JP2014129727A - Combustion state detecting method of multi-cylinder internal combustion engine - Google Patents

Abstract

An ion current detection device 4 is provided in only one cylinder so that preignition of each cylinder can be reliably avoided.
At the time of shipment inspection of an internal combustion engine, an ion current detection device is attached to the ignition plugs of all cylinders (step 1), and the ignition timing is gradually advanced for each cylinder, immediately before the occurrence of a pre-ignition sign. Is determined (steps 3 to 7). After the ignition timing advance amount which becomes the pre-ignition limit of each cylinder is stored in the engine controller as learning correction values H1 to H4 for each cylinder, the ion current detection devices other than the # 1 cylinder are removed (step 11). After shipment, the ignition timing of each cylinder is controlled using learning correction values H1 to H4 for each cylinder. When a pre-ignition sign is detected from the ionic current of the # 1 cylinder, pre-ignition avoidance by ignition timing delay is equally performed for all cylinders.
[Selection] Figure 2

Description

  The present invention relates to a technique for detecting the combustion state of each cylinder in order to avoid abnormal combustion such as pre-ignition, and more particularly to a combustion state detection method in a multi-cylinder internal combustion engine.

  In order to avoid abnormal combustion such as pre-ignition, a technique for detecting the combustion state of each cylinder from the in-cylinder pressure or ion current in the combustion chamber is known.

  Patent Document 1 discloses that an ignition current detection device using a spark plug as a detection probe is used to detect a pre-ignition sign and to perform pre-ignition avoidance control such as reduction of an effective compression ratio at the time of detection. ing.

JP 2009-57940 A

  In the above-described conventional configuration, each cylinder of the multi-cylinder internal combustion engine is provided with an ion current detection device (ion current detection circuit), so that the hardware configuration becomes complicated and large. For example, in one example, the ion current detection circuit is configured as a part of a spark plug drive circuit including an ignition coil, and is individually disposed above the spark plug as one unit for each cylinder. Since the unit including the current detection circuit is relatively large, an occupied space on the upper surface of the cylinder head cover is increased.

  An object of the present invention is to make it possible to correctly represent the combustion states of all the cylinders with the combustion state detection devices of some cylinders, and to reduce the size and simplify the hardware configuration.

A combustion state detection method for a multi-cylinder internal combustion engine according to the present invention includes:
At the time of shipping inspection of the internal combustion engine, attaching a combustion state detection device to all the cylinders and measuring the combustion characteristics for each cylinder;
Obtaining a learning value for each cylinder for averaging the combustion characteristics of all cylinders based on the measurement result of the combustion characteristics of each cylinder, and storing the learning value in the control device of the internal combustion engine;
Removing the combustion state detection device from the other cylinders, leaving the combustion state detection device for at least one cylinder before shipping;
A step of operating the internal combustion engine using the stored learning value for each cylinder;
Correcting the combustion conditions of all cylinders based on the combustion state detected by the remaining combustion state detection device during operation;
It has.

  In this method, before shipment, the combustion characteristics of each cylinder are measured with the combustion state detection devices actually attached to all the cylinders, and the learning value is set so that the combustion characteristics of all the cylinders are averaged. . After shipment, the internal combustion engine is operated using the learned value, so that the combustion characteristics of each cylinder are uniform. In other words, the cylinder-to-cylinder variation in the likelihood of abnormal combustion in each cylinder is offset by the learned value, and the margin of each cylinder against abnormal combustion such as pre-ignition (resistance to abnormal combustion) becomes equal.

  Therefore, during operation after shipment, it is possible to avoid abnormal combustion for all the cylinders by monitoring the combustion state of some cylinders where the combustion state detection device remains.

  According to this invention, since the product after shipment is provided with a combustion state detection device only in some cylinders, the hardware configuration is small and simple, and at the same time, the cost can be reduced. is there. Further, the combustion state of some cylinders accurately represents the combustion state of all cylinders, and abnormal combustion can be reliably avoided for all cylinders.

Explanatory drawing which shows the system configuration | structure of the internal combustion engine after shipment by this invention. The flowchart which shows the flow of the process in one Example of this invention. Explanatory drawing about the ignition timing learning correction value of each cylinder. The flowchart which shows the ignition timing control in the driving | operation after shipment.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows the system configuration of an automotive internal combustion engine 1 to which the present invention is applied. The internal combustion engine 1 is an in-cylinder direct injection type spark ignition type internal combustion engine with four cylinders, and includes a fuel injection valve 2 for injecting fuel into the cylinder for each cylinder, and is generated. A spark plug 3 for igniting the air-fuel mixture is provided. Here, FIG. 1 shows the configuration of the internal combustion engine 1 after the shipment inspection has been completed, and the ion current detection device 4 serving as a combustion state detection device only for the ignition plug 3 of the # 1 cylinder. Is attached. The ion current detection device 4 uses the ignition plug 3 itself as a detection probe, and is actually configured as a single unit including an ignition coil as an ignition plug drive circuit with an ion current detection function. In the other cylinders # 2 to # 4, a normal spark plug drive circuit (not shown) having no ion current detection function is attached to each spark plug 3.

  Each cylinder includes an intake valve 5 and an exhaust valve 7. The intake valve 5 includes a variable valve device 6 that can variably control the opening / closing timing (at least the closing timing) of the intake valve 5. . The variable valve gear 6 and the spark plug drive circuit are controlled by the engine controller 10.

  An electronically controlled throttle valve 12 whose opening degree is controlled by a control signal from the engine controller 10 is interposed upstream of the intake passage 11, and an exhaust recirculation passage 14 extending from the exhaust passage 13 to the intake passage 11 is provided. Is provided with an exhaust gas recirculation control valve 15.

  In addition to the ion current detector 4 described above, the engine controller 10 includes a crank angle sensor 16 for detecting the engine speed, an air flow meter 17 for detecting the intake air amount, an intake air temperature sensor 18 for detecting the intake air temperature, Detection signals from sensors such as a water temperature sensor 19 that detects the cooling water temperature, an oil temperature sensor 20 that detects the lubricating oil temperature, and an accelerator opening sensor 21 that detects the amount of depression of the accelerator pedal operated by the driver are input. ing. Based on these detection signals, the engine controller 10 optimally controls the fuel injection amount and injection timing by the fuel injection valve 2, the ignition timing by the ignition plug 3, the opening and closing timing of the intake valve 5, the opening of the throttle valve 12, and the like. doing.

  Next, based on the flowchart of FIG. 2, the work procedure from the shipment inspection of the internal combustion engine 1 to the shipment will be described.

  The assembled internal combustion engine 1 performs an inspection prior to shipment in order to deal with variations in combustion characteristics of the four cylinders. This shipment inspection may be performed as a bench test before the internal combustion engine 1 is mounted on the vehicle, or may be performed with the internal combustion engine 1 mounted on the vehicle.

  First, as step 1, the ion current detection device 4 is attached to each cylinder. Specifically, a spark plug drive circuit with an ion current detection function is attached to the spark plug 3 of each cylinder.

  Then, under certain environmental conditions, abnormal combustion, here, pre-ignition is inspected (step 2). Note that the environmental condition may be an environmental condition in which pre-ignition is relatively likely to occur, for example, a relatively high temperature condition of the internal combustion engine 1 and a high intake air temperature.

  Specifically, in step 3, the # 1 cylinder is selected as the first cylinder to be inspected, and the combustion characteristics of the cylinder based on the ionic current while operating the internal combustion engine 1 under a low speed and high load condition where preignition is likely to occur, for example. Start measuring. The ignition timing at the start point is a predetermined inspection reference ignition timing at which pre-ignition does not occur. In step 4, the ignition timing of the cylinder is advanced by 1 ° CA. In step 5, it is repeatedly determined whether or not a pre-ignition sign has been detected. The processes in steps 4 and 5 are repeated until a pre-ignition sign is detected in the cylinder. If a pre-ignition sign is detected at a certain ignition timing advance, the ignition timing immediately before that is the pre-ignition occurrence limit, so in step 6, the ignition timing is retarded by 1 ° CA, and in step 7 The ignition timing at this time is determined as the preignition limit of the # 1 cylinder.

  When the measurement of the # 1 cylinder is completed, the ignition timing of the # 1 cylinder is returned to the predetermined reference ignition timing for inspection, and the process returns to step 3 to select the next # 2 cylinder as the inspection target cylinder. Steps 4 and 5 are repeated. When a pre-ignition sign is detected in the # 2 cylinder, it is retarded by 1 ° CA, and the ignition timing at this time is determined as the pre-ignition limit of the # 2 cylinder.

  When the measurement of the # 2 cylinder is completed, the ignition timing of the # 2 cylinder is returned to the predetermined reference ignition timing, and then the process returns to step 3 to select the next # 3 cylinder as the inspection target cylinder. Steps 4 and 5 are repeated. When a pre-ignition sign is detected in the # 3 cylinder, it is retarded by 1 ° CA, and the ignition timing at this time is determined as the pre-ignition limit of the # 3 cylinder.

  The same applies to the # 4 cylinder. When the measurement of the # 3 cylinder is completed, the process returns to step 3, the next # 4 cylinder is selected as the inspection target cylinder, and the processes of steps 4 and 5 are repeated. Then, when a pre-ignition sign is detected in the # 4 cylinder, it is retarded by 1 ° CA, and the ignition timing at this time is determined as the pre-ignition limit of the # 4 cylinder.

  FIG. 3 is an explanatory diagram schematically showing the processing of steps 3 to 7 for each cylinder in time series. The vertical axis represents the ignition timing, but in the example shown, the # 1 cylinder is used for inspection. A preignition sign is generated with an advance amount of + 3 ° CA with respect to the reference ignition timing (initial ignition timing), and therefore, the ignition timing immediately before that (that is, the ignition timing delayed by 1 ° CA) is “the reference ignition for inspection”. “Time + 2 ° CA” is the pre-ignition limit. Similarly, in this example, the pre-ignition limit of the # 2 cylinder is “inspection reference ignition timing + 1 ° CA”, the pre-ignition limit of the # 3 cylinder is “inspection reference ignition timing + 3 ° CA”, and the # 4 cylinder The pre-ignition limit is “standard ignition timing for inspection + 0 ° CA”.

  When the inspection for all cylinders is completed in this way, the process proceeds from step 8 to step 9 in FIG. 2, and the pre-ignition limit of each cylinder obtained by each inspection is determined as the learning correction values H1 to H4 for each cylinder. . In step 10, these learning correction values H1 to H4 are stored in the memory of the engine controller 10. In this example, as shown in FIG. 3, the advance amount from the reference ignition timing for inspection to the pre-ignition limit is used as it is as final learning correction values H1 to H4, but other reference crank angles ( For example, it may be replaced with an advance amount based on the top dead center.

  This completes a series of shipment inspections regarding variations in combustion characteristics. Finally, in step 11, the ion current detection devices 4 of the # 2, # 3, and # 4 cylinders are removed. Specifically, the spark plug drive circuit with the ion current detection function is removed from the spark plugs 3 of the cylinders other than the # 1 cylinder and replaced with a normal spark plug drive circuit that does not have the ion current detection function. In this way, the internal combustion engine 1 is shipped with the ion current detection device 4 left in only the # 1 cylinder.

  As described above, FIG. 1 corresponds to the shipped internal combustion engine 1, and the ion current detection device 4 is provided only in the # 1 cylinder. In the internal combustion engine 1, during the subsequent operation, the ignition timing of each cylinder is set using the learning correction values H1 to H4, and the combustion characteristic measured by the ion current detector 4 of the # 1 cylinder is obtained. Based on this, preignition avoidance control is performed simultaneously for all cylinders.

  FIG. 4 is a flowchart showing ignition timing control executed in the internal combustion engine 1 after shipment. This is repeatedly executed during operation of the internal combustion engine 1. In step 101, the intake air amount Qa and the engine rotational speed Ne are read. In step 102, the intake air amount Qa and the engine rotational speed Ne are read. For example, the basic ignition timing ADV0 is obtained from a predetermined ignition timing map. The basic ignition timing ADV0 is expressed as an advance amount from a certain crank angle.

  Next, in step 103, the ion current that correlates with the combustion characteristics of the # 1 cylinder is detected using the ion current detector 4 for the # 1 cylinder. In step 104, it is determined whether or not there is a pre-ignition sign based on the ion current. If a pre-ignition sign is detected, the process proceeds to step 105, the pre-ignition avoidance retardation correction amount HP is increased by a predetermined minute amount ΔHP, and if there is no pre-ignition sign, the process proceeds to step 108. On the contrary, the pre-ignition avoidance retardation correction amount HP is decreased by a predetermined minute amount ΔHP. Note that HPz is the previous value of the pre-ignition avoidance retardation correction amount HP.

  Further, in step 106 following step 105, the upper limit processing of the gradually increasing pre-ignition avoidance retardation correction amount HP is performed. Therefore, the pre-ignition avoidance retardation correction amount HP is larger than a certain upper limit value. Does not grow. Similarly, in step 109 subsequent to step 108, the zero limit treatment of the gradually decreasing pre-ignition avoidance retardation correction amount HP is performed. Therefore, the pre-ignition avoidance retardation correction amount HP is smaller than zero. Not a value.

  In step 107, final ignition timings ADV1 to ADV4 of each cylinder are calculated. Specifically, the ignition timings ADV1 to ADV4 of the respective cylinders are obtained by adding the learning correction values H1 to H4 to the basic ignition timing ADV0 and subtracting the preignition avoidance delay correction amount HP.

  As apparent from FIG. 4, in the internal combustion engine 1 that has undergone the above-described shipping inspection, assuming that the pre-ignition avoidance retardation correction amount HP is 0, for example, the basic ignition timing ADV0 is set to the learning correction value H1 for each cylinder. The ignition timings ADV1 to ADV4 of each cylinder are given in a form corrected by .about.H4. This is because the ignition correction that is the pre-ignition limit in the shipping inspection is measured for each cylinder, and the learning correction values H1 to H4 are determined so that the respective limits are aligned with the same ignition timing.

  For example, in the example of FIG. 3, the ignition timing that becomes the preignition limit of the # 2 cylinder is only 1 ° CA compared to the # 1 cylinder due to differences in various conditions of each cylinder (for example, variation in the cooling temperature distribution, etc.). It is on the retard side. Similarly, the ignition timing that becomes the pre-ignition limit of the # 3 cylinder is 1 ° CA advance side from the # 1 cylinder, and the ignition timing that becomes the pre-ignition limit of the # 4 cylinder is 2 ° than the # 1 cylinder. On the CA retard side. On the other hand, if the learning correction values H1 to H4 are respectively added to the basic ignition timing ADV0, the difference in the ignition timing that becomes the pre-ignition limit is offset, and the pre-ignition limit of each cylinder is uniformly aligned. For example, in the example of FIG. 3, the ignition timing ADV2 of the # 2 cylinder after adding the learning correction value H2 is 1 ° CA compared to the ignition timing ADV1 of the # 1 cylinder after adding the learning correction value H1. Only on the retard side. Therefore, if the preignition occurs in the # 1 cylinder due to the advance of the basic ignition timing ADV0 accompanying the change in operating conditions, theoretically, the preignition also occurs in the # 2 cylinder. The same applies to the # 3 and # 4 cylinders.

  The internal combustion engine 1 is based on the determination of the pre-ignition in the # 1 cylinder on the premise that the ignition timing that is the pre-ignition limit of each cylinder is uniformly set by the learning correction values H1 to H4. Thus, the same amount of pre-ignition avoidance retardation correction amount HP is given to each cylinder. Therefore, the occurrence of pre-ignition due to changes in operating conditions is reliably avoided in all cylinders.

  In the above-described embodiment, learning correction values H1 to H4 for each cylinder are obtained under one typical operating condition at the time of shipping inspection, and the same learning correction values H1 to H1 in all operating regions during actual operation. Although an example using H4 has been described, the present invention is not limited to this, and learning correction values are obtained for each cylinder under a plurality of operating conditions, and during actual operation, each corresponding to the operating conditions at that time It is also possible to determine the ignition timings ADV1 to ADV4 using the cylinder learning correction value.

  Further, in the above embodiment, preignition avoidance is performed by retarding the ignition timing itself that is subject to learning of variation between cylinders, but the present invention is not limited to this, and various known means such as, for example, It can be combined with preignition avoidance control by increasing the amount of fuel injected into the cylinder by the fuel injection valve 2, decreasing the effective compression ratio using the variable valve device 6, and decreasing the intake air amount by the throttle valve 12. It is.

  In the above embodiment, the variation in the combustion characteristics of each cylinder is learned and corrected by the ignition timing. However, the present invention is not limited to this, and parameters relating to other abnormal combustion, such as the fuel injection amount and the effective compression ratio. May be corrected for learning for each cylinder.

  Furthermore, the cylinders that leave the ion current detection device 4 after the shipping inspection may be a plurality of cylinders, and, of course, are not limited to the # 1 cylinder.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Fuel injection valve 4 ... Ion current sensor 6 ... Variable valve operating apparatus 10 ... Engine controller

Claims (6)

At the time of shipping inspection of the internal combustion engine, attaching a combustion state detection device to all the cylinders and measuring the combustion characteristics for each cylinder;
Obtaining a learning value for each cylinder for averaging the combustion characteristics of all cylinders based on the measurement result of the combustion characteristics of each cylinder, and storing the learning value in the control device of the internal combustion engine;
Removing the combustion state detection device from the other cylinders, leaving the combustion state detection device for at least one cylinder before shipping;
A step of operating the internal combustion engine using the stored learning value for each cylinder;
Correcting the combustion conditions of all cylinders based on the combustion state detected by the remaining combustion state detection device during operation;
A method for detecting the combustion state of a multi-cylinder internal combustion engine.   2. The method for detecting a combustion state of a multi-cylinder internal combustion engine according to claim 1, wherein the combustion state detection device comprises an ion current detection device using a spark plug as a detection probe.   3. The combustion characteristic of each cylinder is measured by advancing the ignition timing and measuring the limit ignition timing at which abnormal combustion or a sign thereof is generated for each cylinder. A combustion state detection method for a multi-cylinder internal combustion engine as described.   The combustion state detection method for a multi-cylinder internal combustion engine according to any one of claims 1 to 3, wherein the learning value is a correction value used for correcting the ignition timing of each cylinder. As an ignition plug drive circuit attached to each ignition plug of an internal combustion engine, a normal ignition plug drive circuit and an ignition plug drive circuit with an ion current detection function are prepared in advance,
The method for detecting a combustion state of a multi-cylinder internal combustion engine according to any one of claims 1 to 4, wherein the attachment and detachment of the combustion state detection device is performed by exchanging both.   The above-described process for correcting the combustion condition is to perform fuel increase or ignition timing delay for equalizing all cylinders equally when pre-ignition signs are detected by the remaining combustion state detection device. The combustion state detection method for a multi-cylinder internal combustion engine according to any one of claims 1 to 5.

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