JPH049265B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for detecting engine rotation speed, and more particularly, to a method for detecting engine rotation speed for engine control such as engine ignition timing control and air-fuel ratio control. .

[Prior art]

Conventionally, various types of engine control, such as ignition timing control, require knowing the engine speed at that point in time. The engine rotation speed was calculated and detected from the pulse interval based on the output signal of the crank angle sensor. However, the pulse signals output at every equal crank angle are not necessarily perfect signals at every equal crank angle due to backlash in the rotation part of the sensor, and the pulse intervals may be slightly shifted.
Furthermore, if the engine speed is simply calculated from the pulse intervals of the constant crank angle signal, the detected speed will vary greatly when the engine is rotating at high speeds due to slight deviations in the intervals, making it impossible to perform accurate ignition timing control.

As a method for solving such problems, an engine rotation speed detection method has been proposed that performs processing as shown in the flowchart shown in FIG.

That is, the process shown in FIG. 1 represents the process executed based on the crank angle signal every 30 degrees output from the rotation angle sensor.

First, when the process starts, in step 100, the time required for outputting the four crank angle signals before the current crank angle signal and the time required up to the current time, that is, the crankshaft
The time required for a 120° rotation is measured.

In the following step 101, the previous step 1
The measured value (required time) measured at 00 is stored in a predetermined first storage means, and the process moves to the next step 102.

In step 102, a so-called "smoothing process" is performed based on the required time stored in the first storage means. In other words, "smoothing" means that the fluctuations in the required time, which represent engine speed fluctuations, are not directly converted to engine speed, but are averaged, thereby suppressing and detecting the fluctuations in engine speed. For example, a weighted average value of the required time calculated based on the required time measured up to that point.
A weighted average of T120M' (stored in the second storage means) and the currently measured required time T120 is determined, and the determined weighted average value is set as a new weighted average value of the required time T120M. This process can be expressed numerically as follows.

T120M=T120-T120M'/K+T120M' (K is a constant) In the following step 103, the previous step 1
Weighted average value of required time calculated in 02
The process of updating the memory of the second storage means is performed using T120M as a new weighted average value of the required time.

Then, perform other processing not shown as necessary,
In step 104, the step 103
The ignition timing advance calculation process is performed based on the new weighted average value of the required time stored in the second storage means, and other processes are performed as necessary. The process shown in is ended.

Through such processing, fluctuations in the measured engine speed are smoothed (averaged), and in ignition timing control using the engine speed as a control parameter, the ignition timing is adjusted due to deviations in the crank angle signal in the high speed range. turbulence can be suppressed.

However, when such processing is performed, another new problem arises: although the disturbance of ignition timing in the high speed range is improved, on the contrary, the follow-up delay during transient periods or in the low speed range increases. A problem arose.

The reason for this is that the above-mentioned "smoothing process" is executed in synchronization with the crank angle signal every 30 degrees, so the frequency components of rotational fluctuations averaged by the "smoothing process" (above the cutoff frequency ωc) For example, the engine speed changes from 600 rpm
When changing in the range of 6000 rpm, the cutoff frequency ωc is expressed as ωc = 1/kτ (K: constant, τ: execution period), so when K = 4, the cutoff frequency ωc is 30rad as shown in Figure 2. It varies in the range of /sec to 300rad/sec.

Therefore, in order to average out the frequency components of rotational fluctuations even in the low-speed rotation range where sensor bumps and the like do not have much of an effect on rotational fluctuations,
It also becomes impossible to accurately detect rotational fluctuations that should be detected and used for control.

[Purpose of the invention]

An object of the present invention is to adjust the engine speed, which is a control parameter used for ignition timing control and fuel injection amount control, from the actually measured engine speed by adjusting the engine speed fluctuation component that has an adverse effect on control according to the current speed range. It is an object of the present invention to provide a method for detecting the engine rotation speed, which is stable from a low speed rotation range to a high speed rotation range, and enables engine control with good followability by performing processing to remove the engine speed.

[Structure of the invention]

In order to achieve such an objective, the present invention provides the third
As shown in the flowchart in the figure, (P1) Every predetermined crank angle rotation of the crankshaft, based on the crank angle signal that is output at every equal crank angle in synchronization with the rotation of the engine crankshaft.
The time required for the rotation is measured, and the required time stored in the first storage means is updated based on the measured time, and (P2) at predetermined time intervals, the first A new averaging process is performed based on the required time stored in the storage means and the averaged value of the previously required time stored in the second storage means, and the processing result is used to calculate the new required time. Performing a memory update process in a second storage means as an averaged value of the time, and (P3) calculating the engine rotation speed based on the averaged value of the required time stored in the second storage means. The gist of this paper is a method for detecting engine speed, which is characterized by:

〔Example〕

The present invention will be described below with reference to examples and drawings.

First, FIG. 4 is a schematic system diagram showing a four-stroke, four-cylinder internal combustion engine and its peripheral equipment in an embodiment to which the method of the present invention is applied.

1 is an engine, 2 is a piston, 3 is a spark plug, 4 is an exhaust manifold, 5 is an oxygen sensor provided in the exhaust manifold 4 and detects the residual oxygen concentration in the exhaust gas, 6 is provided for each cylinder and indicates a fuel 7 is an intake manifold, 7a is an intake port to which the intake manifold 7 is connected, 7b is an intake valve, 8 is provided in the intake manifold 7, and detects the temperature of intake air sent to the engine body 1 9 is a water temperature sensor that detects the engine cooling water temperature; 10 is a water temperature sensor that detects the engine cooling water temperature;
is the throttle valve, 11 is the throttle valve 1
a throttle position sensor that outputs a signal according to the opening degree of the throttle valve 10;
12 is a bypass passage that is an air passage that bypasses the throttle valve 10; 13 is an idle speed control valve (ISCV) that controls the opening area of the bypass passage 12 to control the idle rotation speed; and 14 measures the amount of intake air. Air flow meters 15 each represent an air cleaner that purifies intake air.

Further, 16 is an igniter that is equipped with an ignition coil and outputs the high voltage necessary for ignition, and 17 is a device that is linked to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 3 of each cylinder. A triviewer 18 is installed within the distributor 17, and the distributor 1
A rotation angle sensor 19 outputs 24 pulse signals (crank angle signals) per one revolution of the distributor 17, that is, two revolutions of the crankshaft.
a cylinder discrimination sensor 20 that outputs a pulse signal;
represent electronic control circuits, respectively.

Further, 21 indicates a passage through which air flows bypassing the throttle valve when the engine is cold, that is, a first idle bypass passage. And 22
indicates an air valve that controls the amount of air passing through the first idle bypass passage 21. Note that the air valve 22 operates to open the first idle bypass passage 21 in order to secure the engine rotational speed necessary for warm-up operation when the engine is cold.

Next, FIG. 5 shows a block diagram of the electronic control circuit 20.

30 is a central processing unit (hereinafter simply referred to as CPU) which inputs and calculates data output from each sensor according to a control program, and performs processing to control the operation of various devices such as the fuel injection valve 6 and the igniter 16. 31 is a read-only memory (hereinafter simply referred to as ROM) in which data such as the control program and a map for fuel injection amount calculation is stored; 32 is data input to the electronic control circuit 20 and calculations; A random access memory (hereinafter simply referred to as RAM) 33 is used to temporarily read and write data necessary for control, and is designed to retain learning value data necessary for subsequent engine operation even if a key switch (not shown) is turned off. , backup random access memory backed up by battery (hereinafter simply referred to as backup
34 is an input port (not shown), a waveform shaping circuit provided as necessary, a multiplexer that selectively outputs the output signal of each sensor to the CPU 30, and an A/D that converts analog signals into digital signals. Inputs equipped with transducers, etc. are each represented. 35 is provided with an output port in addition to an input port (not shown), and is also provided with a fuel injection valve 6, an igniter 16, etc. as necessary.
An input/output section 36 is provided with a drive circuit etc. to drive according to a control signal from the CPU 30.
0, ROM 31, and other elements, and the input section 34 and the input/output section 35, each represents a bus line through which each data is sent.

The control of the ignition timing by the CPU 30 is performed by outputting a pulse signal to the igniter 16 at an ignition timing calculated based on the engine rotation speed and, if necessary, the engine load.

Next, the control program for detecting the engine rotational speed of this embodiment is shown in the flowcharts of FIGS. 6 and 7.

The processing shown in the control program of this embodiment will be described below.

First, the "crank angle 30° interrupt" processing routine shown in FIG. 6 will be explained. This routine is a subroutine that performs processing every time the crankshaft rotates 30 degrees, that is, in synchronization with the signal from the rotation angle sensor 18. When the process starts, in step 51, the crankshaft rotates 120 degrees. The time required to do so (required time) T120 is measured. This measurement is obtained, for example, by calculation from the time when the process of this routine started this time and the time when the process of this routine started four times ago.

In the following step 51, the required time T120 measured in the previous step is stored in a predetermined register (hereinafter referred to as the A register) in the RAM 32, and the required time already stored in the A register in the previous process is stored.
Store (update) in place of T120 and proceed to the next step 52
Move on to processing.

In step 52, a known ignition timing advance angle calculation process is performed using the averaged value T120M stored in a predetermined register (hereinafter referred to as B register) in step 62 of the flowchart of FIG. 7, which will be described later. The processing of this routine is then completed. In this routine, other processing may be performed in place of the ignition timing advance angle calculation, for example, fuel injection amount calculation processing, or other processing in addition to these processings, if necessary.

Next, the "timer interrupt" processing routine shown in FIG. 7 will be explained. This routine is executed at predetermined time intervals (for example, from 1 to
5 msec), and first, in step 60, the latest required time T120 stored in the A register in step 51 is read out.

In the following step 61, the average processing value T120M of the required time calculated in the processing of this routine up to that point and stored in the B register is averaged with the latest required time T120 read out in the previous step. The weighted average value F is computed as shown in the following equation, and the result is set as a new averaged value T120M.

F=T120−T120M/K ₁ +T120M (K ₁ ; constant) In the next step 62, a new value from the previous step is stored in the B register in place of the averaged value already stored in the previous processing of this routine. The averaged processing value of the required time obtained in is stored and updated, and the processing of this routine is completed.

Other processing may be performed in this routine as necessary.

By performing the above processing, for example, if the constant K ₁ shown in step 61 is set to 4 and the predetermined time interval at which the "timer interrupt" processing is performed is 1 msec, the execution cycle for performing the averaging processing is The cutoff frequency ωc is constant regardless of the engine speed, and the cutoff frequency ωc is a constant frequency (250 rad/sec) as shown in FIG. 8, regardless of the engine speed.
Therefore, according to this embodiment, in the high speed rotation range, it is possible to detect the engine rotation speed that averages out the fluctuations in the engine rotation speed, and in the low speed rotation range, it is possible to detect the engine rotation speed that averages out the fluctuations in the engine rotation speed more than necessary. This makes it possible to detect engine speeds that would otherwise not be detected.

〔Effect of the invention〕

As described in detail above, the method of the present invention performs the averaging process of the engine speed at regular time intervals, regardless of the engine speed. For this reason,
According to the present invention, fluctuations in engine speed are reliably averaged, especially in the required high speed rotation range, and the effects of averaging processing in the low speed rotation range where such averaging is not so necessary are avoided. It becomes possible to reduce the amount. Therefore, it is possible to detect an appropriate engine speed for control using the engine speed as a control parameter in all speed ranges from low speed to high speed, and as a result, control in the high speed range The effect is that it is possible to eliminate turbulence and improve followability in the low and medium speed rotation range.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing conventional averaging processing, FIG. 2 is a graph showing changes in cut-off frequency corresponding to fluctuations in engine speed due to averaging processing, and FIG. 3 is a flowchart showing the configuration of the method of the present invention. 4 is a schematic system diagram showing an engine and its peripheral equipment in an embodiment to which the method of the present invention is applied, FIG. 5 is a block diagram showing its electronic control circuit, and FIGS. 6 and 7 are examples of the embodiment. FIG. 8 is a flowchart showing the control program and a graph showing the operation of the embodiment. 1...Engine, 3...Spark plug, 18...Rotation angle sensor, 20...Electronic control circuit, 30...CPU, 3
1...ROM, 32...RAM.

Claims (1)

[Claims] 1. Based on a crank angle signal that is output at every equal crank angle in synchronization with the rotation of the crankshaft of the engine, the time required for each rotation of the crankshaft at a predetermined crank angle is measured. , performs a memory update process for the required time stored in the first storage means based on the measured required time, and updates the required time stored in the first storage means and the first storage means at predetermined time intervals. A new averaging process is performed based on the previously averaged value of the required time stored in the second storage means, and the processing result is used as the new averaged value of the required time to be stored in the second storage unit. A method for detecting engine rotation speed, characterized in that the engine rotation speed is calculated based on an averaged value of the required time stored in the second storage means.