JPS6058830B2 - Hot-wire flow velocity measuring device for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow velocity measuring device for an internal combustion engine, and in particular, a hot wire flow velocity detector that generates an electrical signal according to the flow velocity of the intake force into the internal combustion engine, and a hot wire flow velocity detector that samples this electrical signal. The present invention relates to a flow rate measuring device for an internal combustion engine that includes an analog-to-digital (A/D) converter for converting into a digital signal.

Conventionally, such flow rate measuring devices have been used especially for internal combustion engines that measure the intake air amount of an internal combustion engine and digitally process this using a central control device using a digital computer such as a microcomputer to control the air-fuel ratio. It is often used in central control devices for automobiles.

The output voltage of the current velocity detector is sensitive to even minute changes in flow velocity, so if the flow velocity includes changes such as pulsations, this will be reflected sensitively. For example, as is well known, an internal combustion engine periodically repeats the suction, compression, explosion, and exhaust steps, and the output voltage of the hot wire flow rate detector also pulsates in synchronization with this. This pulsation period changes in proportion to the rotational speed of the internal combustion engine. On the other hand, the A/D converter always performs sampling at a predetermined period regardless of fluctuations in the pulsation period of the input signal from the detector, so it is possible to accurately measure the flow velocity in response to pulsations, and also to measure the amount of intake air. There is a drawback that it cannot be done. In addition, the conversion operation of the A/D converter and the processing operation of the subsequent microcomputer are usually based on the case where the pulsation period of the output voltage of the flow rate detector is short, so that accurate flow rate calculations can be performed even in that case. The calculation cycle is set in . Therefore, even if the pulsation period is long and accurate flow rate calculations can be performed even if the calculation period is long, the load on the computer is not reduced, and the computer performs wasteful and low-efficiency processing, only when the pulsation period is long. The disadvantage is that there is little room for other processing to be carried out. SUMMARY OF THE INVENTION An object of the present invention is to provide a flow rate measuring device that can eliminate these conventional drawbacks and perform precise flow rate measurements.

Another object of the present invention is to provide a flow rate measuring device that can reduce the load on a computer connected to a current meter when the pulsation period of the output voltage of the flow rate detector is long.

These objects are achieved by a flow rate measuring device for an internal combustion engine according to the present invention as follows.

That is, this flow rate measuring device includes a speed detection means for detecting the rotational speed of the internal combustion engine, and a control means for energizing the A/D converter to perform sampling at a period corresponding to the detected speed, Thereby, the A/D converter generates a digital output representing the flow velocity at a period corresponding to the rotational speed of the internal combustion engine. According to one aspect of the present invention, the speed detection means has a pulse generator that generates pulses according to the rotation angle of the crankshaft of the internal combustion engine, and the control means is connected to the pulse generator and generates a predetermined number of pulses. It has a cyclic counter that outputs a control signal when counted, and an A/D
The converter performs sampling in response to this control signal. Embodiments of a flow rate measuring device for an internal combustion engine according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a flow rate measuring device according to the present invention. In the same figure, the flow velocity measuring device measures the intake air amount of the engine's fuel injection device (not shown),
The measurement data is transferred to the microcomputer 12 of the automobile central control device via the input/output interface 14. As shown in the figure, this device includes a hot wire flow velocity detector 16 that generates an electric signal (C in Figure 2) in a lead S3 according to the flow velocity of intake air, and a hot wire flow velocity detector 16 that samples this electric signal S3 and converts it into a digital signal. Analog/digital A/D
The output of the converter 18 is supplied to the computer 12 via the interface 14. By the way, a crank angle sensor 20 consisting of a pulse generator that generates counting pulses according to the rotation angle of the engine (not shown) is connected to the crankshaft of the engine (not shown), and its output (A in FIG. 2) is connected to a lead S1. Transfer to counter 22. In this embodiment, the counter 22 outputs one energizing pulse (FIG. 2B) every three output pulses of the sensor 20.
) on lead S2. That is, the counting pulse S1 is set to 1 by the counter 22.
B is stepped down and becomes the energizing pulse S1. In this embodiment, as shown in FIG. 2, the sensor 20 is configured to generate 12 counting pulses S1 during one engine cycle T, and the counter 22 is configured to generate 12 counting pulses S1 during one engine cycle T. An energizing pulse S2 is applied to the A/D converter 18. converter 18
is an electric signal S representing the flow velocity in response to this energizing pulse.
3 and performs A/D conversion. Therefore, the sampling period is shown in Figure 2C.
As shown by the dotted line 30, it becomes T/4. A/D converter 1
8 is configured in this manner, sampling, ie, A/D conversion, is always performed four times during one cycle of the engine operation, regardless of the rotational speed of the engine.

Therefore, although the sampling period becomes shorter as the engine speed increases, sampling is always performed at the phase of the output signal S3 corresponding to a predetermined crankshaft angle.
As is well known, an engine repeats the steps of suction, compression, explosion, and exhaust, and along with this, the hot wire flow rate detector 16
Even if the output S3 pulsates, it is possible to perform stable flow velocity measurement with constant accuracy at a predetermined signal phase, that is, at a predetermined sampling timing. Further, since the number of measurement data items supplied from the converter 18 to the computer 12 per unit time is directly proportional to the engine rotation speed, the processing capacity of the computer 12 has more margin as the engine rotation speed is lower. In other words, the computer can perform more calculations when the engine is rotating at low speed. Therefore, there is also the effect of increasing the utilization efficiency of the computer 12.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram showing a hot wire anemometer for an internal combustion engine and a central control device for an automobile according to the present invention, and FIG. 2 is a time chart showing signal waveforms inside the device shown in FIG. Explanation of symbols of main parts, 16...Hot wire flow velocity detector, 18...Analog-digital converter,
20...Crank angle sensor, 22...゜゜counter.

Claims (1)

[Scope of Claims] 1. Hot-wire flow velocity detection means that generates an analog electrical signal according to the flow velocity of intake air into the internal combustion engine, and an analog-to-digital conversion that samples the level of the analog electrical signal and converts it into a digital signal. A flow rate measuring device for an internal combustion engine, comprising: a speed detection means for detecting the rotational speed of the internal combustion engine; control means for causing said analog
A flow rate measuring device characterized in that the digital converter operates at a sampling period according to the rotational speed of the internal combustion engine. 2. The rotation speed detection means includes a pulse generator that generates pulses according to the rotation angle of the crankshaft of the internal combustion engine,
The control means includes a cycle counter connected to the pulse generator and outputting a control signal when a predetermined number of pulses are counted, and the analog-to-digital converter performs sampling in response to the control signal. A flow rate measuring device according to claim 1.