Technical Field

The present invention relates to a sensor bracket to be assembled to an airbag ECU (electronic control unit) for carrying an external sensor in a vehicle crash test.

Background Art

Airbags of a vehicle are equipped with an ECU which is generally located on the middle tunnel of a vehicle for acquiring acceleration signals by means of an internal acceleration sensor when the vehicle is running, and triggering the airbag when necessary. Typical airbag ECUs generally have metal housings.

Currently, low price vehicles have an increasing market share. Airbag ECUs with plastic housings become popular in low price vehicles.

During the development of vehicle restraint system, it needs to mount an external reference sensor to the housing of the airbag ECU with the main purpose of getting the same signal behavior with an internal sensor. Acceleration signals acquired by the internal and external sensors are used in ECU calibration, such as signal analysis, parameter setting and the like.

The more similarity between the signals of the external sensor and the internal sensor, the better precision of the ECU calibration can be achieved. To ensure calibration performance, qualified crash signals are needed.

For an ECU with a metal housing, the external sensor can be attached to the metal housing directly be adhesion. However, for a low price airbag ECU with a plastic housing, since signal transmitting abilities of plastic materials are low, a metal bracket is needed to carry the external sensor to obtain high quality crash signals.

Figure 1 shows a top view of an airbag ECU. An upper housing part 1 of the airbag ECU is formed with concave mounting portions 2 on right-left or laterally opposite sides. The concave mounting portions 2 are recessed downwards from the top surface of the upper housing part. Each concave mounting portions 2 defines a through hole 3 therein. Figure 2 shows an existing sensor bracket 100, which is in the form of an integral metal piece and comprises a horizontal bridge 112, a tab 114 extending forwards from the middle portion of the bridge, vertical side walls 116 extending downwards and backwards from right and left ends of the bridge, a vertical front wall 118 extending laterally outwards from the front edge of each side wall, a horizontal bottom wall 120 extending laterally outwards from a lower edge of each side wall, and a horizontal mounting seat 122 extending laterally inwards from the lower edge of each side wall. The front wall 118 and the bottom wall 120 at each end define a sensor accommodating portion in which an external sensor 130 can be mounted onto and supported by the bottom wall 120. A through hole 124 is formed through each mounting seat 122. One or more reinforcing ribs 132 are provided between the side wall 116 and the mounting seat 122.

The sensor bracket 100 is mounted to the airbag ECU in a manner shown in Figure 3. That is, the two mounting seats 122 of the sensor bracket 100 are arranged in the opposite concave mounting portions 2 of the upper housing part 1 of the airbag ECU respectively, with the through holes 124 in the mounting seats 122 being aligned with the through holes 3 in the concave mounting portions 2 respectively. Then, the airbag ECU which carries the sensor bracket 100 is mounted on the vehicle middle tunnel by screws passing through the through hole 124, the through hole 3 and corresponding through holes in the lower housing part of the airbag ECU.

It has been found in crash tests that the sensor bracket of prior art has some problems related with data acquisition, such as oscillation and abnormal amplitude of signals of the external reference sensor, which negatively affect calibration precision of the airbag ECU.

Thus, it is desired to make improvements to the sensor bracket to overcome these defects.

Summary of the Invention An object of the invention is to provide an improved sensor bracket for carrying an external sensor on an airbag ECU in a vehicle crash test, by means of which the problems in prior art, such as oscillation and abnormal amplitude of signals of the external reference sensor, can be alleviated or eliminated.

For this end, the invention discloses a sensor bracket for an airbag ECU, the airbag ECU comprising a lower housing part, a circuit board supported by the lower housing part and an upper housing part assembled to the lower housing part, the upper housing part being provided on its laterally opposite sides with concave mounting portions which are recessed downwards from the top surface of the upper housing part, and a through hole being formed in each of the concave mounting portions, wherein the sensor bracket comprises a horizontal bridge, two side walls, which are parallel with each other, extending vertically downwards from laterally opposite ends of the bridge respectively, and a mounting seat extending horizontally inwards from an inner surface of each side wall above a lower edge of the side wall, each mounting seat being formed with a through hole which is adapted to be aligned with the through hole in a corresponding one of the concave mounting portions of the upper housing part.

According to a preferred embodiment of the invention, the bridge is offset with respect to the through holes in the mounting seats in a front-back direction.

According to a preferred embodiment of the invention, a distance between the bottom surface of the bridge and the top surfaces of the mounting seats in a vertical direction is equal to or larger than a distance between the top surface of the upper housing part and the top surfaces of the concave mounting portions in the vertical direction.

According to a preferred embodiment of the invention, a distance between the inner surfaces of the two side walls is equal to or larger than the lateral width of the upper housing part.

According to a preferred embodiment of the invention, the sensor bracket further comprises one or more reinforcing ribs formed between each side wall and a corresponding one of the mounting seats. According to a preferred embodiment of the invention, the one or more reinforcing ribs extend to an upper edge of the side wall from the top surface of the mounting seat.

According to a preferred embodiment of the invention, a portion of each side wall below the bottom surface of the corresponding mounting seat forms an external-sensor carrying segment.

According to a preferred embodiment of the invention, each side wall has fronted and back edges flush with that of the mounting seat.

According to a preferred embodiment of the invention, the sensor bracket is made of stainless steel. Alternatively, the sensor bracket may also be made of aluminum alloy or other metal materials.

According to a preferred embodiment of the invention, the upper and lower housing parts of the airbag ECU are made of plastics. However, the sensor bracket of the invention is also applicable in airbag ECUs having upper and lower housing parts made of metal.

The sensor bracket of the invention has a significantly decreased weight and a substantively increased strength. By using an external reference sensor attached to the sensor bracket of the invention in a vehicle crash test, oscillation of signals of the external sensor can be suppressed, and precise signals of the external reference sensor can be acquired, thus ECU calibration accuracy can be increased.

Further, sensor accommodating portions protruded outwards in the prior art are omitted from the sensor bracket of the invention, thus the overall lateral dimension is reduced, and the flexibility of mounting the sensor bracket together with the ECU and the external sensor on the vehicle tunnel is increased.

Furthermore, by attaching the external sensor to a segment of the side wall below the bottom surface of the mounting seat, the mounting location of the external sensor becomes closer to the internal sensor in both vertical and horizontal directions, thus the external and internal sensors can provide signals with increased similarities, which results in significantly increased precision that can be obtained in ECU calibration. Brief Description of the Drawings Figure 1 is a top view of an airbag ECU.

Figure 2 is a perspective view of a sensor bracket for airbag ECU according to prior art.

Figure 3 is a top view showing the sensor bracket shown in Figure 2 being mounted to the airbag ECU shown in Figure 1.

Figure 4 is a perspective view of a sensor bracket for airbag ECU according to the invention.

Figures 5-7 are front, top and right side views of the sensor bracket shown in Figure 4 respectively.

Figures 8 and 9 are top views showing the sensor bracket shown in Figure 4 being mounted to the airbag ECU shown in Figure 1 in two orientations.

Detailed Description of Preferred Embodiments

Now some preferred embodiments of the sensor bracket of the invention will be described with reference to the drawings.

Figures 4-7 show in perspective, front, top and right side views respectively structural details of a sensor bracket 10 of the invention which is configured for carrying an external sensor 30 on an airbag ECU in a vehicle crash test.

The sensor bracket 10 is formed as an integral metal piece, comprising a horizontal bridge 12, vertical side walls 16 extending downwards and backwards from opposite ends in a right-left direction (lateral direction) of the bridge, and a horizontal mounting seat 22 extending from an inner surface of each side wall laterally inwards at a vertical distance above an lower edge of the side wall. The shapes and locations of the two mounting seats 22 are designed to be located in opposite concave mounting portions 2 of the upper housing part 1 of the airbag ECU shown in Figure 1, and each mounting seat 22 is formed with a through hole 24 to be aligned with the through hole 3 in a corresponding one of the concave mounting portions 2. One or more reinforcing ribs 32 are provided between each side wall 16 and the correlated mounting seat 22.

Compared with the sensor bracket 100 of prior art as shown in Figure 2, the front walls 118 and the bottom walls 120, for defining sensor accommodating portions, are omitted from the sensor bracket 10 of the invention. In order to attach an external sensor 30 to the sensor bracket, according to an embodiment of the invention, side walls 16 extend downwards more than the side walls 116 of prior art. Specifically, in the prior art, the lower edge of each side wall 116 is located at the level of the bottom surface of the mounting seat 122 (the bottom surface of the bottom wall 120 is coplanar with the bottom surface of the mounting seat 122). However, in the invention, the lower edge of each side wall 16 is located at a distance below the bottom surface of the mounting seat 22, thereby forming a side wall segment below the bottom surface of the mounting seat 22. The external sensor 30 can be attached to the outer surface of the side wall segment by direct adhesion or by other means. In this way, the segment of the side wall 16 below the bottom surface of the mounting seat 22 forms an external-sensor carrying segment.

The segment of the side wall 16 below the bottom surface of the mounting seat 22 can be seen clearly from Figure 5, by means of which segment, the overall height HI of the side wall 16 in a vertical direction is larger than the overall height of the side wall 116 of the sensor bracket 100 of prior art in the vertical direction.

By omitting the sensor accommodating portions of the sensor bracket of prior art, the sensor bracket of the invention has a significantly decreased weight and a substantively increased strength, thereby obtaining a more stable structure in crash, which contributes suppressing oscillation of sensor signals.

In addition, by omitting the sensor accommodating portions of the sensor bracket of prior art which protrude outwards, the sensor bracket of the invention has a reduced overall lateral size, which facilitates mounting the sensor bracket together with the ECU and the external sensor on the vehicle tunnel in a more flexible manner.

By disposing the external sensor to the side wall segment which is below the bottom surface of the mounting seat, the mounting location of the external sensor is closer to an internal sensor of the airbag ECU in both vertical and horizontal directions. The internal sensor is disposed on a PCB (printed circuit board) supported by the lower housing part of the airbag ECU.

When the external sensor and the internal sensor are proximal to each other, similarity between the signals of them is increased, and thus the precision that can be obtained in ECU calibration is significantly increased.

As compared with the sensor bracket 100 of prior art shown in Figure 2, the sensor bracket 10 of the invention also comprises an improvement to the configuration of the reinforcing ribs. Specifically, in the sensor bracket 100 of prior art shown in Figure 2, each reinforcing rib 132 between the side wall 116 and the mounting seat 122 only extends through a small distance above the intersecting line of the side wall 116 and the mounting seat 122, so that the free edge of the reinforcing rib 132 forms an angle of about 45° with the top surface of the mounting seat 122. On the contrary, in the invention, each reinforcing rib 32 between the side wall 16 and the mounting seat 22 extends through an increased distance above the intersecting line of the side wall 16 and the mounting seat 22, and may even up to the upper edge of the side wall 16 in the embodiment shown in Figure 5. The rigidity of the sensor bracket can be increased by optimal design of the reinforcing ribs.

The sensor bracket 10 of the invention can be mounted to the airbag ECU in two orientations shown in Figures 8 and 9. In either orientation, the two mounting seats 22 of the sensor bracket 10 can be arranged in the opposite concave mounting portions 2 of the upper housing part 1 of the airbag ECU respectively, with the through hole 24 in each mounting seat 22 being aligned with the through hole 3 in the corresponding concave mounting portion 2. Then, the airbag ECU which carries the sensor bracket 10 is mounted on the vehicle middle tunnel by screws passing through the through holes 24, the through holes 3 and corresponding through holes formed in the lower housing part of the airbag ECU.

The sensor bracket 100 of prior art shown in Figure 2 can be mounted to the airbag ECU only in one orientation as shown in Figure 3. According to the invention, the sensor bracket 10 can be mounted to the airbag ECU in either of two orientations, which is particularly advantage when there is a limited available space surrounding the mounting position of the ECU.

The side wall 16 may have front and back edges flush with that of the mounting seat 22 respectively, so that they have the same width W2 in a front-back direction (see Figure 7).

It can be seen from Figures 6 and 7 that the side wall 16 and the mounting seat 22 are located at a distance backwards from the bridge 12, so that the through holes 24 in the mounting seats 22 are farther away from the bridge 12, which facilitates the screwing and unscrewing of the screws passing through the through holes 24 by a screw driver, or in other words, an enlarged operation space is provided for the screw driver.

In addition, the sensor bracket 100 of prior art shown in Figure 2 is generally made of aluminum alloy, while the sensor bracket 10 of the invention may be made of stainless steel (of course, may also be made of aluminum alloy).

In the case that the sensor bracket 10 is made of stainless steel, the thicknesses Tl and T2 (see Figure 5) of the bridge 12 and the mounting seat 22 in the vertical direction as well as the width Wl (see Figure 6) of the bridge 12 in the front-back direction can be reduced with respect to that of the sensor bracket 100 of prior art. For the sake of these changes in the shapes and dimensions, as well as omitting sensor accommodating portions as described above, the sensor bracket will have a substantively decreased total weight. Meanwhile, the whole sensor bracket may have sufficient tensile strength and yielding strength by optimal design of the reinforcing ribs 32.

The distance between the bridge 12 and the mounting seat 22 in the vertical direction is selected in a way that, in a state that the sensor bracket 10 is mounted to the airbag ECU in either of the orientations shown in Figures 8 and 9 and the mounting seats 22 rest on the concave mounting portions 2 of upper housing part 1 of the airbag ECU, the bottom surface of the bridge 12 just abuts against the top surface of the upper housing part 1 or leaves a small gap therebetween.

A distance between the inner surfaces of the right and left side walls 16 is equal to or larger than the width of the upper housing part 1 in the right-left (lateral) direction.

Some concrete data for comparing structural details of the sensor bracket 100 of prior art shown in Figure 2 and the sensor bracket 10 according to the invention are listed in the table below.

The airbag ECU which carries the sensor bracket of the invention is mounted on the vehicle middle tunnel by two screws. An external sensor is glued to one or each of the external surfaces of the side walls of the sensor bracket. The external sensor and the internal sensor are connected to corresponding data recorders for recording acceleration signal data.

In a crash test, the vehicle runs at a certain speed and impacts an obstacle barrier in the front. The data recorders immediately record sensor signals from both the external sensor and the internal sensor. With the support of the sensor bracket, the acceleration signal from the chassis can be transmitted through the middle tunnel to the sensor bracket fastened by screws, and then acquired by the external sensor on the bracket. The signals from the external and internal sensors are output for ECU calibration.

For checking the effect of the invention, inventors have conducted imitation crash tests and real crash tests through the procedure described above with airbag ECUs having plastic housings and sensor brackets of the invention. Results of both types of crash tests show that, when the sensor bracket of the invention is adopted, no or little oscillation exists in the measured signals of the external sensor, and abnormal signal amplitudes are depressed also, so the final external sensor signals are much similar to the internal sensor signals. This means that precise external sensor signals can be obtained when the sensor bracket of the invention is used, and there is no substantive affect to the ECU internal sensor signals. Thus, the quality of the sensor signals used in ECU calibration can be increased significantly, and the performance of the whole restraint system can be improved.

The sensor bracket of the invention is not only applicable in airbag ECUs having plastic housings, but also applicable in expensive airbag ECUs having metal housings.

The sensor brackets of the invention can be widely used in development of vehicle restraint systems, especially used with airbag ECUs having plastic housings. By means of the bracket of the invention, better performance of data acquisition during crash tests can be provided, which contributes to increasing of calibration precision in real practice. As low price vehicles have an increasing market prospect, airbag ECUs having plastic housings may be widely adopted in the future, thus it is expected that there will be increasing need to the sensor brackets of the invention in development of vehicle restraint systems.