JP2009215959A - Fuel supply device for internal combustion engine - Google Patents

Abstract

In a fuel supply apparatus for an internal combustion engine, by suppressing hunting of fuel pressure, variation in air-fuel ratio is suppressed, and emission can be prevented from deteriorating.
A feed pump (fuel pumping means) 83 that pressurizes and pumps fuel as low-pressure fuel, a high-pressure fuel pump (pressurizer) 85 that boosts low-pressure fuel and pumps it as high-pressure fuel, and a feed pump 83 High-pressure chamber 103 as a fuel passage through which low-pressure fuel passes without being pressurized by high-pressure fuel pump 85, injectors (fuel injection means) 62, 63 for injecting low-pressure fuel or high-pressure fuel into combustion chambers 22, 23, and engine operation Depending on the state, an ECU (fuel control means) 70 for controlling the stop and operation of the low pressure fuel by the high pressure fuel pump 85 is provided. When the ECU 70 switches the high pressure fuel pump 85 from the stop state to the operation state, the vehicle When it is determined that the vehicle is in the slow acceleration state, the switching is canceled.
[Selection] Figure 1

Description

  The present invention relates to a fuel supply device for an internal combustion engine capable of boosting low-pressure fuel into high-pressure fuel and injecting the high-pressure fuel into a combustion chamber of the internal combustion engine.

  2. Description of the Related Art In-cylinder injection internal combustion engines that directly inject fuel into a combustion chamber (cylinder) instead of an intake port are known for internal combustion engines such as gasoline engines and diesel engines mounted on vehicles such as passenger cars and trucks. . In this direct injection internal combustion engine, when the intake valve is opened, air is sucked into the combustion chamber from the intake port, and during this intake stroke or during the compression stroke in which the piston rises to compress the intake air, the fuel injection valve burns. Inject fuel directly into the chamber. Then, high-pressure air and mist-like fuel are mixed in the combustion chamber, and the spark plug ignites and explodes with respect to this air-fuel mixture, and the exhaust gas is discharged from the intake port when the exhaust valve is opened.

  In such a fuel system in a direct injection internal combustion engine, in order to atomize the fuel, the fuel in the fuel tank is pumped up by an electric low pressure fuel pump and pressurized to a predetermined low pressure, and the low pressure fuel is injected into the internal combustion engine. The high pressure fuel is pressurized by a high pressure fuel pump, the high pressure fuel is stored in a delivery pipe, and is injected into each combustion chamber by a plurality of fuel injection valves attached to the delivery pipe. In such a high-pressure fuel pump, the plunger is reciprocated by a cam interlocking with the crankshaft to pressurize the fuel. In this case, the reciprocating movement of the plunger has a suction stroke that moves in a direction that increases the volume of the pressure chamber, and a pressure-feed stroke that moves in a direction that decreases the volume of the pressure chamber. A metering valve is provided in the fuel intake passage that communicates with the pressure chamber. By opening the metering valve during the intake stroke, fuel is sucked into the pressure chamber through the fuel intake passage. By closing the metering valve, the fuel in the pressure chamber is discharged after being pressurized to a predetermined pressure, and by controlling the opening / closing timing of the metering valve, the discharge amount of high-pressure fuel can be adjusted. it can.

  In the fuel system in the above-described cylinder injection internal combustion engine, the plunger is reciprocated by a cam interlocked with the crankshaft, so that the position of the plunger corresponding to the crank angle is detected, and the metering valve is opened and closed accordingly. By setting the timing, proper fuel metering is possible. However, in a relatively quiet operating state such as an idling operation of the internal combustion engine, there is a problem that the operation noise accompanying the opening and closing of the metering valve becomes remarkable and silence is hindered.

  Therefore, for example, in Patent Document 1 below, two high-pressure fuel pumps 30 for boosting low-pressure fuel are provided, and when the required fuel amount of the internal combustion engine is small, the operation of one of the two high-pressure fuel pumps is stopped, By reducing the frequency of operation of the entire fuel pump during a predetermined period and reducing the frequency of operation of the electromagnetic spill valve, the operating noise of the high-pressure fuel pump associated with the opening / closing operation is reduced.

JP 2002-213326 A

  In the above-described conventional fuel supply device for an internal combustion engine, the operation region of the internal combustion engine is divided into two regions based on the rotational speed and the load, and one high-pressure fuel is used when the engine is in the low load region at a low rotational speed. The pump is stopped. However, when the operation and stop of the high-pressure fuel pump are controlled at the boundary set by the rotational speed and the load in this way, for example, when the vehicle is subjected to slow acceleration intermittently due to traffic congestion, The stop is intermittent. Then, there is a problem that hunting of the fuel pressure occurs, the air-fuel ratio varies, and the emission deteriorates.

  The present invention solves such a problem, and provides a fuel supply device for an internal combustion engine that suppresses fuel pressure hunting to suppress variations in air-fuel ratio and prevent emission deterioration. For the purpose.

  In order to solve the above-described problems and achieve the object, a fuel supply device for an internal combustion engine according to the present invention includes a fuel pumping unit that pressurizes fuel and pumps it as low-pressure fuel, and a low-pressure pumped by the fuel pumping unit. Boosting means for boosting fuel and pumping it as high-pressure fuel, a fuel passage through which low-pressure fuel from the fuel pumping means is not boosted by the boosting means, and fuel injection for injecting low-pressure fuel or high-pressure fuel into the combustion chamber A fuel supply device for an internal combustion engine, wherein the fuel control means includes the boosting device, and a fuel control device that controls the stoppage and operation of the boosting of the low-pressure fuel by the boosting device according to the operating state of the internal combustion engine. When the means is switched between the stopped state and the driving state, the switching is canceled when it is determined that the vehicle is in the slow acceleration state or the slow deceleration state. .

  In the fuel supply device for an internal combustion engine according to the present invention, the fuel control means determines a slow acceleration state or a slow deceleration state of the vehicle based on a change rate and a change amount of the engine load.

  In the fuel supply apparatus for an internal combustion engine according to the present invention, the fuel control means determines a slow acceleration state or a slow deceleration state of the vehicle based on a travel stop state of the vehicle.

  In the fuel supply apparatus for an internal combustion engine according to the present invention, the fuel control means may be configured such that, when the boosting means is in an operating state, when the engine load is determined to be lower than a preset first predetermined value, the boosting means Is switched to a stopped state.

  In the fuel supply device for an internal combustion engine according to the present invention, the fuel control means is configured such that when the boosting means is in a stopped state, the vehicle is not in a running state, and the rate of change and the amount of change in the engine load are preset. 2 It is characterized in that when it is determined that the value is higher than a predetermined value, the boosting means is switched to an operating state.

  According to the fuel supply apparatus for an internal combustion engine of the present invention, when the boosting means for the low pressure fuel is switched between the stopped state and the operating state, the switching is canceled when it is determined that the vehicle is in the slow acceleration state or the slow deceleration state. Therefore, frequent switching between operation and stop in the boosting means is eliminated, and hunting of fuel pressure is suppressed, thereby suppressing variations in the air-fuel ratio and preventing emission from deteriorating.

  Embodiments of a fuel supply device for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this Example.

  FIG. 1 is a schematic configuration diagram showing a fuel system in a fuel supply device for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view of a main part of the internal combustion engine of the present embodiment. 3-2 is a schematic diagram showing a high-pressure fuel pump in the fuel supply apparatus for an internal combustion engine of the present embodiment, and FIG. 4 is a flowchart showing operation control of the fuel supply apparatus for the internal combustion engine of the present embodiment.

  In the present embodiment, a V-type 6-cylinder gasoline engine having an in-cylinder fuel injection device is applied as the internal combustion engine. In this V-type 6-cylinder engine (hereinafter simply referred to as an engine), as shown in FIG. 2, the cylinder block 11 has left and right banks 12 and 13 inclined at a predetermined angle at the upper portion. Three cylinder bores 14 and 15 are formed in the cylinders 12 and 13, respectively, and pistons 16 and 17 are fitted to the cylinder bores 14 and 15 so as to be movable up and down. A crankshaft (not shown) is rotatably supported at the lower part of the cylinder block 11, and the pistons 16 and 17 are connected to the crankshaft via connecting rods 18 and 19, respectively.

  On the other hand, cylinder heads 20 and 21 are fastened to the upper portions of the banks 12 and 13 of the cylinder block 11, and the combustion chambers 22 and 23 are constituted by the cylinder block 11, the pistons 16 and 17, and the cylinder heads 20 and 21. ing. The intake ports 24 and 25 and the exhaust ports 26 and 27 are formed on the upper portions of the combustion chambers 22 and 23, that is, the lower surfaces of the cylinder heads 20 and 21 so as to face each other. 27, the lower end portions of the intake valves 28 and 29 and the exhaust valves 30 and 31 are located. The intake valves 28 and 29 and the exhaust valves 30 and 31 are supported by the cylinder heads 20 and 21 so as to be movable in the axial direction, and are attached in a direction to close the intake ports 24 and 25 and the exhaust ports 26 and 27. It is supported. Further, intake camshafts 32 and 33 and exhaust camshafts 34 and 35 are rotatably supported on the cylinder heads 20 and 21, and the intake cams 36 and 37 and the exhaust cams 38 and 39 are interposed via a roller rocker arm (not shown). Are in contact with the upper ends of the intake valves 28 and 29 and the exhaust valves 30 and 31.

  Accordingly, when the intake camshafts 32 and 33 and the exhaust camshafts 34 and 35 rotate in synchronization with the engine, the intake cams 36 and 37 and the exhaust cams 38 and 39 operate the roller rocker arm, and the intake valves 28 and 29 and the exhaust valve 30 and 31 move up and down at a predetermined timing to open and close intake ports 24 and 25 and exhaust ports 26 and 27, intake ports 24 and 25 and combustion chambers 22 and 23, combustion chambers 22 and 23, and exhaust port 26. , 27 can communicate with each other.

  In addition, the valve mechanism of this engine is a variable intake valve timing mechanism (VVT) 40 that controls the intake valves 28 and 29 and the exhaust valves 30 and 31 at an optimal opening / closing timing according to the operating state. 41 and an exhaust variable valve mechanism 42, 43. The intake variable valve operating mechanisms 40 and 41 and the exhaust variable valve operating mechanisms 42 and 43 are configured, for example, by providing VVT controllers at the shaft end portions of the intake camshafts 32 and 33 and the exhaust camshafts 34 and 35. The opening / closing timing of the intake valves 28, 29 and the exhaust valves 30, 31 is advanced or retarded by changing the phase of each camshaft 32, 33, 34, 35 with respect to the cam sprocket by a pump (or electric motor). It is something that can be done. In this case, each variable valve mechanism 40, 41, 42, 43 advances or retards the opening / closing timing with the operating angle (opening period) of intake valves 28, 29 and exhaust valves 30, 31 being constant. The intake camshafts 32, 33 and the exhaust camshafts 34, 35 are provided with cam position sensors 44, 45, 46, 47 for detecting their rotational phases.

  A surge tank 50 is connected to the intake ports 24 and 25 of the cylinder heads 20 and 21 via intake manifolds 48 and 49, and an intake pipe 51 is connected to the surge tank 50. An air cleaner 52 is attached to the intake port. The intake pipe 51 is provided with an electronic throttle device 53 having a throttle valve located on the downstream side of the air cleaner 52. On the other hand, exhaust pipes 56, 57 are connected to the exhaust ports 26, 27 via exhaust manifolds 54, 55. The exhaust pipes 56, 57 are joined by an exhaust collecting pipe 58 and are connected to the exhaust pipes 56, 57. The original catalysts 59 and 60 are attached, and the NOx occlusion reduction type catalyst 61 is attached to the exhaust collecting pipe 58.

  The cylinder heads 20 and 21 are each provided with injectors 62 and 63 for injecting fuel (gasoline) directly into the combustion chambers 22 and 23. The injectors 62 and 63 are attached to delivery pipes 64 and 65, respectively. ing. Therefore, the injectors 62 and 63 can inject the high-pressure fuel stored in the delivery pipes 64 and 65 into the combustion chambers 22 and 23. The cylinder heads 20 and 21 are equipped with spark plugs 66 and 67 that are located above the combustion chambers 22 and 23 and ignite the air-fuel mixture.

  By the way, the vehicle is equipped with an electronic control unit (ECU) 70, which can control the fuel injection timing of each injector 62, 63, the ignition timing of the spark plugs 66, 67, and the like. A fuel injection amount, a fuel injection timing, an ignition timing, and the like are determined based on the detected engine operation state such as the intake air amount, intake air temperature, throttle opening, accelerator opening, engine speed, and coolant temperature.

  That is, an airflow sensor 71 and an intake air temperature sensor 72 are mounted on the upstream side of the intake pipe 51, and the measured intake air amount and intake air temperature are output to the ECU 70. The electronic throttle device 53 is provided with a throttle position sensor 73, and the accelerator pedal is provided with an accelerator position sensor 74, which outputs the current throttle opening and accelerator opening to the ECU 70. Further, a crank angle sensor 75 is provided on the crankshaft, and the detected crank angle is output to the ECU 70, and the ECU 70 calculates the engine speed based on the crank angle. Further, the cylinder block 11 is provided with a water temperature sensor 76 and outputs the detected engine cooling water temperature to the ECU 70. Further, the vehicle is provided with a vehicle speed sensor 77 and outputs the detected vehicle speed to the ECU 70.

  Further, the ECU 70 can control the intake variable valve mechanisms 40 and 41 and the exhaust variable valve mechanisms 42 and 43 based on the engine operating state. That is, when the temperature is low, the engine is started, the engine is idling, or when the load is light, the exhaust gas 30 is exhausted from the intake port 24, 31 by eliminating the overlap between the exhaust valve 30, 31 opening timing and the intake valve 28, 29 opening timing. 25 or the amount of air blown back to the combustion chambers 22 and 23 is reduced, and combustion stability and fuel efficiency can be improved. Further, at the time of medium load, by increasing the overlap, the internal EGR rate is increased to improve the exhaust gas purification efficiency, and the pumping loss is reduced to improve the fuel consumption. Further, at the time of high-load low-medium rotation, the closing timing of the intake valves 28 and 29 is advanced, thereby reducing the amount of intake air blown back to the intake ports 24 and 25 and improving the volume efficiency. At the time of high load and high rotation, the closing timing of the intake valves 28 and 29 is retarded according to the rotational speed, thereby improving the volume efficiency as the timing according to the inertial force of the intake air.

  Here, the fuel system of the above-described V-type 6-cylinder gasoline engine of this embodiment will be described in detail.

  In the engine fuel system of this embodiment, as shown in FIG. 1, injectors (fuel injection means) 62, 63 have base ends connected to delivery pipes 64, 65. High-pressure fuel can be injected into the combustion chambers 22 and 23 provided corresponding to the six cylinders of the engine. One delivery pipe 64 is equipped with a fuel pressure sensor 78 that detects the fuel pressure.

  The fuel tank 81 has a vertical shape divided into a first chamber 81a and a second chamber 82b, and can store a predetermined amount of fuel in each of the chambers 82a and 82b. A low pressure feed pump (fuel pressure feeding means) 83 is attached to the first chamber 82a, and the low pressure feed pump 83 is connected to a high pressure fuel pump (pressure raising means) 85 via a low pressure fuel supply pipe 84. The fuel pump 85 is connected to one end of the delivery pipe 64 via a high-pressure fuel supply pipe 86. The high pressure fuel pump 85 can be driven by one intake camshaft 32, a pulsation damper 87 is attached to the low pressure fuel supply pipe 84, and a check valve 88 is attached to the high pressure fuel supply pipe 86.

  The second chamber 82b is provided with a jet pump 89. The jet pump 89 is connected to a fuel return pipe 91 branched from the low-pressure fuel supply pipe 84 and having a pressure regulator 90. A fuel transfer pipe 92 extending to the chamber 82a is connected. Further, the delivery pipes 64 and 65 are connected by a connecting pipe 93, and the base end portion of the fuel discharge pipe 94 is connected to the other end of the other delivery pipe 65, and the delivery in the fuel discharge pipe 94 is performed. A relief valve 95 is attached to the discharge portion of the pipe 65, and the tip end portion of the fuel discharge pipe 94 is connected to the second chamber 82 b in the fuel tank 81. The high-pressure fuel pump 85 is provided with a return pipe 96 that returns excess low-pressure fuel to the fuel tank 81, and the tip is connected to the fuel discharge pipe 94.

  Therefore, when the engine is started, the low pressure feed pump 83 is driven to pressurize the fuel in the first chamber 82 a in the fuel tank 81, and the low pressure fuel is supplied to the high pressure fuel pump 85 through the low pressure fuel supply pipe 84. The high pressure fuel pump 85 boosts the low pressure fuel and supplies the high pressure fuel to the delivery pipes 64 and 65 through the high pressure fuel supply pipe 86. The injectors 62 and 63 can inject the high-pressure fuel in the delivery pipes 64 and 65 into the combustion chambers 22 and 23. At this time, the ECU 70 drives and controls the high-pressure fuel pump 85 based on the fuel pressure detected by the fuel pressure sensor 78 to maintain the fuel pressure in the delivery pipes 64 and 65 at a predetermined pressure.

  When the fuel pressure in the delivery pipes 64 and 65 becomes higher than a predetermined pressure, the relief valve 95 is opened and high pressure fuel is discharged through the fuel discharge pipe 94 to the second chamber 82b in the fuel tank 81. Further, a part of the low-pressure fuel boosted by the low-pressure feed pump 83 is returned from the low-pressure fuel supply pipe 64 to the second chamber 82b through the fuel return pipe 91, the jet pump 89, and the fuel transfer pipe 92. The pump 89 uses the negative pressure generated when the returned fuel passes through the venturi, and transfers the fuel remaining in the first chamber 82a to the second chamber 82b through the fuel transfer pipe 92.

  The high pressure fuel pump 85 described above will be described in detail. In the high-pressure fuel pump 85, as shown in FIG. 3-1, a plunger 102 is supported on the casing 101 so as to be movable up and down, and a pressure chamber 103 for boosting the fuel is formed. An upper portion of the casing 101 is formed with a suction port 104 that communicates with the low pressure fuel supply pipe 84 and sucks the low pressure fuel, and a discharge port 105 that discharges the pressurized high pressure fuel to the high pressure fuel supply pipe 86. Yes. In addition, a metering valve 106 for opening and closing the suction port 104 is provided at the upper portion of the casing 101. This metering valve 106 is an electromagnetic spill valve, and is biased in a direction to open the suction port 104 by a spring 107. The suction port 104 can be closed by energizing the electromagnetic solenoid 108 that is supported.

  In addition, a lifter 109 is connected to a lower end portion of the plunger 102, and a spring 111 is interposed between the lifter 109 and the cylinder head cover 110, and the plunger 102 is biased and supported through the lifter 109. Yes. On the other hand, a drive cam 112 having three cam peaks 112 a to 112 c is fixed to the outer peripheral portion of the intake camshaft 32, and this drive cam 112 is in contact with the lower surface of the lifter 109.

  Accordingly, as shown in FIG. 3A, the intake camshaft 32 moves in the direction of the arrow from the intake start position where the cam crest 112a of the drive cam 112 of the intake camshaft 32 contacts the lifter 109 and moves the plunger 102 upward. , The cam crest 112a moves away from the lifter 109, and the plunger 102 is lowered via the lifter 109 by the biasing force of the spring 111. At this time, the metering valve 106 opens the suction port 104 by the urging force of the spring 107, and the low pressure fuel in the low pressure fuel supply pipe 84 can be sucked into the pressure chamber 103 through the suction port 107.

  When the drive cam 112 of the intake cam 32 rotates 60 degrees (120 CA) from the intake start position described above, the flat portion between the cam peaks 112a and 112b contacts the lifter 109 as shown in FIG. 3-2. Thus, the suction end position where the plunger 102 descends most, that is, the pressure feeding start position. When the intake camshaft 23 rotates in the direction of the arrow from this pumping start position, the cam crest 112 b moves so as to approach the lifter 109, so that the cam crest 112 b resists the biasing force of the spring 111 and lifts the lifter 109. The plunger 102 is raised. At this time, when the electromagnetic solenoid 108 is energized, the metering valve 106 closes the suction port 104 against the urging force of the spring 107, boosts the low-pressure fuel in the pressure chamber 103, and reaches a predetermined pressure. The pressurized high-pressure fuel can be pumped from the discharge port 105 to the high-pressure fuel supply pipe 83 through the check valve 66.

  Then, when the drive camshaft 112 of the intake cam 32 rotates 60 degrees (120 CA) from the above-described pumping start position, the cam peak 112b raises the plunger 102 most via the lifter 109, that is, the suction start. Position.

  By the way, in the engine of the present embodiment, the high pressure fuel pump 85 reciprocates the plunger 102 by the drive cam 112 of the intake camshaft 32. Therefore, the ECU 70 detects the crank angle sensor 75 (or the cam position sensor 44). Based on the detection signal, the position of the plunger 102 is detected, and the opening / closing timing of the electromagnetic spill valve is set in accordance with the detected position, thereby properly adjusting the fuel. However, in a relatively quiet operating state such as an idling operation of the engine, the operation sound accompanying the opening and closing of the electromagnetic spill valve becomes remarkable, and silence is hindered.

  Therefore, in this embodiment, when the engine is idling, after the warm-up is completed, the cooling water temperature becomes high, the fuel is relatively easy to vaporize and atomize, and the rotation speed is low, so the period from fuel injection to ignition Since the in-cylinder pressure is relatively long and the in-cylinder pressure is also relatively low, even when the low pressure fuel pressurized by the feed pump 83 is injected into the combustion chambers 22 and 23, the low pressure fuel can be sufficiently vaporized and atomized. . Therefore, during this idling operation, the electromagnetic spill valve is stopped at the open position, and the low pressure fuel pressurized by the feed pump 83 bypasses the high pressure fuel pump 85 and is pumped to the second delivery pipes 64, 65, and the injector 62 , 63 injects low pressure fuel into the combustion chambers 22, 23, thereby reducing the operating noise associated with the opening and closing of the electromagnetic spill valve in the high pressure fuel pump 85.

  In this case, the pressure chamber 103 in the casing 101 is applied as a fuel passage through which the low-pressure fuel from the feed pump 83 passes without being pressurized by the high-pressure fuel pump 85. That is, when the metering valve 106 is maintained at the position where the suction port 104 is opened by the urging force of the spring 107 without energizing the electromagnetic solenoid 108 by the high pressure fuel pump 85, the low pressure fuel pressurized by the feed pump 83 is supplied. The low-pressure fuel supply pipe 84 passes through the pressure chamber 103 and is pumped to the high-pressure fuel supply pipe 86 at a low pressure.

  Further, when the operation and stop of the high-pressure fuel pump 85 are controlled according to the operating state of the engine, for example, when the vehicle is intermittently subjected to slow acceleration due to traffic congestion, the operation and stop of the high-pressure fuel pump 85 are intermittently performed. Done. Then, the pressure of the fuel pumped to the delivery pipes 64 and 65 fluctuates in a short time, hunting of the fuel pressure occurs, the air-fuel ratio varies, and the emission may deteriorate.

  Therefore, in this embodiment, as shown in FIG. 1, the ECU 70 as the fuel control means can control the stop and operation of the low-pressure fuel by the high-pressure fuel pump 85 according to the operating state of the engine, and can control the high pressure. When the fuel pump 85 is switched between the stopped state and the operating state, when it is determined that the vehicle is in the slow acceleration state or the slow deceleration state, control is performed so as to cancel this switching.

  In this case, the ECU 70 determines the slow acceleration state or the slow deceleration state of the vehicle based on the change rate and change amount of the engine load. Moreover, ECU70 determines the slow acceleration state or slow deceleration state of a vehicle based on the driving | running | working stop state of a vehicle.

  Specifically, when the high-pressure fuel pump 85 is in the operating state, the ECU 70 switches the high-pressure fuel pump 85 to the stopped state when it is determined that the engine load is lower than the first predetermined value set in advance. Further, the ECU 70 determines that when the high-pressure fuel pump 85 is in a stopped state, the vehicle is not in a traveling state, and that the rate of change and the amount of change in the engine load are higher than a preset second predetermined value. Then, the high pressure fuel pump 85 is switched to the operating state.

  Here, the operation stop control of the high-pressure fuel pump 85 by the ECU 70 will be described in detail based on the flowchart of FIG.

In the operation control of the high pressure fuel pump 85 of the internal combustion engine of the present embodiment, as shown in FIG. 4, in step S11, the ECU 70 determines whether or not the high pressure fuel pump 85 is stopped. If it is determined that the high-pressure fuel pump 85 is not stopped, the current engine speed Ne calculated based on the crank angle detected by the crank angle sensor 75 is determined in step S12. It is determined whether it is lower than the engine speed Nes ₁ (first predetermined value). The predetermined engine speed Nes ₁ is a reference engine speed for stopping the high-pressure fuel pump 85. Here, if it is determined that the current engine speed Ne is lower than the predetermined engine speed Nes _1, whether or not the current fuel injection quantity I is smaller than a predetermined fuel injection quantity I set in advance in step S13. Determine. The predetermined fuel injection amount I is an injection amount that serves as a reference for stopping the high-pressure fuel pump 85. Here, if it is determined that the current fuel injection amount I is smaller than the predetermined fuel injection amount I, the high-pressure fuel pump 85 is stopped in steps and 14.

  Accordingly, as shown in FIGS. 1 and 3-1, the high-pressure fuel pump 85 is maintained at a position where the metering valve 106 opens the suction port 104 by the biasing force of the spring 107. Therefore, the low-pressure fuel pressurized by the feed pump 83 is not pressurized from the low-pressure fuel supply pipe 84 by the high-pressure fuel pump 85, and is pumped to the high-pressure fuel supply pipe 86 through the pressure chamber 103. The low-pressure fuel is pumped to delivery pipes 64 and 65 and injected into the combustion chambers 22 and 23 by injectors 62 and 63. In this case, the engine speed is low and the fuel injection amount is small. For example, if the engine is idling, the low pressure fuel pressurized by the feed pump 83 can be injected into the combustion chambers 22 and 23. In addition, low-pressure fuel can be vaporized and atomized. And since the electromagnetic spill valve in the high-pressure fuel pump 85 is stopped, the operation noise accompanying the opening and closing thereof is reduced.

On the other hand, returning to FIG. 4, at step S11, ECU 70, when the high-pressure fuel pump 85 is determined to be stopped, in step S15, the idling flag _{F I} is OFF to indicate that the engine is idling In this state, it is determined whether the current change amount (change rate) Δta of the throttle opening degree ta detected by the throttle position sensor 73 is larger than a preset predetermined throttle opening change amount (change rate) Δtas. The predetermined throttle opening change amount Δtas is a reference change amount for starting the operation of the high-pressure fuel pump 85. If it is determined that the current throttle opening change amount Δta is larger than the predetermined throttle opening change amount Δtas, the process proceeds to step S16.

In step S16, the ECU 70 determines that the current engine speed Ne calculated based on the crank angle detected by the crank angle sensor 75 is higher than a predetermined engine speed Nes ₂ (second predetermined value) set in advance. Further, it is determined whether or not the vehicle speed V detected by the vehicle speed sensor 77 is greater than a predetermined vehicle speed Vs. The predetermined engine speed Nes ₂ is a reference engine speed for starting the operation of the high-pressure fuel pump 85, and is set higher than the engine speed Nes ₁ described above. The predetermined vehicle speed Vs is a reference vehicle speed for starting operation of the high-pressure fuel pump 85. If it is determined that the current engine speed Ne is higher than the predetermined engine speed Nes ₂ and the current vehicle speed V is higher than the predetermined vehicle speed Vs, the high-pressure fuel pump 85 is started to operate in step S17. To do.

On the other hand, in step S15, it is determined that the engine is in an idling operation state, or the current throttle opening change amount Δta is not larger than the predetermined throttle opening change amount Δtas, or in step S16, the current engine speed is changed. If it is determined that the number Ne is not higher than the predetermined engine speed Nes ₂ or that the current vehicle speed V is not higher than the predetermined vehicle speed Vs, this routine is exited without doing anything. That is, the high pressure fuel pump 85 is kept stopped.

That is, when the high pressure fuel pump 85 is stopped, the ECU 70 recognizes that the current throttle opening change amount Δta is larger than a predetermined value (Δtas) and the vehicle is accelerated ( Or, it is determined that the vehicle is in a deceleration state. Further, the ECU 70 determines that the current engine speed Ne is higher than a predetermined value (Nes ₂ ) and that the current vehicle speed V is higher than the predetermined value (Vs), so that it is not a slow acceleration. Therefore, in this case, the high-pressure fuel pump 85 is switched from the stopped state to the operating state. On the other hand, even if the engine is not in the idling operation state and the current throttle opening change amount Δta is recognized to be larger than the predetermined value (Δtas), it is determined that the vehicle is in the acceleration (or deceleration) state. By recognizing that the number Ne is not higher than the predetermined value (Nes ₂ ) or that the current vehicle speed V is not higher than the predetermined value (Vs), it is determined that this is slow acceleration. Therefore, in this case, the high pressure fuel pump 85 is maintained in the stopped state without switching from the stopped state to the operating state. That is, the switching from the stopped state to the operating state in the high-pressure fuel pump 85 is released.

  Accordingly, when the high-pressure fuel pump 85 is switched from the stopped state to the operating state, the high-pressure fuel pump 85 detects the fuel pressure in the delivery pipes 64 and 65 detected by the fuel pressure sensor 78, as shown in FIGS. Based on this, the metering valve 106 is controlled to open and close. Therefore, the low-pressure fuel pressurized by the feed pump 83 is further pressurized by the high-pressure fuel pump 85 and is sent to the high-pressure fuel supply pipe 86 as high-pressure fuel. The high-pressure fuel is pumped to delivery pipes 64 and 65 and injected into the combustion chambers 22 and 23 by injectors 62 and 63. In this predetermined acceleration state, since the engine speed is high, the operating noise in the high-pressure fuel pump 85 does not become significant.

  As described above, in the fuel supply device for the internal combustion engine of the present embodiment, the feed pump (fuel pumping means) 83 that pressurizes the fuel and pumps it as low-pressure fuel, and the high-pressure that boosts the low-pressure fuel and pumps it as high-pressure fuel. A fuel pump (pressure-increasing means) 85, a high-pressure chamber 103 as a fuel passage through which low-pressure fuel from the feed pump 83 passes without being pressurized by the high-pressure fuel pump 85, and low-pressure fuel or high-pressure fuel is injected into the combustion chambers 22 and 23. Injectors (fuel injection means) 62 and 63, and an ECU (fuel control means) 70 for controlling the stop and operation of boosting of the low-pressure fuel by the high-pressure fuel pump 85 according to the engine operating state. When the pump 85 is switched from the stop state to the driving state, when it is determined that the vehicle is in the slow acceleration state, control is performed so as to cancel the switching. There.

  Accordingly, when the high pressure fuel pump 85 is switched from the stopped state to the operating state, when it is determined that the vehicle is in the slow acceleration state, the high pressure fuel pump 85 is maintained in the stopped state. By eliminating frequent switching and suppressing fuel pressure hunting, variations in the air-fuel ratio can be suppressed and emission deterioration can be prevented.

  Further, in the fuel supply device for an internal combustion engine of the present embodiment, the ECU 70 determines the slow acceleration state of the vehicle based on the change rate and change amount of the throttle opening. Therefore, the slow acceleration state of the vehicle can be determined with high accuracy by using the rate of change or the amount of change in the throttle opening as the determination material for the slow acceleration state of the vehicle. In the fuel supply device for an internal combustion engine according to this embodiment, the ECU 70 determines the slow acceleration state of the vehicle based on the traveling stop state of the vehicle. Therefore, the slow acceleration state of the vehicle can be determined with higher accuracy by using the travel stop state in addition to the change rate and the change amount of the throttle opening.

  In the internal combustion engine fuel supply apparatus according to the present embodiment, when the high pressure fuel pump 85 is in an operating state, the ECU 70 determines that the throttle opening is lower than the first predetermined value set in advance. The fuel pump 85 is switched to a stopped state. On the other hand, when the high pressure fuel pump 85 is in a stopped state, the ECU 70 determines that the vehicle is not in a traveling state and that the change rate and change amount of the throttle opening are higher than a preset second predetermined value. Then, the high-pressure fuel pump 85 is switched to the operating state. In this case, when the high pressure fuel pump 85 is switched from the stopped state to the operating state by setting the second predetermined value to be larger than the first predetermined value, the dead zone is set in the determination reference region, thereby allowing high pressure with a simple configuration. The frequent switching between operation and stop in the fuel pump 85 can be eliminated.

  In the above-described embodiment, the ECU 70 stops the high-pressure fuel pump 85 and supplies the low-pressure fuel pressurized by the feed pump 83 to the delivery pipes 64 and 65 during the idling operation after the engine is warmed up. However, it is not limited to such an operating state. For example, the high pressure pump 85 may be stopped and the low pressure fuel may be supplied to the delivery pipes 64 and 65 at the time of starting the engine or during a low load and high rotation.

  In the above-described embodiment, when the high-pressure fuel pump 85 is switched from the stopped state to the operating state, the switching is released when the slow acceleration of the vehicle is determined, but the high-pressure fuel pump 85 is stopped from the operating state. When switching to, switching may be canceled when it is determined that the vehicle is slowly accelerating. Further, when the high pressure fuel pump 85 is switched between the stopped state and the operating state, the switching is canceled when it is determined that the vehicle is in the slow acceleration state, but when it is determined that the vehicle is in the slow deceleration state. Switching may be canceled.

In the above-described embodiment, it is determined whether or not the current throttle opening change amount Δta is larger than the predetermined throttle opening change amount Δtas. However, the present invention is not limited to this. For example, the rate of change or the amount of change in the engine load, such as the accelerator opening, the engine speed, the intake air amount, or the fuel injection amount, may be used. Further, although it is determined whether the current engine speed Ne is higher than the predetermined engine speed Nes ₂ and the vehicle speed V is higher than the predetermined vehicle speed Vs, the present invention is not limited to this. For example, an engine load such as an accelerator opening, a throttle opening, and an intake air amount may be used.

  The internal combustion engine of the present invention can be applied to all fuel systems that supply fuel to engines that are internal combustion engines such as gasoline engines and diesel engines mounted on vehicles such as passenger cars and trucks. The engine form is not limited to the V-type 6-cylinder engine but may be an in-line 4-cylinder engine, and the number of cylinders is not limited to each embodiment.

  As described above, the fuel supply device for an internal combustion engine according to the present invention appropriately controls switching between operation and stop of the boosting means, thereby suppressing fuel pressure hunting to suppress variation in air-fuel ratio, and reducing emissions. It is possible to prevent deterioration and is useful for the booster that is driven in accordance with the operating state of the internal combustion engine, and in particular, to reduce the influence of pulsation generated from the booster on the fuel system of the internal combustion engine. Suitable for

It is a schematic block diagram showing the fuel system in the fuel supply apparatus of the internal combustion engine which concerns on one Example of this invention. It is a principal part longitudinal cross-sectional view of the internal combustion engine of a present Example. It is the schematic showing the high pressure fuel pump in the supply apparatus of the internal combustion engine of a present Example. It is the schematic showing the high pressure fuel pump in the fuel supply apparatus of the internal combustion engine of a present Example. It is a flowchart showing the operation control of the fuel supply apparatus of the internal combustion engine of a present Example.

Explanation of symbols

22, 23 Combustion chamber 62, 63 Injector (fuel injection means)
64, 65 Delivery pipe 66, 67 Spark plug 70 Electronic control unit, ECU (fuel control means)
78 Fuel pressure sensor 83 Feed pump (Fuel pressure feeding means)
85 High-pressure fuel pump (pressure booster)
103 Pressure chamber (fuel passage)

Claims (5)

Fuel pumping means for pressurizing the fuel and pumping it as low-pressure fuel;
Pressurizing means for boosting the low pressure fuel pumped by the fuel pumping means and pumping it as high pressure fuel;
A fuel passage through which the low-pressure fuel from the fuel pumping means passes without being boosted by the boosting means;
Fuel injection means for injecting low pressure fuel or high pressure fuel into the combustion chamber;
Fuel control means for controlling the stop and operation of the boosting of the low-pressure fuel by the boosting means in accordance with the operating state of the internal combustion engine;
An internal combustion engine fuel supply apparatus comprising:
The fuel control means cancels the switching when it is determined that the vehicle is in the slow acceleration state or the slow deceleration state when the boosting means is switched between the stopped state and the driving state.
A fuel supply device for an internal combustion engine.   2. The fuel supply device for an internal combustion engine according to claim 1, wherein the fuel control means determines a slow acceleration state or a slow deceleration state of the vehicle based on a rate of change and a change amount of the engine load.   The fuel supply device for an internal combustion engine according to claim 2, wherein the fuel control means determines a slow acceleration state or a slow deceleration state of the vehicle based on a running stop state of the vehicle.   The fuel control means switches the pressure-increasing means to a stopped state when it is determined that the engine load is lower than a preset first predetermined value when the pressure-increasing means is in an operating state. Item 4. The fuel supply device for an internal combustion engine according to any one of Items 1 to 3.   The fuel control means, when the boosting means is in a stopped state, when it is determined that the vehicle is not in a running state and the rate of change and amount of change in engine load are higher than a preset second predetermined value. The fuel supply device for an internal combustion engine according to any one of claims 1 to 4, wherein the boosting means is switched to an operating state.

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