MOTOR DRIVE DEVICE CAPABLE OF INFORMING MALFUNCTION IN OPERATION OF FAN, AND METHOD THEREOF

Abstract

A motor drive device can improve the accuracy of detection of malfunction in a fan. The motor drive device includes a fan, a fan controller for controlling the fan, a rotation speed detecting part for detecting the rotation speed of the fan, a relationship acquiring part for acquiring a relationship between a time elapsed from a time point, at which the fan controller changes the rotation speed, and the rotation speed detected by the rotation speed detecting part, a malfunction determining part for determining whether the relationship acquired by the relationship acquiring part is different from a predetermined standard, and a malfunction signal generating part for generating a signal representing the occurrence of malfunction in the fan, when it is determined that the relationship is different from the standard.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a motor drive device capable of informing a user of a malfunction in the operation of a fan, and a method thereof.

2. Description of the Related Art

A device capable of detecting a malfunction in the rotation speed of a fan has been known (see, for example, Japanese Unexamined Patent Publication (Kokai) No. 10-28394).

In a motor drive device for driving a servomotor embedded in a machine tool or an industrial robot, a control scheme for stopping the operation of the motor drive device when a malfunction in a fan is detected is used in some cases.

In this instance, detection of malfunction in the fan directly results in stopping of the operation process. Thus, in the field of motor driving motors, in terms of improving working efficiency, early detection of a warning sign of malfunction in a fan has been required.

SUMMARY OF THE INVENTION

In an aspect of the invention, a motor drive device includes a fan, a fan controller which controls the fan, a rotation speed detecting part which detects the rotation speed of the fan, and a relationship acquiring part which acquires a relationship between a time elapsed from a time point, at which the fan controller changes the rotation speed, and the rotation speed detected by the rotation speed detecting part.

The motor drive device includes a malfunction determining part which determines whether the relationship acquired by the relationship acquiring part is different from a predetermined standard, and a malfunction signal generating part which generates a signal indicating that a malfunction occurs in the fan when the malfunction determining part determines that the relationship is different from the standard.

The relationship acquiring part may acquire, as the relationship, an amount of change in the rotation speed detected by the rotation speed detecting part within a time period until a predetermined time elapses from the time point at which the fan controller sends to the fan a command for changing the rotation speed. The malfunction determining part may determine that the relationship is different from the standard when the acquired amount of change is greater or smaller than a predetermined threshold value.

The relationship acquiring part may calculate, as the relationship, a ratio of an amount of change in the rotation speed detected by the rotation speed detecting part within a time period until a predetermined time elapses from the time point at which the fan controller sends to the fan a command for changing the rotation speed, to the standard. The malfunction determining part may determine that the relationship is different from the standard when the ratio is greater or smaller than a predetermined threshold value.

The relationship acquiring part may acquire, as the relationship, a time until the rotation speed detected by the rotation speed detecting part changes from a first rotation speed to a second rotation speed different from the first rotation speed when the fan controller sends to the fan a command for changing the rotation speed from the first rotation speed to the second rotation speed.

The malfunction determining part may determine that the relationship is different from the standard when the acquired time is greater or smaller than a predetermined threshold value. The motor drive device may further include a timer which measures a time from a time point at which the fan controller changes the rotation speed.

The motor drive device may further include a storage which stores the rotation speed detected by the rotation speed detecting part or the time from the time point at which the fan controller changes the rotation speed. The motor drive device may further include an alarm output part which receives the signal and outputs an alarm to a user.

In another aspect of the invention, a method of notifying a user of an occurrence of a malfunction in a fan provided at a motor drive device comprises changing a rotation speed of the fan, and detecting the rotation speed when changing the rotation speed.

The method comprises acquiring a relationship between a time elapsed from a time point, at which the rotation speed is changed, and the detected rotation speed, determining whether the acquired relationship is different from a predetermined standard, and notifying to a user that a malfunction occurs in the fan when determining that the relationship is different from the standard.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned or other objects, features, and advantages of the invention will be clarified by the detailed description of embodiments with reference to accompanying drawings, in which:

FIG. 1 is a perspective view of a motor drive device according to an embodiment of the invention;

FIG. 2 is a block diagram of the motor drive device shown in FIG. 1;

FIG. 3 is a front view of the fan shown in FIG. 2;

FIG. 4 is a graph representing a relationship between the rotation speed of the fan and time when the rotation speed is decreased;

FIG. 5 is a graph representing a relationship between the rotation speed of the fan and time when the rotation speed is increased;

FIG. 6 is a flowchart of an example of the operation flow of the motor drive device shown in FIG. 1; and

FIG. 7 is a flowchart of another example of the operation flow of the motor drive device shown in FIG. 1.

DETAILED DESCRIPTION

Embodiments of the invention will be described below in detail with reference to the drawings. First, with reference to FIGS. 1 to 3, a motor drive device 10 according to an embodiment of the invention will be described. The motor drive device 10 supplies electric power to a servomotor (not shown) built in e.g. a machine tool or industrial robot in order to drive the servomotor.

As shown in FIG. 1, the motor drive device 10 includes a housing 12. The housing 12 is e.g. a box-shaped member made of resin, and houses therein components including a controller 16 described later. A through-hole 14 is formed at the housing 12.

As shown in FIG. 2, the motor drive device 10 further includes the controller 16, a fan 18, a rotation speed detecting part 19, an alarm output part 20, a timer 22, and a storage 24. The controller 16 includes e.g. a CPU, and is housed in the housing 12. The controller 16 directly or indirectly controls each component of the motor drive device 10.

The fan 18 is housed in the housing 12 so as to face the through-hole 14 formed at the housing 12. As shown in FIG. 3, the fan 18 includes a rotator 28 having a plurality of vanes 26, and a fan motor 30 which rotates the rotator 28.

The rotator 28 is arranged to be adjacent to the through-hole 14 formed at the housing 12. The fan motor 30 is connected to an inverter 32 (FIG. 2). The inverter 32 supplies electric power to the fan motor 30 in accordance with a command from the controller 16.

The fan motor 30 drives the rotator 28 to rotate at the rotation speed corresponding to the electric power supplied from the inverter 32. When the rotator 28 is rotated, an air in the housing 12 is discharged to the outside through the through-hole 14, thereby the motor drive device 10 is cooled.

The rotation speed detecting part 19 includes e.g. an encoder or Hall element, and is attached to the fan 18. The rotation speed detecting part 19 detects the rotation speed of the rotator 28 of the fan 18 in accordance with a command from the controller 16, and sends data of the detected rotation speed of the fan 18 to the controller 16.

The alarm output part 20 includes e.g. a speaker or display part, and outputs a sound or image in accordance with a command from the controller 16. The timer 22 times an elapsed time from a given time point in accordance with a command from the controller 16.

The storage 24 includes e.g. a non-volatile memory such as an EEPROM (registered trademark) which can electrically delete and record data, or a random access memory such as DRAM or SRAM which can rapidly read out and write on data. The controller 16 can record data on, and delete data from the storage 24.

As the fan 18 is driven, foreign substances, such as dust or cutting fluid, etc., gradually accumulate on the rotator 28 of the fan 18, thereby the rotation of the rotator 28 can be disturbed. The motor drive device 10 according to this embodiment detects such malfunction in the fan 18.

Below, with reference to FIGS. 4 and 5, the concept for detecting a malfunction of the fan 18 in the motor drive device 10 will be described. FIG. 4 is a graph showing the relationship between rotation speed R of the fan 18 and time t when the controller 16 sends a rotation speed changing command to the fan motor 30 at a time point t₁ so as to reduces the rotation speed of the fan 18 from a rotation speed R₂ to a rotation speed R₁.

On the other hand, FIG. 5 is a graph showing the relationship between rotation speed R of the fan 18 and time t when the controller 16 sends a rotation speed changing command to the fan motor 30 at a time point t₄ so as to increase the rotation speed of the fan 18 from a rotation speed R₄ to a rotation speed R₅.

A solid line 34 in FIG. 4 and a solid line 38 in

FIG. 5 represent characteristics when the fan 18 normally operates (hereinafter, referred as a “normal product”). On the other hand, a broken line 36 in FIG. 4 and a broken line 40 in FIG. 5 represent characteristics when foreign substances attach to the rotator 28 of the fan 18, thereby an operational malfunction occurs in the fan 18 (hereinafter, referred as a “malfunction product”).

As can been seen from FIG. 4, according to the normal product, when the rotation speed R is decreased, the rotation speed R reduces relatively moderately from the time point t₁, and reaches the rotation speed R₁ at a time point t₃. On the other hand, according to the malfunction product, the rotation speed R decreases from the time point t₁ more sharply than in the normal product, and reaches the rotation speed R₁ at a time point t₂ (<t₃).

Thus, a remarkable difference is made between the relationship between time t and rotation speed R (hereinafter, the “t−R relationship”) of the normal product after the time point t₁, and the t−R relationship after the time point t₁ of the malfunction product. This is caused by the fact that the rotation of the rotator 28 in the malfunction product is disturbed by the foreign substances attached thereto.

The motor drive device 10 according to this embodiment detects a malfunction in the fan 18 by making use of the above-mentioned difference between the t−R relationships of the normal product and the malfunction product. The t−R relationship in the fan 18 can be evaluated by various parameters described below.

As an example, in FIG. 4, an amount of change δR_ref in the rotation speed R of the normal product within a time period t₁₋₂(=t₂−t₁) is δR_ref ≈R₂−R₃. On the other hand, an amount of change δR in the rotation speed R of the malfunction product within the time period t₁₋₂ is δR≈R₂−R₁. As can been seen from FIG. 4, the amount of change δR in the malfunction product is remarkably larger than the amount of change δR_ref in the normal product.

Thus, a malfunction in the operating fan 18 can be detected by acquiring the amount of change δR as a parameter representing the t−R relationship of the fan 18, and comparing it with the δR_ref in the normal product, which is to be used as a standard.

As another example, a malfunction in the operating fan 18 can be detected by calculating, as a parameter representing the t−R relationship in the fan 18, a ratio R of the amount of change δR to the standard δR_ref, i.e., R=δR/δR_ref≈(R₂−R₁)/(R₂−R₃) , and comparing the ratio R with a predetermined threshold value.

As still another example, a time period t₁₋₃(=t₃−t₁) is necessary in the normal product until the rotation speed R changes from R₂ to R₁, whereas a time period t₁₋₂(=t₂−t₁) is necessary in the malfunction product until the rotation speed R changes from R₂ to R₁. As seen from FIG. 4, the time period t₁₋₂ in the malfunction product is remarkably smaller than the time period t₁₋₃ in the normal product.

Accordingly, a malfunction in the operating fan 18 can be detected by obtaining the time period t₁₋₂ as a parameter representing the t−R relationship in the fan 18, and comparing it with the time period t₁₋₃ in the normal product, which is to be used as a standard.

As still another example, a malfunction in the operating fan 18 can be detected by acquiring, as a parameter representing the t−R relationship in the fan 18, a gradient δR/δt of the rotation speed R (i.e., acceleration) in the time period t₁₋₂, i.e., δR/δt=(R₂−R₁)/t₁₋₂, and comparing it with a gradient in the normal product, i.e., δR_ref/δt=(R₂−R₃)/t₁₋₂, which is to be used as a standard.

Referring to FIG. 5, according to the normal product, when the rotation speed R increases, the rotation speed R increases relatively sharply from the time point t₄, and reaches the rotation speed R₅ at a time point t₅. On the other hand, according to the malfunction product, the rotation speed R increases from the time point t₄ more moderately than in the characteristic of the normal product, and reaches the rotation speed R₅ at a time point t₆.

Thus, when the rotation speed R increases, a remarkable difference is made between the t−R relationship in the normal product and the t−R relationship in the malfunction product, after the time point t₄. Accordingly, a malfunction in the fan 18 to be inspected can be detected by making use of such a difference in the t−R relationship between the normal product and the malfunction product.

As an example, in FIG. 5, the amount of change δR_ref in the rotation speed R of the normal product within the time period t₄₋₅ from the time point t₄ to the time point t₅ (i.e., t₄₋₅=t₅−t₄) is δR_ref=R₅−R₄. On the other hand, the amount of change δR in the rotation speed R of the malfunction product within the time period t₄₋₅ is δR=R₆−R₄. As seen from FIG. 5, the amount of change δR of the malfunction product is remarkably smaller than the amount of change δR_ref of the normal product.

Accordingly, a malfunction in the operating fan 18 can be detected by acquiring the amount of change δR as a parameter representing the t−R relationship of the operating fan 18, and comparing it with the δR_ref of the normal product, which is to be used as a standard.

In another example, a malfunction of the operating fan 18 can be detected by calculating, as a parameter representing the t−R relationship of the operating fan 18, a ratio R of the amount of change δR to the standard δR_ref, i.e., R=δR/δR_ref=(R₆−R₄)/(R₅−R₄), and comparing the ratio R with a predetermined threshold value.

In still another example, referring to FIG. 5, a time period t₄₋₅(=t₅−t₄) is necessary in the normal product until the rotation speed R changes from R₄ to R₅, whereas a time period t₄₋₆(=t₆−t₄) is necessary in the malfunction product until the rotation speed R changes from R₄ to R₅. As can been seen from FIG. 5, the time period t₄₋₆ of the malfunction product is remarkably greater than the time period t₄₋₅ of the normal product.

Thus, a malfunction in the operating fan 18 can be detected by acquiring the time period t₄₋₆ as a parameter representing the t−R relationship of the operating fan 18, and comparing it with the time period t₄₋₅ of the normal product, which is to be used as a standard.

In still another example, a malfunction in the operating fan 18 can be detected by acquiring the gradient δR/δt of the rotation speed R within the time period t₄₋₅, i.e., δR/δt=(R₆−R₄)/t₄₋₅, as a parameter representing the t−R relationship of the operating fan 18, and comparing it with the gradient δR_ref/δt of the normal product, i.e., δR_ref/δt=(R₅−R₄)/t₄₋₅, which is to be used as a standard.

Thus, the motor drive device 10 according to this embodiment detects whether a malfunction occurs in the fan 18, by making use of the various parameters (δR, t₁₋₂, δR/δt, t₄₋₆) and standards (δR_ref, t₁₋₃, δR_ref/δt, t₄₋₅).

Next, with reference to FIG. 6, an example of the operation flow of the motor drive device 10 will be described. The flow shown in FIG. 6 is started when the controller 16 receives from a user, host controller or control program a malfunction inspection command for inspecting an operational malfunction in the fan 18.

As an example, the controller 16 receives the malfunction inspection command when it increases the rotation speed of the fan 18 from zero to a normal rotation speed (i.e., when the supply of electric power from the inverter 32 to the fan motor 30 is started) in order to normally operate the fan 18.

As another example, the controller 16 receives the malfunction inspection command when it decreases the rotation speed of the fan 18 from the normal rotation speed to zero (i.e., when the supply of electric power from the inverter 32 to the fan motor 30 is stopped) in order to stop the fan 18 in normal operation.

As still another example, the controller 16 receives the malfunction inspection command when the process is interrupted during the normal operation of the fan 18. Note that, the above-described normal rotation speed is pre-set as a required value for normally operating the fan 18.

At step S1, the controller 16 changes the rotation speed of the fan 18. As an example, as shown in FIG. 4, the controller 16 sends a rotation speed changing command to the inverter 32 so as to decrease the rotation speed R of the fan 18, which is rotating at the rotation speed R₂ (e.g., the normal rotation speed), from the rotation speed R₂ to the rotation speed R₁ (e.g., zero).

As another example, as shown in FIG. 5, the controller 16 sends a rotation speed changing command to the inverter 32 so as to increase the rotation speed R of the fan 18, which is rotating at the rotation speed R₄ (e.g., zero), from the rotation speed R₄ to the rotation speed R₅ (e.g., normal rotation speed).

The inverter 32 controls electric power supplied to the fan motor 30 so as to change the rotation speed R of the fan 18 to a rotation speed (R₁ or R₅) in accordance with the rotation speed changing command received from the controller 16. Thus, in this embodiment, the controller 16 functions as a fan controller 42 (FIG. 2) which controls the operation of the fan 18.

At step S2, the controller 16 acquires a rotation speed R_x of the fan 18. Specifically, the controller 16 sends a command to the rotation speed detecting part 19 so as to detect the rotation speed R_x of the rotator 28 of the fan 18 at this time. The controller 16 receives data of the rotation speed R_x from the rotation speed detecting part 19, and records it on the storage 24.

As an example, when the rotation speed R is decreased from R₂ to R₁ at step S1 (FIG. 4), the rotation speed R_x measured at step S2 substantially coincides with the rotation speed R₂ at the time point t₁ in FIG. 4.

As another example, when the rotation speed R is increased from R₄ to R₅ at step S1 (FIG. 5), the rotation speed R_x measured at step S2 substantially coincides with the rotation speed R₄ at the time point t₄ in FIG. 5.

At step S3, the controller 16 start to time an elapsed time. Specifically, the controller 16 sends a timing start command for starting to time an elapsed time to the timer 22. The timer 22 times an elapsed time t from a time point when it receives the timing start command from the controller 16.

At step S4, the controller 16 acquires a rotation speed R_y of the fan 18 when the elapsed time t timed by the timer 22 reaches a predetermined time. The predetermined time is pre-stored in the storage 24.

As an example, when the rotation speed R is decreased from R₂ to R₁ at step S1 (FIG. 4), the predetermined time is set to the above-mentioned time period t₁₋₂. As another example, when the rotation speed R is increased from R₄ to R₅ at step S1 (FIG. 5), the predetermined time is set to above-mentioned the time period t₄₋₅.

At this step S4, when the predetermined time (e.g., time period t₁₋₂ or t₄₋₅) has elapsed from a time point (e.g., time point t₁ in FIG. 4 or time point t₄ in FIG. 5) when the controller 16 has sent the rotation speed changing command to the fan 18 at step S1, the controller 16 sends a command to the rotation speed detecting part 19, similar to step S2, so as to acquire the rotation speed R_y of the fan 18 at this time.

At step S5, the controller 16 acquires a relationship between time t and rotation speed R (i.e., t−R relationship). As an example, the controller 16 calculates, as a parameter representing the t−R relationship, an amount of change δR_xy=|R_x−R_y|(this value corresponds to the above-mentioned δR) from the rotation speed R_x, acquired at step S2 to the rotation speed R_y acquired at step S4.

As another example, the controller 16 calculates a ratio R=δR_xy/δR_ref as a parameter representing the t−R relationship. As still another example, the controller 16 calculates a gradient δR/δt (corresponding to e.g. (R₂−R₁) /t₁₋₂ or (R₆−R₄)/t₄₋₅ described above) as a parameter representing the t−R relationship.

Thus, in this embodiment, the controller 16 functions as a relationship acquiring part 44 (FIG. 2) which acquires a relationship (i.e., t−R relationship) between the time t from the time point t₁ (t₁₋₂ or t₄₋₅), at which the rotation speed R of the fan 18 is changed, and the rotation speed R of the fan 18.

At step S6, the controller 16 determines whether the t−R relationship acquired at step S5 is different from a predetermined standard. As an example, when the amount of change δR_xy=|R_x−R_y is calculated at step S5, the controller 16 compares the calculated amount of change δR_xy with a threshold value α_l which is set with respect to the standard δR_ref.

For example, when the rotation speed R is decreased from R₂ to R₁ at step S1 (FIG. 4), the controller 16 determines whether the amount of change δR_xy is greater than the threshold value α₁ (e.g., α₁=δR_ref×1.1) .

On the other hand, when the rotation speed R is increased from R₄ to R₅ at step S1 (FIG. 5), the controller 16 determines whether the amount of change δR_xy is smaller than the threshold value α₁ (e.g., α₁=δR_ref×0.9).

When the amount of change δR_xy is greater (or smaller) than the threshold value α₁, the controller 16 determines that the t−R relationship of the fan 18 is different from the standard δR_ref (i.e., determines “YES”).

As another example, when the ratio R is calculated at step S5, the controller 16 compares the ratio R with a predetermined threshold value α₂ which is pre-set with respect to the ratio R.

For example, when the rotation speed R is decreased from R₂ to R₁ at step S1 (FIG. 4), the controller 16 determines whether the calculated ratio R is greater than the threshold value α₂ (e.g., α₂=1.1). On the other hand, when the rotation speed R is increased from R₄ to R₅ at step S1 (FIG. 5), the controller 16 determines whether the calculated ratio R is smaller than the threshold value α₂ (e.g., α₂=0.9).

When the ratio R is greater (or smaller) than the threshold value α₂ the controller 16 determines that the t−R relationship of the fan 18 is different from the standard δR_ref (i.e., determines “YES”).

As still another example, when the gradient δR/δt is calculated at step S5, the controller 16 compares the absolute value of the gradient |δR/δt|, with a threshold value α₃ which is set with respect to the standard δR_ref/δt .

For example, when the rotation speed R is decreased from R₂ to R₁ at step S1 (FIG. 4), the controller 16 determines whether the absolute value of gradient |δR/δt| is greater than the threshold value α₃ (e.g., α₃=|δR_ref/δt|×1.1).

On the other hand, when the rotation speed R is increased from R₄ to R₅ at step S1 (FIG. 5), the controller 16 determines whether the absolute value of gradient |δR/δt| is smaller than the threshold value α₃ (e.g., α₃=|δR_ref/δt|×0.9).

When the absolute value of gradient |δR/δt| is greater (or smaller) than the threshold value α₃, the controller 16 determines that the t−R relationship (δR/δt) of the fan 18 is different from the standard δR_ref/δt (i.e., determines “YES”). Note that, the above-mentioned threshold value α₁, α₂, or α₃ is pre-stored in the storage 24.

When the controller 16 determines “YES” at this step S6, the controller 16 proceeds to step S7. On the other hand, when the controller 16 determines that the t−R relationship is not different from the standard (i.e., determines “NO”), the controller 16 ends the flow shown in FIG. 6.

Thus, in this embodiment, the controller 16 functions as a malfunction determining part 46 (FIG. 2) which determines whether the t−R relationship of the fan 18 is different from the standard.

At step S7, the controller 16 generates a malfunction notifying signal indicating that a malfunction occurs in the fan 18. As an example, the controller 16 generates the malfunction notifying signal in the form of a sound signal of an alarm to be output to a user.

As another example, the controller 16 generates the malfunction notifying signal in the form of an image signal of an alarm visible to a user. Thus, in this embodiment, the controller 16 functions as a malfunction signal generating part 48 (FIG. 2) which generates the malfunction notifying signal.

At step S8, the controller 16 notifies a user of the occurrence of a malfunction in the fan 18 via the alarm output part 20. As an example, when the sound signal of an alarm is generated at step S7, the controller 16 sends the sound signal to the alarm output part 20. In this case, the alarm output part 20 includes a speaker to output the received sound signal as an alarm sound.

As another example, when the image signal of an alarm is generated at step S7, the controller 16 sends the image signal to the alarm output part 20. In this case, the alarm output part 20 includes a display part to display the alarm image corresponding to the received image signal.

In this way, the user can recognize the occurrence of a malfunction in the fan 18 from the alarm sound or the alarm image. Consequently, the user can recognize that it is necessary to carry out maintenance for removing foreign substances attached to the rotator 28 of the fan 18.

As described above, in this embodiment, the relationship between rotation speed R and time t when the rotation speed R of the fan 18 is changed (i.e., the amount of change in the rotation speed R over time) is compared with the relationship of the normal product as a standard, so as to determine whether the rotation speed R of the fan 18 is equal to that of the normal product.

According to this configuration, a malfunction in the rotation speed R of the fan 18 can be more accurately detected, and therefore it is possible to reliably avoid erroneously detecting a malfunction in the fan 18, and thereby avoid unnecessarily stopping the operation of the motor drive device 10. As a result, it is possible to improve the efficiency of operation.

Next, with reference to FIG. 7, another example of the operation flow of the motor drive device 10 will be described. Note that, in the operation flow shown in FIG. 7, steps similar to those in FIG. 6 are assigned the same numeral references, and the detailed description thereof will be omitted.

After step S1, at step S11, the controller 16 starts to measure the rotation speed R of the fan 18. Specifically, the controller 16 sends a command to the rotation speed detecting part 19 so as to periodically detect the rotation speed R of the rotator 28 of the fan 18 at a period τ(e.g., 0.5 sec.). The controller 16 receives data of the rotation speed R from the rotation speed detecting part 19 at the period τ, and stores them in the storage 24.

At step S12, the controller 16 determines whether the rotation speed R of the fan 18 detected at step S11 reaches a predetermined target value R_t.

As an example, when the rotation speed R is decreased from R₂ to R₁ at step S1 (FIG. 4), the target value R_t is set to the rotation speed R₁. As another example, when the rotation speed R is increased from R₄ to R₅ at step S1 (FIG. 5), the target value R_t is set to the rotation speed R₅.

When the controller 16 determines that the rotation speed R detected at step Sll reaches the target value R_t (i.e., determined “YES”), it proceeds to step S13. On the other hand, when the controller 16 determines that the rotation speed R does not reach the target value R_t (i.e., determines “NO”), it repeats step S12.

At step S13, the controller 16 functions as the relationship acquiring part 44 (FIG. 2) so as to acquire the relationship between time t and rotation speed R (i.e., the t−R relationship). Specifically, the controller 16 acquires, as a parameter representing the t−R relationship, the elapsed time t timed by the timer 22 at the time point when it is determined “YES” at step S12, and stores it in the storage 24.

For example, when the rotation speed R is decreased from R₂ to R₁ at step S1 (FIG. 4), the elapsed time t timed at this time point corresponds to the time period (t₁₋₂) from the time point (t₁) when the controller 16 sends the rotation speed changing command at step S1 to the time point (t₂) when the rotation speed R reaches R₁.

On the other hand, when the rotation speed R is increased from R₄ to R₅ at step S1 (FIG. 5), the elapsed time t timed at this time point corresponds to the time period (t₄₋₆) from the time point (t₄) when the controller 16 sends the rotation speed changing command at step S1 to the time point (t₆) when the rotation speed R reaches R₅.

At step S14, the controller 16 functions as the malfunction determining part 46 (FIG. 2) so as to determine whether the t−R relationship acquired at step S13 is different from a predetermined standard.

As an example, when the rotation speed R is decreased from R₂ to R₁ at step S1 (FIG. 4), the controller 16 determines whether the elapsed time t (time period t₁₋₂) acquired at step S13 is smaller than a threshold value α₄ (e.g., α₄=t₁₋₃×0.9) set for the above-described standard (time period t₁₋₃).

As another example, when the rotation speed R is increased from R₄ to R₅ at step S1 (FIG. 5), the controller 16 determines whether the elapsed time t (time period t₄₋₆) acquired at step S13 is greater than the threshold value α₄ (e.g., α₄=t₄₋₅×1.1) set for the above-described standard (time period t₄₋₅). The threshold value α₄ is pre-stored in the storage 24. When the elapsed time t is greater (or smaller) than the threshold value α₄, the controller 16 determines that the t−R relationship of the fan 18 is different from the standard (time period t₁₋₃ or time period t₄₋₅) (i.e., determines “YES”).

The controller 16 proceeds to step S7 when it determines “YES”. On the other hand, the controller 16 ends the flow shown in FIG. 7 when it determines that the t−R relationship is not different from the standard (i.e., determines “NO”).

Thus, according to the operation flow in FIG. 7, a malfunction in the rotation speed R of the fan 18 can be accurately detected, similar to the flow in FIG. 6. Therefore, it is possible to avoid erroneously detecting a malfunction in the fan 18, and thereby avoid unnecessarily stopping the operation of the motor drive device 10. As a result, it is possible to improve the efficiency of operation.

Note that, at least one of the timer 22 and the storage 24 may be incorporated in the controller 16, or in an external device (e.g., server) communicably connected to the controller 16 via a network.

Although the invention has been described above through various embodiments, the embodiments do not limit the inventions according to the claims. Further, a configuration obtained by combining the features described in the embodiments of the invention can be included in the technical scope of the invention. However, all combinations of these features are not necessarily essential for solving means of the invention. Furthermore, it is obvious for a person skilled in the art that various modifications or improvements can be applied to the embodiments.

Regarding the order of operations, such as actions, sequences, steps, processes, and stages, in the devices, systems, programs, and methods indicated in the claims, specification and drawings, it should be noted that the terms “before”, “prior to”, etc. are not explicitly described, and any order can be realized unless the output of a previous operation is used in the subsequent operation. Regarding the processing in the claims, specification, and drawings, even when the order of operations is described using the. terms “first”, “next”, “subsequently”, “then”, etc., for convenience, maintaining this order is not necessarily essential for working the inventions.

Claims

1. A motor drive device comprising:

a fan;

a fan controller which controls the fan;

a rotation speed detecting part which detects a rotation speed of the fan;

a relationship acquiring part which acquires a relationship between a time elapsed from a time point, at which the fan controller changes the rotation speed, and the rotation speed detected by the rotation speed detecting part;

a malfunction determining part which determines whether the relationship acquired by the relationship acquiring part is different from a predetermined standard; and

a malfunction signal generating part which generates a signal indicating that a malfunction occurs in the fan when the malfunction determining part determines that the relationship is different from the standard.

2. The motor drive device according to claim 1, wherein the relationship acquiring part acquires, as the relationship, an amount of change in the rotation speed detected by the rotation speed detecting part within a time period until a predetermined time elapses from the time point at which the fan controller sends to the fan a command for changing the rotation speed,

wherein the malfunction determining part determines that the relationship is different from the standard when the acquired amount of change is greater or smaller than a predetermined threshold value.

3. The motor drive device according to claim 1, wherein the relationship acquiring part acquires, as the relationship, a ratio of an amount of change in the rotation speed detected by the rotation speed detecting part within a time period until a predetermined time elapses from the time point at which the fan controller sends to the fan a command for changing the rotation speed, to the standard,

wherein the malfunction determining part determines that the relationship is different from the standard when the ratio is greater or smaller than a predetermined threshold value.

4. The motor drive device according to claim 1, wherein the relationship acquiring part acquires, as the relationship, a time until the rotation speed detected by the rotation speed detecting part changes from a first rotation speed to a second rotation speed different from the first rotation speed when the fan controller sends to the fan a command for changing the rotation speed from the first rotation speed to the second rotation speed,

wherein the malfunction determining part determines that the relationship is different from the standard when the acquired time is greater or smaller than a predetermined threshold value.

5. The motor drive device according to claim 1, further comprising a timer which measures the time from the time point at which the fan controller changes the rotation speed.

6. The motor drive device according to claim 1, further comprising a storage which stores the rotation speed detected by the rotation speed detecting part or the time from the time point at which the fan controller changes the rotation speed.

7. The motor drive device according to claim 1, further comprising an alarm output part which receives the signal and outputs an alarm to a user.

8. A method of notifying a user of an occurrence of a malfunction in a fan provided at a motor drive device, comprising:

changing a rotation speed of the fan;

detecting the rotation speed when changing the rotation speed;

acquiring a relationship between a time elapsed from a time point, at which the rotation speed is changed, and the detected rotation speed;

determining whether the acquired relationship is different from a predetermined standard; and

notifying to a user that a malfunction occurs in the fan when determining that the relationship is different from the standard.