JPH0694496A - Air flow measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to improve the resistance to radio interference of an air flow measuring device that uses a resin body. [Structure] A conductive material is embedded in the outer periphery of a support pin for fixing a heat-generating resistor and a heat-sensitive resistor. [Effect] An air flow rate measuring device that uses a resin body. The resistance to radio interference can be made as simple as an aluminum body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air flow rate measuring device for measuring the intake air flow rate of an internal combustion engine which requires resistance to radio interference.

[0002]

2. Description of the Related Art As a conventional measure for improving the resistance to radio interference, a structure as described in JP-A-64-10127 can be considered. This structure is considered to be covered with a conductive case as a means for electromagnetically covering the heat generating resistor and the heat sensitive resistor. However, these means increase the number of assembling steps and increase the cost.

[0003]

DISCLOSURE OF THE INVENTION The present invention has made it possible to improve the resistance to electromagnetic interference of a resin body for the purpose of weight reduction by an inexpensive and highly reliable method.

[0004]

In order to achieve the above object, a conductive substance having a cylindrical or polygonal cross section is provided on the outer periphery of a support pin for fixing a heat-sensitive resistor, or a heat-sensitive resistor and a heat-generating resistor. This can be achieved by embedding it on the outer circumference of both support pins that fix the body. Further, it can be achieved by forming a film of a conductive material or a non-magnetic material on the outer periphery of the resin after molding by plating or the like.

[0005]

The air flow rate measuring device is a device for converting the intake air flow rate into an electric signal and detecting the intake air flow rate. Since this air flow rate measuring device is usually installed in the engine room, there is a problem that external radio waves enter the drive circuit and cause malfunction of the drive circuit under the operating environment conditions. Therefore,
Although measures are taken by using a shield structure or a capacitor, when a resin body is used, the body is an insulator and the external radio waves that intrude from the heat-sensitive resistor and the support pins that secure the heat-sensitive resistor are directly driven by the drive circuit. It may cause malfunction and malfunction.

In the present invention, a cylindrical conductive material is attached to the outer periphery of the support pin for fixing the heat-sensitive resistor, or the heat-sensitive resistor,
Improves resistance to electromagnetic interference by adopting a structure that is embedded on the outer periphery of both support pins that fix the heating resistor, or by forming a film of conductive material or non-magnetic material on the outer periphery of the resin after molding by plating etc. can do. That is, by enclosing the periphery of the heat-sensitive resistor and the support pin that fixes the heat-generating resistor with external electric waves with a conductive material, it is possible to block the invasion path of the external electromagnetic waves. In addition, by forming a film by plating a conductive substance or a non-magnetic substance on the outer periphery of a resin forming a base made of a conductive metal and a support pin for fixing the heat sensitive resistor and the heat generating resistor,
It can block the intrusion route of foreign radio waves.

[0007]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 4 is a sectional view of the air flow rate measuring device.

1 and 2 show a structure in which a cylindrical conductive material of the present invention is embedded in the outer circumference of a support pin for fixing a heat-generating resistor and a heat-sensitive resistor. The intake air is supplied to the engine through the main air passage 1 and the sub air passage 2. The main air passage 1 and the sub air passage 2 are provided inside the resin body 3. In the sub air passage 2, a heating resistor 5 for measuring the flow rate of intake air and a heat sensitive resistor 6 for measuring the temperature of intake air are installed. Both the heat generating resistor 5 and the heat sensitive resistor 6 are welded to the support pin 7. Both the support pins 7 are electrically connected to the drive circuit. An electric current for heating the heating resistor 5 to a constant temperature is passed by this drive circuit. This heating temperature maintains a constant difference between the heating resistor 5 and the intake air temperature regardless of the amount of intake air, and the intake air temperature is corrected by the thermosensitive resistor 6. That is, when a high flow rate flows through the air passage, a large current is passed through the heating resistor 5, and when a low flow rate flows, a small current is passed to maintain a constant temperature. There is a monotonically increasing function relationship between the current flowing through the heating resistor 5 and the air flow rate, and the air flow rate is detected by this. As described above, since a weak current is flown depending on the air flow rate, it is necessary to improve the resistance to radio interference. Therefore, external radio waves entering from the heating resistor 5, the thermosensitive resistor 6 and the support pin 7 are blocked by the conductive substance 8 having a cylindrical or polygonal cross section arranged on the outer periphery of the support pin 7, There is an effect that an air flow rate measuring device with good radio interference can be provided. Further, FIG. 3 shows a structure which is one of the present invention. A support pin 7 for fixing the heat-generating resistor 5 and the heat-sensitive resistor 6 and a base 4 made of a conductive metal are insert-molded. A conductive material or a non-magnetic material 9 is formed on the outer periphery of a resin by plating or the like. As a result, it is possible to provide an air flow rate measuring device that blocks external radio waves and has good resistance to radio interference.

[0010]

According to the present invention, it is possible to provide an inexpensive air flow rate measuring device which improves the resistance to radio interference when a resin body is used.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in an axial direction and a radial direction of an air flow measuring device showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view in the axial direction and the radial direction of the air flow rate measuring device showing an embodiment of the present invention.

FIG. 3 is a cross-sectional view in the axial direction and the radial direction of the air flow rate measuring device showing one embodiment of the present invention.

FIG. 4 is a cross-sectional view in the axial direction of the air flow rate measuring device.

[Explanation of symbols]

1 ... Main air passage, 2 ... Sub air passage, 3 ... Resin body, 4
... Base, 5 ... Heating resistor, 6 ... Heat sensitive resistor, 7 ... Support pin, 8 ... Conductive substance having cylindrical or polygonal cross section, 9 ... Conductive substance, non-magnetic substance.

Claims (3)

[Claims] 1. An air flow rate comprising a body provided with a main air passage and an auxiliary air passage for flowing air supplied to an internal combustion engine, and a module having a heat generating resistor and a heat sensitive resistor installed in the sub air passage. In the measuring device, when the support pin for fixing the heat-generating resistor and the heat-sensitive resistor and the base made of conductive metal are insert-molded with resin, a cylindrical or polygonal cross-section is provided on the outer periphery of the support pin for fixing the heat-sensitive resistor. An air flow rate measuring device, characterized in that a conductive substance having the above is embedded. 2. The method according to claim 1, wherein a conductive material having a cylindrical or polygonal cross section is embedded on the outer periphery of the support pin for fixing the heat sensitive resistor and the support pin for fixing the heat generating resistor. Characteristic air flow rate measuring device. 3. The support pin for fixing the heat-generating resistor and the heat-sensitive resistor and a base made of conductive metal are insert-molded with resin, and a conductive material is provided on the outer periphery of the resin covering the support pin. Alternatively, an air flow rate measuring device characterized in that a coating made of a non-magnetic substance is formed.