JPS5942700Y2 - Acceleration sensor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an acceleration sensor that uses inertia to detect, for example, a collision of a car.

For example, conventional sensors of this kind used in automobiles have positive and negative electrodes arranged opposite each other. An inertial body is slidably installed inside the housing, and when a car crash occurs, the inertial body uses its own inertia to・It was configured to slide on the sliding guide surface of the housing to short-circuit the pair of electrodes.

However, with this configuration, when used for a long period of time, the sliding surface of the inertial body gradually wears out due to vibrations, etc., and the frictional force increases, resulting in malfunction.

The present invention was developed in view of the above circumstances, and its purpose is to provide an acceleration sensor that can reduce the effects of changes in frictional force to a negligible level and that operates normally even after long-term use. .

The present invention will be specifically explained below with reference to Examples.

1 to 3 show the first embodiment.
In the figures and FIG. 2, reference numeral 1 denotes a cylindrical housing that is fixed to the body of an automobile, and a conical recess 2 is formed in the center of the lower side, and the upper side is the other side. A bushing 3 is fitted in the center of the section, and a ring 4 is embedded so as to surround the bushing 3.

The bush 3 and the ring 4 are connected to the positive and negative terminals of the battery, respectively, and constitute a kind of switch (detection means), and are configured so that, for example, a fire prevention system of a car is activated when the two are short-circuited. .

Reference numeral 5 denotes a cylindrical seat disposed within the housing 1, and a conical protrusion 6 is integrally formed at the lower end of the seat 5. By making point contact with the apex of the housing 1, the catch seat 5 is supported in an inverted state on the lower surface of the housing 1.

Reference numeral 7 denotes a support member formed entirely into a conical shape so as to form a conical protrusion 8 at its upper end, and a circular hole 9 of a predetermined depth that opens downward as a fitting hole is formed in the center of this support member. ing.

A compression spring 10 as an elastic body is housed in the catch seat 5, and the support member 7 is inserted into the catch seat 5 through the circular hole 9.
This allows the support member T to expand and contract in the vertical direction when combined with the seat 5.

Reference numeral 11 denotes a circular inertial body made of, for example, phosphor bronze, which has a conical recess 12 formed at the center of its lower surface at one end, and a small protrusion 13a at its other end at the center of its upper surface. A circular protrusion 13 having a small diameter is integrally provided.

Such an inertial body 11 connects the apex of the conical recess 12 to the support member 1.
By making point contact with the apex of the conical projection 8, the lower surface side is supported by the support member 7, and the compression spring 1
The upper surface of the circular protrusion 13 is pressed against the step surface 14a of the stepped taper hole 14 formed in the bushing 3 by the upward elastic force received from the bushing 3 to bring the top surface into surface contact with the bushing 3. It is supported.

The small protrusion 13a projects outward from the bush 3 and functions as a knob for restoring the inertial body 11 to its original state when it is tilted as will be described later.

Incidentally, when viewed microscopically, the apexes of the respective conical protrusions 6 and 8 of the seat 5 and the support member 7 are formed in a spherical shape as shown in FIG. The apex of each conical recess 2 and 12 of the inertial body 11 is also formed into a spherical shape.

The mY connecting the vertices of the conical protrusions 6 and 8 coincides with that of the circular protrusion 13 of the inertial body 11, and the circular outer contour of the upper surface of the circular protrusion 13 is located around the axis Y. As a result, the inertial body 11 is always maintained in the state shown by the solid line in FIG.

Now, if we consider the case where a car causes a collision, the housing 1 is suddenly decelerated and stops due to the car's collision, but the inertial body 11 tries to continue moving at the previous speed due to its own inertia. .

Therefore, the inertial body 11 compresses the support body 7, L100
While compressing against the elastic force and tilting the support body 7 and the seat 5 in the direction of arrow A around the apex of the conical projection 6,
The circular protrusion 13 tilts in the direction of arrow B about a point on the outer contour of the upper surface, and comes into contact with the ring 4 as shown by the two-dot chain line in FIG.

This short-circuits the bushing 3 and the ring 4, activating the fire prevention system.

Incidentally, as the inertial body 11 tilts, the apex of the conical protrusion 8 of the support member 7 crosses the straight line connecting the tilting center of the inertial body 11 and the conical protrusion 6 apex of the catch seat 5. 11 is held by a compression spring 10 in the state shown by the two-dot chain line in FIG.

Here, consider how much acceleration is applied to cause the inertial body 11 to tilt.

Now, let μm and μ2 be the friction coefficients of each conical protrusion 6°8, and since these are considered to be approximately equal, let μ be the coefficient of friction.

Also, the weight of the inertial body 110 is W, and the elastic force of the compression spring 10 is F.
s, and the radius of the circular protrusion 13 is a as shown in FIG.
1 The distance between the top surface of the circular protrusion 13 and the center point o1 of the spherical surface of the 8 apex of the conical protrusion is b, and the distance between ol and the center point o2 of the spherical surface of the 6 apex of the conical protrusion is C9 for each conical protrusion. Let the radii of the spherical surfaces at the vertices of parts 8 and 6 be rltr2, respectively.

When the inertial body 11 tries to tilt, the moment M around the center of tilting 00 is expressed as follows.

The force F that acts on the inertial body 11 due to the deceleration acceleration α of the car at the time of a single-force collision is, assuming that the gravitational acceleration is G, F=-・α
The moment (moment around point 0) MI is expressed as M = F - d knee - αd, where d is the distance between the top surface of the circular protrusion 13 and the center of gravity o3 of the inertial body 110.

Therefore, MI>M, that is, α>□・G's d When the inertial body 11 is tilted, from this, Fs.

Sensitivity α can be adjusted by appropriately setting Wsa, b, c, and a.
(acceleration at which the inertial body 11 tilts) can be set.

Furthermore, the rate of change in sensitivity α with respect to the change in friction coefficient μ is calculated by citing specific values for the sensitivity α and its rate of change described above.

First, each dimension in Figure 3 is a = 3 cabinets 1 bat 1 mm,
c=15Mn, d=7.8mm.

Set rl = r2 = 0.3 mm, and W = 30
When g・F s=600 g and μ=0.4,
Therefore, when the acceleration α becomes equal to or more than 0, the inertial body 11 tilts around the point O.

On the other hand, the rate of change in sensitivity α for long-term use is as follows.

As is clear from this, it is understood that even if the friction coefficient μ fluctuates by 50%, the sensitivity α fluctuates by 5% or less.

Further, a circular hole 9 is formed in the support member 7, and the seat 5 and the compression spring 10 are accommodated in the circular hole 9.
Since the conical recess 12 is formed in the conical recess 12 and the upper portion of the support member 7 is housed in the conical recess 12, the overall height can be reduced and the device can be made smaller.

FIG. 4 shows the second embodiment, which differs from the first embodiment in that the apexes of each conical recess 2, 12 are sharpened, and in this case, the seven points around the zero point are , is expressed as .

However, the distance el between the tip of the conical recess 12 and the center 01 of the spherical surface of the 8 apex of the conical projection 8, and the distance between the tip of the conical recess 2 and the center o2 of the spherical surface of the 6 apex of the conical projection 6, 02, the rate of change in the sensitivity α with respect to the change in λ' and the friction coefficient μ is expressed as follows, and as in the first embodiment, the rate of change in sensitivity with respect to the rate of change in the friction coefficient can be ignored. It can be kept within a small range.

In the above embodiment, the apexes of the conical protrusions 6 and 8 are made into spherical shapes with a small radius (approximately 0.3 mm), but it is preferable to make them as sharp as possible in order to reduce frictional force, and this is not ideal. In general, it is desirable to have complete point contact.

Further, in the first embodiment, the circular protrusion 13 of the inertial body 11 was brought into surface contact with the bushing 3, but this is different from the case in which the circular protrusion 13 of the inertial body 11 is in annular contact with the upper surface of the circular protrusion 13 as in the third embodiment shown in FIG. Part 13b
may be provided in a protruding manner so as to be in line contact with the step surface 14a of the bluff 330.

Next, FIGS. 6 to 12 show the fourth to tenth embodiments, respectively. In FIG. 6, the negative electrode side ring 15 is embedded in the inner circumferential surface of the housing 1, and in FIG. Similarly, a cylindrical body 16 on the negative electrode side is erected on the lower surface of the housing 1, and in both cases, the inertial body 11 short-circuits the positive and negative electrodes.

Further, FIG. 8 shows a configuration in which a ring 17 on the positive electrode side and a seat plate 18 on the negative electrode side are both buried in the lower surface of the housing 1 and short-circuited via the seat 5 and the support member 1 between the positive and negative electrodes.
In FIG. 9, a ring 19 on the positive electrode side is embedded in the upper surface of the housing 1, and an inertial body 11 is connected between the positive and negative electrodes. In addition, in FIG. 10, the bushing 3 is formed of an insulating material, and the ring 20 on the positive electrode side is fixed to the inner circumference of the bushing 3. This is a configuration in which the inertial body 11, the support member 7, and the seat 5 are short-circuited, and the positive and negative poles on which the inertial body 11 tilts are opened.

Next, FIG. 11 shows a switch 2 which is a detection means in a housing 1.
1 fixed contact piece 22 and movable contact piece 23 are provided, and the inertial body 11
The movable contact piece 23 is separated from the fixed contact piece 22 by the small protrusion 13a of the tilted tooth, thereby opening the gap between the positive and negative electrodes.

Further, FIG. 12 uses a microswitch 24 as a detection means, and the small protrusion 13a of the inertial body 11 always presses the actuator 24a of the microswitch 24 to hold the microswitch 24 in an OFF state, for example. Inertial body 1
1 is tilted, the suppression of the actuator 24a by the small protrusion 13a is released and the microswitch 24 is turned on.

In addition, in FIGS. 6 to 11, 25 is a battery;
26 is a fire prevention system.

Each of the embodiments described above has been explained by applying it to a collision detection sensor of a car, but seat belts etc. are used to detect changes in acceleration such as when a car crashes or suddenly stops and restrains the occupant. It may be applied to an acceleration sensor for locking, or it may be applied to any other sensor, such as an earthquake detection device, as long as acceleration is applied to the using.

As described above, the present invention can provide an acceleration sensor that can reduce the influence of changes in frictional force to a negligible level, operate normally even during long-term use, and can be configured to be compact as a whole.

[Brief explanation of drawings]

1 to 3 show a first embodiment of the present invention, in which FIG. 1 is an overall longitudinal cross-sectional view, FIG. 2 is an exploded perspective view of the entire structure, and FIG. 3 is an enlarged longitudinal cross-sectional view with a portion cut away. FIG. 4 is a view corresponding to FIG. 3 showing a second embodiment of the present invention, FIG. 5 is a partial vertical sectional view showing a third embodiment of the present invention, and FIGS.
The figure is an overall view showing fourth to tenth embodiments of the present invention. In the figure, 1 is a housing, 2 is a conical recess, 3 is a bush (detection means), 4, 15, 17, 19° 20 is a ring (
Detection means), 5 is a seat, 6 and 8 are conical projections, I is a support member, 9 is a circular hole fitting hole, 10 is a compression spring (elastic body),
12 is a conical recess (recess), 16 is a cylindrical body (detection means)
, 18 is a seat plate (detection means), 21 is a switch (detection means), and 24 is a microswitch (detection means).

Claims (1)

[Scope of utility model registration request] a housing, a seat disposed within the housing and having one end supported on one side of the housing, and a seat having a fitting hole, the seat being fitted into the fitting hole, and the seat being connected to the seat. a support member connected so as to be movable in the expansion/contraction direction in combination;
an elastic body provided in the fitting hole and exerting a resilient force between the seat and the support member; and a recessed portion on one end side, and the supporting member is configured to accommodate the supporting member in the recessed portion. an inertial body supported by the housing and whose other end is pressed against and supported by the other end of the housing by the elastic force of the elastic body;
and detecting means for detecting when acceleration acts on the housing and the inertial body tilts around the supporting portion on the housing side due to its own inertia, and detects when the receiving seat, the housing, and the supporting member Among the supporting structures of the inertial body and the inertial body and the housing, one is a line contact or a surface contact where the outer contour is always a circle, and the remaining two are the support structures at the apex of the conical recess and the conical protrusion. An acceleration sensor characterized by point contact.