Motor drive control device, fan unit, and motor drive control method

Abstract

To enable proper detection of signs of motor end-of-life. [Solution] The motor drive control device (1) comprises a control circuit (2) that generates a drive control signal for controlling the rotation of a motor, and a drive circuit (3) that drives the motor based on the drive control signal. The control circuit is characterized by comprising: a drive control signal generation unit (20) that generates the drive control signal so that the motor rotates at a target rotation speed which is a target value of the motor's rotation speed; a current measurement unit (24) that measures the current of the motor; a storage unit (25) that stores threshold values ​​(Ith1, Ith2) for the current associated with each target rotation speed; and an abnormality determination unit (26) that determines whether the motor is abnormal based on the result of comparing the measured value of the current with the threshold value for the current corresponding to the target rotation speed.

Description

Technical Field

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[0001] The present invention relates to a motor drive control device, a fan unit, and a motor drive control method, and more particularly, to a motor drive control device that controls the rotation of a motor in a fan unit.

Background Art

[0006] This invention has been made in view of the above-mentioned problems, and aims to enable the appropriate detection of signs of motor lifespan deterioration. [Means for solving the problem]

[0007] A motor drive control device according to a typical embodiment of the present invention comprises a control circuit that generates a drive control signal for controlling the rotation of a motor, and a drive circuit that drives the motor based on the drive control signal, wherein the control circuit includes a drive control signal generation unit that generates the drive control signal so that the motor rotates at a target rotation speed which is a target value of the motor's rotation speed, a current measurement unit that measures the current of the motor, a storage unit that stores a threshold value for the current associated with each target rotation speed, and an abnormality determination unit that determines whether or not the motor is abnormal based on a comparison result between the measured value of the current and the threshold value for the current corresponding to the target rotation speed. [Effects of the Invention]

[0008] According to the motor drive control device of the present invention, it is possible to appropriately detect signs of the motor's lifespan ending. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing the configuration of a fan unit according to an embodiment. [Figure 2] This is a schematic perspective view showing the appearance of the fan unit according to the embodiment. [Figure 3] This figure schematically shows a cross-section of the fan unit shown in Figure 2. [Figure 4] This figure shows an example of the relationship between motor rotation speed and rated current. [Figure 5A] This figure shows an example of the time-dependent change in motor current. [Figure 5B] This figure shows an example of the time-dependent change in motor current. [Figure 6] This flowchart shows an example of the process for determining an abnormal state in a motor drive control device according to an embodiment. [Modes for carrying out the invention]

[0010] 1. Overview of the Embodiment First, a general overview of a typical embodiment of the invention disclosed in this application will be provided. In the following description, as an example, reference numerals on the drawings corresponding to the components of the invention are indicated in parentheses.

[0011] [1] A motor drive control device (1) according to a typical embodiment of the present invention comprises a control circuit (2) that generates a drive control signal for controlling the rotation of a motor, and a drive circuit (3) that drives the motor based on the drive control signal, wherein the control circuit is characterized by having a drive control signal generation unit (20) that generates the drive control signal so that the motor rotates at a target rotation speed which is a target value of the rotation speed of the motor, a current measurement unit (24) that measures the current of the motor, a storage unit (25) that stores threshold values ​​(Ith1, Ith2) for the current associated with each target rotation speed, and an abnormality determination unit (26) that determines whether the motor is abnormal or not based on the result of comparing the measured value of the current with the threshold value for the current corresponding to the target rotation speed.

[0012] [2] In the motor drive control device (1) described in [1] above, the threshold value related to the current includes a first current threshold value (Ith2), the storage unit stores a time threshold value (Tth) related to time, and the abnormality determination unit measures the current rise time (Tup) from a first time point (t1) when it is detected that the measured value of the current has started to rise to a second time point (t2) when the measured value of the current reaches the first current threshold value, and when the current rise time is equal to or greater than the time threshold value, it may be determined that the motor is in a predetermined abnormal state.

[0013] [3] In the motor drive control device described in [2] above, when the state where the measured value of the current is equal to or greater than the first current threshold value continues for a predetermined time or more, the abnormality determination unit may determine that the measured value of the current has reached the first current threshold value.

[0014] [4] In the motor drive control device described in [2] or [3] above, the threshold value related to the current includes a second current threshold value (Ith1) smaller than the first current threshold value, and the abnormality determination unit may use the timing when the measured value of the current reaches the second current threshold value as the first time point.

[0015] [5] In the motor drive control device described in [4] above, when the state where the measured value of the current is equal to or greater than the second current threshold value continues for a predetermined time or more, the abnormality determination unit may determine that the measured value of the current has reached the second current threshold value.

[0016] [6] In the motor drive control device described in any one of [2] to [5] above, the abnormality determination unit may use the timing when an increase in the rate of change of the measured value of the current with respect to time is detected as the first time point.

[0017] [7] In the motor drive control device described in any one of [2] to [5] above, when the current rise time is smaller than the time threshold value, the abnormality determination unit may determine that the motor is in an abnormal state different from the predetermined abnormal state.

[0018] 〔8〕In the motor drive control device according to any one of the above〔2〕to〔7〕, the current measurement unit may calculate an average value or a median value of detection values of a plurality of currents and output the calculated value as the measured value of the current.

[0019] 〔9〕A fan unit (7) according to a typical embodiment of the present invention includes the motor (40), an impeller (41) connected to the output shaft of the motor, and the motor drive control device (1) according to any one of the above〔1〕to〔8〕.

[0020] 〔10〕A method according to a typical embodiment of the present invention is a motor drive control method for controlling the rotation of a motor by a motor drive control device. The method includes a first step (S1) of generating a drive control signal for controlling the rotation of the motor so that the motor rotates at a target rotation speed which is a target value of the rotation speed of the motor, a second step (S2) of measuring the current of the motor, and a third step (S3 to S8) of determining whether the motor is abnormal based on a comparison result between the measured value of the current and a threshold value related to the current corresponding to the target rotation speed.

[0021] 〔11〕In the motor drive control method according to the above〔10〕, the threshold value related to the current includes a first current threshold value (Ith2), and the third step includes a step (S4) of measuring a current rise time from a first time point when the measured value of the current starts to rise to a second time point when the measured value of the current reaches the first current threshold value, and a step (S7) of determining that the motor is in a predetermined abnormal state when the current rise time is not less than a time threshold value which is a threshold value related to time.

[0022] 2. Specific Examples of Embodiments Hereinafter, specific examples of embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are given to the common components in each embodiment, and repeated descriptions are omitted.

[0023] ≪Embodiment≫ Figure 1 is a block diagram showing the configuration of the fan unit 7 according to the embodiment. Figure 2 is a schematic perspective view showing the external appearance of the fan unit 7 according to the embodiment. Figure 3 is a schematic diagram showing a cross-section of the fan unit 7 shown in Figure 2.

[0024] The fan unit 7 according to this embodiment is a device that generates wind by rotating an impeller (vanewheel). The fan unit 7 can be used, for example, as a cooling device that expels heat generated inside a device to the outside and cools the inside of that device.

[0025] As shown in Figure 1, the fan unit 7 comprises a fan 4 and a motor drive control device 1. The fan 4 comprises a motor 40 and an impeller 41 attached to the rotating shaft 42 of the motor 40. The fan 4 is, for example, an axial flow fan. As shown in Figure 3, in the fan 4, the motor 40 is located inside the hub of the impeller 41.

[0026] The motor 40 is, for example, an outer rotor type three-phase brushless DC (Direct Current) motor having a rotating shaft 42 to which an impeller 41 is connected, and a rotor connected to the rotating shaft 42 that rotates due to the rotational force of the motor 40. In addition to the rotating shaft 42 described above, the motor 40 includes bearings 43, 44, a stator 45, a magnet 46, a casing 47, and a circuit board 48, etc.

[0027] As shown in Figure 3, the rotating shaft 42 is a rod-shaped member with its longitudinal direction oriented along the axial X direction. The bearings 43 and 44 are supported by a bearing support portion 421 located in the center of the casing 47. The bearings 43 and 44 rotatably support the rotating shaft 42. The bearings 43 and 44 each have an inner ring, an outer ring, and rolling elements.

[0028] The stator 45 is fixed, for example, near the center (axis X) of the rotating shaft 42 in the casing 47. The stator 45 includes, for example, a stator core formed by laminating multiple electromagnetic steel sheets, and coils wound on the stator core via an insulator. The magnet 46 functions as a rotor and is provided with a predetermined gap between it and the stator 45. The circuit board 48 is, for example, a printed circuit board (PCB). The circuit board 48 is an insulating board on which conductive wiring is laid, and electronic components constituting the motor drive control device 1 (control circuit 2, drive circuit 3, and current detection circuit 6) are mounted.

[0029] The motor drive control device 1 is a device for controlling the drive of the motor 40. As shown in Figure 1, the motor drive control device 1 includes, for example, a plurality of external terminals, a control circuit 2, a drive circuit 3, a position detector 5, and a current detection circuit 6. Note that the components of the motor drive control device 1 shown in Figure 1 are only a part of the whole, and the motor drive control device 1 may have other components in addition to those shown in Figure 1.

[0030] As shown in Figure 1, the motor drive control device 1 has a plurality of external terminals, such as a power terminal P1, a ground terminal P2, a signal input terminal P3 for inputting signals, and a signal output terminal P4 for outputting signals.

[0031] The fan unit 7 constitutes a so-called four-wire fan motor. Specifically, as shown in Figures 1 and 2, a signal line 49 is connected to the power terminal P1, a signal line 50 is connected to the ground terminal P2, a signal line 51 is connected to the signal input terminal P3, and a signal line 52 is connected to the signal output terminal P4. As shown in Figure 2, each of the signal lines 49 to 51 is brought out to the outside of the casing 47 of the fan unit 7 and connected to a higher-level device (not shown) and a power supply device (not shown) located outside the fan unit 7, thereby electrically connecting the motor drive control device 1 with the power supply device and the higher-level device.

[0032] A DC voltage Vdc is supplied to the power terminal P1 from the power supply unit via the signal line 49. This supplies the power supply voltage to the control circuit 2 and the drive circuit 3. Alternatively, a regulator may be provided in the motor drive control device 1, which generates a new DC voltage from the DC voltage Vdc and supplies it to the control circuit 2 as the power supply voltage. The ground terminal P2 is connected to the ground potential GND via the signal line 50.

[0033] As described later, a drive command signal Sc, which indicates the motor's drive state, is input to the signal input terminal P3. For example, the signal input terminal P3 is connected to a higher-level device, and the drive command signal Sc output from the higher-level device is input to the signal input terminal P3. As described later, the signal output terminal P4 outputs a rotation state signal So. For example, the signal output terminal P4 is connected to a higher-level device, and the rotation state signal So output from the control circuit 2 is input to the higher-level device from the signal output terminal P4.

[0034] Furthermore, if the fan unit 7 receives power from a higher-level device, the power terminal P1 and ground terminal P2 may be connected to the power line and ground line within the higher-level device, respectively.

[0035] The position detector 5 is a device for detecting the rotational position of the rotation axis (rotor) of the motor 40. The position detector 5 is, for example, a Hall element. For example, three Hall elements corresponding to each phase (U phase, V phase, W phase) of the motor 40 are arranged around the rotor (magnet) of the motor 40 at approximately equal intervals from each other. The number of Hall elements is not particularly limited.

[0036] The position detector 5 outputs a rotational position detection signal (Hall signal) Sh to the control circuit 2. The rotational position detection signal Sh is a signal indicating the rotational position of the motor 40, that is, a signal corresponding to the rotational position of the rotor (magnet) of the motor 40.

[0037] The position detector 5 only needs to have the function of detecting the position information of the rotation axis (rotor) of the motor 40 and outputting it as an electrical signal, and may be, for example, a rotary encoder. Alternatively, the rotation position of the motor 40 may be detected by a so-called sensorless method in which the control circuit 2 detects the back electromotive force induced in each phase (U, V, W phases) of the motor 40 and detects the rotation position of the motor 40 based on that back electromotive force, without providing the position detector 5.

[0038] Control circuit 2 is a circuit that performs overall control in the motor drive control device 1. Control circuit 2 generates a drive control signal Sd for controlling the rotation of the motor 40. Control circuit 2 is a program processing device (for example, various computers such as a microcontroller) in which a processor such as a CPU, various storage devices such as RAM and ROM, and peripheral circuits such as a counter (timer), A / D conversion circuit, D / A conversion circuit, clock generation circuit, and input / output I / F circuit are connected to each other via a bus or dedicated line. Details of control circuit 2 will be described later.

[0039] The drive circuit 3 is a circuit that drives the motor 40 based on the drive control signal Sd. The drive circuit 3 includes, for example, an inverter circuit (not shown) and a pre-drive circuit (not shown). The inverter circuit outputs a drive signal to the motor 40 based on the output signal output from the pre-drive circuit and energizes the three-phase coils of the motor 40. By switching the order in which the three-phase coils are energized, the rotation direction of the motor 40 can be switched. For example, the inverter circuit is configured by arranging a pair of series circuits of two switch elements connected in series between a DC voltage Vdc and ground potential GND for each phase coil. In each pair of two switch elements, the terminals of each phase of the motor 40 are connected to the connection point between the switch elements.

[0040] The pre-drive circuit generates an output signal to drive the inverter circuit based on the drive control signal Sd and outputs it to the inverter circuit. For example, the pre-drive circuit generates and outputs a drive signal to drive each switch element of the inverter circuit based on the drive control signal Sd.

[0041] The drive signal output from the pre-drive circuit turns on / off each switch element that makes up the inverter circuit, thereby supplying power to each phase of the motor 40 and causing the rotor of the motor 40 to rotate.

[0042] The current detection circuit 6 is a circuit that detects the current flowing through the motor 40. The current detection circuit 6 is connected in series with the inverter circuit that constitutes the drive circuit 3, for example, between the power supply line to which the DC voltage Vdc is supplied and the ground potential GND. In this embodiment, as an example, the current detection circuit 6 is assumed to be connected between the drive circuit 3 and the ground potential GND.

[0043] The current detection circuit 6 includes, for example, a shunt resistor. When the motor 40 is rotating, the current flowing through the motor 40's coil flows to ground potential GND through the shunt resistor of the current detection circuit 6. The current detection circuit 6 outputs a current detection signal Si as the voltage generated across the shunt resistor in response to the current flowing into the shunt resistor. The current detection signal Si is input to the control circuit 2.

[0044] Furthermore, the current detection circuit 6 is not limited to the shunt resistor described above, but may be any other known circuit capable of detecting the current of the motor 40. Also, at least a portion of the functional parts of the control circuit 2 and the drive circuit 3 (including the current detection circuit 6) may be packaged as a single semiconductor integrated circuit (IC), or the control circuit 2 and the drive circuit 3 (including the current detection circuit 6) may each be packaged as separate semiconductor integrated circuit devices.

[0045] Next, we will explain control circuit 2 in detail.

[0046] The control circuit 2 generates a drive control signal Sd for controlling the rotation of the motor 40 based on the drive command signal Sc input to the signal input terminal P3. Specifically, the control circuit 2 has the function of generating a drive control signal Sd so that the motor 40 reaches the rotation state specified by the drive command signal Sc.

[0047] The control circuit 2 has a function to detect abnormal conditions in the motor 40 (fan 4).

[0048] Here, an abnormal condition of motor 40 refers to a condition that indicates the end of the motor 40's lifespan. For example, the control circuit 2 has a function to detect abnormal conditions (also referred to as "first abnormal condition") caused by deterioration of the motor 40's bearings 43 and 44. The abnormal conditions caused by deterioration of the motor 40's bearings 43 and 44 will be described below.

[0049] Figure 4 shows an example of the relationship between motor rotation speed and rated current.

[0050] In Figure 4, the horizontal axis represents rotational speed, and the vertical axis represents rated current. Reference numeral 300 represents the characteristic of the rated current with respect to the motor's rotational speed when the motor is in a normal state, and reference numeral 301 represents the characteristic of the rated current with respect to the motor's rotational speed when the motor is in an abnormal state.

[0051] As can be seen from Figure 4, generally, the rated current tends to increase as the rotational speed of the motor increases. Here, the rated current refers to the current that flows through the motor when it rotates at a specific rotational speed. The inventors of this invention have found that the rated current increases when deterioration occurs in the motor bearings. Specifically, as shown in Figure 4, when the motor rotates at a rotational speed ω0, the rated current is "In0" when the motor is in a normal state, and becomes "In1", which is greater than "In0", when the motor is in an abnormal state due to deterioration of the bearings. Furthermore, the inventors of this invention have found that the rated current gradually increases as the deterioration of the bearings progresses.

[0052] Therefore, the control circuit 2 of the motor drive control device 1 according to this embodiment detects an abnormal condition (first abnormal condition) caused by deterioration of the bearings 43 and 44 of the motor 40 by monitoring the current of the motor 40.

[0053] Next, we will describe the functional blocks that implement the above functions of control circuit 2.

[0054] As shown in Figure 1, the control circuit 2 has a drive control signal generation unit 20, a current measurement unit 24, a storage unit 25, and an abnormality determination unit 26 as functional blocks for realizing the above-described functions. These functional blocks are realized, for example, in the control circuit 2 by the CPU executing various arithmetic processes according to a program stored in memory, and controlling peripheral circuits such as A / D conversion circuits and input / output interface circuits based on the processing results. Note that some or all of the drive control signal generation unit 20, current measurement unit 24, storage unit 25, and abnormality determination unit 26 may be realized by dedicated circuits (dedicated hardware logic circuits, etc.).

[0055] The drive control signal generation unit 20 is a functional block that generates a drive control signal Sd. The drive control signal generation unit 20 generates the drive control signal Sd so that the motor 40 rotates at a target rotational speed, which is a target value for rotational speed. For example, the drive control signal generation unit 20 includes a target rotational speed setting unit 21, a signal generation unit 22, and a rotational speed calculation unit 23.

[0056] The target rotational speed setting unit 21 is a functional unit that sets the target rotational speed. For example, when a drive command signal Sc is input to the signal input terminal P3 from an external source (higher-level device), the target rotational speed setting unit 21 analyzes the drive command signal Sc input to the signal input terminal P3. For example, consider the case where the drive command signal Sc is a PWM signal and the target rotational speed is specified by the duty cycle of the PWM signal. In this case, correspondence information showing the relationship between the duty cycle of the PWM signal and the target rotational speed is pre-stored in the storage unit 25. The target rotational speed setting unit 21 analyzes the duty cycle of the PWM signal and determines the target rotational speed of the motor 40 by referring to the above correspondence information based on the analyzed duty cycle. The target rotational speed setting unit 21 outputs the determined target rotational speed information Stv. Note that if no drive command signal Sc is input and the target rotational speed of the fan 4 is fixed, the target rotational speed setting unit 21 may read and output the target rotational speed information Stv that is pre-set in the storage unit 25.

[0057] The rotational speed calculation unit 23 is a functional unit that calculates the actual rotational speed of the motor 40. Based on the rotational position detection signal Sh, the rotational speed calculation unit 23 calculates the rotational speed of the motor 40 using a known calculation method and provides the rotational speed information Sv to the signal generation unit 22. In the case of the sensorless method described above, for example, the rotational speed calculation unit 23 may detect the back electromotive force induced in each phase (U, V, W phases) of the motor 40 and calculate the rotational speed of the motor 40 based on that back electromotive force.

[0058] The signal generation unit 22 generates a drive control signal Sd for the motor 40 based on the target rotational speed information Stv and the rotational speed information Sv of the motor 40. Specifically, the signal generation unit 22 calculates the error between the target rotational speed and the motor's rotational speed, calculates the control amount of the motor 40 to reduce the error to zero, for example using PID (Proportional Integral Differential) control calculation, generates a PWM signal with a duty cycle corresponding to the control amount, and outputs it as the drive control signal Sd.

[0059] In the case of open-loop control, where the motor 40 is not intended to maintain its rotational speed but is intended to rotate with a constant force, the signal generation unit 22 may generate a PWM signal having a duty cycle corresponding to the manipulated amount used to maintain the target rotational speed and output it as a drive control signal Sd.

[0060] The current measurement unit 24 is a functional unit that measures the current of the motor 40. The current measurement unit 24 acquires a detected current value based on the current detection signal Si output from the current detection circuit 6, and generates a measured value of the motor 40's current based on the detected current value. For example, the current measurement unit 24 converts the analog current detection signal Si into a digital value at a predetermined sampling period and acquires a detected current value. The current measurement unit 24 generates and outputs a measured value of the current based on the detected current value. For example, the current measurement unit 24 may output the detected current value as the measured current value, or it may calculate the average value (e.g., moving average) or median value (e.g., moving median) of multiple detected current values ​​and output it as the measured current value.

[0061] The memory unit 25 is a functional unit that stores various data such as parameters and calculation results used in calculations to realize the above functions of the control circuit 2. For example, the memory unit 25 stores correspondence relationship information (Stv-Ith) 250, which shows the correspondence between the target rotational speed of the motor 40 (described later) and a threshold value related to the current of the motor 40, and time threshold value information 251, which is a threshold value related to time.

[0062] The abnormality determination unit 26 is a functional unit that determines whether or not the motor 40 is in an abnormal state. Specifically, it determines whether or not the motor 40 is abnormal based on the comparison result between the measured current and a threshold value for the current corresponding to the target rotational speed. The determination method by the abnormality determination unit 26 will be described in detail below.

[0063] Figures 5A and 5B show an example of the time variation of the motor current.

[0064] In Figures 5A and 5B, the horizontal axis represents time t, and the vertical axis represents the motor current I. Figure 5A shows the temporal change in the motor current I when the motor enters an abnormal state caused by bearing deterioration (also referred to as "first abnormal state"), and Figure 5B shows the temporal change in the motor current I when the motor enters an abnormal state caused by factors other than bearing deterioration (hereinafter also referred to as "second abnormal state").

[0065] As mentioned above, if the motor bearings deteriorate, the motor's rated current will increase. The rate at which the current increases is slower than the rate at which the current increases when the motor malfunctions due to factors other than bearing deterioration. For example, when a motor is overloaded, the motor current increases sharply, but when the motor bearings deteriorate, the motor's rated current increases gradually.

[0066] Therefore, the abnormality determination unit 26 of the motor drive control device 1 according to this embodiment sets a time threshold for the time required for the motor 40 current to rise and a current threshold for the motor 40 current, and then monitors the current measurement value by the current measurement unit 24 and the current rise time to determine whether or not a first abnormal state has occurred.

[0067] In the motor drive control device 1, a current threshold Ith2 is set as a threshold value for current. As described above, the rated current of the motor changes with rotational speed. Therefore, the current threshold Ith2 is set for each target rotational speed. For example, a table or function showing the correspondence relationship (Stv-Ith) between the target rotational speed and the current threshold Ith2 is pre-stored in the storage unit 25 as correspondence relationship information 250. In the correspondence relationship information 250, the current threshold Ith2 is set such that the current threshold Ith2 increases as the target rotational speed increases.

[0068] For example, the abnormality detection unit 26 acquires target rotational speed information Stv and identifies the target rotational speed based on the acquired information. The abnormality detection unit 26 reads the current threshold Ith2 corresponding to the identified target rotational speed from the correspondence relationship information 250 and sets the current threshold Ith2 for each target rotational speed.

[0069] In the motor drive control device 1, a time threshold Tth is set as a time-related threshold. For example, in order to appropriately detect the increase in rated current due to the deterioration of bearings 43 and 44 of the motor 40, the approximate increase time can be measured in advance through experiments, and an appropriate value can be set based on the measured value and stored in the storage unit 25 as the time threshold Tth.

[0070] The abnormality determination unit 26 acquires current measurements from the current measurement unit 24 at predetermined intervals. The abnormality determination unit 26 measures the current rise time Tup from time t1, when it detects that the current measurement value from the current measurement unit 24 has started to rise, to a second time point t2, when the current measurement value reaches the current threshold Ith2. The abnormality determination unit 26 determines that the motor 40 is in a first abnormal state if the current rise time Tup is greater than or equal to the time threshold Tth.

[0071] More specifically, the abnormality detection unit 26 includes, for example, a counter (timekeeping unit). When the abnormality detection unit 26 detects that the current measurement value from the current measurement unit 24 has started to rise, it activates the counter and starts measuring time using the counter. The abnormality detection unit 26 sets the value of the counter as the current rise time Tup.

[0072] After the counter starts measuring the current rise time Tup, the abnormality determination unit 26 determines whether the measured current has become equal to or greater than the current threshold Ith2. For example, if the measured current (moving average or moving median) remains equal to or greater than the current threshold Ith2 for a predetermined period of time or longer, the abnormality determination unit 26 may determine that the measured current has become equal to or greater than the current threshold Ith2 (the measured current has reached the current threshold Ith2). When the measured current value exceeds the current threshold Ith2, the abnormality determination unit 26 stops measuring the current rise time Tup using the counter and determines whether the current rise time Tup at the time of stopping is equal to or greater than the time threshold Tth. The time threshold Tth information 251 is stored in the storage unit 25 beforehand.

[0073] For example, as shown in Figure 5A, if the current rise time Tup from the first time point t1 when an increase in the measured current is detected to the second time point t2 when the measured current reaches the current threshold Ith2 is greater than the time threshold Tth, the abnormality determination unit 26 determines that the motor 40 is in a first abnormal state.

[0074] On the other hand, as shown in Figure 5B, if the current rise time Tup from the first time point t1 when an increase in the measured current is detected to the second time point t2 when the measured current reaches the current threshold Ith2 is smaller than the time threshold Tth, the abnormality determination unit 26 determines that the motor 40 is not in the first abnormal state. In this case, the abnormality determination unit 26 may determine that it is in the second abnormal state.

[0075] Here, determining whether or not the measured current has started to rise can be achieved, for example, by the following method.

[0076] The first method involves using a current threshold Ith1 that is smaller than the current threshold Ith2 as a threshold for current. Specifically, in addition to the current threshold Ith2, a current threshold Ith1 that is smaller than the current threshold Ith2 is further set as a threshold for current. For example, as shown in Figure 5A, it is preferable to set the current threshold Ith1 to a value that is greater than the rated current of the motor 40 and closer to the rated current than the current threshold Ith2. The abnormality determination unit 26 considers the timing when the measured current reaches the current threshold Ith1 as the first time point t1. For example, if the state in which the measured current (e.g., moving average or moving median) is greater than or equal to the current threshold Ith1 continues for a predetermined time or longer, the abnormality determination unit 26 may determine that the measured current has reached the current threshold Ith1.

[0077] The second method uses the rate of change of the measured current. Specifically, the abnormality detection unit 26 sets the timing at which it detects an increase in the rate of change of the measured current relative to time as the first time point t1. For example, the abnormality detection unit 26 acquires the measured current from the current measurement unit 24 at predetermined intervals. Based on the acquired measured current and the measured current acquired in the previous interval, the abnormality detection unit 26 calculates the rate of change of the measured current relative to time at predetermined intervals using a known calculation method. The abnormality detection unit 26 then monitors the rate of change calculated at predetermined intervals and sets the timing at which it detects an increase in the rate of change as the first time point t1.

[0078] Furthermore, the specific method for determining whether or not the measured current has started to rise is not limited to the example described above, and other methods may be used.

[0079] Furthermore, the abnormality detection unit 26 may generate a rotational state signal So indicating the rotational state of the motor 40 and output it from the signal output terminal P4. For example, if no abnormality is detected in the motor 40, the abnormality detection unit 26 generates an FG (Frequency Generator) signal having a frequency based on the rotational speed of the motor 40 and a predetermined duty cycle using a known method based on the rotational position detection signal Sh (Hall signal), and outputs it as the rotational state signal So.

[0080] On the other hand, if the motor 40 is detected to be in a first abnormal state, the abnormality determination unit 26 outputs a signal indicating that the motor 40 is in a first abnormal state as a rotation state signal So. For example, the abnormality determination unit 26 outputs a signal as a rotation state signal So whose signal level is constant at a first logic level (DC voltage Vdc) or a second logic level (ground potential).

[0081] Furthermore, if the abnormality detection unit 26 detects that the motor 40 is in a second abnormal state, it may output a signal indicating that the motor 40 is in a second abnormal state as the rotation state signal So. For example, the abnormality detection unit 26 may output a signal with the opposite logic level to the rotation state signal So output when it detects that the motor 40 is in a first abnormal state as the rotation state signal So.

[0082] Next, we will explain the process flow related to determining whether or not there is an abnormal condition in the motor 40 described above.

[0083] Figure 6 is a flowchart showing an example of the flow of abnormal state determination processing in the motor drive control device 1 according to the embodiment.

[0084] For example, the drive control signal generation unit 20 in the control circuit 2 generates a drive control signal Sd in the manner described above in response to a drive command signal Sc input from an external source, and supplies it to the drive circuit 3, causing the motor 40 to rotate (step S1).

[0085] After the motor 40 starts to run, the current measurement unit 24 in the control circuit 2 starts measuring the current I of the motor 40 (step S2). At this time, the abnormality detection unit 26 monitors the measurement value of the current I of the motor 40 obtained by the current measurement unit 24.

[0086] The abnormality detection unit 26 determines whether the measured value of current I is increasing using the method described above (step S3). If the measured value of current I is not increasing (step S3: NO), the control circuit 2 returns to step S2 and continues measuring the current while driving the motor 40.

[0087] On the other hand, if the measured value of current I is rising (step S3: YES), the abnormality determination unit 26 starts measuring the current rise time Tup using the method described above (step S4).

[0088] The abnormality determination unit 26 determines whether the measured value of current I is greater than or equal to the current threshold Ith2 (step S5). If the measured value of current I is less than the current threshold Ith2 (step S5: NO), the abnormality determination unit 26 continues to measure the current rise time Tup (step S4).

[0089] If the measured value of current I is greater than or equal to the current threshold Ith2 (step S5: YES), the abnormality determination unit 26 determines whether the current rise time Tup is greater than or equal to the time threshold Tth (step S6).

[0090] If the current rise time Tup is greater than or equal to the time threshold Tth (step S6: YES), the abnormality determination unit 26 determines that the motor is in a first abnormal state (step S7). In this case, the abnormality determination unit 26 outputs a rotation state signal So indicating that the motor is in a first abnormal state using the method described above.

[0091] On the other hand, if the current rise time Tup is less than the time threshold Tth (step S6: NO), the abnormality determination unit 26 determines that the motor is not in the first abnormal state (step S8). In this case, the abnormality determination unit 26 determines that the motor is in the second abnormal state and may output a rotation state signal So indicating that the motor is in the second abnormal state using the method described above.

[0092] In the motor drive control device 1 of the fan unit 7 according to the embodiment described above, the control circuit 2 generates a drive control signal Sd so that the motor 40 rotates at a target rotational speed, and determines whether the motor 40 is abnormal based on the comparison result between a threshold value for current associated with each target rotational speed and a measured value of the motor 40's current. This makes it possible to detect abnormal motor conditions, such as when the rotational speed of the motor 40 is controlled in a closed loop, as signs of the motor 40's lifespan appear as changes in the motor's current.

[0093] Specifically, the control circuit 2 measures the current rise time Tup from the first time point t1 when it detects that the measured value of the current starts to increase to the second time point t2 when the measured value of the current reaches the current threshold Ith2. When the current rise time Tup is greater than or equal to the time threshold Tth, it is determined that the motor 40 is in the first abnormal state. According to this, as described above, it is possible to detect signs of the life of the motor 40 caused by deterioration of the bearings 43 and 44 of the motor 40.

[0094] Here, the control circuit 2 can easily detect that the measured value of the current starts to increase by setting the timing when the measured value of the current reaches the current threshold Ith1 (<Ith2) as the first time point t1. Also, the control circuit 2 can easily detect that the measured value of the current starts to increase by setting the timing when it detects an increase in the rate of change of the measured value of the current with respect to time as the first time point t1.

[0095] Also, when the current rise time Tup is less than the time threshold Tth, the control circuit 2 determines that the motor 40 is in the second abnormal state. According to this, it is possible to detect an abnormal state in which the current of the motor increases due to factors other than deterioration of the bearings 43 and 44 of the motor 40.

[0096] Also, as described above, the control circuit 2 may calculate the average value (e.g., moving average) or median value (e.g., moving median) of a plurality of currents and use it as the measured value of the current. According to this, the change in the current value becomes steep microscopically due to fluctuations in the detected value of the current, and it is possible to suppress erroneously detecting the first time point t1 and the second time point t2.

[0097] Also, as described above, when the state where the measured value of the current (e.g., moving average value or moving median value) is greater than or equal to the current threshold Ith1 (Ith2) continues for a predetermined time or more, the control circuit 2 may determine that the measured value of the current has reached the current threshold Ith1 (Ith2). According to this, it is possible to more reliably suppress the misdetection of the first time point t1 and the second time point t2.

[0098] <<Extension of the Embodiment>> Although the present invention has been specifically described above based on embodiments, it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from its essence.

[0099] For example, in the above embodiment, the case in which the abnormal condition detected by the motor drive control device 1 is an abnormal condition caused by deterioration of the motor bearings was described, but it is not limited to this. That is, other abnormal conditions in which the motor current gradually increases due to factors other than deterioration of the motor bearings may also be the target of detection.

[0100] Furthermore, although the above embodiment illustrates the case where motor 40 is a three-phase brushless motor, the type and number of phases of motor 40 are not limited thereto. For example, motor 40 may be a single-phase brushless motor.

[0101] Furthermore, the flowchart described above is merely an example illustrating the operation and is not limited to it. In other words, the steps shown in each diagram of the flowchart are specific examples and are not limited to this flow. For example, the order of some processes may be changed, other processes may be inserted between each process, or some processes may be performed in parallel. [Explanation of Symbols]

[0102] 1...Motor drive control device, 2...Control circuit, 3...Drive circuit, 4...Fan, 5...Position detector, 6...Current detection circuit, 7...Fan unit, 20...Drive control signal generation unit, 21...Target rotation speed setting unit, 22...Signal generation unit, 23...Rotation speed calculation unit, 24...Current measurement unit, 25...Storage unit, 26...Anomaly detection unit, 40...Motor, 41...Impeller, 42...Rotating shaft, 43,44...Bearings, 45...Stator, 46...Magnet, 47...Casing, 48...Circuit board, 49~52...Signal lines, 421...Bearing support unit, Ith1...Current threshold (second current threshold), Ith2...Current threshold (first current threshold), I...Motor current, t1...First time point, t2...Second time point, Tth...Time threshold, Tup...Current rise time.

Claims

1. A control circuit that generates a drive control signal to control the rotation of the motor, The system includes a drive circuit that drives the motor based on the drive control signal, The aforementioned control circuit is A drive control signal generation unit generates a drive control signal so that the motor rotates at a target rotational speed which is a target value for the rotational speed of the motor, A current measuring unit for measuring the current of the motor, A storage unit that stores threshold values ​​for current associated with each of the aforementioned target rotational speeds, The motor has an abnormality determination unit that determines whether or not the motor is abnormal based on the result of comparing the measured value of the current with a threshold value for the current corresponding to the target rotational speed. Motor drive control device.

2. In the motor drive control device according to claim 1, The threshold value for the current includes a first current threshold value. The memory unit stores a time threshold related to time, The abnormality determination unit measures the current rise time from a first time point in time when it detects that the measured current has started to rise, to a second time point in time when the measured current reaches the first current threshold, and determines that the motor is in a predetermined abnormal state if the current rise time is equal to or greater than the time threshold. Motor drive control device.

3. In the motor drive control device according to claim 2, The abnormality determination unit determines that the measured current has reached the first current threshold if the state in which the measured current is equal to or greater than the first current threshold continues for a predetermined period of time or longer. Motor drive control device.

4. In the motor drive control device according to claim 2, The threshold for the current includes a second current threshold that is smaller than the first current threshold. The abnormality determination unit defines the timing at which the measured value of the current reaches the second current threshold as the first time point. Motor drive control device.

5. In the motor drive control device according to claim 4, The abnormality determination unit determines that the measured current has reached the second current threshold if the state in which the measured current is equal to or greater than the second current threshold continues for a predetermined period of time or longer. Motor drive control device.

6. In the motor drive control device according to claim 2, The abnormality determination unit sets the timing at which it detects an increase in the rate of change of the measured value of the current with respect to time as the first time point. Motor drive control device.

7. In the motor drive control device according to claim 2, The abnormality determination unit determines that the motor is in an abnormal state different from the predetermined abnormal state if the current rise time is less than the time threshold. Motor drive control device.

8. In the motor drive control device according to claim 2, The current measuring unit calculates the average or median value of multiple detected currents and outputs it as the measured value of the current. Motor drive control device.

9. The motor and, An impeller connected to the output shaft of the motor, A motor drive control device according to any one of claims 1 to 8, comprising Fan unit.

10. A motor drive control method for controlling the rotation of a motor using a motor drive control device, The first step is to generate a drive control signal for controlling the rotation of the motor so that the motor rotates at a target rotational speed which is a target value of the motor's rotational speed, The second step is to measure the current of the motor, The third step includes determining whether the motor is abnormal based on the result of comparing the measured current with a threshold value for the current corresponding to the target rotational speed. Motor drive control method.

11. In the motor drive control method according to claim 10, The threshold value for the current includes a first current threshold value. The third step is to measure the current rise time from a first point in time when the measured current starts to rise to a second point in time when the measured current reaches the first current threshold, The step includes determining that the motor is in a predetermined abnormal state if the current rise time is greater than or equal to a time threshold, which is a time-related threshold. Motor drive control method.

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