WO2019163759A1

WO2019163759A1 - Seatbelt retractor and seatbelt winding mechanism

Info

Publication number: WO2019163759A1
Application number: PCT/JP2019/006061
Authority: WO
Inventors: 雅人 ▲高▼尾; 篤三原
Original assignee: ＪｏｙｓｏｎＳａｆｅｔｙＳｙｓｔｅｍｓＪａｐａｎ株式会社
Priority date: 2018-02-26
Filing date: 2019-02-19
Publication date: 2019-08-29
Also published as: JP7060983B2; JP2019147438A

Abstract

Provided is a seatbelt retractor comprising: a spool for winding a seatbelt; a motor for rotating the spool; a drive circuit for driving the motor; and at least one rectifier element which is always connected in parallel to the motor and which returns an electric current to the motor, the electric current having been generated in the motor by a counter-electromotive force. Also provided is a seatbelt winding mechanism comprising: a spool for winding a seatbelt; a motor for rotating the spool; and at least one rectifier element which is always connected in parallel to the motor and which returns an electric current to the motor, the electric current having been generated in the motor by a counter-electromotive force.

Description

Seat belt retractor and seat belt retractor

The present invention relates to a seat belt retractor and a seat belt winding mechanism.

2. Description of the Related Art Conventionally, in a seat belt retractor that winds up a seat belt with the power of a motor, a technique for short-circuiting a pair of power feeding terminals of a motor in order to cause a current caused by a counter electromotive force generated in the motor to flow back to the motor is known (for example, Patent Document 1).

JP 2011-093431 A

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

Therefore, the present disclosure provides a seat belt retractor and a seat belt retracting mechanism that can easily return a current caused by a counter electromotive force to a motor.

This disclosure
A spool for winding up the seat belt;
A motor for rotating the spool;
A drive circuit for driving the motor;
Provided is a seat belt retractor comprising at least one rectifier element that is always connected in parallel to the motor and causes the motor to recirculate a current caused by a counter electromotive force generated in the motor.

In addition, this disclosure
A spool for winding up the seat belt;
A motor for rotating the spool;
There is provided a seat belt retracting mechanism including at least one rectifying element that is always connected in parallel to the motor and causes the motor to recirculate a current caused by a counter electromotive force generated in the motor.

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

It is a figure which shows an example of a structure of a seatbelt apparatus. 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 a seatbelt winding-up mechanism. It is a disassembled perspective view which shows the 2nd structural example of a seatbelt winding-up mechanism. It is a figure which shows the engagement relationship of a gear. It is a figure which shows a state in case a motor rotates clockwise (CW direction). It is a figure which shows a state in case a motor rotates counterclockwise (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 seat belt device 100. The seat belt device 100 is a system mounted on a vehicle 13 such as an automobile. The seat belt device 100 includes, for example, a seat belt 2, a shoulder anchor 3, a tongue 4, a buckle 5, and a seat belt retractor (hereinafter simply referred to as “retractor”) 10. The retractor 10 includes a seat belt 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 belt-like member that restrains the occupant 9 sitting on the seat 11 of the vehicle 13, and is wound around the winding mechanism 6 so that it can be pulled out from the winding mechanism 6. One end of the seat belt 2 is connected to the take-up mechanism 6, and the other end of the seat belt 2 is fixed to the vehicle body, the pretensioner device, the seat 11, or the like. The seat belt is also referred to as webbing.

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

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 the floor of the vehicle body or the seat 11, for example.

The retractor 10 is fixed to, for example, the vehicle body near the seat 11 or the seat 11 itself. The retractor 10 includes a winding mechanism 6 that enables the seat belt 2 to be wound or pulled out, and a control device 1 that controls the operation of the winding mechanism 6.

The winding mechanism 6 includes a spool 8 for winding the seat belt 2, a motor 7 that rotates the spool 8, and a power transmission mechanism 17 that transmits 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 that rotates the spool 8. The rotation shaft of the motor 7 is connected to the rotation shaft of the spool 8 via the power transmission mechanism 17.

The controller 1 controls the winding operation (or both the winding operation and the drawing 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 that drives the motor 7 and a control circuit 15 that controls the drive operation of the drive circuit 14.

The drive circuit 14 causes a drive current to drive the motor 7 to flow through the motor 7 in accordance with 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 a high-side switching element, and a low-side drive circuit having only a low-side switching element. It is done. The form of the drive circuit 14 is not limited to these, and is determined according to required specifications.

The control circuit 15 outputs at least one control signal (for example, a PWM control signal) for controlling the magnitude (or magnitude and direction) of the drive current for driving the motor 7 to the drive circuit 14. To do. Each function of the control circuit 15 is realized by operating a CPU (Central Processing Unit) according to a program stored in the memory. A specific example of the control circuit 15 includes a microcomputer having a CPU and a memory.

FIG. 2 is a diagram illustrating a first configuration example of the drive circuit 14. The drive circuit 14 A shown in FIG. 2 is an H-bridge drive circuit that has four

switching elements

21, 22, 23, and 24 and can switch the direction of the drive current that flows to the motor 7. The motor 7 incorporates a coil connected between the first terminal 7a and the second terminal 7b.

The drive circuit 14 A includes a first connection point 12 connected to the first terminal 7 a of the motor 7 and a second connection point 18 connected to the second terminal 7 b 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 14 A is connected between the power supply VB and the ground (GND). 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. Low-

side switching elements

22 and 24 connected to each other. The

switching elements

21, 22, 23, and 24 are semiconductor elements that are turned on / off. For example, the

switching elements

21, 22, 23, and 24 may be voltage controlled transistors such as MOSFETs (Metal / Oxide / Semiconductor / Field / Effect / Transistors) or current controlled bipolar transistors. Good. FIG. 2 illustrates a mode in which the

switching elements

21, 22, 23, and 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 includes an electrode (drain or collector) connected to the power supply VB side, an electrode (source or emitter) connected to the first terminal 7 a via the first connection point 12, and the control circuit 15. A high side arm having 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 7 a via the first connection point 12, and the control circuit 15. A low-side arm having an electrode (gate or base) to be operated.

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

The

diodes

31, 32, 33, and 34 may be body diodes of the switching

elements

21, 22, 23, and 24 corresponding to the

diodes

31, 32, 33, and 34, respectively. A rectifying element may be used.

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 measurement circuit 16 measures the amount of current flowing through the drive circuit 14A using, for example, 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.

Note that the current measurement circuit 16 determines the amount of current flowing through the drive circuit 14A by, for example, a resistor inserted in series in the current path between the high-

side switching elements

21 and 23 of the drive circuit 14A and the power supply VB. You may measure. The current measurement method is not limited to these.

The control circuit 15 is a drive control unit that drives the four

switching elements

21, 22, 23, and 24 that constitute the drive circuit 14 A using the current measurement result by the current measurement circuit 16.

In the mode (winding mode) in which the seat belt 2 is wound around the spool 8, 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. Each switching element of the circuit 14A is controlled. For example, in the winding mode in which the motor 7 is normally rotated, the control circuit 15 turns on / off the switching element 23 by PWM control with a predetermined duty ratio, always turns off the switching

elements

21, 24, and keeps the switching element 22 always on. Turn it on. At this time, the control circuit 15 may turn on the switching element 24 when the switching element 23 is turned off in order to suppress heat generation due to the return current when the switching element 23 is turned off. Alternatively, in the winding mode in which the motor 7 is rotated forward, the control circuit 15 turns on / off the switching element 22 by PWM control with a predetermined duty ratio, always turns off the switching

elements

21, 24, and always turns on the switching element 23. It may be turned on. At this time, the control circuit 15 may turn on the switching element 21 when the switching element 22 is turned off in order to suppress heat generation due to the return current when the switching element 22 is turned off.

By controlling each switching element in this way, the drive circuit 14A can rotate (forward rotation) the motor 7 in the direction (forward rotation direction) in which the spool 8 rotates in the winding direction of the seat belt 2. it can. When the rotation shaft of the motor 7 rotates in the forward direction, the driving force for 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 around the spool 8.

On the other hand, in the mode (drawing mode) in which the seat belt 2 is pulled out from the spool 8, the control circuit 15 drives the driving circuit 14A so that the motor 7 rotates (reversely rotates) in the reverse direction corresponding to the pulling direction of the seat belt 2. Each switching element is controlled. For example, in the drawer mode in which the motor 7 rotates in the reverse direction, the control circuit 15 turns on / off the switching element 21 by PWM control with a predetermined duty ratio, always turns off the switching

elements

22, 23, and always turns on the switching element 24. Let At this time, the control circuit 15 may turn on the switching element 22 when the switching element 21 is turned off in order to suppress heat generation due to the return current 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 on / off the switching element 24 by PWM control with a predetermined duty ratio, always turns off the switching

elements

22 and 23, and always turns on the switching element 21. You may let them. At this time, the control circuit 15 may turn on the switching element 23 when the switching element 24 is turned off in order to suppress heat generation due to the return current when the switching element 24 is turned off.

By controlling each switching element in this way, the drive circuit 14A can rotate (reversely rotate) the motor 7 in the direction (reverse 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.

Incidentally, in the configuration shown in FIG. 2, a reflux circuit 40 that is always connected in parallel to the motor 7 is provided. In a state where the rotation shaft of the motor 7 and the rotation shaft of the spool 8 are connected by the power transmission mechanism 17, when 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 recirculates the current caused by the counter electromotive force to the motor 7 to suppress the rotation of the motor 7 and apply a brake.

The recirculation circuit 40 suppresses the rotation of the motor 7 so that, for example, it is possible to absorb the collision energy that acts on the occupant 9 when the vehicle collides. Further, since the return circuit 40 is always connected in parallel to the motor 7, it is not necessary to control the current caused by the back electromotive force to flow back to the motor 7. Therefore, the current caused by the back electromotive force can be easily supplied to the motor 7. It can be refluxed.

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. It is also difficult to return the motor to the motor 7. On the other hand, in the present embodiment, there is no need for control for returning the current caused by the counter electromotive force to the motor 7. Therefore, even if the power supply VB is lost due to a collision or the like, the current caused by the counter electromotive force can be returned to the motor 7 and the collision energy acting on the occupant 9 at the time of the vehicle collision can be absorbed.

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

As a specific example of an emergency in which a deceleration greater than a predetermined value is applied to the vehicle 13, when a sudden brake that decelerates the vehicle 13 at a deceleration greater than a predetermined value is activated automatically or by a driver's brake operation, the driver's brake operation Even when there is not, there is a case where an automatic brake for automatically decelerating the vehicle 13 at a deceleration greater than a predetermined value is activated. A specific example of an emergency in which a deceleration greater than a predetermined value may be applied to the vehicle 13 includes a time when it is determined that the vehicle 13 may collide.

When a condition such as receiving a command signal from an in-vehicle computer outside the retractor 10 is satisfied in a state where the tongue 4 is engaged with the buckle 5 and the seat belt 2 is attached to the occupant 9, the control circuit 15 The restraint force control for the passenger 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 seat belt 2 in order to prepare for an impact at the time of collision. . When the rotation shaft of the motor 7 rotates in the forward direction, the driving force for 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 around the spool 8. As a result, the restraining force on the occupant 9 by the seat belt 2 increases.

Thereafter, when the occupant 9 moves forward of the vehicle due to inertia at the time of the collision, the seat belt 2 is pulled out of the spool 8 by the inertial force of the occupant 9 toward 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 rotating shaft of the motor 7 by the power transmission mechanism 17. As a result, the rotating 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 the 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 back electromotive force is The first terminal 7 a, the reflux circuit 40, the second terminal 7 b, and the motor 7 circulate in the normal path. In this way, the reflux circuit 40 can suppress the rotation of the motor 7 in the reverse direction in which the spool 8 is rotated in the pull-out direction of the seat belt 2 by causing the motor 7 to return the current due to the counter electromotive force. . As a result, it is possible to absorb the collision energy that acts on the occupant 9 when the vehicle collides.

The reflux 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 caused by the 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 replaced with each other.

The diode 42 is a rectifying element that is always connected in parallel to the motor 7 and causes the motor 7 to return a current caused by the counter electromotive force generated in the motor 7. A diode 42 having an anode on the first terminal 7 a side and a cathode on the second terminal 7 b side is always connected in parallel to the motor 7. The diode 42 connected in this direction can prevent a drive current that rotates the motor 7 in the forward rotation direction corresponding to the winding direction of the seat belt 2 from flowing into the return circuit 40.

The zener diode 41 is also always connected in parallel to the motor 7, and is a rectifying element that causes the motor 7 to return current due to the counter electromotive force generated in the motor 7. Zener diode 41 is connected in series to diode 42. A Zener diode 41 having a cathode on the first terminal 7 a side and an anode on the second terminal 7 b side is always connected in parallel to the motor 7. The zener diode 41 connected in this direction can prevent the drive current that rotates the motor 7 in the reverse direction corresponding to the pulling-out direction of the seat belt 2 from flowing into the reflux 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 to the Zener diode 41 in series. Because the resistance element 43 reduces the return current flowing in the return circuit 40 due to the back electromotive force, the force for suppressing the rotation of the motor 7 can be weakened. That is, the force for suppressing the rotation of the motor 7 can be adjusted by changing the resistance value of the resistance element 43. Note that the resistance element 43 may be omitted.

Further, due to the occurrence of the back 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). May be assumed to be relatively higher). In this case, it is preferable to replace the diode 42 with a Zener diode having the first terminal 7a side as an anode and the second terminal 7b side as a cathode. In the configuration in which the diode 42 is replaced with a Zener diode, when a back 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 back electromotive force is The terminal 7 b, the reflux circuit 40, the first terminal 7 a, and the motor 7 are circulated in the normal path. The Zener voltage of the replaced Zener diode is set to a value larger than the power supply voltage between the power supply VB and the ground. In this way, in the drive circuit 14A shown in FIG. 2, the diode 42 is also changed to a Zener diode, whereby a more preferable configuration can be realized in that it can cope with generation of counter electromotive force in both directions.

FIG. 3 is a diagram illustrating a second configuration example of the drive circuit 14. The description of the same points as in the first configuration example is omitted. The drive circuit 14B shown in FIG. 3 has a high-side switching element 25 and is a high-side drive circuit capable of supplying a drive current only in one direction to the motor 7. The drive circuit 14B is used when, for example, it is not necessary to rotate the motor 7 in the reverse rotation direction corresponding to the pulling direction of the seat belt 2, and the motor 7 is rotated in the forward rotation direction corresponding to the winding direction of the seat belt 2. The driving current to be supplied 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 And a high side arm. The first terminal 7a is connected to the ground. The diode 35 may be a body diode of the switching element 25 or a rectifying element additionally connected to the switching element 25 in parallel.

In the mode (winding mode) in which the seat belt 2 is wound around the spool 8, 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. The switching element 25 of the circuit 14B is controlled. For example, in the winding mode in which the motor 7 is rotated forward, the control circuit 15 turns on / off the switching element 25 by PWM control with a predetermined duty ratio.

By controlling the switching element 25 in this way, the drive circuit 14B can rotate (forward rotation) the motor 7 in the direction (forward rotation direction) in which the spool 8 rotates in the winding direction of the seat belt 2. it can. When the rotation shaft of the motor 7 rotates in the forward direction, the driving force for 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 around the spool 8.

3, a reflux circuit 45 that is always connected in parallel to 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 occurrence of the back electromotive force (in other words, the potential of the second terminal 7b is the first potential). It becomes 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 caused by the back electromotive force is changed to the first terminal 7a, the reflux circuit 45, the second The terminal 7b and the motor 7 are recirculated in the normal path. In this way, the return circuit 45 can suppress the rotation of the motor 7 in the reverse direction that rotates the spool 8 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 is possible to absorb the collision energy that acts on the occupant 9 when the vehicle collides.

The reflux circuit 45 has a Zener diode 44. A Zener diode 44 is inserted in series in a current path through which a current caused by the counter electromotive force flows. The Zener diode 44 is a rectifying element that is always connected in parallel to the motor 7 and causes the motor 7 to return a current caused by the counter electromotive force generated in the motor 7. A Zener diode 44 having the first terminal 7 a side as an anode and the second terminal 7 b side as a cathode is always connected to the motor 7 in parallel. The zener diode 44 connected in such a direction can prevent the drive current that rotates the motor 7 in the forward rotation direction corresponding to the winding direction of the seat belt 2 from flowing into the reflux circuit 45.

Further, due to the occurrence of the back 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). May be assumed to be relatively higher). 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 caused by the back electromotive force is changed to the second terminal 7b, the reflux circuit 40, the first The terminal 7a and the motor 7 are recirculated in the normal path. 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 the ground. Therefore, according to the drive circuit 14B shown in FIG. 3, it is possible to cope with the counter electromotive force in both directions.

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

The zener diode 47 is always connected in parallel to the motor 7 and is a rectifying element that causes the motor 7 to return a current caused by the counter electromotive force generated in the motor 7. Zener diode 47 is connected in series with diode 46. A Zener diode 47 having the first terminal 7 a side as a cathode and the second terminal 7 b side as an anode 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, if the potential difference between the first terminal 7 a and the second terminal 7 b 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 back electromotive force is The first terminal 7 a, the reflux circuit 40, the second terminal 7 b, and the motor 7 circulate in the normal path. In this way, the return circuit 49 can suppress the rotation of the motor 7 in the reverse direction that rotates the spool 8 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 is possible to absorb the collision energy that acts on the occupant 9 when the vehicle collides.

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

The resistance element 48 is connected to the Zener diode 47 in series. The resistance element 48 reduces the return current flowing in the return circuit 49 due to the back electromotive force, so that the force for suppressing the rotation of the motor 7 can be weakened. That is, the force for suppressing the rotation of the motor 7 can be adjusted by changing the resistance value of the resistance element 48. Note that the resistance element 48 may be omitted.

Further, due to the occurrence of the back 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). May be assumed to be relatively higher). In this case, the diode 46 having the first terminal 7a side as an anode and the second terminal 7b side as a cathode is replaced with a Zener diode having the first terminal 7a side as an anode and the second terminal 7b side as a cathode. It is preferable. In the configuration in which the diode 42 is replaced with a Zener diode, when a back 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 back electromotive force is The terminal 7 b, the reflux circuit 40, the first terminal 7 a, and the motor 7 are circulated in the normal path. The Zener voltage of the replaced Zener diode is set to a value larger than the power supply voltage between the power supply VB and the ground. As described above, in the drive circuit 14C shown in FIG. 4, the diode 46 is also changed to a Zener diode, whereby a more preferable configuration can be realized in that it can cope with generation of counter electromotive force in both directions.

FIG. 5 is a cross-sectional view showing a first configuration example of the seat belt retracting mechanism.

The winding mechanism 6A is an example of the above-described winding mechanism 6 and includes the following components.
(1) Spool 101 for winding webbing (not shown)
(2) Torsion bar (spool shaft) 102 fitted as a spool shaft and twisted by a predetermined load
(3) Retractor base 103 that rotatably supports the spool 101 and the torsion bar 102
(4) Internal gear (internal gear) 104 fixed integrally to the retractor base 103 with screws or the like.
(5) Three planetary gears (planetary gears) 105 engaged 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 to the torsion bar 102.
(7) Sun gear (sun gear) 107 engaged with the planetary gear 105
(8) A cylindrical rotor 108 in which the sun gear 107 is integrally formed at the same rotation center.
(9) A ring-shaped magnet 109 that is affixed to the inner surface of the cylindrical peripheral portion 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 constituting the main part of the brushless motor 7A in proximity to the magnet 109
(11) Cover 111 covering brushless motor 7A
(12) A cylindrical bush shaft 112 provided outside the cover 111 and fitted to the torsion bar 102.
(13) A return spring 113 that has one end fixed to the bush shaft 112 and wound in layers, and transmits 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 fixed integrally with the cover 111 and covers the return spring 113.

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

The take-up mechanism 6A is provided with a mechanical EA (EA means energy absorption; hereinafter, this term is used in unison) and an electric EA mechanism. The mechanical EA mechanism absorbs energy by a 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 so as to complement each other.

Hereinafter, the overall operation of the winding mechanism 6A will be described.

In the winding 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. The Due to the rotational force of the rotor 108, the sun gear 107 rotates around the torsion bar 102, and the three planetary gears 105 engaged with the sun gear 107 are given rotational force. Further, since the three planetary gears 105 are engaged with the internal teeth of the stationary internal gear 104 fixed to the retractor base 103, the planetary gears 105 rotate like planets (FIG. 6). , 7 (see symbols 226, 227). The rotation of the planetary gear 105 causes the carrier 106 that is the rotation shaft of the planetary gear 105 to rotate with the rotation of the planetary gear 105 to rotate the torsion bar 102 that is integral with the carrier 106. When the torsion bar 102 rotates, the spool 101 also rotates integrally.

Also, 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 up the return spring 113 in the urging direction or the urging force releasing direction. Since the other configuration is the same as that of the conventional retractor, the description of the configuration is omitted.

Next, the configuration and operation of only the EA mechanism of the winding 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, a positive motor assist load is applied by rotating the spool 101 in a direction opposite to the twisting rotation direction of the torsion bar 102 by the brushless motor 7A. In the second method, the brushless motor 7A rotates the spool 101 both in the same forward direction as the torsional rotation direction of the torsion bar 102 and in the opposite direction to the torsional rotation direction, thereby giving negative and positive motor assist loads. The brushless motor 7A can be rotationally 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 (kilonewtons), the motor assist in a direction opposite to the torsional rotation direction of the torsion bar 102 by the rotation control in the first method. Assume that a load is applied from 0 to 3 kN. Accordingly, when the EA effect of the motor assist load is added to the EA effect of the torsion bar 102, an EA effect from 2.5 kN to 5.5 kN as a whole can be expected.

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 forward direction from −1.5 kN in the direction opposite to the torsional rotation direction of the torsion bar 102 by the rotation control in the second method. Suppose that a motor assist load up to +1.5 kN is applied. Thereby, the EA effect from 2.5 kN to 5.5 kN can be similarly expected as a whole. In this case, when downsizing the motor mounted on the winding mechanism 6A, the second method is preferable because a motor with a smaller output can be used. Further, if a 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 seat belt retracting mechanism. FIG. 7 is a diagram showing a gear engagement relationship of the winding mechanism 6B shown in FIG. In FIG. 7, the explosive pretensioning mechanism is omitted in the drawing. Hereinafter, the configuration of the winding mechanism 6B will be described with reference to FIGS. The winding mechanism 6B is an example of the above-described winding mechanism 6 and includes the following components.

(1) Retainer 220
(2) DC motor 221 mounted integrally with retainer 220
(3) Motor gear 222 provided integrally with the motor shaft of 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 (a large gear 223a and a small gear). 223b), and the motor gear 222 engages with the large gear 223a)
(5) A second gear 224 (specifically, the second gear 224 is integrated with the first gear 223 (specifically, the small gear 223b), which is pivotally supported by a protrusion provided on the retainer 220, Step gear (consisting of a large gear 224a and a small gear 224b), and the small gear 223b engages with the large gear 224a)
(6) A third gear 225 (specifically, the third gear 225, which is engaged with the second gear 224 (specifically, the small gear 224b) is composed of an integral two-stage gear (a large gear 225a and a small gear 225b), (The small gear 224b engages with the large gear 225a)
(7) Three planetary gears 226 engaged with the third gear 225 (specifically, the small gear 225b)
(8) An internal gear 227 that engages with the three planetary gears 226 on the inner teeth 227a formed on the inner side.
(9) External teeth 227b formed on the outer peripheral surface of the internal gear 227
(10) A locking piece 230 that engages with the external tooth 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) A ring member 232 in which the other end of the lever 231 is curled.
(13) A convex annular member 233 around which the ring member 232 is wound (note that the annular member 233 is integrally formed at the same rotation center as the first gear 223).
(14) A friction piece 234 that protrudes from the periphery of the top surface of the annular member 233 and applies a frictional force by pressing the ring member 232.
(15) Carrier 235 for placing three planetary gears 226
(16) Three pins 236 fixed to the carrier 235 by rotatably supporting the three planetary gears 226 on the carrier 235
(17) Deceleration plate 237 inserted between the three pins 236 and the three planetary gears 226 in a swingable manner
(18) The tip 238a is passed through the rotation center hole of the carrier 235 and is integrally fitted at the root of the tip 238a, and the tip 238a is slidably rotatable in the rotation center hole of the third gear 225. Spool 238 to be inserted
(19) Webbing W for constraining the body, one end of which is fixed to spool 238 (arrow A is the pulling direction of webbing W, arrow B is the pulling direction of webbing W)
(20) Cover 239 covering 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 motor 7 described above. The planetary gear mechanism 17B is an example of the power transmission mechanism 17 described above, and includes the above-described components (3) to (17) of the winding mechanism 6B. Hereinafter, the operation of the winding mechanism 6B will be described in more detail.

The control device 1 controls the operation so as to rotate the rotating shaft of the DC motor 221 clockwise or counterclockwise. 8 and 9 are diagrams illustrating the operation of the present embodiment. FIG. 8 is a diagram illustrating a state where the motor rotates in the clockwise direction (CW direction). FIG. 9 illustrates the motor in the counterclockwise direction ( It is a figure which shows the state in the case of rotating in a (CCW direction).

As shown in FIGS. 7 and 9, the take-up mechanism 6B is normally separated from the external teeth 227b as shown in FIG. 7 and FIG. The gear 227 is not restrained. 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 that is integrally fitted to the carrier 235 is not transmitted to the rotational shaft of the DC motor 221 that engages with the third gear 225.

Next, in the event of an emergency such as a sudden braking or a collision, a command signal is output from an in-vehicle computer such as an ABS (anti-lock brake system) mechanism or a collision prediction device. In response to the output command signal, the pretensioning mechanism (mechanism for winding up the webbing W and increasing the tension prior to the explosive pretensioning mechanism) is actuated to rotate the rotating shaft of the DC motor 221 clockwise as shown in FIG. 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 the counterclockwise rotational direction (arrow direction), and the locking piece 230 engages with the external teeth 227b of the internal gear 227, and the internal gear 227 is engaged. The rotation of the gear 227 in the clockwise direction (arrow direction) is locked. As a result, the rotational force of the third gear 225 can be transmitted to the carrier 235 with 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.

Accordingly, the counterclockwise rotation of the third gear 225 causes the small gear 225b integrated with the third gear 225 to rotate counterclockwise, and causes the three planetary gears 226 to rotate clockwise (arrow direction). To communicate. The three planetary gears 226 rotate around the small gear 225b in a counterclockwise direction (arrow direction) like a planet while engaging with the internal teeth 227a of the internal gear 227 whose rotation is restricted 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 (arrow B direction). Therefore, the clockwise rotational force of the DC motor 221 is transmitted as a rotational force for winding the webbing W.

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

At this time, as shown in FIG. 8, since the locking piece 230 is in a state of locking the external teeth 227b, the force with which the webbing W is pulled out from the spool 238 is counterclockwise (arrowed) to the rotating shaft of the DC motor 221. Rotational force is transmitted in the opposite direction). If 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 prevents the rotation is generated. The take-up mechanism 6B is intended to actively utilize this rotational drag for the lock mechanism and the EA mechanism.

As mentioned above, although the seat belt retractor and the seat belt retracting mechanism have been described in the 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.

This international application claims priority based on Japanese Patent Application No. 2018-032289 filed on February 26, 2018. The entire contents of Japanese Patent Application No. 2018-032289 are hereby incorporated by reference. Incorporated into.

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Seat belt 6 Seat belt winding mechanism 7 Motor 8 Spool 10

Seat belt retractor

14,14A, 14B Drive circuit 15 Control circuit 17

Power transmission mechanism

40,45,49 Reflux circuit 100 Seat belt apparatus

Claims

A spool for winding up the seat belt;
A motor for rotating the spool;
A drive circuit for driving the motor;
A seat belt retractor, comprising: at least one rectifier element that is always connected in parallel to the motor and causes the motor to recirculate a current caused by a counter electromotive force generated in the motor.
The motor has a first terminal and a second terminal whose potential is relatively lower than the first terminal due to the generation of the counter electromotive force,
2. The seat belt 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.
3. The seat belt retractor according to claim 2, wherein the rectifier element is connected in series to the diode, and includes a Zener diode having the first terminal side as a cathode and the second terminal side as an anode.
The seat belt retractor according to claim 3, further comprising a resistance element connected in series to the Zener diode.
The drive circuit includes a first high-side switching element connected to the first terminal, a first low-side switching element connected to the first terminal, and a first terminal connected to the second terminal. 4. The seat belt retractor according to claim 3, comprising two high-side switching elements and a second low-side switching element connected to the second terminal.
The seat belt 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 the first terminal due to generation of the counter electromotive force,
2. The seat belt 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 seat belt retractor according to claim 1, wherein a current due to the counter electromotive force is returned to the motor, thereby suppressing rotation of the motor.
The seat belt retractor according to claim 8, wherein the motor is prevented from rotating in a reverse rotation direction in which the spool is rotated in the pull-out direction of the seat belt as a result of the current caused by the counter electromotive force returning to the motor.
A spool for winding up the seat belt;
A motor for rotating the spool;
A seat belt retracting mechanism, comprising: at least one rectifying element that is always connected in parallel to the motor and causes the motor to recirculate a current caused by a counter electromotive force generated in the motor.