JPH0633377Y2 - Heat wire type flow meter - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a hot wire type flow meter suitable for use in detecting the intake air flow rate of, for example, an automobile engine.

[Conventional technology]

 3 to 6 show a conventional hot wire type flow meter.

In the figure, reference numeral 1 denotes an intake pipe, which is connected to, for example, an intake side of an automobile engine (not shown), and allows intake air to flow in the direction of arrow A toward the cylinder side of this engine. It has become. A mounting hole 1A is bored in the intake pipe 1 in the radial direction, and a fitting portion 2A of a circuit casing 2 described later is fitted in the mounting hole 1A.

Reference numeral 2 denotes a circuit casing provided on the outer peripheral side of the intake pipe 1 so as to close the mounting hole 1A of the intake pipe 1. The circuit casing 2 is formed of an insulating resin material, and the intake side is provided on the bottom side thereof. A fitting portion 2A that fits into the mounting hole 1A of the pipe 1 is provided. The circuit casing 2 has an insulating substrate (not shown) made of, for example, a ceramic material.
Further, a flow rate adjusting resistor 12, a reference resistor 13, a differential amplifier 18 and the like, which will be described later, mounted on this substrate are built in.

3 is provided in the circuit casing 2, and the circuit casing 2
2 shows an intake pipe radially projecting from the fitting portion 2A into the intake pipe 1, and the intake pipe 3 is made of an insulating resin material so as to be separable into two parts.
The pipe members 3B and 3C are assembled with the circuit casing 2 by abutting each other along the lines 3A and 3A. Then, the pipe members 3B and 3C are formed into two halves in order to enhance the moldability of the detection passage 4 and the mounting workability of the heat sensitive element 5 which will be described later, and the pipe member 3B is located at the base end side of the intake pipe 3. The pipe member 3C is formed so as to extend in the diametrical direction inside the intake pipe 1 to form a long, substantially cylindrical shape.

Reference numeral 4 denotes a detection passage formed in the intake pipe 3 in order to detect the flow rate of intake air flowing in the intake pipe 1 in the direction of arrow A. The detection passage 4 represents the intake air flowing in the direction of arrow A. In order to introduce a part into the detection passage 4, it opens toward the upstream side of the intake pipe 1, and the inlet 4A formed between the pipe members 3B and 3C and the pipe member 3C extend axially. An axial passage portion 4B communicating with the inflow port 4A and a passage portion 4B formed in the radial direction on the tip side of the pipe member 3C so as to communicate with the passage portion 4B and open toward the downstream side of the intake pipe 1. The first outlet 4C,
It is roughly composed of second outlets 4D, 4D formed on the tip side of the pipe member 3C so as to be orthogonal to the outlet 4C. Then, the detection passage 4 causes a part of the intake air introduced from the inflow port 4A to flow out from the outflow ports 4C and 4D through the passage portion 4B, and the air flows through the inflow port 4A in the direction opposite to the arrow A direction. It is designed to prevent

Reference numeral 5 denotes a heat sensitive element as a heat ray resistance, which is located in the inflow port 4A of the detection passage 4 and is mounted on the pipe member 3B through the terminals 6 and 6. The heat sensitive element 5 is sensitive to temperature changes. A resistor having a small diameter, which is formed by using a material such as platinum whose resistance value R _H changes, and which is formed by winding a platinum wire around an insulating cylindrical body made of, for example, ceramics, or depositing a platinum thin film. It is composed of elements. The heat sensitive element 5 is heated to, for example, about 240 ° C. by energization from the battery 20 described later, and is cooled by the intake air flowing through the inflow port 4A of the detection passage 4, so that the inside of the intake pipe 1 is arrowed. The flow rate of intake air flowing in the direction A is detected.

Reference numerals 7 and 7 denote terminals which are spaced apart from each other in the axial direction of the intake pipe 3 and project from the outer peripheral side of the pipe member 3C, and 8 denotes a temperature compensating resistor attached to the outer peripheral side of the pipe member 3C via the terminals 7. As shown in FIG. 5, the temperature compensating resistor 8 is formed by depositing a platinum thin film 10 on a thin insulating substrate 9 made of a ceramic material such as alumina using a means such as sputtering. Electrodes 11, 11 connected to each terminal 7 are provided on both ends of the platinum thin film 10. Here, the temperature compensation resistor 8 is elongated in the axial direction of the intake pipe 3 and is arranged so as to be orthogonal to the intake air flowing in the intake pipe 1 in the direction of arrow A. The temperature compensating resistor 8 is directly exposed to the flow in the direction of arrow A, and the intake air is circulated along the surface thereof to suppress the air resistance and the like. The substrate 9 is formed as thin as possible in order to reduce the heat capacity and the like.

Reference numerals 12 and 13 denote flow rate adjusting resistors and reference resistors provided outside the intake pipe 1 and provided inside the circuit casing 2. The flow rate adjusting resistors 12 and reference resistors 13 have resistance values R _{2 as} shown in FIG. , R
₃ and are connected in series with the temperature compensation resistor 8 and the heat sensitive element 5 at connection points 14 and 15, respectively. Then, a series circuit consisting of the heat sensitive element 5, the reference resistance 13, the temperature compensation resistance 8, and the flow rate adjustment resistance
The series circuit composed of 12 is connected in parallel between the battery 20 and the ground at connection points 16 and 17 to form a bridge circuit shown in FIG.

Reference numeral 18 represents a differential amplifier whose input side is connected to the connection points 14 and 15 and whose output side is connected to the base side of the power transistor 19, and which is based on the potential difference between the connection points 14 and 15 The supply current supplied from the battery 20 as a power source to the thermosensitive element 5 and the like is controlled via the power transistor 19. Here, the differential amplifier 18 and the power transistor 19 are mounted on the substrate of the circuit casing 2 together with the flow rate adjusting resistor 12 and the reference resistor 13, and are incorporated in the circuit casing 2.

In the hot-wire type flow meter configured as described above, first, in a state where the pipe members 3B and 3C forming the intake pipe 3 are divided, the heat sensitive element 5 is attached to the pipe member 3B via each terminal 6, and then the pipe The members 3B and 3C are abutted against each other at the abutting surfaces 3A, and these are assembled to the circuit casing 2 as shown in the drawing. Next, after mounting the temperature compensating resistor 8 so as to sandwich it between the terminals 7 and 7 provided on the outer peripheral side of the intake pipe 3 and performing soldering, etc., the intake pipe 3 is attached to the intake pipe 1 together with the temperature compensating resistor 8 and the like. The circuit casing 2 etc. is fixed to the outside of the intake pipe 1 by inserting it into the intake pipe 1 through the mounting hole 1A.

Thus, when detecting the intake air flow rate, the battery
Current is supplied from 20 to the heat sensitive element 5, etc.
Heat to about ℃. When the flow velocity of the intake air flowing through the intake pipe 1 is increased and the intake air is increased, the thermosensitive element 5 is cooled more greatly, so that the resistance value _RH of the thermosensitive element 5 tends to decrease and the connection is reduced. The potential at point 15 rises and the potential difference between the connections 14, 15 causes the differential amplifier 18 to control the power transistor 19 to increase the supply current from the battery 20. As a result, the temperature of the heat sensitive element 5 is set to about 240 ° C., and the heat sensitive element 5 can be heated so as to keep its resistance value _RH constant. For example, a voltage signal corresponding to the intake air flow rate is extracted from the voltage across the reference resistor 13. be able to.

[Problems to be solved by the device]

By the way, in the above-mentioned conventional technique, the intake pipe 3
A temperature compensating resistor 8 mounted on the outer peripheral side of each of the terminals via each terminal 7 is formed by depositing a platinum thin film 10 on a thin and brittle ceramic substrate 9 as shown in FIG.
Since the temperature compensation resistor 8 is configured to effectively compensate for the temperature change of the intake air, the temperature compensating resistor 8 may be easily cracked or chipped due to the action of an external force at the time of manufacturing, transferring, or assembling. There is a problem that the yield is very poor and the reliability cannot be improved.

In particular, since the temperature compensating resistor 8 projects radially from the outer peripheral side of the intake pipe 3, when the intake pipe 3 is mounted in the intake pipe 1 via the mounting hole 1A, the periphery of the mounting hole 1A of the intake pipe 1 is The temperature compensating resistor 8 may collide with the temperature compensating resistor 8 to damage the temperature compensating resistor 8, which requires a great deal of time and effort for assembling work, resulting in poor workability.

The present invention has been made in view of the above-mentioned problems of the prior art,
The present invention provides a hot wire type flow meter capable of preventing the temperature compensation resistance from cracking or chipping and improving reliability and workability.

[Means for Solving the Problems]

The feature of the configuration adopted by the present invention to solve the above-mentioned problems is that it is located on the outer peripheral side of the intake pipe, at least on both sides in the length direction of the temperature compensating resistor, near the tip side of the intake pipe. Protect the temperature compensation resistor,
There is a protective straightening plate that also doubles the intake air.

[Action]

With the above configuration, when the intake pipe is inserted into the intake pipe, the protection rectifying plate can prevent the temperature compensation resistance from colliding with the peripheral wall of the intake pipe, and protects the temperature compensation resistance from external obstacles. can do. Further, the flow of intake air flowing around the temperature compensation resistor can be adjusted by the protective rectifying plate, and the temperature compensation action can be enhanced by making the intake air evenly contact with the temperature compensation resistor.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Incidentally, in the embodiment, the above-mentioned FIGS.
The same components as those of the conventional technique shown in the figure are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 21 denotes an intake pipe radially protruding from the fitting portion 2A of the circuit casing 2 into the intake pipe 1, and the intake pipe 21 is the intake pipe 21 described in the prior art.
In the same manner as described above, the intake pipe 21 includes a pipe member 21B, 21C which can be divided into two along the abutting surface 21A, 21A, and the detection passage 4 is formed therein. Two protective rectifying plates 22 and 23 are integrally projected on the outer peripheral side.

Here, the protective rectifying plates 22 and 23 are arranged so that the terminals 7 and 7 projecting axially apart from each other on the outer peripheral side of the pipe member 21C are sandwiched on both sides of the temperature compensation resistor 8 in the length direction. The temperature compensating resistor 8 is arranged on the outer peripheral side so as to protect the temperature compensating resistor 8 from outside obstacles and the like on both sides in its length direction. Also,
The protective rectifying plates 22 and 23 are arranged perpendicularly to the flow of intake air flowing in the intake pipe 1 in the direction of arrow A, and allow the intake air to flow in the plate width direction. The protective rectifying plates 22 and 23 are formed as thin as possible to reduce the air resistance against the flow in the direction of arrow A, and
The flow of the intake air is regulated between the protective straightening plates 22 and 23 so that the surface of the temperature compensating resistor 8 is uniformly contacted with the intake air.

The hot wire type flow meter according to the present embodiment has the above-mentioned configuration, and its basic operation is not particularly different from that according to the prior art.

Therefore, in this embodiment, the pipe member of the intake pipe 21 is
Protective rectifying plates 22 and 23 are formed on both sides of the temperature compensating resistor 8 on the outer circumference side of 21C so as to sandwich each terminal 7, and the temperature compensating resistor 8 is protected by the protective rectifying plates 22 and 23. Therefore, for example, when the intake pipe 21 is inserted into the intake pipe 1 via the mounting hole 1A, the protection straightening plate 22 prevents the temperature compensation resistor 8 from colliding with the periphery of the mounting hole 1A.
The temperature compensating resistor 8 can be prevented from cracking or chipping at the time of mounting.

Further, even before the pipe member 21C is assembled to the pipe member 21B and the circuit casing 2 and the like, both sides in the length direction of the temperature compensation resistor 8 can be protected by the protective rectifying plates 22 and 23, so that when the pipe member 21C is assembled. Further, the temperature compensation resistor 8 can be protected from collision with surrounding obstacles by the protective rectifying plates 22 and 23, and workability and reliability at the time of assembly can be improved. Further, the flow of the intake air can be regulated between the protective straightening plates 22 and 23, and the intake air can be brought into uniform contact with the surface of the temperature compensation resistor 8, thereby improving the responsiveness to the temperature change of the intake air and improving the temperature. Various effects are exhibited such that the compensation action can be performed more effectively.

In the above embodiment, the protective straightening vanes 2 are provided on both sides of the temperature compensating resistor 8 in the length direction and on the outer peripheral side of the intake pipe 21.
Although it has been described that two and 23 are provided, the protective straightening vane 23 located near the base end side of the intake pipe 21 is eliminated, and only the protective straightening vane 22 located near the tip end side of the intake pipe 21 is omitted. May be provided. In this case, the temperature compensation resistor 8 can be protected by the protective rectifying plate 22,
The flow of intake air can be adjusted.

[Effect of device]

As described above in detail, according to the present invention, since the temperature compensation resistance is protected on the outer peripheral side of the intake pipe and the protective rectifying plate which also rectifies the intake air is provided, for example, the intake pipe is inserted into the intake pipe and assembled. At this time, it is possible to protect the temperature compensation resistor from colliding with the peripheral wall of the intake pipe, effectively prevent the temperature compensation resistor from cracking or chipping, and prevent the flow of intake air around the temperature compensation resistor. It can be arranged, the temperature compensation effect can be performed more effectively, etc.
Has various effects.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of an intake pipe provided with a hot-wire flow meter, and FIG.
An enlarged sectional view in the direction of the arrow II-II in the figure, FIGS. 3 to 6 show a conventional technique, FIG. 3 is a longitudinal sectional view of an intake pipe provided with a hot-wire flow meter, and FIG. FIG. 5 is an enlarged sectional view in the direction of arrow IV-IV in the figure, FIG. 5 is a perspective view showing a temperature compensation resistor, and FIG. 6 is an electric circuit diagram of a hot wire type flow meter. 1 ... Intake pipe, 1A ... Mounting hole, 2 ... Circuit casing,
4 ... Detection passage, 4A ... inlet, 4B ... passage, 4C, 4D
...... Outlet, 5 ...... Heat sensitive element (heat wire resistance), 6,7 ...... Terminal, 8 ...... Temperature compensation resistance, 12 ...... Flow rate adjustment resistance,
3 …… Reference resistance, 21 …… Intake pipe, 22,23 ……
Protection straightening plate.

Claims (1)

[Scope of utility model registration request] 1. A circuit casing which is provided on the outer peripheral side of an intake pipe and has a flow rate adjusting resistor and a reference resistor built therein, and a flow rate of intake air which projects radially into the intake pipe from the circuit casing and flows in the intake pipe. An intake pipe in which a detection passage for detecting the temperature of the intake pipe is formed, a heat ray resistance that is provided in the intake pipe in the middle of the detection passage and is cooled by intake air flowing in the detection passage, and the intake pipe. In the hot-wire flowmeter, which is attached to the outer peripheral side of the intake pipe so as to extend in the axial direction of and is composed of a temperature compensating resistor directly exposed to the intake air in the intake pipe, the temperature on the outer peripheral side of the intake pipe is the temperature The temperature compensating resistor is located at least near the tip end side of the intake pipe on both sides of the compensating resistor in the length direction, and the temperature compensating resistor is sucked in. Hot-wire flow meter, characterized in that a protective current plate which also serves as a rectification of the vapor.