JPH0620973Y2 - Thermal flow sensor - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a heat-sensitive flow sensor for detecting the flow rate of a fluid using a heat-sensitive resistor.

[Conventional technology]

2. Description of the Related Art A flow rate sensor of a type that detects a flow rate from a thermal equilibrium state of a bridge circuit including a heat sensitive resistor arranged in a fluid has been conventionally used.

FIG. 2 shows the structure of a conventional heat-sensitive air flow rate sensor, in which a measuring pipe line 2 is provided in a housing 1 serving as a main passage for air, and a thermosensitive resistor 3 and an air temperature sensor 4 are provided in the measuring pipe line 2.
Is installed. The heat sensitive resistor 3 has a flat plate shape in which a platinum thin film resistor is formed on a ceramic substrate, and the heat sensitive resistor 3 constitutes a bridge circuit together with the air temperature sensor 4 and the resistors R ₁ and R ₂ . On the other hand, both inputs of the differential amplifier 101 are connected to the connection points b and f of the bridge circuit,
The output of 1 is connected to the base of transistor 102.
The emitter of the transistor 102 is connected to one end a of the bridge circuit, and the collector of the transistor 102 is connected to the positive electrode of the power supply 103. The arrow 10 indicates the direction of air flow.

FIG. 3 shows a support structure for the heat sensitive resistor 3. A pair of conductive support members 5 also serving as electrical connection leads are erected on the inner circumference of the measurement pipe line 2. Both ends are supported by the support member 5 and arranged in parallel with the flow direction 10,
The locking portion 6 electrically connects the thermosensitive resistor 3 and the support member 5.

Since the operation of the conventional air flow rate sensor having the above-mentioned configuration is well known, its detailed description will be omitted. However, when the voltages at the connection points b and f become equal, this circuit reaches a balanced state, and at this time, the flow rate of the heat sensitive resistor 3 is increased. Current I _H corresponding to
_H is represented by I _H · R ₁ , and this voltage V _H is used as a flow rate signal.

[Problems to be solved by the invention]

The conventional thermal air flow sensor is configured as described above,
In order to improve the responsiveness to changes in the flow rate, a chip type resistor having a small heat capacity is used as the heat sensitive resistor 3. However, since the support member 5 is entirely in contact with both ends of the heat sensitive resistor 3, the support member 5 is different from the heat sensitive resistor 3 in comparison.
However, there is a problem in that the heat capacity becomes large, resulting in a decrease in flow rate detection sensitivity and deterioration in detection response.

The present invention has been made to solve the above problems, and an object thereof is to obtain a heat-sensitive flow sensor capable of improving detection sensitivity and response.

[Means for solving problems]

In the heat-sensitive flow rate sensor according to the present invention, the support member for supporting the heat-sensitive resistor has a shape that supports only the corners of the heat-sensitive resistor, and the heat-sensitive resistor is energized by a separately provided lead wire. It was done.

[Action]

Since the support member of the heat-sensitive resistor according to the present invention supports only the corner portion of the heat-sensitive resistor, its heat capacity is reduced and mechanical strength is maintained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows a support structure for a heat-sensitive resistor according to this embodiment, in which a pair of U-shaped support members 8 are erected opposite to each other in a measurement pipe line 2 made of an insulating material, and a pair of terminals 9 are provided outside thereof. Are set up facing each other. The tip of each support member 8 holds the square of the heat sensitive resistor 3. The thermal resistor 3 is supported parallel to the flow direction 10. Further, the heat sensitive resistor 3 and the terminal 9 are connected by a lead wire 7 for energization. The overall structure of the heat-sensitive air flow rate sensor is as shown in FIG.

In the above configuration, since the support member 8 only needs to support the corners of the heat sensitive resistor 3, the contact area between the two is small, the heat capacity of the support member 8 is also small, and the heat from the heat sensitive resistor 3 to the support member 8 is reduced. The amount of movement decreases. Therefore, the thermal equilibrium state can be accurately controlled, and the detection sensitivity and the responsiveness of detection can be improved. Further, even if the support member 8 is U-shaped, the mechanical strength is not impaired. The support member 8 is preferably formed of an insulating member having a low thermal conductivity, but may be made of metal.

[Effect of device]

As described above, according to the present invention, the support member that supports the heat-sensitive resistor in the fluid passage supports only the corner portion of the heat-sensitive resistor, so that the heat capacity of the support member can be reduced and the heat-sensitive resistor can be reduced. Since the contact area between the body and the support member can also be reduced, the amount of heat transferred from the thermal resistor to the support member can be reduced, and the thermal equilibrium state of the bridge circuit can be controlled accurately and quickly, and the detection sensitivity and detection response It is possible to improve the property. Further, since the support member supports the corner portion of the heat sensitive resistor, the support strength of the heat sensitive resistor is maintained.

[Brief description of drawings]

FIG. 1 is a perspective view of a support structure of a heat sensitive resistor of a heat sensitive air flow sensor according to the present invention, FIG. 2 is a configuration diagram of the heat sensitive air flow sensor, and FIG. 3 is a support of a conventional heat sensitive air flow sensor. It is a perspective view of a structure. 1 ...... housing, 2 ...... metering duct, 3 ...... thermal resistor, 4 ...... air temperature sensor, 7 ...... lead, 8 ...... support _member, R 1, _{R 2} ...... resistance. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] 1. A bridge circuit, which is disposed in a fluid passage and is composed of a flat plate-shaped heat-sensitive resistor and a plurality of resistors, and a bridge circuit that controls a current flowing to the heat-sensitive resistor and has a predetermined bridge circuit. Equipped with a control circuit that controls to maintain the heat balance of
A heat-sensitive flow rate sensor for detecting a flow rate from a thermal equilibrium, characterized in that a heat-sensitive resistor is supported in a fluid passage by a support member that supports only its corners, and a current-carrying lead wire is connected to the heat-sensitive resistor. Thermal flow sensor.