JPS61192832A - Fuel injection timing control for diesel engine - Google Patents

Abstract

PURPOSE:To prevent the growth of knocking noise by determining the upper limit of the correction amount according to the water temperature, for the correction amount for advancing injection timing, in the correction for the fuel injection timing according to the deviation between an aimed ignition timing and the actual ignition timing. CONSTITUTION:In engine operation, an aimed ignition timing is calculated on the basis of each output of an engine revolution sensor 62 and an acceleration sensor 74 in a CPU28A, and the actual ignition timing is detected on the basis of each output of an ignition sensor 72 and a crank-angle standard sensor 63. Then, the deviation between the aimed ignition timing and the actual ignition timing is obtained, and the correction amount of the duty ratio of a timer control valve 48 which is installed onto a fuel injection pump and controls the fuel injection timing according to said deviation, is calculated, and the fundamental duty ratio is corrected according to the correctioln amount. In this case, the advance angle side guard of the above-described correction amount is calculated according to the cooling-water temperature detected by a water- temperature sensor 78, and when the correction amount is larger than the guard, the value of the guard is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a fuel injection timing control method for a diesel engine, and more particularly to a method for correcting injection timing.

[Prior art]

In diesel engines, particularly automobile diesel engines, it is necessary to precisely control the fuel injection timing from the viewpoint of knocking, black smoke, white smoke, emissions, and fuel efficiency. This control method includes a feedback control method that corrects the multiple fuel injection timing based on the difference between the target ignition timing and the actual ignition timing, which are calculated based on the engine speed and the accelerator opening.゜However, in this control method, if an ignition delay occurs due to extremely cold conditions and the actual ignition timing is significantly delayed from the target ignition timing, the amount of correction to advance the fuel injection timing will be too large and the engine will make a loud knocking noise. A problem has arisen in which the discomfort felt by the driver increases.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above problems, and even when the ignition timing is extremely delayed due to extremely cold conditions,
To provide a fuel injection timing control method for a diesel engine capable of preventing a driver from becoming uncomfortable due to an increase in knocking noise.

[Means for solving problems]

The present invention sets an upper limit for the correction amount for advancing the fuel injection timing, and changes this upper limit depending on the engine water temperature.

That is, the present invention relates to a method of correcting the fuel injection timing based on the difference between the target ignition timing and the actual ignition timing calculated based on the engine rotational speed and the accelerator opening, so that the actual ignition timing matches the target ignition timing. It is something. A guard, which is an upper limit of the correction amount, is determined for the correction amount for advancing the injection timing when correcting the fuel injection timing.

This guard is assumed to change depending on the engine water temperature.

By setting the upper limit in this way, even if the actual ignition timing is extremely delayed, the amount of correction of the fuel injection timing can be suppressed to a certain level or less, so that it is possible to prevent the engine knocking noise from becoming louder.

〔Example〕 An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 2 is a schematic diagram of a diesel engine with an electromagnetic spill distribution type fuel injection pump. The fuel filtered by the filter is guided from the fuel supply hole 6 to the pressure regulating pulp 8 by a vane type feed pump (illustrated rotated by 90 degrees) 4 driven by the drive shaft 2. After the pressure is adjusted, the pump chamber 12, which is a low-pressure chamber within the pump 10, is filled. The fuel filled in the pump chamber 12 lubricates the operating parts within the pump chamber 12, and at the same time is sent through the suction port 14 to a high pressure chamber 18 formed at the tip of the plunger 16. A portion of the fuel is also circulated back to the fuel tank through the overflow valve 20 to drain excess fuel and cool working parts.

Suction groups 22 of the same number as the number of cylinders are bored at the tip of the plunger 16, and a distribution port 26 communicating with an axial port 24 is bored in the radial direction of the plunger 16. Further, a cam plate 2 is provided at the tail end of the plunger 16.
8 is fixed, and rollers 32 of the same number as the number of nine cylinders are in contact with the cam plate 28, which are fitted into a roller ring 30.

This plunger 16 is inserted into the cylinder 34 from the distal end side, and a high pressure chamber 18 is formed by the distal end surface of the plunger 16, the inner wall surface of the cylinder 34, and K.

The cylinder 34 is provided with an intake port 14 and a distribution passage 38 of the same number as the number of cylinders, which communicates with the delivery pulp 36 from the inner surface of the cylinder. and,
A solenoid valve 44 is attached to the pump housing 10 to communicate and cut off the communication path 40. This communication path 40
This allows the high pressure chamber 18 and the pump chamber 12 to communicate with each other. Further, when the solenoid 46 is turned on, the electromagnetic valve 44 attracts the valve body 42 to connect the communication passage 40, and when the solenoid is turned off, the valve body protrudes and blocks the communication passage 40. This controls the fuel injection amount.

The drive shaft 2 protrudes toward the pump chamber 12 and is connected to a cam plate 28 via a coupling. The cam plate 28 is fixed to the plunger 16 and covered by the roller 32 by a spring 50. Therefore, the cam plate 28 is rotated by the drive shaft 2, and the roller 32 and the cam plate 2
8, the cam crest of the cam plate 28 climbs up the roller 32, and the plunger 16 is reciprocated by a number of times equal to the number of cylinders during rotation.

At the bottom of the fuel injection pump, there is a hydraulic timer (90° rotation) that changes the phase of the drive shaft 2 and the cam plate 28 that drives the plunger 16 to change the fuel injection timing using changes in the fuel supply pressure. ) 52 is provided. According to this timer 52, the spring 54
is pushing the timer piston 56 in the direction of injection delay,
When the engine speed increases, the oil supply pressure increases and the piston 56 is pushed against the elastic force of the spring 54, so the roller ring 30 is rotated via the iron 58 in the opposite direction to the rotation direction of the injection pump. , the fuel injection timing is advanced in proportion to the oil pressure. The hydraulic pressure acting on the piston 56 is controlled by the solenoid valve 48.

A signal rotor 60 having a plurality of teeth is fixed coaxially with the drive shaft at the tip of the drive shaft 2, and a pickup 62 is attached to the roller ring 30 so as to face the surface of the signal rotator 60. .

Therefore, when the signal rotor rotates together with the drive shaft, the pickup 62 outputs a rotation angle signal.

Further, a fuel cut valve 64 is attached to the pump housing 10 to stop fuel injection by cutting off the suction boat 14.

The tertiary valve 36 is connected to a fuel injection valve 68 installed so as to protrude into the auxiliary combustion chamber of the diesel engine 66. This secondary combustion chamber has a glow plug 70.
is installed so that it protrudes.

In FIG. 2, the accelerator opening is determined by the accelerator sensor 74, the engine water temperature is determined by the water temperature sensor 78, the actual ignition timing is determined by the ignition sensor 72, the engine rotation speed is determined by the big-up 62, and the crank angle is determined by the circumference of the pump pulley. They are each detected by another pickup 63 provided opposite to the surface. Information detected by these sensors is sent to the microcomputer 82.

This microcomputer will be explained with reference to FIG.

This microcomputer 82 is a central processing unit (CPU).
) 82A, read-only memory (ROM) 82B
, random access memory (RAM) 82C, input/output capo) 82D, analog-to-digital converter (A/D) 8
It consists of 2E etc.

Among these, the RAM 82C is a device that temporarily stores the output contents of various sensors and the calculation contents performed by the microcomputer 82, and continues to store the calculation contents, set values, and basic fuel injection amount even when the power is cut off. CPU
82A performs various calculations based on the signals from the various sensors, etc., and can output a drive signal for driving the fuel pump, etc. In addition, the ROM 82B stores in advance the program of the routine described below in FIG. 1, and also includes a two-dimensional fuel injection timing map and injection Basic TCV DUTY that determines the timing
A program etc. for calculating the ratio is stored in advance. The A/D 82E receives output signals from various sensors and sequentially converts them into digital signals according to instructions from the CPU 82A.

Now, the detection signals output from the water temperature sensor 78 and the accelerator sensor 74 are supplied to the multiplexer 82F via the buffer circuit 82G. This multiplexer 82
The detection signal supplied to F is further converted into a digital signal by A/D 82E and supplied as data to input/output port 82D. Also, the ignition sensor 72. The detection signals output by the crank angle reference sensor pickup 63 and the engine rotation sensor pickup 62 are each shaped by a waveform shaping circuit 82H and then sent to the CPU 82.
A is supplied. Also A/D82E input/output boat 82D
A clock pulse is then sent to the CPU 82A by the input circuit 82I.

The CPU 82A then controls the solenoid valve 44, which is a fuel control valve, the solenoid valve 48, which is a timer control valve, and the fuel cut valve 64 via the drive circuit 82J.

Next, a processing routine of the injection timing control method according to this embodiment, which is performed by the microcomputer 82 described above, will be explained with reference to FIG.

■ As explained in FIG. 3, the engine rotational speed (NE) is detected by the engine rotation sensor 62, the accelerator opening (ACCP) is detected by the accelerator sensor 74, the engine water temperature (THW) is detected by the water temperature sensor 78, and the ignition sensor 72 A shift ignition signal (IGS IG) and a shift flank angle reference signal (TDC) are output by the crank angle reference sensor 63, respectively.
It is taken into the microcomputer 82.

■ The target ignition timing (TRG I G
) is calculated. This calculation is performed according to a two-dimensional fuel injection timing map using NE and ACCP as variables, and specifically, the DUTY of the timer control pulp (TCV)
This will determine the ratio.

■ At the same time, the above-mentioned imported IGSIG.

Actual ignition timing (ACTIG) is detected by TDC.

■ The basic TCV DUTY ratio (Tp
BASE) is calculated.

■ Next, the difference between the calculated TRGIG and ACTiG: j
TCVDUTY ratio (7) m positive t (TDUT'Y)
seek. However, the following is done to prevent this correction amount from becoming too large.

■ Calculate the advance side guard (TDGD) of TDUTY using the captured THW.

(2) Then, it is determined whether TDUTY is greater than TDGD.

■ If it is large, change the value of TDGD to TDUTY
be the value of Accordingly, the shift advance side guard (TDGD) has a meaning as an upper limit of the correction amount for advancing the injection timing.

■ If it is not large, the actual control TCVDUTY
The ratio (FDUTY) = TDBASE - TDUTY.

This is the same as normal correction of injection timing.

[Co., Ltd.] FDU timer control pulp (TCV)
Controlled by TY, fuel is injected.

By controlling the fuel injection timing as described above, the advanced angle guard (TDGD) of TDUDY can be calculated based on the captured THW, and this can be set as the upper limit of the correction amount for advancing the injection timing. . Therefore, it is possible to prevent the correction amount for advancing the correction timing from becoming too large due to extremely cold times or the like.

〔Effect of the invention〕

Fuel injection timing side of the diesel engine of the present invention □
According to the control method, it is possible to set an upper limit for the correction amount calculated based on the engine water temperature with respect to the correction amount for advancing the injection timing when correcting the fuel injection timing. This prevents the knocking sound from becoming louder.

[Brief explanation of the drawing]

FIG. 2 is a schematic diagram of a diesel engine fuel injection system in which an embodiment of the present invention is implemented, and FIG. 3 is a flow diagram showing the microcomputer 82 of FIG. 2. FIG. 1 shows a control routine diagram of this embodiment executed by the microcomputer shown in FIG. 62...Pickup, 72...Ignition sensor, 74
...Accelerator Senna% 78'...Water temperature sensor.

Claims (1)

[Claims] A method of correcting fuel injection timing to match the actual ignition timing with the target ignition timing based on the difference between the target ignition timing and the actual ignition timing calculated based on the engine speed and the accelerator opening. , A fuel injection timing for a diesel engine characterized in that a guard is defined as an upper limit of the correction amount for the correction amount for advancing the injection timing when correcting the fuel injection timing, and this guard is changed depending on the engine water temperature. Control method.