JPS59185838A - Fuel injection control for diesel engine - Google Patents

Abstract

PURPOSE:To improve the output performance by correcting the fuel injection amount and injection timing only for a prescribed time when the load is high, in the method for controlling the fuel injection amount and fuel injection timing of a Diesel engine. CONSTITUTION:In Step 1, it is judged whether engine operation state is in high load state or not in accordance with the intake pressure or the opening degree of a throttle. The fuel injection amount and the fuel injection timing are corrected for a prescribed time in Step 3, if the load is high. Thus, the output performance can be improved without deteriorating the fuel consumption performance and the reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control method for a diesel engine, and in particular, a fuel injection control method suitable for use in an automobile diesel engine equipped with an electronically controlled fuel injection pump. This invention relates to an improvement in a fuel injection control method for a diesel engine that controls the injection amount and fuel injection timing.

Generally, in a diesel engine, the fuel supplied to the combustion chamber is controlled by a fuel injection pump that is driven to rotate in synchronization with engine rotation, and a feed pump installed in the fuel injection pump The fuel injection timing is controlled by moving the timer piston and the roller ring at the supply pressure of I have to. However, in the past, both the timer and spill ring were mechanically controlled, making it difficult to perform precise fuel injection control.

On the other hand, in recent years, with the development of electronic control technology, particularly digital control technology, technology for electronically controlling fuel injection pumps and electronically controlling fuel injection in diesel engines has been put into practical use. When such an electronically controlled fuel injection pump is used, the fuel injection amount and fuel injection timing can be accurately controlled depending on the engine operating state.

However, in the past, even in transient states such as during acceleration,
Since the fuel injection control was performed in the same way as in the steady state, there were cases where appropriate fuel injection amount and fuel injection timing could not be obtained depending on the engine operating state.

That is, in general, in a diesel engine, especially in a turbocharged diesel engine, its maximum torque (output at full load) is at the smoke limit at low and medium speeds, and at the exhaust gas temperature and combustion chamber at high speeds. The fuel injection amount Q and the fuel injection timing T are determined by taking these into consideration. In other words, in order to keep the smoke constant at low and medium speeds, by increasing the fuel injection IQ and retarding the fuel injection timing T than the normal setting value, more torque can be produced, but fuel efficiency will deteriorate. I end up. Also, during high-speed rotation, the fuel injection amount Q is increased and the fuel injection timing T is
If the engine is advanced, torque can still be produced, but the combustion chamber temperature and exhaust gas temperature will rise, which poses problems in terms of component reliability.

Therefore, in the past, a single fuel injection amount and fuel injection timing were set so that no problems would occur at either low or medium speeds or high speeds, making it difficult to further improve output. It had some problems.

The present invention was made in order to solve the above-mentioned conventional problems, and in a transient state such as during acceleration, it is possible to obtain a larger torque than the normal setting, and to obtain good transient performance. An object of the present invention is to provide a fuel injection control method for a diesel engine that has almost no effect on the reliability of a diesel engine.

The present invention provides a fuel injection control method for a diesel engine in which the fuel injection amount and fuel injection timing are controlled according to the engine operating condition, as shown in FIG. The above objective is achieved by including the following steps: a procedure for determining whether the engine is in a high load state, and a procedure for correcting the fuel injection amount and fuel injection timing for a while when the engine is in a high load state.

Further, when the high load state occurs, the amount of fuel injection and the amount of correction of the fuel injection timing are changed according to the immediately preceding engine operating state and the engine rotational speed during the high load state, thereby achieving more appropriate fuel injection. The fuel injection amount and fuel injection timing can be obtained.

According to the present invention, when the engine is in a high load state such as during acceleration, the fuel injection amount and fuel injection aJv are maintained for a while.
Since the f period is corrected and the engine torque is improved,
Good transient performance can be obtained. In addition, if we consider transient times, such as during acceleration and for a short period of time after acceleration, it is a good idea to improve output performance even if it means sacrificing fuel efficiency slightly, and the combustion chamber temperature and exhaust gas temperature also decrease. , will not cause any major problems.

Hereinafter, with reference to the drawings, the implementation of an automobile tasel engine with a turbocharger equipped with an electronically controlled fuel injection pump, in which the present invention (this fuel injection control method for a diesel engine is strongly adopted) will be described in detail. Zuru.

In this embodiment, as shown in FIG. 2, an external force 1 is applied to the diesel engine 10. (An air cleaner 12 for taking in the exhausted air, an intake air temperature sensor 14 installed in the air cleaner 12 for detecting the temperature of the intake air, and an intake air temperature sensor 14 installed in the middle of the intake pipe 16) A turbocharger 18 having a compressor 18A for compressing intake air using the energy of one air scum, and a compressor 18 of the turbocharger 18.
An intake throttle valve 22 which is configured to rotate in response to the accelerator pedal disposed on the driver's seat and which limits the flow of intake air compressed by A, and the accelerator pedal 20. Accelerator sensor 24 for detecting opening degree
, an intake pressure sensor 28 that detects the pressure of intake air in the intake pipe 161/i downstream of the intake throttle valve 22, and a drive shaft 34 that rotates in conjunction with the rotation of the crankshaft of the diesel engine 10. , a feed pump 36 for pumping fuel, which is fixed to the drive shaft 34, is 90 in FIG.
(shown in the unfolded state), a fuel pressure adjustment valve 38 for adjusting the fuel supply pressure, and a cap 40 fixed to the drive shaft 34.
An engine rotation sensor 42 consisting of, for example, an electromagnetic pickup for detecting the diesel engine 100 rotation state from the rotational displacement of the engine, a roller ring 44 for controlling fuel injection timing, and a timer piston for driving the roller ring 44. 46 (FIG. 2 shows a 90° expanded state), a timing control valve 48 for controlling the position of the timer piston 4G, and a variable intufftance sensor, for example, for detecting the position of the timer screw (46). a timer position sensor 50 consisting of a spill ring 52 for controlling the fuel injection lid 11; a spill actuator 54 consisting of a plunger 54A, a compression spring 54B, a coil 54G and a coil case 540 for driving the spill ring 52; A spill position sensor 56 consisting of, for example, a variable inductance sensor for detecting the position of the spill ring 52 from the displacement of the plunger 54A, a fuel cut solenoid (hereinafter referred to as FCV) 58 for cutting fuel when the engine is stopped, and a pump. Fuel injection pump 3 having plunger 60 and delivery valve 62
2 and.

The diesel engine 10 burns the fuel discharged from the delivery valve 62 of the fuel injection pump 32! , 10A; a water temperature sensor 72 disposed in the cylinder block 10B of the diesel engine 10 for detecting engine cooling water; and a water temperature sensor 72 disposed in the middle of the exhaust pipe 74. Additionally, a turbine 18B of the turbocharger 18 for rotating the compressor 18Δ by thermal energy of exhaust gas, and an exhaust bypass passage 76 that bypasses the turbine 18B.
and ' an exhaust bypass valve 78 that opens the exhaust bypass passage 76 when the intake air pressure at the outlet side of the compressor 18A of the turbocharger 18 exceeds a predetermined value to prevent excessive supercharging. The target injection timing and target injection amount are determined based on the accelerator opening degree detected from the output of the accelerator sensor 24, the engine rotation speed detected from the output of the engine rotation sensor 42, the engine cooling water temperature detected from the output of the water temperature sensor 72', etc. is determined, and the timing control valve 48, spill actuator 54, etc. are controlled so that the target injection amount of fuel is injected from the fuel injection pump 32 at the target injection timing.
An electronic control unit (hereinafter referred to as ECU) 80,
It consists of

In the figure, 82 is a glow plug.

As shown in detail in FIG. 3, the ECLJ 80 includes: a central processing unit (hereinafter referred to as CPU) 80A consisting of, for example, a microprocessor for performing various arithmetic operations; a clock circuit 1880B generating various clock signals; A random access memory (hereinafter referred to as RA IVI) 80C, which includes a backup random access memory for temporarily storing calculation data, etc. in the CPU 80A, and a backup random access memory for backup in the event of a power failure, and a lead for storing control programs, various data, etc. Only memory (hereinafter referred to as ROtvl) 80D and the water temperature sensor 72 input via a buffer 80E
Output, the intake air temperature sensor 14 output input via buffer 80F, the intake pressure sensor 28 output input via buffer 80G, the accelerator sensor 24 output input via buffer 80H, sensor drive circuit 80
The output of the Subill position sensor 56 is driven by a sensor drive frequency signal of one output and inputted via the sensor signal detection circuit 80J, and is also driven by the sensor drive frequency signal output to the sensor drive circuit 80 to detect the sensor signal. A multiplexer 80 for sequentially taking in the output of the timer position sensor 50, etc. input via the circuit 80L.
M, an analog-to-digital converter (hereinafter referred to as A,-'D converter) 8ON for converting the analog signal output from the multiplexer 80M into a digital signal, and an output from the A/D converter 8ON to the CPU 80A. an input/output boat 800 for inputting the output to the CPU 80A; a waveform shaping circuit 80P for waveform shaping the output of the engine rotation sensor 42 and inputting it directly to the CPU 80A; A drive circuit 80Q for driving the FCV 58, a drive circuit 80R for driving the FCV 58 according to the calculation result in the CPU 80A-, and a digital-to-analog converter (hereinafter referred to as D, /'A converter) 808. a servo amplifier 80T and a drive circuit 80U for driving the spill actuator 54 according to the deviation between the output of the CPU 80A and the output of the spill position sensor 56 converted into an analog signal by It consists of a common lotus 80V to be connected, and.

The action will be explained below.

Calculation of the fuel injection amount and fuel injection timing in this embodiment is performed according to a flowchart as shown in FIG. That is, first in step 110, the intake pressure, engine rotation speed,
A basic injection amount Qo and basic injection timing TO suitable for a steady state are determined according to engine operating conditions such as intake air temperature and engine cooling water temperature.

Next, the process proceeds to step 112, in which it is determined whether or not the engine operating state is in a high load state, depending on, for example, the intake pressure or the throttle opening. If the determination result is negative, the process proceeds to step 114, where the basic injection amount Qo and the basic injection timing To obtained in step 110 are changed to the fuel injection pattern Q.
, fuel injection timing T.

On the other hand, if the determination result in step 112 is positive,
That is, when it is determined that it is necessary to correct the basic injection amount Qo and the basic injection timing To, step 11 is performed.
Proceeding to step 6, it is determined whether the engine rotational speed of the poem is in a low rotational speed state. If the judgment result is positive,
Proceeding to step 118, as shown in the following equation, the integrated value a, which has been added or subtracted depending on the engine operating state before entering the high-load operating state, is multiplied by 1 by a relatively large coefficient suitable for low-speed rotation. By doing so, the correction amount ΔQ of the fuel injection amount is determined.

△Q (-K 1X a... (1) Then, the process proceeds to step 120, where the integration f!+ is added or subtracted depending on the engine operating state, as shown in the following equation.
By multiplying 1 by 2, which is a negative coefficient suitable for low-speed rotation, the fuel injection timing correction amount ΔT is determined.

△T←K 2 X b・・・・・・・・・(2) On the other hand,
If the determination result in step 116 is negative, the process proceeds to step 122, where it is determined whether the engine rotational speed at that time is in a high rotational state. If the determination result is positive, the process proceeds to step 124, where 3 is added to the fi calculation value a to a coefficient of a size suitable for high-speed rotation, as shown in the following equation.
The correction amount ΔQ is determined by multiplying by .

△Q + K 3 By doing so, the correction amount T is determined.

(4Xl at ΔT'-) (4) On the other hand, if the determination result in step 122 is negative, that is, it is determined that the engine rotation speed at that time is in a medium speed rotation state. If so, proceed to step 128, and as shown in the following equation,
Since the integrated value a has a size suitable for medium speed rotation, 5 is added to the integrated value a.
The correction amount ΔQ is determined by multiplying by .

△Q (-K 5 By multiplying a negative coefficient with a smaller absolute value by 6, the correction amount Δt is determined.

△T=6xb・・・・・・・・・6) Step 12
After 0.126 or 130 hiragi, proceed to step 132,
As shown in the following equation, the fuel injection itQ is determined by adding the correction amount ΔQ to the basic injection amount Qo determined in step 110.

Q←Qo×ΔQ・・・・・・・・・＜7) Then, the process proceeds to step 134, and in the same way, as shown in the following equation, by adding the correction amount Δt to the basic injection timing To, the fuel injection is performed. Find the period T.

T←DT△T・・・・・・・・・(8) Step 11
4 or 134, the routine proceeds to step 136, where the determined fuel injection amount Q and fuel injection timing T are output, and this routine ends.

Here, the reason why the correction coefficient is changed according to the engine rotation speed at high load is because, for example, at low speed rotation, the fuel injection amount Q
It is better to increase the fuel injection timing T and retard the fuel injection timing T. At medium speed rotation, the fuel injection amount Q should be similarly increased, and the l, jj: fuel injection timing T should be delayed by a smaller amount than in the low speed range. This is because the optimal correction amount differs in each rotation range, such as increasing the fuel injection amount Q and slightly advancing the fuel injection timing T at high speeds. .

Note that steps 118, 12. of the routine shown in FIG.
The calculation of the integrated values a and b used in 0, 124, 126, 128, 130 is executed by an interrupt routine every predetermined time or every predetermined crank rotation as shown in FIG.

That is, step 210 is entered every predetermined period of time or every predetermined crank rotation, and for example, when the engine rotation speed is 200 Qr.
Since it is below pm and below ffi 14 injection 1 fin Q 15IIn+3/str, it is determined whether the engine operating state is a low load low speed rotation state. If the determination result is positive, the process proceeds to step 212, where the sum of the sum 1[a plus a predetermined value, for example 3, is set as a new sum a, as shown in the following equation.

a←a+3 (9) Next, the process proceeds to step 214, and as shown in the following equation, a predetermined value, for example 8, is added to the integration '@b as a new integration value 1. Zuru.

b + - b + 8 rivers (10) Here, the reason why comparatively large values are added to the integrated values a and 1) during low load and low speed rotation is that After a long period of rotation, Me! This is because, since the first fuel temperature and the exhaust gas temperature are lowered, when the load becomes high thereafter, the amount of correction of the fuel injection amount and the fuel injection timing can be increased.

On the other hand, if the determination result in step 210 is negative, the process proceeds to step 216, where, for example, the engine rotation speed is 300 Ort) m or more and the fuel injection a'l ii
Q is 30 mm3. / str or more, it is determined whether or not the engine operating state is a high-load, high-speed rotation state. If the determination result is positive, step 218
Then, as shown in the following equation, a value obtained by subtracting a predetermined value, for example 4, from the integrated value a is set as a new integrated value.

a←a-4... (11) Then, the process proceeds to step 220, and as shown in the linear equation, the slope obtained by subtracting a predetermined value, for example 1o, from the integrated value l] is calculated as a new integrated value. The value is 1.

b←b-10・・・・・・・・・(12) Here, the reason why both integrated values a and 1] are reduced quickly during high-load high-speed rotation is that The poem was
This is because unless the correction amount is quickly reduced, problems may arise with fuel efficiency, combustion seedling temperature, and exhaust gas temperature.

On the other hand, if the judgment result in step 216 is negative, the process proceeds to step 222, where a predetermined value, for example 1, is subtracted from the navigational cumulative value a, and the resulting value is used as a new cumulative value a, as shown in the following equation. shall be.

a+-a-1...13) Next, the process proceeds to step 224, where a predetermined value, for example 2, is subtracted from the integrated value as a new integrated value, as shown in the following equation. shall be.

b←l+-2・・・・・・・・・(14n) Here, when neither the low-load, low-speed rotation state nor the high-load, high-speed rotation state, the integrated values a and l are both gradually decreased. The reason for this is to gradually reduce the amount of correction so that the negative effects do not remain for a long time.

Step 214. After completing 220 or 224, step 2
In step 26, it is determined whether the integrated values a and b are both within a preset tolerance range.

If the determination result is positive, the obtained integrated values a and b are used as they are to calculate the correction amount for the fuel injection amount and fuel injection timing. On the other hand, if the determination result in step 226 is negative, the process proceeds to step 228, and the integrated value a, 1) is limited to a value within an allowable range.

In this embodiment, the amount of fuel injection and the correction amount of fuel injection timing when the load is high are changed according to the previous engine operating state and the engine rotation speed during the high load, so that The appropriate fuel injection amount and fuel injection timing are corrected. Note that the method of determining the correction amount of fuel injection amount and fuel injection timing when a high load condition occurs is not limited to this, and for example, the method of determining the correction amount of fuel injection amount and fuel injection timing when a high load condition is reached is not limited to this. It is also possible to perform control more precisely by dividing the process into smaller steps.

In the above embodiments, the present invention was applied to an automobile diesel engine equipped with a turbocharger, but the scope of application of the present invention is not limited thereto, and is applicable to an automobile diesel engine equipped with a normal intake system. It is clear that the present invention can be similarly applied to diesel engines and general diesel engines.

As explained above, according to the present invention, it is possible to improve output performance in a transient state such as during acceleration without significantly impairing fuel efficiency, reliability of parts, etc., and therefore, it is possible to obtain good drivability. It has the excellent effect of being able to

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the diesel engine fuel injection control method according to the present invention, and FIG. 2 is a turbocharged automobile diesel engine equipped with an electronically controlled fuel injection pump to which the present invention is adopted. FIG. 3 is a block diagram showing the configuration of the electronic control unit used in the embodiment, and FIG. FIG. 5 is a flowchart showing a routine for calculating the injection timing and fuel injection timing. Similarly, FIG. 3 is a flowchart showing an interrupt routine for every crank cycle or every predetermined crank cycle. DESCRIPTION OF SYMBOLS 10... Diesel engine, 28... Intake pressure sensor, 32... Fuel injection pump, 70... Injection nozzle, 48... Timing control valve, 54...-Spill actuator, 80... Electronic Control unit (ECLI). Agent Takaya Ron (1 idiot)

Claims (2)

[Claims] (1) In a diesel engine fuel injection control method in which the fuel injection amount and fuel injection timing are controlled according to the engine operating state, a procedure for determining whether the engine is in a high load state; A fuel injection control method for a diesel engine, comprising: correcting the fuel injection amount and fuel injection timing for a while when the engine is in a high load state. (2) The correction amount of the fuel injection amount and the fuel injection timing when the high load state is reached is changed according to the immediately preceding engine operating state and the engine rotation speed during the high load state. The fuel injection control method for a diesel engine according to item 1.