JPH06265385A - Air flow rate measuring instrument - Google Patents

Abstract

PURPOSE:To stabilize the measurement accuracy of an air flow rate measuring instrument even when a reverse flow occurs due to large variation of the flowing speed of air by arranging a plurality of pieces of temperature sensitive resistors for detecting the temperature of intake air. CONSTITUTION:An exothermic resistor 4 has such a structure that cannot distinguish the flowing speed of air in the normal direction with that in the reverse direction and causes the jumping of its output voltage by outputting the flowing speed in the reverse direction in the same way as that for the flowing speed in the normal direction. Therefore, a temperature sensitive resistor A 5 is arranged at a position where the resistor A 5 is easily affected by the heat of the resistor 4 when air flows in the reverse direction and another temperature sensible resistor B 6 at another position where the resistor B 6 is hardly affected by the heat of the resistor 4 when the air flows in the normal or reverse direction. The resistor B 6 indicates a fixed intake-air temperature when such a state occurs that a reverse flow is generated at a fixed intake-air temperature, but the resistor A 5 is affected by the heat of the resistor 4 and its detecting temperature abruptly changes only when a reverse flow occurs. On the other hand, the detecting temperature of the resistor A 5 similarly changes when the intake-air temperature changes, but the temperature change is not so abrupt as compared with that at the time of reverse flow. Therefore, the presence/absence and flow rate of a reverse flow in an intake pipe can be discriminated from the variation of the detecting temperature of the resistor A 5.

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 detecting an intake air flow rate of an automobile engine, and more particularly to a temperature sensitive resistor for detecting an intake air temperature and an intake air flow rate. The present invention relates to a heat generating resistance type air flow device having a heat generating resistor.

[0002]

2. Description of the Related Art At present, in automobile engines and the like, in order to improve fuel efficiency and purify exhaust gas, an intake air flow rate is measured to control fuel injection (microcomputer control).
The mainstream system is a system that controls the air-fuel ratio and ignition timing. Some air flow rate measuring devices for measuring such an intake air flow rate measure the air flow rate by utilizing, for example, the resistance temperature characteristic of a heat wire. This type of air flow rate measuring device is suitable for measuring the intake air flow rate of an automobile engine because it has the advantages that it can directly measure the mass flow rate, has excellent high-speed response, and does not require much space for arrangement.

However, in this type of air flow rate measuring device, the fluctuation of the air velocity (pulsation) due to the reciprocating movement of the piston affects the measurement accuracy under a high load of the engine. For example, when the heating resistor cannot distinguish between the forward flow velocity and the reverse flow velocity due to its structure, the forward flow velocity and the reverse flow velocity are output the same, and the reverse flow occurs due to blowback from the engine at high load. A so-called jump-up phenomenon occurs in which the output voltage of the heating resistor becomes larger than the actual intake air flow rate, which is one of the problems to normally control the control system.

As a countermeasure against the spring-up in the heating resistance type air flow meter, a sub air passage is provided in the main air passage as described in JP-A-61-65053, and heat is generated in the sub air passage. It has a structure for arranging resistors.

[0005]

In the conventional air flow rate measuring device as described above, it is possible to prevent the backflow directly entering from the outlet of the sub air flow passage by the sub air flow passage. However, it is known that in the actual intake pipe, the flow velocity in the forward direction also increases in the region where the reverse flow occurs. In this, the part that is blown back as a reverse flow is sucked in as a positive direction part.

Therefore, it is necessary to accurately measure the amount of backflow as a countermeasure against the jumping up of the heating resistor type air flow meter.

The present invention was invented as a measure against the above problems, and an object thereof is to measure an air flow rate while maintaining a stable measurement accuracy even when a backflow occurs due to a large fluctuation of the air velocity. To provide a device.

[0008]

In order to achieve the above object, the present invention arranges one heating resistor and two or more temperature sensitive resistors, one of which is on the upstream side of the heating resistor. The temperature-sensitive resistor 1 detects the temperature of the heating resistor during reverse flow. Thus, the temperature change of the temperature sensitive resistor 1 is used as switching to determine the presence or absence of backflow in the intake pipe.

[0009]

According to the present invention having such a configuration, the presence or absence of backflow in the intake pipe can be determined by the temperature change of the temperature sensitive resistor 1 arranged on the upstream side of the heat generating resistor, and the amount of the temperature change causes heat generation. By correcting the output voltage of the resistor air flow meter, it is possible to maintain stable measurement accuracy even when mounted on an engine with large fluctuations in air velocity, and to provide an air flow measurement device with less pulsation influence. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The air flow measuring device according to the present invention will be described in detail below with reference to the illustrated embodiment, taking a heating resistor type air flow meter as an example.

First, FIG. 1 is a cross-sectional view of an air flow rate measuring apparatus showing an embodiment of the present invention. In the body 2 forming the air passage, a venturi pipe 3 mechanically fixed to the control circuit built-in module 1 is arranged in the main air flow passage 9.
Further, in the venturi pipe 3, a heating resistor 4 for detecting the intake air flow rate and a temperature sensitive resistor A5 and a temperature sensitive resistor B6 for detecting the intake air temperature are installed. Heating resistor 4, temperature-sensitive resistor A5, and temperature-sensitive resistor B
Reference numeral 6 is electrically connected to the control circuit built-in module 1 through a support member 7 made of a conductive member. The heating resistor 4 is heated so as to have a certain temperature difference with respect to the temperature sensitive resistor B6, and the drive circuit is configured to obtain an output characteristic according to the air flow rate. Further, the temperature sensitive resistor B6 has a function of measuring the intake air temperature regardless of the temperature difference between the temperature sensitive resistor B6 and the heating resistor 4. The Venturi tube 3 shown in the figure may be in a state where it is not mounted.

In the heating resistor type air flow meter as in the present embodiment, when the air velocity fluctuation (pulsation) accompanying the reciprocating motion of the piston becomes large under a high load of the engine, the influence of backflow due to blowback from the engine, etc. Causes the output voltage of the heating resistor type air flow meter to jump,
It is generally known that the measurement accuracy is affected.
FIG. 3 shows a diagram of the phenomenon. In the figure, the horizontal axis shows the suction negative pressure in the intake manifold, and the vertical axis shows the output voltage of the heating resistor type air flow meter, with the rotation speed kept constant. When the throttle valve opening is near full opening, a linear state is a normal characteristic, and a sharp rise is a jumping phenomenon. FIG. 2 is a diagram showing intake air pulsation in the intake pipe of the engine. This figure shows a state in which the pulsation is particularly large (around the fully opened throttle valve at low speed). Due to the structure of the heating resistor, it is not possible to distinguish between the forward flow velocity and the backward flow velocity, and it is possible that the backward flow velocity as shown by symbol 12 in FIG. This is the cause of the output voltage of the meter jumping up.

According to the present invention, the heating resistor 4 is used when the backflow occurs.
The temperature-sensitive resistor A5 is placed at a position that is easily affected by the heat of
The temperature sensitive resistor B6 is arranged at a position where it is unlikely to be affected by the heat of the heating resistor 4 in both forward flow and reverse flow. In this structure, when the backflow occurs at a certain constant intake air temperature, the temperature-sensitive resistor B6 shows a constant intake temperature as shown in FIG. 4, but the detected temperature of the temperature-sensitive resistor A5 is Due to the heat effect of the heating resistor 4, the detected temperature changes rapidly only during reverse flow as shown in the figure. Further, when the suction temperature changes, the detected temperature of the temperature sensitive resistor A5 also changes, but the temperature change is not abrupt as compared with the case of backflow. That is, the presence or absence of backflow in the intake pipe can be determined by the degree of change in the detected temperature output of the temperature sensitive resistor A5. In order to know the degree of change in the detected temperature output of the temperature sensitive resistor A5, it is conceivable to use a microcomputer to take the differential value of the change in the detected temperature output of the temperature sensitive resistor A5. Also, the amount of backflow can be known from the magnitude of the differential value.

As described above, by knowing the degree of change in the detected temperature output of the temperature sensitive resistor A5, it is possible to know the presence or absence of backflow and its amount, and the output voltage of the heating resistor type air flow meter jumps. A true intake air flow rate can be measured by correcting the reverse flow rate when going up, and a highly reliable air flow rate measurement device can be provided.
As a matter of course, in the case of the air flow rate measuring device having this structure, the reverse flow rate may be corrected by the air flow rate measuring device itself or by the engine control unit.

[0015]

According to the present invention, it is possible to provide a highly reliable air flow rate measuring device in which the jumping phenomenon due to the influence of pulsation is reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heating resistance type air flow rate measuring device showing an embodiment of the present invention.

FIG. 2 is a simulated diagram of a pulsating waveform in an intake passage of a heating resistance type air flow measuring device.

FIG. 3 is a characteristic diagram showing a jump of a heating resistance type air flow meter.

FIG. 4 is a simulation diagram showing a temperature detected by a temperature-sensitive resistor according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Module with built-in control circuit, 2 ... Body, 3 ... Venturi tube, 4 ... Heating resistor, 5 ... Temperature sensitive resistor A, 6 ... Temperature sensitive resistor B, 7 ... Support material, 9 ... Main air flow path, 10 ... Forward flow velocity, 11 ... Reverse flow velocity, 12 ... Reverse flow erroneous measurement unit of heating resistor.

Claims (5)

[Claims] 1. In an internal combustion engine, air having an exothermic resistor for detecting an intake air flow rate and a temperature sensitive resistor for detecting an intake air temperature in an air flow path for measuring the intake air. The air flow rate measuring device, wherein a plurality of temperature sensitive resistors for detecting the intake air temperature are arranged in the flow rate measuring device. 2. A thermosensitive resistor according to claim 1, wherein at least one of the plurality of temperature-sensitive resistors is placed at a position susceptible to thermal influence of a heat-generating resistor that detects an intake air flow rate when backflowing in an air flow path. An air flow measuring device characterized by being arranged. 3. The air flow rate according to claim 2, wherein the temperature sensitive resistor is arranged substantially upstream of the air flow in the positive direction of the heating resistor for detecting the intake air flow rate. measuring device. 4. The method according to any one of claims 1 to 3, wherein at least one of the temperature-sensitive resistors arranged in plurality takes an independent detection output regardless of the heating temperature of the heating resistor. A characteristic air flow measuring device. 5. The air flow rate measuring device according to any one of claims 1 to 4 is used.
Electronic fuel injection system.