JPS58150864A - Detection of rotational speed of electronically controlled engine - Google Patents

Abstract

PURPOSE:To enable the detection of low rotational speed of an engine at a high accuracy by preparing the measured time required for rotating a crank shaft by a specified crank angle as data corresponding to the rotational speed of the engine. CONSTITUTION:A CPU35, an ROM36, an RAM37, a C-RAM38, an input interface 39 and an input/output interface 40 as digital processer are connected to each other through a pulse 41. On the other hands, the C-RAM38 is fed with a specified power and cab retain the memory thereof during the stoppage of the engine. Analog outputs of a water temperature sensor 18 and a pressure sensor 19 are sent to the input interface 29 containing an A/D converter. Outputs of a throttle switch 16, a crank angle sensor 23, a air-fuel ratio sensor 24 and a vehicle speed sensor 25 are sent to the input/output interface 40 from which electrical signals to a fuel injection valve 14 and an ignition coil 32 are sent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine rotation speed detection method in an electronically controlled engine equipped with a digital processor for calculating various control variables.

The rotational speed of the engine is usually detected by counting the output pulses per unit time of a crank angle sensor that generates a pulse every time the crankshaft rotates by a predetermined crank angle, for example 30 degrees. However, with this method, when the engine speed is low, such as when starting, the number of output pulses per unit time of the crank angle sensor decreases.
The accuracy of detecting engine rotation speed will be significantly reduced.

An object of the present invention is to provide a method for detecting an engine rotation speed in an electronically controlled engine, which is capable of detecting a low rotation speed of the engine with high precision and using a simple program (with a small number of steps).

In order to achieve this object, according to the present invention, the time required for the crankshaft to rotate by a predetermined crank angle is measured, and the measured time itself or the reciprocal of this measured time is used as data corresponding to the engine rotational speed. shall be.

Preferably, a crank angle sensor is provided that generates a pulse every time the crankshaft rotates by a predetermined crank angle, and the time interval between generation of output pulses of the crank angle sensor is set such that the time interval between occurrences of output pulses of the crank angle sensor is set such that the crankshaft generates a pulse every time the crankshaft rotates by a predetermined crank angle. Measure as the time required.

More preferably, a counter is provided that counts clock pulses and is cleared each time an output pulse of the crank angle sensor occurs, and the count value of the counter immediately before being cleared is
Detected as the time interval between output pulses of the crank angle sensor.

The present invention will be described in detail with reference to the drawings.

To roughly explain the entire electronically controlled fuel injection engine to which the present invention is applied in FIG. 4 controls the flow rate, and then the surge tank 5, intake pipe 6, and intake valve 7
The fuel is supplied to the combustion chamber 9 of the engine body 8 via the combustion chamber 9 of the engine body 8.

The air-fuel mixture combusted in the combustion chamber 9 is passed through the exhaust valve 1 as exhaust gas.
0, and is discharged via the exhaust branch pipe 11. An electromagnetic fuel injection valve 14 is provided in the intake pipe 6 corresponding to each combustion chamber 9. The electronic control device 15 includes a throttle switch 16 that detects when the throttle valve 2 is fully closed, a water temperature sensor 18 that is attached to the water jacket 17 of the engine body 8, and a water temperature sensor 18 that is attached to the surge tank 5 that detects the intake pipe pressure related to the intake air flow rate. a pressure sensor 19 that detects the rotation angle of the crankshaft that is connected to the piston 21 via the connecting rod 22, a crank angle sensor 23 that detects the rotation angle of the distributor shaft that is connected to the crankshaft, and an exhaust branch pipe 11.
It receives input signals from an air-fuel ratio sensor 24, which is installed in the vehicle, to detect the oxygen concentration in exhaust gas, a vehicle speed sensor 25, and the like. The rotation angle sensor 23 rotates once per two rotations of the crankshaft.
A portion 26 that generates one pulse, and a portion 27 that generates a pulse every predetermined crank angle, for example 30'. Fuel is force-fed from a fuel tank 30 to the fuel injection valve 14 via a fuel passage 29 by a fuel pump 31.

The electronic control unit 15 calculates the fuel injection amount and fuel injection timing based on various input signals, sends a fuel injection pulse to the fuel injection valve 14, calculates the ignition timing, and sends a signal to the ignition coil 32. The secondary current of the ignition coil 32 is sent to a distributor 33. Note that the injection valve 14 is maintained in the open state only while receiving the pulse from the electronic control device t5.

FIG. 2 is a block diagram of the inside of the electronic control unit 15. As shown in FIG.

CPU (central processing unit) as a digital processor
35, ROM (read-only storage device) 36, RAM
A (direct access storage device) 37, a C-RAM (complementary RAM) 3B, an input interface 39, and an input/output interface 4o are connected to each other via a bus 41. One C-RAM 38 is supplied with a predetermined amount of power and can retain its memory even when the engine is stopped. The input interface 39 has a built-in A/D (analog/digital) converter, and the analog outputs of the water temperature sensor 18 and pressure sensor 19 are connected to the input interface 39.
sent to. Throttle switch 16, crank angle sensor 23, air-fuel ratio sensor 24, and vehicle speed sensor 2
The output of 5 is sent to the input/output interface 4o, and the electrical signals to the fuel injection valve 14 and the ignition coil 32 are also sent to the input/output interface 40.

FIG. 3 is an explanatory diagram illustrating the basic concept of the present invention. A crank angle pulse is generated at portion 27 of crank angle sensor 23 every time the crankshaft rotates 300 crank angles. A clock pulse is generated every predetermined period of time, for example, every 5 msec. Engine rotation speed R=
It is the basis. However, ■ K is a constant, and ■ is the count value of the counter immediately before clearing. When the engine rotation speed R is smaller, the time interval of the crank angle pulse increases, and ■ increases, so the engine rotation speed R
The detection accuracy is high even at low rotational speeds.

4 to 6 are flowcharts of programs for implementing the present invention.

FIG. 4 is a flowchart of an interrupt program executed upon generation of a clock pulse. In step 46, the contents of the counter are incremented by one. FIG. 5 is a flowchart of an interrupt program executed upon generation of a crank angle pulse. In step 50, the count value (■) of the counter is stored. In step 51, the counter is cleared. FIG. 6 is a flowchart of a program for calculating the engine rotational speed R. In step 54, the RAM 37 also reads the count value. In step 55, R=/I is calculated. In the embodiment, the engine rotational speed is calculated more strictly than R=/I, but I itself or 1/I may be used as data corresponding to the engine rotational speed in programs such as calculating the fuel injection amount. It is more practical to use I, 1/I.

In this way, in the present invention, instead of counting the number of crank angle pulses in the conventional method, the time interval of crank angle pulses, that is, the time required for the crankshaft to rotate by a predetermined crank angle, is measured. Engine rotation speed can be detected from the reciprocal of time. The measurement time increases as the engine rotation speed decreases, so even if this measurement time is detected as the number of clock pulses, the number of clock pulses is sufficiently large to ensure detection accuracy at low engine rotation speeds. can be significantly increased.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an electronic control engine to which the present invention is applied, Fig. 2 is a block diagram of the electronic control device of Fig. 1, Fig. 3 is an explanatory diagram explaining the basic concept of the present invention, and Fig. 4 6 through 6 are flowcharts of programs implementing the present invention. 15...Electronic control unit, 23...Crank angle sensor, 27.=part, 35.CPU. Patent applicant Toyota Motor Corporation 36 Figure 3 1 hour Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1゜ An electronically controlled engine characterized in that the time required for the crankshaft to rotate by a predetermined crank angle is measured, and the measured time is used as data corresponding to the engine rotation speed. How to detect engine rotation speed. 2. The detection method according to claim 1, wherein the reciprocal of the measurement time is used as data corresponding to engine rotational speed. 3. A crank angle sensor is provided that generates a pulse every time the Kuralev shaft rotates by a predetermined crank angle, and the time interval between output pulses from the crank angle sensor is set to the time required for the crankshaft to rotate by a predetermined crank angle. 3. The detection method according to claim 2, characterized in that the detection method is measured as a time during which the amount of time has elapsed. 4. Provide a counter that counts clock pulses and is cleared each time an output pulse from the crank angle sensor occurs, and detects the count value of the counter immediately before being cleared as the time interval between occurrences of output pulses from the crank angle sensor. The detection method according to claim 3, characterized in that: