JP7501452B2 - Ball screw maintenance management system and ball screw maintenance management method - Google Patents

Description

The present invention relates to a ball screw maintenance management system and a ball screw maintenance management method.

A ball screw is a drive unit that can move the nut attached to the ball screw along the screw shaft by applying a rotational motion. Ball screws are used as core components in various processing machines, such as injection molding machines.

If the ball screw, a key component, breaks down, it can lead to the production line being shut down. In addition, since the ball screws used in large processing machines such as injection molding machines take time to manufacture, it is necessary to predict when the ball screw will need to be replaced and to arrange for spare ball screws to be prepared in advance.

Patent Document 1 discloses technology relating to an abnormality detection device for a ball screw device that detects vibrations using a vibration sensor attached to a ball screw nut, extracts vibration data in a ball screw abnormality detection frequency band from the vibration data, and detects abnormalities by comparing it with normal data.

JP 2013-257014 A

However, since the vibration sensor attached to the ball screw nut is susceptible to disturbances, the method of Patent Document 1 has the risk of erroneous judgment due to noise caused by disturbances, making it impossible to make an accurate judgment.
On the other hand, the method of detecting damage to a ball screw by measuring the current value of the motor that rotates the ball screw has the problem that it is not possible to detect damage to the ball screw unless the damage requires immediate replacement.

The present invention has been made to solve these problems, and aims to provide a ball screw maintenance management system and a ball screw maintenance management method that can manage the timing of ball screw maintenance.

A ball screw maintenance management system according to one aspect of the present invention includes:
A ball screw;
A motor that drives the ball screw;
a vibration sensor for detecting vibration of the ball screw;
and a first determination means for determining whether or not the ball screw is in a worn state by using vibration information in a constant speed rotation region of the motor from the vibration information of the ball screw acquired from the vibration sensor.

A ball screw maintenance management method according to one aspect of the present invention includes the steps of:
A ball screw maintenance management method for managing ball screw maintenance timing using a computer, comprising the steps of:
acquiring vibration information of the ball screw from a vibration sensor;
The method determines whether or not the ball screw is in a worn state by using vibration information in a constant speed rotation region of a motor that drives the ball screw, out of the vibration information of the ball screw that has been acquired.

When the motor rotates at a constant speed, vibration noise due to disturbances is less likely to occur than when the motor rotates at an accelerating or decelerating speed. A ball screw maintenance management system according to one aspect of the present invention uses vibration information in the constant speed rotation region of the motor from among the vibration information of the ball screw acquired from the vibration sensor to determine whether the ball screw is in a worn state. In other words, the ball screw maintenance management system according to one aspect of the present invention uses vibration information in the constant speed rotation motion of the motor to suppress the effects of disturbances and detect minute vibrations, and can accurately and early detect the wear state of the ball screw, especially initial wear. According to the ball screw maintenance management system according to one aspect of the present invention, by determining the wear state of the ball screw before it is damaged, the maintenance timing of the ball screw can be managed so that a normal state is maintained without any breakdowns or malfunctions.

The present invention provides a ball screw maintenance management system and a ball screw maintenance management method that can manage the timing of ball screw maintenance.

1 is a diagram showing a configuration of a ball screw maintenance management system according to a first embodiment. 4 is a flowchart showing an operation of the ball screw maintenance management system according to the first embodiment. FIG. 2 is a diagram illustrating an example of a hardware configuration of a server of the ball screw maintenance management system according to the first embodiment.

Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following descriptions and drawings have been simplified as appropriate for clarity of explanation.

First Embodiment
<Configuration of the maintenance management system>
The configuration of a ball screw maintenance management system 100 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the ball screw maintenance management system 100. The right-handed xyz orthogonal coordinate system shown in Fig. 1 is for the sake of convenience in explaining the positional relationship of components of a device having a ball screw 1 (hereinafter also referred to as a ball screw device). Usually, the positive direction of the z axis is vertically upward, and the xy plane is a horizontal plane.

The ball screw device managed by the ball screw maintenance management system 100 has a ball screw 1, a bearing 2, a bearing 3, a motor 4, a vibration sensor 5, a current sensor 6, a drive rod 7, a coupling 8, and a base frame 9. The ball screw device may also include other components necessary for operation.

The control panel 20 includes an amplifier 21, an amplifier 22, a logger 23, and a recording medium 24. The vibration sensor 5 and the current sensor 6 of the ball screw device are connected to the amplifier 21 and the amplifier 22 of the control panel 20, respectively. Note that the control panel 20 may include other components necessary for operation.

The server 30 includes a first determination means 31 and a second determination means 32. The first determination means 31 is connected to the vibration sensor 5 via the logger 23 and the amplifier 21. The second determination means 32 is connected to the current sensor 6 via the logger 23 and the amplifier 22. The server 30 may include other components necessary for operation. The server 30 may also be connected to an external network (not shown).

The configuration of the ball screw device, control panel 20, and server 30 of the ball screw maintenance management system 100 according to the first embodiment will be described in detail below.

The ball screw 1 has a ball screw shaft 11 and a movable nut 12 that moves along the ball screw shaft 11. In FIG. 1, the ball screw shaft 11 is provided extending in the x-axis direction. The movable nut 12 is screwed onto the ball screw shaft 11, and moves along the ball screw shaft 11 in the positive x-axis direction and the negative x-axis direction when the ball screw shaft 11 rotates. The movable area of the movable nut 12 is between the bearing 2 and the bearing 3 provided at both ends of the ball screw shaft 11.

The ball screw shaft 11 is supported by the bearing 2 and the bearing 3. As shown in FIG. 1, the ball screw shaft 11 is supported by the bearing 2 at the end of the ball screw shaft 11 on the motor 4 side (the negative x-axis side). The ball screw shaft 11 is fitted into the through hole of the bearing 2.

The bearing 3 is provided at the end on the drive rod 7 side (x-axis positive direction side). The bearing 3 is fixed to a base frame 9, and a ball screw shaft 11 is fitted into a through hole of the bearing 3.
That is, the ball screw shaft 11 is rotatably supported by the base frame 9 via a bearing 2 and a bearing 3 provided at both ends.

The motor 4 is a motor that drives the ball screw 1. Specifically, the motor 4 rotates the ball screw shaft 11 and moves the movable nut 12 along the ball screw shaft 11. The motor 4 is, for example, a servo motor. The motor 4 is connected to the ball screw 1 via a coupling 8. The rotational motion of the motor 4 is transmitted to the ball screw 1 via the coupling 8. When the rotation direction of the motor 4 is changed, the movement direction of the movable nut 12 is changed to the positive x-axis direction or the negative x-axis direction.

The vibration sensor 5 is a sensor that detects vibrations of the ball screw 1. The vibration sensor 5 can be provided at any position of the ball screw device. In order to increase the accuracy of vibration detection, it is preferable that the vibration sensor 5 is provided on the movable nut 12 directly connected to the ball screw 1, the bearing 2, or the bearing 3. In particular, in order to suppress the influence of disturbances, it is even more preferable that the vibration sensor 5 is provided on the bearing 3, which is away from the motor 4. In FIG. 1, the vibration sensor 5 is provided on the bearing 3 as an example.

The vibration sensor 5 is connected to an amplifier 21 of the control panel 20. The vibration detected by the vibration sensor 5 is amplified and filtered by the amplifier 21, and is recorded on a recording medium 24 via a logger 23, and is also acquired by a first determination means 31 of the server 30.

The current sensor 6 is a sensor that detects the current value of the motor 4. In FIG. 1, the current sensor 6 is provided in contact with the motor 4, but it may be provided at any position where the current value of the motor 4 can be detected. For example, it may be provided in the connection line between the control panel 20 and the motor 4, or inside the control panel 20.

The current sensor 6 is connected to an amplifier 22 of the control panel 20. The current value of the motor 4 detected by the current sensor 6 is amplified and filtered by the amplifier 22, and is recorded on the recording medium 24 via the logger 23, and is also acquired by the second determination means 32 of the server 30.

The driving rod 7 is a member capable of arranging an object on the xy plane. The shape of the driving rod 7 can be any shape. The end of the driving rod 7 on the negative x-axis side is fixed to the end face of the movable nut 12 on the positive x-axis side via a connecting part 10. The driving rod 7 and the movable nut 12 may be fixed via multiple connecting parts 10. The fixing method of the driving rod 7 and the movable nut 12 is not limited to this, and it is sufficient that they are fixed so that they can move as a unit. In FIG. 1, the connecting part 10 between the driving rod 7 and the movable nut 12 is shown with diagonal lines to distinguish it from the ball screw shaft 11. The driving rod 7 and the connecting part 10 are configured so as not to interfere with the bearing 3.

Since the driving rod 7 is fixed to the movable nut 12, when the motor 4 drives the ball screw 1, the driving rod 7 also moves in the same direction as the movable nut 12. In other words, when the movable nut 12 moves in the positive direction of the x-axis, the driving rod 7 also moves in the positive direction of the x-axis. Similarly, when the movable nut 12 moves in the negative direction of the x-axis, the driving rod 7 also moves in the negative direction of the x-axis. The movable nut 12 and driving rod 7 move an equal distance as a unit.

The base frame 9 is a frame that supports the bearings 2, 3, and motor 4. The shape of the base frame 9 may be any shape that can support the bearings 2, 3, and motor 4, and is, for example, a plate-like member parallel to the xy plane. The bearings 2, 3, and motor 4 are placed and fixed on the base frame 9. The base frame 9 may be connected to the bearings 2, 3, and motor 4 via other connecting members. Note that the drive rod 7 and base frame 9 are connected, but the connecting portion between the two is omitted in FIG. 1.

The control panel 20 includes an amplifier 21, an amplifier 22, a logger 23, and a recording medium 24. The amplifier 21 is connected to the vibration sensor 5 and is a device that amplifies and filters the vibrations acquired from the vibration sensor 5. The amplifier 22 is connected to the current sensor 6 and is a device that amplifies and filters the current value of the motor 4 acquired from the current sensor 6.

The logger 23 is connected to the amplifiers 21 and 22, and is a device that stores data (vibration information and current value information) measured and collected by the vibration sensor 5 and the current sensor 6. The recording medium 24 is a medium that records the data of the logger 23. The recording medium 24 may be connected to the server 30. For example, the first determination means 31 may obtain vibration information from the recording medium 24 and make a determination. The second determination means may obtain current value information from the recording medium 24 and make a determination.

The server 30 includes a first determination means 31 and a second determination means 32. The server 30 is, for example, a computer device that executes the processing of the first determination means 31 and the second determination means 32. The first determination means 31 and the second determination means 32 may be configured within the control panel 20. The processing related to the first determination means 31 and the second determination means 32 may be executed by another computer device connected to an external network, and the processing of the first determination means 31 and the processing of the second determination means 32 may each be executed by a different computer device.

The first determination means 31 determines whether the ball screw 1 is in a worn state by using vibration information in the constant speed rotation region of the motor 4 from among the vibration information of the ball screw 1 acquired from the vibration sensor 5. The vibration of the ball screw 1 increases as the wear of the ball screw 1 progresses. For example, the first determination means 31 may perform a frequency analysis on the vibration information of the ball screw 1 acquired from the vibration sensor 5, and determine that the ball screw 1 is in a worn state when the vibration in the constant speed rotation region of the motor 4 is equal to or greater than a threshold value. Note that when the rotational motion of the motor 4 is in the constant speed rotation region, the movable nut 12 moves at a constant speed on the ball screw shaft 11.

The second determination means 32 determines whether the ball screw 1 is in a damaged state using the current value of the motor 4 acquired from the current sensor 6. The load on the motor 4 increases as the damage to the ball screw 1 progresses. In other words, the current value of the motor 4 increases. For example, the second determination means 32 may determine that the ball screw 1 is in a damaged state when the current value of the motor 4 acquired from the current sensor 6 is equal to or greater than a threshold value. In order to improve the accuracy of the determination, it is preferable that the second determination means 32 determines whether the ball screw 1 is in a damaged state using the current value in the constant speed rotation region of the motor 4, among the current values of the motor 4 acquired from the current sensor 6.

The ball screw maintenance management system 100 according to this embodiment uses vibration information in the constant speed rotation region of the motor 4 to suppress the effects of disturbances, detect minute vibrations, and accurately and early detect the wear state of the ball screw 1, particularly initial wear. By determining the wear state of the ball screw 1, the ball screw maintenance management system 100 can manage the timing of arranging and preparing spare parts for the ball screw in advance. In other words, the ball screw maintenance management system 100 can manage the timing of maintenance of the ball screw 1.

Furthermore, the ball screw maintenance management system 100 can also determine whether or not the ball screw 1 is damaged, using the current value of the motor 4 obtained from the current sensor 6. This allows the ball screw maintenance management system 100 to manage the replacement timing of the ball screw 1 by detecting the time when damage to the ball screw 1 progresses and a load begins to be applied to the motor 4. In other words, the ball screw maintenance management system 100 not only makes it possible to manage the timing of ordering, but also manages the maintenance timing of the ball screw 1 in accordance with the replacement timing of the ball screw 1. The ball screw maintenance management system 100 makes it possible to use expensive ball screws 1 that were previously still usable, to the limit of their lifespan.

The ball screw maintenance management system 100 may further include a notification unit (not shown) that notifies the user of the ball screw maintenance management system 100 of the judgment result by the first judgment means 31 or the second judgment means 32. This makes it possible to notify the user of the ball screw maintenance management system 100 of the judgment result by the first judgment means 31 or the second judgment means 32.

The notification unit may be provided in, for example, the control panel 20, the server 30, or a terminal (not shown) connected to the server 30 via a network. For example, the notification unit may output an alarm depending on the judgment result by the first judgment means 31 or the second judgment means 32. The notification unit may also transmit a message of the judgment result to the control panel 20, the server 30, or the terminal. For example, when the first judgment means 31 judges that the ball screw 1 is in a worn state, the notification unit may notify that it is time to arrange for the ball screw 1. Similarly, when the second judgment means 32 judges that the ball screw 1 is in a damaged state, the notification unit may notify that it is time to replace the ball screw 1.
This allows the user of the ball screw maintenance management system 100 to easily know when maintenance is required for the ball screw 1.

The notification unit may also generate different alarms for the judgment result of the first judgment means 31 and the judgment result of the second judgment means 32. This allows the user of the ball screw maintenance management system 100 to easily know when to arrange for and replace the ball screw based on the difference between the alarms.

<Maintenance management method>
Next, a ball screw maintenance management method according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the operation of the ball screw maintenance management system 100 according to the first embodiment.

Power is supplied to devices that require power supply, such as the motor 4, vibration sensor 5, current sensor 6, etc. (step S1). Next, measurement of vibration by the vibration sensor 5 and measurement of the current value of the motor 4 by the current sensor 6 are started (step S2).

After starting to measure the vibration and current values, a rotation command is issued to the motor 4, for example, from a motor control device (not shown) on the control panel 20. The motor 4 starts rotating based on the command to start rotation (step S3). After the motor 4 starts rotating, the vibration sensor 5 detects the vibration of the ball screw 1, and the current sensor 6 detects the current value of the motor 4.

The motor 4 accelerates rotation based on the command for accelerated rotation (step S4). When the motor 4 is in the accelerated rotation region, the movable nut 12 and the driving rod 7 fixed to the movable nut 12 are accelerating. After that, the motor 4 rotates at a constant speed based on the command for constant speed rotation (step S5). When the motor 4 is in the constant speed rotation region, the movable nut 12 and the driving rod 7 fixed to the movable nut 12 are moving at a constant speed.

The first determination means 31 determines whether the ball screw 1 is in a worn state by using vibration information in the constant speed rotation region of the motor 4 from the vibration information of the ball screw 1 acquired from the vibration sensor 5 (step S6).

If the vibration of the ball screw 1 is equal to or greater than the threshold value (step S6 YES), the first determination means 31 determines that the ball screw 1 is in a worn state. In this case, the notification unit outputs an alarm indicating that it is time to arrange for the ball screw 1 (step S7). On the other hand, if the vibration of the ball screw 1 is not equal to or greater than the threshold value (step S6 NO), the first determination means 31 determines that the ball screw 1 is not in a worn state. In this case, the first determination means 31 continues making a determination based on the vibration.

The ball screw maintenance management system 100 may also automatically execute arrangement and ordering processes for the ball screw 1 when it is determined that the ball screw 1 is in a worn state. For example, an order management unit (not shown) may be provided in the server 30, and the order management unit may automatically execute arrangement and ordering processes for the ball screw 1 when the first determination means 31 determines that the ball screw 1 is in a worn state. Specifically, the order management unit may send an order request message for the ball screw 1 to an information processing device of a pre-registered business operator for the ball screw 1 that is the maintenance target. The order management unit may also manage the delivery status and arrival date of the ordered ball screw 1. This allows the ball screw maintenance management system 100 to reduce the management work related to the maintenance of the ball screw 1.

The second determination means 32 determines whether the ball screw 1 is in a damaged state using the current value of the motor 4 acquired from the current sensor 6. As shown in FIG. 2, the second determination means 32 preferably determines whether the ball screw 1 is in a damaged state using the current value in the constant speed motion region of the motor 4 among the current values of the motor 4 acquired from the current sensor 6, in order to improve the accuracy of the determination (step S8).

If the current value of the motor 4 is equal to or greater than the threshold value (step S8 YES), the second determination means 32 determines that the ball screw 1 is damaged. In this case, the notification unit outputs an alarm indicating that it is time to replace the ball screw 1 (step S9). On the other hand, if the current value of the motor 4 is not equal to or greater than the threshold value (step S8 NO), the second determination means 32 determines that the ball screw 1 is not damaged. In this case, the second determination means 32 continues to make a determination based on the current value.

The motor 4 decelerates its rotation based on a command to decelerate rotation (step S10). When the motor 4 is in the decelerating rotation region, the movable nut 12 and the driving rod 7 fixed to the movable nut 12 are decelerating. The motor 4 then stops rotating based on a command to stop rotation (step S11). When the motor 4 stops rotating, the movable nut 12 and the driving rod 7 fixed to the movable nut 12 also stop moving.

Steps S1 to S11 may be repeatedly executed each time the ball screw device operates. This allows the ball screw maintenance management system 100 according to this embodiment to continuously determine whether the ball screw 1 is in a worn state and whether it is in a damaged state.

As described above, the ball screw maintenance management system 100 according to this embodiment can manage the timing of procuring the ball screw 1 by determining the wear state using the vibration sensor 5. This eliminates the need to stock spare parts in advance in case of a failure of the ball screw 1, and the number of spare parts for the ball screw 1 can be reduced. It is also possible to prevent the stop of the production line due to a failure of the ball screw 1. Furthermore, the ball screw maintenance management system 100 can manage the timing of replacing the ball screw 1 by determining the damage state using the current sensor 6. The ball screw maintenance management system 100 according to this embodiment can manage the maintenance timing, including the timing of procuring and replacing the ball screw 1.

Using FIG. 3, an example of the hardware configuration of the server 30 of the ball screw maintenance management system 100 according to the first embodiment will be described. The control panel 20 may also have a hardware configuration similar to that of the server 30. In FIG. 3, the server 30 has a processor 101 and a memory 102. The processor 101 may be, for example, a microprocessor, an MPU (Micro Processing Unit), or a CPU (Central Processing Unit). The processor 101 may include multiple processors. The memory 102 is configured by a combination of volatile memory and non-volatile memory. The memory 102 may include storage located away from the processor 101. In this case, the processor 101 may access the memory 102 via an input/output interface not shown.

In addition, each device in the above-described embodiments may be configured with hardware or software, or both, and may be configured with one piece of hardware or software, or may be configured with multiple pieces of hardware or software. The functions (processing) of each device in the above-described embodiments may be realized by a computer. For example, a program for performing the operations in the embodiments may be stored in memory 102, and each function may be realized by executing the program stored in memory 102 by processor 101.

The program includes instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The program may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray (registered trademark) disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, a transitory computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

The present invention is not limited to the above embodiment, and can be modified as appropriate without departing from the spirit and scope of the invention.

REFERENCE SIGNS LIST 1 Ball screw 2 Bearing 3 Bearing 4 Motor 5 Vibration sensor 6 Current sensor 7 Drive rod 8 Coupling 9 Base frame 10 Connection portion 11 Ball screw shaft 12 Movable nut 20 Control panel 21 Amplifier 22 Amplifier 23 Logger 24 Recording medium 30 Server 31 First determination means 32 Second determination means 100 Ball screw maintenance management system 101 Processor 102 Memory

Claims (9)

A ball screw;
A motor that drives the ball screw;
a vibration sensor for detecting vibration of the ball screw;
a first determination means for determining whether or not the ball screw is in a worn state by using vibration information in a constant speed rotation region of the motor among vibration information of the ball screw acquired from the vibration sensor ,
The ball screw has a ball screw shaft and a movable nut that moves along the ball screw shaft,
The vibration sensor is provided on the movable nut.
Ball screw maintenance management system. a current sensor for detecting a current value of the motor;
and a second determination means for determining whether or not the ball screw is damaged by using the current value of the motor acquired from the current sensor.
The ball screw maintenance management system according to claim 1. the second determination means determines whether or not the ball screw is damaged by using a current value in a constant speed rotation region of the motor among the current values of the motor acquired from the current sensor.
The ball screw maintenance management system according to claim 2. Further comprising a notification unit that notifies a result of the determination by the first determination means or the second determination means.
The ball screw maintenance management system according to claim 2 or 3. The ball screw has a ball screw shaft and a movable nut that moves along the ball screw shaft,
Further comprising a bearing for receiving the ball screw shaft,
The vibration sensor is provided in the bearing.
The ball screw maintenance management system according to any one of claims 1 to 4. A ball screw maintenance management method for managing ball screw maintenance timing using a computer, comprising the steps of:
acquiring vibration information of the ball screw from a vibration sensor;
determining whether or not the ball screw is in a worn state by using vibration information in a constant speed rotation region of a motor that drives the ball screw among the vibration information of the ball screw that has been acquired;
The ball screw has a ball screw shaft and a movable nut that moves along the ball screw shaft,
The vibration sensor is provided on the movable nut.
Ball screw maintenance management method. Acquire a current value of the motor from a current sensor;
Using the acquired current value of the motor, it is determined whether or not the ball screw is in a damaged state.
The ball screw maintenance management method according to claim 6 . determining whether or not the ball screw is damaged by using a current value in a constant speed rotation region of the motor among the current values of the motor acquired from the current sensor;
The ball screw maintenance management method according to claim 7 . When it is determined that the ball screw is in a worn state, a process of arranging the ball screw is automatically executed.
The ball screw maintenance management method according to any one of claims 6 to 8 .

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