JP2013117210A - Fuel injection device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device for an internal combustion engine which can perform diagnosis of fuel leakage with higher accuracy.SOLUTION: The fuel injection device 1 for an internal combustion engine which injects a fuel pressurized by a fuel pump 9 into a combustion chamber 3c by an injector 8 includes: an accumulator 7 for storing the high-pressure fuel that is supplied from the fuel pump 9 and injected by the injector 8; a pressure determination means 2 for determining whether a pressure RP of the fuel in the accumulator 7 is stable; a pressure detection means 31 that detects a pressure RP of the fuel when the pressure determination means 2 determines that the pressure RP of the fuel in the accumulator 7 is stable; and a leakage diagnosis means 1 for diagnosing fuel leakage according to the detected pressure RP of the fuel.

Description

  The present invention relates to a fuel injection device of an internal combustion engine for injecting fuel into a combustion chamber, and more particularly to diagnosis of fuel leakage of a stock pressure fuel injection device.

  As a conventional fuel injection device for an internal combustion engine, for example, one disclosed in Patent Document 1 is known. This fuel injection device is a stock pressure type fuel injection device that injects high-pressure fuel supplied from a fuel supply pump and stored in a common rail into a combustion chamber by an injector. It is determined whether or not fuel leakage has occurred due to a failure in the connection part of the part or the injector.

  In this fuel injection device, based on the engine speed, the actual rail pressure that is the pressure of the fuel in the common rail, the command injection amount calculated according to the accelerator depression amount, the temperature of the fuel detected by the temperature sensor, etc. Thus, an estimated amount of fuel leakage is calculated. In addition, a fuel leak determination threshold value is calculated based on the amount of switching leakage of fuel recirculated from the injector to the fuel tank at the time of fuel injection, the steady leak amount that steadily leaks from the injector, the fuel temperature, and the like. The When the estimated fuel leakage amount exceeds the fuel leakage determination threshold value, it is determined that the fuel leakage has occurred in the fuel injection device.

Japanese Patent No. 4488017

  However, in the fuel injection device according to the above-described patent document, the determination of fuel leakage is always performed during the operation of the engine, so that the detection accuracy may deteriorate. That is, although the pressure of the fuel in the common rail is controlled so as to be maintained at the target rail pressure, actually, the injection accuracy of the injector and the switching leak amount, the variation of the pumping amount by the fuel pump, and the injector May not be stable due to pulsation generated by fuel injection or fuel pumping from the fuel supply pump. Therefore, the fuel leak estimation amount calculated based on the fuel pressure, the switching leak amount, etc. and the fuel leak determination threshold value also vary, and there is a possibility that the accuracy of the fuel leak determination by comparing the two will deteriorate. is there.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection device for an internal combustion engine that can perform diagnosis of fuel leakage with higher accuracy.

  In order to achieve the above object, the invention according to claim 1 of the claims is directed to the fuel injection of the internal combustion engine for injecting the fuel pressurized by the fuel pump 9 into the combustion chamber 3 c by the injector 8. A pressure accumulating chamber (common rail 7 in the embodiment (hereinafter the same in this section)) for storing high-pressure fuel supplied from the fuel pump 9 and injected by the injector 8; It is determined by the pressure determination means (ECU 2, step 1 in FIG. 2) which determines whether or not the pressure (rail pressure RP) is stable, and the pressure of the fuel in the animal pressure chamber is stable by the pressure determination means. And a pressure detection means (fuel pressure sensor 31) for detecting the pressure of the fuel, and a leakage diagnosis means (ECU2, FIG. 2) for diagnosing fuel leakage according to the detected fuel pressure. And-up 11), characterized in that it comprises a.

  According to the fuel injection device for an internal combustion engine, the fuel pressurized by the fuel pump is supplied to the pressure chamber, and the high-pressure fuel stored in the pressure chamber is injected into the combustion chamber by the injector. Further, when the pressure determining means determines that the fuel pressure in the stock pressure chamber is stable, the leakage diagnosis means determines the fuel pressure according to the fuel pressure in the stock pressure chamber detected by the pressure detecting means. It is diagnosed whether a leak has occurred.

  As described above, the diagnosis of fuel leakage is performed according to the fuel pressure detected when it is determined that the pressure in the animal pressure chamber is stable. That is, the diagnosis is executed according to the stable pressure of the fuel detected in the absence of a factor that fluctuates the fuel pressure in the animal pressure chamber, for example, the supply of fuel from the fuel pump or the injection of fuel by the injector. Therefore, it is possible to accurately diagnose whether or not fuel leakage has occurred with higher accuracy.

  According to a second aspect of the present invention, in the fuel injection device for an internal combustion engine according to the first aspect of the present invention, the pressure determining means is configured such that the actuator that affects the fuel pressure including the fuel pump 9 and the injector 8 is stopped. When it is controlled, it is determined that the pressure of the fuel in the stock pressure chamber is stable.

  According to the injection device of the internal combustion engine, the pressure determination is performed when the actuator that performs the supply of fuel to the livestock pressure chamber and the discharge of fuel from the livestock pressure chamber, such as a fuel pump and an injector, is controlled to be stopped. The means determines that the fuel pressure in the animal pressure chamber is stable. As a result, the determination by the pressure determination means can be executed reliably under a stable condition without any factor that affects the fuel pressure in the stock pressure chamber, such as fuel supply and discharge, and detection is performed under a stable condition. Depending on the fuel pressure applied, a more accurate diagnosis of fuel leakage can be performed.

  According to a third aspect of the present invention, in the fuel injection device 1 for an internal combustion engine according to the second aspect, the pressure detecting means detects the fuel pressure in the predetermined detection period TMREF, and the pressure in the animal pressure chamber detected by the pressure detecting means is detected. And a leakage amount calculating means (ECU2, steps 7 and 8 in FIG. 2) for calculating a fuel leakage amount (fuel leakage amount QLEAK) in a predetermined detection period TMREF according to the fuel pressure of The fuel leakage is diagnosed based on the amount of fuel leakage calculated by the leakage amount calculation means.

  According to the fuel injection device for the internal combustion engine, the amount of fuel leakage in the predetermined detection period is calculated by the leakage amount calculating means according to the detected fuel pressure in the animal pressure chamber, and based on the calculated leakage amount. Thus, the fuel leakage diagnosis is diagnosed by the fuel leakage diagnosis means. As a result, the fuel leakage diagnosis can be more accurately executed based on the specific leakage amount.

  According to a fourth aspect of the present invention, there is provided a fuel injection device for an internal combustion engine according to the third aspect, wherein a static leak amount calculating means (ECU 2, step 9 of FIG. 2) for calculating a static leak amount QLSTA in a predetermined detection period TMREF; A determination threshold value calculation means (ECU 2, step 10 in FIG. 2) for calculating a determination threshold value QLJD for comparison with the fuel leakage amount calculated by the leakage amount calculation means based on the calculated static leak amount QLSTA; The leakage diagnosis means diagnoses that fuel leakage has occurred when the calculated determination threshold value QLJD exceeds the fuel leakage amount calculated by the leakage amount calculation means. .

  According to the fuel injection device of the internal combustion engine, the static leak amount from the fuel injection device in the predetermined detection period is calculated by the static leak amount calculation means, and is compared with the fuel leakage amount calculated by the leakage amount calculation means. Is determined based on the amount of static leak. When the amount of fuel leakage exceeds the determination threshold, the leakage diagnosis means diagnoses that the fuel is leaking.

  For example, from a slight gap such as a sliding portion of the injector, the fuel constantly leaks slightly regardless of whether fuel is being injected or not. Therefore, the amount of static leakage of fuel that regularly leaks from the joint surface of the parts to which the high pressure of the fuel injection device operates is calculated in advance, and the fuel is calculated by comparing the determination threshold calculated based on the amount of static leakage with the amount of fuel leakage. By diagnosing the leakage of fuel, it is possible to reliably diagnose the occurrence of fuel leakage when there is fuel leakage other than static leakage.

It is a schematic block diagram which shows the fuel-injection apparatus of the internal combustion engine by this invention. It is a flowchart which shows a fuel leak diagnostic process. An example of the rail pressure sampled by the process of FIG. 2 and a straight line approximating this is shown. 3 shows an example of a static leak amount map used in the processing of FIG. It is a timing chart which shows an example of operation | movement of the fuel-injection apparatus of FIG.

  Hereinafter, a fuel injection device for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an internal combustion engine (hereinafter simply referred to as “fuel injection device”) 1 having an internal combustion engine fuel injection device (hereinafter simply referred to as “fuel injection device”) 1 to which the present invention is applied, and an electronic control device that controls the engine 3 ( 2 and the like are schematically shown below.

  The engine 3 is, for example, a four-cylinder (only one is shown) diesel engine mounted on a vehicle (not shown). A combustion chamber 3c is formed between the piston 3a and the cylinder head 3b of each cylinder 6 of the engine 3, and an intake pipe 4 and an exhaust pipe 5 are connected to the cylinder head 3b. The fuel injection device 1 includes a common rail 7 (pressure accumulation chamber), an injector 8, and the like. The common rail 7 is formed in a tubular shape extending in the direction in which the four cylinders 6 are arranged, and is configured to withstand high temperatures and high pressures. Yes.

  A fuel tank 10 is connected to the common rail 7, and a fuel pump 9 is provided between the both 7 and 10. The fuel pump 9 is controlled by a drive signal from the ECU 2 to boost the fuel in the fuel tank 10 and supply the fuel to the common rail 7. Thereby, high-pressure fuel is stored in the common rail 7.

  The common rail 7 is provided with a relief valve 11, and the relief valve 11 is connected to the fuel tank 10. The relief valve 11 is appropriately opened under the control of the ECU 2 so that the fuel pressure (hereinafter referred to as “rail pressure”) RP in the common rail 7 does not become excessive, whereby the fuel is transferred from the common rail 7 to the fuel tank 10. Reflux. The fuel pump 9 and the relief valve 11 are normally controlled so that the rail pressure RP is maintained at a predetermined target rail pressure.

  In addition, the injector 8 is provided for each cylinder 6 and is disposed at the center of the top wall of the combustion chamber 3c so as to face the combustion chamber 3c. Each injector 8 is connected to the common rail 7. The fuel injection time of the injector 8 is calculated by the ECU 2, and the injector 8 is controlled by a drive signal from the ECU 2 so that the high-pressure fuel in the common rail 7 is introduced into the combustion chamber 3c based on the calculated fuel injection time. Spray. Each injector 8 is connected to a fuel tank 10, and part of the fuel supplied from the common rail 7 returns to the fuel tank 10 as the fuel is injected. In addition, even when fuel injection is not being performed, a slight amount of fuel leaked from the sliding portion of the injector 8 and the like due to the high pressure is returned to the fuel pump 10.

  The common rail 7 is provided with, for example, a strain gauge type fuel pressure sensor 31, and this fuel pressure sensor 31 outputs a detection signal representing the rail pressure RP to the ECU 2. Further, the fuel pump 9 is provided with a temperature sensor 32. The temperature sensor 32 detects a fuel temperature TF, which is the temperature of the fuel, and outputs a signal representing the fuel temperature TF to the ECU 2.

  In this embodiment, the ECU 2 constitutes a pressure determination means, a leak amount calculation means, a static leak amount calculation means, a determination threshold value calculation means, and a leak diagnosis means, and includes an I / O interface, CPU, RAM, ROM, and the like. (Neither is shown). The detection signals from the various sensors such as the fuel pressure sensor 31 and the temperature sensor 32 described above are each input to the CPU after A / D conversion and shaping by the I / O interface. In accordance with these input signals, the CPU executes various control processes according to a control program stored in the ROM.

  FIG. 2 shows a fuel leakage diagnosis process executed by the ECU 2. This process diagnoses the presence or absence of fuel leakage from the fuel injection device 1 according to the detected rail pressure RP and the like, and is repeatedly executed at a predetermined cycle during the operation of the engine 3.

  In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), it is determined whether or not fuel supply to the common rail 7 and fuel discharge from the common rail 7 are both stopped. Specifically, the determination is made based on the presence / absence of a drive signal from the ECU 2 to an actuator that may affect the rail pressure RP by being driven, such as the fuel pump 9, the relief valve 11, and the injector 8.

  If the answer is Yes and all the actuators such as the fuel pump 9 are controlled to be stopped, it is determined whether or not the sampling execution flag F_SAMP is “1” (step 2). The sampling execution flag F_SAMP is set to “1” when sampling of the rail pressure RP for executing diagnosis of fuel leakage is being executed.

  When the answer is No and the sampling of the rail pressure RP has not yet started, the sampling of the rail pressure RP at a predetermined cycle (for example, every 20 μsec) is started (step 3). It memorize | stores in the buffer memory (not shown) of a computer.

  Next, the timer value TMSAMP of the sampling timer is set to 0 (step 4), and the sampling execution flag F_SAMP is set to “1” to indicate that the rail pressure RP is being sampled (step 5).

  Next, it is determined whether or not the timer value TMSAMP of the sampling timer set in step 4 is larger than a predetermined detection period TMREF (for example, 1 msec) (step 6). If the answer is No and the detection period TMREF has not yet elapsed since the sampling of the rail pressure RP has started, it is assumed that the sampling will continue to be executed, and this processing is immediately terminated.

  On the other hand, when the sampling execution flag F_SAMP is set to “1” in step 5, the answer to step 2 is Yes in the subsequent loop of this processing, and the sampling execution flag F_SAMP is reset as described later. Steps 3-5 are skipped until done.

  On the other hand, when the answer to Step 6 is Yes and all the actuators that affect the rail pressure RP are stopped, the timer value TMSAMP is set to 0 in Step 4 when the detection period TMREF has elapsed since the start of sampling. The pressure drop α is calculated on the basis of a number of rail pressures RP sampled up to this time after setting (step 7). This pressure drop α represents the degree of pressure drop of the rail pressure RP within the detection period TMREF, and is obtained by the least square method.

  As shown in FIG. 3, since the sampled rail pressure RP varies due to measurement errors and the like, an equation of a straight line L that approximates a plurality of rail pressures RP sampled by the least square method is obtained, and the slope of the straight line L Is calculated as a pressure drop α. The predetermined detection period TMREF described above is set to a period during which the number of samples of the rail pressure RP necessary for accurately calculating the pressure drop α can be secured.

Next, according to the pressure drop α calculated in step 7, the fuel leakage amount QLEAK is calculated as an estimated amount of fuel leaked from the fuel injection device 1 during the detection period TMREF by the following equation (1) (step 8).
QLEAK = (− (α · TMREF) · K / Vhp) / (1−K) (1)
QLEAK: Fuel leakage (mm ³ )
TMREF: Detection period (msec)
K: Fuel bulk modulus (N / m ² )
Vhp: High-pressure part volume (mm ³ )
Here, the high-pressure portion volume Vhp is the total volume of a portion where high pressure acts, such as the common rail 7 between the fuel pump 9 and the injector 9 and the piping connecting them to each other.

  Next, the static leak amount QLSTA is calculated by searching the static leak amount map shown in FIG. 4 according to the rail pressure RP and the fuel temperature TF (step 9). This static leak amount map is obtained by experimentally obtaining in advance a static leak amount of fuel generated in the fuel injection device 1 during a period corresponding to the detection period TMREF when the engine 3 is operated, and obtaining the rail pressure RP and the fuel temperature TF. The map is made accordingly, and is stored in the ROM of the ECU 2 as the static leak amount QLSTA.

  As shown in the figure, as the rail pressure RP increases, the amount of static leak QLSTA also increases and the degree of increase also increases. When the rail pressure RP is the same, the higher the fuel temperature TF, the larger the static leak amount QLSTA.

  Next, a determination threshold value QLJD is calculated by adding a determination margin MGJD to the calculated static leak amount QLSTA (step 10). This determination margin MGJD is set in consideration of the maximum value of the variation in the static leak amount QLSTA for each vehicle body and the change in the static leak amount due to the deterioration of the fuel injection device 1. It is possible to avoid an erroneous determination that may occur when the static leak amount QLSTA is used as it is for the presence / absence determination.

  Next, the fuel leakage amount QLEAK calculated in step 8 is compared with the above-described determination threshold value QLJD to determine whether or not the fuel leakage amount QLEAK is larger than the determination threshold value QLJD (step 11). When this answer is Yes, the occurrence of fuel leakage in the fuel injection device 1 is confirmed (step 12), and the ECU 2 turns on a warning lamp (not shown) provided on the instrument panel of the vehicle, for example. Thus, the driver is notified of the occurrence of fuel leakage.

  Next, the sampling execution flag F_SAMP is reset (step 13), and this process ends.

  On the other hand, if the answer to step 11 is No and the fuel leakage amount QLEAK is equal to or smaller than the determination threshold value QLJD, it is assumed that no fuel leakage has occurred, and the above step 13 is executed and the present process is terminated.

  On the other hand, when the answer to Step 1 is No and any of the actuators that affect the rail pressure RP such as the fuel pump 9 is driven, it is assumed that the rail pressure RP is not stable, and the rail pressure RP is sampled. Is interrupted, step 13 is executed, and the process is terminated.

  FIG. 5 is a timing chart showing an example of the operation of the fuel injection device 1. As shown in the figure, during operation of the engine 3, as the injector 8 is turned on by a drive signal to the injector 8, fuel is supplied to the combustion chamber 3c. When the fuel pump 9 is turned on by a drive signal to the fuel pump 9, the fuel is pumped from the fuel tank 10 to the common rail 7. The rail pressure RP is maintained substantially constant by controlling the supply of fuel to the common rail 7 by the fuel pump 9 and the return from the relief valve 11 to the fuel tank 10.

  From such a state, the rail pressure RP slightly decreases by switching off the fuel pump 9 by stopping the drive signal to the fuel pump 9 at the timing t1 according to the operating state of the engine 3. To do. In a normal state in which no fuel leakage from the fuel injection device 1 has occurred, the rail pressure RP is maintained substantially constant over time as shown by the broken line in FIG. When this occurs, the rail pressure RP gradually decreases with time.

  At timing t2, when the drive signal to the injector 8 or the like is stopped and both the supply and discharge of fuel to the common rail 7 are stopped, the diagnosis permitting that the diagnosis condition for fuel leakage is satisfied is satisfied and diagnosis can be executed. The period TMDIAG is started, and sampling of the rail pressure RP is started at a predetermined interval from timing t3. Then, at the timing t4 when the detection period TMREF elapses, the sampling is finished, and the fuel leakage diagnosis is performed as described above according to the sampled rail pressure RP.

  When the drive of the fuel pump 9 is resumed at timing t5, the diagnosis permission period TMDIAG ends, and the rail pressure RP is controlled to be a predetermined pressure. The diagnosis of fuel leakage as described above is repeatedly executed when any actuator that affects the rail pressure RP is stopped.

  As described above, according to the fuel injection device 1 according to the present embodiment, when the fuel supply to the common rail 7 and the fuel discharge from the common rail 7 are not executed (step 1: Yes), the rail pressure RP Is determined to be stable. When it is determined that the rail pressure RP is stable, it is diagnosed whether or not fuel leakage has occurred according to the rail pressure RP sampled during the predetermined detection period TMREF (step 11). ). In this way, the presence or absence of fuel leakage is accurately diagnosed with higher accuracy in accordance with the rail pressure RP detected under a stable condition without any factor affecting the rail pressure RP such as fuel supply and discharge. be able to.

  Further, the fuel leakage amount QLEAK in the predetermined detection period TMREF is calculated according to the sampled rail pressure RP (steps 7 and 8). Similarly, the ECU 2 calculates the static leak amount QLSTA from the fuel injection device 1 in the predetermined detection period TMREF (step 9), and the fuel leak amount QLEAK exceeds the determination threshold value QLJD obtained by adding the determination margin MGJD to the static leak amount QLSTA. (Step 11: Yes), it is diagnosed that fuel is leaking. Thereby, based on the specific fuel leakage amount QLEAK, when there is fuel leakage in addition to static leakage, regardless of variations in the static leakage amount for each vehicle or changes in the static leakage amount due to deterioration of the fuel injection device 1, It is possible to reliably diagnose the occurrence of fuel leakage.

  Furthermore, the present invention can be applied not only to a diesel engine mounted on a vehicle but also to a direct injection gasoline engine. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 2 ECU (Pressure determination means, leak diagnosis means, leak amount calculation means, static leak amount calculation means,
Determination threshold value calculation means)
3 Engine (Internal combustion engine)
3c Combustion chamber 7 Common rail (accumulation chamber)
8 Injector 9 Fuel pump 11 Relief valve (actuator)
31 Fuel pressure sensor (pressure detection means)
TMREF Predetermined detection period RP Rail pressure (fuel pressure)
QLEAK leakage (fuel leakage)
QLSTA Static leak amount QLJD judgment threshold

Claims (4)

A fuel injection device for an internal combustion engine for injecting fuel pressurized by a fuel pump into a combustion chamber by an injector,
A pressure accumulating chamber for storing high-pressure fuel supplied from the fuel pump and injected by the injector;
Pressure determining means for determining whether or not the pressure of the fuel in the stock pressure chamber is stable;
Pressure detecting means for detecting the pressure of the fuel when the pressure determining means determines that the pressure of the fuel in the animal pressure chamber is stable;
Leakage diagnostic means for diagnosing fuel leakage according to the detected fuel pressure;
A fuel injection device for an internal combustion engine, comprising:   The pressure determining means determines that the fuel pressure in the animal pressure chamber is stable when an actuator that affects the fuel pressure including the fuel pump and the injector is controlled to be stopped. The fuel injection device for an internal combustion engine according to claim 1. The pressure detecting means detects the fuel pressure in a predetermined detection period;
A leakage amount calculating means for calculating a fuel leakage amount in the predetermined detection period according to the pressure of the fuel in the animal pressure chamber detected by the pressure detecting means;
3. The fuel injection device for an internal combustion engine according to claim 2, wherein the leakage diagnosis unit diagnoses fuel leakage based on the fuel leakage amount calculated by the leakage amount calculation unit. A static leak amount calculating means for calculating a static leak amount in the predetermined detection period;
A determination threshold value calculation means for calculating a determination threshold value to be compared with the fuel leakage amount calculated by the leakage amount calculation means based on the calculated static leak amount;
Further comprising
4. The leakage diagnosis means diagnoses that fuel leakage has occurred when the calculated leakage threshold exceeds the calculated leakage threshold by the leakage amount calculation means. 2. A fuel injection device for an internal combustion engine according to 1.

Images