JPH0823340B2 - Exhaust gas recirculation control method for diesel engine - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method for controlling exhaust gas recirculation of a diesel engine, and particularly to an exhaust gas for a diesel engine suitable for use in an electronically controlled diesel engine for automobiles, which is adapted to recirculate exhaust gas even at low speed. The present invention relates to improvement of a recirculation control method.

[Prior art]

In some diesel engines used for vehicles such as automobiles, exhaust gas recirculation (hereinafter referred to as EGR) is adopted for the purpose of reducing NOx which is a harmful component in exhaust gas. Conventionally, this EGR has been cut at low rotation speeds, but in recent years, with the tightening of exhaust gas regulations, it has been considered to perform EGR even at low rotation speeds including idle operation.

[Problems to be Solved by the Invention]

However, when the load such as the power steering device, the air conditioner (hereinafter, referred to as an air conditioner), the automatic transmission (hereinafter, referred to as a torque converter), or the electric load is applied at the time of idling, the engine load increases, so that the fuel injection is performed. The amount increases. At this time, if you apply the same amount of EGR as a normal idle, smoke and white smoke will increase even when idle, not only drastically damaging the image of the vehicle, but in the worst case, the engine will stall Sometimes. This is because when EGR is applied, the ignitability of fuel becomes slower,
This is because a large amount of unburned gas is emitted as smoke and white smoke. In addition, since the output torque of the engine decreases due to the difficulty in burning, there is a problem that the engine may stall especially when the load of the power steering device is overloaded. On the other hand, as something similar to the present invention, Japanese Patent Application Laid-Open No. 56-5695
8 discloses an EGR method and device for a diesel engine in which the EGR amount is decreased as the fuel injection amount is increased. However, this EGR method and device was made by paying attention to the fact that the fuel injection amount and the engine load strictly correspond to each other, and the purpose is to adjust the EGR amount strictly according to the engine load. However, unlike the present invention, it does not prevent a problem at low rotation speed, particularly at idle. Further, the applicant, like the present invention, when the load by the engine driven device such as the air conditioner and the power steering device is added at the time of low rotation, and the fuel injection amount increases, the EGR amount is decreased or zeroed, and Japanese Patent Application No. 61-006962 has already proposed an EGR control method for an electronically controlled diesel engine that prevents the increase of smoke. However, in this method, since the EGR amount is reduced or set to zero when the fuel injection amount becomes equal to or more than the predetermined value, the value of the target fuel injection amount at the time of low engine speed is the variation of the fuel injection system, for example, in the fuel injection pump. Since it varies depending on manufacturing errors, etc., in diesel engines near the upper and lower limits of variation, even if the engine operating conditions are the same, EG
There was a problem that the amount of R reduction was different and an appropriate EGR amount could not be obtained.

[Object of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and the load of the engine driven device is applied to the fuel injection amount when the engine is in the idle state regardless of the variation of the engine and the variation of the fuel injection system. It is an object of the present invention to provide an exhaust gas recirculation control method for a diesel engine capable of reliably preventing an increase in smoke and white smoke by performing an exhaust gas recirculation in an optimum amount when the amount increases.

[Means for solving problems]

DISCLOSURE OF THE INVENTION The present invention is a diesel engine in which exhaust gas recirculation control is performed to recirculate exhaust gas even when the engine speed is low, with respect to an engine that controls fuel injection according to a fuel injection amount Qi obtained from an engine operating state. In the exhaust gas recirculation control method of _{No. 1} , when it is determined that the engine is in the idle state, the current learning value Qn _-1 is updated by updating the previous learning value Qn _-1 using the fuel injection amount Qi. And the injection amount ΔQ is obtained from the difference between the fuel injection amount Qi and the learning value Qn, and when it is determined that the engine is in the idle state, the exhaust gas amount is changed according to the injection amount ΔQ. The object is achieved by correcting the amount of recirculation.

[Action]

In the present invention, a diesel engine that performs exhaust gas recirculation control that recirculates exhaust gas even when the engine speed is low, with respect to an engine that controls fuel injection according to the fuel injection amount Qi obtained from the engine operating state In the exhaust gas recirculation control method of the engine, first, when it is determined that the engine is in the idle state, the previous learning value Q _n-1 is updated by using the fuel injection amount Q i, Learning value
In addition to obtaining Qn, the injection amount ΔQ is obtained from the difference between the fuel injection amount Qi and the learning value Qn. As described above, the injection amount ΔQ is a difference with respect to the learning value Qn, so that the influence of engine variations and fuel injection system variations is smaller. Further, in the present invention, when it is determined that the engine is in the idle state, the exhaust gas recirculation amount is corrected according to the injection amount ΔQ thus obtained. Therefore, regardless of variations in the engine and variations in the fuel injection system, if the load of the engine driven device is applied and the fuel injection amount increases when the engine is in the idle state, the exhaust gas recirculation is optimally performed. Done,
It is possible to reliably prevent the increase of smoke and white smoke.

【Example】

Hereinafter, an automatic dedicated electronically controlled diesel engine embodying the present invention will be described in detail with reference to the drawings. In this embodiment, as shown in FIG. 2, an intake air temperature sensor 12 is provided downstream of the air cleaner 11 for detecting the temperature of intake air. Downstream of the intake air temperature sensor 12, a turbocharger 14 including a turbine 14A rotated by the heat energy of exhaust gas and a compressor 14B rotated in conjunction with the turbine 14A is provided. The upstream side of the turbine 14A of the turbocharger 14 and the downstream side of the compressor 14B are communicated with each other through a waste gate valve 15 for preventing an excessive rise in intake pressure. The bench lily 16 on the downstream side of the compressor 14B has a main intake throttle valve that is configured to rotate in a non-linear manner in conjunction with an accelerator pedal 17 arranged in the driver's seat for limiting the flow rate of intake air during idling. Eighteen are equipped. The opening of the accelerator pedal 17 (hereinafter referred to as the accelerator opening) Accp is detected by an accelerator sensor 20. An auxiliary intake throttle valve 22 is provided in parallel with the main intake throttle valve 18, and the opening degree of the auxiliary intake throttle valve 22 is controlled by a diaphragm device 24. A negative pressure generated by a negative pressure pump (not shown) is supplied to the diaphragm device 24 via a negative pressure switching valve (hereinafter, referred to as VSV) 28 or 30. An intake pressure sensor 32 for detecting the pressure of intake air is provided downstream of the intake throttle valves 18 and 22. The cylinder head 10A of the diesel engine 10 has an injection nozzle 3 whose tip faces the engine combustion chamber 10B.
4, a glow plug 36 and an ignition timing sensor 38 are provided. Also, the cylinder block 10 of the diesel engine 10
C has a water temperature sensor 4 for detecting the engine cooling water temperature.
0 is provided. Fuel is injected from the injection pump 42 to the injection nozzle 34. The injection pump 42 has a diesel engine
A pump drive shaft 42A that is rotated in association with the rotation of the crankshaft 10 and a feed pump 42B fixed to the pump drive shaft 42A for pressurizing fuel (FIG. 2 shows a 90 ° expanded state). And a fuel pressure adjusting valve 42C for adjusting the fuel supply pressure and a rotational displacement of a pump drive shaft pulley 42D fixed to the pump drive shaft 42A to detect a crank angle reference position of the engine, for example, top dead center (TDC). A crank angle sensor 44 composed of, for example, an electromagnetic pickup, an adjusting resistor 45 for electrically adjusting the displacement of the mounting position of the crank angle sensor 44, and an engine speed fixed to the pump drive shaft 42A. Pulser (hereinafter referred to as NE pulser)
An engine speed sensor (hereinafter, referred to as NE sensor) 46, which is fixed to the roller ring 42H and includes, for example, an electromagnetic pick-up, for detecting the engine rotation angle, the tooth-missing position and the engine speed from the rotational displacement of 42E, and A roller ring 42H for reciprocating the face cam 42F and the plunger 42G and changing the timing thereof, and a timer piston 4 for changing the rotational position of the roller ring 42H.
2J (FIG. 2 shows a 90 ° deployed state) and a timing control valve (hereinafter referred to as TCV) 4 for controlling the injection timing by controlling the position of the timer piston 42J.
8 and an electromagnetic spill valve 49 for controlling the fuel injection amount by changing the fuel escape timing from the plunger 42G via the spill port 42K, and cutting the fuel when the engine is stopped or abnormal Fuel cut valve (hereinafter FC
(Referred to as V) 50 and a delivery valve 42L for preventing backflow of fuel and backward drip. The exhaust pipe 52 of the intake pipe 51 of the diesel engine 10 is connected by an exhaust gas recirculation (EGR) passage 53 that connects them. In the middle of the EGR passage 53, an EGR valve 54 for controlling the EGR amount is provided. The negative pressure applied to the diaphragm chamber of the EGR valve 54 is controlled by an electronically controlled negative pressure adjusting valve (hereinafter referred to as EVRV) 55. The EVRV55
Is controlled by an on-off duty signal,
When the control duty ratio Degr increases, the current value of the EVRV55 increases, the negative pressure in the diaphragm chamber of the EGR valve 54 increases, and the EGR amount increases. The intake air temperature sensor 12, the accelerator sensor 20, the intake pressure sensor 32, the ignition timing sensor 38, the water temperature sensor 40, the crank angle sensor 44, the adjusting resistor 45, the NE sensor 46, the key switch, the air conditioner switch, the neutral safety switch output,
The vehicle speed signal and the like are input to and processed by an electronic control unit (hereinafter referred to as ECU) 56, and the VSV 28, 30, TCV 48, electromagnetic spill valve 49, FCV 50, E are output according to the output of the ECU 56.
VRV55 and the like are controlled. The operation of the embodiment will be described below. In the present embodiment, the control of the fuel injection amount is performed by the engine speed NE detected from the output of the NE sensor 46 and the accelerator opening Accp detected from the output of the accelerator position sensor 20.
For example, the target value of the fuel injection amount is calculated according to the engine operating state and the energization time of the electromagnetic spill valve 49 is controlled. Similarly, the fuel injection timing is calculated by calculating the target injection timing from the accelerator opening Accp, the engine speed NE, etc.
By controlling 8, the target value is controlled. Further, the control of the EGR is executed according to the flow chart as shown in FIG. It should be noted that FIG. 9A is a routine for calculating the EGR amount, and FIG. 9B is a routine for calculating the injection amount ΔQ of the difference described later that corresponds to the change amount of the fuel injection amount Q. In the EGR calculation routine shown in FIG. 9A, first, at step 110, a normal EGR control duty ratio Degr is calculated from the engine speed NE and the fuel injection amount Q using a predetermined map. Next, at step 120, it is judged whether or not the engine is in the idle state, based on the state of the idle switch and the engine speed NE. If the determination result is negative, the process proceeds to step 160, and the control duty ratio Degr calculated in the preceding step 110 is output as the command value of this time. On the other hand, when the result of the determination at the above step 120 is positive and it is determined that the vehicle is in the idle state, the routine proceeds to step 130. In step 130, the control duty ratio Didle (for example, 30%) of the EGR dedicated during idle is calculated. Then, at step 140, the current fuel injection amount Q calculated by the fuel injection amount ΔQ calculation routine of FIG.
From the injection amount ΔQ which is the difference between the fuel injection amount and the learned value Qn of the fuel injection amount, for example, using the one-dimensional map as shown in FIG.
The correction amount Δegr of R is calculated. In this case, not only the relationship shown by the solid line in the figure but also the relationship shown by the broken line can be appropriately used. Next, at step 150, a value obtained by subtracting the correction amount ΔEGR from the control duty ratio Didle is put into the control duty ratio Degr as in the following equation (1). Degr ← Didle−ΔDegr (1) Then, in step 150, the control duty ratio Degr is output as the command value of this time, and the EGR amount is controlled. As a result of controlling the EGR amount as described above, the EGR amount decreases as the ejection amount Q increases, so that the optimum EGR amount can be obtained during idling. Next, a routine for calculating the difference injection amount ΔQ will be described based on FIG. 1 (B). The routine for calculating the difference injection amount ΔQ is started every predetermined time. When the engine is started, it is first determined in step 200 whether or not the fuel injection amount Q is in the idle operation state without change, and in step 210, the fuel injection amount does not change or remains small for a certain period of time. Determine whether or not. This determination can be performed by the routine shown in FIG. That is, in this routine, in step 202,
The absolute value of the difference between the previous fuel injection amount Q _i-1 and the current fuel injection amount Q _i is taken, and the difference is compared with a predetermined value. When the difference is equal to or more than the predetermined value, zero is inserted into the time T at step 204, When the value is equal to or less than the predetermined value, step 206 adds T + 1 to the time T and counts the time T to obtain the duration of the idle operation state in which the fuel injection amount does not change. Further, the above determination can also be made by whether or not the idle stable state in which the change in fuel injection amount is 1 mm ³ / str or less continues for 5 seconds or more. If the determination result of step 210 is positive, the process proceeds to step 220, where the current fuel injection amount Qi and the previous fuel injection amount learning value Q _n-1
Therefore, the current fuel injection amount learning value Qn is updated. This learning value Qn is updated by weighting, for example, the following formula (2)
Can be done as follows. Qn = (7Qn _-1 + Qi) / 8 (2) Next, at step 230, the updated fuel injection amount learning value Q
n is stored as the current learned value, and in step 240, the difference injection amount ΔQ is calculated and stored from the difference between the current fuel injection amount Qi and the learned value Qn as in the following equation (3). ΔQ = Qi−Qn (3) On the other hand, when the idle operation state in which the fuel injection amount does not change in the preceding step 210 does not continue for the predetermined time, the learning value Qn that is not updated and the current injection amount, The difference injection amount ΔQ is calculated using the equation (3), and this routine is ended. In steps 200 to 240, the learning value Qn of the injection amount is updated when the idle state in which the fuel injection amount does not change has elapsed for a certain time.However, the gear stage is in the neutral range and the air conditioner is The injection amount Q is learned while the switch is OFF, and the control duty comparison Degr is corrected not only for the power steering load but also for the fuel injection amount increase due to the increase in load due to the drive range and air conditioner switch ON. You can also do it. Further, in step 220, the learning value Qn is updated by weighting with the formula (2), but the formula and the procedure for updating the learning value are limited to using the formula (2). However, the learning value Qn can be updated by another formula or another procedure. In addition, when performing EGR control of the electronically controlled diesel engine according to the present invention, in which the well-known idle speed control is performed or the engine speed greatly changes due to idle up of the air conditioner, etc., a torque converter signal or an air conditioner signal is taken in. Using the easy signal, the air-conditioner is off in the neutral range, the air-conditioner is on in the neutral range, the air-conditioner is off in the drive range, and the air-conditioner is on in the drive range. If you have Qn, a more precise EG
R control can also be performed. In the above embodiment, the present invention was applied to an electronically controlled diesel engine for an automobile equipped with a turbocharger configured to control the fuel injection amount using the electromagnetic spill valve 49. The scope of application is not limited to this, and it is apparent that the same can be applied to a general electronically controlled diesel engine as well.

【The invention's effect】

As described above, according to the present invention, regardless of the variation of the engine and the variation of the fuel injection system, it is optimal when the load of the engine driven device is applied and the fuel injection amount is increased while the engine is in the idle state. EGR in quantity
Therefore, it is possible to reliably prevent an increase in smoke and white smoke, which is an excellent effect.

[Brief description of drawings]

1 (A) to 1 (C) are flow charts showing respective routines for calculating the EGR amount of an electronically controlled diesel engine for an automobile, in which the present invention is carried out, and FIG. 2 shows an overall configuration of the diesel engine. FIG. 3 is a sectional view including a partial block diagram, and FIG. 3 shows the difference injection amount used in the routine.
It is a diagram showing an example of a map of the relationship of the EGR correction amount. 10 …… Diesel engine, 20 …… Accelerator position sensor, 42 …… Fuel injection pump, 46 …… NE sensor, 53 …… EGR passage, 54 …… EGR valve, 55 …… Electronically controlled negative pressure regulating valve (EVRV) , 56 …… Electronic control unit (ECU), Degr …… EGR control duty ratio.

Front page continued (72) Inventor Koji Nomura 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Fumiaki Kobayashi 1, Toyota Town, Aichi Prefecture, Toyota Motor Co., Ltd. (56) Reference Reference: JP-A-62-165567 (JP, A), JP-A-61-41858 (JP, U)

Claims (1)

[Claims] 1. A diesel engine for performing exhaust gas recirculation control for recirculating exhaust gas even at low engine speed, for an engine that controls fuel injection according to a fuel injection amount Qi obtained from an engine operating state. In the engine exhaust gas recirculation control method, when it is determined that the engine is in the idle state,
By updating the previous learning value Q _n-1 using the fuel injection amount Qi, the current learning value Qn is obtained, and the injection amount Δ is calculated from the difference between the fuel injection amount Qi and the learning value Qn.
A method for controlling exhaust gas recirculation of a diesel engine, wherein Q is obtained, and when it is determined that the engine is in an idle state, the exhaust gas recirculation amount is corrected according to the injection amount ΔQ.