JP4529935B2 - In-cylinder direct injection engine start control device - Google Patents

Description

  The present invention relates to an in-cylinder direct injection engine, and more particularly to a start control device for an in-cylinder direct injection engine using high-boiling point fuel.

  In recent years, the diversification of fuel in engines has been studied due to the problem of soaring crude oil prices and their depletion. Thus, alcohol fuels such as ethanol are considered promising as one of alternative fuels to petroleum fuels, and there are some examples that have been put into practical use as so-called alcohol mixed fuels in which gasoline and alcohol are mixed. However, this alcohol-mixed fuel has a higher boiling point than 100% gasoline fuel, and its calorific value and vaporization characteristics differ, and the characteristics also differ depending on the alcohol concentration indicating the mixing ratio with respect to gasoline. If the alcohol-mixed fuel is used as it is in an engine on the premise of using this, the control air-fuel ratio deviates from the stoichiometric air-fuel ratio, the exhaust component changes, and the drivability deteriorates. In particular, startability when the engine is cold at low temperatures becomes a problem.

  Therefore, for example, in Patent Document 1, a main fuel tank and a sub fuel tank provided with a heating means are provided, and it is determined that starting is impossible by comparing the startable determination temperature set with the alcohol concentration as a parameter and the cooling water temperature. The heated fuel in the sub-fuel tank is pumped to circulate the fuel, and the engine is cranked to inject the heated fuel from the injector, thereby supplying the fuel according to the alcohol concentration. A technique is disclosed in which the engine is efficiently heated and supplied to the engine to improve startability.

JP-A-5-149223

  By the way, the technique disclosed in Patent Document 1 aims to improve startability by heating the fuel itself to promote atomization or vaporization. The startability is improved by heating the fuel. However, this heating of the fuel has the detrimental effect of promoting the deposition of deposits on the injector. Further, there is a problem that the system is complicated and the cost is inevitably increased due to the additional sub fuel tank provided with the heating means.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a start control device for a direct injection engine that can obtain a reliable start performance in a short time even when a high boiling point fuel is used with a simple configuration. Is to provide.

  A start control device for an in-cylinder direct injection engine according to an embodiment of the present invention that achieves the above object is provided in an in-cylinder direct injection engine that includes a direct injection injector and an ignition plug that are provided facing a combustion chamber. At the initial stage of the subsequent start, fresh air is introduced into the cylinder in the expansion stroke, a predetermined amount of fuel is injected from the direct injection injector, and initial control is performed so that the ignition plug performs multiple times of ignition. Features.

  Here, it is preferable that the start initial control is continued until the engine speed reaches a predetermined complete explosion speed.

  Further, a fuel type determination unit may be further provided, and when the fuel type determination unit determines that the fuel has a predetermined high boiling point, the start initial control may be executed.

  Furthermore, an engine temperature measuring unit may be provided, and the start initial control may be executed when the engine temperature measuring unit determines that the temperature is equal to or lower than a predetermined temperature.

  According to the start control device for an in-cylinder direct injection engine according to an embodiment of the present invention, at the initial start after cranking starts, fresh air is introduced into the cylinder in the expansion stroke, and a predetermined amount of air is introduced from the direct injection injector. Fuel is injected and ignition is performed multiple times by the spark plug. Thereby, even if it does not reach an explosion, combustion to the extent that the fuel is ignited can be obtained, so that the temperature in the cylinder rises early. Therefore, atomization or vaporization of fuel injected from the direct injection injector after the next cycle is promoted, and normal combustion is obtained at an early stage, thereby improving startability.

  Here, according to the form in which the initial start control is continued until the engine speed reaches a predetermined complete explosion speed, the in-cylinder temperature is raised, so the engine is started in a short time even at an extremely low temperature. can do.

  In addition, when the fuel type determination unit further includes a fuel type determination unit and the fuel type determination unit determines that the fuel has a predetermined high boiling point, the start initial control is performed without performing unnecessary start initial control, It is possible to improve startability with a predetermined high boiling point fuel.

  Further, the engine temperature measuring means is provided, and when it is determined by the engine temperature measuring means that the temperature is equal to or lower than the predetermined temperature, the start initial control is executed. It is possible to improve startability at low temperatures without performing unnecessary start initial control.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  First, an outline of a direct injection engine 100 to which the present invention is applied will be described with reference to FIG. 101 is an engine body, 102 is a cylinder block, 103 is a cylinder head, 104 is a piston, 105 is a combustion chamber, 106 is an intake port, 107 is an exhaust port, 108 is an intake valve, 109 is an exhaust valve, and 110 is in the combustion chamber 105 Each of the spark plugs arranged on the top of the is shown. The engine 100 according to the present embodiment includes, for example, an electromagnetic intake valve drive mechanism 108V that can open and close the intake valve 108 at an arbitrary timing.

  A crankshaft 111 is connected to the lower end portion of the piston 104, and the crankshaft 111 is rotated when the piston 104 moves up and down. Further, a crank position sensor 112 is disposed in the vicinity of the crankshaft 111. The crank position sensor 112 is, for example, an electromagnetic pickup sensor, and is a magnetic rotor connected to the crankshaft 111, for example. It is possible to detect the crank position including the top dead center position, that is, the cylinder, and to detect the crank angular speed, that is, the engine speed, by detecting the crank rotation signal every 10 ° and the missing part. is there.

  The intake port 106 is connected to a surge tank (not shown) via an intake manifold (not shown), and the surge tank is connected to an air cleaner via an intake duct. A throttle valve (not shown) that is driven by a throttle motor is disposed in the intake duct. On the other hand, the exhaust port 107 is connected to the catalytic converter via an exhaust manifold and an exhaust pipe (not shown). Reference numeral 113 denotes a water temperature sensor for detecting the engine cooling water temperature.

  The engine 100 of FIG. 1 includes a fuel supply system that uses an alcohol mixed fuel as an example of a high-boiling point fuel, and this fuel supply system can inject alcohol mixed fuel into a combustion chamber 105 in a cylinder through an injection port. A direct injection injector 120 is provided. The direct injection injector 120 is connected to a fuel tank 124 mounted on a vehicle via an alcohol mixed fuel supply line 122 including a delivery pipe 121. A fuel pump 123 is disposed in the alcohol mixed fuel supply line 122. Further, in the present embodiment, a fuel type determination sensor 125 as a fuel type determination unit is disposed in the fuel tank 124. The fuel type determination sensor 125 is preferably capable of detecting the difference in boiling point particularly when specifying the type of fuel stored in the fuel tank 124.

  Further, as shown in FIG. 1, the above-described spark plug 110 is disposed at the upper center of the combustion chamber 105 between the intake port 106 and the exhaust port 107. The direct injection injector 120 is disposed on the intake port 106 side with its injection port inclined at a predetermined angle with respect to the cylinder center line. Furthermore, a piston cavity 104 </ b> C adapted to the injection direction from the direct injection injector 120 is formed in the upper part of the piston 104 so as to be offset toward the intake port 106. The piston cavity 104C is formed in the shape of a boat bottom that is offset to the intake port 106 side so that the spray flow from the direct injection injector 120 may circulate and cause turbulence near the gap of the spark plug 110. Further, the spray angle and the spray shape of the direct injection injector 120 with respect to the piston cavity 104C are set so that the alcohol mixed fuel can be stratifiedly combusted in the piston cavity 104C.

  The electronic control unit (hereinafter referred to as ECU) 200 is a digital computer, and as is well known, a ROM (Read Only Memory), a RAM (Random Access Memory), and a CPU connected to each other via a bidirectional bus. (Microprocessor), B-RAM (backup RAM) always connected to a power source, an input port, an output port, and the like.

  Signals from the respective sensors described above are input to the input ports of the ECU 200, respectively. Further, an engine switch 114 used for starting the engine is connected to the input port. On the other hand, the output ports of the ECU 200 are connected to the intake valve drive mechanism 108V, the spark plug 110, the throttle motor, the direct injection injector 120, the fuel pump 123, the starter, and the like via corresponding drive circuits.

  In the present embodiment, the amount of fuel to be injected and supplied at the time of start-up is obtained in advance by experiments, set according to the boiling point of the fuel and / or the temperature of the engine coolant, and mapped to the above-described ROM. Stored as data.

  Here, an example of a control routine in the embodiment of the start control device for the direct injection engine according to the present invention will be described with reference to the flowchart of FIG. In this embodiment, when the control is started, it is first determined in step S201 whether or not the engine switch 114 has been turned “ON”, and the process proceeds to step S202 only when the switch is turned “ON”. In step S202, the starter output signal is turned “ON”, and cranking is started by the starter. Further, the process proceeds to the next step S203, where it is determined whether the fuel being used is a high boiling point fuel based on the detection signal from the fuel type determination sensor 125. In the next step S204, it is determined based on the detection signal from the water temperature sensor 113 whether the engine cooling water temperature is equal to or lower than a predetermined temperature.

  As a result of the determination in step S203 and step S204, when both are “NO”, that is, when the fuel being used is not a high boiling point fuel and the engine coolant temperature exceeds a predetermined temperature, and Even if the fuel used is a high-boiling point fuel, if the engine cooling water temperature exceeds the predetermined temperature, it is determined that there is no significant problem with the startability, and the process proceeds to step S207 without executing the initial start control described later. move on.

  On the other hand, in the determination in step S203 and step S204, the fuel used is a high boiling point fuel (step S203: “YES”), and the engine coolant temperature is equal to or lower than a predetermined temperature (step S204: “YES”). ”), The process proceeds to step S205, where start-up initial control is executed.

  This starting initial control will be described with reference to a time chart based on the crank angle (CA) of FIG. In this starting initial control, first, the cylinder that first enters the expansion stroke after the start of cranking is determined. This is a cylinder obtained based on the detection signal from the crank position sensor 112 and having the piston 104 near the top dead center. Now, assuming that the engine 100 is a 4-cylinder engine and the ignition sequence is # 1- # 3- # 4- # 2, the time chart of FIG. An example of starting the expansion stroke from (0 ° CA) is shown.

  Therefore, in the # 1 cylinder in the expansion stroke, the intake valve drive mechanism 108V is driven to open the intake valve 108 and fresh air is introduced, and a predetermined amount of fuel is injected from the direct injection injector 120. The predetermined amount of fuel is set by reading the mapped data stored in the ROM as described above. Then, ignition by the spark plug 110 is performed a plurality of times in the same expansion stroke. Thus, in the # 1 cylinder, the combustion in such a degree that the fuel is ignited can be obtained even if the explosion does not occur, so that the temperature in the cylinder rises early.

  Similarly, fresh air is introduced in the expansion stroke of the first cycle after the start of cranking in the # 3 cylinder, the next # 4 cylinder, and the # 2 cylinder, which is the next ignition order of the # 1 cylinder. At the same time, a predetermined amount of fuel is injected and ignition is performed a plurality of times. After the next cycle, in addition to normal operation by introduction of fresh air in the intake stroke, fuel injection in the intake stroke and / or compression stroke, and single ignition in the latter half of the compression stroke, Until the rotational speed reaches a predetermined complete explosion rotational speed, initial start control including introduction of fresh air in the expansion stroke, fuel injection, and execution of multiple ignitions is performed.

  Therefore, as a result of the introduction of fresh air, the injection of fuel and the execution of multiple times of ignition in the expansion stroke of the first cycle after the start of cranking, the in-cylinder temperature rises early, so that the direct injection injectors after the next cycle The atomization or vaporization of the fuel injected from 120 is promoted and normal combustion is obtained at an early stage, whereby the startability is improved.

  Here, returning to the flowchart of FIG. 2 again, the above-described start initial control in step S205 is executed, and the process proceeds to the next step S206. In step S206 and step S207 in the case where the engine is started in the normal operation mode without executing the above-described start initial control, it is determined whether or not the engine speed has reached a predetermined complete explosion speed. In any case, only when the engine speed reaches the predetermined complete explosion speed, the engine is completely started so as to be able to rotate independently, and the process proceeds to the next step S208, where the starter output signal is turned “OFF” and the starter Is stopped. That is, as shown in the time chart of FIG. 4, after the starter output signal is turned “ON” at time t0 and driven at a predetermined cranking speed by the starter, the engine speed reaches the complete explosion speed. At tc, the starter output signal is turned “OFF”.

  The present invention has been described with respect to an engine using alcohol mixed fuel as a fuel engine in which high-boiling point fuel is injected and supplied by a direct injection injector. However, the fuel is not limited to the alcohol mixed fuel illustrated, and is low. Octane gasoline, light oil, or the like can be used. In short, the present invention can be applied to all types of engines that inject and supply low-volatile fuel into a cylinder.

It is a schematic structure figure showing an engine provided with a direct injection injector to which the present invention is applied. It is a flowchart which shows an example of the control procedure in embodiment of this invention. 3 is a crank angle (CA) reference time chart showing the relationship between fuel injection and ignition timing in an embodiment of the present invention. It is a time chart which shows the relationship between the engine speed in Embodiment of this invention, and a starter output signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 In-cylinder direct injection engine 103 Cylinder head 104 Piston 105 Combustion chamber 110 Spark plug 120 Direct injection injector 200 Electronic control unit (ECU)

Claims (4)

In-cylinder direct-injection engine using a high-boiling point fuel , provided with a direct-injector and spark plug provided facing the combustion chamber,
In the initial start after cranking is started by the starter, fresh air is introduced into the cylinder in the expansion stroke of the first cycle through the intake valve and a predetermined amount of fuel is injected from the direct injection injector. After the next cycle, fresh ignition is introduced in the intake stroke, fuel is injected in the intake stroke and / or compression stroke, and normal operation is performed in the latter half of the compression stroke. the introduction of fresh air, fuel injection and multiple ignition start control apparatus for a cylinder direct injection engine, which comprises starting initial control to so that is performed.   2. The in-cylinder direct injection engine start control device according to claim 1, wherein the initial start control is continued until the engine speed reaches a predetermined complete explosion speed. Further comprising a fuel type determining means, when it is determined not to be given a high boiling point fuel by fuel type determining means, the cylinder according to claim 1 or 2, characterized in that the initial start-up control is not performed Start control device for internal direct injection engine. Further comprising an engine temperature measuring means, when it is determined to exceed the predetermined temperature by the engine temperature measuring means, any one of claims 1 to 3, characterized in that the initial start-up control is not performed A start control device for an in-cylinder direct injection engine as described in 1.

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