JP2002206976A - Seatbelt tension measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seatbelt tension measuring apparatus being easy to manufacture and capable of being miniaturized and detecting tension with accuracy. SOLUTION: A shaft bar 30 is an approximately square member made of a zinc die-cast alloy and two holes 30a and 30b are bored through the right side face of an upper member 31. Tapping screws 35 and 36 are driven into the holes 30a and 30b in the shaft bar 30 through two outer holes 40a and 40b provided in the fixed part 41 of an arm spring 40, whereby the arm spring 40 is fixed to the shaft bar. Since the holes 30a and 30b are formed in the portions of the member which do not coincide with the seams of die casting molds, the apparatus can be manufactured by die casting without requiring mechanical working.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seat belt tension measuring device installed on an anchor for fixing a seat belt to a vehicle body and measuring a tension applied to the belt. Both are related to a seat belt tension measuring device that can be reduced in size and can accurately detect tension.

[0002]

2. Description of the Related Art Many automobiles include an airbag as a device for ensuring the safety of occupants. Typical airbags are designed to have sufficient deployment gas pressure to restrain adults in high-speed collisions. However, when the occupant is a child sitting in a child seat, the airbag does not need to be deployed like an adult. For this reason, there has recently been a trend to detect the state of the occupant by measuring the seat belt tension in order to more appropriately operate the airbag, and to control the operation of the airbag accordingly.

A device for detecting the seat belt tension is based on a voltage signal detected by a Hall effect sensor.
A microprocessor that calculates seat belt tension has been developed. If the device detects high belt tension (generally high enough to make the occupant feel uncomfortable), the airbag control system will
It determines that the child seat is secured by the seat belt and prevents the deployment of the airbag.

[0004]

SUMMARY OF THE INVENTION As a seat belt tension measuring device used for such a purpose, the inventors have developed a device having a structure as shown in FIGS. FIG. 3 is an exploded perspective view of the seat belt tension measuring device, and FIG. 4 is an assembled perspective view thereof (excluding a cover). Hereinafter, these seat belt tension measuring devices may be referred to as conventional tension measuring devices, conventional products, and the like, but this does not mean that these devices have been known.

The seat belt tension measuring device is roughly divided into a base plate 10, a sensor mechanism including a sensor base 20, a sensor plate 21, a shaft bar 30 and an arm spring 40, and a cover 50.

The base plate 10 is a part (anchor connecting member) fixed to the vehicle body, and is made of a steel plate (S
PFH). A connecting portion 11 is formed at the tip of the base plate 10, and a hole 12 is formed at the center thereof. Anchor bolts (not shown) for fixing the connecting portion 11 to the body structure are pushed through the holes 12. The outer peripheral edge of the connecting portion 11 is formed in a semicircular shape. On both widthwise sides of the other end of the base plate 10,
The upright vertical root portion 13 is formed. Both vertical roots 1
A substantially semicircular engagement notch 14 is formed in the upper edge of 3. A hole 15 is formed in the middle between both vertical roots 13. An intermediate portion 16 for attaching the sensor mechanism and the cover 50 is provided in the middle of the portion where the connecting portion 11 and the two vertical root portions 13 are formed, and has screw holes 10a to 10e.

The sensor base 20 is made of an aluminum die-cast alloy or the like, and is a substantially U-shaped member. A sensor plate 21 is attached to the sensor base 20, and a screw 22 is provided in a hole 20a of the sensor plate 21.
A screw 23 is inserted through Ob and is fixed to the screw holes 10a and 10b of the base plate 10, respectively. Screw 2
3 is also inserted through the hole 21a of the sensor plate 21, thereby forming the sensor plate 21 made of a stainless steel sheet or the like.
Are fixed to the sensor base 20.

[0008] The sensor plate 21 has four strain gauges attached thereto, and an ASIC (Application Speci- fication) for converting a detection value of the strain gauge into an electric signal.
ficIntegrated Circuit) is attached. Further, a point pin 24 is attached to the hole 21b of the sensor plate 21.

The shaft bar 30 forms a part of the sensor mechanism and constitutes a webbing connecting member connected to the webbing. This is a substantially square-shaped member formed of, for example, a zinc die-cast alloy.
1, a side member 32 and a lower member 33 are integrally formed. Further, on both sides of the upper member 31, a cylindrical rotating shaft member 3 is provided.
4 are also integrally formed. Three holes 30a, 30b, and 30c are formed on the upper surface of the upper member 31, and tapping screws 35, 36, and 37 are inserted through the holes 40a, 40b, and 40c of the arm spring 40, and these holes 30a to 30c are formed. The arm spring 40 is fixed to the shaft bar 30 by being screwed into 30c.

The arm spring 40 is a spring plate made of a thin stainless steel plate or the like, and has a fixed portion 41 and an extending portion 42 extending obliquely downward from the fixed portion 41. The distal end of the extension part 42 is a contact part 43. Fixed part 41
Is fixed to the shaft bar 30 as described above.
The contact part 43 is a point pin 2 of the sensor plate 21.
4 is in contact with the tip.

The cover 50 has screws 51, 52, 53
The screw holes 10c, 10d, and 1 of the base plate 10 are inserted through the holes 50a, 50b, and 50c formed in the cover 50.
It is fixed to the base plate 10 by being screwed into 0e.

In the assembled state shown in FIG. 4, the rotation shaft member 34 of the shaft bar 30 is fitted into the engagement cuts 14 formed in both the vertical roots 13 of the base plate 10 and is supported rotatably. Then, the lower member 33 of the shaft bar 30 is fitted into the hole 15 of the base plate 10, and can be rotated within the range of the hole 15. A webbing is wound around and joined to the lower member 33 of the shaft bar 30.

In FIG. 4, when tension is applied to the webbing, the base plate 10 is fixed to the vehicle body.
The shaft bar 30 is attached to both longitudinal roots 1 of the base plate 10.
Rotating shaft member 3 fitted in engagement notch 14 formed in 3
4 around the counterclockwise direction in the figure, whereby the arm spring 40 is deformed and its contact portion 43
Presses the point pin 24 of the sensor plate 21. This pressing force also deforms the sensor plate 21,
An output corresponding to the tension is generated from the strain gauge affixed thereto. Therefore, by measuring this output, the seat belt tension can be measured.

[0014] However, such a seat belt tension measuring device has the following problems. That is, such a seat belt tension measuring device needs to be made as small as possible because of its attachment to the vehicle body. However, since the arm spring 40 is screwed above the shaft bar 30, there is a problem that the thickness is increased by the arm spring 40 and the tapping screws 35, 36, 37.

When casting the shaft bar 30,
Since the mold is divided into two parts in the direction of decreasing the thickness, just the upper surface in FIG. 3, that is, the holes 30a to 30c
Is formed as a mating surface of both molds, and a hole cannot be formed in this portion by die casting. Therefore, the holes 30a to 30c have to be formed by machining after die casting, and there is a problem that the number of steps for that purpose increases.

Further, since the free end of the arm spring has a curved surface, there is a problem that bending is required, and the transmission of force to the sensor plate is not stable, and hysteresis occurs.

The present invention has been made in view of such circumstances, and provides a seat belt tension measuring device which is easy to manufacture, can be miniaturized, and can accurately detect tension. Make it an issue.

[0018]

A first means for solving the above-mentioned problem is a seat belt tension measuring device installed on an anchor portion for fixing an end of a seat belt to a vehicle body, which is connected to the vehicle body. An anchor connecting member, a webbing connecting member connected to the seat belt, and a sensor mechanism for detecting a force applied between these two members,
The sensor mechanism has a shaft bar that rotates by a relative movement of the two members generated by a force applied between the two members, and an arm spring that rotates together with the shaft bar is attached to the shaft bar. The arm spring is configured to apply a pressing force to the sensor plate to which the strain gauge is attached while deforming with the rotation of the shaft bar, and the shaft bar is formed by die casting and divided. 2. A seat belt tension measuring device according to claim 1, wherein said arm spring is fixed to said shaft bar by screwing a tapping screw into said hole. ).

In this means, since the holes of the arm springs provided for fixing the arm springs by tapping screws are formed in portions which do not become joints of the divided molds, these holes are formed by the die. It can be formed by casting. Therefore, the step of forming a hole by machining, which was conventionally required, can be omitted.

A second means for solving the above-mentioned problem is as follows.
The first means, wherein the arm spring is divided into a fixing portion fixed to the shaft bar and another free end portion, the free end portion is flat, and the fixing portion is bent from the free end portion. And being fixed to the shaft bar (claim 2).

In this means, since the free end is flat, the bending of the arm spring is not required, and the force is smoothly transmitted to the sensor plate, thereby preventing the occurrence of hysteresis. can do.

The phrase "bent and fixed to the shaft bar" specifies the shape, but does not mean that it is bent at the time of mounting in the actual manufacturing process.

A third means for solving the above-mentioned problem is:
The second means, wherein the shaft bar is formed of a substantially square-shaped member, and the arm spring has a free end along the inner side of the square-shaped portion of the shaft bar, and the thickness of the shaft bar. The present invention is characterized in that it is bent from one side to the other side in the direction and is bent there, so that the fixing portion is fixed to the side surface of the square-shaped portion of the shaft bar (Claim 3).

In this means, since the free end of the arm spring is provided along the inside of the square shape of the shaft bar, the height at which the arm spring is located can be reduced accordingly. Therefore, the height at which the sensor plate is located can be reduced, and the thickness of the sensor base can be reduced accordingly, so that the weight can be reduced and the price can be reduced. Further, since the portion for fixing the arm spring is on the opposite side to the direction in which the free end of the arm spring extends, the fixing operation with the tapping screw is easy.

It should be noted that the term "bent" specifies a shape and does not mean that it is actually bent at the time of mounting in a manufacturing process.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of a seat belt tension measuring device according to an embodiment of the present invention,
FIG. 2 is an assembled perspective view.

The principle of tension measurement in this embodiment is the same as that of the conventional tension measuring device shown in FIGS. 3 and 4, and its basic configuration is the same. The same components as those shown are denoted by the same reference numerals. However, since improvements and design changes have been made in addition to the present invention, the shapes and numbers of the respective components are slightly different from those in FIGS.

This seat belt tension measuring device is roughly divided into a base plate 10, a sensor base comprising a sensor base 20, a sensor plate 21, a shaft bar 30, and an arm spring 40;
0 ".

The base plate 10 is a portion (anchor connecting member) fixed to the vehicle body, and is made of a steel plate (S
PFH). A connecting portion 11 is formed at the tip of the base plate 10, and a hole 12 is formed at the center thereof. Anchor bolts (not shown) for fixing the connecting portion 11 to the body structure are pushed through the holes 12. The outer peripheral edge of the connecting portion 11 is formed in a semicircular shape. On both widthwise sides of the other end of the base plate 10,
The upright vertical root portion 13 is formed. Both vertical roots 1
A substantially semicircular engagement notch 14 is formed in the upper edge of 3. A hole 15 is formed in the middle between both vertical roots 13. An intermediate portion 16 for attaching the sensor mechanism is provided between the connecting portion 11 and the portion where the vertical root portions 13 are formed.
Are provided, and holes for inserting bolts and screws are formed.

The sensor base 20 is made of an aluminum die-cast alloy or the like, and is a substantially U-shaped member. A sensor plate 21 is attached to the sensor base 20, and bolts 22 and 23 are inserted into holes of the sensor plate 21 so as to be fixed to the base plate 10. The bolts 22 and 23 also pass through holes in the sensor plate 21, thereby fixing the sensor plate 21 made of a thin stainless steel plate or the like to the sensor base 20.

Four strain gauges are attached to the sensor plate 21, and an ASIC (Application Speci? Er) for converting the detected value of the strain gauge into an electric signal.
ficIntegrated Circuit) is attached. Further, a point pin 24 is attached to the sensor plate 21.

The shaft bar 30 forms a part of the sensor mechanism and constitutes a webbing connecting member connected to the webbing. This is a substantially square-shaped member formed of, for example, a zinc die-cast alloy.
1, a side member 32 and a lower member 33 are integrally formed. Further, on both sides of the upper member 31, a cylindrical rotating shaft member 3 is provided.
4 are also integrally formed. On the right side surface of the upper member 31 in FIG. 1, two holes 30a and 30b are formed, and positioning projections 30d and 30e are provided.

The arm spring 40 is a spring plate made of a thin stainless steel plate or the like, and has a fixed portion 41 and an extending portion 42. The distal end of the extension part 42 is a contact part 43. The extending portion 42 has a planar shape and forms an angle of 90 ° with the fixing portion 41. The fixing part 41 has four holes. The extension portion 42 contacts the shaft bar 31 along the upper inside surface (lower surface of the upper member 31) of the square shape of the shaft bar 31 from the left side in FIG. Of the two holes, the center two
A positioning projection 30d provided on the shaft bar 30;
By fitting into 30e, the positional relationship with shaft bar 30 is determined.

Then, tapping screws 35 and 36 are
The arm spring 40 is fixed to the shaft bar 30 by screwing into the holes 30a, 30b of the shaft bar 30 through the two outer holes 40a, 40b provided in the fixing portion 41 of the arm spring 40. Then, the shaft bar 30 and the arm spring 40 are rotatably supported by the vertical root portion 13 of the base plate 10 by engaging the rotary member 34 of the shaft bar 30 with the engagement notch 14 of the vertical root portion 13. become. In this state, the contact portion 43, which is the tip of the extension portion 42 extending in a planar shape, comes into contact with the tip of the point pin 24 of the sensor plate 21.

The cover is divided into two parts, and the upper cover 5
By fixing the 0 'and the lower cover 50 "with the screws 51, 52, 53, the main part contributing to the tension measurement is accommodated therein.

In the assembled state shown in FIG. 2, the rotating shaft member 34 of the shaft bar 30 is fitted into the engagement cuts 14 formed in both the vertical roots 13 of the base plate 10 and is supported rotatably. Then, the lower member 33 of the shaft bar 30 is fitted into the hole 15 of the base plate 10, and can be rotated within the range of the hole 15. A webbing is wound around and joined to the lower member 33 of the shaft bar 30.

In FIG. 4, when tension is applied to the webbing, the base plate 10 is fixed to the vehicle body.
The shaft bar 30 is attached to both longitudinal roots 1 of the base plate 10.
Rotating shaft member 3 fitted in engagement notch 14 formed in 3
4, the arm spring 40 is deformed, and the contact 43 presses the point pin 24 of the sensor plate 21.
This pressing force also deforms the sensor plate 21, and an output corresponding to the tension is generated from the strain gauge attached to the sensor plate. Therefore, by measuring this output, the seat belt tension can be measured.

As can be seen from a comparison between FIG. 1 and FIG. 3, in the conventional sensor mechanism, the shaft bar 3 is provided.
Arm spring 40 has a tapping screw 3
5, 36, 37, the shaft bar 30 according to the embodiment of the present invention.
Is fixed on the side surface (the side surface in the thickness direction) of the device by tapping screws 35 and 36.

Although various shapes of the shaft bar 30 are conceivable, all are in the vertical and horizontal directions (in this case, the vertical and horizontal directions of the square).
The dimensions are large and the dimensions are small in the thickness direction perpendicular to them. Therefore, when a member having such a shape is formed by die casting, the mold is split into two pieces in the thickness direction having a small dimension, and the two pieces are laminated and then cast. Therefore, it is difficult to form a hole by die-casting on the upper surface of the shaft bar 30 which is in the bonding direction of the mold. In the conventional product shown in FIG.
-30c were manufactured by machining.

On the other hand, in the embodiment of the present invention shown in FIG. 1, the portions where the holes 30a and 30b are formed are:
Since it is not in the direction in which the molds are bonded, it is easy to form holes by die casting. Therefore, since it is not necessary to manufacture a hole by machining, a machining step conventionally required can be omitted.

A second difference that can be seen by comparing FIGS. 1 and 3 is that, in the conventional sensor mechanism, the extending portion 42, which is the free end of the arm spring 40, has a curved surface and is Figure 1
In the embodiment of the present invention shown in FIG.
The extended portion 42, which is a free end portion, has a planar shape and is in contact with the point pin 24. This allows
The transmission of the force from the shaft bar 30 to the sensor plate 21 via the arm spring 40 becomes smooth, the hysteresis is reduced, and the accuracy of the tension measurement is improved.

The extension 4 of the arm spring 40
2 extends from the left side (one side in the thickness direction of the shaft bar) of FIG. 1 to the right side (the other side) along the lower surface side of the upper member 31 of the shaft bar 30, that is, along the inside of the square portion. It is bent so that the fixing portion 41 is fixed to the side surface of the upper member 31 (the side surface of the square-shaped portion of the shaft bar). This is the third difference.

As a result, the position at which the arm spring 40 is attached is lower than that of the conventional sensor mechanism. Therefore, even if the free end of the arm spring 40 is flat, the position of the sensor plate 21 needs to be increased. This eliminates the need to increase the thickness of the base plate 20.

In the embodiment shown in FIG. 1, the arm spring 40 is turned from one side in the thickness direction of the shaft bar 30 to the other side, and is bent and fixed there. Instead, the fixing portion 41 may be fixed to the side surface opposite to the upper member 31 in FIG. However, the fixing method shown in FIG. 1 can easily perform the screwing step.

The embodiment shown in FIG. 1 corresponds to claim 3 and has the functions and effects of all the claims of the present invention, but the functions and effects of each claim are independent. Only the configuration can be applied as appropriate. For example, if only the method of attaching the arm spring 40 to the shaft bar 30 is as shown in FIG. 1 and the shape of the arm spring 40 is as shown in FIG. 3, a certain effect can be obtained.

In FIG. 1, the arm spring 40 is fixed to the side surface of the upper member 31 through the lower side of the upper member 31. However, the arm spring 40 is fixed to the side surface of the upper member 31 through the upper side of the upper member 31. However, a certain effect can be obtained.

[0047]

As described above, according to the present invention, it is possible to obtain a seat belt tension measuring device which is easy to manufacture, can be miniaturized, and can accurately detect the tension.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a seat belt tension measuring device according to an embodiment of the present invention.

FIG. 2 is an assembled perspective view of the seat belt tension measuring device shown in FIG.

FIG. 3 is an exploded perspective view of a conventional seat belt tension measuring device.

4 is an assembled perspective view of the seat belt tension measuring device shown in FIG.

[Explanation of symbols]

10: base plate, 10a to 10e: screw holes, 11
... connecting part, 12 ... hole, 13 ... vertical root part, 14 ... engagement notch,
15 ... hole, 16 ... middle part, 20 ... sensor base, 20
a: hole, 21: sensor plate, 21b: hole, 22,
23: Screw (bolt), 24: Point pin, 30: Shaft bar, 30a, 30b, 30c: Hole, 30d, 3
0e: Projection, 31: Upper member, 32: Side member, 33 ...
Lower member, 34: rotating shaft member, 35, 36, 37: tapping screw, 40: arm spring, 40a, 40
b, 40c: hole, 41: fixing part, 42: extension part, 43 ...
Contact part, 50, 50 ', 50 "... cover, 50a, 50
b, 50c ... holes, 51, 52, 53 ... screws,

Claims (3)

[Claims] 1. A seat belt tension measuring device installed on an anchor portion for fixing an end of a seat belt to a vehicle body, comprising: an anchor connecting member connected to the vehicle body; a webbing connecting member connected to the seat belt; A sensor mechanism for detecting a force applied between the two members, the sensor mechanism including a shaft bar that is rotated by a relative movement of the two members generated by the force applied between the two members. An arm spring that rotates with the shaft bar is attached to the shaft bar. The arm spring deforms with the rotation of the shaft bar and applies a pressing force to the sensor plate on which the strain gauge is attached. The shaft bar is formed by die-casting, and a portion that does not become a joint of the divided molds is formed. The arm spring, by screwing a tapping screw into the hole,
A seat belt tension measuring device fixed to the shaft bar. 2. The seat belt tension measuring device according to claim 1, wherein the arm spring is divided into a fixing portion fixed to the shaft bar and another free end, and the free end is a flat surface. Wherein the fixing part is bent from a free end and fixed to the shaft bar. 3. The seat belt tension measuring device according to claim 2, wherein the shaft bar is formed of a substantially square-shaped member, and the arm spring has a free end corresponding to the square-shaped portion of the shaft bar. Along the inside, from one side in the thickness direction of the shaft bar to the other side, where it is bent,
A seat belt tension measuring device, wherein a fixing portion is fixed to a side surface of the square portion of the shaft bar.