Wiper drive

Abstract

A wiper drive device comprises: a circuit (37, 47) connected to a wiper motor (100); a driving element (39, 49) configured to apply a voltage to the wiper motor via the circuit by being turned on, so as to rotate the wiper motor; a braking element (57) configured to brake the wiper motor by being turned on when the driving element is turned off, so as to flow a current corresponding to the rotational energy of the wiper motor; and a determining unit (60) configured to determine that the braking element is abnormal when a time period from when the wiper motor is braked to when the potential (V_Lo, V_Hi) of the circuit becomes equal to or less than a predetermined threshold potential (V_Lo_th, V_Hi_th) is longer than a predetermined value, the predetermined value being a time period when the braking element is normal.

Description

Technical Field

[0001] The present disclosure relates to a wiper driving device. Background Art

[0002] Typically, as described in JP2002-37032A, a wiper control device includes a wiper motor, a first semiconductor switching element, a second semiconductor switching element, and a controller. The first semiconductor switching element switches the power supply to the wiper motor on and off. The second semiconductor switching element completes a closed circuit, which, when the power supply to the wiper motor is disconnected, causes reverse current to flow through the wiper motor for braking. The controller controls the first and second semiconductor switching elements. Summary of the Invention

[0003] According to the inventors' research, a wiper control device can detect abnormalities such as failure to turn on the second semiconductor switching element by detecting the voltage applied to the wiper motor during braking. However, because the wiper motor has relatively low impedance, the voltage applied to the wiper motor when it is stopped is the same as the voltage applied to ground and other components connected to the wiper motor. Therefore, the change in the voltage applied to the wiper motor when it is stopped is relatively small. Simply detecting the voltage applied to the wiper motor when it is stopped and comparing the detected voltage with a threshold value makes it difficult to detect abnormalities in the semiconductor switching element.

[0004] An object of the present disclosure is to provide a wiper driving device capable of easily detecting an abnormality in a component that brakes a wiper motor.

[0005] According to a first aspect, a wiper drive device includes a circuit, a driving element, a braking element, and a determination unit. The circuit is connected to a wiper motor; the driving element is configured to apply a voltage to the wiper motor via the circuit by being turned on, thereby rotating the wiper motor; the braking element is configured to brake the wiper motor by being turned on when the driving element is turned off, thereby causing a current corresponding to the rotational energy of the wiper motor to flow; and the determination unit is configured to determine that the braking element is abnormal if a period of time from when the wiper motor is braked to when the potential of the circuit becomes equal to or less than a predetermined threshold potential is longer than a predetermined value, the predetermined value being a period of time when the braking element is normal.

[0006] Thus, the abnormality of the brake element is determined based on the time period until the potential of the line becomes equal to or lower than the predetermined threshold potential. Therefore, it is easier to determine whether the brake element is abnormal than in a case where the abnormality of the brake element is determined based solely on the potential of the line connected to the wiper motor.

[0007] According to a second aspect, a wiper drive device includes a circuit, a driving element, a braking element, and a determination unit. The circuit is connected to a wiper motor; the driving element is configured to apply a voltage to the wiper motor via the circuit by being turned on, thereby rotating the wiper motor; the braking element is configured to brake the wiper motor by being turned on when the driving element is turned off, thereby flowing a current corresponding to the rotational energy of the wiper motor; and the determination unit is configured to determine that the braking element is abnormal when, after braking the wiper motor, the potential drop per unit time of the circuit is equal to or less than a predetermined value, the predetermined value being less than the potential drop when the braking element is normal.

[0008] Thus, the abnormality of the brake element is determined based on the potential drop per unit time of the line. Therefore, it is easier to determine whether the brake element is abnormal than when the abnormality of the brake element is determined based only on the potential of the line connected to the wiper motor.

[0009] The reference numerals attached to each component or the like represent an example of a corresponding relationship between the component or the like and a specific component or the like described in the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 FIG. 1 is a configuration diagram of a wiper driving system using a wiper driving device according to an embodiment.

[0011] Figure 2 FIG2 is a timing chart showing the processing when the wiper operation state is set to the intermittent mode.

[0012] Figure 3 The following is a timing chart showing that the intelligent power device (IPD) in the wiper drive device is in an abnormal state. DETAILED DESCRIPTION

[0013] Hereinafter, the embodiments will be described with reference to the accompanying drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals, and their description will be omitted.

[0014] The wiper drive device 30 of the present embodiment is used in a wiper drive system 1 of a vehicle. First, the wiper drive system 1 will be described.

[0015] like Figure 1 As shown, the wiper drive system 1 includes a motor unit 10, a motor ground 12, a motor battery 14, a control battery 16, a motor fuse 18, and a control fuse 20. The wiper drive system 1 also includes a wiper switch 22, a wiper drive device 30, a first ground 81, and a second ground 82.

[0016] The motor unit 10 includes a wiper motor 100 and a cam switch 102. The wiper motor 100 includes a Hi terminal 104, a Lo terminal 106, and a GND terminal 108. The Hi terminal 104 and the Lo terminal 106 are connected to the wiper drive device 30 to be described later. The GND terminal 108 is connected to the motor ground 12. When the Hi terminal 104 is energized, the wiper motor 100 rotates at a relatively high speed. When the Lo terminal 106 is energized, the wiper motor 100 rotates at a speed lower than when the Hi terminal 104 is energized. The rotation of the wiper motor 100 rotates the wipers (not shown) of the vehicle.

[0017] The cam switch 102 is turned on and off by the rotation of the wiper motor 100. When the cam switch 102 is off, the wiper drive device 30 (to be described later) is electrically connected to the GND terminal 108 and the motor ground 12. In addition, when the cam switch 102 is on, the wiper drive device 30 is electrically disconnected from the GND terminal 108 and the motor ground 12.

[0018] The motor battery 14 and the control battery 16 are secondary batteries, such as lithium-ion batteries, nickel metal hydride batteries, and lead-acid batteries. The voltage of the motor battery 14 and the control battery 16 is, for example, 12 V. One end of the motor battery 14 and one end of the control battery 16 are connected to ground (not shown).

[0019] One end of the motor fuse 18 is connected to the other end of the motor battery 14 . The other end of the motor fuse 18 is connected to the wiper driving device 30 . The motor fuse 18 prevents an overcurrent from flowing from the motor battery 14 to the wiper motor 100 via the wiper driving device 30 .

[0020] One end of the control fuse 20 is connected to the other end of the control battery 16. The other end of the control fuse 20 is connected to the wiper driving device 30. The control fuse 20 prevents an overcurrent from flowing from the control battery 16 to the IPD 57 and the controller 60 of the wiper driving device 30.

[0021] The wiper switch 22 is operated by an operator to output a signal to the controller 60 of the wiper driving device 30 , thereby setting the operation state of the wiper to one of a continuous high-speed mode, a continuous low-speed mode, and an intermittent mode.

[0022] The wiper drive device 30 controls the wiper motor 100 by controlling the voltage applied to the wiper motor 100. Thus, the wiper drive device 30 controls the drive of the wiper connected to the wiper motor 100. Specifically, the wiper drive device 30 includes a first motor diode 31, a second motor diode 32, a motor power terminal 33, a Hi relay 35, a Hi line 37, and a Hi field effect transistor (FET) 39. The wiper drive device 30 includes a Lo relay 45, a Lo line 47, a Lo FET 49, a control diode 51, a control power terminal 53, a buck converter 55, an IPD 57, and a controller 60. Note that IPD is an abbreviation for Intelligent Power Device.

[0023] The anode of the first motor diode 31 is connected to the other end of the motor fuse 18 via the motor power terminal 33. The cathode of the first motor diode 31 is connected to one end of the Hi coil 351 of the Hi relay 35. The first motor diode 31 suppresses current from flowing from the wiper drive device 30 to the motor battery 14.

[0024] The anode of the second motor diode 32 is connected to the other end of the motor fuse 18 via the motor power supply terminal 33. The cathode of the second motor diode 32 is connected to one end of the Hi coil 351 of the Hi relay 35. The second motor diode 32 prevents current from flowing from the wiper drive unit 30 to the motor battery 14. The second motor diode 32 is connected in parallel with the first motor diode 31. Therefore, even if one of the first motor diode 31 and the second motor diode 32 fails, voltage can be supplied from the motor battery 14 to the Hi coil 351 and the Lo coil 451.

[0025] The Hi relay 35 includes a Hi coil 351 and a Hi switch 352. One end of the Hi coil 351 is connected to the cathode of the first motor diode 31 and the cathode of the second motor diode 32. The Hi switch 352 is turned on and off by the electromagnetic force generated by the current flowing through the Hi coil 351. One end of the Hi switch 352 is connected to the other end of the motor fuse 18 via the motor power terminal 33. The other end of the Hi switch 352 is connected to the Hi terminal 104 via the Hi line 37.

[0026] The Hi FET 39 corresponds to a driving element such as an N-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). The drain of the Hi FET 39 is connected to the other end of the Hi coil 351. The source of the Hi FET 39 is connected to the first ground 81. The gate of the Hi FET 39 is connected to the controller 60.

[0027] The Lo relay 45 includes a Lo coil 451 and a Lo switch 452. One end of the Lo coil 451 is connected to the cathode of the first motor diode 31 and the cathode of the second motor diode 32. The Lo switch 452 is turned on and off by the electromagnetic force generated by the current flowing through the Lo coil 451. One end of the Lo switch 452 is connected to the other end of the motor fuse 18 via the motor power supply terminal 33. The other end of the Lo switch 452 is connected to the Lo terminal 106 via the Lo line 47.

[0028] The Lo FET 49 corresponds to a driving element such as an N-channel MOSFET, etc. The drain of the Lo FET 49 is connected to the other end of the Lo coil 451. The source of the Lo FET 49 is connected to the first ground 81. The gate of the Lo FET 49 is connected to the controller 60.

[0029] The anode of the control diode 51 is connected to the other end of the control fuse 20 via the control power supply terminal 53. The cathode of the control diode 51 is connected to the step-down converter 55 and the IPD 57. The control diode 51 suppresses current from flowing from the wiper drive device 30 to the control battery 16.

[0030] The step-down converter 55 is connected to the cathode of the control diode 51 and the controller 60. The step-down converter 55 steps down the 12 V voltage supplied to the step-down converter 55 from the control battery 16 via the control fuse 20, the control power supply terminal 53, and the control diode 51, to, for example, 5 V. The step-down converter 55 then supplies the stepped-down voltage to the controller 60.

[0031] IPD 57 corresponds to a braking element and includes a FET, a protection circuit, and the like. The FET of IPD 57 is, for example, an N-channel MOSFET. The drain of the FET of IPD 57 is connected to Lo line 47. The source of the FET of IPD 57 is connected to second ground 82. The gate of the FET of IPD 57 is connected to controller 60. The protection circuit of IPD 57 is connected to the cathode of control diode 51. The protection circuit in IPD 57 is driven by the voltage from control battery 16 to protect the FET of IPD 57.

[0032] The controller 60 corresponds to the determining unit and is primarily composed of a microcomputer. It includes a CPU, ROM (Read Only Memory), flash memory, RAM (Random Access Memory), I / O (Input / Output), a driver circuit, an A / D (Analog / Digital) converter, and a bus connecting them. The controller 60 is driven by the voltage from the step-down converter 55. By executing a program stored in the ROM, the controller 60 controls the voltage applied to the wiper motor 100 based on the signal from the wiper switch 22. This allows the wiper to operate in one of the following modes: continuous high-speed mode, continuous low-speed mode, and intermittent mode. Furthermore, by executing a program stored in the ROM, the controller 60 determines whether the FETs in the IPD 57 are abnormal based on the potentials of the Hi line 37 and the Lo line 47.

[0033] The wiper driving system 1 is configured as described above. Next, how the controller 60 controls the wiper motor 100 to change the operating state of the wiper to the continuous high speed mode, the continuous low speed mode, and the intermittent mode will be described.

[0034] (Continuous high-speed mode)

[0035] When the wiper switch 22 is operated by the operator to output a signal to the controller 60 to change the wiper operating state to continuous high-speed mode, the controller 60 changes the gate voltage level of the Hi FET 39 from a low level to a high level. Consequently, the Hi FET 39 turns on. Accordingly, current flows from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Hi coil 351, and the Hi FET 39. At this time, since current flows through the Hi coil 351, the Hi switch 352 turns on. Consequently, voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Hi switch 352, the Hi line 37, and the Hi terminal 104. Consequently, the wiper motor 100 rotates at a higher speed than when the Lo terminal 106 is energized. Consequently, the wiper (not shown) connected to the wiper motor 100 rotates at a high speed, causing the wiper operating state to change to continuous high-speed mode. At this time, the Lo FET 49 is turned off. Therefore, since no current flows through the Lo coil 451, the Lo switch 452 is opened. Likewise, the FET in the IPD 57 is turned off.

[0036] (Continuous low speed mode)

[0037] When the wiper switch 22 is operated by the operator to output a signal to the controller 60 to change the wiper operating state to the continuous low-speed mode, the controller 60 changes the gate voltage level of the Lo FET 49 from a low level to a high level. As a result, the Lo FET 49 turns on. Accordingly, current flows from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, and the Lo FET 49. At this time, since current flows through the Lo coil 451, the Lo switch 452 is turned on. Consequently, voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47, and the Lo terminal 106. Consequently, the wiper motor 100 rotates at a speed lower than when the Hi terminal 104 is energized. Therefore, when a wiper (not shown) connected to the wiper motor 100 rotates at a low speed, the wiper operating state changes to the continuous low-speed mode. At this time, the Hi FET 39 is turned off. Therefore, since no current flows through the Hi coil 351, the Hi switch 352 is turned off. Likewise, the FET in the IPD 57 is turned off.

[0038] (Intermittent mode)

[0039] Next, we will refer to Figure 2 The timing diagram in FIG. 1 describes the intermittent mode, which is the working state of the wiper set by the controller 60 by controlling the wiper motor 100.

[0040] During the period from time t0 to time t1, when the wiper switch 22 is operated by the operator to output a signal to the controller 60 to change the operating state of the wiper to the intermittent mode, the controller 60 changes the gate voltage of the Lo FET 49 from a low level to a high level. Therefore, the Lo FET 49 is turned on. Accordingly, current flows from the motor battery 14 and through the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451 and the Lo FET 49 to the first ground 81. At this time, since the current flows through the Lo coil 451, the Lo switch 452 is turned on. Therefore, voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47 and the Lo terminal 106. Therefore, the wiper motor 100 rotates at a speed lower than when the Hi terminal 104 is energized. Therefore, the wiper (not shown) connected to the wiper motor 100 rotates at a low speed. Figure 2, the Lo FET 49 is shown as Lo_FET. The gate voltage of the Lo FET 49 is shown as Vg_Lo_FET. At this time, the controller 60 sets the voltage level of the gate voltage of the FET of the IPD 57 to a low level. Therefore, the FET of the IPD 57 is turned off. In addition, Figure 2 , the gate voltage of the FET of the IPD 57 is shown as Vg_IPD. The controller 60 sets the voltage level of the gate voltage of the HiFET 39 to a low level. Therefore, the HiFET 39 is turned off. Therefore, since no current flows through the Hi coil 351, the Hi switch 352 is turned off.

[0041] Furthermore, at this time, the rotation of the wiper motor 100 turns on the cam switch 102 . Therefore, the wiper driving device 30 is electrically disconnected from the GND terminal 108 and the motor ground 12 .

[0042] The potential of the Lo line 47 is substantially the same as the potential of the motor battery 14. Since the Hi line 37 is connected to the Lo line 47 via the wiper motor 100, the potential of the Hi line 37 is lower than the potential of the Lo line 47 due to the voltage drop caused by the wiper motor 100. Figure 2 , the potential of the Lo line 47 is represented as V_Lo, and the potential of the Hi line 37 is represented as V_Hi.

[0043] During the period from time t1 to time t2, the wiper switch 22 outputs a signal to the controller 60 to change the wiper's operating state to intermittent mode. The rotation of the wiper motor 100 switches the cam switch 102 from on to off. As a result, the wiper drive device 30 is electrically connected to the GND terminal 108 and the motor ground 12. The controller 60 then acquires the potential of the cam switch 102. Furthermore, the controller 60 determines whether the acquired potential of the cam switch 102 is the potential of the motor ground 12. Based on this determination, the controller 60 switches the Lo FET 49 from on to off and switches the FET of the IPD 57 from off to on.

[0044] However, at this time, since the potential of the cam switch 102 is not equal to the potential of the motor ground 12, the controller 60 maintains the gate voltage of the Lo FET 49 at a high level. Consequently, the Lo FET 49 is turned on. Accordingly, current flows from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, and the Lo FET 49. Since current flows through the Lo coil 451, the Lo switch 452 is turned on. Consequently, voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47, and the Lo terminal 106. Consequently, the wiper motor 100 rotates at a lower speed than when the Hi terminal 104 is energized. Consequently, the wiper (not shown) connected to the wiper motor 100 rotates at a lower speed.

[0045] The potential of the Lo line 47 is substantially the same as the potential of the motor battery 14. Furthermore, since the Hi line 37 is connected to the Lo line 47 via the wiper motor 100, the potential of the Hi line 37 is lower than that of the Lo line 47 due to a voltage drop caused by the wiper motor 100.

[0046] During the period from time t2 to time t3, the wiper switch 22 outputs a signal to the controller 60 to change the wiper operation mode to intermittent mode. Furthermore, the rotation of the wiper motor 100 turns off the cam switch 102. As a result, the wiper drive device 30 is electrically connected to the GND terminal 108 and the motor ground 12. The controller 60 then obtains the potential of the cam switch 102.

[0047] At this time, since the potential of the cam switch 102 reaches the potential of the motor ground 12, the controller 60 changes the gate voltage of the Lo FET 49 from a high level to a low level. Consequently, the Lo FET 49 is turned off. Accordingly, current does not flow from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, and the Lo FET 49. At this time, since no current flows through the Lo coil 451, the Lo switch 452 is opened. Consequently, no voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47, and the Lo terminal 106. Consequently, the potential of the Lo line 47 decreases. Since the Hi line 37 is connected to the Lo line 47 via the wiper motor 100, the potential of the Lo line 47 decreases, and thus the potential of the Hi line 37 also decreases.

[0048] At this time, the wiper motor 100 rotates due to inertia. Therefore, the wiper (not shown) connected to the wiper motor 100 rotates due to inertia.

[0049] Furthermore, at this time, the controller 60 changes the gate voltage level of the FET of the IPD 57 from a low level to a high level. Consequently, the FET of the IPD 57 changes from being off (OFF) to being on (ON). Consequently, a current corresponding to the inertial rotational energy of the wiper motor 100 flows from the wiper motor 100 to the second ground 82 via the IPD 57. Consequently, the electrical energy corresponding to the inertial rotational energy of the wiper motor 100 decreases, causing the wiper motor 100 to be braked.

[0050] During the period from time t3 to time t4, the wiper switch 22 outputs a signal to the controller 60 to change the wiper operation mode to intermittent mode. The rotation of the wiper motor 100 turns off the cam switch 102. As a result, the wiper drive device 30 is electrically connected to the GND terminal 108 and the motor ground 12. The controller 60 then obtains the potential of the cam switch 102.

[0051] At this time, since the potential of the cam switch 102 is at the motor ground 12, the controller 60 sets the gate voltage of the Lo FET 49 to a low level. Consequently, the Lo FET 49 is turned off. Consequently, no current flows from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, and the Lo FET 49. Since no current flows through the Lo coil 451 at this time, the Lo switch 452 is opened. Consequently, no voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47, and the Lo terminal 106. Consequently, the potential of the Lo line 47 decreases. Since the Hi line 37 is connected to the Lo line 47 via the wiper motor 100, the potential of the Lo line 47 decreases, and the potential of the Hi line 37 also decreases to or below the Hi predetermined threshold potential V_Hi_th. Note that the Hi predetermined threshold potential V_Hi_th is the potential of the Hi line 37 when the wiper motor 100 rotating by inertia stops, and is 1.0 V, for example.

[0052] At this time, the wiper motor 100 stops rotating, and the position of the wiper motor 100 returns to the initial position, and the position of the wiper (not shown) connected to the wiper motor 100 returns to the initial position.

[0053] Furthermore, at this time, the controller 60 maintains the gate voltage of the FET of the IPD 57 at a high level. As a result, the FET of the IPD 57 is turned on. Consequently, a current corresponding to the inertial rotational energy of the wiper motor 100 flows from the wiper motor 100 to the second ground 82 via the IPD 57. Consequently, the electrical energy corresponding to the inertial rotational energy of the wiper motor 100 decreases, causing the wiper motor 100 to be braked.

[0054] During the period from time t4 to time t5, the wiper switch 22 outputs a signal to the controller 60 to change the wiper's operating state to intermittent mode. Furthermore, since the wiper motor 100 is stopped, the cam switch 102 is turned off. This electrically connects the wiper drive 30 to the GND terminal 108 and the motor ground 12. The controller 60 then obtains the potential of the cam switch 102.

[0055] At this time, since the potential of the cam switch 102 is at the motor ground 12, the controller 60 maintains the gate voltage of the Lo FET 49 at a low level. Therefore, the Lo FET 49 is turned off. Accordingly, current does not flow from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, and the Lo FET 49. Since no current flows through the Lo coil 451 at this time, the Lo switch 452 is opened. Consequently, no voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47, and the Lo terminal 106. Consequently, the potential of the Lo line 47 drops to or below the predetermined Lo threshold potential V_Lo_th. The Hi line 37 is connected to the Lo line 47 via the wiper motor 100, and the potential of the Lo line 47 drops, causing the potential of the Hi line 37 to drop below the predetermined Hi threshold potential V_Hi_th. The Lo predetermined threshold potential V_Lo_th is the potential of the Lo line 47 when the wiper motor 100 rotating by inertia stops, and is, for example, 1.0 V.

[0056] At this time, since the wiper motor 100 stops rotating, the wiper motor 100 returns to the initial position, and the wiper (not shown) connected to the wiper motor 100 returns to the initial position.

[0057] Furthermore, at this time, the controller 60 changes the voltage level of the gate voltage of the FET of the IPD 57 from a high level to a low level, thereby turning off the FET of the IPD 57 .

[0058] After time t5, the wiper switch 22 outputs a signal to the controller 60 to change the operation state of the wiper to the intermittent mode. Since the wiper motor 100 stops, the cam switch 102 is turned off.

[0059] At this point, the controller 60 performs the same process as at time t0. Specifically, the controller 60 changes the gate voltage of the Lo FET 49 from a low level to a high level. As a result, the Lo FET 49 turns on. Accordingly, current flows from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, and the Lo FET 49. At this point, since current flows through the Lo coil 451, the Lo switch 452 is turned on. Consequently, voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47, and the Lo terminal 106. Consequently, the wiper motor 100 rotates at a lower speed than when the Hi terminal 104 is energized. Consequently, the wiper connected to the wiper motor 100 rotates at a lower speed. Thereafter, the controller 60 repeats the same processing as that during the period from time t0 to time t5, thereby intermittently rotating the wiper motor 100 and the wiper connected to the wiper motor 100. Thus, the operation state of the wiper is in the intermittent mode.

[0060] As described above, the controller 60 controls the wiper motor 100 to set the wiper operating state to one of the continuous high-speed mode, the continuous low-speed mode, and the intermittent mode. As described below, based on the potentials of the Hi line 37 and the Lo line 47, the wiper drive device 30 of this embodiment can easily detect an abnormality, such as the FET of the IPD 57 failing to turn on, serving as a switching element for braking the wiper motor 100.

[0061] Here, we will refer to Figure 3 The timing diagram in the figure describes the situation where the FET of IPD 57 cannot be turned on. Figure 3 In the period from time t10 to time t12, the same processing as that in the period from time t0 to time t2 is performed, and therefore the description is omitted.

[0062] During the period from time t12 to time t13, the wiper switch 22 outputs a signal to the controller 60 to change the wiper operation mode to intermittent mode. Furthermore, the rotation of the wiper motor 100 turns off the cam switch 102. As a result, the wiper drive device 30 is electrically connected to the GND terminal 108 and the motor ground 12. The controller 60 then obtains the potential of the cam switch 102.

[0063] At this time, since the potential of the cam switch 102 reaches the potential of the motor ground 12, the controller 60 changes the gate voltage of the Lo FET 49 from a high level to a low level. Consequently, the Lo FET 49 is turned off. Accordingly, current does not flow from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, and the Lo FET 49. At this time, since no current flows through the Lo coil 451, the Lo switch 452 is opened. Consequently, no voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47, and the Lo terminal 106. Consequently, the potential of the Lo line 47 decreases. Furthermore, since the Hi line 37 is connected to the Lo line 47 via the wiper motor 100 and the potential of the Lo line 47 decreases, the potential of the Hi line 37 also decreases.

[0064] At this time, the wiper motor 100 rotates due to inertia. Therefore, the wiper (not shown) connected to the wiper motor 100 rotates due to inertia.

[0065] Furthermore, at this time, the controller 60 changes the gate voltage level of the FET of the IPD 57 from a low level to a high level. However, the FET of the IPD 57 is not conducting due to an abnormality. Therefore, the wiper motor 100 is electrically disconnected from the second ground 82. Consequently, current corresponding to the inertial rotational energy of the wiper motor 100 does not flow from the wiper motor 100 to the second ground 82 via the IPD 57. Therefore, the wiper motor 100 is not braked by the flow of current corresponding to the inertial rotational energy of the wiper motor 100. Instead, the wiper motor 100 and the wiper connected to it are braked due to friction with an object contacting the wiper motor (e.g., the windshield). Therefore, the amount of electrical energy corresponding to the inertial rotational energy of the wiper motor 100 decreases less than at time t2. Consequently, at this time, the potential of the Lo line 47 and Hi line 37 connected to the wiper motor 100 decreases less than at time t2.

[0066] After time t13, the wiper switch 22 outputs a signal to the controller 60 to change the wiper's operating state to intermittent mode. Furthermore, the rotation of the wiper motor 100 turns off the cam switch 102. This electrically connects the wiper drive 30 to the GND terminal 108 and the motor ground 12. The controller 60 then obtains the potential of the cam switch 102.

[0067] At this time, since the potential of the cam switch 102 is at the motor ground 12, the controller 60 sets the gate voltage of the Lo FET 49 to a low level. Consequently, the Lo FET 49 is turned off. Consequently, no current flows from the motor battery 14 to the first ground 81 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, and the Lo FET 49. Since no current flows through the Lo coil 451 at this time, the Lo switch 452 is opened. Consequently, no voltage is applied from the motor battery 14 to the wiper motor 100 via the motor power terminal 33, the Lo switch 452, the Lo line 47, and the Lo terminal 106. Consequently, the potential of the Lo line 47 drops to or below the predetermined Lo threshold potential V_Lo_th. Furthermore, since the Hi line 37 is connected to the Lo line 47 via the wiper motor 100 and the potential of the Lo line 47 drops, the potential of the Hi line 37 also drops to or below the predetermined Hi threshold potential V_Hi_th.

[0068] At this time, since the wiper motor 100 stops rotating, the wiper connected to the wiper motor 100 stops.

[0069] Therefore, since the amount of decrease in the potential of the Lo line 47 and the Hi line 37 is smaller than at time t2, the time period from time t12 to time t13 is longer than the time period from time t2 to time t3 and the time period from time t2 to time t4. That is, when the FET of the IPD 57 is abnormal, the time period from the start of braking of the wiper motor 100 until the potential of the Lo line 47 becomes equal to or lower than the Lo predetermined threshold potential V_Lo_th is longer than when the FET of the IPD 57 is normal. When the FET of the IPD 57 is abnormal, the time period from the start of braking of the wiper motor 100 until the potential of the Hi line 37 becomes equal to or lower than the Hi predetermined threshold potential V_Hi_th is longer than when the FET of the IPD 57 is normal.

[0070] Therefore, in the wiper drive device 30 of this embodiment, the controller 60 determines whether the time period from the start of braking of the wiper motor 100 until the potential of the Lo line 47 becomes equal to or lower than the Lo threshold potential V_Lo_th is equal to or longer than the predetermined Lo time period. Thus, the controller 60 determines whether the FET of the IPD 57 is abnormal. The predetermined Lo time period is longer than the time period from the start of braking of the wiper motor 100 until the potential of the Lo line 47 becomes equal to or lower than the Lo threshold potential V_Lo_th when the FET of the IPD 57 is normal. The predetermined Lo time period is set through experiments, simulations, etc. to achieve such a result.

[0071] When the time period from when the wiper motor 100 starts braking until the potential of the Lo line 47 becomes equal to or less than the Lo threshold potential V_Lo_th is longer than the predetermined Lo time period, the time period is long due to an abnormality in the FET of the IPD 57. Therefore, at this time, the controller 60 determines that the FET of the IPD 57 is abnormal. Furthermore, when the time period from when the wiper motor 100 starts braking until the potential of the Lo line 47 becomes equal to or less than the Lo threshold potential V_Lo_th is shorter than the predetermined Lo time period, the FET of the IPD 57 is normal. Therefore, at this time, the controller 60 determines that the FET of the IPD 57 is normal.

[0072] Furthermore, the controller 60 determines whether the period from when the wiper motor 100 starts braking until the potential of the Hi line 37 becomes equal to or less than the Hi threshold potential V_Hi_th is equal to or longer than the predetermined Hi period. Thus, the controller 60 determines that the FET of the IPD 57 is abnormal. The predetermined Hi period is longer than the period from when the wiper motor 100 starts braking until the potential of the Hi line 37 becomes equal to or less than the Hi threshold potential V_Hi_th when the FET of the IPD 57 is normal. The predetermined Hi period is set through experiments, simulations, and the like to achieve this result.

[0073] When the time period from when the wiper motor 100 starts braking until the potential of the Hi line 37 becomes equal to or less than the Hi threshold potential V_Hi_th is longer than the predetermined Hi time period, the time period is long due to an abnormality in the FET of the IPD 57. Therefore, at this time, the controller 60 determines that the FET of the IPD 57 is abnormal. Furthermore, when the time period from when the wiper motor 100 starts braking until the potential of the Hi line 37 becomes equal to or less than the Hi threshold potential V_Hi_th is shorter than the predetermined Hi time period, the FET of the IPD 57 is normal. Therefore, at this time, the controller 60 determines that the FET of the IPD 57 is normal.

[0074] The controller 60 determines whether the FET of the IPD 57 is abnormal based on a time period until the potentials of the Lo line 47 and the Hi line 37 become equal to or lower than a predetermined threshold potential. For this reason, in the wiper drive device 30 of the present embodiment, it is easy to determine whether the FET of the IPD 57 is abnormal, compared to a case where the FET of the IPD 57 is determined to be abnormal based only on a threshold determination of the potentials of the Lo line 47 and the Hi line 37 connected to the wiper motor 100.

[0075] Furthermore, the wiper driving device 30 of this embodiment also has the following effects.

[0076] Assume that due to a malfunction of the controller 60, the FET of the IPD 57 is turned on while the Lo FET 49 is turned on. At this time, an overcurrent flows from the motor battery 14 to the second ground 82 via the motor fuse 18, the motor power terminal 33, the first motor diode 31, the second motor diode 32, the Lo coil 451, the Lo line 47, and the IPD 57. This overcurrent damages the FET of the IPD 57.

[0077] Therefore, the FET of the IPD 57 is turned on after the Lo FET 49 is turned off. This suppresses the overcurrent from flowing to the FET of the IPD 57, thereby suppressing damage to the FET of the IPD 57.

[0078] Furthermore, when the FET of the IPD 57 is turned on while the Lo FET 49 is turned on, the protection circuit of the IPD 57 automatically turns off the FET of the IPD 57. This suppresses an overcurrent from flowing to the FET of the IPD 57, thereby suppressing damage to the FET of the IPD 57.

[0079] (Other embodiments)

[0080] The present disclosure is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate. In each of the above-described embodiments, it is self-evident that any element constituting the embodiment is not necessarily required, except in the following cases: where it is explicitly stated that such an element is particularly required; and where it can be considered that such an element is obviously required in principle.

[0081] The controller, determination unit and their techniques according to the present disclosure can be implemented by one or more special-purpose computers. Such a special-purpose computer can be provided by configuring a processor and a memory programmed to perform one or more functions embodied by a computer program. Alternatively, the controller, determination unit, etc. and their methods described in the present disclosure can be implemented by a special-purpose computer, which is provided by configuring a processor consisting of one or more special-purpose hardware logic circuits. Alternatively, the controller, determination unit, etc. and their methods described in the present disclosure can be implemented by one or more special-purpose computers, which are composed of a combination of a processor and a memory programmed to perform one or more functions and a processor consisting of one or more hardware logic circuits. The computer program can be stored in a computer-readable non-transitory tangible storage medium as instructions executed by a computer.

[0082] In the above embodiment, MOSFETs are used as switching elements for the Hi FET 39, Lo FET 49, and FETs of the IPD 57. However, the switching elements are not limited to MOSFETs, and may be other elements such as IGBTs (Insulated Gate Bipolar Transistors).

[0083] In the above embodiment, the controller 60 controls the on / off switching of the Lo FET 49 and the FETs of the IPD 57 to set the wiper operation state to the intermittent mode. The controller 60 is not limited to switching the wiper operation state to the intermittent mode by controlling the on / off switching of the Lo FET 49 and the FETs in the IPD 57. For example, the drain of the FET of the IPD 57 may be connected to the Hi line 37, and the controller 60 may control the on / off switching of the Hi FET 39 and the FETs of the IPD 57 to operate the wiper in the intermittent mode.

[0084] In the above-described embodiment, the controller 60 determines an abnormality in the FET of the IPD 57 based on the time period required for the potentials of the Lo line 47 and the Hi line 37 to become equal to or lower than the predetermined potential. The controller 60 is not limited to determining an abnormality in the FET of the IPD 57 based on the time period until the potentials of the Lo line 47 and the Hi line 37 become equal to or lower than the predetermined potential. For example, after the wiper motor 100 starts braking, the controller 60 may determine that the FET of the IPD 57 is abnormal when the amount of decrease per unit time in the potential of the Lo line 47 and the Hi line 37 is equal to or less than a predetermined amount (the predetermined amount is smaller than the amount of decrease when the FET of the IPD 57 is normal).

Claims

1. A wiper driving device, the wiper driving device being configured to drive a wiper by rotating a wiper motor (100), the wiper driving device comprising: a line (37, 47), said line (37, 47) being connected to said wiper motor; a driving element (39, 49) configured to be turned on and apply a voltage to the wiper motor via the line to rotate the wiper motor; a brake element (57) configured to brake the wiper motor by being turned on when the drive element is turned off, so that a current corresponding to the rotational energy of the wiper motor flows; as well as A determination unit (60) is configured to determine that the brake element is abnormal when a time period from when the wiper motor is braked to when the potential (V_Lo, V_Hi) of the line becomes equal to or less than a predetermined threshold potential (V_Lo_th, V_Hi_th) is longer than a predetermined value, the predetermined value being a time period when the brake element is normal.

2. The wiper drive device according to claim 1, wherein: After the drive element is switched off, the brake element is switched on.

3. The wiper driving device according to claim 1, wherein: When the driving element is turned on while the braking element is turned on, the braking element is automatically turned off.

4. A wiper driving device, the wiper driving device being configured to drive a wiper by rotating a wiper motor (100), the wiper driving device comprising: a line (37, 47), said line (37, 47) being connected to said wiper motor; a driving element (39, 49) configured to be turned on and apply a voltage to the wiper motor via the line to rotate the wiper motor; a brake element (57) configured to brake the wiper motor by being turned on when the drive element is turned off, so that a current corresponding to the rotational energy of the wiper motor flows; as well as A determination unit (60) is configured to determine that the brake element is abnormal when the amount of decrease per unit time of the potential (V_Lo, V_Hi) of the line after braking the wiper motor is equal to or less than a predetermined value, the predetermined value being smaller than the amount of decrease when the brake element is normal.

5. The wiper driving device according to claim 4, wherein: After the drive element is switched off, the brake element is switched on.

6. The wiper driving device according to claim 4, wherein: When the driving element is turned on while the braking element is turned on, the braking element is automatically turned off.

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