Seat belt device, and control system and control method thereof

Abstract

To provide a seat belt device capable of controlling proportional or gradual increase of tension of a seat belt without changing composition of a seat belt device, and to provide a control system and a control method of the seat belt device.SOLUTION: A control system of a seat belt device comprises a retractor for a seat belt is configured to wind a seat belt for vehicle. The retractor for a seat belt includes a spindle for winding the seat belt, a motor which generates a power for rotating the spindle and a power transmission mechanism which transmits the power from the motor to the spindle. The control system includes a control device 200 which drives a motor so as to generate an intermittent pulse-like torque which exceeds the maximum static friction force when driving the motor.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a seat belt device, its control system, and a control method.

Background Art

[0002] A seat belt device equipped with a retractor (also called a pre - pretensioner or PP (Pre - Pretensioner)) that retracts by winding up a seat belt (webbing) using a motor is used (see, for example, Patent Document 1). When the motor is a DC motor, torque proportional to the magnitude of the current flowing through the DC motor can be generated. Also, one method of controlling the current flowing through the motor is PWM control, and by proportionally increasing the PWM duty value, proportional or step - changing torque can be generated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when attempting to generate proportional or step - changing torque as described above in a seat belt device, it may actually be difficult to control the tension proportionally or step - by - step (see FIG. 9).

[0005] Therefore, an object of the present invention is to provide a seat belt device, its control system, and a control method that enable proportional or step - by - step control of the tension of the seat belt without changing the configuration of the seat belt device.

Means for Solving the Problems

[0006] In order to solve such problems, the present inventors have considered and studied, paying attention to the influence of friction in the mechanism part. Even when the torque is changed proportionally or stepwise, due to the influence of friction in the mechanism parts such as the motor, shaft, gear, and webbing, it is considered difficult to change the tension proportionally or stepwise, so further study was conducted on the frictional force. There are static friction and dynamic friction for the frictional force. Among them, until the mechanism etc. starts moving from the stationary state, it is under the influence of the former (static friction) (see Fig. 10). That is, even if the duty value of PWM is increased to increase the torque of the motor, the static friction also increases up to the maximum static friction in proportion to the PWM accordingly. During that time, the seat belt is not wound up and the belt tension does not increase (see Fig. 11). After that, when the torque of the motor further increases and exceeds the maximum static friction, the seat belt is wound up and the tension increases. However, as the tension increases, the static friction in the next stage also increases, and due to this influence, the mechanism stops and the winding is interrupted (see Fig. 12). When such a flow is repeated, as a result, it is considered that a phenomenon occurs in which even if the duty value of PWM is increased proportionally or stepwise, the tension of the seat belt does not increase correspondingly.

[0007] The present invention is based on the knowledge arrived at through such careful consideration. One aspect thereof is a control system for a seat belt device including a seat belt retractor configured to wind up a vehicle seat belt, The seat belt retractor includes a spindle for winding up the seat belt, a motor that generates power for rotating the spindle, a power transmission mechanism that transmits the power from the motor to the spindle, and is provided with The control system is a control system for a seat belt device including a control device that drives the motor so as to generate an intermittent pulse-like torque exceeding the maximum static friction when driving the motor.

[0008] In such a control system, the control device drives the motor so as to generate an intermittent pulsed torque exceeding the maximum static friction force, thereby generating a torque capable of overcoming the maximum static friction force for a very short time imperceptible to the user as a countermeasure against the static friction force, bringing the state under the domination of the dynamic friction force, and making it possible to maintain a continuous winding state. According to this, an object is to provide a seat belt device, its control system, and a control method capable of controlling the tension of the seat belt proportionally or stepwise without changing the configuration of the seat belt device.

[0009] In the control system of the seat belt device as described above, the maximum static friction force may be the maximum static friction force when driving a stationary motor to operate the power transmission mechanism and the spindle.

[0010] In the control system of the seat belt device as described above, the motor may be PWM-controlled by the control device.

[0011] In the control system of the seat belt device as described above, a pulsed superimposed duty value for generating a torque exceeding the maximum static friction force may be intermittently added to the basic duty value during PWM control.

[0012] In the control system of the seat belt device as described above, the basic duty value of PWM may be increased stepwise.

[0013] In the control system of the seat belt device as described above, the pulsed superimposed duty value may be added to the basic duty value once at each step.

[0014] In the control system of the seat belt device as described above, the pulsed superimposed duty value may be added to the basic duty value a plurality of times at each step.

[0015] In the control system of the seat belt device as described above, a pulsed superimposed duty value may be continuously added within the step.

[0016] In the control system of the seat belt device as described above, the amplitude and period of the pulsed superimposed duty value may be set targeting the torque that exceeds the maximum static friction force and is the lowest among them.

[0017] In the control system of the seat belt device as described above, the amplitude of the pulsed superimposed duty value may be constant.

[0018] In the control system of the seat belt device as described above, the amplitude of the pulsed superimposed duty value may be increased as the basic duty value increases.

[0019] A seat belt device according to another aspect of the present invention includes the control system as described above.

[0020] Yet another aspect of the present invention is a control method for a seat belt device including a seat belt retractor configured to wind up a vehicle seat belt, a control method for a seat belt device, in which when driving a motor that rotates a spindle for winding up a seat belt, the motor is driven to generate an intermittent pulsed torque exceeding the maximum static friction force.

Advantages of the Invention

[0021] According to the present invention, it becomes possible to perform control to increase the tension of the seat belt proportionally or stepwise without changing the configuration of the seat belt device.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

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Figure 8

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Figure 10

Figure 11

Figure 12

[0023] Hereinafter, a preferred embodiment of a seat belt device and its control system according to the present invention will be described in detail with reference to the drawings (see Figs. 1 to 8, etc.).

[0024] [Outline of the configuration of a seat belt retractor] First, the configuration of a seat belt retractor 4 constituting a seat belt device 1 will be described (see Fig. 1).

[0025] The seat belt retractor 4 is a vehicle device configured to wind up the seat belt 2, also called a pre-pretensioner or PP (Pre-Pretensioner). The seat belt retractor 4 of the present embodiment is a retractor with a motor for a seat belt with a motor (sometimes called "PP" (Pre-Pretensioner)) that winds up the seat belt 2 with the force of a motor, and is composed of a spindle 10, a driving motor 20, a power transmission mechanism 30, a final gear 33, a clutch 34, etc. (see FIG. 1).

[0026] The spindle 10 is a member for winding up the seat belt 2 and is provided so as to be rotatable forward and backward about the central axis (see FIG. 1). In this specification, for the sake of convenience, regarding the rotation direction of the spindle 10 etc., the forward rotation direction for winding up the seat belt 2 is called the "winding-up direction", and the reverse rotation direction for feeding out the seat belt 2 is called the "clutch release direction".

[0027] The driving motor 20 is a power source that generates power for rotating the spindle 10. When the motor 20 is rotated in one direction (referred to as the "first direction" in this specification), power is transmitted by the clutch 34, and the spindle 10 rotates in the winding-up direction. Also, when the motor 20 is rotated in the second direction opposite to the first direction, the final gear 33 rotates in the clutch release direction (see FIG. 1).

[0028] The power transmission mechanism 30 is a mechanism for transmitting the power of the motor 20 to the spindle 10. For example, in the present embodiment, a power transmission mechanism 30 including a motor gear 31, a transmission shaft (intermediate gear) 32, a final gear 33, and a clutch 34 is used. The motor gear 31 is composed of a worm attached to the output shaft 21 of the motor 20 (see FIG. 1). The transmission shaft 32 is a member for transmitting the power of the motor 20 to the final gear 33. A first helical gear 32a that meshes with the motor gear 31 and a second helical gear 32b that meshes with the final gear 33 are provided on the transmission shaft 32 (see FIG. 1).

[0029] The final gear 33 is one of the gears constituting the power transmission mechanism 30, and is composed of a large-diameter helical gear rotatably arranged on the central axis of the spindle 10. The final gear 33 of the present embodiment is a gear arranged at the end of the gear train constituting the power transmission mechanism 30. On the outer periphery of the final gear 33, a helical tooth 33a is formed with which the second helical gear 32b of the transmission shaft 32 meshes.

[0030] The clutch 34 is a mechanism for transmitting or blocking the rotation of the final gear 33 to the spindle 10 and is arranged between the final gear 33 and the spindle 10 (see FIG. 1). In the present embodiment, when the motor 20 is rotated in the first direction, it is in a coupled state and transmits the rotation of the final gear 33 to the spindle 10. On the other hand, when the motor 20 is rotated in the second direction, it is not coupled. That is, a so-called one-way clutch is used for this clutch 34. Since the configuration of the one-way clutch itself is the same as that in the conventional seat belt retractor 4, the details thereof will be omitted in this specification. For example, a one-way clutch pawl (latch) 34b that engages with the ratchet gear 35a only when the final gear 33 rotates in one direction is applicable (see FIG. 1).

[0031] [Control System of Seat Belt Device] The seat belt device 1 of the present embodiment including the seat belt retractor 4 as described above includes a control system 100 including an ECU (control device) 200 (see FIG. 2 etc.). The ECU 200 drives the motor 20 so as to generate an intermittent pulsed torque exceeding the maximum static friction force MSFF when driving the stationary motor 20 to operate the power transmission mechanism 30 and the spindle 10. The ECU 200 includes a signal generation unit (signal processor) 240, a comparator 250, a motor drive circuit 260, etc. (see FIGS. 2 and 3).

[0032] The signal generation unit 240 processes the input signal and performs pulse modulation processing according to the difference between the input signal and a predetermined threshold value at regular intervals, so as to process the input signal so that it can be used as the motor drive timing. The signal generation unit 240 in the ECU 200 of this embodiment is equipped with a low-pass filter (LPF) that attenuates the high-frequency components of the input signal (see FIG. 3). Of course, instead of this, a high-pass filter (HPF) that attenuates the low-frequency components of the input signal may be equipped. Note that AI may be installed as the signal generation unit 240 to process the input signal and generate a drive signal.

[0033] The comparator 250 outputs a signal for driving, for example, the motor 20 according to the signal output from the signal generation unit 240. The motor drive circuit 260 flows a current (constant current value) for driving, for example, the motor 20 to the motor connection line 270 based on the signal output from the comparator 250 (see FIG. 2).

[0034] An example will be described in which the control system 100 performs PWM control of the motor 20 to increase the tension of the seat belt 2 in proportion to time, that is, torque control of the motor 20 by pulse width modulation processing (PWM conversion). In the PWM control of the motor 20, pulse width modulation processing (PWM conversion) is performed every constant PWM cycle. If the duty of the PWM (PWM Duty, that is, motor drive time / PWM cycle [%]) is increased, the drive time of the motor 20 becomes longer, and accordingly, the seat belt 2 is wound up more, and the tension of the seat belt 2 increases. On the other hand, if the duty is decreased, the drive time of the motor 20 becomes shorter. That is, since the torque of the motor 20 is proportional to the duty value of the PWM, as shown in FIG. 12, if the duty of the PWM is increased, the motor 20 generates a corresponding torque. However, even in such a case, due to the influence of the static friction force of the seat belt drive system, the tension of the seat belt 2 cannot change following the torque of the motor 20 (see FIG. 9). Further, once the torque exceeds the static friction force and the winding of the seat belt 2 starts, the static friction force also increases according to the tension, so the winding stops again and the same state is repeated (see FIGS. 10 and 11). Considering these points, in the present embodiment, the control system 100 causes the motor 20 to generate a torque that can overcome the maximum static friction force MSFF for a very short time that is imperceptible to the user as a countermeasure against the static friction force, so that the state is always above the maximum static friction force MSFF (in other words, a state dominated by dynamic friction force), and a continuous winding state is maintained.

[0035] A functional block diagram of a control circuit in a control system 100 that performs such control is shown in FIG. 3. In the control system 100 of the present embodiment, a trigger signal is input from an external ECU to a communication I / F 110, and a basic duty for controlling the tension of the seat belt 2 is generated by a Base waveform generator 120. For this basic duty, a Modulating waveform generator 140 generates pulses (hereinafter also referred to as startup pulses) for a very short time, and a modulator 130 further modulates the PWM duty (PWM Duty, that is, motor drive time / PWM cycle [%]) (see FIG. 3). As a result, a pulsed superimposed duty value Ds sufficient to generate a torque exceeding the maximum static friction force MSFF is intermittently added to the basic duty value Db during PWM control to be superimposed, thereby realizing control for eliminating the influence of the above static friction force.

[0036] The following can be considered as specific examples of the startup pulses generated by the above-described modulating waveform generator 140. First, it is necessary to control the amplitude, period, and duty of the startup pulse. Since it is basically preferable to control the static friction force so that the user is not aware of the change in the startup pulse, the minimum amplitude and period that can break free from the static friction force are set. Also, regarding the period, it is conceivable to make the period less likely to include a frequency that generates audible noise. Regarding the amplitude of the startup pulse, in addition to setting it to be constant, a method of setting the amplitude of the startup pulse multiplicatively in response to an increase such as a stepwise increase in the basic duty can be considered so as to be able to cope with an increase in the static friction force accompanying an increase in the tension of the seat belt 2. When performing multiplicative startup pulse amplitude setting, the maximum duty value should not exceed the absolute maximum rating of the motor 20. Specific examples of such startup pulse shapes include a rectangular wave shape (FIG. 4(A)), a sawtooth shape (FIG. 4(B)), an inverse sawtooth shape (FIG. 4(C)), a triangular shape (FIG. 4(D)), a sine wave shape (FIG. 4(E)), and the like.

[0037] As patterns of modulation of the starting pulse, a pattern of modulating it singly (see Fig. 5) or a pattern of modulating it continuously (see Fig. 6) can be considered. Note that the examples shown in these figures are examples of modulation with respect to the basic duty shown in Fig. 12. When adding the superimposed duty value Ds by modulating a single starting pulse (see Fig. 5), the amplitude of the pulse-shaped superimposed duty value Ds may be constant, or the amplitude may be increased as the basic duty value Db increases. For example, if the basic duty for controlling the tension of the seat belt 2 is increased stepwise at regular intervals of 100 msec, the superimposed duty value Ds may be added once at each step by setting and modulating the amplitude of the starting pulse multiplicatively accordingly. When using multiplication, in order to avoid applying an input that exceeds the maximum rating of the motor 20, for example, a process of saturating to about 80% in 3000 msec may be performed (see Fig. 7). In the example shown in Fig. 7, as described for the amplitude setting of the above starting pulse, in addition to the method of making it difficult for the user to notice the tension change by the starting pulse by setting the amplitude as the minimum value that can overcome the maximum static frictional force MSFF, it is also conceivable to adopt a method of intentionally setting the amplitude of the starting pulse high to increase the tension while making the user notice. This method can be an effective technique when transmitting an alarm signal. When adopting the method of making it difficult for the user to notice the tension change by the starting pulse as in the former case, the amplitude and period of the pulse-shaped superimposed duty value Ds may be set targeting the torque that exceeds the static frictional force and is the lowest among them.

[0038] Alternatively, the superimposed duty value Ds may be added multiple times by continuously modulating the starting pulse (see Fig. 8). For example, the superimposed duty value Ds may be added multiple times at each step of the basic duty that increases stepwise, or the superimposed duty value Ds may be continuously added within the step at equal intervals or continuously in a form such as without interruption. By using this method, a smoother increase in tension can be obtained than in the case of single modulation. Here, it is preferable to modulate the starting pulse at a period that is difficult to feel as vibration by removing the audible range noise generated by modulating the starting pulse or the frequency components in the audible range that the user may feel as vibration. The amplitude control is the same as in the case of modulating a single starting pulse. On the other hand, for the same reason as in the case of modulating a single starting pulse (see Fig. 7), it is also conceivable to control the period so as to increase the tension while making the user feel the operation. In the case of continuous driving, if the period and duty of the starting pulse are set longer, the repetition of the starting pulse appears as vibration. This is a method of utilizing such vibration.

[0039] According to the seat belt device 1 and its control system 100 of the present embodiment as described above, by driving the motor 20 so as to generate intermittent pulsed torque exceeding the maximum static frictional force MSFF, torque capable of overcoming the maximum static frictional force MSFF is generated to bring it into a state dominated by dynamic friction, and it becomes possible to maintain a continuous winding state. According to this, it becomes possible to perform control to increase the tension of the seat belt 2 proportionally or stepwise without changing the configuration of the seat belt device 1. Further, according to this, 1) To gently and smoothly fasten the seat belt 2 for vehicle users 2) To perform information transmission using the tension change of the seat belt 2 3) To realize the above functions without changing the mechanism of the conventional electric motor-driven pretensioner is possible.

[0040] Note that the above-described embodiments are merely preferred examples of the present invention and are not limited thereto. Various modifications can be made without departing from the gist of the present invention.

Industrial Applicability

[0041] The present invention is suitable for application to a seat belt device and its control system.

Explanation of Reference Numerals

[0042] 1…Seat belt device 2…Seat belt 4…Seat belt retractor 10…Spindle 20…Motor 21…Output shaft 30…Power transmission mechanism 31…Motor gear 32…Transmission shaft 32a…First helical gear 32b…Second helical gear 33…Final gear (first rotation gear) 33a…Rack 34…Clutch 34b…Pawl for one-way clutch 35…Clutch housing 35a…Ratchet gear 100…Control system 110…Communication I / F 120…Basic waveform generator 130…Modulator 140…Modulated waveform generator 200…ECU (control device) 260…Motor drive circuit 270…Motor connection wire Db…Basic duty value Ds…Superimposed duty value MSFF…Maximum static friction force

Claims

1. A control system for a seat belt device including a seat belt retractor configured to retract a seat belt for a vehicle, The seat belt retractor includes: A spindle for winding the seat belt; A motor that generates power to rotate the spindle; a power transmission mechanism that transmits power from the motor to the spindle; Equipped with The control system of the seat belt device includes a control device that drives the motor so as to generate an intermittent pulse torque that exceeds the maximum static friction force when driving the motor.

2. The seat belt device control system according to claim 1 , wherein the maximum static friction force is a maximum static friction force when the motor in a stationary state is driven to operate the power transmission mechanism and the spindle.

3. 3. The seat belt device control system according to claim 2, wherein the motor is PWM controlled by the control device.

4. 4. The seat belt device control system according to claim 3, wherein a pulse-like superimposed duty value that generates a torque exceeding the maximum static friction force is intermittently added to a basic duty value during PWM control.

5. 5. The seat belt device control system according to claim 4, wherein the basic duty value of the PWM is increased in a stepwise manner.

6. 6. The seat belt device control system according to claim 5, wherein the pulse-like superimposed duty value is added to the basic duty value once in each step.

7. 6. The seat belt device control system according to claim 5, wherein the pulse-like superimposed duty value is added to the basic duty value a plurality of times in each step.

8. 8. The seat belt device control system according to claim 7, wherein the pulse-like superimposed duty value is continuously applied within each step.

9. 9. The seat belt device control system according to claim 5, wherein the amplitude and period of the pulse-like superimposed duty value are set to a torque that exceeds the maximum static friction force and is the minimum torque among the maximum static friction force.

10. 10. The seat belt device control system according to claim 9, wherein the amplitude of the pulse-like superimposed duty value is made constant.

11. 10. The seat belt device control system according to claim 9, wherein the amplitude of the pulse-like superimposed duty value is increased as the basic duty value increases.

12. A seat belt device comprising a control system according to any one of claims 1 to 8.

13. A method for controlling a seat belt device including a seat belt retractor configured to retract a seat belt for a vehicle, comprising: A control method for a seat belt device, comprising: driving a motor that rotates a spindle for winding up the seat belt so as to generate an intermittent pulse-like torque exceeding a maximum static friction force when driving the motor.

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