JP5422292B2 - Vehicle seat belt retractor control device - Google Patents

Description

  The present invention relates to a control device for a motor control circuit driven by PWM control, and more particularly to a vehicle seat belt retractor control device.

  The conventional device is an inverter fan motor safety device described in Japanese Patent Application Laid-Open No. 7-337029 (Patent Document 1). When the output current of the inverter becomes larger than the limit value, the inverter main circuit All the switching elements are turned off to cut off the output of the inverter, and the switching frequency for each switching element of the main circuit is set lower than the value in the steady operation state.

  Another conventional device is an overload in an inverter device having a control device for controlling pulse width modulation (PWM), such as the inverter device described in Japanese Patent Laid-Open No. 11-69830 (Patent Document 2). During normal times when there is no output from the detector, the frequency divider outputs a predetermined frequency, and when the output from the overload detector is overloaded, the frequency divider outputs a frequency lower than the predetermined frequency. It was.

  However, in the above prior art, when the output current becomes larger than the limit value or when there is an output from the overload detector, the control device sets the frequency low. For this reason, in the seatbelt retractor control device, the overload protection function of the motor control circuit operates when the overload and the overtemperature state due to overload are detected, and the energization of the motor is stopped. That is, there is a possibility that the tension for restraining the occupant cannot be maintained by stopping the operation of the seat belt.

JP 7-337029 A JP-A-11-69830

  The subject of this invention is improving the reliability of a seatbelt retractor device and improving the safety | security with respect to a passenger | crew.

  The vehicle seat belt retractor control device according to the present invention includes a first control mode for PWM controlling the motor drive circuit so that a current output from the motor drive circuit to the motor becomes a first current, and the motor A second control mode for PWM controlling the motor drive circuit so that a current output from the drive circuit to the motor is a second current different from the first current, and switching in the first control mode The frequency and the switching frequency of the second control mode are made different.

  As a result, the frequency of the control mode in which a large current may flow can be set small, so that the heat generation of the motor drive circuit is suppressed, the reliability of the seat belt retractor device is improved, and the safety for the occupant is improved. Can do.

  Preferably, in the vehicle seat belt retractor control device according to the present invention, the first control mode is a winding control mode in which the motor is driven so that the seat belt retractor winds up the seat belt. The second control mode is a pull-out control mode in which the motor is driven so that the seat belt retractor pulls out the seat belt, and the switching frequency in the winding control mode is higher than the switching frequency in the pull-out control mode. small.

  Preferably, in the vehicle seat belt retractor control device according to the present invention, in the first control mode, the occupant is restrained to the seat belt during a first predetermined time after the motor generates the driving force. The emergency control mode for controlling the seat belt retractor as described above, wherein the second control mode is a predetermined tightening force during a second predetermined time that is greater than the first predetermined time of the emergency control mode. In the seat belt retracting control mode for controlling the seat belt retractor so as to fix an occupant to the seat belt, the switching frequency in the emergency control mode is lower than the switching frequency in the seat belt retracting control mode.

  Preferably, the vehicle seat belt retractor control device according to the present invention is configured to control the ambient temperature of the vehicle seat belt retractor control device or the temperature of a control component used in the vehicle seat belt retractor control device. When the detection result of the detection circuit unit is lower than the first predetermined temperature, the emergency control mode is close to the switching frequency of the seat belt storage control mode. Increase the switching frequency of the emergency control mode.

  Preferably, the vehicle seat belt retractor control device according to the present invention is configured to control the ambient temperature of the vehicle seat belt retractor control device or the temperature of a control component used in the vehicle seat belt retractor control device. A detection circuit unit for detecting, and when the detection result of the detection circuit unit is higher than a second predetermined temperature, the seat belt storage control mode is brought closer to the switching frequency of the emergency control mode, The switching frequency of the seat belt storage control mode is reduced.

  Preferably, in the vehicle seat belt retractor control device according to the present invention, in the first control mode, the occupant is restrained by the seat belt during a predetermined time after the motor generates the driving force. An emergency control mode for controlling the seat belt retractor, wherein the second control mode controls the motor to flow a current smaller than a current flowing through the motor drive circuit in the emergency control mode; and This is a warning control mode for issuing a warning to an occupant, and the switching frequency in the emergency control mode is smaller than the switching frequency in the warning control mode.

  Preferably, in the vehicle seat belt retractor control device according to the present invention, when the number of warnings is a predetermined number or more in the warning control mode, the switching frequency of the warning control mode is set to the emergency control mode. Reduce to approach the switching frequency.

  According to the present invention, it is possible to improve the reliability of the seat belt retractor and improve the safety for passengers.

It is a safety device connection figure in vehicles concerning this embodiment. It is a passenger | crew restraint figure to the seat concerning this embodiment. It is a disassembled perspective view of the electromechanical integrated retractor concerning this embodiment. It is a functional block diagram concerning this embodiment. FIG. 6A is an explanatory diagram of an emergency current path according to the present embodiment. (B) is an explanatory view of current paths at the time of storing the belt and at the time of warning according to the present embodiment. (C) is a current path explanatory view at the time of belt release according to the present embodiment. It is a feedback system block diagram in the conventional method. FIG. 2A is a feedback system block diagram according to the present embodiment. (B) is a switching frequency determination flow explanatory diagram according to the present embodiment. It is the electric current and voltage waveform of MOSFET concerning this embodiment. It is the relationship between the drive frequency and heat generation in the conventional method. It is the relationship between the drive frequency concerning this embodiment, and heat_generation | fever. FIG. 6 is a relationship diagram between the number of times of driving and a temperature increase according to the present embodiment.

(Example)
First, FIG. 1 shows a connection diagram of a collision safety device in a vehicle. In the vehicle 112, an obstacle sensor 102 that outputs a signal corresponding to the distance from 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 or not the vehicle 112 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 shorter than a predetermined value and the vehicle speed obtained from the output signal of the wheel speed sensor 104 is higher than the predetermined value, The collision determination controller 106 determines that the vehicle 112 collides with an obstacle, and outputs a command signal to the brake assist device 108 and the seat belt drive controller 110 before the vehicle 112 collides with the obstacle.

  The brake assist device 108 and the seat belt drive controller 110 are electrically connected to the collision determination controller 106, and each execute a predetermined operation based on a command signal from the collision determination controller 106. The seat belt drive controller 110 is included in the retractor 100 and controls power feeding to the retractor 100.

  FIG. 2 shows an occupant restraint diagram for the seat. A motor 200 is attached to the retractor 100, and the seat belt 206 can be wound by rotating the motor 200. For example, let us consider a case where the occupant 202 is moving in the forward direction of the vehicle while the occupant 202 is driving the vehicle 112, and a gap is generated between the occupant 202 and the seat 204. In such a situation, when the vehicle 112 collides with an obstacle, the occupant is not restrained by the seat 204 and is strongly hit against the seat 204. However, according to the present system, the gap between the occupant 202 and the seat 204 is eliminated by operating the motor 200 attached to the retractor 100 and winding the seat belt 206 before the vehicle 112 and the obstacle collide. It is possible. Accordingly, when the vehicle 112 and the obstacle collide with each other, the passenger 202 is already restrained by the seat 204, so that the impact on the passenger 202 can be reduced.

  Further, when the output of the wheel speed sensor 104 exceeds a predetermined amount of change, that is, when the vehicle 112 suddenly starts or stops, the seat belt 206 is instantaneously repeated so that the passenger 202 can be A warning may be urged.

  Similarly, when the output of the wheel speed sensor 104 exceeds a predetermined value, that is, when the vehicle 112 exceeds a predetermined traveling speed, the seat belt 206 is instantaneously repeated to allow the occupant 202 to take up the seat belt 206. A warning may be urged.

  FIG. 3 shows an exploded perspective view of the electromechanical integrated retractor 100 which is one of the retractors. The electromechanical integrated retractor 100 is fitted with a spool 300 for winding the seat belt 206, a gear box 322 in which a gear for transmitting a rotational force to the spool 300 is housed, and a gear in the gear box 322, and the electric energy And a circuit board 314 that supplies electric power to the motor 200 via a motor terminal 310 connected to the motor 200. Further, the motor 200 is communicated with a central processing unit (hereinafter referred to as CPU) 412 that controls the calculation process, a connector 312 for receiving power supply from the vehicle battery, and a command from the CPU 400. A motor driver circuit 410 and the like for switching the power supply are mounted on the circuit board 314. The motor driver circuit 410 may be, for example, an H bridge for driving a DC motor or a three-phase driving circuit for driving a brushless motor. The CPU 400 mounted on the circuit board 314 includes a nonvolatile memory such as a Flash ROM, and a program executed by the CPU 400 is stored in the nonvolatile memory.

  FIG. 4 shows a functional block diagram of the electromechanical integrated retractor. The circuit board 314 includes a CPU 400 that performs calculation processing, a power supply circuit unit 402 that generates a constant voltage from the vehicle battery power source, and a control area network (hereinafter referred to as CAN) communication unit 404 that performs communication with other control devices 414 of the vehicle. A switch input unit 406 that captures vehicle information such as a door switch 416 as a switch input, a non-volatile memory 408 represented by an EEPROM that stores control parameters of the motor 200, and a motor that switches power supply to the motor 200 based on commands from the CPU 400 A driver circuit 410, a current measuring unit 412 that measures the current flowing through the motor 200, and the like are mounted. The current flowing through the motor 200 is converted into a rotational force by the motor 200 and further transmitted to the spool 300 via the gear box 322. The winding force and the loosening operation of the seat belt 206 are realized by the rotational force transmitted to the spool 300.

  The CPU 400 determines the operation mode of the seat belt 206 based on information input from the CAN communication unit 404 or the switch input unit 406. This operation mode is determined in advance and is described by a software program installed in the CPU 400. The CPU 400 implements various operations by executing software programs.

  In the case of a seat belt retractor, the operation mode may be an emergency operation, an operation intended for warning, or an operation to release the seat belt. In the present embodiment, Pulse Width Modulation (hereinafter referred to as PWM) control is adopted in order to realize the motor output torque corresponding to each operation.

  5 (A), 5 (B), and 5 (C) show the motor current in the drive mode of the operation in the event of an emergency, the operation for the purpose of warning, or the operation of releasing the winding of the seat belt. The flow path and the switching state of the MOSFETs (410a, 410b, 410c, 410d) constituting the motor driver circuit 410 are shown.

  FIG. 5A shows a path through which a motor current flows in an emergency operation and a switching state of MOSFETs (410a, 410b, 410c, 410d) included in the motor driver circuit 410.

  FIG. 5 (B) shows the motor current path and the switching state of the MOSFETs (410a, 410b, 410c, 410d) constituting the motor driver circuit 410 in the operation for the purpose of warning.

  FIG. 5C shows a motor current path and a switching state of the MOSFETs (410a, 410b, 410c, 410d) constituting the motor driver circuit 410 in the operation of releasing the winding of the seat belt.

  The positive electrode (VB in the figure) of the battery is connected to the source electrodes of the MOSFET 410a as the P channel and the MOSFET 410c as the P channel installed on the battery side (hereinafter referred to as the high side) of the motor 200 as the load. The drain electrode is connected to the drain electrode of the motor 200 and the MOSFET 410b which is an N channel and the MOSFET 410d which is an N channel installed on the GND side (hereinafter, low side) of the motor 200 which is a load. The source electrodes of the N channel MOSFET 410b and the N channel MOSFET 410d are connected to the negative electrode of the vehicle battery. Here, the P-channel MOSFET connected to the high side can be replaced with an N-channel MOSFET depending on the drive circuit, such as a drive circuit having a booster circuit.

  FIG. 5A shows a current path in an emergency of the retractor. A P-channel MOSFET 410a, which is one of the P-channel MOSFETs, is always on, and during this on-state, the N-channel MOSFET 410d repeats an on-state and an off-state at a predetermined cycle. Here, the ON state is the energization state of the MOSFET, and the OFF state is the non-energization state of the MOSFET. While the N-channel MOSFET 410d is in the on state, the motor current flows from the positive electrode of the battery in the negative direction of the battery (current path 500). However, while the N-channel MOS 410d is in the off state, a regenerative current is generated by the inductance component of the motor 200. A current flows through the current path 502.

  Since this regenerative current also flows to the P-channel MOSFET 410c, when the P-channel MOSFET 410c is off, current flows to the internal parasitic diode, and the P-channel MOSFET 410c generates a large amount of heat due to the product of the regenerative current 502 and the voltage drop generated by the parasitic diode. Therefore, during the time when the regenerative current is generated, the heat generated in the P-channel MOSFET 410c is reduced by turning on the P-channel MOSFET 410c. As described above, the N-channel MOSFET 410d and the P-channel MOSFET 410c repeat the on-state and the off-state in a relationship of opposite phases (on-state and off-state are alternately repeated). Hereinafter, the cycle in which the on state and the off state are repeated is referred to as a switching cycle, and the reciprocal of the switching cycle is referred to as a switching frequency. The ratio of the on-state and the off-state of the P-channel MOSFET 410d with respect to one cycle is referred to as a duty ratio, and the current supplied to the motor 200 increases as the duty ratio increases. In an emergency, the output torque of the motor 200 is set high because it is necessary to instantaneously loosen the seat belt 206 and restrain the occupant to the seat in a short time between 100 msec and 200 msec. For this reason, the duty ratio is often set to 70% or more.

  FIG. 5B shows a current path when retracting the belt of the retractor or warning. The current path is the same as that shown in FIG. 5A. However, unlike an emergency, an instantaneous large current is not required in a short time, and over a relatively long time of about 2 seconds to 10 seconds, for example, about 5A to 10A. Current is required. Also in this case, in order to rotate the motor in the direction to wind up the seat belt 206, the P-channel MOSFET 410a is always turned on, and the downstream N-channel MOSFET 401d is driven by PWM control that repeats the on-state and off-state according to the duty ratio. . In the ON state of the N-channel MOSFET 401d, a current is supplied to the motor 200 through the current path 504. In the OFF state of the N-channel MOSFET 401d, the regenerative current of the motor 200 is generated in the current path 506. Therefore, the P-channel MOSFET 410c is turned on to suppress the heat generated in the P-channel MOSFET 410c by the current path 506. To do. When the belt is stored or at the time of warning, since the current flowing in the motor drive circuit is smaller than in an emergency, the heat generated in the P-channel MOSFET 410a, the P-channel MOSFET 410c, and the N-channel MOSFET 410d is smaller than that in the emergency operation. ,Few.

  Next, FIG. 5C shows a current path when the retractor belt is released. When the belt is released, the motor is driven in the direction opposite to that in an emergency or when the belt is retracted. For this reason, the operation of the motor driver circuit is also different from the above. The P-channel MOS 410c is always in an ON state, and the downstream N-channel MOSFET 410b is driven by PWM control that repeats an on state and an off state in accordance with the duty ratio. When the N-channel MOSFET 410b is on, current is supplied to the motor 200 through the current path 508. In the OFF state of the N-channel MOSFET 410b, the regenerative current of the motor 200 flows through the path of the current path 510. Therefore, the heat generated in the P-channel MOSFET 410a by the current path 510 is suppressed by turning on the P-channel MOSFET 410a. .

  In general, the switching frequency of PWM control is set to a higher frequency range than the audible frequency range, and thus is often set to 16 Khz or more. The duty ratio is defined by the on-time / PWM period x100 [%], and the current supplied to the motor increases as the duty ratio increases.

  For example, in the emergency operation shown in FIG. 5A, since it is necessary to supply a current of about 20 A to 30 A to the motor, the duty ratio is set to 70% to 90%.

  For example, when the belt is stored as shown in FIG. 5B or when the warning is performed, it is necessary to supply a current of about 5 A to 10 A to the motor, so the duty ratio is set to 20% to 50%. .

  For example, when the belt is released as shown in FIG. 5C, it is necessary to supply a current of about 2 A to 3 A to the motor, so the duty ratio is set to 5% to 10%.

  FIGS. 6 and 7A are feedback system block diagrams of motor current control in the retractor according to the conventional method and the method of the present invention, respectively. In the conventional method, after the operation mode is determined (600), the target current is determined according to the operation mode (602). For example, if the operation is an emergency, the target current is set to 20A, and if the operation is performed when the belt is stored, the target current is set to 10A. Next, the current current value is read from the current detection unit (604), and the difference from the target current value (hereinafter referred to as current deviation difference) is input to the controller (606) of the program installed in the CPU. The controller (606) calculates the duty ratio of PWM control using a method such as PID control based on the current deviation, and outputs a command signal to the drive circuit (608). In this method, a constant switching frequency is used regardless of the operation mode. For example, it is conceivable to use a common switching frequency of 16 Khz in an emergency or during belt storage.

  In the feedback block diagram of the motor current control according to the present embodiment in FIG. 7A, the drive mode is first determined (600), and then the switching frequency according to the drive mode is determined (702). Here, for example, the switching frequency is set to 10 Khz in an emergency operation, and is set to 20 kHz when the belt is stored or the belt is released. Next, the current current value is read from the current detection unit (604), and the difference from the target current value (hereinafter referred to as current deviation) is input to the controller (606). The controller (606) 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 drive circuit (608). In this method, the switching frequency can be switched depending on the drive mode.

  FIG. 7B shows a flowchart for determining the switching frequency. It is determined whether or not the drive mode is mode 1 (704). If the drive mode is mode 1, the switching frequency is set to 10 Khz, for example (706), and whether or not the mode is mode 2 or not. When the drive mode is mode 2, the switching frequency is set to, for example, 16 Khz (710). Further, when the drive mode is neither mode 1 nor mode 2, The switching frequency is set to 20 Khz, for example (712).

In retractor, for example the drive mode 3 operation when the belt release, the drive mode 2 operation at or WARNING belt storage, driving mode 1 is considered to be defined as the operation of the emergency. Further, for example, a detection circuit unit for detecting the ambient temperature of the retractor control device or the temperature of the control component of the retractor control device is provided, and the operation mode is switched based on the detection result of the detection circuit unit. Also good. For example, when the ambient temperature is a low temperature such as 0 ° C. or less, it is defined as the operation mode 3 regardless of the driving mode such as emergency or belt storage, and the switching frequency is set to be close to 20 Khz or 20 Khz. On the other hand, when the ambient temperature exceeds 100 ° C., it is defined as operation mode 1 regardless of the driving mode such as emergency or belt storage, and the switching frequency is set to be close to 10 Khz or 10 Khz.

  Furthermore, the operation mode may be switched depending on the driving frequency. For example, when the number of occurrences of the warning operation per unit time is less than 10, it is defined as operation mode 2 and the switching frequency is set to be close to 16 Khz or 16 Khz. Or when the frequency | count of warning operation generation | occurrence | production per unit time is 10 times or more, it defines as the operation mode 1 and sets a switching frequency so that it may approach 10 kHz or 10 kHz.

  Next, heat generation of the MOSFET in the PWM control will be described. FIG. 8 shows current / voltage waveforms in the switching operation of the PWM control of the MOSFET. Here, the current is a drain current (hereinafter referred to as ID) flowing between the drain and source of the MOSFET. The voltage is a drain-source voltage (hereinafter referred to as VDS) generated between the drain and the source. In PWM control, the power supplied to the motor is controlled by repeating the on-state and off-state of the MOSFET at high speed, i.e., switching. The MOSFET is controlled from the on-state in addition to the on-state and off-state. It is necessary to consider an off state or a state in which the state changes from the off state to the on state.

  In the state transition section from the off state to the on state (described as tr in FIG. 8), the VDS decreases and the ID increases. For example, in the case of a control device in a vehicle such as a retractor control device, VDS decreases from a battery voltage that is normally 13.5 V, and changes to a voltage determined by IDmax × Rdson (where Rdson is the MOSFET's voltage). Means on-resistance). On the other hand, the drain current ID increases from 0 A and increases to a predetermined current value. The predetermined current value is determined by the inductance of the motor, the resistance value of the motor, and the counter electromotive force of the motor.

  In the on period (described as ton in FIG. 8) in the on state, VDS has a substantially constant value, which is a voltage determined by IDmax × Rdson. On the other hand, the drain current continuously increases during the ton time according to a function determined by the inductance of the motor, the resistance value of the motor, and the counter electromotive force of the motor.

  In the state transition interval from the on state to the off state (denoted as tf in FIG. 8), VDS increases and ID decreases, contrary to the ton interval. tf is the time until the ID decreases to approximately 0A. tr and tf do not necessarily have to be the same time, and a time difference generally occurs due to a driving circuit for driving the MOSFET, a parasitic capacitance of the MOSFET, and the like.

In the off state, the drain current ID is a leak current of about 10 ^(-6) A, but can be regarded as almost 0 A. On the other hand, VDS has a predetermined voltage value. For example, the battery voltage is normally 13.5V.

  Here, heat generated in the MOSFET will be described. The definition of heat generation is the product of current and voltage, and in this case, ID × VDS. When calculating the heat generation in each of the on section, the off section, the state transition section from the on state to the off state, and the state transition section from the off state to the on state, Ptr, Ptf, Pton, and Ptoff described in Expression (1) Become.

  Here, for the sake of simplicity, it is assumed that the current change in the tr interval and the tf interval changes in a linear function with respect to time. In the ton interval, ID is assumed to be a constant value. The heat generation of the MOSFET in PWM control is the sum of Ptr, Ptf, Pton, and Ptoff, and is expressed by P in Expression (2).

  Referring to equation (2), it can be seen that P is a function having ID, VDS, tr, tf, f, Rdson, and Duty as variables. Among these variables, ID, VDS, tf, tf, and Rdson are determined by the electrical characteristics of the MOSFET, its drive circuit, and the motor. The duty is determined by the current value necessary to obtain a desired torque from the motor. However, the switching frequency f need only be sufficiently faster than the mechanical frequency response of the motor determined from the mechanical time constant of the motor. For example, in a retractor control device, it is free between 10 Khz and 20 Khz. Can be set. From equation (2), it can be seen that heat generation increases more when the switching frequency is higher. For example, when the switching frequency is compared between 10 Khz and 20 Khz, if ID = 20 A, VDS = 13 V, tr = tf = 5 usec, Rdson = 10 mΩ, and Duty = 90%, a difference in calorific value of about 4.4 W occurs.

  Next, the effect of switching the switching frequency will be described. FIG. 9 shows the relationship between the motor current and switching frequency and the motor current and heat generation in the conventional method. The heat generation here means heat generation of the MOSFET that repeats switching in PWM control. According to FIG. 9, for example, when the switching frequency is a constant value at 20 Khz, the heat generation P increases with ID, that is, the motor current. This is clear from the equation (2). FIG. 10 shows the relationship between the motor current and switching frequency and the motor current and heat generation according to the method of the present application.

  In FIG. 10, the switching frequency is switched in mode (1), mode (2), and mode (3), respectively, and even if the current value increases, it is possible to keep heat generation within a certain range. In general, when lowering the switching frequency, especially when the switching frequency is set to an audible frequency range such as 10 Khz, the motor resonance sound due to switching is heard by the occupant when the motor is driven, which increases the comfort of riding. There is a risk of damage. However, in the retractor control device that drives the seat belt, it is necessary to prioritize the emergency operation over the comfort.

  Also, when the ambient temperature rises, or when the temperature of the retractor control device rises due to continuous operation, even if the normal switching frequency is overtemperature and the operation stops, the switching frequency is reduced to the audible frequency. It is possible to drop and achieve the operation. As described above, an effect obtained by switching the switching frequency can be obtained.

  FIG. 11A shows the relationship between the number of driving times and the temperature rise in the conventional method. The seat belt retractor control device executes a warning operation (1104a) for a predetermined time, for example, and then enters a stop state where power supply to the motor 200 is stopped for a predetermined time (1104b). While the warning operation is being executed (1104a), the MOSFETs constituting the motor driver circuit 410 are heated by the heat generated by the expression (2), and the temperature of the MOSFET and its surroundings rises (1102a). On the other hand, in the stopped state (1104b), no current flows through the MOSFETs constituting the motor driver circuit 410, so the temperature of the MOSFET and its surroundings decreases (1102b). By repeating the above series of operations, the temperature of the MOSFET repeatedly rises and falls, but when the operation frequency is high, the MOSFET and its surrounding temperature exceed a specified value (1100) as shown in FIG. There are cases. This is because, in the seat belt retractor control device, when the warning operation occurs at a certain frequency or in the emergency winding operation after the warning operation is repeated several times, the MOSFET becomes overtemperature, It means that it is difficult to continue.

  FIG. 11B shows the relationship between the number of times of driving and the temperature rise in the method of the present application. The seat belt retractor control device executes a warning operation (1104a) for a predetermined time, for example, and then enters a stop state where power supply to the motor 200 is stopped for a predetermined time (1104b). While the warning operation is being executed (1104a), the MOSFETs constituting the motor driver circuit 410 are heated by the heat generated by the expression (2), and the temperature of the MOSFET and its surroundings rises (1102a). On the other hand, in the stopped state (1104b), no current flows through the MOSFETs constituting the motor driver circuit 410, so the temperature of the MOSFET and its surroundings decreases (1102b). By repeating the above series of operations, the temperature of the MOSFET repeatedly rises and falls. However, when the operation frequency is high, the MOSFET and its surrounding temperature have a quasi-specified value (1106) as shown in FIG. It may be exceeded. The semi-specified value (1106) is set at a lower temperature than the specified value (1100). When the MOSFET or its ambient temperature exceeds the forward specified value (1106), the switching frequency is lowered to the audible frequency, thereby reducing the heat generation of the MOSFET and continuing the operation (1104c). Continuous operation is possible by reducing the switching frequency.

  According to this embodiment, it is possible to optimize the heat generation of the switching elements forming the motor control device and provide a seat belt retractor motor control device that is smaller and less expensive. In addition, the high temperature operation required for a control device mounted on a vehicle, particularly a control device that requires a plurality of predetermined operations, such as a control device for a seat belt retractor motor, is effective. .

200 Motor 202 Crew 206 Seat belt 300 Spool 322 Motor power transmission mechanism 400 Microcomputer 402 Power supply circuit 404 CAN communication circuit 406 Input interface circuit 408 Non-volatile memory 410 Motor drive circuit 412 Current sensor circuit 414 Other control unit 416 Switch 418 Ignition switch

Claims (6)

A vehicle seat belt retractor control device for controlling a motor provided in a vehicle seat belt retractor,
A first control mode for PWM controlling the motor drive circuit such that the current output from the motor drive circuit to the motor is the first current;
A second control mode for PWM controlling the motor drive circuit so that a current output from the motor drive circuit to the motor is a second current different from the first current;
The first control mode is a winding control mode in which the motor is driven so that the seat belt retractor winds up a seat belt,
The second control mode is a pull-out control mode for driving the motor so that the seat belt retractor pulls out a seat belt,
The switching frequency of the winding control mode is smaller cars dual seat belt retractor control device than the switching frequency of the extraction control mode. A vehicle seat belt retractor control device for controlling a motor provided in a vehicle seat belt retractor,
A first control mode for PWM controlling the motor drive circuit such that the current output from the motor drive circuit to the motor is the first current;
A second control mode for PWM controlling the motor drive circuit so that a current output from the motor drive circuit to the motor is a second current different from the first current;
The first control mode is an emergency control mode for controlling the seat belt retractor so as to restrain an occupant to a seat belt during a first predetermined time after the motor generates a driving force.
In the second control mode, the seat belt retractor is controlled so that the occupant is fixed to the seat belt with a predetermined tightening force during a second predetermined time that is greater than the first predetermined time in the emergency control mode. Seat belt storage control mode,
The switching frequency of the emergency control mode, the seat belt storage control mode small car dual seat belt retractor control device than the switching frequency of the. The vehicle seat belt retractor control device according to claim 2,
A detection circuit unit for detecting the ambient temperature of the vehicle seat belt retractor control device or the temperature of a control component used in the vehicle seat belt retractor control device;
When the detection result of the detection circuit unit is lower than the first predetermined temperature, the switching frequency of the emergency control mode is increased so that the emergency control mode approaches the switching frequency of the seat belt storage control mode. Vehicle seat belt retractor control device. The vehicle seat belt retractor control device according to claim 3,
When the detection result of the detection circuit unit is higher than the second predetermined temperature, the seat belt storage control mode is set to a switching frequency of the seat belt storage control mode so as to approach the switching frequency of the emergency control mode. Vehicle seat belt retractor control device to be reduced. A vehicle seat belt retractor control device for controlling a motor provided in a vehicle seat belt retractor,
A first control mode for PWM controlling the motor drive circuit such that the current output from the motor drive circuit to the motor is the first current;
A second control mode for PWM controlling the motor drive circuit so that a current output from the motor drive circuit to the motor is a second current different from the first current;
The first control mode is an emergency control mode for controlling the seat belt retractor so as to restrain an occupant to a seat belt during a predetermined time after the motor generates a driving force;
The second control mode is a warning control mode for controlling a current smaller than a current flowing in the motor drive circuit in the emergency control mode to flow through the motor and issuing a warning to a passenger.
The switching frequency of the emergency control mode, small car dual seat belt retractor control device than the switching frequency of the warning control mode. The vehicle seat belt retractor control device according to claim 5,
A vehicle seat belt retractor control device that reduces a switching frequency in the warning control mode to be close to a switching frequency in the emergency control mode when the number of warnings is equal to or greater than a predetermined number in the warning control mode.

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