JPH0720142A - Deceleration sensor - Google Patents

Abstract

PURPOSE:To provide a deceleration sensor for detecting the deceleration based on the movement of a mover sliding in a housing in which bouncing of the mover at the stroke can be prevented through a simple structure upon application of a high deceleration. CONSTITUTION:A mover 4 is housed slidingly in the housings 2, 3. A stopper 5 regulates the displacement stroke of the mover 4. Springs 9, 10 are arranged on the opposite sides of the mover 4 in order to urge the mover 4 toward the stopper 5 with a predetermined combined force. A fluid channel 11 becoming shallower toward the left side is made in the inner wall of the housing 2 while conducting the spaces on the opposite sides of the mover 4. When the mover 4 moves close to the left stroke end, the fluid resistance of the channel 11 increases to lower the displacement speed of the mover 4 and thereby the conductive plate 8 does not bounce on the electrodes 6, 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deceleration sensor, and more particularly to a deceleration sensor for detecting deceleration based on the movement of a mover sliding inside a housing.

[0002]

2. Description of the Related Art A movable element which can slide within a housing for a predetermined stroke is provided in the housing, and the movable element is biased toward one stroke end by a spring or the like, so that a steady state is achieved. Then, the mover does not show displacement. On the other hand, when the deceleration acts in the direction in which the mover presses the spring, the mover is displaced in the housing according to the magnitude of the deceleration.

Therefore, if the displacement of the mover is detected,
It is possible to estimate the magnitude of the deceleration that has occurred,
A deceleration sensor utilizing such a principle has been conventionally known. In addition, as a mechanism for detecting the displacement of the mover in such a deceleration sensor, a contact switch is generally turned on when the mover is displaced to the stroke end against the urging force of a spring or the like. Is.

By the way, in the deceleration sensor having the above-mentioned structure,
When a deceleration exceeding a preset threshold is applied to the deceleration sensor, it is required that the contact switch be turned on promptly and surely. Therefore, in the design, it is necessary to set the urging force of the spring and the like and the mass of the mover to an appropriate level according to the threshold value of deceleration to be detected.

However, there is a problem in simply adapting the operating region of the mover to the deceleration threshold to be detected. This is because when a deceleration that greatly exceeds the threshold value is applied, the mover that reaches the stroke end bounces, which may result in insufficient on-time of the contact-type switch.

Japanese Patent Laid-Open No. 62-198764 discloses a deceleration sensor which pays attention to such a point and disposes a cushion material near the stroke end of the mover to prevent the mover from rebounding at the stroke end. ing. According to this structure, the mover sensitively reacts to deceleration near the threshold value and does not bounce even when the deceleration greatly exceeds the threshold value. Will be realized.

[0007]

However, the above-mentioned conventional deceleration sensor adds a cushioning material in addition to the components necessary for the basic structure, and therefore the raw material cost and the processing man-hour are increased due to the increase in the number of components. It is accompanied by an increase in cost. Therefore, although the function of the deceleration sensor is improved, the profitability is decreased or the selling price is increased.

The present invention has been made in view of the above points, and a passage whose effective passage area changes according to the displacement of the mover is provided on the inner wall of the housing which is a basic component.
An object of the present invention is to provide a deceleration sensor that can solve the above problems by ensuring a large displacement resistance of the mover near the stroke end.

[0009]

The above object is to provide a deceleration sensor for detecting deceleration by detecting the movement of a mover arranged slidably within a housing with a predetermined stroke width. This is achieved by a deceleration sensor including an inner wall of the housing, a fluid passage communicating with spaces on both sides of the mover and narrowing an effective passage area as the mover approaches at least one stroke end.

[0010]

In the deceleration sensor according to the present invention, the fluid passage functions as a passage for the fluid existing in the space on both sides of the mover when the mover is displaced in the housing. That is, the displacement of the mover is accompanied by the circulation of the fluid in the fluid passage. Therefore, when the flow resistance of the fluid passage changes, the displacement resistance of the mover also changes.

Since the fluid passage narrows its effective passage area as the mover approaches the stroke end, the flow resistance of the fluid increases and a large displacement resistance of the mover is secured near the stroke end. become. Further, the fluid passage is provided in the housing, which is a basic component of the deceleration sensor, and the number of components does not increase.

[0012]

1 is a side sectional view showing the structure of a deceleration sensor 1 according to an embodiment of the present invention. In the figure, reference numerals 2 and 3 denote housings of the deceleration sensor 1, which are members to be fitted to each other in a state where functional components described later are housed therein.

The mover 4 housed inside the housings 2 and 3 is arranged inside the housing 2 with the guide shaft 5 inserted in the center, and the outer peripheral surface thereof is the inner peripheral surface of the housing 2. It can be displaced along the guide shaft 5 while sliding. Then, the displacement stroke is the moving element 4
It is regulated by a stopper 5 provided on the outer circumference of the small diameter portion 4a.

That is, the stroke end of the mover 4 in the right direction in the figure is the position where the large diameter portion 4b of the mover 4 contacts the left surface of the stopper 5. On the other hand, a conductive plate 8 capable of abutting equally to a pair of electrodes 6 and 7 arranged on the right surface of the stopper 5 is fixed to the small-diameter portion 4a of the mover 4. Therefore,
The left stroke end of the mover 4 is the position where the conductive plate 8 contacts the electrodes 6 and 7. At this time, the electrodes 6 and 7 are
The conductive plate 8 is electrically connected.

Further, the movable element 4 is biased by springs 9 and 10 arranged on both sides thereof.
That is, the mover 4 is moved to the right side in the drawing by the spring 9,
Further, it is biased to the left side in the figure by the spring 10.
In the deceleration sensor 1 of the present embodiment, the biasing force of the spring 9 is set to exceed the biasing force of the spring 10, so that the biasing force in the right direction in FIG. In the steady state, the large diameter portion 4b is in contact with the stopper 5.

When a negative acceleration is generated in the deceleration sensor 1 leftward in the figure, that is, when the deceleration is generated from the state where the deceleration sensor 1 is moving leftward at a predetermined speed, the inertia is caused by inertia. The mover 4 is displaced in the direction in which the spring 9 contracts, and the deceleration of the mover 4 causes the springs 9 and 10 to move.
If the set threshold is exceeded due to the characteristics of
As described above, the conductive plate 8 comes into contact with the electrodes 6 and 7.

Therefore, when the electric resistance between the electrodes 6 and 7 is monitored, if the resistance value is significantly decreased, it is assumed that the conductive plate 8 makes the electrodes 6 and 7 conductive, and the deceleration exceeding the threshold value. It is possible to detect that it is occurring.

By the way, the deceleration sensor 1 of this embodiment is
It is characterized in that a fluid passage 11 is provided on the inner wall of the housing 2. As shown in FIG. 1, the fluid passage 11 is formed by a groove that communicates the space on the left and right of the mover 4 with the outer circumference of the mover 4. Therefore, when the mover 4 is displaced in the housing 2, the fluid such as air or liquid existing in the housings 2 and 3 is appropriately flowed through the fluid passage 11
Will be distributed.

Here, the fluid passage 11 of the deceleration sensor 1
Are provided such that the groove becomes shallower toward the left in the figure.
Therefore, the effective passage area of the fluid passage 11 is maximized when the mover 4 is located at the right stroke end as shown in FIG. 1, and the mover 4 moves from the state shown in the drawing toward the left stroke end. It will change slightly as you move.

Hereinafter, the effect of providing the fluid passage 11 will be described in detail with reference to the characteristic diagram of the deceleration sensor 1 shown in FIG. 2. Prior to that, the characteristics required of the deceleration sensor 1 will be described. Will be explained.

FIG. 3 is a perspective perspective view showing the entire structure of an airbag system for detecting a collision of the vehicle 20 by using the deceleration sensor 1 of this embodiment as a safing sensor 25 described later.

The airbag system shown in FIG.
A front air bag sensor 21 arranged at the left and right front corners of the vehicle 20 to detect the impact generated on the vehicle 0;
A wheel pad 23, which is located in the center of the steering wheel 22 and has a bag 23a and an inflator 23b that is a mechanism for inflating the bag, and a center airbag sensor 24, which is a semiconductor deceleration sensor, are provided inside. An electronic device that is built-in and determines the operation of the bag 23a by considering the state of the center airbag sensor 24, the state of the safing sensor 25 that reacts to a relatively low deceleration, and the state of the front airbag sensor 21 together. This is a configuration including the control device 26.

The front airbag sensor 21 is a deceleration sensor that is turned on when a strong deceleration of, for example, about 10 G occurs, and detects a sudden deceleration that occurs when the vehicle 20 has a frontal collision. It is provided for the purpose. Further, the center airbag sensor 24 provided in the electronic control unit 26 accumulates the magnitude of the deceleration when the deceleration exceeding the predetermined level occurs in the vehicle 20, and when the accumulated value reaches the predetermined value. It is a sensor that turns on. Then, the safing sensor 25 realized by the deceleration sensor 1 of the present embodiment is a sensor which is turned on at a relatively low deceleration (about 2 G) as described above.

FIG. 4 is a diagram showing an operation process of the airbag system having such a configuration. The operation will be briefly described below with reference to FIG.

As shown in FIG. 4 (A), the air bag system is designed to inflate the bag when the vehicle 20 collides from the front and to alleviate the impact when the driver is thrown forward. is there. Therefore, in the airbag system, when a collision occurs in the vehicle 20, it is necessary to accurately detect the collision.

Here, when the vehicle 20 has a violent collision to the extent that it is necessary to operate the airbag, as shown in FIG.
As shown in (B), a large shock that is not normally generated, that is, a significantly large deceleration is generated. The airbag system detects the deceleration and detects the collision of the vehicle 20.

That is, as shown in FIG. 4C, ignition determination is performed based on the output states of the front airbag sensor 21, the center airbag sensor 24, and the safing sensor 25 provided in the vehicle 20, and the vehicle 20 is predetermined. When it is determined that the deceleration exceeding the level is generated, the gas generating agent is detonated by the ignition device in the inflator 23b of the wheel pad 23 to inflate the bag 23a.

By the way, when the vehicle 20 has a violent collision, a remarkably large deceleration is temporarily generated at the front portion of the vehicle 20. The shocking deceleration cannot occur when the vehicle 20 is normally traveling. Therefore, the collision of the vehicle 20 cannot be detected only by the front airbag sensor 21 depending on the setting of the front airbag sensor 21 arranged at the front corner of the vehicle 20.

However, the airbag system is used in the vehicle 20.
Should not always be activated in the event of a collision with the bag 23, but only if there is a large impact to some extent.
It is necessary to set the conditions so that b opens. This is because it is inconvenient to handle if the bag 23b is opened every time a slight collision occurs.

However, it is practically difficult to judge whether or not the airbag needs to be operated only by the maximum value of the deceleration generated in the vehicle 20. Depending on the mode of collision, even if a momentary large impact occurs, if the time is extremely short, the damage to the vehicle 20 may be small. Conversely, if the impact is not a significant impact, the impact continues. This may cause a great damage to the vehicle 20.

Further, in consideration of the characteristics of the airbag, which is an extremely occupant protection device, the bag 23b can be reliably held in the event of a collision.
However, it is also necessary to consider that the bag 23b is not easily opened by impacting a part of the vehicle 20 with a hammer or the like.

As shown in FIG. 3, in the airbag system, in addition to the front airbag sensor 21, a center airbag sensor 24 and a safing sensor 25 provided in the vehicle compartment are used to determine the ignition of the inflator 23a. This is because the operating conditions are strictly determined in view of the above reason.

Here, the deceleration that occurs in the passenger compartment when the vehicle 20 collides, that is, the center airbag sensor 2
4 and the safing sensor 25 are not the same as the deceleration received by the front portion of the vehicle 20, that is, the front airbag sensor 21. This is because the vehicle body functions as a cushioning material and the impact of a collision is dampened.

Therefore, at the time of collision of the vehicle 20, the deceleration at the front portion of the vehicle is instantaneously and remarkably large, whereas the deceleration occurring in the vehicle compartment is relatively low G as shown in FIG. Will continue for a long time. Further, the center airbag sensor 24 and the safing sensor 25 are not turned on only by a shock that is substantially undamaged to the vehicle 20.

Therefore, when the front airbag sensor 21 detects an extremely large deceleration and the safing sensor 25 detects an appropriate level of deceleration, it is determined that the vehicle 20 has definitely caused a collision. can do.

Further, although the generated deceleration has not reached the level at which the front airbag sensor 21 is turned on, it continues at an appropriate level in the passenger compartment, and the safing sensor 25 and the center airbag sensor 24 simultaneously. Even when the vehicle is turned on, it can be determined that the vehicle 20 is considerably damaged.

Therefore, the ignition determination in the airbag system is performed by determining the above-mentioned conditions.
The ignition determination circuit 26 shown in (C) is generally composed of a logic circuit as shown in FIG. That is, the safing sensor 25 that is widely turned on from the low G region is on, and at least one of the front airbag sensor 21 that responds to high G and the center airbag sensor 24 that responds to continuous deceleration is on. Only when it is, the ignition command is issued to the inflator 23b.

As described above, in the airbag system, it is necessary to pay special attention to the operating conditions, and the ignition condition of the inflator is judged under strict logical judgment. At this time, as a premise of the logical determination, each sensor that detects the deceleration must surely emit a signal according to the deceleration.

Particularly, the safing sensor 25 is required to have high responsiveness and reliability. When the vehicle 20 collides, the front airbag sensor 21 is turned on for a relatively short period of time, and the safing sensor 25 must be able to follow this, and the center airbag sensor 24 can detect the continuous deceleration. This is because if the safing sensor 25 is unduly turned off when is turned on, it may cause a delay in the operation timing.

Therefore, the safing sensor 25 has
There is a demand for a configuration that is sensitive to deceleration in the vicinity of the set operation range and that can reliably maintain the ON state when the deceleration in the range exceeding the operation range is added.

The fluid passage 11 of the deceleration sensor 1 shown in FIG. 1 is provided so as to easily meet the above requirements. That is, in order to ensure appropriate responsiveness in the deceleration sensor 1, the spring constants of the springs 9 and 10 have certain restrictions, and if no consideration is given,
As described above, when a large deceleration occurs, the conductive plate 8 and the electrodes 6, 7 bounce at the stroke end.

However, the deceleration sensor 1 is constructed so that the displacement resistance corresponding to the flow resistance of the fluid passage 11 is generated in the mover 4 as described above. Then, the flow resistance increases as the mover 4 is displaced toward the left stroke end. Therefore, regarding the relationship between the displacement resistance of the mover 4 and the movement stroke amount, when the movement amount is “0” in the state shown in FIG. 1, the displacement resistance increases as the movement stroke increases as shown in FIG. Becomes

In other words, the mover 4 of the deceleration sensor 1
Can be moved with a comparatively small force near the right stroke end, while a large force is required to cause a slight displacement near the left stroke end. For this reason, rebound when a large deceleration occurs can be appropriately prevented without deteriorating the responsiveness to a relatively low deceleration.

Further, since the deceleration sensor 1 secures such a function by additionally machining the fluid passage 11 in the housing 2, the number of parts is smaller than that of the conventional deceleration sensor which does not have the bounce prevention mechanism. It can be easily realized without increasing the cost and the labor cost.

FIG. 7 is a side sectional view showing the structure of another embodiment of the deceleration sensor according to the present invention. The deceleration sensor 31 of this embodiment is characterized in that the fluid passage 32 is provided in a spiral shape. Since the other components are the same as those of the deceleration sensor 1 shown in FIG. 1, the same reference numerals are given and the description thereof is omitted.

The fluid passage 32 of the deceleration sensor 31 is shown in FIG.
As shown in FIG. 4, the groove is formed as a spiral groove and communicates the spaces on both sides of the mover 4. The depth of the fluid passage 32 is set to be shallower toward the left side in the figure.

Therefore, as in the case of the fluid passage 11 of the deceleration sensor 1 described above, the effective passage area decreases as the mover 4 is displaced from the right stroke end to the left stroke end, and therefore the mover 4 is reduced. The displacement resistance of is increased. Therefore, the deceleration sensor 31 of the present embodiment
Also, similarly to the deceleration sensor 1, it is possible to appropriately prevent the movable element 4 from bouncing back while maintaining good responsiveness.

By the way, the front airbag sensor 21 shown in FIG. 3 is required to have a characteristic of being turned on in response to a high G of about 10 G as described above, and has a different operating region from the safing sensor 25. Is. Therefore, it is generally necessary to change the spring constant between the spring used as the biasing member for the front airbag sensor 21 and the spring used for the safing sensor 25.

However, as described above, by changing the effective passage area of the fluid passages 11 and 32 communicating between the spaces on both sides of the mover 4 as a function of the movement stroke amount of the mover 4, the displacement resistance at the right stroke end and the left side It is possible to set the displacement resistance at the stroke end to a different value, and if this principle is used, the spring used in the safing sensor 25 can be used as the front airbag sensor 2
1 can be realized.

FIG. 8 is a side sectional view showing the construction of another embodiment of the deceleration sensor according to the present invention, which is devised to realize the front airbag sensor 21 according to the above principle. The deceleration sensor 41 of this embodiment is characterized by the shape of the fluid passage 42, and the other components are the same as those of the deceleration sensors 1 and 31 described above. Therefore, the same parts as those of the deceleration sensors 1 and 31 are designated by the same reference numerals, and the description thereof will be omitted.

Fluid passage 4 provided in deceleration sensor 41
As shown in FIG. 8, 2 is shallower as it moves from the left side of the mover 4 to the side of the mover 4, and the depth is set to “0” before reaching the position of the stopper 5. There is. Therefore, when the mover 4 is in contact with the stopper 5, that is, at the right stroke end, the effective passage area of the flow passage 42 is “0”.

Therefore, in the deceleration sensor 41, when the mover 4 is located at the right stalk end, the spaces on both sides of the mover 4 are substantially cut off, and the mover 4 is moved leftward from this state. In order to displace to (4), in addition to the urging force of the springs 9 and 10, a force sufficient to break the above-mentioned cutoff state is required.

On the other hand, when the mover 4 is displaced by a certain distance and the spaces on both sides thereof are brought into communication with each other by the fluid passages 42, the drag force applied to the mover 9 is no longer limited to the biasing force of the springs 9 and 10. The displacement resistance rapidly decreases. That is, with respect to the deceleration sensor 41 of this embodiment, when the relationship between the movement stroke of the mover 4 and the displacement resistance is measured, a characteristic curve as shown in FIG. 9 is obtained.

From FIG. 9, in order to displace the mover 4 in the deceleration sensor 41, a large deceleration is required,
It can be seen that it functions as a high G type sensor. Also,
Once the mover 4 breaks the above-mentioned space interruption state and is displaced, the mover 4 does not easily return to the right stroke end,
The on-time required for the front airbag sensor 21 is sufficiently secured.

[0055]

As described above, according to the present invention, the displacement resistance of the mover sliding in the housing can be increased in the vicinity of one stroke end, and even when an excessive deceleration occurs, it This prevents the mover from colliding with the stroke end and bouncing back.

Therefore, according to the deceleration sensor of the present invention, it is possible to realize a deceleration sensor which is inexpensive, excellent in productivity, and capable of ensuring excellent characteristics without adding any parts to the basic structural parts. It has the feature of being able to.

[Brief description of drawings]

FIG. 1 is a side sectional view of a deceleration sensor that is an embodiment of the present invention.

FIG. 2 is a diagram showing characteristics of a deceleration sensor of the present embodiment.

FIG. 3 is an overall configuration diagram of an airbag system configured using the deceleration sensor of this embodiment.

FIG. 4 is an operation process diagram of the airbag system.

FIG. 5 is a deceleration waveform that is propagated into the vehicle interior during a collision.

FIG. 6 is a diagram showing an ignition condition determination logic in the airbag system.

FIG. 7 is another embodiment of the deceleration sensor according to the present invention.

FIG. 8 is another embodiment of the deceleration sensor according to the present invention.

FIG. 9 is a diagram showing characteristics of another embodiment of the deceleration sensor according to the present invention.

[Explanation of symbols]

 1, 31, 41 Deceleration sensor 2, 3 Housing 4 Mover 5 Stopper 6, 7 Electrode 8 Conductive plate 9, 10 Spring 11, 32, 42 Fluid passage 20 Vehicle 21 Front airbag sensor 23 Wheel pad 24 Center airbag sensor 25 safing sensor

Claims (1)

[Claims] 1. A deceleration sensor for detecting deceleration by detecting a movement of a mover disposed slidably within a housing filled with fluid with a predetermined stroke width, wherein the inner wall of the housing comprises: A deceleration sensor, comprising: a fluid passage that communicates chambers on both sides of the mover and narrows an effective passage area as the mover approaches at least one stroke end.