JPS63109251A - Fuel feeding quantity control method for engine - Google Patents

Abstract

PURPOSE:To prevent the undershoot and hunting of engine speed by increasing fuel quantity until a lower limit value which is a defined value higher than a target idling engine speed is obtained when idling engine speed is lowered. CONSTITUTION:An electronic control device 56 controls a fuel injection quantity via an electromagnetic spill valve 50, fuel cut at the time of deceleration via a fuel cut valve 52, and injection timing via a timing control valve 48, based on the outputs of an accelerator opening sensor 20, an engine speed sensor 46, an intake air temp. sensor 12, an intake pressure sensor 32, an ignition timing sensor 38, an air conditioner switch, a neutral safety output, etc. And, at the time of idling, it carries out the control of fuel injection quantity so as to obtain a target idling engine speed corresponding to a load while, when engine speed is lowered due to fuel cut at the time of deceleration, etc., it increases fuel quantity until the engine speed becomes a value which is a defined value higher than a target idling engine speed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for controlling the amount of fuel supplied to an engine, and more particularly to an improvement in a method for controlling the amount of fuel supplied to an engine, which is suitable for use in an electronically controlled diesel engine.

[Conventional technology]

2. Description of the Related Art So-called electronically controlled diesel engines have been put into practical use, in which the injection pattern is electronically controlled according to engine operating conditions. In this electronically controlled diesel engine, like a gasoline engine, when the fuel cut condition is met in the engine deceleration state with the accelerator opening 0%, fuel injection is stopped and the engine speed drops to the predetermined fuel return speed. A so-called fuel cut is performed in which fuel injection is restored when the However, if the fuel return rotation speed is low, the engine rotation speed will drop too much before the torque generated by the engine becomes sufficiently large, resulting in engine stall. On the other hand, if the fuel return rotation speed is increased in order to prevent engine stalling, the amount of white smoke and HC discharged during deceleration will increase, and fuel efficiency will also deteriorate. In order to solve such problems, for example,
No. 188,737 proposes that when fuel supply is restored, the fuel injection group is corrected only once by anticipatory control in accordance with the amount of drop in engine speed.

[Problems to be solved by the invention]

However, this is only a one-time predictive control of the fuel injection unit in response to a drop in engine speed. Therefore, it is necessary to prevent the engine from stalling under all operating conditions, including the state of engine friction when the engine is new or after sufficient running-in, variations in the engagement time lag of the torque converter, high and low engine water temperatures, etc. In order to do so, the return fuel correction f (estimated injection amount) must be set to a large value in consideration of individual differences in the amount of rotational speed drop due to variations between engines and between transmissions. Therefore, depending on the engine, there is a problem in which the engine speed increases abnormally when performing anticipatory injection to prevent engine stalling, or the problem that engine stalling still occurs under special conditions. It was inevitable. Regarding these problems, the applicant has already filed a patent application in 1986-1.
No. 50528 proposes a fuel cut control method for an electronically controlled engine that detects the amount of drop in engine speed during operation during deceleration (decrease in engine speed) and increases the injection amount according to the amount of drop. are doing. This control method is a method that can reliably prevent an engine stall or an abnormal increase in engine speed when returning from a fuel cut as described above. By the way, in this control method, when the engine speed drops, the amount of fuel is increased until the engine speed reaches a predetermined speed. It is better to set this predetermined rotational speed to the lowest possible rotational speed to eliminate negative overshoot (undershoot) of the engine rotational speed. However, when the engine is cold or when the air conditioner is turned on, the idle speed is increased, so if the predetermined speed is not set to a higher value than the engine speed at that time, the amount of fuel will be increased during normal idling. Engine rotation may become hunting. Therefore, the fuel cut control method has a problem in that it is not possible to prevent the undershoot and hunting at the same time.

[Purpose of the invention]

The present invention has been made in view of the above conventional problems, and provides an engine fuel supply amount control method that can reliably prevent engine speed from undershooting or hunting when the engine speed decreases. The purpose is to

[Means to solve the problem]

The present invention determines an increase value of the fuel supply amount when the engine speed decreases according to the basis of the decrease in the engine speed, and when the engine is idling, the fuel supply amount is adjusted to a target rotation speed according to the engine operating state. 2. A fuel supply amount control method for an engine, wherein the increase value is determined until the engine speed reaches a lower limit value, and the lower limit value is set to be a certain value higher than the target engine speed. By setting the value as a value, the above objective is achieved.

[Effect]

When the engine speed decreases, the increase value of the fuel supply amount is determined according to the decrease in the engine speed, and the fuel supply amount is controlled so that the target speed corresponds to the engine operating state during idling. , if the lower limit of the engine rotational speed for determining the increase value is set to a value lower than the target rotational speed at idle, in addition to the increase to reach the target rotational speed, the engine speed will be increased according to the amount of rotational speed drop. On the other hand, if the lower limit value of the engine rotation speed is much higher than the target rotation speed, the engine rotation speed becomes less than the lower limit value, and the increase in the amount of fuel supply becomes impossible. When the engine speed is finished, the engine speed becomes less than the lower limit value, and furthermore, the engine speed undershoots from the target speed during idling. Therefore, in the present invention, the increase value is determined until the engine speed reaches the lower limit value, and the lower limit value is set to a value that is a certain value higher than the target engine speed during idling. Therefore, it is possible to reliably prevent hunting and undershoot as described above from occurring when the engine speed decreases. Therefore, even when the engine suddenly decelerates, for example, the desired engine speed can be smoothly achieved without deteriorating drivability.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an electronically controlled diesel engine for automobiles in which a method for controlling a fuel supply plate for an engine according to the present invention is adopted will be described in detail with reference to the drawings. As shown in FIG. 2, this embodiment includes an intake air temperature sensor 12 disposed downstream of an air cleaner (not shown) for detecting the temperature of intake air. A turbocharger l11 is provided downstream of the intake air temperature sensor 12, and includes a turbine 14A rotated by the energy of exhaust gas and a compressor 14B rotated in conjunction with the turbine 14A. The turbocharger 14
The upstream side of the turbine 14A and the downstream side of the compressor 14B are communicated via a wastegate valve 15 for preventing an excessive rise in intake pressure. The intake air passage 16 on the downstream side of the compressor 14B is configured to rotate non-linearly in conjunction with an accelerator pedal 17 disposed at the driver's seat to limit the flow rate of intake air during idling. A main intake throttle valve 18 is provided. The opening degree of the accelerator pedal 17 (hereinafter referred to as accelerator opening degree) ACCρ is detected by an accelerator opening sensor 20 . A sub-intake throttle valve 22 is provided in parallel with the main intake throttle valve 18 , and the opening degree of the sub-intake throttle valve 22 is controlled by a diaphragm device 24 . Negative pressure generated by a negative pressure pump 26 is supplied to the diaphragm device 24 via a negative pressure switching valve (hereinafter referred to as VS) 28 or 30. An intake pressure sensor 32 for detecting the pressure of intake air is provided downstream of the intake throttle valve 18.22. In the cylinder head 10A of the diesel engine 10,
An injection nozzle 34 whose tip faces the engine combustion chamber 10B, a glow plug 36, and an ignition timing sensor 38 are provided. A glow current is supplied to the glow plug 36 via a glow relay 37. In addition, the cylinder block IOC of the diesel engine 10 includes
A water temperature sensor 40 is provided for detecting engine cooling water temperature. Fuel is fed under pressure to the injection nozzle 34 from an injection pump 42 . The injection pump 42 includes a pump drive shaft 42A that rotates in conjunction with the rotation of the crankshaft of the diesel engine 10.
, a feed pump 42B (FIG. 2 shows a 90° expanded state) for pressurizing fuel, which is fixed to the pump drive shaft 42A, and a fuel pressure adjustment valve 42C for adjusting the fuel supply pressure. a reference position sensor 44 made of, for example, an electromagnetic pickup, for detecting a crank angle reference position, for example, top dead center ("I'DC") from rotational displacement of a pump drive pulley 42D fixed to the pump drive shaft 42A;
A roller ring 42 for detecting the engine rotation angle and the position of missing teeth from the rotational displacement of a gear 42H, which is also fixed to the pump drive shaft 42A and has missing teeth corresponding to the number of cylinders.
An engine rotation sensor 46 provided on the H, for example, consisting of a 1E magnetic pickup, a face cam, a roller ring 42H for reciprocating the '12F and the plunger 42G, and changing the timing thereof, and the roller ring 42H. A timer piston 42J (FIG. 2 shows a 90" expanded state) for changing the rotational position of the timer piston 42J, and a timing control valve (hereinafter referred to as ,TCV
) 48, and an electromagnetic spill valve 50 for controlling the fuel injection wall by changing the timing of releasing fuel from the plunger 42G via the spill boat 42K.
A fuel cut valve 52 for cutting fuel, a delivery valve 42L for preventing backflow of fuel and after-effects,
is provided. The intake temperature sensor 12, the accelerator opening sensor 20, the intake pressure sensor 32, the ignition timing sensor 38, the water temperature sensor 40,
A reference position sensor 44, an engine rotation sensor 46, a glow current sensor 54 that detects the glow current flowing through the glow plug 36, a key switch, an air conditioner switch, a neutral safety switch output, a vehicle speed signal, etc. are controlled by an electronic control unit (hereinafter referred to as The VSV
28.30, glow relay 37, TCV 48, electromagnetic spill valve 50, and fuel cut valve 52 are controlled. As shown in detail in FIG. 3, the ECU 36 includes a central processing unit (hereinafter referred to as CPU) 56A for performing various arithmetic processes, and a read-only memory for storing control programs, various data, etc. (hereinafter referred to as ROM) 56B, and a random access memory (hereinafter referred to as ROM) for temporarily storing calculation data etc. in the CPU 56A.
(hereinafter referred to as R and AM) 56C, a clock 56D that generates a clock signal, the output of the water temperature sensor 40 inputted via the buffer 56E, and the buffer 56.
In order to sequentially take in the output of the intake temperature sensor 12 inputted via F, the output of the intake pressure sensor 32 inputted via the buffer 56G, the output of the accelerator opening sensor 20 inputted via the buffer 56H, etc. multiplexer (hereinafter referred to as MPX) 56, and the M P
6. An analog-to-digital converter (hereinafter referred to as an A/D converter) 56L for converting the analog signal of the K output into a digital signal, and the output of the A/D converter 56L is connected to the CPU.
Input/output port 56M for inputting to 56A, starter signal input via buffer 56N, buffer 56
an air conditioner signal input from the air conditioner via P;
1 to 1 input from the automatic transmission via the buffer 56Q
an input/output board 56S for inputting the ignition timing sensor 38 output, etc. input via the waveform shaping circuit 56R into the CPU 56A; 1
- Said waveform shaping circuit 56 for direct input into ICAP2
R, a waveform shaping circuit 56T for shaping the output of the reference position sensor 44 and directly importing it into the same input interrupt baud of the CPU 56A)-ICAP2, and a waveform shaping circuit 56T for shaping the output of the engine rotation sensor 46 and inputting it directly to the same input interrupt baud of the CPU 56A. A waveform shaping circuit 56U for directly capturing the input interrupt baud 1-ICAPI, and a drive circuit 56V for driving the electromagnetic spill valve 50 according to the calculation result of the CPU 56A.
and the TCV 4 according to the calculation result of the CPU 56A.
a drive circuit 56W for driving the CPU 56;
It is comprised of a drive circuit 56X for driving the fuel cut valve 52 according to the calculation result of A, and a common bus 56Y for connecting each of the coffin construction devices and transferring data and instructions. Here, the ignition signal output from the waveform shaping circuit 56R is inputted not only to the input interrupt baud of the CPU 56A but also to the input/output capo 1-563.
(same input interrupt baud) This is a slant to distinguish it from the reference position signal of the output of the waveform shaping circuit 56T input to ICAP2. The effects of the embodiment will be explained below. The control of the fuel injection amount in this embodiment is performed by increasing the fuel injection amount during the main routine as shown in FIG.
This is done according to a routine for calculating eC. The routine shown in the figure is a routine that starts at regular intervals, for example, every 10 milliseconds, and when it starts, it first goes to step 110.
In steps 130 to 130, a cycle for calculating the increase value Q reC is determined. That is, in step 110, 1 is subtracted from the cycle determination constant CQrec, and in step 120, the cycle determination constant CQrec is subtracted from the cycle determination constant CQrec.
Determine whether Q reC is zero. When the determination result is positive, that is, when the increase value Q reC should not be calculated, the process proceeds to step 130, and 3 is entered into the cycle determination constant CQ reC. On the other hand, if the determination result is negative, step 19
Go to 0. Therefore, the previous cycle determination constant CQ re
Only when C is 1, the processing from step 130 onwards is performed,
In the end, steps 130 to 180 are performed once every 30 milliseconds. Then, in step 140, when the engine is idling, the target rotation speed NF required to control the fuel supply amount to the target rotation speed according to the engine operating state is set to turn on/off the air conditioner (near conditioner), automatic transmission, etc. Calculated from various conditions such as neutral range, drive range, and water temperature THw. Then step 15
0, the engine speed NE is within the range in which the fuel supply amount should be increased, that is, the increase value Qrec (in the case of the example,
(expressed as duty ratio) is within the calculation range.
For example, the determination is made based on whether or not the engine speed is within a range expressed by the following equation (1). NF+100≦NE≦1100 (1) When the judgment result is positive, that is, when it is within the calculation range of the increase value Q reC, the process proceeds to step 160, and the engine speed NE is lower than the previously stored value NEL. Whether or not it has decreased is determined by whether or not the following equation (2) holds true. NEL-NE>O (2) When the determination result is positive, that is, when the engine speed NE is lower than the previously stored value NFL, the process proceeds to step 170, and the engine Amount of decrease in rotation speed NED (=NFL-NE)
An increase value Qrec corresponding to the amount is calculated using a map such as that shown in FIG. 4, for example. The process then proceeds to step 180, and the previous step 150
．． If the determination result at step 160 is negative, the process also proceeds to step 180. In this step 180, the current engine speed NE is entered into the lick NEL to be used in the next execution.Then, the process proceeds to step 190, and if the determination result in the previous step 120 is negative, that is, the increase value QreC is calculated. If it is not a cycle, the process also proceeds to step 190. In this step 190, it is determined whether or not the increase value Q reC is zero, and if the determination result is positive, this routine is temporarily terminated. On the other hand, when the determination result is negative, that is, when it is necessary to reduce the increase value Q reC, in steps 200 and 210, when the increase value Q reC is 6% or less, the increase value Q re
Subtract 0.03% from C to reduce the increase value Q reC. If the increase value QreC is greater than 6%, the process proceeds to step 220 and is set to 6%. As a result, the increase value Q rec is not immediately set to zero when the engine rotational speed at which the increase value Q rec is calculated (in the case of the embodiment, the range shown in equation (1)) becomes lower, but the increase value Q rec is not immediately set to zero. As shown at 210, the increase value Q r
When ec is less than a predetermined value, for example 6%, the increase value Q reC
By gradually reducing the amount (0°03% in the case of the example), the engine speed can be smoothly lowered. Therefore, it is possible to prevent a sudden drop in the engine speed NE due to a sudden decrease in the increase value QreC, and in turn, it is possible to prevent the engine from stalling. In the above embodiment, the increase value Q reC of the fuel injection amount was determined using the routine shown in FIG. 1 and the map shown in FIG. The routine and map for determining the increase value of the amount are not limited to this, and the increase value can also be determined using other routines and maps. In this case, the condition for the engine speed NE for calculating the increase value Q reC in the routine was set to the range shown in equation (1), but the conditions for determining the increase value according to the present invention are not limited to this, and the engine speed If the lower limit value of the number NH is an appropriate value that is a certain value higher than the target rotational speed during idling, conditions for other values can be set in consideration of engine properties, for example. Furthermore, in the above embodiments, the present invention was applied to a diesel engine having a configuration as shown in FIGS. It is clear that the same applies to gasoline engines.

【Effect of the invention】

As described above, according to the present invention, it is possible to reliably prevent engine rotational speed undershoot and hunting when the engine rotational speed decreases. Therefore, for example, even when the engine suddenly decelerates, an excellent effect can be obtained in that a predetermined engine speed can be smoothly achieved without deteriorating drivability.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a routine for determining the fuel injection amount increase value of an electronically controlled diesel engine for automobiles, in which the present invention is adopted, and FIG. 2 shows the overall configuration of the diesel engine. FIG. 3 is a block diagram showing the structure of the electronic control unit used in the above embodiment, and FIG. 4 is a diagram showing the relationship between the increase value and the engine speed decrease used in the routine. FIG. 3 is a diagram showing an example of a map. DESCRIPTION OF SYMBOLS 10... Diesel engine, 20... Accelerator opening sensor, 42... Injection pump, 46... Engine rotation sensor, NE... Engine rotation speed, 56... Electronic control unit (ECU), Q rec・
...Increase value of fuel injection amount.

Claims (1)

[Claims] (1) When the engine speed decreases, the increase value of the fuel supply amount is determined according to the amount of decrease in the engine speed, and when the engine is idling, the fuel supply amount is increased so that the target speed corresponds to the engine operating state. A fuel supply amount control method for a controlled engine, wherein the increase value is determined until the engine speed reaches a lower limit value, and the lower limit value is set to a value that is a certain value higher than the target engine speed. A method for controlling the amount of fuel supplied to an engine, characterized in that: