JP2013160110A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of improving the determination accuracy of a fuel property.SOLUTION: To a common rail 12, a high pressure pump 13 which discharges fuel after increasing the pressure of the fuel is connected, and an injector 11 which injects the high pressure fuel in the common rail 12 to an engine is connected. Furthermore, a pressure reducing valve 18 is provided in the common rail 12. An ECU 30 implements fuel injection using the injector 11 on the basis of an engine operation state and opens the pressure reducing valve 18 on the basis of a pressure reducing request to the common rail 12. Moreover, particularly, the ECU 30 reduces pressure in the common rail 12 by opening the pressure reducing valve 18 after an engine stop, detects rail pressure while opening the pressure reducing valve 18, and determines a property of fuel to be used on the basis of a reduction amount of the detected rail pressure.

Description

  The present invention relates to a fuel injection control device.

  If the properties of the fuel used in the internal combustion engine are different, the combustion state in the internal combustion engine is different. For this reason, if the properties of the fuel used are not known, there is a concern that a desired engine output cannot be obtained, or that troubles such as damage to components due to deterioration of the combustion state may occur. For this reason, various techniques for determining fuel properties have been proposed.

  For example, in the pressure-accumulation fuel injection device disclosed in Patent Document 1, the amount of decrease in fuel pressure based on fuel leak after the fuel pump discharge is stopped using the fact that fuel leak occurs from the seal portion of the fuel injection valve or the seal portion of the fuel pump. The fuel properties are estimated based on the above.

JP 2003-239794 A

  However, in the above prior art, the decrease in the fuel pressure after stopping the discharge of the fuel pump depends on the fuel leak in each seal portion, and the amount of fuel leak varies depending on the state of the fuel pressure at each time. In this case, there is a concern that the accuracy of determining the fuel property is lowered.

  The main object of the present invention is to provide a fuel injection control device that can improve the accuracy of determination of fuel properties.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The invention described in claim 1 includes a fuel pump (13) that discharges fuel at a high pressure, a pressure accumulator (12) into which the fuel that has been pressurized by the fuel pump is introduced, and a high-pressure fuel in the pressure accumulator. The present invention is applied to a fuel injection system including a fuel injection valve (11) that injects into an internal combustion engine and a pressure reducing valve (18) that discharges high-pressure fuel in the pressure accumulator and depressurizes the pressure accumulator. Based on this, fuel injection by the fuel injection valve is performed, and the pressure reducing valve is opened based on a pressure reduction request of the pressure accumulating unit. And, after the internal combustion engine is stopped, the pressure reducing control means for opening the pressure reducing valve to reduce the pressure in the pressure accumulating portion, and detecting the fuel pressure in the pressure accumulating portion in the state where the pressure reducing valve is opened by the pressure reducing control means, And a property determining means for determining the property of the fuel used based on the detected decrease in fuel pressure.

  In the above configuration, after the internal combustion engine is stopped, the pressure reducing valve is opened to forcibly reduce the fuel pressure in the pressure accumulating portion. At this time, for example, the slope of the pressure drop (pressure reducing speed) according to the viscosity of the fuel used. ) Are different, the properties of the fuel used can be determined. In this case, in particular, in the above-described configuration in which the fuel pressure is positively reduced as the pressure reducing valve is opened, it is possible to appropriately set under what pressure conditions (pressure range) the pressure reduction is caused with respect to the pressure reduction. The fuel properties can be determined after grasping the preconditions. Therefore, it is possible to improve the fuel property determination accuracy.

  According to a second aspect of the present invention, the pressure reducing control means opens the pressure reducing valve to reduce the fuel pressure in the pressure accumulating section to a predetermined pressure after the internal combustion engine is stopped. In addition, after the first decompression process is performed, a second decompression process is performed to open the decompression valve so as to perform a property determination by the property determination unit, and the property determination unit includes the first decompression process. After the fuel pressure in the pressure accumulating portion is reduced to the predetermined pressure, the property of the fuel to be used is determined based on the detected amount of decrease in the fuel pressure under the state where the fuel pressure is reduced by the second decompression process. .

  According to the above configuration, the property determination of the used fuel is performed after the fuel pressure in the pressure accumulating portion is lowered to a predetermined pressure, and therefore the property determination can be performed under the same pressure condition. In this case, if the pressure conditions are different, the fuel pressure decrease amount may be the same even if the properties of the fuel used are different. The determination can be performed, and as a result, the determination accuracy of the fuel property can be improved.

The block diagram which shows the outline | summary of a common rail type fuel injection system. The flowchart which shows the determination process of a fuel property. The time chart for demonstrating a property determination process more concretely. The figure which shows the relationship between fuel temperature and rail pressure fall amount.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. The present embodiment embodies the present invention as a common rail fuel injection system for a multi-cylinder diesel engine for a vehicle, and the detailed configuration thereof will be described below.

  In FIG. 1, a four-cylinder diesel engine (hereinafter referred to as an engine) 10 is provided with an electromagnetic injector 11 for each cylinder, and these injectors 11 are connected to a common rail (pressure accumulator) 12 common to each cylinder. A high pressure pump 13 as a fuel pump is connected to the common rail 12, the fuel is increased in pressure as the high pressure pump 13 is driven, and high pressure fuel corresponding to the injection pressure is continuously accumulated in the common rail 12. The high-pressure pump 13 is driven as the engine 10 rotates, and fuel is repeatedly sucked and discharged in synchronization with the engine rotation. The high-pressure pump 13 is provided with an electromagnetically driven suction metering valve (SCV) 13a at its fuel suction portion, and the low-pressure fuel pumped from the fuel tank 15 by the feed pump 14 passes through the suction metering valve 13a. And sucked into the fuel chamber of the pump 13.

  The common rail 12 is provided with a pressure sensor 16 and a temperature sensor 17. The pressure sensor 16 sequentially detects the fuel pressure in the common rail 12 (hereinafter also referred to as rail pressure), and the temperature sensor 17 detects the fuel temperature in the common rail 12. Are sequentially detected. The common rail 12 is provided with an electromagnetically driven pressure reducing valve 18, and when the pressure reducing valve 18 is opened, the high pressure fuel in the common rail 12 is discharged toward the fuel tank 15 via the discharge pipe 19. It has come to be. The discharge of the high-pressure fuel causes the common rail 12 to be depressurized.

  In the present embodiment, leak-less operation is achieved on the high-pressure side of the fuel injection system, and the high-pressure fuel supplied to the injector 11 does not leak to the low-pressure side. Specifically, the injector 11 employs a leakless structure that eliminates leakage (leakage) of high pressure fuel to the low pressure side. The leakless structure of the injector 11 includes a so-called direct-acting injector structure in which the valve body is directly moved by an electromagnetic solenoid (actuator), and a structure in which the sliding diameter of the valve body is reduced and the sliding gap is made minute. is assumed. It is also possible to employ a direct-acting injector using a piezo element.

  A rotation speed sensor 22 for detecting the rotation speed of the crankshaft 21 is provided near the crankshaft 21 of the engine 10. The rotational speed sensor 22 is, for example, an electromagnetic pickup type sensor that detects the passage of teeth of a timing rotor provided integrally with the crankshaft 21, and a pulsed rotational speed is obtained by shaping the detection signal of the sensor 22. A signal (NE pulse) is generated. In the present embodiment, the NE pulse angle interval (angle between pulse rising edges) is 6 ° CA, and the rotation speed can be detected at a cycle of 6 ° CA.

  The ECU 30 is an electronic control unit including a known microcomputer including a CPU, a ROM, a RAM, an EEPROM, and the like, and performs various controls according to a control program stored in the ROM. In addition to detection signals from the pressure sensor 16 and the rotation speed sensor 22, detection signals are sequentially input to the ECU 30 from various sensors such as an accelerator opening sensor and a vehicle speed sensor. Then, the ECU 30 determines the fuel injection amount and the injection timing as the fuel injection mode based on the engine operation information such as the engine rotation speed and the accelerator opening, and outputs an injection control signal corresponding to the fuel injection amount to the injector 11. By such fuel injection control, fuel injection from the injector 11 to the combustion chamber is controlled in each cylinder.

  Further, the ECU 30 feedback-controls the rail pressure based on each engine operating state. Specifically, the target rail pressure is calculated based on the engine operating state, and the energization control of the intake metering valve 13a is performed so that the actual rail pressure detected by the pressure sensor 16 becomes the target rail pressure. In this case, the rail pressure is adjusted within a predetermined range, and in this embodiment, the rail pressure is adjusted within a range of 30 to 200 MPa.

  Further, the ECU 30 has a pressure reduction control function for reducing the rail pressure by opening the pressure reducing valve 18 based on a request for pressure reduction. For example, when the actual rail pressure in the common rail 12 is greater than the target rail pressure, a pressure reduction request is generated, and an opening command is issued from the ECU 30 to the pressure reducing valve 18. As the pressure reducing valve 18 is opened, the rail pressure decreases.

  Further, in the fuel injection system of the present embodiment, after the engine 10 is stopped, the pressure reducing valve 18 is opened to lower the rail, and the amount of fuel used is reduced based on the change in the rail pressure when the pressure reducing valve 18 is open. The property is determined, and the details will be described below.

  FIG. 2 is a flowchart showing the fuel property determination process. This process is repeatedly executed by the ECU 30 at predetermined time intervals, for example, after the operation of the engine 10 is stopped.

  In FIG. 2, in step S11, the current rail pressure Pc and fuel temperature Tc are acquired. In subsequent step S12, it is determined whether or not the rail pressure Pc has decreased to a predetermined value P1 after the engine is stopped (whether Pc ≦ P1). The predetermined value P1 is, for example, a lower limit value (30 MPa) within the rail pressure adjustment range. And if step S12 is NO, it will progress to step S13, will open the pressure-reduction valve 18 (equivalent to a 1st pressure reduction process), and will once complete | finish this process after that. That is, the rail pressure Pc is controlled to be equal to or higher than the predetermined value P1 during engine operation, and the rail pressure Pc is equal to or higher than the predetermined value P1 immediately after the engine is stopped. When the pressure reducing valve 18 is opened in this state, the rail pressure Pc decreases.

  If YES in step S12, the process proceeds to step S14 to determine whether or not the fuel temperature Tc has decreased to a predetermined temperature K1 (for example, 30 ° C.) after engine stop (whether Tc ≦ K1). . And if step S14 is NO, this process will be complete | finished as it is, and if it is YES, it will progress to subsequent step S15. That is, in step S14, standby processing is performed to wait for the fuel temperature Tc to decrease to the predetermined temperature K1. In step S15, the pressure reducing valve 18 is opened (corresponding to the second pressure reducing process).

  Thereafter, in step S16, it is determined whether or not a predetermined time α has elapsed since the pressure reducing valve 18 was opened as both conditions of steps S12 and S14 were established. And if it is YES, it will progress to step S17 and will calculate rail pressure fall amount (DELTA) Pc by the comparison of the rail pressure before and behind predetermined time (alpha) ((DELTA) Pc = P1-Pc). Here, the predetermined value P1 is used as the rail pressure before the passage of α, but it is also possible to use the actually measured rail pressure (the rail pressure Pc when both steps S12 & S14 are YES).

  Thereafter, in step S18, the rail pressure decrease amount ΔPc is compared with the standard decrease amount ΔP0, and it is determined whether or not ΔPc> ΔP0. The standard decrease amount ΔP0 is a rail pressure decrease amount when a predetermined standard fuel is used, and is a value that is adapted particularly under the condition that the fuel temperature Tc = K1. If ΔPc> ΔP0, the process proceeds to step S19, where it is determined that the currently used fuel is a low-viscosity fuel.

  When it is determined that the fuel used is a low-viscosity fuel, processing for protecting the injection system components is performed. Specifically, after the next engine start, a limited operation is performed to limit at least one of the engine rotation speed, the fuel pressure, and the injection amount.

  FIG. 3 is a time chart for more specifically explaining the property determination process. In FIG. 3, a change in rail pressure indicated by a solid line indicates a change in rail pressure with standard fuel, and a change in rail pressure indicated by a one-dot chain line indicates a change in rail pressure with low-viscosity fuel.

  In FIG. 3, the engine 10 is stopped at the timing t <b> 0, and the rail pressure Pc is equal to or higher than the predetermined value P <b> 1 at that time. When the rail pressure Pc decreases to the predetermined value P1 at timing t1, the pressure reducing valve 18 is closed. In the closed state of the pressure reducing valve 18 (timing t1 to t2), no fuel leak occurs on the high pressure side, and the rail pressure Pc is kept constant.

  Thereafter, the pressure reducing valve 18 is opened again at the timing t2 after waiting for the fuel temperature to fall to a predetermined temperature. As a result, the rail pressure Pc decreases again. Then, at the timing t3 when the predetermined time α has elapsed from the timing t2, the rail pressure decrease amount ΔPc is calculated, and the fuel property is determined based on the rail pressure decrease amount ΔPc. At this time, if the fuel used is a low-viscosity fuel, the slope of the pressure drop is large (the pressure drop rate is large), and ΔPc> ΔP0. Thereby, it can be determined that the currently used fuel is a low-viscosity fuel.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  After the engine stops, the rail pressure Pc is detected in a state where the pressure reducing valve 18 is opened to reduce the pressure in the common rail 12, and the property of the fuel used is determined based on the detected decrease amount (ΔPc) of the rail pressure Pc. The configuration. In this case, since the pressure reducing valve 18 is opened to forcibly reduce the rail pressure Pc, it is possible to appropriately set under what pressure condition (pressure range) the pressure drop is caused with respect to the reduction of the rail pressure Pc. The fuel properties can be determined after understanding the preconditions for implementation. Therefore, it is possible to improve the fuel property determination accuracy.

  After the engine is stopped, the first pressure reducing process for opening the pressure reducing valve 18 to reduce the rail pressure Pc to the predetermined value P1 is performed, and the pressure reducing valve 18 is set to perform the property determination after the first pressure reducing process is performed. The second decompression process for setting the open state was performed. Then, after the rail pressure Pc is reduced to the predetermined value P1 by the first pressure reduction process, the property of the fuel to be used is determined based on the rail pressure reduction amount ΔPc in a state where the rail pressure Pc is reduced by the second pressure reduction process. I made it. According to the above configuration, the property determination of the used fuel is performed after the rail pressure Pc decreases to the predetermined value P1, and therefore the property determination can be performed under the same pressure condition. In this case, if the pressure conditions are different, the rail pressure drop amount ΔPc may be the same even if the properties of the fuel used are different. However, since the above-mentioned configuration uses the same pressure conditions, the properties are based on the same criteria. The determination can be performed, and as a result, the determination accuracy of the fuel property can be improved.

  In the fuel injection system, the high pressure side portion including the injector 11 has a leakless structure. Therefore, the open / close state of the pressure reducing valve 18 and the lowering behavior of the rail pressure Pc can be matched, and the pressure condition for property determination can be easily set. Further, it is possible to suppress the disadvantage that the accuracy of determining the fuel property is lowered due to the variation in the fuel leak amount.

  The fuel temperature Tc in the common rail 12 when the engine is stopped is acquired, and the fuel property is determined based on the rail pressure decrease amount ΔPc and the fuel temperature Tc. More specifically, the condition for determining the property is that the fuel temperature Tc has decreased to the predetermined temperature K1 after the engine is stopped, and the fuel property is determined based on the rail pressure decrease amount ΔPc when the fuel temperature is decreased. I did it. When the fuel temperature is different, the viscosity of the fuel is different. As a result, the slope (decompression speed) at which the rail pressure Pc decreases as the fuel is discharged from the common rail 12 is different, but because the fuel temperature is taken into account as described above, The determination accuracy of the fuel property can be further increased. Further, in the above configuration, the property determination can be performed by reducing the rail pressure Pc under a constant temperature condition, and the determination accuracy can be improved by the property determination under a certain condition. In addition, it is not necessary to prepare a standard decrease amount ΔP0 (property determination value) for each of a plurality of fuel temperatures, and it is possible to save time and trouble of adaptation and simulation for obtaining the standard decrease amount ΔP0. The data storage capacity of the memory for storing ΔP0 can be reduced.

(Other embodiments)
You may change the said embodiment as follows, for example.

  In the above embodiment, as the fuel property determination process, the rail pressure decrease amount ΔPc is compared with the standard decrease amount ΔP0 to determine whether or not the fuel used is a low-viscosity fuel. May be. For example, for each of a plurality of fuels having different viscosities, a standard value of the rail pressure decrease amount is determined for each fuel, and the actual rail pressure decrease amount after the engine stops matches which fuel standard value (or which fuel standard value) The fuel property may be determined based on whether it is closest to the value.

  The amount of decrease in the rail pressure Pc after the engine is stopped is associated with each different fuel temperature and stored as pressure decrease amount data in a memory (ROM in the ECU 30), and the pressure decrease amount data The fuel property may be determined based on the above. Specifically, as shown in FIG. 4, reference values (a1, a2, a3 in the figure) of rail pressure drop amounts are determined for different fuel temperatures as standard fuel pressure drop amount data. Then, the property determination is performed by selectively using any one of the reference values a1 to a3 according to the fuel temperature at each time.

  According to the above configuration, since the pressure drop amount data is associated with the fuel temperature, the highly accurate property determination can be performed by using the pressure drop amount data.

  Further, as shown in FIG. 4, the reference value for the amount of rail pressure drop may be determined for a fuel having a viscosity lower than that of the standard fuel. In the drawing, low viscosity 1 and low viscosity 2 indicate fuels having different viscosities, and the low viscosity 2 fuel has a lower viscosity than the low viscosity 1 fuel. In this case, the reference value (b1, b2, b3, c1, c2, c3 in the figure) of the rail pressure drop amount is determined for each different fuel temperature as the pressure drop amount data of the low viscosity 1, 2 fuels. Then, the property determination is performed by selectively using any one of the reference values b1 to b3 and c1 to c3 according to the fuel temperature at each time.

  In the above embodiment, the rail pressure Pc is reduced to the lower limit (30 MPa) within the rail pressure adjustment range as the first pressure reduction process after the engine is stopped, but this is changed and the rail pressure Pc is changed as the first pressure reduction process. Pc may be lowered to a pressure lower than the lower limit value in the rail pressure adjustment range. Alternatively, the rail pressure Pc may be decreased to an intermediate pressure (for example, 50 MPa) within the rail pressure adjustment range as the first pressure reduction process. Moreover, it is good also as a structure which does not implement a 1st pressure reduction process but uses the rail pressure Pc at the time of an engine stop as a starting pressure, and determines a property based on rail pressure fall amount (DELTA) Pc from the starting pressure.

  In the above embodiment, the fuel property is determined based on the rail pressure decrease amount ΔPc within a predetermined time in the open state of the pressure reducing valve 18 after the engine is stopped. However, this may be changed. For example, the fuel property may be determined based on the time required for the rail pressure decrease amount ΔPc to reach a predetermined value when the pressure reducing valve 18 is open. In this case, when the time required for the rail pressure decrease amount ΔPc to reach a predetermined value is shorter than the standard time, it is determined that the fuel is low viscosity. Or it determines with the viscosity of a fuel being so small that the time required is short.

  The pressure reducing valve 18 may be configured so that the opening degree in the open state can be variably adjusted in addition to the switch between the open state and the closed state. In this case, by adjusting the opening degree of the pressure reducing valve 18, the slope (pressure reduction speed) of the decrease in the rail pressure Pc can be arbitrarily adjusted, and the property determination can be performed after setting the desired pressure reduction speed. .

  In the above embodiment, the high pressure side portion including the injector 11 in the fuel injection system has a leakless structure. However, for example, the present invention can be applied to a system in which fuel leakage occurs in the injector 11. In this case, the property determination value may be determined in consideration of the amount of fuel leak at the sliding portion or the like.

  -It is good also as a structure which determines that it is various fuels, such as biofuel, as a property determination of the use fuel. In this case, for example, it is determined whether or not biofuel is mixed with fossil fuel (light oil), what kind of biofuel is mixed, and what is the mixing ratio of biofuel.

  In the above-described embodiment, an example of a self-ignition type diesel engine has been described. However, a spark ignition type engine (a gasoline engine or the like) can be used instead. In this case, the pressure reducing process may be performed using a pressure reducing valve provided in a delivery pipe as a pressure accumulating unit.

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 11 ... Injector (fuel injection valve), 12 ... Common rail (pressure accumulation part), 13 ... High pressure pump (fuel pump), 18 ... Pressure reducing valve, 30 ... ECU (fuel injection control device, pressure reduction control) Means, property determination means, temperature acquisition means).

Claims (5)

A fuel pump (13) that discharges the fuel at a high pressure, a pressure accumulator (12) into which the fuel increased in pressure by the fuel pump is introduced, and a fuel injection valve that injects the high-pressure fuel in the pressure accumulator into the internal combustion engine ( 11) and a pressure reducing valve (18) that discharges the high-pressure fuel in the pressure accumulator and depressurizes the pressure accumulator, and is applied to a fuel injection system.
In the fuel injection control device that performs fuel injection by the fuel injection valve based on the operating state of the internal combustion engine and opens the pressure reduction valve based on a pressure reduction request of the pressure accumulating unit,
A decompression control means for opening the decompression valve and decompressing the pressure accumulating section after the internal combustion engine is stopped;
A property determining means for detecting the fuel pressure in the pressure accumulating portion in a state where the pressure reducing valve is opened by the pressure reducing control means, and for determining the property of the fuel used based on the detected amount of decrease in the fuel pressure;
A fuel injection control device comprising: The decompression control means performs a first decompression process for opening the decompression valve to reduce the fuel pressure in the accumulator to a predetermined pressure after the internal combustion engine is stopped. Performing a second pressure reducing process for opening the pressure reducing valve in order to perform property determination by the property determining means after execution;
The property determination means sets the amount of decrease in the fuel pressure under a state in which the fuel pressure is reduced by the second pressure reduction process after the fuel pressure in the pressure accumulating portion is reduced to the predetermined pressure by the first pressure reduction process. The fuel injection control device according to claim 1, wherein the property of the used fuel is determined on the basis of the property. A temperature acquisition means for acquiring a fuel temperature in the pressure accumulator when the internal combustion engine is stopped;
3. The property determination unit according to claim 1, wherein the property determination unit determines the property of the fuel used based on a fuel pressure decrease amount detected in an open state of the pressure reducing valve and a fuel temperature acquired by the temperature acquisition unit. Fuel injection control device. The pressure drop amount of the high-pressure fuel after the internal combustion engine is stopped is associated with each different fuel temperature as pressure drop amount data, and the data is stored in a memory,
The fuel injection control device according to claim 3, wherein the property determination unit determines a fuel property based on the pressure drop amount data.   The property determination means uses the condition for determining the property that the fuel temperature in the pressure accumulating portion has decreased to a predetermined temperature after the internal combustion engine is stopped, and the fuel pressure decreases in a state where the condition is satisfied. The fuel injection control device according to any one of claims 1 to 4, wherein the fuel property is determined based on the amount.

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