JP2560715Y2 - Vibration sensor for compressor - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention utilizes a compressor using two piezoelectric elements.
The present invention relates to a vibration sensor for a compressor that measures vibration of a compressor.

(Prior Art) In recent years, attention has been paid to a noise silencing technique for suppressing noise emitted from a compressor disposed in a machine room to the outside. In such a noise reduction technique, a noise frequency emitted from a compressor is required as a calculation factor for performing a calculation for performing the noise reduction. Therefore, a vibration sensor is attached to a compressor, and the vibration sensor (corresponding to the frequency of noise from the compressor) is directly detected by the vibration sensor.
In this case, a piezoelectric element is generally used as a vibration sensor.

FIG. 5 shows an example of the piezoelectric element. In FIG. 5, the piezoelectric element 1 is polarized according to the applied pressure to generate a voltage, and a pair of a positive electrode 1a and a negative electrode 1b are formed in the polarization direction. And this piezoelectric element 1
Is fixed to a thin metal plate, and the metal plate is fixed to the compressor, whereby the metal is bent and deformed in response to the vibration of the compressor, and the vibration acceleration is applied to the piezoelectric element 1. Therefore, the piezoelectric element 1 is polarized with the vibration of the compressor, and a voltage signal corresponding to the vibration acceleration is generated between the electrodes 1a and 1b. Thus, the vibration of the compressor is detected based on the voltage signal output from the vibration sensor. be able to.

(Problems to be Solved by the Invention) Since the piezoelectric element has a pyroelectric effect that polarizes in response to a temperature change in addition to the piezoelectric effect, the compressor is operated intermittently according to the temperature of the freezing compartment. In the attached piezoelectric element, a pyroelectric effect occurs as the temperature of the compressor fluctuates in a short time. Therefore, the sixth
As shown in the figure, there is a problem that a noise voltage is generated in the piezoelectric element 1 in accordance with a temperature change of the compressor, and the detection of the vibration frequency of the compressor based on the voltage signal from the vibration sensor becomes inaccurate.

The present invention has been made in view of the above circumstances, and has as its object to provide a vibration sensor for a compressor that can accurately detect the vibration of the compressor without being affected by heat from the compressor that is intermittently operated. It is in.

[Structure of the Invention] (Means for Solving the Problems) The vibration sensor of the present invention includes two voltage elements that output a voltage signal according to an applied pressure from between first and second electrodes having different polarities. These piezoelectric elements are fixed to the compressor in an overlapping manner with the polarization directions of the respective piezoelectric elements coincident with the vibration direction of the compressor, and the first electrodes of the piezoelectric elements are connected in the fixed state. A fixing device is provided, and a weight corresponding to the vibration of the compressor is applied to each of the piezoelectric elements, and a weight attached to the fixing device is provided, and the fixing device is disposed in an open space separated from the compressor. In a state where the second electrodes of the respective piezoelectric elements are electrically connected to each other, a voltage signal is obtained from between the second electrodes and the first electrodes in the connection state.

(Operation) When the compressor is operated, the vibration sensor fixed to the fixture vibrates. At this time, since the weight mounted on the fixture tries to stay at that position, a pressure corresponding to the vibration is applied to the piezoelectric element according to the vibration of the compressor. Therefore, when the first electrode of the piezoelectric element is used as a reference, a voltage signal of the same polarity is output from the second electrode of each piezoelectric element, and a compressor is provided between the first electrode and the second electrode. A voltage signal corresponding to the vibration of the is output.

Thus, when the temperature of the compressor fluctuates, the temperature fluctuation is transmitted to the piezoelectric element. At this time, since the piezoelectric element is located in the open space and is fixed in an overlapping manner by being fixed to the open space separated from the compressor by the fixture, the temperature of the piezoelectric element changes at a constant gradient. ing. Therefore, in the two superposed piezoelectric elements, the voltage due to the pyroelectric effect generated between each first electrode and the second electrode has the opposite polarity, and therefore, the voltage between the first electrode and the second electrode is changed. The noise voltage due to the generated pyroelectric effect is nullified.

(Embodiment) A first embodiment in which the present invention is applied to a vibration sensor for a compressor will be described below with reference to FIGS.

A rotary compressor is installed in the refrigerator's machine room (not shown).
A vibration sensor 12 is fixed to the outer peripheral surface of the rotary compressor 11. This vibration sensor
Numeral 12 is provided for measuring the vibration frequency of the rotary compressor 11, and the measured vibration frequency of the rotary compressor 11 is used for noise reduction control.
That is, a speaker (not shown) is provided in the machine room of the refrigerator, and a sound having a phase opposite to that of the noise from the rotary compressor 11 is emitted from the speaker at the opening of the machine room. This is to muffle noise radiated from the opening to the outside. Therefore, in order to perform such silencing control, it is necessary to detect the frequency of the noise from the rotary compressor 11, and for that purpose, the vibration of the rotary compressor 11 is directly detected and used as a calculation factor when executing the silencing control.

Next, the vibration sensor 12 will be described in detail. That is, a stay 13 as a fixture is fixed to the rotary compressor 11 by welding, and a bolt 14 as a fixture is screwed to the stay 13. A weight 15 and two annular piezoelectric elements 16 and 17 are inserted into the bolt 14 by screwing a nut 18 in such a manner that the piezoelectric elements 16 and 17 are overlapped. Fixed to 13. This piezoelectric element 16
(17) polarizes according to the applied pressure and outputs a voltage according to the applied pressure between the positive electrode 16a (17a) and the negative electrode 16b (17b) (see FIG. 2). In this case, the rotary compressor 11
Vibrates along the direction of arrow A in FIG. 1, so that the polarization directions of the piezoelectric elements 16 and 17 mounted on the rotary compressor 11 match the vibration direction of the rotary compressor 11. As shown in FIG. 2, the superposed piezoelectric elements 16 and 17 are electrically connected to each other when the negative electrodes 16b and 17b come into contact with each other, whereby the negative electrodes 16b and 17b are connected to the first electrodes 16b and 17b.
Are set for the electrodes. In FIG. 1, 19 is a signal terminal plate, 20, 21 are ground terminal plates, 22, 23 are washers,
24 and 25 are electrical insulating plates. Here, the nut 18 may be omitted and the bolt 14 may be directly screwed to the stay 13. May be tightened.

On the other hand, each of the negative electrodes 16b, 17b is connected to the ground line 26a of the coaxial cable 26, and the positive electrodes 16a, 17a are connected to the core wire 26b of the coaxial cable 26 to conduct electricity. The electrodes 16a and 16b are set as the second electrodes. The core wire 26b of the coaxial cable 26 is connected to an amplifier circuit 27 of a signal processing circuit for silencing control.

 Next, the operation of the above configuration will be described.

When the sound of the freezer (not shown) rises above the set temperature,
The rotary compressor 11 is driven. Then, the outer peripheral surface of the rotary compressor 11 vibrates along the direction of arrow A shown in FIG. 1 and the vibration acceleration is applied to the vibration sensor 12. At this time, since the weight 15 tries to stay at that position, a pressure corresponding to the vibration acceleration is applied to the piezoelectric elements 16 and 17, whereby the piezoelectric elements 16 and 17 are polarized and are applied between each positive electrode and the negative electrode. Voltage is generated. At this time, since the same electrodes are connected to the piezoelectric elements 16 and 17,
The voltages generated at the negative electrodes 16b and 17b have the same polarity. Therefore, the compressor 16 is connected to the negative electrodes 16b and 17b of the piezoelectric elements 16 and 17.
Since a voltage signal corresponding to the vibration of 11 is generated, the voltage signal is output from the signal terminal board 19 via the coaxial cable 26 to the amplifier circuit 27 of the signal processing circuit for silencing control. As a result, the control sound for silencing is output from the speaker, and the noise from the compressor 11 is silenced in the opening of the machine room.

Now, with the operation of the compressor 11, the compressor
When the temperature of 11 rises, the piezoelectric elements 16, 1
The temperature of 7 rises, and accordingly, the piezoelectric elements 16 and 17 generate a pyroelectric effect and polarize. At this time, since the piezoelectric elements 16 and 17 are located in the open space, the temperature of the piezoelectric element 17 on the stay 13 side is high, while the temperature of the piezoelectric element 16 on the weight 15 side is low, and the temperature gradient is It is constant. As a result, the piezoelectric element 1
The polarization due to the pyroelectric effect of 6, 17 is caused by the negative electrode 16 in contact.
b, 17b are generated in the opposite direction with the boundary, so each piezoelectric element 1
The noise voltage due to the pyroelectric effect output from 6, 17 is canceled out at the signal terminal board 19 as shown in FIG.
Therefore, with the temperature change of the compressor 11, each piezoelectric element
The noise voltages generated at 16 and 17 are not output from the signal terminal board 19 to the signal processing circuit.

In short, according to the above embodiment, the noise voltage due to the pyroelectric effect generated in the piezoelectric element is reduced by the two piezoelectric elements 16 and 1.
Because it was made to invalidate using 7, unlike the conventional example that detects the vibration of the compressor with one piezoelectric element,
Based on the voltage signal output from the vibration sensor 12, the noise reduction control for the noise of the rotary compressor 11 can be reliably performed.

FIG. 4 shows a second embodiment of the present invention.
The same parts as those in the embodiment are denoted by the same reference numerals, and the description thereof will be omitted.
The different parts will be described below.

That is, an electromagnetic wave shield 28 is fastened together with the bolt 14, and the piezoelectric elements 16, 17 are covered with the electromagnetic wave shield 28. This electromagnetic wave shield 28 is a piezoelectric element
In addition to blocking electromagnetic noise that reaches 16 and 17,
It also has the function of the weight 15 in the embodiment. In this case, the ground terminal plates 20, 21 are connected by bolts 14.

In the case of the second embodiment, since electromagnetic wave noise that reaches the piezoelectric elements 16 and 17 from outside can be cut off by the electromagnetic wave shield 28, the vibration of the compressor 11 can be reliably detected. Moreover, such an electromagnetic wave shield
Even when the electromagnetic wave shield 28 is provided, the electromagnetic wave shield 28 also serves as the weight 15, so that the entire vibration sensor does not become large.

In the above embodiments, the stay 13 is fixed to the compressor 11 by welding. However, a heat insulating material such as a bake material or a ceramic material may be bolted to the compressor 11.

Also, a bolt fixing the vibration sensor 12 to the stay 13
The material of 14 may be changed to plastic, and a metal foil or a conductive sheet may be used as the electromagnetic wave shield 28.

Further, the present invention may be applied to vibration detection of a vibrating body such as a motor.

[Effects of the Invention] As is clear from the above description, according to the vibration sensor for a compressor of the present invention, by using two piezoelectric elements, the noise voltage due to the pyroelectric effect generated in these piezoelectric elements can be reduced. Since it is invalidated, there is an excellent effect that the vibration of the compressor can be accurately detected without being affected by heat from the compressor that is intermittently operated.

[Brief description of the drawings]

FIGS. 1 to 3 show a first embodiment of the present invention.
1 is a front view of a vibration sensor attached to a compressor, FIG. 2 is a perspective view showing a cross section of a piezoelectric element, and FIG. 3 is a relationship between a noise voltage generated in the piezoelectric element and a temperature change. FIG. FIG. 4 is a view corresponding to FIG. 1 showing a second embodiment of the present invention. FIGS. 5 and 6 are equivalent to FIGS. 2 and 3, respectively, showing a conventional example. In the figure, 11 is a compressor, 12 is a vibration sensor, 13 is a stay (fixing tool), 14 is a bolt (fixing tool), 15 is a weight, 16 and 17 are piezoelectric elements, 16a and 17a are positive electrodes (second electrodes). ), 16b and 17b are negative electrodes (first electrodes), 28 ... electromagnetic wave shields (weights).

Claims (1)

(57) [Scope of request for utility model registration] 1. Two piezoelectric elements for measuring the vibration of a compressor that is operated intermittently and outputting a voltage signal corresponding to an applied pressure between first and second electrodes having different polarities, These piezoelectric elements are provided so as to be fixed to each other in a superimposed state with the polarization directions of the respective piezoelectric elements coincident with the vibration direction of the compressor with respect to the compressor, and the first electrodes of the piezoelectric elements are fixed in the fixed state. And a weight attached to the fixture to apply a pressure corresponding to the vibration of the compressor to each of the piezoelectric elements, and the piezoelectric element and the weight integrated by the fixture Are arranged in an open space separated from the compressor, and the second electrodes of the piezoelectric elements are electrically connected to each other, between the second electrode and the first electrode in the connected state. Vibration sensor compressor, characterized by being configured to obtain a Luo voltage signal.