JPH022105B2 - - Google Patents

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. This type of acceleration sensor measures electrical resistance, so it is difficult to adjust the electrical resistance when replacing the resistance wire strain gauge.
It lacked 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, 1 is a ceramic substrate as a base, and by firing a conductive paste, input patterns 2a, 2b, output patterns 2c,
Polar pattern 2d, holding patterns 2e, 2f, 2
g, 2h are provided. 3 and 4 are AT-cut crystal oscillators that are piezoelectric oscillators, and perform thickness-shear vibration. The crystal oscillators 3 and 4 have a rectangular shape whose longitudinal direction coincides with the X axis, and drive electrodes 3a, 3a, 4a, and 4a are formed on both main surfaces. Reference numerals 5, 5, 6, and 6 are holding springs, which are made of phosphor bronze, stainless steel, or the like. One end of the holding springs 5, 5 is connected to the drive electrode 3 of the crystal resonator 3.
a, 3a, respectively, in a conductive state, and the other end is fixed, in a conductive state, to each of the holding patterns 2e, 2f of the substrate 1. In this manner, the crystal resonator 3 is held cantilevered by the holding springs 5, 5. One end of the holding springs 6, 6 is fixed to each of the drive electrodes 4a, 4a of the crystal resonator 4 in a conductive state, and the other end is fixed to each of the holding patterns 2g, 2h of the substrate 1 in a conductive state. The crystal resonator 4 is thus held cantilevered by the holding springs 6, 6, and 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 3, 4 by adhesive or the like. A support member 9 for supporting a weight 8 having a mass m is stretched between the engagement pieces 7, 7. Support member 9
In this embodiment, a weight 8 is fixed to the center,
Both side portions are coil spring portions 9a, 9a.
The crystal oscillators 3, 4, including the holding springs 5, 5, 6, 6 and the engaging pieces 7, 7, are coated with Teflon to prevent the resonance frequency from changing due to the influence of moisture or the like. Reference numeral 10 denotes an integrated circuit element, which includes two oscillation circuits 10a and 10b that oscillate crystal oscillators 3 and 4, respectively, and a mixer 10c that indicates the difference in output frequency and polarity of these oscillation circuits. Oscillation circuits 10a, 10b and mixer 10c are connected as shown in FIG. Fourth
The figure shows the rate of change Δf/f of the resonance frequency when an external force F is applied to the AT-cut crystal resonator Q.
A straight line 11 indicates the rate of change when a pushing force F is applied to the crystal oscillator Q in the X-axis direction, which is about 0.1 to
Indicates a value of 0.2PPM/g. Further, a straight line 12 indicates the rate of change when a pushing force F is applied to the crystal resonator Q in the Z'-axis direction, and shows a value of about -0.06 PPM. If an 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 resonators 3 and 4 are AT-cut crystal resonators c of the same type, and have substantially the same temperature characteristics and aging characteristics. The output frequency of the crystal oscillator circuits 10a and 10b is set to be f _{0 when the acceleration is 0, that is, when the tensions applied to the crystal oscillators 3 and 4 are F 0 and} substantially equal. Now, when the acceleration sensors shown in the first and second figures move in the direction of arrow A with acceleration a, the tension applied to the left crystal oscillator 3 becomes F ₀ -ma,
The tension applied to the right crystal oscillator 4 is F ₀ +
Become ma. The longitudinal direction of the crystal oscillators 3 and 4 is the X-axis direction, and since the tension in the X-axis direction changes, the output frequencies ₃ and f ₄ of the crystal oscillator circuits 10a and 10b change along the straight line 11 shown in the fourth diagram. . That is, since the tension applied to the crystal oscillator 3 decreases, the output frequency of the crystal oscillation circuit 10a increases, and f ₃ = f ₀ + △f
becomes. Furthermore, since the tension applied to the crystal resonator 4 increases, the output frequency of the crystal oscillation circuit 10b decreases to become f ₄ =f ₀ -Δf. △f above is the change in tension
It is proportional to ma, and Δf=kma.
Then, the output of the mixer 10c is f ₃ −f ₄ =2△f=
2 kma, and the acceleration a can be found from the twice the output frequency change. In addition, when acceleration acts in the opposite direction to the direction of arrow A, the output of mixer 10c becomes -2 kma, and the polarity pattern 2d determines whether it is positive or negative.
Set it to output from. In this way, the magnitude and direction of acceleration are determined from the difference in the output frequencies of the two crystal oscillators.

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 orthogonal X-axis, Y-axis, and Z-axis directions to determine the acceleration in each axis direction.

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

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 AD converter. It also has the advantage of having little change over time and excellent compatibility.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view, FIG. 2 is a front view, FIG. 3 is a block diagram, and FIG.
The figure is a characteristic diagram showing the rate of change in resonance frequency when an external force is applied to the AT-cut crystal resonator. 3, 4... Crystal resonator, 8... Weight, 9... Support member, 9a... Coil spring part, 10a, 10b
...Oscillation circuit, 10c...Mixer.

[Claims]

1. A receiving section that receives the Loran C signal, a sampling signal generating means that outputs a sampling signal of a constant period, and a holding means that samples and holds the Loran C signal received by the receiving section based on the sampling signal. storage means for repeatedly storing the Loran signal information held in the holding means at every predetermined cycle of the Loran signal; and determining means for determining the presence or absence of the Loran C signal based on the Loran signal information stored in the storage means; An automatic detection device for a Loran C signal, comprising: a control means for controlling the operation of the sampling signal generation means, the holding means, the storage means, and the determination means.