JPH05231899A - Intake air amount detector - Google Patents

Abstract

PURPOSE:To obtain an intake air amount detector capable of reducing the output error by improving the heat radiation of the control circuit without increasing the air intake resistance. CONSTITUTION:An air intake amount detector 10 is provided with a bridge circuit 11 including a flow velocity detection element 12 arranged for flow velocity detection by using a support part 25 in an air intake channel 2 and a temperature detection element 3 for temperature detection and a control circuit 5 to heat and control the flow velocity detection element 12 in accordance with the intake air amount. The support part 25 is made of metal material The control circuit 15 is fixed on a circuit board 20 and the circuit board 20 is contactly fixed to the support part 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal type intake air amount detecting device for detecting an intake air amount of an internal combustion engine such as an automobile.

[0002]

2. Description of the Related Art As a device for detecting the amount of intake air in an internal combustion engine, a heat-sensitive resistor (heating resistor) is arranged in the intake passage, and while the resistor is heated, the resistance of the resistor is reduced by the cooling action of the intake air. A thermal type intake air amount detection device that detects a temperature change as a change in the resistance value of the resistor and outputs an electric signal according to the intake air amount is used in an automobile or the like.

The electric circuit of such a detecting device is composed of a thermosensitive resistor, a bridge circuit including a flow velocity detecting element and a temperature detecting element, a control circuit including an operational amplifier (IC) and a transistor for current control. It consists of and.

Since this control circuit itself generates heat by its operation, and a rise in the temperature of the circuit causes an error in the detection output of the intake air amount, it is generally disclosed, for example, in Japanese Utility Model Laid-Open No. 61-182820. In addition, the control circuit is separated from the flow velocity detecting element and the temperature detecting element and attached outside the intake passage.

Further, in order to reduce a detection output error, a device has been proposed in which a heat sink for dissipating heat of a control circuit is provided and a heat radiation fin of the heat sink is provided in an intake passage (for example, Japanese Patent Laid-Open Publication No. Sho. 63-128
43 publication).

[0006]

However, in the intake air amount detecting device provided with such a radiation fin, since the radiation fin is provided so as to project into the intake passage, the radiation fin prevents the intake air from flowing through the intake passage. There was a problem that the intake resistance increased.

The present invention has been made to solve the above problems, and it is an object of the present invention to improve the heat radiation of the control circuit and reduce the output error without increasing the intake resistance. It is intended to provide an intake air amount detection device.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and is a flow velocity detecting element for detecting a flow velocity and a temperature detecting element arranged in the intake passage via a supporting member. An intake air amount detection device comprising: a bridge circuit including a temperature detection element; and a control circuit for heating and controlling the flow velocity detection element in accordance with the amount of air taken in, wherein the support member is made of a metal material. The control circuit is formed, and the control circuit is attached to a circuit board, and the circuit board is fixed in close contact with the support member.

[0009]

The present invention is configured as described above, and the heat generated in the control circuit is transmitted to the support member via the circuit board. The support member is cooled by the flow of intake air in the intake passage and suppresses the temperature rise of the control circuit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In the figure, reference numeral 10 is an intake air amount detecting device, which is arranged in an intake passage 2 in an intake cylinder 1 connected to an intake pipe of an internal combustion engine.

The intake air amount detecting device 10 comprises a bridge circuit 11 including a flow velocity detecting element 12 and a temperature detecting element 13, and a control circuit 15 for heating and controlling the flow velocity detecting element 12. Circuit 15 is
It is fixed to the circuit board 20 and is attached to a support member 25 disposed in the intake passage 2.

The bridge circuit 11 is composed of a flow velocity detecting element 12, a temperature detecting element 13, and fixed resistors R1 and R2.

The flow velocity detecting element 12 is formed, for example, by fixing a heat sensitive resistor made of a platinum thin film on an insulating substrate made of zirconia, and the temperature detecting element 13 is similar to the above.
The thermosensitive resistor is fixedly formed. Both the flow velocity detecting element 12 and the temperature detecting element 13 have a large temperature coefficient and linearity, and the flow velocity detecting element 12
Is formed so as to have a resistance value smaller than that of the temperature detection element 13. As shown in FIG. 5, the flow velocity detecting element 12 and the temperature detecting element 13 are respectively connected in series with a fixed resistor R1 and a fixed resistor R2 to form a bridge circuit 11.

The control circuit 15 is composed of an operational amplifier 16 and a transistor 17. Operational amplifier 16
Is an IC configured to increase / decrease the output signal according to the potential difference between the midpoints a and b of the bridge circuit 11, and the transistor 17 supplies the current supplied to the bridge circuit 11 based on the output signal from the operational amplifier 16. Shaped to control. The control circuit 15 is fixed on the circuit board 20 together with the bridge circuit 11.

The circuit board 20 is made of a ceramic plate material having good electric insulation, and a circuit pattern (not shown) of the bridge circuit 11 and the control circuit 15 is formed on the upper surface of the circuit board 20 by printing. The components of the bridge circuit 11 and the control circuit 15 are surface-mounted on the surface of the circuit board 20 by soldering, and the flow velocity detecting element 12 and the temperature detecting element 13 are coaxial with the intake passage 2. A synthetic resin cover 21 having a detection passage 22 is provided.

The heat dissipation plate 23 is made of a metal material having a high thermal conductivity,
For example, it is formed of an aluminum plate into a flat plate having substantially the same size as the circuit board 20, and is fixed to the lower surface of the circuit board 20 by an adhesive or the like.

In the embodiment, the support member 25 is formed of a metal material having a high thermal conductivity, for example, an aluminum material, into a rectangular tubular shape with rounded corners, and a fitting hole of the cover 21 at a predetermined position. Is provided. The cross-sectional shape of the support member 25 may be oval, streamlined, or the like.

The circuit board 2 is provided inside the support member 25.
One surface of the heat dissipation plate 23 that is in close contact with 0 is fixed in close contact with an adhesive. As a result, the circuit board 20 is fixed in close contact with the support member 25 via the heat dissipation plate 23.

In the intake air amount detecting device 10 thus formed, the axis of the detecting passage 22 is arranged in parallel with the intake flow F, and both ends of the supporting member 25 are supported by the intake cylinder 1 and the intake air is taken in. It is arranged in the passage 2. Reference numeral 28 is a connector for electrically connecting the intake air amount detection device 10 to the outside.

Next, the operation of the intake air amount detecting device will be described.

When the intake air is not introduced into the intake passage 2, a current flows through the flow velocity detecting element 12 to generate heat, which is higher than the intake temperature detected by the temperature detecting element 13 by a predetermined temperature. Therefore, the bridge circuit 11 is balanced.

When the intake air flows into the intake passage 2, the flow velocity detecting element 12 which is generating heat is deprived of heat by the air flow, and the temperature is lowered. Therefore, its resistance value decreases,
The balance condition of the bridge circuit 11 is broken, and the non-inverting input of the operational amplifier 16 of the control circuit 11 becomes high level.

As a result, a high level signal is output from the operational amplifier 16, and the transistor 17 increases the current supplied to the bridge circuit 11. Then, the flow velocity detecting element 1
2 is heated and its resistance value increases, and the bridge circuit 11
The equilibrium condition of is restored.

This supply current has a predetermined relationship with the flow velocity of the intake air, and the higher the flow velocity, the larger the supply current. A high flow velocity means a high flow rate, so
The flow velocity of the intake air indicates the intake air amount, and the bridge circuit 11
The voltage at the midpoint a is taken out as the intake air amount signal.

During this time, the operational amplifier 16 and the transistor 17 of the control circuit 11 generate heat by their operation, and the generated heat is transferred to the support member 25 via the heat dissipation plate 23. The support member 25 is cooled by the flow of intake air in the intake passage 2 and dissipates the transferred heat to actively cool the control circuit 11. Therefore, the temperature rise of the control circuit 11 is suppressed and the detection output error is reduced.

[0027]

As described above, the intake air amount detecting device of the present invention includes the flow velocity detecting element for detecting the flow velocity and the temperature detecting element for detecting the temperature, which are arranged in the intake passage via the supporting member. An intake air amount detection device comprising: a bridge circuit; and a control circuit for heating and controlling the flow velocity detection element in accordance with the amount of intake air, wherein the support member is made of a metal material, and the control circuit is Since the circuit board is attached to the circuit board and is fixed in close contact with the support member, the heat dissipation of the control circuit can be improved without increasing the intake resistance of the intake passage for heat dissipation of the control circuit. Can be improved. Therefore, the detection output error of the intake air amount due to the temperature rise of the control circuit of the device can be reduced.

Further, when the material forming the intake cylinder is made of synthetic resin, the structure of the present invention can further improve the heat radiation effect as compared with the conventional example.

[Brief description of drawings]

FIG. 1 is a plan sectional view of an intake air amount detection device according to an embodiment of the present invention.

FIG. 2 is a bottom sectional view of the same.

FIG. 3 is a front sectional view of the same.

FIG. 4 is a sectional view taken along the line AA of FIG.

FIG. 5 is an electric circuit diagram of the device.

[Explanation of symbols]

 2 Intake passage 10 Intake air amount detection device 11 Bridge circuit 12 Flow velocity detection element 13 Temperature detection element 15 Control circuit 20 Circuit board 23 Heat sink 25 Support member

Claims (1)

[Claims] 1. A bridge circuit including a flow velocity detecting element for detecting a flow velocity and a temperature detecting element for detecting a temperature, which is arranged in the intake passage via a supporting member, and the flow velocity detecting device in accordance with an amount of air taken in. An intake air amount detection device comprising: a control circuit for heating and controlling an element, wherein the support member is formed of a metal material, and the control circuit is attached to a circuit board, and the circuit board supports the support circuit. An intake air amount detection device, which is in close contact with and fixed to a member.