JP3473133B2 - Flowmeter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter for measuring the flow rate of fluid.

[0002]

2. Description of the Related Art For example, in an automobile or the like, a thermal type flow meter is used to measure the amount of intake gas drawn into an engine. As this thermal type flow meter, for example, there is a flow meter disclosed in Japanese Patent Application Laid-Open No. 5-340777. As shown in FIGS. 6 and 7, this flow meter is composed of a housing 160, an outer cylinder 100, a flow sensor (not shown), a control circuit section 114, a conductive member 35, and the like.

This conductive member 35, as shown in FIG.
The rib 1 is composed of lead wires 31, 32, 33, 34 for electrically conducting the flow sensor and the control circuit unit 114.
It is provided in 40. Further, in recent years, the housing 160 and the outer cylinder 100 have been shifting from metal to resin from the viewpoint of weight reduction.

A problem with such a thermal flowmeter made of resin is a problem due to incoming radio noise.
In a conventional flowmeter with a metal housing,
Sufficient countermeasures against radio wave noise can be taken by preventing radio wave noise from entering the control circuit unit 114 attached to the outside of the housing. That is, it is possible to deal with the radio noise directly flying to the control circuit unit 114 by providing the circuit container 110 housing the control circuit unit 114 with an electromagnetic shield function. In addition, the lead wires 71, 72 that are electrically connected to the outside
And the radio noise that tries to enter through the conductors 711 and 721 can be dealt with by the feedthrough capacitors 55 and 56.

However, in the case having the resin housing 160, a new problem that radio noise passes through the housing 160 and reaches the flow rate sensor or the conductive member 35 and enters the control circuit section 114 through them. There has occurred. Therefore, as shown in FIGS. 6 and 7, the feedthrough capacitors 51, 52, 53, and 54 are provided in the conductive member 35 to prevent radio wave noise from entering the control circuit unit 114 from the flow rate sensor and the electromagnetic shield member 35. Methods to prevent it have been proposed. Note that reference numeral 73 in FIG. 7 is a ground wire, and reference numeral 731 is a conductive wire that electrically connects it to the control circuit unit 114.

[0006]

However, the above-mentioned conventional flowmeter has the following problems. That is, since the feedthrough capacitor is small, it is difficult to assemble it automatically in the automatic assembly line when assembling the flowmeter. Therefore, the assembling work is manual work, and the work efficiency is poor. The present invention has been made in view of such conventional problems, and can sufficiently shield radio noise,
It is to provide a flow meter that can be easily assembled.

[0007]

According to the present invention, there is provided a synthetic resin outer cylinder connected to a gas flow path, and a control circuit portion provided in the outer cylinder and having an electromagnetic shield function and for inputting a signal from a flow rate sensor. A circuit container, a synthetic resin housing provided inside the outer cylinder, having an internal passage for introducing a gas to be measured and a flow sensor for measuring a flow amount arranged in the internal passage. ， Synthetic tree that connects the outer cylinder and the housing
And fat made of ribs, more becomes conductive member having a plurality of lead wires establishing electrical continuity between the control circuit unit and the flow sensor, the conductive member, at least one of the plurality of lead wires in the lead wire has an electromagnetic shielding member around a portion of its length, the electromagnetic shielding member and
The flowmeter is characterized in that the lead wire is integrally molded in advance with a synthetic resin, and the integrally molded conductive member is built in the rib .

What is most noticeable in the present invention is that the conductive member has the electromagnetic shielding member and is integrally molded in advance with a synthetic resin. The conductive member has four lead wires, two for the heater section and two for the thermometer section, which will be described later. Then, at least one lead wire is provided with an electromagnetic shielding member so as to surround it at some midpoint in the length direction. Further, when the electromagnetic shielding member is provided on all the four lead wires, the most excellent electromagnetic shielding effect is exhibited.

The electromagnetic shielding function of the circuit container can be obtained by covering the control circuit portion with a metal such as brass or aluminum. The flow rate sensor is composed of a heater section which is a flow rate measuring resistor and a temperature compensating thermometer section, both of which are made of temperature sensitive resistors having the same characteristics. Both ends of the heater section and both ends of the thermometer section are electrically connected to the control circuit section by the lead wires.

The electromagnetic shielding member may be ferrite, amorphous or the like, but ferrite is most preferable. Ferrite has a sufficient shielding effect especially for radio noise in the high frequency range. Further, it is preferable that the electromagnetic shield member is disposed near the control circuit section. As a result, even when the conductive member is long,
It is possible to shield radio noise entering the lead wire in the middle of the conductive member near the control circuit section.

[0011]

In the flowmeter of the present invention, the gas to be measured that has flowed into the outer cylinder flows into the internal passage of the housing. Then, the gas to be measured flowing into the internal passage comes into contact with the sensor arranged in the internal passage, and the flow rate of the gas to be measured is measured.

Next, the function and effect of shielding when radio noise is about to enter the control circuit will be described. First,
The incoming radio wave noise that attempts to directly enter the control circuit unit can be shielded by the above-described circuit container made of metal and having an electromagnetic shield function.

Radio wave noise that passes through the outer cylinder and housing made of synthetic resin, jumps to the flow rate sensor and the conductive member, and tries to enter the control circuit section through these,
It is attenuated and shielded by an electromagnetic shield member provided on the lead wire of the control circuit unit. In this way, even with a housing made of synthetic resin, the electromagnetic shielding member can sufficiently prevent the entry of radio noise from the sensor unit into the control circuit unit.

Further, in the conductive member, the lead wire and the electromagnetic shield member are integrally molded in advance with a synthetic resin. Therefore, when assembling the flow meter, the integrated conductive member can be easily assembled by disposing the integrated conductive member in a molding die and insert molding the synthetic resin. That is, unlike the prior art, it is not necessary to assemble a small feedthrough capacitor to the control circuit section and the lead wire one by one.

As described above, according to the present invention, it is possible to provide a flow meter which can sufficiently shield radio noise and can be easily assembled.

[0016]

FIG. 1 shows a flowmeter according to an embodiment of the present invention.
~ It demonstrates using FIG. The flowmeter 1 of this example is arranged in an intake system passage of an automobile engine and is used as an air flow meter for detecting the intake air amount.

As shown in FIGS. 1 and 2, the flowmeter 1 includes a synthetic resin outer cylinder 100 connected in the middle of an intake system passage, which is a gas flow passage, and an electromagnetic shield provided on the outer cylinder 100. A circuit container 110 having a function and having a control circuit section 114 for inputting a signal from the flow rate sensor 500, an internal passage 410 arranged inside the outer cylinder 100 for introducing a gas to be measured, and the inside of the internal passage 410. And a housing 160 having a flow rate sensor 500 for measuring the flow rate.

Further, the flowmeter 1 includes a plurality of lead wires 31 for electrically connecting the rib 140 connecting the outer cylinder 100 and the housing 160, the control circuit 114 and the flow sensor 500. , 32, 33, 34 having a conductive member 35. And these are integrally molded by synthetic resin. In addition, the conductive member 35
In the plurality of lead wires 31, 32, 33, 34, the electromagnetic shielding member 4 is formed around a part of the length thereof
1, 42, 43, 44, and the conductive member 35 is integrally molded in advance with synthetic resin.

As shown in FIG. 1, the outer cylinder 100 has an upstream side cylindrical portion 200 upstream thereof and a downstream side cylindrical portion 300 downstream thereof. The upstream cylindrical portion 200 is connected to a gas flow path of an air cleaner (not shown), and the downstream cylindrical portion 300 is connected to an intake duct (not shown). A resin case 111 is integrally formed on the outer side of the outer cylinder 100 made of synthetic resin, and a resin cover 64 is covered. The circuit case 110 is housed in the resin case 111. The circuit container 110 includes a metal case 60 made of copper and a metal cover 63 made of copper.
It is housed so as to surround the whole 4.

Inside the outer cylinder 100, four ribs 140 and the housing 160 are integrally formed of synthetic resin. In the rib 140, a conductive member 35 molded in advance with a synthetic resin is incorporated. That is, in this integral molding, the conductive member 35 previously molded as described above is placed in a molding die and insert molding is performed using a synthetic resin.

As shown in FIG. 1, a sensor insertion hole 165 is provided at the center of the housing 160, and a measuring tube 430 is provided while holding a gas passage by a central rib 167 provided radially. An internal passage 410 is formed inside the measuring pipe 430, and an external passage 439 through which gas can flow is formed behind and inside the internal passage 410. In addition, a cylindrical resin portion 510 of a flow rate sensor 500 described later is inserted into the sensor insertion hole 165.

An upstream housing 260 and a downstream housing 360 are provided in front of and behind the housing 160. The upstream housing 260 has an internal passage 410 and an external passage 439 which communicate with the housing 160. Further, the downstream housing 360 has a bowl shape surrounding the rear portion of the flow sensor 500, and has four rear ribs 340 on the outside. The rear rib 340 is provided so as to be continuous with the rear of the rib 140 provided on the housing 160.

Further, as shown in FIG. 3, the flow rate sensor 500 includes two conductive long support pins 520 supporting a heater portion 570 and two short support pins 540 supporting a thermometer portion 580. And a cylindrical resin portion 510 that is insert-molded so that they protrude forward and backward. Both the heater part 570 and the thermometer part 580 are temperature-sensitive resistors having the same characteristics in which platinum wires are wound around the outer circumference of a ceramic bobbin and connected to the lead wires at both ends of the bobbin.

Further, as shown in FIG. 4, the conductive member 35 is made by integrally molding the lead wires 31, 32, 33 and 34 by the resin portion 39 before the assembly to the flowmeter. This lead wire 31 (3 unless otherwise specified
Ferrite beads 41 (hereinafter, the same applies to 42 to 44 unless otherwise specified) are preliminarily mounted and integrally molded in the vicinity of the control circuit unit 114 (the same applies to 2 to 34). The ferrite beads 41 are made of a cylindrical ferrite material and have an inner hole into which the lead wire 31 is inserted.

The two long support pins 520 projecting to the downstream side of the flow rate sensor 500 are connected to the lead wires 32 and 33 by metal wires 22 and 23, respectively. Similarly, the two short support pins 540 are connected to the lead wires 31 and 34 of the conductive member 35 by the metal wires 21 and 24, respectively.

Further, the lead wires 31, 3 of the conductive member 35
2, 33 and 34 are arranged so as to project in the vicinity of the circuit container as shown in FIGS.
It is connected to the control circuit unit 114 via 1,331,341. In addition, as shown in FIGS. 2 and 5, the control circuit unit 114 includes the conductive wires 711 and 721 and the lead wires 71 and 72.
It is connected to an external power supply and output circuit via the, and is also connected to an external ground wire 73 via a conducting wire 731. Then, the lead wires 711 and 721 are provided with feedthrough capacitors 55 and 56 for shielding radio noise that enters from the outside through the lead wires 71 and 72.

Next, the function and effect of this example will be described. In the flowmeter 1 of the present example, as shown in FIG. 1, the gas to be measured flows in the direction of arrow A from the gas flow path of the air cleaner (not shown) connected to the upstream side cylinder portion 200. A part of the measured gas that has flowed in flows into the internal passage 410, contacts and passes through the heater unit 570 and the thermometer unit 580 in the measurement pipe 430 as shown by an arrow B, and the outside of the measurement pipe 430. Housing 160 through the external passage 439 of
Get out of.

At this time, if the flow rate of the gas to be measured passing in contact with the heater part 570 increases or decreases, the amount of heat taken from the heater part 570 in contact with it increases or decreases, and the resistance value tends to change with temperature. On the other hand, the heater part 570 is controlled so that a current for maintaining a constant resistance value is supplied. That is, the value of the current flowing through the heater unit 570 changes according to the flow rate of the gas to be measured.

Further, the influence of the change in the temperature of the gas to be measured is compensated by the action of the thermometer section 580 which is composed of a temperature sensitive resistor having the same characteristics as the heater section 570. Therefore, the current value flowing through the heater unit 570 has a correlation with the flow rate of the gas to be measured, and the flow rate of the gas to be measured can be obtained by measuring the current value.

Next, the shielding effect when radio noise is about to enter the control circuit section 114 will be described.
First, the incoming radio wave noise that tries to directly enter the control circuit unit 114 and the radio wave noise that tries to enter from the lead wires 71 and 72 that are electrically connected to the outside are the above-mentioned circuit container 110 having a metal electromagnetic shield function and the penetration. It can be shielded by the capacitors 55 and 56.

Radio wave noise that passes through the synthetic resin outer cylinder 100 and the housing 160, jumps to the flow rate sensor 500 and the conductive member 35, and tries to enter the control circuit section 114 through them is controlled by the control circuit. The ferrite beads 41 provided on the lead wire 31 of the portion 114 can attenuate and shield.

In this way, the synthetic resin housing 16
Even if it is 0, the flow sensor 500 to the control circuit 114
The ferrite beads 41 can sufficiently prevent the intrusion of radio noise into the.

The conductive member 35 is formed by integrally molding the lead wire 31 and the ferrite beads 41 provided on the lead wire 31 in advance with a synthetic resin. Therefore, when assembling the flowmeter 1, the integrally molded conductive member 35 may be inserted into a molding die and integrally molded with synthetic resin. Therefore, the work of assembling the feedthrough capacitor on the lead wire 31 is not necessary for the conductive member 35 as in the conventional case.

[Brief description of drawings]

FIG. 1 is a sectional view of a flow meter according to a first embodiment.

FIG. 2 is a partially cutaway sectional view of the flowmeter according to the first embodiment.

FIG. 3 is a front view of the flow sensor according to the first embodiment.

FIG. 4 is a partially cutaway sectional view of the conductive member according to the first embodiment.

FIG. 5 is a connection explanatory diagram of a control circuit unit and a conductive member of the flowmeter according to the first embodiment.

FIG. 6 is a partially cutaway sectional view of a flow meter according to a conventional example.

FIG. 7 is a connection explanatory diagram of a control circuit unit and a conductive member of a flow meter according to a conventional example.

[Explanation of symbols]

1. ． ． Flowmeter, 10. ． ． Outer cylinder, 110. ． ． Circuit container, 114. ． ． Control circuit part, 140. ． ． rib, 160. ． ． housing, 31, 32, 33, 34. ． ． Lead, 41, 42, 43, 44. ． ． Ferrite bead, 410. ． ． Internal passage, 439. ． ． External passage, 500. ． ． Flow sensor, 55, 56. ． ． Feedthrough capacitor, 570. ． ． Heater part, 580. ． ． Thermometer part,

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasushi Kono 1-1, Showa-cho, Kariya city, Aichi Japan Denso Co., Ltd. (56) References JP-A-5-340777 (JP, A) JP-A-6- 94496 (JP, A) JP-A-5-259686 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01F 1/00-9/02

Claims (3)

(57) [Claims] 1. An outer cylinder made of synthetic resin connected to a gas flow path, a circuit container provided on the outer cylinder, having an electromagnetic shield function, and having a control circuit section for inputting a signal from a flow sensor, A housing made of synthetic resin, which is provided inside the outer cylinder and has an internal passage for introducing the gas to be measured and a flow rate sensor for measuring the flow rate disposed in the internal passage, and the outer cylinder and the housing are connected to each other. a synthetic resin re <br/> blanking for more becomes conductive member having a plurality of lead wires establishing electrical continuity between the control circuit unit and the flow sensor, the conductive members, the plurality At least one of the lead wires
One lead wire has an electromagnetic shielding member around a part of its length, and the electromagnetic shielding member and the lead
Lines are formed in advance integrally by synthetic resin, the
A flowmeter, wherein an integrally formed conductive member is incorporated in the rib . 2. The flowmeter according to claim 1, wherein the electromagnetic shield member is ferrite. 3. The flowmeter according to claim 1, wherein the electromagnetic shield member is arranged near the control circuit section.