JPH07209319A - Gas rate sensor - Google Patents

Abstract

PURPOSE:To make performance improvement and process control easy and suppress noises generating together with rate sensor output in a gas rate sesnor in which a sensor element is arranged within a sealing container filled with a gas so that a rate may be detected based on the change in output of sensor element that is generated by the change in gas flow when a rate is given from the outside. CONSTITUTION:A pump assembly 13 for a piezo-electric pump using a piezo-electric element and a flow sensor part 15 having a sensor element to which a discharge gas from the pump is given are separately arranged in this sensor, and the both are connected with each other by an accumulator 14 having a gas smoothing mechanism. In addition, the assembly 15 and accumulator 14 are connected with each other by means of an O ring, and a rubber tube is prepared on a slip-stream side of a discharging port for a gas flowing from the pump, then a rubber tube 18 having the same orifice is prepared at a discharge port for the accumulator 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas rate sensor used in a navigation system, a vehicle attitude control device, a robot such as a manipulator, or the like.

[0002]

2. Description of the Related Art A gas rate sensor includes a holder assembly having a flow sensor and the like in a hermetically sealed casing, a gas flow is jetted toward the temperature sensor of the flow sensor, and an angular velocity motion applied from the outside. The angular velocity (rate) is detected from the change in the sensor output that occurs when the gas flow is deflected by the influence of.

FIG. 8 is a sectional view showing the basic structure of such a conventional gas rate sensor. In the figure, 1 is a holder assembly having a flow sensor and the like inside,
Reference numeral 2 denotes a metal casing that accommodates the holder assembly 1, and the inside is hermetically sealed. A heater wire 3 for keeping a constant internal temperature is spirally wound on the outside of the casing 2 via an insulator, and a thermistor 4 as a temperature detecting element is attached to the outer surface of the casing 2 with an adhesive or the like. It is installed by.

The holder portion 1a of the holder assembly 1 holds temperature-sensitive elements 5a and 5b and a piezo plate (piezoelectric vibrating plate) 6 which constitute the flow sensor. Then, due to the pumping action of the piezo plate 6, the gas flows from the discharge port 7 between the holder assembly 1 and the casing 2 through the nozzle 8 at the end of the holder assembly 1 and enters the inside of the holder assembly as shown by the arrow in the figure. The road is formed.

In the gas rate sensor constructed as described above, the temperature sensitive elements 5a, 5b from the nozzle 8 to the flow sensor are provided inside the casing 2 sealed as described above.
A constant gas flow is ejected toward the. Then, when the influence of the angular velocity motion is applied from the outside, the gas flow is deflected. At this time, the output of the flow sensor changes, and by detecting this, the magnitude of the applied angular velocity can be detected.

Here, the basic shape of the conventional gas rate sensor is as shown in FIG. 8, and includes a pump portion composed of the piezo plate 6 and its periphery, and a flow sensor portion having temperature sensitive elements 5a and 5b. , The nozzle portion having the nozzle 8 is integrated as the holder assembly 1.
Then, the holder assembly 1 is housed in the casing 2, and the spaces 10a, 10b, 1 in the casing 2 formed when the holder assembly 1 is covered with the hermetic seal base 9 are formed.
0c serves as a reservoir for the slightly compressed gas discharged from the discharge port 7 when the pump is driven, and is an important constituent element that makes the gas flow through the nozzle 8 to the temperature sensitive elements 5a and 5b.

Therefore, the hermetic seal base 9
When the holder assembly 1 is removed from the casing 2 or when the holder assembly 1 is removed from the casing 2, the pump portion does not exhibit a pump function even when the pump is driven, and the gas flow from the nozzle 8 to the temperature sensitive elements 5a and 5b is also reduced. Does not occur.

Further, each of the above-mentioned spaces 10a, 10b, 10
c also has a function of smoothing the pulsation of the gas discharged from the pump part, and the gas blown out as a laminar flow from the nozzle 8 is sufficiently smoothed. Therefore,
For example, there is no problem in detecting the minimum sensing rate 0.02 deg / sec for an output having a sensitivity of 1 deg / sec = 50 mV.

FIG. 9 is a sectional view showing a basic structure of a conventional example in which an accumulator for smoothing a pulsating flow is integrally connected to the pump section. In this pump unit, a pump 102 assembled and configured using a piezo plate 101 and an accumulator 105 that is a hollow container are fixed by an adhesive,
A seal is provided to seal the gas.

With this structure, the gas sucked from the suction port 103 when the pump 102 is driven is discharged from the discharge port 1.
04, and the space 10 in the accumulator 105
Fill up to 6. At this time, the flow of the gas discharged from the discharge port 104 of the pump 102 is in a pulsating state with a high flow velocity, but the pulsating flow of the gas is smoothed in the space 106 in the accumulator 105, and further the accumulator 105. The flow is rectified at the discharge port 107 and flows to the flow sensor. As a result, it is possible to reduce noise in the output of the rate sensor and stabilize the offset drift.

Here, in order to reduce noise in the rate sensor output to a level at which there is no problem, the above structure requires an absolute volume of the accumulator 105. However, the capacity of the normal accumulator 105 as shown in FIG. 9 has a low ability to smooth the pulsating flow, and the silencing effect on the driving sound of the pump 102 is also low in this structure.

Therefore, due to this pulsating flow, the gas flow to the heat wire portion in the flow sensor becomes irregular and non-uniform, and at the same time, the gas flow is disturbed by the above-mentioned sound.
Further, since the heat wire further vibrates, the gas molecules may not be able to appropriately remove heat from the heat wire.

[0013]

By the way, in the conventional gas rate sensor as described above, since the pump portion and the sensor portion are integrally formed, it is not possible to individually evaluate each of them, so that performance improvement and There is a problem that process control is not easy, there is almost no degree of freedom in external shape and dimensions, and the cost is high.

That is, the performance of the gas rate sensor is determined to a considerable extent depending on the quality of the characteristics of the pump section and the sensor section. However, in the conventional case, the pump section is sealed together with the gas in the casing as described above. Since it functions only for the first time, it is not possible to individually evaluate the characteristics related to the flow rate of the pump section. Therefore, there is a problem that the performance cannot be known unless it is completed as a product, and it is difficult to select at the pump level and it is difficult to individually verify the pump. It is subject to significant restrictions.

Further, because of the integrated shape, there is almost no degree of freedom in the external shape and dimension, and the number of parts to be machined increases in order to secure dimensional accuracy, which is a factor of high cost.

Further, in the accumulator as described above, since the function of smoothing the pulsating flow of gas and the sound deadening function are insufficient, as a result, noise that cannot be ignored is added to the output of the rate sensor, and the minimum sensing rate, offset drift, etc. There was a problem that performance was inconvenient. At this time, the smoothing function of the pulsating flow and the muffling function can be enhanced by increasing the volume of the accumulator, but there is a problem that the overall structure becomes large and cannot be downsized.

Further, if a partition plate or an orifice plate is provided in the accumulator in order to enhance the sound deadening function, they act as a resistance against the flow of gas, the flow rate efficiency drops significantly, and only rate sensitivity is obtained. There is a problem that gas does not flow to the flow sensor. At the same time, the inside of the accumulator has a complicated structure, and assembly processing is added to the molding process, which increases component parts and process time, resulting in high cost. Further, when the assembly structure is adopted, durability reliability and airtightness of the adhesive portion become problems.

The present invention has been made by paying attention to the above problems. It is possible to individually evaluate the pump part and the sensor part, the performance improvement and the process control are facilitated, and the external shape and size can be freely selected. The purpose is to obtain a gas rate sensor that can be manufactured at a reduced cost.

It is another object of the present invention to obtain a gas rate sensor having a high performance and a high reliability, which is capable of suppressing noise on the output of the rate sensor with a small size and a simple structure.

[0020]

In the gas rate sensor of the present invention, the sensor element is arranged in a hermetically sealed container in which a gas is enclosed, and when the rate is applied from the outside, the gas rate sensor is generated by a change in the flow of the gas. In a gas rate sensor for detecting a rate applied from a change in the output of a sensor element, a pump section for generating a constant gas flow in the closed container, and a sensor section having the sensor element for receiving the gas flow. A separate structure is used, and the pump section and the sensor section are connected via an accumulator having a gas smoothing function.

Further, a step portion is provided on the outer periphery of the casing of the pump portion on the discharge port side, and a step portion corresponding to the step portion is provided on the inner periphery near the opening of the accumulator, and both step portions are sealing members. It is connected through.

Further, the piezoelectric pump of the pump section is formed by a piezoelectric vibrating plate using a piezoelectric element, and a tube constituting an orifice is provided after the discharge port of the gas discharged from the piezoelectric pump to the accumulator. .

[0023]

In the gas rate sensor of the present invention, the pump portion and the sensor portion are separated from each other and are connected to each other through the accumulator, and each can be individually evaluated.

Further, the gas discharged from the piezoelectric pump of the pump section to the accumulator is rectified and silenced when passing through the orifice of the tube provided after the discharge port.

[0025]

1 is an exploded perspective view showing the structure of a gas rate sensor according to an embodiment of the present invention. In the figure, 1
1 is the upper case. Reference numeral 12 is a stem that serves as a hermetic seal member.
In the inner space of the main body case formed by, there is a pump assembly (pump part) 13 for generating a constant gas flow in a closed container, and a sensor element (temperature sensitive element) for receiving the gas flow via an accumulator 14. The flow sensor unit 15 is stored.

The accumulator 14 has a function of smoothing the gas sent from the pump of the pump assembly 13 through the rubber tube 16, that is, a function as a filter for reducing the pulsating flow by the pump. It is connected to the assembly 13 via a rubber O-ring 17 which is a sealing member. Further, the flow sensor unit 15 includes the rubber tube 18 through the accumulator 14.
The nozzle 12 is fixed to the stem 12 via a ceramic substrate 19 provided with wiring, which includes a nozzle portion for ejecting the gas passing therethrough toward a sensor element.

Further, the pump assembly 13 has a stem 12 via a vibration-proof sheet 20 which absorbs the vibration of the pump.
The pump assembly 13 and the accumulator 14 are also connected to each other by screws.

2, 3 and 4 show a holder 21 and a bottom 22 which are components of the pump assembly 13 described above.
6A and 6B are diagrams showing the shapes of a piezo plate (piezoelectric diaphragm) 23. 2A is a top view, FIG. 2B is a front view, FIG. 2C is a side sectional view, FIG. 3A is a front view, FIG. 3B is a side sectional view, and FIG. 4A is a front view and FIG. 4B is a back view, and FIG. 4C is a view showing the polarization direction of the piezoelectric element 23a. Further, FIG. 5 shows the accumulator 1.
4A and 4B are views showing the shape of FIG. 4, in which FIG. 4A is a front view and FIG.

The pump assembly 13 is constituted by the holder 21, the bottom 22, the piezo plate 23, screws and a small amount of adhesive, and is formed as follows. That is, first, the piezo plate 23 is dropped into the inner diameter portion 21a of the holder 21, and the discharge hole 21
After aligning b with the orifice 23c, the bottom 2
The holder 21 is pressed by 2. And the holder 21
The four corners of each flange portion of the bottom 22 and the bottom 22 are evenly screwed and fixed. At this time, a silicone adhesive is applied to a portion where the piezo plate 23, the holder 21 and the bottom 22 are in pressure contact with each other, and is fixed after being screwed and fixed.

Next, the step portion 2 provided on the holder 21 of the pump assembly 13 assembled and formed as described above.
The above-mentioned O-ring 17 is fitted into 1c, and the accumulator 14 is covered. Then, the O-ring 17 is pressed by the step portion 14a provided in the accumulator 14, and both flange portions are screwed and fixed.

The piezo plate 23 forms a piezo pump (piezoelectric pump) of the pump assembly 13, and the diaphragm 23 is made of a material such as iron or nickel.
The above-mentioned piezoelectric element 23a is bonded to b. The piezoelectric element 23a is a bimorph type, and the vibration plate 23b
It is necessary for the hole processing to be free of burrs and warpage. Also, use a heat-resistant adhesive, 80 ℃
It is desirable that the adhesive be cured at a position, and it is desirable that the protrusion of the adhesive be small, and at the worst, it is necessary that the orifice 23c is not covered.

FIG. 6 is a sectional view showing in detail a state in which the above-mentioned pump assembly 13 and the accumulator 14 are connected. The arrows in the figure show the flow direction of the gas in the closed space, and the gas discharged from the discharge port 24 by the pumping action of the piezo plate 23 is rectified and silenced by the orifice of the rubber tube 25 in the subsequent stage, and the accumulator. 1
4 enters the discharge side volume 26, where the sound is silenced and decelerated. Further, the rubber tube 18 is configured so that it is further muffled and rectified by the orifice and ejected to the sensor element in the flow sensor section 15. A suction side volume 28 is provided at the suction port 27 of the pump.

The step portion 21c is provided on the outer periphery of the pump assembly 13 on the discharge side of the casing, and the step portion 21c is provided on the inner periphery of the accumulator 14 near the opening.
Is provided with a step portion 14a corresponding to
1c and 14a are connected via an O-ring 17.
Further, the bottom 22 of the pump assembly 13 is mounted on the bracket 3 via a damper member 29 similar to the vibration isolating sheet 20.
The bracket 30 is fixed to the pedestal 31 on the stem 12 via the vibration-proof sheet 20.

The above-mentioned sensor element is arranged in a hermetically sealed container in which a gas is sealed, but this sensor element is provided with a resistor which forms a bridge circuit with each pair of heat wires arranged in the hermetically sealed container as one side. It has been configured. Then, when the rate is applied from the outside, the temperature change of the heat ray generated by the change of the gas flow is converted into a resistance value change, and the applied rate is detected from the output change.

Further, the piezo pump comprising the piezo plate 23 generates a pressure difference by using the amplitude vibration of the vibration plate 23b obtained by applying the electric energy to the piezoelectric element 23a as a volume change, thereby moving the fluid (gas). It is a pump that makes it possible.

Here, in the above-mentioned embodiment, the pump assembly 13 and the flow sensor section 15 have a separated structure, and the pump assembly 13 alone can serve to send out the gas in a certain direction, that is, serve as a source of the gas flow. It has a structure. Therefore, the performance of the pump assembly 13 can be evaluated independently, but if the flow sensor unit 15 including the nozzle unit and the pump assembly 13 are connected directly or through a tubular shape, the rate sensor output is obtained. Non-negligible noise is introduced, which causes performance problems such as minimum sensing rate and offset drift.

Therefore, in this embodiment, the accumulator 1 which is a functional component for smoothing the gas discharged from the pump.
4 is inserted and connected between the discharge side of the pump assembly 13 and the inflow side to the nozzle located on the upstream side of the flow sensor unit 15, thereby eliminating the above inconvenience.

As described above, since the pump assembly 13 and the flow sensor unit 15 are separated from each other and connected to each other through the accumulator 14 having a gas smoothing function, the pump assembly 13 and the flow sensor unit 1 are connected.
5 can be individually evaluated, the performance can be improved and the process can be easily controlled, the external shape and dimension can be freely selected to some extent, and the cost can be reduced.

Further, in the above-mentioned embodiment, the smoothing function of the pulsating flow and the sound deadening function, the sealing property and the durability are maintained without deteriorating the moldability and the assembling property and greatly reducing the flow rate efficiency of the gas flowing to the flow sensor. The structure is improved.

That is, a rubber tube 25 having a tubular shape and an orifice at the tip is attached to the discharge port 24 of the pump assembly 13, and a rubber tube 18 of the same shape and material is also attached to the discharge port of the accumulator 14. . The pump assembly 13 and the accumulator 14 are connected by fitting an O-ring 17 between the step portions 21c and 14a of each other.

In such a structure, the rubber tube 25 is used for the gas discharged from the discharge port 24 of the pump section.
The pump driving sound is attenuated by the resistance action of the orifice of the above, and the sound transmitted to the gas is silenced by the sound absorbing effect of the rubber material. The flow rate of the gas discharged from the orifice of the rubber tube 25 is delayed due to volume expansion in the discharge side volume section 26 in the accumulator 14, whereby the flow rate distribution is made uniform and the pulsating flow is smoothed. . At the same time, due to this volume expanding action, a sound deadening effect also appears.

The rectified and silenced gas is further rectified in the rubber tube 18 by the same action as the rubber tube 25. The traveling direction of the gas to the rubber tube 18 is that of the rubber tube 25. Since the discharge direction is perpendicular to the direction of sound propagation from the sound source, the silencing effect is large. And the gas is this rubber tube 1
By passing through the orifice of No. 8, a rectified gas having a high flow velocity is obtained again, and this silenced and rectified gas flows to the flow sensor.

Further, since the suction side volume 28 is provided in the accumulator 14 with respect to the suction port 27 of the pump, the pump driving sound transmitted from the suction port 27 to the outside is attenuated and the flow sensor is less affected. Has become. At the same time, since the tube 18 is also made of rubber, the vibration of the piezo plate 23 transmitted from the pump through the body of the accumulator 14 is also absorbed and damped, and is not transmitted to the flow sensor.

FIG. 7 shows the noise characteristics of the above-mentioned pump discharge gas, and shows the discharge gas flow rate (SCC) at room temperature.
The relationship between M) and noise (dVB) is shown. The solid line A in the figure shows the characteristic of the present embodiment, and the broken line B shows the characteristic when the conventional accumulator is used, and there is a considerable difference in the magnitude of noise depending on whether or not the structure of the present embodiment is used. I understand.

As described above, with the structure of this embodiment, it is possible to suppress the noise on the output of the rate sensor with a small and simple structure, improve the sensitivity, and secure the stability of the offset drift. It is possible to obtain a gas rate sensor with high performance and high reliability.

The holder 21 and the bottom 22 of the pump assembly 13 are generally made of iron or aluminum. For example, iron-based powder molding can be used, but die casting, lost wax or the like may be used. . As for the accumulator 14, a resin molded product or the like is sufficient due to its nature, and the tubes 18, 2
As for 5, rubber molded products are also sufficient.

Further, the rubber tube 25 provided after the discharge port 24 of the pump portion may be of a single stage or of a plurality of stages.

[0048]

As described above, according to the present invention, the pump part for generating the gas flow and the sensor part for receiving the gas flow are separated from each other and are connected to each other through the accumulator having the gas smoothing function. Therefore, the pump part and the sensor part can be individually evaluated, performance improvement and process control can be facilitated, the appearance shape can be freely selected to some extent, and the cost can be reduced.

Further, since the piezoelectric pump is formed by using the piezoelectric element and the tube constituting the orifice is provided after the discharge port of the gas discharged from the piezoelectric pump to the accumulator, the rate is small and simple. It is possible to suppress noise carried on the sensor output, and it is possible to improve the performance and reliability.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing the configuration of an embodiment of the present invention.

FIG. 2 is an explanatory view showing the shape of a holder of the pump assembly.

FIG. 3 is an explanatory diagram showing the shape of the bottom of the pump assembly.

FIG. 4 is an explanatory diagram showing the shape of a piezo plate of the pump assembly.

FIG. 5 is an explanatory view showing the shape of the accumulator.

FIG. 6 is a sectional view showing a state in which the pump assembly and the accumulator are connected to each other.

FIG. 7 is a characteristic diagram showing noise characteristics of pump discharge gas.

FIG. 8 is a sectional view showing a configuration of a conventional example.

FIG. 9 is a sectional view showing the configuration of another conventional example.

[Explanation of symbols]

 13 Pump Assembly (Pump Part) 14 Accumulator 15 Flow Sensor Part 16 Rubber Tube 17 O-ring (Seal Member) 18 Rubber Tube 21 Holder 21c Step Part 22 Bottom 23 Piezo Plate (Piezoelectric Vibration Plate) 23a Piezoelectric Element 23b Vibration Plate 24 Discharge Port 25 Rubber Tube 26 Discharge Side Volume 27 Intake Port 28 Suction Side Volume

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Saito 2-14-1, Eda Nishi, Midori-ku, Yokohama-shi, Kanagawa Stanley Electric Co., Ltd. Yokohama Technical Center (72) Toshihiko Tsuboi, Eta, Midori-ku, Yokohama-shi, Kanagawa West 2-14-1 Stanley Electric Co., Ltd. Yokohama Technical Center (72) Inventor Kazuhiko Sugimura 2-14-1 Eda Nishi, Midori Ward, Yokohama City, Kanagawa Prefecture Stanley Electric Co., Ltd. Yokohama Technical Center (72) Inventor Shiraishi Katsu 2-14-1 Edanishi, Midori-ku, Yokohama-shi, Kanagawa Stanley Electric Co., Ltd. Yokohama Technical Center (72) Inventor Masayuki Takahashi 2-14-1, Edanishi, Midori-ku, Yokohama-shi, Kanagawa Pref. In the center

Claims (3)

[Claims] 1. A sensor element is arranged in a closed container in which a gas is sealed, and a rate applied from a change in output of the sensor element caused by a change in a flow of the gas when a rate is applied from the outside is measured. In the gas rate sensor for detecting, a pump part for generating a constant gas flow in the closed container and a sensor part having the sensor element for receiving the gas flow are separated structures, and the pump part and the sensor part are A gas rate sensor characterized by being connected via an accumulator having a gas smoothing function. 2. A step portion is provided on the outer periphery of the casing of the pump portion on the discharge port side, and a step portion corresponding to the step portion is provided on the inner periphery near the opening of the accumulator, and both step portions are provided with sealing members. It couple | bonded through through, The Claim 1 characterized by the above-mentioned.
The gas rate sensor described. 3. A piezoelectric diaphragm of a pump portion is formed by a piezoelectric vibrating plate using a piezoelectric element, and a tube constituting an orifice is provided after a discharge port of gas discharged from the piezoelectric pump to an accumulator. The gas rate sensor according to claim 1 or 2.