Motor drive device

Abstract

A motor drive device that drives a motor, has: a rotation speed acquisition section that acquires a rotation speed that rotates the motor; a duty ratio setting section that sets a duty ratio of a PWM signal that drives the motor in accordance with the rotation speed acquired by the rotation speed acquisition section; a PWM signal output section that outputs the PWM signal of the duty ratio set by the duty ratio setting section; a driver that drives the motor in accordance with the PWM signal output by the PWM signal output section; and a current detection section that detects a current that flows in the motor, the duty ratio setting section performs: first control that sets the duty ratio to an initial value at the time of starting to drive the motor or a prescribed value that is larger than the initial value when the current detected by the current detection section reaches a first threshold value; and second control that sets the duty ratio to the initial value when the current detected by the current detection section reaches a second threshold value, the duty ratio setting section changes at least one of the first threshold value and the second threshold value in accordance with the rotation speed acquired by the rotation speed acquisition section.

Description

Technical Field

[0001] This invention relates to motor drive devices. Background Technology

[0002] In the past, various drive controls were implemented to make the motor rotate at a desired speed. In motor drive control, it is important to prevent abnormal current from flowing through the motor even under abnormal conditions such as external disturbances, thereby protecting the circuit or motor and ensuring stable drive.

[0003] For example, in the drive control of a vector-based motor, there is a known structure where, upon detecting that the current flowing in the motor exceeds a threshold, the d-axis voltage command value or the q-axis voltage command value is corrected, thereby stabilizing the control. This is disclosed, for example, in Patent Document 1.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6095561 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the past, motors were driven stably by comparing the current flowing in the motor with a threshold. However, if the threshold was not appropriate, the motor could not be driven efficiently, which could lead to inefficient operation.

[0009] The purpose of this invention is to provide a motor drive device that efficiently drives a motor.

[0010] Methods for solving problems

[0011] An exemplary first invention of this application is a motor drive device that drives a motor, wherein the motor drive device comprises: a speed acquisition unit that acquires a speed that rotates the motor; a duty cycle setting unit that sets a duty cycle of a PWM signal driving the motor based on the speed acquired by the speed acquisition unit; a PWM signal output unit that outputs a PWM signal with a duty cycle set by the duty cycle setting unit; a driver that drives the motor based on the PWM signal output by the PWM signal output unit; and a current detection unit that detects the current flowing in the motor. The duty cycle setting unit performs the following control: a first control, in which the duty cycle is set to an initial value or a predetermined value greater than the initial value when the current detected by the current detection unit reaches a first threshold; and a second control, in which the duty cycle is set to the initial value when the current detected by the current detection unit reaches a second threshold. The duty cycle setting unit changes at least one of the first threshold and the second threshold based on the speed acquired by the speed acquisition unit.

[0012] Invention Effects

[0013] According to the exemplary first invention of this application, a motor can be driven efficiently. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view showing the motor driven by the motor drive device of the first embodiment of the present invention, cut by a plane perpendicular to the Y-axis and passing through the central axis J.

[0015] Figure 2 yes Figure 1 A 3D view of motor 10.

[0016] Figure 3 From Figure 2 The motor 10 has its motor housing 23 removed and is viewed from above in a top view.

[0017] Figure 4 This is a block diagram illustrating the structure of a motor drive device according to an embodiment of the present invention.

[0018] Figure 5 This is a flowchart illustrating the motor drive process performed by the motor drive device 100.

[0019] Figure 6 This is a flowchart illustrating the duty cycle setting process performed by the motor drive unit 100.

[0020] Figure 7 It is shown Figure 6 The flowchart for the first control is shown.

[0021] Figure 8It is shown Figure 6 The flowchart for the second control is shown.

[0022] Figure 9 It is shown Figure 6 The flowchart for the third control is shown. Detailed Implementation

[0023] Hereinafter, a motor drive device according to an embodiment of the present invention will be described with reference to the accompanying drawings. Furthermore, in the following drawings, for ease of understanding of each structure, the actual construction may sometimes differ from the scale and quantities shown in each construction.

[0024] Additionally, the XYZ coordinate system is appropriately shown as a three-dimensional orthogonal coordinate system in the accompanying drawings. In the XYZ coordinate system, the Z-axis direction is perpendicular to... Figure 1 The direction shown is parallel to the axial direction of the central axis J. The X-axis direction is radial relative to the central axis J. The Y-axis direction is perpendicular to both the X-axis and Z-axis directions. In any of the X-axis, Y-axis, and Z-axis directions, the side indicated by the arrow in the figure is designated as the "+" side, and the opposite side is designated as the "-" side.

[0025] In the following explanation, the positive side (+Z side) in the Z-axis direction will be referred to as the "front side" or "one side," and the negative side (-Z side) in the Z-axis direction will be referred to as the "rear side" or "the other side." Furthermore, "rear side" (the other side) and "front side" (one side) are merely names used for illustrative purposes and do not limit the actual positional relationship or direction. Unless otherwise specified, the direction parallel to the central axis J (Z-axis direction) will be simply referred to as the "axial direction," the radial direction centered on the central axis J will be simply referred to as the "radial direction," and the circumferential direction centered on the central axis J, i.e., the direction around the central axis J, will be simply referred to as the "circumferential direction." The side radially closer to the central axis J will be called the "radial inner side," and the side farther from the central axis J will be called the "radial outer side."

[0026] In addition, in this specification, the term "extending along the axial direction" includes not only the case of extending strictly along the axial direction (Z-axis direction), but also the case of extending in a direction inclined relative to the axial direction within a range of less than 45°.

[0027] Furthermore, in this specification, the term "extending radially" includes not only the case of extending strictly radially, i.e., in a direction perpendicular to the axial direction (Z-axis direction), but also the case of extending in a direction inclined relative to the radial direction within a range of less than 45°. Similarly, "parallel" includes not only the case of being strictly parallel, but also the case of being inclined within a range of less than 45° between the two directions.

[0028] In addition, in this specification, the term "rotation speed" refers to the rotation speed per unit time. For example, when the rotation speed is 1300, it means that the rotation speed is 1300 revolutions per minute, or 1300 [rpm].

[0029] [First Implementation Method]

[0030] <Motor Structure>

[0031] Figure 1 This is a cross-sectional view showing the motor driven by the motor drive device of the first embodiment of the present invention, cut by a plane perpendicular to the Y-axis and passing through the central axis J.

[0032] Figure 2 yes Figure 1 A 3D view of motor 10.

[0033] In this embodiment, motor 10 is a brushless DC motor. Motor 10 has motor housings 21 and 23 that house a motor section 30 and a circuit board 80. The motor section 30 has a rotor 50 and a stator 40. The circuit board 80 is equipped with a drive circuit 81 and the like for driving the motor section 30. The rotor 50 has a motor shaft 41 arranged along a central axis J extending axially. The stator 40 is radially opposed to the rotor 50 with a gap between them. Motor housings 21 and 23 are arranged from one axial side toward the other axial side, housing the circuit board 80 and the rotor 50 in sequence.

[0034] Motor 10 has a stator 40, and the stator 40 has a stator yoke 42. Motor 10 has a circuit board 80 on one axial side of the stator yoke 42. The circuit board 80 has a through hole 80a extending axially. Motor shaft 41 passes through the through hole 80a. Motor 10 has bearings 55a and 55b. Bearing 55a is disposed on the other axial side of motor housing 23. Bearing 55b is disposed on one axial side of motor housing 21. Additionally, bearing 55a is disposed at one axial end of motor shaft 41. Bearing 55b is disposed at the other axial end of motor shaft 41. Bearings 55a and 55b support motor shaft 41 for rotation. The shape, construction, etc., of bearings 55a and 55b are not particularly limited, and any known bearings may be used.

[0035] The rotor 50 has a rotor magnet 51. The rotor magnet 51 surrounds the motor shaft 41 around an axis and is fixed to the motor shaft 41.

[0036] Motor 10 has a bottomed cylindrical motor housing 21. Motor portion 30 is housed radially inside motor housing 21. Motor housing 21 can be cylindrical or rectangular. Motor housing 21 is, for example, die-cast aluminum. Motor 10 has a bottomed cylindrical motor housing 23 on one axial side of circuit board 80. Motor housing 23 can be cylindrical or rectangular. Motor housing 23 is, for example, die-cast aluminum. Motor housing 21 has an opening on one axial side, and motor housing 23 has an opening on the other axial side. The opening on one axial side of motor housing 21 is closed by motor housing 23, and the opening on the other axial side of motor housing 23 is closed by motor housing 21.

[0037] Motor housing 21 has a flange 21a extending radially outward at one end along the axial direction. The flange 21a has a through hole 21aa extending axially. Motor housing 23 has a flange 23a extending radially outward at the other end along the axial direction. The flange 23a has a through hole 23aa extending axially. The axial and circumferential positions of the through holes 21aa and 23aa are consistent, forming a continuous through hole. Motor housing 21 and motor housing 23 can be secured by threaded fastening through the through holes 21aa and 23aa.

[0038] Figure 3 From Figure 2 The motor 10 is shown in a perspective view with the motor housing 23 removed.

[0039] The circuit board 80 has a shape corresponding to the shape of the cylindrical hole in the motor housing 21. In this embodiment, the circuit board 80 is circular. The drive circuit 81 is composed of multiple electronic components. The drive circuit 81 includes, for example, at least one of IGBT, bridge diode, MOSFET, IPM, and DC / DC converter. IGBT is short for Insulated Gate Bipolar Transistor. MOSFET is short for Metal-Oxide-Semiconductor Field-Effect Transistor. IPM is short for Intelligent Power Module. The drive circuit 81 is externally connected to the motor 10 via wiring connected to connector 82. The wiring connected to connector 82 passes through through holes 83 provided in the motor housings 21 and 23.

[0040] <Structure of Motor Drive Unit>

[0041] Figure 4 This is a block diagram illustrating the structure of a motor drive device according to an embodiment of the present invention.

[0042] The motor drive unit 100 is a device that drives the motor 300. Figure 1 The motor 30 is Figure 4 This is an example of a motor 300. The motor drive device 100 includes a microcomputer 101, a driver 102, and a current detection unit 103. The microcomputer 101 includes: a speed acquisition unit 104, which acquires the speed at which the motor 300 rotates; a duty cycle setting unit 105, which sets the duty cycle of the PWM signal driving the motor 300 based on the speed acquired by the speed acquisition unit 104; and a PWM signal output unit 106, which outputs a PWM signal with the duty cycle set by the duty cycle setting unit 105. The driver 102 drives the motor 300 based on the PWM signal output by the PWM signal output unit 106. The current detection unit 103, for example, is composed of a shunt resistor, and detects the current flowing in the motor 300. In this embodiment, the speed acquisition unit 104, the duty cycle setting unit 105, and the PWM signal output unit 106 are implemented by the microcomputer 101 executing a program. The motor drive device 100 has a storage unit that stores the program executed by the microcomputer 101. The speed acquisition unit 104, the duty cycle setting unit 105, and the PWM signal output unit 106 can also be implemented in hardware. Figure 1 The drive circuit 81 is Figure 4 An example of a microcomputer 101, a driver 102, and a current detection unit 103. Alternatively, Figure 4 A portion of the structure of the motor drive unit 100 is set in Figure 1 The external drive circuit 81.

[0043] The motor drive unit 100 may also have a sensor for detecting the rotational position of the motor 300, and the rotational position of the motor 300 may be detected based on the detection result of the sensor. Alternatively, the motor drive unit 100 may not have a sensor for detecting the rotational position of the motor 300, thus performing sensorless control.

[0044] The speed setting unit 200 sets the rotational speed at which the motor 300 is rotated by the motor drive device 100. The speed acquisition unit 104 acquires the rotational speed at which the motor 300 is rotated, set by the speed setting unit 200. The motor drive device 100 rotates the motor 300 at the speed set by the speed setting unit 200. The motor drive device 100 may also include the speed setting unit 200. The speed setting unit 200 is, for example, a dual in-line package (DIP) switch mounted on the circuit board 80. When the speed setting unit 200 is a DIP switch, the operator can set the rotational speed of the motor 300 by switching the DIP switch on / off. In addition to DIP switches or rotary switches, the speed setting unit 200 can also be configured as a switch using resistors, jumpers, solder, etc., mounted on the circuit board 80 to set the rotational speed of the motor 300. Furthermore, the speed acquisition unit 104 can also acquire the rotational speed of the motor from an external source via communication.

[0045] <Operation of the motor drive unit>

[0046] The duty cycle setting unit 105 performs the following controls: a first control, whereby when the current detected by the current detection unit 103 reaches a first threshold, the duty cycle is set to the initial value when the motor 300 is started, or a predetermined value greater than the initial value; and a second control, whereby when the current detected by the current detection unit 103 reaches a second threshold, the duty cycle is set to the initial value. Furthermore, the duty cycle setting unit 105 changes at least one of the first and second thresholds based on the rotational speed acquired by the rotational speed acquisition unit 104. Additionally, the duty cycle setting unit 105 also has a third control: when the current detected by the current detection unit 103 reaches a third threshold, the duty cycle is set to 0% for a predetermined time. The third threshold is greater than the second threshold, and the second threshold is greater than the first threshold.

[0047] Figure 5 This is a flowchart illustrating the motor drive process performed by the motor drive device 100.

[0048] In step S501, the motor drive unit 100 waits for an instruction from the operator to start the motor drive. This instruction may be, for example, a power-on signal or a switch operation. Upon receiving the operator's instruction to start the motor drive (step S501: "Yes"), the motor drive unit 100 repeats the speed acquisition process in step S502, the duty cycle setting process in step S503, and the PWM signal output process in step S504, until it receives an instruction from the operator to stop the motor (step S505: "Yes").

[0049] The speed acquisition process in step S502 is the process by which the speed acquisition unit 104 acquires the speed set by the speed setting unit 200. The speed acquired in the speed acquisition process is then transferred to the duty cycle setting process. In the duty cycle setting process in step S503, reference is made to... Figures 6-9 As explained later, the duty cycle is set by the duty cycle setting unit 105. The duty cycle set in the duty cycle setting process is transferred to the PWM signal output process. In the PWM signal output process of step S504, a PWM signal with the duty cycle set in the duty cycle setting process is generated and the PWM signal is output to the driver 102.

[0050] Figure 6 This is a flowchart illustrating the duty cycle setting process performed by the motor drive unit 100.

[0051] First, in step S601, the duty cycle setting unit 105 sets the duty cycle to an initial value. This initial value is a value predetermined based on the characteristics of the driven motor 300, and is the duty cycle used to ensure smooth and efficient operation of the motor 300 when it is in a stopped state. This initial value is, for example, 1%.

[0052] Next, in step S602, the duty cycle setting unit 105 changes the threshold according to the rotational speed. The threshold changed here is either the first threshold used in the first control or the second threshold used in the second control. Alternatively, the duty cycle setting unit 105 may change only either the first threshold or the second threshold.

[0053] First, the change of the first threshold will be explained. The duty cycle setting unit 105 calculates the first threshold corresponding to the rotational speed at which the motor 300 rotates. For example, the manufacturer or user of the motor drive device 100 determines a rotational speed at which the motor 300 rotates as the initial setting speed, and calculates a first threshold that enables efficient driving of the motor 300 when the motor 300 rotates at that initial setting speed as the first threshold for the initial setting. This initial setting first threshold can be obtained, for example, by actually measuring the efficiency when the motor 300 is actually driven. For example, the manufacturer or user of the motor drive device 100 stores the initial setting speed and the corresponding initial setting first threshold in advance in the storage unit of the motor drive device 100. The duty cycle setting unit 105 uses the initial setting speed and the initial setting first threshold stored in the storage unit to calculate the first threshold when the rotational speed transferred from the speed acquisition unit 104 is different from the initial setting speed.

[0054] For example, when the initial speed is N1, the initial threshold is X1, and the speed transferred from the speed acquisition unit 104 is N2, the first threshold X2 used when driving the motor 300 with the speed N2 transferred from the speed acquisition unit 104 is calculated by formula (1).

[0055] X2 = (N1 / N2)*X1 (where / is the division operator and * is the multiplication operator.) ... Equation (1)

[0056] That is, when the rotational speed of the motor 300 is changed from N1 to N2, the duty cycle setting unit 105 changes the first threshold from X1 to X2 calculated by formula (1).

[0057] The duty cycle setting unit 105 can also calculate the first threshold using equation (1) each time the speed is transferred by the speed acquisition unit 104. Alternatively, the first threshold can be pre-calculated using equation (1) for each speed at which the motor 300 can be driven, and these thresholds can be stored in a corresponding table, for example. The first threshold corresponding to the speed transferred from the speed acquisition unit 104 can be read from the table and used in the first control. For example, the duty cycle setting unit 105 sets the first threshold to 0.63A (Amperes) when the speed is 1300 rpm, sets the first threshold to 0.52A (Amperes) when the speed is 1550 rpm, and sets the first threshold to 0.45A (Amperes) when the speed is 1800 rpm.

[0058] The change of the second threshold will be explained. The duty cycle setting unit 105 calculates a second threshold corresponding to the rotational speed at which the motor 300 rotates. For example, the manufacturer or user of the motor drive device 100 determines a rotational speed at which the motor 300 rotates as the initial setting speed, and calculates a second threshold that enables efficient driving of the motor 300 when the motor 300 rotates at that initial setting speed as the second threshold for the initial setting. This second threshold for the initial setting can be obtained, for example, by actually measuring the efficiency when the motor 300 is actually driven. For example, the manufacturer or user of the motor drive device 100 stores the initial setting speed and the corresponding initial setting second threshold in advance in the storage unit of the motor drive device 100. The duty cycle setting unit 105 uses the initial setting speed and the initial setting second threshold stored in the storage unit to calculate a second threshold when the rotational speed transferred from the speed acquisition unit 104 is different from the initial setting speed.

[0059] For example, when the initial speed is N1, the second threshold is Y1, and the speed transferred from the speed acquisition unit 104 is N2, the second threshold Y2 used when driving the motor 300 with the speed N2 transferred from the speed acquisition unit 104 is calculated by formula (2).

[0060] Y2 = (N1 / N2) * Y1 (where / is the division operator and * is the multiplication operator.) ... Equation (2)

[0061] That is, when the speed of motor 300 is changed from N1 to N2, the duty cycle setting unit 105 changes the second threshold from Y1 to Y2 calculated by formula (2).

[0062] The duty cycle setting unit 105 can also calculate the second threshold using equation (2) each time the speed is transferred by the speed acquisition unit 104. Alternatively, the second threshold can be pre-calculated using equation (2) for each speed at which the motor 300 can be driven, and these thresholds can be stored in a corresponding table, for example. The second threshold corresponding to the speed transferred from the speed acquisition unit 104 can be read from the table and used in the second control. For example, the duty cycle setting unit 105 sets the second threshold to 0.80A (Amperes) when the speed is 1300 rpm, to 0.67A (Amperes) when the speed is 1550 rpm, and to 0.58A (Amperes) when the speed is 1800 rpm.

[0063] The duty cycle setting unit 105 performs first control in step S603, second control in step S604, and third control in step S605. In the first and second controls, the first and second threshold values ​​modified in step S602 are used. Furthermore, the first, second, and third controls are executed at predetermined cycles, for example, through timed interrupts, during the driving process of the motor drive device 100 on the motor 300. For details regarding the first, second, and third controls, please refer to... Figure 7 , Figure 8 as well as Figure 9 The explanation will follow.

[0064] During the driving of the motor 300, the duty cycle setting unit 105 gradually increases and updates the duty cycle from the initial value set in step S601 when the motor 300 starts rotating, until it reaches the duty cycle corresponding to the speed transferred from the speed acquisition unit 104. In steps S606 and S607, the process of updating this duty cycle is performed. In step S606, the duty cycle setting unit 105 determines whether the current duty cycle corresponds to the speed transferred from the speed acquisition unit 104. If the current duty cycle corresponds to the speed transferred from the speed acquisition unit 104 (step S606: "Yes"), the duty cycle setting unit 105 returns to step S602. If the current duty cycle does not correspond to the speed transferred from the speed acquisition unit 104 (step S606: "No"), the duty cycle setting unit 105 proceeds to step S607. In step S607, the duty cycle setting unit 105 increases the duty cycle by a predetermined amount (e.g., 2%) and updates it. After step S607, the duty cycle setting unit 105 returns to step S602.

[0065] Figure 7 It is shown Figure 6 The flowchart of the first control is shown. Under the first control, if the number of times the threshold is exceeded reaches a predetermined number (e.g., 30 times) within a predetermined time (e.g., 0.1 seconds), the determination in step S701 is executed. The first control is executed, for example, once every approximately 350 microseconds.

[0066] First, in step S701, the duty cycle setting unit 105 determines whether the current detected by the current detection unit 103 reaches a first threshold, that is, whether the current detected by the current detection unit 103 is above the first threshold. If the current detected by the current detection unit 103 is not above the first threshold (step S701: "No"), then step S701 is stopped. If the current detected by the current detection unit 103 is above the first threshold (step S701: "Yes"), then step S702 is executed.

[0067] In step S702, the duty cycle setting unit 105 sets the duty cycle to a predetermined value. This predetermined value can be a pre-determined constant value, a value predetermined for each current duty cycle, or a value obtained by subtracting a predetermined ratio (e.g., 5%) from the current duty cycle. For example, when driving the motor 300 at a 50% duty cycle, if the current detected by the current detection unit 103 exceeds a first threshold, the duty cycle is set to 45%. The predetermined value set in step S702 is larger than the initial duty cycle value set in step S601. The duty cycle setting unit 105 returns to step S701 after step S702. Furthermore, the first control proceeds after a series of processes, i.e., when it is "No" in step S701 and after step S702. Figure 6 S604.

[0068] Figure 8 It is shown Figure 6 The flowchart for the second control is shown. Under the second control, the determination in step S801 is executed immediately after the threshold is exceeded. The second control is executed, for example, in nanoseconds per PWM cycle.

[0069] First, in step S801, the duty cycle setting unit 105 determines whether the current detected by the current detection unit 103 reaches the second threshold, that is, whether the current detected by the current detection unit 103 is above the second threshold. If the current detected by the current detection unit 103 is not above the second threshold (step S801: "No"), then step S801 is stopped. If the current detected by the current detection unit 103 is above the second threshold (step S801: "Yes"), then step S802 is entered.

[0070] In step S802, the duty cycle setting unit 105 sets the duty cycle to an initial value. This initial value is the initial value of the duty cycle set in step S601. This initial value is, for example, 1%. After step S802, the duty cycle setting unit 105 returns to step S801. Furthermore, the second control enters a new state after a series of processes have completed, i.e., after the condition is "No" in step S801 and after step S802 has ended. Figure 6 The S605.

[0071] Figure 9 It is shown Figure 6 The flowchart for the third control is shown. Under the third control, the determination in step S901 is executed immediately after the threshold is exceeded. The third control is executed, for example, once every approximately 350 microseconds.

[0072] First, in step S901, the duty cycle setting unit 105 determines whether the current detected by the current detection unit 103 reaches the third threshold, that is, whether the current detected by the current detection unit 103 is above the third threshold. If the current detected by the current detection unit 103 is not above the third threshold (step S901: "No"), then the process stops at step S901. Furthermore, the third control proceeds if the current detected by the current detection unit 103 is less than the third threshold, that is, if step S901 is "No". Figure 6 S606. If the current detected by the current detection unit 103 is above the third threshold (step S901: "Yes"), proceed to step S902. The third threshold is a threshold used to protect the motor drive device 100 and the motor 300 from being burned out by overcurrent, etc. It is a constant value that is independent of the rotational speed transferred from the rotational speed acquisition unit 104, for example, 1A (Ampere).

[0073] In step S902, the duty cycle setting unit 105 sets the duty cycle to 0%, that is, stops the motor 300. Then, in step S903, the duty cycle setting unit 105 waits for a predetermined time (e.g., 6 seconds) to elapse. If the predetermined time has elapsed (step S903: "Yes"), the microcomputer 101 resets the processing and restarts processing from step S501.

[0074] <Function and Effect of Motor Drive Unit 100>

[0075] Next, the function and effect of the motor drive device 100 will be explained.

[0076] In the invention described above, a motor drive device for driving a motor is provided, comprising: a speed acquisition unit that acquires a speed at which the motor rotates; a duty cycle setting unit that sets a duty cycle of a PWM signal for driving the motor based on the speed acquired by the speed acquisition unit; a PWM signal output unit that outputs a PWM signal with a duty cycle set by the duty cycle setting unit; a driver that drives the motor based on the PWM signal output by the PWM signal output unit; and a current detection unit that detects current flowing in the motor. The duty cycle setting unit performs the following control: a first control, in which the duty cycle is set to an initial value or a predetermined value greater than the initial value when the current detected by the current detection unit reaches a first threshold; and a second control, in which the duty cycle is set to the initial value when the current detected by the current detection unit reaches a second threshold. The duty cycle setting unit changes at least one of the first threshold and the second threshold based on the speed acquired by the speed acquisition unit.

[0077] Therefore, it can drive the motor efficiently.

[0078] In addition, torque control can be performed in a simple way, which can suppress the rise in motor temperature.

[0079] In addition, the duty cycle setting unit also has the following third control: when the current detected by the current detection unit reaches a third threshold, the duty cycle is set to 0% within a specified time, wherein the third threshold is greater than the second threshold and the second threshold is greater than the first threshold.

[0080] Therefore, even if the current detected by the current detection unit cannot be limited by the first threshold and the current rises further, the current can be limited by reaching the second threshold, thereby enabling stable motor drive. Furthermore, before the current detected by the current detection unit reaches the third threshold and stops the motor, the current can be limited by reaching the second threshold, enabling stable motor drive.

[0081] In addition, the duty cycle setting unit executes the first control with a first cycle and executes the second control with a second cycle that is shorter than the first cycle.

[0082] Therefore, compared with the frequency of the first control which compares the current detected by the current detection unit with the first threshold, the frequency of the second control which compares the current with the second threshold is higher. Thus, it is possible to detect the current reaching the second threshold more reliably, thereby enabling stable motor drive.

[0083] Furthermore, when the motor speed N1 is changed to N2, the duty cycle setting unit changes the first threshold X1 to X2, which is represented by X2 = (N1 / N2)*X1 (where / is the division operator and * is the multiplication operator).

[0084] Therefore, the modified first threshold can be calculated using a simple mathematical formula.

[0085] In addition, N1 is the motor speed at the initial setting, and X1 is the first threshold at the initial setting.

[0086] Therefore, the revised first threshold is derived from a highly reliable initial setting, thus enabling the determination of a reliable value.

[0087] Furthermore, when the motor speed N1 is changed to N2, the duty cycle setting unit changes the second threshold Y1 to Y2, which is represented by Y2 = (N1 / N2) * Y1 (where / is the division operator and * is the multiplication operator).

[0088] Therefore, the modified second threshold can be calculated using a simple mathematical formula.

[0089] Additionally, N1 is the motor speed at the initial setting, and Y1 is the second threshold at the initial setting.

[0090] Therefore, the revised second threshold is derived from a highly reliable initial setting, thus enabling the determination of a reliable value.

[0091] In addition, the motor drive device also has a speed setting unit that sets the speed at which the motor rotates, and the speed acquisition unit acquires the speed set by the speed setting unit.

[0092] Therefore, the motor speed can be set via the speed setting unit.

[0093] In addition, the speed setting unit is a switch on the circuit board.

[0094] Therefore, the motor speed can be easily set using a switch on the circuit board.

[0095] In addition, the speed acquisition unit acquires the speed at which the motor rotates from an external source via communication.

[0096] Therefore, the motor speed can be easily set from the outside via communication.

[0097] In addition, the motor is a motor that rotates an axial fan.

[0098] Therefore, in the motor used for axial fans, an appropriate threshold corresponding to the rotational speed can be set to suppress the rise in motor temperature.

[0099] The application of the motor driven by the motor drive device of the above embodiments is not particularly limited. For example, the motor of the above embodiments is a motor for rotating an axial fan. Furthermore, the above structures can be appropriately combined within a range that does not contradict each other.

[0100] The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and variations can be made within its scope. These embodiments and their variations are included in the scope and spirit of the invention, and are also included within the scope of the invention as described in the claims and their equivalents.

[0101] Label Explanation

[0102] 10: Motor; 21: Motor housing; 30: Motor section; 40: Stator; 50: Rotor; 80: Circuit board; 81: Drive circuit; 100: Motor drive unit; 101: Microcomputer; 102: Driver; 103: Current detection unit; 104: Speed ​​acquisition unit; 105: Duty cycle setting unit; 106: PWM signal output unit; 200: Speed ​​setting unit; 300: Motor.

Claims

1. A motor driving device that drives a motor, wherein the motor driving device has: a rotation speed acquisition section that acquires a rotation speed at which the motor rotates; a duty ratio setting section that sets a duty ratio of a PWM signal that drives the motor, in accordance with the rotation speed acquired by the rotation speed acquisition section; a PWM signal output section that outputs the PWM signal of the duty ratio set by the duty ratio setting section; a driver that drives the motor in accordance with the PWM signal output by the PWM signal output section; and a current detection section that detects a current flowing in the motor, the duty ratio setting section performs: a first control that sets the duty ratio to a prescribed value that is larger than an initial value at the time of starting to drive the motor, when the current detected by the current detection section reaches a first threshold value; and a second control that sets the duty ratio to the initial value, when the current detected by the current detection section reaches a second threshold value that is larger than the first threshold value, the duty ratio setting section changes at least one of the first threshold value and the second threshold value in accordance with the rotation speed acquired by the rotation speed acquisition section.

2. The motor driving device according to claim 1, wherein the duty ratio setting section further has a third control that sets the duty ratio to 0% for a prescribed time, when the current detected by the current detection section reaches a third threshold value that is larger than the second threshold value.

3. The motor driving device according to claim 1 or 2, wherein the duty ratio setting section performs the first control with a first period, and performs the second control with a second period that is shorter than the first period.

4. The motor driving device according to claim 1 or 2, wherein in a case where a rotation speed Nl of the motor is changed to N2, the duty ratio setting section changes the first threshold value Xl to X2, where X2 = (Nl / N2)*Xl, / is an operator of division, and * is an operator of multiplication.

5. The motor driving device according to claim 4, wherein the Nl is a motor rotation speed at the time of initial setting, and the Xl is the first threshold value at the time of initial setting.

6. The motor driving device according to claim 1 or 2, wherein in a case where a rotation speed Nl of the motor is changed to N2, the duty ratio setting section changes the second threshold value Yl to Y2, where Y2 = (Nl / N2)*Yl, / is an operator of division, and * is an operator of multiplication.

7. The motor driving device according to claim 6, wherein the Nl is a motor rotation speed at the time of initial setting, and the Yl is the second threshold value at the time of initial setting.

8. The motor driving device according to claim 1 or 2, wherein the motor driving device further has a rotation speed setting section that sets a rotation speed at which the motor rotates, the rotation speed acquisition section acquires the rotation speed set by the rotation speed setting section.

9. The motor driving device according to claim 8, wherein the rotation speed setting section is a switch on a circuit board.

10. The motor driving device according to claim 1 or 2, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The rotation speed acquisition section acquires the rotation speed of the motor rotating the shaft fan from the outside through communication.

11. The motor drive apparatus according to claim 1 or 2, wherein The motor is a motor that rotates a shaft flow fan.

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