JP2018172996A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detection accuracy of knocking which occurs during an expansion stroke of a cylinder.SOLUTION: In a control device of an internal combustion engine which detects vibration transmitted to a cylinder block for encapsulating cylinders by a knock sensor, and determines the presence or absence of knocking which occurs in the cylinders by referring to a vibration signal, the control device stores a magnitude of the vibration of noise other than that resulting from the knocking which occurs according to an operation region of the internal combustion engine in each of individual regions of the internal combustion engine in a memory, and when determining the presence or absence of the knocking, the control device reads the magnitude of the noise corresponding to a current operation region of the internal combustion engine from the memory, and compares a value obtained by subtracting the magnitude from a vibration signal which is obtained by the knock sensor with a determination threshold.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device that controls an internal combustion engine mounted on a vehicle or the like.

  Knock is sensed via a vibration type knock sensor installed in the cylinder block of the internal combustion engine. When knocking occurs, the ignition timing is retarded, and the knocking timing is advanced as long as knocking does not occur. Control systems are known (see, for example, the following patent document).

JP 2017-040236 A

  The knock sensor detects not only vibration caused by knocking. The knock sensor is also input with the vibration of the operating internal combustion engine that originally exists even if knocking does not occur. That is, background noise is mixed in the vibration signal obtained via the knock sensor. The magnitude of the background noise varies depending on the operating region of the internal combustion engine. The background noise level is greater during high load operation than during low load operation.

  In order to appropriately remove the influence of background noise, conventionally, vibration signals are repeatedly sampled at a predetermined period, and plural maximum values of amplitudes of vibration signals obtained in the past multiple sampling opportunities are obtained. The magnitude of the background noise is obtained by averaging, and the result obtained by subtracting the background noise from the vibration signal is compared with a determination threshold value to determine the presence or absence of knocking.

  However, even with such a method, when the operating range of the internal combustion engine changes suddenly, it is not possible to cope with an event in which the background noise suddenly increases particularly when the engine load factor increases rapidly. As a result, in the knock control system that refers to the vibration signal, even though knocking does not actually occur, the background noise vibration is mistakenly attributed to knocking, and the ignition timing is unnecessarily corrected. It could have happened. Reducing the ignition timing is not preferable because it leads to a decrease in the thermomechanical conversion efficiency of the internal combustion engine, and consequently a decrease in output or fuel consumption performance.

  The present invention has been made by paying attention to the above-mentioned problems for the first time, and an object thereof is to improve the detection accuracy of knocking that occurs during the expansion stroke of a cylinder.

In order to solve the above-described problem, vibration transmitted to a cylinder block containing a cylinder is detected via a knock sensor, and the presence or absence of knocking in the cylinder is determined with reference to the vibration signal.
The magnitude of noise vibration other than the vibration caused by knocking, which occurs according to the operating region of the internal combustion engine, is stored in the memory for each individual operating region of the internal combustion engine, and the presence or absence of knocking is determined. In doing so, a control device for an internal combustion engine which reads out the magnitude of noise vibration corresponding to the current operating region of the internal combustion engine from a memory and compares the vibration signal obtained via the knock sensor with a determination threshold value. Configured.

  According to the present invention, it is possible to improve the detection accuracy of knocking that occurs during the expansion stroke of a cylinder.

The figure which shows schematic structure of the internal combustion engine for vehicles and control apparatus in one Embodiment of this invention. The figure which illustrates the map data of the magnitude | size of the background noise which the control apparatus of the embodiment memorize | stores in memory. The figure which illustrates the vibration containing a background noise detected via a knock sensor in the same embodiment.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine of the present embodiment is a port injection type four-stroke spark ignition engine, and includes a plurality of cylinders 1 (for example, three cylinders, one of which is shown in FIG. 1). In the vicinity of the intake port 13 of each cylinder 1, an injector 11 for injecting fuel is provided for each cylinder 1. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port 13 of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port 14 of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  The external EGR (Exhaust Gas Recirculation) device 2 realizes a so-called high pressure loop EGR, and an external EGR passage 21 that connects the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3. The EGR cooler 22 provided on the EGR passage 21 and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 are used as elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, particularly to the surge tank 33.

  The internal combustion engine of the present embodiment is accompanied by a VVT (Variable Valve Timing) mechanism 6 that can variably control at least the opening / closing timing of the intake valve of each cylinder 1. The VVT mechanism 6 for adjusting the intake valve timing is changed by a vane type that changes the rotation phase of the camshaft that drives the intake valve of each cylinder 1 with respect to the crankshaft by hydraulic pressure (lubricating oil pressure) or by an electric motor. It is an electric type (motor drive VVT). As is well known, the camshaft is supplied with a rotational driving force from a crankshaft that is an output shaft of the internal combustion engine, and rotates following the crankshaft. A winding transmission device (not shown) for transmitting a rotational driving force is interposed between the crankshaft and the camshaft. The winding transmission device includes a crank sprocket (or pulley) provided on the crankshaft side, a cam sprocket (or pulley) provided on the camshaft side, and a timing chain (or pulley) wound around these sprockets (or pulleys). , Timing belt). The VVT mechanism 6 changes the rotation phase of the camshaft relative to the crankshaft by rotating the camshaft relative to the cam sprocket, thereby changing the opening / closing timing of the intake valve.

  Similarly, the VVT mechanism for adjusting the exhaust valve timing changes the rotational phase of the camshaft that drives the exhaust valve of each cylinder 1 with respect to the crankshaft by hydraulic pressure or an electric motor. Note that this VVT mechanism may not exist, and in this case, the opening / closing timing of the exhaust valve is not changed.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft and the engine speed, and an accelerator pedal. The accelerator opening signal c output from a sensor that detects the amount of depression of the engine or the opening of the throttle valve 32 as an accelerator opening (so-called required engine load factor), an intake passage 3 connected to the cylinder 1 (especially a surge tank) 33) an intake air temperature / intake pressure signal e output from a temperature / pressure sensor for detecting intake air temperature and intake pressure, and a cooling water temperature signal f output from a water temperature sensor for detecting a cooling water temperature indicating the temperature of the internal combustion engine. The cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake camshaft includes a plurality of cylinders 1. Vibration signal h or the like to be output from the vibration type knock sensor 5 for detecting the magnitude of the vibration of the cylinder block 10 is entered.

  From the output interface of the ECU 0, the ignition signal i for the igniter, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, the opening operation signal l for the EGR valve 23, VVT. A valve timing control signal m or the like is output to the mechanism 6.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR rate) Amount), opening / closing timing of the intake valve and / or exhaust valve, and the like. The ECU 0 applies various control signals i, j, k, l and m corresponding to the operation parameters via the output interface.

  The opening and closing timing of the intake valve embodied by the VVT mechanism 6 is the operating region of the internal combustion engine at that time [engine speed, required load factor (or intake pressure in the surge tank 33, opening of the throttle valve 32, filling into the cylinder 1) Intake (fresh air) amount or fuel injection amount)] to be set.

  Further, the ignition timing for the air-fuel mixture filled in the cylinder 1 is determined by adding the correction amount by the knock control system to the basic timing corresponding to the operating region of the internal combustion engine at that time. That is, the ECU 0 refers to the vibration signal h and determines whether or not the cylinder 1 is knocked. When it is determined that knocking has occurred in the cylinder 1, the ignition timing of the cylinder 1 is gradually retarded until knocking does not occur thereafter. On the other hand, if it is determined that knocking has not occurred, the ignition timing of the cylinder 1 is gradually advanced as long as knocking does not occur (and MBT (Minimum Advance for Best Torque) is the upper limit). The determination of the presence or absence of knocking and the retard / advance correction of the ignition timing can be performed individually for each cylinder 1.

  The vibration signal h obtained via the knock sensor 5 is also input with the vibration of the internal combustion engine during operation, which originally occurs without knocking. In short, background noise is mixed in the vibration signal h. The magnitude of the background noise varies depending on the operating region of the internal combustion engine. For example, the level of background noise is greater during high load operation than during low load operation. Therefore, there is a need for a means for preventing the noise vibration from being mistaken for vibration caused by knocking.

  The ECU 0 according to the present embodiment stores, in a memory, a predicted value of the magnitude of background noise that is generated during the operation of the internal combustion engine and mixed into the vibration signal h for each operation region of the internal combustion engine. doing. The map data stored and held by the ECU 0 is expected to be generated under the parameters [engine speed, required load factor (or intake pressure in the surge tank 33, etc.)] indicating the operation region of the internal combustion engine and the operation region. This is related to the value of the magnitude of background noise.

  As schematically shown in FIG. 2, in the present embodiment, the value of the background noise for each operation region held as map data is divided into a basic amount and a learning value added to the basic amount. Yes. The basic amount of background noise is experimentally obtained in advance at the design stage and the adaptation stage of the internal combustion engine. On the other hand, the learning value corresponds to the change in background noise that changes according to individual differences and aging of the internal combustion engine, and is online while the internal combustion engine is in operation (when knocking does not occur). Obtained by actual measurement.

  The learning of the background noise learning value is desirably performed when the internal combustion engine or the vehicle is in steady operation. Specifically, the required load factor (or the intake pressure in the surge tank 33, the opening of the throttle valve 32, the intake (fresh air) amount or fuel injection amount charged in the cylinder 1), the engine speed, or the vehicle speed When the state in which the amount of change per unit time is smaller than a predetermined value continues for a certain period of time (and it is considered that knocking does not occur in the cylinder 1), the internal combustion engine or the vehicle is currently in steady operation. The learning value corresponding to the operation region of the internal combustion engine at that time is learned. In learning of the learning value, the vibration signal h obtained from the knock sensor 5 is sampled, and the maximum value of the amplitude or the maximum values of the amplitude of the vibration signal h obtained in the most recent past sampling occasions are obtained. Find the average value. Then, the difference between the maximum value of the amplitude or the average value of the maximum values and the basic amount of background noise (stored in memory as map data) corresponding to the operation region is calculated, and the difference is updated. As a new learning value, it is stored in the memory in association with parameters [engine speed, required load factor (or intake pressure in surge tank 33, etc.)] indicating the operation region.

  The ECU 0 of the present embodiment determines the amount of background noise corresponding to the current operation region of the internal combustion engine [engine speed, required load factor (or intake pressure in the surge tank 33, etc.)] The predicted value (= basic amount + learned value) is read from the map data, and the predicted value is subtracted from the sampling value of the vibration signal h obtained via the knock sensor 5. Then, the value of the vibration signal h obtained by subtracting the background noise is compared with a determination threshold value. If the value of the vibration signal h obtained by subtracting the background noise is larger than the determination threshold value, it is determined that knocking has occurred in the cylinder 1. Otherwise, it is determined that knocking has not occurred in the cylinder 1. The determination threshold is preferably set individually for each operation region of the internal combustion engine. This is because the amplitude of the vibration caused by knocking differs depending on the operating region of the internal combustion engine.

  Note that the determination of the presence or absence of knocking when the internal combustion engine or the vehicle is in steady operation may be performed according to the conventional method described above. The determination of the presence or absence of knocking using the map data of the predicted value of the background noise stored in the memory is limited to the transition period in which the operating region of the internal combustion engine or the vehicle speed changes.

  In this embodiment, vibration transmitted to the cylinder block 10 containing the cylinder 1 is detected via the knock sensor 5, and the presence or absence of knocking in the cylinder 1 is determined with reference to the vibration signal h. The magnitude of the vibration of noise other than the vibration caused by knocking, which occurs according to the operating region of the engine, is stored in the memory for each individual operating region of the internal combustion engine, and is used for determining the presence or absence of knocking. A control device for an internal combustion engine that reads out the magnitude of noise vibration corresponding to the current operating range of the internal combustion engine from a memory and compares the subtraction of the vibration signal h obtained through the knock sensor 5 with a determination threshold value 0 was configured.

  According to this embodiment, the detection accuracy of knocking that occurs during the expansion stroke of the cylinder 1 is improved. In particular, as shown in FIG. 3, when the engine load factor increases and the background noise superimposed on the vibration signal h suddenly increases, the vibration of the noise even though no knocking actually occurs. It is possible to avoid misrecognizing that is due to knocking and unnecessarily correcting the ignition timing. As a result, the thermomechanical conversion efficiency of the internal combustion engine can be maintained high. In the conventional technique, the magnitude of the background noise (represented by a chain line in FIG. 3) is obtained by averaging a plurality of maximum values of the amplitude of the vibration signal h obtained at the most recent sampling occasions. Therefore, when the background noise suddenly increases, the value obtained by subtracting the background noise from the vibration signal h may exceed the determination threshold even if knocking does not occur. On the other hand, in the method of the present embodiment, the magnitude of the background noise that changes suddenly (represented by a broken line in FIG. 3) can be accurately predicted from the map data stored in the memory, so that knocking is prevented. As long as it does not occur, that is, unless vibration caused by knocking is added to the vibration signal h, the value obtained by subtracting the background noise from the vibration signal h does not exceed the determination threshold.

  The present invention is not limited to the embodiment described in detail above. Various modifications can be made to the specific configuration of each part, processing procedure, and the like without departing from the spirit of the present invention.

  The present invention can be used for controlling an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 12 ... Spark plug 6 ... Variable valve timing (VVT) mechanism i ... Ignition signal h ... Vibration signal

Claims (1)

The vibration transmitted to the cylinder block containing the cylinder is detected via a knock sensor, and the presence or absence of knocking in the cylinder is determined with reference to the vibration signal,
The magnitude of vibration of noise other than the vibration generated due to knocking that occurs according to the operating region of the internal combustion engine is stored in the memory for each individual operating region of the internal combustion engine,
When determining the presence or absence of knocking, the magnitude of noise vibration corresponding to the current operating region of the internal combustion engine is read from the memory, and the vibration signal obtained via the knock sensor is subtracted from the vibration signal and compared with a determination threshold value. Control device for internal combustion engine.

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