JP2016223324A - Engine control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To immediately and accurately detect a cetane number of fuel in an engine, and to reflect the detection to the control of the engine.SOLUTION: An engine control system includes a temperature sensor, a cetane number estimation section, and a fuel injection control section. The temperature sensor detects a combustion temperature of fuel in a cylinder of an engine. The cetane number estimation section estimates a cetane number of the fuel based on a detection value of the temperature sensor (step S103). The fuel injection control section controls injection of the fuel based on the cetane number estimated by the cetane number estimation section (steps S105-S107).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a configuration for performing control according to a cetane number of a fuel in a diesel engine.

  Diesel engines are widely used in the field of agricultural work vehicles such as tractors. A diesel engine is described in Patent Documents 1 to 4, for example.

  Various control parameters (for example, the number of times of fuel injection, timing, and interval) of the diesel engine have different optimum values depending on the cetane number of light oil as fuel. If a fuel different from the assumed cetane number is used, not only will the engine's original performance not be achieved, but it will be unfavorable in terms of the environment, such as the generation of unburned fuel, and the engine may be adversely affected. .

  Diesel oil is produced all over the world, but its cetane number varies from country to country. For example, there are many low cetane number diesel oils in North America, etc., and Japanese diesel oil has a relatively high cetane number. Thus, for example, it is conceivable that engine specifications are different between North America and Japan. However, in this case, since products with different specifications are sold in North America and Japan, there is a problem that product development becomes complicated and product management costs and manufacturing costs increase.

  In this regard, for example, Patent Documents 1 and 2 describe a configuration in which engine control parameters are changed in accordance with a set cetane number (paragraphs 0089 to 0090 in Patent Document 1, paragraph 0056 in Patent Document 2). ). According to this, even with the same engine, it is possible to perform optimal engine control in North America and Japan by changing the cetane number setting. Therefore, it is not necessary to prepare engines with different specifications for each country. However, in the case of the configurations described in Patent Documents 1 and 2, it is necessary to set a correct cetane number in order to appropriately control the engine. For this reason, it is necessary to know the cetane number of the fuel in advance, and appropriate control cannot be performed when the cetane number of the fuel is unknown or when a fuel having a cetane number different from the assumption is supplied.

  In this regard, Patent Documents 3 and 4 disclose a configuration in which the cetane number of the fuel is estimated according to the measured values of various sensors, and control is performed based on the estimated cetane number. Thus, if the cetane number of the fuel can be estimated, it is considered that optimum engine control corresponding to the cetane number can be realized.

JP 2006-241978 A JP 2008-25551 A JP 2007-321706 A JP 2004-340026 A

  However, in the configuration of Patent Document 3, when vibration in the engine is large, noise is likely to be mixed into the angular velocity amplitude value measured by the sensor, and the cetane number is estimated based on the measured angular velocity amplitude value to control the engine. Even if it went, it was difficult to control precisely. In the configuration of Patent Document 4, if the engine speed is not kept constant, the engine will vibrate due to factors other than the in-cylinder pressure, and the cetane number is estimated based on the measured excitation force. Even if the engine is controlled, it is difficult to precisely control the engine.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a configuration in which the cetane number of fuel can be immediately detected in an engine and reflected in engine control.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to an aspect of the present invention, the following engine control system is provided. That is, the engine control system includes a temperature sensor, a cetane number estimation unit, and a fuel injection control unit. The temperature sensor detects the combustion temperature of the fuel in the cylinder of the engine. The cetane number estimation unit estimates the cetane number of the fuel based on the detection value of the temperature sensor. The injection control unit controls fuel injection based on the cetane number estimated by the cetane number estimation unit.

  That is, stable combustion can be realized by estimating the cetane number of the fuel based on the combustion temperature and controlling the fuel injection according to the cetane number.

  The engine control system is preferably configured as follows. That is, the cetane number estimation unit includes a storage unit that stores a correspondence relationship between the combustion temperature and the cetane number. And the said cetane number estimation part estimates the cetane number of a fuel based on the detected value of the said temperature sensor, and the said corresponding relationship memorize | stored in the said memory | storage part.

  Thus, the cetane number can be accurately estimated by measuring and storing the correspondence relationship between the combustion temperature and the cetane number in advance.

  The engine control system is preferably configured as follows. That is, the fuel injection control unit controls the fuel injection timing based on the cetane number estimated by the cetane number estimation unit.

  Thus, by varying the fuel injection timing according to the cetane number, the normal combustion state of the engine can be maintained regardless of the cetane number.

  The engine control system is preferably configured as follows. That is, the diesel oxidation catalyst is connected to the engine having the engine control system.

  That is, when the combustion control according to the cetane number as described in the present application is applied to an engine to which a diesel oxidation catalyst (DOC) is connected, it is possible to prevent discharge of unburned fuel to the DOC and excessive temperature rise of the DOC. Is particularly suitable.

  The engine control system is preferably configured as follows. That is, the engine is a multi-cylinder engine. The temperature sensor is provided only in any one cylinder.

  Thereby, since it is not necessary to provide a sensor in every cylinder, cost reduction can be achieved.

  The engine control system is preferably configured as follows. That is, this engine control system includes a pressure sensor and an abnormal combustion detection unit. The pressure sensor detects a pressure in the cylinder. The abnormal combustion detection unit detects abnormal combustion based on detection values of the temperature sensor and the pressure sensor. The fuel injection control unit controls fuel injection based on a detection result of the abnormal combustion detection unit.

  In this way, combustion can be more appropriately controlled using the temperature sensor and pressure sensor in the cylinder.

1 is a schematic diagram showing an overall configuration of an engine having an engine control system according to an embodiment of the present invention. The block diagram which shows the electrical structure of an engine. The figure explaining the estimation table which shows the relationship between the combustion temperature of a fuel, and a cetane number. The flowchart which shows an example of the control processing according to the cetane number of the fuel performed in an engine.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an engine 1 having the engine control system of the present embodiment.

  An engine 1 shown in FIG. 1 includes an engine body 2, a common rail fuel injection device 3, an EGR device (exhaust gas recirculation device) 4, an exhaust turbine supercharger 5, an exhaust purification device 6, ECU (engine control unit) 7.

  The engine body 2 is combusted by supplying fuel to compressed air, and obtains rotational power from the expansion energy generated by the combustion. The engine body 2 includes a cylinder block and a cylinder head. The engine body 2 of the present embodiment is a known in-line four-cylinder type diesel engine, and four cylindrical cylinders are provided at equal intervals in the cylinder block. A piston is slidably provided in each cylinder. The cylinder head is attached to the cylinder block so as to close the opening of the cylinder. A combustion chamber 23 is formed between the piston, the cylinder, and the cylinder head.

  The engine body 2 includes an intake manifold 25 and an exhaust manifold 26. An intake pipe 27 that introduces intake air into the intake manifold 25 is connected to the intake manifold 25. An exhaust pipe 28 through which exhaust from the exhaust manifold 26 is discharged is connected to the exhaust manifold 26.

  The common rail fuel injection device 3 includes a supply pump (not shown), a common rail 31, injectors 32, 32, and the like. The fuel pumped by the supply pump is stored in the common rail 31 at a high pressure, and the fuel in the common rail 31 is injected into the combustion chambers 23, 23... From the injectors 32, 32. The electronic control valves of the injectors 32, 32... Are connected to the ECU 7. When signals from the ECU 7 are input to the electronic control valves, the injectors 32, 32.・ ・ Fuel is injected inside. The ECU 7 can control the fuel injection state by controlling the fuel injection from the injector 32 at an appropriate number of times, timings, and intervals, whereby the engine speed and torque of the engine body 2 can be changed. Is adjustable.

  Moreover, in this embodiment, the temperature sensor 11 which detects the temperature in the combustion chamber 23 in the said cylinder is provided in the vicinity of one of the injectors 32, 32 ... (refer FIG. 2). The temperature sensor 11 is connected to the ECU 7, and a detection value of the temperature sensor 11 is input to the ECU 7. From the detection value of the temperature sensor 11, the combustion temperature in the combustion chamber 23 shown in FIG. 1 can be estimated. Four temperature sensors 11 may be provided so as to correspond to each cylinder. However, since the combustion temperature is considered to be the same in all cylinders (internal combustion chambers), at least one of the cylinders is required. It is enough if it is provided.

  Moreover, in this embodiment, the pressure sensor 12 which detects a cylinder pressure is provided in one of the said cylinders (refer FIG. 2). The pressure sensor 12 is connected to the ECU 7, and a detection value of the pressure sensor 12 is input to the ECU 7.

  The EGR device 4 shown in FIG. 1 includes an EGR pipe 41, an EGR valve 42, and an EGR cooler 43. The EGR pipe 41 connects the intake pipe 27 and the exhaust pipe 28, and the exhaust gas is recirculated to the intake air via the EGR pipe 41. The EGR valve 42 is provided in the EGR pipe 41, and the EGR valve 42 is connected to the ECU 7. The ECU 7 controls the opening degree of the EGR valve 42 so that the exhaust gas recirculation amount is adjusted. The EGR cooler 43 cools the exhaust gas flowing through the EGR pipe 41.

  The supercharger 5 shown in FIG. 1 includes a turbine 51 that rotates by exhaust flowing through the exhaust pipe 28, and a compressor 52 that rotates integrally with the turbine 51. The compressor 52 is disposed in the intake pipe 27, and the intake air is compressed by the rotation of the compressor 52 and sent to the cylinder of the engine body 2.

  The exhaust purification device 6 is provided at the outlet of the exhaust pipe 28. The exhaust purification device 6 includes a diesel oxidation catalyst (DOC) 61 and a DPF (diesel particulate filter) 62 disposed on the downstream side of the DOC 61. The DOC 61 is a catalyst for oxidizing (burning) unburned fuel, carbon monoxide CO, nitrogen monoxide NO, and the like contained in the exhaust gas. The DPF 62 is configured as a fall flow type filter, for example, and collects PM (particulate matter) included in the exhaust gas processed by the DOC 61. Further, the exhaust purification device 6 includes a temperature sensor 63 that detects the temperature of the DOC 61 and a temperature sensor 64 that detects the temperature of the DPF 62. Detection values of the temperature sensors 63 and 64 are output to the ECU 7.

When it is detected from the detection results of the temperature sensors 63 and 64 that the amount of PM accumulated in the DPF 62 exceeds a predetermined amount, the operating conditions of the engine 1 are changed to raise the exhaust gas temperature, thereby The oxidation reaction of PM by NO ₂ and O ₂ contained in the exhaust gas is promoted, and the PM can be removed from the DPF 62 as harmless CO ₂ gas. Hereinafter, this process is referred to as “forced regeneration”. The forced regeneration is performed by the regeneration processing unit 78 of the ECU 7 shown in FIG.

  The ECU 7 shown in FIGS. 1 and 2 is configured as a computer that realizes a predetermined function by executing a built-in program. Specifically, as described above, the ECU 7 of the present embodiment serves as the fuel injection control unit 71 that appropriately controls the number, timing, and interval of fuel injection from the injector 32 to the combustion chamber 23 of the cylinder. It has a function. In addition, the ECU 7 of the present embodiment also has functions as a cetane number estimation unit 72 and an abnormal combustion detection unit 73. Furthermore, the ECU 7 of this embodiment also has a function as a regeneration processing unit 78 that performs forced regeneration of the DPF 62 and a function as an EGR control unit 79 that controls the amount of EGR.

  Subsequently, a characteristic configuration of the present embodiment will be described. As described above, the ECU 7 has functions as the cetane number estimation unit 72 and the abnormal combustion detection unit 73.

  The storage unit 77 of the cetane number estimation unit 72 of the ECU 7 stores an estimation table 75 showing the correspondence between the combustion temperature in the combustion chamber 23 estimated from the detection value of the temperature sensor 11 and the cetane number of the fuel. (See FIG. 3). The estimation table 75 shown in FIG. 3 is created in advance by the correspondence between the combustion temperature of the fuel and the cetane number by measurement or the like by the engine manufacturer, and is stored in the storage unit.

  The cetane number estimation unit 72 of the ECU 7 estimates the combustion temperature of the fuel in the combustion chamber 23 from the detection value of the temperature sensor 11, and refers to the estimation table 75 based on the combustion temperature, thereby burning at that time Estimate the cetane number of the fuel corresponding to the temperature. The ECU 7 controls the fuel injection timing based on the estimated cetane number so that the fuel combustion state is maintained in a stable state.

  Below, an example of the control according to the cetane number of the fuel performed in the engine 1 of this embodiment is demonstrated with reference to the flowchart of FIG.

  When it is instructed to start control according to the cetane number by an operation signal from a predetermined operation tool, the cetane number estimation unit 72 and the abnormal combustion detection unit 73 of the ECU 7 first detect the detected value of the temperature sensor 11. Tn and the detected value Pn of the pressure sensor 12 are acquired (step S101). Then, the cetane number estimating unit 72 of the ECU 7 estimates and acquires the combustion temperature Cn of the fuel in the combustion chamber 23 (cylinder) from the detection value Tn of the temperature sensor 11 (step S102).

  Subsequently, the cetane number estimation unit 72 of the ECU 7 estimates and acquires the cetane number Sn corresponding to the combustion temperature Cn detected in step S102 by referring to the estimation table 75 stored in the storage unit 77 (step). S103).

  Next, the abnormal combustion detection unit 73 of the ECU 7 determines whether abnormal combustion such as knocking has occurred in the cylinder based on the detection value Tn of the temperature sensor 11 and the detection value Pn of the pressure sensor 12 detected in step S101. It is determined whether or not (step S104). As a result, when it is determined that abnormal combustion has not occurred, the ECU 7 proceeds to a process (from step S105 to step S107) for performing control according to the cetane number.

  On the other hand, if it is determined in step S104 that abnormal combustion has occurred, the fuel injection control unit 71 of the ECU 7 delays the ignition timing by appropriately delaying the fuel injection timing from the injector 32 (step S108). The occurrence of abnormal combustion in the cylinder is suppressed. Thereby, the combustion state of the fuel in the cylinder becomes a stable state.

  When the abnormal combustion detection unit 73 determines that the abnormal combustion has not occurred, the fuel injection control unit 71 of the ECU 7 determines whether or not the cetane number Sn estimated in step S103 is smaller than a preset reference value Sb. Is determined (step S104). As a result, when the cetane number at that time is smaller than the reference value Sb, the fuel injection control unit 71 executes a process of quickly advancing the fuel injection timing from the injector 32 by a predetermined amount for a predetermined time (step S105). . After this process, the fuel injection control unit 71 executes a process of gradually delaying until the fuel injection timing from the injector 32 reaches the target value (step S106). On the other hand, when it is determined in step S104 that the cetane number at that time is equal to or greater than the reference value Sb, the fuel injection control unit 71 does not advance the fuel injection timing from the injector 32 until the target value is reached. A process of gradually delaying is executed (step S106). Thereby, the combustion state of the fuel in the cylinder becomes a stable state.

  As described above, in the engine control system included in the engine 1 of the present embodiment, the cetane number Sn of the fuel is estimated and detected in real time, and control is performed so that fuel injection according to the cetane number Sn is performed. Thus, stable combustion can be realized.

  Further, in the engine control system of the engine 1 of the present embodiment, stable combustion according to the cetane number Sn of the fuel can be realized, so that unburned fuel becomes difficult to be supplied to the DOC 61, and the DOC 61 is excessive. Temperature rise is prevented.

  As described above, the engine control system of the present embodiment includes the temperature sensor 11, the cetane number estimation unit 72, and the fuel injection control unit 71. The temperature sensor 11 detects the combustion temperature Cn of the fuel in the cylinder of the engine 1. The cetane number estimation unit 72 estimates the cetane number Sn of the fuel based on the detection value of the temperature sensor 11. The fuel injection control unit 71 controls fuel injection based on the cetane number Sn estimated by the cetane number estimation unit 72.

  Thus, the cetane number Sn of the fuel can be estimated based on the combustion temperature Cn. And stable combustion is realizable by controlling fuel injection according to the estimated cetane number Sn.

  Further, in the engine control system of the present embodiment, the cetane number estimation unit 72 includes a storage unit 77 that stores an estimation table 75 indicating a correspondence relationship between the combustion temperature Cn and the cetane number Sn. Then, the cetane number estimation unit 72 estimates the cetane number Sn of the fuel based on the detected value Tn of the temperature sensor and the estimation table 75 stored in the storage unit 77.

  Thereby, by measuring the correspondence between the combustion temperature Cn and the cetane number Sn in advance and storing it as the estimation table 75, the cetane number Sn can be estimated with high accuracy.

  In the engine control system of the present embodiment, the fuel injection control unit 71 controls the fuel injection timing based on the cetane number Sn estimated by the cetane number estimation unit 72.

  Thus, by varying the fuel injection timing according to the cetane number Sn, the normal combustion state of the engine can be maintained regardless of the cetane number.

  In the engine control system of the present embodiment, a DOC is connected to the engine 1.

  Thereby, when the combustion control according to the cetane number Sn as described above is applied to the engine 1 to which the DOC is connected, discharge of unburned fuel to the DOC and excessive temperature rise of the DOC can be prevented. Therefore, it is particularly suitable.

  The engine 1 having the engine control system of the present embodiment is a multi-cylinder engine. And the temperature sensor 11 is provided only in any one cylinder.

  Thereby, since it is not necessary to provide the temperature sensor 11 in every cylinder, cost reduction can be aimed at.

  The engine control system of the present embodiment includes a pressure sensor 12 and an abnormal combustion detection unit 73. The pressure sensor 12 detects the pressure in the cylinder. The abnormal combustion detection unit 73 detects abnormal combustion based on the detection values of the temperature sensor 11 and the pressure sensor 12. The fuel injection control unit 71 controls fuel injection based on the detection result of the abnormal combustion detection unit 73.

  Thereby, combustion control can be performed more appropriately using the temperature sensor 11 and the pressure sensor 12 in the cylinder.

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  In the above-described embodiment, the fuel injection timing is controlled based on the estimated cetane number of the fuel so that the combustion state of the fuel is maintained in a stable state. Not limited to. For example, the number of fuel injections, the injection pressure, or the injection interval may be controlled based on the estimated cetane number of the fuel.

  In the above embodiment, the combustion temperature Cn of the fuel in the cylinder (combustion chamber) is estimated based on both the detection value Tn of the temperature sensor 11 and the detection value Pn of the pressure sensor 12, but this is not limitative. First, the combustion temperature Cn of the fuel in the cylinder (combustion chamber) is estimated based on either the detection value Tn of the temperature sensor 11 or the detection value Pn of the pressure sensor 12, thereby estimating the cetane number of the fuel. May be.

  In the above embodiment, the fuel injection is controlled according to the estimated cetane number of the fuel. However, the present invention is not limited to this. For example, the EGR amount may be controlled according to the estimated cetane number of the fuel. . As a specific example, after the cetane number estimation unit 72 of the ECU 7 performs the processing from step S101 to step S103, the EGR control unit 79 of the ECU 7 determines that the estimated cetane number Sn of the fuel is smaller than the reference value Sb. Further, a process for increasing the opening degree of the EGR valve 42 can be executed. As a result, when the cetane number of the fuel is low, the opening of the EGR valve 42 is increased to increase the EGR amount, so that the intake air sent into the combustion chamber 23 can be heated to improve the ignitability of the fuel. And by extension, stable combustion can be realized.

  Alternatively, other parameters can be controlled according to the cetane number, such as controlling the boost pressure according to the estimated cetane number of the fuel.

  In the above embodiment, the control according to the cetane number of the fuel is performed only while a predetermined operation tool is being operated. However, the present invention is not limited to this, and the control may be performed constantly, or the control may be performed periodically (for example, every hour) by detecting the cetane number.

1 engine (diesel engine)
DESCRIPTION OF SYMBOLS 11 Temperature sensor 61 Diesel oxidation catalyst 71 Fuel injection control part 72 Cetane number estimation part 75 Estimation table Cn Combustion temperature Sn Cetane number

Claims (6)

A temperature sensor for detecting the combustion temperature of the fuel in the cylinder of the diesel engine;
A cetane number estimation unit for estimating a cetane number of the fuel based on a detection value of the temperature sensor;
A fuel injection control unit that controls fuel injection based on the cetane number estimated by the cetane number estimation unit;
An engine control system comprising: The engine control system according to claim 1,
The cetane number estimation unit includes a storage unit that stores a correspondence relationship between the combustion temperature and the cetane number,
The cetane number estimation unit estimates the cetane number of fuel based on the detected value of the temperature sensor and the correspondence relationship stored in the storage unit. The engine control system according to claim 1 or 2,
The engine control system, wherein the fuel injection control unit controls fuel injection timing based on the estimated cetane number. The engine control system according to any one of claims 1 to 3,
An engine control system, wherein a diesel oxidation catalyst is connected to the diesel engine. An engine control system according to any one of claims 1 to 4,
The engine having the engine control system is a multi-cylinder engine, and the temperature sensor is provided in only one of the cylinders. An engine control system according to any one of claims 1 to 5,
A pressure sensor for detecting the pressure in the cylinder;
An abnormal combustion detector for detecting abnormal combustion based on the detected values of the temperature sensor and the pressure sensor;
With
The engine control system, wherein the fuel injection control unit controls fuel injection based on a detection result of the abnormal combustion detection unit.

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