JPH04231878A - Detecting sensor for detecting acceleration and/or inclination of moving body - Google Patents

Abstract

PURPOSE: To make it possible to use the gradient and/or acceleration detecting sensor for a moving body for a passenger's protecting unit or navigation apparatus of a vehicle by enhancing the detecting accuracy of the sensor. CONSTITUTION: At least two heatable electric circuit elements 17, 18 sensitive to temperature and disposed oppositely in a hollow chamber 12 slightly filled with liquid of a casing 11 are moistened the same with the liquid 15 when a sensor 10 is disposed at the initial position where the acceleration and gradient of a moving body are equal to zero or the operations of the acceleration and gradient cancel to one another or the moistened states of at least the two elements 17, 18 are different by the acceleration or gradient of the body when the operations of the acceleration and gradient do not cancel to one another.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting acceleration and/or inclination of a moving body.

0002

[Prior Art] Unpublished German Patent Application No. 3939410
BACKGROUND OF THE INVENTION Heat-sensitive acceleration and inclination sensors are known from this document, which are fixed to a mobile object, such as a motor vehicle, for example. The casing forms a rotationally symmetrical hollow chamber which tapers conically upwardly. The hollow chamber is completely filled with liquid except for the bubble region. On the inside of the casing, on the cover plate, an electrical circuit element is provided, which is designed as an ohmic resistance element and forms part of the evaluation circuit of the sensor in the form of a Wheatstone bridge circuit. Furthermore, it is described that electrically heatable and temperature-sensitive electrical circuit elements are produced by thick film technology. The operation of the sensor is based on the fact that the resistance of the circuit element, which is designed as an ohmic resistor and is heated to a certain temperature, changes with a change in the amount of heat released. In the rest position, the circuit element is in thermal communication with the air bubble within the sensor. When the sensor is accelerated and/or tilted, the bubble moves and the circuit elements are surrounded by the liquid flow. Changes in heat dissipation conditions cause changes in the ohmic resistance of the circuit elements, and this change is detected by the evaluation circuit. This sensor is particularly suitable for threshold detection of tilt and acceleration of moving objects.

0003

Compared to the prior art, the sensor according to the invention has the advantage that the inclination and/or acceleration of a moving body can be detected particularly accurately. In the automotive field this not only makes it possible to use passenger protection equipment in the event of an accident, but also allows the use of navigation devices. Another one of the sensors of the invention for mechanically operated tilt and acceleration sensors
One advantage is that hysteresis due to friction does not occur and affect the measurement characteristics.

It is also an advantage that the temperature dependence of the sensor is very low, since the characteristics of the measuring resistors change identically to one another when the ambient temperature varies and only the resistance differences are evaluated. This allows the sensor to be used within a wide temperature range. The low dependence of the output signal on the liquid medium used is also an advantage. A further advantage is that the circuit cost required for signal evaluation is low.

[0005] In another embodiment of the invention, a significant advantage is achieved by mounting electrical circuit elements in the form of ohmic resistors in a bubble produced in thick-film technology and raised inside the cavity. brought about. In other words, this provides the advantage that the sensor responds quickly because the heat capacity of the thick film on which the resistive element is mounted is small. Furthermore, it can be produced inexpensively with hybrid technology, which makes it possible to advantageously integrate the evaluation circuit. It is a great advantage that the measurement accuracy of the sensor can be easily varied by adjusting the spacing between the resistive elements. A further advantage is that by mutually adjusting the geometrical dimensions of the sensor cavity and the liquid temperature, the damping characteristics of the sensor can be matched very easily to different applications. It is particularly advantageous to provide two resistors in each case on opposite sides of the sensor cavity and to connect these resistors to a bridge circuit. The circuit of FIG. 3 advantageously makes it possible to increase the amplitude of the output signal of the measuring bridge circuit and thus also makes it possible to increase the sensitivity of the sensor. Another advantage of this circuit is that the output signal is independent of ambient temperature. By manufacturing the resistive elements in thick-film technology and by suitably arranging these resistors, the tilt angle range and the sensitivity can be advantageously varied.

[0006]

EXAMPLES Next, the present invention will be explained in detail based on examples and with reference to the drawings.

In FIGS. 1A to 1C, a sensor is designated by 10 and has a casing 11 which defines a hollow chamber 12. In FIGS. The casing 11 may be rectangular or cylindrical, for example, or may have any other suitable shape. A gas 14 and a liquid 15 are present in the hollow chamber 12 of the sensor 10 to the extent that a liquid surface separating the liquid 15 from the gas 14 exists. Thick-film bubble bags 16 and 18 are raised into the hollow chamber 12 of the sensor 10 starting from the two side walls 131 and 132 of the casing 11 . One or more thick film bubble bags 16, 18 are provided on each of the side walls 131, 132. In this example, thick film bubble bags 16 and 1
two resistors 171, 172 and 191 respectively in 8
, 192 are integrated, and resistors 171, 172 and 1
91, 192 can be electrically heated and their resistance changes with temperature. In the initial position of the sensor 10, where the acceleration and tilt are equal to zero, or if the acceleration and tilt cancel each other out, the resistances 171, 172
and 191, 192, significant portions are wetted by the liquid 15. This means that both resistances 171 and 172
This means that the same heat release state prevails in and 191 and 192. Unlike FIG. 1A, where the sensor 10 is shown in its initial position, FIG. 1B shows the sensor 10 tilted by an angle α. In this case, the resistors 171 and 172 are wetted more widely with the liquid 15 than the resistors 191 and 192. Resistance 171, 172
and 191, 192 change in mutually opposite directions compared to the initial position, which causes the resistances 171, 192 to change in opposite directions.
The resistance values of 172, 191, and 192 change in opposite directions. The change in resistance depends on the tilt angle α and is detected by an evaluation circuit.

FIG. 1C shows a front view of side wall 131 of sensor 10. FIG. The shape of the side wall 131 is similar to that of the side wall 13
It corresponds to a side wall 132 located opposite to 1. Resistors 171 and 172 are each integrated within a thick film bubble bag 16. Resistors 171 and 172 are arranged such that resistors 171 and 172 are wetted to the same extent by liquid 15 in the rest position of sensor 10 . The liquid level in the rest position is designated by 21, and by 22 the liquid level surface corresponding to the deviation of the angle α shown in FIG. 1B.

In FIGS. 2A to 2C, the cylindrical sensor 1
A front view of the side wall 131 of 0 is shown. Side wall 132 located opposite side wall 131 is formed identically. In this sensor 10, two thick film bubble bags 161 and 162 are raised on side walls 131 and 132, respectively, located opposite to each other. Inside the thick film bubble bags 161 and 162, there are two resistive elements 171.1,
171.2 and 172.1 and 172.2 are arranged on the side wall 131 in such a way that these resistive elements are wetted by the liquid 15 to the same extent in the initial position of the sensor 10. In this example, resistor elements 171.1,1
71.2 and 172.1 and 172.2 are crescent-shaped and planar, and are located perpendicular to the liquid surface of the sensor 10, respectively. Thereby, it is possible to detect both a tilt around the sensor axis and a tilt around an axis perpendicular to the sensor axis. The sensor 10 can be constructed to respond with very high sensitivity by forming resistive elements on the sidewalls in a clever planar configuration. The operating principle of the sensor 10 of FIGS. 2A-C is based on the operating principle of the sensor 10 of FIGS. 1A-C. Unlike FIG. 1B, where the sensor 10 is tilted about an axis perpendicular to the sensor axis, in FIG. 2B the sensor is shown tilted about the sensor axis by an angle α. There is. Four resistive elements 171.1 on both side walls 131 and 132 of the sensor 10,
By arranging 171.2, 172.1, and 172.2, such an inclination angle can be detected.

In FIG. 2C, a longitudinal section through the sensor is shown. By adjusting the spacing of the side walls 131 and 132 containing the sensor resistance, the sensitivity of the sensor 10 to tilt about an axis perpendicular to the sensor axis can be adjusted. The larger the interval, the higher the measurement accuracy. Furthermore, the damping properties of the sensor 10 can be adjusted via the geometric dimensions of the sensor cavity 12 and the viscosity of the liquid 15.

In FIG. 3A, the sensor rich circuit 30 of the sensors A to C in FIG. 1 is shown. This device consists essentially of two parallel connected branches 31 and 3.
2, each branch 31 and 32 has a side wall 13.
1 resistor 171 or 172 and a resistor 191 of the side wall 132
or 192 are connected in series, that is, one branch 31 has resistors 171 and 191 connected in series, and the other branch 32 has resistors 192 and 172 connected in series. A constant voltage U is applied to both branches. Resistors 171, 172 and 191 and 192
are heated by the current flowing through these resistors. The resistance values of resistors 171, 172, 191 and 192 depend on temperature. The output voltage Ua is tapped and taken out between points 1 and 2 as a measurement signal. Point 1 is located above branch 31 and between resistor 171 and resistor 191. Point 2 is located above second branch 32 and between resistor 192 and resistor 172. The voltage Ua is the resistance 1 with respect to the resistance 171.
It becomes zero when the relative change in resistance value of resistor 91 is exactly the same as the relative change in resistance value of resistor 172 with respect to resistor 192. The resistors 171 and 172 are on one side wall 131 of the sensor cavity 12, the resistors 191 and 192 are on the other side wall 132 of the sensor cavity 12, and the two resistors on one side wall are shown in FIG. Since the sensor 10 is arranged as shown in C of 1, when the sensor 10 is tilted around an axis perpendicular to the sensor axis, the combined resistance value of the resistors 171 and 172 and the combined resistance value of the resistors 191 and 192 are and change inversely to each other. This increases the amplitude of the measurement signal Ua. All the resistors of the sensor rich circuit 30 are heated by a constant voltage, the characteristics of all the resistors change the same as the ambient temperature changes, and the temperature difference is evaluated, so this circuit arrangement is independent of the ambient temperature. Quite unrelated.

To detect the tilt of the sensor 10 about the sensor axis as shown in FIG. 2B, four resistors placed on the bubble bag are used as shown in FIG. 3B. You must connect it as if it were connected. In this case, resistors 171.1 and 172.1 varying oppositely to each other are connected in series above the branch 31 and corresponding resistors 191.1 and 192.1.
1 are connected in series above branch 32. The evaluation of the measurement signal is carried out according to the same principle as the circuit shown in FIG. 3A.

[Brief explanation of the drawing]

1 shows a longitudinal section of the sensor in the rest position and tilted by an angle α, as well as a front view of the sensor; FIG.

FIG. 2 shows a front view of the side wall of another sensor in its rest position and tilted by an angle α and a longitudinal section through the sensor;

3 is a circuit diagram of a circuit arrangement of the sensor of FIG. 1 and a circuit diagram of a circuit arrangement of the sensor of FIG. 2; FIG.

[Explanation of symbols]

10 Sensor 11 Casing 12 Hollow chamber 131, 132 Side wall 14 Gas 15 Liquid 16 Thick film bubble bag 18 Thick film bubble bag 161, 162, 181, 182 Thick film bubble bag 1
71,172,191,192 Resistance 30
sensor bridge circuit

Claims (1)

[Claims] [Claim 1] A casing forming a hollow chamber;
A mobile object, such as a car, which has a liquid that is not completely filled in the hollow chamber and an electrically heatable and temperature-sensitive electric circuit element as a component of the evaluation circuit. In a sensor for detecting acceleration and/or inclination, at least two heatable, temperature-sensitive electrical circuit elements (17, 19) located opposite each other in the hollow space (12) of the casing (11). However, the sensor (1
0), the two circuit elements (17, 19) are uniformly wetted by the liquid (15), and due to the acceleration and/or inclination of the moving body, the wetting state of at least two circuit elements (17, 19) is caused by the action of the acceleration and the action of the inclination. A sensor for detecting acceleration and/or inclination of a moving body, characterized in that the acceleration and/or inclination of a moving body are different when they do not cancel each other out.