JPH0252112B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection control method for an electronically controlled diesel engine, and particularly to a fuel injection control method for optimally controlling fuel injection when moving to deceleration driving. Regarding.

[Prior art] and [Problem to be solved by the invention] Conventionally, the fuel injection amount Q of diesel engines has been
is determined from the engine rotational speed N _E and the accelerator opening degree Accp, as shown in FIG. The V-shaped portion on the envelope in the figure is provided for compensation when the engine is started in a cold state.

Now, in Figure 1, for example, when the accelerator opening is 60% and the engine speed is 4000 rpm, if the accelerator opening is suddenly reduced to 0%, the injection amount Q suddenly drops to 0. becomes. If such a sudden change in the injection amount occurs while the vehicle is running, the vehicle will experience a strong deceleration shock. Such deceleration shocks occur when the accelerator is turned off when transitioning from acceleration to deceleration or from steady driving to deceleration in manual transmission vehicles, and pose problems in terms of drivability and ride comfort. .

The purpose of the present invention is to accelerate from high to medium speed driving.
It is an object of the present invention to provide a fuel injection control method for an electronic diesel engine that alleviates the deceleration shock when the engine is turned off and eliminates the above-mentioned conventional drawbacks.

[Means to solve the problem]

In this invention, there is provided a fuel injection control method for a diesel engine in which fuel is supplied to the diesel engine from a fuel injection pump controlled by an electronic control device through an injection nozzle, based on the operating state of the diesel engine. The fuel injection amount is calculated at a predetermined period, and the current calculated injection amount Q _I is compared with a predetermined set value Q _A. If Q _I > Q _A , Q _I is changed to the current final injection amount. If the command value Q _FIN has changed to Q _I ≦ Q _A and is not accelerating, then the value obtained by subtracting a constant amount α from the previous calculated injection amount Q _I-1 with Q _A as the initial value ( Q _I-1 − α) and Q _I , and if Q _I > (Q _I-1 − α), Q _I is set as the current final injection amount command value Q _FIN , and the previous calculated injection amount is Set as Q _I-1 , Q _I
In the case of ≦(Q _I-1 − α), (Q _I-1 − α) is set as the current final injection amount command value Q _FIN and the previously calculated injection amount Q _I-1 .

[Effect]

In this invention, two-stage control is executed. In other words, when stopping fuel injection and applying engine braking on a vehicle that is driving at medium or high speeds, the fuel injection amount will quickly decrease to the set value Q _A to ensure deceleration by engine braking, and from then on it will reduce to the target value. The fuel injection command value was gradually decreased by -α until reaching (the current fuel injection command value).

As a result, the engine brake is quickly applied, and the engine stops smoothly (or shifts to an idling state) immediately before stopping.

〔Example〕

FIG. 2 shows a fuel injection pump and a control device suitable for applying the present invention.

A fuel injection pump 1 includes a drive shaft 11 driven by an engine, a gear 12 provided at an end of the drive shaft 11, and a roller 1.
3. A cam plate 14 loosely connected to the roller 13, a pump plunger 15 connected to the cam plate 14 for sending fuel to the injection nozzle 2 of the engine, a pump/plunger 15 for sending fuel to the injection nozzle 2 of the engine, and a timer. A fuel pump 17 that sends fuel to the piston 16, a timer position sensor 18 that electrically detects the position of the timer piston 16, a timing control valve 19 that determines advance angle adjustment, and an electromagnetic pickup sensor that outputs a pulse signal according to the rotational speed of the gear 12. 20, a spill ring 21 that is driven by a linear solenoid 22 to adjust the injection amount;
A linear solenoid 22 that drives the spill ring 21, a coil 23 that constitutes 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 pump plunger 15. FCV that controls on/off the fuel amount of
26 (consisting of excitation coil 27 and valve 28), delivery valve 56 for preventing backflow and dripping of fuel from pump plunger 15
and a regulating valve 29.

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 drive shaft 11. pump·
The fuel is distributed by rotating the plunger 15. Regarding the adjustment of the injection quantity, the maximum injection quantity is determined by the effective stroke of the pump plunger 15. Excess fuel in the pump is returned to the pump 17 via the orifice 30. Further, the linear solenoid 22 and FCV 26 in the fuel pump 1 are controlled by the control device 3, and output signals from various sensors are taken in for this purpose. That is, they are pump-side information and engine-side information of the engine rotational speed signal S _N from the electromagnetic pickup sensor 20 and the output signal S _S of the spill position sensor 25. Note that the timer position sensor 18 is used for timing control and is not related to the present invention, so a description thereof will be omitted. As information on the engine side, the output signal Sa of the intake temperature sensor 5 provided in the intake manifold 4,
There is an output signal _Sp of the intake pressure sensor 6 provided in Some of the information is also used for air/fuel ratio control.
The figure is shown here to show that the control device 3 handles other processing as well as controlling the FCV 26.

FIG. 3 is a detailed block diagram of the control device 3 which is an embodiment of the present invention.

With a central processing unit (CPU) 31 as the core, a read-only memory (ROM) 32 stores processing programs and monitor programs for executing various processes, and temporarily stores calculation contents and output contents of each sensor. A random access memory (RAM) 33 having a backup memory that stores calculation contents, set values, etc. even when the power is turned off, and first and second input/output circuits 34 and 35 connect the bus line 36. Through
It is connected to the CPU 31 and constitutes a so-called microcomputer. The output devices connected to and controlled by the CPU 31 are a lamp 10 for failure diagnosis, an FCV 26, and an FCV 26, and the lamp 10 and the linear solenoid 22 are connected to a drive circuit 37,
38, and the linear solenoid 22 is driven via a D/A converter 39, a servo amplifier 40, and a drive circuit 41. The input/output circuit 34 is for receiving sensor outputs, and outputs the outputs of the sensors 5, 6, 7, 9, and 25 (taken out via buffers 42, 43, 44, 45, and 46) to a multiplexer (MPX).
47 to sequentially or select one of the A/D
The data is converted into a digital signal by a converter 48 and then output to the bus line 36. On the other hand, the input/output circuit 35 is connected to an ignition off sensor 49 via a buffer 50 that detects whether or not the ignition switch is turned off.
A vehicle speed sensor 51 that detects whether the vehicle speed is 0 or not is connected via a buffer 52. Furthermore, a rotation speed detector 53 for detecting the rotation speed of the engine is provided,
The output signal is waveform-shaped by a waveform shaping circuit 54 and then sent to the CPU 31. A clock circuit 55 is provided to send clock pulses to each of the CPU 31, input/output circuits 34, 35, A/D converter 48, and D/A converter 39.

FIG. 4 is a flowchart showing an example of processing by the control device 3 shown in FIG. The processing shown here is executed regularly or irregularly. First, in step 101, the rotation speed signal S _N accelerator opening
Take in the signals of S _ACC , intake pressure S _P , and intake air temperature Sa,
Next, the current injection amount Q _I is calculated based on the data acquired in step 102. The calculated Q _I is compared with a predetermined set value Q _A in step 103. Q _I ＞
In the case of Q _A , the process moves to step 104 and the Q _A at that time is
Let be Q _I-1 . Further, in step 105, Q _I is set as the final injection amount command value (Q _FIN ), and in step 106, Q _I-1 to be used in the next calculation is stored. Next, in step 107, Q _FIN obtained in step 105 is converted to a control output value V _SPP and outputted to the drive circuit 38.
In step 108, the linear solenoid 22 is activated.

On the other hand, if it is determined in step 103 that Q _I <Q _A , it is determined in step 109 whether or not the vehicle is being accelerated (that is, it is determined whether or not a deceleration shock is occurring). If the engine is accelerating, Q _I is set as the final injection amount command value (Q _FIN ) in step 110. Also, if the vehicle is decelerating, in step 111 the Q _I-1 stored in the previous step 106 is
is read out, and in step 112, a certain amount α is subtracted.
Get Q _I-1 . Note that the judgment in step 103 is made first.
The value of Q _I-1 when it changes to NO is the value of step 104 and
106 makes it Q _A , so the value of Q _I-1 is
The initial value is Q _A. Then step
Compare the fuel injection amount Q _I calculated in step 113 with the injection amount Q _I-1 obtained by subtracting a predetermined α, and if Q _I > Q′ _I-1 , Q _I is determined to be Q _I-1 . Then, set Q _I to Q _FIN and proceed to step 106. Also, if Q _I <Q′ _I-1 , then Q _I-1
is set as Q _FIN in step 114. Each of Q _FIN obtained in step 114 and Q _FIN obtained in step 110 is determined to be Q _I-1 in step 115, and the process proceeds to step 106. Since the subsequent processing is as described above, the explanation will be omitted, but ultimately the linear solenoid 22 is driven in accordance with Q _FIN obtained in step 114 or 110.

Note that for the fuel injection amount Q _I , the basic injection amount Q _BASE is determined from the engine speed N _E and the accelerator opening degree Accp, and the maximum injection amount Q _FULL is determined when smoke begins to appear in the exhaust gas. Further, a value Q′ _FULL is obtained by multiplying Q _FULL by a constant K _a determined according to the intake pressure Ps and a constant K _b determined according to the intake air temperature Sa. this
Q′ _FULL and the above-mentioned Q _BASE are compared, and the smaller of the two is determined as the injection amount Q _I.

FIGS. 5a and 5b are explanatory diagrams of control during deceleration of the embodiment shown in FIG. 4. Steps in Figure 4
Figure 5a shows the injection quantity control when decelerating from the injection quantity above the injection quantity set value Q _A shown in Figure 103, and Fig. 5 b shows the injection quantity control when the injection quantity is below the above injection quantity set value Q _A. FIG. 3 is an explanatory diagram of control when decelerating from . In the explanatory diagrams a and b, the solid lines indicate the case according to the conventional method, and the dotted lines indicate the case according to this embodiment.

When the calculated injection amount Q _I is larger than the injection amount set value Q _A , injection is executed using the calculated injection amount Q _I as the final injection amount command value Q _FIN according to steps 105, 107, and 108 in Fig. 4. Therefore, as shown in FIG. 5a, the actual injection amount is rapidly reduced in accordance with the calculated injection amount Q _I when Q _I >Q _A.

On the other hand, the calculated injection amount further decreases to the above set value.
When the current calculated injection amount _{Q I} is equal to or lower than the previous calculated injection amount, in steps 111, 112, and 113 of Fig. 4, if the current calculated injection amount _Q
Q Determine whether or not it is below the minute setting value α from _I-1 . If it is below, proceed to step 4 in Figure 4.
Final injection amount setting value with the reduction amount limited to α at 114
_Set Q _FIN to
Since Q _FIN is assumed, the actual injection amount will be gradually reduced, with the maximum reduction amount being α, as shown by the dotted line in FIG. 5a. In other words, the injection amount each time is limited to the range between the previous injection amount (Q _FIN =Q _I-1 ) and the value obtained by subtracting α from the previous injection amount (Q _I-1 − α).

In addition, Fig. 5b shows that the calculated injection amount Q _I is from the beginning.
This shows the control when decelerating from a state below Q _A , and in this case, the speed is not from the initial value Q _A ,
As shown by the dotted line in the figure, the injection amount in that state is gradually reduced, with the maximum reduction amount being α, as described above.

〔Effect of the invention〕

As is clear from the above, according to the present invention, during deceleration, the fuel is quickly reduced to a predetermined injection amount, and after reaching this injection amount, the fuel is gradually reduced, thereby eliminating the deceleration shock and achieving smooth deceleration. You get a feeling.

[Brief explanation of drawings]

FIG. 1 is a fuel injection pattern diagram of a diesel engine, FIG. 2 is a configuration diagram of a fuel injection pump and control device suitable for applying the present invention, and FIG.
FIG. 4 is a detailed block diagram of the control device 3 shown in the figure, FIG. 4 is a processing flow chart of the present invention, and FIGS. 5 a and 5 b are explanatory diagrams of the present invention and the conventional control, respectively. 1...Fuel injection pump, 3...Control device, 5...
... Intake temperature sensor, 6 ... Intake pressure sensor, 7 ... Water temperature sensor, 9 ... Accelerator sensor, 10 ... Lamp, 15 ... Plunger, 21 ... Spill ring, 22 ... Linear solenoid, 23 ... Coil , 24... Plunger, 25... Spill position sensor, 26... Fuel cutoff valve (FVC), 27... Excitation coil, 28... Valve, 31... Central processing unit (CPU), 32... Lead on・Memory (ROM), 33... Random access memory (RAM), 34, 35... Input/output circuit, 36...
Bus line, 37, 38, 41...drive circuit, 3
9...D/A converter, 40...Servo amplifier, 4
2 to 46, 50, 52... Buffer, 47... Multiplexer (MPX), 48... A/D converter,
49... Ignition off sensor, 51... Vehicle speed sensor, 53... Rotation speed detector, 54... Waveform shaping circuit.

Claims (1)

[Claims] 1. A diesel engine fuel injection control method for supplying fuel to a diesel engine from a fuel injection pump controlled by an electronic control device via an injection nozzle, wherein _{Calculate the fuel} injection amount _with
In this case, Q _I is the current final injection amount command value Q _FIN , and after changing to Q _I ≦ Q _A and when acceleration is not in progress, the previous calculated injection amount Q with Q _A as the initial value is used. The value obtained by subtracting a constant amount α from _I-1 (Q _I-1 − α) and Q _I
If Q _I > (Q _I-1 − α), Q _I is set as the current final injection amount command value Q _FIN and the previous calculated injection amount Q _I-1 , and Q _I ≦(Q _I-1 −α)
In this case, (Q _I-1 − α) is set as the current final injection amount command value Q _FIN and the previous calculated injection amount Q _I-1. Method.