JP2006242084A - Control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid adhesion of deposit on a tip part of an injector in an engine injecting main fuel composed of one or both of gasoline and alcohol from an injector for cylinder injection. <P>SOLUTION: This control device for the engine is provided with a main fuel supply system 13, an alcohol fuel supply system 17, a switching means 16, an injector tip temperature derivation means and a change over control means. The change over control means transmits signal to a change over means 16 according to tip temperature of an injector 4 and changes operation between an operation using main fuel and an operation using alcohol fuel. As a result, operation can be changed over to operation using alcohol fuel containing less high boiling point composition than main fuel when tip temperature of the injector 4 is temperature at which possibility of adhesion of deposit is high, and adhesion of deposit to the tip part of the injector 4 can be avoided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device, and more particularly to an engine control device that can use alcohol and gasoline as fuels alone or in combination, and directly injects this fuel from a cylinder injector into a cylinder. About.

  In recent years, a system that can simultaneously use alcohol as an alternative fuel in addition to gasoline fuel is being put into practical use. In vehicles such as automobiles (FFV) equipped with this system, not only gasoline, The vehicle can be run only with a mixed fuel of alcohol and gasoline, or alcohol.

  On the other hand, a direct injection engine that directly injects fuel from the in-cylinder injector into the cylinder is also known. However, when gasoline is used as fuel in this direct injection engine, the following problem of deposit adhesion on the injector tip is caused. is there. That is, in the direct injection engine, the in-cylinder injector is disposed in the cylinder head, and the tip of the injector faces the combustion chamber. Therefore, the temperature of the tip of the injector tends to be relatively high due to combustion heat in the cylinder. When the tip temperature of the injector becomes higher than, for example, T90 (temperature at which 90% of the components in the fuel evaporate), high-boiling components (aroma) in gasoline mainly adhere to or remain around the nozzle hole at the tip of the injector. Sometimes. And when this high boiling point component evaporates, combustion products, such as soot, will generate | occur | produce and will aggregate and adhere as deposit (fuel carbide) in a nozzle part. Such deposits are unlikely to flow during the next fuel injection, and as deposit builds up at the nozzle, the opening area of the nozzle decreases, the amount of fuel injected from the injector decreases, and engine output decreases. This will cause problems with the engine operating condition.

  In order to solve this problem, in the combustion control device for an internal combustion engine described in Patent Document 1, when it is determined that the temperature of the engine is higher than the reference temperature, the ignition timing is controlled to the retard side to substantially Thus, the combustion temperature is lowered, and with this, the accumulation of deposits on the nozzle part of the fuel injection valve is suppressed.

JP-A-9-287525

  The FFV engine described above can also be of a direct injection type that includes an in-cylinder injector and directly injects fuel into the cylinder. However, if 100% gasoline fuel or a relatively low alcohol concentration fuel is used in such an engine, the problem of deposit adhesion on the tip of the injector occurs as in the case of the direct injection gasoline engine. To do.

  The technique described in Patent Document 1 is not necessarily optimal for avoiding this problem in the FFV engine. That is, in the FFV engine, the fuel properties vary greatly depending on the alcohol concentration in the fuel, and the fuel injection amount, ignition timing, and the like must be appropriately controlled in accordance with the alcohol concentration. However, the technique described in Patent Document 1 does not consider the fuel property based on the alcohol concentration in the fuel, and there remains a question as to whether or not the technique can be applied to an FFV engine as it is.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an engine control device that can suitably avoid deposits on the tip of an injector in an FFV engine having an in-cylinder injector.

  An engine control device that achieves the above object includes a main fuel supply system for supplying main fuel comprising one or both of gasoline and alcohol from a main fuel tank to a delivery pipe communicated with an in-cylinder injector. Deriving the tip temperature of the in-cylinder injector, the alcohol fuel supply system for supplying alcohol fuel to the delivery pipe from the alcohol fuel tank, switching means for switching between the main fuel supply system and the alcohol fuel supply system And a switching control means for controlling the switching means in accordance with the tip temperature of the in-cylinder injector derived by the injector tip temperature deriving means.

  Here, preferably, when the fuel recovery system for recovering fuel from the delivery pipe to the main fuel tank, the shut-off valve provided in the fuel recovery system, and the switching means are operated, the shut-off valve is set for a predetermined period. And a shut-off valve control means for controlling the opening.

  According to the present invention, the switching means is controlled in correspondence with the tip temperature of the in-cylinder injector derived by the injector tip temperature deriving means. For example, when the tip temperature of the injector is not relatively high, the switching means is switched to the main fuel supply system, and the engine is operated using the main fuel. On the other hand, when the tip temperature of the injector reaches a relatively high temperature, the switching means is switched to the alcohol fuel supply system side and the operation of the engine using alcohol fuel is switched. Alcohol has fewer high-boiling components that cause deposits than gasoline. Thus, by switching to the operation using alcohol fuel in this way, deposit adhesion to the injector can be suitably avoided.

  Further, according to the embodiment including the fuel recovery system, the shut-off valve, and the shut-off valve control means, the shut-off valve is opened when the switching means is operated, so that the fuel in the delivery pipe can be quickly transferred to the main fuel tank. It is possible to recover and replace the main fuel and alcohol fuel.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic plan view showing a system configuration according to an embodiment of an engine control apparatus according to the present invention. First, in FIG. 1, the combustion chamber 5 of each cylinder of the FFV engine 1 is controlled by an electric throttle valve (not shown) from an air cleaner (not shown), via a surge tank 2 and an intake passage 3. Air is inhaled. An electromagnetic injector 4 is provided on the cylinder head of the engine 1 so that fuel such as main fuel is directly injected into the combustion chamber 5, that is, in-cylinder injection. A nozzle hole is provided at the tip of the injector 4, and this tip faces the combustion chamber 5. The injector 4 is energized to open a solenoid valve by an injection pulse signal output in synchronism with engine rotation from an electronic control unit (hereinafter referred to as ECU) 30 described later, and the delivery pipe 18 is adjusted to a predetermined pressure. The fuel inside is designed to be injected. The injected fuel forms an air-fuel mixture in the combustion chamber 5, and is ignited by the spark plug 6 and burned based on an ignition signal from the ECU 30 described later. Exhaust gas from the engine 1 is discharged from an exhaust passage 7, and an exhaust purification catalyst 8 is interposed in the exhaust passage 7.

  The injector 4 is connected to a delivery pipe 18, and main fuel is supplied to the delivery pipe 18 from the main fuel tank 10 through the main fuel supply system 13. The feed pump 11 supplies fuel from the main fuel tank 10 to the main fuel supply system 13. Here, the term “main fuel” in the present invention is used to include not only a mixed fuel of gasoline and alcohol but also a fuel of 100% gasoline and a fuel of 100% alcohol. In the main fuel supply system 13, an alcohol concentration sensor 21 serving as an alcohol concentration detecting means for detecting the alcohol concentration of the main fuel is disposed downstream of the feed pump 11, and further the fuel is pressurized to a high pressure downstream to deliver the fuel. A high-pressure fuel pump 12 for sending to the pipe 18 is arranged. The delivery pipe 18 is provided with a temperature sensor 22 as temperature detecting means for detecting the temperature of fuel in the delivery pipe 18 and a pressure sensor 23 for detecting pressure.

  In particular, in the present embodiment, an alcohol fuel tank 14 for storing alcohol fuel is provided separately from the main fuel tank 10 for storing main fuel, and the alcohol fuel in the alcohol fuel tank 14 passes through the alcohol fuel supply system 17. It is also supplied to the delivery pipe 18. The main fuel supply system 13 and the alcohol fuel supply system 17 are switched by a switching valve 16 as switching means. In the present embodiment, the switching valve 16 is constituted by a three-way electromagnetic valve, and is disposed at a position between the alcohol concentration sensor 21 and the high-pressure fuel pump 12 in the main fuel supply system 13. The alcohol fuel supply system 17 is connected to the switching valve 16 so that alcohol fuel can be supplied to the delivery pipe 18 through the switching valve 16 and the main fuel supply system 13 downstream thereof.

  Therefore, the main fuel can be supplied from the main fuel supply system 13 to the delivery pipe 18 communicated with the injector 4, and the alcohol fuel supply system 17 controls the alcohol fuel by switching the switching valve 16. Can be supplied. The pump pressure of the feed pump 15 of the alcohol fuel supply system 17 is set higher than the pump pressure of the feed pump 11 of the main fuel supply system 13. In the present embodiment, the alcohol fuel supply system 17 is connected to the main fuel supply system 13 via the switching valve 16, but the alcohol fuel supply system 17 can also be directly connected to the delivery pipe 18. .

  The delivery pipe 18 has a long shape in the cylinder row direction and communicates with the injectors 4 for all the cylinders (four). The main fuel supply system 13 is connected to one end of the delivery pipe 18 in the longitudinal direction. On the other hand, a fuel recovery system 20 that recovers the fuel in the delivery pipe 18 to the main fuel tank 10 is connected to the other end of the delivery pipe 18. In the fuel recovery system 20 of the present embodiment, the delivery pipe 18 and the main fuel tank 10 are communicated with each other, and a shutoff valve 19 including a two-way electromagnetic valve is provided at a connection position with the delivery pipe 18. The fuel recovery system 20 may be provided with a pump for quickly recovering the fuel in the delivery pipe 18 to the main fuel tank 10.

  The ECU 30 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, receives input signals from various sensors described later, and performs various arithmetic processes based on the signals. The control is performed to control the operation of the electric throttle valve, the injector 4, the spark plug 6, the switching valve 16, the cutoff valve 19, the various pumps 11, 12, 15 and the like.

  As the various sensors, a crank position sensor 24 for detecting the rotation of the crankshaft of the engine 1 is provided. The crank position sensor 24 outputs a pulse signal at a predetermined crank angle interval during rotation of the crankshaft. The ECU 30 calculates the engine speed from this pulse signal. Other examples of the sensor include an accelerator opening sensor 25 that detects the accelerator opening, an intake air temperature sensor 26 that detects the intake air temperature in the air cleaner, a throttle position sensor 27 that detects the opening of the throttle valve, and the engine 1. A water temperature sensor 28 for detecting the cooling water temperature, an intake pressure sensor 29 for detecting the pressure (intake pressure) in the intake passage downstream of the throttle valve, the alcohol concentration sensor 21, the temperature sensor 22, and the pressure sensor 23 described above. it can.

  As will be described later, in the present embodiment, the temperature of the injector 4, particularly the temperature at its tip, is estimated from the engine speed determined by the crank position sensor 24 and the intake pressure determined by the intake pressure sensor 29. To be derived. However, in the present invention, the tip temperature of the injector 4 may be directly detected and derived, or the tip temperature of the injector 4 may be estimated and derived using a detection value by another sensor. For example, the accelerator opening can be obtained from a signal from the accelerator opening sensor 25, and the temperature of the injector 4 can be estimated from this and the engine speed.

  The engine 1 of this embodiment is normally controlled by the ECU 30 so that the switching valve 16 is closed with respect to the alcohol fuel system 17 and is operated using the main fuel from the main fuel supply system 13. . The ECU 30 corrects basic values such as the fuel injection amount, the fuel injection timing, and the ignition timing based on the alcohol concentration in the main fuel, and sends an operation signal to the injector 4 and the spark plug 6 based on the corrected values. Output. Specifically, the ECU 30 first searches or calculates each basic control map stored in advance in the ROM of the ECU 30 based on values relating to the current engine speed and engine load, and uses them as basic values. The basic fuel injection amount, basic fuel injection timing, and basic ignition timing are calculated. On the other hand, in order to correct each of them based on the alcohol concentration, a correction map is searched to obtain a correction value corresponding to the detection value of the alcohol concentration sensor 21. Then, each of these basic values is subjected to a correction calculation with a correction value, and the ECU 30 outputs an operation signal to the injector 4, the spark plug 6, etc. in order to control the engine 1 based on the value thus obtained.

  Next, an example of the control performed by the ECU 30 in the present embodiment having the above-described system configuration will be described with reference to the flowchart of the control routine shown in FIG.

  First, in step S201, based on the input signal from the alcohol concentration sensor 21, the alcohol concentration a in the main fuel being used is detected. The alcohol concentration a detected in this way is expressed as a percentage, and hereinafter expressed as a%. Next, in step S <b> 203, as the operating state of the engine 1, the engine speed is detected by an input signal from the crank position sensor 24, and the intake pressure is detected by an input signal from the intake pressure sensor 29. In the next step S205, it is determined whether or not the alcohol concentration a% detected in step S201 is lower than a predetermined alcohol concentration upper limit b%. Here, the alcohol concentration upper limit b% is a threshold value for determining whether or not the alcohol concentration in the main fuel is so high that the control by the present control routine is not substantially required.

  When it is determined that the alcohol concentration a% is equal to or higher than the alcohol concentration upper limit b%, the alcohol concentration a% in the original main fuel is very high and the possibility of deposit adherence to the injector 4 is low. Then, normal operation control of the engine 1 is performed using the main fuel having the alcohol concentration a%. At this time, the feed pump 11 of the main fuel supply system 13 is turned on, the feed pump 15 of the alcohol fuel supply system 17 is turned off, and the switching valve 16 is controlled to be switched to the main fuel tank 10 side. Thereby, alcohol fuel from the alcohol fuel supply system 17 is shut off by the switching valve 16, while main fuel from the main fuel supply system 13 passes through the switching valve 16 and is pumped to the delivery pipe 18 by the high-pressure fuel pump 12. Will be. At this time, the shutoff valve 19 is turned off, that is, closed. This routine is completed by executing step S229.

  On the other hand, when the alcohol concentration a% is lower than the alcohol concentration upper limit b% in step S205, the process proceeds to step S207. In this step S207, the temperature of the injector 4, in particular, the injector tip temperature Ti is estimated by searching the data stored in the ROM of the ECU 30 based on the operating state of the engine 1 and obtained in advance through experiments. The In the present embodiment, the map shown in FIG. 3 is stored in the ROM of the ECU 30, and the injector tip temperature Ti is estimated by searching the map based on the engine speed and the intake pressure obtained in step S203. Is done.

In the map of FIG. 3, the higher the intake pressure expressed in absolute pressure, that is, the higher the engine load, the higher the injector tip temperature Ti, while the higher the engine speed, the higher the injector tip temperature Ti. The relationship is expressed.
Next, in step S209, the upper limit temperature Tm at the tip of the injector is searched by searching the data stored in the ROM of the ECU 30 based on the alcohol concentration a% detected in step S201. (First upper limit temperature) is determined. Here, the upper limit temperature Tm is an upper limit value of the temperature at which deposits are difficult to adhere to the injector 4, and deposits are expected to adhere to the injector 4 above this upper limit value. More specifically, if the tip temperature of the injector 4 is higher than the upper limit temperature Tm, the high boiling point component of the gasoline fuel attached or remaining around the injection hole in the injector 4 evaporates, soot as a deposit precursor, etc. The combustion product is produced. And the possibility that these aggregate and the deposit adheres to the injector 4 becomes high. In the present embodiment, the map shown in FIG. 4 is stored in the ROM of the ECU 30, and the upper limit temperature Tm is determined by searching this map based on the alcohol concentration a%.

  The map of FIG. 4 shows a relationship in which the upper limit temperature Tm decreases as the alcohol concentration in the main fuel increases. In the map of FIG. 4, data below the alcohol concentration upper limit b% described in relation to step S205 is stored.

  Next, in step S211, it is determined whether or not the injector tip temperature Ti estimated in step S207 is lower than the upper limit temperature Tm of the injector tip determined in step S209.

  When it is determined that the injector tip temperature Ti is lower than the upper limit temperature Tm of the injector tip, there is a low possibility of deposits adhering to the injector 4, and therefore the routine proceeds to step S229, where the normal engine 1 using main fuel is used. This routine is terminated.

  On the other hand, if it is determined that the injector tip temperature Ti is equal to or higher than the upper limit temperature Tm, the process proceeds to step S213 in order to avoid deposit adhesion to the injector 4. In step S213, first, the feed pump 15 of the alcohol fuel supply system 17 is turned on and the feed pump 11 of the main fuel supply system 13 is turned on in order to switch from main fuel to operation of the engine 1 using alcohol fuel. The switching valve 16 is controlled to be switched to the alcohol fuel supply system 17 side by a switching signal from the ECU 30. Thereby, the main fuel from the main fuel supply system 13 is shut off by the switching valve 16, while the alcohol fuel from the alcohol fuel supply system 17 passes through the switching valve 16 and is pumped to the delivery pipe 18 by the high-pressure fuel pump 12. Will be. As a result, the operation is performed using an alcohol fuel having no high boiling point component or less, and adhesion of deposits to the injector 4 is avoided. On the other hand, simultaneously with the operation of the switching valve 16, the shutoff valve 19 is controlled to be opened by the ECU 30, and the main fuel already remaining in the delivery pipe 18 is recovered in the main fuel tank 10 by the fuel recovery system 20. That is, the fuel in the delivery pipe 18 is quickly replaced with alcohol fuel. Thereafter, in step S215, the opening time of the shutoff valve 19 is compared with a predetermined time τ previously obtained by experiment and stored in the ROM. When the open time of the shutoff valve 19 is equal to or shorter than the predetermined time τ, the process returns to step S213. When the opening time of the shutoff valve 19 exceeds the predetermined time τ, the process proceeds to step S217, and the shutoff valve 19 is closed. Thereby, the fuel recovery from the delivery pipe 18 is completed. Note that the opening time of the shut-off valve 19 is measured by a timer built in the ECU 30 at the same time that the shut-off valve 19 is opened in step S213, and when the process proceeds to step S217, the timer is stopped and the timer is reset.

  If the main fuel in the delivery pipe 18 is recovered before the predetermined time τ elapses, the shutoff valve 19 is opened even after the main fuel recovery is completed. As a result, the alcohol fuel newly sent to the delivery pipe 18 is also collected in the main fuel tank 10. That is, alcohol fuel is recovered from the delivery pipe 18 to the main fuel tank 10 after replacement of the main fuel with alcohol fuel in the delivery pipe 18, so that the content of the main fuel in the main fuel tank 10 is increased. The alcohol concentration increases. Thus, when the fuel is switched from the main fuel to the alcohol fuel in step S217, another engine control map for 100% alcohol fuel is used as the engine control map.

  In the next step S219, the operating state of the engine 1 is detected as in step S203, and in step S221, the injector tip temperature Ti is estimated using the map of FIG. 3 as in step S207. In step S223, the upper limit temperature Tm2 (second upper limit temperature) of the injector tip obtained in advance by experiment and stored in the ROM is read out. Here, since the fuel used is alcohol fuel and the alcohol concentration is 100%, the upper limit temperature Tm2 is stored as a constant value.

  In the next step S225, it is determined whether or not the injector tip temperature Ti estimated in step S221 is lower than the upper limit temperature Tm2 of the injector tip read in step S223. When the injector tip temperature Ti is equal to or higher than the upper limit temperature Tm2, there is a high possibility that deposits still adhere to the injector 4 when returning to the operation using the main fuel containing gasoline, so the process returns to step S219 again. Is done. When it is determined that the injector tip temperature Ti has dropped below the upper limit temperature Tm2, the process proceeds to step S227, and control for switching to operation using the main fuel is performed. Specifically, the feed pump 11 of the main fuel supply system 13 is turned on, the feed pump 15 of the alcohol fuel supply system 17 is turned off, and the switching valve 16 is switched to the main fuel tank 10 side. Thereby, alcohol fuel from the alcohol fuel supply system 17 is shut off by the switching valve 16, while main fuel from the main fuel supply system 13 passes through the switching valve 16 and is pumped to the delivery pipe 18 by the high-pressure fuel pump 12. Will be. In the present embodiment, at this time, the shutoff valve 19 is kept closed, but the alcohol fuel remaining in the delivery pipe 18 is recovered by the fuel recovery system 20 into the main fuel tank 10. The shut-off valve 19 may be opened for a predetermined time. Thus, this control is finished.

  As described above, according to the present embodiment, during operation using the main fuel, the tip temperature of the injector 4 exceeds the upper limit temperature which is the predetermined temperature (step S211: NO), and deposits are deposited on the injector 4. Even when it becomes easy to adhere, by switching to the operation using alcohol fuel (step S213), it becomes possible to appropriately prevent the deposit from adhering to the injector 4. In addition, the fuel is switched in this way and alcohol fuel is sent into the delivery pipe 18, while the shut-off valve 19 is opened, and the main fuel in the delivery pipe 18 is collected into the main fuel tank 10. Done quickly. If the shut-off valve 19 is opened even after the recovery of the main fuel is completed, the alcohol fuel sent to the delivery pipe 18 is also recovered in the main fuel tank 10. This causes an increase in the alcohol concentration in the main fuel, and decreases the volume ratio of the high boiling point component in the main fuel in the main fuel tank 10. As a result, when the operation is switched to the operation using the main fuel later (step S227), the possibility that the deposit adheres to the injector 4 is reduced.

  While the present invention has been described based on the above embodiment, various other embodiments of the present invention are conceivable. For example, the present invention can also be applied to an engine that employs a dual injection system that includes two types of injectors, an in-cylinder injector and an intake passage injector. Moreover, in the said embodiment, when the engine 1 was operated using the alcohol fuel in the alcohol fuel tank 14, the engine 1 was controlled using the dedicated map. For example, the basic control map during normal operation may be used, and the engine 1 may be controlled by correcting the basic value obtained from this map when the alcohol concentration is 100%.

1 is a schematic plan view showing a system configuration according to an embodiment of an engine control apparatus according to the present invention. It is a flowchart which shows an example of the control routine in one embodiment of this invention. It is an example of the map for estimating injector tip temperature. It is an example of the map for determining the upper limit temperature of an injector front-end | tip.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 4 Injector 10 Main fuel tank 11 Feed pump 12 High pressure fuel pump 13 Main fuel supply system 14 Alcohol fuel tank 15 Feed pump 16 Switching valve 17 Alcohol fuel supply system 18 Delivery pipe 19 Shut-off valve 20 Fuel recovery system 21 Alcohol concentration sensor 30 Electronic control unit

Claims (2)

A main fuel supply system for supplying main fuel consisting of one or both of gasoline and alcohol from a main fuel tank to a delivery pipe communicated with an in-cylinder injector;
An alcohol fuel supply system for supplying alcohol fuel to the delivery pipe from an alcohol fuel tank;
Switching means for switching between the main fuel supply system and the alcohol fuel supply system;
Injector tip temperature deriving means for deriving the tip temperature of the in-cylinder injector;
Switching control means for controlling the switching means in correspondence with the tip temperature of the in-cylinder injector derived by the injector tip temperature deriving means;
An engine control device comprising: A fuel recovery system for recovering fuel from the delivery pipe to the main fuel tank;
A shut-off valve provided in the fuel recovery system;
Shut-off valve control means for opening the shut-off valve for a predetermined period when the switching means is activated;
The engine control device according to claim 1, further comprising:

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