JPH04215068A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor which is simplified in structure, easily reduced in size, with improved shock resistance, and is eastoy set detecting sensitivity. CONSTITUTION:A pendulum 5 is vertically movably arranged in a housing 1 through a ball bearing 3. Coil springs 7 and 9 to normally hold the pendulum 5 in a given position and cause vertical movement of the penduclum 5 only when the housing 1 is vertically vibrated are provided. Meanwhile, an LED 11 to radiate light is located to the tip of the pendulum 5 and a photo position sensor 43 is located in a position opposite to the LED and through this arrangement, movement of the pendulum 5 is detected by a photo position sensor 43. The housing 1 is filled with silicon oil.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor, and particularly to an acceleration sensor suitable for detecting vertical acceleration of a vehicle to control suspension.

0002

[Prior Art] Conventionally, an acceleration sensor is equipped with a pendulum and an electromagnet for holding the pendulum in a predetermined position, and detects acceleration from the amount of current flowing through the electromagnet necessary to hold the pendulum in a predetermined position. There are known servo-type acceleration sensors that utilize the piezoresistance effect of semiconductor piezoelectric elements.

0003

[Problem to be Solved by the Invention] However, in the former servo-type acceleration sensor mentioned above, acceleration is determined from the current value of the electromagnet necessary to hold the pendulum in a predetermined position, so acceleration is detected with high accuracy. Although it is possible, the sensitivity is too high when used to detect the acceleration in the upper limit direction of the vehicle in order to control the vehicle's suspension.
There is a problem in that fine vibrations of the vehicle that are unnecessary for control due to unevenness of the road surface, etc. are detected, and control cannot be performed satisfactorily.

[0004] Furthermore, the servo-type acceleration sensor has a problem in that the structure of the servo system for detecting deviation of the pendulum from a predetermined position and controlling the energization of the electromagnet is complicated, making it impossible to miniaturize the sensor.

On the other hand, the latter semiconductor type acceleration sensor is
Since it can be manufactured by forming a cantilever on a silicon chip, it is easy to miniaturize the sensor, but since the cantilever needs to be very small, it is vulnerable to shock, and since a semiconductor is used, the detection characteristics are poor. There is a problem that it is easily affected by the ambient temperature, so it is not suitable for use in vehicle suspension control, etc.

The present invention was developed in view of these problems, and has a simple structure, can be easily miniaturized, and has high impact resistance.
The purpose of this invention is to provide an acceleration sensor whose detection sensitivity can be easily set.

[0007]

[Means for Solving the Problems] That is, the present invention, which has been made to achieve the above object, includes a photoconductive film and a resistor laminated on the photoconductive film, and a position where light is irradiated onto the resistor. an optical position sensor that outputs a signal according to a signal, a housing that is filled with oil, and is provided within the housing so as to be movable in a predetermined direction in response to vibrations of the housing, and irradiates light to the optical position sensor. An acceleration sensor comprising: a pendulum including a light emitting member; and a biasing member that generates a biasing force for holding the pendulum in a predetermined position within a housing.

[0008]

[Operation] In the acceleration sensor of the present invention constructed as described above, the pendulum is normally held at a predetermined position within the housing by the biasing force from the biasing member. On the other hand, when the housing vibrates, the pendulum moves in a predetermined direction in response to the vibration, and the position of the light irradiated from the light emitting member to the optical position sensor is displaced. Therefore, acceleration in a predetermined direction corresponding to the direction of movement of the pendulum can be detected from the detection signal of the optical position sensor.

[0009] Furthermore, since the oil sealed in the housing functions as a damper to suppress the vibration of the pendulum, the pendulum does not respond to high frequency components of the vibration of the housing. In other words, the oil sealed in the housing suppresses acceleration detection sensitivity.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. First, FIG. 1 shows the configuration of the acceleration sensor of this embodiment, and (
(a) is a cross-sectional view of the acceleration sensor viewed from the left, and (b) is a cross-sectional view of the acceleration sensor viewed from the front.

The acceleration sensor of this embodiment is installed in a vehicle to detect acceleration in the vertical direction of the vehicle body.As shown in FIG. 1, a ball bearing 3 is housed in a housing 1 filled with silicone oil. A pendulum 5 is provided so as to be movable in the vertical direction around the pendulum.

The pendulum 5 is biased vertically by two coil springs 7 and 9 as biasing members.
It is normally held at a balanced predetermined position by the biasing forces of the coil springs 7 and 9. In addition, an LED 11 as a light emitting member is embedded in the tip of the pendulum 5.
The light from the LED 11 can be irradiated to the outside as a spot light through a pinhole 13.

On the other hand, the housing 1 includes a housing main body 15 which is a box with the right side and back side open, and a bolt 17.
It consists of a side cover 19 attached to the right side via bolts 21, and a back cover 23 attached to the back via bolts 21. Each of these parts 15, 19, and 23 is made of conductive metal, and as described below, the LED
It functions as a ground electrode of 11.

The housing body 15 has a power supply electrode 2
A hole 27 for attaching the coil spring 9 is formed, and a protrusion 29 is formed, and one end of the coil spring 9 is connected to the protrusion 29. Further, a power supply electrode 25 is fixed to the hole 27 via an insulating seal 31 for sealing the inside of the housing 1 and insulating the power supply electrode 25 and the housing body 15. is connected to one end of the coil spring 7.

On the other hand, the other end of the coil spring 7 is connected to the pendulum 5 via an insulating resin 33, and the other end of the coil spring 9 is directly connected to the pendulum 5. and coil spring 7
is electrically connected to the positive electrode of the LED 11 via the lead wire 35, and the coil spring 9 is electrically connected to the negative electrode of the LED 11 via the lead wire 37 and the pendulum 5.

That is, in this embodiment, the coil springs 7 and 9 are
It is used to supply power to the ED 11, and by applying a predetermined power voltage of the power supply electrode 25 and grounding the housing 1, the LED 11 can be turned on.

Next, a support member 39 for supporting the pendulum 5 within the housing 1 via a ball bearing 3 is integrally molded on the side cover 19 of the housing 1.
9 is fixed to the housing body 15 by inserting the support member 39 into the housing body 15. Further, an O-ring 41 is provided at the insertion portion of the support member 39 into the housing body 15, so that the inside of the housing 1 can be sealed.

Further, an optical position sensor 43 is provided on the back cover 23 of the housing 1. And back cover 2
3, an oil seal packing 45 is disposed around the periphery of the optical position sensor 43, and the packing 45 is placed between the housing body 15 and a sensor mounting protrusion 47 formed on the housing body 15. attached. Therefore, the silicone oil is sealed inside the housing 1 by the housing body 15, the side lid 19, and the optical position sensor 43.

Next, the optical position sensor 43 is a well-known type that is manufactured by laminating a photoconductive film 51 such as an a-Si multilayer film on a substrate, and further laminating a resistor pattern 53 thereon. In this embodiment, in order to detect the irradiation position of the spotlight from the LED 11 provided on the pendulum 5, the resistor pattern 53 is arranged in an arc shape corresponding to the irradiation position of the spot light that changes as the pendulum 5 moves. It is formed.

The optical position sensor 43 applies a voltage to both ends of a resistor pattern 53 and irradiates a spot light onto the resistor pattern 53, thereby generating a potential according to the irradiation position. Therefore, three output electrodes 55, 56, and 57 are provided. Therefore, in this embodiment, each of these electrodes 55 to 57 is connected to an insulating resin 5.
The optical position sensor 43 is attached to the back cover 23 by being fixed to the back cover 23 via the optical fiber 8.

The structure and operation of the optical position sensor 43 are described in detail in, for example, Japanese Patent Laid-Open No. 59-229116, and are well known in the art, so a detailed explanation will be omitted.

In the acceleration sensor of this embodiment constructed as described above, when the housing 1 is stationary, the pendulum 5 is held in a predetermined position by the two coil springs 7 and 9; When the pendulum 1 vibrates in the vertical direction, the pendulum 5 moves up and down accordingly, and the position of the LED 11 provided at the tip of the pendulum 5 changes significantly.

For this reason, as shown in FIG.
By applying a DC voltage Va (for example, 5 V) to the optical position sensor 5 via the current limiting resistor R1 and grounding the housing 1, the LED 11 is turned on and the optical position sensor 4
A drive voltage Vb (for example, 5V) is applied between the output electrodes 55 and 57 of
) and activates the optical position sensor 43,
From the potential of the output electrode 56 of the optical position sensor 43, the irradiation position of the spot light, that is, the position of the pendulum 5 can be determined.

Therefore, by attaching the acceleration sensor to the vehicle body and inputting the potential of the output electrode 56 to the suspension control circuit via the buffer consisting of the operational amplifier OP1, the vertical movement of the vehicle to which the acceleration sensor is attached is controlled. It becomes possible to execute suspension control accordingly. Furthermore, the output voltage V from the operational amplifier OP1
As shown in FIG. 3, out changes linearly in response to vertical acceleration.

In addition, in the acceleration sensor of this embodiment, the movement of the pendulum 5 with respect to vertical acceleration is controlled by the coil springs 7 and 9.
The movement of the pendulum 5 due to minute vibrations is suppressed by the silicone oil sealed in the housing 1. Therefore, according to the acceleration sensor of this embodiment, as shown in FIG. 4, for example, a detection characteristic B having a lower responsive frequency than a detection characteristic A of a conventional servo type acceleration sensor can be obtained.

In addition, B in FIG. 4 shows that the viscosity of silicone oil is 1.
It shows the detection characteristics when it is set to 0 centipoise,
By increasing the viscosity of the silicone oil or adjusting the spring constants of the coil springs 7 and 9, the responsive frequency can be further lowered, and it is also possible to obtain detection characteristics that can be used as is for suspension control. In other words, in conventional suspension control, the vertical movement speed of the vehicle body as shown in C and D in Fig. 4 is determined by integrating the output signal from the acceleration sensor, and suspension control is performed based on this. According to the acceleration sensor of the embodiment, the sensitive frequency can be adjusted by adjusting the viscosity of the silicone oil, the spring constants of the coil springs 7 and 9, etc., so the acceleration sensor can obtain detection characteristics that can be used directly for suspension control without performing integration processing. It is also possible to create In FIG. 4, C represents the integral value of the detection signal A from the servo type acceleration sensor, and D represents the integral value of the detection signal B from the acceleration sensor of this embodiment.

In the above embodiment, two coil springs 7 are used as biasing members to hold the pendulum 5 in a predetermined position.
, 9 was used, but as shown in FIG. The pendulum 5 may be urged to a predetermined position by the repulsive force with the magnets 62 and 63.

In this case, the power supply electrode 25 is connected to the side cover 19.
A lead wire 3 connected to the positive electrode of the LED 11
5 through the shaft of the ball bearing 3 to connect the power supply electrode 25.
By connecting to the LED 11, power can be supplied to the LED 11. In this case, the repulsive force of each magnet is determined by the size and distance of the magnet, but this repulsive force can be easily adjusted by sliding the magnets 62 and 63 on the wall surface of the housing body 15. can. Moreover, rare earth metals may be used for the magnet.

Furthermore, since the repulsive force of the magnet is inversely proportional to the square of the distance, if the width of the resistor pattern of the optical position sensor is kept constant, the output characteristics will become saturated at large accelerations. Therefore, when using a magnet as an acceleration sensor, it is necessary to devise a pattern width of the optical position sensor. In other words, if the width of the resistor pattern of the optical position sensor is made thinner towards both ends, the output will change greatly with a small displacement of the pendulum in areas where acceleration is large, so when using a magnet as described above, In this case, it is necessary to adjust the width of the resistor pattern of the optical position sensor in this manner so that output characteristics corresponding to acceleration on a one-to-one basis can be obtained.

[0030] When the repulsive force of the magnet is used to hold the pendulum 5 in a predetermined position as described above, there is no member attached to the pendulum 5 as in the above embodiment.
The pendulum 5 moves more smoothly, and the holding position of the pendulum 5 can be easily adjusted.

Next, the pendulum 5 is shown in FIG. 1 or FIG.
As shown in FIG.
As shown in FIG. 2, the pendulum 5 may be composed of a light emitting section 71 provided with an LED 11 and two leaf springs 73 and 75 that support the light emitting section 71 so as to be movable in the vertical direction. In this case, the plate springs 73 and 75 function as biasing members like the coil springs 7 and 9 and the magnets 61 to 63, so
A special mechanism for holding the pendulum 5 in a predetermined position is not required, and the configuration can be made simpler.

In this case, one leaf spring 73 is
By using the lead wire D11 as a lead wire for the positive electrode and the other leaf spring 75 as a lead wire for the negative electrode of the LED 11, power can be supplied to the LED 11.

[0033]

As described in detail above, in the acceleration sensor of the present invention, the motion of the pendulum in response to acceleration is determined by the biasing force on the biasing member and the moment of inertia of the pendulum. Since the movement of the pendulum in response to minute vibrations is suppressed, detection sensitivity can be lowered compared to conventional servo acceleration sensors. Further, this detection sensitivity can be arbitrarily set by adjusting the viscosity of the oil sealed in the housing and the urging force of the urging member. Therefore, it becomes an optimal acceleration sensor for vehicle control such as suspension control.

Furthermore, since an optical position sensor is used to detect acceleration, it is possible to obtain detection characteristics that continuously change depending on the acceleration.Furthermore, the optical position sensor allows detection results to be taken out as a voltage signal. ,
A circuit for processing the detection signal is not required, and its structure is simplified. Therefore, the sensor can be made smaller.

Furthermore, since the vibration of the pendulum is transmitted to the optical position sensor by light and the optical position sensor is not subjected to mechanical impact, impact resistance can also be ensured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an acceleration sensor according to an example.

FIG. 2 is a circuit diagram showing the configuration of a detection circuit using the acceleration sensor of the embodiment.

FIG. 3 is a diagram showing acceleration detection characteristics obtained by the detection circuit of FIG. 2;

FIG. 4 is an explanatory diagram illustrating a comparison between the vehicle body vibration detection characteristics of the acceleration sensor of the embodiment and the vehicle body vibration detection characteristics of a conventional servo type acceleration sensor.

FIG. 5 is a cross-sectional view illustrating the configuration of an acceleration sensor using a magnet as a biasing member.

FIG. 6 is a partially cutaway perspective view illustrating the configuration of an acceleration sensor using a leaf spring as a part of the pendulum.

[Explanation of symbols]

1... Housing 3... Ball bearing 5... Pendulum 7, 9... Coil spring 11... LED
15...Housing body 19...Side cover 23...Back cover 25.
...Power supply electrode 43...Optical position sensor 51...Photoconductive film 53...Resistor pattern 55, 56, 5
7... Output electrodes 61, 62, 63... Magnet 71... Light emitting part 73, 75... Leaf spring

Claims (1)

[Claims] 1. An optical position sensor comprising a photoconductive film and a resistor layered on the photoconductive film, and outputting a signal according to a position of light irradiation on the resistor; and a housing filled with oil. , a pendulum provided within the housing so as to be movable in a predetermined direction in response to vibrations of the housing, and including a light emitting member that irradiates light to the optical position sensor, and holding the pendulum at a predetermined position within the housing. An acceleration sensor comprising: a biasing member that generates a biasing force for