JP2011127493A - Control device for diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a diesel engine capable of certainly suppressing the generation of HC in a transient state. <P>SOLUTION: The control device for the diesel engine 1 provided with an EGR device 2 for recirculating a part of exhaust gas to an intake system includes a glow plug 16 and a control unit 9. The glow plug 16 is arranged in the cylinder of the diesel engine 1 and develops heat in an energized state. The control unit 9 determines whether the operating state of the diesel engine 1 is a transient state. When the control unit determines that the operating state is the transient state, the glow plug 16 is set to an energized state. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for a diesel engine equipped with an EGR device.

  In a diesel engine using light oil as a fuel, an EGR device (exhaust gas recirculation device) is effective in reducing nitrogen oxides (NOx) in exhaust gas. The EGR device recirculates a part of the exhaust gas, which is an inert gas, to the intake system, thereby suppressing the combustion temperature and suppressing the generation of NOx. Suppression of NOx generation is promoted as the exhaust gas recirculation amount increases. However, since the increase in the exhaust gas recirculation amount causes soot, the exhaust gas recirculation amount matches the operating conditions of the vehicle. Therefore, it is adjusted to an appropriate amount considering the avoidance of soot generation.

  On the other hand, development of diesel engines using dimethyl ether (DME) as an alternative fuel for light oil is underway. Since DME is synthesized from natural gas and biogas and does not generate sulfur oxides and PM that cause pollution in the exhaust gas, it is attracting attention as a clean fuel.

JP 2009-79527 A JP 2008-8152 A

  As described above, the exhaust gas recirculation amount in the EGR device is set in consideration of the suppression of NOx generation and the avoidance of soot generation. For this reason, for example, when the operating state of the engine is in a transient state, there is a possibility that hydrocarbons (HC) in the exhaust gas increase. In particular, in an engine using DME as fuel, it is not necessary to consider the generation of soot, so a large amount of exhaust gas recirculation is set to reduce NOx. , There is a high possibility that the amount of supplied air will be insufficient and HC will increase.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a diesel engine control device capable of reliably suppressing the generation of HC in a transient state.

  In order to achieve the above object, the present invention is a control device for a diesel engine having an EGR device that recirculates a part of exhaust gas to an intake system, and includes a glow plug, a determination unit, and a control unit. The glow plug is disposed in the cylinder of the diesel engine and generates heat when energized. The determination means determines whether or not the operating state of the diesel engine is a transient state. The control means sets the glow plug to the energized state when the determination means determines that the operating state of the diesel engine is a transient state.

  In the above configuration, when the determination unit determines that the operation state of the diesel engine is a transient state, the control unit sets the glow plug to the energized state, and the temperature in the cylinder rises. This temperature rise suppresses the generation of hydrocarbons (HC) and reduces the content of HC in the exhaust gas.

  Further, when the diesel engine fuel is dimethyl ether (DME), it is necessary to set the exhaust gas recirculation amount in consideration of the suppression of HC generation. The recirculation amount of the exhaust gas can be increased while suppressing.

  According to the present invention, generation of HC in a transient state can be reliably suppressed.

It is a mimetic diagram showing a schematic structure of a diesel engine concerning this embodiment. It is a block diagram which shows the electric constitution of this embodiment. It is a flowchart which shows combustion chamber heating control.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of a diesel engine according to the present embodiment, FIG. 2 is a block diagram showing an electrical configuration of the present embodiment, and FIG. 3 is a flowchart showing combustion chamber heating control.

  As shown in FIGS. 1 and 2, the diesel engine 1 of the present embodiment includes an EGR device 2 and a turbocharger 3 and is driven using dimethyl ether (DME) as fuel. The EGR device 2 recirculates a part of the exhaust gas to the intake system. The turbocharger 3 has a turbine 4 that is rotated by exhaust gas, and compressed air pressurized by the turbine 4 is supplied to an intake system via an intercooler 5.

  The EGR device 2 includes an EGR passage 6, an EGR valve 8, and a control unit 9. The EGR passage 6 communicates the exhaust passage 11 and the intake passage 12 of the diesel engine 1. An EGR cooler 7 for cooling the exhaust gas is provided in the middle of the EGR passage 6. The EGR valve 8 opens and closes the EGR passage 6 to increase / decrease the exhaust gas recirculation amount. The control unit 9 is set in consideration of the balance between NOx reduction and combustion efficiency, based on the operating state determined by the basic fuel injection amount Q-fin, the engine speed Ne detected by the engine speed sensor 13, and the like. The valve opening (valve lift) of the EGR valve 8 is controlled so as to achieve the target EGR rate.

  For example, map data indicating the relationship between the engine speed Ne, the basic fuel injection amount Q-fin, and the target EGR valve lift is stored in the control unit 9 in advance, and the control unit 9 stores the detected engine speed Ne and EGR lift control (EGR valve) that obtains a target EGR valve lift from the basic fuel injection amount Q-fin and map data, and performs feedback control using the detected value of the lift sensor of the EGR valve 8 so as to be the target EGR valve lift In addition to the EGR lift control and the EGR lift control, the target EGR rate is calculated for the EGR rate, and the EGR rate estimated from the air flow sensor (MAF sensor), the intake pressure sensor, the intake air temperature sensor, etc. is used. EGR rate feedback control or the like for feedback control is executed.

  Moreover, the turbocharger 3 of this embodiment is a type in which the intake pressure can be adjusted by controlling the valve opening lift amount of an intake pressure adjusting valve (VNT) 14 such as a variable vane. When the operating state of the engine 1 is low speed rotation and high load, the VNT 14 is throttled so that the intake pressure increases. When the engine 1 is rotating at high speed, the throttle of the VNT 14 is reduced so that the intake air amount may be small. However, control for reducing the aperture of the VNT 14 is executed to improve fuel efficiency.

  For example, the control unit 9 sets the target VNT set in advance so that the exhaust gas, the fuel consumption, and the output are optimized in accordance with the engine operating state determined by the engine rotational speed Ne, the basic fuel injection amount Q-fin, and the like. The lift is calculated, and the VNT lift control is executed to perform feedback control using the detected value of the lift sensor with respect to the valve lift of the VNT 14 so as to be the target VNT lift. Further, in addition to the VNT lift control, the intake pressure feedback control that performs feedback control using the detected value of the intake pressure sensor with the target intake pressure determined by the engine operating state as the target value may be executed. Good.

  In each cylinder 15 of the diesel engine 1, a glow plug (preheating plug) 16 that generates heat when energized is disposed. The glow plug 16 is used as an auxiliary heat source for preventing the starting failure by raising the temperature in the combustion chamber in advance when starting the diesel engine 1 with the cylinder head or the cylinder block cooled in a cold time. The

  The engine rotation speed sensor 13 detects the engine rotation speed every predetermined time and outputs it to the control unit 9. Further, the accelerator opening sensor 17 detects the accelerator opening every predetermined time and outputs it to the control unit 9. The control unit 9 determines whether the operation state of the diesel engine 1 is a normal state (normal mode) or a transient state (transient mode) based on the engine speed, the accelerator opening, the accelerator opening change rate, and the like. Then, when it is determined that the operation state is a transient state, the combustion chamber heating control for setting the glow plug 16 to the energized state is repeatedly executed every predetermined time. That is, the control unit 9 functions as a determination unit and a control unit. The transient state refers to a state in which the engine speed and load increase or decrease in a short time.

  That is, in the combustion chamber heating control, as shown in FIG. 3, the control unit 9 determines whether the operation state of the diesel engine 1 is a normal state (normal mode) (step S1) and is in a transient state. Is determined (step S1: Yes), the glow plug 16 is set in an energized state (glow plug ON) (step S2). On the other hand, when it is determined that the state is not a transient state (normal state) (step S1: No), the glow plug 16 is set to a non-energized state (glow plug OFF) (step S3), and this process is terminated.

  According to the present embodiment, when the operation state of the diesel engine 1 is in a transient state, the glow plug 16 is set to an energized state, and the temperature in the cylinder 15 rises. Due to this temperature rise, the generation of HC is suppressed, and the content of HC in the exhaust gas is reduced.

  In particular, when the fuel of the diesel engine 1 is dimethyl ether (DME), it is necessary to set the exhaust gas recirculation amount in consideration of the suppression of the generation of HC, but in this embodiment, a transient state in which HC easily occurs. The generation of HC in the combustion chamber is suppressed by increasing the temperature of the combustion chamber, so that the generation of HC can be suppressed without specially adjusting the amount of exhaust gas recirculation in the transient state to suppress the generation of HC. It is possible to increase the NOx reduction effect by increasing the exhaust gas recirculation amount.

  In addition, since the glow plug 16 disposed to prevent starting failure at low temperatures is used, the generation of HC in a transient state can be suppressed without adding new parts.

  In addition, although the said embodiment demonstrated the diesel engine 1 which uses DME as a fuel, you may apply this invention to the diesel engine which uses other fuels, such as light oil.

  As mentioned above, although the embodiment to which the invention made by the present inventor is applied has been described, the present invention is not limited by the discussion and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

  The present invention is widely applicable to diesel engines.

DESCRIPTION OF SYMBOLS 1 Diesel engine 2 EGR apparatus 3 Turbocharger 9 Control unit (determination means, control means)
13 Engine speed sensor 15 Cylinder 16 Glow plug 17 Accelerator opening sensor

Claims (2)

A control device for a diesel engine having an EGR device for recirculating a part of exhaust gas to an intake system,
A glow plug that is arranged in a cylinder of the diesel engine and generates heat when energized;
Determining means for determining whether or not the operating state of the diesel engine is in a transient state;
A control device for a diesel engine, comprising: a control unit that sets the glow plug to an energized state when the determination unit determines that the operation state of the diesel engine is a transient state. The diesel engine control device according to claim 1, wherein the fuel of the diesel engine is dimethyl ether.

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