Fan motor control device

Abstract

Fan motor control device (10) configured to control the drive of a fan motor (14A, 14B) to cool a device (16) which generates heat during operation, the fan motor control device (10) comprising: a unit (20A, 20B) for detecting a rotational speed, configured to detect a rotational speed of the fan motor (14A, 14B); and a unit (28) for controlling an anomaly decision, configured to execute an anomaly decision mode during the operation of the device (16) in which the fan motor is repeatedly switched from a stop state to an drive state by switching the power supply to the fan motor (14A, 14B) from off to on and switching the fan motor from the drive state to the stop state by switching the power supply to the fan motor (14A, 14B) from on to off, and to assess the anomaly of the fan motor (14A, 14B) based on the speed of the fan motor (14A, 14B) measured when the power supply to the fan motor is switched from off to on, and also based on the speed of the fan motor measured when the power supply to the fan motor is switched from on to off, during the execution of the anomaly decision mode, wherein the unit (28) for controlling an anomaly decision assesses that the fan motor (14A, 14B) is anomalous if the unit (28) for controlling an anomaly decision detects that the speed of the fan motor (14A, 14B) does not reach a preset predetermined speed within a preset predetermined time after the fan motor (14A, 14B) has been switched on during the execution of the anomaly decision mode.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a fan motor control device that controls the drive of a fan motor.

[0002] JP H05-187392 A discloses a technique as a device for detecting an abnormality of a fan motor. JP H05-187392 A discloses a device that judges that the fan motor is abnormal when a rotational speed does not reach a set speed within a set time after the fan motor is activated.

[0003] JP 2008 - 208 806 A describes a method in which a first speed is detected after the power supply of the fan motor is switched from on to off. The method includes comparing the first speed with a second speed stored in a memory unit, and judging an abnormality of the fan motor in the event that the speed of the fan motor does not change after the power supply of the fan motor is switched from on to off.

[0004] EP 2 163 768 A1 concerns an outdoor fan controlled by inverters. Since outdoor fans are easily subjected to forward or reverse rotational stresses due to natural wind, problems such as overcurrents, overvoltages, and loss of synchronization can sometimes occur, causing the fan to stop abnormally. To prevent overcurrents, the speed is reduced if overcurrents are detected.

[0005] JP 2015 - 108 468 A relates to a method for monitoring a fan filter unit for a clean room. A fault diagnosis means drives the motor at a speed different from a normal speed and receives information from speed detection means, current detection means, and sensors to assess faults.

[0006] DE 100 40 440 A1 relates to a method for controlling a DC fan with an electronically commutated motor. The signal corresponding to the off-time interval (ASZ) and the signal corresponding to the on-time interval (ESZ) are fed to a summing unit, which calculates an actual speed value signal (DZIW) from this. The error detector checks whether the actual speed value DZIW lies within a target speed interval derived from the target speed value. SUMMARY OF THE INVENTION

[0007] The technique of Japanese Patent Laid-Open No. 05-187392 is problematic in that the fan motor abnormality can only be determined when the motor is activated, which provides limited opportunities for assessment.

[0008] The present invention was conceived to solve the above problem. An object of the present invention is to provide a fan motor control device that can increase the frequency of judgment of fan motor abnormalities to improve the accuracy of the decision regarding the fan motor abnormality.

[0009] According to a first aspect of the present invention, claim 1 defines a fan motor control device.

[0010] An example that facilitates understanding of the invention is a fan motor control method for controlling the drive of a fan motor to cool a device that generates heat during operation, the fan motor control method comprising: a rotation speed detecting step of detecting a rotation speed of the fan motor; and an abnormality decision controlling step of executing an abnormality decision mode that consists of repeatedly switching the power supply for the fan motor between off and on during operation of the device and determining the abnormality of the fan motor based on the rotation speed of the fan motor during execution of the abnormality decision mode.

[0011] According to the present invention, it is possible to improve the accuracy of the decision with respect to the abnormality of the fan motor.

[0012] The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] They show: Fig. 1 is a block diagram of a fan motor control device; Fig. 2A is an explanatory diagram showing how to judge an abnormality when the power supply for a fan motor is switched from off to on; Fig. 2B is an explanatory diagram showing how to judge an abnormality when the power supply for the fan motor is switched from on to off; Fig. 3 is an explanatory diagram of an anomaly decision mode; Fig. 4 a flowchart illustrating the control of a decision on a fan motor anomaly; Fig. 5 is a flowchart illustrating a process for setting a predetermined time and a predetermined speed; Fig. 6 is a view illustrating a relationship between a first speed threshold, a second speed threshold, a third speed threshold, and a rated speed used in the process of setting the predetermined time and the predetermined speed; and Fig. 7 is a flowchart illustrating a process for making a decision about a fan motor anomaly. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of a fan motor control device according to the present invention will be described in detail with reference to the accompanying drawings.

[0015] First, the configuration of the fan motor control device is described.

[0016] Fig. 1 is a block diagram of a fan motor control device 10. The fan motor control device 10 controls the drive of a fan motor 14A and a fan motor 14B, which drive and rotate a fan 12A and a fan 12B, respectively. The fans 12A, 12B and the fan motors 14A, 14B will hereinafter be referred to as the fan 12 and the fan motor 14, respectively, when generally explained. The fan 12 exhausts air from inside a casing of a numerical control device that controls a machine tool (not shown) to enable cooling of a device, such as a CPU 16, inside the casing. A rotation speed of the fan motor 14 can be controlled by controlling the supply voltage (supply current) through pulse control. However, the explanation of the present embodiment will be based on the rotation speed controlled by varying the supply voltage.

[0017] The fan motor control device 10 includes a microcomputer 18, speed sensors 20A, 20B, a notification unit 22, and a power supply 24. The microcomputer 18 includes a microprocessor, and the microcomputer 18 includes a fan motor control unit 26, an abnormality decision control unit 28, and a replacement judgment unit 30.

[0018] The speed sensors 20A, 20B respectively detect the speeds of the fan motors 14A, 14B and output information of the detected speeds to the microcomputer 18. The notification unit 22 notifies an operator operating the machine tool of the abnormality using sounds, characters, images, lights, or a combination thereof based on a command from the abnormality decision control unit 28. The fan motor control unit 26 controls an electric voltage supplied to the fan motors 14A, 14B from the power supply 24 according to a temperature of the CPU 16 to control the speeds of the fan motors 14A, 14B. Hereinafter, in order to simplify an example of the present embodiment, the explanation will be given based on the assumption that the fan motor control unit 26 controls such that a rated voltage is supplied to the fan motors 14A, 14B such that the rotational speeds of the fan motors 14A, 14B are at a rated speed.

[0019] The abnormality decision control unit 28 determines an abnormality of the fan motors 14A, 14B. When an abnormality decision mode described below is executed with respect to the fan motors 14A, 14B, the abnormality decision control unit 28 controls the fan motors 14A, 14B. The abnormality decision control unit 28 determines the fan motor 14A or the fan motor 14B as abnormal and then controls the fan motors 14A, 14B. The replacement judgment unit 30 decides that the fan motors 14A, 14B have been replaced.

[0020] The following describes the assessment of a fan motor abnormality.

[0021] A basic concept of assessing an abnormality with respect to the fan motor 14 is described. Fig. 2A is an explanatory diagram showing how to judge an abnormality of the fan motor 14 when the power supply to the fan motor 14 is switched from off to on. The abnormality decision control unit 28 judges that the fan motor 14 is normal when a rotation speed N of the fan motor 14 at a predetermined time T1 after the power supply to the fan motor 14 is switched from off to on is a predetermined rotation speed N1 or more. On the other hand, the abnormality decision control unit 28 judges that the fan motor 14 is abnormal when the rotation speed N of the fan motor 14 at a predetermined time T1 after the power supply to the fan motor 14 is switched from off to on is less than a predetermined rotation speed N1.

[0022] Fig. 2B is an explanatory diagram showing how to judge an abnormality of the fan motor 14 when the power supply to the fan motor 14 is switched from on to off. The abnormality decision control unit 28 judges that the fan motor 14 is normal when the rotational speed N of the fan motor 14 is a predetermined rotational speed N2 or more at a predetermined time T2 after the power supply to the fan motor 14 is switched from on to off. On the other hand, the abnormality decision control unit 28 judges that the fan motor 14 is abnormal when the rotational speed N of the fan motor 14 is less than a predetermined rotational speed N2 at a predetermined time T2 after the power supply to the fan motor 14 is switched from on to off.

[0023] The judgment of the abnormality of the fan motor 14 when the power supply to the fan motor 14 is switched from off to on will be described in more detail below. The judgment of the abnormality of the fan motor 14 when the power supply to the fan motor 14 is switched from on to off can also be performed in substantially the same way.

[0024] Anomaly decision mode is described below.

[0025] Normally, the fan motor control unit 26 switches the power supply of the fan motor 14 from off to on when the CPU 16 is activated, and switches the power supply of the fan motor 14 from on to off after the CPU 16 is stopped. The judgment of the abnormality of the fan motor 14 is performed when the power supply of the fan motor 14 is switched from off to on or from on to off. Therefore, the opportunities for performing judgments on the abnormality of the fan motor 14 are limited.

[0026] In the present embodiment, even during the operation of the CPU 16, the abnormality decision control unit 28 executes an abnormality decision mode of repeatedly switching between turning on and off the fan motor 14, and increases the frequency of judging the abnormality of the fan motor 14.

[0027] Fig. 3 is a view for explaining the anomaly decision mode. Fig. 3 depicts the fan motor 14A as “Fan Motor A” and the fan motor 14B as “Fan Motor B”. As in Fig. As shown in Figure 3, while the CPU 16 is operating, the abnormality decision mode of repeatedly switching the power supply on and off for the fan motor 14A is executed. When the abnormality decision mode with respect to the fan motor 14A is being executed, the abnormality decision mode with respect to the fan motor 14B is not executed. After the execution of the abnormality decision mode with respect to the fan motor 14A is completed, the abnormality decision mode with respect to the fan motor 14B is executed. While the abnormality decision mode with respect to the fan motor 14B is being executed, the abnormality decision mode with respect to the fan motor 14A is not executed.

[0028] While the abnormality decision mode is being executed with respect to the fan motor 14A, the abnormality decision control unit 28 controls the rotational speed of the fan motor 14B to be higher than the rotational speed before the abnormality decision mode is being executed with respect to the fan motor 14A. Similarly, while the abnormality decision mode is being executed with respect to the fan motor 14B, the abnormality decision control unit 28 controls the rotational speed of the fan motor 14A to be higher than the rotational speed before the abnormality decision mode is being executed with respect to the fan motor 14B. With this arrangement, deterioration in cooling performance of the CPU 16 or the like during the execution of the abnormality decision mode with respect to one of the fan motors 14 can be compensated by the other of the fan motors 14.

[0029] In the present embodiment, during an abnormality decision mode, the power supply to the fan motor 14 is repeatedly switched between off and on five times. However, the frequency may be greater than five or less than five. The abnormality decision mode may be executed multiple times during the operation of the CPU 16, or it may be executed only once. The abnormality decision mode may be executed each time the CPU 16 is activated, or it may be executed only once for multiple activations of the CPU 16. The present embodiment describes an example in which the abnormality decision mode is executed with respect to the two fan motors 14A, 14B.Even if the abnormality decision mode is executed with respect to three or more fan motors, the abnormality decision mode with respect to a single fan motor may be executed at once, and the abnormality decision mode with respect to the other fan motors may not be executed.

[0030] Anomaly decision control is described below.

[0031] Fig. 4 is a flowchart illustrating an abnormality decision control of the fan motors 14. Fig. 4 depicts the fan motor 14A as the “fan motor A” and the fan motor 14B as the “fan motor B”.

[0032] In step S1, it is judged whether the fan motor 14A has just been replaced (when it is controlled to be driven for the first time after replacement). If the fan motor 14A has just been replaced, the flow proceeds to step S2. Otherwise, the flow proceeds to step S3. In step S2, a predetermined time and a predetermined rotation speed to be used for judging the abnormality of the fan motor 14A are set, and the flow proceeds to step S3. The predetermined time and the predetermined rotation speed indicate the predetermined time T1 and the predetermined rotation speed N1 in Fig. 2A. Setting the predetermined time and the predetermined speed will be described below with reference to Fig. 5 and Fig. 6 described in detail.

[0033] In step S3, it is judged whether the fan motor 14B has just been replaced (when it is controlled to be driven for the first time after replacement). If the fan motor 14B has just been replaced, the flow proceeds to step S4. Otherwise, the flow proceeds to step S5. In step S4, a predetermined time and a predetermined rotational speed to be used for judging the abnormality of the fan motor 14B are set, and the flow proceeds to step S5.

[0034] In step S5, if the fan motor 14A is judged to be normal, a judgment result of the preceding step S6 is confirmed. If the fan motor 14A has been judged to be normal or has just been replaced, the flow proceeds to step S6. If the fan motor 14A has been judged to be abnormal, the flow proceeds to step S7. In step S6, abnormality decision processing is executed with respect to the fan motor 14A, and the flow proceeds to step S7.

[0035] In step S7, a judgment result of the previous step S8 is confirmed if it is judged that the fan motor 14B is normal. If the fan motor 14B has been judged to be normal or has just been replaced, the flow goes to step S8. If the fan motor 14B has been judged to be abnormal, the flow goes to step S5. In step S8, the abnormality decision processing with respect to the fan motor 14B is executed, and the flow goes to step S5. The abnormality decision processing with respect to the fan motors 14A, 14B will be described below with reference to Fig. 7 described in detail.

[0036] The following describes the process for setting a predetermined time and a predetermined speed.

[0037] The fan motors 14 are designed to drive at a predetermined rated speed when power is supplied at a rated current and voltage. The predetermined time and predetermined speed used for the abnormality decision with respect to the fan motors 14 are given in advance based on the fan motors 14 according to their designs. However, even when the fan motors 14 are shipped from the manufacturers, the performance varies depending on the products or deteriorates due to long-term storage. Some of the fan motors 14 are unable to sufficiently exhibit the expected performance even immediately after replacement. Therefore, in the present embodiment, the predetermined time and predetermined speed used for the abnormality decision with respect to the fan motor 14 are compensated by the fan motor 14.

[0038] Fig. 5 is a flowchart illustrating the process for setting the predetermined time and the predetermined speed. Fig. 6 is a view illustrating a relationship between a first speed threshold, a second speed threshold, a third speed threshold, and a rated speed used in the predetermined time and predetermined speed setting process. The same predetermined time and predetermined speed setting process is applied to both fan motors 14A, 14B. Only the predetermined time and predetermined speed setting processing used for the abnormality decision with respect to fan motor 14A will be described below.

[0039] The predetermined time and predetermined speed used to judge the abnormality of the fan motor 14A are set according to a constant speed of the fan motor 14A driven at a rated voltage. The constant speed is the average value of the speed values ​​measured approximately 100 times in a steady state where the speed that has changed since the fan motor 14A was turned on stabilizes after a certain period of time has elapsed.

[0040] In step S11, it is judged whether the constant speed of the fan motor 14A is less than the first speed threshold and equal to or greater than the second speed threshold. If the constant speed of the fan motor 14A is less than the first speed threshold and equal to or greater than the second speed threshold, the process proceeds to step S12. If the constant speed of the fan motor 14A is equal to or greater than the first speed threshold or less than the second speed threshold, the process proceeds to step S13. At this time, the first speed threshold is set to be a speed lower than the rated speed of the fan motor 14A, and is set to, for example, a speed that is -1% of the rated speed of the fan motor 14A.The second speed threshold is a speed that is lower than the first speed threshold and is set, for example, to a speed that is -4% of the rated speed of the fan motor 14A (see . Fig. 6).

[0041] In step S12, the predetermined time is set longer than a preset time (or the predetermined rotation speed is set lower than the preset rotation speed). Setting the predetermined time to be longer than the preset time or setting the predetermined rotation speed to be lower than the preset rotation speed means that the value for judging an abnormality of the fan motor 14A is set less strictly (less likely to be judged abnormally). This is because the constant rotation speed of the fan motor 14A, which is slightly lower than the rated rotation speed, has little influence on the performance for cooling the CPU 16 and the like, because a rotating portion such as a bearing of the fan motor 14A would not wear much, and a long service life of the fan motor 14A would be expected.

[0042] In step S13, it is judged whether the constant speed of the fan motor 14A is less than the second speed threshold. If the constant speed of the fan motor 14A is less than the second speed threshold, the flow proceeds to step S15. If the rated speed of the fan motor 14A is the second speed threshold or greater, the flow proceeds to step S14.

[0043] In step S14, it is judged that the constant speed of the fan motor 14A is greater than the third speed threshold. If the constant speed of the fan motor 14A is greater than the third speed threshold, the process proceeds to step S15. If the constant speed of the fan motor 14A is less than the third speed threshold, the process proceeds to step S16. If the third speed threshold is a speed higher than the rated speed of the fan motor 14A, for example, is set to a speed that is +1% of the rated speed of the fan motor 14A (see Fig. 6).

[0044] In step S15, the predetermined time is set shorter than the preset time (or the predetermined rotation speed is set higher than the preset rotation speed). Setting the predetermined time to be shorter than the preset time or setting the predetermined rotation speed to be higher than the preset rotation speed means that the value for judging an abnormality of the fan motor 14A is set more strictly (higher probability of abnormal judgment). This is because the constant rotation speed of the fan motor 14A is much lower than the rated rotation speed, because the rotating portion, such as a bearing of the fan motor 14A, is in poor condition, because grease begins to adhere to the rotating portion, because a long service life of the fan motor 14 is not expected, and therefore an operator is prompted to prepare for replacement in the short term.Alternatively, if the constant speed of the fan motor 14A is higher than the rated speed, the rotating section such as a bearing will wear out quickly, a long service life of the fan motor 14A cannot be expected, and therefore the operator is required to quickly prepare for replacement.

[0045] In step S16, the predetermined time and the predetermined speed are set to normal values ​​(preset values), and the processing is terminated. The rated voltage and the rated speed described here may be replaced by a predetermined reference voltage and reference speed that are different from the rated voltage and the rated speed.

[0046] The following describes the processing of the anomaly decision.

[0047] Fig. Figure 7 is a flowchart illustrating a process for making a decision about the abnormality of the fan motor 14. The same abnormality decision processing is performed on both fan motors 14A and 14B. Only the abnormality decision processing with respect to the fan motor 14A will be described.

[0048] In step S21, a variable m and a variable n are reset (0 is substituted for the variable m and the variable n), and the flow proceeds to step S22. In step S22, the fan motor 14A is turned off, and the flow proceeds to step S23. In step S22, the fan motor 14A is turned on, and the flow proceeds to step S24.

[0049] In step S24, a timer is started, and the flow proceeds to step S25. In step S25, it is judged whether or not an elapsed time T after the timer is started (the fan motor 14A is turned on) has reached the predetermined time. If the elapsed time T has reached the predetermined time, the flow proceeds to step S26. Meanwhile, if the elapsed time T has not reached the predetermined time, the processing in step S25 is repeated.

[0050] In step S26, it is judged whether the rotational speed N of the fan motor 14A is equal to or greater than the predetermined rotational speed. If the rotational speed N of the fan motor 14A is equal to or greater than the predetermined rotational speed, the process proceeds to step S27. If the rotational speed N of the fan motor 14A is less than the predetermined speed threshold, the process proceeds to step S30.

[0051] In step S27, the variable m is incremented, and the flow proceeds to step S28. In step S28, it is judged whether the variable m is equal to "5" or not. If the variable m is equal to "5", the flow proceeds to step S29. If the variable m is not equal to "5", the flow returns to step S22. In the present embodiment, during an abnormality decision mode, the power supply to the fan motor 14A is repeatedly switched between off and on five times. Therefore, in step S28, it is judged whether the variable m is equal to "5" or not. The frequency of repeatedly switching between off and on the power supply to the fan motor 14A during an abnormality decision mode can be arbitrarily set, and the condition in step S28 can be set according to the set number of switching times. In step S29, it is determined that the fan motor 14A is normal, and the processing is terminated.

[0052] In step S30, the variable n is incremented, and the flow proceeds to step S31. In step S31, it is judged whether the variable n is equal to "3." If the variable n is equal to "3," the flow proceeds to step S32. If the variable n is not equal to "3," the flow proceeds to step S27. In the present embodiment, it is determined that the fan motor 14A is abnormal provided that the condition of step S26 is not satisfied at least three times while the power supply to the fan motor 14A is repeatedly switched between off and on five times. Therefore, in step S31, it is judged whether the variable n is equal to "3." The number of times the condition of step S26 is not satisfied can be arbitrarily set, and a condition of step S31 can be set according to the set number of times. In step S32, it is judged that the fan motor 14A is abnormal, and the flow proceeds to step S33.

[0053] In step S33, the notification unit 22 notifies the operator of the abnormality, and the flow proceeds to step S34. In step S34, the execution of the abnormality decision mode with respect to the fan motor 14A is prohibited, and the processing is terminated.

[0054] The following describes how to control the fan motor determined to be abnormal.

[0055] For example, if the fan motor 14A is judged to be abnormal, the abnormality decision control unit 28 controls the rotational speed of the fan motor 14A to be higher than the rotational speed before the fan motor 14A was judged to be abnormal. Therefore, if dust adheres to the fan motor 14A, it is possible to blow off the dust by increasing the rotational speed of the fan motor 14 to return the fan motor 14 to a normal state. Control of the other fan motor after the abnormality decision is described below.

[0056] For example, if the fan motor 14A is judged to be abnormal, the abnormality decision control unit 28 controls the rotation speed of the fan motor 14B to be higher than a rotation speed before the fan motor 14A was judged to be abnormal. With this arrangement, the other fan motor 14B can compensate for the reduced performance for cooling the CPU 16 or the like caused by the abnormality of one fan motor 14A. Then, after the replacement judgment unit 30 judges that the fan motor 14A has been replaced, the fan motor control unit 26 controls the fan motor 14B normally.

[0057] The unit for assessing an exchange is described below.

[0058] The replacement judging unit 30 has unique identification numbers for each of the fan motor 14A and the fan motor 14B. The identification numbers can be input to the replacement judging unit 30 via an input unit not shown. In the present embodiment, the processing (the compensation process of compensating the predetermined time and the predetermined rotational speed) in steps S1 to S4 shown in Fig. 4. This compensation process of compensating for the predetermined time and the predetermined speed may not be executed. Furthermore, the abnormality decision processing with respect to the fan motor A (or the fan motor B) in the current processing is executed only when the previous processing has determined that the fan motor 14A (or the fan motor 14B) is normal. However, even after it is determined that the fan motor 14A (or the fan motor 14B) is abnormal, the abnormality decision processing may be executed.

[0059] Even if the compensation process of compensating for the predetermined time and the predetermined speed is not performed, or if the abnormality decision processing is performed even after determining that the fan motor 14A (or the fan motor 14B) is abnormal, the replacement judging unit 30 may judge that the fan motor 14A and the fan motor 14B have been replaced. For example, in the case where, after the abnormality decision control unit 28 determined that the fan motor 14A was abnormal, the numerical control device (CPU 16) was turned off, and then turned on, if the abnormality decision control unit 28 does not judge the fan motor 14A to be abnormal, the replacement judging unit judges that the fan motor 14A has been replaced.

[0060] The function and effect are described below.

[0061] The abnormality decision regarding the fan motor 14 is executed when the power supply to the fan motor 14 is switched from off to on or from on to off. Specifically, when the power supply to the fan motor 14 is switched from off to on, the fan motor 14 is driven from a stopped state. Therefore, static friction significantly affects the increase in the speed of the fan motor 14, making it easy to detect an abnormality of the fan motor 14.

[0062] However, according to normal control of the fan motor 14, the power supply to the fan motor 14 is switched from off to on when the CPU 16 or the like is activated, or the power supply to the fan motor 14 is switched from on to off after the CPU 16 or the like is stopped. Accordingly, the power supply to the fan motor 14 is rarely switched from off to on and from on to off, which provides limited opportunities to determine the abnormality of the fan motor 14. Therefore, it has been difficult to improve the control of an abnormality decision with respect to the fan motor 14. Even if there is a state where the fan motor 14 is assumed to be abnormal during the operation of the CPU 16, it is not possible to determine whether the fan motor 14 is abnormal during the operation of the fan motor 14.

[0063] The function and effect of the present embodiment will be described below. A case where the abnormality decision mode is executed with respect to the fan motor 14A and it is judged that the fan motor 14A is abnormal will be described as an example. When the abnormality decision mode is executed with respect to the fan motor 14B and it is determined that the fan motor 14B is abnormal, the explanation can be regarded as the same, except that the control and function of the fan motor 14A and the control and function of the fan motor 14B described below are applied inversely.

[0064] In the present embodiment, the fan motor control device 10, which controls the drive of the fan motor 14A that cools the CPU 16 (a device that generates heat during operation), includes the rotation speed sensor (rotation speed detection unit) 20A that detects the rotation speed of the fan motor 14A, and the abnormality decision control unit 28, which executes the abnormality decision mode of repeatedly switching the power supply to the fan motor 14A on and off during the operation of the CPU 16, and determines the abnormality of the fan motor 14A based on the rotation speed of the fan motor 14A during the execution of the abnormality decision mode.

[0065] Consequently, the abnormality decision control unit 28 can judge the abnormality of the fan motor 14A multiple times even during the operation of the CPU 16. Therefore, it is possible to improve the accuracy of the abnormality decision with respect to the fan motor 14. Furthermore, it is possible to determine the abnormality of the fan motor 14A during the operation of the CPU 16 and detect the abnormality of the fan motor 14A early.

[0066] In the event that the abnormality decision control unit 28 detects that the rotational speed of the fan motor 14A does not reach the preset predetermined speed within the preset time after the fan motor 14A is turned on during the execution of the abnormality decision mode, the abnormality decision control unit 28 decides that the fan motor 14A is abnormal.

[0067] With this arrangement, it is possible to determine the abnormality of the fan motor 14A at a time when the abnormality of the fan motor 14A can be easily detected due to the significant influence of static friction on the increase in the rotational speed of the fan motor 14A. This can improve the accuracy of the abnormality decision.

[0068] In the event that the abnormality decision control unit 28 detects that the set frequency at which the rotational speed of the fan motor 14A does not reach the preset predetermined speed within the preset predetermined time after the fan motor 14A is turned on during the execution of the abnormality decision mode, the abnormality decision control unit 28 determines that the fan motor 14A is abnormal. With this arrangement, it is possible to reduce a risk that the fan motor 14A is erroneously determined to be abnormal, so that the accuracy of the abnormality decision with respect to the fan motor 14A can be improved.

[0069] When the fan motor 14A is replaced and then the replaced fan motor 14A is controlled to be driven for the first time, the abnormality decision control unit 28 compensates for the predetermined time and the predetermined speed used for the abnormality decision. If the constant speed for the case of supplying the rated voltage (predetermined reference voltage) to the fan motor 14A is less than the first speed threshold, which is a speed lower than the rated speed (predetermined reference speed), and is equal to or greater than the second speed threshold, which is the speed lower than the first speed threshold, the abnormality decision control unit 28 sets the predetermined time to be longer than the predetermined time or sets the predetermined speed to be lower than the preset speed.When the rated speed of the fan motor 14A is less than the second speed threshold, the abnormality decision control unit 28 sets the predetermined time to be shorter than the predetermined time or sets the predetermined speed to be higher than the preset speed.

[0070] Therefore, it is possible to set the predetermined time or the predetermined speed to be used for the abnormality decision with respect to the fan motor 14A according to a product variation of the fan motor 14A. Thus, the abnormality decision can be made according to the product variation of the fan motor 14A.

[0071] When the fan motor 14A is replaced and then the replaced fan motor 14A is controlled to be driven for the first time, the abnormality decision control unit 28 compensates for the predetermined time and the predetermined speed to be used for the abnormality decision. If the constant speed in the case where the power supply of the rated voltage (predetermined reference voltage) for the fan motor 14A is greater than the third speed threshold, which is the speed higher than the predetermined reference speed, the abnormality decision control unit 28 sets the predetermined time to be shorter than the preset time or sets the predetermined speed to be higher than the preset speed.

[0072] Therefore, it is possible to set the predetermined time or the predetermined rotation speed to be used for the abnormality decision with respect to the fan motor 14A according to the product variation of the fan motor 14A. This allows the abnormality decision to be made according to the product variation of the fan motor 14A.

[0073] The fan motor control device 10 includes the replacement judging unit 30 that judges that the fan motor 14A has been replaced. When the abnormality decision control unit 28 determines that the fan motor 14A is abnormal, the abnormality decision control unit 28 controls the fan motor 14B, other than the fan motor 14A, at a higher speed than before the abnormality of the fan motor 14A was determined. Consequently, the fan motor 14B can compensate for the deterioration in cooling performance of the CPU 16 or the like caused by the abnormality of one fan motor 14A.

[0074] After the abnormality decision control unit 28 determines the abnormality of the fan motor 14A, when the power supply to the numerical control device (CPU 16) is turned off and then turned back on, provided that the abnormality decision control unit 28 does not determine that the fan motor 14A is abnormal, the replacement judgment unit 30 judges that the fan motor 14A has been replaced. To determine that the fan motor 14A has been replaced, the replacement judgment unit 30 may read an individual identification number of the fan motor 14A. However, a device that reads individual identification numbers must be added, and there are concerns that this will result in increased costs.On the other hand, by determining that the fan motor 14A has been replaced as described previously, it is not necessary to add a device and it is possible to avoid an increase in costs.

[0075] The fan motor control device 10 includes the notification unit 22, which notifies an abnormality when the abnormality decision control unit 28 determines that the fan motor 14A is abnormal. After the notification unit 22 notifies the abnormality, the abnormality decision control unit 28 prohibits the abnormality decision mode from being executed with respect to the fan motor 14A determined to be abnormal.

[0076] A large torque is required to drive the fan motor 14A from a stopped state, compared to the torque at constant rotation. After the fan motor 14A, which is determined to be abnormal, is stopped, the fan motor 14A cannot be driven again. The abnormality decision mode prevents the fan motor 14A from stopping when determined to be abnormal, thus reducing the possibility of the fan motor 14A not being driven again.

[0077] When the abnormality decision control unit 28 determines that the fan motor 14A is abnormal, the abnormality decision control unit 28 controls the fan motor 14A at a speed higher than a speed before the determination of the abnormality of the fan motor 14A.

[0078] With this arrangement, when dust adheres to the fan motor 14A, it is possible to blow off the dust by increasing the speed of the fan motor 14A, so that the fan motor 14A returns to a normal state.

[0079] The abnormality decision control unit 28 executes the abnormality decision mode with respect to one fan motor 14A among a plurality of fan motors 14A, 14B, and does not simultaneously execute the abnormality decision mode with respect to the plurality of fan motors 14A, 14B. Therefore, the cooling performance of the CPU 16 can be prevented from decreasing.

[0080] While executing the abnormality decision mode with respect to one fan motor 14A of the plurality of fan motors 14A, 14B, the abnormality decision control unit 28 controls the other fan motor 14B at a speed higher than the speed before the abnormality decision mode was executed with respect to the one fan motor 14A. Consequently, the other fan motor 14B can compensate for the deterioration in cooling performance of the CPU 16 or the like caused when the abnormality decision mode is executed with respect to the one fan motor 14A.

[0081] The present invention has been described above based on the present embodiment. A specific configuration of each invention is not limited to the embodiment, and design changes made without departing from the scope of the present invention are included in the present invention.

[0082] The abnormality decision with respect to the fan motor 14 in the case where the power supply for the fan motor 14 is switched from on to off can also be carried out in substantially the same way. In this regard, the processing of setting the predetermined time and the predetermined rotational speed used for the abnormality decision with respect to the fan motor 14 in step S12, which is shown in Fig. 5 depicted as "setting the predetermined time to be longer than the preset time (or setting the predetermined speed to be lower than the preset speed)" shall be replaced with "setting the predetermined time to be shorter than the preset time (or setting the predetermined speed to be lower than the preset speed)".

Claims

[1] A fan motor control device (10) configured to control the drive of a fan motor (14A, 14B) to cool a device (16) that generates heat during operation, the fan motor control device (10) comprising: a rotation speed detecting unit (20A, 20B) configured to detect a rotation speed of the fan motor (14A, 14B); and an abnormality decision control unit (28) configured to execute an abnormality decision mode during operation of the device (16) in which the fan motor is repeatedly switched from a stop state to a drive state by switching the power supply for the fan motor (14A, 14B) from off to on and switching the fan motor from the drive state to the stop state by switching the power supply of the fan motor (14A, 14B) from on to off, and to judge the abnormality of the fan motor (14A, 14B) based on the rotational speed of the fan motor (14A, 14B) measured when the power supply of the fan motor is switched from off to on, and also based on the rotational speed of the fan motor measured when the power supply of the fan motor is switched from on to off, during the execution of the abnormality decision mode, wherein the abnormality decision control unit (28) judges that the fan motor (14A, 14B) is abnormal in the event that the abnormality decision control unit (28) detects that the rotational speed of the fan motor (14A, 14B) does not reach a preset predetermined rotational speed within a preset predetermined time after the fan motor (14A, 14B) is turned on during execution of the abnormality decision mode. [2] The fan motor control device (10) according to claim 1, wherein the abnormality decision control unit (28) determines that the fan motor (14A, 14B) is abnormal in the event that the abnormality decision control unit (28) detects a set number of times that the rotational speed of the fan motor (14A, 14B) does not reach a preset predetermined rotational speed within a preset predetermined time after the fan motor (14A, 14B) is turned on during execution of the abnormality decision mode. [3] The fan motor control device (10) according to claim 1 or 2, further comprising a replacement judging unit (30) configured to judge that the fan motor (14A, 14B) has been replaced, wherein, in the case that the fan motor (14A, 14B) is drive-controlled for the first time since the replacement judging unit (30) judged that the fan motor (14A, 14B) was replaced, the abnormality decision controlling unit (28) compensates for the predetermined time and the predetermined speed, wherein the predetermined time is compensated to be longer than a preset time, or the predetermined rotational speed is compensated to be lower than a preset rotational speed if a constant rotational speed, which is a rotational speed of the fan motor (14A, 14B) supplied with electric power at a predetermined reference voltage, is lower than a first rotational speed threshold, which is a rotational speed lower than a predetermined reference rotational speed, and is equal to or higher than a second rotational speed threshold, which is a rotational speed lower than the first rotational speed threshold, and wherein the predetermined time is compensated to be shorter than the preset time, or the predetermined speed is compensated to be higher than a preset speed if the constant speed of the fan motor (14A, 14B) is lower than the second speed threshold. [4] Fan motor control device (10) according to one of claims 1 to 3, further comprising a replacement judging unit (30) configured to judge that the fan motor (14A, 14B) has been replaced, wherein, in the case that the fan motor (14A, 14B) is drive-controlled for the first time since the replacement judging unit (30) judged that the fan motor (14A, 14B) was replaced, the abnormality decision controlling unit (28) compensates for the predetermined time and the predetermined speed, and wherein the predetermined time is set to be shorter than the preset time, or the predetermined speed is set to be higher than a preset speed if a constant speed, which is a speed of the fan motor (14A, 14B) supplied with electric power at a predetermined reference voltage, is higher than a third speed threshold, which is a speed higher than a predetermined reference speed. [5] Fan motor control device (10) according to claim 1 or 2, further comprising: a plurality of fan motors (14A, 14B); and a replacement judging unit (30) configured to judge that the fan motors (14A, 14B) have been replaced, wherein, when the abnormality decision control unit (28) determines that one of the fan motors (14A, 14B) is abnormal, the abnormality decision control unit (28) controls another of the fan motors (14A, 14B) to be driven at a speed higher than a speed before the determination of an abnormality of the one of the fan motors (14A, 14B) until the one of the fan motors (14A, 14B) determined to be abnormal is replaced. [6] The fan motor control device (10) according to claim 5, wherein the replacement judging unit (30) judges that the one of the fan motors (14A, 14B) has been replaced, provided that the one of the fan motors (14A, 14B) is not determined to be abnormal by the abnormality decision control unit (28) after being determined to be abnormal and after the device (16) is turned off and then turned on. [7] The fan motor control device (10) according to any one of claims 1 to 5, further comprising a notification unit (22) configured to notify that the abnormality decision control unit (28) determines the fan motor (14A, 14B) to be abnormal, wherein the abnormality decision control unit (28) prevents the abnormality decision mode from being executed with respect to the fan motor (14A, 14B) determined to be abnormal after the notification by the notification unit. [8] The fan motor control device (10) according to any one of claims 1 to 7, wherein the abnormality decision control unit (28) controls the fan motor (14A, 14B) determined to be abnormal to increase the rotational speed compared to the rotational speed before the determination of the abnormality of the fan motor (14A, 14B). [9] The fan motor control device (10) according to any one of claims 1 to 8, further comprising a plurality of said fan motors (14A, 14B), wherein said abnormality decision control unit (28) executes said abnormality decision mode with respect to one of said fan motors (14A, 14B) among said plurality of fan motors (14A, 14B), and does not simultaneously execute said abnormality decision mode with respect to said plurality of fan motors (14A, 14B). [10] The fan motor control device (10) according to claim 9, wherein while the abnormality decision control unit (28) executes the abnormality decision mode with respect to the one of the plurality of fan motors (14A, 14B), the abnormality decision control unit (28) controls another one of the fan motors (14A, 14B) to increase the rotational speed compared to the rotational speed before the execution of the abnormality decision mode with respect to the one of the fan motors (14A, 14B).

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