JPH031494B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control method for a diesel engine.

In diesel engines installed in automobiles, the fuel injection amount is controlled by air supply pressure. In this control, the injection amount is increased when the air supply pressure is high, and the injection amount is decreased when the air supply pressure is low. However, in a diesel engine equipped with a supercharger, if a waste gate valve, diaphragm, or the like that constitutes the supercharger breaks down, the air supply pressure may become abnormally high. As the charge air pressure increases in this way, the fuel injection amount increases, and as a result, the temperature of the engine's exhaust manifold, supercharger, etc. increases. If such a situation occurs, it may cause damage to the engine or supercharger.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional drawbacks, and to provide a fuel injection control method for a diesel engine that does not damage the engine and supercharger even when the intake pressure becomes high.

In order to achieve the above object, the present invention provides a fuel injection control method for electrically controlling the amount of fuel injection supplied to a diesel engine equipped with a supercharger. The basic injection amount is calculated based on the state, and the smaller of the basic injection amount and the preset maximum injection amount is set as the injection amount command value, and the intake pressure on the outlet side of the supercharger is equal to or higher than a predetermined value. The above-mentioned maximum injection amount is reduced when the temperature reaches a certain temperature. The principle of the present invention will be explained based on FIGS. 1 and 2.

Figure 1 shows engine speed N _E and accelerator opening.
This is a diagram showing the relationship between ACCP, and the injection amount that provides the optimal accelerator opening for N _E is the basic injection amount.
Q _BASE . As shown in Figure 2, this basic injection amount Q _BASE is calculated as follows:
It has the characteristic of decreasing as N _E increases. In Figure 2, the characteristics are during normal supercharging (=Q _FULL ×
K ₂ (where K ₂ is a correction coefficient), the characteristic is the standard state (Q _FULL meaning no supercharging), and the characteristic is the abnormal supercharging (=Q _FULL × K ₂ ). If the boost pressure at the turbocharger exit side is normal,
By adding correction to Q _FULL shown in the characteristics, (Q _FULL
×K ₂ ), and this is set as the maximum value Q′ _FULL of the fuel injection amount to be currently controlled. This corresponds to the characteristic in FIG. Also, Q _BASE > Q′ _FULL
In a state showing the relationship _Q'FULL , the fuel injection amount is controlled using Q'FULL, and further, in a state showing the relationship _QBASE <_Q'FULL , the fuel injection amount is controlled using _QBASE . That is, the maximum injection amount is controlled according to the supercharging state of the supercharger. Correction coefficient used for the above correction
Figure 3 shows the characteristics of K ₂ .

As described above, the present invention reduces the fuel injection amount when the intake pressure (supercharging pressure) becomes abnormally high, and there are the following three methods for controlling this reduction.

(i) When the inspiratory pressure exceeds a certain value
Decrease the correction factor K ₂ of Q _FULL . This reduction may be done by control logic or by following the characteristics shown in FIG. This correction factor K ₂
According to the control method that reduces the maximum injection amount Q′ _FULL
has the characteristics shown in FIG.

(ii) Reduce the calculated maximum accelerator opening during abnormal supercharging. For example, the actual accelerator opening is 80%
Even if it is, in the case of abnormal supercharging, the accelerator opening is set to 60% and the fuel is injected.

(iii) Decrease the fuel injection amount by a certain amount at the time of abnormal supercharging.

FIG. 5 is a flowchart showing an example of processing by a computer for the control method (i) among the aforementioned control methods.

At step 101, the rotational speed N _E , intake pressure P _M , and accelerator opening degree ACCP are taken in. Intake pressure P _M
Based on Fig. 4, the correction coefficient K ₂ is calculated in step 1.
Calculate with 02. It is compared whether the intake pressure P _M exceeds a comparison reference value (for example, an absolute value of 1300 mmHg). This comparison reference value means the boundary of abnormal supercharging. Intake pressure P _M is 1300mmHg
(ABS: absolute value), it is determined in steps 104 and 105 whether or not this state continues for a certain period of time. This is because performing injection control in response to instantaneous abnormalities impairs safety.
First, the number of abnormal conditions is counted in step 104, and it is determined in step 105 whether or not the set number of times (20 times in this embodiment) has been reached. (T)
is established in step 106 and at the same time in step 1
For example, in 07, the correction coefficient K′ ₂ (previously executed value) is
It is decreased at a rate of 0.01 to obtain a new correction coefficient value, and at step 108, abnormal supercharging is notified to the driver (by lighting a lamp, etc.). On the other hand, the intake pressure
If P _M is less than the set value (1300 mmHg), the count value C is cleared in step 109, and it is determined in step 110 whether FLAG (T) is established. This determination is to check whether abnormal supercharging occurred during the previous calculation. If FLAG(T) exists, the correction coefficient calculated in step 102
K ₂ and the actual value K' ₂ are compared in step 111.
If K' ₂ > K _{' 2} (the same applies even if the flag is not established in step 110), the calculation result of step 102 is used as the current correction coefficient value, and if K _{' 2} >K' ₂ , the injection amount is too small. Then, in step 113, the correction coefficient K' ₂ (the previously executed value) is increased by, for example, 0.01. Above steps 105, 108,
Each output of 110, 112 and 113 is the coefficient value calculated or corrected in step 114.
K′ ₂ is memorized. Furthermore, in step 115, a basic injection amount Q _BASE as shown in FIG. 2 is calculated based on the rotational speed N _E and the accelerator opening degree ACCP.
Further, in step 116, the corrected maximum allowable injection quantity Q' _FULL is calculated as (theoretical maximum injection quantity Q _FULL ×K' ₂ ). This calculated corrected maximum injection amount Q′ _FULL
is Q _BASE calculated in step 115 and step 1
17 to be compared. That is, if Q _BASE >Q' _FULL , the final injection amount Q _FIN is set in step 118.
If Q' _FULL is selected and Q' _BASE is selected, Q _BASE is selected as Q _FIN in step 119, and each selected output is converted to a spill command value in step 120 to drive the spill ring in the fuel injection pump. and controls the fuel injection amount.

FIG. 6 shows an example of a device that executes the above processing.

The fuel injection pump 1 includes a drive shaft 11 driven by an engine, a gear 12 and a roller 13 provided at the end of the drive shaft,
A cam plate 1 loosely connected to the roller 13
4. Pump plunger 15 coupled to the plate 14 for delivering fuel to the injection nozzle 2 of the engine, fuel pump 17 for delivering fuel to the injection nozzle 2 and timer piston 16, and timer piston 16; A timer position sensor 18 that electrically detects, a timing control valve 19 that determines advance angle adjustment, an electromagnetic pickup sensor 20 that outputs a pulse signal according to the rotation speed of the gear 12, and a drive unit that reciprocates the pump plunger 15. a spill ring 21, a linear solenoid 22 that drives the spill ring 21,
A coil 23 constituting the linear solenoid 22, a plunger 24 that drives the spill ring 21, a spill position sensor 25 that detects the amount of movement of the plunger 24, and a fuel control valve (FCV) that controls the amount of fuel to the pump plunger 15. )26
(consisting of excitation coil 27 and valve 26A),
It consists of a delivery valve 28 and a regulating valve 29 that distribute fuel from the pump plunger 15 to a plurality of injection nozzles.

The cam plate 14 rotates and reciprocates together with the pump plunger 15. This reciprocating motion is caused by the cam plate 14 riding on the roller 13, which is rotatable but fixed in the axial direction of the shaft 1. Injection timing is given by rotation of the pump plunger 15. Regarding the regulation of the injection quantity, the maximum injection quantity is determined by the effective stroke of the pump plunger 15, and the partial load adjusts the fuel supply to the pump plunger 15 by moving the plunger 24. The residual fuel within the pump is returned to the pump inlet via orifice 30.

On the other hand, on the engine side, a supercharger 200 that is involved in intake and exhaust is connected to an intake manifold 4 and an exhaust manifold 300. Supercharger 2
On the exhaust side of 00, an intake manifold 4 and an exhaust manifold 3 are connected via a waste gate valve 400.
00 is in communication. As is well known, a supercharger consists of a turbine and a compressor.The turbine recovers the thermal energy contained in the exhaust gas, and the compressor sends the compressed air to the combustion chamber to improve engine power. It is something to do.

The control device 3 controls the linear solenoid 22 and FCV 26 that are involved in controlling the amount of fuel.
For this purpose, output signals from various sensors are captured. That is, the engine speed signal N _E from the electromagnetic pickup sensor 20, the output signal S _S from the spill position sensor 25, and engine side information (the timer position sensor 18 is used for timing control and is not related to the present invention). Therefore, the explanation is omitted). The engine side information is the output signal Sa of the intake temperature sensor 5 provided in the intake manifold 4,
The output signal P _{M of} the intake pressure sensor 6 provided at The parts according to the invention are the intake pressure sensor 6 and the accelerator sensor 9, and the others are used for calculations such as air-fuel ratio control. Here, control device 3 is FCV26
This figure is shown to show that other controls are also handled in addition to the control of .

FIG. 7 is a detailed block diagram of the control device 3 shown in FIG. 6, and shows an example in which a microcomputer is used as the control device 3.

A read-only memory (ROM) 3 stores processing programs and monitor programs for executing various processes in addition to the processes shown in FIG. 5, with a central processing unit (CPU) 31 as the core.
2. Random access with backup memory that temporarily stores calculation contents ( _K'2 value of step 114, etc.) and output contents of each sensor, and continues to store calculation contents, set values, etc. even when the power is turned off. - A memory (RAM) 33 and an input/output circuit 34 are connected to the CPU 31 via a bus line 36, forming a so-called microcomputer. The output devices connected to and controlled by the CPU 31 include the lamp 10 that is turned on in the process of step 108 shown in FIG. 4 during abnormal supercharging, the linear solenoid 22, and the fuel injection amount.
The lamp 10 and FCV 22 are driven through drive circuits 37 and 38, and the linear solenoid 22 is driven through a D/A converter 39, a servo amplifier 40, and a drive circuit 41. . The input/output circuit 34 is for receiving sensor output, and is for receiving sensor output from each sensor 5, 6, 7, 9,
25 outputs (buffers 42, 43, 44, 45,
A multiplexer (MPX) 47 sequentially or selectively selects one of the signals (taken out via the A/D converter 46) and outputs the data to the bus line 36 after converting it into a digital signal using an A/D converter 48. Further, the rotation speed detector (electromagnetic pickup sensor) 20 for detecting the engine rotation speed N _E has its output signal waveform shaped by a waveform shaping circuit 49 and then sends it to the CPU 31 . Furthermore, a clock circuit 35 is provided for sending clock pulses to each of the CPU 31, input/output device 34, A/D converter 48, and A/D converter 39. Based on the above sensor outputs, the control device 3 executes the process according to the flowchart in FIG.
ultimately control. The execution of FIG. 5 is carried out periodically or irregularly such as when an interrupt occurs, but after the processing of step 120 is completed, the process may return to the first step, but normally, when using a microcomputer etc. Since it is possible to execute a plurality of processes, it is possible to process not only fuel injection control but also air-fuel ratio control, advance angle control, air conditioning control, etc. FIG. 8 is an explanatory diagram showing the control according to the present invention using waveform changes. This figure shows changes in the intake pressure, injection amount, and correction coefficient _K2 during the process in which the accelerator opening is accelerated from an idling state and reaches 100%. As the accelerator opening increases, the intake pressure P _M increases. At this time, the injection amount changes as a value multiplied by the coefficient K ₂ and shows an increasing tendency. Intake pressure
When _PM reaches the set value (1300 mmHg), abnormal supercharging is detected via the intake pressure sensor 6. Therefore, it is determined whether this abnormal supercharging state has continued for a certain period of time (an example of 2 seconds in Figure 8), and if it continues as shown in the figure, the correction coefficient K ₂ is decreased (the control device in Figure 6 3) to reduce the fuel injection amount and lower the intake pressure P _M.

This control prevents turbocharger variations and failures (wastegate valve, diaphragm failure, etc.)
Even if there is a problem, the supercharging pressure is always kept below a certain set value, and the exhaust manifold is prevented from becoming abnormally hot in the supercharger or the turbocharger's turbine rotation is abnormally increased.

As explained above, according to the present invention, the maximum injection amount is controlled according to the supercharging state of the supercharger, so even if the supercharger fails, an abnormal increase in intake pressure can be suppressed, and the engine and damage to the supercharger can be prevented.

Although only one of the three control methods has been illustrated as an embodiment of the present invention, other processes can be easily implemented by creating a suitable control program and applying it to a computer.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram of accelerator opening with respect to engine rotational speed, Figure 2 is a characteristic diagram of fuel injection amount with respect to engine rotational speed, Figure 3 is a characteristic diagram of correction coefficient with respect to boost pressure, and Figure 4 is for calculating the correction coefficient. FIG. 5 is a processing flowchart of the present invention, FIG. 6 is a configuration diagram showing a fuel injection pump and control device suitable for applying the present invention, and FIG. FIG. 8 is a detailed block diagram of control, and is a control waveform diagram of each part in an embodiment of the present invention. 1...Fuel injection pump, 3...Control device, 6...
...Intake pressure sensor, 9...Accelerator sensor, 10...
... Lamp, 15 ... Plunger, 20 ... Electromagnetic pick-up sensor, 21 ... Spill ring, 2
2... Linear solenoid, 26... Fuel control valve (FVC), 27... Excitation coil, 28... Valve,
31... Central processing unit (CPU), 32... Read on memory (ROM), 33... Random access memory (RAM), 34... Input/output circuit, 36... Bus line, 37, 38 ,41
...Drive circuit, 39...A/D converter, 40...
Servo amplifier, 42-46, 50, 52...Buffer, 47...Multiplexer, 48...A/D
Converter, 49...Waveform shaping circuit.

Claims (1)

[Scope of Claims] 1. In a fuel injection control method for electrically controlling the amount of fuel injection supplied to a diesel engine equipped with a supercharger, the basic method is based on the engine state including the engine rotation speed and the accelerator opening. The injection amount is calculated, and the smaller of the basic injection amount and the preset maximum injection amount is set as the injection amount command value, and when the intake pressure on the outlet side of the supercharger exceeds a predetermined value, the maximum A fuel injection control method for a diesel engine, characterized by reducing the injection amount. 2. The fuel injection control method for a diesel engine according to claim 1, wherein the control to reduce the maximum injection amount is performed by decreasing a correction coefficient for the maximum injection amount in accordance with the intake pressure. 3. The fuel injection control method for a diesel engine according to claim 1, wherein the control to reduce the maximum injection amount is performed by decreasing a calculated maximum accelerator opening. 4. The fuel injection control method for a diesel engine according to claim 1, wherein the control to reduce the maximum injection amount is performed by reducing the injection amount by a predetermined constant amount.