JPH0988763A - Fuel pressure control device of high pressure fuel injection type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent growth of vapor after stopping an engine and to provide favourable restarting performance. SOLUTION: A pressure regulator 6 for high pressure provided on the downstream of a high pressure line 2b to connect an injector 1 is made of a contantly closed type to open a valve at the time of driving an engine, and a thermostat valve 10 to close at the time when fuel temperature is high and a constantly opened type solenoid valve 11 to work to close at the time of driving the engine are interposed in a fuel relief line 2e to by-pass this pressure regulator 6 for high pressure. In the case when fuel temperature of a high pressure line at the time of stopping the engine, the thermostat valve 10 is closed, fuel residual pressure of the high pressure line is held in a high pressure state, growth of vapor is prevented and restartability is secured. When the aforementioned fuel temperature becomes lower than specified temperature, the thermostat valve 10 opens, fuel residual pressure of the high pressure line is released and a pressure load applied on the injector 1, etc., is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel for a high-pressure fuel injection engine which prevents the generation of vapor by adjusting the residual fuel pressure in the high-pressure line according to the change in the fuel temperature in the high-pressure line after the engine is stopped. The present invention relates to a pressure control device.

[0002]

2. Description of the Related Art Generally, in a high-pressure fuel injection engine that injects high-pressure fuel, fuel pressurized by a high-pressure fuel pump is supplied to a high-pressure line, and the fuel pressure in this high-pressure line is adjusted by a high-pressure pressure regulator. There is a type that employs a so-called line pressure holding type high pressure fuel injection system in which a predetermined high pressure state is maintained and the injector connected to this high pressure line directly injects it into the combustion chamber.

In such a line pressure holding type high pressure fuel injection system, after the engine is stopped, the residual fuel pressure in the high pressure line is released to reduce the pressure load on each component such as the injector, thereby improving durability and reliability. However, if the fuel pressure in the high-pressure line is suddenly reduced after the engine is stopped, the fuel in the high-pressure line is easily heated to a high temperature due to the effects of radiant heat in the engine chamber. In particular, when the fuel used contains a relatively large amount of low boiling point components such as gasoline, vapor is likely to be generated.

In such a situation, even if an attempt is made to restart the engine (so-called thermal restart), the fuel is not properly injected from the injector due to the generation of vapor, which makes startup difficult.

To cope with this, in the intake manifold injection type engine, as disclosed in, for example, Japanese Patent Laid-Open No. 1-133841, when the fuel temperature at the time of engine start is above a predetermined value, a pressure regulator is used. The flow rate of the return fuel from the high pressure line is limited, the fuel pressure in the high pressure line is made relatively high to suppress the generation of vapor, and after a lapse of a predetermined time after the engine is started, the pressure regulator is set to a relative pressure with respect to the intake pipe pressure. There is known a technique of gradually shifting to normal control that operates according to the above.

[0006]

However, the fuel pressure control range of the high pressure fuel injection type engine is about 5 to 20 MPa,
It is much higher than the fuel pressure control range (0 to 0.3MPa) of the intake manifold injection type engine described above, and if the residual fuel pressure is released after the engine is stopped, it is easy to generate vapor under high temperature conditions and restart itself is difficult. become. In the above-mentioned prior art, since the pressure of the high pressure line is increased after starting to suppress the generation of vapor, it is impossible to deal with the case where vapor has already been generated at the time of starting.

[0007] Therefore, the applicant of the present invention is disclosed in Japanese Patent Laid-Open No. 4-339.
In Japanese Patent No. 143, after the engine is stopped, the high-pressure pressure regulator is fully closed until the predetermined time elapses to maintain the residual fuel pressure in the high-pressure line at a high pressure to prevent the generation of vapor, and after the predetermined time elapses, That is, a technique has been proposed in which, after the fuel in the high-pressure line has been cooled to a predetermined level, the high-pressure pressure regulator is fully opened to release the residual fuel pressure in the high-pressure line.

However, in this prior art, in order to maintain the residual fuel pressure in the high pressure line in a high pressure state even after the engine is stopped, the pressure regulator for high pressure is energized and the fully closed state of this pressure regulator is maintained. In addition, the pressure regulator is uniquely energized regardless of the fuel temperature, which imposes a heavy load on the battery when the engine is stopped and shortens the life of the battery. There is a problem that the engine load after starting increases due to charging and the fuel consumption rate deteriorates.

In view of the above circumstances, the present invention prevents the generation of vapor after the engine is stopped while reducing the engine load due to battery charging to prevent the deterioration of the fuel consumption rate without burdening the battery. An object of the present invention is to provide a fuel pressure control device for a high pressure fuel injection type engine that can obtain good restart performance.

[0010]

To achieve the above object, the present invention provides a high-pressure fuel pump in a fuel line and a high-pressure pressure regulator downstream of the high-pressure fuel pump. A high-pressure line is provided between the high-pressure fuel pump and the high-pressure pressure regulator, a low-pressure delivery line is provided from the fuel tank to the high-pressure fuel pump upstream, and a low-pressure return line is provided from the high-pressure pressure regulator downstream to the fuel tank. In a high-pressure fuel injection engine in which an injector for directly injecting fuel into the combustion chamber is connected to the high-pressure line, the high-pressure pressure regulator is a normally-closed type that is fully closed when the engine is stopped, and the high-pressure pressure regulator upstream Fuel release between the high pressure line and the low pressure return line downstream Bypass connection via a line, the fuel relief line, at the time of the thermostat valve and the engine operation in which the fuel temperature is opened below the set temperature, characterized in that interposed between normally open control valve for closing.

According to the present invention, according to the present invention, the normally open type switching valve which is interposed in the fuel relief line which bypasses the high pressure regulator and connects the upstream high pressure line and the downstream low pressure return line while the engine is operating. Shuts off this fuel relief line. As a result, the fuel in the high-pressure line is pressurized by the high-pressure fuel pump, regulated by the high-pressure pressure regulator and held at a predetermined high pressure state, and the fuel, which is metered in a predetermined amount from the injector, is injected into the combustion chamber. . On the other hand, when the engine stops, the high pressure pressure regulator is fully closed,
Further, when the switching valve is opened and the fuel temperature in the high pressure line is high, the thermostat valve interposed in the fuel relief line is closed. When the thermostat valve is closed, the fuel relief line is shut off, so that the residual fuel pressure in the high pressure line is maintained in a high pressure state and vapor is prevented from being generated. After that, when the fuel in the high pressure line is cooled to a predetermined level, the thermostat valve is opened, and the fuel residual pressure in the high pressure line is released.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall schematic diagram centering on a fuel line of a high-pressure fuel injection engine. A high-pressure fuel injection engine (hereinafter, simply referred to as “engine”) A shown in the present embodiment is a horizontally opposed engine or a multi-cylinder engine having left and right banks, such as a V-type engine,
The injector 1 for injecting fuel into the cylinder faces the combustion chamber of each cylinder.

The fuel line 2 for supplying fuel to the injector 1 constitutes a so-called line pressure holding type high pressure injection system, and a low pressure delivery line 2a is provided to an in-tank type fuel feed pump 4 provided in the fuel tank 3. The high-pressure fuel pump 5 is communicated via the high-pressure fuel pump 5, and the high-pressure electromagnetic pressure regulator 6 is interposed downstream of the high-pressure fuel pump 5 via the high-pressure line 2b. It faces the fuel tank 3 through a return line 2c.

Further, the suction port of the high-pressure fuel pump 5 which communicates with the low-pressure delivery line 2a communicates with the low-pressure return line 2c through a fuel bypass line 2d, and the high-pressure fuel line 2d receives the high pressure. A diaphragm-type relief valve 7 that regulates the pressure of the fuel supplied to the fuel pump 5 is installed.

The high-pressure fuel pump 5 is an engine-driven type which is continuously connected to an output shaft such as a crankshaft or a camshaft provided in the engine A via transmission means, and the high-pressure electromagnetic pressure regulator. The valve opening 6 is controlled by the control current supplied to the solenoid coil or the duty ratio of the duty signal.

The high-pressure electromagnetic pressure regulator 6 is a normally closed type, and the valve opening degree increases as the control current for the solenoid coil increases or the duty ratio of the duty signal increases. The control current for the solenoid coil or the duty ratio of the duty signal is set on the basis of the engine speed or the like. By controlling the valve opening of the high pressure pressure regulator 6, the fuel pressure in the high pressure line 2b becomes equal to the engine speed or the like. The optimum state is set.

Further, a fuel manifold 8 is interposed in the high pressure line 2b, and bank fuel rails 9L and 9R provided on both left and right banks are branched and connected to the fuel manifold 8 and their discharge sides are gathered. And is communicated with the high pressure electromagnetic pressure regulator 6. Then, each bank fuel rail 9L,
The injector 1 provided for each cylinder is connected to 9R.

On the other hand, the high-pressure line 2b upstream of the high-pressure electromagnetic pressure regulator 6 and the low-pressure return line 2c downstream are bypass-connected via a fuel relief line 2e, and a thermostat is provided at the inlet of the fuel relief line 2e. A valve 10 is installed, and a normally open electromagnetic switching valve 11 is installed in the middle thereof. As shown in FIG. 4, the thermostat valve 10 employed in the present embodiment is of a wax pellet type, and the thermowax enclosed in the wax case 10a exposed to the high pressure line 2b undergoes a phase change from solid to liquid. Due to body expansion,
The wax case 10a slides along the shaft 10b in the vertical direction in the figure, and the valve body 10c fixed to the wax case 10a opens and closes. That is, when the fuel temperature in the high pressure line 2b is high, the wax enclosed in the wax case 10a is heated and expanded as shown in FIG. 3A, and the valve body 10c is expanded through the wax case 10a. The fuel relief line 2e is cut off by moving downward in the drawing while resisting the urging force of the spring 10d to close the valve. On the other hand, when the fuel temperature in the high pressure line 2b is low, the wax contracts and the valve body 10c opens by receiving the biasing force of the spring 10d, as shown in FIG. The temperature at which the valve element 10c starts to open is experimentally determined from the temperature range in which vapor is generated from the fuel temperature increase characteristic in the high pressure line 2b after the engine is stopped, and is set based on this temperature range.

The normally open electromagnetic switching valve 11 closes when the solenoid coil is excited by a drive signal from an electronic control unit (ECU) 12, and shuts off the fuel relief line 2e.

Next, the operation of this embodiment having the above configuration will be described. Ignition switch (not shown)
When the power is turned on, the electronic control unit 12 is turned on, the fuel feed pump 4 is energized, the fuel supply to the high pressure fuel pump 5 is started, and
The flow path switching control routine shown in is executed every predetermined time.

In this flow path switching routine, first, in step S1, the crank pulse is read, and in step S2,
It is determined from the crank pulse input interval whether the engine is stopped. That is, when the crank pulse is not input for a predetermined time, it is determined that the engine is stopped and the routine is exited.

On the other hand, when it is judged in step S2 that the engine is operating based on the crank pulse input interval, and when the operation proceeds to step S3, the solenoid coil of the electromagnetic switching valve 11 interposed in the fuel relief line 2e of the fuel line 2 is energized. Then, after closing the electromagnetic switching valve 11, the routine is exited.

When the ignition switch is turned off, the power supply to the electronic control unit 12 is cut off.
The energization of the electromagnetic switching valve 11 is turned off, and the electromagnetic switching valve 11 opens.

Next, the control operation of the entire fuel system will be described. When the ignition switch is turned on, fuel supply to the high-pressure fuel pump 5 by the fuel feed pump 4 is started. However, since the high-pressure fuel pump 5 is an engine-driven type, when the engine is stopped immediately after the ignition switch is turned on, Since the fuel has not been driven yet, therefore, the fuel flows from the fuel bypass line 2d communicating with the suction port of the high-pressure fuel pump 5 to the diaphragm type relief valve 7.
Is returned to the low-pressure return line 2c via.

When the engine A is started, the high pressure fuel pump 5 is driven to start the supply of the pressurized fuel to the high pressure line 2b. The fuel pressure in the high pressure line 2b is adjusted by the high pressure pressure regulator 6. The high-pressure pressure regulator 6 is a normally closed type, and while the engine is operating, the high-pressure line 2 is based on the engine speed and the like.
The fuel pressure of b is controlled so as to maintain a substantially constant state. The opening control of the high pressure pressure regulator 6 is described in detail in Japanese Patent Application Laid-Open No. 4-339143 and the like, which has been disclosed in the related art, and therefore the description thereof is omitted here. However, the high-pressure pressure regulator disclosed in the publication is a normally open type, and the control is opposite to that of the present application.

FIG. 2 shows the high pressure line 2b during engine operation.
Shows the fuel path of. The figure (a) shows the case where the fuel temperature during engine operation is low, and the figure (b) shows the case where the fuel temperature during engine operation is high. As described above, since the electromagnetic switching valve 11 interposed in the fuel relief line 2e bypassing the high pressure pressure regulator 6 closes during engine operation, the fuel relief valve 10 operates regardless of whether the thermostat valve 10 is opened or closed. The line 2e is shut off, and the fuel pressure in the high pressure line 2b is properly adjusted by the high pressure pressure regulator 6.

FIG. 3 shows the fuel path of the high pressure line 2b when the engine is stopped. The figure (a) shows the case where the fuel temperature is low while the engine is stopped, and the figure (b) shows the case where the fuel temperature is high while the engine is stopped. When the ignition switch is turned off to stop the engine, the electromagnetic switching valve 11 is de-energized, so that the electromagnetic switching valve 11 opens the fuel relief line 2e. At the same time, the power supply to the high pressure pressure regulator 6 is also cut off, so that the high pressure pressure regulator 6 closes. On the other hand, when the fuel temperature in the high pressure line 2b is high when the engine is stopped, the thermostat valve 10 provided at the inlet of the fuel relief line 2e is shown in FIG.
And as shown in FIG. 4A, the wax enclosed in the wax case 10a expands and pushes down the valve body 10c,
The fuel relief line 2e is closed.

As a result, as shown in FIG. 3 (b), the high pressure line 2b is closed, the residual fuel pressure is maintained at a high pressure, and the generation of vapor is prevented. Therefore, not only good starting performance can be obtained even in a thermal restart, but the residual fuel pressure is maintained at a high pressure, so that the fuel pressure rises quickly at the time of startup, and it is possible to restart in a short time. It will be possible.

After the engine is stopped, when the fuel in the high pressure line 2b is cooled to a predetermined temperature at which vapor is not likely to occur, the thermostat valve 1 is activated.
The wax enclosed in the wax case 10a of No. 0 contracts, and the valve body 10c opens by the biasing force of the spring 10d, as shown in FIG. 4 (b). As a result, FIG.
As shown in (a), the residual fuel pressure in the high-pressure line 2b is released through the fuel relief line 2e, the pressure load on each component such as the injector 1 is reduced, and the durability is secured.

The present invention is not limited to the above embodiment, but for example, the normally open solenoid operated directional control valve 11 may be interlocked with an ignition switch so that the ignition switch is turned on to close the valve.

[0031]

As described above, according to the present invention,
The high-pressure pressure regulator is a normally closed type that is fully closed when the engine is stopped, and the fuel relief line that bypass-connects the high-pressure line upstream and the low-pressure return line downstream of this high-pressure pressure regulator has a fuel temperature below the set temperature. Since the thermostat valve that opens and the normally open switching valve that closes when the engine is operating are installed,
When the fuel temperature in the high pressure line is high when the engine is stopped, the thermostat valve closes to maintain the residual fuel pressure in the high pressure line at a high pressure state, so even if the fuel is heated due to the radiant heat of the engine, etc. It is possible to obtain a good thermal restart performance without the occurrence of fuel, and because the residual fuel pressure is maintained at a high pressure state, the fuel pressure rises quickly at restart, and for that much time It will be possible to restart with.

Further, after the engine is stopped, when the fuel in the high pressure line is cooled to a predetermined temperature or lower, the thermostat valve is opened and the residual fuel pressure in the high pressure line is released. Therefore, each component such as an injector is opened. The pressure load applied to is reduced and durability is secured.

Furthermore, since the residual fuel pressure in the high pressure line is maintained by the normally closed high pressure pressure regulator and the closing operation of the thermostat valve, no power source is required and therefore the battery is not burdened and the battery is charged. As a result, the engine load due to is reduced and the deterioration of the fuel consumption rate can be prevented.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram centering on a fuel line of a high-pressure fuel injection engine.

FIG. 2 is an explanatory view of a main part showing a fuel path of a fuel line during engine operation.

FIG. 3 is an explanatory view of a main part showing a fuel path of a fuel line when the engine is stopped.

FIG. 4 is a side view showing the operation of the thermostat valve.

FIG. 5 is a flowchart showing a control routine of a normally-open electromagnetic switching valve.

[Explanation of symbols]

 1 injector 2 fuel line 2a low pressure delivery line 2b high pressure line 2c low pressure return line 2e fuel relief line 3 fuel tank 5 high pressure fuel pump 6 high pressure pressure regulator 10 thermostat valve 11 normally open electromagnetic switching valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02M 69/00 340 F02M 69/00 340Z

Claims (1)

[Claims] 1. A high-pressure fuel pump is provided in a fuel line, and a high-pressure pressure regulator is provided downstream of the high-pressure fuel pump, and the high-pressure fuel pump and the high-pressure pressure regulator are provided between the high-pressure fuel pump and the high-pressure fuel regulator. Is a high-pressure line, the fuel tank to the high-pressure fuel pump upstream is a low-pressure delivery line, the high-pressure pressure regulator downstream to the fuel tank is a low-pressure return line, and fuel is directly injected into the combustion chamber in the high-pressure line. In a high-pressure fuel injection engine to which an injector is connected, the high-pressure pressure regulator is a normally closed type that is fully closed when the engine is stopped, and the high-pressure line upstream of this high-pressure pressure regulator and the low-pressure return line downstream are fuel relief lines. Bypass connection via the The Furain, the fuel pressure control apparatus for a high pressure fuel injection type engine at the time of the thermostat valve and the engine operation, characterized in that interposed between normally open control valve for closing the fuel temperature is opened below the set temperature.