JP6580412B2 - Engine control device - Google Patents

Description

  The present invention relates to an injector, a fuel rail connected to the injector, a high-pressure fuel pump that pumps fuel to the fuel rail via a high-pressure side fuel line, and fuel to the high-pressure fuel pump via a low-pressure side fuel line. The present invention relates to an engine control device including a low-pressure fuel pump that pumps pressure.

  Conventionally, in an engine, fuel is pumped from a fuel tank to a high-pressure fuel pump by a low-pressure fuel pump, fuel is further pumped from a high-pressure fuel pump to a fuel rail, and fuel in the fuel rail is injected into a cylinder by an injector. To be done.

  Here, when the pressure of the fuel flowing through the fuel supply line connecting the fuel rail and the low-pressure fuel pump becomes lower than the saturated vapor pressure, bubbles or vapor are generated in the fuel supply line. If vapor occurs in the fuel supply line, the fuel cannot be properly pumped to the fuel rail by the pump, and an appropriate amount of fuel may not be supplied into the cylinder.

  On the other hand, for example, in Patent Document 1, vapor is generated when a state in which the actual pressure value is lower than the target value of the pressure in the delivery pipe (fuel rail) by a predetermined value or more continues for a predetermined time. An apparatus is disclosed that is configured to determine and eliminate the vapor by increasing the discharge pressure of the low-pressure fuel pump. In other words, when vapor is generated, the high pressure fuel pump cannot properly pump the fuel, and the phenomenon that the discharge pressure does not reach the target value at any time occurs. Judgment.

JP 2014-231746 A

  In the vapor generation determination procedure according to Patent Document 1, the vapor is generated only after a state in which the actual pressure value is lower than the target value of the pressure in the delivery pipe (fuel rail) by a predetermined value or more continues for a predetermined time. It is determined that Therefore, it takes a relatively long time until it is determined that vapor is generated after vapor is generated, and until control for eliminating the vapor is performed. Therefore, there is a risk that the engine torque decreases due to the generation of vapor, and the amount of emission deterioration increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine control device that can detect the occurrence of vapor earlier with a simple configuration.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research. As a result, pressure fluctuations occur around the high-pressure pump as the high-pressure pump is driven, and this pressure fluctuation is transmitted to the low-pressure side fuel line. When pressure pulsation occurs in the fuel line and vapor occurs in the low-pressure side fuel line, the vapor absorbs pressure fluctuations, or the high pressure fuel pump bites the vapor, thereby reducing the amplitude of the pressure pulsation. I found out.

The present invention has been made based on this finding, and includes an injector, a fuel rail connected to the injector, a high-pressure fuel pump that pumps fuel to the fuel rail via a high-pressure side fuel line, and a low-pressure side. An engine control device comprising a low-pressure fuel pump that pumps fuel to the high-pressure fuel pump through a fuel line, the pressure detection means for detecting the pressure of the fuel in the low-pressure side fuel line, and the low-pressure side Vapor determination means for determining whether or not vapor is generated in the fuel line, wherein the vapor determination means is configured such that an injection amount, which is a fuel amount injected from the injector, is equal to or less than a preset reference injection amount to, implement determination of whether the vapor is generated, the amplitude of the fuel pressure in the low-pressure fuel in the line detected by the pressure detecting means, pre If the set is less than the reference value, and determines that the vapor has occurred (Claim 1).

  According to the present invention, the vapor is generated when the amplitude of the fuel pressure in the low-pressure side fuel line detected by the pressure detection means becomes below the reference value, that is, when the amplitude of the pressure pulsation becomes small. Therefore, it is possible to detect the occurrence of vapor early with a simple configuration.

Moreover, in the present invention , the vapor determining means determines whether or not the vapor is generated when the injection amount, which is the fuel amount injected from the injector, is equal to or less than a preset reference injection amount. you.

  In this way, when the amplitude of the pressure pulsation in the low-pressure side fuel line increases as the injection amount is small, the occurrence of vapor is determined based on the change in this amplitude. The occurrence of vapor can be detected with higher accuracy. That is, when the injection amount is small, the amount of fuel pushed back to the low-pressure side fuel line increases, and the pressure fluctuation of the low-pressure side fuel line increases. For this reason, if the determination based on the change in the amplitude is performed under an operation condition with a small injection amount in which the amplitude of the pressure pulsation is small, the change in the amplitude can be detected more appropriately.

The present invention also provides an injector, a fuel rail connected to the injector, a high-pressure fuel pump for pumping fuel to the fuel rail via a high-pressure side fuel line, and the high-pressure fuel pump via a low-pressure side fuel line. And a low pressure fuel pump for pumping fuel to the pressure control means for detecting fuel pressure in the low pressure side fuel line, and whether vapor is generated in the low pressure side fuel line. Vapor determining means for determining whether or not, and high-pressure side pump control means for feedback-controlling the discharge amount of the high-pressure fuel pump based on the deviation between the pressure in the fuel rail and the target value of the pressure, The vapor determination unit is configured such that the amplitude of the fuel pressure in the low-pressure side fuel line detected by the pressure detection unit is equal to or less than a preset reference value. A predetermined period of a control amount of feedback control performed by the high-pressure side pump control means even if it is determined that the vapor is generated and the amplitude of the fuel pressure in the low-pressure side fuel line is larger than the reference value When the amount of increase in is larger than a preset reference increase rate, it is determined that the vapor is generated.

In this way, in addition to the determination based on the change in the amplitude of the pressure pulsation of the low-pressure side fuel line, the occurrence of vapor is determined based on the rate of increase in the control amount of the feedback control (the increase amount in the predetermined period). Therefore, it is possible to secure many opportunities for determining the occurrence of vapor, and it is possible to more reliably detect the occurrence of vapor.

In the present invention, the vapor determining unit, when the following reference rail pressure change rate change amount in a predetermined period is preset target value of the pressure in the fuel rail, whether the vapor is generated It is preferable to carry out this determination (claim 3).

  In this way, it is possible to perform the vapor determination without being affected by the change in the amplitude of the transient pressure pulsation that accompanies when the target value of the rail pressure increases rapidly. Can do.

In the present invention, the low pressure side pump control means for controlling the low pressure fuel pump is provided, and the low pressure side pump control means has the low pressure fuel when the vapor judging means determines that the vapor is generated. the pump will be controlled so that the fuel in the low-pressure fuel in the line to boost preferable (claim 4).

  As described above, according to the present invention, since the occurrence of vapor can be detected at an early stage, the fuel in the low-pressure side fuel line is connected to the low-pressure fuel pump as it is determined that vapor has occurred. If applied to a system that controls to increase the pressure, the fuel in the low-pressure side fuel line can be boosted earlier and the vapor can be extinguished, and the decrease in engine torque and the deterioration in exhaust performance can be suppressed more reliably. Can do.

  As described above, according to the engine control apparatus of the present invention, it is possible to detect the occurrence of vapor earlier with a simple configuration.

It is a figure showing composition of an engine system concerning one embodiment of the present invention. It is the schematic block diagram which showed the fuel supply system. It is the block diagram which showed the control system of the engine system shown in FIG. It is the flowchart which showed the control procedure of the high pressure pump. It is the flowchart which showed the control procedure of the low pressure pump. It is the flowchart which showed the control procedure regarding the success or failure of vapor determination prohibition conditions. It is the schematic diagram which showed the change of each parameter at the time of vapor generation when the discharge pressure of a low pressure pump is made constant.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing a configuration of an engine system to which an engine control device according to an embodiment of the present invention is applied. The engine system of the present embodiment includes a four-stroke engine main body 1, an intake passage 50 for introducing combustion air (intake air) into the engine main body 1, and exhaust for exhausting exhaust from the engine main body 1 to the outside. And a passage 60. The engine body 1 is, for example, a four-cylinder engine having four cylinders 2a arranged in a direction orthogonal to the paper surface of FIG.

  The engine body 1 includes a cylinder block 2 in which a cylinder 2a is formed, a cylinder head 3 provided on the upper surface of the cylinder block 2, and a piston 4 inserted into the cylinder 2a so as to be slidable back and forth. Yes.

  A combustion chamber 5 is formed above the piston 4. Fuel is injected from the injector 11 into the combustion chamber 5. The injected fuel / air mixture is combusted in the combustion chamber 5, and the piston 4 is pushed down by the expansion force generated by the combustion and reciprocates up and down.

  The piston 4 is connected to the crankshaft 15 via a connecting rod, and the crankshaft 15 rotates around the central axis according to the reciprocating motion of the piston 4.

  The cylinder block 2 is provided with an engine speed sensor SW1 that detects the speed of the crankshaft 15 as the engine speed.

  The cylinder head 3 is provided with a pair of injectors 11 and spark plugs 10 for igniting a mixture of fuel and air injected from the injectors 11 by spark discharge for each cylinder 2a.

  The injector 11 has a plurality of injection holes serving as fuel injection ports at its tip, and is provided so as to face the combustion chamber 5 of each cylinder 2a from the side on the intake side. The fuel in the fuel tank 21 is supplied to the injector 11 via a pump or the like. A specific configuration for supplying fuel to the injector 11 will be described later.

  The spark plug 10 has an electrode for discharging sparks at the tip, and is provided so as to face the combustion chamber 5 of each cylinder 2a from above.

  The cylinder head 3 includes an intake port 6 for introducing air supplied from the intake passage 50 into the combustion chamber 5 of each cylinder 2a, an intake valve 8 for opening and closing the intake port 6, and the combustion chamber 5 of each cylinder 2a. Are provided with an exhaust port 7 for leading the exhaust gas generated in step 1 to the exhaust passage 60 and an exhaust valve 9 for opening and closing the exhaust port 7.

  An air cleaner 51, a compressor 52, an intercooler 53, a throttle valve 54, and a surge tank 55 are provided in the intake passage 50 in order from the upstream side. The engine body 1 is compressed by the compressor 52 and then intercooler 53. Chilled air is introduced. A passage that bypasses the compressor 52 may be provided. The throttle valve 54 is a valve that can open and close the intake passage 50, and the amount of intake air flowing through the intake passage 50 is adjusted according to the opening of the throttle valve 54. The intake passage 50 is provided with an air flow sensor SW2 for detecting the flow rate of the intake air flowing through the intake passage 50 and an intake air temperature sensor SW3 for detecting the temperature of the intake air. In the present embodiment, the air flow sensor SW2 and the intake air temperature sensor SW3 are provided in a portion of the intake passage 50 between the air cleaner 51 and the compressor 52 (immediately downstream of the air cleaner 51).

  The exhaust passage 60 is provided with a catalytic converter 63 containing a turbine 61 and a catalyst such as a three-way catalyst in order from the upstream side. The exhaust passage 60 has a bypass passage 62a for bypassing the turbine 61, and a waist for allowing the exhaust discharged from the engine body 1 to flow into the bypass passage 62a and bypassing the turbine 61. A gate valve 62b is provided.

(2) Fuel Supply System Next, a system configuration for sharing fuel to the injector 11 will be described with reference to FIGS. 1 and 2.

  Each injector 11 is connected to a fuel rail 12 that stores fuel inside. The fuel rail 12 is connected to a fuel tank 21 via a fuel supply line 22. The fuel in the fuel tank 21 is pumped and stored in the fuel rail 12. Each injector 11 injects fuel supplied from the fuel rail 12 into the cylinder 2a. As shown in FIG. 2, each injector 11 is connected to one fuel rail 12 extending in the cylinder arrangement direction, and fuel is supplied from the fuel rail 12 to each injector 11. The fuel rail 12 is provided with a rail pressure sensor SW4 for detecting the pressure of the fuel stored in the fuel rail 12 (hereinafter, the fuel pressure in the fuel rail 12 is appropriately referred to as rail pressure). In addition, a return passage 21b for returning excess fuel in the fuel rail 12 to the fuel supply line 22 is connected to the fuel rail 12 via a relief valve 21a.

  The fuel supply line 22 is provided with a low-pressure pump (low-pressure fuel pump) 24, a filter 25a, and a high-pressure pump (high-pressure fuel pump) 40 from the fuel tank 21 side. Hereinafter, the portion of the fuel supply line 22 between the low pressure pump 24 and the high pressure pump 40 is referred to as a low pressure side fuel line 22a, and the portion of the fuel supply line 22 between the high pressure pump 40 and the fuel rail 12 is on the high pressure side. This is referred to as fuel line 22b.

  The low pressure pump 24 is a pump for pumping up the fuel in the fuel tank 21 and sending it to the high pressure pump 40 side. The high pressure pump 40 is supplied with fuel that has been pressurized by the low pressure pump 24 and passed through the filter 25a. The low-pressure pump 24 is a rotary pump, and is rotated by being driven by the electric motor 28 to pump fuel. In addition, the fuel after passing through the filter 25b flows into the low-pressure pump 24.

  The low pressure side fuel line 22a is provided with a low pressure side fuel temperature sensor SW5 and a low pressure side fuel pressure sensor (pressure detection means) SW6 for detecting the temperature and pressure of the fuel in the low pressure side fuel line 22a.

  The high-pressure pump 40 is a pump for increasing the pressure of the fuel fed from the low-pressure pump 24 and supplying it to the fuel rail 12. The high-pressure pump 40 is a reciprocating pump and is driven by a high-pressure pump cam 9 a provided on the exhaust camshaft that drives the exhaust valve 9 to boost the fuel.

  Specifically, the high-pressure pump 40 includes a suction port 41a that communicates with the low-pressure side fuel line 22a, a discharge port 41b that communicates with the high-pressure side fuel line 22b, and a pressurization chamber that communicates with the suction port 41a and the discharge port 41b. It has a main body 41 in which 41c is formed and a plunger 42 whose tip is inserted into the pressurizing chamber 41c.

  The plunger 42 is disposed above the high-pressure pump cam 9a so as to contact with the high-pressure pump cam 9a, and is reciprocated up and down as the high-pressure pump cam 9a rotates by being pressed by the high-pressure pump cam 9a. That is, in the present embodiment, the high-pressure pump 40 is disposed on the upper surface of the cylinder head 3 on the exhaust side so that the plunger 42 contacts the high-pressure pump cam 9a. The plunger 42 reciprocates in the pressurizing chamber 41c to change the volume in the pressurizing chamber 41c, thereby boosting the fuel flowing into the pressurizing chamber 41c in the pressurizing chamber 41c, that is, from the suction port 41a. . The pressurized fuel is sent from the discharge port 41b to the fuel rail 12 through the high-pressure side fuel line 22b. A check valve 44 is provided at the discharge port 41b so that fuel does not flow backward from the fuel rail 12 side to the high-pressure pump 40 side.

  The inlet 41a is provided with a spill valve 43 that opens and closes the inlet 41a. The spill valve 43 is a normally open electromagnetic valve that closes the suction port 41a when energized and controls the amount of fuel fed into the high-pressure side fuel line 22b. In the present embodiment, the amount of fuel (discharge amount) pumped from the high-pressure pump 40 to the fuel rail 12 is changed by the closing period of the spill valve 43. More specifically, the spill valve 43 is configured to open until the plunger 42 reaches the lower end position from the upper end position, and then closes at a predetermined timing until the plunger 42 reaches the upper end position. The valve closing period is changed by changing the timing. Then, the closing timing of the spill valve 43 is advanced and the closing period of the spill valve 43 is lengthened, so that the amount of fuel pushed back from the pressurizing chamber 41c to the low pressure side fuel line 22a becomes small, and the pressurizing chamber 41c. Therefore, the amount of fuel pumped to the high-pressure side fuel line 22b, that is, the discharge amount of the high-pressure pump 40 is increased.

(3) Control System Next, the control system of the engine system will be described with reference to FIG. The engine system of the present embodiment is mounted on a vehicle such as an automobile and is controlled by an ECU (Engine Control Unit) 100 provided in the vehicle. As is well known, the ECU 100 is a microprocessor including a CPU, ROM, RAM, I / F, and the like.

  Information from various sensors is input to the ECU 100. For example, the ECU 100 is electrically connected to an engine speed sensor SW1, an air flow sensor SW2, an intake air temperature sensor SW3, a rail pressure sensor SW4, a low pressure side fuel temperature sensor SW5, and a low pressure side fuel pressure sensor SW6. Input signals (engine speed, intake air amount, intake air temperature, rail pressure, fuel temperature in the low-pressure side fuel line, fuel pressure in the low-pressure side fuel line) are received. The vehicle is also provided with an accelerator opening sensor SW7 for detecting the opening of an accelerator pedal (not shown) operated by the driver, a vehicle speed sensor SW8 for detecting the vehicle speed, and an ignition switch (IG switch) SW9. The detection signals from these sensors SW7 and SW8 and the signal from the IG switch SW9 are also input to the ECU 100.

  The ECU 100 controls each part of the engine system while executing various calculations based on input signals from the sensors (SW1 to SW8, etc.) and the switches (SW9, etc.). That is, the ECU 100 is electrically connected to the injector 11, the spark plug 10, the throttle valve 54, the low pressure pump 24 (motor that drives the low pressure pump 24), the spill valve 43 (drive mechanism that drives the spill valve 43), and the like. Then, based on the result of the above calculation, a drive control signal is output to each of these devices.

  The ECU 100 functionally includes a high pressure side pump control unit 102 (high pressure side pump control means) that controls the spill valve 43, that is, the high pressure pump 40, and a low pressure that controls the low pressure pump 24, that is, the motor that drives the low pressure pump 24. Side pump control unit (low pressure side pump control means) 104.

  The low-pressure side pump control unit 104 functionally includes a vapor determination unit 106 (vapor determination unit) that determines whether or not vapor is generated in the fuel supply line 22, more specifically, in the low-pressure side fuel line 22a. That is, in the low-pressure side fuel line 22a, when the fuel pressure becomes lower than the saturated vapor pressure at that temperature, bubbles, so-called vapor, are generated in the low-pressure side fuel line 22a. The vapor determination unit 106 is a part that determines whether or not this vapor has occurred. Further, the low-pressure side pump control unit 104 determines whether or not a vapor determination prohibition condition, which is a condition for prohibiting the vapor determination by the vapor determination unit 106, is established. A vapor determination prohibiting unit 108 (vapor determination prohibiting means) that prohibits occurrence determination is provided.

  Next, control procedures performed in each of the units 102, 104, 106, and 108 will be described with reference to FIGS.

(I) High pressure side pump control part The control procedure of the spill valve 43 by the high pressure side pump control part 102 is demonstrated using FIG.

  First, the high-pressure side pump control unit 102 sets a target rail pressure that is a target value of the rail pressure according to the operation state in step S1. The high-pressure side pump control unit 102 sets the target rail pressure based on, for example, the engine speed and the engine load (accelerator opening).

  Next, in step S <b> 2, the high-pressure side pump control unit 102 calculates a basic spill valve closing period that is a basic valve closing period of the spill valve 43. For example, the high-pressure side pump control unit 102 sets the target rail pressure set in step S1 and the current engine speed from a map that is set and stored in advance for the rail pressure, the engine speed, and the valve closing period of the spill valve 43. The basic spill valve closing period is determined by extracting values corresponding to.

  Next, in step S3, the high-pressure side pump control unit 102 reads the actual rail pressure that is the current rail pressure detected by the rail pressure sensor SW4.

  Next, in step S4, the high-pressure side pump control unit 102 calculates a deviation between the target rail pressure set in step S1 and the actual rail pressure read in step S3.

  Next, in step S5, the high-pressure side pump control unit 102 calculates the feedback amount during the valve closing period of the spill valve 43 based on the rail pressure deviation calculated in step S4. Specifically, in step S5, a P term (proportional term) proportional to the deviation is calculated, and an I term (integral term), which is a value obtained by integrating amounts proportional to the deviation, is calculated. As described above, in this embodiment, the discharge amount of the high-pressure pump 40 is set to be increased by increasing the valve closing period of the spill valve 43. For example, the actual rail pressure is lower than the target rail pressure. When it is necessary to increase the discharge amount of the high-pressure pump 40, the P term becomes a value larger than 0 and the I term increases.

  Next, in step S6, the high-pressure side pump control unit 102 adds the basic spill valve closing period calculated in step S2 and the P term and I term calculated in step S5 to obtain the final spill valve. The final spill valve closing period that is the valve closing period is calculated.

  Finally, in step S7, the high-pressure side pump control unit 102 drives the spill valve 43 so that the spill valve 43 is closed only during the final spill valve closing period calculated in step S7.

  Thus, in this embodiment, the high-pressure side pump control unit 102 performs PI control (proportional integral control) on the discharge amount of the high-pressure pump 40, that is, the valve closing period of the spill valve 43.

(Ii) Low pressure side pump control part The control procedure of the low pressure pump 24 by the low pressure side pump control part 104 is demonstrated using FIG.

  First, in step S11, the low pressure side pump control unit 104 determines the amplitude of the low pressure side fuel pressure, the injection amount, the target rail pressure set in step S1, and the I term (high pressure side pump calculated in step S5). The fuel pressure F / B amount (feedback amount) of the high-pressure pump 40 calculated by the control unit 102, the actual rail pressure, and the like are read.

  The low-pressure side fuel pressure is the pressure of the fuel in the low-pressure side fuel line 22a detected by the low-pressure side fuel pressure sensor SW6, and the amplitude of the low-pressure side fuel pressure is the amplitude of pressure pulsation generated in the low-pressure side fuel line 22a. . That is, as the plunger 42 of the high-pressure pump 40 reciprocates in synchronization with the engine speed as described above, pressure vibration in synchronization with the engine speed occurs around the high-pressure pump 40. The pressure vibration is transmitted to the low pressure side fuel line 22a, so that pressure pulsation is generated in the low pressure side fuel line 22a. The amplitude of the low pressure side fuel pressure is the amplitude of the pressure pulsation thus generated.

  The injection amount is a flow rate of fuel injected from the injector 11 and can be calculated from an amount (command injection amount) commanded by the ECU 100 to inject into the injector 11. The command injection amount is calculated based on the engine speed, the accelerator opening, and the like.

  Next, in step S12, the low-pressure side pump control unit 104 determines whether or not the vapor determination execution condition is satisfied, in other words, whether or not the vapor determination prohibition condition is not satisfied. The vapor determination execution condition and the vapor determination prohibition condition will be described later.

  When the determination in step S12 is NO and the vapor determination execution condition is not satisfied (when the vapor determination prohibition condition is satisfied), the low-pressure side pump control unit 104 ends the process as it is. On the other hand, if the determination in step S12 is YES and the vapor determination execution condition is satisfied, the process proceeds to step S13.

In step S13, the low-pressure side pump control unit 104 determines whether or not the injection amount read in step S1 is equal to or less than the reference injection amount. The reference injection amount is the maximum value of the injection amount at which the amount of fuel pushed back to the low-pressure side fuel line 22a increases and the amplitude of the pressure pulsation generated in the low-pressure side fuel line 22a is greater than a predetermined value. That is, when the injection amount is small, the discharge amount of the high-pressure pump 40 becomes small, and the amount of fuel pushed back from the pressurizing chamber 41c into the low-pressure side fuel line 22a becomes large. Therefore, the amplitude of the pressure pulsation generated in the low pressure side fuel line 22a is increased. In other words, when the injection amount is large and the discharge amount of the high-pressure pump 40 is large, the amount of fuel pushed back from the pressurizing chamber 41c into the low-pressure side fuel line 22a is small, so the pressure pulsation in the low-pressure side fuel line 22a is small. Become.

  When the determination in step S13 is NO and the injection amount is larger than the reference injection amount, that is, when the amplitude of the pressure pulsation generated in the low-pressure side fuel line 22a is equal to or smaller than a predetermined value, it is performed in step S15 described later. Without the vapor generation determination based on this amplitude, the process proceeds to step S21. That is, when the pressure pulsation amplitude is small, it is difficult to determine the occurrence of vapor based on the pressure pulsation amplitude (the possibility of erroneous determination that vapor has occurred despite the absence of vapor). This determination is not performed.

  On the other hand, if the determination in step S13 is YES, the injection amount is equal to or less than the reference injection amount, and the amplitude of the pressure pulsation generated in the low pressure side fuel line 22a is greater than the predetermined value, the process proceeds to step S14.

  In step S14, the low-pressure side pump control unit 104 determines whether or not the change rate of the target rail pressure read in step S1 (change amount in a predetermined period) is equal to or less than the reference rail pressure change rate. The reference rail pressure change rate changes to a state where the amplitude of the pressure pulsation generated in the low-pressure side fuel line 22a becomes transiently smaller than a predetermined value, for example, when the injection amount rapidly increases due to rapid acceleration or the like. It is the maximum value of the change rate of rail pressure. In the present embodiment, in step S14, it is determined whether or not the absolute value of the change rate of the target rail pressure is equal to or less than the reference rail pressure change rate. That is, when the absolute value of the change rate of the target rail pressure is small, the engine operating state is stable, so the amplitude of the pressure pulsation generated in the low-pressure side fuel line 22a increases. In addition, when the target rail pressure increases as the injection amount increases, the change rate (a value that is not an absolute value) of the target rail pressure may be compared with the reference rail pressure change rate.

  If the determination in step S14 is NO and the rate of change of the target rail pressure is larger than the rate of change of the reference rail pressure, that is, the amplitude of the pressure pulsation that occurs in the low-pressure side fuel line 22a becomes transiently below a predetermined value. Accordingly, when it becomes difficult to determine the occurrence of vapor based on the amplitude of the pressure pulsation as described above, the processing is terminated as it is.

  On the other hand, if the determination in step S14 is YES, the change rate of the target rail pressure is equal to or less than the reference rail pressure change rate, and the amplitude of the pressure pulsation generated in the low pressure side fuel line 22a is larger than the predetermined value, the process proceeds to step S15. . That is, in this embodiment, only when the injection amount is equal to or less than the reference injection amount and the change rate of the target rail pressure is equal to or less than the reference rail pressure change rate, and accordingly, the amplitude of the pressure pulsation is detected to be large. The process proceeds to step S15.

  In step S15, the low-pressure side pump control unit 104 determines whether or not the amplitude of the low-pressure side fuel pressure read in step S11 is equal to or less than a reference amplitude (reference value). The reference amplitude is the maximum value of the amplitude when vapor is generated in the low-pressure side fuel line 22a, and is set in advance by experiments or the like. That is, when vapor is generated in the low-pressure side fuel line 22a, the vapor absorbs the pressure fluctuation in the low-pressure side fuel line 22a, or the pressure is changed around the high-pressure pump 40 because the vapor is engaged with the high-pressure pump 40. Along with being suppressed, the amplitude of the pressure pulsation in the low pressure side fuel line 22a becomes smaller. The reference amplitude is the amplitude of the pressure pulsation in the low-pressure fuel line 22a when the vapor is generated to some extent as described above. If the amplitude of the pressure pulsation is equal to or less than the reference amplitude, it is considered that the vapor is generated.

  If the determination in step S15 is NO and the amplitude of the low-pressure fuel pressure is greater than the reference amplitude, the process proceeds to step S21.

  On the other hand, if the determination in step S15 is YES and the amplitude of the low-pressure side fuel pressure is smaller than the reference amplitude, the pump control unit 104 proceeds to step S16 and vapor is generated in the low-pressure side fuel line 22a. Is determined.

  After step S16, the process proceeds to step S17.

  On the other hand, in step S21 that proceeds when the determinations in steps S13 to S15 are NO, the low-pressure side pump control unit 104 determines whether or not the vehicle is in steady running. Specifically, in step S21, the low-pressure side pump control unit 104 determines whether or not the engine speed, engine load, and vehicle speed change rate (change amount and absolute value in a predetermined period) are each equal to or less than a predetermined value. If the rate of change of the engine speed or the engine load is equal to or less than a predetermined value and the rate of change of the vehicle speed is equal to or less than the predetermined value, it is determined that the vehicle is in steady running.

  If the determination in step S21 is NO and the vehicle is not in steady running, the low-pressure side pump control unit 104 ends the process as it is. On the other hand, if the determination in step S21 is yes and the vehicle is traveling normally, the process proceeds to step S22.

  In step S22, the low-pressure side pump control unit 104 obtains the change rate (change amount, absolute value in a predetermined period) and the change rate of actual rail pressure (change amount, absolute value in a predetermined period) read in step S11. It is determined whether or not each is below a preset allowable value and is stable.

  If the determination in step S22 is NO and the rate of change of the I term and the rate of change of the actual rail pressure are greater than the allowable values, and the term I or the actual rail pressure changes abruptly, the low-pressure side pump control unit 104 remains unchanged. End the process. On the other hand, if the determination in step S22 is YES and the rate of change of the I term and the actual rail pressure are within the allowable values and these are stable, the process proceeds to step S23.

  In step S23, the low-pressure side pump control unit 104 determines whether or not the average increase rate of the I term is larger than a preset reference increase rate. Specifically, the low-pressure side pump control unit 104 determines the increase rate of the I term (a change amount of the predetermined time, a value in which the increase side is a positive value and a decrease side is a negative value) for a predetermined time. An average value is calculated, and it is determined whether or not this average value is larger than the reference increase rate. The reference increase rate is set to a predetermined value greater than zero.

  When the determination in step S23 is NO and the average increase rate of the I term is equal to or less than the reference increase rate, the low-pressure side pump control unit 104 ends the process as it is. On the other hand, when the determination in step S23 is YES, the average increase rate of the I term is larger than the reference increase rate, the I term is increasing, and the increase rate is higher than the reference increase rate on average. Advances to step S16 and determines that vapor is generated. Thereafter, the process proceeds to step S17.

  In step S <b> 17, the low pressure side pump control unit 104 boosts the fuel by the low pressure pump 24.

  As described above, in this embodiment, when it is determined that the vapor is generated, the low-pressure side pump control unit 104 boosts the fuel in the low-pressure side fuel line 22a. That is, if vapor is generated in the low-pressure side fuel line 22a, the fuel does not properly flow into the high-pressure pump 40, and an appropriate amount of fuel may not be injected from the injector 11, which may cause engine stall or the like. Therefore, in this embodiment, when it is determined that vapor is generated, the fuel in the low-pressure side fuel line 22a is boosted to make the fuel pressure higher than the saturated vapor pressure, thereby eliminating the vapor.

  In the present embodiment, the injection amount is equal to or less than the reference injection amount, and the change rate of the target rail pressure is equal to or less than the reference rail pressure change rate, and accordingly, the amplitude of the pressure pulsation is stably detected to be large. In the operating state, if the amplitude of the low-pressure side fuel pressure is below the reference amplitude, it is determined that vapor is generated, and vapor is also generated based on the average increase rate of the I term (high pressure pump fuel pressure F / B amount). Is judged. That is, when vapor is generated, the fuel does not flow properly into the high-pressure pump 40. Therefore, no matter how much the spill valve 43 is closed, the rail pressure does not reach the target rail pressure. The calculated I term will continue to increase. Therefore, if the average change rate of the I term is larger than the reference increase rate, it is considered that vapor is generated in the low-pressure side fuel line 22a. Thus, the reference increase rate is the minimum value of the increase rate of I-high when vapor is generated in the low-pressure side fuel line 22a.

  This will be specifically described with reference to FIG. FIG. 7 shows the rail pressure, the I term, the P term, and the low pressure side fuel line when vapor is generated in the low pressure side fuel line 22a at time t1 with the discharge pressure (feed pressure) of the low pressure pump 24 kept constant. It is shown schematically showing the time change of the pressure in 22a.

  When the vapor is generated at time t1, as described above, the vapor absorbs the pressure fluctuation in the low-pressure side fuel line 22a, so the amplitude of the pressure pulsation in the low-pressure side fuel line 22a becomes small. In particular, when the vapor grows, the amount of pressure fluctuation absorbed by the vapor increases accordingly, and the amplitude of the pressure pulsation gradually decreases.

  Further, the rail pressure follows the target rail pressure until vapor is generated at time t1. However, when vapor is generated in the low-pressure side fuel line 22a at time t1, the amount of fuel pumped to the high-pressure pump 40 and thus to the fuel rail 12 decreases, so that the rail pressure decreases. When the rail pressure falls below the target rail pressure, feedback control is performed to converge the rail pressure to the target rail pressure, and the P term and the I term are increased. And the valve closing period of the spill valve 43 is changed in the direction in which the discharge amount of the high-pressure pump 40 increases. As a result, the rail pressure temporarily increases. However, since the vapor is generated, an appropriate amount of fuel corresponding to the closing period of the spill valve 43 does not flow into the high-pressure pump 40, so the rail pressure does not converge to the target value and gradually decreases while hunting. To go. As the rail pressure gradually decreases, the I term gradually increases. Therefore, it is considered that vapor is generated when the average change rate of the I term is a positive value and becomes larger than a predetermined value (reference increase rate) as described above.

Further, in the present embodiment, when the vehicle is not in steady running (when the change rate of the engine speed, engine load, and vehicle speed is large), and when the I term and the actual rail pressure are not stable (change rate of the I term, When the rate of change of the actual rail pressure is large), the determination of whether or not vapor is generated is stopped. That is, when the rate of change of the engine speed, engine load, and vehicle speed is large, the average rate of change of the I term may be calculated large even when no vapor is generated. Even when no vapor is generated, the actual rail pressure may be instantaneously reduced due to noise or the like, and the I term may be instantaneously increased. Therefore, in this embodiment, when the rate of change of the I term is larger than the allowable value or when the rate of change of the actual rail pressure is larger than the allowable value, the vapor determination based on the average rate of change of the I term is stopped, and the engine It is avoided that the average change rate of the I term is largely calculated due to the influence of the fluctuation of the rail pressure and the noise accompanying the change of the rotation speed, the engine load, and the vehicle speed, and that the vapor is generated.

  Further, in the present embodiment, even when the vapor determination prohibition condition is satisfied, the determination of whether or not the vapor is generated is stopped, and the determination of the vapor is performed with higher accuracy. The vapor determination prohibition condition will be described next.

(Iii) Vapor Determination Prohibition Condition A procedure for determining whether or not the vapor determination prohibition condition (vapor determination execution condition) is successful by the low-pressure side pump control unit 104 will be described with reference to FIG.

  First, in step S31, the low-pressure side pump control unit 104 calculates a target high-pressure pump discharge amount that is a target value of the discharge amount of the high-pressure pump 40. The low-pressure side pump control unit 104 calculates a target high-pressure pump discharge amount based on the target rail pressure, the engine speed, and the like.

  Next, in step S32, the low-pressure side pump control unit 104 reads the low-pressure side fuel temperature, the injection amount, the predicted engine room temperature, the IG signal (signal of the IG switch SW9), and the pump failure flag.

  The low pressure side fuel temperature is the temperature of the fuel in the low pressure side fuel line 22a detected by the low pressure side fuel temperature sensor SW5. The predicted engine room temperature is a temperature in the engine room in which the engine is arranged, and is a value obtained by predicting the temperature around the engine body 1 in the engine room. The ECU 100 predicts this temperature from time to time. Yes. For example, the ECU 100 calculates the predicted engine room temperature based on the vehicle speed and the intake air temperature detected by the intake air temperature sensor SW3. In this case, if the vehicle speed is high, the amount by which the engine room is cooled by the traveling wind increases. Therefore, the predicted engine room temperature is predicted to be lower as the vehicle speed is higher. The pump failure flag is a flag that is output when the high-pressure pump 40 has failed by the ECU 100. The ECU 100 determines whether or not the high-pressure pump 40 has failed based on the detection value of a current sensor or the like provided in the drive circuit of the high-pressure pump 40, and if it determines that it has failed, the pump failure flag Set to 1.

  Next, in step S33, the low-pressure side pump control unit 104 determines whether or not the pump failure flag is 1. If the determination in step S33 is YES, that is, if the pump failure flag is 1 and it is determined that the high-pressure pump 40 has failed, the process proceeds to step S40. In step S40, it is determined that the vapor determination prohibition condition is satisfied.

  On the other hand, if the determination in step S33 is no, the process proceeds to step S34.

  In step S34, the low-pressure side pump control unit 104 determines whether or not the low-pressure side fuel temperature is equal to or lower than a preset minimum guaranteed temperature. The minimum guaranteed temperature is the saturated vapor temperature at the minimum pressure of the fuel pressure in the low-pressure side fuel line 22 a guaranteed by the low-pressure pump 24. That is, the low-pressure pump 24 is configured to maintain the fuel pressure in the low-pressure side fuel line 22a at the minimum pressure or higher in the operating state, and the minimum guaranteed temperature is the saturated vapor temperature of the fuel at the minimum pressure. It is. When the determination in step S34 is YES and the low-pressure side fuel temperature is equal to or lower than the minimum guaranteed temperature, the low-pressure side pump control unit 104 proceeds to step S40 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, if the determination in step S34 is NO and the low-pressure side fuel temperature is higher than the minimum guaranteed temperature, the low-pressure side pump control unit 104 proceeds to step S35.

  The low-pressure side pump control unit 104 determines whether or not the injection amount is larger than a preset non-vapor generation injection amount. The non-vapor generated injection amount is the minimum value of the injection amount at which no vapor is generated in the low pressure side fuel line 22a even if the temperature around the low pressure side fuel line 22a is high. That is, when the injection amount is large and the fuel is flowing through the low-pressure side fuel line 22a at high speed, the amount of heat received per unit mass of the fuel can be kept small and the temperature rise of the fuel can be kept small even if the ambient temperature is high. . The non-vapor generated injection amount is the minimum value of the flow rate at which the amount of heat received per unit mass of the fuel is suppressed to a predetermined value or less and the fuel does not evaporate. If the determination in step S35 is YES and the injection amount is greater than the non-vapor generated injection amount, the low pressure side pump control unit 104 proceeds to step S40 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, when the determination in step S35 is NO and the injection amount is equal to or less than the non-vapor generated injection amount, the low pressure side pump control unit 104 proceeds to step S36.

  In step S36, the low-pressure side pump control unit 104 determines whether or not the predicted engine room temperature read in step S32 is equal to or lower than the reference engine room temperature. The reference engine room temperature is the maximum value of the engine room temperature at which no vapor is generated in the low-pressure side fuel line 22a, and is set in advance through experiments or the like. That is, if the temperature around the engine room and the low-pressure side fuel line 22a is low, the temperature of the fuel in the low-pressure side fuel line 22a is also kept low and no vapor is generated. The reference engine room temperature is the maximum value of the engine room temperature at which the temperature of the fuel in the low-pressure side fuel line 22a is kept lower than the predetermined temperature and no vapor is generated. When the determination in step S36 is YES and the predicted engine room temperature is equal to or lower than the reference engine room temperature, the low-pressure side pump control unit 104 proceeds to step S40 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, when the determination in step S36 is NO and the predicted engine room temperature is higher than the reference engine room temperature, the low-pressure side pump control unit 104 proceeds to step S37.

  In step S37, the low-pressure side pump control unit 104 determines whether or not the target high-pressure pump discharge amount calculated in step S31 is unstable. Specifically, it is determined whether or not a state in which the change rate of the target high-pressure pump discharge amount (change amount in a predetermined time, absolute value) is equal to or less than a preset reference discharge amount change rate has continued for a predetermined time or more. If the determination in step S37 is NO and the rate of change in the target high-pressure pump discharge rate is not lower than the reference discharge rate change rate for a predetermined time and the target high-pressure pump discharge rate is not stable, The pump control unit 104 proceeds to step S40 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, when the determination in step S37 is YES and the target high-pressure pump discharge amount is stable, the low-pressure side pump control unit 104 proceeds to step S38.

  In step S38, the low-pressure side pump control unit 104 determines whether or not the engine is started based on the IG signal read in step S32 (specifically, immediately after starting the engine and during a predetermined time from the start of starting). Determine whether. If the determination in step S38 is YES and the engine is being started, the low-pressure side pump control unit 104 proceeds to step S40 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, if the determination in step S38 is NO and the engine is not being started, the low-pressure side pump control unit 104 proceeds to step S39.

  In step S39, the low pressure side pump control unit 104 determines that the vapor determination execution condition is satisfied.

  Thus, in this embodiment, if any one of the determinations in steps S33 to S38 is YES, it is determined that the vapor determination prohibition condition is satisfied.

  That is, when the pump failure flag is 1 and it is determined that the high-pressure pump 40 has failed, when the low-pressure side fuel temperature is equal to or lower than the minimum guaranteed temperature, or when the injection amount is greater than the non-vapor generated injection amount, When the predicted engine room temperature is equal to or lower than the reference engine room temperature, when the target high-pressure pump discharge amount is not stable, or when the engine is started, it is determined that the vapor determination prohibition condition is satisfied. In this case, it is prohibited to determine whether or not vapor is generated.

(4) Operation and the like As described above, in the present embodiment, the phenomenon that the amplitude of the pressure pulsation in the low-pressure side fuel line 22a is reduced when vapor is generated in the low-pressure side fuel line 22a is utilized. Pressure pulsation (pressure) in the fuel line 22a is detected, and it is determined that vapor is generated in the low-pressure side fuel line 22a when the amplitude of the pressure pulsation becomes equal to or less than a preset reference value. Therefore, it is possible to detect the occurrence of vapor with a relatively simple configuration with high accuracy and at an earlier stage. In addition, along with this, it is possible to avoid engine stall or the like due to the generation of vapor, and it is possible to further reduce the driving force of the low-pressure pump 24 and improve fuel efficiency. That is, by detecting the occurrence of vapor at an early stage, the fuel in the low-pressure side fuel line 22a can be boosted earlier, and the vapor can be extinguished, thereby more reliably reducing engine torque and exhaust performance. Can be suppressed. As described above, when the driving force of the low-pressure pump 24 is increased when vapor is generated, if the generation of vapor is erroneously determined, the driving force of the low-pressure pump 24 is unnecessarily increased. , Fuel economy performance deteriorates. On the other hand, in this embodiment, an unnecessary increase in the driving force of the low-pressure pump 24 can be avoided.

  In particular, in this embodiment, when the injection amount is small and the change rate of the target value of the rail pressure is small, and the amplitude of the pressure pulsation of the low-pressure side fuel line 22a is increased accordingly, the change in the amplitude is changed. Based on generating vapor. Therefore, it is possible to detect the change in amplitude and the occurrence of vapor more accurately.

  In this embodiment, whether or not vapor is generated is also determined based on the average increase rate of the term I (high pressure pump fuel pressure F / B amount). Therefore, many opportunities for determining whether or not vapor has occurred can be secured, and the occurrence of vapor can be more reliably detected.

  Furthermore, in the present embodiment, an operation state in which no vapor is generated (the amount of generated vapor is smaller than a predetermined value), that is, a state in which the low-pressure side fuel temperature is equal to or lower than the minimum guaranteed temperature, and the predicted engine room temperature is the reference engine room Vapor determination is prohibited when the temperature is below the temperature. Therefore, it is erroneously determined that vapor is generated when the amplitude of the pressure pulsation is reduced or the increase rate of the I term is larger than the reference increase rate due to factors other than vapor in these operating conditions. Can be avoided.

  Further, in this embodiment, an operating state in which the increase rate of the I term is larger than the reference increase rate regardless of the occurrence of vapor, that is, a state in which the target high-pressure fuel pump discharge amount is unstable, or an engine start At the time (immediately after starting), vapor determination is prohibited. Therefore, when the target high-pressure fuel pump discharge amount is unstable or when the engine is started, it is erroneously determined that vapor is generated when the average increase rate of the I term becomes larger than the reference increase rate. Can be avoided. That is, when the target value itself of the high-pressure fuel pump discharge amount has increased rapidly, the I term is calculated to be large accordingly. Further, when the engine is started (immediately after the start), it is necessary to rapidly increase the pressure in the fuel rail 12 that has decreased as the engine is stopped. The target rail pressure increases rapidly, and the I term increases accordingly. Calculated. Therefore, in these cases, there is a possibility that it is erroneously determined that vapor is generated even though vapor is not generated due to the increase in the I term. On the other hand, in this embodiment, since vapor determination is prohibited in these cases, this erroneous determination can be avoided.

(5) Modification In the above embodiment, the amplitude of the pressure pulsation of the low-pressure side fuel line 22a only when the injection amount is equal to or less than the reference injection amount and the change rate of the target rail pressure is equal to or less than the reference rail pressure change rate. In the case where it is determined whether or not vapor is generated based on the above, when the injection amount is larger than the reference injection amount or when the change rate of the target value of the rail pressure is larger than the reference rail pressure change rate, Vapor generation determination may be performed based on the pressure pulsation amplitude. However, as described above, in these cases, since the amplitude of the pressure pulsation itself becomes small, it is relatively difficult to detect the change in the amplitude. Therefore, if the vapor generation determination based on the pressure pulsation amplitude is performed only in the above case, the generation of vapor can be detected more accurately.

  Also, the vapor generation determination based on the pressure pulsation amplitude is performed only when either the injection amount is less than the reference injection amount or the change rate of the target value of the rail pressure is less than the reference rail pressure change rate. You may implement. However, if this determination is made only in both cases, the occurrence of vapor can be detected more accurately.

  Further, the vapor generation determination based on the increase rate of the I term may be omitted. However, if the determination based on this I term is performed in addition to the determination based on the amplitude of the pressure pulsation, the occurrence of vapor can be detected more reliably.

DESCRIPTION OF SYMBOLS 1 Engine main body 2a Cylinder 12 Fuel rail 22a Low pressure side fuel line 24 Low pressure fuel pump 40 High pressure fuel pump 102 High pressure side pump control part (high pressure side pump control means)
104 Low pressure side pump controller (Low pressure side pump control means)
106 Vapor determination unit (vapor determination means)
SW6 Low pressure side fuel pressure sensor (pressure detection means)

Claims (4)

An injector, a fuel rail connected to the injector, a high-pressure fuel pump that pumps fuel to the fuel rail via a high-pressure fuel line, and a low-pressure that pumps fuel to the high-pressure fuel pump via a low-pressure fuel line An engine control device comprising a fuel pump,
Pressure detecting means for detecting the pressure of the fuel in the low pressure side fuel line;
Vapor determination means for determining whether or not vapor is generated in the low-pressure side fuel line,
The vapor determining means is:
When the injection amount, which is the amount of fuel injected from the injector, is equal to or less than a preset reference injection amount, it is determined whether or not the vapor is generated,
The engine is characterized in that it is determined that the vapor is generated when the amplitude of the fuel pressure in the low pressure side fuel line detected by the pressure detecting means is not more than a preset reference value. Control device. An injector, a fuel rail connected to the injector, a high-pressure fuel pump that pumps fuel to the fuel rail via a high-pressure fuel line, and a low-pressure that pumps fuel to the high-pressure fuel pump via a low-pressure fuel line An engine control device comprising a fuel pump,
Pressure detecting means for detecting the pressure of the fuel in the low pressure side fuel line;
Vapor determination means for determining whether or not vapor is generated in the low-pressure side fuel line;
High pressure side pump control means for feedback controlling the discharge amount of the high pressure fuel pump based on the deviation between the pressure in the fuel rail and the target value of the pressure,
The vapor determining means is:
When the amplitude of the fuel pressure in the low pressure side fuel line detected by the pressure detecting means is equal to or less than a preset reference value, it is determined that the vapor is generated,
Even if the amplitude of the fuel pressure in the low pressure side fuel line is larger than the reference value, the amount of increase in the control amount of the feedback control performed by the high pressure side pump control means in a predetermined period is larger than a preset reference increase rate. If it is too large, it is determined that the vapor is generated . The engine control apparatus according to claim 1 or 2,
The vapor determining unit, when the following reference rail pressure change rate change amount in a predetermined period is preset target value of the pressure in the fuel rail, carrying out determination of whether the vapor is generated An engine control device. The engine control apparatus according to any one of claims 1 to 3 ,
Comprising low pressure side pump control means for controlling the low pressure fuel pump,
The low-pressure side pump control unit controls the low-pressure fuel pump so that the fuel in the low-pressure side fuel line is boosted when the vapor determining unit determines that the vapor is generated. Engine control device.

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