JPS63218821A - Thermal air amount measuring apparatus for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the change of a thermal flowmeter with the elapse of time by reducing the amount of the dust particle adhered to a heat-sensitive resistor, by providing a conductive air pervious body to the air passage part on the upstream side of the heat-sensitive resistor in a thermal air amount measuring apparatus in an earthed state. CONSTITUTION:The dust particle introduced into an air cleaner passes through an air cleaner element 10 to be charged by the friction with the element 10 but the charge of the charged dust particle is neutralized by the ion formed by the discharge of a conductive fiber 11. Since the dust particle having residual charge not neutralized is collided with and adhered to a metallic distributing element 12 as an earthed conductive air pervious body and the residual charge is leaked, the charge of the dust particle reaching the detection element of a heat generating resistor 6 is reduced to a large extent. As a result, the electrostatic force acting on the dust particle becomes a negligible level and the adhesion amount of the dust particle to the surface of the detection element of the heat generating resistor 6 is reduced and the change of a thermal flowmeter with the elapse of time can be reduced.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention is particularly applicable to internal combustion engines, in which the amount of heat released from a heated temperature-dependent resistor that is disposed in a passage downstream of an air cleaner changes depending on the flow rate. The present invention relates to a thermal air amount measuring device for measuring intake air amount, etc.

[Prior Art] A thermal flow rate needle for measuring the intake air of an internal combustion engine utilizes a well-known constant temperature measurement method. Figure 2 is an example of document S.
It is an exploded perspective view showing the conventional thermal flow needle shown in AE paper N1800468, and in the figure, (1) is a housing made of plastic, (2) is a housing (1).
A net (3) is a spring that holds the net (2), (4) is an inner tube arranged parallel to the housing (1), (5) is a precision resistor,
6) is a heat-generating resistor made of a platinum wire with a diameter of 70 μm, which is a flow velocity detection element, and (7) is a temperature compensation resistor, and each of the resistors +51 + +61 and (7) are arranged inside the inner tube (4). It is set up. (8) is each of the above resistances (5) and (6)
This is an HIC consisting of a circuit that is electrically connected to (7) and outputs a signal according to the flow/amount.

This thermal flow meter is placed in the air passage on the downstream side of the air cleaner, and while it has the advantage of being able to directly detect the mass flow rate,
In order to use the heat transfer characteristics of the flow velocity detection element as constant,
They have the disadvantage that their characteristics tend to change over time due to the adhesion of dust passing through the air cleaner and the adhesion of carbon due to backfire from the engine. Furthermore, when an oil-immersed air cleaner element is used, oil particles carried away by the air adhere to the detection element, causing apparent output voltage fluctuations.

As a countermeasure to this problem, a method is adopted in which the detection element is self-heated to incinerate the attached organic matter. However, the cleaning effect is incomplete due to residual inorganic substances, especially when dust passes through the air cleaner element made of polyester nonwoven fabric.
@Dust or electrostatic charge due to rubbing.

For this reason or other reasons, attachment to the detection element was promoted, resulting in changes over time in many cases. The smaller the diameter of the dust particles and the larger the specific resistance, the more the electrostatic charge on the detection element tJit increases.

[Problems to be Solved by the Invention] Since the conventional thermal air amount measuring device for an internal combustion engine is configured as described above, when the dust passes through the air cleaner, the charged dust adheres to the surface of the detection element due to electrostatic force. However, there was a problem that the heat transfer characteristics changed over time.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a thermal air amount measuring device in which dust contained in intake air is less likely to adhere to a detection element.

[Means for solving problems]

The air amount measuring device according to the present invention is a thermal type air amount measuring device for an internal combustion engine, in which a heat-sensitive resistor is disposed in an air passage downstream of an air cleaner, and the air cover flowing through the air passage is measured based on a signal change of the heat-sensitive resistor. The air passage section upstream of the heat-sensitive resistor is provided with an electrically conductive air permeable material grounded.

[Effect]

The air permeable body in this invention removes the charge from dust particles contained in the air and prevents dust from adhering to the heat-sensitive resistor.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, a housing (1) constituting the Ichiju style flow pointer,
The inner tube (4), precision resistor (5), heat generating resistor (6), temperature compensation resistor (7) and HI Ci3) are the same as before.

A honeycomb-shaped metal rectifying element (2) is provided as a conductive air permeable body at the upstream opening of the housing (1), and is grounded via a bonding wire. An air cleaner is provided on the upstream side of the rectifying element 02,
A polyester thread woven fabric type air cleaner element 00 is provided inside the iron air cleaner housing (9), and a conductive air passing body with a diameter of 20 to 30 mm is installed inside the element.
Conductive fibers with a diameter of .mu.m are mixed in, and the metal fastener is grounded together with the air cleaner housing via a tool.

When the dust introduced into the air cleaner passes through the air cleaner element aυ, the dust particles become electrically charged due to friction with the element, or the electric charge of the charged particles is neutralized by ions generated by discharge of the conductive fibers. In addition, when dust particles with unneutralized residual charges collide with the grounded rectifying element (12), the 14X charge is leaked, so the amount of charge of the dust particles reaching the detection element of the heating resistor (6) is As a result, the electrostatic force acting on dust particles becomes negligible, the amount of heat-generating resistor attached to the detection element surface is reduced, and the aging of the thermal flowmeter can be reduced.

In the above embodiment, a honeycomb-like element was provided in the rectifying element 0, but the same effect can be achieved by arranging a plurality of stainless steel wire meshes to increase the chance of adhesion with dust and thereby promoting charge leakage. .

〔Effect of the invention〕

As described above, according to the present invention, a thermal air amount measuring device for an internal combustion engine is provided, in which a heat-sensitive resistor is arranged in the air passage downstream of an air cleaner, and the air needle flowing through the air passage is measured by the signal impairing of the heat-sensitive resistor. In this case, since an electrically conductive air passage member is grounded in the air passage section upstream of the heat-sensitive resistor, the amount of dust particles adhering to the heat-sensitive resistor is reduced, resulting in less change over time. be.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram showing a thermal air metering device for an internal combustion engine according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view showing a conventional thermal flow meter. In the figure, (1) is the housing, (4) is the inner tube, and (5) is the housing.
) is a precision resistor, (6) is a heating resistor, (7) is a temperature control resistor, and (8) is an HI C- (91 is an air cleaner housing, [101 is an air cleaner element, αυ is a conductive fiber, and O3 is a rectifier. The same reference numerals in each figure indicate the same or corresponding parts.

Claims (4)

[Claims] (1) In a thermal air flow measuring device for an internal combustion engine, which measures the amount of air flowing through the air passage by disposing a heat-sensitive resistor in the air passage downstream of the air cleaner and measuring the amount of air flowing through the air passage based on a change in the signal of the heat-sensitive resistor. A thermal air amount measuring device for an internal combustion engine, characterized in that an electrically conductive air permeable body is grounded and provided in an upstream air passage section. (2) The thermal air amount measuring device for an internal combustion engine according to claim 1, wherein the air permeable body is a rectifying element provided in an air passage between the air cleaner and the heat-sensitive resistor. (3) The thermal air amount measuring device for an internal combustion engine according to claim 2, wherein the rectifying element is constituted by a plurality of wire meshes. (4) The thermal air amount measuring device for an internal combustion engine according to any one of claims 1 to 3, wherein the air permeable body is a conductive fiber mixed into an air cleaner element in an air cleaner.