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

Abstract

The purpose of the present invention is to notify the rotation direction of a motor to the outside.　In a motor drive control device (1), a control circuit (2) comprises: a drive control signal generation unit (20) that generates a drive control signal (Sd) such that a motor (40) rotates in a first direction or a second direction opposite to the first direction; a rotation direction determination unit (24) that determines the rotation direction of the motor (40); and a rotation state signal generation unit (25) that generates a rotation state signal (So) indicating the rotation state of the motor (40) on the basis of the determination result from the rotation direction determination unit (24), and outputs the rotation state signal (So) from a signal output terminal (P4). When the motor (40) is rotating in the first direction, the rotation state signal generation unit (25) generates a first signal (Ss) having a frequency based on the rotation speed of the motor (40) and a predetermined duty ratio and outputs the first signal as the rotation state signal (So). When the motor (40) is rotating in the second direction, the rotation state signal generation unit (25) generates a second signal (Sa) in which at least one of the duty ratio and the frequency is different from the first signal (Ss), and outputs the second signal as the rotation state signal (So).

Description

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

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

[0002] Fans (fan motors) have been widely known as cooling devices for dissipating heat generated inside electrical equipment and the like to the outside and cooling the inside of the equipment. The fan has a motor and an impeller connected to the motor's output shaft, and generates airflow (wind) by rotating the impeller in response to rotation of the motor's output shaft. The fan, for example, constitutes a single fan unit together with a motor drive control device for controlling the drive of the fan motor.

[0003] Generally, in a fan unit, a motor drive control device drives a motor in response to instructions from a host device, causing the fan (motor) to rotate in one direction at a constant rotation speed (see Patent Document 1).

[0004] Japanese Unexamined Patent Publication No. 167389 / 1989

[0005] Prior to filing this application, the inventors of the present application considered developing a fan unit capable of switching the rotation direction of the fan. Through this consideration, it became clear that there were the following problems.

[0006] Generally, most motor drive control devices rotate a motor in one direction and generate a frequency generator (FG) signal, which is a periodic signal having a frequency corresponding to the rotation speed of the motor, in response to the rotation of the motor, and output the signal from a single external terminal. By referencing the FG signal output from the external terminal of the motor drive control device, a higher-level device can determine whether the motor is rotating and the rotation speed of the motor.

[0007] In the case of the fan unit described above, which can switch the rotation direction of the fan, the host device specifies the rotation direction of the motor to the motor drive control device, and the host device must determine whether the motor is actually rotating in the specified direction based on a signal from the motor drive control device.

[0008] However, since the FG signal output from a conventional motor drive control device is the same when the motor is rotating in the forward direction as when the motor is rotating in the reverse direction, the host device cannot determine the rotation direction of the motor by simply referring to the FG signal.

[0009] On the other hand, the above-mentioned Patent Document 1 discloses a technology for outputting an alarm indicating that a motor is rotating in the reverse direction, but does not disclose a specific method for outputting an alarm indicating that a motor is rotating in the reverse direction.

[0010] The present invention has been made in view of the above-mentioned problems, and has an object to make it possible to notify the rotation direction of a motor to an external device.

[0011] A motor drive control device according to a representative embodiment of the present invention comprises a control circuit that generates a drive control signal for controlling the rotation of a motor, a drive circuit that drives the motor based on the drive control signal, and a signal output terminal for outputting a signal. The control circuit has: a drive control signal generation unit that generates the drive control signal so that the motor rotates in a first direction or a second direction opposite to the first direction; a rotation direction determination unit that determines the rotation direction of the motor; and a rotation state signal generation unit that generates a rotation state signal indicative of the rotation state of the motor based on the determination result by the rotation direction determination unit and outputs the signal from the signal output terminal. When the motor rotates in the first direction, the rotation state signal generation unit generates a first signal having a frequency based on the rotation speed of the motor and a predetermined duty ratio, and outputs the first signal as the rotation state signal. When the motor rotates in the second direction, the rotation state signal generation unit generates a second signal having at least one of the duty ratio and frequency different from that of the first signal, and outputs the second signal as the rotation state signal.

[0012] The motor drive control device according to the present invention can notify the rotation direction of the motor to the outside.

[0013] FIG. 1 is a block diagram showing the configuration of a fan unit according to embodiment 1. FIG. 2 is a perspective view showing typically the appearance of the fan unit according to embodiment 1. FIG. 3 is a diagram showing typically the cross section of the fan unit shown in FIG. 2. FIG. 4 is a diagram showing an example of an output waveform of a rotation state signal So according to embodiment 1. FIG. 5 is a diagram showing an example of an output waveform of a rotation state signal So according to embodiment 1. FIG. 6 is a flowchart showing the flow of control processing by a control circuit in the motor drive control device according to embodiment 1. FIG. 7 is a block diagram showing the configuration of a fan unit according to embodiment 2. FIG. 8 is a diagram showing an example of an output waveform of a rotation state signal So according to embodiment 2.

[0014] 1. Overview of the Embodiments First, an overview of representative embodiments of the invention disclosed in this application will be described. Note that in the following description, as an example, reference numerals in the drawings corresponding to components of the invention are written in parentheses.

[0015] [1] A motor drive control device (1, 1A) according to a representative embodiment of the present invention includes a control circuit (2, 2A) that generates a drive control signal (Sd) for controlling the rotation of a motor (40), a drive circuit (3) that drives the motor based on the drive control signal, and a signal output terminal (P4) for outputting a signal, and the control circuit includes a drive control signal generation unit (20) that generates the drive control signal so that the motor rotates in a first direction or a second direction opposite to the first direction, a rotation direction determination unit (24) that determines the rotation direction of the motor, and a signal output terminal (P4) that outputs a signal based on the determination result by the rotation direction determination unit. and a rotational state signal generating unit (25, 25A) that generates a rotational state signal (So) indicating the rotational state of the motor based on the rotational speed of the motor and outputs the signal from the signal output terminal, wherein when the motor is rotating in the first direction, the rotational state signal generating unit generates a first signal (Ss) having a frequency based on the rotational speed of the motor and a predetermined duty ratio, and outputs the first signal as the rotational state signal, and when the motor is rotating in the second direction, it generates a second signal (Sa) having at least one of the duty ratio and the frequency different from those of the first signal, and outputs the second signal as the rotational state signal.

[0016] [2] In the motor drive control device (1) described in [1] above, the difference between the duty ratio of the second signal and the predetermined duty ratio may be 10% or more.

[0017] [3] In the motor drive control device described in [1] or [2] above, the duty ratio of the second signal may be different from the duty ratio of the second signal in the immediately preceding cycle.

[0018] [4] In the motor drive control device described in any one of [1] to [3] above, the control circuit may have a first memory unit (26), and the rotation state signal generation unit may determine the duty ratio of the second signal based on a value set in the first memory unit.

[0019] [5] In the motor drive control device (1A) described in any one of [1] to [4] above, the frequency of the second signal may be higher than the maximum frequency that the first signal can have.

[0020] [6] In the motor drive control device described above in [5], the frequency of the second signal may be at least 1000 Hz or more higher than the frequency corresponding to the rotational speed of the motor.

[0021] [7] In the motor drive control device (1A) described in any one of [1] to [6] above, the control circuit may have a second memory unit (26A), and the rotational state signal generating unit may generate the second signal having a frequency obtained by adding a frequency based on a value set in the second memory unit to a frequency corresponding to the rotational speed of the motor rotating in the second direction.

[0022] [8] A fan unit (6, 6A) according to a representative embodiment of the present invention is characterized by comprising the motor (40), an impeller (41) connected to the output shaft of the motor, and a motor drive control device (1, 1A) described in any one of [1] to [7] above.

[0023] [9] A method according to a representative embodiment of the present invention is a motor drive control method for controlling the rotation of a motor (40) by a motor drive control device (1, 1A). This method includes a first step (S1, S2) of generating a drive control signal for controlling the rotation of the motor so that the motor rotates in a first direction or a second direction opposite to the first direction; a second step (S2) of driving the motor based on the drive control signal; a third step (S3) of determining the rotation direction of the motor; and a fourth step (S4, S5) of generating a rotation state signal (So) indicating the rotation state of the motor based on the determination result in the third step, wherein the fourth step includes a fifth step (S4) of generating a first signal (Ss) having a frequency based on the rotation speed of the motor and a predetermined duty ratio when the motor is rotating in the first direction, and outputting the first signal from a signal output terminal (P4) of the motor drive control device as the rotation state signal; and a sixth step (S5) of generating a second signal (Sa) having at least one of a duty ratio and a frequency different from that of the first signal when the motor is rotating in the second direction, and outputting the second signal from the motor drive control device.

[0024] 2. Specific Examples of Embodiments Specific examples of embodiments of the present invention will be described below with reference to the drawings. In the following description, components common to the embodiments will be designated by the same reference numerals, and repeated description will be omitted.

[0025] First Embodiment Fig. 1 is a block diagram showing the configuration of a fan unit 6 according to the first embodiment. Fig. 2 is a perspective view schematically showing the appearance of the fan unit 6 according to the first embodiment. Fig. 3 is a view schematically showing a cross section of the fan unit 6 shown in Fig. 2.

[0026] The fan unit 6 according to the first embodiment is a device that generates wind by rotating an impeller. The fan unit 6 can be used as one of cooling devices that exhausts heat generated inside a device to the outside and cools the inside of the device.

[0027] As shown in Fig. 1, the fan unit 6 includes a fan 4 and a motor drive control device 1. The fan 4 includes a motor 40 and an impeller 41 attached to a rotary shaft 42 of the motor 40. The fan 4 is, for example, an axial flow fan. As shown in Fig. 3, in the fan 4, the motor 40 is disposed inside the hub of the impeller 41.

[0028] 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 coupled, and a rotor connected to the rotating shaft 42 and rotated by the torque of the motor 40. In addition to the rotating shaft 42 described above, the motor 40 also includes bearings 43 and 44, a stator 45, a magnet 46, a casing 47, a circuit board 48, and the like.

[0029] 3, the rotating shaft 42 is a rod-shaped member arranged with its longitudinal direction aligned with the axis X. 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. Each of the bearings 43 and 44 has an inner ring, an outer ring, and rolling elements.

[0030] 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 stacking multiple electromagnetic steel plates and a coil wound around 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 with conductor wiring, and electronic components that constitute the motor drive control device 1 (control circuit 2 and drive circuit 3) are mounted on the board.

[0031] The motor drive control device 1 is a device for controlling the drive of a motor 40. As shown in Fig. 1, the motor drive control device 1 includes a plurality of external terminals, a control circuit 2, a drive circuit 3, and a position detector 5. Note that the components of the motor drive control device 1 shown in Fig. 1 are only a part of the whole, and the motor drive control device 1 may include other components in addition to those shown in Fig. 1.

[0032] As shown in FIG. 1, the motor drive control device 1 has a plurality of external terminals, including a power supply terminal P1, a ground terminal P2, a signal input terminal P3 for inputting a signal, and a signal output terminal P4 for outputting a signal.

[0033] 2, a signal line 49 is connected to the power supply 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 Fig. 2, each of the signal lines 49 to 51 is drawn out to the outside of the casing 47 of the fan unit 6 and connected to a host device (not shown) and a power supply device (not shown) provided outside the fan unit 6, thereby electrically connecting the motor drive control device 1 to the power supply device and the host device.

[0034] A DC voltage Vdc is supplied to the power supply terminal P1 from the power supply device via a signal line 49. This supplies the power supply voltage to the control circuit 2 and the drive circuit 3. Note that a regulator may be provided in the motor drive control device 1, and the regulator may generate a new DC voltage from the DC voltage Vdc and supply it as the power supply voltage to the control circuit 2. The ground terminal P2 is connected to the ground potential GND via a signal line 50.

[0035] The signal input terminal P3 is connected to a host device, and receives a drive command signal Sc from the host device as described below. The signal output terminal P4 is connected to a host device, and outputs a rotation state signal So to the host device as described below.

[0036] When the fan unit 6 receives power from a host device, the power supply terminal P1 and the ground terminal P2 may be connected to a power line and a ground line, respectively, within the host device.

[0037] The position detector 5 is a device for detecting the rotational position of the rotating shaft 42 (rotor) of the motor 40. The position detector 5 is, for example, a Hall element. For example, three Hall elements corresponding to the respective phases (U phase, V phase, W phase) of the motor 40 are arranged at approximately equal intervals around the rotor (magnet 46) of the motor 40. For example, the Hall elements are mounted on a circuit board 48. There is no particular limitation on the number of Hall elements.

[0038] 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 that indicates the rotational position of the motor 40, i.e., a signal that corresponds to the rotational position of the rotor (magnet 46) of the motor 40.

[0039] The position detector 5 may be any device that has the function of detecting the position information of the rotating shaft 42 and outputting it as an electrical signal, and may be, for example, a rotary encoder. Alternatively, without providing the position detector 5, the rotational position of the motor 40 may be detected by a so-called sensorless method in which the control circuit 2 detects the back electromotive voltage induced in each phase (U phase, V phase, W phase) of the motor 40 and detects the rotational position of the motor 40 based on the back electromotive voltage.

[0040] The control circuit 2 is a circuit that performs overall control of the motor drive control device 1. As will be described in detail below, the control circuit 2 generates a drive control signal Sd for controlling the rotation of the motor 40. The control circuit 2 is, for example, a program processing device (for example, a computer such as a microcontroller) that has a configuration in which a processor such as a CPU, various storage devices such as RAM and ROM, and peripheral circuits such as a counter (timer), an A / D conversion circuit, a D / A conversion circuit, a clock generation circuit, and an input / output I / F circuit are connected to each other via a bus or dedicated lines.

[0041] 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 from the pre-drive circuit, and energizes the three-phase coils of the motor 40. The rotation direction of the motor 40 can be changed by switching the order in which the three-phase coils are energized. For example, the inverter circuit is configured by a pair of series circuits of two switch elements connected in series between a DC voltage Vdc and a ground potential GND, each pair being arranged for one phase of the coil. In each pair of two switch elements, a terminal of each phase of the motor 40 is connected to the connection point between the switch elements.

[0042] The pre-drive circuit generates an output signal for driving the inverter circuit based on the drive control signal Sd and outputs it to the inverter circuit. The pre-drive circuit generates and outputs drive signals for driving each switch element of the inverter circuit based on the drive control signal Sd, for example.

[0043] The drive signal output from the pre-drive circuit turns on / off each switch element constituting the inverter circuit, thereby supplying power to each phase of the motor 40 and causing the rotor of the motor 40 to rotate.

[0044] In the motor drive control device 1, at least some of the functional parts of the control circuit 2 and the drive circuit 3 may be packaged as a single semiconductor integrated circuit device (IC: Integrated Circuit), or the drive circuit 3 and the control circuit 2 may each be packaged as individual semiconductor integrated circuit devices.

[0045] Next, the control circuit 2 will be described in detail.

[0046] The control circuit 2 has a function of generating a drive control signal Sd so that the motor 40 is in a rotation state specified by the drive command signal Sc. The control circuit 2 also has a function of switching the rotation direction of the motor 40. That is, the control circuit 2 can rotate the motor 40 in a first direction or a second direction opposite to the first direction in response to the drive command signal Sc. The control circuit 2 also has a function of outputting a signal indicating the rotation direction of the motor 40 to the outside.

[0047] 1, the control circuit 2 has functional blocks for realizing the above-mentioned functions, including a drive control signal generation unit 20, a rotation direction determination unit 24, and a rotation state signal generation unit 25. These functional blocks are realized, for example, by a CPU in the control circuit 2 executing various arithmetic processing according to programs stored in memory and controlling peripheral circuits such as an A / D conversion circuit and an input / output interface circuit based on the processing results. Note that some or all of the drive control signal generation unit 20, the rotation direction determination unit 24, and the rotation state signal generation unit 25 may be realized by dedicated circuits (such as dedicated hardware logic circuits).

[0048] The drive control signal generator 20 is a functional block that generates a drive control signal Sd so that the motor 40 rotates in a first direction or a second direction. In the following description, the first direction may be referred to as the "forward direction" and the second direction may be referred to as the "reverse direction."

[0049] The drive control signal generating unit 20 includes, for example, a drive command signal analyzing unit 21 , a signal generating unit 22 , and a rotation speed calculating unit 23 .

[0050] The drive command signal analysis unit 21 analyzes the drive command signal Sc input to the signal input terminal P3 from an external device (host device).

[0051] The drive command signal Sc is a signal that indicates a target drive state of the motor 40. The drive command signal Sc includes, for example, information on a target rotation speed Stv that is a target value for the rotation speed of the motor 40, and information on a designated rotation direction Str that indicates the rotation direction of the motor.

[0052] The drive command signal analysis unit 21 analyzes the drive command signal Sc to obtain information on the target rotation speed Stv and provide it to the signal generation unit 22, and also obtains information on the specified rotation direction Str and provide it to the signal generation unit 22 and the rotation direction determination unit 24 described later.

[0053] The rotation speed calculation unit 23 is a functional unit that calculates the actual rotation speed of the motor 40. The rotation speed calculation unit 23 calculates the rotation speed Sv of the motor 40 based on the rotation position detection signal Sh and provides it to the signal generation unit 22. In the case of the sensorless system described above, for example, the rotation speed calculation unit 23 detects a back electromotive force induced in each phase (U phase, V phase, W phase) of the motor 40 and calculates the rotation speed of the motor 40 based on the back electromotive force.

[0054] The signal generating unit 22 generates a drive control signal Sd for the motor 40 based on the designated rotation direction Str of the motor 40, the target rotation speed Stv of the motor 40, and the rotation speed Sv of the motor 40. Specifically, the signal generating unit 22 calculates the error between the target rotation speed Stv and the rotation speed Sv of the motor, calculates the manipulated variable of the motor 40 so that the error becomes zero, for example, by PID (Proportional Integral Differential) control calculation, and generates a PWM signal having a duty ratio according to the manipulated variable so that the motor 40 rotates in the designated rotation direction Str, and outputs the PWM signal as the drive control signal Sd.

[0055] In the case of open-loop control, which does not attempt to maintain the rotational speed of the motor 40 but instead attempts to rotate it with a constant force, the signal generating unit 22 generates a PWM signal having a duty ratio according to the amount of operation for maintaining the predetermined rotational speed, and outputs it as the drive control signal Sd.

[0056] The rotation direction determination unit 24 determines the rotation direction of the motor 40. Specifically, the rotation direction determination unit 24 determines the rotation direction of the motor 40 based on the information of the specified rotation direction Str, and provides the determination result indicating the rotation direction (forward or reverse) of the motor 40 to the rotation state signal generation unit 25.

[0057] The method by which the rotation direction determination unit 24 determines the rotation direction of the motor 40 is not limited to the method based on the information of the specified rotation direction Str described above, and various known techniques for detecting the rotation direction of a motor may be adopted.

[0058] The rotation state signal generator 25 generates a rotation state signal So indicating the rotation state of the motor based on the determination result by the rotation direction determiner 24, and outputs it from a signal output terminal P4.

[0059] Specifically, when the motor 40 is rotating in the forward direction (first direction), the rotational state signal generating unit 25 generates a first signal Ss having a frequency based on the rotational speed of the motor 40 and a predetermined duty ratio, and outputs it as a rotational state signal So from the signal output terminal P4.

[0060] Here, the first signal Ss is, for example, a pulse signal (FG signal) having a frequency corresponding to the rotation speed of the motor 40 and a duty ratio of 50%. The rotation state signal generator 25 generates the FG signal by a known method, for example, based on a Hall signal serving as the rotation position detection signal Sh. In the following description, the first signal Ss may be referred to as the "FG signal Ss."

[0061] For example, when the determination result by the rotation direction determination unit 24 indicates the "forward direction," the rotation state signal generation unit 25 generates an FG signal having a frequency corresponding to the period of the rotation position detection signal Sh and a duty ratio of 50%, and outputs it from the signal output terminal P4 as the rotation state signal So.

[0062] On the other hand, when the motor 40 is rotating in the reverse direction (second direction), the rotation state signal generator 25 generates a second signal Sa having a duty ratio different from that of the above-mentioned FG signal (first signal) and outputs it as the rotation state signal So. For example, the second signal Sa is a pulse-like signal having a duty ratio different from that of the FG signal (first signal) Ss. In the following description, the second signal Sa may be referred to as the "reverse rotation detection signal Sa."

[0063] For example, as shown in FIG. 1 , the rotation state signal generator 25 has a storage unit 26. The storage unit 26 has a value Vdty that specifies the duty ratio of the reverse rotation detection signal (second signal) Sa. The storage unit 26 has, for example, a rewritable storage area. For example, the value Vdty that specifies the duty ratio of the second signal Sa can be written in advance to the storage area of ​​the storage unit 26 of the microcontroller serving as the control circuit 2.

[0064] More specifically, when the determination result by the rotation direction determination unit 24 indicates the "reverse direction," the rotation state signal generation unit 25 generates a reverse rotation detection signal Sa having a frequency corresponding to the period of the rotation position detection signal Sh and a duty ratio based on the value Vdty set in the memory unit 26, and outputs it from the signal output terminal P4 as the rotation state signal So.

[0065] 4A, 4B, and 4C show examples of output waveforms of the rotation state signal So according to the first embodiment.

[0066] 4A, 4B, and 4C show timing charts illustrating the temporal changes in the rotation state signal So when the motor 40 switches from a state in which it is rotating in the forward direction to a state in which it is rotating in the reverse direction.

[0067] It is preferable that the difference between the duty ratio (Z%) of the reverse rotation detection signal Sa as the second signal and the duty ratio (Y%) of the FG signal Ss as the first signal is large. For example, the difference between the duty ratio (Z%) of the reverse rotation detection signal Sa and the duty ratio (Y%) of the FG signal Ss is 10% or more (Z≧(Y+10)% or Z≦(Y−10)%). Preferably, the difference between the duty ratio of the reverse rotation detection signal Sa and the duty ratio of the FG signal Ss is 20% or more (Z≧(Y+20)% or Z≦(Y−20)%). More preferably, the difference between the duty ratio of the reverse rotation detection signal Sa and the duty ratio of the FG signal Ss is 40% or more (Z≧(Y+40)% or Z≦(Y−40)%).

[0068] 4A, when the duty ratio of the FG signal Ss is 50%, the reverse rotation detection signal Sa may be a pulse signal having a frequency corresponding to the rotation speed of the motor 40 rotating in the reverse direction and a duty ratio of 25%. In this case, the memory unit 26 is set with a value Vdty that specifies "25%" as the duty ratio of the reverse rotation detection signal (second signal) Sa.

[0069] 4B , when the duty ratio of the FG signal Ss is 50%, the reverse rotation detection signal Sa may be a pulse signal having a frequency corresponding to the rotation speed of the motor 40 rotating in the reverse direction and a duty ratio of 75%. In this case, the memory unit 26 is set with a value Vdty that specifies "75%" as the duty ratio of the reverse rotation detection signal (second signal) Sa.

[0070] Furthermore, the duty ratio of the reverse rotation detection signal Sa as the second signal may be different from the duty ratio of the reverse rotation detection signal Sa output immediately before. That is, the duty ratio of the reverse rotation detection signal Sa may be different from the duty ratio of the reverse rotation detection signal Sa in the immediately preceding cycle. For example, as shown in FIG. 4C , the duty ratio of the reverse rotation detection signal Sa output in the first cycle Ta1 after the motor 40 starts rotating in the reverse direction is 75%, and the duty ratio of the reverse rotation detection signal Sa output in the cycle Ta2 following cycle Ta1 is 10%. The duty ratio of the reverse rotation detection signal Sa output in the cycle Ta3 following cycle Ta2 is 70%, and the duty ratio of the reverse rotation detection signal Sa output in the cycle Ta4 following cycle Ta3 is 25%. In this way, the rotation state signal generator 25 may generate the reverse rotation detection signal Sa so that the duty ratio changes randomly for each cycle of the reverse rotation detection signal Sa.

[0071] Alternatively, the rotation state signal generator 25 may periodically change the duty ratio of the reverse rotation detection signal Sa. For example, when the motor 40 is rotating in the reverse direction, the rotation state signal generator 25 may alternately switch the duty ratio of the reverse rotation detection signal Sa between 25% and 75%.

[0072] Next, the flow of control processing by the control circuit 2 will be described.

[0073] FIG. 5 is a flowchart showing the flow of control processing by the control circuit 2 in the motor drive control device 1 according to the first embodiment.

[0074] 5, first, the control circuit 2 analyzes the drive command signal Sc input from the outside (host device) (step S1). Specifically, as described above, the drive command signal analyzer 21 acquires information on the target rotation speed Stv and the designated rotation direction Str included in the drive command signal Sc.

[0075] Next, the control circuit 2 generates a drive control signal Sd so that the motor 40 is in the rotation state specified by the drive command signal Sc (step S2). Specifically, as described above, the signal generator 22 generates the drive control signal Sd so that the motor 40 rotates in the specified rotation direction Str at the target rotation speed Stv. This causes the motor 40 to rotate.

[0076] The control circuit 2 also determines whether the rotation direction of the motor 40 is the forward direction (step S3). If the designated rotation direction Str is the "forward direction" (step S3: YES), the rotation direction determination unit 24 determines that the motor 40 is rotating in the forward direction, and the rotation state signal generation unit 25 generates an FG signal Ss having a frequency corresponding to the rotation speed of the motor 40 and a duty ratio of 50% based on the rotation position detection signal Sh using the method described above, and outputs the FG signal Ss as the rotation state signal So from the signal output terminal P4 (step S4).

[0077] On the other hand, if the specified rotation direction Str is the "reverse direction" (step S3: NO), the rotation direction determination unit 24 determines that the motor 40 is rotating in the reverse direction, and the rotation status signal generation unit 25 generates a reverse rotation detection signal Sa based on the rotation position detection signal Sh using the method described above, which has a frequency corresponding to the rotation speed of the motor 40 and a duty ratio different from that of the FG signal Ss, and outputs it as the rotation status signal So from the signal output terminal P4 (step S5).

[0078] As described above, according to the motor drive control device 1 in the fan unit 6 of embodiment 1, when the motor 40 is rotating in the forward direction (first direction), the control circuit 2 generates an FG signal (first signal) Ss having a frequency based on the rotational speed of the motor 40 and a predetermined duty ratio (e.g., 50%) and outputs it from the signal output terminal P4 as a rotation status signal So, and when the motor 40 is rotating in the reverse direction (second direction), the control circuit 2 generates a reverse rotation detection signal (second signal) Sa having a duty ratio different from that of the FG signal Ss and outputs it as the rotation status signal So.

[0079] As a result, the duty ratio of the rotation state signal So when the motor 40 is rotating in the forward direction differs from the duty ratio of the rotation state signal So when the motor 40 is rotating in the reverse direction, and therefore an external device (host device) of the fan unit 6 can determine the rotation direction of the motor 40 by analyzing the duty ratio of the rotation state signal So. In this way, the motor drive control device 1 according to the first embodiment can notify the outside of the rotation direction of the motor 40.

[0080] Furthermore, because the FG signal Ss and the reverse rotation detection signal Sa are output as the rotation status signal So from a single external terminal (signal output terminal P4), there is no need to provide a new external terminal in the motor drive control device 1 to notify the outside that the motor 40 is rotating in the reverse direction. This makes it easy to replace a conventional fan unit that rotates only in one direction with the fan unit 6 that can rotate in the reverse direction.

[0081] Furthermore, as described above, in the motor drive control device 1, it is preferable that the difference between the duty ratio of the reverse rotation detection signal Sa and the duty ratio of the FG signal Ss be 20% or more (see FIGS. 4A and 4B), which allows the host device to accurately distinguish between the FG signal Ss and the reverse rotation detection signal Sa.

[0082] Furthermore, the duty ratio of the reverse rotation detection signal Sa may be set to a value that is 40% or more greater than the duty ratio of the FG signal Ss, thereby enabling the host device to more accurately distinguish between the FG signal Ss and the reverse rotation detection signal Sa.

[0083] Furthermore, as described above, in the motor drive control device 1, the duty ratio of the reverse rotation detection signal Sa may be different from the duty ratio of the reverse rotation detection signal Sa that was output immediately before (see FIG. 4C ). In this way, while the duty ratio of the rotation status signal So (FG signal Ss) is fixed when the motor 40 is rotating in the forward direction, the duty ratio of the rotation status signal So (reverse rotation detection signal Sa) changes when the motor 40 is rotating in the reverse direction, so that the higher-level device can accurately distinguish between the FG signal Ss and the reverse rotation detection signal Sa.

[0084] Furthermore, in the motor drive control device 1, as described above, the control circuit 2 may have the storage unit 26, and the rotation state signal generator 25 may determine the duty ratio of the reverse rotation detection signal Sa based on a value set in the storage unit 26. In this way, by changing the value set in the storage unit 26, it is possible to set the duty ratio of the reverse rotation detection signal Sa to any value.

[0085] Second Embodiment FIG. 6 is a block diagram showing the configuration of a fan unit 6A according to a second embodiment.

[0086] The fan unit 6A of embodiment 2 differs from the fan unit 6 of embodiment 1 in that it outputs a reverse rotation detection signal Sa having a different frequency from the FG signal Ss, but is otherwise similar to the fan unit 6 of embodiment 1.

[0087] Specifically, as shown in FIG. 6, in the motor drive control device 1A of the fan unit 6A according to the second embodiment, the control circuit 2A has a rotation state signal generating unit 25A instead of the rotation state signal generating unit 25 according to the first embodiment.

[0088] The rotation state signal generator 25A generates a rotation state signal So indicating the rotation state of the motor based on the determination result (forward or reverse direction) by the rotation direction determiner 24, and outputs the generated signal from the signal output terminal P4. Specifically, when the motor 40 is rotating in the forward direction (first direction), the rotation state signal generator 25A, like the rotation state signal generator 25 according to the first embodiment, generates an FG signal (first signal) Ss having a frequency based on the rotation speed of the motor 40 and a predetermined duty ratio (for example, 50%), and outputs the generated signal from the signal output terminal P4 as the rotation state signal So.

[0089] On the other hand, when the motor 40 is rotating in the reverse direction (second direction), the rotation state signal generator 25A generates a reverse rotation detection signal (second signal) Sa having a frequency different from that of the above-mentioned FG signal (first signal) Ss and outputs the reverse rotation detection signal (second signal) Sa from the signal output terminal P4 as the rotation state signal So. Specifically, the rotation state signal generator 25A generates the reverse rotation detection signal (second signal) Sa having a frequency higher than that of the FG signal (first signal) Ss.

[0090] FIG. 7 shows an example of the output waveform of the rotation state signal So according to the second embodiment.

[0091] FIG. 7 is a timing chart showing the temporal change in the rotation state signal So when the motor 40 switches from a state in which it is rotating in the forward direction to a state in which it is rotating in the reverse direction.

[0092] Specifically, the frequency of the reverse rotation detection signal Sa as the second signal is higher than the maximum frequency that the FG signal Ss as the first signal can have. In other words, as shown in FIG. 7 , the frequency of the reverse rotation detection signal Sa is preferably sufficiently higher than the frequency corresponding to the maximum target rotation speed Stv that can be set for the motor 40. For example, the frequency of the reverse rotation detection signal Sa is preferably at least 200 Hz higher than the frequency corresponding to the rotation speed of the motor 40. More preferably, the frequency of the reverse rotation detection signal Sa is at least 500 Hz higher than the frequency corresponding to the rotation speed of the motor 40. Even more preferably, the frequency of the reverse rotation detection signal Sa is at least 1000 Hz higher than the frequency corresponding to the rotation speed of the motor 40.

[0093] Here, the duty ratio of the reverse rotation detection signal (second signal) Sa may be the same as that of the FG signal Ss (50%), or may be a value different from that of the FG signal Ss.

[0094] As shown in FIG. 6 , the rotation state signal generator 25A includes a storage unit 26A. A value Vfrq that specifies the frequency of the reverse rotation detection signal (second signal) Sa is set in the storage unit 26A. The storage unit 26A has, for example, a rewritable storage area. For example, the value Vfrq that specifies the frequency of the second signal Sa can be written in advance to the storage area of ​​the storage unit 26A of a microcontroller serving as the control circuit 2A.

[0095] When the determination result by the rotation direction determination unit 24 indicates the "reverse direction," the rotation state signal generation unit 25A generates a reverse rotation detection signal Sa having a frequency obtained by adding a frequency corresponding to the rotation speed of the motor 40 rotating in the reverse direction (a frequency corresponding to the period of the rotation position detection signal Sh) to a frequency fx based on the value Vfrq set in the memory unit 26A, and outputs the generated signal from the signal output terminal P4 as the rotation state signal So.

[0096] For example, as shown in FIG. 7, if the frequency corresponding to the rotational speed of the motor 40 rotating in the reverse direction is "f0" and the value Vfrq specifying the frequency of the reverse rotation detection signal (second signal) Sa is "1000 Hz", the rotation state signal generating unit 25 generates a pulse signal of (f0 + 1000) Hz as the reverse rotation detection signal Sa.

[0097] As described above, according to the motor drive control device 1A in the fan unit 6A of embodiment 2, when the motor 40 is rotating in the forward direction (first direction), the control circuit 2A generates an FG signal (first signal) Ss having a frequency based on the rotational speed of the motor 40 and a predetermined duty ratio (e.g., 50%) and outputs it from the signal output terminal P4 as a rotation status signal So, and when the motor 40 is rotating in the reverse direction (second direction), the control circuit 2A generates a reverse rotation detection signal (second signal) Sa having a frequency greater than that of the FG signal Ss and outputs it as the rotation status signal So.

[0098] As a result, the frequency of the rotation state signal So when the motor 40 is rotating in the forward direction is different from the frequency of the rotation state signal So when the motor 40 is rotating in the reverse direction, so that an external device (host device) of the fan unit 6 can determine the rotation direction of the motor 40 by analyzing the duty ratio of the rotation state signal So.

[0099] Furthermore, in the motor drive control device 1A, as described above, it is preferable that the frequency of the reverse rotation detection signal Sa is at least 1000 Hz higher than the frequency corresponding to the rotation speed of the motor 40 (see FIG. 7 ). This allows the higher-level device to more accurately distinguish between the FG signal Ss and the reverse rotation detection signal Sa.

[0100] Furthermore, in the motor drive control device 1A, as described above, the control circuit 2A has a memory unit 26A, and the rotation state signal generation unit 25A may generate a reverse rotation detection signal Sa having a frequency (f0+fx) obtained by adding a frequency f0 corresponding to the rotation speed of the motor 40 rotating in the reverse direction to a frequency fx based on the value Vfrq set in the memory unit 26A, and output this signal from the signal output terminal P4 as the rotation state signal So.

[0101] This makes it possible to set the frequency of the reverse rotation detection signal Sa to any value by changing the value Vfrq set in the storage unit 26. Furthermore, the higher-level device can easily estimate the rotation speed of the motor 40 rotating in the reverse direction by subtracting the value of the frequency fx based on the value Vfrq set in the storage unit 26A from the frequency of the reverse rotation detection signal Sa.

[0102] <<Extending the Embodiments>> The invention made by the present inventor has been specifically described above based on the embodiments, but it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0103] For example, in the above embodiment, the reverse rotation detection signal Sa as the second signal is described as having at least one of a duty ratio and a frequency different from that of the FG signal Ss as the first signal, but the reverse rotation detection signal Sa may be different from that of the FG signal Ss in both a duty ratio and a frequency. In this case, the rotation state signal generator 25 (25A) has a memory unit 26 and a memory unit 26A, and determines the duty ratio and the frequency of the reverse rotation detection signal Sa based on the values ​​Vdty and Vfrq set in the memory unit 26 and the memory unit 26A, respectively, using the method described above.

[0104] Furthermore, in the above embodiment, the case has been described in which the control circuits 2, 2A have the function of switching the rotation direction of the motor 40. However, even if the control circuits 2, 2A do not have the function of switching the rotation direction of the motor 40 and only control the motor 40 to rotate in one direction, the reverse rotation detection signal Sa can be generated and output as the rotation status signal So. For example, in the control circuits 2, 2A, if the rotation direction determination unit 24 detects that the motor 40 is rotating in the reverse direction using a known method, the rotation status signal generation unit 25, 25A may use the above-mentioned method to generate the reverse rotation detection signal Sa, which has at least one of a duty ratio and a frequency different from that of the FG signal Ss when the motor 40 is rotating in the forward direction, and output the reverse rotation detection signal Sa as the rotation status signal So.

[0105] Furthermore, in the above embodiment, a case has been described in which a drive command signal Sc including a target rotation speed Stv and a designated rotation direction Str is input to the motor drive control device 1, 1A, but this is not limited to this. For example, if the target rotation speed of the motor 40 is preset in the control circuit 2 (e.g., in the case of open-loop control of rotation speed), only the designated rotation direction Str may be specified to the motor drive control device 1, 1A by the drive command signal Sc. Furthermore, if the target rotation speed of the motor 40 is preset in the control circuit 2 and the control circuit 2 is configured to switch the rotation direction of the motor at predetermined timing, the drive command signal Sc does not need to be input to the motor drive control device 1, 1A.

[0106] In addition, in the above embodiment, the motor 40 is a three-phase brushless motor, but the type and number of phases of the motor 40 are not limited to this. For example, the motor 40 may be a single-phase brushless motor.

[0107] Furthermore, the above-described flowcharts are merely examples for explaining the operation, and are not intended to be limiting. That is, the steps shown in each diagram of the flowchart are specific examples, and the present invention is not limited to these flows. For example, the order of some processes may be changed, other processes may be inserted between processes, or some processes may be performed in parallel.

[0108] 1, 1A...motor drive control device, 2, 2A...control circuit, 3...drive circuit, 4...fan, 5...position detector, 6, 6A...fan unit, 20...drive control signal generation unit, 21...drive command signal analysis unit, 22...signal generation unit, 23...rotational speed calculation unit, 24...rotation direction determination unit, 25...rotation state signal generation unit, 26, 26A...memory unit, 40...motor, 41...impeller, 42...rotating shaft, 43, 44...bearing, 45...stator, 46...magnet, 47...casing, 48...circuit board, 49-52...signal line, 421...bearing support unit.

Claims

1. A motor drive control device comprising: a control circuit that generates a drive control signal for controlling the rotation of a motor; a drive circuit that drives the motor based on the drive control signal; and a signal output terminal for outputting a signal, wherein the control circuit has: a drive control signal generation unit that generates the drive control signal so that the motor rotates in a first direction or a second direction opposite to the first direction; a rotation direction determination unit that determines the rotation direction of the motor; and a rotation state signal generation unit that generates a rotation state signal indicative of the rotation state of the motor based on a result of the determination by the rotation direction determination unit and outputs the signal from the signal output terminal, wherein the rotation state signal generation unit generates a first signal having a frequency based on the rotation speed of the motor and a predetermined duty ratio when the motor rotates in the first direction, and outputs the first signal as the rotation state signal, and generates a second signal having at least one of the duty ratio and the frequency different from that of the first signal when the motor rotates in the second direction, and outputs the second signal as the rotation state signal.

2. A motor drive control device according to claim 1, wherein the difference between the duty ratio of the second signal and the predetermined duty ratio is 10% or more.

3. A motor drive control device according to claim 1, wherein the duty ratio of the second signal is different from the duty ratio of the second signal in the immediately previous cycle.

4. A motor drive control device as claimed in claim 2, wherein the control circuit has a first storage section, and the rotation state signal generating section determines the duty ratio of the second signal based on a value set in the first storage section.

5. A motor drive control device according to claim 1, wherein the frequency of the second signal is higher than a maximum frequency that the first signal can have.

6. A motor drive control device according to claim 5, wherein the frequency of the second signal is at least 1000 Hz higher than the frequency corresponding to the rotational speed of the motor.

7. A motor drive control device as claimed in claim 5, wherein the control circuit has a second memory section, and the rotation state signal generating section generates the second signal having a frequency obtained by adding a frequency based on a value set in the second memory section to a frequency corresponding to the rotation speed of the motor rotating in the second direction.

8. A fan unit comprising: the motor; an impeller connected to an output shaft of the motor; and the motor drive control device according to any one of claims 1 to 7.

9. A motor drive control method for controlling the rotation of a motor by a motor drive control device, comprising: a first step of generating a drive control signal for controlling the rotation of the motor so that the motor rotates in a first direction or a second direction opposite to the first direction; a second step of driving the motor based on the drive control signal; a third step of determining the rotation direction of the motor; and a fourth step of generating a rotation state signal indicative of the rotation state of the motor based on the determination result in the third step, wherein the fourth step includes: a fifth step of generating a first signal having a frequency based on the rotation speed of the motor and a predetermined duty ratio, when the motor rotates in the first direction, and outputting the first signal from a signal output terminal of the motor drive control device as the rotation state signal; and a sixth step of generating a second signal having at least one of a duty ratio and a frequency different from that of the first signal, and outputting the second signal from the motor drive control device, when the motor rotates in the second direction.

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