JP2017031959A - Control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more accurately determine generation of vapor.SOLUTION: A control device for an engine includes: high pressure side pump control means 102 for performing feedback control of discharge amount of a high pressure fuel pump 40 on the basis of a deviation of pressure in a fuel rail 12 from a target value of the pressure; vapor determination means 106 for determining that vapor is generated when increase of the control amount of the feedback control for a predetermined period is larger than a reference increase rate; and vapor determination prohibition means 108 for prohibiting the determination of the vapor generation. The vapor determination prohibition means 108 determines whether or not an operating state of the engine is in a first specific operating state preset as an operating state where the amount of vapor generated in a fuel supply line 22 is smaller than predetermined reference amount, and prohibits the determination of the vapor generation when the operating state of the engine is in the first specific operating state.SELECTED DRAWING: Figure 5

Description

  The present invention includes an injector, a fuel rail connected to the injector, a fuel supply line connected to the fuel rail, a low-pressure fuel pump that pumps fuel to the fuel supply line, and a pump that is pumped by the low-pressure fuel pump. The present invention relates to an engine control device provided with a high-pressure fuel pump that pumps the fuel to the fuel rail.

  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, that is, 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, Patent Document 1 discloses an engine control device that performs proportional integral control of the drive duty ratio of a high-pressure fuel pump based on a deviation between a target value and an actual value of the discharge pressure of the high-pressure fuel pump. Thus, it has been disclosed that when the integral term used for proportional-integral control increases, it is determined that vapor is generated, and the discharge pressure of the low-pressure fuel pump is increased to eliminate the vapor. That is, in the apparatus of Patent Document 1, 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 will occur. Thus, it is determined that vapor has occurred when the integral term increases.

Japanese Patent No. 5494818

  In the vapor generation determination procedure according to Patent Document 1, there is a risk of erroneous determination that vapor is generated even when vapor is not generated. For example, it may be erroneously determined that vapor is generated even though the integral term is increased due to a pump failure or the like. And although the vapor | steam has not actually generate | occur | produced, the discharge pressure of a low pressure fuel pump will be raised, and there exists a possibility that the energy consumption concerning a low pressure fuel pump may become excessive, and a fuel consumption performance may deteriorate.

  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 determine the occurrence of vapor more accurately.

  As a result of intensive studies to solve the above problems, the present inventors have found that there are operating conditions in which the amount of vapor generated in the fuel supply line is less than a predetermined reference amount and almost no vapor is generated.

  The present invention has been made on the basis of the above knowledge, and includes an injector, a fuel rail connected to the injector, a fuel supply line connected to the fuel rail, and a low pressure for pumping fuel to the fuel supply line. An engine control device comprising a fuel pump and a high-pressure fuel pump that pumps fuel pumped by the low-pressure fuel pump to the fuel rail, wherein a pressure in the fuel rail and a target value of the pressure Based on the deviation, a high-pressure pump control unit that feedback-controls the discharge amount of the high-pressure fuel pump, and a reference in which an increase amount in a predetermined period of a control amount of feedback control performed by the high-pressure pump control unit is set in advance. Vapor determination means for determining that the vapor is generated when the rate of increase is greater, and the vapor determination means Vapor determination prohibiting means for prohibiting the determination of the occurrence of vapor, wherein the vapor determination prohibiting means is an operating state in which the operating state of the engine is such that the amount of vapor generated in the fuel supply line is less than a predetermined reference amount. It is determined whether or not the first specific operation state is set in advance, and when the engine operation state is in the first specific operation state, the determination of the occurrence of vapor is prohibited (claim) Item 1).

  According to the present invention, the vapor generation determination in the operation state (first specific operation state) in which vapor is considered not to be generated is prohibited, so that the increase rate of the control amount despite the absence of vapor. It is possible to reduce the chance of misjudging that vapor is occurring due to the (increased amount in a predetermined period) becoming larger than the reference increase rate, and it is possible to more accurately determine the occurrence of vapor. .

  In the present invention, the vapor determination prohibiting means, when the temperature of the fuel flowing through the portion of the fuel supply line between the low pressure fuel pump and the high pressure fuel pump is below a preset minimum guaranteed temperature, When the flow rate of the fuel flowing through the fuel supply line is larger than a preset reference flow rate, or when the ambient temperature of the engine body is equal to or lower than a preset reference ambient temperature, the engine operating state is the first. It is preferable to determine that the specific operation state is set (claim 2).

  According to this configuration, when the temperature of the fuel flowing through the fuel supply line is less than the minimum guaranteed temperature and it is considered that the fuel does not substantially evaporate, or when the flow rate of the fuel flowing through the fuel supply line is large, the fuel The amount of heat per unit mass received from the surroundings is considered to be small and the fuel is unlikely to evaporate, and the amount of heat received from the surroundings by the low ambient temperature of the engine body is considered to be difficult to evaporate the fuel. In such a case, since the determination of the occurrence of vapor is prohibited, it is possible to more reliably avoid the erroneous determination that the vapor is generated even though the vapor is not generated.

  Further, in the present invention, the vapor determination prohibiting means is set in advance as an operating state in which the engine operating state is such that the amount of increase in the control amount in a predetermined period is larger than the reference increase rate regardless of the state of vapor generation. It is preferable to determine whether or not the engine is in the second specific operation state, and prohibit the determination of the occurrence of the vapor even when the engine operation state is in the second specific operation state.

  In this way, it is possible to more reliably avoid erroneous determination that vapor is generated when the increase rate of the control amount is greater than the reference increase rate due to factors other than vapor.

  In the above configuration, the vapor determination prohibiting means is configured such that the amount of change in the target value of the discharge amount of the high-pressure fuel pump corresponding to the target value of the pressure of the fuel rail is equal to or less than a preset reference discharge amount change rate. It is preferable to determine that the operating state of the engine is the second specific operating state when the state is not continued for a predetermined time or immediately after the engine is started (Claim 4).

  According to this configuration, the target value of the discharge amount of the high-pressure fuel pump has increased rapidly, and the amount of fuel discharged from the high-pressure fuel pump to the fuel rail immediately after the start of the engine must be increased rapidly. Thus, when the control amount increases, it is possible to avoid the determination that vapor is generated, and it is possible to avoid erroneous determination that vapor is generated in these cases. .

  As described above, according to the engine control apparatus of the present invention, it is possible to suppress the erroneous determination that the vapor is generated even though the vapor is not generated, and to determine the generation of the vapor more accurately. can do.

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 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.). In other words, the ECU 100 is electrically connected to the spark plug 10, the injector 11, 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 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 term I calculated in step S5 by the high-pressure side pump control unit 102 (the fuel pressure F / of the high-pressure pump 40 calculated by the high-pressure side pump control unit 102). B amount (feedback amount)) and actual rail pressure etc. are read.

  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, when the determination in step S12 is YES and the vapor determination execution condition is satisfied (when the vapor determination prohibition condition is not satisfied), the process proceeds to step S13.

  In step S13, the low-pressure side pump control unit 104 determines whether or not the vehicle is in steady running. Specifically, in step S13, the low-pressure side pump control unit 104 determines whether or not the engine rotation 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.

  When the determination in step S13 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 S13 is yes and the vehicle is traveling normally, the process proceeds to step S14.

  In step S14, the low-pressure side pump control unit 104 obtains the rate of change (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 S14 is NO, 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. The process ends. On the other hand, if the determination in step S14 is YES and the rate of change of the I term and the actual rail pressure are stable within the allowable values, the process proceeds to step S15.

  In step S15, 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 S15 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 S15 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.

  In step S16, the low pressure side pump control unit 104 determines that vapor is generated in the low pressure side fuel line 22a. Then, the process proceeds to step S17, and the pressure in the low-pressure fuel line 22a is increased by the low-pressure pump 24. Specifically, the low-pressure side pump control unit 104 increases the driving force of the motor that drives 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.

  Moreover, in this embodiment, it determines with the vapor | steam having generate | occur | produced based on the average rate of change of I term (high pressure pump fuel pressure F / B amount). 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 increase 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 temporal changes in rail pressure, I term, and P term 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. This is schematically shown.

  The rail pressure follows the target rail pressure until vapor is generated at time t1. On the other hand, 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 hence 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 or the actual rail pressure is not stable (the 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, It is avoided that the average change rate of the I term is greatly calculated due to the influence of the fluctuation of the rail pressure and the noise accompanying the changes in the engine 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 (vapor determination execution condition)
The 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 S <b> 21, 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 S22, 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 injection amount is the flow rate of the fuel injected from the injector 11 and can be calculated from the 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. 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 S23, the low-pressure side pump control unit 104 determines whether or not the pump failure flag is 1. If the determination in step S23 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 S30. In step S30, it is determined that the vapor determination prohibition condition is satisfied.

  On the other hand, if the determination in step S23 is no, the process proceeds to step S24.

  In step S24, 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 S24 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 S30 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, if the determination in step S24 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 S25.

  In step S25, the low pressure side pump control unit 104 determines whether or not the injection amount is larger than the reference injection amount. The reference injection amount is the minimum 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. When the determination in step S35 is YES and the injection amount is larger than the reference injection amount, the low-pressure side pump control unit 104 proceeds to step S30 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, when the determination in step S25 is NO and the injection amount is equal to or less than the reference injection amount, the low-pressure side pump control unit 104 proceeds to step S26.

  In step S26, the low-pressure side pump control unit 104 determines whether or not the predicted engine room temperature read in step S22 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 S26 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 S30 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, when the determination in step S26 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 S27.

  In step S27, the low-pressure side pump control unit 104 determines whether or not the target high-pressure pump discharge amount calculated in step S21 is unstable. Specifically, it is determined whether or not the state in which the absolute value of the change rate of the target high-pressure pump discharge amount (change amount in a predetermined period) 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 S27 is NO and the rate of change of 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 S30 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, when the determination in step S27 is YES and the target high-pressure pump discharge amount is stable, the low-pressure side pump control unit 104 proceeds to step S28.

  In step S28, the low-pressure side pump control unit 104 determines whether or not the engine is started based on the IG signal read in step S22 (specifically, immediately after the engine is started and during a predetermined time from the start of the engine). Determine whether. If the determination in step S28 is YES and the engine is starting, the low-pressure side pump control unit 104 proceeds to step S30 and determines that the vapor determination prohibition condition is satisfied.

  On the other hand, if the determination in step S28 is NO and the engine is not being started, the low-pressure side pump control unit 104 proceeds to step S29.

  In step S29, 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 S23 to S28 is YES, it is determined that the vapor determination prohibition condition is satisfied (the vapor determination execution condition is not satisfied).

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

(4) Operation and the like As described above, in this embodiment, the discharge amount of the high-pressure pump 40 is PI-controlled based on the deviation of the rail pressure from the target value (target rail pressure). Basically, it is determined that the vapor is generated if the increase rate of the I term calculated when the PI control is performed is larger than the reference increase rate, but the vapor determination prohibition condition set as described above is If established, this determination is stopped. Therefore, it is possible to avoid erroneously determining that vapor is generated even though vapor is not generated, and it is possible to determine the occurrence of vapor more accurately. As a result, the driving force of the low-pressure pump 24 can be further reduced, and the fuel efficiency can be improved. That is, as described above, when the driving force of the low pressure pump 24 is increased when the vapor is generated, if the generation of the 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.

  More specifically, in this embodiment, vapor is not generated (the amount of vapor generated is smaller than a predetermined value) (first specific operation state), that is, the low-pressure side fuel temperature is lower than the minimum guaranteed temperature. In the state where the injection amount is larger than the reference injection amount and the predicted engine room temperature is lower than the reference engine room temperature, vapor determination is prohibited. Therefore, it is possible to avoid erroneous determination that vapor is generated when the increase rate of the I term becomes larger than the reference increase rate due to factors other than vapor in these operating states.

  In this embodiment, the operating state (second specific 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, the change rate of the target high-pressure fuel pump discharge amount is the reference discharge. Vapor determination is prohibited in a state where the state below the amount change rate has not continued for a predetermined time, or when the engine is started (immediately after starting). Therefore, it is possible to avoid erroneous determination that vapor is generated when the increase rate of the I term becomes larger than the reference increase rate due to these operating states. That is, when the target value itself of the high-pressure fuel pump discharge amount increases rapidly (especially when the increase rate of the target value of the high-pressure fuel pump discharge amount increases rapidly), the pressure in the fuel rail 12 is rapidly increased accordingly. It is necessary to calculate a large I term. 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 with the stop of the engine, and the I term is greatly calculated accordingly. 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. In particular, in this embodiment, the state where the absolute value of the change rate of the target high-pressure fuel pump discharge rate is equal to or less than the reference discharge rate change rate has not continued for a predetermined time, and the engine operating state is not stable. Since it is prohibited to judge vapor in possible states, it is possible to avoid misjudging that vapor is generated due to the effects of noise fluctuations, rail pressure fluctuations, etc. due to sudden changes in engine operating conditions. it can.

(5) Modification In the above embodiment, in addition to the case where the vapor is not generated (the first specific operation state), the operation in which the increase rate of the I term is larger than the reference increase rate regardless of the vapor generation state. The case where the vapor determination is prohibited in the state (second specific operation state) has been described, but the vapor determination is prohibited only when the vapor is not generated (first specific operation state). Also good. However, if the determination of vapor is prohibited in both of these operating states, it is possible to avoid erroneous determination that vapor is generated more reliably.

  Further, in the operation state (first specific operation state) in which no vapor is generated (the amount of vapor generated is smaller than a predetermined value), the low-pressure side fuel temperature is lower than the minimum guaranteed temperature, and the injection amount is the reference injection amount. It is not limited to a state where the predicted engine room temperature is lower than the reference engine room temperature. However, since it is clear that vapor does not occur in these states, if the determination of vapor is prohibited in these operating states, it is possible to avoid erroneously determining that vapor has occurred more reliably. Can do.

  In addition, in an operating state (second specific operating state) in which the increase rate of the I term is greater than the reference increase rate regardless of the occurrence of vapor, the change rate of the target high-pressure fuel pump discharge rate is less than or equal to the reference discharge rate change rate. It is not limited to a state where the state does not continue for a predetermined time or when the engine is started. However, in these cases, it is clear that the increase rate of the I term will be larger than the reference increase rate regardless of the occurrence of vapor, so if the vapor judgment is prohibited in these cases, the vapor will be more reliably It is possible to avoid misjudgment that the occurrence has occurred. Also, the change rate of the target high pressure fuel pump discharge amount, which is not an absolute value, is compared with the reference discharge amount change rate, and the change rate of the target high pressure fuel pump discharge amount increases rapidly. The vapor determination may be prohibited when the pressure in the rail 12 needs to be increased rapidly.

  In the above embodiment, the case where the average value of the change rate of the I term and the reference increase rate are compared in step S15 has been described, but the increase rate of the I term and the reference increase rate at each time are compared. Also good.

1 Engine Body 2a Cylinder 12 Fuel Rail 22 Fuel Supply Line 24 Low Pressure Pump (Low Pressure Fuel Pump)
40 High-pressure pump (high-pressure fuel pump)
102 High-pressure side pump control unit (high-pressure side pump control means)
106 Vapor determination unit (vapor determination means)
108 Vapor determination prohibition unit (vapor determination prohibition means)

Claims (4)

An injector, a fuel rail connected to the injector, a fuel supply line connected to the fuel rail, a low-pressure fuel pump for pumping fuel to the fuel supply line, and fuel pumped by the low-pressure fuel pump An engine control device comprising a high-pressure fuel pump for pumping to a fuel rail,
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;
A vapor determination means for determining that the vapor is generated when an increase amount in a predetermined period of a control amount of feedback control performed by the high-pressure side pump control means is larger than a preset reference increase rate;
Vapor determination prohibiting means for prohibiting the determination of the occurrence of vapor by the vapor determination means,
The vapor determination prohibiting means determines whether or not the engine operating state is a first specific operating state preset as an operating state in which the amount of vapor generated in the fuel supply line is less than a predetermined reference amount. An engine control device that determines and prohibits the determination of the occurrence of vapor when the operating state of the engine is in the first specific operating state. The engine control device according to claim 1,
The vapor determination prohibiting means, when the temperature of the fuel flowing through the portion of the fuel supply line between the low pressure fuel pump and the high pressure fuel pump is equal to or lower than a preset minimum guaranteed temperature, When the flow rate of the fuel flowing through the engine is larger than a preset reference flow rate, or when the ambient temperature of the engine body is equal to or lower than a preset reference ambient temperature, the engine operating state is the first specific operating state. A control apparatus for an engine, characterized in that it is determined to be present. The engine control apparatus according to claim 1 or 2,
The vapor determination prohibiting means determines whether or not the engine operating state is a second specific operating state set in advance as an operating state in which the increasing rate of the control amount is greater than the reference increasing rate regardless of the occurrence of vapor. An engine control device characterized by prohibiting the determination of the occurrence of vapor even when the engine operating state is in the second specific operating state. The engine control device according to claim 3,
The vapor determination prohibiting means has a state in which the change amount of the target value of the discharge amount of the high-pressure fuel pump corresponding to the target value of the pressure of the fuel rail is equal to or less than a preset reference discharge amount change rate. An engine control device that determines that the operating state of the engine is the second specific operating state when the engine does not continue for a predetermined time or immediately after the engine is started.

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