JP7060983B2 - Seatbelt retractor and seatbelt take-up mechanism - Google Patents

Description

The present invention relates to a seatbelt retractor and a seatbelt winding mechanism.

Conventionally, in a seatbelt retractor that winds up a seatbelt by the power of a motor, a technique of short-circuiting a pair of power feeding terminals of the motor is known in order to return a current due to a counter electromotive force generated in the motor to the motor (for example). See Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-093431

However, in the conventional technique, since a signal for short-circuiting the pair of power feeding terminals of the motor must be output from the control unit, complicated control for returning the current due to the counter electromotive force to the motor is required.

Therefore, the present disclosure provides a seatbelt retractor and a seatbelt winding mechanism capable of easily returning a current due to a counter electromotive force to a motor.

This disclosure is
A spool for winding up the seat belt and
A motor having a rotating shaft connected to the rotating shaft of the spool via a power transmission mechanism and rotating the spool,
The drive circuit that drives the motor and
At least one rectifying element which is always connected in parallel to the motor and causes the current generated by the counter electromotive force generated in the motor to be returned to the motor by rotating the motor by an external force applied to the spool. Prepare ,
Provided is a seatbelt retractor that suppresses the rotation of the motor in the direction of rotating the spool in the drawing direction of the seatbelt by refluxing the current to the motor .

In addition, this disclosure is
A spool for winding up the seat belt and
A motor having a rotating shaft connected to the rotating shaft of the spool via a power transmission mechanism and rotating the spool,
At least one rectifying element which is always connected in parallel to the motor and causes the current generated by the counter electromotive force generated in the motor to be returned to the motor by rotating the motor by an external force applied to the spool. Prepare ,
Provided is a seatbelt winding mechanism that suppresses the rotation of the motor in the direction of rotating the spool in the drawing direction of the seatbelt by refluxing the current to the motor .

According to the present disclosure, it is possible to easily return the current due to the counter electromotive force to the motor.

It is a figure which shows an example of the structure of a seat belt device. It is a figure which shows the 1st structural example of a drive circuit. It is a figure which shows the 2nd structural example of a drive circuit. It is a figure which shows the 3rd structural example of a drive circuit. It is sectional drawing which shows the 1st structural example of the seat belt take-up mechanism. It is an exploded perspective view which shows the 2nd structural example of a seat belt take-up mechanism. It is a figure which shows the engagement relation of a gear. It is a figure which shows the state when the motor rotates in the clockwise direction (CW direction). It is a figure which shows the state when the motor rotates in the counterclockwise direction (CCW direction).

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.

FIG. 1 is a configuration diagram schematically showing an example of a seatbelt device 100. The seatbelt device 100 is a system mounted on a vehicle 13 such as an automobile. The seatbelt device 100 includes, for example, a seatbelt 2, a shoulder anchor 3, a tongue 4, a buckle 5, and a seatbelt retractor (hereinafter, also simply referred to as “retractor”) 10. The retractor 10 includes a seatbelt winding mechanism (hereinafter, also simply referred to as “winding mechanism”) 6 and a control device 1.

The seat belt 2 is an example of a band-shaped member that restrains the occupant 9 sitting on the seat 11 of the vehicle 13, and is wound around the winding mechanism 6 so as to be able to be pulled out from the winding mechanism 6. One end of the seatbelt 2 is connected to the take-up mechanism 6, and the other end of the seatbelt 2 is fixed to the vehicle body, the pretensioner device, the seat 11, or the like. Seat belts are also called webbing.

The shoulder anchor 3 is a guide member that guides the seat belt 2 pulled out from the take-up mechanism 6 toward the shoulder portion of the occupant 9, and is fixed to, for example, the floor of the vehicle body or the seat 11.

The tongue 4 is a member that is slidably attached to the seat belt 2 guided by the shoulder anchor 3.

The buckle 5 is an example of a member to which the tongue 4 is detachably engaged, and is fixed to, for example, the floor or the seat 11 of the vehicle body.

The retractor 10 is fixed to, for example, a vehicle body in the vicinity of the seat 11 or the seat 11 itself. The retractor 10 includes a take-up mechanism 6 that enables the take-up or pull-out of the seat belt 2 and a control device 1 that controls the operation of the take-up mechanism 6.

The winding mechanism 6 includes a spool 8 for winding the seat belt 2, a motor 7 for rotating the spool 8, and a power transmission mechanism 17 for transmitting power between the motor 7 and the spool 8. One end of the seat belt 2 is fixed to the spool 8. The motor 7 generates a driving force for rotating the spool 8. The rotating shaft of the motor 7 is connected to the rotating shaft of the spool 8 via the power transmission mechanism 17.

The control device 1 controls the winding operation (or both the winding operation and the pulling operation) of the seat belt 2 by the winding mechanism 6 by driving the motor 7. The control device 1 includes a drive circuit 14 for driving the motor 7 and a control circuit 15 for controlling the drive operation of the drive circuit 14.

The drive circuit 14 sends a drive current for driving the motor 7 to the motor 7 according to at least one control signal (for example, a PWM (pulse width modulation) control signal) supplied from the control circuit 15. Specific examples of the drive circuit 14 include an H-bridge drive circuit having four switching elements, a half-bridge drive circuit, a high-side drive circuit having only high-side switching elements, and a low-side drive circuit having only low-side switching elements. Be done. The form of the drive circuit 14 is not limited to these, and is determined according to the required specifications.

The control circuit 15 outputs at least one control signal (for example, a PWM control signal) that controls the magnitude (or the magnitude and direction of the drive current) of the drive current that drives the motor 7 to the drive circuit 14. do. Each function of the control circuit 15 is realized by operating the CPU (Central Processing Unit) according to the program stored in the memory. Specific examples of the control circuit 15 include a microcomputer provided with a CPU and a memory.

FIG. 2 is a diagram showing a first configuration example of the drive circuit 14. The drive circuit 14A shown in FIG. 2 is an H-bridge drive circuit having four switching elements 21, 22, 23, 24 and capable of switching the direction of the drive current flowing through the motor 7. The motor 7 has a built-in coil connected between the first terminal 7a and the second terminal 7b.

The drive circuit 14A has a first connection point 12 connected to the first terminal 7a of the motor 7 and a second connection point 18 connected to the second terminal 7b of the motor 7. A drive current is passed through the first connection point 12 and the second connection point 18. The first connection point 12 is an intermediate node to which the switching element 21 and the switching element 22 are connected, and the second connection point 18 is an intermediate node to which the switching element 23 and the switching element 24 are connected.

The drive circuit 14A is connected between the power supply VB and the ground (GND), and the high-side switching elements 21 and 23 connected to the power supply VB side with respect to the motor 7 and the ground side with respect to the motor 7. The low-side switching elements 22 and 24 connected to the above are provided. The switching elements 21, 22, 23, 24 are semiconductor elements that operate on / off, and may be, for example, a voltage control type transistor such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or a current control type bipolar transistor. good. FIG. 2 illustrates a mode in which the switching elements 21, 22, 23, 24 are N-channel MOSFETs.

The switching element 21 is an example of a first high-side switching element connected to the first terminal 7a. The switching element 21 has an electrode (drain or collector) connected to the power supply VB side, an electrode (source or emitter) connected to the first terminal 7a via the first connection point 12, and a control circuit 15. A high side arm with an electrode (gate or base) to be connected.

The switching element 22 is an example of a first low-side switching element connected to the first terminal 7a. The switching element 22 is connected to an electrode (source or emitter) connected to the ground side, an electrode (drain or collector) connected to the first terminal 7a via the first connection point 12, and a control circuit 15. It is a low side arm having an electrode (gate or base) to be formed.

The switching element 23 is an example of a second high-side switching element connected to the second terminal 7b. The switching element 23 has an electrode (drain or collector) connected to the power supply VB side, an electrode (source or emitter) connected to the second terminal 7b via the second connection point 18, and a control circuit 15. A high side arm with an electrode (gate or base) to be connected.

The switching element 24 is an example of a second low-side switching element connected to the second terminal 7b. The switching element 24 is connected to an electrode (source or emitter) connected to the ground side, an electrode (drain or collector) connected to the second terminal 7b via a second connection point 18, and a control circuit 15. It is a low side arm having an electrode (gate or source) to be formed.

The diodes 31, 32, 33, 34 may be body diodes of switching elements 21, 22, 23, 24 corresponding to each, or are additionally connected in parallel to the switching elements 21, 22, 23, 24 corresponding to each. It may be a rectifying element.

The current measurement circuit 16 is a current measurement unit that measures the current flowing through the drive circuit 14A and outputs the measurement result to the control circuit 15. The current measuring circuit 16 measures, for example, the amount of current flowing through the drive circuit 14A by a resistor inserted in series in the current path between the low-side switching elements 22 and 24 of the drive circuit 14A and the ground.

The current measuring circuit 16 measures the amount of current flowing in the drive circuit 14A by, for example, a resistor inserted in series in the current path between the switching elements 21 and 23 on the high side of the drive circuit 14A and the power supply VB. It may be measured. The current measurement method is not limited to these.

The control circuit 15 is a drive control unit that drives four switching elements 21, 22, 23, 24 constituting the drive circuit 14A by using the current measurement result or the like by the current measurement circuit 16.

The control circuit 15 is driven so that the motor 7 rotates (forward rotation) in the forward rotation direction corresponding to the winding direction of the seat belt 2 in the mode (winding mode) in which the seat belt 2 is wound on the spool 8. It controls each switching element of the circuit 14A. For example, in the take-up mode in which the motor 7 is rotated in the forward direction, the control circuit 15 turns on / off the switching element 23 by PWM control of a predetermined duty ratio, always turns off the switching elements 21 and 24, and always turns the switching element 22. Turn it on. At this time, in order to suppress heat generation due to the reflux current when the switching element 23 is turned off, the control circuit 15 may turn on the switching element 24 when the switching element 23 is turned off. Alternatively, in the take-up mode in which the motor 7 is rotated in the forward direction, the control circuit 15 turns on / off the switching element 22 by PWM control of a predetermined duty ratio, always turns off the switching elements 21 and 24, and always turns the switching element 23. You may turn it on. At this time, in order to suppress heat generation due to the reflux current when the switching element 22 is turned off, the control circuit 15 may turn on the switching element 21 when the switching element 22 is turned off.

By controlling each switching element in this way, the drive circuit 14A can rotate the motor 7 in the direction of rotating the spool 8 in the winding direction of the seatbelt 2 (normal rotation direction). can. When the rotation shaft of the motor 7 rotates in the forward direction, the driving force of the forward rotation is transmitted to the spool 8 by the power transmission mechanism 17. As a result, the spool 8 rotates in the direction in which the seat belt 2 is wound, so that the seat belt 2 is wound on the spool 8.

On the other hand, the control circuit 15 drives the drive circuit 14A so that the motor 7 rotates (reverse rotation) in the reverse direction corresponding to the pull-out direction of the seat belt 2 in the mode (pull-out mode) in which the seat belt 2 is pulled out from the spool 8. Control each switching element of. For example, in the pull-out mode in which the motor 7 is rotated in the reverse direction, the control circuit 15 turns the switching element 21 on / off by PWM control of a predetermined duty ratio, always turns off the switching elements 22 and 23, and always turns on the switching element 24. Let me. At this time, in order to suppress heat generation due to the reflux current when the switching element 21 is turned off, the control circuit 15 may turn on the switching element 22 when the switching element 21 is turned off. Alternatively, in the pull-out mode in which the motor 7 is rotated in the reverse direction, the control circuit 15 turns the switching element 24 on / off by PWM control of a predetermined duty ratio, always turns off the switching elements 22 and 23, and always turns on the switching element 21. You may let me. At this time, in order to suppress heat generation due to the reflux current when the switching element 24 is turned off, the control circuit 15 may turn on the switching element 23 when the switching element 24 is turned off.

By controlling each switching element in this way, the drive circuit 14A can rotate the motor 7 (reverse rotation) in the direction (reverse rotation direction) in which the spool 8 is rotated in the pull-out direction of the seat belt 2. When the rotation shaft of the motor 7 rotates in the reverse direction, the driving force of the reverse rotation is transmitted to the spool 8 by the power transmission mechanism 17. As a result, the spool 8 rotates in the direction in which the seat belt 2 is pulled out, so that the seat belt 2 is pulled out from the spool 8.

By the way, in the configuration shown in FIG. 2, a reflux circuit 40 that is always connected in parallel with the motor 7 is provided. When the rotary shaft of the motor 7 and the rotary shaft of the spool 8 are connected by the power transmission mechanism 17 and the motor 7 is rotated by an external force applied to the spool 8, a counter electromotive force is generated in the motor 7. The recirculation circuit 40 suppresses the rotation of the motor 7 and applies a brake by recirculating the current due to the counter electromotive force to the motor 7.

By suppressing the rotation of the motor 7 by the return circuit 40, for example, it becomes possible to absorb the collision energy acting on the occupant 9 at the time of a vehicle collision. Further, since the recirculation circuit 40 is always connected in parallel with the motor 7, control for recirculating the current due to the counter electromotive force to the motor 7 becomes unnecessary, so that the current due to the counter electromotive force can be easily transferred to the motor 7. It becomes possible to recirculate.

Further, in a configuration that requires control for returning the current due to the counter electromotive force to the motor 7, if the power supply VB fails due to a collision or the like, it becomes difficult to continue the control, and as a result, the current due to the counter electromotive force. Is also difficult to return to the motor 7. On the other hand, in the present embodiment, control for returning the current due to the counter electromotive force to the motor 7 is unnecessary. Therefore, even if the power supply VB fails due to a collision or the like, the current due to the counter electromotive force can be returned to the motor 7, and the collision energy acting on the occupant 9 at the time of a vehicle collision can be absorbed.

For example, an in-vehicle computer outside the retractor 10 transmits a command signal for starting binding force control to the occupant 9 of the seatbelt 2 in an emergency in which a deceleration of a predetermined value or more is applied to or may be applied to the vehicle 13. ..

As a specific example of an emergency in which a deceleration of a predetermined value or more is applied to the vehicle 13, the driver's brake operation is performed when a sudden brake that decelerates the vehicle 13 at a deceleration of a predetermined value or more is activated by automatic or driver's brake operation. For example, when the automatic brake that automatically decelerates the vehicle 13 at a deceleration of a predetermined value or more is activated even if there is no such thing. As a specific example of an emergency in which a deceleration of a predetermined value or more may be applied to the vehicle 13, there is a case where it is determined that the vehicle 13 may collide.

The control circuit 15 receives a command signal from an in-vehicle computer outside the retractor 10 in a state where the tongue 4 is engaged with the buckle 5 and the seatbelt 2 is fastened to the occupant 9, and the seatbelt 2 is satisfied. The binding force control for the occupant 9 is started.

The control circuit 15 controls each switching element of the drive circuit 14A so that the motor 7 rotates (forward rotation) in the forward rotation direction corresponding to the winding direction of the seatbelt 2 in order to prepare for an impact at the time of a collision. .. When the rotation shaft of the motor 7 rotates in the forward direction, the driving force of the forward rotation is transmitted to the spool 8 by the power transmission mechanism 17. As a result, the spool 8 rotates in the direction in which the seat belt 2 is wound, so that the seat belt 2 is wound on the spool 8. As a result, the binding force of the seat belt 2 on the occupant 9 increases.

After that, when the occupant 9 moves to the front of the vehicle due to the inertia at the time of collision, the seat belt 2 is pulled out from the spool 8 by the inertial force of the occupant 9 to the front of the vehicle. When the spool 8 rotates in the direction in which the seat belt 2 is pulled out from the spool 8, the rotational force is transmitted to the rotation shaft of the motor 7 by the power transmission mechanism 17. As a result, the rotation shaft of the motor 7 is rotated in the reverse direction, so that a counter electromotive force is generated in the motor 7. Due to the generation of this counter electromotive force, the potential of the first terminal 7a becomes relatively higher than the potential of the second terminal 7b (in other words, the potential of the second terminal 7b is higher than the potential of the first terminal 7a. Is also relatively low).

In the configuration of FIG. 2, when the potential difference between the first terminal 7a and the second terminal 7b exceeds the sum of the forward voltage of the diode 42 and the Zener voltage of the Zener diode 41, the current due to the counter electromotive force is generated. , The first terminal 7a, the recirculation circuit 40, the second terminal 7b, and the motor 7 recirculate. In this way, the return circuit 40 can prevent the motor 7 from rotating in the reverse direction in which the spool 8 is rotated in the pull-out direction of the seat belt 2 by returning the current due to the counter electromotive force to the motor 7. .. As a result, it becomes possible to absorb the collision energy acting on the occupant 9 at the time of a vehicle collision.

The return circuit 40 has a series configuration in which a diode 42, a Zener diode 41, and a resistance element 43 are connected in series. A diode 42, a Zener diode 41, and a resistance element 43 are inserted in series in a current path through which a current due to a counter electromotive force flows. The positions where the diode 42, the Zener diode 41, and the resistance element 43 are inserted in series may be substituted with each other.

The diode 42 is a rectifying element that is always connected in parallel to the motor 7 and returns the current due to the counter electromotive force generated in the motor 7 to the motor 7. A diode 42 having the first terminal 7a side as the anode and the second terminal 7b side as the cathode is always connected in parallel to the motor 7. The diode 42 connected in this direction can prevent the drive current for rotating the motor 7 in the forward rotation direction corresponding to the winding direction of the seat belt 2 from flowing to the recirculation circuit 40.

The Zener diode 41 is also always connected in parallel with the motor 7, and is a rectifying element that returns the current due to the counter electromotive force generated in the motor 7 to the motor 7. The Zener diode 41 is connected in series with the diode 42. A Zener diode 41 having a cathode on the first terminal 7a side and an anode on the second terminal 7b side is always connected to the motor 7 in parallel. The Zener diode 41 connected in this direction can prevent the drive current for rotating the motor 7 in the reverse direction corresponding to the pull-out direction of the seatbelt 2 from flowing to the return circuit 40. The Zener voltage of the Zener diode 41 is set to a value larger than the power supply voltage between the power supply VB and the ground.

The resistance element 43 is connected in series with the Zener diode 41. Since the resistance element 43 reduces the recirculation current flowing through the recirculation circuit 40 due to the counter electromotive force, the force for suppressing the rotation of the motor 7 can be weakened. That is, by changing the resistance value of the resistance element 43, the force for suppressing the rotation of the motor 7 can be adjusted. The resistance element 43 may be omitted.

Further, due to the generation of the counter electromotive force, the potential of the first terminal 7a becomes relatively lower than the potential of the second terminal 7b (in other words, the potential of the second terminal 7b becomes the potential of the first terminal 7a. (Relatively higher than) may be expected. In this case, it is preferable to replace the diode 42 with a Zener diode having the first terminal 7a side as the anode and the second terminal 7b side as the cathode. In the configuration in which the diode 42 is replaced with a Zener diode, when a counter electromotive force is generated in which the potential of the first terminal 7a is relatively lower than the potential of the second terminal 7b, the current due to the counter electromotive force is the second. It recirculates in the route of the terminal 7b, the recirculation circuit 40, the first terminal 7a, and the motor 7. The Zener voltage of this replaced Zener diode is set to a value larger than the power supply voltage between the power supply VB and ground. As described above, in the drive circuit 14A shown in FIG. 2, by changing the diode 42 to the Zener diode, a more preferable configuration can be realized in that it can cope with the generation of counter electromotive force in both directions.

FIG. 3 is a diagram showing a second configuration example of the drive circuit 14. The same points as in the first configuration example will be omitted. The drive circuit 14B shown in FIG. 3 is a high-side drive circuit having a high-side switching element 25 and capable of supplying a drive current in only one direction to the motor 7. The drive circuit 14B is used, for example, when it is not necessary to rotate the motor 7 in the reverse direction corresponding to the pull-out direction of the seatbelt 2, and rotates the motor 7 in the forward rotation direction corresponding to the winding direction of the seatbelt 2. The drive current to be driven can be supplied to the motor 7.

The drive circuit 14B is connected between the power supply VB and the ground (GND), and includes a high-side switching element 25 connected to the power supply VB side with respect to the motor 7. The switching element 25 includes an electrode (drain or collector) connected to the power supply VB side, an electrode (source or emitter) connected to the second terminal 7b, and an electrode (gate or base) connected to the control circuit 15. It is a high side arm having and. The first terminal 7a is connected to the ground. The diode 35 may be a body diode of the switching element 25, or may be a rectifying element additionally connected in parallel with the switching element 25.

The control circuit 15 is driven so that the motor 7 rotates (forward rotation) in the forward rotation direction corresponding to the winding direction of the seat belt 2 in the mode (winding mode) in which the seat belt 2 is wound on the spool 8. The switching element 25 of the circuit 14B is controlled. For example, the control circuit 15 turns the switching element 25 on / off by PWM control of a predetermined duty ratio in the take-up mode in which the motor 7 is rotated in the forward direction.

By controlling the switching element 25 in this way, the drive circuit 14B can rotate the motor 7 (forward rotation) in the direction (forward rotation direction) in which the spool 8 is rotated in the winding direction of the seatbelt 2. can. When the rotation shaft of the motor 7 rotates in the forward direction, the driving force of the forward rotation is transmitted to the spool 8 by the power transmission mechanism 17. As a result, the spool 8 rotates in the direction in which the seat belt 2 is wound, so that the seat belt 2 is wound on the spool 8.

In the configuration shown in FIG. 3, a reflux circuit 45 that is always connected in parallel with the motor 7 is provided. In the configuration of FIG. 3, the potential of the first terminal 7a becomes relatively higher than the potential of the second terminal 7b due to the generation of the counter electromotive force (in other words, the potential of the second terminal 7b is the first. It is relatively lower than the potential of the terminal 7a). Therefore, when the potential difference between the first terminal 7a and the second terminal 7b exceeds the forward voltage of the Zener diode 44, the current due to the back electromotive force becomes the first terminal 7a, the recirculation circuit 45, and the second terminal. It recirculates in the route of the terminal 7b and the motor 7. In this way, the return circuit 45 can prevent the motor 7 from rotating in the reverse direction in which the spool 8 is rotated in the pull-out direction of the seat belt 2 by returning the current due to the counter electromotive force to the motor 7. .. As a result, it becomes possible to absorb the collision energy acting on the occupant 9 at the time of a vehicle collision.

The return circuit 45 has a Zener diode 44. A Zener diode 44 is inserted in series in a current path through which a counter electromotive current flows. The Zener diode 44 is a rectifying element that is always connected in parallel with the motor 7 and recirculates the current due to the counter electromotive force generated in the motor 7 to the motor 7. A Zener diode 44 having an anode on the first terminal 7a side and a cathode on the second terminal 7b side is always connected in parallel to the motor 7. The Zener diode 44 connected in such an orientation can prevent the drive current for rotating the motor 7 in the forward rotation direction corresponding to the winding direction of the seat belt 2 from flowing to the return circuit 45.

Further, due to the generation of the counter electromotive force, the potential of the first terminal 7a becomes relatively lower than the potential of the second terminal 7b (in other words, the potential of the second terminal 7b becomes the potential of the first terminal 7a. (Relatively higher than) may be expected. In this case, when the potential difference between the first terminal 7a and the second terminal 7b exceeds the Zener voltage of the Zener diode 44, the current due to the counter electromotive force is the second terminal 7b, the recirculation circuit 40, and the first. It recirculates in the route of the terminal 7a and the motor 7. The Zener voltage of the Zener diode 44 is set to a value larger than the power supply voltage between the power supply VB and ground. Therefore, according to the drive circuit 14B shown in FIG. 3, it is possible to deal with counter electromotive forces in both directions.

FIG. 4 is a diagram showing a third configuration example of the drive circuit 14. The same points as those of the first and second configuration examples will be omitted. In the drive circuit 14C shown in FIG. 4, a reflux circuit 49 that is always connected in parallel with the motor 7 is provided. The recirculation circuit 49 has a configuration in which a Zener diode 47 and a resistance element 48 are added to the recirculation circuit 45 of FIG.

The Zener diode 47 is a rectifying element that is always connected in parallel with the motor 7 and recirculates the current due to the counter electromotive force generated in the motor 7 to the motor 7. The Zener diode 47 is connected in series with the diode 46. A Zener diode 47 having a cathode on the first terminal 7a side and an anode on the second terminal 7b side is always connected to the motor 7 in parallel. The Zener voltage of the Zener diode 47 is set to a value larger than the power supply voltage between the power supply VB and the ground.

In the configuration of FIG. 4, when the potential difference between the first terminal 7a and the second terminal 7b exceeds the sum of the forward voltage of the diode 46 and the Zener voltage of the Zener diode 47, the current due to the counter electromotive force is generated. , The first terminal 7a, the recirculation circuit 40, the second terminal 7b, and the motor 7 recirculate. In this way, the return circuit 49 can prevent the motor 7 from rotating in the reverse direction in which the spool 8 is rotated in the pull-out direction of the seat belt 2 by returning the current due to the counter electromotive force to the motor 7. .. As a result, it becomes possible to absorb the collision energy acting on the occupant 9 at the time of a vehicle collision.

Further, in the configuration of FIG. 4, when the potential of the first terminal 7a becomes relatively higher than the potential of the second terminal 7b due to the generation of the counter electromotive force, the first is performed when the current is returned by the counter electromotive force. The potential difference between the terminal 7a and the second terminal 7b is clamped at a higher voltage than that of the configuration of FIG. Therefore, the heat generation of the reflux circuit can be suppressed, and the period for absorbing energy can be shortened.

The resistance element 48 is connected in series with the Zener diode 47. Since the resistance element 48 reduces the recirculation current flowing through the recirculation circuit 49 due to the counter electromotive force, the force for suppressing the rotation of the motor 7 can be weakened. That is, by changing the resistance value of the resistance element 48, the force for suppressing the rotation of the motor 7 can be adjusted. The resistance element 48 may be omitted.

Further, due to the generation of the counter electromotive force, the potential of the first terminal 7a becomes relatively lower than the potential of the second terminal 7b (in other words, the potential of the second terminal 7b becomes the potential of the first terminal 7a. (Relatively higher than) may be expected. In this case, the diode 46 having the first terminal 7a side as the anode and the second terminal 7b side as the cathode is replaced with a Zener diode having the first terminal 7a side as the anode and the second terminal 7b side as the cathode. Is preferable. In the configuration in which the diode 42 is replaced with a Zener diode, when a counter electromotive force is generated in which the potential of the first terminal 7a is relatively lower than the potential of the second terminal 7b, the current due to the counter electromotive force is the second. It recirculates in the route of the terminal 7b, the recirculation circuit 40, the first terminal 7a, and the motor 7. The Zener voltage of this replaced Zener diode is set to a value larger than the power supply voltage between the power supply VB and ground. As described above, in the drive circuit 14C shown in FIG. 4, by changing the diode 46 to a Zener diode, a more preferable configuration can be realized in that it can cope with the generation of counter electromotive force in both directions.

FIG. 5 is a cross-sectional view showing a first configuration example of the seatbelt winding mechanism.

The take-up mechanism 6A is an example of the take-up mechanism 6 described above, and has the following components.
(1) Spool 101 for winding webbing (not shown)
(2) Torsion bar (spool shaft) 102 that is fitted as a spool shaft and twists with a predetermined load.
(3) Retractor base 103 that rotatably supports the spool 101 and the torsion bar 102.
(4) Internal gear (internal gear) 104 integrally fixed to the retractor base 103 with screws or the like.
(5) Three planetary gears (planetary gears) 105 that engage with the internal teeth of the internal gear 104 (only one is shown in the figure).
(6) A carrier (output shaft) 106 that is a rotation center shaft of the planetary gear 105 and is integrally fitted and mounted on the torsion bar 102.
(7) Sun gear 107 that engages with the planetary gear 105
(8) Cylindrical rotor 108 in which the sun gear 107 is integrally formed at the same center of rotation.
(9) A ring-shaped magnet 109 that is attached to the inner side surface of the peripheral surface of the cylinder of the rotor 108 with an adhesive or the like and constitutes the main part of the brushless motor 7A.
(10) A plurality of drive coils 110 that form a main part of the brushless motor 7A in close proximity to the magnet 109.
(11) Cover 111 for covering the brushless motor 7A
(12) A columnar bush shaft 112 provided on the outside of the cover 111 and fitted and mounted on the torsion bar 102.
(13) A return spring 113 having one end fixed to the bush shaft 112 and wound in multiple layers to transmit a driving force to the torsion bar 102.
(14) The other end of the return spring 113 is fixed, and the spring cover 114 is integrally fixed to the cover 111 and covers the return spring 113.

The brushless motor 7A is an example of the above-mentioned motor 7, and has a rotor 108, a magnet 109, and a drive coil 110. The planetary gear mechanism 17A is an example of the above-mentioned power transmission mechanism 17, and has a planetary gear 105, a carrier 106, and a sun gear 107. Hereinafter, the configuration of the take-up mechanism 6A will be described in more detail.

The take-up mechanism 6A is provided with a mechanism that uses both a mechanical EA mechanism (EA means energy absorption and the following terms are used in a unified manner) and an electric EA mechanism. In the mechanical EA mechanism, energy is absorbed by the twisting phenomenon of the torsion bar 102 when a torque exceeding a predetermined limit load is applied.

On the other hand, the electric EA mechanism is performed by applying an assist force by the brushless motor 7A. These two mechanisms are used to complement each other.

Hereinafter, the overall operation of the take-up mechanism 6A will be described.

In this take-up mechanism 6A, when a drive current is sent to the drive coil 110 by the drive circuit 14, a magnetic field is generated in the drive coil 110, a repulsive force is generated in the magnet 109, and a rotational force is generated in the rotor 108 of the brushless motor 7A. To. The rotational force of the rotor 108 causes the sun gear 107 to rotate around the torsion bar 102, and the three planetary gears 105 that engage the sun gear 107 are given rotational force. Further, since the three planetary gears 105 are engaged with the internal teeth of the immovable internal gear 104 fixed to the retractor base 103, they rotate in the internal gear 104 like a planet (FIG. 6). , 7 reference numeral 226, 227). By the rotation of the planetary gear 105, the carrier 106, which is the rotation axis of the planetary gear 105, rotates with the rotation of the planetary gear 105, and rotates the torsion bar 102 integrated with the carrier 106. When the torsion bar 102 rotates, the spool 101 also rotates integrally.

Further, the bush shaft 112 integrally provided at the end of the torsion bar 102 rotates with the rotation of the torsion bar 102, and winds the return spring 113 in the urging direction or the urging force release direction. Since the other configurations are the same as those of the conventional retractor, the description of the configuration is omitted.

Next, the configuration and operation of only the EA mechanism of the take-up mechanism 6A will be described. There are roughly two methods for mutually complementing the two EA mechanisms, that is, the EA mechanism of the torsion bar 102 and the EA mechanism of the motor assist load. In the first method, the brushless motor 7A rotates the spool 101 in the direction opposite to the twisting rotation direction of the torsion bar 102 to give a positive motor assist load. In the second method, the brushless motor 7A rotates the spool 101 in both the same forward direction as the torsion rotation direction of the torsion bar 102 and the direction opposite to the torsion rotation direction to apply negative and positive motor assist loads. The rotation of the brushless motor 7A can be controlled by the control device 1.

For example, in the case of a winding mechanism using a torsion bar 102 with a limit load of 2.5 kN (kilonewton), the rotation control by the first method causes motor assist in the direction opposite to the torsional rotation direction of the torsion bar 102. It is assumed that the load is applied from 0 to 3 kN. As a result, when the EA effect of the motor assist load is added to the EA effect of the torsion bar 102, an EA effect of 2.5 kN to 5.5 kN can be expected as a whole.

On the other hand, for example, in the case of a winding mechanism using a torsion bar 102 with a limit load of 4 kN, the rotation control by the second method is performed in the forward direction from -1.5 kN in the direction opposite to the torsional rotation direction of the torsion bar 102. It is assumed that a motor assist load of up to + 1.5 kN is applied. As a result, an EA effect of 2.5 kN to 5.5 kN can be expected as a whole. In this case, when the motor mounted on the take-up mechanism 6A is to be miniaturized, the second method is preferable because a motor having a small output can be utilized. Further, if the Hall element is arranged around the drive coil 110, the rotational state of the rotor 108 can be sensed.

FIG. 6 is an exploded perspective view showing a second configuration example of the seatbelt winding mechanism. FIG. 7 is a diagram showing the engagement relationship of the gears of the take-up mechanism 6B shown in FIG. In FIG. 7, the explosive type pretension mechanism is omitted in the drawing. Hereinafter, the configuration of the winding mechanism 6B will be described with reference to FIGS. 6 and 7. The take-up mechanism 6B is an example of the take-up mechanism 6 described above, and has the following components.

(1) Retainer 220
(2) DC motor 221 integrally mounted on the retainer 220
(3) Motor gear 222 integrally provided on the motor shaft of the DC motor 221
(4) A first gear 223 that is pivotally supported by a protrusion provided on the retainer 220 and engages with the motor gear 222 (specifically, the first gear 223 is an integral two-stage gear (large gear 223a and small gear). 223b), the motor gear 222 engages with the large gear 223a)
(5) The second gear 224 (specifically, the second gear 224 is an integral 2) that is pivotally supported by a protrusion provided on the retainer 220 and engages with the first gear 223 (specifically, the small gear 223b). It is composed of step gears (large gear 224a and small gear 224b), and the small gear 223b engages with the large gear 224a).
(6) The third gear 225 that engages with the second gear 224 (specifically, the small gear 224b) (specifically, the third gear 225 is composed of an integrated two-stage gear (large gear 225a and small gear 225b). The small gear 224b engages with the large gear 225a)
(7) Three planetary gears 226 that engage with the third gear 225 (specifically, the small gear 225b).
(8) Internal gear 227 that engages with three planetary gears 226 on the internal teeth 227a formed inside.
(9) External teeth 227b formed on the outer peripheral surface of the internal gear 227
(10) Locking piece 230 that fits into the external teeth 227b and locks the clockwise rotation of the internal gear 227.
(11) A lever 231 made of a spring that supports the locking piece 230 at one end.
(12) Ring member 232 in which the other end of the lever 231 is formed in a curled shape.
(13) A convex annular member 233 around which the ring member 232 is wound (the annular member 233 is integrally formed at the same rotation center as the first gear 223).
(14) Friction piece 234 which is projected from the peripheral edge of the top surface of the annular member 233 and presses the ring member 232 to give a frictional force.
(15) Carrier 235 for mounting three planetary gears 226
(16) Three pins 236 that rotatably support the three planetary gears 226 on the carrier 235 and fix them to the carrier 235.
(17) A reduction plate 237 that is swingably inserted between the three pins 236 and the three planetary gears 226.
(18) The tip portion 238a is passed through the rotation center hole of the carrier 235 and integrally fitted at the base portion of the tip portion 238a, and the tip portion 238a is slidably rotatable in the rotation center hole of the third gear 225. Spool 238 to be inserted
(19) Webbing W for restraining the body whose one end is fixed to the spool 238 (arrow A is the pull-out direction of the webbing W, arrow B is the pull-in direction of the webbing W).
(20) Cover 239 that covers the entire gear group
(21) A plurality of screws 240 for attaching the cover 239 to the retainer 220.

The DC motor 221 is an example of the above-mentioned motor 7. The planetary gear mechanism 17B is an example of the above-mentioned power transmission mechanism 17, and has the above-mentioned components (3) to (17) of the take-up mechanism 6B. Hereinafter, the operation of the take-up mechanism 6B will be described in more detail.

The control device 1 controls the operation so as to rotate the rotation axis of the DC motor 221 clockwise or counterclockwise. 8 and 9 are diagrams showing the operation of this embodiment, FIG. 8 is a diagram showing a state when the motor rotates in the clockwise direction (CW direction), and FIG. 9 is a diagram showing a state in which the motor rotates in the counterclockwise direction (counterclockwise direction). It is a figure which shows the state in the case of rotating in the CCW direction).

In the winding mechanism 6B, during normal times (except in an emergency such as a sudden braking or a collision), as shown in FIGS. 7 and 9, the locking piece 230 is separated from the external teeth 227b and is internal. Gear 227 is not constrained. Therefore, due to the characteristics of the planetary gear, the rotational force of the carrier 235 is not transmitted to the third gear 225. Therefore, the rotational force of the spool 238 integrally fitted to the carrier 235 is not transmitted to the rotating shaft of the DC motor 221 engaged with the third gear 225.

Next, in the event of an emergency such as sudden braking or a collision, a command signal is output from an in-vehicle computer such as an ABS (anti-lock braking system) mechanism or a collision prediction device. The output command signal activates the pretension mechanism (a mechanism that winds up the webbing W to increase the tension prior to the explosive pretension mechanism), and the rotation axis of the DC motor 221 is rotated clockwise (as shown in FIG. 8). Rotate in the direction of the arrow).

Then, the clockwise rotational force of the motor gear 222 is transmitted to the first gear 223 as a counterclockwise (arrow direction) rotational force, and the locking piece 230 engages with the external teeth 227b of the internal gear 227 to be internal. Locks the clockwise (arrow direction) rotation of the gear 227. As a result, the rotational force of the third gear 225 can be transmitted to the carrier 235 to which the spool 238 is integrally fitted. Further, the rotational force of the first gear 223 is transmitted to the second gear 224 as a rotational force in the clockwise direction (arrow direction), and the rotational force in the counterclockwise direction (arrow direction) is transmitted to the third gear 225.

Therefore, the counterclockwise rotation of the third gear 225 causes the small gear 225b integrated with the third gear 225 to rotate counterclockwise, and the rotational force in the clockwise direction (arrow direction) of each of the three planetary gears 226. To convey. The three planetary gears 226 rotate counterclockwise (arrow direction) around the small gear 225b while engaging with the internal teeth 227a of the internal gear 227 whose rotation is constrained by the locking piece 230. Move. The three planetary gears 226 rotate the carrier 235 that pivotally supports the three planetary gears 226 in the counterclockwise direction (arrow direction). Therefore, the spool 238 fitted to the carrier 235 rotates counterclockwise and winds up the webbing W (in the direction of arrow B). Therefore, the clockwise rotational force of the DC motor 221 is transmitted as the rotational force for winding up the webbing W.

Next, an impact force is transmitted to the vehicle body due to a collision, an impact detection signal is output from an acceleration sensor (not shown) or a crash sensor (not shown), an explosive-type pretension mechanism (not shown) is activated, and the webbing W is drawn into the take-up mechanism 6B. The initial restraint of the occupants is secured. Next, the webbing W is pulled out by the inertial force in front of the occupant (arrow A in FIG. 8).

At this time, as shown in FIG. 8, since the locking piece 230 is in the state of locking the external teeth 227b, the force with which the webbing W is pulled out from the spool 238 is counterclockwise (arrow) with respect to the rotation axis of the DC motor 221. The rotational force is transmitted in the opposite direction). When the DC motor 221 is in an energized state or a short-circuited state, a counter electromotive force is generated by the rotation of the rotating shaft, and a rotational drag force that hinders the rotation is generated. The take-up mechanism 6B intends to positively utilize this rotational drag force in the lock mechanism and the EA mechanism.

Although the seatbelt retractor and the seatbelt winding mechanism have been described above by embodiment, the present invention is not limited to the above embodiment. Various modifications and improvements, such as combinations and substitutions with some or all of the other embodiments, are possible within the scope of the present invention.

1 Control device 2 Seatbelt 6 Seatbelt take-up mechanism 7 Motor 8 Spool 10 Seatbelt retractor 14, 14A, 14B Drive circuit 15 Control circuit 17 Power transmission mechanism 40, 45, 49 Circulation circuit 100 Seatbelt device

Claims (10)

A spool for winding up the seat belt and
A motor having a rotating shaft connected to the rotating shaft of the spool via a power transmission mechanism and rotating the spool,
The drive circuit that drives the motor and
At least one rectifying element which is always connected in parallel to the motor and causes the current generated by the counter electromotive force generated in the motor to be returned to the motor by rotating the motor by an external force applied to the spool. Prepare ,
A seatbelt retractor that recirculates the current to the motor to prevent the motor from rotating in the direction of rotating the spool in the direction of pulling out the seatbelt. The motor has a first terminal and a second terminal whose potential is relatively lower than that of the first terminal due to the generation of the counter electromotive force.
The seatbelt retractor according to claim 1, wherein the rectifying element includes a diode having the first terminal side as an anode and the second terminal side as a cathode. The seatbelt retractor according to claim 2, wherein the rectifying element is connected in series with the diode and includes a Zener diode having the first terminal side as a cathode and the second terminal side as an anode. The seatbelt retractor according to claim 3, further comprising a resistance element connected in series with the Zener diode. The drive circuit has a first high-side switching element connected to the first terminal, a first low-side switching element connected to the first terminal, and a second terminal connected to the second terminal. The seatbelt retractor according to claim 3 or 4, further comprising a high-side switching element (2) and a second low-side switching element connected to the second terminal. The seatbelt retractor according to claim 5, wherein the diode having the first terminal side as an anode and the second terminal side as a cathode is a Zener diode. The motor has a first terminal and a second terminal whose potential is relatively higher than that of the first terminal due to the generation of the counter electromotive force.
The seatbelt retractor according to claim 1, wherein the rectifying element includes a Zener diode having the first terminal side as an anode and the second terminal side as a cathode. The seatbelt retractor according to any one of claims 1 to 7, wherein the current due to the counter electromotive force returns to the motor to suppress the rotation of the motor. The claim that the current is returned to the motor to suppress the rotation of the motor in the direction of rotating the spool in the pull-out direction of the seatbelt and to absorb the collision energy acting on the occupant in the event of a vehicle collision. The seatbelt retractor according to any one of 1 to 8 . A spool for winding up the seat belt and
A motor having a rotating shaft connected to the rotating shaft of the spool via a power transmission mechanism and rotating the spool,
At least one rectifying element which is always connected in parallel to the motor and causes the current generated by the counter electromotive force generated in the motor to be returned to the motor by rotating the motor by an external force applied to the spool. Prepare ,
A seatbelt winding mechanism that suppresses the rotation of the motor in the direction of rotating the spool in the pull-out direction of the seatbelt by recirculating the current to the motor .

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