JPS61239119A - Air flow rate detector - Google Patents

Abstract

PURPOSE:To detect an air flow rate with a high accuracy, even when a body temperature and a detected air temperature are different from each other, by correcting a difference of an air passage wall temperature and an air temperature by an electronic circuit, and superposing it on an air flow rate output signal. CONSTITUTION:In an engine control system provided with a control device 50 using a microcomputer, an arithmetic processing part 41, a data storage part 42 and an electric power output part 44, when an optimum fuel quantity signal 43 required for an engine is outputted, from a suction air quantity Q of the engine and a revolving speed signal of the engine, first of all, resistance values of a heating resistor 1, an air temperature measuring resistance 2, and a body wall temperature measuring resistance 3 are inputted as an input signal of the suction air quantity Q of the engine to an electronic circuit. Subsequently, electric power is fed back to the resistor 1 through the electric power output part 44, so that a temperature difference of an air temperature and the heating resistor 1 becomes a prescribed value, a correction value which has been stored in advance in the data storage part 42 is added to its output from the resistance value of the resistance 3, and the flow rate Q is calculated by the arithmetic processing part 41. Next, a signal 43 based on its result is outputted.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an air flow rate detector that detects the amount of air taken into an automobile engine, and particularly relates to an air flow rate detector that detects the amount of air taken into an automobile engine, and particularly relates to an air flow rate detector that uses a hot wire and a temperature compensation resistor. relating to air flow rate detectors.

[Background of the invention]

It is known from experience that if a heating resistor for measuring the flow rate is attached and the temperature of the body forming the detected air passage is different from the detected air temperature, an air amount detection error will occur. As a method for reducing this detection error,
As shown in Publication No. 8908 and Japanese Patent Laid-open No. 18721/1989, the heat generating resistor and the total air temperature measuring resistor are made to have the same shape and the same support structure, and are symmetrically positioned on the same plane perpendicular to the air flow rate. ! 1 is known.

However, if the heating resistor and the total air temperature measuring resistor are installed close to each other, the total air temperature measuring resistor will be heated by the radiant heat of the heating resistor, and conversely, the total air temperature measuring resistor will generate heat. There are problems in that the flow of air in the resistor section is disturbed, and there are major restrictions on the structural design, and in some cases, it is impossible to simultaneously meet the above problems.

[Purpose of the invention]

An object of the present invention is to provide an air flow rate detector that can accurately detect air flow rate even when the temperature of a body constituting an air passage and the detected air temperature are different.

[Summary of the invention]

In addition to the heating resistor and the total air temperature measuring resistor provided in the air passage, the present invention includes a temperature detection resistor for detecting the temperature of the side wall of the air passage of a body forming the air passage, and an electronic circuit is used to detect the temperature. By superimposing the correction for the difference between the air passage wall temperature and the air temperature on the air flow rate output signal, the air flow rate can be detected accurately even when the temperature of the body that makes up the air passage and the detected air temperature are different. The aim is to make it possible.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the present invention, and FIG. 2 is a plan view thereof. In the diagram M1, reference numeral 1 denotes a heating resistor, a two-piece total air temperature measuring resistor, and a resistor for measuring the temperature of the wall of the 3Vi air passage body 20.

4 is a holder in which a pin 11 supporting the heat generating resistor 1 and a bottle 12 supporting the air temperature measuring resistor 2 are molded.
An electronic circuit board 5 is bonded. On the other hand, Podi 20ba,
It is composed of a main passage 22 and a bypass passage 21, and a three-quarter ring-shaped groove 23 is formed in the downstream part. 4 holders, bypass passage 21 of body 20
1' is inserted, and the O-ring 6 makes airtight.

The structures of the heating resistor 1 and the total air temperature measuring resistor 2 are as shown in FIG. That is, a platinum wire 102 is wound around a ceramic bobbin 101, both ends of the platinum wire are connected to leads 103, and then glass 104 is coated. Further, the heat generating resistor 1, the lead 103 of the total temperature measuring resistor, and the support pins 11 and 12 are connected by welding, respectively. Furthermore, the body wall temperature detection resistor uses a positive temperature coefficient thermistor and is integrated with the holder 4. FIG. 4 shows the electronic circuit of the circuit board 5. As shown in FIG. 51 to 53 are differential amplifiers, T transistors, R1 to R3, [1,7 to S + abo-R
tt + RX, Ry, RJt are resistors, E
R is the drive voltage.

Next, the operation will be explained. In Figure 1, the detected air Q is %Q
The air that is divided into O and QIK and flows into the bypass passage 21 passes through the heating resistor 1, the total air temperature measuring resistor 2, passes through 'Pt and Ps of ring i'+423, and Q at P4. join with. This air flow fiQ.

In FIG. 4, it is converted into a voltage signal at the V2 terminal.

That is, differential amplifiers 51 and 52, resistors R7 to R8R?
, Rs, and the transistor JZT so that the temperature difference between the heating resistor 1 and the total air temperature measuring resistor 2 is always kept at a constant value m, so that the air flow rate Q.

, 'The power that should be supplied to the heating resistor IVC is approximately (
1) It is shown by the Nino formula.

Ih2FLh=(A+Bv'head)(ThTq)...(
1) Here, h: Current flowing through the heating resistor Rh: Resistance value of the heating resistor A, B: Constant Th: Temperature of the heating resistor Tq: Air temperature Therefore, the detection voltage v2 of the electronic circuit is =IITXR
, so Equation (2) is obtained, and an air flow signal can be obtained.

As is clear from equation (2), K for obtaining a high fPIX signal requires that (Th TQ) be highly accurate. This (Th-TQ) is affected by the wall temperature of the body 20, as shown in FIG. In Figure 7, body 20
The amount of heat λH1λC conducted from the holder 4, which is at the same temperature, by thermal conduction via the support bins 11 and 12, and the lengths LH and L of the heating resistor 1 and the air temperature detection resistor 2.
Since C is different, (ThTq) appears to change, so V in equation (2) and the output change. Furthermore, depending on the structure of the ring groove 23, a temperature difference occurs between the air in the bypass passage and the air in the main passage, and the thermal expansion of the bypass air causes a change in the division ratio between Q and Q. As shown in FIG.

This temperature effect on the body wall becomes a particular problem in the throttle body integrated system, which is expected to be developed in the future due to the miniaturization of engines, as shown in FIG. 9. In Figure 9, 31
1 is a throttle body that integrates a throttle valve 30, a slot (not shown) opening sensor, a fuel injection valve, etc., and is a system that is directly attached to the intake pipe 32 of the engine.

The reason why the error in FIG. 8 is small at a high flow rate is because the wall surface of the body 20 is cooled or heated by the air, and the difference in temperature between the air temperature and the body 20 becomes small.

Next, the correction operation for this body wall temperature influence will be explained.

, In Fig. 4, the detection voltage V and the output voltage V
. The relationship is shown by equation (3).

Here, Rw is the resistance value of the body wall temperature measuring resistor 3. It can be seen that multi-temperature correction is possible by changing Z. On the other hand, since the relationship between the air flow rate and the v2 terminal voltage shown in equation (2) is as shown in Figure 5, the flow rate point with the smallest error shown in Figure 8, that is, the maximum point of the flow rate Q, Qma
x's output voltage V, and KER3-! of equation (3). By setting - to the same value, it is possible to correct only the low flow rate region.

FIG. 6 shows this operation.

That is, it can be seen that there is no change in the output voltage v0 at QmaxK, and the correction is added as ■ becomes smaller.

FIG. 10 shows the wall temperature measurement sensor of the body 20 in the body 2 (
1 This shows an example of direct attachment.

This example has exactly the same effect.

FIG. 11 shows another embodiment. This example is in an engine control system. 40 is a control device using a microcomputer, and includes an arithmetic processing section 41, a data storage section 42, and a power output section 44. This system outputs an optimal fuel amount signal 43 required for the engine from the engine intake air amount Q and an engine rotational speed signal (not shown).

Input the resistance values of heating resistor 1, air temperature measuring resistor 2, and body wall temperature measuring resistor 3 as the input signal for the intake air amount Q of the engine, and the temperature difference between the air temperature and heating resistor 1 becomes a constant value. As shown in FIG.
A correction value stored in advance in the data storage section 42VC is added to calculate the flow rate Q in the arithmetic processing section, and a fuel amount 43 based on the result is output.

〔Effect of the invention〕

As explained above, according to the present invention, even if there is a difference between the body wall temperature of the air passage and the air temperature, highly accurate flow rate detection can be obtained, and the dwarfness of the structural design is expanded. Effective in downsizing.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a configuration diagram of a heating resistor and a temperature measuring resistor.
Fig. 4 is a circuit diagram of the embodiment, Fig. 5 is an output voltage percentage diagram, Fig. 6 is a correction percentage spout, Fig. 7 is a partially enlarged view of Fig. 1, and Fig. 8
Figure 9 is a characteristic diagram during body heating, Figure 9 is a diagram showing an example of mounting an engine, Figure 10 is a diagram showing another embodiment of the present invention, Figure 1
FIG. 1 is a diagram showing another embodiment of the present invention. 1... Heat generating resistor, 2... Total air temperature measuring resistor, 3
...Air passage body wall temperature measuring resistor, 4...Holder, 5...Electronic circuit board.

Claims (1)

[Claims] 1. In an air flow rate detector consisting of a heat generating resistor and a total air temperature measuring resistor installed in the intake air flow path of an engine, the temperature of the wall surface of the air passage wall of the heat generating resistor and the air temperature measuring resistor is measured. A temperature detection resistor is installed to detect the temperature.
An air flow rate detector comprising means for correcting the air flow rate detected by the heating resistor and the air temperature measuring resistor with the temperature detected by the temperature detecting resistor.