JPH02249975A - Magnetic acceleration sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a system for controlling suspensions, anti-lock brakes, traction systems, etc., which is attached to the body of an automobile and improves steering stability and riding comfort for one occupant. The present invention relates to an acceleration sensor used in a system, and particularly relates to an acceleration sensor structure that is highly accurate, reliable, and can be assembled at low cost.

[Conventional technology]

As known from Japanese Utility Model Application Publication No. 63-111667, a method is known in which an acceleration sensor is used as a detection means by applying a displacement to a leaf spring, regardless of its size.6 [Problems to be Solved by the Invention] ] In the case of a car, some kind of vibration always occurs when it is in operation, and generally the vibration spectrum is
Frequency is high from DC to 50Hz, then 50 to 100H
Although the frequency decreases as we move to higher frequency ranges, DC~I K ! (The frequency band up to Z is a region that must always be considered to exist as dark vibration. Generally, if the length of the leaf spring is 10
Around m.

When using the full scale displacement of a leaf spring in the range of several millimeters to several tens of micrometers, the resonance point is
It falls within the range of 200Hz. Therefore, it is essential to take measures to attenuate the amplitude near the resonance frequency to below O dB. Generally, as a measure against damping, as is clear from the references, the leaf spring of the movable part is housed in a sealed chamber, the sealed chamber is filled with oil, and the movement of the leaf spring is damped by the viscosity of the oil. The purpose is to

However, the viscosity coefficient of oil changes with temperature, so for example, when the environmental temperature of a car changes from -40°C to 110°C, the viscosity of the oil will be about 3 times higher at low temperatures compared to 20°C. , it decreases to about 1/3 on the high temperature side. Therefore, even if the gain of the amplitude at the resonance point can be lowered by appropriately selecting and combining the viscosity coefficients of the oil at around room temperature, the phase will be significantly delayed at low temperatures, which will impede signal transmission. On the other hand, on the high temperature side, the viscosity of the oil decreases, and the gain at the resonance point, which was not noticeable at room temperature, increases. Under the influence of the dark vibration of the car, the amplitude of the leaf spring constantly expands, making it difficult to accurately Acceleration signals cannot be obtained. Further, the coefficient of volumetric expansion of oil is large, and one volume changes by 15% or more for a change of about 100°C. Therefore, as the temperature rises, the internal pressure inside the closed container increases, and there is a problem in that it is necessary to take measures against oil leakage, for example, to absorb volumetric expansion using a diaphragm.

[Means to solve the problem]

In the present invention, as a measure against resonance of the leaf spring, an air damper with low temperature dependence is used instead of an oil damper. Specifically, assuming that the air damper is operated by the throttling effect of the piston structure, where: k constant, μ is the viscous damping coefficient, a is the gap dimension, Q is the gap length, and A is the piston's It is the cross-sectional area.

Since air with a small viscosity coefficient is used, in order to obtain the same damping force, the first step is to increase the cross-sectional area of the piston. Second, reduce the gap between the cylinder pistons. Third, countermeasures can be taken such as increasing the length of the gap.

In addition, in order to reduce the number of parts as much as possible,
- It was decided to form a leaf spring by machining a U-shaped groove on a plate. As a means for processing a groove of minute width, processing methods such as etching, a combination of etching and plating, a laser beam, and pressing can be used. - If the groove width is too wide and the effect is low with single plates, stack multiple plates to
It is also possible to keep the correlation between and a within a certain value. Furthermore, if the groove width Qh is t≧0.2, the plate thickness t of the plate spring is
When the relationship with the groove width Qh is t/Q h≧4, the damping effect becomes large.

Furthermore, a similar damping effect can be obtained by providing a depression in the opposing wall surface facing the outer periphery of the weight of the movable part and forming a minute gap between the inner walls of the depression. Moreover, the same effect can be obtained by making the movable side hollow and making the wall surface 1 protrude.

Furthermore, a similar damping effect can be obtained by fixing something equivalent to a piston on the movable side and fitting it into the cylinder portion on the wall side.

[Effect]

The magnetic acceleration sensor of the present invention has a structure that combines a permanent magnet and a Hall element integrated circuit, and converts displacement into a change in magnetic flux density, and further converts it electrically. That is, a permanent magnet that also serves as an inertial weight is attached to the tip of the leaf spring, and the other end is used as a cantilever beam that can be moved as a fulcrum. The permanent magnet at the tip of the movable part has N-8 magnetic poles in the direction of movement, and as the permanent magnet moves with the inertial force caused by acceleration, changes in magnetic flux density that occur are absorbed by a Hall element fixed to the wall or This method detects the signal using a Hall element integrated circuit, performs magnetoelectric conversion, and extracts the signal.

In the case of sudden braking or sudden acceleration, the vibration frequency of the car body is from DC to 5Hz, and the magnitude of acceleration is 9.
, within 8m/see”, or within the handlebar, etc.↓
The resulting lateral acceleration is 9.8 m/sec at DC ~ 5 Hz.
On the other hand, the vibration on the springs of the wheels varies depending on the car model, but it is said to be within 25 Hz at DC to 20 Hz.
m/see" or less.

The acceleration sensor, whose purpose is to detect these acceleration ranges and control the posture of the vehicle, uses a temporary spring to act as an air damper to prevent the output signal from shifting due to the influence of dark vibrations of the vehicle. . In other words, when the leaf spring reaches the resonance point and the amplitude is about to increase, the inertial weight, which moves under the inertial force caused by acceleration, fills the small gap between the end of the leaf spring and the stationary side wall with air. The damping force due to the viscosity of the air as it moves acts, suppressing and reducing the amplitude.

If the amplitude level does not fall within the commonly used frequency band, for example, a low-pass filter can be added to the final stage of the electronic circuit to attenuate it.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the spring 1 is made of a negative plate and is separated into a stationary side and a movable side with a U-shaped groove 2 as a boundary, and a weight 4 having a permanent magnet 3 is attached to the movable side. Fix it. On the other hand, on the stationary side, the outside of the U-shaped groove 2 of the leaf spring is viewed from both sides by the frames 5, 5.
’ to hold it in place.

A small U-shaped groove 7 is formed on the side of the fulcrum 6 of the leaf spring, and the width of the fulcrum of the leaf spring 1 can be arbitrarily determined depending on the displacement to be set. The distance between the opposing walls of the frames 5, 5' and the movable part serves to prevent a load exceeding the allowable stress of the leaf spring 1 from being applied due to abnormal expansion of the sphere of the movable part. On the opposite surface of the frame 5, a Hall element 8 or a Hall element integrated circuit 8' is located at the center of the weight at the tip of the leaf spring 1, facing the permanent magnet 3 whose magnetic poles coincide in the direction of movement. It is fixed to a flexible wiring board 9, and one end is connected to the printed board 2.
6. Furthermore, the beam board 1 is removed from the printed board 26.
0 supplies power and extracts signals. Note that the frame body 5 side has a hole for fixing the acceleration sensor.

The output voltage is filtered through a low-pass filter 11 as necessary to eliminate resonance points in the low frequency range.

When the leaf spring 1 is made from two plates, there is a method of masking a phosphor bronze or stainless steel plate and dipping it in an etching solution to dissolve the U-shaped grooves 2 and 7 and the mounting hole 12tt. However, if the widths of the grooves 2 and 7 are to be made smaller, the etching mask may be left as is and the metal material 13 may be deposited, for example, by plating with copper or nickel.

Additionally, grooves may be processed using the heat of laser beams. Other methods of narrowing the groove width include a method of applying a resin film 14 to the groove portion of a leaf spring formed in advance, and a method of attaching and forming rubber 15 to the edge portion of the groove.

Alternatively, as shown in Figure 6, the shape of the weight may be flattened,
Margin of groove - may be by forming cup 16 9
It is also possible to press-form the leaf spring 1 having such a groove 2 with a small width. However, the groove width 2 is limited by the lifespan of the mold, etc., so if you want to make the groove width narrower, for example, you can divide the leaf spring into three parts and combine them to obtain a predetermined groove width. In some cases, it may be advantageous to configure the system so that it can be used. In addition, if the purpose cannot be achieved with just one leaf spring, the thickness of the plate can be made thinner to make it easier to machine the groove width of the predetermined dimension, and multiple leaf springs of the same shape can be stacked together and made into one piece. It can also be used as

without relying on the slight gap between the edge of the movable leaf spring and the stationary side.
The small gap between the movable part and the stationary part can also be formed using other methods and structures. In the case of Figure 7. This structure utilizes a gap 19 formed between the outer periphery 17 of the heavy peg 4 and the inner periphery of the stationary side recess 18. In addition, in the following example, two plates 20 and 20' are installed at a predetermined interval in the weight 4 part on the movable side, and the plate 21 on the stationary side is placed in the center of these plates, so that the space between them is It has a structure with small gaps. The example shown in FIG. 9 is the opposite of the concept shown in FIG. This structure has a smaller gap between the outer circumference and the outer circumference.

Fig. 10 shows a disc 24 with one end fixed to a movable part fitted into a recess 25 in a stationary side wall surface, and the fitted part has a single cantilever structure in which they face each other with a small gap. In addition to the leaf spring of , a leaf spring with a multiple support structure that is symmetrical around a weight can also have the same or similar structure.
A similar function can be achieved by forming a small gap between the movable side and the stationary side.

Next, the operation will be explained. As shown in Figure 2. When the heavy peg 4 receives an inertial force from the outside, a moment acts around the fulcrum 6 of the leaf spring, causing displacement.

For example, when the distance between the Hall element 8 and the permanent magnet 3 increases, the output voltage decreases from Voo to Vow in the graph shown in FIG. In other words, the acceleration sensor has detected negative acceleration. That is.

The relationship between the distance between the permanent magnet 3 and the Hall element 8 and the output of the Hall element is shown in the graph of Fig. 14. If the positive acceleration side corresponds to the shorter distance, the curve curves slightly downward. When the displacement of the leaf spring corresponding to the measured acceleration range is set small, the output voltage with respect to distance and the output voltage with respect to acceleration approach a straight line, as shown by the solid line in FIG. In other words, the acceleration applied to the inertial weight is proportional to the displacement of the leaf spring. Therefore, the fourteenth
As shown in the figure, when the leaf spring is displaced, the output voltage increases or decreases with respect to the output voltage Voo at the neutral point of the leaf spring, and the magnitude and direction of the acceleration can be read from the graph. When an acceleration sensor is fixed to the body of a car and detects acceleration during acceleration, deceleration, or turning, for example, the 14th
On the graph in the figure, the magnitude of acceleration during acceleration is V
It can be determined from the difference in output voltage in the negative direction from oo.

In such a case, the periodic fluctuation of the output is also relatively small, within DC~5I(z), and the acceleration detection range is also set to be at most ±1.OX9.8m/5ee2 or less.

However, the range of acceleration in the vertical direction of the vehicle body is wider, the frequency is DC ~ 20 Hz, and the acceleration is up to 2.5X.
It is said to be 9.8m'/5ec2. The frequency spectrum of the vertical acceleration of the vehicle body during engine operation or driving ranges from DC to IKHz, particularly from DC to 50Hz,
The frequency is higher in the order of 20 Hz to 100 Hz.

Therefore, an acceleration sensor having a resonance point in this range must have a structure that is not affected by these dark vibrations. - The U-shaped micro-gap groove formed in the plate is placed inside a closed chamber surrounded by a frame in which air exists. In this case, when a leaf spring moves together with a weight on which an inertial force is applied due to an external force, the pressure in one room increases as the volume decreases, and the pressure in the other room increases, with the leaf spring serving as the neutral point as a boundary. increases, so the pressure decreases. This difference in pressure causes air to move through the small gap at the edge of the leaf spring. At this time, a viscous damping force is generated that is generally proportional to the viscosity coefficient of the air and the length of the gap, and inversely proportional to the cube of the gap, and suppresses the movement of the leaf spring from increasing its amplitude. As the movement of the external force becomes faster, this viscous damping force increases almost proportionally, so it is possible to suppress the amplitude expansion at the resonance point of the leaf spring. If it cannot be suppressed completely as shown in FIG. 15a, it can be suppressed as shown in b by placing a low-pass filter at the final stage of the output signal. Conventionally, as shown in FIG. 16, an air damper has improved temperature dependence compared to an oil damper. This means that the viscosity coefficient of air is 1.86X10 at 20℃.
-8kgs/m”, 2.23X10-6Js at 100℃
/m2 and its rate of change is about 20%, which is about 1/10 of that of oil. Also, in the case of oil,
The viscosity coefficient tends to decrease as the temperature increases, but in the case of air, it tends to increase as the temperature increases.

According to one embodiment of the present invention, the following effects can be obtained.

1. A leaf spring to which a weight with a permanent magnet embedded can attenuate the amplitude of the resonance point by applying air damping using the small gap between the edge of the leaf spring and the stationary side wall. , it is possible to detect acceleration with high precision without being affected by background vibrations of the vehicle body.

2. Since a leaf spring with air damping is used, the temperature dependence of the damping is reduced, making it possible to detect acceleration with high precision without being affected by dark vibrations of the vehicle body.

3. The leaf spring that exerts air damping can be formed with a slight groove by laser beam cutting, etching, or a combination of etching and plating, so the grooves that affect damping can be formed with high precision. Processing is possible. It can also be done cheaply.

4. Rubber is baked or bonded to the edges of the grooves of the leaf spring where air damping is applied to increase the length of the passage through which air passes within the grooves, making it easier for damping to occur.

5. The leaf spring that causes air damping is made easier to effect air damping by machining a U-shaped groove on the negative plate and using a plurality of leaf springs stacked one on top of the other.

6. A leaf spring having a small gap for air damping can be divided into a plurality of parts, press-formed, and used in combination, making it possible to form grooves with high precision for damping.

7. A combination of the outer periphery of the weight on the movable side and a recess on the wall side, or a combination of a recess on the movable side and a protrusion on the wall side, or a combination of a disk fixed on the movable side and a recess on the wall side. Since air damping is applied, it is possible to detect acceleration with high precision without being affected by background vibrations of the vehicle body.

8. Set the distance between the end of the movable part and the wall to the default value in advance,
Since the stress applied to the fulcrum of the leaf spring can be suppressed below a certain level, the life of the leaf spring can be extended and its reliability can be improved.

〔Effect of the invention〕

According to the present invention, a highly accurate, reliable and inexpensive acceleration sensor can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation status of the movable part in FIG. 1, and FIG. 3 is a detailed explanatory diagram of the parts of the movable part in FIG. 1. Figure 4 shows the Q of the leaf spring in Figure 3.
Figure 5 is a detailed explanatory diagram of other parts of the movable part, Figure 6 is an explanatory diagram of the configuration of the movable part weight, and Figure 7 is a diagram showing the fit between the outer periphery of the weight and the recess on the wall side. An explanatory diagram of the mating state, Figure 8 is an explanatory diagram of the effect of the gap between the plates extending from the weight side and the stationary side,
FIG. 9 is an explanatory diagram of the fitted state between the weight-side recess and the outer periphery of the protruding portion on the wall side. FIG. 10 is an explanatory diagram of the fitted state between the disc fixed to the weight and the wall-side recess. Figure 11 is an external view of a leaf spring separated into multiple parts and press-formed, and Figure 12 is an external view of a leaf spring separated into multiple parts and pressed.
Figure 1 is a divided single-piece diagram of the leaf spring explained in Figure 1, Figure 13 is a block diagram showing the circuit configuration of the acceleration sensor, and Figure 14 is a block diagram showing the circuit configuration of the acceleration sensor.
Figure 15 is a graph showing the correspondence between the output characteristics of the acceleration sensor and dynamic output, Figure 15 is a graph showing a comparison of frequency characteristics before and after attenuation, Figure 16 is a graph showing the temperature dependence of transfer characteristics, and Figure 17 is a graph showing the correspondence between the output characteristics of the acceleration sensor and dynamic output. The figure is an external view showing an example of a leaf spring that is symmetrical around a weight. 1... Leaf spring, 2... Groove, 3... Permanent magnet, 4...
... Weight, 5... Frame, 5'... Frame, 6... Fulcrum, 7... Groove, 8... Hall element, 8'... Hall element integrated circuit, 9 ... Wiring board, 10... Lead,
11...Low pass filter, 12...Mounting hole, 13
...Metal material, 14...Resin film, 15...Rubber,
16... Flat weight, 17... Weight outer circumference, 18...
Hollow, 19... Gap, 20... Board, 20'... Board, 21... Board, 22... Hollow, 23... Projection, 24... Disk, 25... Hollow, 26...Printed board.

Claims (2)

[Claims] 1. A permanent magnet is fixed to the movable part of a leaf spring with a heavy stud,
In an acceleration sensor that detects acceleration caused by vehicle body vibration, sudden acceleration/deceleration, skidding, etc., by placing a Hall element on a partition wall facing the direction of movement of a permanent magnet, the leaf spring is a single plate. 1. An acceleration sensor characterized in that a long groove with a minute width is bored in the groove, the long groove is used as a boundary to separate a stationary part and a movable part, and a weight is fixed to the movable part. 2. A permanent magnet is fixed to the movable part of a leaf spring with a weight,
In an acceleration sensor that detects acceleration caused by vehicle body vibration, sudden acceleration/deceleration, skidding, etc., a Hall element is arranged on a partition wall facing the moving direction of a permanent magnet. An acceleration sensor characterized in that an elongated groove is formed at one or more places, and the inside of the elongated groove becomes a movable part having a weight, and the outside becomes a stationary part held by a frame.