JPH07198438A - Temperature-sensitive intake air flow rate detection device for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the detection accuracy of the temperature-sensitive flowmeter from deteriorating due to backflow of intake air. A funnel-shaped backflow detection suppressing member (21) that gradually reduces the effective opening area of the intake duct (13) is provided downstream of the temperature-sensitive resistor ( _RH) arranged in the intake duct (13). . Then, the amount of the backflowing air reaching the temperature sensitive resistance R _H is limited by the narrow opening at the downstream end of the member 21. Further, a pressure accumulating chamber 22 for accumulating the backflowing air is formed in the outer peripheral portion of the member 21 to suppress the pressure rise and the occurrence of intake pulsation due to the arrangement of the member 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature-sensitive intake air flow rate detecting device for an internal combustion engine, and more particularly to a device for detecting an intake air flow rate of the engine based on a temperature-sensitive resistance arranged in an intake passage of the internal combustion engine. Regarding

[0002]

2. Description of the Related Art An electronically controlled fuel injection system for an internal combustion engine is equipped with an air flow meter (air flow meter) for detecting an intake air flow rate Q of the engine, and the intake air flow rate Q detected by this air flow meter is A configuration is known in which the basic fuel injection amount Tp = K × Q / Ne (K is a constant) by the fuel injection valve is calculated from the engine speed Ne, and as the air flow meter, the actual flow rate is 59-78926. A temperature-sensitive flow meter as disclosed in Japanese Laid-Open Patent Publication is used.

In the temperature-sensitive flowmeter, a so-called hot wire type or hot film type temperature sensitive resistor is arranged in the intake passage, and a current is supplied to the temperature sensitive resistor to generate heat at a constant temperature (resistance value). Then, the temperature decrease due to the intake air is compensated for by increasing the current, and the intake air flow rate is obtained from the current value. That is, the temperature-sensitive flow meter 1 in FIG. 3 will be described as an example. In addition to the temperature-sensitive resistance R _H (hot wire or hot film), temperature compensation resistance R _K, reference resistance R _s, fixed resistance R _{1 ,} R ₂ and bridge circuit B
Is configured.

The temperature sensing resistor R of the bridge circuit B
_H and the reference resistance R _s are connected in series, the potential of the voltage dividing point (the terminal voltage of the reference resistance R _s ) and the temperature compensation resistance R
_K and the potential at the voltage dividing point on the side where the fixed resistors R _{1 and} R ₂ are connected in series (the terminal voltage of the fixed resistor R ₂ ) are input to the differential amplifier OP. The supply current to the bridge circuit B is corrected via the transistor Tr according to the output of the dynamic amplifier OP.

That is, when the intake air flow rate of the engine increases, for example, when the bridge circuit B is in a balanced state,
The temperature sensitive resistance R _H is further cooled by this air flow, its resistance value decreases, and the terminal voltage of the reference resistance R _s increases,
The bridge circuit B becomes unbalanced and the output of the differential amplifier OP increases. As a result, the supply current to the bridge circuit B controlled by the transistor Tr increases, the temperature-sensitive resistor R _H is heated, and its resistance value increases, whereby the balanced condition of the bridge circuit B is restored.

Here, when the temperature of the intake air decreases, for example, the temperature-sensitive resistor R _H is cooled and its resistance value decreases, but the temperature-compensating resistor R _{K in the} same atmosphere as the temperature-sensitive resistor R _H.
At the same time, the resistance value of the bridge circuit B is reduced and the resistance value of the bridge circuit B is reduced, so that the current value supplied to the bridge circuit B is prevented from changing due to the temperature change of the intake air. Therefore, the intake air flow rate Q of the engine and the current supplied to the bridge circuit B correspond independently of the intake air temperature, and the intake air flow rate Q is measured by detecting the terminal voltage Us of the reference resistance R _s. can do.

In the example shown in FIG. 3, the terminal voltage Us of the reference resistor R _s is A / D converted by the A / D converter 3 and read by the microcomputer 4,
Then, a table for converting the terminal voltage Us into the intake air flow rate Q is provided in advance, and the terminal voltage U is converted using the table.
The information of s is converted into the intake air flow rate Q to detect the intake air flow rate Q of the engine. Then, the amount of fuel to be injected and supplied from a fuel injection valve (not shown) is determined based on the information of the intake air flow rate Q, and an air-fuel mixture having a predetermined air-fuel ratio is formed.

In FIG. 3, reference numeral 2 is an ignition switch, and a battery voltage VB is applied to the temperature-sensitive flow meter 1 and the microcomputer 4 via the ignition switch 2.

[0009]

By the way, when the throttle valve opening is large and the engine speed is in the low speed region or the high speed region, the intake pulsation including the backflow component is applied to the temperature sensitive flowmeter from the cylinder side. It may reach the temperature-sensitive resistance R _H. At this time, since the flow direction of the temperature-sensitive resistor R _H cannot be determined, the reverse flow is also detected in the same manner as the positive direction (see FIG. 4), and as a result, a value larger than the true intake air flow rate is detected as the average flow rate. There was a problem that it would end up.

As described above, when the detected value of the intake air flow rate becomes larger than the true intake air flow rate, the extra fuel is injected and supplied by the electronic fuel injection control based on the detected value. The air-fuel ratio will be made richer than the target air-fuel ratio. The present invention has been made in view of the above problems, and even if intake pulsation containing a backflow component occurs, it is possible to prevent the backflow of the intake air from being transmitted to the temperature-sensitive resistance, thereby detecting the intake air flow rate. The purpose is to improve.

[0011]

Therefore, in the present invention, a temperature-sensing system for detecting an intake air flow rate of an engine based on a resistance value change of a temperature-sensitive resistance arranged in an intake passage of an internal combustion engine according to an intake air flow rate. In the intake air flow rate detection device, a funnel-shaped backflow detection suppression member is provided which is interposed in the intake passage on the downstream side of the temperature-sensitive resistor and gradually reduces the effective opening area of the intake passage toward the downstream side. did.

[0012]

With this structure, the intake air in the positive direction from the temperature-sensitive resistance side toward the internal combustion engine side is guided to the funnel-shaped backflow detection suppressing member that gradually reduces the effective opening area of the intake passage toward the downstream side. , All the passing air of the temperature sensitive resistance flows to the engine side. On the other hand, in the intake backflow from the internal combustion engine side toward the temperature-sensitive resistance side, the temperature-sensitive resistance is limited to the flow through the thinnest opening at the downstream end of the backflow detection suppressing member. Thus, the amount of backflow detected can be sufficiently suppressed.

[0013]

EXAMPLES Examples of the present invention will be described below. Figure 1
FIG. 3 is a diagram showing an arrangement state of temperature-sensitive resistors R _H in the present embodiment with respect to an engine. In FIG. 1, the internal combustion engine 11 includes
Air cleaner 12, intake duct 13, throttle chamber 1
4, air is taken in through the intake collector section 15 and the intake manifold 16.

A temperature-sensitive resistor R _H constituting the temperature-sensitive flow meter 1 shown in FIG. 3 is interposed in the intake duct 13 upstream of the throttle chamber 14. Since the configuration and operation of the temperature-sensitive flow meter 1 of FIG. 3 have been described above, the description thereof will be omitted here. A throttle-type throttle valve 17 is interposed in the throttle chamber 14, and a fuel injection valve 18 is provided in each branch of the intake manifold 16 for each cylinder.
Is provided.

A wax pellet type auxiliary air amount control valve 20 is provided in an auxiliary air passage 19 which bypasses the throttle valve 17, and the auxiliary air passage 19 is provided in accordance with the cooling water temperature. It is designed to open and close. Further, as a characteristic configuration of the present embodiment, the effective opening area of the intake duct 13 (intake passage) gradually increases in the intake duct 13 between the temperature-sensitive resistor R _H and the throttle valve 17 toward the downstream side. A funnel-shaped backflow detection suppressing member (21) for reducing the current is interposed. Further, a pressure accumulating chamber 22 having a predetermined volume is formed at an upstream end of a space portion surrounded by the outer circumference of the backflow detection suppressing member 21 and the inner circumference of the intake duct 13.

According to this structure, the intake air in the forward direction from the temperature-sensitive resistor R _H side toward the internal combustion engine side 11 is guided to the reverse flow detection inhibiting member 21, and all the air passing through the temperature-sensitive resistor R _H is transferred to the engine. It will flow to the 11th side. On the other hand, when the throttle valve opening is large and the engine speed is in the low speed range or the high speed range, when an intake backflow from the internal combustion engine 11 side toward the temperature-sensitive resistance _RH side occurs, the intake backflow is: Not all are transmitted to the temperature sensitive resistance R _H , but the backflow detection inhibiting member 21.
Will be regulated by.

That is, the backflow detection inhibiting member 21 is not provided.
In the case, all of the backflow is temperature-sensitive resistance R _HWill lead to
However, in the case of this embodiment, the temperature-sensitive resistance R_HThe backflow to
Pass the thinnest opening at the downstream end of the backflow detection suppression member 21.
Flow is limited to
The detection amount can be suppressed sufficiently. Therefore, backflow
Suppresses deterioration of detection accuracy of intake air flow rate Q due to detection of minute
It is possible to detect the intake air flow rate with high accuracy.
Become so.

On the other hand, the backflow detection inhibiting member 21 does not pass through the thinnest opening at the downstream end of the backflow detection inhibiting member 21.
Backflow air flowing toward the upstream side of the outer periphery of the backflow is stored in the pressure accumulating chamber 22 having a predetermined volume, so that the pressure at the downstream end of the backflow detection inhibiting member 21 is prevented from rising when a backflow occurs. In addition, it is possible to avoid an increase in intake pulsation due to the provision of the backflow detection suppressing member 21.

By the way, in the first embodiment described above, all the air taken into the engine passes through the temperature sensitive resistance R _H , but as shown in FIG. 2, the intake duct 13 is replaced by the main duct 13a. And a bypass duct 13b provided by bypassing the main duct 13a, a temperature sensing resistor _RH and a backflow detection inhibiting member 21 are provided on the side of the bypass duct 13b, and a pressure accumulating chamber 22 is formed. It may be allowed to.

In FIG. 2, the same elements as those in FIG. 1 are designated by the same reference numerals, and the description of the above-mentioned configuration will be omitted. According to the second embodiment shown in FIG. 2, similar to the first embodiment shown in FIG. 1, the backflow is detected and the intake pulsation is suppressed, and most of the intake air can flow into the main duct 13a. The unique effect is that the pressure loss due to the backflow detection suppressing member 21 is smaller than that in the case of the first embodiment.

In the second embodiment, the main duct 13
Although a and the bypass duct 13b are formed separately, a partition wall may be formed in the intake duct 13 to separate the main duct part and the bypass duct part. Although only the temperature-sensitive resistor R _H is shown in FIGS. 1 and 2, it is preferable to arrange the temperature-compensating resistor R _K shown in FIG. 3 in parallel with the temperature-sensitive resistor R _H in FIGS. 1 and 2.

[0022]

As described above, according to the present invention, even if the intake pulsation containing the backflow component occurs, the amount of the backflow component reaching the temperature-sensitive resistance can be sufficiently reduced. There is an effect that it becomes possible to prevent deterioration of the detection accuracy of the intake air flow rate due to the detection of the backflow component.

[Brief description of drawings]

FIG. 1 is a system schematic diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic view of a system showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a circuit configuration of a temperature-sensitive flow meter.

FIG. 4 is a time chart showing characteristics of backflow detection.

[Explanation of symbols]

11 Internal Combustion Engine 13 Intake Duct 14 Throttle Chamber 17 Throttle Valve 21 Backflow Detection Suppression Member 22 Accumulation Chamber _RH Temperature Sensitive Resistance

Claims (1)

[Claims] 1. A temperature-sensitive intake air flow rate detecting device for detecting an intake air flow rate of an engine based on a resistance value change of a temperature-sensitive resistance arranged in an intake passage of an internal combustion engine according to an intake air flow rate. A temperature-sensing internal combustion engine characterized in that a funnel-shaped backflow detection suppressing member is provided in the intake passage on the downstream side of the temperature resistance and gradually reduces the effective opening area of the intake passage toward the downstream side. Type intake air flow rate detection device.