Engine control device

Abstract

To provide an engine control device which can avoid the deterioration in drivability caused by the run-out (or shortage) of remaining fuel in a sub-tank though fuel remains in a fuel tank.SOLUTION: An ECU 50 determines whether or not an engine is in an engine operation region in which a surplus fuel quantity which is returned to a jet pump 68 becomes smaller than a prescribed quantity on the basis of an operation state of an engine 10, acquires a remaining fuel quantity in a sub-tank 66 on the basis of a traveling state of a vehicle when the engine enters the engine operation region in which the surplus fuel quantity becomes smaller than the prescribed quantity, acquires an integrated fuel injection amount by integrating a fuel injection amount (consumption amount) after the engine has entered the engine operation region in which the surplus fuel quantity becomes smaller than the prescribed quantity, and limits maximum torque at each engine rotation number of the engine 10 when the remaining fuel quantity in the sub-tank 66 becomes smaller than the integrated fuel injection amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine control device. [Background technology]

[0002] For example, Patent Document 1 discloses a fuel supply system having a fuel tank for storing fuel, a sub-tank (swirl tank) disposed within the fuel tank, a fuel pump disposed within the sub-tank for pressurizing the fuel and sending it to the engine, a return pipe (return pipe) for returning excess fuel (surplus fuel) from the fuel sent from the fuel pump to the sub-tank, and a jet pump installed in the return pipe for transferring fuel stored in the fuel tank to the sub-tank by utilizing the Venturi effect of the excess fuel returned to the sub-tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-53334 Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the engine operating conditions (for example, in a high-speed, high-load range where the fuel injection amount (consumption amount) is large), the fuel injection amount (consumption amount) increases relative to the fuel pump discharge amount (supply amount), which can reduce the amount of fuel returned (excess fuel), causing the jet pump to stop functioning (or functioning poorly), making it impossible to transfer fuel to the sub-tank (or reducing the amount transferred). If the engine continues to operate (consumption of fuel) under such conditions, the amount of fuel in the sub-tank (remaining fuel amount) will decrease.

[0005] Furthermore, the amount of fuel in the sub-tank may change depending on, for example, the vehicle's driving conditions (road gradient, acceleration, etc.) If the remaining fuel in the sub-tank runs out (or becomes too low) and the fuel pump is no longer able to deliver fuel, there is a risk that drivability will deteriorate due to a lack of fuel supply, even if there is fuel remaining in the fuel tank.

[0006] The present invention has been made to solve the above problems, and aims to provide an engine control device that can avoid deterioration of drivability caused by the remaining fuel in the sub-tank running out (or becoming low) even though there is fuel remaining in the fuel tank. [Means for solving the problem]

[0007] An engine control device according to one aspect of the present invention comprises a fuel supply device having a fuel tank for storing fuel, a sub-tank disposed within the fuel tank, a fuel pump disposed within the sub-tank for pressurizing the fuel and sending it to the engine, a return pipe for returning surplus fuel from the fuel pump to the sub-tank, and a jet pump disposed in the return pipe for transferring the fuel stored in the fuel tank to the sub-tank by utilizing the Venturi effect of the surplus fuel returned to the sub-tank; and a control unit for controlling the amount of fuel injection and the amount of intake air of the engine, wherein the control unit determines, based on the operating state of the engine, whether the engine is in an operating range in which the amount of surplus fuel returned to the jet pump is less than a predetermined amount, and when the engine enters the operating range in which the amount of surplus fuel returned to the jet pump is less than the predetermined amount, calculates the amount of remaining fuel in the sub-tank based on the running state of the vehicle, and calculates an accumulated fuel injection amount by accumulating the fuel injection amount since the engine entered the operating range in which the amount of surplus fuel returned to the jet pump is less than the predetermined amount, and when the amount of remaining fuel in the sub-tank is less than the accumulated fuel injection amount, the control unit limits the maximum torque for each engine speed.

[0008] According to one aspect of the present invention, an engine control device determines whether the engine is in an operating range where the amount of surplus fuel returned to the jet pump is less than a predetermined amount based on the engine operating state. When the engine enters the operating range where the amount of surplus fuel is less than the predetermined amount, the amount of remaining fuel in the sub-tank is calculated based on the vehicle's running state, and the fuel injection amount since entering the engine operating range where the amount of surplus fuel is less than the predetermined amount is calculated to calculate an integrated fuel injection amount. When the amount of remaining fuel in the sub-tank falls below the integrated fuel injection amount, the maximum torque for each engine speed of the engine is limited. Therefore, the fuel injection amount decreases (the operating point shifts) due to the torque limit, and the amount of surplus fuel returned to the jet pump increases. This restores the function of the jet pump (the Venturi effect) and transfers fuel to the sub-tank, thereby avoiding deterioration of drivability due to a lack of fuel supply, etc. [Effects of the Invention]

[0009] According to the present invention, it is possible to avoid deterioration of drivability caused by the sub-tank having no (or little) remaining fuel even though there is fuel remaining in the fuel tank. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing the configuration of an engine control device according to an embodiment, and a direct injection engine to which the engine control device is applied; [Figure 2] FIG. 1 is a diagram showing an example of a map showing an engine operating region where the fuel (excess fuel) returned to the jet pump may be insufficient. [Figure 3] FIG. 10 is a diagram showing the relationship between vehicle acceleration and the amount of fuel in the sub-tank (inclination of the liquid level). [Figure 4] 4 is a flowchart showing a processing procedure of a maximum torque limiting process performed by the engine control device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and redundant explanations will be omitted.

[0012] First, the configuration of an engine control device 1 according to the embodiment and a direct injection engine 10 to which the engine control device 1 is applied will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the engine control device 1 and a direct injection engine (hereinafter also simply referred to as "engine") 10 to which the engine control device 1 is applied.

[0013] The engine 10 is, for example, a horizontally opposed four-cylinder gasoline engine. The engine 10 is a direct-injection engine that directly injects fuel into the cylinders. In the engine 10, air is drawn in through an air cleaner 16, throttled by an electronically controlled throttle valve (hereinafter simply referred to as a "throttle valve") 13 provided in an intake pipe 15, and then passes through an intake manifold 11 and is drawn into each cylinder formed in the engine 10. The amount of air drawn in through the air cleaner 16 (the amount of air drawn into the engine 10) is detected by an air flow meter 14 disposed between the air cleaner 16 and the throttle valve 13. A vacuum sensor 30 that detects the pressure inside the intake manifold 11 is disposed inside a collector (surge tank) that constitutes the intake manifold 11. A throttle position sensor 31 that detects the opening of the throttle valve 13 is disposed in the throttle valve 13.

[0014] The cylinder head is formed with an intake port 22 and an exhaust port 23 for each cylinder (only one bank is shown in FIG. 1). Each intake port 22 and exhaust port 23 is provided with an intake valve 24 and an exhaust valve 25 that open and close the intake port 22 and exhaust port 23, respectively. A variable valve timing mechanism 26 is disposed between the intake cam pulley and an intake camshaft 28 that drives the intake valve 24. The variable valve timing mechanism 26 rotates the intake cam pulley and the intake camshaft 28 relative to each other, continuously changing the rotational phase (displacement angle) of the intake camshaft 28 with respect to the crankshaft 10a, thereby advancing or retarding the valve timing (opening / closing timing) of the intake valve 24. The variable valve timing mechanism 26 variably sets the opening and closing timing of the intake valve 24 according to the engine operating conditions.

[0015] Similarly, a variable valve timing mechanism 27 is disposed between the exhaust camshaft 29 and the exhaust cam pulley, which rotates the exhaust cam pulley and the exhaust camshaft 29 relative to each other to continuously change the rotational phase (displacement angle) of the exhaust camshaft 29 relative to the crankshaft 10a, thereby advancing or retarding the valve timing (opening / closing timing) of the exhaust valve 25. The variable valve timing mechanism 27 variably sets the opening / closing timing of the exhaust valve 25 according to the engine operating state.

[0016] An injector 12 that injects fuel into the cylinder is attached to each cylinder of the engine 10. The injector 12 injects fuel pressurized by a high-pressure fuel pump 60 directly into the combustion chamber of each cylinder.

[0017] The injectors 12 are connected to a delivery pipe (common rail) 61. The delivery pipe 61 distributes fuel pumped from a high-pressure fuel pump 60 through a high-pressure fuel pipe 62 to each injector 12. The high-pressure fuel pump 60 pressurizes fuel that is drawn up from a fuel tank 63 by a feed pump (low-pressure fuel pump) 64 (corresponding to a fuel pump in the claims) and supplied through a low-pressure fuel pipe 65 to a high pressure (for example, 8 to 13 MPa) depending on the operating state, and supplies the fuel to the delivery pipe 61. In this embodiment, a type of high-pressure fuel pump 60 that is driven by the camshaft 28 of the engine 10 is used as the high-pressure fuel pump 60.

[0018] Here, a cylindrical sub-tank (reservoir) 66, for example, is disposed inside a fuel tank 63 that stores fuel, and a feed pump 64 is disposed inside the sub-tank 66, which is driven by an electric motor and pressurizes the fuel and sends (supplies) it to the engine 10 (injector 12).

[0019] In addition, a return pipe 67 is connected to the low-pressure fuel pipe 65, which returns surplus fuel (excess fuel) from the fuel sent (supplied) from the feed pump 64 to the engine 10 (injector 12) to the sub-tank 66. A jet pump 68 is installed in the return pipe 67, which transfers fuel stored in the fuel tank 63 to the sub-tank 66 by utilizing the Venturi effect of the surplus fuel returned to the sub-tank 66. The sub-tank 66, the feed pump 64, the return pipe 67, and the jet pump 68 constitute a fuel supply device described in the claims. Note that these components may be publicly known.

[0020] The cylinder head of each cylinder is fitted with a spark plug 17 that ignites the air-fuel mixture, and an igniter-integrated coil 21 that applies high voltage to the spark plug 17. In each cylinder of the engine 10, the air-fuel mixture of intake air and fuel injected by the injector 12 is ignited by the spark plug 17 and combusted. Exhaust gas after combustion is discharged through an exhaust pipe 18.

[0021] An air-fuel ratio sensor 19A that outputs a signal corresponding to the oxygen concentration in the exhaust gas is attached to the exhaust pipe 18. A linear air-fuel ratio sensor (LAF sensor) that can linearly detect the exhaust air-fuel ratio is used as the air-fuel ratio sensor 19A. Note that an O2 sensor that detects the exhaust air-fuel ratio in an on-off manner may also be used as the air-fuel ratio sensor 19A.

[0022] Further, an exhaust purification catalyst (CAT) 20 is disposed downstream of the air-fuel ratio sensor 19A. The exhaust purification catalyst 20 is a three-way catalyst that simultaneously oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and reduces nitrogen oxides (NOx), thereby purifying harmful gas components in the exhaust gas into harmless carbon dioxide (CO2), water vapor (H2O), and nitrogen (N2). Downstream of the exhaust purification catalyst 20, a rear (after CAT) O2 sensor 19B is provided that detects the exhaust air-fuel ratio on and off.

[0023] In addition to the air flow meter 14, LAF sensor 19A, O2 sensor 19B, vacuum sensor 30, and throttle opening sensor 31 described above, a cam angle sensor 32 for identifying the cylinders of the engine 10 is attached near the camshaft 28 of the engine 10. Here, the cam angle sensor 32 outputs an electrical signal that indicates the rotational position of the camshaft 28, and also outputs an electrical signal that indicates the rotational position of a pump drive cam of the high-pressure fuel pump 60, which rotates in conjunction with the rotation of the camshaft 28.

[0024] A crank angle sensor 33 that detects the rotational position of crankshaft 10a is attached near crankshaft 10a of engine 10. Here, a timing rotor 33a having, for example, 34 protrusions with two teeth missing and spaced at 10° intervals is attached to the end of crankshaft 10a, and crank angle sensor 33 detects the rotational position of crankshaft 10a by detecting the presence or absence of the protrusions on timing rotor 33a. The cam angle sensor 32 and crank angle sensor 33 may be, for example, electromagnetic pickup types.

[0025] These sensors are connected to the ECU 50. Also connected to the ECU 50 are various sensors, such as a water temperature sensor 34 that detects the temperature of the engine 10's coolant, an oil temperature sensor 35 that detects the temperature of the lubricating oil, an accelerator operation amount sensor 36 that detects the amount of accelerator pedal depression, i.e., the accelerator pedal operation amount, and an intake air temperature sensor 37 that detects the intake air temperature. Also connected to the ECU 50 are a fuel pressure sensor 38 attached to the delivery pipe 61, for example, that detects the pressure of the fuel supplied to the injector 12 (fuel pressure boosted by the high-pressure fuel pump 60), and a fuel gauge 39 that detects the amount of fuel (fuel level) stored in the fuel tank 63. The fuel gauge 39 may be, for example, a type that has an arm attached to a float floating in the fuel tank 63 and detects the position of the float (i.e., the amount of fuel) as a change in electrical resistance. Alternatively, a capacitance-type sensor or the like may be used as the fuel gauge 39.

[0026] The ECU 50 is connected to a vehicle dynamics control unit (hereinafter referred to as "VDCU") 70 and the like via a CAN (Controller Area Network) 100, for example, so as to be able to communicate with each other.

[0027] The VDCU 70 is connected to a brake switch 71 that detects whether the brake pedal is depressed or not, and a brake fluid pressure sensor 72 that detects the master cylinder pressure (brake hydraulic pressure) of the brake actuator. Also connected to the VDCU 70 are a wheel speed sensor 73 that detects the rotational speed of each wheel of the vehicle (vehicle speed), and a steering angle sensor 75 that detects the turning angle of the front wheels (i.e., the steering angle of the steering wheel) by detecting the rotation angle of the pinion shaft. Furthermore, the VDCU 70 is also connected to a longitudinal acceleration sensor 76 that detects the longitudinal acceleration acting on the vehicle, a lateral acceleration sensor 77 that detects the lateral acceleration acting on the vehicle (vehicle width direction), etc.

[0028] Here, for example, the road surface gradient can be detected based on the difference between a corrected acceleration sensor value obtained by adding a zero-point learning value to the longitudinal acceleration of the vehicle detected using the longitudinal acceleration sensor 76 and a derivative value of the vehicle speed. The road surface gradient can also be estimated based on the driving force calculated from the output torque of the engine 10, the vehicle acceleration calculated from the derivative value of the vehicle speed, and a preset vehicle weight.

[0029] The VDCU 70 drives the brake actuator in accordance with the amount of brake pedal operation (amount of depression) to brake the vehicle, and detects vehicle behavior using various sensors (e.g., wheel speed sensor 73, steering angle sensor 75, longitudinal acceleration sensor 76, lateral acceleration sensor 77, yaw rate sensor, etc.), and suppresses skidding and ensures vehicle stability when cornering by controlling the brakes through automatic pressure application and torque control of the engine 10.

[0030] The VDCU 70 transmits detected braking information (brake operation information) such as brake switch 71 and brake fluid pressure, wheel speed (vehicle speed), longitudinal acceleration, lateral acceleration, road surface gradient, etc. to the ECU 50 via the CAN 100.

[0031] The ECU 50 is configured to include a microprocessor that performs calculations, an EEPROM that stores programs and the like for causing the microprocessor to execute various processes, a RAM that stores various data such as calculation results, a backup RAM in which the stored contents are maintained by a 12V battery, an input / output I / F, etc. The ECU 50 also includes an injector driver that drives the injector 12, an output circuit that outputs an ignition signal, and a motor driver that drives the electric motor 13a that opens and closes the electronically controlled throttle valve 13. The ECU 50 also includes a driver that drives an electromagnetic valve that constitutes the high-pressure fuel pump 60, etc.

[0032] The ECU 50 identifies the cylinder from the output of the cam angle sensor 32, and determines the engine speed from the output of the crank angle sensor 33. The ECU 50 also acquires various information such as the intake air amount, intake pipe negative pressure, accelerator pedal operation amount, air-fuel ratio of the mixture, intake air temperature, and water temperature and oil temperature of the engine 10 based on detection signals input from the various sensors described above. The ECU 50 also receives braking information (brake operation information) such as brake switch 71 and brake fluid pressure, wheel speed (vehicle speed), longitudinal acceleration, lateral acceleration, road gradient, etc. via the CAN 100.

[0033] Based on the acquired information, the ECU 50 controls various devices such as the fuel injection amount, fuel injection timing, ignition timing, and throttle valve 13 (intake air amount), thereby comprehensively controlling the engine 10. In other words, the ECU 50 functions as a control unit as defined in the claims.

[0034] In particular, the ECU 50 has a function to avoid deterioration of drivability caused by the sub-tank 66 running out of (or becoming low in) fuel even though there is fuel remaining in the fuel tank 63. In the ECU 50, this function is realized by a microprocessor executing a program stored in an EEPROM or the like.

[0035] First, the ECU 50 determines, based on the operating state of the engine 10, whether or not the engine is in an operating region (hereinafter referred to as a "starved fuel operating region") where the amount of surplus fuel returned to the jet pump 68 (the amount of fuel returned) is less than a predetermined amount (the jet pump 68 may no longer function). In other words, the ECU 50 determines whether or not the operating point of the engine 10 is in an operating region where the fuel injection amount (amount consumed) is large relative to the fuel pump discharge amount (amount supplied), the amount of fuel returned (amount of surplus fuel) is reduced, the venturi effect of the jet pump 68 is reduced (performance is reduced), and fuel cannot be transferred to the sub-tank 66 (or the amount transferred is less than the amount consumed).

[0036] More specifically, the ECU 50 determines whether the engine is in an operating range (starved fuel operating range) in which the amount of excess fuel (returned amount of fuel) returned to the jet pump 68 is less than a predetermined amount (the jet pump 68 may stop functioning) based on the engine speed and intake air amount (load, boost pressure) or the engine speed and fuel injection amount (fuel injection time).

[0037] An example of a map showing an operating range of engine 10 where the fuel returned to jet pump 68 (excess fuel) may be insufficient is shown in Figure 2. The horizontal axis of Figure 2 represents engine speed (rpm), and the vertical axis represents the fuel injection pulse width (ms) applied to injector 12, i.e., the valve opening time of injector 12 (fuel injection time ∝ fuel injection amount). As shown in Figure 2, in an operating range where the fuel injection amount (consumption amount) is large, such as a high-speed, high-load range, the fuel injection amount (consumption amount) increases relative to the fuel pump discharge amount (supply amount), thereby reducing the amount of fuel returned (excess fuel). This may cause jet pump 68 to stop functioning (or functioning poorly), making it impossible to transfer fuel to sub-tank 66 (or reducing the amount transferred).

[0038] Next, when the engine enters an engine operating range (starved fuel operating range) in which the amount of excess fuel (returned amount of fuel) returned to the jet pump 68 becomes less than a predetermined amount, the ECU 50 calculates the amount of remaining fuel in the sub-tank 66 (when the engine enters the starved fuel operating range) based on the vehicle's running state.

[0039] The relationship between vehicle acceleration and the amount of fuel in the sub-tank 66 (inclination of the liquid level) is shown in Figure 3. For example, in Figure 3, when the vehicle accelerates to the left (for example, forward), the fuel is biased to the right (for example, rearward), causing the liquid level of the fuel to incline so that the right side is higher. Depending on the magnitude of the acceleration, the fuel may overflow from the edge of the sub-tank 66.

[0040] Therefore, when the vehicle enters the fuel starvation operating range, the ECU 50 calculates the amount of remaining fuel in the sub-tank 66 based on the gradient of the road on which the vehicle is traveling and the acceleration of the vehicle. At that time, the ECU 50 calculates the amount of remaining fuel in the sub-tank 66 by using, for example, a map that defines the relationship between the gradient of the road, the acceleration of the vehicle, and the liquid level angle of the fuel in the sub-tank 66.

[0041] In addition, the ECU 50 calculates the accumulated fuel injection amount (consumption amount) by accumulating the fuel injection amount (consumption amount) after the engine enters an operating range (starved fuel operating range) in which the amount of excess fuel (return amount of fuel) returned to the jet pump 68 becomes less than a predetermined amount.

[0042] More specifically, the ECU 50 sets the fuel injection amount based on the operating state of the engine 10, and calculates the current value of the integrated fuel injection amount (consumption amount) by adding the current fuel injection amount (consumption amount) to the previous value of the integrated fuel injection amount (consumption amount). Here, the fuel injection amount Ginj injected by the injector 12 (or the valve opening time of the injector 12 for fuel injection) is determined by the following equation (1). Ginj = GF × α + β (1) GF is a basic fuel injection amount that is set based on the intake air amount and engine speed. A map (basic fuel injection amount map) that defines the relationship between the intake air amount, engine speed, and basic fuel injection amount GF is stored in the ECU 50 (EEPROM, etc.). The final fuel injection amount Ginj is determined by correcting this basic fuel injection amount GF with various correction coefficients α and β.

[0043] Then, when the amount of remaining fuel in the sub-tank 66 becomes less than the cumulative fuel injection amount (consumption amount), the ECU 50 limits the maximum torque for each engine rotation speed of the engine 10. More specifically, the ECU 50 controls the throttle valve 13, for example, to close it. That is, the ECU 50 moves the operating point of the engine 10 out of an operating region where the amount of returned fuel may be insufficient (starved fuel operating region). Such torque limitation (movement of the operating point) reduces the fuel injection amount, increases the amount of surplus fuel returned to the jet pump 68, and restores the function of the jet pump 68 (venturi effect).

[0044] On the other hand, after the engine operation range (starved fuel operation range) in which the amount of excess fuel (returned fuel amount) returned to the jet pump 68 falls below a predetermined amount (the jet pump 68 may stop functioning) has fallen out of place, the ECU 50 calculates the amount of fuel (including the returned fuel amount) transferred from the fuel tank 63 to the sub-tank 66 by the jet pump 68 based on the returned fuel amount (excess fuel amount) calculated according to the operating state of the engine 10 (engine speed, intake air amount), and calculates the accumulated fuel transfer amount by integrating this fuel amount. Note that the returned fuel amount (returned amount) can be calculated using, for example, a map (fuel return amount map) that defines the relationship between the engine speed, intake air amount, and returned fuel amount, and the various correction coefficients α and β described above.

[0045] Then, when the cumulative fuel transfer amount becomes equal to or exceeds a predetermined amount (set in consideration of the capacity of the sub-tank 66), the ECU 50 cancels the maximum torque limit (torque guard) for each engine speed of the engine 10 (returns to normal control). In other words, the ECU 50 cancels the maximum torque limit of the engine 10 when the amount of fuel in the sub-tank 66 is restored.

[0046] Next, the operation of the engine control device 1 will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the procedure of maximum torque limiting processing by the engine control device 1. This processing is executed mainly by the ECU 50 repeatedly at predetermined timings.

[0047] In step S100, a determination is made based on the operating state of the engine 10 (engine speed and intake air amount, or engine speed and fuel injection amount (fuel injection time)) as to whether or not the engine is in an operating range (starved fuel operating range) in which the amount of excess fuel (returned fuel amount) returned to the jet pump 68 is less than a predetermined amount (the jet pump 68 may stop functioning). If the operating range is not starved fuel, the process temporarily exits. On the other hand, if the operating range is starved fuel, the process proceeds to step S102. The method for determining whether or not the operating range is starved fuel is as described above, and a detailed description thereof will be omitted here.

[0048] When the vehicle enters the fuel starvation operating region, in step S102, the amount of remaining fuel in the sub-tank 66 is calculated based on the vehicle's running conditions (road gradient, vehicle acceleration). Note that the method for calculating the amount of remaining fuel in the sub-tank 66 is as described above, and therefore a detailed explanation will be omitted here.

[0049] Next, in step S104, the fuel injection amount (consumption amount) after entering the fuel starvation operation region is integrated to obtain the integrated fuel injection amount (consumption amount). Note that the method for obtaining the integrated fuel injection amount is as described above, and therefore a detailed description thereof will be omitted here.

[0050] Next, in step S106, it is determined whether the amount of remaining fuel in the sub-tank 66 is less than the integrated fuel injection amount. If the amount of remaining fuel in the sub-tank 66 is less than the integrated fuel injection amount, the process proceeds to step S108. On the other hand, if the amount of remaining fuel in the sub-tank 66 is not less than the integrated fuel injection amount, the process proceeds to step S107.

[0051] In step S107, it is determined whether or not the engine is in the fuel-starved operating range. If the engine is not in the fuel-starved operating range, the process temporarily exits. On the other hand, if the engine is in the fuel-starved operating range, the process proceeds to step S104, and the above-described steps S104 to S106 are executed again (repeatedly).

[0052] In step S108, the maximum torque for each engine speed of the engine 10 is limited. For example, the throttle valve 13 is driven to the closing side, and the amount of intake air is reduced.

[0053] Next, in step S110, a determination is made as to whether the engine has left an operating range (starved fuel operating range) in which the amount of excess fuel returned to the jet pump 68 (the amount of fuel returned) becomes less than a predetermined amount (the jet pump 68 may stop functioning). If the engine has not left the starved fuel operating range, the process proceeds to step S108, and the processes of steps S108 to S110 described above are executed again (repeatedly). On the other hand, if the engine has left the starved fuel operating range, the process proceeds to step S112.

[0054] In step S112, the amount of fuel (including the amount of fuel returned) transferred from the fuel tank 63 to the sub-tank 66 by the jet pump 68 is calculated based on the amount of fuel returned (excess fuel amount) calculated according to the operating state of the engine 10, and this amount of fuel is accumulated to calculate the accumulated fuel transfer amount.

[0055] Next, in step S114, it is determined whether the cumulative fuel transfer amount is equal to or greater than a predetermined amount. If the cumulative fuel transfer amount is not equal to or greater than the predetermined amount, the process proceeds to step S112, and the processes of steps S112 to S114 described above are executed again (repeatedly). On the other hand, if the cumulative fuel transfer amount is equal to or greater than the predetermined amount, the process proceeds to step S116.

[0056] In step S116, the maximum torque limit (torque guard) for each engine speed of the engine 10 is released. That is, the control returns to normal control. Then, the process exits from this process.

[0057] As described above in detail, according to this embodiment, it is determined whether the engine is in an engine operating range (starved fuel operating range) where the amount of surplus fuel returned to the jet pump 68 is less than a predetermined amount based on the operating state of the engine 10. When the engine enters the starved fuel operating range, the amount of remaining fuel in the sub-tank 66 is calculated based on the running state of the vehicle, and the fuel injection amount since entering the starved fuel operating range is integrated to calculate the integrated fuel injection amount. When the amount of remaining fuel in the sub-tank 66 falls below the integrated fuel injection amount, the maximum torque of the engine 10 for each engine rotation speed is limited. Therefore, the fuel injection amount decreases (the operating point moves) as the torque is limited, and the amount of surplus fuel returned to the jet pump 68 increases. This restores the function (Venturi effect) of the jet pump 68, allowing fuel to be transferred to the sub-tank 66, thereby preventing deterioration in drivability due to a lack of fuel supply, etc.

[0058] As a result, according to this embodiment, it is possible to avoid deterioration of drivability caused by the sub-tank 66 having no (or little) remaining fuel even though there is fuel remaining in the fuel tank 63.

[0059] In this case, according to this embodiment, it is possible to appropriately determine whether the engine is in an operating range (starved fuel operating range) where the amount of excess fuel (returned amount of fuel) returned to the jet pump 68 is less than a predetermined amount (i.e., the jet pump 68 may stop functioning) based on the engine speed and intake air amount (load, boost pressure) or the engine speed and fuel injection amount (time).

[0060] Furthermore, according to this embodiment, the amount of remaining fuel in the sub-tank 66 can be appropriately determined based on the gradient of the road surface on which the vehicle is traveling and the acceleration of the vehicle when the vehicle enters the fuel starvation operating range.

[0061] Furthermore, according to this embodiment, the current fuel injection amount is added to the previous value of the cumulative fuel injection amount to calculate the current value of the cumulative fuel injection amount, so that the cumulative fuel injection amount (consumption amount) after entering the fuel-starved operating region can be appropriately determined.

[0062] According to this embodiment, after the engine 10 leaves the fuel starvation operating region, the amount of fuel (including the amount of returned fuel) transferred from the fuel tank 63 to the sub-tank 66 by the jet pump 68 is calculated based on the amount of returned fuel (excess fuel amount) calculated according to the operating state of the engine 10, and the amount of fuel is integrated to calculate the integrated fuel transfer amount, and when the integrated fuel transfer amount becomes equal to or greater than a predetermined amount, the maximum torque limit of the engine 10 is released. Therefore, when the amount of fuel in the sub-tank 66 is restored, the maximum torque limit for each engine speed can be appropriately released (ended).

[0063] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, a direct injection engine has been described as an example of engine 10, but engine 10 may be a port injection engine. Furthermore, engine 10 may be one that uses a combination of in-cylinder injection injectors and port injection injectors. Furthermore, in the above embodiments, a naturally aspirated (NA) engine has been described as an example of engine 10, but engine 10 may be an engine equipped with a supercharger (such as a turbocharger).

[0064] Furthermore, in the above embodiment, the present invention is applied to a conventional engine vehicle, but the present invention can also be applied to, for example, an engine for a hybrid vehicle (HEV).

[0065] Furthermore, the system configuration of the control units such as ECU 50 and VDCU 70, and the allocation of functions among the control units are not limited to those in the above embodiment. For example, in the above embodiment, the longitudinal acceleration sensor 76, the lateral acceleration sensor 77, etc. are connected to the VDCU 70, and the read longitudinal acceleration and lateral acceleration are transmitted to the ECU 50 via the CAN 100. However, the longitudinal acceleration sensor 76, the lateral acceleration sensor 77, etc. may be directly connected to (input from) the ECU 50. Furthermore, the ECU 50 and the VDCU 70 may be configured as an integrated piece of hardware.

[0066] Further, when the amount of fuel (fuel level) in the fuel tank 63 is less than a predetermined amount (the fuel level is equal to or lower than the height of the sub-tank 66), the above control (maximum torque limiting process) may be executed. [Explanation of symbols]

[0067] 1 Engine control device 10 Engine 12 injectors 38 Fuel pressure sensor 39 Fuel gauge 50 ECU 60 High-pressure fuel pump 61 Delivery Pipe 62 High-pressure fuel pipe 63 Fuel Tank 64 Feed pump (low pressure fuel pump) 65 Low pressure fuel piping 66 Subtank (reservoir) 67 Return pipe 68 Jet Pump 70 VDCU 71 Brake switch 72 Brake fluid pressure sensor 73 Wheel speed sensor 75 Steering angle sensor 76 Front and rear acceleration sensor 77 Lateral acceleration sensor 100 CAN

Claims

1. a fuel supply device including a fuel tank for storing fuel, a sub-tank disposed within the fuel tank, a fuel pump disposed within the sub-tank for pressurizing fuel and sending it to an engine, a return pipe for returning surplus fuel sent from the fuel pump to the engine to the sub-tank, and a jet pump disposed in the return pipe for transferring fuel stored in the fuel tank to the sub-tank by utilizing a Venturi effect caused by the surplus fuel returned to the sub-tank; a control unit for controlling a fuel injection amount and an intake air amount of the engine, The control unit includes: determining whether the engine is in an operating region where an amount of surplus fuel returned to the jet pump is less than a predetermined amount based on an operating state of the engine; When the engine enters an engine operating region in which the amount of surplus fuel returned to the jet pump becomes less than a predetermined amount, the amount of remaining fuel in the sub-tank is calculated based on a running state of the vehicle; calculating an integrated fuel injection amount by integrating a fuel injection amount after the engine enters an operating region where the amount of surplus fuel returned to the jet pump becomes less than a predetermined amount; When the amount of remaining fuel in the sub-tank becomes less than the integrated fuel injection amount, the maximum torque for each engine revolution speed of the engine is limited. An engine control device comprising:

2. 2. The engine control device according to claim 1, wherein the control unit determines whether the engine is in an operating range in which the amount of surplus fuel returned to the jet pump is less than a predetermined amount, based on the engine speed and the amount of intake air, or the engine speed and the amount of fuel injection.

3. 3. The engine control device according to claim 2, wherein the control unit determines the amount of remaining fuel in the sub-tank based on a gradient of a road surface on which the vehicle is traveling and an acceleration of the vehicle when the engine enters an engine operating region in which the amount of surplus fuel returned to the jet pump becomes less than a predetermined amount.

4. 4. The engine control device according to claim 3, wherein the control unit sets a fuel injection amount based on an operating state of the engine, and calculates a current value of the integrated fuel injection amount by adding a current fuel injection amount to a previous value of the integrated fuel injection amount.

5. 5. The engine control device according to claim 4, wherein after the engine operating range falls outside a range in which the amount of surplus fuel returned to the jet pump becomes less than a predetermined amount, the control unit calculates an amount of fuel transferred from the fuel tank to the sub-tank by the jet pump based on the amount of surplus fuel, and calculates an integrated fuel transfer amount by integrating the fuel amount, and when the integrated fuel transfer amount becomes equal to or greater than a predetermined amount, releases the maximum torque limit for each engine speed of the engine.

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