JPS6127691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake air amount measuring device for an internal combustion engine that prevents malfunction of an engine air flow sensor due to electromagnetic interference.

Figure 1 is a block diagram showing the configuration of a conventional intake air amount measuring device for an internal combustion engine, and shows an example in which an ultrasonic detection type Karman vortex flowmeter is applied to an automobile intake air amount sensor. .

In FIG. 1, 1 is an air cleaner main body, and a cleaner element 2 is housed inside the air cleaner main body. This air cleaner body 1 has an intake passage 5
It is connected to an engine (not shown) via a vortex generating column 4 on the upstream side of the intake passage 5 .

Further, reference numeral 3 denotes an intake air amount measuring device, which is composed of an air amount detecting section 6, a flow rate measuring circuit 7, and an intake air temperature sensor 9. Among these, air amount detection section 6
On the downstream side of the vortex generating column 4, an ultrasonic transmitter 61 and an ultrasonic receiver 62 are arranged facing each other via the intake passage 5, and the ultrasonic transmitter 31 and the ultrasonic receiver 62 are arranged opposite to each other via the intake passage 5. It is connected to the flow rate measuring circuit 7 via conducting wires 63 and 64. The flow rate measuring circuit 7 is housed in a case 8.

This flow rate measuring circuit 7 is supplied with power by a battery 10 and outputs to an engine control device 11, and the output from the intake noise sensor 9 is also introduced to the engine control device 11 via a conductor 91. ing.

With this configuration, the number of Karman vortex streets generated on the downstream side of the vortex generating column 4 is determined by the modulation received by the ultrasonic wave transmitted from the ultrasonic transmitter 61 and received by the ultrasonic receiver 62. The flow velocity measurement circuit 7
It is counted by demodulating it with Thereby, the flow velocity measurement circuit 7 detects the Karman vortex frequency proportional to the flow velocity, and outputs the output to the engine control device 11.

The engine control device 11 receives the output of the flow rate measuring circuit 7 and the output of the intake air temperature sensor 9 to control the engine.

The conventional intake air amount measuring device for an internal combustion engine is configured as described above, and because it is a device for measuring the intake air amount of the engine, it is installed in the engine room. There are many sources of electromagnetic interference in this engine room, such as noise generated by the ignition system and electrical noise generated by the horn, which can be induced into the power supply lines or input/output signal conductors and cause malfunctions.

In particular, in devices that detect the amount of intake air,
A sensor for detecting a physical quantity corresponding to the amount of intake air is attached to the air amount detection section 6, and the electrical signal obtained by the sensor is sent via conductive wires 63 and 64 to a flow rate measuring circuit 7 made up of a complicated electronic circuit. must be sent.

Normally, sensors (ultrasonic transmitter 61, ultrasonic receiver 62) that detect a physical quantity corresponding to the amount of air output a weak analog signal, and the electronic circuit constituting the flow velocity measuring circuit 7 also handles analog signals. This first
In the illustrated example as well, if a weak analog signal is generated as the output signal of the ultrasonic receiver 62, the flow rate measuring circuit 7 may malfunction due to the noise signal.

Furthermore, in recent years, the output of in-vehicle transceivers has increased, and the radiated electromagnetic waves generate induced noise in the sensor of the air amount detection section 6 or in the conductors 63 and 64, causing the flow rate measurement circuit 7 to malfunction. . Furthermore, if the intake air amount measuring device 3 is connected in series on the downstream side of the air cleaner main body 1,
That much space is required.

This invention was made to eliminate the above-mentioned conventional drawbacks, and by using the air cleaner body as a shield case, it is possible to improve the noise resistance and make the entire device more compact. The object of the present invention is to provide a quantity measuring device.

Embodiments of the intake air amount measuring device for an internal combustion engine according to the present invention will be described below with reference to the drawings. Second
The figure is a block diagram showing the configuration of one embodiment. In FIG. 2, the same parts as in FIG. 1 will be described with the same reference numerals.

In FIG. 2, an air cleaner main body 1 is made of a conductive material, in which a cleaner element 2 is housed, as well as an entire intake air amount device 3, and an intake passage 5 is connected to an engine (not shown). ) is connected to. On the upstream side of the intake passage 5 housed in the air cleaner body 1, there is a first
As in the case shown in the figure, a vortex generating column 4 is arranged, and an ultrasonic transmitter 61 and an ultrasonic receiver 62 are arranged facing each other on the downstream side of the column via the intake passage 5. . The ultrasonic transmitter 61 and the ultrasonic receiver 62 are connected to the flow rate measurement circuit 7 via conductive wires 63 and 64, respectively. An air amount detection section 6 is configured.

The flow rate measuring circuit 7 is housed in a case 8, and the case 8 is connected to the air cleaner main body 1 through a connection line 201. In addition, the flow velocity measuring circuit 7 is connected to the battery 1.
The output of the flow velocity measuring circuit 7 is sent to the engine control device 11, and the output of the intake temperature sensor 9 is introduced to the engine control device 11 through a conductor 91. .
Of course, this intake temperature sensor 9 is also connected to the air cleaner body 1.
It is stored inside.

This configuration is similar to the first one except that the entire intake air amount measuring device 3 is housed inside the air cleaner body 1.
It is the same as the figure, and the explanation of the operation related to the detection of the intake air amount is omitted to avoid duplication.
I will now explain the part related to the shield.

That is, as described above, since the air cleaner body 1 is made of a conductive material and the entire intake air amount measuring device 3 is housed within the air cleaner body 1, the air cleaner body serves as an electrostatic and electromagnetic shield. This prevents noise induced in the ultrasonic transmitter 61, ultrasonic receiver 62, and conductive wires 63, 64 that constitute the air amount detection section 6, and noise induced in the flow rate measuring circuit 7 from being introduced.

Furthermore, the flow rate measuring circuit 7 is shielded by a case 8 made of a conductor, and since the case 8 is connected to the air cleaner main body 1 through a connecting wire 201, they are at the same potential. Therefore, the flow rate measuring circuit 7 is double shielded by the case 8 and the air cleaner main body 1, and becomes less susceptible to the influence of induced noise.

Furthermore, by incorporating the intake air amount measuring device 3 into the air cleaner main body 1, there is an advantage that the entire device can be made more compact than a structure in which the air cleaner main body and the intake air amount measuring device 3 are each independent.

FIG. 3 is a block diagram showing the structure of the intake air amount measuring device for an internal combustion engine according to the present invention. In FIG. 3, in order to simplify the explanation, the same parts as in FIG.
I will focus on the parts that are different from those in Figure 2.

As is clear from comparing FIG. 3 with FIG. 2, the air cleaner main body 1 is made of a conductive material, and the entire intake air amount measuring device 3 is housed therein.
The case 8 is connected to the cleaner main body 1 by a connecting wire 201 as in FIG. 2, but the following points differ from FIG. 2.

That is, the entire intake passage 5 or a portion of the air amount detection unit 6 is formed of a conductive material, and the ultrasonic transmitter 61 and the ultrasonic transmitter 62 are arranged within the intake passage 5 formed of this conductive material. As such, it is surrounded by the intake passage 5. The case 8 is connected to the intake passage 5 through a connection line 301. Therefore, the intake passage 5, the case 8, and the air cleaner body 1 are at the same potential.

With this configuration, the ultrasonic transmitter 61 and the ultrasonic receiver 62 are doubly shielded by the intake passage 5 and the air cleaner body 1.
It is possible to further reduce the noise induced in the

In addition, it is made of a conductive material so that the induced noise transmitted through the conductive wire 91 of the intake air temperature sensor 9 will not be guided to the ultrasonic receiver 61, the ultrasonic receiver 62, and the conductive wires 63, 64 thereof and cause malfunction. A shield plate 302 is provided between the conducting wire 91, the case 8, and the intake passage 5 in the air cleaner main body 1. This stiffening plate 302 is connected to the air cleaner main body 1, and the air cleaner main body 1
It is at the same potential as. The other configurations are the same as in FIG. 2.

FIG. 4 is a block diagram showing the structure of a third embodiment of the intake air amount measuring device for an internal combustion engine according to the present invention. In FIG. 4 as well, the same parts as those in FIG. 2 are given the same reference numerals, and the explanation thereof will be omitted, and the parts different from those in FIG. 2 will be mainly described.

By the way, normally, the air cleaner body 1 is attached to the vehicle body 4.
03, vibration isolating rubber is sandwiched between the air cleaner body 1 and the vehicle body 403 and screwed to the vehicle body 403 to electrically insulate the air cleaner body 1 and the vehicle body 403.

As in each of the above embodiments, in order to shield the entire intake air amount measuring device with the case 8 and the air cleaner main body 1, the case 8 and the air cleaner main body 1 are
Even if the potential is not fixed, there is some effect.

However, in order to make the shield more effective, as shown in Figure 4, it is necessary to
The power supply line 402 connected to the (-) side terminal and the case 8 may be connected using the connection line 401.

Originally, the electromagnetic shield room from the on-board equipment was battery 1.
Since the (-) side of 0 is grounded to the vehicle body 403, it is generated based on the (-) potential of the battery 10, and the potential of the shield is also the same as that of the battery 10.
It is best to set it to (-) potential.

Even if sufficient shielding is performed, some or all of the power supply lines or input/output lines may be affected by noise induced into the power supply line or induced noise due to high-frequency electromagnetic waves entering through gaps in the air cleaner body 1. Inserting a filter is effective.

Therefore, in this FIG. 4, in addition to the configuration shown in FIG. A filter 404 is inserted between them. As the filter 405, a π type filter 405 may be used.

Furthermore, within this case 8, a filter 4
The filter 407 is inserted between the output line of the flow rate measurement circuit 7, the power supply line on the (+) side of the battery 10, and the flow rate measurement circuit 7.
Ground wire 406 of filter 404, filter 40
The ground wires 403 of No. 7 are both connected to the case 8, and the case 8 is connected to the power supply line 402 via the connection wire 401 as already mentioned.
Then, the case 8 has a connection line 201 as shown in FIG.
It is connected to the air cleaner main body 1 via.

Therefore, the air cleaner body 1 and the vehicle body 403
Even if the air cleaner body 1 is electrically floating because it is attached with a vibration-proof rubber between the The shield effect can be made stronger than usual. In addition, filter 404,
407 is inserted and is set at the same potential as case 8, so that induced noise can be further prevented.

By the way, each of the above embodiments describes the case where electromagnetic interference is prevented when an ultrasonic detection type Karman vortex flowmeter is applied to an automobile intake air amount sensor, but it is not possible to prevent electromagnetic interference using a thermistor or pressure sensor other than ultrasonic waves. A similar effect can be expected with an intake air amount measuring device using a Karman vortex flowmeter.

Further, similar effects can be expected with a hot-wire type intake air amount measuring device other than the Karman vortex flowmeter, for example.

As described above, according to the intake air amount measuring device for an internal combustion engine of the present invention, the air cleaner main body is made of a conductive material and doubles as a shield case.
Since the intake air amount measuring device is housed inside the air cleaner, noise resistance can be greatly improved, and malfunctions of the flow rate measuring circuit due to electromagnetic interference can be prevented, and the intake air amount measuring device and the air cleaner body are independent. This has the effect of making it more compact than if it were configured in the same way. In addition, a shield plate with the same potential as the air cleaner body is installed between the air temperature sensor housed in the air cleaner body, its conductor wire, and the case of the flow rate measurement circuit, so that there is no induction effect on the flow rate measurement circuit and its conductor wires. Furthermore, by providing a filter between the conductors of the ultrasonic transceiver and between the flow rate measuring circuit and the battery, induced noise can be prevented, further promoting the above effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional intake air amount measuring device for an internal combustion engine, FIG. 2 is a block diagram showing the configuration of an embodiment of the intake air amount measuring device for an internal combustion engine according to the present invention, and FIG. and FIG. 4 are block diagrams showing the structure of other embodiments of the intake air amount measuring device for an internal combustion engine according to the present invention. DESCRIPTION OF SYMBOLS 1... Air cleaner body, 2... Cleaner element, 4... Vortex generation column, 5... Intake passage, 6...
... Air amount detection section, 7 ... Flow velocity measurement circuit, 8 ... Case, 9 ... Intake temperature sensor, 10 ... Battery,
11...Engine control device, 61...Ultrasonic transmitter, 62...Ultrasonic receiver, 63, 64, 91...
... Conductor wire, 201, 401 ... Connection wire, 302 ...
Shiyahei board, 403...Car body, 404,407...
...filter. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. An air amount detection section that is provided in the intake air passage and detects the amount of air taken into the engine; an electric signal corresponding to the intake air amount upon receiving the output from the air amount detection section; A flow rate measurement circuit to output, a conductive case that houses the flow rate measurement circuit, the passage section, the air amount detection section, the flow rate measurement circuit, and the case, which are made of a conductive material and have the same potential as the case. What is claimed is: 1. An intake air amount measuring device for an internal combustion engine, comprising an air cleaner main body connected in a manner similar to the above. 2. Claim 1, characterized in that the entire intake air passage or the passage surrounding the air amount detection unit is formed of a conductor and is electrically connected to the case and the air cleaner body. Intake air amount measurement device for internal combustion engines. 3. The intake air amount measuring device for an internal combustion engine according to claim 1 or 2, wherein the air amount detection section is a Karman vortex flow meter. 4. The intake air amount measuring device for an internal combustion engine according to claim 1 or 2, wherein the air amount detection section is an ultrasonic transmitter. 5. The intake air amount measuring device for an internal combustion engine according to claim 1 or 2, wherein the air amount detecting section is a hot wire flow meter. 6. The intake air amount measuring device for an internal combustion engine according to claim 1 or 2, wherein the air amount detection element is a heat-sensitive element. 7. The intake air amount measuring device for an internal combustion engine according to claim 1 or 2, wherein the air amount detection section is a pressure detector. 8. The internal combustion engine according to any one of claims 1 to 7, characterized in that the power supply line on the (-) side of the battery is electrically connected to the case housing the flow rate measuring circuit. Intake air amount measuring device. 9. An air amount detection section that is installed in the intake air passage and detects the amount of air taken into the engine; a flow rate measurement circuit that receives the output from the air amount detection section and outputs an electrical signal corresponding to the amount of intake air; A conductive case that houses the flow rate measurement circuit, an air cleaner that houses the passage section, the air amount detection section, the flow rate measurement circuit, and the case, and is made of a conductive material and connected to the case so as to have the same potential. A main body, an intake temperature sensor housed in the air cleaner main body, and a conductive shield plate provided between the intake temperature sensor and its conductor and the case and connected to the same potential as the air cleaner main body. An intake air amount measuring device for an internal combustion engine, characterized by: 10 An air amount detection section that has an ultrasonic transmitter and an ultrasonic receiver and is installed in the intake air passage and detects the amount of air taken into the engine; an air amount detection section that detects the amount of intake air in response to the output from this air amount detection section; A flow velocity measurement circuit that outputs an electric signal corresponding to the flow velocity measurement circuit, a conductive case that houses the flow velocity measurement circuit, a conductive case that houses the passage section, the air amount detection section, the flow velocity measurement circuit, and the case, and that is made of a conductive material and The air cleaner body is connected to the same potential as the case.
A ground wire is provided between the conductor connecting the flow velocity measurement circuit and the ultrasonic transmitter and ultrasonic receiver, and between the power supply line on the (+) side of the battery and the output line of the flow velocity measurement circuit, and the ground wire is connected to the above case. An intake air amount measuring device for an internal combustion engine, comprising connected filters.