Wiper drive device and wiper drive method

Abstract

To appropriately control a motor according to a load generated in a forward direction and a load generated in a return direction.SOLUTION: A wiper driving device includes: a motor for driving a wiper arm; a load state determination part for generating an index value for determining a load state of the motor and determining whether the load state of the motor is a low load state or a high load state based on the index value; and a driving control part for driving the motor by switching between three-phase energization and two-phase energization. When the load state of the motor is determined to be a high load state, the driving control part drives the motor at three-phase energization in a period when the wiper arm is moved in a forward direction, and drives the motor at two-phase energization in a period when the wiper arm is moved in a return direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a wiper driving device and a wiper driving method.

Background Art

[0002] In recent years, motor control devices that switch between different driving schemes according to the magnitude of a load in motor control, such as a less-ripple driving scheme and a rectangular wave driving scheme, for example, are known. Here, the less-ripple driving scheme is a driving scheme configured to output a PWM (Pulse Width Modulation) phase having an intermediate duty ratio during the OFF phase in the rectangular wave driving scheme, thereby reducing operating noise. The less-ripple driving scheme provides lower output compared to the rectangular wave driving scheme. In Patent Document 1, driving scheme switching control is performed such that when the load on the motor is small, the motor is driven by the less-ripple driving scheme, and when the load is large, the motor is driven by the rectangular wave driving scheme.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] A load on a motor can be either a load that applies torque in the opposite direction to the motor's rotation direction, or a load that applies torque in the same direction as the motor's rotation direction. For example, in a wiper system, the wiper arm moves from the lower edge of the front windshield towards the top (forward movement), and when it reaches the upper inversion position, the movement of the wiper arm reverses and it moves from the top towards the lower edge (return movement). When the wipers are operated while driving, in the forward movement, the direction of the airflow is the same as the direction of the wiper arm's movement, so the load applies torque in the same direction as the rotation direction of the motor driving the wiper arm. In contrast, in the return movement, the direction of the airflow is opposite to the direction of the wiper arm's movement, so the load applies torque in the opposite direction to the rotation direction of the motor driving the wiper arm.

[0005] When a load applies torque in the opposite direction to the motor's rotation, this can be addressed by increasing the motor's output. However, for loads that generate torque in the same direction as the motor's rotation, it is necessary to apply a braking force to the motor.

[0006] In view of the above-mentioned problems, the present invention aims to provide a wiper drive device and a wiper drive method that enable the motor to be appropriately controlled according to the load generated in the forward direction and the load generated in the return direction of the wiper arm. [Means for solving the problem]

[0007] One aspect of the present invention is: Vehicle The system includes a motor that drives a wiper arm, a load state determination unit that generates an index value for determining the load state on the motor and determines whether the load state on the motor is low load or high load based on the index value, and a drive control unit that drives the motor by switching between 3-phase and 2-phase energization, wherein the drive control unit determines that the load state on the motor is high load, and then drives the wiper arm It is in the same direction as the airflow direction relative to the vehicle. During the period when the motor is moved in the forward direction, This generates a braking force greater than that of the aforementioned two-phase energization. It is driven by three-phase power supply, and the wiper arm It is in the opposite direction to the aforementioned airflow direction. During the period when moving in the return direction, the motor The aforementioned It is driven by two-phase power.

[0008] By configuring it in this way, the motor can be appropriately controlled according to the load generated in the forward direction and the load generated in the return direction. This ensures that the motor is reliably braked when moving the wiper in the forward direction.

[0009] Aspect 2 of the present invention is the apparatus of aspect 1, wherein the load state determination unit sets a first threshold for detecting a change from a low load state to a high load state and a second threshold for detecting a change from a high load state to a low load state, and the first threshold is set to a value greater than the second threshold.

[0010] This configuration prevents the drive mode from changing frequently.

[0011] A third aspect of the present invention is the apparatus of the first aspect, wherein the load state determination unit generates an index value for determining the load state of the motor, which is obtained by accumulating values ​​determined according to the load.

[0012] This configuration prevents malfunctions caused by temporary increases or decreases in load or measurement errors.

[0013] A fourth aspect of the present invention is the device of the third aspect, wherein the value determined according to the load is the vehicle speed.

[0014] This configuration allows for reliable detection of the load applied to the motor that drives the wiper.

[0017] Embodiments of the present invention 5 teeth, Vehicle The motor that drives the wiper arm Drive A wiper driving method comprising the steps of: generating an index value for determining the load state on the motor, determining whether the load state on the motor is low load or high load based on the index value; and, if it is determined that the load state on the motor is high load, the wiper arm It is in the same direction as the airflow direction relative to the vehicle. During the period when the motor is moved in the forward direction, This generates a braking force greater than that of the aforementioned two-phase energization.driven by three-phase energization, and driving the motor during a period in which the wiper arm is It is in the opposite direction to the aforementioned airflow direction. moved in the return direction, the step of driving the motor The aforementioned by two-phase energization.

[0018] With this configuration, the motor can be appropriately controlled in accordance with the load generated in the forward direction and the load generated in the return direction.

Effect of the Invention

[0019] According to the present invention, during a period in which the wiper arm is moved in the forward direction, the motor is driven by three-phase energization to secure sufficient braking force, and during a period in which the wiper arm is moved in the return direction, the motor is driven by two-phase energization to secure sufficient driving force, whereby the motor can be appropriately controlled in accordance with the load generated in the forward direction and the load generated in the return direction.

Brief Description of Drawings

[0020] [Figure 1] It is a configuration diagram showing an example of the wiper driving device according to the present embodiment. [Figure 2] It is a block diagram of a motor driving unit in the wiper driving device according to the present embodiment. [Figure 3] It is a diagram showing an example of a rectangular wave driving pattern in the present embodiment. [Figure 4] It is a diagram summarizing an example of a rectangular wave driving pattern in the present embodiment in a table. [Figure 5] It is a diagram showing a first example of a sensorless driving pattern in the present embodiment. [Figure 6] It is a diagram summarizing the first example of a sensorless driving pattern in the present embodiment in a table. [Figure 7] It is a diagram used for explaining a current flow during rectangular wave driving in the present embodiment. [Figure 8] It is a diagram used for explaining a current flow during sensorless driving in the present embodiment. [Figure 9] It is a diagram showing a second example of a sensorless driving pattern in the present embodiment. [Figure 10] This diagram shows a table summarizing a second example of the freeless drive pattern in this embodiment. [Figure 11] This figure shows an example of what happens when the conditions are changed in the square wave driving pattern of this embodiment. [Figure 12] This figure shows the case where the conditions are changed in the first example of the free-response drive pattern in this embodiment. [Figure 13] This figure shows the case where the conditions are changed in the second example of the free-response drive pattern in this embodiment. [Figure 14] This figure shows an example of the operation of switching the drive mode of the motor control device according to this embodiment. [Figure 15] This flowchart shows an example of the operation of switching the drive mode of the motor control device according to this embodiment. [Figure 16] This flowchart shows an example of the motor drive operation in the drive mode of the motor control device according to this embodiment. [Figure 17] This diagram is used to illustrate other examples of three-phase power supply. [Figure 18] This diagram is used to illustrate yet another example of three-phase power supply. [Modes for carrying out the invention]

[0021] Hereinafter, a wiper drive device and wiper drive method according to one embodiment of the present invention will be described with reference to the drawings.

[0022] Figure 1 is a configuration diagram showing an example of a wiper drive device 100 according to this embodiment. As shown in Figure 1, the wiper drive unit 100 performs a wiping operation on the window surface of the vehicle 1's window glass 10. The wiper drive unit 100 comprises a motor 2, a link mechanism 11, two wiper arms 12, and wiper blades 13 attached to the tips of each wiper arm 12.

[0023] The wiper arm 12 operates on the window surface of the window glass 10 through the rotational drive of the motor 2, and performs a wiping action with the wiper blade 13 attached to its tip. The two wiper arms 12 are connected by a link mechanism 11.

[0024] The wiper blade 13 is positioned so as to be pressed against the window glass 10 by the wiper arm 12. The wiper blade 13 includes a blade rubber (not shown) held in a blade holder attached to the tip of the wiper arm 12. When the wiper arm 12 is oscillated by the motor 2, the wiper blade 13 reciprocates within a wiping range on the outer surface of the window glass 10, wiping the window glass 10 with the blade rubber (not shown).

[0025] In the following explanation, the path by which the wiper arm 12 moves from the lower edge of the window glass 10 towards the top, to the inverted position, as indicated by arrow A1, is called the forward path. Also, the path by which the wiper arm 12 moves from the inverted position towards the top, to the inverted position, towards the lower edge, as indicated by arrow A2, is called the return path.

[0026] Figure 2 is a block diagram of the motor drive unit 200 in the wiper drive device 100 according to this embodiment. As shown in Figure 2, the motor drive unit 200 comprises a control unit 40 and an inverter 50.

[0027] For example, a three-phase, four-pole brushless motor is used as motor 2. Motor 2 is driven to rotate by the output signal (applied voltage) output by the inverter 50 based on the drive signal described later.

[0028] Power is supplied to the inverter 50 from the battery 3. The control unit 40 is connected to the ECU 4 (Electronic Control Unit).

[0029] Motor 2 comprises a stator 21 and a rotor 22. The stator 21 is fixed to the inner circumference of the motor 2 case. The stator 21 has three phase windings (21u, 21v, 21w). The stator 21 has the windings (21u, 21v, 21w) wound around it. For example, the three phase windings (21u, 21v, 21w) are connected by a delta connection.

[0030] The rotor 22 is located inside the stator 21. The rotor 22 comprises, for example, a rotor shaft 22a and a four-pole permanent magnet 22b attached to the rotor shaft 22a. Multiple bearings (not shown) are provided inside the motor 2 case, and the rotor shaft 22a is rotatably supported by the multiple bearings.

[0031] The position detection unit 30 detects a signal corresponding to the rotation of the rotor 22. The position detection unit 30 includes, for example, three Hall elements (30u, 30v, 30w). When the rotor 22 rotates, these three Hall elements (30u, 30v, 30w) output pulse signals with different phases to the control unit 40. That is, as the rotor 22 rotates, the position detection unit 30 generates pulse signals based on the change in the magnetic poles of a sensor magnet (not shown) placed on the rotor shaft 22a and outputs them to the control unit 40.

[0032] In this embodiment, Hall element 30u outputs a digital signal corresponding to the U phase (position detection signal Hu), Hall element 30v outputs a digital signal corresponding to the V phase (position detection signal Hv), and Hall element 30w outputs a digital signal corresponding to the W phase (position detection signal Hw).

[0033] The inverter 50 is controlled, for example, by PWM (Pulse Width Modulation) based on the drive signal generated by the drive control unit 43 (described later), and applies voltage to the three phase windings (21u, 21v, 21w) of the motor 2. That is, the inverter 50 switches the switching elements (51a~51f) (conducting / non-conducting) based on the drive signal generated by the drive control unit 43, thereby changing the magnitude of the output voltage applied to the motor 2 (duty cycle), the energizing period (energetic angle), and the energizing timing (advance angle). Here, the duty cycle represents the ratio of the duration of the conduction period and the duration of the non-conduction period of the corresponding switching element in the PWM period.

[0034] The inverter 50 generates the applied voltage using DC power supplied from the battery 3. The battery 3 is a DC power source such as a lead-acid battery or a lithium-ion battery, and supplies power to drive the motor 2.

[0035] The inverter 50 comprises six three-phase bridge-connected switching elements 51a to 51f and diodes 52a to 52f. The switching elements 51a to 51f are, for example, N-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and constitute a three-phase bridge circuit.

[0036] Switching elements 51a and 51d are connected in series between the positive and negative terminals of the battery 3, forming a U-phase bridge circuit. Switching element 51a has its drain terminal connected to the positive terminal of the battery 3, its source terminal connected to node N1, and its gate terminal connected to the signal line of the U-phase high-side drive signal. Switching element 51d has its drain terminal connected to node N1, its source terminal connected to the negative terminal of the battery 3, and its gate terminal connected to the signal line of the U-phase low-side drive signal. Node N1 is connected to the connection point 21a of the motor 2.

[0037] Switching elements 51b and 51e are connected in series between the positive and negative terminals of the battery 3, forming a V-phase bridge circuit. Switching element 51b has its drain terminal connected to the positive terminal of the battery 3, its source terminal connected to node N2, and its gate terminal connected to the V-phase high-side drive signal line. Switching element 51e has its drain terminal connected to node N2, its source terminal connected to the negative terminal of the battery 3, and its gate terminal connected to the V-phase low-side drive signal line. Node N2 is connected to the motor 2 connection point 21b.

[0038] Switching elements 51c and 51f are connected in series between the positive and negative terminals of the battery 3, forming a W-phase bridge circuit. Switching element 51c has its drain terminal connected to the positive terminal of the battery 3, its source terminal connected to node N3, and its gate terminal connected to the signal line of the W-phase high-side drive signal. Switching element 51f has its drain terminal connected to node N3, its source terminal connected to the negative terminal of the battery 3, and its gate terminal connected to the signal line of the W-phase low-side drive signal. Node N3 is connected to the connection point 21c of the motor 2.

[0039] Furthermore, diode 52a has its anode terminal connected to node N1 and its cathode terminal connected to the positive terminal of battery 3. Similarly, diode 52d has its anode terminal connected to the negative terminal of battery 3 and its cathode terminal connected to node N1.

[0040] Furthermore, diode 52b has its anode terminal connected to node N2 and its cathode terminal connected to the positive terminal of battery 3. Similarly, diode 52e has its anode terminal connected to the negative terminal of battery 3 and its cathode terminal connected to node N2.

[0041] Furthermore, diode 52c has its anode terminal connected to node N3 and its cathode terminal connected to the positive terminal of battery 3. Similarly, diode 52f has its anode terminal connected to the negative terminal of battery 3 and its cathode terminal connected to node N3.

[0042] The control unit 40 is a processor, for example, a CPU (Central Processing Unit), and comprehensively controls the motor drive unit 200. The control unit 40 generates a drive signal corresponding to the rotational output of the target rotor 22 (for example, the target rotational speed TRPM) and outputs the generated drive signal to the inverter 50. The control unit 40 transmits and receives predetermined information between the ECU 4 and the motor 2. Furthermore, the control unit 40 includes a load state determination unit 41, a vehicle speed detection unit 42, and a drive control unit 43.

[0043] The load state determination unit 41 accumulates a value determined according to the load on the motor 2, and uses this accumulated load value as an index value to determine whether the state is high load or low load. The value determined according to the load is, for example, the vehicle speed. That is, as the vehicle speed increases, the wind pressure hitting the wiper blade 13 becomes stronger, and the load on the motor 2 increases. Also, when a strong load is placed on the motor 2, the rotational speed of the motor 2 increases or decreases from the set value, and the duty cycle also increases or decreases. From this, the rotational speed and duty cycle of the motor 2 can be used as values ​​determined according to the load. Furthermore, the load state determination unit 41 can calculate an index value for determining whether the state is high load or low load by comprehensively using the vehicle speed, motor speed, duty cycle, and power supply voltage, etc., as values ​​determined according to the load, and accumulating these values ​​as appropriate.

[0044] As will be described later, in the case of the motor 2 that drives the wiper arm 12, the load received during travel is in the same direction as the rotation of motor 2 during the forward journey, and in the opposite direction during the return journey. When the load is in the opposite direction to the rotation of motor 2, the rotational speed of motor 2 decreases below the set value when the load is applied, and the duty cycle increases in order to increase the rotation. On the other hand, when the load is in the same direction as the rotation of motor 2, the rotational speed of motor 2 increases above the set value when the load is applied, and the duty cycle decreases in order to decrease the rotation. Therefore, when using the rotational speed and duty cycle of motor 2 as values ​​determined according to the load, it is necessary to consider whether it is in the forward or return direction.

[0045] The integrated load value will be a large positive value because it will show a series of positive values ​​when a high load condition persists. On the other hand, when a light load condition persists, it will show a series of zeros or negative values, resulting in a value of zero or less. Here, the integrated load value is treated as zero if it is zero or less, so when motor 2 is operating normally, the integrated load value will show zero. Also, if the motor was under high load but then the load was reduced to a controllable range, the integrated load value will gradually decrease and eventually converge to zero or a small positive value. Therefore, by looking at the integrated load value, it is possible to determine the current status of motor 2, and if the value exceeds a certain level, it can be judged as being under high load. Thus, the integrated load value is an indicator value for determining whether the load on motor 2 is high load or low load.

[0046] The vehicle speed detection unit 42 detects the vehicle speed, which is the speed at which the vehicle on which the motor 2 is mounted is traveling. The vehicle speed detection unit 42 detects the vehicle speed based on the vehicle speed signal output from the ECU 4.

[0047] The drive control unit 43 generates a drive signal corresponding to the rotational output of the target rotor 22 (for example, the target rotational speed TRPM) and outputs the generated drive signal to the inverter 50. The drive control unit 43 controls the drive of the motor 2 by switching between a high-load mode and a low-load mode. The low-load mode is the mode used when the load on the motor 2 is small. The high-load mode is the mode used when the load on the motor 2 is large.

[0048] As shown in Figure 1, the load on the motor 2 that drives the wiper arm 12 is such that, on the outward journey, the direction of the airflow (arrow B1) is the same as the direction of movement of the wiper arm 12 (arrow A1), resulting in a load that applies torque in the same direction as the rotation, accelerating the rotation of the motor 2. On the return journey, the direction of the airflow (arrow B1) is opposite to the direction of movement of the wiper arm 12 (arrow A2), resulting in a load that applies torque in the opposite direction to the rotation of the motor 2, decelerating the rotation of the motor 2.

[0049] In this embodiment, the drive control unit 43 controls the drive of the motor 2 by switching between a high-load mode and a low-load mode according to the cumulative load value. In the low-load mode, the drive control unit 43 drives the motor 2 using a free-response drive method to enable quiet operation. When the drive control unit 43 switches to the high-load mode, on the return journey, a load is applied that results in torque in the opposite direction to the rotation direction of the motor 2, so the motor 2 is driven using a square wave drive method. The square wave drive method drives the motor 2 with two-phase energization and can drive with higher output than the free-response drive method. On the forward journey, a load is applied that results in torque in the same direction as the rotation direction of the motor 2, so the motor 2 is driven using a free-response drive method. Since the free-response drive method uses three-phase energization, a stronger braking force can be obtained compared to the square wave drive method.

[0050] Here, we will explain the details of square wave driving and free-less driving with reference to Figures 3 to 13.

[0051] Figures 3, 5, and 9 are explanatory diagrams illustrating the position detection signals (Hu, Hv, Hw) output by the Hall element (30u, 30v, 30w) and an example of the advance angle and energization angle in the energization control of the inverter 50. Figures 3, 5, and 9 show the correspondence between the position detection signals (Hu, Hv, Hw) and the angular range in which the switching elements 51a to 51f are turned on. The horizontal axis represents the rotational position of the magnetic poles of the rotor 22 of the motor 2 in terms of electrical angles.

[0052] The position detection signals (Hu, Hv, Hw) have a phase difference of 60 degrees from each other, with an electrical angle of 360 degrees as one period, and change to either an H state (High state) or an L state (Low state) every 180 degrees. In this embodiment, the change of the position detection signal Hu from the L state to the H state is referred to as Hall edge HE2, and the change from the H state to the L state is referred to as Hall edge HE5. Similarly, the change of the position detection signal Hv from the L state to the H state is referred to as Hall edge HE3, and the change from the H state to the L state is referred to as Hall edge HE6. Furthermore, the change of the position detection signal Hw from the L state to the H state is referred to as Hall edge HE4, and the change from the H state to the L state is referred to as Hall edge HE1. The electrical angle between each Hall edge is 60 degrees.

[0053] Furthermore, the space between hole edge HE1 and hole edge HE2 is referred to as hole stage 1 (hereinafter simply referred to as stage 1 (hereinafter the same)), the space between hole edge HE2 and hole edge HE3 is referred to as stage 2, and the space between hole edge HE3 and hole edge HE4 is referred to as stage 3. Furthermore, the space between hole edge HE4 and hole edge HE5 is referred to as stage 4, the space between hole edge HE5 and hole edge HE6 is referred to as stage 5, and the space between hole edge HE6 and hole edge HE1 is referred to as stage 6.

[0054] Figure 3 shows an example of a current supply pattern for rectangular wave driving in this embodiment. Figure 3 shows the correspondence between the position detection signals (Hu, Hv, Hw) and the energization patterns of each switching element 51a to 51f, with the horizontal axis representing the electrical angle. One example of energization control shown in Figure 3 is when the advance angle is 20 degrees and the energization angle is 130 degrees.

[0055] The energizing pattern is a combination of one of the following states: a state in which the high-side switching element among the switching elements 51a to 51f is continuously ON and the low-side switching element is continuously OFF; a state in which all switching elements 51a to 51f are continuously OFF (the "OFF phase" period); or a state in which all switching elements 51a to 51f are controlled to be ON or OFF at a constant period (a PWM controlled state) ("PWM phase"). Each stage 1 to 6 is further divided into sections A', B', and C'. An individual energizing pattern is set for sections A', B', and C'. The duration (electrical angle) of sections A', B', and C' changes depending on the advance angle value and the energizing angle value.

[0056] For example, in stage 1 enclosed by hole edge HE1 and hole edge HE2, the energizing pattern in section A' is a combination of "ON", "OFF", "PWM", "PWM", "OFF", and "OFF" for switching elements 51a to 51f, respectively. The energizing pattern in section B' is a combination of "ON", "OFF", "PWM", "PWM", "ON", and "OFF" for switching elements 51a to 51f, respectively. Also, the energizing pattern in section C' is a combination of "OFF", "OFF", "PWM", "PWM", "ON", and "OFF" for switching elements 51a to 51f, respectively.

[0057] Figure 4 is a table summarizing an example of the rectangular wave energization pattern in this embodiment shown in Figure 3. The ROM (not shown) in the control unit 40 stores the rectangular wave energization pattern in a format such as that shown in Figure 4. In Figure 4, "1" represents on, "0" represents off, and "P" represents PWM.

[0058] As mentioned above, there are three possible combinations that constitute a square wave current pattern: (1) to (3) below. (1) First state: In one of the bridge circuits, either the U-phase bridge circuit, the V-phase bridge circuit or the W-phase bridge circuit, the high-side switching element is continuously turned on and the low-side switching element is continuously turned off. (2) Second state: In any of the bridge circuits, including the U-phase bridge circuit, V-phase bridge circuit, and W-phase bridge circuit, both the high-side and low-side are continuously turned OFF (OFF phase). (3) Third state: In one of the bridge circuits, either the U-phase bridge circuit, the V-phase bridge circuit, or the W-phase bridge circuit, one of the switching elements on the high-side or low-side is on, and the other switching element is controlled to be on or off at a constant period (PWM controlled state) ("PWM").

[0059] In this way, the drive control unit 43 controls the conduction (energy supply) of the switching elements 51a to 51f in square wave drive using the square wave energization pattern described above.

[0060] As shown in Figure 3, in square wave driving, among the U-phase bridge circuit, V-phase bridge circuit, and W-phase bridge circuit, the first bridge circuit is in a state where both the high-side and low-side are continuously turned off (OFF phase), the second bridge circuit is in a state where the high-side switching element is continuously turned on and the low-side switching element is continuously turned off, and the third bridge circuit is in a state where it is controlled to be turned on or off at a constant period (PWM phase). For example, during period C' of Stage 1, the U-phase bridge circuit is in the OFF phase, the V-phase bridge circuit is in the PWM phase, and the W-phase bridge circuit has the high-side switching element continuously turned on and the low-side switching element continuously turned off. Furthermore, for example, during period C' of stage 2, the U-phase bridge circuit is in the PWM phase, the V-phase bridge circuit is in the OFF phase, and the W-phase bridge circuit has the high-side switching element continuously turned on and the low-side switching element continuously turned off. Furthermore, for example, during the C' phase of Stage 3, the U-phase bridge circuit is in the PWM phase, the V-phase bridge circuit has the high-side switching element continuously on and the low-side switching element continuously off, and the W-phase bridge circuit is in the OFF phase. Furthermore, for example, if any of the U-phase, V-phase, or W-phase bridge circuits is in the PWM phase, then the high-side and low-side switching elements of the bridge circuit in the PWM phase are input with an inversely phased PWM signal. Specifically, for example, during period C' of stage 1, the V-phase bridge circuit is in the PWM phase, and the V-phase bridge circuit is input with an inversely phased PWM signal such that when the high-side switching element is on, the low-side switching element is turned off, and when the high-side switching element is off, the low-side switching element is turned on.

[0061] Thus, in square wave driving, there is an OFF phase in which both the high-side switching element and the low-side switching element are turned OFF. For example, during period C' of Stage 1 in Figure 3, both the high-side and low-side switching elements of the U-phase (switching elements 51a and 51d) are OFF. Similarly, during period C' of Stage 2, both the high-side and low-side switching elements of the V-phase (switching elements 51b and 51e) are OFF. Furthermore, during period C' of Stage 3, both the high-side and low-side switching elements of the W-phase (switching elements 51c and 51f) are OFF. Thus, during periods when both the high-side and low-side switching elements of any of the bridge circuits (U-phase, V-phase, or W-phase) are OFF, two-phase power is supplied.

[0062] It should be noted that two-phase energization is not limited to period C' in each stage. For example, during period B' in stage 1, the high-side switching element 51a of the U phase is "ON" and the low-side switching element 51d is "OFF". Also, the high-side switching element 51c of the W phase is "ON" and the low-side switching element 51f is "OFF". Therefore, nodes N1 and N3 are at the same potential, no current flows through the coil between nodes N1 and N3, and two-phase energization occurs.

[0063] With square wave drive, higher output can be obtained compared to free-less drive. However, because square wave drive uses two-phase current, the braking force is weaker compared to free-less drive.

[0064] Next, we will explain free-response driving. There are two methods for controlling the free-resistance energization pattern used in free-resistance drive:

[0065] The first method of free-response power supply involves replacing the OFF phase period in square wave drive with a PWM phase with an intermediate duty cycle (e.g., 50% duty cycle). The second method of free-response power supply involves replacing the OFF phase period in square wave drive with a PWM phase with a duty cycle of half the specified duty cycle.

[0066] In the drive and energization using the free-resistance energization pattern of the first method, the drive is performed in the following three states (4) to (6).

[0067] (4) Fourth state: The state is PWM controlled by a PWM signal with the maximum duty cycle (MAX DUTY) (hereinafter referred to as the "PL" state). (5) Fifth state: The state is PWM controlled by a PWM signal with the minimum duty cycle (MIN DUTY) (hereinafter referred to as the "PS" state). (6) Sixth state: The state is controlled by a PWM signal with a duty cycle between the maximum duty cycle and the minimum duty cycle (Duty=50%) (hereinafter referred to as the "PM" state).

[0068] In the free-resist current pattern, the timing at which the U-phase, V-phase, and W-phase windings (21u, 21v, 21w) enter the PM state is the same as the timing at which the U-phase, V-phase, and W-phase windings (21u, 21v, 21w) enter the OFF-phase coil in the square wave current pattern.

[0069] In the free-energy pattern using the first method, the OFF phase period in square wave driving is replaced with a PWM phase with an intermediate duty cycle. The PWM signal with the indicated duty cycle is then split into a PWM signal with the maximum duty cycle and a PWM signal with the minimum duty cycle, such that the PWM signal with the intermediate duty cycle becomes the midpoint.

[0070] In this embodiment, the intermediate duty cycle is 50%. The maximum duty cycle is the intermediate duty cycle plus half of the externally inputted instruction duty cycle. The minimum duty cycle is the intermediate duty cycle minus half of the instruction duty cycle.

[0071] For example, if the instructed duty cycle is 80%, the intermediate duty cycle is pre-set to 50%, so the maximum duty cycle is (50 + 80 ÷ 2) = 90%, and the minimum duty cycle is (50 - 80 ÷ 2) = 10%. The instructed duty cycle is assumed to be pre-stored by the user in the ROM (not shown) of the control unit 40. Here, the low-side switching elements 51d to 51f receive a PWM signal that is in the opposite phase to the PWM signal input to the high-side switching elements 51a to 51c.

[0072] Figure 5 shows an example of a free-resist current flow pattern for the first method. Figure 5 shows the correspondence between the position detection signals (Hu, Hv, Hw) and the energization patterns of each switching element 51a to 51f, with the horizontal axis representing the electrical angle.

[0073] The example of energization control shown in Figure 5 is for a case where the advance angle is 20 degrees and the energization angle is 130 degrees. The energization pattern is a combination of the following states in which each switching element 51a to 51f is driven: a state in which it is driven by a PWM signal with the maximum duty cycle (PWM phase (MAX DUTY)) (4th state), a state in which it is driven by a PWM signal with a duty cycle of 50% (PWM phase (DUTY=50)) (6th state), and a state in which it is driven by a PWM signal with the minimum duty cycle (PWM phase (MIN DUTY)) (5th state).

[0074] Each stage from 1 to 6 is further divided into sections A, B, and C. Each section A, B, and C has its own set energization pattern. The duration (electrical angle) of each section A, B, and C changes depending on the advance angle and the energization angle.

[0075] In the PWM-controlled state, each switching element 51a to 51f repeatedly switches between ON and OFF, so the waveform is actually a rectangular wave with multiple peaks and valleys. However, for convenience, the ON / OFF states of each switching element 51a to 51f are not explicitly stated, and the term "PWM phase" is used. In Figure 5, the "PL" state is denoted as "PWM phase (MAX Duty)", the "PS" state as "PWM phase (MIN Duty)", and the "PM" state as "PWM phase (Duty=50)".

[0076] For example, in stage 1, which is enclosed by hole edge HE1 and hole edge HE2, the energizing pattern in section A is such that the switching elements 51a to 51f are in the combinations of "PL", "PL", "PS", "PS", "PM", and "PM", respectively. The energizing pattern in section B is such that the switching elements 51a to 51f are in the combinations of "PL", "PL", "PS", "PS", "PL", and "PL", respectively. Also, the energizing pattern in section C is such that the switching elements 51a to 51f are in the combinations of "PM", "PM", "PS", "PS", "PL", and "PL", respectively.

[0077] Furthermore, Figure 6 is a table summarizing an example of the free-resistance energizing pattern of the first method shown in Figure 5. The ROM (not shown) in the control unit 40 stores the free-resistance energizing pattern in a format such as that shown in Figure 6.

[0078] In free-response drive systems, even at timings where the motor would be turned off with square wave current flow, PWM control can be used to smooth the current waveform during commutation, resulting in quieter operation (reduced motor noise).

[0079] Furthermore, in free-response drive, at the timing when the square wave drive is OFF, a PWM drive with a duty cycle of 50% is used. As a result, three phases of power are supplied, and the braking force against loads in the same direction as the motor's rotation is greater compared to the case of square wave drive. This will be explained with reference to Figures 7 and 8.

[0080] Figure 7 shows the current flow during the period when the U-phase switching elements 51a and 51d are OFF in the square wave drive. As shown in Figure 7, during the period when both the high-side and low-side switching elements 51a and 51d of the U-phase are OFF, in the W-phase the high-side switching element 51c is continuously ON and the low-side switching element 51f is continuously OFF, while in the V-phase the switching elements 51b and 51e are alternately turned ON or OFF by the PWM signal of the indicated duty cycle (see period C' of stage 1 in the square wave drive method in Figure 3).

[0081] Here, the instruction PWM signal supplied to the gates of the V-phase switching elements 51b and 51e causes the switching elements 51b and 51e to alternately turn on and off, resulting in a current flowing through the windings (21u, 21v, 21w) of the stator 21 according to the pulse width. That is, when the high-side switching element 51b is on and the low-side switching element 51e is off, no current flows from the W-phase switching element 51c to the V-phase switching element 51e. When the instruction PWM signal turns the high-side switching element 51b off and the low-side switching element 51e on, current flows from the W-phase switching element 51c to the V-phase switching element 51e. As a result, a magnetic flux corresponding to the pulse width of the instruction PWM signal is generated from the windings (21u, 21v, 21w). When current flows from the W-phase switching element 51c to the V-phase switching element 51e, as shown in Figure 7, the U-phase high-side and low-side switching elements 51a and 51d are both "OFF". Therefore, no current flows from the W-phase switching elements 51c and 51f to the U-phase switching elements 51a and 51b. Thus, in square wave drive, only the W-phase and V-phase are energized.

[0082] In contrast, as shown in Figure 8, in the free-response drive method, during the period when the U-phase switching elements 51a and 51d are "OFF" in the square wave drive, the U-phase high-side and low-side switching elements 51a and 51d are alternately turned on / off by pulses with a duty cycle of 50% (see period C in Stage 1 of the square wave drive method in Figure 5). A pulse signal with a duty cycle of 50% corresponds to half the voltage in analog value. That is, if the H level is, for example, 14V, the connection point of the U-phase high-side and low-side switching elements 51a and 51e corresponds to 7V in analog value. Therefore, a current corresponding to a potential difference of (14V - 7V) flows from the W-phase switching element 51c towards the connection point of the switching elements 51a and 51e. Therefore, as shown in Figure 8, when the high-side switching element 51b is turned off and the low-side switching element 51e is turned on by the instruction PWM signal, current flows from the W-phase switching element 51c to the V-phase switching element 51e. At the same time, current also flows from the W-phase switching element 51c towards the connection point of switching elements 51a and 51d. Thus, in free-less drive, three phases of power are supplied: W-phase, U-phase, and V-phase.

[0083] As described above, in square wave drive, there is a period when one of the three phases (U, V, and W) is OFF, resulting in two-phase energization. In contrast, in free-less drive, the period when the OFF phase is used in square wave drive is replaced by a PWM phase with an intermediate duty cycle, resulting in three-phase energization. With two-phase energized square wave drive, the output can be increased, but since it is driven by two of the U, V, and W phases, the braking force that brakes the rotation of the rotor 22 is weaker compared to free-less drive which uses three-phase energization. In contrast, with three-phase energized free-less drive, the braking force that brakes the rotation of the rotor 22 is stronger compared to two-phase energized square wave drive.

[0084] Next, we will explain the free-restraint energization pattern using the second method. In the free-restraint energization pattern using the second method, the drive is performed in the following three states: (7) to (9).

[0085] (7) Seventh state: Of the switching elements 51a to 51f, the high-side switching elements are continuously turned on, and the low-side switching elements are continuously turned off. (8) Eighth state: The switching elements 51a to 51f are in a state where they are PWM controlled by a PWM signal of an externally inputted instruction duty cycle (hereinafter referred to as the "P1" state). (9) Ninth state: The switching elements 51a to 51f are in a state where they are PWM controlled by a PWM signal with a duty cycle of 1 / 2 of the instructed duty cycle input from an external source (hereinafter referred to as the "P2" state).

[0086] In the free-energy pattern using the second method, the OFF phase period in square wave driving is replaced with a PWM phase with a duty cycle of half the specified duty cycle.

[0087] In this embodiment, for example, if the indicated duty cycle is 80%, the duty cycle in the eighth state will be 80%, and the duty cycle in the ninth state will be 80 ÷ 2 = 40%. The instructed duty cycle is to be stored in advance by the user in the ROM (not shown) of the control unit 40.

[0088] Figure 9 shows an example of a free-resist current flow pattern for the second method. Figure 9 shows the correspondence between the position detection signals (Hu, Hv, Hw) and the energization patterns of each switching element 51a to 51f, with the horizontal axis representing the electrical angle.

[0089] The example of energization control shown in Figure 9 is for a case where the advance angle is 20 degrees and the energization angle is 130 degrees. The energization pattern is a combination of one of the following: a state in which the high-side switching element of each switching element 51a to 51f is continuously turned on and the low-side switching element is continuously turned off (7th state); a state in which the system is PWM controlled by a PWM signal with a duty cycle of half the instructed duty cycle (PWM 1 / 2DUTY) (9th state); or a state in which the system is PWM controlled by a PWM signal with an instructed duty cycle (PWM instructed DUTY) (8th state). Each stage 1 to 6 is further divided into sections A", B", and C".

[0090] For example, in stage 1 enclosed by hole edge HE1 and hole edge HE2, the energizing pattern in section A" is such that the switching elements 51a to 51f are in the combinations of "1", "0", "P1", "P1", "P2", and "P2", respectively. The energizing pattern in section B" is such that the switching elements 51a to 51f are in the combinations of "1", "0", "P1", "P1", "1", and "0", respectively. Also, the energizing pattern in section C" is such that the switching elements 51a to 51f are in the combinations of "P2", "P2", "P1", "P1", "1", and "0", respectively.

[0091] Furthermore, Figure 10 is a table summarizing an example of the freeless energization pattern of the second method shown in Figure 9. The ROM (not shown) in the control unit 40 stores the freeless energization pattern in a format such as that shown in Figure 10. In Figure 10, "P1" represents the eighth state controlled by a PWM signal with an externally input instruction duty cycle, "P2" represents the ninth state controlled by a PWM signal with a duty cycle of half the instruction duty cycle, "1" represents on, and "0" represents off.

[0092] Note that the above example of power supply control is for a case where the advance angle is 20 degrees and the power supply angle is 130 degrees. If the advance angle is 20 degrees and the power supply angle is 140 degrees, the power supply pattern will be as follows.

[0093] Figure 11 shows the energization pattern when a square wave drive is performed with an advance angle of 20 degrees and an energization angle of 140 degrees. Figure 12 shows the energization pattern when the first type of free-less drive is performed with an advance angle of 20 degrees and an energization angle of 140 degrees. Figure 13 shows the energization pattern when the second type of free-less drive is performed with an advance angle of 20 degrees and an energization angle of 140 degrees.

[0094] Next, the control of the motor 2 in this embodiment will be described. As mentioned above, in this embodiment, the load state determination unit 41 of the control unit 40 in Figure 2 acquires a value determined according to the load, and the load integrated value obtained by accumulating these values ​​is used as an index value to determine whether the load on the motor 2 is in a high load state or a low load state.

[0095] In this embodiment, the value determined according to the load is, for example, the vehicle speed. The load state determination unit 41 generates a load integrated value by integrating the values ​​obtained from this vehicle speed, and uses this load integrated value as an index value to determine whether the state is high load or low load.

[0096] Figure 14 shows an example of the drive mode switching operation in the motor drive unit 200 according to the first embodiment. In the following example, the vehicle speed is used as the value determined according to the load on the motor 2.

[0097] In Figure 14, the horizontal axis represents time, and the vertical axis represents vehicle speed. Waveform W1 shows an example of the change in the integrated load value over time. The integrated load value is calculated by accumulating values ​​obtained from vehicle speed and serves as an indicator for determining whether the vehicle is in a high-load or low-load state. Periods TR1 and TR3 represent periods in low-load mode, and period TR2 represents periods in high-load mode.

[0098] Threshold Vth1 (first threshold) is the threshold for switching from low-load mode to high-load mode. Threshold Vth2 (second threshold) is the threshold for switching from high-load mode to low-load mode.

[0099] For example, as the vehicle speed increases, the integrated load value increases, as shown in Figure 14. When the integrated load value exceeds the threshold Vth1, the drive control unit 43 considers that the state has changed from low load to high load and switches from low load mode to high load mode. Conversely, as the vehicle speed decreases, the integrated load value decreases. When the integrated load value falls below the threshold Vth2, the drive control unit 43 considers that the state has changed from high load to low load and switches from high load mode to low load mode. Here, the threshold Vth1 used to determine when a system has switched from a low-load state to a high-load state is greater than the threshold Vth2 used to determine when a system has switched from a high-load state to a low-load state (Vth1 ≥ Vth2), and is, for example, within the range of 1.1 to 6.6 times.

[0100] Thus, in this embodiment, the relationship between the threshold Vth1 used to determine when switching from a low-load state to a high-load state and the threshold Vth2 used to determine when switching from a high-load mode to a low-load mode is set to Vth1 ≥ Vth2. This prevents the drive mode from changing frequently depending on the vehicle speed.

[0101] Furthermore, in this embodiment, a value is calculated by integrating values ​​determined according to the load on the motor 2, and this integrated load value is used as an index value to determine whether the load is large or not. Therefore, malfunctions due to temporary increases or decreases in load or measurement errors can be prevented.

[0102] Figure 15 is a flowchart showing an example of the switching operation of the drive mode of the motor drive unit 200 according to the first embodiment. In this example, the vehicle speed is used as the value determined according to the load on the motor 2.

[0103] (Step S101) The vehicle speed detection unit 42 of the control unit 40 detects the vehicle speed based on the vehicle speed signal output from the ECU 4.

[0104] (Step S102) Next, the drive control unit 43 of the control unit 40 determines whether the drive mode of the motor 2 is the low-load mode. If the drive mode is the low-load mode (Step S102: Yes), the drive control unit 43 proceeds to step S103. If the drive mode is not the low-load mode (Step S102: No), the drive control unit 43 proceeds to step S107.

[0105] (Step S103) The load state determination unit 41 accumulates a value corresponding to the vehicle speed and determines whether this accumulated load value (index value) is greater than or equal to the threshold Vth1. If the accumulated load value (index value) is greater than or equal to the threshold Vth1 (Step S103: Yes), the load state determination unit 41 proceeds to step S104. If the accumulated load value (index value) is less than the threshold Vth1 (Step S103: No), the load state determination unit 41 proceeds to step S111.

[0106] (Step S104) The drive control unit 43 switches from low load mode to high load mode.

[0107] (Step S105) The load state determination unit 41 initializes the accumulated load value (index value) it has generated (returns it to "0").

[0108] (Step S106) The drive control unit 43 deactivates the energy mode (Step S106). Here, the energy mode is a protection mode that limits the output when the load cumulative value (index value) becomes very large (when the load becomes large). After the processing in Step S106, the drive control unit 43 proceeds to the processing in Step S111.

[0109] (Step S107) The load state determination unit 41 determines whether the cumulative load value (index value) is less than or equal to the threshold Vth2. If the cumulative load value (index value) is less than or equal to the threshold Vth2 (Step S107: YES), the load state determination unit 41 proceeds to step S108. If the cumulative load value (index value) is greater than the threshold Vth2 (Step S107: No), the load state determination unit 41 proceeds to step S111.

[0110] (Step S108) The drive control unit 43 switches from high load mode to low load mode.

[0111] (Step S109) The load state determination unit 41 initializes the load cumulative value (index value) (returns it to "0").

[0112] (Step S110) The drive control unit 43 cancels the energy mode (Step S110). After the processing in Step S110, the drive control unit 43 proceeds to the processing in Step S111.

[0113] (Step S111) The drive control unit 43 drives the motor 2 according to the drive mode and returns the process to step S101.

[0114] Figure 16 is a flowchart showing the motor drive process according to the drive mode in step S111. (Step S201) The drive control unit 43 acquires the setting status of the drive mode of the motor 2.

[0115] (Step S202) The drive control unit 43 determines whether or not it is set to high load mode. If it is not set to high load mode (Step S202: No), the drive control unit 43 proceeds to step S203, and if it is set to high load mode (Step S202: Yes), the process proceeds to step S204.

[0116] (Step S203) If it is determined in step S202 that the high load mode is not set (Step S202: No), the wiper drive mode is set to low load mode. In this case, the drive control unit 43 drives the motor 2 using a free-response drive method.

[0117] (Step S204) If it is determined in step S202 that the system is set to high load mode (Step S202: Yes), the drive control unit 43 determines whether or not the wiper arm 12 is being moved in the return direction. If the drive control unit 43 is not moving the wiper arm 12 in the return direction (Step S204: No), the process proceeds to step S205, and if the wiper arm 12 is being moved in the return direction (Step S204: Yes), the process proceeds to step S206.

[0118] (Step S205) If it is determined that the wiper arm 12 has not been moved in the return direction (Step S204: No), the wiper arm 12 is moved in the forward direction. When the wiper arm 12 is moved in the forward direction, the direction of the airflow is the same as the direction of movement of the wiper arm 12, so it becomes a load that applies torque in the same direction as the rotation direction of the motor 2. In this case, the drive control unit 43 drives the motor 2 in a free-response drive manner so that sufficient braking force is obtained.

[0119] (Step S206) When the wiper arm 12 is moved in the return direction (Step S204: Yes), the direction of the airflow becomes opposite to the direction of movement of the wiper arm 12, resulting in a load that applies torque in the opposite direction to the rotation direction of the motor 2. In this case, the drive control unit 43 drives the motor 2 using a square wave drive method to obtain sufficient driving force.

[0120] As explained above, in this embodiment, when the wiper arm 12 is moved in the return direction, a torque is applied in the opposite direction to the rotation direction of the motor 2, so the motor 2 is driven using a square wave drive method to obtain sufficient driving force. Also, when the wiper arm 12 is moved in the forward direction, a torque is applied in the same direction as the rotation direction of the motor 2, so the motor 2 is driven using a free-response drive method to obtain sufficient braking force. As a result, the wiper arm 12 can be controlled to move at a predetermined speed in both the forward and return directions.

[0121] In the above embodiment, the motor 2 is driven using a free-response drive method when a torque is applied in the same direction as the rotation direction of the motor 2. However, the motor 2 can be driven in any way as long as it can be energized in three phases. For example, as shown in Figure 17, the motor 2 may be driven with a sinusoidal wave, or as shown in Figure 18, it may be driven by superimposing a third harmonic.

[0122] Furthermore, in the above embodiment, vehicle speed is used as the value determined according to the load on motor 2. However, any value that reflects the load applied to motor 2 may be used as the value determined according to the load on motor 2, such as the rotational speed of motor 2, duty cycle, power supply voltage, etc. Alternatively, the rotational speed of motor 2, duty cycle, power supply voltage, vehicle speed, etc. may be combined as appropriate to determine the load.

[0123] Furthermore, the motor control method of the present invention can be applied not only to wiper motor control but also to the control of other motors. For example, the motor control method of the present invention can be applied to the driving of motors for power windows and sunroofs. Specifically, when opening a window using a power window while driving, the direction of window movement and the direction of wind pressure are the same, so the motor is driven using a three-phase free-response drive system to obtain sufficient braking force, and when closing the window, the motor is driven using a square wave drive system to obtain sufficient output. Similarly, when opening a sunroof while driving, the direction of sunroof movement and the direction of wind pressure are the same, so the motor is driven using a three-phase free-response drive system to obtain sufficient braking force, and when closing the sunroof, the direction of sunroof movement and the direction of wind pressure are opposite, so the motor is driven using a square wave drive system to obtain sufficient output.

[0124] As described above, according to the embodiment of the present invention, the motor 2 is driven with three-phase power during the period when the wiper arm 12 is moved in the forward direction, and the motor 2 is driven with two-phase power during the period when the wiper arm 12 is moved in the return direction, thereby allowing the motor to be appropriately controlled according to the load generated in the forward direction and the load generated in the return direction.

[0125] Furthermore, this makes motor damage less likely, thus contributing to Goal 7, "Ensure access to affordable, reliable, sustainable, and modern energy for all," and Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation," both of which are led by the United Nations.

[0126] The wiper drive device 100 in the above-described embodiment may be implemented in whole or in part by a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. The term "computer system" here includes hardware such as an OS and peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into a computer system. Furthermore, the term "computer-readable recording medium" may also include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside a computer system that acts as a server or client in such cases. The program may be for implementing a part of the aforementioned function, or it may be a program that can implement the aforementioned function in combination with a program already recorded in the computer system, or it may be implemented using a programmable logic device such as an FPGA.

[0127] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention. [Explanation of Symbols]

[0128] 2...Motor, 12...Wiper arm, 21...Stator, 22...Rotor, 40...Control unit, 41...Load state determination unit, 42...Vehicle speed detection unit, 43...Drive control unit, 50...Inverter, 51a~51f...Switching elements

Claims

1. A motor for driving the wiper arm of a vehicle, A load state determination unit generates an index value for determining the load state on the motor, and determines whether the load state on the motor is low load or high load based on the index value. The motor is driven by a drive control unit that switches between three-phase and two-phase energization, The drive control unit, If it is determined that the load condition on the motor is a high load condition, During the period in which the wiper arm is moved in the forward direction, which is the same direction as the airflow relative to the vehicle, the motor is driven with a three-phase current that generates a greater braking force than the two-phase current. During the period when the wiper arm is moved in the return direction, which is the opposite direction to the direction of the airflow, the motor is driven by the two-phase energization. Wiper drive mechanism.

2. The load state determination unit sets a first threshold for detecting a change from a low load state to a high load state, and a second threshold for detecting a change from a high load state to a low load state. The first threshold is set to be greater than the second threshold. The wiper drive device according to claim 1.

3. The wiper drive device according to claim 1, wherein the load state determination unit generates a value obtained by accumulating values ​​determined according to the load, as an index value for determining the load state on the motor.

4. The wiper drive device according to claim 3, wherein the value determined according to the load is the vehicle speed.

5. A wiper driving method for driving a motor that drives a wiper arm of a vehicle, A step of generating an index value for determining the load state on the motor, and determining whether the load state on the motor is a low load state or a high load state based on the index value, If it is determined that the load on the motor is a high load, the motor is driven with three-phase power, which generates a greater braking force than the two-phase power, during the period when the wiper arm is moved in the forward direction, which is the same direction as the airflow relative to the vehicle, and the motor is driven with two-phase power, during the period when the wiper arm is moved in the return direction, which is the opposite direction to the airflow. A wiper drive method including the following.

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