JPH06288322A - Fuel injection device of engine - Google Patents

Abstract

PURPOSE:To expedite atomization of fuel while preventing torque shock at the time of transistion to a off-idling condition by starting supply of assisting air when an engine reaches a specified load and varying assisting air supply startup load in response to acceleration grade. CONSTITUTION:Calculations of a fuel injection quantity, an ignition timing, an ISC(idling speed control) control quantity are performed by a control unit 16, based on input information from various kinds of sensors such as an air-flow sensor 3, and ON/OFF judgement of the assisting air is performed. An assisting control valve (AMI) 9 is set OFF in an idling range and the supply of assisting air is stopped under a warming-up condition where an engine water temperature becomes warmer than a specified value. And switching load line from the AMI/ OFF to the AMI/ON that is an assisting air supply startup load, is set to the low load when a variable rate of an intake charge quantity is large, and the assisting air supply startup line is set to a high load when the variable rate is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for supplying assist air for atomizing fuel.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Examined Patent Publication No. 55-9555.
As described in Japanese Patent Publication, an assist air passage that connects the upstream side of the throttle valve of the intake passage and the vicinity of the injection port of the fuel injection valve is provided, and it is injected from the fuel injection valve during cold with poor vaporization and atomization. It is known that fuel is atomized by assist air. In addition, such supply of assist air for atomizing the fuel is not normally performed during warm idling. It is IS when idle
If the assist air is supplied while the engine speed is controlled to the target speed by C (idle speed control), the intake air amount increases by that amount and the idle speed increases, which deteriorates fuel efficiency. It depends on the reason. On the other hand, even when the engine is idle, the target rotation speed is originally increased to add a small amount of assist air, so that assist air is supplied to accelerate atomization of the fuel.

[0003]

In the case of assisting atomization of fuel by assist air, it is common to stop the supply of assist air during warm idle as described above. There is a problem that a torque shock occurs with the start of the supply of assist air at the time of transition from to idle. If the assist air supply is started when acceleration accelerates and the throttle opening becomes large to some extent and the ratio of the assist air amount to the main air amount becomes small, such torque shock will be reduced. The start is delayed and the original purpose of promoting fuel atomization cannot be fully achieved.

The present invention has been made in view of the above problems, and has the effect of promoting fuel atomization by assist air while preventing torque shock accompanying start of assist air supply at the time of transition from idle to off-idle. The purpose is to raise.

[0005]

SUMMARY OF THE INVENTION The present invention is for atomizing fuel near the injection port of a fuel injection valve at the time of off-idling through an assist air passage that connects the upstream side of the throttle valve of the intake passage and the vicinity of the injection port of the fuel injection valve. When the engine load reaches a predetermined assist air supply start load due to the transition from the idle region where the supply of assist air is stopped to the off-idle, A feature is provided to start the assist air supply and to change the assist air supply start load according to the acceleration of the engine so as to accelerate the assist air supply start within the range where torque shock can be suppressed. And

The assist air supply start load is a load level at which the ratio of the assist air amount to the main air amount supplied through the throttle valve is set to a ratio at which the torque shock accompanying the start of the assist air supply can be suppressed below a predetermined level. Set.

[0007]

According to the present invention, the supply of assist air is stopped during idling, and when the engine shifts from idle to off-idling, the assist air supply is started when the engine load reaches the predetermined assist air supply start load. And
The setting of the assist air supply start load is changed according to the degree of acceleration of the engine, and preferably, the ratio of the assist air amount to the main air amount supplied via the throttle valve is the torque shock accompanying the start of the assist air supply. Is set to such a ratio that can be suppressed below a predetermined level, whereby the start of assist air supply can be expedited as early as possible within the range in which torque shock can be suppressed.

When the degree of acceleration is large, it means that the driver has suddenly stepped on the accelerator. In this state, even if some torque fluctuation occurs due to the assist air supply being started on the low load side. It is unlikely that you will experience a shock. Therefore, when the acceleration degree is large as described above, the assist air supply start load can be set to the low load side to accelerate the start of the assist air supply and enhance the effect of promoting fuel atomization. Also, when the acceleration is small, it is easy for the driver to experience a torque shock because the driver is stepping on the accelerator slowly.In this state, however, the assist air supply start load depends on the main air amount. Since the ratio of the amount of assist air is set to the high load side so that the torque shock can be suppressed below a predetermined level, the occurrence of torque shock is suppressed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall view of an embodiment of the present invention. In this embodiment, an air flow sensor 3 for detecting an intake air amount is sequentially installed in an intake passage 2 of an engine 1 from the upstream side.
, A throttle valve 4 for adjusting the intake air amount, and a fuel injection valve 5
And a bypass passage 6 for bypassing the throttle valve 4 is formed, and an ISC valve 7 composed of an electromagnetic valve is arranged in the bypass passage 6. An assist air passage 8 that bypasses the throttle valve 4 and communicates the upstream side of the intake passage 2 with the vicinity of the injection port of the fuel injection valve 5 is formed, and the assist air control valve that opens and closes the passage is formed in the assist air passage 8. 9 is provided. Further, a catalyst device 11 for purifying exhaust gas is provided in the exhaust passage 10 of the engine 1. And the combustion chamber 12 of the engine
An ignition plug 13 is provided in the ignition plug 13, and the ignition plug 13 is connected to an igniter 15 via a distributor 14.

The control of the fuel injection amount of the engine 1, the ignition timing control, the ISC (idle speed control), the assist air control and the like are performed by the control unit 16 which is composed of a microcomputer. Therefore, the control unit 16 includes a intake air amount signal from the air flow sensor 3, a crank angle signal and a rotation signal which are outputs of a crank angle sensor and a rotation sensor attached to the distributor 14, and a water temperature sensor 17 which detects an engine water temperature. The engine water temperature signal and the like are input as control information.

The control unit 16 calculates the fuel injection amount, the ignition timing, the ISC control amount based on these input information, and also determines whether the assist air is on or off. Then, each control signal is output to the fuel injection valve 5, the igniter 15, the ISC valve 7 and the assist air control valve 9. Then, in the control of the fuel injection amount, the injection amount set according to the load and the engine speed of the engine is corrected by the water temperature and the like, and the air-fuel ratio feedback correction based on the output of the air-fuel ratio sensor (not shown) is performed to perform the injection. The fuel injection valve 5 is driven by the injection pulse according to the amount. In the ignition timing control, the ignition timing is set according to the engine speed and the intake charge amount, and an ignition signal is output to the igniter 14. In the ISC control, the bypass air amount is set according to the engine water temperature and the ISC valve 7 is controlled.

The assist air control of this embodiment is as follows.

FIG. 2 is a region diagram of assist air control in this embodiment. As shown in this figure, in a warm state where the engine water temperature is equal to or higher than a predetermined value, the assist air control valve (AMI) 9 is turned off (closed) in the idle region, and the supply of assist air is stopped. And this AMI O
The load line for switching from FF to AMI / ON (open), that is, the assist air supply start load is changed depending on the magnitude of the change rate (dCe) of the intake charge amount. That is, the assist air supply start load is set to the low load side when the change rate of the intake air charge amount is large, and the assist air supply start line is set to the high load side when the change rate is small.

FIG. 3 is a time chart showing the assist air control of this embodiment. (A) shows the assist air control at the time of rapid acceleration with a large load change, and (b) at the time of gentle acceleration with a small load change. The assist air control of is shown. As shown in (a) of FIG. 3, the intake charge amount (Ce) rises sharply at the time of rapid acceleration in which the throttle opening (TVO) changes rapidly, and the difference from the averaged value (Ceb) of Ce is large. , C
The rate of change of e (dCe) becomes large. This state is determined by the change rate (dCe) exceeding the set value (Kd), and at this time, the load level (threshold value) serving as a threshold value for shifting the assist air supply from OFF (stop) to ON (execution). CeON) is set to the low load side. And C
When e becomes equal to or higher than CeON, the supply of assist air is started. XAMI is an assist air supply flag,
1 indicates a supply state, and 0 indicates a stop state. Further, as shown in FIG. 3B, the change in the throttle opening (TVO) is gentle, and during normal acceleration, the rise of the intake charge amount (Ce) is also gentle, and the difference from the smoothed value (Ceb) is small. ,
The rate of change of Ce (dCe) does not exceed the above Kd. At this time, CeON is set to a high load, and when Ce reaches this high load setting CeON, the supply of assist air is started.

FIG. 4A shows an assist air control valve (AM
I) shows the flow coefficient characteristic with respect to the intake pipe pressure of 7
(B) shows a characteristic line in which the ratio of the assist air amount to the main air amount is constant. When the load is high, the intake pipe pressure is high and the differential pressure between the inlet side and the outlet side of the assist air passage 8 is small, so that the flow coefficient of the assist air control valve decreases as shown in FIG. 4 (a). ,
As shown in (b), the ratio of the assist air amount to the main air amount becomes small. Therefore, as described above, the CeON is set to the high load side during the slow acceleration, so that the torque shock due to the start of the assist air supply is reduced. The 5% line shown in (b) of FIG. 4 is a line in which a torque shock is felt during gentle acceleration when the ratio of the assist air amount is larger than this, and is a plot of the function f ₂ (Ne) in the flowchart described later. Equivalent to. Also, the 100% line in the figure is f ₁ in the flowchart described later.
This corresponds to a plot of (Ne).

5 and 6 are flow charts for executing the above assist air control. This control is S1-S1
When starting, the engine speed (Ne) is read in S1 and then the intake air amount (Qa) is read in S2. Then, in S3, the value obtained by dividing Qa by Ne is multiplied by a constant (K) to calculate the intake charge amount (Ce), and then in S4, a low response charge amount that is a smoothed value to be used as a reference for the transient determination. Calculate (Ceb). That is, the current Ceb is calculated by adding the previously calculated Ceb multiplied by the predetermined weighting factor (kα) to the actual filling amount (Ce) multiplied by (1-kα). And
In S5, the difference between the current filling amount (Ce) and Ceb is calculated as a transient determination value, and in S6 it is checked whether dCe is larger than the set value (Kd). If dCe> Kd, the process proceeds to S7. Set AMI on / off load for sudden acceleration with high transient demand. That is, Ce · ON is a function f ₁ (N
e), and Ce / OFF is also the function f
Set by ₁ (Ne). Further, when dCe ≦ Kd, the process proceeds to S8, and the AM for slow acceleration with low transient demand is supported.
I Set the on / off load. That is, Ce · ON is set by the function f ₂ (Ne), and Ce · OFF is set by the function f ₁ (Ne).

Next, in S9, it is judged by the flag (XAMI) whether or not it is the current AMI / ON area. Then, in the case of the AMI / ON area, Ce <Ce · in S10.
When it is determined that Ce <Ce · OFF, the flag is set to zero (0) in S11, and the AMI is closed in S12. When Ce ≧ Ce · OFF, X
Since AMI remains 1, XAMI is set to 1 in S13.
And open the AMI in S14.

In S9, the current AMI / OFF area (X
When AMI = 0), Ce ≧ Ce · ON in S15
When Ce ≧ Ce · ON, the flag is set to 1 in S13 and the AMI is opened in S14. Further, when Ce <Ce · ON, it means that XAMI = 0, so that the process proceeds to S11 and XAMI is set to zero (0),
The AMI is closed in S12.

[0019]

Since the present invention is constructed as described above, the start of the supply of assist air is accelerated as early as possible while preventing the torque shock associated with the supply of assist air during the transition from idle to off-idle. It can accelerate fuel atomization and improve vaporization and atomization.

[Brief description of drawings]

FIG. 1 is an overall view of an embodiment of the present invention

FIG. 2 is a region diagram of assist air control in one embodiment of the present invention.

FIG. 3 is a time chart showing assist air control in one embodiment of the present invention.

FIG. 4 is a characteristic diagram of assist air control in one embodiment of the present invention.

FIG. 5 is a flowchart (part 1) of executing assist air control according to an embodiment of the present invention.

FIG. 6 is a flowchart (part 2) of executing the assist air control according to the embodiment of the present invention.

[Explanation of symbols]

 1 engine 3 air flow sensor 5 fuel injection valve 8 assist air passage 9 assist air control valve 15 control unit

Claims (2)

[Claims] 1. An engine for supplying assist air for atomizing fuel to the vicinity of the injection port of the fuel injection valve during off-idling through an assist air passage that connects the upstream side of the throttle valve of the intake passage and the vicinity of the injection port of the fuel injection valve. In this fuel injection device, the assist air supply is started when the load of the engine reaches a predetermined load for starting the assist air supply with the transition from the idle region in which the supply of the assist air is stopped to the off-idle, and the engine acceleration A fuel injection device for an engine, characterized in that a means for changing the assist air supply start load according to the above is provided. 2. The assist air supply start load is set such that the ratio of the assist air amount to the main air amount supplied via the throttle valve is a ratio capable of suppressing the torque shock due to the start of the assist air supply to a predetermined level or less. The engine fuel injection device according to claim 1, wherein the fuel injection device is set to a load level.