JP2011037299A - Webbing winding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a webbing winding device which absorbs the tension to be applied to a webbing belt by the drag generated by the back electromotive voltage generated in a motor, and correctly changes its absorption amount based on the magnitude or the like of the tension. <P>SOLUTION: When the detection signal Rs according to the rotational speed in the drawing direction of a spool is output from a hole sensor 122, an ECU 102 with the detection signal Rs input therein outputs the drive control signal Ds corresponding to the rotational speed in the drawing direction of the spool and the set value of the preset drag. A drive circuit 104 with the drive control signal Ds input therein turns ON/OFF an electric field effect transistor FET1 at the duty ratio in which the drag generated by a motor 70 in this state is the preset value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a webbing retractor that winds and stores a belt member such as a webbing belt for restraining the body of an occupant seated in a vehicle seat.

  In the webbing retractor (motor-type seat belt retractor) disclosed in Patent Document 1 below, a planetary gear mechanism is interposed between a spool for winding the webbing belt (webbing) and the motor, and the external gear In a state where the engaging piece is engaged with the teeth, the output shaft of the motor and the spool are mechanically connected to each other so that the driving force of the motor can be transmitted to the spool.

  When the motor is energized or short-circuited, the motor output shaft and the spool are connected. In this state, when the spool is rotated in the direction of pulling out the webbing belt from the spool, the rotational force of the spool is applied to the motor output shaft. Entered. As a result, a counter electromotive force is generated in the motor, and a rotational drag against the rotation of the output shaft is generated by the counter electromotive force. The following Patent Document 1 discloses a configuration in which the rotational drag generated in this way is superimposed on the EA load in an energy absorbing member such as a torsion shaft to adjust the load limit value, rising gradient, and falling gradient of the EA load. ing.

JP 2001-270423 A

  By the way, in the configuration disclosed in Patent Document 1, the load limit value of the EA load and the rising gradient are switched by switching the gear between the spool and the motor, or by switching the ratio of the short circuit time to the non-short circuit time in the motor. Adjust the falling slope. However, switching the gear between the spool and the motor, or switching the ratio of the short circuit time to the non-short circuit time in the motor is only selected and switched according to the weight of the occupant's weight and the speed at which the vehicle collides. is there. Therefore, the load limit value, rising gradient, and falling gradient of the EA load cannot be adjusted after switching, and it is particularly difficult to make the rising and falling gradients of the EA load steep and smoothly adjusted between them. .

  In consideration of the above facts, the present invention can absorb the tensile force applied to the webbing belt by the drag generated by the counter electromotive voltage generated by the motor, and the amount of absorption can be accurately determined based on the magnitude of the tensile force. The object is to obtain a webbing take-up device that can be changed.

  A webbing take-up device according to a first aspect of the present invention includes a spool that winds the webbing belt by rotating in the take-up direction, with the longitudinal base end portion of the long webbing belt being locked. When the spool rotates with the output shaft connected to the spool, the motor to which the rotational force of the spool is input and the pull-out load that pulls the webbing belt to the front end side are detected directly or indirectly. The drawing load detection means for controlling the circuit including the motor is short-circuited between both terminals of the motor, and in this state, the rotational force of the spool is input to the motor short-circuited between the terminals. The counter electromotive force generated by the rotation causes a drag force against the rotation of the spool, and the magnitude of the drag force is estimated based on the detection result of the pull-out load detection means. And and a control means for generating the drag of predetermined size to control the circuit based on the estimation result.

  In the webbing take-up device according to the first aspect of the present invention, the output shaft includes a motor that can be coupled to the spool, and the webbing is wound on the spool in a state where the output shaft of the motor is coupled to the spool. When the belt is pulled out, a rotational force in the pulling direction opposite to the winding direction is input to the motor. When the rotational force of the spool is input to the motor in this way, the circuit including the motor is controlled by the control means, and when both terminals of the motor are short-circuited, the terminals are short-circuited. When the rotational force of the spool is input to the motor, a counter electromotive voltage is generated in the motor.

  When a counter electromotive voltage is generated in the motor and a current flows through the circuit in this manner, a force for rotating the output shaft, that is, a drag force against the rotational force of the spool is generated. The drag generated in this way becomes resistance for pulling out the webbing belt from the spool, and at least a part of the energy used for pulling the webbing belt is absorbed.

  On the other hand, in the webbing take-up device according to the present invention, the pulling-out load for pulling the webbing belt toward the tip side is detected by the pulling-out load detecting means. When the vehicle suddenly decelerates, the occupant of the vehicle pulls the webbing belt in an attempt to move inertially toward the front side of the vehicle. At this time, the detection result of the extraction load by the extraction load detection unit is input to the control unit. The control unit controls the above-described circuit including the motor based on the input detection result of the extraction load detection unit, and the drag generated in the motor is preset by the spool rotating in the extraction direction. Make it big.

  As described above, in the webbing take-up device according to the present invention, the magnitude of the drag is controlled based on the pull-out load that pulls the webbing belt toward the tip end side thereof, so that a drag of a suitable magnitude is generated to pull the webbing belt. It is possible to effectively absorb at least a part of the energy provided to.

  A webbing retractor according to a second aspect of the present invention is the webbing retractor according to the first aspect of the present invention, wherein the pull-out load detecting means includes a rotational speed detecting means for detecting the rotational speed of the spool. Yes.

  In the webbing take-up device according to the second aspect of the present invention, the pull-out load detection means includes rotation speed detection means for detecting the rotation speed of the spool. When the vehicle decelerates suddenly, the vehicle occupant pulls the webbing belt to move inertially toward the front of the vehicle and rotates the spool in the pull-out direction. At this time, the rotation speed detecting means rotates the spool in the pull-out direction. The detection result is input to the control means.

  The control means controls the above-described circuit including the motor based on the input detection result of the rotational speed detection means, and the drag generated in the motor is preset by the spool rotating in the pull-out direction. Make it big. As described above, in the webbing take-up device according to the present invention, since the magnitude of the drag is controlled based on the rotation speed of the spool, the drag of a suitable magnitude is generated and the energy supplied to the webbing belt is pulled. At least a portion can be effectively absorbed.

  A webbing take-up device according to a third aspect of the present invention is the webbing retractor according to the first or second aspect, wherein the webbing retractor is interposed between both terminals of the motor in a short-circuited state in a closed state. The circuit is configured to include a switch unit that short-circuits between both terminals of the motor and disconnects between both terminals of the motor in an open state, and the control unit includes a drag of a predetermined magnitude and the extraction load. The drag force is changed by changing a duty ratio that is a ratio of a time length of the open state of the switch means and a time length of the closed state based on the pull-out load detected by the detection means. It is a feature.

  According to the webbing take-up device of the present invention as set forth in claim 3, the switch means is provided between the two terminals of the motor in the short-circuit state, and the switch means when the two terminals of the motor are short-circuited. Maintains an open state and a closed state, or alternately switches between an open state and a closed state.

  By operating the switch means in this way, the current value of the current flowing between the two terminals of the motor is blocked out of the current value of the current flowing when the switch means is maintained in the closed state and the switching period of the switch means. This is the product of the ratio of the time length of the state (that is, the duty ratio). In the webbing take-up device according to the present invention, since the switching period of the switch means is changed according to the rotation speed of the spool in the pulling direction, the drag generated by the motor depends on the pulling load applied to the webbing belt. The size can be changed appropriately.

  As described above, in the webbing take-up device according to the present invention, the magnitude of the drag based on the counter electromotive voltage generated by the motor is appropriately changed based on the magnitude of the tensile force applied to the webbing belt. be able to.

1 is a composite diagram of a block diagram and a circuit diagram schematically showing a configuration of control means of a webbing take-up device according to an embodiment of the present invention. 1 is a front view schematically showing an overall configuration of a webbing take-up device according to an embodiment of the present invention. It is a side view which shows the structure of the rotational speed detection means of the webbing winding apparatus which concerns on one embodiment of this invention.

<Configuration of the present embodiment>
FIG. 2 is a front sectional view showing an outline of the entire configuration of the webbing take-up device 10 according to an embodiment of the present invention. FIG. 1 shows an outline of a system of the webbing take-up device 10. ing.

  As shown in FIG. 2, the webbing retractor 10 includes a frame 12. The frame 12 includes a flat plate 14. The back plate 14 is fixed to the vehicle body by fastening means (not shown) such as a bolt, for example, in the vicinity of the lower end of the center pillar of the vehicle. The taking device 10 is attached to the vehicle body. From both ends in the width direction of the back plate 14, a pair of leg plates 16 and 18 facing each other substantially in the vehicle front-rear direction are extended in parallel to each other. A substantially cylindrical spool 20 is disposed between the leg plates 16 and 18.

  The spool 20 has an axial direction opposite to the leg plates 16 and 18 and is rotatable around its own axis. Further, the longitudinal base end portion of the long belt-like webbing belt 22 is locked to the spool 20. The webbing belt 22 is wound around the outer peripheral portion of the spool 20 in the form of a layer from the base end side and stored by rotating the spool 20 in a winding direction around one of its axes. Further, when the webbing belt 22 is pulled from the front end side, the webbing belt 22 wound around the spool 20 is pulled out, and accordingly, the spool 20 rotates in a pulling direction opposite to the winding direction.

  On the other hand, as shown in FIG. 2, the spool 20 is provided with a torsion shaft 24 as load absorbing means. The torsion shaft 24 is a rod-shaped member whose axial direction is along the axial direction of the spool 20, and at least the middle portion in the longitudinal direction of the torsion shaft 24 is disposed coaxially with the spool 20 inside the spool 20. A coupling portion 26 is formed at a side end portion of the leg plate 18 of the torsion shaft 24. The coupling portion 26 has a non-circular outer peripheral shape in a cross section cut in a direction orthogonal to the axial direction of the torsion shaft 24.

  An adapter 28 is provided on the leg plate 18 side of the spool 20 corresponding to the coupling portion 26. The adapter 28 has a non-circular inner peripheral shape that is substantially the same as the outer peripheral shape of the coupling portion 26, the coupling portion 26 enters the inside of the adapter 28, and the adapter 28 is attached to the coupling portion 26. Further, the outer peripheral shape of the cross section of the adapter 28 when the adapter 28 is cut in a direction orthogonal to the axial direction of the torsion shaft 24 is non-circular. An insertion hole 30 is formed on the leg plate 18 side of the spool 20 so that the inner peripheral shape is substantially the same as the outer peripheral shape of the adapter 28, and the adapter 28 into which the coupling portion 26 is inserted is inserted into the insertion hole 30. It is.

  Since the outer peripheral portion of the coupling portion 26 and the inner peripheral portion of the adapter 28 are non-circular, one of the torsion shaft 24 and the adapter 28 cannot rotate relative to the other around the central axis of the torsion shaft 24. . Furthermore, since the outer peripheral portion of the adapter 28 and the inner peripheral portion of the fitting insertion hole 30 are non-circular, one of the spool 20 and the adapter 28 rotates relative to the other around the central axis of the spool 20. Can not. Therefore, basically, the spool 20 and the torsion shaft 24 rotate coaxially and integrally.

  On the other hand, as shown in FIG. 2, a housing 42 of the lock mechanism 40 is attached to the leg plate 16 on the opposite side of the leg plate 16 from the leg plate 18. A lock base 44 constituting the lock mechanism 40 is provided inside the housing 42. The lock base 44 is fitted into a fitting insertion hole 46 formed on the leg plate 16 side of the spool 20 so as to be coaxially rotatable with respect to the spool 20 around the central axis of the spool 20. A coupling portion 48 is formed on the leg plate 16 side of the torsion shaft 24 corresponding to the lock base 44.

  Similar to the coupling portion 26, the coupling portion 48 has a noncircular outer peripheral shape in a cross section cut in a direction orthogonal to the axial direction of the torsion shaft 24. A fitting insertion hole 50 is formed in the lock base 44 corresponding to the coupling portion 48. The inner circumferential shape of the fitting insertion hole 50 is substantially the same as the outer circumferential shape of the coupling portion 48, and the coupling portion 48 is fitted into the fitting insertion hole 50. For this reason, one of the lock base 44 and the torsion shaft 24 cannot rotate around the central axis of the torsion shaft 24 with respect to the other.

  Therefore, although the lock base 44 is inserted into the insertion hole 46 so as to be rotatable relative to the spool 20, the torsion shaft 24 cannot be rotated relative to the lock base 44, and the torsion shaft 24 is connected to the spool 20. Therefore, any one of the lock base 44 and the spool 20 cannot basically rotate relative to any one of the lock base 44 and the spool 20.

  A lock pawl 52 is provided on the outer side of the lock base 44 in the rotational radius direction. The insertion hole 50 is supported by the leg plate 16 so as to be rotatable around an axis whose axial direction is the same as the central axis of the spool 20. Engagement teeth 54 are formed on the lock pawl 52, and the engagement pawl 52 moves toward or away from the outer peripheral portion of the lock base 44 as the lock pawl 52 rotates around the support position on the leg plate 16. . Ratchet teeth 56 are formed on the outer periphery of the lock base 44 corresponding to the engaging teeth 54. When the lock pawl 52 rotates so as to approach the outer periphery of the lock base 44, the engagement teeth 54 can mesh with the ratchet teeth 56. In a state where the engagement teeth 54 are engaged with the ratchet teeth 56, the rotation of the lock base 44 in the pull-out direction is restricted.

  The housing 42 accommodates various members constituting an acceleration (deceleration) in a sudden deceleration state of the vehicle and a mechanism that operates when the lock base 44 suddenly rotates in the pull-out direction. When the lock base 44 is suddenly decelerated or the lock base 44 is suddenly rotated in the pull-out direction, this mechanism is activated to rotate the lock pawl 52 in a direction to engage the engagement teeth 54 with the ratchet teeth 56. Let

  On the other hand, a motor 70 in which the axial direction of the output shaft 72 is the same as the direction of the central axis of the spool 20 is disposed on the outer side in the rotational radius direction of the spool 20. A flat toothed external gear 74 is coaxially and integrally attached to the output shaft 72 of the output shaft 72 of the motor 70. On the outer side in the rotational radius direction of the gear 74, external gear teeth 76 having a larger number of teeth than the gear 74 and a spur gear 76 are rotatably supported by the leg plate 18 while meshing with the gear 74. On the side of the leg plate 18 of the gear 76, an externally toothed spur gear 78 having fewer teeth than the gear 76 is coaxially and integrally attached to the gear 76.

  On the outer side in the rotational radius direction of the gear 78, external gears having more teeth than the gear 78 and a spur gear 80 are rotatably supported by the leg plate 18 in mesh with the gear 78. On the other side of the gear 80 via the leg plate 18 (that is, outside the leg plate 18), external gears with fewer teeth than the gear 80 and a spur gear 82 are coaxially and integrally with the gear 80. Is provided. The adapter 28 is provided with a clutch 90 corresponding to the gear 82.

  The clutch 90 includes a gear ring 92 that is coaxial with the spool 20. An outer toothed spur gear 94 is formed on the outer periphery of the gear ring 92 and meshes with the gear 82. On the inner side of the gear ring 92, there are a clutch pawl that is interlocked with the rotation of the gear ring 92 in the winding direction, a clutch adapter that is attached to the adapter 28 in a state where it cannot rotate coaxially with the adapter 28, etc. When the gear ring 92 rotates in the winding direction to move the clutch pawl and the clutch pawl engages with the clutch adapter, the rotation of the gear ring 92 in the winding direction via the clutch adapter causes the adapter 28 to rotate. It has come to be transmitted to.

  When the clutch pawl is engaged with the clutch adapter, the engagement between the clutch adapter and the clutch pawl is not canceled unless the gear ring 92 rotates relative to the clutch adapter in the pull-out direction. In the state where the clutch pawl and the clutch pawl are engaged with each other, the rotation of the adapter 28 in either the winding direction or the drawing direction is transmitted to the gear ring 92 so that the gear ring 92 can be rotated.

  On the other hand, FIG. 1 shows an outline of the configuration of a control device 100 as a control means for controlling the motor 70 described above. FIG. 1 is shown very schematically in order to facilitate understanding of the gist of the present embodiment.

  As shown in FIG. 1, the control device 100 includes a pair of input / output terminals T1 and T2. One terminal of the motor 70 is connected to the input / output terminal T1, and the other terminal of the motor 70 is connected to the input / output terminal T2. The control device 100 includes an input terminal T3 and an output terminal T4. The positive terminal of the battery 106 is connected to the input terminal T3, and the negative terminal of the battery 106 is connected to the output terminal T4.

  In addition, the control device 100 includes a plurality of field effect transistors FET1, FET2, FET3, and FET4, each serving as a switch unit. In the present embodiment, the field effect transistors FET1, FET2, FET3, and FET4 are so-called N-channel MOS field effect transistors (Metal Oxide Semiconductor Field Effect Transistors). However, the switch means in the present invention is not limited to such an N-channel MOS field effect transistor.

  That is, a MOS field effect transistor or a P channel MOS field effect transistor may be used as the switching means, or an N channel MOS field effect transistor and a P channel MOS field effect transistor may be used. You may use it in combination. In addition, other types of field effect transistors, for example, junction type field effect transistors, or transistors other than the field effect transistors, for example, bipolar transistors, may be used for the switch means.

  Each of the field effect transistors FET1 to FET4 constituting the switch means becomes conductive between the drain terminal and the source terminal only when a high level signal voltage is applied to the gate terminal, from the drain terminal side to the source terminal side. Current flows. In the following description, a state in which a high level signal voltage is applied to the gate terminals of the field effect transistors FET1 to FET4 and the drain terminals and the source terminals of the field effect transistors FET1 to FET4 are electrically connected to each other. The field effect transistors FET1 to FET4 are referred to as ON states, and the state in which the space between the drain terminals and the source terminals of the field effect transistors FET1 to FET4 is blocked is referred to as the OFF state of the field effect transistors FET1 to FET4.

  Among these field effect transistors FET1 to FET4, the drain terminal of the field effect transistor FET1 is connected to the input terminal T3, and the source terminal of the field effect transistor FET1 is connected to the drain terminal of the field effect transistor FET2. The source terminal of the field effect transistor FET2 is connected between the output terminal T4.

  On the other hand, the drain terminal of the field effect transistor FET3 is connected between the drain terminal of the field effect transistor FET1 and the input terminal T3, and the source terminal of the field effect transistor FET3 is connected to the drain terminal of the field effect transistor FET4. ing. The source terminal of the field effect transistor FET4 is connected between the source terminal of the field effect transistor FET2 and the output terminal T4.

  One terminal of the motor 70 is connected between the source terminal of the field effect transistor FET1 and the drain terminal of the field effect transistor FET2, and one terminal of the motor 70 is connected to the source terminal of the field effect transistor FET3. It is connected between the drain terminal of the transistor FET4. Therefore, if the field effect transistors FET1 and FET4 are in the ON state and the field effect transistors FET2 and FET3 are in the OFF state, the forward drive current flows from one terminal of the motor 70 to the other terminal, and the field effect transistors FET2 and FET2 If the FET 3 is ON and the field effect transistors FET1 and FET4 are OFF, a reverse drive current flows from the other terminal of the motor 70 toward one terminal.

  Further, the gate terminals of the field effect transistors FET1 to FET4 are connected to the drive circuit 104 which constitutes the control device 100 together with the field effect transistors FET1 to FET4, and based on the signal voltage output from the drive circuit 104. Between the drain terminal and the source terminal of each field effect transistor FET1 to FET4, a conductive state or an insulating state is established. The drive circuit 104 is electrically connected to the ECU 102, and a drive control signal Ds output from the ECU 102 is input to the drive circuit 104. The drive circuit 104 switches the signal voltage applied to the gate terminals of the field effect transistors FET1 to FET4 based on the input drive control signal Ds.

  On the other hand, as shown in FIGS. 1 and 2, the ECU 102 is directly or indirectly connected to a hall sensor 122 that constitutes a pull-out load detection means as a rotation speed detection means. As shown in FIG. 1, the Hall sensor 122 is provided in the vicinity of the outer peripheral portion of the gear 80 (that is, outside the rotation center of the gear 80) so as to face the gear 80 along the rotation axis direction of the gear 80. Yes.

  As shown in FIG. 3, a ring-shaped magnet 124 is coaxially and integrally attached to the gear 80 corresponding to the hall sensor 122. The magnet 124 is alternately formed with N poles and S poles at predetermined angles along the circumferential direction. Therefore, the magnetic field detected by the Hall sensor 122 every time the gear 80 rotates by a certain angle changes, and the detection signal Rs corresponding to the detected change in the magnetic field is output from the Hall sensor 122. The detection signal Rs output from the hall sensor 122 is input to the ECU 102.

  Further, the ECU 102 is directly or indirectly connected to the front monitoring device 128. The front monitoring device 128 emits a radio wave of a predetermined frequency, an obstacle detection wave such as a radar or an infrared ray to the front of the vehicle on which the webbing take-up device 10 is mounted, and is reflected by an obstacle ahead. And a detection wave input unit to which the detection wave returned is input. In the control device 100, the vehicle travels in front of the vehicle on which the webbing retractor 10 is mounted based on the time from when the detection wave is output from the detection wave output unit to when it is input to the detection wave input unit. Vehicles and obstacles in front of the vehicle on which the webbing take-up device 10 is mounted (hereinafter referred to as obstacles including other vehicles traveling in front of the vehicle on which the webbing take-up device 10 is mounted). ) Is calculated.

  Further, the ECU 102 is directly or indirectly connected to an airbag ECU 130 as trigger means. The airbag ECU 130 constitutes control means for an airbag device (not shown) that inflates and deploys the bag body in front of the seat corresponding to the webbing retractor 10 in a vehicle sudden deceleration state or the like. The forward monitoring signal Os output from is input to the ECU 102.

<Operation and effect of the present embodiment>
Next, the operation and effect of the webbing take-up device 10 will be described.

  In the webbing take-up device 10, the ECU 102 of the control device 100 calculates the distance to the obstacle ahead based on a signal from the front monitoring device 128 while the vehicle equipped with the webbing take-up device 10 is traveling. . When the distance to the obstacle, which is the calculation result, is less than a certain value, the ECU 102 of the control device 100 switches the drive control signal Ds. Based on the switched drive control signal Ds, the drive circuit 104 uses the field effect transistors FET2, FET3. Is turned off, and the field effect transistors FET1 and FET4 are turned on.

  As a result, a forward current flows through the motor 70, and the motor 70 is driven to rotate forward. When the output shaft 72 rotates in the forward direction by the normal rotation driving force of the motor 70, the rotational force of the output shaft 72 is transmitted to the gear ring 92 of the clutch 90 through the gears 74 to 80, and the gear ring 92 is rotated in the winding direction. As the gear ring 92 rotates in the winding direction, the clutch pawl in the gear ring 92 is engaged with the clutch adapter.

  Thereby, the rotation of the gear ring 92 in the winding direction is transmitted to the adapter 28 through the clutch adapter, and the spool 20 is rotated in the winding direction. Thus, when the spool 20 rotates in the winding direction, the webbing belt 22 is wound around the spool 20 from the base end side, and the webbing belt 22 attached to the body of the passenger is slightly loosened, so-called “slack”. Is resolved.

  In this state, an occupant avoids an obstacle by performing a braking operation or a steering operation of the vehicle. As a result, when the calculation result of the distance to the obstacle in the control device 100 exceeds a predetermined value, the control device 100 The ECU 102 switches the output drive control signal Ds. Based on the switched drive control signal Ds, the drive circuit 104 turns off the field effect transistors FET1 and FET4 and turns on the field effect transistors FET2 and FET3. As a result, a reverse current flows through the motor 70 and the motor 70 is driven in reverse. The reverse rotation of the output shaft 72 due to the reverse driving force of the motor 70 is transmitted to the gear ring 92 of the clutch 90 via the gears 74 to 80, and rotates the gear ring 92 in the pull-out direction. By the rotation of the gear ring 92 in the pull-out direction, the engagement between the clutch pawl and the clutch adapter is released.

  On the other hand, the vehicle is suddenly decelerated to such an extent that the airbag device is operated, or the body of the occupant suddenly pulls the webbing belt 22 due to the inertia of the vehicle sudden deceleration. When the shaft 44 is suddenly rotated in the pulling direction, the lock mechanism 40 is operated, and the lock pawl 52 is rotated so that the engagement teeth 54 mesh with the ratchet teeth 56. When the engagement teeth 54 mesh with the ratchet teeth 56, the rotation of the lock base 44 in the pull-out direction, that is, the rotation of the spool 20 in the pull-out direction is restricted.

  In this manner, the pulling of the webbing belt 22 from the spool 20 is restricted by restricting the rotation of the spool 20 in the drawing direction. As a result, the body of the occupant who intends to move inertially toward the vehicle front side due to the inertia when the vehicle suddenly decelerates can be firmly held by the webbing belt 22.

  In this state, when the occupant's body pulls the webbing belt 22 and the rotational force in the pull-out direction applied from the webbing belt 22 to the spool 20 exceeds the mechanical strength of the torsion shaft 24, Torsional deformation occurs between the other end of the torsion shaft 24 held by the engagement of the lock pawl 52 and one end of the torsion shaft 24. Since the rotation of the spool 20 in the pull-out direction is allowed by the torsional deformation of the torsion shaft 24, the pull-out of the webbing belt 22 is allowed. Thus, the pull-out allowable amount of the webbing belt 22 is allowed to the front side of the vehicle. The occupant is allowed to move inertially, and the deformation of the torsion shaft 24 absorbs a part of the energy of the tensile force applied to the webbing belt 22 by the occupant's body.

  Further, as described above, when the vehicle suddenly decelerates, the airbag device is activated, and the airbag ECU 130 at this time switches the activation signal Ss to be output. When the switched drive control signal Ds is output from the ECU 102, the drive circuit 104 maintains the field effect transistors FET2 and FET4 in the OFF state and maintains the field effect transistor FET3 in the ON state. Further, the field effect transistor FET1 is repeatedly switched between an ON state and an OFF state at a predetermined duty ratio. When the field effect transistor FET3 is further turned on with the field effect transistors FET1 to FET4 being controlled as described above, the motor 70 is short-circuited.

  Here, in the state where the activation signal Ss is output from the airbag ECU 130 as described above, that is, in the state where the airbag device is activated, the engagement between the clutch pawl and the clutch adapter in the gear ring 92 is maintained. Therefore, in this state, when the spool 20 rotates in the pull-out direction as described above, the rotation of the spool 20 in the pull-out direction is transmitted to the output shaft 72 of the motor 70, and the output shaft 72 is rotated. As described above, in this state, the motor 70 is short-circuited when the field effect transistor FET1 is turned on, so that a counter electromotive voltage is generated in the motor 70 when the output shaft 72 is rotated. When a current that flows from the motor 70 to the motor 70 through the field effect transistor FET1 and the field effect transistor FET3 flows due to the counter electromotive voltage, an output is generated by the interaction between this current and the magnetic field of the permanent magnet that constitutes the motor 70. A force in a direction against the rotation of the shaft 72, that is, a drag force (load) is generated.

  For this reason, in this state, the rotational force in the pull-out direction corresponding to the sum of the force that deforms the torsion shaft 24 exceeding the mechanical strength of the torsion shaft 24 and the drag force thus generated is the torsion shaft. The torsion shaft 24 cannot be twisted and deformed unless it is applied to the end portion of the 24 coupling portion 26 side.

  Further, in the webbing take-up device 10, when the spool 20 rotates in the pull-out direction as described above, the electric field is based on the detection signal Rs output from the hall sensor 122 and the set value of the drag set in advance in the ECU 102. The duty ratio of ON and OFF in the effect transistor FET1 is set.

  That is, in the circuit in the control device 100, the magnitude of the drag generated by the motor 70 in which the field effect transistors FET2 and FET4 are in the OFF state and the field effect transistors FET1 and FET3 are in the ON state is the pulling speed of the webbing belt 22 (webbing belt). 22) (the magnitude of the drag generated by the motor 70 is a function of the pulling speed of the webbing belt 22), and further, when the field effect transistor FET1 is turned on and off at a predetermined duty ratio, the motor The magnitude of the drag generated at 70 is determined by the ON / OFF duty ratio of the field effect transistor FET1 in addition to the pulling speed of the webbing belt 22 (the magnitude of the drag generated by the motor 70 is the pulling speed of the webbing belt 22). And function of duty ratio)

  Therefore, the magnitude of the pulling force that causes the occupant's body to pull the webbing belt 22 due to the sudden deceleration of the vehicle and the rotation of the spool 20 in the pull-out direction that occurs when the occupant's body pulls the webbing belt 22 in this way change. Even if the duty ratio of the field effect transistor FET1 is appropriately increased or decreased according to the increase or decrease of the rotational speed in the pull-out direction of the spool 20 so as to conform to the set value of the drag set in advance in the ECU 102, the drag can be set. It is possible to generate a drag of a magnitude corresponding to the value.

  Thus, for example, a desired amount of energy is generated, for example, a constant amount of drag is always generated from the start of generation of the drag of the motor 70 and the amount of energy absorbed by the drag generated by the motor 70 is constant. Can be absorbed.

  In addition, as described above, the hall sensor 122 constantly detects the drawing speed of the webbing belt 22, and the drive control signal Ds is output from the ECU 102 based on the detection signal Rs output from the hall sensor 122. Further, since the drive circuit 104 appropriately increases / decreases the duty ratio of the field effect transistor FET1 based on the drive control signal Ds, even if the pulling speed of the webbing belt 22 is not assumed, the drive circuit 104 can respond to the pulling speed of the webbing belt 22. A drag of a certain size can be generated.

  In addition, in this embodiment, in the present embodiment, when the drag is generated in the motor 70, the field effect transistors FET2 and FET4 are turned off, and the direction of the current flowing when the counter electromotive voltage is generated in the motor 70 is set. The field effect transistor FET3 located relatively downstream is turned on, and the field effect transistor FET1 located relatively upstream is switched between the ON state and the OFF state based on the duty ratio based on the signal output by the ECU 102. It was a configuration.

  On the other hand, the field effect transistor FET1 located on the relatively upstream side is maintained in the ON state, and the field effect transistor FET3 located on the relatively downstream side is turned on with a duty ratio based on the signal output by the ECU 102. When the state and the OFF state are switched, a current flows even if the field effect transistor FET3 is switched from the ON state to the OFF state due to the effect of the parasitic diode of the field effect transistor FET3. As a result, the magnitude of the drag cannot be changed.

  Therefore, as described above, the field effect transistor FET3 positioned relatively downstream is turned on in the direction of the current flowing when the back electromotive voltage is generated in the motor 70, and the electric field positioned relatively upstream is set. The effect transistor FET1 must be configured to switch between the ON state and the OFF state based on the duty ratio based on the signal output from the ECU 102.

  In the present embodiment, the set value of the drag set in the ECU 102 is constant. However, this is merely an example, and a configuration in which the set value of the drag changes with time may be used.

  Further, in the present embodiment, when the drag is generated in the motor 70, the field effect transistor FET3 located relatively downstream is turned on in the direction of the current flowing when the counter electromotive voltage is generated in the motor 70. Thus, the field effect transistor FET1 positioned relatively upstream is switched between the ON state and the OFF state based on the duty ratio based on the signal output from the ECU 102. However, the configuration may be such that both the electric field effect transistors FET1 and FET3 are switched between the ON state and the OFF state at a duty ratio based on the drive control signal Ds output by the ECU 102 at the same timing.

  In addition, the field effect transistors FET1 and FET3 are turned off, and the field effect transistor FET4 located relatively downstream is turned on in the direction of the current flowing when the counter electromotive voltage is generated in the motor 70. Alternatively, the field effect transistor FET2 positioned on the upstream side may be configured to switch the drive circuit 104 between the ON state and the OFF state at a duty ratio based on the drive control signal Ds output by the ECU 102. Further, the field effect transistors FET1 and FET3 are turned off, and both the field effect transistor FET2 and the field effect transistor FET4 are turned on and off at a duty ratio based on the drive control signal Ds output by the ECU 102 at the same timing. It is good also as a structure which switches a state.

  In the present embodiment, the torsion shaft 24 is provided as load absorbing means for absorbing the load by being deformed, and the drag generated by the motor 70 is superimposed on the load required to deform the torsion shaft 24. It was the structure which absorbs the energy corresponding to the load of. However, the aspect of the load absorbing means is not limited to such a configuration of the torsion shaft 24. If the load absorbing means conforms to the configuration of the present embodiment, the load absorbing means can be configured such that the spool 20 is relative to the lock base 44. Any configuration may be used as long as it is deformed by rotating in the pull-out direction. Furthermore, from the viewpoint of the present invention, the load absorbing means itself may not be provided, and only the energy corresponding to the drag generated by the motor 70 may be absorbed.

  In the present embodiment, the rotation speed detection means constituting the extraction load detection means is the Hall sensor 122 that detects the rotation of the gear 80, but the configuration of the rotation speed detection means is limited to such a Hall sensor 122. It is not something. For example, even if the hall sensor 122 is used, the magnet 124 may be provided on the spool 20 to directly detect the rotation of the spool 20. Further, rotation of the spool 20 or the gear 80 may be detected using a magnetic sensor different from the Hall sensor 122, for example, a magnetoresistive element or the like.

  Furthermore, the configuration of the extraction load detection means is not limited to such a rotation speed detection means. For example, the webbing belt 22 (or an identification part such as a marking set on the webbing belt 22) is detected by an optical sensor, and the withdrawal speed of the webbing belt 22 (that is, the withdrawal load of the webbing belt 22) based on the detection result. ) May be configured to be estimated by the ECU 102.

  In addition to the rotation speed of the spool 20 and the pulling speed of the webbing belt 22, for example, when the output shaft 72 of the motor 70 is rotated by pulling the webbing belt 22, the counter electromotive voltage is generated by the motor 70 as described above. As a result, a current flows from the motor 70 through the field effect transistor FET1 and the field effect transistor FET3 and returns to the motor 70. The magnitude of the pull-out load of the webbing belt 22 is a function of the current value of this current. expressed. Therefore, a pull-out load detection unit including a current detection unit that detects such a current may be configured, and the ECU 102 may estimate the pull-out load of the webbing belt 22 based on the current value.

DESCRIPTION OF SYMBOLS 10 Webbing winding device 20 Spool 22 Webbing belt 70 Motor 100 Control device (control means)
122 Hall sensor (rotational speed detection means, extraction load detection means)
FET1 field effect transistor (switching means)
FET2 field effect transistor (switching means)
FET3 field effect transistor (switching means)
FET4 field effect transistor (switching means)

Claims (3)

A spool that winds up the webbing belt by locking the longitudinal base end of the belt-like webbing belt and rotating in the winding direction;
When the spool rotates with the output shaft connected to the spool, a motor to which the rotational force of the spool is input;
A drawing load detecting means for directly or indirectly detecting a drawing load for pulling the webbing belt to the tip side;
A circuit including the motor is controlled to short-circuit both terminals of the motor, and in this state, the back electromotive force generated by inputting the rotational force of the spool to the motor short-circuited between the two terminals. A resistance against rotation of the spool is generated by the voltage, the magnitude of the drag is estimated based on the detection result of the pull-out load detection means, and the circuit is controlled in advance based on the estimation result. Control means for generating the drag of magnitude;
A webbing take-up device comprising:   2. The webbing take-up device according to claim 1, wherein the pull-out load detection means includes a rotation speed detection means for detecting the rotation speed of the spool.   The circuit including switch means for interposing between both terminals of the motor in a short-circuited state, short-circuiting between both terminals of the motor in a closed state, and blocking between both terminals of the motor in an open state The control means is configured so that the switch means has a time length in the open state and a time in the closed state based on a drag having a preset magnitude and the pull-out load detected by the pull-out load detection means. The webbing retractor according to claim 1 or 2, wherein the drag force is changed by changing a duty ratio that is a ratio of a target length.

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