JP4053113B2 - Fuel supply structure of in-cylinder fuel injection engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply system structure of an in-cylinder fuel injection engine that supplies fuel from a fuel tank to a high-pressure pump by a low-pressure pump, further boosts the fuel by the high-pressure pump, and supplies high-pressure fuel to an injector. Relates to a fuel supply system structure of an in-cylinder fuel injection engine that can achieve both a reduction in capacity of a low-pressure pump and an improvement in volumetric efficiency of the high-pressure pump.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an in-cylinder fuel injection engine that directly injects fuel into a cylinder (combustion chamber) and ignites and burns the injected fuel with a spark plug for the purpose of improving fuel consumption, engine output, and exhaust emission. Are known.
[0003]
In this in-cylinder fuel injection engine, as disclosed in JP-A-2-16934, JP-A-8-177699, etc., the fuel is directly injected into the cylinder against the in-cylinder pressure. Therefore, it is necessary to maintain the fuel pressure supplied to the injector at a high pressure. The fuel from the fuel tank is supplied to the high pressure pump by the low pressure pump (feed pump), and the fuel is further pressurized by the high pressure pump. Is supplied to the injector.
[0004]
That is, since the high-pressure pump has insufficient self-priming capability, an electric low-pressure pump is disposed upstream of the high-pressure pump, and fuel is supplied from the fuel tank to the high-pressure pump by this low-pressure pump.
[0005]
[Problems to be solved by the invention]
However, since the low-pressure pump and the high-pressure pump are arranged in series in the fuel passage from the fuel tank to the injector, and all the fuel supply to the high-pressure pump is covered by the low-pressure pump, this low-pressure pump has the maximum discharge flow rate of the high-pressure pump. It is necessary to adopt a discharge flow capacity that is equal to or greater than that, which causes an increase in current consumption by the low-pressure pump. Therefore, the low-pressure pump usually has a capacity that is slightly higher than the maximum discharge flow rate of the high-pressure pump.
[0006]
For this reason, When using an engine-driven high-pressure pump as disclosed in JP-A-8-177699, In areas where the fuel discharge flow rate by the high-pressure pump is low, such as in the low engine rotation range, there is no problem because the fuel is sufficiently supplied to the high-pressure pump by the low-pressure pump. In the region, the fuel flow path resistance due to the supply of fuel to the high pressure pump via the low pressure pump increases, and accordingly, the fuel suction resistance of the high pressure pump increases and the volume efficiency of the high pressure pump decreases. There is.
[0007]
In view of the above circumstances, an object of the present invention is to provide a fuel supply system structure of a cylinder fuel injection engine capable of achieving both a reduction in the capacity of a low-pressure pump and an improvement in volumetric efficiency of the high-pressure pump.
[0008]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that fuel is supplied from a fuel tank to an engine-driven high-pressure pump by an electric low-pressure pump, and the pressure of the fuel is further increased by the high-pressure pump. In a fuel supply system structure of an in-cylinder fuel injection engine for supplying high-pressure fuel to an injector for injecting fuel into the fuel, a fuel bypass passage for bypassing the upstream and downstream of the low-pressure pump is provided, and the engine bypass rotates in the fuel bypass passage Sometimes In a state where both the high pressure pump and the low pressure pump are driven. Prevents back flow of fuel to the upstream side of the low-pressure pump, during high engine rotation In a state where both the high pressure pump and the low pressure pump are driven. A check valve that allows fuel flow from the upstream side of the low-pressure pump is provided.
[0009]
According to a second aspect of the invention, there is provided an injector for supplying fuel from a fuel tank to an engine-driven high-pressure pump by an electric low-pressure pump, further boosting the fuel by the high-pressure pump, and injecting the fuel into a cylinder. In the fuel supply system structure of the in-cylinder fuel injection engine for supplying high-pressure fuel, a fuel bypass passage is provided that connects a low-pressure fuel passage from the low-pressure pump to the high-pressure pump and a fuel tank. When rotating In a state where both the high pressure pump and the low pressure pump are driven. Prevents the backflow of fuel to the above fuel tank, at high engine speed In a state where both the high pressure pump and the low pressure pump are driven. A check valve that allows fuel flow from the fuel tank is provided.
[0010]
That is, in the first aspect of the invention, the engine low speed Engine driven In areas where the high-pressure pump has insufficient self-priming capacity and the fuel discharge flow rate of the high-pressure pump is small, Electric The backflow of the fuel delivered by the low pressure pump to the upstream side of the low pressure pump through the fuel bypass passage is prevented by a check valve disposed in the fuel bypass passage, and a sufficient amount of fuel from the low pressure pump to the high pressure pump is prevented. Since the fuel is supplied, the high pressure pump can suck the fuel without resistance and operates under good volumetric efficiency. And engine high rotation Time In a region where the fuel discharge flow rate by the high-pressure pump is large, the fuel suction capability by the high-pressure pump itself is increased. Therefore, the high-pressure pump is connected to the upstream of the low-pressure pump through the fuel bypass passage by the self-priming action together with the fuel supply from the low-pressure pump. It becomes possible to directly inhale the fuel from the tank. Therefore, high engine speed of time Even in the region where the fuel discharge flow rate of the high-pressure pump is large, the high-pressure pump does not increase the fuel suction resistance, and a sufficient fuel flow rate to the high-pressure pump is ensured. The volumetric efficiency of the pump can be improved.
[0011]
In the invention according to claim 2, the engine low speed Engine driven In areas where the high-pressure pump has insufficient self-priming capacity and the fuel discharge flow rate of the high-pressure pump is small, Electric Backflow of fuel delivered by the low pressure pump to the fuel tank through the fuel bypass passage is prevented by a check valve disposed in the fuel bypass passage, and a sufficient amount of fuel is supplied from the low pressure pump to the high pressure pump. As supplied, the high pressure pump can draw fuel without resistance and operates under good volumetric efficiency. And engine high rotation of time In a region where the fuel discharge flow rate by the high-pressure pump is large, the fuel suction capability by the high-pressure pump itself increases, so that the fuel is supplied from the low-pressure pump and the high-pressure pump directly fuels from the fuel tank through the fuel bypass passage by the self-priming action. Can be inhaled. Therefore, high engine speed of time In the region where the fuel discharge flow rate of the high-pressure pump is large, the fuel suction resistance of the high-pressure pump can be further reduced, and a sufficient fuel flow rate to the high-pressure pump is ensured, and a low-capacity low-pressure pump is adopted. It becomes possible to further improve the volumetric efficiency of the high-pressure pump.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a first embodiment of the present invention.
[0013]
First, a schematic configuration of the in-cylinder fuel injection engine will be described with reference to FIG. In the figure, reference numeral 1 denotes a horizontally opposed four-cycle four-cylinder direct injection gasoline engine (hereinafter simply referred to as “engine”) for a vehicle such as an automobile as an example of an in-cylinder fuel injection engine. Cylinder heads 2 are provided in both the left and right banks of the cylinder block 1a of the engine 1, and each cylinder head 2 is formed with an intake port 2a and an exhaust port 2b corresponding to each cylinder.
[0014]
In the intake system of the engine 1, an intake manifold 3 is communicated with each intake port 2a, and a throttle chamber 5 is communicated with the intake manifold 3 via an air chamber 4 in which intake passages of the respective cylinders are gathered. An air cleaner 7 is attached to the upstream side of the chamber 5 via an intake pipe 6, and the air cleaner 7 communicates with an air intake chamber 8.
[0015]
The throttle chamber 5 is provided with a throttle valve 5a that is linked to an accelerator pedal 9. And in order to detect the depression amount (accelerator opening degree) of the said accelerator pedal 9 showing a required load, the accelerator opening degree sensor 10 which consists of a potentiometer etc. is attached to the support part of this accelerator pedal 9.
[0016]
The intake pipe 6 is connected to a bypass passage 11 that bypasses the throttle valve 5a. The amount of bypass air flowing through the bypass passage 11 is adjusted to the bypass passage 11 according to the valve opening degree at the time of idling. An idle speed control valve (ISC valve) 12 for controlling the speed is provided.
[0017]
Further, the cylinder head 2 is provided with an injector 14 for injecting fuel directly into the combustion chamber 13 (inside the cylinder) for each cylinder. An ignition plug 15 that exposes the discharge electrode at the tip to the combustion chamber 13 is attached to each cylinder of the cylinder head 2. The ignition plug 15 is connected to the ignition plug 15 via an ignition coil 16 provided for each cylinder. An igniter 17 is connected.
[0018]
In addition, a cooling water temperature sensor 19 is exposed in the cooling water passage 18 that communicates the left and right banks of the cylinder block 1a.
[0019]
On the other hand, as an exhaust system of the engine 1, an exhaust pipe 21 is communicated with a collection portion of an exhaust manifold 20 communicating with each exhaust port 2b of the cylinder head 2, and a catalytic converter 22 is interposed in the exhaust pipe 21 so that a muffler. 23 is communicated.
[0020]
A crank rotor 24 having a crank angle detection protrusion formed on the outer periphery for each predetermined crank angle is attached to a crank shaft 1b of the engine 1, and a crank angle sensor 25 is provided on the crank rotor 24. Further, a cam rotor 27 having a cylinder discriminating protrusion formed on the outer periphery is connected to a camshaft 26 that rotates 1/2 with respect to the crankshaft 1b, and a cylinder discriminating sensor 28 is opposed to the cam rotor 27.
[0021]
Next, the fuel supply system structure of the engine 1 as the gist of the present invention will be described with reference to FIGS. Reference numeral 29 in FIGS. 1 and 2 denotes a fuel passage for supplying fuel from the fuel tank 30 to each of the injectors 14. The fuel passage 29 is sequentially discharged from the upstream side as an example of a fuel filter 31 and a low pressure pump. A tank-type electric feed pump 32, a high-pressure pump 33 for boosting the fuel from the feed pump 32 to a predetermined high pressure, a common rail 34 communicating with the injectors 14, and a fuel pressure to the injector 14 A high pressure regulator 35 including a high pressure mechanical pressure regulator or the like for adjusting the pressure to a high pressure (for example, 7 MPa) is interposed.
[0022]
In the present embodiment, the high-pressure pump 33 operates by being transmitted power from the crankshaft 1b of the engine 1 through a power transmission mechanism such as a pulley and a belt, and is composed of an engine-driven plunger pump or the like. A fuel discharge capacity sufficient to cover the maximum fuel injection amount of 1 is adopted.
[0023]
The upstream side of the high-pressure pump 33 in the fuel passage 29 constitutes a low-pressure fuel passage 29a for sending fuel from the fuel tank 30 by the feed pump 32, and the low-pressure fuel passage 29a is between the high-pressure pump 33 and the high-pressure regulator 35. The high pressure fuel passage 29b is configured to pressurize the fuel from the fuel and supply high pressure fuel to the injectors 14 described above.
[0024]
A low pressure fuel passage 29a downstream of the feed pump 32 and the fuel tank 30 are communicated with each other via a fuel return passage 29c, and the fuel pressure in the low pressure fuel passage 29a is set to a predetermined pressure (for example, 0.2 MPa) to the fuel return passage 29c. A low-pressure regulator 36 comprising a diaphragm pressure regulator or the like for regulating the pressure is interposed.
[0025]
Further, the downstream side of the high pressure regulator 35 is connected to a fuel return passage 29c between the low pressure fuel passage 29a downstream of the feed pump 32 and the low pressure regulator 36, and surplus fuel from the high pressure regulator 35 is returned to the low pressure fuel passage 24a. This also makes it possible to employ a feed pump 32 having a smaller capacity than the conventional one.
[0026]
On the other hand, a fuel bypass passage 29d that bypasses the upstream and downstream of the feed pump 32 is connected to the low-pressure fuel passage 29a. The fuel bypass passage 29d prevents the fuel from flowing backward to the upstream side of the feed pump 32. A check valve 37 that allows only fuel flow to the high-pressure pump 33 side is provided.
[0027]
Further, a vapor processing valve 38 formed of an electromagnetic switching valve is disposed in a purge passage 29e that communicates a high pressure fuel passage 29b between the common rail 34 and the high pressure regulator 35 and a fuel return passage 29c downstream of the low pressure regulator 36. Yes.
[0028]
The common rail 34 is provided with a fuel pressure sensor 39 for detecting the fuel pressure in the high pressure fuel passage 29b.
[0029]
On the other hand, calculation of control amounts for the injector 14, spark plug 15, and ISC valve 12, output of control signals, that is, fuel injection control, ignition timing control, idle speed control, and feed pump 32 operation control, vapor processing valve Engine control such as opening / closing control 38 is performed by an electronic control unit (ECU) 40 shown in FIG.
[0030]
The ECU 40 is configured with a microcomputer as a center, and also includes peripheral circuits such as a drive circuit and an A / D converter.
[0031]
The ECU 40 is connected to the battery 42 via the first relay contact of the power relay 41 having two circuit relay contacts. The relay coil of the power relay 41 is connected to the battery 42 via the ignition switch 43. When the ignition switch 43 is turned on and the contact of the power relay 41 is closed, the ECU 40 is turned on.
[0032]
Further, the feed pump 32 is connected to the battery 42 via a relay contact of a feed pump relay 44. A power line for supplying power from the battery 42 to each actuator is connected to the second relay contact of the power relay 41.
[0033]
Input ports of the ECU 40 include the accelerator opening sensor 10, the coolant temperature sensor 19, the crank angle sensor 25, the cylinder discrimination sensor 28, the fuel pressure sensor 39, and a starter switch 45 for detecting the engine start state. Various sensors and switches are connected. Further, the ISC valve 12, the injector 14, the igniter 17, the vapor processing valve 38, and the relay coil of the feed pump relay 44 are connected to the output port of the ECU 40.
[0034]
The ECU 40 processes detection signals from the sensors and switches that are input in accordance with the stored control program, and based on various data based on these detection signals, the fuel injection amount, the ignition timing, and the drive signal for the ISC valve 12 And the engine control such as fuel injection control, ignition timing control, idle speed control, feed pump 32 operation control, and vapor processing valve 38 open / close control is performed.
[0035]
Next, the effect | action by this Embodiment is demonstrated.
[0036]
First, when the ignition switch 43 is turned on and the ECU 40 is powered on, the system is initialized, the vapor processing valve 38 is opened by the drive signal from the ECU 40, and the common rail 34 and the high-pressure regulator are connected via the purge passage 29e. The high pressure fuel passage 29b between the low pressure regulator 36 and the fuel return passage 29c downstream of the low pressure regulator 36 communicates with each other, the feed pump relay 44 is turned on and the feed pump 32 is energized, and the operation of the feed pump 32 is started. Is done.
[0037]
Thereby, the fuel in the fuel tank 30 is sent out by the feed pump 32 through the filter 31 interposed in the low pressure fuel passage 29a. The fuel delivered by the feed pump 32 is regulated by the low pressure regulator 36 and supplied to the high pressure pump 33, and surplus fuel is returned from the low pressure regulator 36 to the fuel tank 30 via the fuel return passage 29c.
[0038]
At this time, the engine 1 is not started yet and the high-pressure pump 33 is stopped. However, the high-pressure pump 33 is composed of an engine-driven plunger pump or the like as described above, and has a suction port and a discharge port. Each check valve is provided (not shown). Accordingly, the check valve allows the fuel to flow through the high pressure pump 33 to the high pressure fuel passage 29b. Further, when the vapor processing valve 38 is opened, the high pressure fuel passage 29b between the common rail 34 and the high pressure regulator 35 and the fuel return passage 29c downstream of the low pressure regulator 36 are communicated via the purge passage 29e. Thus, the fuel is returned from the high-pressure fuel passage 29b to the fuel tank 30 via the purge passage 29e and the fuel return passage 29c.
[0039]
Therefore, even if vapor is generated in the fuel passage 29, the vapor is discharged to the fuel tank 30. As a result, deterioration of the fuel injection controllability due to vapor is prevented in advance, and the engine 1 is prepared for starting.
[0040]
When the starter switch 45 is turned on and the engine 1 is started, the ECU 40 calculates the engine speed based on the input interval time of the crank angle signal every time the crank angle signal is input from the crank angle sensor 25, and Cylinder discrimination signals such as a fuel injection target cylinder and an ignition target cylinder are discriminated by inputting a cylinder discrimination signal from the cylinder discrimination sensor 28. Then, the ECU 40 performs various operations such as a fuel injection pulse width that determines the fuel injection amount, an ignition timing, and a duty ratio of a drive signal for the ISC valve 12 based on the engine speed and the engine operating state detected by the sensors. A control amount is calculated, and a drive signal based on the fuel injection pulse width is output to the injector 14 of the fuel injection target cylinder at a predetermined timing, and an ignition signal is output to the igniter 17 at a predetermined ignition timing. The ignition plug 15 is ignited and a drive signal based on the above-described duty ratio is output to the ISC valve 12 to perform engine control such as fuel injection control, ignition timing control, and idle speed control.
[0041]
Further, the ECU 40 closes the vapor processing valve 38 in synchronization with the starter switch 45 being turned ON, and thereafter, the high pressure fuel passage between the common rail 34 and the high pressure regulator 35 via the purge passage 29e. Communication between the fuel return passage 29c and the fuel return passage 29c downstream of the low pressure regulator 36 is blocked.
[0042]
As the engine 1 is started, the high-pressure pump 33 is driven, the fuel delivered from the feed pump 32 is pressurized by the high-pressure pump 33, and the fuel pressure adjustment in the high-pressure regulator 35 is performed by closing the vapor processing valve 38. The predetermined high-pressure fuel regulated by the high-pressure regulator 35 is supplied to the injectors 14 of the respective cylinders via the common rail 34.
[0043]
That is, after the engine 1 is started, the fuel pressure in the high-pressure fuel passage 29b is maintained at a predetermined high pressure by the high-pressure regulator 35, so that the amount of fuel injected into the combustion chamber 13 (in-cylinder) is reduced from the ECU 40. Accurate measurement can be performed according to the valve opening time of the injector 14 based on the output fuel injection pulse width drive signal.
[0044]
After the engine is started, when the engine is running at a low speed, the drive speed of the high-pressure pump 33 is low, and the self-priming capability of the high-pressure pump 33 is insufficient. The check valve 37 is provided in the fuel bypass passage 29d so that the flow rate of the fuel discharged by the feed pump 32 is small, and the reverse flow of the fuel delivered by the feed pump 32 to the upstream side of the feed pump 32 through the fuel bypass passage 29d is disposed. Therefore, a sufficient amount of fuel is supplied from the feed pump 32 to the high-pressure pump 33. Thereby, at the time of low engine rotation, the high-pressure pump 33 can suck the fuel with a small suction resistance as in the conventional case, and operates under a good volumetric efficiency.
[0045]
At this time, since the required fuel injection amount is small, a sufficient amount of high-pressure fuel can be stably supplied to the injector 14 of each cylinder even if the fuel discharge flow rate by the high-pressure pump 33 is small.
[0046]
On the other hand, as the engine speed increases, the drive speed of the high-pressure pump 33 increases, so that the fuel suction capability of the high-pressure pump 33 increases and the fuel discharge flow rate by the high-pressure pump 33 increases.
[0047]
In a region where the fuel discharge flow rate by the high-pressure pump 33 is large, such as a high engine speed region, the fuel suction capability of the high-pressure pump 33 itself is increased. The fuel can be directly sucked from the upstream of the feed pump 32 through the passage 29d. Further, the check valve 37 disposed in the fuel bypass passage 29d prevents the fuel from flowing backward to the upstream side of the feed pump 32 and allows only the fuel flow to the high-pressure pump 33 side. The check valve 37 is opened by the fuel suction action of 33, and the high-pressure pump 33 can perform fuel self-priming through the fuel bypass passage 29d.
[0048]
As a result, in a region where the high-pressure pump 33 rotates at a high speed and the fuel discharge flow rate of the high-pressure pump 33 is large during high engine rotation, fuel is supplied from the feed pump 32 and the high-pressure pump 33 is self-priming through the fuel bypass passage 29d. By directly sucking the fuel from the upstream of the feed pump 32 into the high pressure pump 33, the direct current resistance of the fuel by the feed pump 32 can be reduced, and a sufficient amount of fuel can be secured on the suction side of the high pressure pump 33. The fuel suction resistance of the high-pressure pump 33 can be reduced.
[0049]
Therefore, the fuel suction resistance of the high-pressure pump 33 does not increase and the sufficient pressure to the high-pressure pump 33 can be obtained even in a region where the high-pressure pump 33 rotates at a high speed, such as a high engine speed region. Since the fuel flow rate is ensured, it is possible to employ a small-capacity feed pump 32, and it is possible to improve the volumetric efficiency of the high-pressure pump 33 while employing the small-capacity feed pump 32.
[0050]
In addition, this makes it possible to supply a sufficient amount of stable high-pressure fuel to the injectors 14 of each cylinder even when the required fuel injection amount is large in response to high engine speed and high load. It is possible to improve.
[0051]
Next, based on FIG.3 and FIG.4, 2nd Embodiment of this invention is described.
[0052]
The same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
[0053]
Hereinafter, the fuel supply system structure of the present embodiment will be described.
[0054]
In the first embodiment, an out-tank type electric feed pump is adopted as the low-pressure pump, whereas in this embodiment, an in-tank type electric feed pump 50 disposed in the fuel tank 30 is used. adopt. This in-tank type electric feed pump 50 is a well-known turbine type electric pump, and a filter 51 is attached to the suction port.
[0055]
A feed pump 50 is connected to the battery 42 via a relay contact of a feed pump relay 44.
[0056]
In addition, a low pressure fuel passage 52a extending from the feed pump 50 to the high pressure pump 33 and the fuel tank 30 are communicated with each other via a fuel bypass passage 52d, and a reverse flow of fuel to the fuel tank 30 is caused to flow through the fuel bypass passage 52d. A check valve 53 is provided that blocks only the fuel flow to the high pressure pump 33 side.
[0057]
In the fuel tank 30, the open end of the fuel bypass passage 52d extends in the bottom direction, and a filter 54 is attached to the open end. Note that a filter may be interposed in the fuel bypass passage 52d upstream of the check valve 53 without attaching the filter 54 to the opening end of the fuel bypass passage 52d.
[0058]
Further, the upstream side of the low pressure regulator 36 in the fuel return passage 29c is connected to the low pressure fuel passage 52a, and the rest of the configuration is the same as in the first embodiment.
[0059]
Next, the operation of the present embodiment will be described.
[0060]
When the ignition switch 43 is turned on and the ECU 40 is powered on, the system is initialized, the purge processing valve 38 is opened by the drive signal from the ECU 40, the feed pump relay 44 is turned on, and the feed pump 50 is turned on. Is energized, and the operation of the feed pump 50 is started.
[0061]
Then, by the operation of the feed pump 50, the fuel in the fuel tank 30 is sent through the filter 51 through the low pressure fuel passage 52a. The fuel delivered by the feed pump 50 is regulated by the low-pressure regulator 36 and supplied to the high-pressure pump 33, and is provided at the suction port and the discharge port of the high-pressure pump 33 as in the first embodiment. By a check valve (not shown), the fuel flows into the high-pressure fuel passage 29b via the high-pressure pump 33, and surplus fuel is returned from the low-pressure regulator 36 to the fuel tank 30 via the fuel return passage 29c.
[0062]
Further, when the vapor processing valve 38 is opened, the high pressure fuel passage 29b between the common rail 34 and the high pressure regulator 35 and the fuel return passage 29c downstream of the low pressure regulator 36 are communicated via the purge passage 29e. Thus, the fuel is returned from the high-pressure fuel passage 29b to the fuel tank 30 through the purge passage 29e and the fuel return passage 29c, so that even if vapor is generated in the fuel passage, the vapor is discharged to the fuel tank 30. The engine 1 is prepared for starting.
[0063]
When the starter switch 45 is turned on and the engine 1 is started, the ECU 40 closes the vapor processing valve 38 in synchronism with the starter switch 45 being turned on. The communication between the high pressure fuel passage 29b between the common rail 34 and the high pressure regulator 35 and the fuel return passage 29c downstream of the low pressure regulator 36 is blocked.
[0064]
The high-pressure pump 33 is driven as the engine 1 is started, and the fuel delivered from the feed pump 50 is pressurized by the high-pressure pump 33, and the fuel pressure adjustment by the high-pressure regulator 35 is performed by closing the vapor processing valve 38. The predetermined high-pressure fuel regulated by the high-pressure regulator 35 is supplied to the injectors 14 of the respective cylinders via the common rail 34.
[0065]
After the engine is started, when the engine is running at a low speed, the drive speed of the high-pressure pump 33 is low, and the self-priming capability of the high-pressure pump 33 is insufficient. The flow rate of the fuel discharged by the feed pump 50 is small, and the backflow of the fuel delivered by the feed pump 50 to the fuel tank 30 through the fuel bypass passage 52d is prevented by a check valve 53 provided in the fuel bypass passage 52d. Then, a sufficient amount of fuel is supplied from the feed pump 50 to the high-pressure pump 33.
[0066]
Therefore, at the time of low engine rotation, as in the first embodiment, the high-pressure pump 33 can suck the fuel with a low suction resistance and operates under good volumetric efficiency.
[0067]
On the other hand, as the engine speed increases, the drive speed of the high-pressure pump 33 increases, so that the fuel suction capability of the high-pressure pump 33 increases and the fuel discharge flow rate by the high-pressure pump 33 increases.
[0068]
In a region where the fuel discharge flow rate by the high-pressure pump 33 is large, such as a high engine speed region, the fuel suction capability of the high-pressure pump 33 itself is increased. The fuel can be directly sucked from the fuel tank 30 through the passage 52d.
[0069]
Further, the check valve 53 disposed in the fuel bypass passage 52d prevents the fuel from flowing back to the fuel tank 30 and allows only the fuel flow to the high pressure pump 33. The check valve 53 is opened by the suction action, and the high-pressure pump 33 can perform fuel self-priming through the fuel bypass passage 52d.
[0070]
As a result, when the engine is rotating at high speed, in the region where the high-pressure pump 33 rotates at a high speed and the fuel discharge flow rate of the high-pressure pump 33 is large, the fuel is supplied from the feed pump 50 and the high-pressure pump 33 is self-priming. By directly sucking fuel from the fuel tank 30 into the high pressure pump 33 via 52d, the direct current resistance of the fuel by the feed pump 50 can be reduced, and a sufficient amount of fuel can be secured on the suction side of the high pressure pump 33. It becomes possible. Further, since the fuel bypass passage 52 is directly connected to the fuel tank 30, the fuel suction resistance of the high-pressure pump 33 can be further reduced.
[0071]
Therefore, even in a region where the fuel discharge flow rate of the high-pressure pump 33 is large due to the high-speed rotation of the high-pressure pump 33 such as a high engine speed region, the fuel suction resistance of the high-pressure pump 33 is further reduced and sufficient fuel is supplied to the high-pressure pump 33. Since the flow rate is ensured, it is possible to employ a small-capacity feed pump 50, and it is possible to further improve the volumetric efficiency of the high-pressure pump 33 while employing the small-capacity feed pump 50.
[0072]
This also ensures that a sufficient amount of stable high-pressure fuel can be reliably supplied to the injectors 14 of each cylinder even when the required fuel injection amount is large in response to high engine speed and high load. Further improvement is possible.
[0073]
The present invention is not limited to each of the above embodiments. For example, the fuel bypass passage 29d of the first embodiment employing an out-tank type feed pump 32 is connected to the fuel passage upstream of the feed pump 32. Instead, it may be directly connected to the fuel tank 30 as in the second embodiment. In this case, as in the second embodiment, the open end of the fuel bypass passage 29d extends in the bottom direction in the fuel tank 30. Then, a filter is attached to the open end, or a filter is interposed upstream of the check valve 37 in the fuel bypass passage 29d.
[0074]
【The invention's effect】
As described above, according to the first aspect of the present invention, the fuel bypass passage is provided that bypasses the upstream and downstream of the electric low-pressure pump that supplies fuel from the fuel tank to the engine-driven high-pressure pump, In this fuel bypass passage, at low engine speed In a state where both the high pressure pump and the low pressure pump are driven. Prevents back flow of fuel to the upstream side of the low pressure pump. In a state where both the high pressure pump and the low pressure pump are driven. Since a check valve that allows fuel flow from the upstream side of the low-pressure pump is installed, the self-priming capacity of the high-pressure pump is insufficient when the engine is running at low speed, and the low-pressure pump is used in areas where the fuel discharge flow rate is low. Is prevented by the check valve disposed in the fuel bypass passage, and a sufficient amount of fuel is supplied from the low pressure pump to the high pressure pump. Supplied. Therefore, in the region where the fuel discharge flow rate by the high-pressure pump is low when the engine is running at a low speed, the high-pressure pump can suck fuel with low suction resistance and operate with good volumetric efficiency, as in the past. Can do.
[0075]
Also, high engine speed of time In a region where the fuel discharge flow rate by the high-pressure pump is large, the fuel suction capability by the high-pressure pump itself increases, so the check valve disposed in the fuel bypass passage is opened by the suction action by the high-pressure pump. Along with the fuel supply, the high pressure pump can suck the fuel directly from the upstream of the low pressure pump through the fuel bypass passage by the self-priming action. This makes the engine high rotation of In a region where the fuel discharge flow rate of the high pressure pump is large, the direct current resistance of the fuel by the low pressure pump is reduced, and even in this case, a sufficient amount of fuel can be secured on the suction side of the high pressure pump. Inhalation resistance can be reduced.
[0076]
Therefore, high engine speed of time Even in the region where the fuel discharge flow rate of the high-pressure pump is large, the fuel suction resistance of the high-pressure pump does not increase, and a sufficient fuel flow rate to the high-pressure pump is ensured. This makes it possible to improve the volumetric efficiency of the high-pressure pump while employing a low-capacity low-pressure pump.
[0077]
Further, even when the required fuel injection amount is large in response to the high engine speed and high load, a sufficient amount of stable high-pressure fuel can be supplied to the injector, and the fuel injection control accuracy can be improved. .
[0078]
According to the second aspect of the present invention, the fuel bypass passage that connects the fuel tank and the low pressure fuel passage from the electric low pressure pump that feeds fuel to the engine driven high pressure pump to the high pressure fuel pump is provided. Installed in this fuel bypass passage at low engine speed In a state where both the high pressure pump and the low pressure pump are driven. Prevents backflow of fuel to the fuel tank, during high engine rotation In a state where both the high pressure pump and the low pressure pump are driven. Since a check valve that allows fuel flow from the fuel tank is installed, the self-priming capacity of the high-pressure pump is insufficient when the engine is running at low speed, and the low-pressure pump sends out fuel in the region where the fuel discharge flow rate is low. The reverse flow of the fuel to the fuel tank through the fuel bypass passage is prevented by a check valve disposed in the fuel bypass passage, and a sufficient amount of fuel is supplied from the low pressure pump to the high pressure pump. Therefore, in the region where the flow rate of fuel discharged by the high-pressure pump is low when the engine is running at a low speed, the high-pressure pump can suck the fuel with a low suction resistance, as in the first aspect of the invention. Can operate below.
[0079]
Also, high engine speed of time In a region where the fuel discharge flow rate by the high-pressure pump is large, the fuel suction capability by the high-pressure pump itself increases, so the check valve disposed in the fuel bypass passage is opened by the suction action by the high-pressure pump. Along with the fuel supply, the high pressure pump can suck the fuel directly from the fuel tank through the fuel bypass passage by the self-priming action. This makes the engine high rotation of time In a region where the fuel discharge flow rate of the high pressure pump is large, the direct current resistance of the fuel by the low pressure pump is reduced, and even in this case, a sufficient amount of fuel can be secured on the suction side of the high pressure pump. Further, since the fuel bypass passage is directly connected to the fuel tank, the fuel suction resistance of the high-pressure pump can be further reduced as compared with the first aspect of the invention.
[0080]
Therefore, high engine speed of time Even in the region where the fuel discharge flow rate of the high-pressure pump is large, the fuel suction resistance of the high-pressure pump is further reduced, and a sufficient fuel flow rate to the high-pressure pump is secured, so it is possible to adopt a low-pressure pump with a small capacity. Thus, the volumetric efficiency of the high-pressure pump can be further improved while employing a low-capacity low-pressure pump.
[0081]
Furthermore, even when the required fuel injection amount is large in response to high engine speed and high load, a sufficient amount of stable high-pressure fuel can be reliably supplied to the injector, and the fuel injection control accuracy can be further improved. Has an effect.
[Brief description of the drawings]
FIG. 1 is an overall schematic diagram of an in-cylinder fuel injection engine according to a first embodiment of the present invention.
[Fig. 2] Same as above, schematic configuration diagram of fuel supply system
FIG. 3 is an overall schematic diagram of an in-cylinder fuel injection engine according to a second embodiment of the present invention.
FIG. 4 is a schematic diagram of the fuel supply system
[Explanation of symbols]
1 In-cylinder fuel injection engine
14 Injector
29a, 52a Low pressure fuel passage
29d, 52d Fuel bypass passage
30 Fuel tank
32, 50 Feed pump (low pressure pump)
33 High pressure pump
37, 53 Check valve

Claims (2)

In-cylinder fuel that supplies fuel from a fuel tank to an engine-driven high-pressure pump by an electric low-pressure pump, further boosts the fuel by the high-pressure pump, and supplies high-pressure fuel to an injector that injects the fuel into the cylinder In the fuel supply system structure of the injection engine,
A fuel bypass passage that bypasses the upstream and downstream of the low-pressure pump is provided, and the high-pressure pump and the low-pressure pump are both driven to the upstream side of the low- pressure pump when the engine is running at low speed. A check valve that prevents fuel flow from the upstream side of the low-pressure pump in a state where both the high-pressure pump and the low-pressure pump are driven at the time of high engine rotation is prevented. A fuel supply system structure of an in-cylinder fuel injection engine. In-cylinder fuel that supplies fuel from a fuel tank to an engine-driven high-pressure pump by an electric low-pressure pump, further boosts the fuel by the high-pressure pump, and supplies high-pressure fuel to an injector that injects the fuel into the cylinder In the fuel supply system structure of the injection engine,
A fuel bypass passage that communicates a fuel tank and a low-pressure fuel passage from the low-pressure pump to the high-pressure pump is provided, and the high-pressure pump and the low-pressure pump are both driven in the fuel bypass passage when the engine is running at a low speed. in preventing the backflow of fuel into the fuel tank, at the time of high engine rotation is disposed a check valve that allows fuel flow from the fuel tank while driving both the said high-pressure pump and the low-pressure pump A fuel supply system structure for an in-cylinder fuel injection engine.

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