Seat belt retractor, seat belt device, and method for controlling seat belt retractor

Abstract

This seat belt retractor is provided with: a spool for winding a webbing; a motor for rotating the spool; and a control device for adjusting the tension of the webbing by controlling the output of the motor. The control device estimates the tension of the webbing and controls the motor on the basis of the estimation result.

Description

Seatbelt retractor, seatbelt device, and method for controlling seatbelt retractor

[0001] The present disclosure relates to a seat belt retractor, a seat belt device, and a method for controlling a seat belt retractor.

[0002] 2. Description of the Related Art A seat belt retractor having a motor for rotating a spool is known.

[0003] Patent Document 1 proposes a method for suppressing a decrease in tension in such a motorized seat belt retractor by adjusting the tension of the webbing by controlling the current flowing through the motor.

[0004] Japanese Patent Application Laid-Open No. 2022-035300

[0005] However, the conventional methods such as those described in Patent Document 1 leave room for improvement in terms of stabilizing the webbing tension.

[0006] The present disclosure aims to provide a seat belt retractor, a seat belt device, and a control method for a seat belt retractor that is configured to include a motor for rotating a spool and that can adjust webbing tension more stably by controlling the motor.

[0007] A seat belt retractor according to one aspect of an embodiment of the present invention includes a spool that winds up a webbing, a motor that rotates the spool, and a control device that controls the output of the motor to adjust the tension of the webbing, wherein the control device estimates the tension of the webbing and controls the motor based on the estimation result.

[0008] According to the present disclosure, it is possible to provide a seat belt retractor, a seat belt device, and a control method for a seat belt retractor that are configured to include a motor for rotating a spool and that can adjust webbing tension more stably by controlling the motor.

[0009] 6 is a perspective view showing an example of a structure for detecting the number of rotations of a motor; FIG. 7 is a diagram showing an example of a transition in motor speed and acceleration; FIG. 8 is a diagram showing a pattern of a motor state exemplified in FIG. 6; FIG. 9 is a perspective view showing an example of a structure for detecting the tension of a webbing according to a second embodiment;

[0010] Hereinafter, embodiments will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0011] [First embodiment] A first embodiment will be described with reference to Figures 1 to 7. First, an example of the overall configuration of a seat belt device 100 according to an embodiment will be described with reference to Figure 1.

[0012] 1 is a schematic diagram showing an example of a seat belt device 100. The seat belt device 100 is 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 also 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.

[0013] The seat belt 2 is an example of a belt-shaped member that restrains an occupant 9 seated in a seat 11 of a vehicle 13, and is wound around the winding mechanism 6 so as to be able to be pulled out from the winding mechanism 6. One end of the seat belt 2 is connected to the winding mechanism 6, and the other end of the seat belt 2 is fixed to the vehicle body, a pretensioner device, the seat 11, or the like. The seat belt is also called a webbing.

[0014] The shoulder anchor 3 is a guide member that guides the seat belt 2 pulled out from the retraction mechanism 6 toward the shoulder of the occupant 9, and is fixed to, for example, a side wall of the vehicle compartment or a seat 11.

[0015] The tongue 4 is a member slidably attached to the seat belt 2 guided by the shoulder anchor 3 .

[0016] The buckle 5 is an example of a member to which the tongue 4 is detachably engaged, and is fixed to, for example, the floor of the vehicle body or the seat 11 .

[0017] The retractor 10 is fixed, for example, to the vehicle body near the seat 11 or to the seat 11 itself. The retractor 10 includes a retraction mechanism 6 that enables the seat belt 2 to be retracted or unretracted, and a control device 1 that controls the operation of the retraction mechanism 6.

[0018] The retraction mechanism 6 includes a spool 8 for retracting the seat belt (webbing) 2, a motor 7 for rotating the spool 8, and a power transmission mechanism 17 for transmitting power between the motor 7 and the spool 8. One end of the seat belt 2 is fixed to the spool 8. The motor 7 generates a driving force for rotating the spool 8. A rotating shaft of the motor 7 is connected to a rotating shaft of the spool 8 via the power transmission mechanism 17.

[0019] The control device 1 drives the motor 7 to control the retraction operation (or both the retraction operation and the unretraction operation) of the seat belt 2 by the retraction mechanism 6. 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.

[0020] The drive circuit 14 supplies a drive current to the motor 7 in accordance with at least one control signal (e.g., 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 that drives the motor 7 with four switching elements, and an inverter circuit that drives the motor 7 with multiple switching elements. The form of the drive circuit 14 is not limited to these and can be determined according to the required specifications.

[0021] The control circuit 15 outputs at least one control signal (for example, a PWM control signal) to the drive circuit 14, which controls the magnitude (or the magnitude and direction of the drive current) of the drive current that drives the motor 7. Each function of the control circuit 15 is realized by the operation of a processor such as a CPU (Central Processing Unit) in accordance with a program stored in memory. A specific example of the control circuit 15 is a microcomputer equipped with a CPU and a memory.

[0022] The control circuit 15 is a drive control unit that drives a plurality of switching elements included in the drive circuit 14 using current measurement results obtained by a current measurement circuit that detects the current flowing through the motor 7 .

[0023] In a mode in which the seat belt 2 is wound onto the spool 8 (winding mode), the control circuit 15 controls each switching element of the drive circuit 14 so that the motor 7 rotates in the forward direction (forward rotation) corresponding to the winding direction of the seat belt 2.

[0024] By controlling each switching element in this manner, the drive circuit 14 can rotate (forward rotation) the motor 7 in a direction (forward rotation direction) that rotates the spool 8 in the direction of retracting the seat belt 2. When the rotary shaft of the motor 7 rotates forward, the driving force of the forward rotation is transmitted to the spool 8 by the power transmission mechanism 17. As a result, the spool 8 rotates in the direction of retracting the seat belt 2, and the seat belt 2 is retracted onto the spool 8.

[0025] On the other hand, in a mode in which the seat belt 2 is withdrawn from the spool 8 (withdrawal mode), the control circuit 15 controls each switching element of the drive circuit 14 so that the motor 7 rotates (reversely rotates) in the reverse direction corresponding to the withdrawal direction of the seat belt 2.

[0026] By controlling each switching element in this manner, the drive circuit 14 can rotate (reversely rotate) the motor 7 in a direction (reverse direction) that rotates the spool 8 in the direction of withdrawing the seat belt 2. When the rotary 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 of withdrawing the seat belt 2, and the seat belt 2 is withdrawn from the spool 8.

[0027] Furthermore, when the rotating shaft of motor 7 and the rotating shaft of spool 8 are connected by power transmission mechanism 17 and the motor 7 is rotated by an external force applied to spool 8, a counter electromotive force is generated in motor 7. Control circuit 15 controls drive circuit 14 to return the current generated by this counter electromotive force (also called regenerative current or brake current) to motor 7, thereby suppressing the rotation of motor 7 and applying the brakes.

[0028] The control circuit 15 controls the drive circuit 14 to suppress the rotation of the motor 7, thereby making it possible to absorb, for example, collision energy acting on the occupant 9 in the event of a vehicle collision.

[0029] For example, when a collision of the vehicle 13 is detected or predicted, an on-board computer outside the retractor 10 sends a command signal to start controlling the restraining force of the seat belt 2 on the occupant 9 .

[0030] When the tongue 4 is engaged with the buckle 5 and the seat belt 2 is fastened to the occupant 9, the control circuit 15 begins to control the restraining force of the seat belt 2 against the occupant 9 when certain conditions are met, such as receiving a command signal from an on-board computer outside the retractor 10.

[0031] When this condition is met, the control circuit 15 controls each switching element of the drive circuit 14 so that the motor 7 rotates in the forward direction (forward rotation) corresponding to the retracting direction of the seat belt 2, in order to prepare for the impact of a collision. When the rotary shaft of the motor 7 rotates forward, the driving force of the forward rotation is transmitted to the spool 8 by the power transmission mechanism 17. As a result, the spool 8 rotates in the direction to retract the seat belt 2, and the seat belt 2 is retracted onto the spool 8. As a result, the restraining force of the seat belt 2 on the occupant 9 increases.

[0032] Thereafter, when the occupant 9 moves forward in the vehicle due to inertia during the collision, the inertial force of the occupant 9 toward the front of the vehicle causes the seat belt 2 to be withdrawn from the spool 8. When the spool 8 rotates in the direction in which the seat belt 2 is withdrawn from the spool 8, the rotational force is transmitted to the rotary shaft of the motor 7 by the power transmission mechanism 17. As a result, the rotary shaft of the motor 7 is rotated in the reverse direction, and a counter electromotive force is generated in the motor 7.

[0033] The control circuit 15 controls the drive circuit 14 to return the current generated by this back electromotive force (also called a regenerative current or a brake current) to the motor 7, thereby preventing the motor 7 from rotating in the reverse direction that rotates the spool 8 in the direction of withdrawing the seat belt 2. As a result, it becomes possible to absorb the collision energy acting on the occupant 9 in the event of a vehicle collision.

[0034] However, since the tension of the seat belt 2 is proportional to the unwinding speed of the seat belt 2, if the unwinding speed of the seat belt 2 is low, only the control of preventing the unwinding of the seat belt 2 by the brake current may result in insufficient tension of the seat belt 2. In this embodiment, the control circuit 15 of the control device 1 executes restraint force control using a control method that can compensate for the insufficient tension of the seat belt 2 and suppress a decrease in the tension of the seat belt 2.

[0035] The control device 1 (control circuit 15) of the seat belt retractor 10 controls the output of the motor 7 to adjust the tension of the webbing 2. The control device 1 estimates the tension of the webbing 2 and controls the motor 7 based on the estimation result. In particular, in the first embodiment, the control device 1 calculates the estimated tension of the webbing 2 using an equation of motion, taking into consideration two types of torque: a "current torque" generated by the motor 7 due to the current flowing through the motor 7, and an "inertia torque" generated around the rotation axis of the motor 7. Then, the control device 1 controls the motor 7 based on the calculated estimated tension.

[0036] The calculation of the estimated tension and the control of the motor 7 can be represented, for example, by the block diagram shown in Fig. 2. Fig. 2 is a block diagram of tension control by the control device 1 according to the first embodiment.

[0037] 2 , the control device 1 calculates an estimated tension of the webbing 2 based on the operating state (current and rotation angle) of the motor 7, and performs feedback control using the calculated estimated tension so that the actual tension of the webbing 2 becomes a predetermined target tension. The calculation process of the estimated tension will be described in detail below.

[0038] Here, the rotational angular velocity of the rotor of the motor 7 is ω. The moment of inertia of the entire system up to the rotation axis of the motor 7 is J. The torque generated by the motor 7 (current x torque constant) is T. Ｍ The torque generated in the webbing 2 is defined as the load torque T Ｌ The reduction ratio of the power transmission mechanism 17 is z. The current value flowing through the motor 7 is I. The torque constant of the motor 7 is Kt. The radius of the retractor 10, i.e., the radius of the spool 8 around which the webbing 2 is wound, is r. The tension generated in the webbing 2 is F ＲＥＴ Using these parameters, the torque T generated by the motor is Ｍ and load torque T Ｌ The following equations (1) to (3) hold true for

[0039]

[0040]

[0041]

[0042] Here, the right side of equation (2) (Kt×I) is the above-mentioned "current torque generated by the motor 7 due to the current flowing through the motor 7." From equation (2), the current torque will be denoted by the symbol T Ｍ Furthermore, J·dω / dt on the right side of equation (1) is the above-mentioned "inertia torque generated around the rotation shaft of the motor 7."

[0043] From equations (1) to (3), the webbing tension equation, i.e., the estimated tension F of the webbing 2, is obtained. ＲＥＴ The following equation (4) can be derived as an equation of motion for deriving

[0044]

[0045] The tension above the wire according to equation (4) is the current torque T Ｍ It can be seen that it does not depend only on (=Kt×I), but also has a large effect on the inertia torque J·dω / dt.

[0046] In addition, when the gear efficiency (transmission efficiency) η of the power transmission mechanism 17 is taken into consideration, the estimated tension F when the retractor 10 retracts the webbing 2 is ＲＥＴ The derivation formula for the above can be expressed by the following formula (5): Here, the number of gear stages of the power transmission mechanism 17 is assumed to be β.

[0047]

[0048] On the other hand, the estimated tension F when the webbing 2 is pulled out from the retractor 10 ＲＥＴ The derivation formula can be expressed as the following formula (6).

[0049]

[0050] The feedback loop portion in the block diagram of Fig. 2 corresponds to any one of the above equations (4) to (6). In other words, the feedback loop portion corresponds to the estimation step of estimating the tension of the webbing 2 in the control method for the seat belt retractor 10. The motor current I can be obtained, for example, from a current signal input from the control device 1 to the motor 7. The motor angle can be obtained from a detection signal of a rotation sensor 20 (see Fig. 5) mounted on the motor 7 (or spool 8).

[0051] 2, the control device 1 performs PID control as an example of feedback control. ＲＥＴ The manipulated variable input to the controller is controlled by three elements: the deviation e between the target tension and a predetermined target tension input to the control system, the integral value e / s of the deviation, and the differential value e·s of the deviation. In the block diagram of Figure 2, the controller is configured to perform PWM control, and the manipulated variable generated by PID control is, for example, a control signal for PWM control. The controller supplies a drive current to the motor 7 in accordance with the input control signal. In other words, the PID control and PWM control portions in the block diagram of Figure 2 correspond to a motor control step in the control method for the seat belt retractor 10, in which the motor 7 is controlled based on the estimation result in the estimation step.

[0052] In the block diagram of Fig. 2, among the elements of the control device 1 surrounded by a dotted line, the controller that performs PWM control corresponds to the drive circuit 14 shown in Fig. 1, and the elements other than the controller correspond to the control circuit 15 shown in Fig. 1. The target value of the feedback control (target tension in Fig. 2) can set, for example, a load applied to any one of the webbings 2.

[0053] As described above, the seat belt retractor 10 in the first embodiment includes the spool 8 that winds up the webbing 2, the motor 7 that rotates the spool 8, and the control device 1 that controls the output of the motor 7 to adjust the tension of the webbing 2. The control device 1 estimates the tension of the webbing 2 and controls the motor 7 based on the estimation result.

[0054] With this configuration, in the seat belt retractor 10 including the motor 7 for rotating the spool 8, the tension of the webbing 2 can be estimated and the motor 7 can be controlled based on the estimation result. That is, the target information for controlling the motor 7 becomes the estimated tension of the webbing 2, and the output information by controlling the motor 7 becomes the tension generated in the webbing 2. As a result, since both the target information and the output information for controlling the motor 7 can be tension, the tension of the webbing 2 generated as a result of controlling the motor 7 can be made to approach the estimated tension with higher accuracy. As a result, the seat belt retractor 10 of the first embodiment can more stably adjust the tension of the webbing 2 by controlling the motor 7.

[0055] Incidentally, in a configuration including a motor 7 for rotating a spool 8, such as the seat belt retractor 10 of the first embodiment, the tension of the webbing 2 has often been controlled by only performing feedback control of the value of the current flowing through the motor 7. However, in the actual behavior of the webbing 2, a disturbance such as a forward leaning movement of an occupant during a vehicle collision can occur, and therefore the torque of the motor 7 may not have a simple proportional relationship with the current. This is thought to be because the tension of the webbing 2 generated while the motor 7 is rotating at a speed that varies includes not only tension generated by the current but also tension due to motor inertia, and the inertial tension is generated and fluctuates during the speed change of the motor 7 due to a disturbance. For this reason, if only the current is controlled, the tension actually generated in the webbing 2 may deviate from the target tension, making it difficult to obtain a stable tension.

[0056] To address these conventional problems, in the seat belt retractor 10 of the first embodiment, the control device 1 uses the equations of motion (4) to (6) above to calculate an estimated tension in consideration of the current torque generated by the motor 7 due to the current flowing through the motor 7 and the inertia torque generated around the rotation axis of the motor 7, and controls the motor 7 based on the calculated estimated tension.

[0057] This configuration makes it possible to take into consideration the inertia torque in addition to the current torque in controlling the motor 7, and therefore the tension of the webbing 2 can be adjusted more reliably and stably by controlling the motor 7.

[0058] Here, in the seat belt retractor 10 of the first embodiment, the duty voltage for retraction control or brake control is calculated according to the operation amount calculated by the PID controller, and the FET (high-side or low-side) of the drive circuit 14 is controlled to control the motor 7 and bring the tension closer to the target tension. Such tension control can be performed, for example, according to the flowchart shown in Fig. 3. Fig. 3 is a flowchart of tension control by the control device 1 according to the first embodiment.

[0059] In step S1, the control circuit 15 of the control device 1 calculates the manipulated variable by PID control.

[0060] In step S2, the drive circuit 14 of the control device 1 determines whether the manipulated variable calculated in step S1 is equal to or greater than a given threshold value. ＲＥＴ is equal to or less than the target tension (Yes in step S2), the process proceeds to step S3, where the drive circuit 14 continues to calculate the duty voltage for winding control (winding duty).

[0061] In step S4, the drive circuit 14 controls the high-side FET of the drive circuit 14 in accordance with the duty voltage for winding control calculated in step S3.

[0062] In step S5, as a result of the control in step S4, the motor 7 performs winding control to increase the tension of the webbing 2. When the processing in step S5 is completed, this control flow ends.

[0063] On the other hand, if the operation amount calculated in step S1 is less than an arbitrary threshold value (for example, the estimated tension F ＲＥＴ is greater than the target tension (No in step S2), the process proceeds to step S6, where the drive circuit 14 continues to calculate the duty voltage for brake control (brake duty).

[0064] In step S7, the drive circuit 14 controls the low-side FET of the drive circuit 14 in accordance with the duty voltage of the brake control calculated in step S6.

[0065] In step S8, as a result of the control in step S7, the motor 7 performs brake control to reduce the tension of the webbing 2. When the processing in step S8 is completed, this control flow ends.

[0066] FIG. 4 is a diagram showing motor output due to tension control shown in FIG. 3. As shown in FIG. 4, the strength of the retraction control or brake control can be adjusted between a duty of 100% and 0% depending on the amount of operation. Here, a retraction duty of 0% is the same as a brake duty of 100%. In other words, the increase in the tension of the webbing 2 increases as the retraction duty approaches 100% from 0%. On the other hand, the decrease in the tension of the webbing 2 increases as the brake duty approaches 0% from 100%.

[0067] As described with reference to FIGS. 3 and 4, the tension of the webbing 2 can be adjusted as desired by continuous control of the winding control and brake control of the retractor 10.

[0068] In this way, in the seat belt retractor 10 of the first embodiment, the control device 1 can be configured to switch between retraction control and brake control in accordance with the result of estimating the tension of the webbing 2. This configuration makes it easier to adjust the increase or decrease in the tension of the webbing 2, so that the tension of the webbing 2 can be adjusted more reliably and stably by controlling the motor 7.

[0069] FIG. 5 is a perspective view showing an example of a structure for detecting the rotation speed of the motor 7. In the retractor 10 shown in FIG. 5, a highly sensitive rotation sensor 20 is mounted on the rotation shaft of the motor 7. The highly sensitive rotation sensor 20 includes, for example, a resolver or an encoder. By transmitting the signal of the rotation sensor 20 to the control device 1 in real time, the control device 1 can check the angle information of the motor 7 in real time. In addition, the control device 1 can calculate the rotational acceleration dω / dt of the motor 7 by differentiating the angle information detected by the rotation sensor 20 twice.

[0070] The rotation sensor may be any sensor that can obtain angle information, and does not have to be the rotation sensor 20 coaxial with the rotation axis of the motor 7 as shown in FIG.

[0071] In addition, in this embodiment, the state of the motor 7 can be easily determined from the rotation angle signal detected by the rotation sensor 20, so the control device 1 can adjust the control amount according to the state of the motor 7.

[0072] Such adjustment of the control amount will be described with reference to Figures 6 and 7. Figure 6 is a diagram showing an example of changes in motor speed and acceleration. Figure 7 is a diagram showing patterns of the motor state exemplified in Figure 6.

[0073] For example, when the rotational acceleration is equal to or greater than 0, the above-described equations of motion (formulas (4) to (6)) have a relationship of "current torque - (+ inertia torque)," and therefore it is necessary to increase the current torque in order to bring the tension of the webbing 2 closer to the target tension. In this case, the control device 1 sets a large PID gain (at least one of Kp, Ki, and Kd of the PID controller in FIG. 2) and increases the manipulated variable input to the controller, thereby making it possible to bring the tension of the webbing 2 closer to the target tension.

[0074] On the other hand, when the rotational acceleration is 0 or less, the above-described equations of motion (formulas (4) to (6)) have a relationship of "current torque - (-inertia torque)," and therefore, tension in the webbing 2 that is equal to or greater than the target tension may be generated. In this case, the control device 1 sets the PID gain to be smaller than when the above-described rotational acceleration is 0 or more, and relatively reduces the manipulated variable input to the controller, thereby making it possible to generate a more stable tension in the webbing 2.

[0075] Furthermore, by taking into consideration the rotation speed (rotation direction) of the motor 7 and setting the parameter values ​​of the PID gains that are more optimal for the situation, it is possible to generate a more stable tension in the webbing 2.

[0076] In section (A) shown in Figure 6, the state of the motor 7 is a state where the rotational speed and rotational acceleration are both positive (+). In section (B), the state of the motor 7 is a state where the rotational speed is positive (+) and the rotational acceleration is negative (-). In section (C), the state of the motor 7 is a state where the rotational speed and rotational acceleration are both negative (-). In section (D), the state of the motor 7 is a state where the rotational speed is negative (-) and the rotational acceleration is positive (+).

[0077] As shown in FIG. 7 , the states of these four sections (A) to (D) can be classified into four patterns (A) to (D) based on the combination of rotational speed and rotational acceleration. Therefore, by using angle information acquired from the rotation sensor 20 to monitor in real time which of patterns (A) to (D) the combination of rotational speed and rotational acceleration of the motor 7 corresponds to, the control device 1 can appropriately change the set values ​​of the PID gains depending on the pattern, thereby enabling adjustment of the above-mentioned control variables. In the example of FIG. 7 , when the pattern corresponds to patterns (A) or (D) in which the rotational acceleration is positive, a relatively large value can be set for the PID gains. Furthermore, since the rotation direction of the motor 7 is reversed in patterns (A) and (D), the PID gains may be changed depending on the rotation direction.

[0078] On the other hand, when the pattern (B) or (C) applies, in which the rotational acceleration is negative, the PID gains may be set to relatively small values. Also, since the rotation direction of the motor 7 is reversed in the patterns (B) and (C), the PID gains may be changed depending on the rotation direction.

[0079] As described above, in the seat belt retractor 10 of the first embodiment, the control device 1 can be configured to feedback-control the output of the motor 7 and change the feedback gain of the feedback control in accordance with the operation of the motor 7. This configuration makes it possible to adjust the manipulated variable of the controller to be appropriate for the operating state of the motor 7 (for example, whether the rotational acceleration is positive or negative, or whether the rotational speed is positive or negative, etc.), and therefore the tension of the webbing 2 can be adjusted more reliably and stably by controlling the motor 7.

[0080] Second Embodiment A second embodiment will be described with reference to FIGS.

[0081] In the second embodiment, the retractor 10 includes a webbing tension sensor 21 that detects information related to the tension generated in the webbing 2. In the second embodiment, the control device 1 estimates the tension of the webbing 2 based on the information detected by the webbing tension sensor 21.

[0082] Fig. 8 is a perspective view showing an example of a structure for detecting the tension of the webbing 2 according to the second embodiment. Fig. 8 shows an exploded perspective view of a structure in which the retractor 10 is connected and fixed to a bracket 22. As shown in Fig. 8, the retractor 10 is connected and fixed to the bracket 22 that is fixed to the vehicle body. In the example of Fig. 8, the motor 7 is disposed on the opposite side of the bracket 22 with respect to the retraction mechanism 6 of the retractor 10.

[0083] 9A and 9B are a front view and a cross-sectional view of a retractor 10 showing an example of a structure for detecting the tension of a webbing 2 according to a second embodiment. Fig. 9A is a front view of the retractor 10 attached to a bracket 22 as viewed from the motor 7 side. Fig. 9B is a cross-sectional view taken along the cross-sectional line A-A shown in Fig. 9A.

[0084] 9(b), the webbing 2 wound around the spool 8 of the retractor 10 is pulled out upward in the figure from the retraction mechanism 6. Above the retraction mechanism 6 in the figure, the webbing tension sensor 21 is disposed adjacent to the retraction mechanism 6 and is held between the retraction mechanism 6 and the bracket 22 by the connector bracket 23. The webbing 2 pulled out upward in the figure from the retraction mechanism 6 of the retractor 10 passes through the inside of the webbing tension sensor 21 and continues to extend upward in the figure.

[0085] As shown in Figures 8 and 9, the webbing tension sensor 21 extends horizontally in the figures and has three rods 21A, 21B, and 21C arranged in parallel in the vertical direction in the figures. The rods are arranged in the order of rod 21B, rod 21A, and rod 21C from top to bottom in the figures. Furthermore, the rod 21A, which is arranged in the center in the vertical direction, is arranged on the opposite side of the webbing 2 from the other two rods 21B and 21C. In Figure 9(b) , the rod 21A is arranged in contact with one main surface of the webbing 2 facing the left side in the figure, and the other two rods 21B and 21C are arranged in contact with the other main surface of the webbing 2 facing the right side in the figure. Both ends of the rod 21A are electrically connected to the control device 1, and the rod 21A is configured to output a signal corresponding to the tension of the webbing 2 to the control device 1 from the contact portion with the webbing 2.

[0086] With the retractor 10, the webbing tension sensor 21, and the bracket 22 arranged in this manner, the webbing tension sensor 21 comes into contact with the webbing 2 passing through the interior thereof, and is thereby able to detect information relating to the tension of the webbing 2 from the contact portion with the webbing 2 and output the information to the control device 1.

[0087] If the retractor 10 is configured to include a sensor or mechanism that can measure a signal corresponding to the tension of the webbing 2, like the webbing tension sensor 21 of the second embodiment, the control device 1 can perform feedback control of the tension of the webbing 2 without performing processing to calculate the estimated tension.

[0088] Fig. 10 is a block diagram of tension control by the control device 1 according to the second embodiment. In the block diagram of Fig. 10, the information that is fed back is information related to the tension of the webbing 2 detected by the webbing tension sensor 21. The control device 1 estimates the tension of the webbing 2 based on the information input from the webbing tension sensor 21, and performs PID control using the estimated tension and a target tension to calculate the manipulated variable to be input to the controller.

[0089] As described above, the seat belt retractor 10 according to the second embodiment includes the webbing tension sensor 21 that detects information related to the tension generated in the webbing 2. The control device 1 estimates the tension of the webbing 2 based on the information detected by the webbing tension sensor 21. Then, the control device 1 controls the motor 7 based on the result of the estimation of the tension of the webbing 2. With this configuration, the information related to the tension of the webbing 2 itself can be feedback-controlled, thereby enabling more accurate control of the tension of the webbing 2.

[0090] Also, similar to the configuration described with reference to FIGS. 3 and 4 in the first embodiment, the control device 1 calculates the duty voltage for retraction control or brake control in accordance with the operation amount calculated by the PID controller, and controls the high-side or low-side of the FET of the drive circuit 14, thereby controlling the motor 7 and performing tension control so as to bring the tension of the webbing 2 closer to the target tension.

[0091] Also in the second embodiment, similarly to the first embodiment, by mounting the rotation sensor 20 on the motor 7, it becomes possible to set a PID gain according to the rotation state of the motor 7, and it becomes possible to output a more stable tension to the webbing 2.

[0092] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise.

[0093] This international application claims priority based on Japanese Patent Application No. 2024-069596, filed on April 23, 2024, the entire contents of which are incorporated herein by reference.

[0094] REFERENCE SIGNS LIST 1 control device 2 seat belt (webbing) 4 tongue 5 buckle 7 motor 8 spool 10 seat belt retractor 100 seat belt device 20 rotation sensor 21 webbing tension sensor

Claims

1. A seat belt retractor comprising: a spool that winds up a webbing; a motor that rotates the spool; and a control device that controls the output of the motor to adjust the tension of the webbing, wherein the control device estimates the tension of the webbing and controls the motor based on the estimated tension.

2. A seat belt retractor as claimed in claim 1, wherein the control device uses an equation of motion to calculate an estimated tension in consideration of the current torque generated by the motor due to the current flowing through the motor and the inertia torque generated around the rotation axis of the motor, and controls the motor based on the calculated estimated tension.

3. The seat belt retractor according to claim 1, further comprising a webbing tension sensor that detects information related to the tension generated in the webbing, and the control device estimates the tension based on the information detected by the webbing tension sensor.

4. The seat belt retractor according to claim 2, wherein the control device switches between retraction control and braking control in accordance with the result of the estimation.

5. The seat belt retractor according to claim 2, wherein the control device feedback-controls the output of the motor and changes a feedback gain of the feedback control in accordance with the operation of the motor.

6. The seat belt retractor according to claim 3, wherein the control device switches between retraction control and braking control in accordance with the result of the estimation.

7. The seat belt retractor according to claim 3, wherein the control device feedback-controls the output of the motor, and changes a feedback gain of the feedback control in accordance with the operation of the motor.

8. A seat belt device comprising: a webbing; a seat belt retractor that controls winding and unwinding of the webbing; a tongue attached to the webbing; and a buckle with which the tongue is detachably engaged, wherein the seat belt retractor comprises: a spool that winds up the webbing; a motor that rotates the spool; and a control device that controls the output of the motor to adjust the tension of the webbing, and the control device estimates the tension of the webbing and controls the motor based on the estimation result.

9. A control method for a seat belt retractor comprising: a spool that winds up a webbing; a motor that rotates the spool; and a control device that controls the output of the motor to adjust the tension of the webbing, the control method including: an estimation step of estimating the tension of the webbing by the control device; and a motor control step of controlling the motor based on the estimation result in the estimation step by the control device.

Images