JPH06108907A - Fuel supplying device of engine - Google Patents

Abstract

PURPOSE:To provide a fuel supplying device of engine by promoting lean burning at the time of a low load, so as to improve fuel consumption performance and emission performance, and by promoting uniform combustion at the time of a high load so as to improve engine output. CONSTITUTION:At the time of a low load, fuel is injected from a mixture air forming port fuel injection valve 29, and mixture air which flows from a mixture gas forming port 7 into a combustion chamber 2 is concentrated around an ignition plug 8. On the other hand, since fuel is not injected from an intake port fuel injection valve 19, there is only air in the circumferential part of the combustion chamber 2, so that mixture gas is stratified to carry out lean burning. At the time of a high load, fuel is injected from both fuel injection valves 19, 29, and it is distributed in the combustion chamber 2 uniformly, and then uniform combustion is carried out so as to improve engine output. The amount of fuel injected from the mixture gas forming port fuel injection valve 29 is reduced according to increase in an engine load so as to promote uniform combustion at the time of the high load to more extent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine fuel supply system.

[0002]

2. Description of the Related Art Generally, in an engine, when the load is low, the fuel or air-fuel mixture is concentrated around the spark plug to stratify the air-fuel mixture, and stratified charge combustion (lean burn) enhances the fuel efficiency and the emission performance. It is sometimes preferable to evenly distribute the fuel in the combustion chamber and increase the engine output by uniform combustion. Therefore, in order to stratify the air-fuel mixture when the load is low, an engine in which the in-cylinder fuel injection valve is arranged toward the ignition plug has been proposed.However, in such an engine, the fuel from the fuel injection valve exerts considerable momentum. Since the fuel is injected, the fuel penetrates the vicinity of the spark plug, and there is a problem that the mixture cannot be effectively stratified.

In order to improve this, an in-cylinder fuel injection valve that opens toward the vicinity of the spark plug arranged in the center of the combustion chamber is provided, while the intake port is a swirl generating port, and the swirl ( A fuel supply device for an engine is proposed in which a vortex flow flowing in the cylinder circumferential direction) is generated to collect the fuel injected from a fuel injection valve around a spark plug (Japanese Patent Laid-Open No. 60-67721).
(See Japanese Patent Publication). In this engine fuel supply device, a manifold fuel injection valve is also provided in the intake passage, and when the load is high, fuel is injected from the manifold injection valve to perform uniform combustion and increase engine output. . However, even if the stratification is promoted by the swirl as described above, the fuel injected from the in-cylinder fuel injection valve still has a strong momentum, so that there is a problem that it tends to penetrate through the vicinity of the spark plug.

Therefore, the intake port for supplying air to the combustion chamber is used as a swirl generation port, and a mixture forming port opened toward the vicinity of the spark plug and a mixture for injecting fuel into the mixture forming port. A fuel injection valve for the formation port and a timing valve for opening the mixture formation port in the latter half of the intake stroke are provided, and the mixture around the ignition plug is mixed by the weak mixture flowing from the mixture formation port into the combustion chamber in the latter half of the intake stroke. There has been proposed an engine fuel supply device that concentrates air to promote stratification (see, for example, Japanese Utility Model Laid-Open No. 62-18335). In this fuel supply device, an intake port fuel injection valve that injects fuel into the intake port (intake passage) is provided.

[0005]

[Problems to be Solved by the Invention]
In the conventional fuel supply device disclosed in Japanese Patent No. 18335, in a region exceeding a predetermined load, fuel injection from the mixture forming port fuel injection valve is stopped, while fuel is injected from the intake port fuel injection valve, The engine output is improved by promoting uniform combustion.

However, in this conventional fuel supply device, at the time of high load, some of the fuel particles in the air flowing into the combustion chamber from the intake port are attached to the wall surface of the combustion chamber by the swirl, and the center of the combustion chamber is There is a problem that the side becomes lean and sufficient uniform combustion cannot be performed, and the engine output cannot be sufficiently increased.

The present invention has been made in order to solve the above-mentioned conventional problems. When the load is low, stratification is used to promote lean burn, and fuel consumption performance and emission performance can be sufficiently improved. An object of the present invention is to provide a fuel supply device for an engine, which can promote uniform combustion under load and sufficiently increase engine output.

[0008]

To achieve the above object, a first aspect of the present invention is directed to an intake port for supplying air into a cylinder, an intake port fuel injection valve for injecting fuel into the intake port, and an intake port. A mixture forming port for supplying a gas having a pressure higher than the cylinder pressure in the stroke period into the cylinder, a mixture forming port fuel injection valve for injecting fuel into the mixture forming port, and the mixture forming port. In a fuel supply device for an engine provided with a timing valve that opens inside the cylinder in the latter stage of the intake stroke, when the throttle valve opening is smaller than a predetermined opening, the fuel injection from the intake port fuel injection valve is stopped while the throttle valve is opened. The fuel injection amount of the mixture forming port fuel injection valve is increased in response to the increase in the valve opening,
On the other hand, when the throttle valve opening is equal to or more than the above-mentioned predetermined opening, the fuel injection amount of the mixture forming port fuel injection valve is gradually decreased in response to the increase of the throttle valve opening while the fuel of the intake port fuel injection valve is reduced. Provided is a fuel supply device for an engine, which is provided with fuel supply control means for increasing the injection amount.

According to a second aspect of the present invention, in the fuel supply system for an engine according to the first aspect, the intake port is a swirl generating port, and the swirl generating port generates swirl in the cylinder even in a high load region. A fuel supply device for an engine is provided.

A third aspect of the invention is the fuel supply system for an engine according to the first or second aspect, wherein the intake port is 2
One of them is a swirl generating port, an intake port fuel injection valve is provided for the swirl generating port, and a port opening / closing valve that is opened on the higher load side than a predetermined load is provided on the other intake port. The fuel supply control means reduces the fuel injection amount of the mixture forming port fuel injection valve in accordance with the port opening / closing valve opening in the region where the port opening / closing valve is opened, while the fuel of the intake port fuel injection valve is reduced. A fuel supply device for an engine, characterized in that the injection amount is increased.

According to a fourth aspect of the present invention, in the engine fuel supply apparatus according to the third aspect, the fuel supply control means opens the intake port fuel injection valve from a load lower than a predetermined load at which the port opening / closing valve is opened. A fuel supply system for an engine is provided.

[0012]

EXAMPLES Examples of the present invention will be specifically described below. <First Embodiment> As shown in FIG. 1, first to fourth cylinders # 1
A combustion chamber 2 is provided in each cylinder 1 of a four-cylinder engine CE equipped with # 4 to # 4, and an intake side half of each combustion chamber 2 is provided.
While the first and second intake ports 3 and 4 are opened in the left half portion in FIG. 1, the first and second intake ports 3 and 4 are opened in the exhaust side half portion in the right half portion in FIG.
The exhaust ports 5 and 6 are open. Further, a mixture forming port 7 is opened in the combustion chamber 2 between the first intake port 3 and the second intake port 4. An ignition plug 8 is arranged at a position slightly closer to the exhaust side than the center of the combustion chamber 2.

Here, the first intake port 3 is a tangential port that opens substantially in the circumferential direction of the cylinder 1 (combustion chamber 2), and the air flowing into the combustion chamber 2 from the first intake port 3 is A swirl is generated in the combustion chamber 2. That is, the first intake port 3 is a swirl generation port. The first intake port 3 is adapted to effectively generate swirl not only in the low load region but also in the high load region. The first intake port 3 may be used as a helical port to generate swirl. The first intake port 3 is opened and closed by the first intake valve 9 at a predetermined timing (for example, 13 ° before the top dead center of the crank angle to 43 ° after the bottom dead center).
The first intake valve 9 is operated by a valve mechanism (not shown). Similarly, the second intake port 4 is opened and closed by the second intake valve 10. The first and second exhaust ports 5 and 6 are opened and closed by the first and second exhaust valves 11 and 12, respectively.

A timing valve 13 is provided at the opening of the mixture forming port 7 to the combustion chamber 2, and the mixture forming port 7
Is opened by the timing valve 13 almost in the latter half of the intake stroke. That is, the mixture forming port 7
Are opened and closed later than the first and second intake ports 3 and 4 (for example, 90 degrees after the top dead center of the crank angle).
° to 90 ° after bottom dead center).

In order to supply air to each combustion chamber 2, an independent intake passage 15 is provided for each cylinder, and the upstream ends of these independent intake passages 15 are connected to a surge tank 16 for stabilizing the air flow. ing. It should be noted that air is supplied to the surge tank 16 from a common intake passage 18 in which a throttle valve 17 is interposed. The first and second intake ports 3 and 4 are connected to the downstream end of each independent intake passage 15. An intake port fuel injection valve 19 for injecting fuel into the air in the first intake port 3 is provided for the first intake port 3. The fuel injection amount and injection timing of the intake port fuel injection valve 19 are controlled by the control unit 40. The control unit 40
Is a comprehensive control means of the engine CE including the "fuel supply control means" described in the claims, and is a throttle opening (engine load) detected by the throttle opening sensor 41, a rotational speed Various engine controls are performed using the engine speed and the like detected by the sensor 42 as control information.

Further, the second intake port 4 is provided with a port opening / closing valve 20 for opening / closing the second intake port 4. The port opening / closing valve 20 is provided to adjust the swirl strength of the first intake port 3, and the swirl is strengthened as the opening degree thereof is smaller. Port on-off valve 20
In accordance with a command from the control unit 40, is closed by the negative pressure responsive first actuator 21 on the lower load side than the predetermined load and opened on the high load side according to the load. Specifically, the negative pressure supply passage 22 is connected to the pressure chamber of the first actuator 21, and the upstream end of the negative pressure supply passage 22 is connected to the surge tank 16. A vacuum tank 25 that stores a negative pressure and a first duty solenoid valve 23 are provided in the negative pressure supply passage 22. Here, the negative pressure applied to the pressure chamber of the actuator 21 is adjusted according to the duty ratio applied from the control unit 40 to the first duty solenoid valve 23, and the opening degree of the port opening / closing valve 20 is adjusted accordingly. It is like this.

The upstream end of each air-fuel mixture forming port 7 is connected to a pressurized air supply passage 26, and the upstream end of this pressurized air supply passage 26 is connected to an air pump 28 that pressurizes and discharges air. A pressure regulator 27 is provided in the pressurized air supply passage 26. As described above, the air-fuel mixture forming port 7 has the first and second intake ports 3 and 4 after the bottom dead center.
Since the gas (mixture) is supplied into the combustion chamber 2 even after the gas is closed, it is necessary to push such gas into the combustion chamber 2. Therefore, the pressurized air is supplied to the mixture forming port 7 in this way. It should be noted that exhaust gas accompanied by exhaust pressure may be supplied to the mixture forming port 7 instead of supplying the pressurized air.

For the mixture forming port 7, a mixture forming port fuel injection valve 29 for injecting fuel into the air in the mixture forming port 7 is provided. here,
The fuel injection amount and injection timing of the mixture forming port fuel injection valve 29 are controlled by the control unit 40.

A throttle valve 30 for adjusting the flow rate of the pressurized air is provided in the air-fuel mixture forming port 7 slightly upstream of the air-fuel mixture forming port fuel injection valve 29. The throttle valve 30 is opened and closed by a negative pressure responsive actuator 31 according to a command from the control unit 40. A branch negative pressure supply passage 32 branched from the negative pressure supply passage 22 is connected to the pressure chamber of the actuator 31, and a duty solenoid valve 33 is provided in the branch negative pressure supply passage 32. Then, the opening degree of the throttle valve 30 is adjusted according to the duty ratio applied to the duty solenoid valve 33 from the control unit 40, and specifically, the throttle valve 30 is opened more widely when the load is higher. .

The mixture forming port 7 is mainly used for the combustion chamber 2.
It is provided to form a relatively rich air-fuel mixture in the vicinity of the center of the. That is, before the timing valve 13 is opened, the fuel is injected into the pressurized air from the air-fuel mixture forming port fuel injection valve 29, and the air-fuel mixture having a relatively high pressure is held in the air-fuel mixture forming port 7. . Then, when the timing valve 13 is opened, this air-fuel mixture flows into the combustion chamber 2 toward the vicinity of the center of the combustion chamber, that is, the vicinity of the spark plug 8. However, this air-fuel mixture is not so vigorous, so it is just the combustion chamber. They will gather near the center, that is, around the spark plug 8. Therefore, when the fuel is supplied to the combustion chamber 2 only from the mixture forming port 7, the spark plug 8
The air-fuel mixture is formed only around, and the air-fuel mixture is stratified.

The specific structure around the cylinder 1 of the engine CE is as shown in FIGS. Note that FIG.
, Z ₁ and Z ₂ are respectively the intake port fuel injection valve 1
9 and the fuel injected from the mixture forming port fuel injection valve 29 are shown. Further, in FIG. 5, reference numeral 45 is a piston, 46 is a mask for generating squish when the piston is compressed, X is a mixture lump flowing into the combustion chamber 2 from the mixture forming port 7, and arrow Y is Shows swirl flow.

By the way, as described above, the engine CE
In the above, various engine controls are performed by the control unit 40.
Since the general control of E is well known and is not the gist of the present invention, the description thereof is omitted. Below, only the fuel supply control according to the engine load or the throttle opening degree according to the gist of the present invention will be described. explain.

(1) Low load region (stratified combustion) In the region where the engine load (throttle opening) in FIG. 6 is smaller than a predetermined value S ₂ (low load region), stratified combustion is promoted.
Specifically, the port opening / closing valve 20 is closed, air is supplied from the first intake port 3 into the combustion chamber 2, and a strong swirl is generated in the combustion chamber 2. On the other hand, basically (when the engine load is S ₁ or less), the fuel injection of the intake port fuel injection valve 19 (hereinafter, referred to as port injection) is stopped.
(G ₂ ), the fuel is injected only from the mixture forming port fuel injection valve 29 (hereinafter, this is referred to as direct injection) (G ₁ ). Then, the direct injection amount is increased almost in proportion to the engine load and reaches the maximum value f ₁ when the engine load is S ₂ .

In this case, while the air-fuel mixture flowing from the air-fuel mixture forming port 7 into the combustion chamber 2 is concentrated near the center of the combustion chamber, that is, around the spark plug 8, no fuel is supplied from the first intake port 3. Since the air-fuel mixture exists only around the spark plug 8, the air-fuel mixture in the combustion chamber 2 is effectively stratified and stratified combustion, that is, lean burn is performed. At this time, the strong swirl suppresses diffusion of the air-fuel mixture around the spark plug 8 to the peripheral portion, further promotes stratification, enables lean burn in a very lean region, and significantly improves fuel efficiency and emission performance. Be raised to. In this case, since the direct injection amount is almost proportional to the engine load, it is needless to say that the fuel corresponding to the engine load is supplied and the required engine output is secured.

Even in the low load region where the engine load is S ₂ or less, that is, in the region where the port opening / closing valve 20 is closed, when the engine load becomes S ₁ or more, as will be described later, Injection is started, and the port injection amount is increased almost linearly as the engine load increases on the higher load side than S ₁ .

(2) High load region (uniform combustion) In the region where the engine load is S ₂ or more in FIG. 6, uniform combustion is promoted. Specifically, the intake port opening / closing valve 20 is
Both fuel injection valves 19, which are opened according to the engine load,
Fuel is injected from 29. Since swirls are generated in the combustion chamber 2 even under high load, a part of the fuel injected through the port adheres to the inner peripheral surface of the combustion chamber 2 due to the swirl, and therefore, near the center of the combustion chamber. The amount of fuel that reaches the fuel cell decreases, the fuel concentration near the center of the combustion chamber decreases, and uniform combustion is hindered. Therefore, direct injection and port injection are used together to promote uniform combustion. Here, the intake port opening / closing valve 20 is opened as the engine load increases.
That is, the swirl is weakened as the engine load increases. The intake port opening / closing valve 20 may be fully opened when the engine load becomes S ₂ .

The basic idea of fuel supply in the high load region is as follows. That is, in principle, in the high load region where the engine load is S ₂ or more, the direct injection amount is fixed to the maximum value f ₁ in the low load region (G ₁ '), while the port injection is used to increase the engine load. Along with this, it is linearly increased so that the total of the direct injection amount and the port injection amount is on the extension line of the direct injection amount in the low load region. Therefore, basically, the total fuel injection amount is increased almost in proportion to the engine load regardless of whether it is in the low load region or the high load region. However, in the low load region, only direct injection is performed in order to stratify the fuel around the spark plug 8,
In the high load region, direct injection and port injection are used together in order to evenly distribute the fuel in the combustion chamber 2.

However, the above principle is modified in the following two points. That is, first, the direct injection amount is gradually reduced as the engine load increases (G ₁ ). Timing valve 13
At the time when is opened, the pressure in the combustion chamber 2 rises as the engine load increases. Therefore, the gas or the air-fuel mixture in the air-fuel mixture forming port 7 becomes difficult to enter the combustion chamber 2 as the engine load increases. Therefore, the direct injection amount
Since it is fixed at f ₁ , the mixture forming port 7 to the combustion chamber 2
The air-fuel mixture flowing into the inside becomes excessively rich, which causes deterioration of combustibility or emission in the combustion chamber 2. Therefore, the direct injection amount is reduced by an amount commensurate with the decrease in the gas supply amount from the mixture forming port 7 due to the increase in the engine load. As a result, the combustibility in the high load region is enhanced and uniform combustion is promoted.

Further, the port injection amount starts from S ₁ which is slightly lower than S ₂ and increases substantially linearly with increasing engine load on the higher load side.
When the port injection is started from S ₂ , the port opening / closing valve 20 is opened and the swirl is weakened before the port injection is started. Therefore, the port injected fuel is initially swirled when the port opening / closing valve 20 is opened. The fuel will stay in place and will hinder uniform combustion, causing a temporary drop in engine output and a jerkiness. Therefore, the port injection is started from S _1, which is the low load region, so that sufficient uniform combustion is performed even when the port opening / closing valve 20 is opened. This facilitates switching from the low load region to the high load region.

As described above, according to the first embodiment, in the low load region, stratified combustion promotes stratified combustion, that is, lean burn, fuel consumption performance and emission performance are enhanced, and uniform combustion is promoted in the high load region. The output is increased. When the load is low, as shown in Fig. 7 (a), the valve lift amount of the timing valve 13 is reduced to within the deflector height d, and in the high load region, the lift of the timing valve 13 is increased as shown in Fig. 7 (b). The amount may be larger than the deflector height d. By doing so, the range in which the air-fuel mixture disperses at a low load is reduced to A ₁ so that stratified combustion is further promoted and the range in which the air-fuel mixture disperses at a high load is widened like A _2. Combustion is further promoted. In some cases, such timing valve 1
There is a possibility that the stratified charge combustion and the uniform combustion can be switched only by switching the lift amount of 3.

<Second Embodiment> The second embodiment will be described below with reference to FIG. 2. The second embodiment is the first embodiment shown in FIG.
Since the basic parts are the same as those of the first embodiment, only different points from the first embodiment will be described below in order to avoid duplication of description. In the second embodiment, the same members as those in the first embodiment are designated by the same reference numerals as those in the first embodiment. In the second embodiment, the one-way valve 5 is connected to the mixture forming port 7 on the upstream side of the mixture forming port fuel injection valve 29.
Two are provided. The upstream end of the air passage 26 is located upstream of the throttle valve 17 and in the air flow meter 5
Connected to the common intake passage 18 at a position downstream of 1,
No air pump is provided. Further, the throttle valve and the opening / closing mechanism of the throttle valve are not provided.

In the second embodiment, the compression pressure in the combustion chamber 2 immediately before the timing valve 7 is closed is stored in the mixture forming port downstream of the one-way valve 52.
With the stored compression pressure, the next time the mixture is pushed into the combustion chamber 2 from the mixture forming port 7. Therefore, an air pump is not required, and the air supply system to the mixture forming port 7 is simplified. The air passage 26
From the to the air-fuel mixture forming port 7, air is supplied via the one-way valve 52 when the pressure drops at the beginning when the timing valve 13 is opened.

[0033]

According to the first aspect of the present invention, when the throttle opening is smaller than the predetermined opening, that is, when the load is low, the fuel is injected from the mixture forming port combustion injection valve. By the air-fuel mixture supplied from the air-fuel mixture, the air-fuel mixture concentrates near the center of the cylinder, that is, around the spark plug. On the other hand, since no fuel is injected from the intake port fuel injection valve, the inner peripheral edge of the cylinder is almost entirely air. Therefore, stratification of the air-fuel mixture is promoted, lean burn can be performed in a leaner region, and fuel consumption performance and emission performance are improved. Also, when the load is high,
Since fuel is injected from both fuel injection valves, the fuel is distributed throughout the cylinder, uniform combustion is promoted, and engine output is increased. Further, as the engine load increases, the fuel injection to the air-fuel mixture forming port is gradually reduced, so that the air-fuel mixture due to the decrease in the gas inflow amount from the air-fuel mixture forming port into the cylinder caused by the increase in the cylinder pressure. Is prevented, and uniform combustion at high load is further promoted.

According to the second invention, basically, the same action and effect as the first invention can be obtained. Further, since the intake port is used as the swirl generation port, stratification of the air-fuel mixture is further promoted when the load is low.

According to the third invention, basically, the same action and effect as those of the first or second invention can be obtained. further,
Since the fuel supply amount is adjusted according to the opening degree of the intake port opening / closing valve, that is, according to the strength of the swirl, uniform combustion under high load is further promoted.

According to the fourth invention, basically, the same action and effect as the third invention can be obtained. Further, when the engine load increases, the intake port fuel injection valve is opened before the intake port opening / closing valve is opened, so the fuel injected from the intake port fuel injection valve at the beginning when the intake port opening / closing valve was opened. Does not occur and does not cause a jerkiness.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an engine showing a first embodiment of the present invention.

FIG. 2 is a system configuration diagram of an engine showing a second embodiment of the present invention.

3 is an elevational cross-sectional explanatory view near the upper portion of the combustion chamber of the engine shown in FIG.

FIG. 4 is an explanatory plan view around a cylinder of the engine shown in FIG.

5 is a perspective explanatory view around a cylinder of the engine shown in FIG. 1. FIG.

FIG. 6 is a diagram showing characteristics of a direct injection amount and a port injection amount with respect to an engine load.

FIG. 7A is a diagram showing a lifted state of the timing valve at a low load, and FIG. 7B is a diagram showing a lifted state of the timing valve at a high load.

[Explanation of symbols]

 CE ... Engine 1 ... Cylinder 2 ... Combustion chamber 3,4 ... First and second intake ports 7 ... Mixture mixture port 13 ... Timing valve 17 ... Throttle valve 19 ... Intake port fuel injection valve 20 ... Intake port opening / closing valve 29 ... Mixture formation port Fuel injection valve 40 ... Control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location F02M 69/00 360 G 7825-3G (72) Inventor Toshihide Yamamoto Shinchi No. 3 Fuchu-cho, Aki-gun, Hiroshima Prefecture No. 1 in Mazda Motor Corporation

Claims (4)

[Claims] 1. An intake port for supplying air into a cylinder,
An intake port fuel injection valve for injecting fuel into the intake port, an air-fuel mixture forming port for supplying a gas having a pressure higher than the in-cylinder pressure in the intake stroke period into the cylinder, and a fuel mixture in the air-fuel mixture forming port. In a fuel supply device for an engine provided with a fuel injection valve for injecting air-fuel mixture and a timing valve for opening the air-fuel mixture forming port to the inner side of the cylinder in the latter stage of the intake stroke, the throttle valve opening is more than a predetermined opening. When the value is small, the fuel injection from the intake port fuel injection valve is stopped, while the fuel injection amount of the mixture forming port fuel injection valve is increased in response to the increase in the throttle valve opening degree. When the opening is equal to or more than the opening, the fuel injection amount of the mixture forming port fuel injection valve is gradually decreased in response to the increase of the throttle valve opening while the intake port fuel injection valve The fuel supply system for an engine, wherein the fuel supply control means for increasing the injection quantity is provided. 2. The fuel supply system for an engine according to claim 1, wherein the intake port is a swirl generation port, and the swirl generation port is formed so as to generate swirl in the cylinder even in a high load region. A fuel supply device for an engine, characterized in that 3. The engine fuel supply device according to claim 1 or 2, wherein two intake ports are provided, and one of them is a swirl generation port, and the intake port is connected to the swirl generation port. A port fuel injection valve is provided, and a port opening / closing valve that opens on the higher load side than a predetermined load is provided on the other intake port, and the fuel supply control means controls the port opening / closing valve opening degree in the region where the port opening / closing valve is opened. A fuel supply device for an engine, wherein the fuel injection amount of the air-fuel mixture forming port fuel injection valve is decreased and the fuel injection amount of the intake port fuel injection valve is increased corresponding to the above. 4. The engine fuel supply device according to claim 3, wherein the fuel supply control means opens the intake port fuel injection valve from a lower load side than a predetermined load at which the port opening / closing valve is opened. A fuel supply device for an engine, characterized in that