JP2009097455A - Fuel injection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection system in which emission does not unnecessarily deteriorate and an engine exhibits a predetermined performance, even if an air/fuel ratio sensor does not normally function. <P>SOLUTION: A process performed in this fuel injection system is started in an ECU simultaneously with starting of operation of an engine. In step S31, it is determined whether or not an A/F sensor is in an abnormal state. When the A/F sensor is in the abnormal state, in step S32, it is determined whether or not a fuel injection device performs multiple injection. When the fuel injection device performs the multiple injection, in step S33, the number of multiple injection is reduced. For example, the number of injection in a suction stroke is reduced from three times to two times. At that time, the total amount of fuel injected in all the number of injection is injected at a time. Thereby, it is possible to minimize deviation between the current-carrying period of the fuel injection device and an opening period and to excellently keep a fuel combustion state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection system that injects fuel directly into a combustion chamber of an internal combustion engine and multiple times for one combustion.

  Sensors are attached to the internal combustion engine, that is, the engine, and the ECU controls the amount of fuel injected by the fuel injection device and the ignition timing according to information from the sensors.

In order to cope with individual differences and deterioration with time of the fuel injection device, a configuration is known in which variation in injection amount and deterioration with time are learned. Learning is performed while setting the fuel injection timing or the like to a constant value using information from sensors and reducing the number of fuel injections for one combustion. The ECU corrects the fuel injection amount and the injection period using the learning value obtained in this way (Patent Document 1).
JP 2004-11511 A

  However, if the information from the sensors used to set the fuel injection timing etc. to a certain value is incorrect, it will not be possible to obtain an accurate learning value even if learning is performed. There is a possibility that the injection amount or the like cannot be controlled properly. If the air / fuel ratio cannot be properly controlled, the desired air / fuel ratio cannot be obtained, the emission may be deteriorated, and the engine may not be able to exhibit the predetermined performance.

  In view of the above problems, the present invention has an object to provide a fuel injection system and an engine in which emissions do not deteriorate more than necessary even when an air-fuel ratio sensor does not function normally and the engine exhibits predetermined performance. To do.

  A fuel injection system according to a first invention of the present application is an air-fuel ratio detecting means attached to an exhaust system of an internal combustion engine, and a fuel that injects fuel directly into a combustion chamber of the internal combustion engine and multiple times for one combustion. The fuel injection means reduces the number of fuel injections injected by the fuel injection means relative to the number of injections when the air-fuel ratio detection means is normal when an abnormality occurs in the air-fuel ratio detection means. It is characterized by that. The fuel injection means injects the fuel a plurality of times in any one or a plurality of strokes from the intake stroke to the exhaust stroke of the internal combustion engine. Thereby, even if the air-fuel ratio sensor does not function normally, predetermined performance can be obtained without deteriorating engine emission more than necessary.

  It is preferable that the injection control means injects the same amount of fuel as the fuel injection amount for all the injections before the decrease. Thereby, the required fuel injection amount can be ensured and the output of the spark ignition type direct injection internal combustion engine can be prevented from decreasing.

  A spark ignition direct injection internal combustion engine according to a second invention of the present application is characterized by comprising the above fuel injection system. Thereby, even if the air-fuel ratio sensor does not function normally, it is possible to obtain a spark ignition type direct injection internal combustion engine that does not deteriorate the emission more than necessary and can exhibit a predetermined performance.

  According to the present invention, even if the air-fuel ratio sensor does not function normally, the fuel injection system is obtained in which the engine does not deteriorate more than necessary and the engine exhibits a predetermined performance.

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

  An embodiment of a fuel injection system according to the present invention will be described with reference to FIG.

  The fuel injection system is attached to a spark ignition direct injection internal combustion engine. A spark ignition direct injection internal combustion engine (hereinafter referred to as an engine) 110 sucks air sucked from an air cleaner 131 into a combustion chamber 141. Fuel is injected from the fuel injection device 111 into the combustion chamber 141. Air is mixed with fuel in the combustion chamber 141. A spark plug 142 is provided at the top of the combustion chamber 141 and ignites the fuel / air mixture in accordance with a signal from the ECU 112. After the air-fuel mixture burns, it becomes exhaust gas and is discharged to the exhaust pipe 151. The exhaust gas is purified by the exhaust gas purification catalyst 152 and then released to the atmosphere. An A / F sensor 113 is attached to the exhaust pipe 151, detects the air-fuel ratio from the exhaust gas, and transmits it to the ECU 112.

  Fuel is injected into the common rail 115 by a fuel pump 114 from a fuel tank (not shown) and pressurized. A fuel pressure sensor 117 for measuring the fuel pressure accumulated in the common rail 115, that is, a fuel pressure, is attached to the common rail 115, and the fuel pressure value is transmitted to the ECU 112. The common rail 115 and the fuel injection device 111 are connected by a fuel pipe 116, and pressurized fuel is supplied to the fuel injection device 111.

  The fuel injection device 111 is provided so that the injection nozzle 118 protrudes from the cylinder head 143 to the combustion chamber 141. An opening / closing valve 120 is provided inside the injection nozzle 118, and fuel is injected into the combustion chamber 141 by opening / closing the opening / closing valve 120. An EDU (injector drive unit) 119 is connected to the fuel injection device 111. The EDU 119 energizes the fuel injection device 111 in accordance with the fuel injection signal from the ECU 112. The fuel injection device 111 injects fuel only during the energization period in which power is supplied from the EDU 119.

  The fuel injection device 111 performs multi-injection. The multi-injection is to inject fuel a plurality of times in any one of the strokes from the intake stroke to the exhaust stroke of the engine 110. By performing multi-injection when the engine is operating at a high load, the homogeneity of the fuel in the combustion chamber is improved. For example, fuel is injected at BTDC 320 °, 300 °, 280 °.

  The ECU 112 performs air-fuel ratio feedback control using the air-fuel ratio measured by the A / F sensor 113. In the air-fuel ratio feedback control, the ECU 112 detects a deviation between the measured air-fuel ratio and a desired air-fuel ratio, determines the fuel injection amount so as to eliminate the deviation, and sends the fuel injection to the fuel injection device 111. It is control which injects quantity.

  The relationship between the energization period of the fuel injection device 111 and the opening period of the on-off valve 120 will be described using the timing chart of FIG.

  Since the on-off valve 120 provided in the fuel injection device 111 is mechanically operated, for example, is constituted by a solenoid valve, the valve transition period Td from the completely closed state to the fully opened state or vice versa is physically changed. Need to. Since the valve transition period Td occupies a non-negligible ratio with respect to the opening period To from when the on-off valve 120 starts to open until it completely closes, the period between the energization period Te of the fuel injection device 111 and the actual fuel injection period To There is a time lag. Furthermore, since it is physically impossible for the on-off valve 120 to operate following the energization completely, the energization start timing, the on-off valve 120 opening timing, the energization end timing, and the on-off valve 120 closing A time lag Tb also occurs between the start time. The ECU 112 cannot obtain a desired fuel injection amount at a desired time unless fuel injection is performed in consideration of these periods and time lags. The opening period and timing of the valve are determined by the fuel injection amount and the fuel pressure in the common rail 115. The ECU 112 has a map that determines the opening period and timing in consideration of the valve transition period Td from the fuel injection amount and the fuel pressure value, and transmits a fuel injection signal corresponding to the opening period and timing calculated from this map to the EDU 119. Ensure proper fuel injection amount.

  The fuel pressure in the direct injection fuel injection device that directly injects fuel into the combustion chamber 141 of the internal combustion engine is higher than the fuel pressure of the port injection fuel injection device that injects fuel into the intake port of the internal combustion engine. Therefore, when both inject the same amount of fuel, the open period To of the direct injection type fuel injection device is shorter than the open period of the port injection type fuel injection device. When the opening period is shortened, the ratio of the valve transition period Td to the opening period is increased. That is, in the direct injection type fuel injection device, the influence of the period and the timing shift is larger than that of the port injection type fuel injection device.

  On the other hand, the time period and the time difference may be caused by a fuel system failure such as the fuel pump 114 or the like. There is a risk of further expansion when an abnormality occurs in the injector 111. When these abnormalities occur, an amount of fuel different from the desired fuel injection amount is injected, so that the air-fuel ratio greatly differs from the desired value. That is, when the actual air-fuel ratio measured by the A / F sensor 113 is different from the desired air-fuel ratio, it is determined that an abnormality has occurred.

  If multi-injection is performed when this abnormality occurs, the period and time lag that occurs for each injection accumulates. On the other hand, by reducing the number of times of fuel injection or setting it once, it is possible to suppress the influence of the period and the time lag.

  However, when an abnormality occurs in the A / F sensor 113, even if the fuel system is normal, the abnormal value is transmitted to the ECU 112, so that the air-fuel ratio control cannot be performed appropriately. That is, since the ECU 112 determines the actual fuel injection amount according to this abnormal value, the actual fuel injection amount is different from the fuel injection amount required to obtain a desired air-fuel ratio, and the actual fuel injection amount is injected. The actual air / fuel ratio at that time will not match the desired air / fuel ratio. When multi-injection is being performed, an error between the actual fuel injection amount and the desired fuel injection amount is accumulated each time fuel injection is performed, and the error between the actual air-fuel ratio and the desired air-fuel ratio increases. .

  A process performed in the fuel injection system to solve this will be described with reference to FIG.

  This control is executed in the ECU 112 at regular time intervals after the A / F sensor 113 is warmed and functions. First, in step S31, it is determined whether or not the A / F sensor 113 is in an abnormal state. For example, when the output from the A / F sensor 113 does not change, it is determined that there is an abnormal state. This process ends when the A / F sensor 113 is not in an abnormal state. When the A / F sensor 113 is in an abnormal state, the process proceeds to step S32.

  Next, in step S32, it is determined whether or not the fuel injection device 111 is performing multi-injection. This process ends when the multi-injection is not performed. When multi-injection is being performed, the number of multi-injections is decreased in step S33. For example, the number of three injections in the suction stroke is reduced to two. At this time, the total amount of fuel injected by all the injections is injected at a time.

  This process is executed only once after an abnormality has occurred in the A / F sensor 113, and is not executed again. That is, once the number of injections is reduced, it is not further reduced and does not change thereafter.

  As a result, it is possible to prevent the time lag and time lag that occur for each injection from accumulating and the time lag of the last injection in multi-injection from expanding. Further, by ensuring the fuel injection amount required by the engine 110, minimizing the difference between the energization period and the open period of the fuel injection device 111, and maintaining the fuel combustion state in good condition, the emission is more than necessary. The engine 110 can exhibit predetermined performance without deteriorating.

  In step S33, the number of injections may be one. At this time, the total amount of fuel injected by all the injections is injected at a time. This process is executed only once after an abnormality has occurred in the A / F sensor 113, and the number of injections thereafter is one. As a result, it is possible to maintain the fuel combustion state while securing the amount of fuel necessary for engine combustion, thereby preventing the engine 110 from exhibiting predetermined performance without deteriorating emissions more than necessary. Become.

  It should be noted that not when an abnormality occurs in the A / F sensor 113 but when the fuel pressure inside the common rail 115 does not satisfy the required value due to an abnormality in the fuel system such as the fuel pump 114, when an abnormality occurs in the EDU 119, or for example, opening and closing When an abnormality occurs in the fuel injection device 111 such as aging deterioration of the valve 120, the number of fuel injections may be decreased. Even when an abnormality occurs in the fuel system, the EDU 119, and the fuel injection device 111, the emission does not deteriorate more than necessary, and the engine 110 can exhibit predetermined performance.

  In the above-described embodiment, the multi-injection injects the fuel a plurality of times in the intake stroke. However, the present invention is not limited to this, and the fuel is injected a plurality of times in another stroke of the engine 110 or over a plurality of strokes. You may inject. That is, for example, fuel may be injected a plurality of times in the compression stroke, the expansion stroke, and the exhaust stroke after being injected in the intake stroke.

It is the figure which showed typically the fuel-injection system connected to the spark ignition type direct injection internal combustion engine. 3 is a timing chart showing the relationship between the energization period of the fuel injection device and the opening / closing period of the on-off valve. It is the flowchart which showed the process in a fuel-injection system.

Explanation of symbols

110 Engine 111 Fuel injection device 112 ECU
113 A / F sensor (air-fuel ratio meter)
114 Fuel pump 115 Common rail 117 Fuel pressure gauge 118 Injection nozzle 119 EDU (Injector drive unit)
120 On-off valve

Claims (3)

Air-fuel ratio detection means attached to the exhaust system of the internal combustion engine;
Fuel injection means for injecting fuel directly into the combustion chamber of the internal combustion engine and multiple times for one combustion;
The fuel injection means, when an abnormality occurs in the air-fuel ratio detection means, reduces the number of fuel injections by the fuel injection means relative to the number of injections when the air-fuel ratio detection means is normal. system.   2. The fuel injection system according to claim 1, wherein the injection control unit injects the same amount of fuel as a fuel injection amount for all injections before the decrease. A spark ignition direct injection internal combustion engine comprising the fuel injection system according to claim 1.

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