JP3397866B2 - Engine fuel supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an engine, which is provided with a mixture forming port for mixing pressurized air and fuel and supplying the mixture to a combustion chamber, separately from an intake port.

[0002]

2. Description of the Related Art Conventionally, various fuel supply systems for engines have been known which are designed to reduce fuel consumption and improve emissions by performing stratification by unevenly distributing an air-fuel mixture around a spark plug at a low load. .

For example, in the device disclosed in Japanese Patent Laid-Open No. 60-67721, an in-cylinder fuel injection valve which opens toward the vicinity of an ignition plug arranged in the center of a combustion chamber is provided,
The intake port is used as a swirl generating port to generate swirl in the combustion chamber when the load is low and collect the fuel injected from the in-cylinder fuel injection valve around the spark plug. In addition, in this device, a fuel injection valve is also provided in the intake passage, and when the load is high, fuel is injected from the fuel injection valve in the intake passage to perform uniform combustion.

However, in this device, the fuel injected from the in-cylinder fuel injection valve is not sufficiently promoted to atomize when the load is low, and the momentum of the injection is too strong to easily penetrate near the spark plug. There's a problem.

Therefore, as disclosed in Japanese Utility Model Laid-Open No. 62-18335, in addition to the first and second intake ports for supplying air to the combustion chamber, a port for forming an air-fuel mixture is opened in the combustion chamber, A fuel injection valve is provided at the port for forming the air-fuel mixture, the port is connected to a pressurized air supply passage equipped with a supercharger for supplying pressurized air, and the valve opening timing for opening and closing this port There has been proposed a device in which is set to be later than the opening timing of the intake valves of the first and second intake ports. In this device, the fuel and the pressurized air are mixed in the air-fuel mixture forming port, and the air-fuel mixture is separated from the air sucked from the intake port in the combustion chamber in the latter half of the intake stroke. The fuel is atomized and stratified at a low load by being fed near the center of the.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
As shown in Japanese Patent No. 8335, in the case where a port for air-fuel mixture formation is provided separately from an intake port for supplying air, uniform combustion is required only by providing a fuel injection valve in the port for air-fuel mixture formation. In such an operating region, it is not always possible to supply fuel that meets the requirements. Therefore, it has been considered to provide a fuel injection valve in the intake port in addition to the fuel injection valve in the air-fuel mixture formation port so that both fuel injection valves are used properly according to the operating state.

When the fuel injection valves are respectively provided in the air-fuel mixture forming port and the intake port as described above, the fuel is injected only from the fuel-injection valve of the air-fuel mixture forming port when the load is low when fuel consumption is required to be improved. At the time of high load required to be improved, it is common to supply fuel from at least the fuel injection valve of the intake port to promote uniform combustion.

However, particularly at low speed and high load, even if uniform combustion is promoted, if knocking is likely to occur, it is necessary to retard the ignition timing accordingly, so that torque increase is hindered. Such points have not been sufficiently taken into consideration in the past.

In view of the above circumstances, the present invention aims to reduce fuel consumption by stratifying when the load is low and to improve the output when the load is high. Especially, when the load is low and the load is high, the knock resistance is improved and the engine output is effectively increased. It is an object of the present invention to provide a fuel supply device for an engine that can be used.

[0010]

According to the present invention, an intake port for supplying air into a cylinder of an engine, a mixture forming port connected to a pressurized air source, and fuel injection into the mixture forming port. A fuel supply device for an engine, comprising: a fuel-air mixture formation port fuel injection valve to be supplied; and a timing valve for opening the air-fuel mixture formation port from the latter half of the intake stroke to the first half of the compression stroke with respect to the combustion chamber. An intake port fuel injection valve for injecting and supplying fuel therein is provided, and fuel is supplied only from the mixture forming port fuel injection valve and at least fuel is supplied from the intake port fuel injection valve in accordance with operating conditions. A control means for controlling both the fuel injection valves is provided so that the engine speed changes to a low load range in which the engine speed is equal to or lower than a predetermined speed. The fuel is supplied only from the air-fuel mixture forming port fuel injection valve in the entire region up to the full-open load region, and the fuel injection amount from the fuel-injection valve of the air-fuel mixture forming port is increased as the load increases. In the high load region in the region higher than the predetermined speed, the fuel is supplied from both of the mixture forming port fuel injection valve and the intake port fuel injection valve or only the intake port fuel injection valve. It is a thing.

The throat diameter of the mixture forming port is preferably smaller than the throat diameter of the intake port.

[0012]

According to the present invention, a large amount of fuel commensurate with the load is supplied only from the air-fuel mixture forming port in the high load region in the region where the rotational speed is lower than the predetermined value. In this case, in the low speed region, the flow rate of the mixture forming port is higher than that in the high speed region, so that even if a large amount of fuel is mixed,
The air-fuel mixture flowing into the combustion chamber from the air-fuel mixture forming port does not collect too close to the air-fuel mixture forming port, and
A stratified state is obtained to some extent without reaching the cylinder peripheral wall. Therefore, the combustion speed is increased and the knock resistance is enhanced, and the ignition timing can be advanced by that much.

Further, in the region on the higher speed side than the above-mentioned predetermined number of revolutions, the absolute time of the valve opening period of the air-fuel mixture forming port is shortened to decrease the flow rate of the air-fuel mixture forming port. In the above, the fuel is supplied from the intake port fuel injection valve to promote uniform combustion, thereby improving the combustibility.

[0014]

Embodiments of the present invention will be described with reference to the drawings.

1 to 4 show a fuel supply device according to a first embodiment of the present invention. In these figures, a combustion chamber 2 is formed in each cylinder 1 of the engine, the volume of which changes with the operation of a piston (not shown). This combustion chamber 2
The first and second intake ports 3 and 4 open on the intake side half (the left side half in FIG. 1), while the exhaust side half (the right side half in FIG. 1) of the combustion chamber 2 First and second exhaust ports 5, 6
Is open. Furthermore, a mixture forming port 7 is opened in the combustion chamber 2 between the intake ports 3 and 4. Further, an ignition plug 8 is provided at a substantially central portion of the combustion chamber 2.

First and second intake valves 11 and 12 are provided at the openings of the first and second intake ports 3 and 4 to the combustion chamber 2, respectively, and the first and second exhaust ports 5 and 6 are connected. First and second exhaust valves 13 and 14 are provided at the openings to the combustion chamber 2, respectively. These intake valves 11 and 12 and exhaust valve 1
The valves 3 and 14 are operated by a valve mechanism (not shown) including a camshaft and the like. A timing valve 15 is provided at the opening of the mixture forming port 7 to the combustion chamber 2.

The timing valve 15 opens the mixture forming port 7 between the latter half of the intake stroke and the first half of the compression stroke. That is, the opening / closing timings and lift amounts of the exhaust valves 13 and 14, the intake valves 11 and 12, and the timing valve 15 are as shown in FIG.
Is opened and closed after the intake valves 11 and 12, for example, is opened slightly before the bottom dead center (BDC) of the intake stroke, and is closed a predetermined amount later than the intake valve closing timing after bottom dead center. Has become.

An intake passage 16 is provided to introduce air into the intake ports 3 and 4, and the intake passage 16 is provided.
Is a common intake passage 16a in which an air flow meter 17 for detecting the intake flow rate and a throttle valve 18 for adjusting the intake flow rate are provided, and a surge tank 16 formed downstream thereof.
b and the branch intake passage 16c downstream of the surge tank 16c
And have. Then, the first and second intake ports 3 and 4 of each cylinder 1 are connected to the respective branch intake passages 16c.

Of the intake ports 3 and 4, the first intake port 3 opens in the circumferential direction of the combustion chamber 2, and the air flowing into the combustion chamber 2 through the first intake port 3 is the combustion chamber. It creates a swirl within 2. This first
An intake port fuel injection valve (hereinafter referred to as a side fuel injection valve) 21 for injecting fuel into the port 3 is provided for the intake port 3.

On the other hand, the second intake port 4 is provided with a swirl control valve 22 for opening and closing the second intake port 4, and the swirl is strengthened as the opening degree of the swirl control valve 22 becomes smaller. The swirl control valve 22 is operated by an actuator 23 controlled by a control unit 50 described later. The intake ports 3 and 4 are formed so that a certain amount of swirl is generated even when the swirl control valve 22 is fully opened.

The mixture forming port 7 is connected to the pressurized air supply passage 25. This pressurized air passage 2
5 is branched from the intake passage 16 between the air flow meter 17 and the throttle valve 18, and is provided with an air pump 26 as a pressurized air source in the middle of the passage and a pressure regulator 27 downstream of the air pump 26. A surge tank 28 for pressurized air is provided downstream, and the surge tank 28 for pressurized air is provided.
The air-fuel mixture forming port 7 of each cylinder is connected to. By supplying the pressurized air to the mixture forming port 7 in this way, even after the intake valves of both the intake ports 3 and 4 are closed, the mixture is mixed at a pressure higher than the cylinder pressure at that time. The air-fuel mixture can be sent into the combustion chamber 2 from the air forming port 7. The air-fuel mixture forming port 7 has a throat diameter of the intake ports 3 and 4 so that a stratification effect at a low load as described later can be favorably obtained.
It is set smaller than the diameter of the tote.

A fuel mixture forming port fuel injection valve (hereinafter referred to as a center fuel injection valve) 31 for injecting and supplying fuel upstream of the timing valve 15 is provided for the fuel mixture forming port 7. Further, a throttle valve 32 that restricts the flow of the pressurized air is provided upstream of the center fuel injection valve 31. The throttle valve 32 is an actuator 33 controlled by a control unit 50 described later.
It is designed to be activated by.

The side fuel injection valve 21 and the center fuel injection valve 31 are provided with a fuel passage 41 for the side fuel injection valve.
And the fuel passage 42 for the center fuel injection valve, and the fuel passages 41 and 42 are connected to the fuel pumps 43 and 44 and the pressure regulators 45 and 46, respectively. Then, the pressure regulators 45 and 46 inject fuel from the side fuel injection valve 21 at a fuel pressure higher than the intake pressure (pressure in the surge tank 16c) by a predetermined amount, and pressurize it from the center fuel injection valve 31. The fuel is injected at a fuel pressure higher than the pressure of the air (pressure in the pressurized air surge tank 28) by a predetermined amount.

Further, the swirl control valve 22,
For the throttle valve 32 and each of the fuel injection valves 21 and 25, a control unit (control means) 50 including a microcomputer or the like for controlling these is provided. The control unit 36 includes a rotation speed sensor 51 for detecting a signal from the air flow meter 17 and an engine rotation speed.
From the engine load sensor 52 for detecting the engine load equivalent amount such as the throttle opening.

The control unit 50 controls the swirl control valve 22 to be closed on the low load side from a predetermined load (S2 in FIG. 8) and to increase the opening degree in accordance with the increase of the load above the predetermined load. In addition, the throttle valve is controlled to have a relatively small opening in the idling region and the low-speed low-load region in the vicinity thereof, and the opening is increased as the engine speed increases and the engine load increases.

Further, the control unit 50 controls the fuel injection from the fuel injection valves 21 and 25 as shown in FIGS. 6 to 8 according to the engine speed and the engine load.

That is, the predetermined engine speed shown in FIG. 6 (the engine speed corresponding to the intersection of the torque curves of curves A and A'and the torque curves of curves B and B ', which will be described later) N1
In the region on the lower speed side, the fuel is injected and supplied only from the center fuel injection valve 31 not only in the low load region but also in the high load region. That is, in this low speed range, as shown in FIG.
As shown in FIG. 5, the fuel injection amount from the center fuel injection valve 31 is increased as the engine load is increased (intake air amount is increased) from the low load to the fully open load, and only the center fuel injection valve 31 is increased. Fuel injection from.

On the other hand, in a region on the higher speed side than the above-mentioned predetermined number of revolutions, fuel is injected from both the side fuel injection valve 21 and the center fuel injection valve 31 in the high load region. For example, in the region on the high speed side, as shown in FIG. 8, in the low load region, the fuel injection amount G1 from the center fuel injection valve 31 is increased according to the increase of the engine load, and only the center fuel injection valve 31 is increased. Inject fuel. When the engine load exceeds the set load S1,
Fuel is also injected from the side fuel injection valve 21, and the fuel injection amount from the side fuel injection valve 21 is increased from the set load S1 in a substantially temporary functional manner as the load increases. On the other hand, the fuel injection amount from the center fuel injection valve is limited to a fixed value.

In the example shown in FIG. 8, the fuel injection amount from the center fuel injection valve 31 is reduced as the full load is approached in the high load region in the high speed region. This is to promote uniform combustion under high load. Further, the load S1 for starting the fuel injection from the side fuel injection valve 21 is set to be slightly lower than the load S2 for the swirl control valve 22 to start to open, and is set slightly lower than this. This is because if the fuel injection from the side fuel injection valve 21 is started at the same time when the valve 22 starts to open, the combustion state is likely to change suddenly.

The predetermined rotation speed N1 shown in FIG. 6 as described above.
The map of the operating region at the boundary and the characteristics of the fuel injection amount shown in FIGS. 7 and 8 are stored in advance in the control unit 50, and the injection amounts of the fuel injection valves 21 and 25 are controlled based on this. Further, it is a region lean burn region on the low speed and low load side of the one-dot chain line in FIG. 6, and in this region, the fuel injection amount is controlled so that the air-fuel ratio becomes larger than the theoretical air-fuel ratio.

In the above embodiment, the fuel injection is performed from both fuel injection valves 21 and 32 at the time of high speed and high load, but the fuel injection may be performed only from the side fuel injection valve 21 at the time of high speed and high load. Good. In this case, in the high speed range, as the load changes from the low load to the high load, the fuel injection by only the center fuel injection valve 31 is switched to the fuel injection by only the side fuel injection valve 21, or only by the center fuel injection valve 31. It suffices to shift from the fuel injection to the fuel injection by only the side fuel injection valve 21 through the fuel injection by both fuel injection valves 21 and 31.

According to the fuel supply system of this embodiment as described above, during low load operation, the stratified charge combustion is favorably carried out to save fuel consumption. That is, the compressed air is supplied to the mixture forming port 7 and the fuel is injected and supplied from the center fuel injection valve 31, and the compressed air is supplied to the mixture forming port 7 during the opening period of the timing valve 15. While the fuel and the fuel are mixed, the air-fuel mixture from the air-fuel mixture forming port 7 having a relatively small throat has a moderate flow velocity and the combustion chamber 2
Flows in. Then, the atomization of the fuel is promoted by mixing the fuel and the pressurized air in the mixture forming port 7, and the mixture is supplied from the mixture forming port 7 to the ignition plug 8 with an appropriate penetration force. By doing so, stratification is achieved, and lean burn is favorably performed.

Further, when the load is high, the engine output is sufficiently increased. In particular, by the action described in detail later,
When the fuel is injected from only the center fuel injection valve 31, the torque curve (change in torque depending on the engine speed) at full load is the curves A and A'in FIG. 6 and the two fuel injection valves 21 and 31. (Or side fuel injector 21 only)
When the fuel injection is performed from, the curves B and B'in the figure are obtained, and at the time of low speed and high load, the center fuel injection valve 31
It is possible to increase the engine output by injecting fuel only. Therefore, at the time of high load, fuel is injected only from the center fuel injection valve 31 in the low speed region with a predetermined rotational speed N1 corresponding to the intersection of both torque curves (curves A and A'and curves B and B ') as a boundary. Both fuel injection valves 2 at high speeds
By injecting fuel only from 1, 31 or the side fuel injection valve 21, the engine torque at full engine load becomes like the solid line portions A and B of the torque curve, and the engine output increases in the low speed region and the high speed region, respectively. To be

This operation will be described more specifically with reference to FIGS. 9 and 10.

FIG. 9 shows the relationship between the flow rate of the air-fuel mixture forming port 7 per engine cycle and the engine speed at the full open load. As shown in FIG. 9, the flow rate at the full open load corresponds to the engine speed. On the other hand, it changes inversely and increases as the engine speed decreases. That is, since the throat diameter of the air-fuel mixture forming port 7 is smaller than that of the intake ports 3 and 4, and the opening period of the timing valve 15 is regulated as described above, the absolute opening period is not limited. When the engine speed is high, the flow rate of the mixture forming port 7 is significantly reduced. However, when the engine speed is low, the flow rate of the mixture forming port 7 is increased because the absolute time of the valve opening period is long. .

In this way, in the low speed region, since the flow rate of the mixture forming port 7 is relatively large, a large amount of fuel required at the time of a high load such as a fully open load is supplied to the center fuel injection valve 31.
Even if the mixture is injected from only, the fuel is atomized finely by mixing, and the penetration force of the mixture flowing into the combustion chamber 2 from the mixture forming port 7 is strengthened as the flow rate is increased. It is possible to avoid a situation in which the rich mixture is unevenly distributed near the formation port 7. Moreover, the air-fuel mixture does not reach the cylinder peripheral wall,
A certain degree of stratification is obtained. Therefore, the combustion speed is increased, that is, the combustion is normally performed by the normal flame propagation, so that knocking is suppressed.

Since the knock resistance is enhanced in this way, the ignition timing can be advanced by that amount. That is, generally, the ignition timing of the engine at low speed and high load is set near the knocking limit on the retard side with respect to MBT (ignition timing at which torque becomes highest). Under such an ignition timing setting condition, as shown in FIG. 10, when the fuel is injected from only the center fuel injection valve 31 as described above, the ignition timing (solid line) at the time of full open load and high load in the low speed range is As compared with the case where fuel injection is performed from both fuel injection valves 21 and 31 (broken line) and the case where fuel injection is performed from only port fuel injection valve 21 (dashed line), the angle is advanced toward MBT.

Therefore, at low speed and high load, by injecting fuel from only the center fuel injection valve 31, the engine torque is higher than that in the case of injecting fuel from both fuel injection valves 21, 31 or side fuel injection valve 21 alone. It will be raised.

On the other hand, at high speed and high load, the flow rate of the air-fuel mixture forming port 7 decreases as described above. Therefore, when a large amount of fuel is injected only from the center fuel injection valve 31, sufficient atomization of fuel by mixing can be obtained. However, the rich air-fuel mixture is unevenly distributed, which deteriorates the combustibility and increases the emission amount of unburned components. That is, when the fuel injection is performed from both fuel injection valves 21 and 31, or the fuel injection is performed only from the port fuel injection valve 21, the combustibility is enhanced by promoting uniform combustion.

Therefore, at the time of high speed and high load, by injecting fuel only from both fuel injection valves or side fuel injection valves, the engine torque can be increased as compared with the case where fuel injection is performed only from the center fuel injection valve.

[0041]

As described above, according to the present invention, a fuel injection valve is provided in each of the air-fuel mixture forming port and the intake port, and fuel is supplied only from the air-fuel mixture forming port fuel injection valve according to the operating state. Since both fuel injection valves are controlled so that at least the fuel is supplied from the intake port fuel injection valve, there is a demand for fuel efficiency reduction due to stratified combustion at low load, output improvement at high load, etc. The fuel supply state to the combustion chamber can be changed to satisfy the above condition.
In particular, in the entire range from the low load range to the fully open load range where the engine speed is equal to or lower than the predetermined speed, the fuel is supplied only from the mixture forming port fuel injection valve. When the load is applied, the combustion speed is increased to improve the knock resistance, whereby the ignition timing can be advanced and the engine output can be increased.

In addition to the above structure, in the high load region in the region higher than the predetermined speed, the fuel is supplied only from the both fuel injection valves or the intake port fuel injection valves. At high speed and high load, where the absolute time of the mixture formation port opening period is shortened and the flow rate of this mixture supply port is reduced, excessive uneven distribution of the mixture is avoided and uniform combustion is promoted to promote engine combustion. The output can be increased. Therefore, the engine output can be increased from the low speed region to the high speed region.

[Brief description of drawings]

FIG. 1 is an overall schematic plan view of a fuel supply device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of the fuel supply device.

FIG. 3 is a plan view of a main part of the fuel supply device.

FIG. 4 is a perspective view of a main part of the fuel supply device.

FIG. 5 is an explanatory diagram showing opening / closing characteristics of an exhaust valve, an intake valve, and a timing valve.

FIG. 6 is an explanatory diagram showing a torque curve at the time of setting a region for control of a fuel injection valve and a fully open load.

FIG. 7 is a diagram showing characteristics of fuel supply control according to a load in a low speed range.

FIG. 8 is a diagram showing characteristics of fuel supply control according to a load in a high speed range.

FIG. 9 is a diagram showing a relationship between a flow rate of a mixture forming port and an engine speed.

FIG. 10 is a diagram showing ignition timing in a low speed range.

[Explanation of symbols] 1 cylinder 3,4 intake port 7 Mixture formation port 15 Timing valve 21 Intake port fuel injection valve 31 Mixture formation port Fuel injection valve 50 control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihide Yamamoto 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-5-202753 (JP, A) (58) Survey Fields (Int.Cl. ⁷ , DB name) F02M 69/00 360 F02M 69/08 F02D 41/34 F02D 41/04 F02B 17/00 F02B 13/02

Claims (2)

(57) [Claims] 1. An intake port for supplying air into a cylinder of an engine, a mixture forming port connected to a pressurized air source, and a mixture forming port fuel injection for injecting fuel into the mixture forming port. In a fuel supply device for an engine, which is provided with a valve and a timing valve for opening the mixture forming port with respect to the combustion chamber during the latter half of the intake stroke to the first half of the compression stroke, In addition to providing the port fuel injection valve, both of the above two types are provided so as to change the state in which the fuel is supplied only from the air-fuel mixture forming port fuel injection valve and the state in which the fuel is supplied from at least the intake port fuel injection valve according to the operating state. control means for controlling the fuel injection valve is provided, the control means, the entire region from the low load region the engine rotational speed is in the region below the predetermined rotational speed to a fully open load range Contact
In addition, the fuel is supplied only from the air-fuel mixture forming port fuel injection valve, and the air-fuel mixture forming port increases as the load increases.
The amount of fuel injected from the fuel injection valve
In the high load area in the area higher than the above specified speed
Is the mixture forming port fuel injection valve and the intake port.
Both fuel injection valves or the above intake port fuel injection
An engine fuel supply device characterized in that fuel is supplied only from a valve . 2. The fuel supply system for an engine according to claim 1, wherein the throat diameter of the mixture forming port is smaller than the throat diameter of the intake port.