JPS62189324A - Intake device of engine - Google Patents

Abstract

PURPOSE:To stabilize combustion in acceleration by providing devices for controlling air-fuel ratio of mixture and swirl to restrain the formation of swirl in acceleration while making the air-fuel ratio rich. CONSTITUTION:A combustion chamber 103 is provided with a port 104 to form swirl and a port 101 for direct suction and further a fuel injection unit capable of controlling air-fuel ratio. A valve 100 is closed in low load on an engine to form swirl and make the air-fuel ratio lean. In the acceleration of engine, an acceleration responsive means 107 in a controller is operated according to the signal of an acceleration detecting means 105 to operate a swirl forming means in the direction of restraining swirl while controlling fuel injection in the direction of making the air-fuel ratio rich.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake system for an engine, and more particularly to improvements in improving acceleration response in a low load range of a lean burn engine having a swirl generation mechanism.

[Prior Art] Lean-burn engines with a swirl generation mechanism have been realized in the past as engines aimed at reducing fuel consumption and the like.

This is to achieve the best fuel efficiency by burning an air-fuel mixture that is leaner than the air-fuel mixture at the stoichiometric air-fuel ratio in the engine's steady rotation range or low load range. Particularly in the low-load range, the aim is to increase the flow rate of the lean mixture and generate swirl to achieve complete combustion of the mixture.

However, in a lean burn engine having a swirl generation mechanism, the lean burn operation region is basically a low load range, so the structure is such that swirl is maintained even during acceleration. When swirl is generated in this way, the intake passage is curved or constricted, so the intake resistance is greater than when swirl is not generated, and it is disadvantageous in terms of response to acceleration compared to when swirl is not generated. Ta.

On the other hand, a Miller cycle lean burn engine has been proposed (Japanese Patent Application Laid-Open No. 58-23245) with the aim of reducing fuel consumption and pumping loss, but this Miller cycle lean burn engine also has a swirl generation mechanism. Similarly, the above-mentioned problem of acceleration response in the low load region also exists.

In order to improve this acceleration response, it is advantageous to prevent swirl from occurring, but simply stopping swirl formation poses a problem with combustibility under lean burn conditions.

By the way, for example, as in JP-A-58-13131, there is an idea to increase fuel during acceleration to supply a rich mixture to ensure acceleration response, but this can only be done with fuel. , and there is no relationship with the swirl generation mechanism.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to create a swirl in a low load range and perform lean combustion by relying on the swirl generation mechanism. The purpose of the present invention is to propose an intake system for an engine that has excellent acceleration response.

[Means for Solving the Problems] In order to achieve the above object, for example, the engine intake system of the embodiment shown in FIG. Further, an acceleration detection means 105 detects a sudden acceleration state or a slow acceleration state from, for example, the opening degree (α) of the accelerator and the time change of α,
An intake passage 101 equipped with a shutter valve 100 and an intake passage 1 for swirl generation that bypasses this intake passage 101
04, and a swirl generating means 10 that controls swirl generation by opening and closing the shutter valve 100 in a predetermined operating range.
2, an air-fuel ratio adjusting means 106 for adjusting the air-fuel ratio of the air-fuel mixture to a rich, stoichiometric air-fuel ratio or rich by making the intake air and fuel injection amounts variable, for example, and a swirl generating means 102. Acceleration response means 1 that corrects the air-fuel ratio to the rich side and suppresses swirl during sudden acceleration even in a lean burn operation region that normally involves swirl generation.
It consists of 07.

[Function] With the above configuration, when the acceleration detection means 105 detects sudden acceleration during low load, the swirl generation means 102 activates the shutter valve 1.
00 by a predetermined opening degree to improve the intake air filling property, and at the same time or slightly before this, the air-fuel ratio adjusting means 106 adjusts the rich air-fuel mixture (meaning a richer air-fuel mixture than the lean air-fuel ratio). (including the stoichiometric air-fuel ratio), the acceleration response means 107. is activated. This improves acceleration response without impeding combustion stability when acceleration is requested in a lean burn operation region that normally involves swirl generation.

[Embodiments] The embodiments according to the present invention will be described below according to the attached drawings.
V m +y 'aes old X KaTn t-J t
/7'l An explanation of the intake system applied to a lean burn engine equipped with a 7ry-le Shibata block (Figures 2 to 8). Next, an explanation of the intake system applied to a Miller cycle lean burn engine ( Figure 9 below).

<Lean Burn Engine> FIG. 2 shows a lean burn engine equipped with a swirl mechanism to which an intake system according to an embodiment of the present invention is applied.

In FIG. 2, the engine body 1 is of a reciprocating type in which a combustion chamber 4 is defined by a piston 3 slidably inserted into a cylinder block 2, and an intake boat opening into the combustion chamber 4. 5 is opened and closed by an intake valve 6, and an exhaust boat 7 is opened and closed by an exhaust valve 8 at known timings.

In the intake passage 9 connected to the intake boat 5, an air cleaner 10, a flap-type air flow meter 11, a throttle valve 12, and a surge tank 13 are disposed in order from the upstream side. The output (Q8) of the air flow meter 11 is detected by the air flow sensor 21. In the exhaust passage 17 connected to the exhaust boat 7, an air-fuel ratio sensor 18 and a three-way catalyst 19 are arranged in order from the upstream side. This air-fuel ratio sensor 18 is a so-called lean sensor, and its output characteristics continuously change according to changes in the oxygen concentration in the exhaust gas.

In the example shown in Fig. 2, acceleration detection is performed using the opening angle (α) of the throttle valve 12.
) is detected by the throttle sensor 22 and its time change
The time change in the amount of acceleration is detected from (dα/dt). The amount of acceleration may be detected from the amount of depression of the accelerator as in other embodiments described later. The intake passage downstream of the surge tank 13 is divided into a main intake passage 9A with a large effective opening area by the partition wall 14 at least in the vicinity of the intake boat 5, and a main intake passage 9A with a small effective opening area and the combustion chamber 4 as shown in FIG. It has a divided configuration with an auxiliary bypass intake passage 9B oriented in the tangential direction. A shutter valve 15 and a fuel injection QJ valve 16 are disposed in this main intake passage 9A in this order from the upstream side, and the shutter valve 15 closes when the load is low, i.e., when the shutter valve drive actuator 23 is closed by a command from the control unit 20. It is designed to be fully closed or closed to a slight opening.

With this configuration, in a steady state when the engine is under low load, the shutter valve 15 is closed, so that intake air is supplied only through the auxiliary intake passage 9B. This results in
The intake flow rate is increased and sufficient swirl is generated within the combustion chamber 4, ensuring combustion stability at low loads. On the other hand, when the engine is under high load, the shutter valve 15 opens, so that intake air is supplied from the intake passage 9A, which has a large effective opening area. This improves filling efficiency and ensures sufficient output. Also, in the low load range, sudden acceleration [
dα/dt > (dα/dt). ] is detected from the output of the throttle sensor 22, the fuel injection valve 16 is operated to increase the fuel injection amount to make the mixture rich (including the stoichiometric air-fuel ratio), and at the same time, as shown in FIG. 4(a'). As shown in FIG.
30%) to improve intake air filling efficiency, improving acceleration response. At this time, shutter valve 1
It is preferable that the swirl effect remains by opening 5 not fully but only by an intermediate amount to improve combustion stability.

FIG. 4(b) is a characteristic diagram of engine load (Q, /N) with respect to engine speed (N, □). If λ is the excess air ratio, the stoichiometric air-fuel ratio is A/F = approximately 14.7, and the λ depth is 1. In lean mode, for example, A/F = 20. For example, in rich mode, A/F=13. In this example, we use Fig. 4 (
a) Or as shown in the timing chart of FIG. 8, which will be described later, when acceleration is detected during low load, the shutter valve 15, which is normally closed, is opened to an intermediate position. On the other hand, by adjusting the pulse interval applied to the fuel injection valve 16 and adjusting the fuel injection amount (Qd) so that λ becomes 1, lean combustion is stopped in response to swirl suppression.

FIG. 5 is a detailed block diagram of the control section 20. Each component within the control unit 20 is connected by a bus 35, and the CP
028 is a microprocessor that performs logical operations and logical judgments required within the control section 20, and these controls are shown in a flowchart as shown in FIG. 7 stored in the storage area 40 in the ROM 29. Please follow the given program. The RAM 30 is a memory that temporarily stores various intermediate data required for engine control, and the engine rotation speed counter 31 is connected to the engine rotation speed sensor 29.
Count the pulses from the engine rotation speed (N t
p-), and also has the function of causing the interconnected control unit 32 to interrupt the CPO 28, for example, every revolution of the engine. The timer 33 is a programmable timer that counts periodic pulses, and when a set count value is reached, the interlaced control section 32 causes the CPU 28 to perform timer interoperation. A/
The D converter 34 converts the outputs of the air flow sensor 21 and throttle sensor 22 into digital values. Further, the output interface 36 drives driver circuits 37 and 39 that drive the shutter valve 15 and the fuel injection valve 16 of each cylinder by a predetermined amount according to a command from the CPU 28.

The parts indicated by dotted lines in FIG. 5 are components used in the embodiment of the Miller cycle engine, and details will be explained in the embodiment of the Miller cycle engine.

Furthermore, as shown in FIG. 6(a), the ROM 29 contains a parameter 41 that determines the basic fuel injection amount (Qf), which changes depending on the engine speed (NrPl, ), intake air amount (Q8), etc. (In this example, Qt=fr(N.

), and the opening angle 1 (S
) should be determined by the parameter 42 (in this example, S=f,
(expressed as a number between α)) is stored. These (7)
Qf=fr(N,Q-) and S=f,(α) roughly correspond to the quantities established for conventional lean-burn engines. Further, the ROM 29 contains a fuel injection function that determines the amount to correct the fuel injection amount (Qr) when the acceleration exceeds a predetermined value ((dα/dt)o stored in the storage area 45) in the low-load operating range. Amount correction parameter Cr (Cr = gt (d
α/dt); stored in the storage area 43), and a shutter valve opening angle correction parameter C, (CS-8, (dα/dt); stored in the storage area 44) for correcting the opening angle of the shutter valve 15. has been done. Each of the above parameters may be calculated using a predetermined formula, or a map table may be developed in the ROM 29 and determined from the table. The storage area 46 stores a predetermined throttle opening (α0).

On the other hand, as shown in FIG. 6(b), the RAM 30 has
Fuel injection amount (Qr) calculated or read from ROM29,
The opening angle (S) of the shutter valve 15, etc. are stored in the storage area 50.
The engine rotation speed (N), air flow amount (Q, ), throttle opening angle (α), etc., which are stored in 51 and detected by the sensor, are stored in area storages 52, 53, and 54, respectively.

FIG. 7 shows an example of a flowchart of a control procedure according to the embodiment. Note that in FIG. 7, the time of deceleration is not directly related to the present invention and is therefore excluded from the flowchart.

The program shown in FIG. 7 is called by the interconnected control unit 32 every revolution of the engine. First, in step S2, the engine revolutions (N,
□).

Air flow amount (Q,) and throttle opening (α) are RA
It is stored in the predetermined location in M30. Next step S
4, the engine rotation speed (Nrps
), air flow amount (Q a), and acceleration amount (α),
The reference fuel injection amount (Qr
= f r (N, Q-)), shutter valve angle amount (S
=f, (α)), and further, in step S6, it is checked whether α is larger than the predetermined throttle opening degree α0 stored in the storage area 46. This α. In other words, it is an amount that can be used as a guideline for when the engine is running lean or under low load.
) etc. are possible. If the determination in step S6 is NO, the process proceeds to step S8, and the step s8.
sio opens the fuel injection valve 16 and shutter valve 15, respectively.

On the other hand, if the determination in step S6 is YES, the process advances to step S12 and dα/dt is calculated. It is checked whether this calculated value is larger than (dα/dt)o stored in area 45 (ie, whether it is rapid acceleration, slow acceleration, or steady operation). The judgment at step 312 is N.
If o, the process advances to step 514. In such a case, it is possible that the load is relaxed in a low load range. In this case, the shutter valve opening degree S is set to "0" in step S14, and step S16. In S18, the fuel injection and shutter valve closing operations are performed, respectively (in such a case, the shutter valve 15
may already be closed). In this way, during slow acceleration during lean operation, the shutter valve 15 remains closed and only the throttle valve 12 opens, so the lean state of the air-fuel mixture is maintained, and since the shutter valve 15 is closed, there is no swirl. Since it is strongly generated, it gradually accelerates with optimal fuel consumption.

On the other hand, if the determination in step S12 is YES, the process proceeds to step S20, and a correction parameter C for the fuel reference injection amount and a correction parameter C1 for the shutter opening degree are calculated based on dα/dt.

As mentioned above, this may be successively read from the ROM 29 or may be calculated.
The corrected fuel injection amount Qt is calculated by multiplying the Qt obtained by the correction amount C, and in step S24, the opening angle of the shutter valve after the correction is also calculated. Then, step S26
．． In S28, the fuel injection valve 16 and shutter valve 15 are driven. As is well known, this drive is performed at a predetermined crank angle. Note that in the above procedure, since the time required for each step to proceed is short, the setting of the fuel injection valve 16 and the setting of the shutter valve 15 are substantially performed at the same time.

In this way, when the degree of acceleration exceeds a certain amount (that is, sudden acceleration), the shutter valve 15 is closed for a certain amount of time to increase the amount of intake air to improve acceleration response and enrich the air-fuel ratio to improve combustion. Harvest rice while ensuring stability. FIG. 8 is a timing chart showing the control based on the flowchart of FIG. 7 under certain conditions.

<Example of Miller Cycle Engine> An example of a Miller cycle engine is shown in FIG. Components that are substantially the same as those in the embodiment shown in FIG. 2 are given the same numbers. In this embodiment, the accelerator opening sensor 60 detects the amount of depression of the accelerator pedal as α.

65 is a rotary valve that rotates at a predetermined rotation speed ratio with respect to the rotation of the engine, and as is well known, a notch 66 is provided in a part of the rotary valve 65. At a certain rotation angle of the valve 65, the intake passages 9B and 90 are communicated with each other to form an intake passage for generating swirl. Therefore, the actual intake during the intake cycle is notched? ! 66 is performed only when the intake passages 9B and 90 are communicated with each other. Furthermore, the rotation of the rotary valve 65 has a phase amount with respect to the intake cycle of the intake valve 6, and therefore, as will be clear from the explanation that follows, the intake cycle is substantially interrupted in the middle, resulting in the intake cycle being interrupted. This eliminates negative work (bumping loss) due to resistance in the passageway, contributing to improved engine fuel efficiency. The rotary valve phase changing actuator 63 is an actuator for changing the phase angle of the notch 66 with respect to the cycle of the intake valve 6, as shown in FIG. The phase detection sensor 61 is connected to the rotary valve 65 by the rotary valve phase change actuator 63.
This is a sensor that detects the amount of phase that actually changes after the phase has been changed. The structure occupied in the control section 20, such as the above-mentioned sensor and actuator, is shown in FIG. 2 in addition to the block diagram of the control section of the above embodiment. In the figure, the parts indicated by broken lines are parts specific to the Miller cycle engine shown in FIG.

Next, the phase angle changing operation of the rotary valve 65 will be explained. In Fig. 10, the top dead center of the piston 3 (TDC) is plotted on the horizontal axis.
) to bottom dead center (BDC), and the vertical axis shows the opening degree of the intake valve 6 and the opening/closing timing of the rotary valve 65. The opening/closing timing advances as it shifts to the left, and delays as it shifts to the right. As is clear from FIG. 10, in order for air to actually be taken into the combustion chamber, the intake valve 6 must open and the rotary valve 65 must open.
must be open. Furthermore, the amount of intake air generally increases as the time period during which the intake valve 6 is open and the time period during which the rotary valve 65 is open overlaps with each other. Therefore, in the example of FIG. 10, the amount of intake air at the delay timing shown by the broken line is greater than at the opening timing of the rotary valve shown by the solid line. In a low load region where the shutter valve 15 does not open, the phase of the closing timing of the rotary valve 65 is controlled to be slightly delayed, thereby increasing the amount of intake air commensurate with the increase in accelerator pedal pressure. In the Miller cycle engine of this embodiment, the phase control of the rotary valve 65 is also used for other purposes as described below.

That is, when the pedal opening reaches a predetermined opening due to depression of the accelerator pedal and the shutter valve 15 is opened unconditionally, the intake air amount in the intake cycle suddenly changes due to the intake air from the intake passage 9A, causing a torque shock. However, in the Miller cycle engine of this embodiment, the shutter valve 150 function (S) as shown in FIG.
) The timing and the amount of delay (R) of the rotary valve 65 will be taken into account. To explain further, a predetermined accelerator opening degree (α.

), the shutter valve 15 is kept fully closed, and the delay angle (R) is delayed until the end of intake (BDC). If you do this, the accelerator opening will be α. Even if the shutter valve 15 starts to open even further than before, the intake timing has already ended, so a sudden change in the amount of intake air will not occur, and therefore no torque shock will occur.

The phase change of the rotary valve explained above is an example of the patent application filed in 1983.
A planetary gear mechanism such as -205786 may be used.

The above is an explanation of the phase angle control of the rotary valve 65 of the Miller cycle engine. Therefore, in this embodiment, in order to further ensure acceleration response and combustion stability during acceleration in the low load range, when the acceleration level is more than a predetermined value, that is, during sudden acceleration, the normally closed region is A certain shutter valve 15 is opened to secure the intake air amount to improve acceleration response, and to prevent deterioration of combustion stability due to the reduction in swirl caused by opening the shutter valve, the air-fuel ratio is changed from lean to rich (stoichiometric air-fuel ratio). The aim is to improve this by making adjustments to

FIGS. 12(a) and 12(b) show various data used for controlling the intake system according to the embodiment of the Miller cycle engine stored in the ROM 29. Showing how it is stored in RAM 30,
The role of data is basically the same as in Figures 6(a) and (b), so to explain the difference, R=f
*(α)73 is the phase angle of the rotary valve, and RMIX7
4 is the delay phase angle at which the maximum intake amount is obtained. This RMA×
In this case, the closing timing of the rotary valve 65 is delayed to the maximum, and therefore the rotary valve 65 remains open until the end of intake. Also, the basic fuel injection amount Q, 71. Shutter valve distance S
72. It goes without saying that the shutter valve opening correction parameter 0.76 and the like is different data from those in FIG. 6(a), which is not a Miller cycle engine. Figure 12 (
R183 in b) is the delayed phase angle actually detected by the phase detection sensor 61.

Next, the process will be explained according to the flowchart shown in FIG. First, in step S30, the engine rotation speed N, the intake air amount Q1
．． The basic fuel injection amount Qf, the shutter valve opening S, and the rotary valve delay phase angle R are determined in step S32 from the various detected quantities by inputting the accelerator distance α from each sensor h) according to a predetermined formula. calculate. In step S34, the degree of acceleration is detected, and the time change in the opening angle of the accelerator is determined by a predetermined value (dα/d
t) Check whether it is greater than o. If there is no sudden acceleration, the determination in step S34 is NO and the process proceeds to step S35.
Proceed to and perform fuel injection according to the basic fuel injection amount Qt.
In step 336, the phase angle of rotary valve 650 is delayed according to the phase R determined in step S32. Step S38
Then, the actual phase delay R1 of the rotary valve 65 is detected, and in step S40, the magnitude relationship between this R1 and RMAX is checked. If R1 is smaller than RMAX, the process proceeds to step S42, and the shutter valve opening degree S is set to 0 in order not to disturb the swirl.
When R1 is not smaller than RMAX, the phase is at the maximum lag, which corresponds to a high engine load state, and the demand for intake air filling is high, so the shutter valve 15 is opened. In step S44, step S
Shutter valve 1 with the shutter valve opening amount calculated in 32
Open 5. Step S30→S32→S34→S35→
The loop of S36 → S38 → S40 → (S42) → S44 is during lean burn and when driving without sudden acceleration,
The best fuel efficiency and minimum pumping loss can be achieved. Note that changing the phase delay angle takes time until the phase is actually changed, so it is better if the fuel injection timing and phase angle are changed taking this time into consideration.

Next, to explain the case of sudden acceleration, step S34
The process then proceeds to step S46, where acceleration correction parameters such as CI+Cf are calculated. In step 348, a corrected fuel injection amount for improving combustion stability is calculated, and in step S50, the fuel injection amount is increased by Cf and injected. In step S52, in order to improve acceleration response,
In order to prevent further torque shock from occurring by increasing the opening degree of the shutter valve, the delay phase angle R of the rotary valve 65 is set to R.
MAl+, and the shutter valve 15 is set to MAl+ in step S54.
and drives the rotary valve 65.

In this way, even during sudden acceleration, combustion stability is ensured, acceleration response is improved, torque shock is prevented, and the output of the 5 engine is expected to increase smoothly. FIG. 14 shows a timing chart for the acceleration response of the Miller cycle engine.

The present invention has been explained using the above two embodiments. According to the above embodiment, when sudden acceleration in a low load region is detected,
A lean burn engine with a normal swirl generation mechanism.
It is possible to suppress swirl generation, improve intake air filling efficiency, promote improvement in acceleration response, and prevent combustion stability from being inhibited by weakening swirl by making the air-fuel ratio rich. Also, in Miller cycle engines, swirl is weak due to its structure, so by making the mixture richer, misfires etc. can be prevented, and by increasing the amount of intake air, acceleration response can be improved, and the phase lag angle of the rotary valve can be adjusted. By setting it to the maximum, it is possible to promote a smooth transition from the mirror cycle to the normal cycle (Otsuto cycle) and prevent the occurrence of torque shock.

In the control procedure in the above-described embodiment, it is preferable that the rich fuel injection and the increase in the intake air amount be performed at the same time or at least at a slight timing, and that the CPU of the control unit is a digital computer or an analog computer. It is applicable to both.

[Effects of the Invention] As explained above, according to the engine intake system of the present invention, it is possible to ensure combustion stability against sudden acceleration in a low load range and improve acceleration response in an engine equipped with a swirl generation mechanism. It can be achieved.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of an embodiment according to the present invention, FIG. 2 is a configuration diagram of an intake system of an ordinary lean burn engine embodiment, FIG. 3 is a diagram explaining swirl generation, and FIG. 4(a) Figure 4(b) is a diagram explaining the relationship between the opening degree of the shutter valve and the degree of acceleration in the embodiment shown in Figure 2; is a block diagram of the control unit of the embodiment shown in FIG. 2 or 9; FIGS. 6(a) and 6(b) are storage explanatory diagrams of control data quantities in the embodiment shown in FIG. 2, respectively; FIG. is a flowchart explaining the control procedure of the embodiment of FIG. 2, FIG. 8 is a timing chart explaining the response to acceleration of the embodiment of FIG. 2, and FIG. 9 is a flowchart of an embodiment of the intake system of a Miller cycle engine. 10 is a timing chart explaining the relationship between the intake valve and the rotary valve in a Miller cycle engine; FIG. 11 is a diagram explaining the relationship between the delayed phase angle of the shutter valve and the rotary valve in the Miller cycle engine; 12(a) and 12(b) are respectively explanatory diagrams of storage of control data quantities in the embodiment of FIG. 9, FIG. 13 is a flowchart explaining the control procedure of the embodiment of the intake system of a Miller cycle engine, and FIG. 14. is a timing chart illustrating a response to acceleration in a Miller cycle engine. In the diagram, 1... Engine body, 3... Piston, 4,103
... Combustion chamber, 6... Intake valve, 7... Exhaust valve, 9
A-main intake passage, 9B... bypass intake passage, 11.
...Air flow meter, 12...Throttle valve, 1
5,100...Shutter valve, 16...Fuel injection valve,
20... Control unit, 21... Air flow sensor, 2
2... Throttle sensor, 23... Shutter valve drive actuator, 24... Fuel supply path, 28... C
PU, 29...ROM, 30-...RAM, 60-...
・Accelerator opening sensor, 61... Phase detection sensor, 6
3...Rotary valve phase change actuator, 65...
- Rotary valve, 66... Notch, 101... Intake passage, 102... Swirl generation means, 104... Bypass intake passage, 105... Acceleration detection means, 106.
. . . air-fuel ratio adjustment means, 107 . . . acceleration response means. Figure 3 4th prisoner (0) Figure 4 (b) If you are satisfied with your wish 0-If you are jealous of your feelings, ρ) 1 is also δ cx-.

Claims (3)

[Claims] (1) Air-fuel ratio adjusting means for adjusting the air-fuel ratio of the air-fuel mixture to a lean, stoichiometric air-fuel ratio, or rich value; swirl generating means for generating swirl within the engine combustion chamber; and acceleration detection for detecting the acceleration state of the engine. and controlling the air-fuel ratio adjusting means and the swirl generating means to adjust the air-fuel ratio to a lean value and generate swirl in a predetermined low-load operation region, while controlling the air-fuel ratio adjusting means and the swirl generating means to Acceleration response means controls the air-fuel ratio adjusting means and the swirl generating means so as to correct the air-fuel ratio to the rich side and suppress swirl even in the predetermined low-load operating region when a sudden acceleration state is detected. An engine intake device characterized by comprising: (2) The swirl generating means is a first
It consists of an intake passage, a shutter valve provided in the first intake passage, and a second intake passage for generating a swirl that bypasses the shutter valve and guides the intake air to the engine combustion chamber, and is configured to operate in the predetermined low-load operating region. The intake system for an engine according to claim 1, wherein the shutter valve is closed while the acceleration detection means detects a state other than a sudden acceleration state, and opens when a sudden acceleration state is detected. . (3) The swirl generating means includes a first intake passage leading to the engine combustion chamber, a shutter valve provided in the first intake passage, and a swirl generating means for guiding intake air to the engine combustion chamber by bypassing the shutter valve. a second intake passage, and an on-off valve that opens and closes the bypass passage during the intake stroke, and closes the shutter valve and opens and closes the on-off valve according to the load when not in a sudden acceleration state under low load. The engine intake system according to claim 1, wherein the shutter valve is opened when sudden acceleration is detected.