JP2005344521A - Fuel supply system abnormality diagnosis device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply system abnormality diagnosis device for an internal combustion engine enabling more accurate abnormality diagnosis of a fuel supply system. <P>SOLUTION: This invented fuel supply system abnormality diagnosis device for the internal combustion engine is provided with a fuel injection means 3 injecting liquid fuel in an intake air passage or a combustion chamber of the internal combustion engine, an injection control means 10 controlling fuel injection by the fuel injection means 3, an accumulation chamber 4 provided on a fuel supply passage 2 supplying fuel to a fuel injection means 3 and accumulating liquid fuel under high pressure, a fuel pressure detection means 6 detecting fuel pressure in the accumulation chamber 4, and a failure determination means 10 determining whether a failure occurs in a fuel supply system or not based on fuel pressure detected by the fuel pressure detection means 6 when the injection control means 3 stops injection of liquid fuel during operation of the internal combustion engine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for diagnosing abnormality in a fuel system that supplies fuel on an intake passage of an internal combustion engine or into a combustion chamber.

Conventionally, devices described in the following [Patent Document 1] are known as devices for diagnosing abnormalities in a fuel supply system. In the apparatus described in [Patent Document 1], abnormality diagnosis of the fuel system is performed based on the fuel pressure (fuel pressure) on the fuel supply passage. For example, if there is a leak in the fuel supply passage, the fuel pressure will be abnormally reduced. In the apparatus described in [Patent Document 1] described above, such an abnormality diagnosis of the fuel supply system is performed during a period in which fuel injection is performed while the internal combustion engine is operating.
JP 2002-47983 A

  However, since pressure detection during fuel injection is affected by pressure pulsation in the fuel supply passage, there has been a problem that accurate abnormality diagnosis is difficult to perform. For example, if there is pressure pulsation, subtle leakage from the fuel pipe is included in the error range, and there is a possibility that accurate determination cannot be performed. In particular, in high-pressure fuel supply systems that have high-pressure fuel accumulators such as common rails and delivery pipes, pulsations are generated inside the common rails and delivery pipes due to the operation of the injector during fuel injection. . Accordingly, an object of the present invention is to provide a fuel supply system abnormality diagnosis device for an internal combustion engine that enables more accurate abnormality diagnosis of the fuel supply system.

  The fuel supply system abnormality diagnosis device for an internal combustion engine according to claim 1 is a fuel injection means for injecting liquid fuel on an intake passage or a combustion chamber of the internal combustion engine, and an injection control means for controlling fuel injection by the fuel injection means. An accumulator that is disposed on a fuel supply passage for supplying fuel to the fuel injector and that stores liquid fuel under high pressure; a fuel pressure detector that detects fuel pressure in the accumulator; and an injection controller that is operating the internal combustion engine. And an abnormality determining means for determining whether or not an abnormality has occurred in the fuel supply system based on the fuel pressure detected by the fuel pressure detecting means when the liquid fuel injection is stopped. .

  According to a second aspect of the present invention, in the fuel supply system abnormality diagnosis device for an internal combustion engine according to the first aspect, the abnormality determination means performs fuel injection based on the fuel pressure at the start of fuel injection stop detected by the fuel pressure detection means. The fuel pressure change during stoppage is predicted, and abnormality determination is performed based on the predicted fuel pressure and the fuel pressure during fuel injection stoppage detected by the fuel pressure detection means.

  According to a third aspect of the present invention, in the fuel supply system abnormality diagnosis device for an internal combustion engine according to the first or second aspect, the abnormality determination means is based on the fuel pressure at the start of fuel injection stop detected by the fuel pressure detection means. A converged fuel pressure at which the fuel pressure in the pressure accumulating chamber converges while the fuel injection is stopped is estimated, and abnormality determination is performed based on the estimated fuel pressure and the fuel pressure during the fuel injection stop detected by the fuel pressure detecting means.

  According to the fuel supply system abnormality diagnosis device for an internal combustion engine according to the first aspect, the fuel pressure in the pressure accumulating chamber is detected when the fuel injection is stopped, and abnormality diagnosis is performed based on the fuel pressure. When fuel injection is stopped, pressure pulsation associated with fuel injection is eliminated, so that accurate abnormality diagnosis can be performed.

  According to the fuel supply system abnormality diagnosis device for an internal combustion engine according to claim 2, the fuel pressure change during the stop of the fuel injection is predicted based on the fuel pressure at the start of the fuel injection stop, and is detected by the predicted fuel pressure and the fuel pressure detecting means. The abnormality is determined based on the fuel pressure when the fuel injection is stopped. In the normal case where there is no fuel leakage, the fuel pressure in the pressure accumulating chamber after fuel injection stops gradually rises under the influence of temperature. For this reason, here, a more accurate diagnosis can be performed by predicting a change in the fuel pressure and performing an abnormality diagnosis using the predicted fuel pressure.

  According to the fuel supply system abnormality diagnosis device for an internal combustion engine according to claim 3, the estimated fuel pressure is estimated by estimating the convergent fuel pressure at which the fuel pressure in the pressure accumulating chamber converges during the stop of fuel injection based on the fuel pressure at the start of fuel injection stop. And abnormality determination based on the fuel pressure during fuel injection stop detected by the fuel pressure detection means. As described above, in a normal state where there is no fuel leakage or the like, the fuel pressure in the pressure accumulating chamber after stopping fuel injection gradually increases under the influence of temperature and converges to a predetermined fuel pressure. For this reason, a more accurate diagnosis can be performed here by predicting the convergent fuel pressure and performing an abnormality diagnosis using the convergent fuel pressure. In addition, you may use invention of Claim 2 and Claim 3 together, and a more exact abnormality diagnosis can be performed by using together.

  An embodiment of the abnormality diagnosis apparatus of the present invention will be described below. FIG. 1 shows the configuration of a fuel supply system of an internal combustion engine equipped with the abnormality diagnosis device of the present embodiment. As shown in FIG. 1, the fuel is stored in a fuel tank 1, and the fuel in the fuel tank 1 is supplied to an injector (fuel injection means) 3 through a fuel passage 2. The internal combustion engine of this embodiment is of an in-line four cylinder, and a total of four injectors 3 are provided, one for each cylinder. The injector 3 is attached to a delivery pipe (pressure accumulating chamber) 4 and the inside of the delivery pipe 4 is controlled to a predetermined fuel pressure by a high-pressure fuel pump 5 described later. The delivery pipe 4 is a part of the fuel passage 2, but will be described with a reference numeral different from that of the fuel passage 2. By making the inside of the delivery pipe 4 have a predetermined fuel pressure, fuel injection from all the injectors 3 can be performed with high accuracy. A fuel pressure sensor (fuel pressure detecting means) 6 for detecting the internal fuel pressure is attached to the delivery pipe 4.

  The fuel in the fuel tank 1 is sent to the fuel passage 2 by the low pressure fuel pump 7. The fuel delivered by the low-pressure fuel pump 7 is maintained at a constant fuel pressure by the pressure regulator 8. A pulsation damper 9 is disposed on the fuel passage 2 on the downstream side of the pressure regulator 8. The pulsation damper 9 is for suppressing pulsation generated in the fuel passage 2 and realizing accurate fuel injection. Further, a high-pressure fuel pump 5 is disposed on the downstream side of the pulsation damper 9, and the pressure of the fuel is further increased by the high-pressure fuel pump. The high-pressure fuel pump 5 is mainly composed of a spill valve 5a and a plunger 5b. The spill valve 5 a opens and closes between the fuel passage 2 and the inside of the high-pressure fuel pump 5.

  Open / close control of the spill valve 5a is performed by an electronic control unit (ECU) 10 to be described later. The plunger 5 b is disposed inside the high-pressure fuel pump 5 so as to be able to reciprocate, and changes the internal volume of the high-pressure fuel pump 5. The plunger 5b is always reciprocated by an elliptical cam 5e provided on the camshaft 5d in accordance with the rotational speed of the camshaft 5d. A pipe connected to the delivery pipe 4 described above is connected to the high-pressure fuel pump 5 having a spill valve 5a and a plunger 5b inside, and a check valve 11 is arranged on this pipe. The check valve 11 functions as a check valve and has a role of maintaining the fuel pressure downstream of the check valve 11.

  Here, when the spill valve 5a is closed, the internal volume of the high-pressure fuel pump 5 is reduced and the fuel pressure is increased by the upward movement of the plunger 5b in FIG. Due to this increase in fuel pressure, the check valve 11 is opened, and fuel with a high fuel pressure is supplied downstream from the check valve 11. Further, when the internal volume of the high-pressure fuel pump 5 is increased by the downward movement of the high-pressure fuel pump 5 in FIG. 1 when the spill valve 5 a is opened, new fuel is supplied inside the high-pressure fuel pump 5. To be introduced. Then, the spill valve 5 a is closed again to increase the pressure, and fuel with a high fuel pressure is supplied downstream from the check valve 11.

  On the fuel passage 2, the low pressure side is from the low pressure fuel pump 7 to the high pressure fuel pump 5, and the high pressure side is from the high pressure fuel pump 5 to the delivery pipe 4. The pressure on the low pressure side is kept constant by the pressure regulator 8, and the high pressure side is controlled to a predetermined pressure by controlling the high pressure fuel pump 5. The electromagnetic coil 5c and the fuel pressure sensor 6 that drive the spill valve 5a described above are connected to the ECU 10, and the ECU 10 controls the opening and closing of the spill valve 5a while monitoring the fuel pressure with the fuel pressure sensor 6. A camshaft position sensor 12 for detecting the rotation is also attached to the camshaft 5d, and the camshaft position sensor 12 is also connected to the ECU 10.

  The ECU 10 includes a CPU, a RAM, a ROM, and the like, and a control calculation described later is performed by a program stored in the ROM. The above-described injector 3 is also connected to the ECU 10, and the injector 3 is controlled by the ECU 10. The fuel injection amount from the injector 3 is controlled based on the valve opening time, and the ECU 10 functions as an injection control means. The internal combustion engine of this embodiment is also provided with a return pipe 13 for returning excess fuel that has not been injected from the delivery pipe 4 to the fuel tank 1 (or on the fuel passage 2). One end of the return pipe 13 is connected to the delivery pipe 4, and the other end is located inside the fuel tank 1.

  A relief valve 14 is attached in the vicinity of the connection portion of the return pipe 13 to the delivery pipe 4. The excess fuel that has been supplied to the delivery pipe 4 but not injected from the injector 3 is opened to the fuel tank 1 through the return pipe 13 by opening the relief valve 14 due to the increase in fuel pressure. The return pipe 13 is branched in the middle, and the branched tip is connected to the plunger 5b portion. The fuel returned to the fuel passage 2 by the branched return pipe 13 is supplied again to the delivery pipe 4 by the high-pressure fuel pump 5.

  Next, fuel pressure control and abnormality determination control by the control device having the above-described configuration will be described. Flow charts of the abnormality determination control are shown in FIGS. First, as shown in FIG. 2, it is first determined whether or not the engine (internal combustion engine) is starting (step 200). If step 200 is affirmative and if it is starting, the number of integrations α described later is reset. (Step 205). If step 200 is negative, step 205 is skipped. Each time the engine is started in steps 200 and 205, the cumulative number α is reset.

  Next, it is determined whether or not this failure flag is OFF (step 210). As will be described in detail later, in the present embodiment, a temporary failure flag is set when an event that seems to be abnormal occurs, and it is assumed that an abnormality has actually occurred when the temporary failure flag satisfies a predetermined condition. Is established. In step 210, it is determined whether or not it is possible to determine that this failure flag is OFF, that is, it is not determined that the failure is really a failure. If step 210 is affirmed and the failure flag is OFF, it is next determined whether or not the high-pressure pump is stopped (the fuel is not being pumped) (step 215).

  If the high-pressure fuel pump 5d is stopped, it is next determined whether or not a fuel cut (F / C) is being performed (step 220). If all of Steps 210 to 220 are affirmed, first, the fuel pressure inside the delivery pipe 4 is taken in by the fuel pressure sensor 6 in order to make an abnormality determination (Step 225). If even one of Step 210 to Step 220 is negative, a determination count S described later is reset (Step 230), and the control of the flowchart of FIG.

  Here, if step 210 is negative and the failure flag is ON, it is already detected that there is an abnormality, and thus abnormality diagnosis is not performed (after step 230, the process is temporarily terminated). If step 215 is negative and the high-pressure fuel pump 5 is being driven (fuel pumping), there is a fuel pressure pulsation associated with the fuel pumping, so no abnormality diagnosis is performed (after step 230, the process is temporarily terminated). (That is, abnormality diagnosis is performed only when there is no fuel entering or leaving the delivery pipe 4.) If step 220 is negative and the engine is not in F / C, abnormality diagnosis is performed because there is also pressure pulsation due to fuel injection. No (after step 230 once).

  Although the fuel pressure is taken in in step 225, the fuel pressure when the fuel pressure is first affirmed after step 220 is denied, that is, the fuel pressure immediately after the start of the F / C is stored in the RAM or the like in the ECU 10. Further, after the start of F / C, the fuel pressure is continuously detected during F / C in step 225. After step 225, it is determined whether the detected fuel pressure is equal to or lower than a predetermined value (step 235). If step 235 is denied and the fuel pressure exceeds the predetermined value, it can be determined that there is no leakage because it is close to the theoretical maximum pressure (the operating pressure of the safety valve) inside the delivery pipe 4, so that no abnormality diagnosis is performed. The control in the flowchart of FIG. 2 is temporarily terminated (if a leak occurs, the temperature is not increased to near the theoretical maximum pressure).

  Note that the control of the flowchart shown in FIG. 2 is repeatedly executed every predetermined time after the engine is started. When step 235 is affirmed (when the detected fuel pressure is less than or equal to a predetermined value), the fuel pressure behavior predicted during F / C (hereinafter referred to as the predicted fuel pressure) and the fuel pressure during F / C Is calculated (hereinafter referred to as converged fuel pressure) (step 240), and an abnormality diagnosis using the predicted fuel pressure and an abnormality diagnosis using the convergent fuel pressure are performed (step 245). The control flowchart in step 240 is shown in FIG. 3, and the control flowchart in step 245 is shown in FIG.

  As shown in FIG. 5, when calculating the predicted fuel pressure, first, the above-described fuel pressure at the start of F / C is read (step 300). Next, the engine speed NE and the engine load KL are read (step 305). Then, based on a map relating to the engine speed NE and the engine load KL created in advance through an experiment, a value at which the fuel pressure converges during F / C (converged fuel pressure A) is determined '(step 310). At this time, the fuel pressure at the start of F / C is also taken into consideration. As described above, the fuel pressure inside the delivery pipe 4 after F / C gradually increases because the fuel expands due to heat, and converges at a constant fuel pressure. Here, the fuel pressure at this time is estimated as the convergent fuel pressure A.

  Further, the fuel pressure in F / C gradually rises due to the influence of heat as described above and converges to a certain value (F / C may be released before convergence), but the change in fuel pressure is It shows a first-order lag behavior with respect to a convergent pressure value determined by a function of temperature. Therefore, after step 310, a first-order lag time constant is calculated in order to predict this change in fuel pressure (step 315). The calculation of the time constant is also performed based on a map relating to the engine speed NE and the engine load KL created through experiments. Then, based on the fuel pressure at the start of F / C and the determined time constant, a change in fuel pressure after the start of F / C is predicted (this is the predicted fuel pressure).

  FIG. 5A shows the state of the F / C flag. While the F / C flag is ON, F / C is in progress and fuel injection is stopped. FIG. 5B shows the convergent fuel pressure A and the predicted fuel pressure. In addition, X in FIG.5 (b) is a fuel pressure at the time of F / C start. In addition, since calculation of the convergence fuel pressure A and calculation of the predicted fuel pressure are performed independently, the fuel pressure at the time of convergence of the predicted fuel pressure may not match the convergence fuel pressure A. Hereinafter, the abnormality diagnosis using the convergent fuel pressure A and the abnormality diagnosis using the predicted fuel pressure (step 245) will be described with reference to FIG.

  Steps 400 to 410 and steps 415 to 435 in the flowchart of FIG. 4 are parallel processing. After both steps 400 to 410 and steps 415 to 435 are completed, the process proceeds to step 440. First, steps 400 to 410 will be described. Here, the diagnosis using the above-described convergent fuel pressure A is performed. First, it is determined whether a predetermined time has elapsed after the start of F / C (step 400). This predetermined time is set as a time required for the fuel pressure to converge. If step 400 is negative, the fuel pressure has not yet converged, so step 405 and step 410 are skipped, and abnormality determination is not performed in the diagnosis using the convergent fuel pressure A.

  When step 400 is affirmed, the actual fuel pressure at that time is detected by the fuel pressure sensor 6, and it is determined whether or not this is less than the convergent fuel pressure A (step 405). If step 405 is negative, step 410 is skipped assuming that no abnormality has occurred. On the other hand, if step 405 is affirmed, since the actual fuel pressure has not reached the convergent fuel pressure A even though the time required for convergence has already elapsed, the provisional failure flag 1 is determined to be abnormal. It is set to ON (step 410).

  Next, step 415 to step 435 will be described. Here, the diagnosis using the predicted fuel pressure described above is performed. First, the actual fuel pressure at that time is detected by the fuel pressure sensor 6, and the difference between this actual fuel pressure and the predicted fuel pressure at that time is calculated (step 415). The change in the fuel pressure difference is shown in FIG. Then, it is determined whether or not the calculated fuel pressure difference is larger than a predetermined value B (step 420). This predetermined value B is set as a reference for determining that the difference between the actual fuel pressure and the predicted fuel pressure is too large.

When step 420 is affirmed, the determination count S for counting the number of determinations that the difference between the actual fuel pressure and the predicted fuel pressure is open is incremented by one (step 425). In FIG. 5 (c), the steps 420 between times _t 1 ~t ₂ has a situation to be positive. When step 420 is negative, the determination number S is not counted up (step 425 is skipped). Next, it is determined whether or not the number of determinations exceeds a predetermined number C (step 430). The predetermined number of times C is set as a reference for determining that an abnormality has occurred because the difference between the actual fuel pressure and the predicted fuel pressure is frequently open.

  If step 430 is negative, it is determined that no abnormality has occurred and step 435 is skipped. On the other hand, if step 430 is positive, it is determined that an abnormality has occurred, and the temporary failure flag 2 is set to ON (step 435). After both steps 400 to 410 and steps 415 to 435 are completed, it is determined whether or not at least one of the temporary failure flags 1 and 2 is ON (step 440).

  If step 440 is negative, that is, if both of the temporary failure flags 1 and 2 are OFF, the control of the flowchart of FIG. 4 is terminated assuming that no abnormality has occurred. On the other hand, when step 440 is affirmed, the counter α that counts that at least one of the temporary failure flags 1 and 2 is in an abnormal state is incremented by one (step 445). After step 445, it is determined whether or not the cumulative number α exceeds a predetermined number D (step 450). The predetermined value D is set as a reference for determining that the abnormality is really occurring because the frequency at which step 440 is positive is high.

  If step 450 is affirmed, it is determined that an abnormality has actually occurred, and this failure flag is set to ON instead of the temporary failure flag (step 455). On the other hand, if step 450 is negative, step 455 is skipped and the control of the flowchart of FIG. 4 is finished. When this failure flag is turned ON, the driver is notified by blinking a warning light or the like. In the present embodiment, as described above, if a situation that seems to be abnormal occurs, it is not determined immediately that it is abnormal, but the number of occurrences is accumulated, and when the number of occurrences is accumulated a predetermined number It is determined that By doing so, the accuracy of abnormality diagnosis is improved and unnecessary warnings are prevented from being issued.

  In the present embodiment, diagnosis accuracy is improved by performing abnormality diagnosis during F / C that is not affected by fuel pressure pulsation. Since it is not affected by fuel pressure pulsation, it is possible to detect even a small amount of fuel leakage. Further, in the present embodiment, the diagnosis accuracy is improved by performing an abnormality diagnosis in consideration of the fuel pressure change in the F / C using the convergent fuel pressure A and the predicted fuel pressure.

  In the above-described embodiment, the ECU 10 functions as an injection control unit / abnormality determination unit. The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the return pipe 13 is provided. However, the present invention can also be applied to a so-called returnless system that does not have a return pipe. The main purpose of the returnless system is to prevent the fuel heated by the heat of the internal combustion engine from flowing back to the fuel tank, and to suppress the temperature rise in the fuel tank to suppress the evaporation of the fuel. Moreover, although the delivery pipe 4 was demonstrated to the example in embodiment mentioned above, this invention is applicable also when a pressure accumulation chamber is what is called a common rail (it is called in this way in the case of a diesel engine).

It is sectional drawing which shows the structure of the fuel supply system of the internal combustion engine provided with one Embodiment of the abnormality diagnosis apparatus of this invention. It is a flowchart which shows the main control part of abnormality diagnosis control. It is a flowchart of a prediction fuel pressure and a convergence fuel pressure calculation routine. It is a flowchart of an abnormality (failure) diagnosis routine. FIG. 4 shows time changes such as the fuel pressure during F / C, (a) shows the F / C flag, (b) shows various fuel pressure changes, and (c) shows the deviation between the predicted fuel pressure and the actual fuel pressure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 2 ... Fuel passage, 3 ... Injector (fuel injection means), 4 ... Delivery pipe (fuel passage), 5 ... High pressure fuel pump, 5a ... Spill valve, 5a ... Spill valve, 5b ... Plunger, 5c ... Electromagnetic coil, 5d ... cam shaft, 5e ... cam, 6 ... fuel pressure sensor (fuel pressure detection means), 7 ... low pressure fuel pump, 8 ... pressure regulator, 9 ... pulsation damper, 10 ... ECU (injection control means, abnormality determination means) ), 11 ... Check valve, 12 ... Camshaft position sensor, 12 ... Cam position sensor, 13 ... Return piping, 14 ... Relief valve.

Claims (3)

Fuel injection means for injecting liquid fuel onto the intake passage of the internal combustion engine or into the combustion chamber;
Injection control means for controlling fuel injection by the fuel injection means;
A pressure accumulation chamber disposed on a fuel supply passage for supplying fuel to the fuel injection means, and storing liquid fuel under high pressure;
Fuel pressure detecting means for detecting the fuel pressure in the pressure accumulating chamber;
An abnormality that determines whether an abnormality has occurred in the fuel supply system based on the fuel pressure detected by the fuel pressure detection means when the injection control means stops the injection of liquid fuel during operation of the internal combustion engine A fuel supply system abnormality diagnosis device for an internal combustion engine, comprising: a determination unit.   The abnormality determination means predicts a change in fuel pressure during fuel injection stop based on the fuel pressure at the start of fuel injection stop detected by the fuel pressure detection means, and the fuel injection stop detected by the predicted fuel pressure and the fuel pressure detection means The fuel supply system abnormality diagnosis apparatus for an internal combustion engine according to claim 1, wherein abnormality determination is performed based on the fuel pressure in the internal combustion engine.   The abnormality determination means estimates a convergent fuel pressure at which the fuel pressure in the pressure accumulating chamber converges during fuel injection stop based on the fuel pressure at the start of fuel injection stop detected by the fuel pressure detection means, and the estimated fuel pressure and the fuel pressure detection The fuel supply system abnormality diagnosis apparatus for an internal combustion engine according to claim 1 or 2, wherein abnormality determination is performed based on the fuel pressure during fuel injection stop detected by the means.

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