JP7528860B2 - Key wear detector - Google Patents

Description

The present invention relates to a key wear detection device that detects wear on a key used in the connection between a rotating shaft and a rotating body.

2. Description of the Related Art In a conventional power transmission device, it is known to use a key as a mechanical element at a connection between a rotating body such as a belt or gear and a rotating shaft that transmits power to the rotating body.
The key fits into both a groove formed on the outer wall of the driving shaft and a groove formed on the driven rotor, preventing circumferential slippage and ensuring that the rotational force of the driving shaft is transmitted to the driven side.

However, this key requires replacement of elements due to mechanical wear, the extent of which cannot be visually ascertained by external inspection while the driveline is in operation.
For this reason, while the power transmission device is in operation, it is difficult to visually recognize the time and timing when it is necessary to stop the power transmission device.

The key at the connection part becomes mechanically worn due to the drive motor repeatedly rotating forward and backward. In machines or equipment that use this key structure, when the degree of wear on the key becomes significant due to aging, it is necessary to stop the power transmission device to replace the part.

The device in Patent Document 1 is not intended to detect the amount of wear on the key while the power unit is in operation.

JP 2003-172668 A

Previously, the only way to detect whether or not a key was worn and the amount of wear was to stop the power transmission equipment and inspect and investigate the amount of wear on the key. This required a long period of work suspension due to equipment shutdown, which resulted in a decrease in equipment operating rates.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a key wear detection device that can detect the degree of wear on a key in a power transmission system while the power transmission device is in operation, without stopping the equipment.

The key wear detection device of the present invention is configured to include a rotating shaft (3) of a drive motor (2), a rotating body (10) that rotates in sync with the rotating shaft, a load means (20) that applies a load to the rotating body, a key member (30) having one end (31) that fits into a first groove (5) formed in the rotating shaft and the other end (32) that fits into a second groove (12) formed in the rotating body, a torque detection means (51) that detects the torque value output by the drive motor, and a key wear determination means (53) that determines the degree of key wear based on the detected torque value detected by the torque detection means.

For example, one end of the key member is fitted into the first groove formed in the outer peripheral wall (4) of the rotating shaft, and the other end is fitted into the second groove formed in the inner peripheral wall (11) of the rotating body.
The load means may be any one of a gear device, a cam device, and a belt transmission device, but is not limited to these devices.

In general, when operating a power transmission device such as a gear device, cam device, or belt transmission device, the key member that mechanically connects the rotating shaft of the drive motor to the rotating body experiences increased wear at the mechanical connection points each time the power transmission is turned on and off.

As a result of the magnitude of the wear amount, the key wear amount determining means outputs a signal based on the torque value detected by the torque detecting means.
Based on the output result of the key wear amount determining means, the operator can know the degree of wear of the key member.

Therefore, an operator can detect the degree of wear on the key component while operating a machine equipped with a power transmission device. Since the operator can know the actual physical degree of wear on the key component without having to investigate the degree of wear on the key component at the site where the key component is located, the operator can determine whether or not the key component needs to be replaced based on the results of this key wear determination means.

Therefore, by replacing the key parts before the machinery or equipment breaks down, the number of breakdowns can be reduced and a decrease in the availability rate of the equipment or machinery in operation can be prevented. Wear detection can be performed while the equipment or machinery is operating without having to stop operation.

1 is a perspective view of a first embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a first embodiment of the present invention. FIG. 4 is a characteristic diagram showing the relationship between the amount of key wear, the detected torque value, and the motor operation, according to the first embodiment of the present invention. 4 is a schematic diagram showing an operation state and an operation image in relation to FIG. 3 . FIG. 4 is a characteristic diagram showing the relationship between the amount of key wear and the detected torque value, showing experimental data of the device according to the first embodiment of the present invention. 5 is a diagram for explaining an assumed phenomenon when the detected torque value of the device according to the first embodiment of the present invention differs from the positional relationship between the key member, the rotating shaft, and the rotating body. FIG. 1 is a block diagram of an apparatus according to a first embodiment of the present invention; 2 is a flow chart of an apparatus according to a first embodiment of the present invention. FIG. 6 is a schematic diagram showing changes in wear amount of a key member over time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in a plurality of embodiments, substantially the same components are denoted by the same reference numerals, and description thereof will be omitted.
First Embodiment

In the first embodiment, a key wear detection device of the present invention is applied to a belt transmission device.
1 shows a mechanical portion of a key wear detection device to which the present invention is applied. This key wear detection device shows an embodiment in which the key wear detection device is applied to a key structure that connects a drive pulley of a belt transmission device and a rotary shaft of a drive motor.

As shown in FIG. 1, a rotating shaft 3 of a servo motor 2 serving as a drive motor attached to a frame 1 is connected to a drive pulley 10 serving as a rotating body by a key structure. A belt 20 is wound around the drive pulley 10, and then wound around a tail pulley (not shown) via bend pulleys 41 and 42. A feed mechanism, for example, as a load means is provided on the driven pulley (not shown) side by the drive of this belt 20. The operation of this feed mechanism, for example, transports in and out a pallet (not shown).

As shown in Figures 1 and 2, a first groove 5 serving as a keyway is formed in the outer peripheral wall 4 of the rotating shaft 3 of the servo motor 2. A second groove 12 serving as a keyway is formed in the inner peripheral wall 11 of the driving pulley 10 serving as a rotating body. One end 31 of a rod-shaped key member 30 fits into the first groove 5, and the other end 32 fits into the second groove 12. This mechanically connects the rotating shaft 3 and the driving pulley 10, and the torque of the rotating shaft 3 on the driving side is transmitted to the driving pulley 10 on the driven side. The rotating shaft 3 rotates in both the forward and reverse directions.

The servo motor 2 performs one of three operations: forward rotation, reverse rotation, or stop. As shown in FIG. 7, during operation, a programmable logic controller (PLC) 52 as a control device issues instructions to a servo driver 51 in response to a command from a personal computer (PC) 53, and the servo driver 51 outputs a drive signal to the servo motor 2.

The servo driver 51 follows commands from the PLC 52 and controls the output torque, rotational speed, and position of the servo motor 2. The PLC 52 outputs a target value for the belt position to the servo motor 2. A servo amplifier (not shown) receives the target value from the PLC 52 and supplies the output (power) required for the servo motor 2 to move according to the target value. An encoder (not shown) detects the actual rotational position and speed of the servo motor 2, and returns the electrical signal to the servo amplifier as a feedback signal. The encoder takes in the signal from the servo motor 2 and returns it to the servo amplifier. The target value output by the PLC 52 is then compared with the feedback signal, and the output of the servo motor 2 is controlled so that the error approaches zero.

As a result, the drive pulley 10 operates as desired in unison with the rotating shaft 3 of the servo motor 2. When the rotating shaft 3 rotates forward, reverses, or stops, the drive pulley 10 rotates forward, reverses, or stops in synchronization.

In the belt transmission device, the key member 30 that mechanically connects the rotating shaft 3 and the drive pulley 10 is subject to mechanical wear due to deterioration of materials, deterioration of parts, generation of frictional force, and the like.
FIG. 9 is a schematic diagram showing a number of key shapes exhibiting different degrees of key wear.

For example, as shown in Figure 9, which shows the amount of wear δ of the key member, over time, the shape of the key member 30 changes due to wear in the order of (A), (B), and (C). From the initial state (A) where there is no wear, the amount of wear δ increases as the time of use increases.

If the wear amount continues to increase through the intermediate period (B) of wear amount δ1 and then left unattended, it will reach the final period (C) of wear amount δ2 (> δ1) and will stop operating when it breaks down.

This change in the amount of wear δ affects the value of the load caused by the reaction of the driving force of the servo motor 2. The load acts on the rotating shaft 3 of the servo motor 2 through the belt 20 shown in FIG. 1, the drive pulley 10, and the key member 30.

As shown in FIG. 7, the servo driver 51 detects the load acting on the servo motor 2, and outputs the detected load signal to the PC 53 via the PLC 52. The PC 53 then calculates, processes, and judges the detected torque value.

As shown in FIG. 8, the PC 53 detects the input detected torque value (step S55), determines whether the detected torque value exceeds a reference value (step S56), and if the detected torque value exceeds the reference value, determines that the wear is abnormal and issues a warning indicating abnormal wear (step S57). If the detected torque value does not exceed the reference value, the process returns to the previous step.

In this manner, the torque value is analyzed based on the load acting on the servo motor 2, and the operator is notified of any abnormal wear of the key member 30.
(Experiment 1)

In experiment 1, the load on the servo motor, which varies with the wear amount of the key member as one of its factors, was compared for an operating period of 2 seconds with changes in the detected torque value output during this operating period.
The raw waveform of one cycle of the servo motor torque experiment results is shown in Fig. 3. Fig. 3 shows the transition of the detected torque value for each of Experimental Examples 1 to 4, which have different amounts of key wear.

The experimental conditions were the same for Experimental Examples 1 to 4, a load of 60 kg and a belt tension of 320 N. For Experimental Examples 1 to 4, the wear amount δ (mm) of the key member was used as a variable.
Experimental Example 1: Wear amount δ=0,
Experimental Example 2: Wear amount δ=0.1,
Experimental Example 3: Wear amount δ=0.2,
Experimental Example 4: The amount of wear δ was set to 0.5.

For Experimental Examples 1 to 4, one cycle consisted of stopping, rotating forward, stopping, and rotating backward for two seconds.

The detected torque value was analyzed by dividing it into a stop period A, a forward rotation period B, a stop period C, and a reverse rotation period D. The waveform of the detected torque value is as shown in FIG.
For each experimental example, the image of the rotational positions of the rotating shaft, rotating body, and drive pulley during the operation period of 2 seconds is as shown in FIG.

A, B, C, and D shown in FIG. 4 show instantaneous images of the operating state during the stop period A, forward rotation period B, stop period C, and reverse rotation period D shown in FIG.
(Experiment 2)

In experiment 2, the peak values of the detected torque were compared based on the experimental data obtained in experiment 1.
FIG. 5 shows experimental data extracted for each experimental example from the graph shown in FIG.

During forward rotation of the servo motor, the peaks of the detected torque value are designated as positive peaks 35, 36, 37, and 38 in the first to fourth experimental examples, respectively.
During reverse rotation of the servo motor, the peaks of the detected torque value are valley (negative) peaks 55, 56, 57, and 58 for Experimental Examples 1 to 4, respectively.

Normality or abnormality was determined depending on whether these peak values exceeded or fell below the standard values of the peaks or valleys.
As a result of the analysis, comparing Experimental Examples 1 to 4, the number of peaks of mountains or valleys (positive or negative) during acceleration during rotation increases in both forward and reverse directions as the amount of key wear increases.

At this time, it can be seen that a torque peak occurs when slippage occurs between the rotating shaft and the drive pulley during both forward and reverse rotation.
When slip occurs during forward rotation, slip occurs at the peak values of the torque crests indicated by reference numerals 35, 36, 37, and 38, and when slip occurs during reverse rotation, slip occurs at the peak values of the torque valleys indicated by reference numerals 55, 56, 57, and 58.

The expected phenomenon is shown in a schematic diagram in Figure 6. When the detected torque value exceeds the torque corresponding to the maximum static friction force, slip occurs.
In Figure 6, A shows the positions and relative positional relationships of the rotating shaft, key member, and drive pulley when they rotate together, B shows the case when the detected torque value is equal to or less than the torque value corresponding to the maximum static friction force, C shows the case when the detected torque value exceeds the torque corresponding to the maximum static friction force and slippage occurs, and D shows the case when they rotate together due to the key member being maintained engaged.

In FIG. 6A, when the rotating shaft rotates clockwise, the drive pulley rotates in the same direction as the rotating shaft via the key member.
In FIG. 6B, when the rotating shaft rotates clockwise, if the torque corresponding to the frictional force is greater than the detected torque, they rotate together.
In FIG. 6C, when the detected torque becomes larger than the torque equivalent to the frictional force, the torque rotating the rotating shaft in the clockwise direction becomes larger than the torque equivalent to the frictional force that tries to stop the drive pulley from the load means, causing the rotating shaft to slip.
In FIG. 6D, although there is slippage, the rotary shaft and the drive pulley rotate together due to the keyed connection.

The positive torque value reaches a peak value during acceleration at the start of forward rotation. The negative torque value reaches a peak value during acceleration at the start of reverse rotation. In all experimental examples 1, 2, 3, and 4, the detected torque value reaches a peak value during forward rotation acceleration and reverse rotation acceleration.

It can be seen that the detected torque value increases as the amount of key wear increases. A reference detection torque value for the detected torque value was identified.

In this embodiment, when the detected torque value exceeds a specific reference value, it is determined that an abnormal value for wear needs to be reported.

According to this embodiment, in a power transmission device having a key structure, it is possible to detect key wear while the machine equipment is in operation.
In the present invention, an abnormality in the key member can be notified based on the analysis results of the detected torque value.
Other Embodiments

The judgment in the first embodiment described above was made based on the change in the detected torque value over one cycle of the drive motor rotating forward, stopped, reverse, and stopped again, but the judgment of the present invention is not limited to this and can also be made based on the change in the detected torque value over the above-mentioned multiple cycles.
The determination of the analysis result of the present invention is not limited to the flowchart shown in FIG.

The judgment was made by comparing the peak value of the crest during forward rotation with a reference value, and by comparing the peak value of the trough during reverse rotation with a reference value, but in the present invention, an abnormality may be notified when it is detected that either the peak value of the crest or the peak value of the trough exceeds the reference value, or when it is detected that both exceed the reference value.

In the present invention, the judgment may be made by selecting a peak value or by determining whether the characteristics of the detected torque waveform deviate from a standard.

The first embodiment described above is applied to a key structure that connects the belt transmission motor shaft and the drive pulley as a rotating body, but the present invention can be applied to power transmission devices with other types of key structures.

As another embodiment, the embodiment is not limited as long as the rotating body is connected to the rotating shaft using a key member instead of a pulley. The rotating body may be, for example, a gear or other rotating body for transmitting power.

The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the invention.

2 servo motor (drive motor),
3. Rotation axis,
4 outer wall,
5 First groove,
10 Drive pulley (rotating body),
11 Inner peripheral wall,
12 second groove,
20 Belt (loading means),
30 key member,
31 One end,
32 other end,
41 Bend pulley,
42 Bend pulley,
50 servo motor,
51 Servo driver (torque detection means),
52 Programmable Logic Controller (PLC),
53 Personal computer (PC) (key wear determining means).

Claims (7)

A rotating shaft (3) of a drive motor (2);
A rotating body (10) that rotates in synchronization with the rotating shaft;
A load means (20) for applying a load to the rotating body;
a key member (30) having one end (31) fitted into a first groove (5) formed in the rotating shaft and having the other end (32) fitted into a second groove (12) formed in the rotating body;
A torque detection means (51) for detecting a torque value output by the drive motor;
and a key wear determination means (53) for determining the degree of key wear based on the detected torque value detected by the torque detection means. The key wear detection device according to claim 1, wherein one end of the key member fits into the first groove formed in the outer peripheral wall (4) of the rotating shaft, and the other end fits into the second groove formed in the inner peripheral wall (11) of the rotating body. The key wear detection device according to claim 1 or 2, wherein the load means is a gear device. The key wear detection device according to claim 1 or 2, wherein the load means is a cam device. The key wear detection device according to claim 1 or 2, wherein the load means is a belt transmission device. Manufacturing device. The key wear detection device according to any one of claims 1 to 5, characterized in that the key wear determination means compares the peak value of the detected torque value with a reference value and determines that the key is worn when the peak value exceeds the reference value. The key wear detection device according to any one of claims 1 to 5, characterized in that the key wear determination means compares the peak value of the detected torque value with a reference value based on the transition of the detected torque value in one cycle of forward rotation, stop, reverse rotation, and stop of the drive motor, and determines that the key is worn when the peak value exceeds the reference value.

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