JPH0247552A - Engine-speed detecting apparatus - Google Patents

Abstract

PURPOSE:To prevent erroneous detection by reading a time period from a time when a previous pulse signal is generated to a time when a pulse signal at this time is generated as the period of the pulse signal only when said time period exceeds a specified value. CONSTITUTION:A specified value which is slightly larger than a chattering generating period is set in a judging means 3. When a pulse signal is generated from a crank angle sensor 1, a time period from a time when a previous signal is generated is computed in a time computing means 2. The time period and the preset value in the means 3 are compared. Only when the time period is larger than the preset value, the time period is read with a period reading means 4 as the period of the pulse signals.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an engine rotation speed detection device that detects the engine rotation speed by measuring the period of a pulse signal generated from a crank angle sensor at each reference crank angle.

<Prior Art> In order to control an internal combustion engine, detection of the engine rotation speed is essential, and a crank angle sensor is used to detect the engine rotation speed (see Japanese Patent Laid-Open No. 61-190142, etc.).

A crank angle sensor is a rotating body that rotates in synchronization with engine rotation, with marks (e.g. protrusions or slits) placed at each reference crank angle. These marks are detected by an electromagnetic or photoelectric detector and output as a pulse signal. It is something to do.

Then, by measuring the cycle of the pulse signal from this crank angle sensor, the engine rotation speed is detected by calculation from the cycle.

Figure 3 shows the case where the pulse signal REF is output every 180 degrees of crank angle (in the case of 4 cylinders), and its period T, lty
(s), the engine rotation speed N (rp
m) can be calculated.

N = 60/ (TIIEFX 2) (Problem to be solved by the invention) By the way, due to the recent demand for more compact engines, crank angle sensors have changed from the type in which the rotating body is attached to the crankshaft to the type in which the rotating body is attached to the camshaft. and moved on.

However, if the rotating body 11 of the crank angle sensor 10 is attached to the camshaft 4 as shown in FIG. This will be communicated as follows. In the figure, 12 is a slit serving as a mark, and 13 is a photoelectric detector.

Therefore, the deflection of the belt or chain that drives the camshaft rotation relative to the actual rotation of the crankshaft.

When the camshaft is subjected to small vibrations due to backlash, etc., and this matches the timing of the pulse signal generation, chattering occurs in the pulse signal as shown in the example in Figure 5, and this causes the true period T R
Wrong period T instead of tF. There was a problem in that the engine speed was incorrectly detected because the engine speed was read as 6.

In view of these conventional problems, the present invention provides an engine rotation system that allows engine rotation speed to be detected based on the correct cycle without reading an incorrect cycle even if chattering occurs in the pulse signal from the crank angle sensor. The purpose of this invention is to provide a number detection device.

<Means for Solving the Problems> For this reason, the present invention detects marks provided on a rotating body that is rotationally driven by the engine's crankshaft via a power transmission mechanism, and outputs a pulse signal at each reference crank angle. In an engine rotation speed detection device that monitors a pulse signal from a crank angle sensor and measures its period to obtain a signal related to the engine rotation speed, as shown in Fig. 1, the pulse signal from the crank angle sensor is measured. a time calculation means for calculating the time since the generation of the previous pulse signal at the time of generation; a determination means for comparing this time with a predetermined value to determine whether or not it is greater than the predetermined value; and when it is determined that the time is greater than the predetermined value Only read this time as the period of the pulse signal! tJl reading means.

Note that the predetermined value here may be a predetermined constant value, or may be a value that is a constant percentage of the cycle read last time.

<Operation> In the above configuration, even if chattering occurs in the pulse signal from the crank angle sensor, the time calculated by the time calculation means will be extremely short in this case, so the determination means will determine if it is less than a predetermined value. In this case, the cycle reading means does not read the cycle.

<Example> The present invention will be explained in detail below.

The configuration of the crank angle sensor is the same as the conventional one, and a microcomputer to which the pulse signal REF from the crank angle sensor is input monitors the generation of the pulse signal REF. The routine shown in the flowchart in Figure 2 is executed.

In step 1 (denoted as Sl in the figure; the same applies hereinafter), the current time is read and set as AIIEF.

In step 2, the current time AIl! The time L REF when the previous pulse signal was generated is subtracted from F to calculate the time M T *E v from when the previous pulse signal was generated. This part corresponds to the time calculation means.

In step 3, time MTREF is compared with a predetermined value (fixed time) To, which is slightly larger than TE and 1R at the time of chattering, to determine whether or not time MT, E is equal to or greater than predetermined value T0. This part corresponds to the determining means.

Note that the predetermined value T0 for comparison is not only a predetermined constant value but also a value (T+I
EFXP%; 2% is a constant value).

If M T II E F≧T0, it is normal, so proceed to step 4 and change the time M T , E, to the period T R
EF, and this is used to calculate the engine speed N. This part corresponds to the periodic reading means.

In addition, the calculation of the engine speed N is performed when the pulse signal is crank angle 1.
When output is performed every 80 degrees, the following equation is used.

N = 60/ (T IIEF X 2 ) However, since the period T REF is a signal related to the engine speed N,
It is not always necessary to perform this calculation, and the period T LoF may be used instead of the engine rotation speed N as the parameter for controlling the internal combustion engine.

If M T * t r < T o, it is considered to be abnormal and the above-mentioned chattering has occurred, and step 4 is not executed. In other words, the cycle is not read.

This can prevent incorrect detection of engine speed.

After that, in step 5, for the next calculation, time A
Substitute Rt F into LoF and end this routine.

<Effects of the Invention> As explained above, according to the present invention, even if chattering occurs in the pulse signal from the crank angle sensor, it is possible to read the correct period of the pulse signal without making an error, and the period of the pulse signal can be read stably. This has the effect of making it possible to detect the engine rotational speed.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing the configuration of the present invention, Fig. 2 is a flowchart showing an embodiment of the invention, Fig. 3 is a waveform diagram of a pulse signal from the crank angle sensor, and Fig. 4 is a diagram of the pulse signal from the crank angle sensor. FIG. 5 is a diagram showing how chattering occurs in the pulse signal. Patent applicant: Japan Electronics Co., Ltd. Attorney: Fujio Sasashima

Claims (1)

[Claims] The cycle is measured by monitoring the pulse signal from the crank angle sensor, which detects marks provided on a rotating body that is rotationally driven by the engine's crankshaft via a power transmission mechanism and outputs a pulse signal at each reference crank angle. The engine speed detecting device for obtaining a signal related to the engine speed includes a time calculation means for calculating the time since the generation of the previous pulse signal when the pulse signal is generated, and a time calculation means for calculating the time since the generation of the previous pulse signal, and comparing this time with a predetermined value. An engine rotation speed detecting device comprising: a determining means for determining whether the time is greater than or equal to a predetermined value; and a period reading means for reading this time as the period of a pulse signal only when it is determined that the time is greater than or equal to the predetermined value.