology, for example, the coil can be formed with high accuracy with an accuracy of about 10 μm. Therefore, the first winding coil and the second winding coil are extremely accurate. It becomes congruent or symmetric, and it is possible to easily obtain an electromagnetic balance between the two without performing delicate and difficult adjustments.

  The failure prediction apparatus according to the second aspect of the present invention includes a sensor coil unit including a first winding coil and a second winding coil, an excitation circuit, and a measurement circuit. The wire coil and the second winding coil are arranged so as to be orthogonal to each other and share a symmetry axis so that the mutual inductance is zero in the air, and a through hole passing through the shared symmetry axis is connected to the first winding coil. The first winding coil and the second winding coil are formed from the position sandwiched between the second winding coil to the position sandwiched between the first winding coil and the second winding coil that are opposed to each other. It is protected by applying an insulating coating leaving behind.

The first winding coil is connected to the excitation circuit, and the second winding coil is connected to the output measurement circuit to detect iron powder in the grease passing through the through hole.
The sensor coil section is in the form of a small sphere with a single through-hole passing through the center, and is installed so as to be immersed in the grease liquid surface inside the reducer, etc. Grease is distributed.

  The sensor coil portion of the second failure prediction device of the present invention has an electromotive force in the second winding coil because the mutual inductance is zero even in the air or high-purity grease even if the first winding coil is excited at high frequency. However, when iron powder is contained in the grease, the magnetic flux generated in the second winding coil is attracted by the iron powder in the through hole and becomes asymmetrical, resulting in mutual inductance. An electromotive force is generated between both ends of the. Thus, since this electromotive force corresponds to the amount of iron powder in the through hole, the concentration of grease iron powder can be known from the measured current value.

  The failure prediction device of the present invention can be installed in advance in a reduction gear or a bearing because the sensor portion can be formed sufficiently small. If a reduction gear equipped with a sensor is filled with grease and operated, the iron is contained in the grease as the operating time elapses, and is detected by the failure prediction device through the through-hole. From the above, the progress of wear can be estimated. Since the life of the speed reducer and the like can be estimated from the worn state, it is possible to extend the life of the speed reducer and carry out efficient operation by taking time to repair in advance.

  The failure prediction device of the present invention is intended for parts such as a reduction gear, a reduction unit, or a rolling bearing, in which the magnetic material of the inner wall or rolling part worn by friction is mixed into the lubricating grease as a powder. This is a device in which the sensor part is installed at a position where it is immersed in the grease inside the part, and the magnetic powder concentration is detected online by the so-called magnetic balance type electromagnetic induction method to predict and notify in advance of the failure of the part.

Hereinafter, the failure prediction apparatus of the present invention will be described in detail based on embodiments with reference to the drawings.
FIGS. 1 to 5 are diagrams for explaining a failure prediction apparatus according to a first embodiment of the present invention, and FIGS. 6 and 7 are drawings showing a sensor portion of a second embodiment of the present invention.
FIG. 8 is a principle diagram of a conventional off-line grease iron powder concentration meter.

FIG. 1 is a plan view of the sensor coil portion of the first embodiment, FIG. 2 is a sectional view taken along line II-II in FIG. 1, FIG. 3 is a block diagram of a failure prediction device, and FIG. FIG. 5 is a block diagram of the failure prediction system.
In the failure prediction apparatus of the present embodiment, as shown in FIGS. 1 and 2, the sensor coil unit 1 is composed of three winding coils formed on a circuit board 10 by printed circuit technology.

The first winding coil 11 and the second winding coil 12 are formed so as to be congruent or symmetrical with each other and have the same electromagnetic characteristics.
If the technology for manufacturing a printed circuit board is applied, the conductive wire portion and the insulating portion can be accurately formed at a level of 10 μm, so that a completely identical or symmetric and electromagnetically equivalent winding coil is easily formed. be able to. This eliminates the need for delicate magnetic balance adjustment.
Further, by using the printed circuit technology, it is possible to manufacture an extremely small and thin sensor coil unit 1 that can be installed in a very small space inside the speed reducer or the bearing.

  A through hole 14 is provided at the center of the first winding coil 11. The through hole 14 is a portion through which the lubricating oil flows when the sensor coil unit 1 is installed in the speed reducer. The central portion 15 of the second winding coil 12 is closed with a printed circuit board material having a relative permeability close to 1, and grease cannot enter the core portion of the second winding coil 12.

A third winding coil 13 is formed surrounding the two winding coils 11 and 12.
A protective coating 16 is applied over the winding coils 11, 12, and 13 so that iron powder or the like does not directly contact the coil or the electric wiring portion when installed in the speed reducer. Further, the protective coating 16 is formed of a material having a magnetic permeability equivalent to that of grease, such as synthetic resin, and stabilizes the electromagnetic characteristics of the reference second winding coil 12 against changes in the iron powder concentration in the grease. It also has a function.
Further, the coating 16 on the second winding coil 12 side is sufficiently thick so that grease containing iron powder does not affect the reference detection coil.

As shown in FIG. 3, the first winding coil 11 and the second winding coil 12 are connected in series and then connected to the excitation circuit 2 as an excitation coil. The third winding coil 13 is connected to the measurement circuit 3 as a detection coil.
When the first winding coil 11 and the second winding coil 12 are symmetrical, the terminal at the winding start position of one coil is connected to the terminal at the winding end position of the other coil, and both coils are congruent. Sometimes one terminal at a symmetrical position is connected.

  When a high frequency current is supplied from the excitation circuit 2 to the winding coils 11 and 12 connected in this way, the same current in the opposite direction flows through both coils. Therefore, when both coils are immersed in clean grease, equal amounts of magnetic flux are generated in opposite directions, so that the magnetic fluxes cancel each other and the third winding that surrounds the two winding coils 11 and 12 together. In the end, no magnetic flux is generated in the wire coil 13, and no detection signal is transmitted to the measurement circuit 3.

  When the iron powder is contained in the grease, the magnetic flux generated by the first winding coil 11 having the through hole is larger than the reverse magnetic flux generated by the second winding coil 12, so that the third winding The coil 13 transmits the current induced in accordance with the difference magnetic flux to the measurement circuit 3.

The induced current of the third winding coil 13 increases as the amount of iron powder in the through hole 14 increases, and the amount of iron powder in the grease can be estimated from the current value. Since the higher the excitation current frequency, the higher the detection sensitivity, the sensitivity of the apparatus can be adjusted using the excitation current frequency.
Since the iron powder in the grease is iron powder generated by wear in the speed reducer, the wear state in the speed reducer can be estimated from the output of the measurement circuit 3 of the failure prediction apparatus of the present embodiment.

FIG. 4 is a cross-sectional view showing a state in which the sensor coil unit of the present embodiment is installed in the speed reducer installed in the robot arm.
A second robot arm 53 is rotatably connected to the first robot arm 52, and the first robot arm 52 is provided with a motor 51 that rotates the second robot arm 53 about its axis. A speed reducer 4 that gradually reduces the rotation of the motor 51 is provided at the joint between the first robot arm 52 and the second robot arm 53.
Lubricating grease 41 is injected into the speed reducer 4 to form a grease level 42.

When the first robot arm 52 moves, the speed reducer 4 rotates and the grease level 42 also fluctuates, but the sensor coil unit 1 is fixed at a position that is always below the grease level 42 in the speed reducer 4 and is always immersed in grease. The iron powder concentration in the grease is constantly detected.
The current generated in the sensor coil unit 1 is transmitted to the measurement circuit 3 through the communication line. In the measurement circuit 3, it analyzes using the relationship between an electric current value and iron powder density | concentration, estimates the wear state of the reduction gear 4, and alert | reports a result.

If the second winding coil 12 is surrounded by grease containing iron powder, it is affected by the iron powder present around the coil and lowers the detection sensitivity. Therefore, only the first winding coil 11 having the through hole 14 is used. May be soaked in grease, and the sensor coil portion 1 may be installed so that the portion of the second winding coil 12 is exposed to the air.
Further, instead of supplying the exciting current to the first winding coil 11 and the second winding coil 12, the exciting current is supplied to the third winding coil 13 surrounding them, and the first winding coil connected in series. 11 and the second winding coil 12 may be used as detection coils. This method has an advantage that the output current of the detection coil is not easily affected by the noise because the magnetic noise generated from the motor or the like is canceled out by the two reverse winding coils.

FIG. 5 is a block diagram showing a system for monitoring failure of a robot speed reducer online.
The sensor coil unit 1 is incorporated in each of the speed reducers 4 installed in the robot, and the sensor output is transmitted to the measurement circuit 3. The measurement circuit 3 may include a signal amplifier for each sensor coil unit 1 or may be shared by using a scanner amplifier. A concentration value signal corresponding to the iron powder concentration generated by the measurement circuit 3 is transmitted to the robot controller 31.
The robot controller 31 is composed of an electronic computer including an input / output device, an arithmetic device, and a storage device, and is provided with a failure prediction arithmetic device that determines the life of the reduction gear.

For each reducer, iron powder concentration measurement data in grease is periodically taken into the controller of the robot during operation, and the life of each reducer can be judged by comparing it with a predetermined threshold value. .
For example, if the iron powder concentration is in the range of 0.5% to 1%, it is determined that minor damage has occurred, and if it is 2% to 4%, it is determined that severe damage has occurred. The determination result can be displayed on the monitor of the controller.

The failure prediction apparatus according to the second embodiment of the present invention has a sensor coil section formed in a spherical shape using two coils, and other than the sensor coil section is the same as the failure prediction apparatus according to the first embodiment described above.
FIG. 6 is a perspective view of the sensor portion of the second embodiment, and FIG. 7 is a conceptual diagram illustrating the operating principle of this embodiment.

In the sensor coil section 6 of this embodiment, the excitation coil 61 and the detection coil 62 are arranged at a right angle sharing the central axis, and one through hole 63 through which grease flows is formed therein. The through hole 63 is disposed so as to be inclined by 45 degrees with respect to the excitation coil and the detection coil.
The sensor coil portion 6 is formed in a spherical shape that does not allow the grease to enter except for the through-hole 63, and is installed so as to be immersed in a lubricating grease liquid such as a speed reducer.

FIG. 7A shows a case where the magnetic flux penetrating the coil is balanced. As shown in the figure, even if an exciting current is passed through the exciting coil 61 when there is no iron powder in the through-hole 63, the generated magnetic flux is balanced and there is no magnetic flux across the detecting coil 62. The induced current at is zero and no output is produced.
On the other hand, when the iron powder is contained in the grease flowing through the through hole 63 that intersects both coils at 45 degrees, the path of the magnetic flux generated in the exciting coil 61 is the through hole as shown in FIG. The balance is lost by being dragged to 63, a current flows through the detection coil 62, and a signal is output.
The magnitude of the signal corresponds to the amount of iron powder in the through hole 63.

In the same manner as shown in FIG. 5, the detection signal is amplified by the amplifier circuit, converted into a concentration signal, digitized, and transmitted to the robot controller. The robot controller determines the life of each reduction gear and displays the result.
The maintenance staff can prepare an appropriate maintenance plan for the reduction gear whose life is a problem based on the life judgment, and can cope with it early.

  Since the sensor coil unit 6 of the present embodiment uses only two coils, the volume of the sensor unit can be reduced and the installation location is not selected, so that it can be widely applied to various parts.

It is a top view of the sensor coil part of the failure prediction apparatus which concerns on 1st Example of this invention. FIG. 2 is a sectional view taken along line II-II in FIG. 1. It is a block diagram of the failure prediction apparatus of 1st Example. It is sectional drawing which shows the installation state of the sensor coil part of 1st Example. It is a block diagram of the failure prediction system using 1st Example. It is a perspective view of the sensor coil part of the failure prediction apparatus which concerns on 2nd Example of this invention. It is a conceptual diagram explaining the working principle of 2nd Example. It is a principle figure of the grease iron powder concentration meter for off-line concerning a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor coil part 10 Circuit board 11 1st coil | winding coil 12 2nd coil | winding coil 13 3rd coil | winding coil 14 Through-hole 15 Center part dummy 16 Protective coating 2 Excitation circuit 3 Measurement circuit 31 Robot controller 4 Reducer 41 For lubrication Grease 42 Grease level 51 Motor 52 First robot arm 53 Second robot arm 6 Sensor coil section 61 Excitation coil 62 Detection coil 63 Through hole

Claims (5)

A sensor coil unit, an excitation circuit, and a measurement circuit that are formed by passing the excitation coil and the detection coil in the air so that mutual inductance is zero in the air, and the sensor coil unit is configured so that current flows in opposite directions. A first coil group composed of congruent first winding coil and second winding coil connected in series, and a second coil group composed of a third winding coil surrounding the pair of winding coils; One of the excitation coil and the detection coil is composed of the first coil group, and the other is composed of the second coil group. The first winding coil is filled with lubricating grease in the component to be measured. When the first coil group and the second coil group are provided with one through hole through which the grease circulates when installed so as to be immersed in the second winding coil, the grease does not flow through the second coil. Leaving the through hole Coated with a material having a magnetic permeability equivalent to that of grease, and when the excitation coil is connected to the excitation circuit and a high-frequency current is supplied, iron powder in the through-holes causes the excitation coil and the detection coil to The measurement circuit detects the change in the induced current of the detection coil that occurs in relation to the amount of iron powder due to the loss of magnetic balance, determines the iron powder concentration in the grease , and based on the determined iron powder concentration A failure prediction device that predicts failure of components to be measured. Failure prediction apparatus according to claim 1, wherein said first winding coil and a second winding coil and the third winding coils are formed by printing on a printed circuit board. 3. The failure prediction apparatus according to claim 1, wherein the first coil group is connected to an excitation circuit, and the second coil group is connected to a measurement circuit. The failure prediction apparatus according to claim 1 or 2, wherein the first coil group is connected to a measurement circuit, and the second coil group is connected to an excitation circuit. The excitation coil and the detection coil of the sensor coil unit are arranged so as to be orthogonal to each other sharing a symmetry axis, and the center of the sensor coil unit from the position where the through hole is sandwiched between the excitation coil and the detection coil. The failure prediction device according to any one of claims 1 to 4, wherein the failure prediction device is formed up to a position sandwiched between the excitation coil and the detection coil that pass through and face each other .

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