JPS6033057A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To improve detection precision by providing a weight attached by a support member and a circuit which calculates the difference in output frequency between two oscillation circuits which oscillate two piezoelectric vibrators, and measuring acceleration from the output of the circuit. CONSTITUTION:When an acceleration sensor moves with acceleration alpha as shown by an arrow A, the tensile strength applied to a left-side crystal resonator 3 becomes F0-malpha, and the tensile strength applied to a right-side crystal resonator 4 becomes F0+malpha. Consequently, the tensile force applied to the crystal resonator 3 decreases, so the output frequency of the crystal oscillation circuit 10a increases up to f3=f0+DELTAf. Further, the tensile strength applied to the crystal resonator 4 increases, so the output frequency of the crystal oscillation circuit 10b decreases to f4=f0-DELTAf. Consequently, the acceleration alpha is calculated through a mixer 10c from two-fold output frequency variation. Thus, a high-precision measurement of the acceleration is taken.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acceleration sensor that measures acceleration.

An example of a conventional acceleration sensor is one in which a weight is supported by a cantilever beam or the like, and the strain of the cantilever beam due to acceleration is converted into a change in electrical resistance using a resistance wire strain meter or the like and measured. This type of acceleration sensor measures electrical resistance, so it is difficult to adjust the electrical resistance when replacing a resistance wire strain gauge, and there is little compatibility. Another drawback was that the accuracy of detecting minute accelerations was poor. Furthermore, when connecting acceleration information to a computer or the like, an AD converter was required.

The present invention eliminates the above-mentioned drawbacks and provides an acceleration sensor that has excellent compatibility, high detection accuracy, and is capable of direct digital processing.

An embodiment of the present invention will be described in detail below.

In FIGS. 1 and 2, reference numeral 1 denotes a lamic substrate as a base, and by firing a conductive paste, an incoming cover turn 2α, 2bl and an outgoing cover turn 2c are formed.

Polar pattern 2d, retention pattern 2g, 2/, 21.2
h is provided. 3 and 4 are AT-cut crystal oscillators that are piezoelectric oscillators, and have a thickness sliding vibration.

It is something that performs actions. The longitudinal direction of crystal oscillator 3.4 is X
It has a rectangular shape that coincides with the axis, and the drive electrode 3 is mounted on the ambiguous surface.
α, 3α, 4α, 4α are formed. 5, 5, 6.6
is a retaining spring, which is made of phosphor bronze, stainless steel, or the like. One end of the holding springs 5, 5 is a drive electrode 3α of the crystal resonator 3.

3α in a conductive state, and the other end is fixed in a conductive state to each of the holding patterns 2g and 2f of the substrate 1. In this way, the crystal resonator 3 is attached to the holding spring 5,
It is held cantilevered by 5. One end of the holding spring 6 is fixed to each of the drive electrodes 4α, 4α of the crystal resonator 4 in a conductive state, and the other end is fixed to each of the holding patterns 21.2 of the substrate 1 in a conductive state. crystal oscillator 4
is thus held cantilevered by the holding spring 6.6,
Its free end faces the free end of the crystal resonator 3. Engagement pieces 7.7 are fixed to opposing free ends of the crystal oscillators 6, 4 by adhesive or the like. A support member 9 is stretched between the engagement pieces 7 and 7 and supports a weight of 1 mm.

In this embodiment, the support member 9 has a weight 8 fixed to its center, and coil spring portions 9α, 9α on both sides. The crystal oscillator 5.4 has holding springs 5, 5, 6. ．． 5. Engagement piece 7
．． 7 and 10 are coated to prevent the resonant frequency from changing due to the influence of moisture. Reference numeral 10 denotes an integrated circuit element, which includes two oscillation circuits 10α and 10b that respectively oscillate a crystal resonator 3.4, and a mixer 10C that indicates the difference in output frequency and polarity of these oscillation circuits. Oscillation circuits 10α, 10h and mixer 10C are connected as shown in FIG. Figure @4 shows the rate of change Δf/f of the resonant frequency when an external force F is applied to the AT-cut crystal resonator Q. Straight! j 11 indicates the rate of change when pressing force F is applied to the crystal oscillator Q in the X-axis direction, approximately 0.1 to 0.2 P P M / g
indicates the value of In addition, a straight line 12 indicates the rate of change when a pushing force F is applied to the crystal resonator Q in the 2'-axis direction, which is approximately -0,
06P P M / (indicates the value of i. If opposite tension is applied to the crystal oscillator Q, the sign of the above value will be the opposite rate of change.

Next, measurement of acceleration using the acceleration sensor of the present invention will be described. The crystal oscillators 3 and 4 are the same type of AT-cut crystal oscillators, and have substantially the same temperature characteristics, aging characteristics, and the like. The output frequency of the crystal oscillator circuits 10α and 10h is the same when the acceleration is 0, that is, when the crystal oscillator 3
, 4 is set to be 10 when the tension applied to Fo is approximately equal. Now, when the acceleration sensors shown in the first and second figures move in the direction of arrow A with acceleration α, the tension applied to the left crystal oscillator 3 becomes F o-mα, which is applied to the right crystal oscillator 4. The tension is Fo-1-mα
becomes. The longitudinal direction of the crystal oscillators 6 and 4 is the X-axis direction, and since the tension in the X-axis direction changes, the crystal oscillation circuit 10α,
The output frequency f3+f4 for 10h is the straight line 11 shown in the fourth diagram.
changes along.

In other words, since the tension applied to the crystal oscillator 3 decreases, the output frequency of the crystal oscillation circuit 10a increases /s''/
It becomes o+Δf. Furthermore, since the tension applied to the crystal resonator 4 increases, the output frequency of the crystal oscillation circuit 10b decreases to /4=10-Δf. The above Δf is the variation of tension α
It is proportional to 1Δ/''kmα゛.

The output of the mixer 10C is f, -f4 = 2Δf = 2kfrLα, and the acceleration α can be determined by the twice the output frequency change. Also, when acceleration acts in the direction opposite to the direction of arrow A, mixer 10
The output of C is -2ktILα, and the positive/negative determination is set to be output from the polarity pattern 2d. In this way, the magnitude and direction of acceleration are determined from the difference in the output frequencies of the two crystal oscillators.

Note that although a spring is used as an example of applying tension to the support member, the present invention is not limited to this, and the spring may be used only on one side.

The weight can be guided so as to be movable in only one direction, and acceleration sensors can be installed in the orthogonal directions of the y and z axes to measure the acceleration in each axis direction.

Further, the integrated circuit element may be molded using a molding material, and the integrated circuit element may also be sealed with a sealing cap or the like, including the two crystal oscillators.

As described above, according to the present invention, highly accurate and highly sensitive acceleration measurement is possible, power consumption is extremely low, and acceleration information can be directly digitally processed without an A-D converter. It also has the advantage of having little change over time and excellent compatibility.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, with FIG. 1 being a plan view and FIG.
The figure is a front view, FIG. 3 is a block diagram, and FIG. 4 is a characteristic diagram showing the rate of change in resonance frequency when an external force is applied to the AT-cut crystal resonator. 6.4... Crystal resonator 8... Weight Weight 9... Support member 9α... Coil spring portion 101Z, 10h... Oscillation circuit 10C...・Mixer and above Applicant: Seikosha Co., Ltd.

Claims (1)

[Claims] Two piezoelectric vibrators, a support member stretched between the two piezoelectric vibrators, a weight attached to the support member, and each of the two piezoelectric vibrators. An acceleration sensor comprising two oscillator JR circuits that oscillate, and a circuit that takes the difference in the output frequencies of the two oscillation circuits, and that measures acceleration based on the output of the circuit that takes the difference in the output frequencies. .