JPH0344560A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To prevent deflection of a beam due to a force, such as a pressing force applied to a built-in part, other than an acceleration by sealing a control fluid by two flexible seal members disposed on the upper and lower surfaces of detecting members. CONSTITUTION:A silicone oil 8 is filled up, together with a weight 1 and an arm 2, in an inner space 7 of a case made up of a beam holder 11, a beam base 12 and a weight stopper 13a. By the viscosity of the oil, the motion of the weight 1 is held down and the vibration thereof is prevented. Since sealing is necessitated for preventing the silicone oil from leaking, on the occasion, a plane of contact of the beam base 12 with the weight stopper 13a is sealed with an O-ring 6 and a plane of contact of the upper surface of the beam base 12 with the lower surface of a beam plate 20 is sealed with an annular seal member 15 inserted into the part of this plane, while a plane of contact of the upper surface of the plate 20 with the lower surface of the beam holder 11 is sealed with a seal member 14 inserted into the part of this plane.

Description

[Detailed Description of the Invention] [Object of the Invention] [Industrial Application Field] The present invention relates to a sensor that detects a change in acceleration as a change in stress applied to a beam, and particularly relates to a sensor for damping a weight that generates inertia. The present invention relates to an acceleration sensor in which a damping fluid such as oil is sealed inside the sensor.

[Prior Art] As shown in, for example, Japanese Unexamined Patent Publication No. 59-111065, an acceleration sensor includes a weight that generates inertia inside its housing, and when the sensor receives acceleration,
Since the weight inside the housing is displaced relative to the housing due to its inertia, acceleration can be detected by detecting the amount of displacement.

By the way, in this type of acceleration sensor, it is necessary to prevent unnecessary vibration of the weight. That is.

For example, if a weight vibrates in response to temporal acceleration in one direction, displacement signals in the forward and reverse directions will be detected alternately, and this signal will continue even after the acceleration has become zero. Accurate acceleration cannot be detected.

Therefore, damping the vibration of the weight is very important in this type of acceleration sensor. In order to effectively damp the vibration of a weight, it is necessary to seal the space in which the weight is placed, for example, and fill the space with oil or the like.

[Problem to be solved by the invention] In an acceleration sensor that contains a fluid such as oil for vibration damping, it is necessary to prevent oil from leaking to the outside of the sensor.
It is necessary to seal the joint surfaces of each member.

In an acceleration sensor that uses a flat detection member that detects the displacement of a weight as the deflection of a beam, the center of the detection member is immersed in oil, and the periphery of the detection member is sandwiched from above and below between members such as a housing. Since it needs to be fixed, at each contact surface between the detection member and the member sandwiching it,
Must be sealed.

By the way, when sealing an uneven surface.

Alternatively, if a vulnerable member with low mechanical strength is placed on the surface to be sealed, a flexible member such as rubber may be placed on the sealing surface to protect the weak member.
It is necessary to press the sealing surface to secure it.

Even in the case of an acceleration sensor that uses a flat detection member that detects the displacement of a weight as the deflection of a beam, the detection member is easily damaged, so a flexible member is used to seal both the top and bottom surfaces of the detection member. It is necessary to do it.

However, if both the upper and lower surfaces of the flat detection member are supported by flexible sealing members, both the upper and lower supporting parts are deformable, so the force applied to the upper surface and the lower surface are If the balance with the applied force is lost, the beam of the detection member will bend due to the force for supporting the detection member. This type of deflection leads to acceleration detection errors. For example, when pressing the detection member and the sealing member using screws, even if the balance is well adjusted at the time of manufacture to eliminate deflection of the beam.

Due to loosening of screws over time, the force balance is disrupted and the beam becomes deflected.

An object of the present invention is to prevent the occurrence of deflection of a beam due to a force other than acceleration, such as a pressing force applied to a part during assembly, in an acceleration sensor incorporating a damping fluid such as oil.

[Structure of the Invention] [One Means for Solving the Problems] In order to solve the above problems, one aspect of the present invention includes a flexible beam formed in the center thereof and a deflection detection device for detecting the deflection of the beam. a detecting member formed in a substantially flat plate shape, a weight disposed to engage with a beam of the detecting member, and a weight disposed opposite to an upper surface and a lower surface in the thickness direction of a peripheral portion of the detecting member, respectively; first and second supporting members disposed;
A flexible first member inserted between the supporting member and the detecting member.
In an acceleration sensor comprising a seal member, a flexible second seal member interposed between the second support member and the detection member, and a damping fluid filled in a space around the weight; A position where the first seal member contacts the upper surface of the detection member and a position where the second seal member contacts the lower surface of the detection member are shifted from each other.

[Operation] According to the present invention, the first seal member can seal the upper surface of the detection member and the opposing surface of the first support member, and the second seal member can seal the lower surface of the detection member and the second support member. The surface facing the support member can be sealed.

Furthermore, at the position where the upper surface of the detection member contacts the first seal member, there is no second seal member at the position where the upper surface of the detection member contacts the lower surface of the detection member, and that surface contacts and is supported by the second support member. . Therefore, unless the second support member is a flexible member such as a seal member, in that position, regardless of the magnitude of the pressure or force between the second support member and the detection member, the lower surface of the detection member maintains the shape along the surface of the second support member. In other words, if the upper surface of the second support member has a flat shape, even if the pressing force of one assembly changes, there is no possibility that the beam of the detection member will bend.

Similarly, at the position where the lower surface of the detection member abuts the second seal member, the first
There is no sealing member, and its surface abuts and is supported by the first support member. Therefore, unless the first support member is a flexible member such as a seal member, at that position, regardless of the magnitude of the pressing force between the first support member and the detection member, the upper surface of the detection member will be , maintains the shape along the surface of the first support member. In other words, if the lower surface of the first support member has a flat shape, even if the pressing force of one assembly changes, there is no fear that the beam of the detection member will bend.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[Example 1] Fig. 1 shows a longitudinal section of an acceleration sensor according to an example, and
The figure shows the main part of the cross section taken along line nn in FIG. 1. First, the configuration will be explained with reference to FIG.

The weight 1 is made of metal, has a cylindrical shape, and has a through hole in the center. The rod-shaped arm 2 has its lower end pushed into the through hole of the weight 1.

It is constructed integrally with the weight 1 by a flange 4 integrated with the arm 2 for positioning the ring 3 and the weight 1. What is the space in which the weight l is placed?

Beam holder 11. It is formed in the inner space of a case composed of a beam base 12 and a weight stopper 13. The weight stopper 13 is in the shape of a circular cup, has an inner diameter slightly larger than the outer diameter of the weight 1, and has a flange portion 13a at the top. The beam base 12 has a shape that can fit into the weight stopper 13, and has a cylindrical protrusion 12a that fits into the weight stopper and a flange 12b.

The beam plate 20 is placed between the beam holder 11 and the beam base 12 from above and below. Between the top surface of the beam plate 20 and the bottom surface of the beam holder 1■,
and the lower surface of the beam plate 20 and the beam base 12
Rubber sealing materials 14 and 15 are respectively inserted between the upper surfaces of the .

One sealing material 15 is formed into a ring shape. The other sealing material 14 is formed into a cap shape and has a flange portion 14a at the portion where it comes into contact with the beam plate 20. The contact surface between the upper surface of the beam plate 20 and the flange portion 14a of the sealing material 14, and the contact surface between the lower surface of the beam plate 20 and the sealing material 15 are formed in a concentric ring shape so as to surround the periphery of the arm 2. is formed. The former ring has a smaller diameter than the latter ring, and the two ring surfaces are offset from each other so that they do not face each other.

In other words, the flange portion 14a of the sealing material 14.

It faces a position on the upper surface of the beam base 12 where the sealant 15 is not present, with the beam plate 20 interposed therebetween.

Furthermore, the contact surface between the sealing material 15 and the beam plate 20 is
It faces a position on the lower surface of the beam holder 11 where the sealing material 14 is not present, with the beam plate 20 interposed therebetween.

Therefore, at least one of the front and back surfaces of each supported portion of the thin beam plate 20 is supported by a flat metal surface (11 or 12).

The beam holder 11 and the flange portion 1 of the weight stop collar are connected by four screws including the screws 51 and 52 shown in FIG.
3a are combined. Therefore, the beam base 12 is sandwiched and fixed between the beam holder 11 and the weight stopper 13, and the beam plate 20 is sandwiched and fixed between the beam holder 11 and the beam base 12. The flange portion 14a of the sealing material 14 is inserted between the beam holder 11 and the upper surface of the beam plate 20, and the sealing material 15 is inserted between the lower surface of the beam plate 20 and the beam base 12.

The beam plate 20 has a thin plate shape and is easily bent. Therefore, when a force is applied to the front or back surface of the beam plate 20, the beam plate 20 tends to bend due to the force. However, in this example, in the part that supports the beam plate 20.

At least one of the front and back surfaces of the beam plate 20 is
Since it is in contact with a metal flat surface, no matter what kind of pressing force is applied from the beam holder 11 and the beam base 12, it maintains its shape along the flat surface and does not bend.

Therefore, even if the tightening torque of the screws (51, 52) changes, the deformation characteristics of the beam plate 20 will not change. Since the change in torque does not affect the deflection of the beam plate 20, there is no possibility that the zero point of the acceleration sensor will shift.

An enlarged plan view of the beam plate 20 is shown in FIG. Referring to FIG. 3, near the center of the beam plate 20 there is an elongated 2
Two openings 21,22 are provided between which an elongated beam 23 is formed. A hole 23a is opened in the center of the beam 23 through which the arm 2 shown in FIG. 1 passes. That is, the arm 2 has its top 2a fixed to the center of the channel 23 by passing the top 2a of the arm 2 through the hole 23a and attaching the arm stopper 16 to the top 2a.

Supported by 23 years old. That is, weight 1 is.

It is suspended from a beam 23 via an arm 2.

The base of the beam plate 20 is very thin (thickness is 0).
, 1 mm) is composed of a flat plate of metal (SUS304), on which various film-like parts are formed. Since the beam plate 20 is very thin, when the weight attached to the beam 23 is tilted, the lI 23 is deflected accordingly. 8 on the culvert 23 to detect its deflection.
Two strain gauge parts P1゜P2. P3. P4. P5. P6.
P7 and P8 are provided, and the other ends of the wiring patterns 25 connected to these are arranged in a concentrated manner at the terminal portion 20a at the right end of the beam plate 20. The wiring pattern 25 includes nine lines 251 to 25s.

Part 6a of the strain gauge part pt-ps in Fig. 3 is enlarged.
Referring to FIG. 6a shown in FIG. constitute one line. Therefore, most of the electrical resistance of the strain gauge portion P3 is obtained by the thin and long pattern portion extending in the Y direction, and the influence of the portion extending in the X direction is small.

In other words, the electrical resistance of the strain gauge part P3 changes greatly when it receives stress in the Y direction, but hardly changes in response to stress in the X direction.

Both ends of the strain gauge part P3 are connected to the wiring pattern 2, respectively.
51 and 252. Note that the other strain gauge parts Pi, P2, and P4 are also configured to have the same pattern shape and orientation as the strain gauge part P3.

Referring to FIG. 6b, in the strain gauge section P'5.

Long and thin pattern parts formed in the direction of arrow A1 inclined at 45 degrees with respect to the X and Y directions and thick and short pattern parts formed in the direction of arrow A2 inclined at 90 degrees with respect to the arrow A1 are alternately formed, and there is one pattern in total. It makes up the lines of Therefore,
Most of the electrical resistance of the strain gauge portion P5 is obtained by the thin and long pattern portion extending in the A2 direction, and the influence of the portion extending in the At direction is small.

In other words, the electrical resistance of the strain gauge part P5 changes greatly when it receives stress in the A2 direction, but hardly changes when it receives stress in the A1 direction.
are connected to wiring patterns 257 and 258, respectively.
It is connected to the. Note that the strain gauge portion P8 is also formed in the same pattern shape and orientation as the strain gauge portion P5.

The strain gauge portion P6 is formed such that the elongated portion and the thick and short portion of the pattern are oriented 90 degrees apart from the strain gauge portion P5. Therefore, in the case of the strain gauge part P6, when it receives stress in the At direction, its electrical resistance changes greatly;
Both ends of the strain gauge part P6, which hardly change due to stress in two directions, are connected to wiring patterns 257.
and 256. In addition, the strain gauge part P7 is also included.

It is formed in the same pattern shape and direction as the strain gauge part P6.

Figures 7a, 7b, and 7c schematically show the direction and distribution of stress in vIk23 when accelerations in the Y direction, X direction, and two directions are applied to this sensor, respectively. Please note that the shapes and structures of the members shown in Figures 7b and 7c are quite different from the actual ones.

When acceleration in the Y direction is applied, compressive stress and tensile stress in the Y direction act on the dye as shown in Section 7a. Therefore, when strain gauge parts P1 and P2 receive compressive stress and their electrical resistance decreases, other strain gauge parts P
3. P4 receives tensile stress and its electrical resistance increases, strain gauge part Pl.

When P2 is subjected to tensile stress and its electrical resistance increases, other strain gauge parts P3. P4 receives compressive stress and its electrical resistance decreases. In other words, four strain gauge parts P1 to P4
If they are electrically connected to form a Wheatstone bridge, it is possible to detect stress corresponding to acceleration in the Y direction.

When acceleration in the X direction is applied, compressive stress or tensile stress in the direction of inclination (At, A2) acts on the dyeing as shown in FIG. 7b. Therefore.

Strain gauge part P5. When P8 receives compressive stress and its electrical resistance decreases, other strain gauge parts P6 and P8 receive tensile stress and their electrical resistance increases, and strain gauge parts P5. P
7 receives tension and its electrical resistance increases, the other strain gauge parts P6. P8 receives compressive stress and its electrical resistance decreases. That is, if the strain gauge parts P5 to P8 are electrically connected to form a Wheatstone bridge, stress corresponding to acceleration in the X direction can be detected thereby.

Furthermore, when acceleration in the X direction is applied, compressive force core and tensile stress are applied to the dyeing surface in the Y direction, as shown in Figure 7c, but in this case, at symmetrical positions on both sides of the beam. The same stress acts. Therefore, when strain gauge parts PI, P2 receive compressive stress, other strain gauge parts P3. P4 also receives compressive stress, and when strain gauge parts Pi and P2 receive tensile stress, other strain gauge parts P3. Since P4 also receives tensile stress, the changes in electrical resistance of the four strain gauge parts P1 to P4 are the same, and no signal is output from the Wheatstone bridge in response to acceleration in two directions.

Figure 8 shows the beam plate 20 and its arrangement wc251~
25g, strain gauge parts PI, P2. P3 and P4 constitute a Wheatstone bridge.

The remaining strain gauge sections P5 to P8 constitute another Wheatstone bridge. A voltage vy corresponding to the acceleration in the Y direction is obtained at the output terminal of the former bridge.

A voltage Vx corresponding to the acceleration in the X direction is obtained at the output terminal of the latter bridge.

In addition, in the bridge composed of strain gauge parts P1 to P4, strain gauge parts Pl and P2, and strain gauge part P
Note that 3 and P4 are connected such that they are each located on opposite sides of the bridge.

Referring to FIG. 5, which shows a partially enlarged cross section of the beam plate 2o in the thickness direction, the beam plate 20 has an insulating film 27 formed on one side of the base 26.
It has a conductive pattern 28 and an insulating film 29. The base 26 is a thin metal plate with a thickness of 0.1 mm and is conductive, so an insulating film 27 is formed over the entire one surface of the base 26 in order to form an electric circuit thereon. .

This insulating film 27 is formed by coating SiO2.

The conductive pattern 28 is a Ni-based conductor a film formed by sputtering, and by etching it, the required patterns of each of the strain gauge parts P1 to P8 and the wiring 25 are formed. After the formation of this pattern is completed, a protective film of SiO2 is formed on the pattern except for the terminal portion 20a that requires electrical connection.

Referring to FIG. 1, beam holder 11. Inner space 7 of the case consisting of beam base] 2 and weight stopper 13
, along with weight 1 and arm 2, silicone oil 8
is filled. This silicone oil 8 suppresses the movement of the weight 1 due to its viscosity and prevents vibration.

In this embodiment, since the inner space 7 is filled with silicone oil 8, it is necessary to provide sufficient sealing at the abutting portions of each member constituting the case so that the silicone oil does not leak from the space. The contact surfaces between the beam base 12 and the weight stopper 13 are sealed by an O-ring 6. Also.

The abutment surface between the upper surface of the beam base 12 and the lower surface of the beam plate 2o is sealed with an annular sealing material (rubber) 15 inserted in that area, and the abutment surface between the upper surface of the beam plate 20 and the lower surface of the beam holder 11 is sealed. The contact surface is sealed by a sealing material 14 inserted therein. Seal material 1
4 is formed to cover the entire circumference of the top portion 2a of the arm 2 and the arm stopper 16. Note that since the sealing materials 14 and 15 are both made of a flexible material (rubber), even when the sealing materials 14 and 15 are relatively strongly pressed against the beam plates 1 to 20, the beam plates 20 There is no need to worry about damaging the surface.

In this example, the beam plate 20 is very thin, and the patterns such as wiring formed on it are formed into an even thinner film, so that the beam plate 20, the beam holder 11, and the beam base 12 are connected to each other. There are almost no irregularities on the contact surface. Therefore, the seals for those parts are
This can be done extremely easily and reliably using only sealing materials 14 and 15 having a simple shape as shown in FIG.

Note that the beam holder 11. Beam base 12 and beam 1
1. The four screws for fixing the plate 20 are each inserted into the hole 20b of the beam plate 20 shown in FIG.

20c, 20d and 20e. As shown in FIG. 1, the beam holder 11. The outside of the case consisting of the beam base 12 and the weight stopper 13 is covered with cushioning materials 31, 32 and 33 made of sponge sheets, and inside the housing consisting of various members 41, 42, 43 and 44. Fixed.

[Effect] As described above, according to the present invention, the flexible first and second
Since the sealing members are disposed on the upper and lower surfaces of the detection member to seal the damping fluid, the sealing can be performed reliably without damaging the detection member. Further, a position where the first seal member and the upper surface of the detection member abut,
Since the positions where the second seal member and the lower surface of the detection member abut are shifted from each other, the other surface of the portion of the detection member that abuts the first and second seal members is bent. The second and first support members come into contact with surfaces that are difficult to maintain. Therefore, even if the force with which the first and second seal members and the detection member are pressed changes, there is no risk of deformation of their contact surfaces. In other words, in the acceleration sensor of the present invention, there is no possibility that the zero point (the sensor output state S when the acceleration is zero) will shift.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an acceleration sensor according to an embodiment. FIG. 2 is a cross-sectional view showing the main part of the cross section taken along line nn in FIG.
3 is an enlarged plan view showing the appearance of the beam plate 20 shown in FIG. 1, and FIG. 4 is an enlarged sectional view showing a portion of FIG. 1. FIG. 5 is a sectional view showing a section of a portion of the beam plate 20 in the thickness direction. FIGS. 6a and 6b are plan views each showing an enlarged strain gauge section on the beam plate 20. FIGS. FIGS. 7a, 7b, and 7c are perspective views schematically showing the stress distribution of the conduit 23 when subjected to acceleration in different directions. FIG. 8 is a wiring diagram showing a connection state of some electric elements of the acceleration sensor of FIG. 1. FIG. 1: Weight 2: Arm 3: Ring 4: Flange 6: O-ring 7: Inner space 8: Silicone oil (damping fluid) 11: Beam holder (first support member) 12: Beam base (second support member) 13: Weight stopper 14: Seal material (first seal member) 15: Seal material (second seal member) 20: Beam plate (detection member) 21. 22: Opening 23: Dye 25: Wiring pattern 251-259: Wiring P1-P
8: Strain gauge part (deflection detection means) 26: Base
27: Insulating film 28: Conductive pattern 29: Insulating film 31°32°: Cushioning material

Claims (1)

[Scope of Claims] A detection member formed in a substantially flat plate shape, including a flexible beam formed in the center thereof and a deflection detection means for detecting the deflection of the beam; an attached weight, first and second support members arranged to face each other on the upper and lower surfaces in the thickness direction of the peripheral portion of the detection member, and inserted between the first support member and the detection member; a flexible first seal member inserted between the second supporting member and the detection member, and a control member filled in a space around the weight. In an acceleration sensor including a vibrating fluid; the position where the first sealing member contacts the upper surface of the detection member and the position where the second sealing member contacts the lower surface of the detection member are shifted from each other. sensor.