JPH06307266A - Fuel injection controller for internal combustion engine with mechanical supercharger - Google Patents

Abstract

PURPOSE:To predict an intake air amount precisely by providing a delay means, which switches two kinds of intake air amount maps according to the on/off of a supercharger and switches the intake air amount maps when the predetermined time passes after switching the supercharger from its off to on. CONSTITUTION:A mechanical supercharger 3 is belt-driven by the crank pulley 4 of an engine main body 1 via an electromagnetic clutch 5, and is operated/ stopped according to on/off of an electromagnetic clutch 5. A fuel injection valve 11 for injecting fuel toward an intake port 10 is arranged in the intake pipe 2 of the engine main body 1. The injection valve 11 is controlled by an ECU 30 on the basis of each of detection signals at least from a throttle valve opening sensor 17 and a crank angle sensor 19. In this case, two kinds of intake amount maps are mutually switched according to on/off of the supercharger 3 in the ECU 30. The intake amount map is delayed so as to be switched when the predetermined time passes after the supercharger 3 is switched from off to on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine with a mechanical supercharger, and more particularly to controlling the fuel injection by predicting the engine intake air amount by an intake air amount map according to the throttle opening and the engine speed. The present invention relates to a fuel injection control device.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 62-265449 discloses
With a throttle valve opening sensor and a crank angle sensor,
An internal combustion engine is disclosed in which an intake air amount is estimated based on a throttle valve opening detected by a throttle valve opening sensor and an engine speed calculated based on a detection signal of a crank angle sensor.

However, even when the intake air amount is estimated in this way, a supercharger is arranged in the engine intake passage, a bypass passage is provided to bypass the supercharger, and the engine is in an operating state in the bypass passage. In an internal combustion engine having a bypass control valve whose opening is controlled accordingly, the intake air amount changes depending on the opening of the bypass control valve.Therefore, the intake air amount is adjusted based only on the throttle valve opening and the engine speed. Even if estimated, there arises a problem that the amount of intake air deviates.

Therefore, the applicant has filed a prior application, Japanese Patent Application No. 4-1.
No. 83835, not only throttle valve opening and engine speed, but also bypass control valve opening (supercharged or non-supercharged)
In consideration of the above, an intake air amount detection device for an internal combustion engine with a supercharger is proposed in which the intake air amount is obtained.

[0005]

However, in the above intake air amount detecting device, when the intake air amount control map is switched between supercharging and non-supercharging, the timing of the switching is set to that of the mechanical supercharger. When energizing the electromagnetic clutch, switching to the control map for supercharging occurs before the point when the supercharger actually operates and the supercharging pressure rises due to the delay in engagement of the electromagnetic clutch. Becomes For this reason,
During acceleration (transition) when the supercharger shifts from the OFF state to the ON state, the intake air amount cannot be accurately predicted, and thus it becomes difficult to accurately control the fuel injection amount, and the operability of the engine is reduced. , The exhaust characteristics, fuel consumption, etc. will be adversely affected.

As a means for solving such a problem,
First, a method of detecting the engagement of the electromagnetic clutch (such as detection of a clutch disc clearance by a gap sensor, detection of a rotational speed difference between a driving side and a driven side) can be considered, but it is costly and unrealistic. Therefore, it is an object of the present invention to more accurately predict the intake air amount in consideration of the engagement delay of the electromagnetic clutch of the supercharger.

[0007]

In order to solve the above problems, the present invention has a mechanical supercharger arranged in the engine intake passage, and means for detecting the opening of the throttle valve and the engine speed. In the fuel injection control device for the internal combustion engine, the engine intake amount is predicted by the intake amount map corresponding to the throttle valve opening and the engine speed, and the fuel injection control device controls the fuel injection based on the predicted value. Means for detecting ON / OFF of the turbocharger, two kinds of intake air amount maps corresponding to ON / OFF of the supercharger, means for switching the intake air amount map, and supercharger switching from OFF to ON And a delay means for switching the intake air amount map after a lapse of a predetermined time after detecting the signal.

[0008]

Since the intake air amount map is switched after a predetermined time has elapsed after the signal for switching the supercharger from OFF to ON is detected, the supercharging pressure due to the engagement delay of the electromagnetic clutch of the supercharger can be reduced. It will no longer switch to the control map for supercharging before rising, and accurate prediction of the intake air amount will be possible even during acceleration (transition) when the supercharger shifts from the OFF state to the ON state. It will be possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an overall view of an internal combustion engine equipped with a mechanical supercharger. Referring to FIG. 1, 1 is an engine body, 2 is an intake pipe, and 3 is a mechanical supercharger. In this embodiment, a roots compressor is used as the supercharger. The supercharger 3 is belt-driven from a crank pulley 4 provided on the crankshaft of the engine via an electromagnetic clutch 5, and the electromagnetic clutch 5 is turned ON / O.
The supercharger 3 is operated / stopped by the FF. The intake pipe 2 is provided with a bypass passage 6 that bypasses the supercharger 3,
A bypass control valve 7 is arranged in the bypass passage 6. The opening degree of the bypass control valve 7 is controlled by a stepper motor 8 in accordance with the engine operating state, whereby the amount of air recirculated from the downstream side to the upstream side of the supercharger 3 through the bypass passage 6 is adjusted. The supply pressure can be controlled.

The throttle valve 9 is provided on the upstream side of the supercharger 3 (and the bypass passage 6), and its opening is controlled in conjunction with the operation of the accelerator pedal (not shown) by the driver. A fuel injection valve 11 is arranged in the intake pipe 2 near the engine body 1 so as to inject fuel toward the intake port 10. Electronic control unit (EC
U) 30 performs ignition timing control, fuel injection control, supercharging pressure control, and the like.

The ECU 30 includes an air flow meter 16 for detecting an intake air amount, a throttle valve opening sensor 17 for detecting a throttle valve opening, a bypass control valve opening sensor 18 for detecting a bypass control valve opening, and an engine speed. The signals from the crank angle sensor 19 for detecting the are respectively input. On the other hand, the ECU 30 is connected to and controls the electromagnetic clutch 5, the stepper motor 8, and the fuel injection valve 11. Also, during control, the electromagnetic clutch 5
When issuing a command to turn ON, the flag for turning ON the electromagnetic clutch is set (YSMC = 1).

During the transient operation, the intake air amount detected by the air flow meter deviates from the actual intake air amount. Therefore, if the fuel injection amount is calculated based on the intake air amount detected by the air flow meter. , The air-fuel ratio deviates from the target air-fuel ratio. Therefore,
Considering that the intake air amount behaves in a first-order lag system with respect to the change in the throttle valve opening, the intake air amount at the time of closing the intake valve is estimated based on the throttle valve opening and the engine speed. There is.

However, even if the intake air amount is estimated in this way, in the engine in which the supercharger is arranged in the engine intake passage, the electromagnetic clutch 5 of the supercharger 3 is accelerated before the electromagnetic clutch 5 changes from OFF to ON. As described above, there is a delay in the engagement of the electromagnetic clutch. Therefore, if the control map is switched based on the flag (YSMC) when the electromagnetic clutch is turned on, the actual boost pressure does not rise (i.e. Despite the fact that the feeder is turned off), only the control map is switched, which causes a problem that accurate predictive control of the air amount cannot be performed. Further, in an internal combustion engine in which a bypass passage is provided to bypass the supercharger, and a bypass control valve whose opening is controlled according to the engine operating state is arranged in this bypass passage, the intake air amount depends on the opening of the bypass control valve. Because of the change, even if the intake air amount is estimated based only on the throttle valve opening and the engine speed, there arises a problem that the intake air amount deviates from the actual intake air amount.

Therefore, in this embodiment, a delay flag in consideration of the engagement delay of the electromagnetic clutch 5 is provided, and the supercharging / non-supercharging is determined by this. FIG. 2 is a control flowchart for flag switching according to the first embodiment of the present invention, showing a case where the electromagnetic clutch 4 switches from OFF to ON. First, in step 30, whether the electromagnetic clutch 4 is currently ON or OFF is detected by an electromagnetic clutch ON / OFF flag (YSMC).
If the electromagnetic clutch 4 is ON (YSMC = 1), the process proceeds to step 32, and the electromagnetic clutch at the previous calculation is OFF.
If (YSMCO = 0), after setting the delay counter to 0 (CSCDLY = 0) in step 34,
Go to step 36. The electromagnetic clutch at the time of the previous calculation is ON
If it is, the process proceeds directly to step 36.

In step 36, it is detected whether or not the delay counter has reached a value corresponding to a fixed time (for example, an amount equivalent to 0.4 seconds) (CSCDLY <KTSCDLY?), And if the fixed time has elapsed, step 38 is entered. The electromagnetic clutch engagement flag is set (XSMCDLY = 1). If the fixed time has not elapsed, the delay counter is incremented in step 37, and the electromagnetic clutch engagement flag is reset in step 40 (XSMCDLY =
0). When the processing of steps 38 and 40 is completed, the flag is updated in step 42 (YSMCO = YSMC).

In this embodiment, the delay time is fixed time (0.
4 seconds). This is the electromagnetic clutch 4 from OFF to ON
It is the time from when the supercharging pressure is actually switched to when the supercharging pressure starts to increase after switching to. When the electromagnetic clutch 4 is switched from ON to OFF, the bypass control valve 7 is fully opened and a large difference in air amount does not occur.
Simultaneously with the detection of the OFF signal of, the intake air amount control map is switched from that for supercharging to that for non-supercharging.

FIGS. 3 and 4 are control flowcharts for flag switching according to the second embodiment of the present invention, FIG. 3 is a rotor rotation speed calculation routine, and FIG. 4 is a delay time calculation routine. In the first embodiment, the delay time is set to a constant value (0.4 seconds) as described above, but it actually changes depending on the difference in the rotational speeds of the drive side and the driven side of the supercharger 3. When the turbocharger 3 is off, the bypass control valve 7 is fully open, so the driven-side clutch disk is assumed to hardly rotate, and when the off-state shifts to the on-state, it depends on the engine speed. The delay time is determined.

However, this is a case where the supercharger is turned on after being kept in the off state for a long time.
Then, when it is turned on again immediately, the rotor of the supercharger rotates due to inertia, so that it is not suitable. Therefore, since the engine speed at the time when the supercharger is turned off is stored, and the rotor speed is used as the rotor speed, the present rotor speed (ROREV) can be predicted to some extent. ) And the number of rotations of the rotor (ROREV), the delay time (KTSCDLY) is obtained.

That is, in step 50, it is detected whether the electromagnetic clutch is OFF or ON, and if it is ON, the engine speed (NE) is set to the rotor speed (ROREV) in step 54. If it is turned off, the rotor speed is attenuated in step 52. Note that K is a time attenuation coefficient. Then, the delay process is performed by replacing steps 30 to 34 in FIG. 2 with the following. Step 60,
At 62, the time point at which the electromagnetic clutch changes from OFF to ON is detected, and at step 64, the rotational speed difference (tNRATIO) between the drive side and the driven side of the supercharger rotor at that time is referred to as the engine rotational speed (NE). It is calculated as the difference from the attenuated rotor speed (ROREV) calculated in. Step 6
At 0, the delay time is searched from the map based on this rotation speed difference, and the delay time is determined at step 68. Further, in step 70, the delay counter is cleared.

In addition to these, it is possible to change the time decay of the rotor rotation by the air amount and the opening degree of the bypass control valve. 5 to 7 show examples in which the intake air amount at the time of closing the intake valve is estimated based not only on the throttle valve opening and the engine speed but also on the bypass control valve opening. As a result, an accurate intake air amount can be calculated even during transient operation, and thus the air-fuel ratio can be accurately controlled to the target air-fuel ratio.

5 and 6, the predicted intake air amount (QN
2 shows a routine for calculating FWD). This routine is executed by interruption every fixed time, for example, every 8 msec. Referring to FIGS. 5 and 6, first, step 8
At 0, the engine speed N _e , the throttle valve opening θ _T , and the bypass control valve opening θ _ABV are read. Next, at step 82, as shown by the following equation, the intake air amount (QNAFM) obtained from the detection signal of the air flow meter is subjected to a first-order delay process to obtain QNSM.

QNSM = QNSM '+ (QNAFM-Q
NSM ′) × K ₁ where QNSM ′ is QN in the previous processing cycle.
SM and K ₁ is a time constant determined by the engine speed. In step 84, the amount of change Δθ _T of the throttle valve opening per unit time is calculated. In step 86, it is determined whether the supercharger 3 is operating. This determination is made based on whether or not the above-mentioned electromagnetic clutch engagement flag (XSMCDLY) is set. When the supercharger 3 is not in operation, the routine proceeds to step 88, where the intake air amount (QNT during steady state) based on the map (not shown) when the supercharger is stopped is used.
A) is required.

On the other hand, when the supercharger 3 is operating, the
Proceed to Step 90, and map (not shown) when the supercharger is operating.
Value) based on the normal intake air amount map value (MQNT
A) is required. MQNTA is bypass control valve fully closed
Throttle valve opening θ _TAnd engine speed N_eAnd
This is the value obtained from In step 92, the correction coefficient K₂
Is the detected bypass control valve opening θ_ABVAnd unit time
From a map (not shown) based on the amount of intake air per unit
Desired. K₂Is the bypass control valve opening θ_ABVSucked by
This is a coefficient for correcting the influence on the amount of incoming air. Step
In P94, the steady-state intake air amount (QNTA) is calculated by the following formula.
Desired.

QNTA = MQNTA × K _{2 In} step 96, the true intake air amount (QNCRT) is obtained by subjecting the steady-state intake air amount QNTA to the first-order delay processing, as shown by the following equation. QNCRT = QNCRT '+ (QNTA-QNCR
T ′) × K ₃ where QNCRT ′ is Q in the previous processing cycle.
NCRT, and K ₃ is a time constant determined by the engine speed N _e and QNTA.

At step 98, the true intake air amount (QNCRT) is subjected to the first-order delay processing to obtain QNCRT4, as shown by the following equation. QNCRT4 is QNS
It is the estimated air volume created as having the same response as M. QNCRT4 = QNCRT4 '+ (QNCRT-QNC
RT4 ') × K ₄ where, QNCRT4' is QNCRT4 in the previous processing cycle, K ₄ is the time constant for the same response as QNSM.

Next, at step 100, the throttle valve opening (TAO) when the intake valve is closed is calculated by the following equation. TAO = θ _T + Δθ _T × T Here, T is the time from the present time to the time of closing the intake valve.
In step 102, QNTAB is calculated based on N _e and TAO.
O is calculated. In step 104, the number of calculations n is calculated by dividing the time (Tmsec) from the present time to the intake valve closing time by the calculation cycle Δt (8 nsec) of the routines of FIGS. 5 and 6. In step 106, the intake air amount (QNVLV) when the intake valve is closed, which is estimated from the throttle valve opening θ _T and the engine speed, is calculated by the following equation.

A _i = A _i−1 + (QNTABO−A _i−1 ) × K _{3 In} this formula, the initial value A _o is equal to QNCRT, and A _n when this formula is repeatedly calculated n times is QNVLV. is there. In step 108, QNFWD is calculated by the following equation. QNFWD = QNSM + (QNVLV-QNCRT4) In step 110, to prepare for the next processing cycle,
QNSM ', QNCRT', and QNCRT4 'store QNSM, QNCRT, and QNCRT4, respectively, and this routine ends.

Next, another example of the routine for calculating the QNFWD will be described with reference to FIG. Only steps different from the examples of FIGS. 5 and 6 will be described. As described above, when it is determined in step 86 that the supercharger is stopped, the routine proceeds to step 88, where the steady-state intake air amount (QNTA) is calculated based on the map (not shown) when the supercharger is stopped.
Is required.

On the other hand, when the supercharger 3 is in operation, the routine proceeds to step 120, where the steady-state intake air amount map value (MQNT) is based on a map (not shown) when the supercharger is operating.
A) is required. Since the target bypass control valve opening θ _TRG is determined by the throttle valve opening θ _T and the engine speed N _e as described above, the intake air amount considering the bypass control valve opening is basically the throttle valve opening. It depends on θ _T and the engine speed N _e . Therefore, MQNTA is a value calculated from the target bypass control valve opening θ _TRG , the throttle valve opening θ _T , and the engine speed N _e .

By the way, since the bypass control valve 7 has a response delay, the actual bypass control valve opening θ _ABV deviates from the target bypass control valve opening θ _TRG during the transient operation.
Since the amount of intake air changes due to this deviation, correction is performed in steps 122 to 126. In step 122, the deviation Δ of the actual bypass control valve opening θ _{ABV from} the target bypass control valve opening θ _{TRG is calculated} by the following equation.
Calculate θ _ABV .

Δθ _ABV = θ _ABV −θ _TRG Next, at step 124, the coefficient K ₅ is obtained from the map based on Δθ _ABV (see FIG. 12). Step 1
At 26, MQNTA is subjected to the first-order delay processing as shown by the following equation to obtain the steady-state intake air amount (QNTA). QNTA = QNTA ′ + (MQMTA−QNTA ′) ×
K ₅ Here, QNTA 'is QN in the previous processing cycle.
It is TA.

After this, the process proceeds to step 96 and the subsequent steps.

[0033]

According to the present invention, since the intake air amount map is switched by detecting a signal for switching the supercharger from OFF to ON and delaying the signal for a predetermined time, the supercharger is turned OFF. It is possible to accurately predict the intake air amount based on the actual supercharging state even during acceleration (transition time) when the state changes to the ON state. Therefore, it is possible to accurately control the fuel injection amount, and it is possible to improve the drivability of the engine, the exhaust characteristics, the fuel consumption, and the like.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine with a supercharger.

FIG. 2 is a flow chart for performing control switching of a control map when the electromagnetic clutch is displaced from OFF to ON.

FIG. 3 is a flowchart for calculating a rotor rotation speed.

FIG. 4 is a flowchart for calculating a delay time.

FIG. 5 is a flow chart for calculating QNFWD.

FIG. 6 is a flowchart for calculating QNFWD (continuation of FIG. 5).

FIG. 7 is a flowchart of another example of calculating QNFWD.

[Explanation of symbols]

 3 ... Supercharger 5 ... Electromagnetic clutch 6 ... Bypass passage 7 ... Bypass control valve 9 ... Throttle valve 17 ... Throttle valve opening sensor 19 ... Crank angle sensor 20 ... Electromagnetic clutch ON / OFF sensor

Claims (1)

[Claims] 1. A map of an intake air amount according to a throttle valve opening and an engine speed, comprising a mechanical supercharger arranged in an engine intake passage, and means for detecting a throttle valve opening and an engine speed. In the fuel injection control device for an internal combustion engine, which comprises: means for predicting the engine intake air amount by means of, and means for controlling fuel injection based on the predicted value, means for detecting ON / OFF of the supercharger; Two types of the intake air amount maps depending on ON and OFF, a means for switching the intake air amount maps, and a delay means for switching the intake air amount maps after a predetermined time has elapsed after detecting a signal for switching the supercharger from OFF to ON. A fuel injection control device for an internal combustion engine with a mechanical supercharger, comprising: