JPH0443792Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a vibration-type displacement sensor using a cantilever beam, and particularly to a vibration-type displacement sensor that has a simplified configuration and improved accuracy. .

<Prior art> An example of a prior art applied to an electropneumatic positioner will be explained with reference to FIG. A shows a longitudinal cross-sectional view of a vibrating displacement sensor coupled to an electropneumatic positioner, and B shows a plan view of the sensor portion. 1 is an operating valve driven by a pneumatic signal A from a pilot valve, 2 is a valve stem, and 3 is a lever for taking out the displacement of the valve stem, one end of which is rotatably fixed at a fulcrum 4, and the other end of which is connected to the valve stem 2. It engages with a clamp pin 201 attached to the valve stem 2, and converts vertical displacement of the valve stem 2 into a rotational displacement as shown by arrow B.

5 is a cantilever made of elastic material, with one end 50
1 is fixed to the support member 7 by bolts 6, 6',
A pin 8 formed on the other end side 502 and a pin 9 formed in the middle of the lever 3 are connected by a helical spring 10 constituting a displacement-force conversion means,
The displacement x of the lever 3 via this helical spring 10
is converted into a force F in a direction perpendicular to the cantilever beam 5 and applied to the other end of the cantilever beam 5.

Reference numeral 503 denotes a thin plate-like vibrating section formed near the fixed portion of the cantilever beam, and is realized by etching or the like on the diameter portion in the longitudinal direction of the through hole 504.

Reference numerals 11 and 12 denote a pair of piezoelectric elements bonded to both ends of the vibrating section 503. The voltage generated at 11 is applied to the input section of the amplifier 13, and the output of the amplifier 13 is polarized so that it becomes positive feedback. A positive feedback loop is formed, and vibration with a frequency f determined by a constant specific to the vibrating section 503 is continuously generated, and this vibration can be extracted from the output section of the amplifier 13 as an electric signal. Since the inherent constant that determines the vibration frequency changes with the tension T applied to the cantilever beam 5, the change in tension due to the force F can be detected as a change in the vibration frequency f, thus relating the displacement x to the vibration frequency f. be able to.

The input displacement x and the tension T are proportional, but the tension T and the vibration frequency f are not proportional, as follows.

T=Kx (1) f=P·√1+ (2) Here, K, P, and Q are constants determined by the dimensions and physical properties of the vibrating part. From equations (1) and (2), the relationship between f and x is as follows, when R=KQ, f=P·√1+ (3), and the displacement x and vibration frequency f have a nonlinear relationship.

<Problems to be solved by the invention> However, since these conventional vibrating displacement sensors use a helical spring to convert displacement into force, they easily respond to external vibrations.
Another problem is that the number of parts increases.

<Means for solving the problem> In order to solve the above problem, this invention includes a vibrating part formed near a fixed part of a cantilever beam with one end fixed, and a vibrating part formed at both ends of the vibrating part. A fixed pair of piezoelectric elements, an amplifying means in which these piezoelectric elements are connected to an input end and an output end to form an oscillation circuit, a leaf spring part formed on a part of a cantilever beam, and this plate. It consists of a cam mechanism that applies displacement to a spring portion, and is configured to extract an output corresponding to the displacement from the amplification means.

<Function> In this way, the present invention applies displacement to the cantilever beam via the cam mechanism, thereby outputting a vibration frequency corresponding to the tension generated in the leaf spring section.
A part of the cantilever beam can also be used as a leaf spring, and a vibration-type displacement sensor that is resistant to external vibrations can be obtained.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. Note that parts having the same functions as those in the prior art are designated by the same reference numerals, and their explanations will be omitted as appropriate.

Reference numeral 14 denotes a lever formed in an L-shape, and the tip 141 of one side of this L-shape is connected to the clamp pin 20.
1, and the other end 142 is rotatably fixed on the fulcrum 4. An arc-shaped cam 143 is formed at the tip of the other side of the L-shape.

The cantilever beam 15 is made of an elastic material, and the end portion 151 is fixed to the support member 7 with bolts 6, 6'.
The other end 152 is pressed by the cam 143 of the lever 14. Reference numeral 153 denotes a thin plate-like vibrating section formed near the end 151 of the cantilever beam 15, and is formed into a bridge shape by etching or the like at the diameter portion in the longitudinal direction of the through hole 154. Piezoelectric elements 11 and 12 are provided at both ends of the vibrating section 153.
is fixed by adhesive or the like, and constitutes an oscillation circuit together with the amplifier 13. A groove 153 is formed on the right side of the vibrating part 153, and a plate spring part 156 is formed, and the cam 14
3, the displacement Y of the end 152 of the cantilever 15 is converted into a force F.

With the above configuration, the vertical movement of the valve stem 2 converts the lever 14 into a rotational displacement as shown by the arrow B around the fulcrum 4, which causes a vertical displacement Y in the cam 143. The end portion 152 of the cantilever beam 15 is deformed due to the displacement Y, and the leaf spring portion 1
It is converted into force F at 56. Due to this force F, the tension of the vibrating part 153 changes, so that the natural frequency f
changes. As a result, a change in the natural frequency f corresponding to the displacement of the valve stem 2 can be obtained.

FIG. 2 is a block diagram showing another embodiment of the present invention. In the embodiment shown in FIG. 1, a normal cam is used to convert the rotational displacement B into a displacement Y.
43 and the end 152 of the cantilever 15 rub against each other, which is not very preferable. In the embodiment shown in FIG. 2, wear on the end 152 of the cantilever beam 15 can be reduced by utilizing the rotation of an eccentric cam 16 having an eccentric shaft l and a bearing 17 attached to its tip. It is something.

<Effects of the invention> As described above in detail with the embodiments, according to the invention, the displacement/force converting mechanism section and the force/frequency converting mechanism section are integrated into one unit because displacement is applied directly to the cantilever beam section. In addition to reducing the number of parts, the use of a cam mechanism allows the functional relationship between displacement and frequency change to be set arbitrarily. Furthermore, since the leaf spring portion is in contact with the cam via the end of the cantilever, vibrations from the outside are less likely to be transmitted than to conventional helical springs.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing one embodiment of the present invention;
This figure is a block diagram showing another embodiment of the present invention, and FIG. 3 is a block diagram showing the structure of a conventional vibration type displacement sensor. 1...operation valve, 2...valve stem, 5,
15... Cantilever beam, 7... Support material, 10... Spiral spring, 11, 12... Piezoelectric element, 13... Amplifier, 14... Lever, 16... Eccentric cam, 17
... Bearing, 143 ... Cam, 153 ... Vibration section, 156 ... Leaf spring section.

Claims (1)

[Scope of utility model registration request] A vibrating part formed near a fixed part of a cantilever beam with one end fixed, a pair of piezoelectric elements fixed to both ends of this vibrating part, and these piezoelectric elements connected to an input end and an output end. an amplifying means forming an oscillation circuit, a leaf spring portion formed on a part of the cantilever beam, and a cam mechanism for displacing the leaf spring portion, and outputting an output corresponding to the displacement from the amplifying means. A vibrating displacement sensor that is removable.