JP3345694B2 - Gas type momentum sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a gas-type momentum sensor that detects a change state of a gas flow when momentum such as acceleration is applied.

[0002]

2. Description of the Related Art Conventionally, as a gas-type momentum sensor for detecting an angular velocity applied to a sensor body, for example, a heat-sensitive resistance element provided in a pair on the left and right in a gas passage from a nozzle hole in the sensor body by driving a pump. When the gas is ejected toward the heat wire pair consisting of: and when the gas flow flowing in the gas passage is deflected in the left and right direction due to the angular velocity motion applied to the sensor body, the difference between the respective thermal outputs generated by the heat wire pair , And each of the heat wires and a pair of reference resistance elements provided outside the gas passage are taken out as an unbalanced output from a bridge circuit provided in each branch, and then are output to the sensor body. The operating angular velocity is detected.

In such a conventional sensor, since the heat-sensitive resistance element is provided in a small space in the sensor, the resistance value (about 8Ω) of the heat-sensitive resistance element provided in the sensor body is provided outside. The resistance is set to be smaller than the resistance value of the reference resistance element (about 150Ω) (see Japanese Patent Publication No. 57-53545).

Further, for example, as a gas type momentum sensor for detecting an angular velocity applied to a sensor main body, a heat wire is provided inside the sensor main body, and gas is sealed inside the sensor main body, so that acceleration motion is applied to the sensor main body. Sensing the state of the gas flow caused by the heat wire,
An unbalanced output at that time is extracted from a bridge circuit formed by a heat wire and a reference resistance element provided outside, and the acceleration acting on the sensor body at that time is detected.

[0005] However, in such a gas type momentum sensor, since it senses the state of the gas flow in the sensor body as a change in the resistance value of the thermal resistance element, the detection sensitivity is changed by the change in the environmental temperature. It fluctuates.

Therefore, conventionally, the detection sensitivity is stabilized by placing the sensor body in a constant temperature bath, and the temperature correction of the detection value is performed by arithmetic processing using a sensitivity characteristic according to a preset temperature. However, the overall configuration is complicated.

Recently, as a gas type momentum sensor for detecting an angular velocity applied to a sensor main body, a sensor main body comprising a gas passage and a pair of heat wires provided in the gas passage is provided on a semiconductor substrate using an IC manufacturing technology. An ultra-small one in which the sensor main body is formed to have a size of several mm by machining has been developed (see JP-A-3-29858).

However, in such an ultra-small one,
In particular, the detection sensitivity does not fluctuate due to temperature changes by simple means without complicating and enlarging the sensor output without using the temperature correction means of the sensor output due to constant temperature of the sensor body or arithmetic processing. It is required to do so.

[0009]

A problem to be solved is a gas-type momentum sensor for detecting momentum such as angular velocity and acceleration applied to a sensor body, and the detection sensitivity may fluctuate due to a change in environmental temperature. If the temperature of the sensor output is corrected by the constant temperature of the sensor main body or the arithmetic processing so that the temperature of the sensor body is not increased, the overall configuration becomes complicated and large.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a gas-type momentum sensor, comprising: By setting the resistance ratio of the resistance element to an optimum range of 1 or more and 10 or less, the current flowing through the thermosensitive resistance element increases as the temperature increases, and the sensitivity adjustment according to the temperature change is automatically performed. I am trying to be.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of a gas type momentum sensor, an angular velocity sensor for detecting an angular velocity applied to a sensor body will be described below.

FIGS. 1 to 3 show a sensor body of a microminiature angular velocity sensor formed by micromachining a semiconductor substrate.

Here, the lower semiconductor substrate 1 and the upper semiconductor substrate 2 each having a half hole 31 forming the nozzle hole 3 and a half groove 41 forming the gas passage 4 connected thereto are formed in the semiconductor substrate by etching. The nozzle holes 3 and the gas passages 4 are formed by overlapping the half holes 31 and the half grooves 41 so as to abut each other and bonding them.

A gas passage 4 is formed in the lower semiconductor substrate 1.
Is formed, and a pair of heat wires 51 and 52 are pattern-formed on the upper surface of the bridge 6.

In the figure, reference numeral 7 denotes a pair of heat wires 51,5.
2 are electrode portions pattern-formed on the lower semiconductor substrate 1 on both sides.

FIG. 4 shows a configuration of a detection circuit portion of the angular velocity sensor.
A bridge circuit 10 in which a constant current source 9 is connected with a cold wire 81, 82 serving as a reference resistance element provided outside the sensor body in each branch, and an output when the bridge circuit 10 is unbalanced And an amplifier 11 for amplifying the voltage.

The cold wires 81 and 82 are pattern-formed by etching using the same material (for example, Pt) as the heat wires 51 and 52.

In the angular velocity sensor configured as described above,
An inert gas such as N ₂ or Ar is sent from a nozzle hole 3 of the sensor main body as a laminar flow toward a pair of right and left heat wires 51 and 52 in a gas passage 4 by a micropump (not shown). When the gas flow flowing in the gas passage 4 is deflected in the left-right direction due to the angular velocity motion applied to the air-conditioner, a detection signal corresponding to the difference between the respective thermal outputs generated in the pair of heat wires 51 and 52 is unbalanced from the bridge circuit 9. Taken as output.

However, in such an angular velocity sensor,
As described above, the detection sensitivity fluctuates due to a change in the environmental temperature because the state of the gas flow in the sensor body is regarded as a change in the resistance value of the pair of heat wires 51 and 52.

The main cause of the change in the detection sensitivity is that the thermal conductivity of the gas changes depending on the temperature. However, there is no gas whose thermal conductivity does not change, and the detection is performed by changing the type of gas. It has become difficult to cope with changes in sensitivity.

Therefore, in the present invention, the resistance ratio of the heat wires 51, 52 to the cold wires 81, 82 in the bridge circuit 10 is set in a range of 1 or more and 10 or less, and the current flowing through the heat wires 51, 52 depends on the temperature. The sensitivity is adjusted automatically.

The temperature difference between the heat wires 51 and 52 and the cold wires 81 and 82 during use is 150 to 25.
Since the difference is large at about 0 ° C., the apparent temperature resistance coefficients of the cold wires 81 and 82 are larger than those of the cold wires 81 and 82. Therefore, the change in the resistance value when the outside air temperature is changed is larger for the cold wires 81 and 82.

Therefore, when the bridge circuit 10 is driven at a constant current, the current flowing through the heat wires 51 and 52 increases with the temperature as shown in FIG. In that case, the heat wires 51 and 52 and the cold wire 8
The larger the resistance ratio HW / CW with respect to the temperature of the heat wires 51 and 52, the larger the current flowing through the heat wires 51 and 52 with respect to the change in temperature.

At this time, if the resistance ratio HW / CW between the heat wires 51, 52 and the cold wires 81, 82 is set to an appropriate value, the change in the detection sensitivity when the temperature changes is applied to the heat wires 51, 52. It can be compensated by the change in the flowing current.

The resistance ratio HW / CW between the heat wires 51, 52 and the cold wires 81, 82, which can effectively suppress the fluctuation of the detection sensitivity with respect to the temperature change, is 1 or more and 10 when used in a normal temperature environment. It is clear from actual measurement that the following is the optimum range.

FIG. 6 shows the characteristics of the detection sensitivity with respect to the gas flow rate when the external temperature is variously changed when the resistance ratio HW / CW = 0.2. FIG. 7 shows the resistance ratio HW /
In the case of CW = 1.36, the characteristics of the detection sensitivity with respect to the gas flow rate when the external temperature is variously changed are shown.

Here, comparing the characteristics of the two, it can be seen from FIG. 6 that the change in the detection sensitivity is 13
In FIG. 7, the change in the detection sensitivity is 3% or less for a temperature change of 0 to 80 ° C.
Fluctuations in detection sensitivity due to temperature changes are effectively suppressed.

According to the present invention, the state of the gas flow generated by the acceleration motion applied to the sensor main body is sensed by a heat wire, and a bridge circuit formed by the heat wire and a reference resistance element provided outside is used to detect the state of the gas flow. The same applies to an acceleration sensor that takes out the unbalanced output at the time and detects the acceleration acting on the sensor body at that time, or another sensor with a similar configuration. is there.

[0029]

As described above, in the gas type momentum sensor according to the present invention, no special means is separately provided.
By simply setting the resistance ratio of the thermal resistance element to the reference resistance element in the bridge circuit within the optimal range of 1 or more and 10 or less, the change in the detection sensitivity when the temperature changes is compensated by the change in the current flowing through the thermal resistance element. This has the advantage that the momentum such as the angular velocity and acceleration applied to the sensor body can be accurately detected without being affected by the temperature change.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration example of a sensor main body in an angular velocity sensor.

FIG. 2 is a plan view of a lower semiconductor substrate of the sensor main body shown in FIG. 1;

FIG. 3 is a front sectional view of the sensor main body shown in FIG. 1;

FIG. 4 is a diagram illustrating a configuration of a detection circuit unit in the angular velocity sensor.

FIG. 5 is a characteristic diagram showing a change state of a current flowing through a thermosensitive resistor with respect to a temperature when a resistance ratio of the thermosensitive resistor to a reference resistor in a bridge circuit is variously changed.

FIG. 6 is a diagram illustrating characteristics of detection sensitivity with respect to a gas flow rate when a temperature is set as a parameter when a resistance ratio of a thermosensitive resistor to a reference resistor in a bridge circuit is set to 0.2.

FIG. 7 is a diagram showing characteristics of detection sensitivity with respect to a gas flow rate when a temperature is set as a parameter when a resistance ratio of a thermosensitive resistor to a reference resistor in a bridge circuit is set to 1.36.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower semiconductor substrate 2 Upper semiconductor substrate 3 Nozzle hole 4 Gas passage 51 Heat wire (Thermal resistance element) 52 Heat wire (Thermal resistance element) 81 Cold wire (Reference resistance element) 82 Cold wire (Reference resistance element) 9 Constant current Source 10 Bridge circuit 11 Amplifier

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-255918 (JP, A) JP-A-2-22515 (JP, A) JP-A 2-55166 (JP, U) JP-A 58-58 32366 (JP, U) JP-B-57-53545 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 9/00 G01C 19/00

Claims (1)

(57) [Claims] 1. A sensor body using a bridge circuit in which a pair of heat-sensitive resistance elements provided inside a gas passage and a pair of reference resistance elements provided outside the gas passage are provided in each branch. A gas-type momentum in which the change in the gas flow in the gas passage when momentum such as angular velocity and acceleration is applied is detected by a pair of thermal resistance elements, and the momentum at that time is extracted as an unbalanced output of the bridge circuit. 2. The gas momentum sensor according to claim 1, wherein a resistance ratio of the heat-sensitive resistance element to the reference resistance element is set in a range of 1 to 10 in the sensor.