JPH0640866U - Acceleration sensor - Google Patents

Abstract

(57) [Summary] [Purpose] The G sensor chip is forcibly vibrated to perform failure diagnosis of the G sensor chip and improve reliability. [Structure] An operating means for forcibly operating a mass holding portion provided on the free end side of a cantilevered G sensor chip is provided, and a signal for forcibly displacing the mass holding portion is provided to this operating means. Based on the signal from the strain gauge obtained when the G is applied, whether or not the G sensor chip is normal is diagnosed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a semiconductor type acceleration sensor used in automobiles and the like, and particularly to an acceleration sensor capable of improving operational reliability.

[0002]

[Prior art]

 As a conventional semiconductor acceleration sensor of this type, there is one having a structure as shown in FIGS. That is, reference numeral 1 denotes a package base plate, and the package base plate 1 is formed of a conductive member, and a pedestal 2 is fixed to the upper surface thereof. Further, on this pedestal 2, one end of a G (acceleration) sensor chip 3 formed in a rectangular shape in a plane is attached in a cantilever manner. As shown in FIG. 3, the sectional shape of the G sensor chip 3 is such that the central portion thereof is thin, and the strain gauge 4 is printed in a bridge shape on the upper surface of the thin portion, and the G sensor. It is composed of a thick mass holding portion 6 formed on the free end side of the tip 3. Reference numeral 7 denotes a lead terminal that penetrates the base plate 1 and is fixed to the base plate 1 via an insulator 8. The lead terminals 7 and the sensor circuits including the strain gauge 4 correspond to each other. They are connected via lead wires 9. Reference numeral 10 denotes a cap which is airtightly covered on the base plate 1 so as to cover the G sensor chip 3, the lead terminals 7, the lead wires 9 and the like. The space created between is filled with the silicone oil 11 for damping (mechanical resonance prevention).

[0003]

[Problems to be solved by the device]

 However, in the semiconductor type acceleration sensor having such a structure, when the sensor is subjected to the G direction operation shown in FIG. 3, the mass holding portion 6 is displaced (flexed), and as a result, the strain gauge 4 is strained. The G sensor chip 3 is broken due to the abnormal (excessive) impact force applied to this acceleration sensor, and the G sensor chip 3 is broken without notice. If it is used in, the acceleration sensor cannot detect proper acceleration.

Therefore, it is necessary to periodically check whether or not an abnormality has occurred in the G sensor chip 3, but since the inside of the acceleration sensor is hermetically sealed, the state of the G sensor chip 3 is visually checked ( There was the inconvenience of not being able to diagnose abnormalities.

[0005]

[Means for Solving the Problems]

 This invention has been made in order to eliminate such inconvenience, and an operating means for forcibly operating the mass holding portion provided on the free end side of the cantilevered G sensor chip is provided. An acceleration sensor capable of diagnosing whether or not the G sensor chip is normal based on the signal from the strain gauge obtained when a signal for forcibly displacing the mass holding unit is given to the operating means. To provide.

[0006]

【Example】

 The present invention will be described in detail below based on the embodiment shown in FIG. 1. The same parts as the structure of this embodiment and the structure described in the conventional example are designated by the reference numerals used in the conventional example. The description of the same structural parts will be omitted, and only different parts will be described.

That is, in this embodiment, the pedestal 2 ′ of the G sensor chip 3 is formed of an electrically insulating member such as glass and has a predetermined capacitance (capacitance) between the pedestal 2 ′ and the metal conductive base plate 1. Are formed. Further, the G sensor chip 3 and the base plate 1 are connected to an external circuit by lead wires (not shown) and lead terminals connected to the G sensor chip 3 and the base plate 1, which are periodically or as needed. A sinusoidal signal from is supplied.

A capacitor formed by the G sensor chip 3 and the base plate 1 constitutes a diagnostic capacitance means.

The above is the configuration of this embodiment, and its operation will be described below.

When diagnosing whether or not the G sensor chip 3 is normal, a sine wave signal having a predetermined frequency is supplied from an external circuit between the G sensor chip 3 and the base plate 1, An electrostatic force that fluctuates at the same frequency as the sine wave signal is generated between the two. As a result, since the G sensor chip 3 is cantilevered and fixedly supported, the free end vibrates in the vertical direction, and the vibration of the mass holding unit 6 impairs the bridge balance of the strain gauge 4, resulting in a sensor output. Change.

Therefore, the maximum vibration amount, the vibration frequency, the vibration waveform, etc. of the G sensor chip 3 when the G sensor chip 3 is normal (when the breakage or the like does not occur) are stored in an external memory (not shown). By comparing the output of the strain gauge 4, which is the sensor output, with the data stored in the external memory, it is possible to quantitatively detect the degree of deterioration of the operating characteristics of the G sensor chip 3.

Since the G sensor chip 3 is made of a semiconductor and has a larger resistance value than a conductor such as aluminum, a conductive metal such as aluminum is vapor-deposited on the surface of the G sensor chip 3. Then, an electrically conductive layer may be formed.

Further, when the electric resistance value between the G sensor chip 3 and the base plate 1 is constantly measured, for example, when the G sensor chip 3 is broken or comes into contact with the base plate 1, Since it can be detected instantly, it is a very effective fault diagnosis method when combined with the fault judgment using the electrostatic force.

[0014]

[Effect of device]

 As explained above, according to the present invention, the mass holding member 6 is forcibly operated by the diagnostic means to detect the output from the sensor by this operation, and this output value and the previously known normal sensor By comparing the output values from the sensors, it is possible to effectively detect the damage or deterioration of the G sensor chip 3, and thus the reliability of the acceleration sensor itself and the use of this acceleration sensor, for example, in an airbag system. The effect is that the reliability can be greatly improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of a sectional structure of an acceleration sensor according to the present invention.

FIG. 2 is a plan view illustrating a conventional acceleration sensor.

FIG. 3 is an explanatory view of a sectional structure of a conventional acceleration sensor.

[Explanation of symbols]

 1 Base Plate 2, 2'Pedestal 3 G Sensor Chip 4 Strain Gauge 5 Acceleration Detecting Section 6 Mass Holding Section 7 Lead Terminal 8 Insulator 9 Lead Wire 10 Cap 11 Silicon Oil

Claims (1)

[Scope of utility model registration request] 1. An acceleration sensing part (5) which is rectangular and at least one side of which is fixedly supported by a base plate (1) via a pedestal 2 and which is provided with a sensor (4).
In the acceleration sensor having the G sensor chip (3) in which the mass holding portion (6) and the mass holding portion (6) are integrally formed,
Is formed of an electrically insulating material, and a diagnostic capacitance means is formed by both the base plate portion (1) and the G sensor chip (3).