JP5548141B2 - Control device for seat belt retractor - Google Patents

Description

  The present invention relates to a seat belt retractor control device, and more particularly to a seat belt retractor control device using a motor drive circuit that is driven and controlled by PWM control.

  2. Description of the Related Art Conventionally, as a vehicle safety system, a pre-crash safety system that winds up a seat belt when a collision sensor mounted on a vehicle determines that a collision with another vehicle or an obstacle cannot be avoided is known.

  In recent years, a motor is attached to the seat belt retractor. For example, when the seat belt is attached or detached, the motor is rotated to remove the slack of the seat belt, thereby improving the comfort of the passenger wearing the seat belt. Improvements are being made. In the event of an emergency in which a collision is predicted by a collision sensor mounted on the vehicle when the distance to other vehicles or obstacles is close, the occupant can be restrained to the vehicle seat before the collision, The occupant's impact at the time of collision can be reduced.

  In this way, in an emergency where a collision is predicted, it is necessary to apply a large current to the seat belt retractor motor in order to instantaneously wind up the seat belt. On the other hand, in daily operations other than in an emergency, it is necessary to suppress the current value to be energized in order to suppress noise for other devices including accessories such as radios.

  Patent Document 1 discloses a seat belt control device for achieving both such an emergency energization performance and a normal noise performance. This seat belt control device is provided with two systems of lines with and without a noise filter in the power line of the motor drive circuit, and has a means for switching between the emergency filter and the normal switch, thereby providing a noise filter. The size of the seat belt control device has been reduced by downsizing.

  FIG. 11 shows an overall configuration diagram of such a conventional seatbelt retractor control device, and this seatbelt retractor control device 500 ′ is roughly composed of a motor 200 ′ and a motor drive circuit 300 ′. ing. The motor drive circuit 300 ′ includes a power supply unit 400 ′ that transmits power supplied from a vehicle battery (not shown), a GND unit 410 ′ that is connected to the vehicle GND, and a coil that constitutes a noise filter circuit for noise suppression. 412 ', a capacitor 414', an H bridge circuit power line noise filter switching circuit component 416 'that can be energized without passing through the coil 412' at a large current, and an H bridge circuit 401 '. Further, the H-bridge circuit 401 ′ includes a first MOSFET 402 ′, a second MOSFET 404 ′, a third MOSFET 406 ′, and a fourth MOSFET 408 ′. Here, the gate terminals (denoted as G in the figure) of the MOSFETs 402 ′, 404 ′, 406 ′, and 408 ′ are respectively connected to the output terminals of the CPU 301 ′, and each MOSFET is connected in accordance with the output signal of the CPU 301 ′. By turning on or off, the driving of the motor 200 ′ connected to the H-bridge circuit 401 ′ is controlled. Here, the CPU 301 ′ has an output terminal that can drive the MOSFETs 402 ′, 404 ′, 406 ′, and 408 ′. However, the driving capability may be supplemented by another component such as a pre-driver circuit.

  FIG. 12 shows a feedback system block diagram of motor current control in a conventional seat belt retractor. For example, an H bridge is provided by switching means between emergency and normal such as a noise filter switching circuit component 416 ′. A feedback system block diagram in the case where a preset drive mode is applied to the circuit 401 ′ is shown. First, a specific drive mode such as emergency or normal time is determined in advance by the drive mode determining means 501 ′ provided in the control device 500 ′ (see FIG. 11), and then the drive mode such as emergency or normal time is determined. Accordingly, the target current is determined by the target current determining means 502 ′. For example, the target current can be set to 20 A when the emergency driving mode is determined, and the target current can be set to 10 A when the normal belt storing mode is determined. Next, the current current value is read from the current detection means 503 ′, and the difference from the target current value (hereinafter referred to as “current deviation”) is input to the controller 504 ′ of the program installed in the CPU 301 ′. The controller 504 ′ calculates a duty ratio of PWM control using a method such as PID control based on the current deviation, and outputs a command signal to the motor drive circuit 300 ′. Based on the command signal, the H bridge circuit 401 ′ of the motor drive circuit 300 ′ is controlled to drive the motor 200 ′. In such a control device 500 ′, the driving mode of the H bridge circuit 401 ′ is controlled by switching the noise filter of the power supply line of the H bridge circuit 401 ′ using the switching means between the emergency time and the normal time. Can do. If there is no means for switching between an emergency time and a normal time, the drive mode of the H-bridge circuit of the motor drive circuit 300 ′ is fixed in advance regardless of the emergency time or the normal time. The driving mode at the time of winding the belt is executed.

JP 2008-6998 A

  However, the seat belt control device disclosed in Patent Document 1 requires a noise filter switching circuit component for the H-bridge circuit power line, and the circuit component energizes a large current during an emergency operation. Since it is necessary to provide the capability, there is a problem that downsizing of the seat belt control device is hindered.

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to provide a seat belt retractor that can realize a reduction in size while achieving both an energization performance in an emergency and a noise performance in a normal time. It is to provide a control device.

  In order to solve the above-described problem, a seatbelt retractor control device according to the present invention is a seatbelt retractor control device including a seatbelt retractor motor and an H-bridge circuit having a MOSFET. Controls the driving of the motor by controlling the H-bridge circuit in a plurality of driving modes.

  As can be understood from the above description, according to the seatbelt retractor control device of the present invention, it is possible to achieve both the energization performance in an emergency and the noise performance in the normal time, and the noise of the noise filter and the power supply line for the H bridge circuit. A filter switching circuit component is not required, and the size of the filter can be reduced.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a basic configuration diagram of a vehicle safety system to which an embodiment of a control device for a seat belt retractor according to the present invention is applied. The figure which showed the restraint state of the passenger | crew using the seatbelt retractor to which one Embodiment of the control apparatus of the seatbelt retractor which concerns on this invention is applied. FIG. 3 is an exploded perspective view of the electromechanical integrated retractor shown in FIG. 2. BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram of one Embodiment of the control apparatus of the seatbelt retractor which concerns on this invention. 5A and 5B are diagrams illustrating a driving mode of the H-bridge circuit constituting the control device shown in FIG. 4, in which FIG. 5A is a diagram illustrating a driving mode 1 of a belt winding operation in an emergency, and FIG. The figure which showed the driving mode 2 of winding operation | movement, (C) is the figure which showed the driving mode 3 of belt drawing-out operation | movement. It is the figure which showed embodiment of MOSFET which the H bridge circuit shown in FIG. 5 has, (A) is the figure which showed the form by which gate resistance was inserted in the gate part of MOSFET, (B) is the gate part of MOSFET The figure which showed the form by which the ferrite bead was inserted, (C) is the figure which showed the form by which the capacitor was added between the gate part and source part of MOSFET. FIG. 7 is a diagram showing MOSFET turn-on and turn-off waveforms during belt winding, where (A) shows a MOSFET turn-on waveform in drive mode 1, and (B) shows a MOSFET turn-off waveform in drive mode 1. (C) is a diagram showing a MOSFET turn-on waveform in drive mode 2, and (D) is a diagram showing a MOSFET turn-off waveform in drive mode 2. The feedback system block diagram of the motor current control in a seatbelt retractor when one Embodiment of the control apparatus of the seatbelt retractor which concerns on this invention is applied. The flowchart which determines the drive mode of belt winding-up operation. It is the figure which showed the relationship between a motor current, the emitted-heat amount, and a noise level, (A) is the figure which showed the relationship between the motor current, the emitted-heat amount, and a noise level at the time of applying only the drive mode 1, (B). These are the figures which showed the relationship between the motor current at the time of applying the drive mode 1 and the drive mode 2, and the emitted-heat amount and a noise level. The whole block diagram of the control apparatus of the conventional seatbelt retractor. The feedback system block diagram of the motor current control in the conventional seatbelt retractor.

  Embodiments of a seat belt retractor control device according to the present invention will be described below with reference to the drawings.

  FIG. 1 shows a basic configuration diagram of a vehicle safety system to which a control device for a seat belt retractor according to the present invention is applied. In the vehicle 110 of the vehicle safety system 1000 shown in the figure, an obstacle sensor 102 that outputs a signal corresponding to the distance to the obstacle is attached to the front portion of the vehicle. The output signal of the obstacle sensor 102 is transmitted to the collision determination controller 106 that is electrically connected to the obstacle sensor 102. A signal from the wheel speed sensor 104 that outputs a signal corresponding to the speed of the vehicle is also transmitted to the collision determination controller 106 that is electrically connected to the wheel speed sensor 104. The collision determination controller 106 determines whether the vehicle 110 collides with an obstacle based on signals from the obstacle sensor 102 and the wheel speed sensor 104. For example, when the distance to the obstacle obtained from the output signal of the obstacle sensor 102 is smaller than a predetermined value and the vehicle speed obtained from the output signal of the wheel speed sensor 104 is larger than the predetermined value, The collision determination controller 106 determines that the vehicle 110 collides with an obstacle, and outputs a command signal to the brake assist device 108 and the electromechanically integrated retractor 100 before the vehicle 110 collides with the obstacle.

  The brake assist device 108 and the electromechanically integrated retractor 100 are electrically connected to the collision determination controller 106, and each executes a preset operation based on a command signal from the collision determination controller 106.

  FIG. 2 shows a restrained state of the occupant using the seat belt retractor to which the seat belt retractor control device according to the present invention is applied. Here, the electromechanically integrated retractor 100 is provided with a motor 200, and the seat belt 201 can be taken up by the motor 200 being driven to rotate. For example, in a state where the occupant A is driving the vehicle 110, the occupant A moves slightly in the forward direction relative to the vehicle 110, and a gap is generated between the occupant A and the seat 111. Under such circumstances, when the vehicle 110 collides with an obstacle, the occupant A is not restrained by the seat 111 and is thus strongly hit against the seat 111 by the collision. However, according to the vehicle safety system 1000 described above, the motor 200 attached to the retractor 100 is driven to wind the seat belt 201 before the vehicle 110 collides with an obstacle, so that the occupant A and the seat 111 It is possible to eliminate the gap. Therefore, since the occupant A is already restrained by the seat 111 when the vehicle 110 and the obstacle collide, the impact on the occupant A due to the collision can be reduced.

  Further, when the output of the wheel speed sensor 104 exceeds a predetermined amount of change, that is, when the vehicle 110 suddenly starts or stops, the passenger A is warned by instantaneously repeating the winding operation of the seat belt 201. Can be encouraged.

  Similarly, when the output of the wheel speed sensor 104 exceeds a predetermined value, that is, when the vehicle 110 exceeds a predetermined traveling speed, the seat belt 201 is wound up to instantaneously repeat the winding operation. A warning can be urged to A.

  FIG. 3 is an exploded perspective view of an electromechanically integrated retractor 100 which is a kind of retractor. The illustrated electromechanically integrated retractor 100 includes a spool 202 for winding a seat belt 201, a gear box 210 in which a motor power transmission mechanism 211 that transmits rotational force to the spool 202 is housed, and a gear in the gear box 210. And a circuit board 310 for supplying electric power to the motor 200 via the motor terminals 203 and 204 connected to the motor 200. ing. The circuit board 310 includes a central processing unit (CPU) 301 that controls calculation processing, a communication with other control devices mounted on the vehicle, a connector 302 for receiving power supply from a vehicle battery, and a command from the CPU 301. A motor drive circuit 300 or the like that switches power supply to the motor 200 is mounted. As the motor drive circuit 300, for example, an H bridge circuit for driving a DC motor, a three-phase drive circuit for driving a brushless motor, or the like is used. The CPU 301 mounted on the circuit board 310 includes a nonvolatile memory such as a Flash ROM, and a program executed by the CPU 301 is stored in the nonvolatile memory.

  FIG. 4 is an overall configuration diagram of the seat belt retractor control device 500 including the motor driving circuit 300 and the motor 200 shown in FIG. The motor drive circuit 300 is mainly composed of a power supply unit 400 that transmits power supplied from a vehicle battery (not shown), a GND unit 410 that is connected to the vehicle GND, and an H bridge circuit 401. Is composed of a first MOSFET 402, a second MOSFET 404, a third MOSFET 406, and a fourth MOSFET 408. Note that the gate terminals (denoted as G in the figure) of the MOSFETs 402, 404, 406, and 408 are respectively connected to the output terminal of the CPU 301, and each MOSFET is turned on or off in accordance with the output signal of the CPU 301. The driving of the motor 200 connected to the H bridge circuit 401 is controlled.

  The seat belt retractor control device 500 shown in FIG. 4 is different from the conventional seat belt retractor control device 500 ′ shown in FIG. 11 in that the gate terminals of the first MOSFET 402 and the second MOSFET 404 constituting the H-bridge circuit 401. (Gate part) The gate resistors 412 and 414 are connected between the G and the output terminal of the CPU 301, respectively. Thereby, the switching speed (the speed at which the first MOSFET 402 and the second MOSFET 404 are switched from the on state to the off state, or the speed at which the off state is switched to the on state) is compared with the third MOSFET 406 and the fourth MOSFET 408. And switching noise generated during switching is suppressed. According to this embodiment, the driving mode of the H-bridge circuit 401 is switched as appropriate, and the first MOSFET 402 and the second MOSFET 404 are switched, compared with the case where the third MOSFET 406 and the fourth MOSFET 408 are switched. Thus, the generation of noise can be further suppressed.

  FIG. 5 explains the drive mode of the H-bridge circuit 401 shown in FIG. 4 for driving the motor 200. When the belt is wound, the energization direction to the motor 200 is from left to right in the drawing, and when the belt is released (drawn), the energization direction is from right to left.

  FIG. 5A shows a driving mode (driving mode 1) at the time of winding the belt in an emergency, for example, when a collision with another vehicle or an obstacle is predicted. In such driving mode 1, for example, in order to wind up the seat belt belt instantaneously, it is necessary to energize the motor with a larger current than in the normal state. Therefore, during motor driving, the first MOSFET 402 is always turned on, the second MOSFET 404 is always turned off, and the fourth MOSFET 408 is switched at a high speed according to the drive duty ratio. In this case, the drive duty ratio is 0% to 100%, and the switching speed is set in the range of 5 kHz to 20 kHz.

  For example, when 90% of the power generated in the power supply unit 400 and the GND unit 410 is supplied to the motor at a switching speed of 10 kHz, the duty ratio is 90%, and the fourth MOSFET 408 has an on time of 90 μsec and an off time. Will repeat the operation for 10 μsec. Even during the period in which the fourth MOSFET 408 is off, the regenerative current is passed through the motor 200 by the inductance component inherent to the motor 200. Therefore, it is known that the third MOSFET 406 is turned on in a phase opposite to that of the fourth MOSFET 408 to suppress heat generation in the third MOSFET 406 due to the regenerative current. That is, the third MOSFET 406 repeats an operation with an on-time of 10 μsec and an off-time of 90 μsec. Note that the dead time can be provided by adjusting the on-time and off-time of each MOSFET so that the third MOSFET 406 and the fourth MOSFET 408 are not turned on simultaneously.

  Here, the illustrated gate drive signals 403, 405, 407, and 409 are output signals of the CPU 301 (see FIG. 4), the gate drive signal 403 is a signal for driving the first MOSFET 402, and the gate drive signal 405 is the second signal. A signal for driving the MOSFET 404, a gate drive signal 407 is a signal for driving the third MOSFET 406, and a gate drive signal 409 is a signal for driving the fourth MOSFET 408. As described above, during the motor drive, the gate drive signal 403 is always on, the gate drive signal 405 is always off, and the gate drive signal 407 is a reverse-phase PWM signal and gate drive signal with an on time of 10 μsec and an off time of 90 μsec. Reference numeral 409 denotes a positive phase PWM signal having an on time of 90 μsec and an off time of 10 μsec.

  FIG. 5B shows a driving mode (driving mode 2) at the time of winding the belt in a normal time other than an emergency, for example. In such a driving mode 2, a relatively small current is applied compared to that in an emergency, and the noise level is suppressed. Therefore, during the motor drive, the fourth MOSFET 408 is always turned on, the third MOSFET 406 is always turned off, and the first MOSFET 402 is switched at a high speed according to the drive duty ratio. In this case, the drive duty ratio is 0% to 100%, and the switching speed is set in the range of 5 kHz to 20 kHz.

  For example, when 90% of the power generated in the power supply unit 400 and the GND unit 410 is supplied to the motor at a switching speed of 10 kHz, the duty ratio is 90%, and the first MOSFET 402 has an on time of 90 μsec and an off time. Will repeat the operation for 10 μsec. Even during the period when the first MOSFET 402 is off, the motor 200 is supplied with a regenerative current by an inductance component unique to the motor 200. Therefore, it is known that the second MOSFET 404 is turned on in a phase opposite to that of the first MOSFET 402 to suppress heat generation in the second MOSFET 404 due to a regenerative current. That is, the second MOSFET 404 repeats an operation with an on-time of 10 μsec and an off-time of 90 μsec. Note that the dead time can be provided by adjusting the on-time and the off-time of each MOSFET so that the first MOSFET 402 and the second MOSFET 404 are not turned on at the same time.

  Here, the illustrated gate drive signals 413, 415, 417, and 419 are output signals of the CPU 301 (see FIG. 4), the gate drive signal 413 is a signal for driving the first MOSFET 402, and the gate drive signal 415 is the second signal. A signal for driving the MOSFET 404, a gate drive signal 417 is a signal for driving the third MOSFET 406, and a gate drive signal 419 is a signal for driving the fourth MOSFET 408. As described above, during motor driving, the gate drive signal 413 is a positive phase PWM signal with an on time of 90 μsec and an off time of 10 μsec, and the gate drive signal 415 is a reverse phase PWM with an on time of 10 μsec and an off time of 90 μsec. The signal and gate drive signal 417 are always off, and the gate drive signal 419 is always on.

  FIG. 5C shows a drive mode (drive mode 3) when the belt is released (drawn). When the belt is released, the energization direction of the motor 200 is changed from the right to the left in the drawing. During the motor driving, the third MOSFET 406 is always turned on, the fourth MOSFET 408 is always turned off, and the second MOSFET 404 is driven. Switching at high speed according to In this case, the drive duty ratio is 0% to 100%, and the switching speed is set in the range of 5 kHz to 20 kHz. In drive mode 3, generally, a relatively small current is applied to motor 200 as compared with an emergency.

  For example, when 90% of the power generated in the power supply unit 400 and the GND unit 410 is supplied to the motor at a switching speed of 10 kHz, the duty ratio is 90%, and the second MOSFET 404 has an on time of 90 μsec and an off time. Will repeat the operation for 10 μsec. Further, even during the period in which the second MOSFET 404 is off, the motor 200 is supplied with a regenerative current by an inductance component unique to the motor 200. Therefore, it is known that the first MOSFET 402 is turned on in a phase opposite to that of the second MOSFET 404 to suppress heat generation in the first MOSFET 402 due to a regenerative current. That is, the first MOSFET 402 repeats an operation with an on-time of 10 μsec and an off-time of 90 μsec. Note that the dead time can be provided by adjusting the on-time and the off-time of each MOSFET so that the first MOSFET 402 and the second MOSFET 404 are not turned on at the same time.

  Here, the illustrated gate drive signals 423, 425, 427, and 429 are output signals of the CPU 301 (see FIG. 4), the gate drive signal 423 is a signal that drives the first MOSFET 402, and the gate drive signal 425 is the second signal. A signal for driving the MOSFET 404, a gate drive signal 427 is a signal for driving the third MOSFET 406, and a gate drive signal 429 is a signal for driving the fourth MOSFET 408. As described above, during motor driving, the gate drive signal 423 is a reverse phase PWM signal with an on time of 10 μsec and an off time of 90 μsec, and the gate drive signal 425 is a positive phase PWM with an on time of 90 μsec and an off time of 10 μsec. The signal and gate drive signal 427 are always on, and the gate drive signal 429 is always off.

  In the conventional control device, the belt winding is performed by applying, for example, a preset driving mode (driving mode 1) at the time of belt winding in an emergency regardless of different belt winding states in an emergency or normal time. I was taking it. For this reason, the MOSFET to be switched is always fixed, which is a factor that generates a large amount of noise in normal times.

  On the other hand, in the control device of the present embodiment, the belt is wound by applying different driving modes for winding the belt in different belt winding states such as emergency and normal times. That is, the drive mode 1 can be applied in an emergency, and the drive mode 2 can be applied in a normal time other than an emergency. Therefore, the MOSFET to be switched becomes variable according to the winding state, and the noise performance at the normal time can be improved while maintaining the energization performance in an emergency.

  FIG. 6 shows an embodiment of the first MOSFET 402 included in the H-bridge circuit 401 and shows means for adjusting the switching speed of the first MOSFET 402. Note that the same means can be applied to the second MOSFET 404.

  6A shows a form in which a gate resistor 412 is inserted in the gate part G of the MOSFET 402, as in the embodiment shown in FIG. As a result, the gate current can be limited, and the switching speed of the MOSFET 402 can be delayed by delaying the rising and falling speeds of the gate voltage.

  FIG. 6B shows a form in which ferrite beads 412A are inserted into the gate portion G of the MOSFET 402 instead of the gate resistor 412 shown in FIG. 6A. This makes it possible to increase the impedance of the high-frequency component in the gate voltage, delay the rising and falling speeds of the gate voltage, and delay the switching speed of the MOSFET 402.

  FIG. 6C shows a mode in which a capacitor 412B is added between the gate part G and the source part S of the MOSFET 402. FIG. As a result, the apparent gate capacitance increases, and the switching speed of the MOSFET 402 can be delayed by delaying the rising and falling speeds of the gate voltage.

  4 to 6, the gate resistance or the like is applied only to the first MOSFET 402 and the second MOSFET 404, but the resistance value different from the gate resistance connected to the first MOSFET 402 and the second MOSFET 404 is used. The provided gate resistor or the like can also be connected to the third MOSFET 406 or the fourth MOSFET 408. In addition, a capacitor having a different capacity from the capacitor added between the gate portion and the source portion of the first MOSFET 402 or the second MOSFET 404 is provided between the gate portion and the source portion of the third MOSFET 406 or the fourth MOSFET 408. Can be added to.

  FIG. 7 shows a MOSFET turn-on and turn-off waveform at the time of winding the belt. FIG. 7A shows a MOSFET turn-on waveform in the driving mode 1 at the time of belt winding in an emergency, for example. ) Shows the MOSFET turn-off waveform, FIG. 7C shows, for example, the MOSFET turn-on waveform in the driving mode 2 during normal belt winding, and FIG. 7D shows the MOSFET turn-off waveform. . 7A and 7C, the time for the gate voltage (VGS) to reach from 10% voltage to 90% voltage is defined as the turn-on time (Ton), and FIG. 7B and FIG. ), The time for the drain voltage (VDS) to reach from 10% voltage to 90% voltage is defined as the turn-off time (Toff).

  Comparing FIG. 7A and FIG. 7C, the drive mode 2 has a longer turn-on time (Ton). As a result, in the driving mode 2, the MOSFET is turned on more slowly, and noise generated during switching can be further reduced. Similarly, comparing FIG. 7B and FIG. 7D, the drive mode 2 has a longer turn-off time (Toff). As a result, in the driving mode 2, the MOSFET is turned off more slowly, and noise generated during switching can be further reduced. As described above, the switching noise in the driving mode 2 at the time of normal belt winding is reduced as compared with the switching noise in the driving mode 1 at the time of belt winding in an emergency, and the noise performance at the normal time is improved. Can understand.

  FIG. 8 shows a feedback system block diagram of motor current control in the seat belt retractor when an embodiment of the seat belt retractor control device according to the present invention is applied. In contrast to the feedback system block diagram of the motor current control in the conventional seat belt retractor shown in FIG. 12, the feedback system block diagram shown in FIG. 8 is mainly in response to an emergency, normal time, or belt winding or withdrawal. The difference is that drive mode selection means 505 for selecting the drive mode of the H-bridge circuit is added.

  As shown in the figure, first, the drive mode determining means 501 provided in the control device 500 (see FIG. 4) preliminarily determines the drive mode such as emergency or normal time, and the drive mode selecting means 505 determines the emergency mode. The driving mode of the H-bridge circuit is selected at normal times or according to the winding and withdrawal of the belt. Here, the selected drive mode is, for example, the drive mode 1 shown in FIG. 5A when the belt is taken up in an emergency, and shown in FIG. 5B when the belt is stored other than the emergency. Drive mode 2 is selected, and drive mode 3 shown in FIG. 5C is selected when the belt is released. Then, the target current is determined by the target current determining means 502 according to the selected drive mode. Next, the current value is read from the current detection means 503, and the current deviation is input to the controller 504 of the program installed in the CPU 301. The controller 504 calculates a duty ratio of PWM control using a method such as PID control based on the current deviation, and outputs a command signal to the motor drive circuit 300. Based on the command signal, the H bridge circuit 401 of the motor drive circuit 300 is controlled to drive the motor 200. According to this embodiment, it is possible to switch the switching frequency according to the driving mode and control the driving of each MOSFET of the H bridge circuit 401.

  FIG. 9 shows a flowchart for selecting a drive mode by the drive mode selection means 505 in FIG. The drive mode selection means 505 determines whether or not the drive mode is emergency (S50), and if the drive mode is emergency, selects the drive mode 1 shown in FIG. 5A (S51). If the operation mode is other than emergency, the drive mode 2 shown in FIG. 5B is selected (S52). Further, the drive mode selection means 505 can determine whether the seat belt is wound or pulled out before determining whether or not it is an emergency.

  FIG. 10 shows the relationship between the motor current, the heat generation amount, and the noise level. FIG. 10A does not switch the drive mode. For example, only the drive mode 1 shown in FIG. The relationship between the motor current, the noise level, and the amount of heat generated when is applied. FIG. 10B shows the relationship between the motor current, noise level, and heat generation when the drive modes are switched and different drive modes 1 and 2 are applied. In the figure, the horizontal axis represents the motor current, and the vertical axis represents the noise level and the heat generation amount. Here, the heat generation means heat generation of the MOSFET that repeats switching in PWM control.

  As shown in FIG. 10A, when only the single drive mode 1 is applied, the noise level and the heat generation amount increase substantially linearly as the motor current increases. In the low current region, the noise level is suppressed because the coil serving as the noise filter exhibits its function. On the other hand, in FIG. 10B, although the driving mode 2 is selected in the low current region and the heat generation amount is increased by slowing the switching speed, it occurs at the time of switching with respect to the noise level of FIG. The noise level to be reduced is low. Therefore, the generation of noise is effectively suppressed in the low current region, that is, normally. On the other hand, in the high current region, the same drive mode 1 as the drive mode shown in FIG. 10A is selected, and the same noise level and heat generation amount are shown for the motor current. However, in the event of an emergency in which a collision with a high current region, that is, an obstacle or the like is predicted and the seat belt needs to be taken up instantaneously, such a large noise can be allowed to be generated, and high energization performance is achieved. Can be maintained.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files that realize each function can be stored in a storage device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 100 Electromechanical integrated retractor 102 Obstacle sensor 104 Wheel speed sensor 106 Collision judgment controller 108 Brake assist device 110 Vehicle 111 Seat 200 Motor 201 Seat belt 202 Spool 210 Gear box 211 Motor power transmission mechanism unit 300 Motor drive circuit 301 Central Processing Unit ( CPU)
302 Connector 310 Circuit board 400 Power supply unit 401 H-bridge circuit 402, 404, 406, 408 MOSFET
410 GND parts 412 and 414 Gate resistance 412A Ferrite beads 412B Capacitor 500 Seat belt retractor control device 501 Driving mode determining means 502 Target current determining means 503 Current detecting means 504 Controller 505 Driving mode selecting means 1000 Vehicle safety system

Claims (4)

A control device for a seat belt retractor comprising a motor for a seat belt retractor and an H bridge circuit having a plurality of MOSFETs,
The control device controls the driving of the motor by controlling the H bridge circuit in a plurality of driving modes,
The plurality of drive modes include a first drive mode at the time of retracting an emergency seat belt and a second drive mode at the time of retracting a normal seat belt other than emergency ,
The MOSFET to be switched is changed in the first drive mode and the second drive mode, and the switching speed of the MOSFET to be switched is slower in the second drive mode than in the first drive mode. The seat belt retractor control device. A control device for a seat belt retractor according to claim 1,
A control device for a seat belt retractor, wherein a ferrite bead is provided at a gate portion of a MOSFET that is switched in the second drive mode . A control device for a seat belt retractor according to claim 1,
A control device for a seat belt retractor, wherein a capacitor is provided between a gate portion and a source portion of a MOSFET that is switched in the second drive mode . A control device for a seat belt retractor according to any one of claims 1 to 3,
Wherein the plurality of driving modes, further comprising in that the seat belt retractor control device of the third drive mode during the seat belt pull-out out.

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