Seat belt retractor

Abstract

The present invention provides a seat belt retractor that reduces the biasing force in the direction of retracting the seat belt when an occupant fastens the seat belt. [Solution] The seat belt winding device 1 of the present invention comprises a spool 20 for winding a seat belt 10 for restraining an occupant, and a mainspring 30 connected to the spool for applying a biasing force to the seat belt in the winding direction. Furthermore, it comprises an electric actuator 40 that applies rotational force to the spool around its axis, a detection means 60 for detecting the occupant's operation to pull out the seat belt, and a control means 70. The control means receives a detection signal of the seat belt pulling operation transmitted from the detection means and drives the electric actuator to rotate the spool in a direction that reduces the biasing force in the winding direction. This releases the elastic energy stored in the mainspring, significantly reducing the tension felt by the occupant when pulling out the seat belt.

Description

Technical Field

[0001] The present invention relates to a seat belt retractor capable of reducing the biasing force in the seat belt retracting direction when an occupant fastens the seat belt.

Background Art

[0002] In a conventional general seat belt retractor, a biasing means such as a spiral spring is connected to a spool (retracting shaft) so that the seat belt can be automatically retracted without slack. When an occupant fastens the seat belt, it is necessary to pull out the seat belt together with the tongue against the biasing force of the spiral spring.

[0003] However, the resistance of the spiral spring imposes a considerable burden on elderly people with weak strength and small-sized occupants, which poses a problem that it becomes difficult to fasten the seat belt. In particular, when starting to pull out the seat belt or when it is necessary to pull out the seat belt for a long distance, the large resistance has been a factor that makes occupants hesitate to fasten the seat belt.

[0004] To address such problems, techniques for adjusting the biasing force itself of the spiral spring have been devised. For example, Patent Document 1 discloses a technique of providing a tension reducer in a seat belt retractor. The main purpose of this technique is to cancel the torque of the conventional spiral spring by using the tension of a reduce balance spring (canceling biasing means) after the occupant has fastened the seat belt, so as not to give the occupant a feeling of pressure due to tightening. The reduce balance spring described in Patent Document 1 increases the biasing force by rotating its inner end relatively in the retracting direction, and uses the increased biasing force to reduce the tightening torque applied to the occupant when the seat belt is fastened.

Prior Art Literature

Patent Literature

[0005]

Patent Document 1

[0006] However, the technology described in Patent Document 1 is intended to reduce the tightness (pressure) on the occupant when the seat belt is already fastened, and is not intended to eliminate the resistance of the spring when pulling out the seat belt. Therefore, conventional technology has not yet solved the fundamental problem of difficulty in pulling out the seatbelt due to the tension of the spring when elderly people start to fasten their seatbelts.

[0007] The present invention aims to provide a seat belt retractor that can reduce the biasing force in the direction of retracting the seat belt when an occupant fastens the seat belt, taking into consideration the problems described above. [Means for solving the problem]

[0008] The seat belt winding device of the present invention comprises a spool for winding a seat belt for restraining an occupant, a spring connected to the spool for applying a biasing force to the seat belt in the winding direction, an electric actuator that applies rotational force to the spool around its axis, and a detection means for detecting the occupant's operation to pull out the seat belt. A transmission mechanism for transmitting the rotational force of the electric actuator to the spool, The system includes a control means, the control means receiving a detection signal of the seat belt extension operation transmitted from the detection means, Switching the transmission mechanism to the transmission state, The electric actuator is driven By rotating the spool in the opposite direction to the direction of rotation (pull-out direction) when the seat belt is pulled out, the biasing force in the winding direction of the mainspring is reduced, and the transmission mechanism is switched to a disconnected state while the occupant is pulling out the seat belt further. It is characterized by the following: [Effects of the Invention]

[0009] In the seat belt retraction device of the present invention, when an occupant attempts to fasten the seat belt, the control means drives an electric actuator to rotate the spool in a direction that reduces the biasing force in the winding direction. This releases the elastic energy stored in the mainspring, thereby significantly reducing the tension felt by the occupant when pulling out the seat belt. Furthermore, it is equipped with a transmission mechanism that transmits / interrupts the rotational force of the electric actuator to the spool. In the interrupted state, the transmission of force (or torque) from the spool to the electric actuator is prevented, allowing the occupant to continue pulling out the seat belt with minimal resistance. On the other hand, in the transmission state, the biasing force of the mainspring is designed to overcome the resistance of the electric actuator's motor, thereby eliminating any slack in the seat belt after fastening and ensuring an appropriate restraining force for the occupant. [Brief explanation of the drawing]

[0010] [Figure 1] Schematic diagrams (a) and (b) showing the structure and operation of the seat belt retractor. [Figure 2] Block diagram showing the configuration of the seat belt retractor. [Figure 3] Figure (a) shows the transmission state by the transmission mechanism, and Figure (b) shows the interruption state. [Figure 4] Schematic diagrams (a) and (b) showing the structure and operation of the seat belt retractor. [Figure 5] Schematic diagrams (a) and (b) showing the structure and operation of modified seat belt retractors. [Modes for carrying out the invention]

[0011] The seat belt winding device of the present invention will be described with reference to the drawings. As shown in Figures 1 to 3, the seat belt retractor 1 is generally composed of a seat belt 10, a spool 20, a mainspring 30, an electric actuator 40, a transmission mechanism 50, a detection means 60, and a control means 70. Note that the figures are simplified for ease of understanding and do not represent the actual structure of each component.

[0012] The spool 20 is the shaft for winding the seat belt 10, and its axis of rotation is rotatably supported by the housing 80. Specifically, the longitudinal base end of the long, strip-shaped seat belt 10 is fixed to the spool 20. When an occupant pulls the seat belt 10 toward the end to fasten it, the spool 20 rotates in the pull-out direction A (see arrow in Figure 1(b)), and the seat belt 10 wound on the spool 20 is pulled out from the spool 20. On the other hand, the spool 20 is always subjected to a biasing force in the winding direction (opposite direction to the pull-out direction A) by the mainspring 30, and when the spool 20 rotates in the winding direction due to this biasing force, the seat belt 10 is wound from its longitudinal base end.

[0013] The mainspring 30 is a component that imparts a biasing force to the spool 20 in the winding direction. The outer end 31 of the mainspring 30 in the spiral direction is fixed to the housing 80, and the inner end 32 is fixed to the spool 20. Figure 1(a) shows the seat belt 10 wound onto the spool 20, that is, the state before the occupant fastens the seat belt 10. When the occupant pulls the seat belt 10 (or tongue) from this state, as shown in Figure 1(b), the spool 20 rotates in the pulling direction A against the biasing force, and the mainspring 30 is tightened around the spool 20 as a whole. The greater the amount the seat belt 10 (tongue) is pulled out, the more the mainspring 30 is tightened around the spool 20, increasing the elastic energy stored in the mainspring 30 and increasing the biasing force (or torque) on the spool 20 in the winding direction. This biasing force becomes the force that automatically winds up the slack after the seat belt 10 is fastened, and also the force that automatically winds up the seat belt 10 when the tongue is released.

[0014] The electric actuator 40 is constituted by a small motor (not shown), a control gear (not shown) that reduces the rotation speed of the motor and amplifies torque, and the like. The rotating shaft (output shaft) 41 of the control gear is connected to the spool 20 via a transmission mechanism 50 described later. The transmission mechanism 50 is a mechanism for transmitting the rotational force of the electric actuator 40 to the spool 20, and is constituted by a well-known one-way clutch or a ratchet mechanism. Specifically, the transmission mechanism 50 includes an electromagnetic solenoid or a small switching motor (not shown) so that it can be switched between a transmission state and a cutoff state based on a signal from the control means 70. Examples of the one-way clutch include, but are not limited to, a roller clutch or a sprag clutch; examples of the ratchet mechanism include, but are not limited to, a combination of a pawl and a ratchet gear whose engagement is controlled by an electromagnetic solenoid.

[0015] The detection means 60 is constituted by an optical sensor (not shown) that detects an operation in which an occupant grasps the seatbelt 10 (or a tongue) and tries to pull it out, for example, detects that the tongue has moved beyond a predetermined minute movement amount (e.g., 3 mm to 5 mm) from a stationary state, or an encoder (not shown) that detects minute rotational movement of the spool 20, or the like. Furthermore, a control logic for determining the timing immediately before the start of the pull-out operation may be configured in combination with a vehicle door opening / closing detection sensor and an occupant seating sensor. The control means 70 is a control unit including a microcomputer (not shown), a storage section (not shown) and the like. The control means 70 receives a signal from the detection means 60, and performs integrated control on the driving of the electric actuator 40 and the transmission mechanism 50.

[0016] Next, the operation of the seatbelt retractor 1 will be described. When an occupant performs an operation to pull out the seatbelt 10 to fasten the seatbelt 10, the detection means 60 detects the pull-out operation and transmits a detection signal to the control means 70. Upon receiving the detection signal, the control means 70 switches the transmission mechanism 50 to the transmission state, as shown in Figure 3(a), and connects the rotating shaft 41 of the electric actuator 40 to the spool 20. At this point, as shown in Figure 4(a), most of the mainspring 30 is densely packed and housed within the housing 80. The mainspring 30 is also densely wound around the spool 20 several times, and a biasing force in the winding direction is applied to the spool 20 from the mainspring 30.

[0017] Next, the control means 70 drives the electric actuator 40 and rotates the spool 20 slightly in the opposite direction to the pulling direction A, that is, in the direction that reduces the biasing force on the spool 20 in the winding direction, as shown in Figure 4(b) (for example, about 2 to 3 turns). Then, the control means 70 stops driving the electric actuator 40 when a predetermined time or a predetermined amount of rotation has been reached. As described above, the inner end 32 of the mainspring 30 is fixed to the spool 20, so the inner end 32 also rotates with the spool 20, and the mainspring 30, which was tightly wound around the spool 20 as shown in Figure 4(a), expands to a looser spiral shape as shown in Figure 4(b). As a result, the elastic energy stored in the mainspring 30 is released, and the biasing force (or torque) of the mainspring 30 in the winding direction decreases. As a result, the tension felt by the occupant when pulling out the seat belt 10 becomes virtually zero.

[0018] While the occupant is further pulling out the seat belt 10, the control means 70 switches the transmission mechanism 50 to a disconnected state, as shown in Figure 3(b). In this disconnected state, the transmission of force (or torque) from the spool 20 to the electric actuator 40 is prevented, so the occupant can continue to pull out the seat belt 10 with minimal resistance. In this way, the transmission mechanism 50, by means of a one-way clutch or ratchet mechanism, allows the spool 20 to rotate in the direction in which the mainspring 30 is tightened, that is, in the direction in which the seat belt 10 is pulled out (pulling direction A). Assuming that the control means 70 maintains the transmission state of the transmission mechanism 50 as shown in Figure 3(a) while the occupant is pulling out the seat belt 10, the force attempting to rotate the spool 20 in the direction that the mainspring 30 is tightened is transmitted through the transmission mechanism 50 to the stopped electric actuator 40. Since the stopped motor becomes a large source of resistance, a problem arises in that the occupant must pull out the seat belt 10 with great force, overcoming not only the force of the mainspring 30 but also the rotational resistance of the motor (inertia and holding torque).

[0019] When the detection means 60 or other sensors detect that the occupant has inserted the tongue into the buckle and the seat belt 10 has been fastened, the control means 70 releases the disconnection state of the transmission mechanism 50 and returns to a state where the power transmission path from the electric actuator 40 is secured, as shown in Figure 3(a). By designing the biasing force of the mainspring 30 in this state to overcome the resistance force of the motor of the electric actuator 40, the slack in the seat belt 10 after fastening is eliminated by the biasing force of the mainspring 30, ensuring an appropriate restraining force for the occupant.

[0020] Furthermore, if the transmission mechanism 50 is configured to switch between the transmission state and the disconnection state of the electric actuator 40 to the spool 20 as described above, the electric actuator 40 and the transmission mechanism 50 may be arranged between the housing 80 and the seat belt winding section 90, for example, as shown in Figure 5. A typical vehicle seat belt mechanism is equipped with an emergency lock retractor (ELR) (not shown). The ELR mechanically locks the spool 20 in the event of sudden deceleration of the vehicle, etc. In the present invention, in the event of an emergency when the ELR mechanism is activated, the control means 70 controls the transmission mechanism 50 to shut it off, completely disconnecting power from the electric actuator 40, and ensuring that the mechanical locking operation of the spool 20 by the ELR is not interfered with in any way. [Industrial applicability]

[0021] The present invention, taking into consideration the above-mentioned problems, is a seat belt retraction device that can reduce the biasing force in the direction of retracting the seat belt when an occupant fastens the seat belt, and has industrial applicability. [Explanation of Symbols]

[0022] A Pulling direction 1. Seat belt retractor 10 Seat belts 20 spools 30 mainsprings 31 Outer edge 32 Inner end 40 Electric Actuators 41 Rotation axis 50 Transmission mechanism 60 Detection means 70 Control means 80 Housing 90 Seatbelt retractor

Claims

[Claim 1] A seat belt winding device comprising a spool for winding a seat belt for restraining an occupant, and a spring connected to the spool for applying a biasing force to the seat belt in the winding direction, The system comprises an electric actuator that applies rotational force to the spool around its axis, a detection means for detecting the occupant's operation to pull out the seat belt, a transmission mechanism for transmitting the rotational force of the electric actuator to the spool, and a control means. The seat belt winding device is characterized in that the control means receives a detection signal of the seat belt pulling operation transmitted from the detection means, switches the transmission mechanism to a transmission state, drives the electric actuator to rotate in the opposite direction to the rotation direction (pulling direction) of the spool when the seat belt is pulled out, thereby reducing the biasing force in the winding direction of the mainspring, and switches the transmission mechanism to a disconnected state while the occupant is pulling out the seat belt further.

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