JP2001159350A - Fuel pressure control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve combustibility in a low load area and charging efficiency in a high load area and to prevent blow-by of a fuel in an engine designed to control the intake air quantity by controlling the closing timing of an intake valve in an early closing direction in a wide range. SOLUTION: In a low load area (A-area) wherein the closing timing of an intake valve is set before the bottom dead center of intake to perform Miller cycle operation, fuel pressure is set higher than a medium load area (C-area) to improve atomization to thereby suppress worsening of combustion caused by a lowering of an effective compression ratio (S5). In a high load area (B- area), valve timing is controlled to evacuate the exhaust side in a valve overlap period so as to perform scavenging using pressure difference, while injection start timing is delayed so as not to cause fuel blow-by by scavenging, and fuel pressure is heightened corresponding to shortening of an injectable period, to increase an injection rate (S6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pressure control device for an engine, and more particularly, to an engine configured to control the intake air amount by controlling the closing timing of an intake valve. The present invention relates to a device for controlling pressure (hereinafter, referred to as fuel pressure).

[0002]

2. Description of the Related Art In recent years, a valve mechanism capable of arbitrarily controlling the opening and closing timing of intake and exhaust valves such as an electromagnetic valve mechanism has been provided.
A low load in which the intake air amount of the engine is controlled by continuously controlling the closing timing of the intake valve to be advanced using the valve operating mechanism, and the closing timing of the intake valve is before the intake bottom dead center. An engine having a configuration in which a so-called early closing Miller cycle operation is performed in a region has been developed (Japanese Patent Application No. 10-025964).
No.).

[0003]

In the Miller cycle operation performed in the low load region, the effective compression ratio (actual compression ratio) is reduced, so that the combustion is slowed down. In some cases.

Further, in a high load region, the valve timing (opening timing of the exhaust valve) is controlled so that the exhaust system pressure becomes negative during the overlap period of the intake and exhaust valves, and scavenging is performed by a pressure difference. In this configuration, the fuel injected upstream of the intake valve before the opening timing of the intake valve blows to the exhaust side during the overlap period in which scavenging is performed. There was a possibility.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a valve operating mechanism capable of controlling the opening / closing timing of an intake / exhaust valve in a wide range and continuously controlling the closing timing of an intake valve in a direction to advance the timing. It is an object of the present invention to provide a fuel pressure control device capable of suppressing deterioration of combustion in a Miller cycle operation region in an engine configured to control an intake air amount of the engine.

It is another object of the present invention to provide a fuel pressure control device capable of injecting a required amount of fuel while preventing fuel blow-through while improving the filling efficiency in a high load region in the engine having the above-described structure. I do.

[0007]

SUMMARY OF THE INVENTION Therefore, the invention according to a first aspect of the present invention is directed to an engine configured to control the intake air amount by continuously changing the closing timing of the intake valve in a direction to advance the closing timing. It is configured to control to a different value for each operating region of the engine.

According to this configuration, in the operation region where the fuel pressure is controlled to be high, the atomization of the fuel can be improved, and the injection rate can be increased to inject the same amount of fuel in a shorter time. It becomes possible.

According to the present invention, the fuel pressure is controlled to be higher than the basic pressure in a predetermined low load area and a high load area, and the fuel pressure is controlled to the basic pressure in a predetermined medium load area. .

According to this structure, the fuel pressure is increased in the low-load and high-load regions to improve the fuel atomization and increase the injection rate, while the fuel pressure is reduced in the middle-load region by reducing the fuel pressure. Avoid excessive force.

In the third aspect of the present invention, the fuel pressure is controlled to be higher than the basic pressure in an operation region in which the intake valve is closed before the intake bottom dead center and the Miller cycle operation is performed.
According to such a configuration, in the operating region where the effective compression ratio (actual compression ratio) is reduced by the Miller cycle operation, the fuel pressure is increased and the atomization is improved.

According to the present invention, the valve timing is controlled so that the pressure of the exhaust system becomes negative during the overlap period of the intake and exhaust valves in a predetermined high load region, and the predetermined timing is provided. In the high load range, the fuel injection start timing is configured to be delayed, and the fuel pressure is controlled to be higher than the basic pressure.

According to this configuration, if the valve timing is controlled so that the pressure in the exhaust system becomes negative during the valve overlap period, scavenging is performed by the pressure difference. Along with delaying the timing, increasing the fuel pressure to increase the injection rate,
The required amount of fuel is injected in a short time at a delayed timing.

[0014]

According to the first aspect of the present invention, the fuel pressure is increased as necessary for each operation region, the atomization is improved in the region where combustion is deteriorated, and the period during which the fuel can be injected is shortened. In such a region, there is an effect that the injection rate can be increased and the required fuel amount can be injected in a short injection time.

According to the second aspect of the invention, it is possible to improve the atomization of the fuel in the low load region where the combustion deteriorates to suppress the deterioration of the combustion, and to increase the injection rate in the high load region where the injection period is restricted. The required amount of fuel can be injected in a short time, and further, in the middle load region, the fuel pressure can be reduced to prevent the penetration of the fuel spray from becoming excessive, thereby preventing the deterioration of the exhaust properties.

According to the third aspect of the present invention, in the Miller cycle operation region in which the effective compression ratio (actual compression ratio) decreases and combustion deteriorates, the deterioration of combustion is suppressed by increasing the fuel pressure to improve atomization. Therefore, there is an effect that deterioration of exhaust characteristics and reduction of torque can be suppressed.

According to the fourth aspect of the present invention, the required amount can be reliably injected at the delayed injection timing while improving the charging efficiency by performing scavenging by the pressure difference in the high load region. This has the effect of preventing blow-through of fuel and preventing deterioration of exhaust characteristics and air-fuel ratio control accuracy.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1 showing the entire configuration of the embodiment, an intake valve 3 and an exhaust valve 4 whose opening / closing timing is electronically controlled by an electromagnetic valve mechanism 2 are mounted on each cylinder of the gasoline engine 1.

A fuel injection valve 6 is mounted on the intake port 5 on the upstream side of the intake valve 3 of each cylinder, and an ignition plug 8 is mounted on the combustion chamber 7. Further, each ignition plug 8 has an ignition coil 9.
Is provided.

The main body of the engine 1 outputs a reference signal at a reference crank angle of each cylinder, a crank angle sensor 10 for outputting a unit angle signal for each unit crank angle, an air flow meter 11 for detecting an intake air flow rate, A water temperature sensor 12 for detecting a cooling water temperature is mounted. In addition, an accelerator opening sensor 13 for detecting the opening APO of an accelerator pedal of the vehicle (not shown), a vehicle speed sensor 14, and the like are provided.

The detection signals of the various sensors are output to the control unit 15, and the control unit 15
Based on these detection signals, an injection pulse signal is output to the fuel injection valve 6 to control the injection amount and the injection timing, and an ignition signal is output to the ignition coil 9 to control the ignition timing. A valve drive signal is output to the electromagnetic valve mechanism 2 to control the opening / closing timing of the intake valve 3 and the exhaust valve 4.

FIG. 2 shows the structure of the electromagnetic valve mechanism 2.
In FIG. 2, the electromagnetic valve mechanism 2 is provided integrally with a housing 21 made of a non-magnetic material provided on a cylinder head and a stem 31 of an intake valve 3 (or an exhaust valve 4, hereinafter represented by the intake valve 3). Armature 22 that is freely movable within housing 21 and a position facing housing 21 at a position facing the upper surface of armature 22 so as to exert an electromagnetic force for sucking armature 22 and closing intake valve 3. A valve-closing electromagnet 23 fixedly disposed in the housing 21 at a position opposed to the lower surface of the armature 22 so as to exert an electromagnetic force for attracting the armature 22 and opening the intake valve 3. Valve-opening electromagnet 24 and a valve-closing-side return spring 25 for urging the armature 22 in the valve-closing direction of the intake valve 3.
And a valve-opening-side return spring 26 that urges the armature 22 in the valve opening direction of the intake valve 3. When both the valve-closing electromagnet 23 and the valve-opening electromagnet 24 are demagnetized, the valve-closing-side return spring 25 and the valve-closing-side return spring 25 are moved so that the intake valve 3 is located substantially at the center between the fully-open position and the valve-closing position. Valve open side return spring
26, the intake valve 3 is driven to close when only the valve-closing electromagnet 23 is excited, and the intake valve 3 is opened when only the valve-opening electromagnet 24 is excited. You.

The opening / closing timing of the intake valve 3 and the exhaust valve 4 by the electromagnetic valve mechanism 2 is controlled so as to be a target opening / closing timing set based on the operating conditions of the engine 1. Is controlled in a wide range in the early closing direction based on the accelerator opening APO and the engine rotation speed Ne or the target cylinder intake air amount (target torque) set based on these, to adjust the cylinder intake air IVC. The amount is controlled for each cylinder, whereby a so-called early closing Miller cycle operation is performed in a low load region where the closing timing IVC is before the intake bottom dead center.

The air amount control by controlling the closing timing IVC of the intake valve 3 is basically performed with the intake pressure set to the atmospheric pressure state (the throttle valve is fully opened).
The throttle valve may be closed to reduce the air amount in a region where the target torque cannot be controlled even if the closing timing IVC is controlled to the minimum operating angle by maximizing the closing timing IVC.

Further, in a predetermined high load region, the phase of the exhaust pulsation is adjusted by controlling the opening timing EVO of the exhaust valve 4, and the exhaust pressure is controlled during the valve overlap (O / L) period of the intake and exhaust valves. Is set to a negative pressure, and scavenging is performed by the pressure difference between the intake side and the exhaust side (see FIG. 3).

On the other hand, the fuel injection valve 6 has a fuel pump
The fuel sucked from the fuel tank 17 is fed by pressure by the fuel pump 16, and the fuel pressure is adjusted by the amount of fuel (return fuel amount) returned from the pressure regulator 18 into the fuel tank 17. I have. The amount of fuel returned from the pressure regulator 18 is controlled by the control unit 15, and the control unit 15 is configured to perform control based on the difference between the actual fuel pressure detected by the fuel pressure sensor 19 and the target fuel pressure. The actual fuel pressure is feedback-controlled to the target fuel pressure by controlling the return fuel amount.

The fuel pump 16 and the pressure regulator 18 are provided inside a fuel tank 17. Here, the details of the fuel pressure control by the control unit 15 will be described with reference to the flowchart of FIG.

First, at S1, information on the engine speed (rpm) and torque is read. In S2, three areas A, B, and C are set in advance according to the engine speed (rpm) and the torque.
Reference is made to the operation area divided into.

A region A2 shown in S2 of FIG. 4 is a low load region in which the closing timing IVC of the intake valve 3 is before the bottom dead center of the intake and a so-called early closing mirror cycle operation is performed. The region is a high load region in which scavenging is performed by setting the pressure on the exhaust side to a negative pressure during the valve overlap period, and the remaining medium load region is a C region. still,
On the higher load side than the region A, the intake air amount of the engine 1 is controlled by controlling the closing timing IVC of the intake valve 3 within the control range after the intake bottom dead center.

In S3, it is determined which of the three areas A, B, and C corresponds. If it is determined in S3 that it is the C region, the process proceeds to S4, and a basic pressure is set as the target fuel pressure. The basic pressure is a multipoint injection (MPI) type electronically controlled fuel which is generally a 4-cycle engine of an Otto cycle in which air amount is controlled by a throttle valve and which has a fuel injection valve at each intake port. The pressure corresponds to the fuel pressure in the injection device.

On the other hand, if it is determined in S3 that it is the area A, the process proceeds to S5, and the target fuel pressure is set to a predetermined pressure higher than the basic pressure. The region A is a region where the Miller cycle operation is performed as described above, and is a region where the combustion is slowed down due to a low effective compression ratio (actual compression ratio) and the combustion deteriorates. This improves the atomization of the fuel and suppresses the deterioration of combustion due to a decrease in the effective compression ratio.

When it is determined in step S3 that the engine is in the region B, the process proceeds to step S6, in which the target fuel pressure is set to a predetermined pressure higher than the basic pressure, and the fuel injection valve 6 starts injection. Is set to be delayed as compared with the A and C areas.

That is, in the region B, as shown in FIG. 3, scavenging is performed using the pressure difference between the intake side and the exhaust side during the valve overlap (O / L) period of the intake and exhaust valves. If the fuel injection is performed at an early stage, when the scavenging is performed, the fuel blows to the exhaust side.

For this reason, as shown in FIG. 3, in order to avoid blow-by by scavenging, in the A and C regions, the fuel is injected at an injection start timing such that the injection is substantially completed before the opening timing IVO of the intake valve 3. On the other hand, in the region B, the injection start timing is set to be delayed slightly before the closing timing EVC of the exhaust valve 4 in consideration of the fuel transport time.

However, if the end time of the injection is shifted backwards with the delay of the injection start timing, the intake valve 3
There is a possibility that fuel that will stay on the upstream side of the intake valve 3 before the closing timing of the fuel may be generated, and the period during which the fuel can be injected is shortened (see FIG. 3). Therefore, the fuel pressure is increased to increase the injection amount per unit time (injection rate),
This is to make it possible to inject the same amount of fuel in a shorter time so that the required fuel amount can be reliably supplied to the cylinder even if the injection start timing is delayed.

As described above, the fuel pressure is controlled to a pressure higher than the basic pressure in the areas A and B, whereas the basic pressure is controlled to be lower in the area C than in the other areas. However, by suppressing the fuel pressure relatively low in the C region, it is possible to avoid deterioration of the exhaust properties due to the fuel spray having an excessive penetration force.

In the high load range, the opening timing EV of the exhaust valve 4
By controlling the phase of exhaust pulsation by controlling O, the pressure on the exhaust side becomes negative pressure during the valve overlap period of the intake and exhaust valves, and scavenging is performed by the pressure difference between the intake side and the exhaust side. The control to increase the fuel pressure while configuring and delaying the injection start timing in the high load region is not limited to the engine of the type in which the intake air amount is controlled by controlling the closing timing of the intake valve. The present invention can also be applied to an engine configured to adjust the intake air amount by opening and closing a throttle valve.

Further, the above-described scavenging may not be performed in the high load region. In this case, the basic pressure is controlled in both the B and C regions, and the fuel pressure may be increased only in the A region. .

Further, in the above-described embodiment, the electromagnetic valve mechanism is used. However, any structure capable of arbitrarily controlling the opening / closing timing of the intake / exhaust valve may be used. For example, the intake / exhaust valve is driven using hydraulic pressure. It may be a configuration or the like.

The fuel pressure is adjusted by adjusting the return fuel amount as described above.
For example, a method of controlling the 16 discharge amounts may be used.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an engine according to an embodiment.

FIG. 2 is a sectional view showing the configuration of the electromagnetic valve mechanism in the embodiment.

FIG. 3 is a diagram for explaining a state of scavenging in a high load region in the embodiment.

FIG. 4 is a flowchart showing a state of fuel pressure control in the embodiment.

[Explanation of symbols]

 Reference Signs List 1 engine 2 electromagnetic valve mechanism 3 intake valve 4 exhaust valve 6 fuel injection valve 7 combustion chamber 10 crank angle sensor 11 air flow meter 12 water temperature sensor 13 accelerator opening sensor 15 control unit 16 fuel pump 17 fuel tank 18 pressure regulator 19 fuel pressure sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 43/00 301 F02D 43/00 301Z F02M 37/00 F02M 37/00 A 69/00 340 69/00 340R F-term (for reference) 3G084 AA00 BA15 BA23 CA03 CA04 DA01 DA10 EB12 EC02 EC08 FA05 FA07 FA10 FA18 FA20 FA38 3G092 AA01 AA11 BA01 BB06 DA01 DA02 DA07 DA12 DC03 DD03 DG02 DG09 EA01 EA03 EA04 EA22 HA01 HA03 HE01 GA03 HF08Z HF21Z 3G301 HA00 HA19 JA01 JA21 KA08 KA09 LA03 LA07 LC02 MA00 MA11 MA18 MA27 ND02 NE11 NE12 PA01Z PA17Z PB08A PB08Z PE01Z PE03Z PE06A PE06Z PE08Z PE10A PE10Z PF01Z PF03Z

Claims (4)

[Claims] In an engine configured to control an intake air amount by continuously changing the closing timing of an intake valve in a direction to advance an intake valve timing, a fuel pressure is controlled to a different value for each operating region of the engine. A fuel pressure control device for an engine. 2. The fuel supply system according to claim 1, wherein the fuel pressure is controlled to be higher than the basic pressure in a predetermined low load area and a high load area, and the fuel pressure is controlled to the basic pressure in a predetermined medium load area.
The fuel pressure control device for an engine according to any one of the preceding claims. 3. The fuel pressure control system for an engine according to claim 1, wherein the fuel pressure is controlled to be higher than the basic pressure in an operation region in which the intake valve is closed before the intake bottom dead center and the Miller cycle operation is performed. 4. The valve timing is controlled so that the exhaust system pressure becomes negative during the overlap period of the intake and exhaust valves in a predetermined high load region. The fuel pressure control device for an engine according to claim 1, wherein the fuel pressure control device is configured to delay injection start timing and to control the fuel pressure to be higher than a basic pressure.