JP7749482B2 - Spline diagnostic device, hoist, and electric vehicle - Google Patents

Description

The present invention relates to a spline diagnostic device that diagnoses the wear and deterioration of splines, which are part of a power transmission mechanism, as well as a hoist and an electric vehicle.

A spline is a connection method used to transmit mechanical rotational force. One of the shafts that make up the spline (hereafter referred to as the spline shaft) has gear teeth machined into its outer periphery, while the other shaft (hereafter referred to as the boss) has a concave-convex groove machined into which the spline shaft's gear is inserted.

By fitting a splined shaft into a boss, it is possible to transmit large rotational forces. In this way, the gears on the splined shaft are fitted into the grooves of the boss, which has the advantage that no slippage occurs even when large rotational forces are applied, compared to power transmission mechanisms such as couplings, and therefore it is often used in applications where large rotational forces are to be transmitted.

In addition, since the gear on the spline shaft fits into the axial groove formed in the boss, there is a tiny gap between the two. Because it is movable in the axial direction, even if slight axial displacement occurs on the spline shaft or boss side, that movement can be absorbed.

One application of splines is in hoists. A hoist is a lifting device equipped with an electric motor, and is an industrial machine that moves a suspended load upward by winding up a wire rope and moves it downward by winding down the wire rope.

In a hoist, if slippage occurs in the torque transmission section while lifting a load, there is a risk that the load may tilt. To prevent this slippage, a spline connection method is used to transmit the torque of the electric motor to the hoisting mechanism.

As mentioned above, there is a tiny gap between the gear on the spline shaft and the groove on the boss, which causes the gear on the outer periphery of the spline shaft to make partial contact with the groove on the boss when the electric motor rotates. In the case of a hoist, the rotation direction of the electric motor is reversed when raising and lowering the load, so the tooth surface on the different side of the gear during forward and reverse rotation makes partial contact with the wall of the groove.

Furthermore, when a hoist is used over an extended period of time, the tooth surfaces of the spline shaft gear gradually wear down and deteriorate, which can lead to problems with the transmission of rotational force. For this reason, it is important to inspect the spline shaft periodically to check for deterioration. However, because the spline shaft gear is fitted into a groove in the boss, it is impossible to visually check the condition of the gear while it is fitted. Therefore, for inspection, the spline shaft must be removed from the boss and opened for inspection, which is a labor-intensive process. Furthermore, this method does not provide any insight into impending failure.

To solve this problem, methods for checking the wear and deterioration of splines without removing the spline shaft from the boss are known, as described in Japanese Patent Laid-Open Nos. 5-164656 (Patent Document 1) and 5-346323 (Patent Document 2).

Patent Document 1 describes a method that uses a vibration sensor attached near the spline shaft. Specifically, because there is a very high correlation between the vibration velocity or vibration acceleration detected by the vibration sensor and the actually measured wear amount of the gears on the spline shaft, it is possible to estimate the wear amount of the gears on the spline shaft from the values of the dynamic velocity or vibration acceleration.

Patent Document 2 also describes a method that uses a displacement meter installed on a spline shaft. Specifically, the displacement meter measures the circumferential gap when the spline shaft is accelerated or decelerated, and the amount of wear on the gears of the spline shaft is estimated from the gap amount, making it possible to inspect the wear on the gears of the spline shaft without releasing the spline.

Japanese Patent Application Publication No. 5-164656 Japanese Patent Application Publication No. 5-346323

However, the methods described in Patent Documents 1 and 2 require the installation of a vibration sensor or displacement gauge near the spline shaft, which may make it impossible to install the sensor due to spatial constraints. Furthermore, if an abnormality occurs in the vibration sensor or displacement gauge, the area near the spline shaft must be opened to allow maintenance of the sensor itself.

The object of the present invention is to provide a spline diagnostic device, hoist, and electric vehicle that can check the wear and deterioration of the gears on a spline shaft without removing the spline shaft from the boss, and that does not require opening the area near the spline shaft for maintenance of the sensor itself.

The present invention features a spline diagnostic device that includes a current measurement unit that measures the current of an electric motor that drives a spline shaft, a frequency component calculation unit that performs frequency analysis of the current measured by the current measurement unit to calculate specific frequency components, and a wear condition estimation unit that estimates the wear condition of the gears of the spline shaft based on the specific frequency components calculated by the frequency component calculation unit.

This invention makes it possible to estimate the wear and deterioration of the gears on the spline shaft based on the current of the electric motor that drives the spline shaft, eliminating the need for open inspection of the spline. Furthermore, because a current sensor is installed on the cable that supplies power to the electric motor, there is no need to open the area near the spline shaft even if a malfunction occurs in the sensor.

1 is a configuration diagram showing the configuration of a crane to which the present invention is applied. 10 is an explanatory diagram showing the state in which the spline shaft and the boss portion are fitted together, showing a state in which the teeth of the spline and the concave-convex grooves of the boss are not in contact with each other. FIG. 10 is an explanatory diagram showing the state in which the spline shaft and the boss portion are fitted together, showing the state in which the teeth of the spline and the concave-convex grooves of the boss are in contact with each other. FIG. FIG. 4 is a flowchart showing a flow of diagnosis of wear of a spline according to an embodiment of the present invention. 10 is an explanatory diagram illustrating a process from current measurement to calculation of a parameter P (current intensity) according to an embodiment of the present invention. FIG. FIG. 10 is an explanatory diagram illustrating the feature amount of a normal spline. FIG. 10 is an explanatory diagram illustrating a feature amount of a worn spline. FIG. 10 is an explanatory diagram illustrating the distribution of the number of driving operations and the feature amount. FIG. 10 is a configuration diagram showing the configuration of a crane according to another embodiment of the present invention. 7 is an explanatory diagram illustrating the relationship between the amount of lifting load and the characteristic amount of a normal spline in the hoist A in the embodiment shown in FIG. 6. FIG. 7 is a diagram illustrating the relationship between the amount of suspended load and the characteristic amount of the spline where wear has occurred in the hoist A in the embodiment shown in FIG. 6 . 7 is an explanatory diagram illustrating the relationship between the amount of lifting load and the characteristic amount of a normal spline in the hoist B in the embodiment shown in FIG. 6. FIG. 7 is a diagram illustrating the relationship between the amount of suspended load and the characteristic amount of the spline where wear has occurred in the hoist B in the embodiment shown in FIG. 6 . 7 is an explanatory diagram illustrating the relationship between the amount of lifting load and the characteristic amount of a normal spline in the hoist C in the embodiment shown in FIG. 6. 7 is a diagram illustrating the relationship between the amount of suspended load and the characteristic amount of the spline where wear has occurred in the hoist C in the embodiment shown in FIG. 6 .

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and its scope also includes various modifications and applications within the technical concept of the present invention.

Note that while the following example of the application of the spline connection method focuses on the splines of a hoist, it is not limited to hoists and the present invention can be applied to any spline shaft driven by an electric motor, including mechanisms that use electric motors to drive the wheels, such as those found in electric and hybrid vehicles.

Figure 1 shows the basic configuration of a hoist. As shown in Figure 1, the hoist motor 10 is connected to a power source 12 via an electric wire 11, and a three-phase voltage is applied to the hoist motor 10. When the three-phase voltage is applied, the hoist motor 10 rotates, which in turn rotates the shaft 13 of the hoist motor 10. The outer circumferential surface of one end of the shaft 13 is a spline shaft 13S that is gear-shaped and is fitted into a concave-convex groove in a boss 14 for connection.

This transmits the rotational force of the hoisting motor 10 to the hoisting mechanism (hoist drum) 15. When the hoisting mechanism 15 rotates, the wire rope 16 attached to the hoisting mechanism 15 is wound up, and the hook 17 at the end and the suspended load 18 fixed to the hook 17 are raised. Furthermore, when the rotation direction of the hoisting motor 10 is reversed, the wire rope 16 is unwound, causing the hook 17 to move downward. This also allows the suspended load 18 to move downward and be lowered.

In this way, the basic operation of the hoist is to hoist the load 18 using the rotational force of the hoisting motor 10. In addition, a current measurement means 19 for measuring current is provided in at least one phase of the electric wire 11. The current data measured by the current measurement means 19 is input into the diagnostic device 20, which diagnoses the wear and deterioration state of the spline shaft 13S. The results of the diagnosis are displayed on the display unit 21.

Note that while Figure 1 shows an example in which the current measurement means 19 is installed on the electric wire 11, if the power source 12 is an inverter, it is also possible to use information such as the current feedback value and current command value used to control the inverter instead. Furthermore, the diagnostic device 20 can also be implemented in an electronic component capable of performing calculations, such as a microcomputer inside the inverter.

Figure 2(a) shows a diagram simulating the cross section of the spline shaft 13S and the grooves of the boss 14. Note that the cross-sectional shape of the gear of the spline shaft 13S is an example and is not limited to this. As shown in Figure 2(a), the spline 22 is such that the gear 23 of the spline shaft 13S is fitted and coupled to the groove 24 of the boss 14 in the axial direction. To enable this fitting coupling, a small gap G exists between the gear 23 and the groove 24. The gears 23 are provided on the spline shaft 13S at regular intervals around the circumference. The gear 23 has tooth surfaces 23f and 23r that come into contact with the groove 24 of the boss 14.

On the other hand, Figure 2(b) shows the rotation of the spline shaft 13S, which is the drive shaft. When the spline shaft 13S rotates in the direction of arrow (F), the tooth surface 23f of the gear 23 comes into contact with the wall surface of the concave-convex groove 24 of the boss 14, transmitting rotational force from the spline shaft 13S to the boss 14. Although not shown, when the spline shaft 13S rotates in the opposite direction to the direction of arrow (F), the tooth surface 23r of the gear 23 comes into contact with the opposite wall surface of the concave-convex groove 24 of the boss 14, transmitting rotational force in the direction opposite to the arrow (F) to the boss 14.

In the case of a hoist, for example, rotating in the direction of arrow (F) raises the load 18, and rotating in the opposite direction to arrow (F) lowers the load 18. By repeating these operations, the spline shaft 13S rotates forward and backward repeatedly, which causes the tooth surfaces 23f and 23r to wear down and become damaged, leading to increased wear.

Furthermore, as mentioned above, because the operation differs between the forward and reverse directions, wear may not progress uniformly on tooth surfaces 23f and 23r of gear 23. If wear on tooth surfaces 23f and 23r progresses, gear 23 may lose its functionality, resulting in poor transmission of rotational force. Therefore, it is necessary to detect deterioration of gear 23 before it loses its functionality.

Next, we will explain the operation (wear detection method) of the spline diagnostic device 20 proposed in this invention to address the above-mentioned issues. Note that the following explanation can also be applied to diagnosing the occurrence of a failure and predicting the occurrence of a failure.

Figure 3 shows a flowchart illustrating the processing flow of the diagnostic device 20, and Figure 4 shows a method for diagnosing faults using current.

In "Step S1," as shown in Figure 4(a), the current measuring means 19 acquires the current flowing through the hoist motor 10 for the Δt interval. The method of acquiring the current for the Δt interval may involve moving to "Step S2" (sequential calculation) once only the Δt interval has been acquired, or it may involve measuring data for the entire interval (here, interval T), dividing the data into Δt intervals, and then moving to Step S2 (on-demand calculation).

Next, in steps S2 to S4, as shown in Figure 4(b), a frequency analysis such as a fast Fourier transform (FFT) is performed on the current in the Δt interval to calculate the frequency spectrum. As shown in Figure 4(b), the frequency spectrum of the current has a peak at the fundamental frequency of the current, and then declines from there to the low-frequency and high-frequency sides.

From this frequency spectrum, a specific frequency spectrum is extracted and stored as parameter P. In the example of hoist spline diagnosis, the value of a specific frequency component (indicated by the arrow (P) in Figure 4(b)) that appears as a sideband of the fundamental frequency of the current is extracted as parameter P (current strength).

The specific frequency component mentioned above is a sideband component of the current drive frequency (Fb) in the frequency spectrum obtained by frequency analysis of the current, and is the current intensity of at least one of the frequencies (Fb+Fr and Fb-Fr) resulting from the motor rotation frequency (Fr).

This embodiment is characterized by detecting the phenomenon of rotational wobble caused by wear on the tooth surface of the gear 23 of the hoist spline shaft 13S using the current flowing through the hoist motor 10. In this embodiment, in order to extract multiple parameters P from the current data during a single drive of the hoist motor 10, data for a T interval is divided into multiple Δt intervals (T > Δt), and the parameter P is calculated for each Δt interval. Here, the Δt interval is set to be greater than the reciprocal (1/Fb) of the current drive frequency (Fb).

By dividing in this way, T/Δt parameters P can be calculated and stored. The stored parameters P will have a frequency distribution similar to that shown in Figure 4(c). As will be described later, diagnosis is performed by focusing on the fact that the distribution of parameters P changes due to the influence of rotational wobble caused by wear of the spline 22.

Therefore, in "Step S5", it is determined whether T/Δt (a predetermined number) of parameters P have been stored. If the predetermined number of parameters P have not been stored, the process returns to "Step S1" and executes the same process again. On the other hand, if the predetermined number of parameters P have been stored, the process proceeds to "Step S6".

In "Step S6", statistics of information related to the distribution of T/Δt parameters P (hereinafter referred to as the parameter group) are extracted as features. Specific examples of statistics include the following: In the frequency distribution of Figure 4(c), in addition to the maximum, minimum, and mean values, there are also the median, which represents the position where the left and right areas of the distribution are equal, and the mode, which is the most frequent value. In this embodiment, the mean value described above is used as the feature.

In addition, other statistics that represent the spread of a distribution, such as range (the difference between maximum and minimum), variance, and standard deviation, can also be used. Furthermore, statistics that represent the shape of a frequency distribution, such as skewness and kurtosis, can also be used. Furthermore, the feature is not limited to one, and multiple statistics can be used, or a new evaluation index calculated from multiple statistics can be used as a feature. In this way, the key is to use the statistics of information related to the distribution of a group of parameters as a feature.

Finally, in "Step S7", the state of the spline is judged based on the feature amount (average value). To explain one example of the judgment method, first, the feature amount (average value) when the spline 22 is in a normal state is used as learning data (reference value for judgment = threshold value). Next, the degree of deviation between the feature amount (average value) at the time of diagnosis and the learning data (reference value for judgment = threshold value) is calculated, and if this degree of deviation exceeds a predetermined degree of deviation, it is judged that "the state of the spline is abnormal (worn)."

Figures 5(a) and 5(b) show the frequency distribution of parameter P when the hoist's spline 22 is in a normal state and when wear has progressed. Note that only the state of the spline 22 is different; the load of the suspended load, operating time, etc. are the same.

As shown in Figures 5(a) and 5(b), the shape of the frequency distribution differs depending on the state of wear of the gear 23 on the spline shaft 13S of the spline 22. In this example, the average value of the distribution of parameter P is lower in the frequency distribution of Figure 5(b), which shows a deteriorated spline 22, than in the frequency distribution of Figure 5(a), which shows a normal spline 22. In this way, wear on the gear 23 on the spline shaft 13S can be determined using feature quantities.

Figure 5(c) shows the results of confirming reproducibility. A spline 22 in a normal state and a spline 22 with advanced wear were installed on a hoist and operated multiple times, and a feature value (in this example, the average value of parameter P) was extracted from the current data for each run.

As can be seen from Figure 5(c), if the condition remains the same, the feature value remains stable, and the magnitude of the feature value can be used to determine whether the gear 23 of the spline shaft 13S is normal or has progressed in wear. In this way, in this embodiment, the wear state of the spline 22 is diagnosed based on the fact that, under the same operating conditions, the distribution of the parameter P calculated from the current changes depending on the wear state of the spline 22. Note that, although the current intensity is used as the parameter P in this embodiment, it is not limited to this as long as it represents the wear of the spline.

Next, Figure 6 shows an embodiment for improving diagnostic accuracy of the spline 22. This embodiment differs from the configuration shown in Figure 1 above in that a hoisting load meter 25 is added as an input for diagnosis. The principle behind improving diagnostic accuracy by adding the hoisting load is explained below.

Figures 7 to 9 show the results of measuring the current of the hoisting motor 10 when three different types of hoists (A, B, C) were driven with the lifting load changed to three different loads (W1 < W2 < W3), and calculating the above-mentioned characteristic quantities (average values of parameter P shown in Figures 5(a) and 5(b)). Note that these show the characteristic quantities when the hoists were operated multiple times with each lifting load, and are the results of an evaluation that takes into account measurement variability.

Figure 7(a) shows the correlation between the feature quantity and the amount of lifted load obtained from the current of the hoisting motor 10 measured when a normal spline was installed in an arbitrary hoist (referred to as hoist A). On the other hand, Figure 7(b) shows the correlation between the feature quantity and the amount of lifted load obtained from the current of the hoisting motor 10 measured when only the spline of hoist A was replaced with a worn part.

As shown in Figure 7(a), for a normal spline, the feature quantity has a positive correlation (positive slope Sn) with an increase in the hanging load (W1<W2<W3), whereas as shown in Figure 7(b), for a worn spline, the feature quantity has a negative correlation (negative slope Sd) with an increase in the hanging load (W1<W2<W3).

In this study, only the splines were changed from normal to worn, so the change in the correlation between the feature amount and the amount of lifting load can be attributed to the effect of spline wear. Therefore, it is possible to diagnose spline wear based on the correlation between the feature amount and the amount of lifting load (for example, the difference between the slope Sn and the slope Sd).

We will also explain why diagnosis is based on the correlation between feature values and the amount of lifting load, rather than on the magnitude of feature values. For example, in the examples of Figures 7(a) and 7(b), the feature values for a lifting load (W2) are nearly identical for a normal spline and a worn spline, making it difficult to diagnose using feature values alone. However, by also evaluating feature values for other lifting loads (W1 and W3), spline wear can be diagnosed with high accuracy.

Next, Figures 8(a) and 8(b) show an example of a case examined using another hoist (referred to as hoist B). In the case of hoist B, the correlation between the feature value and the amount of lifted load is positive (both the slope Sn and the slope Sd are positive) for both normal and worn splines. However, it can be seen that the magnitude of the slope is "Sn > Sd."

In this study, as mentioned above, only the spline on hoist B was changed from a normal part to a worn part, so it can be assumed that the change in the correlation between the feature amount and the lifting load amount is due to the effect of spline wear. Therefore, this case also shows that spline wear can be detected by the correlation (magnitude of the slope) between the feature amount and the lifting load amount.

Furthermore, as with Hoist A, when diagnosis is made based solely on the magnitude of the feature values, the feature values for normal and worn splines at the time of the lifting load (W2) are nearly identical, making it clear that diagnosis based solely on feature values is difficult. These results also show that spline wear can be accurately detected by making a diagnosis based on the correlation between feature values and lifting load.

Next, Figures 9(a) and 9(b) show a case study using yet another hoist (called Hoist C). In the case of Hoist C, the correlation between the feature value and the amount of lifted load is negative (both the slope Sn and the slope Sd are negative) for both normal and worn splines. However, it can be seen that the magnitude of the slope is "Sn < Sd."

In this study, just like with Hoist A and Hoist B described above, only the splines were changed from normal to worn, so the change in the correlation between the feature values and the amount of lifted load can be assumed to be due to the effect of spline wear. Furthermore, for Hoist C, when a diagnosis is made based solely on the magnitude of the feature values, the feature values at the time of the lifted load (W1) are almost the same when normal and when worn, demonstrating that diagnosis based solely on the feature values is difficult. These results suggest that spline wear can be accurately detected by making a diagnosis based on the correlation (magnitude of the slope) between the feature values and the amount of lifted load.

Finally, an example of a method for evaluating the degree of wear (hereinafter referred to as wear degree D) will be described. In this embodiment, the wear degree D of the spline is evaluated based on the "correlation between the feature amount and the hanging load amount," and therefore the following evaluation formula (1) can be considered.
D=|S−Sn|…(1)
In the above equation, "S" is the slope of the correlation between the feature amount and the hanging load amount at the time of diagnosis, and "Sn" is the slope of the correlation between the reference feature amount and the hanging load amount (for example, the slope calculated when the spline is new).

By taking the absolute value of the difference between the slope (S) and slope (Sn) as the degree of wear (D), it is possible to assess that a large change in slope indicates a significant increase in wear. Note that the above formula simply shows the simplest way to assess the degree of wear (D), and is not limited to this.

For example, a cluster of normal slopes (Sn) may be defined, and the degree of deviation from that cluster may be evaluated as the degree of wear (D). Furthermore, to increase the sensitivity of the degree of wear (D), the slopes (S) and (Sn) may be weighted by multiplying them by a coefficient, or an index representing the correlation between the feature value and the amount of lifted load may be used instead of the slopes (S) and (Sn).

The embodiment described above relates to a hoist, but it can also be applied to electric vehicles such as electric cars and hybrid cars. In other words, when the power source 12 described above is a lithium power source, the hoisting motor 10 is a wheel drive motor, and the hoisting device 15 is a wheel, the configuration of this embodiment can be applied when power is transmitted using a spline to the connecting mechanism between the wheel drive motor and the wheel. The current measurement unit measures the current flowing in the wheel drive motor that drives the vehicle, and can diagnose spline wear based on the current flowing in the wheel drive motor.

As such, the present invention features a spline diagnostic device that includes a current measurement unit that measures the current of an electric motor that drives a spline shaft, a frequency component calculation unit that performs frequency analysis of the current measured by the current measurement unit to calculate specific frequency components, and a condition estimation unit that estimates the wear state of the gears of the spline shaft based on the specific frequency components calculated by the frequency component calculation unit.

This makes it possible to estimate the wear and deterioration of the spline shaft gears based on the current of the electric motor that drives the spline shaft, eliminating the need for open inspection of the spline. Furthermore, because the current sensor is installed on the cable that supplies power to the electric motor, there is no need to open the area near the spline shaft even if a malfunction occurs in the sensor.

The present invention is not limited to the several embodiments described above, and includes various modifications. The above embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the configurations described. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations with respect to the configuration of each embodiment.

10...hoisting motor, 11...electric wire, 12...three-phase power supply, 13S...spline shaft, 14...boss, 15...hoisting device, 19...current measuring unit, 20...diagnostic device, 21...display unit, 22...spline, 23...gear, 23f, 23r...tooth surface, 24...concave and recessed groove.

Claims (9)

A spline diagnostic device for diagnosing the wear state of gears on a spline shaft,
a current measuring unit that measures a current of an electric motor that drives the spline shaft;
a frequency component calculation unit that performs frequency analysis on the current measured by the current measurement unit to calculate a specific frequency component;
a wear state estimation unit that estimates a wear state of the spline shaft based on the specific frequency component calculated by the frequency component calculation unit ,
the frequency component calculation unit divides the current in a predetermined section measured by the current measurement unit into a plurality of analysis sections, and performs frequency analysis on the current in the analysis sections to calculate the specific frequency component;
The wear state estimation unit estimates the wear state of the spline shaft based on information related to the distribution of the specific frequency components in the plurality of analysis sections.
A diagnostic device for a spline. 2. The spline diagnostic device according to claim 1,
When the predetermined section is a T section and the analysis section is a Δt section, the current in the T section measured by the current measurement unit is divided into the Δt sections (<T),
the frequency component calculation unit performs frequency analysis on the current in the Δt section to calculate the specific frequency component;
The wear state estimation unit estimates the wear state of the spline shaft based on information relating to the distribution of the T/Δt number of specific frequency components.
A diagnostic device for a spline. 3. The spline diagnostic device according to claim 2,
The specific frequency component is a sideband component of the drive frequency (Fb) of the current in the frequency spectrum obtained by frequency analysis of the current, and is the current intensity of at least one frequency among frequencies (Fb+Fr and Fb-Fr) resulting from the rotation frequency (Fr) of the electric motor.
A diagnostic device for a spline. 4. The spline diagnostic device according to claim 3,
The Δt section is greater than the reciprocal (1/Fb) of the drive frequency (Fb) of the current.
A diagnostic device for a spline. 5. The spline diagnostic device according to claim 2, wherein:
The information relating to the distribution of the specific frequency components is at least one physical quantity selected from the maximum value, minimum value, average value, median value, and mode value of the T/Δt number of specific frequency components.
A diagnostic device for a spline. 5. The spline diagnostic device according to claim 2, wherein:
The information relating to the distribution of the specific frequency components is at least one physical quantity among the variance, standard deviation, skewness, and kurtosis of the T/Δt specific frequency components.
A diagnostic device for a spline. A hoist comprising a hoisting mechanism for hoisting/lowering a suspended load and a hoisting motor for driving the hoisting mechanism, wherein a shaft of the hoisting motor and a boss of the hoisting mechanism are fitted and connected by a spline,
The hoist is
a diagnostic device including a current measurement unit that measures a current of the hoisting motor that drives a spline shaft of the spline; a frequency component calculation unit that calculates a specific frequency component by performing frequency analysis on the current measured by the current measurement unit; and a wear state estimation unit that estimates a wear state of the spline shaft based on the specific frequency component calculated by the frequency component calculation unit,
the frequency component calculation unit divides the current in a predetermined section measured by the current measurement unit into a plurality of analysis sections, and performs frequency analysis on the current in the analysis sections to calculate the specific frequency component;
The wear state estimation unit estimates the wear state of the spline shaft based on information related to the distribution of the specific frequency components in the plurality of analysis sections.
A hoist characterized by: A hoist comprising a hoisting mechanism for hoisting/lowering a suspended load and a hoisting motor for driving the hoisting mechanism, wherein a shaft of the hoisting motor and a boss of the hoisting mechanism are fitted and connected by a spline,
The hoist is
a diagnostic device including a current measurement unit that measures a current of the hoisting motor that drives a spline shaft of the spline; a frequency component calculation unit that calculates a specific frequency component by performing frequency analysis on the current measured by the current measurement unit; and a wear state estimation unit that estimates a wear state of the spline shaft based on the specific frequency component calculated by the frequency component calculation unit,
The wear state estimation unit receives the weight of the load as an input in addition to the current of the hoisting motor, and estimates the wear state of the spline shaft based on information related to the distribution of the specific frequency component derived from the weight of the load and the current.
A hoist characterized by: An electric vehicle includes a drive wheel and a wheel drive motor that rotates and drives the drive wheel, and power is transmitted to a connecting mechanism between the wheel drive motor and the drive wheel using a spline,
The electric vehicle includes:
a diagnostic device including a current measurement unit that measures a current of the wheel drive motor that drives a spline shaft of the spline; a frequency component calculation unit that calculates a specific frequency component by performing frequency analysis on the current measured by the current measurement unit; and a wear state estimation unit that estimates a wear state of the spline shaft based on the specific frequency component calculated by the frequency component calculation unit,
the frequency component calculation unit divides the current in a predetermined section measured by the current measurement unit into a plurality of analysis sections, and performs frequency analysis on the current in the analysis sections to calculate the specific frequency component;
The wear state estimation unit estimates the wear state of the spline shaft based on information related to the distribution of the specific frequency components in the plurality of analysis sections.
An electric vehicle characterized by: