JPH063164B2 - Fuel injection timing control method for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection timing control method for a diesel engine, and is particularly suitable for controlling the fuel injection timing of a diesel engine that employs an electronic fuel injection system. Fuel injection timing control method for various diesel engines.

[Conventional technology]

In a diesel engine based on an electronic fuel injection control system, as described in Japanese Patent Laid-Open No. 58-25584, a target ignition timing determined from an engine speed and an engine load is set as an ignition timing suitable for an engine operating condition. Ignition timing feedback control is employed in which the target ignition timing is set, the target ignition timing is compared with the actual ignition timing, and fuel is injected at a timing that matches the actual ignition timing with the target ignition timing. If the fuel injection timing is controlled by this ignition timing feedback control, the fuel injection timing can be maintained at the optimum timing.

[Problems to be solved by the invention]

However, at the time of starting, especially at low temperature starting, the ignition becomes unstable. Therefore, if the ignition timing feedback control is performed even at the time of starting, the fuel injection timing greatly deviates from the optimum fuel injection timing, and the startability deteriorates. Occurred.

The present invention has been made in view of the above conventional problems, and an object thereof is a fuel injection timing control method for a diesel engine that can improve startability in a diesel engine that employs ignition timing feedback control. To provide.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention compares the target ignition timing determined from the engine speed and the engine load with the actual ignition timing as shown in FIG. 1, and compares the actual ignition timing with the target ignition timing. In a fuel injection timing control method for a diesel engine that uses ignition timing feedback control for injecting fuel at a timing that matches the above, at the time of engine start (steps 200 and 202), the ignition timing feedback control is not executed The fuel is injected at a timing determined by the number and the engine cooling water temperature (step 206).

[Action]

In the present invention, since the ignition timing feedback control is not executed when the engine is started, the fuel injection timing is not unduly advanced due to the ignition timing, and the startability is deteriorated due to the unintended advance. Is prevented.

By the way, the optimum fuel injection timing at the time of starting the diesel engine should be set as a timing at which an appropriate amount of fuel can be supplied before the combustion chamber reaches a predetermined compression state (hereinafter referred to as proper ignition timing). If excessive fuel is supplied before the proper ignition timing, it may cause knocking,
Also, if the supply is insufficient, the ignitability deteriorates.

Further, the ignitability of fuel has a deep correlation with the vaporization property of fuel,
This vaporizability is a function of the engine temperature, that is, the engine coolant temperature. Therefore, the amount of fuel to be supplied by the proper ignition timing can be obtained as a function of the engine cooling water temperature.

On the other hand, the fuel supply amount in the diesel engine can be controlled by the fuel injection time. And
The fuel injection time before the proper ignition timing is a concept that is determined by the crank angle position at which fuel injection is started and the engine speed, that is, the engine speed.

On the other hand, the present invention sets the fuel injection timing at the engine start to the crank angle position set based on the engine speed and the engine cooling water temperature.

Therefore, the fuel injection timing set when the engine is started in the present invention is always the optimum fuel injection timing that ensures good startability.

〔Example〕

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment to which the present invention is applied, and shows the configuration of a diesel engine equipped with an electromagnetic spill type distribution type fuel injection pump. In FIG. 2, the fuel filtered by the filter is guided from a fuel inlet 6 to a pressure regulating valve 8 by a vane type feed pump (developed by 90 °) 4 driven by a drive shaft 2, and this pressure regulator is After the pressure is adjusted by the rating valve 8, the pump housing 10
It is introduced into the pump chamber 12, which is a low pressure chamber inside. The fuel filled in the pump chamber 12 lubricates the operating portion in the pump chamber 12, and at the same time, is sent to the high pressure chamber 18 formed at the tip of the plunger 16 via the suction port 14. In addition, a part of the fuel is returned to the fuel tank from the over-throw valve 20 for discharging excess fuel and cooling the operating part.

The same number of suction groups 22 as the number of cylinders are bored at the tip of the plunger 16. A cam plate 28 is fixed to the end of the plunger 16, and as many rollers 32 as the number of cylinders fitted to the roller ring 30 are in contact with the cam plate 28. This plunger 16
Is inserted into the cylinder 34 from the tip side and the plunger 1
6 and the inner wall surface of the cylinder 34, the high pressure chamber 18
Is formed. The intake port 14 is formed in the cylinder 34, and the delivery valve 36 is inserted from the inner surface of the cylinder.
The same number of distribution passages 38 as the number of cylinders communicating with the. An electromagnetic valve 44 that connects and disconnects the communication passage 40 is attached to the pump housing 10. The communication passage 40 connects the high pressure chamber 18 and the pump chamber 12 with each other. Further, when the solenoid 46 is turned on, the solenoid valve 44 attracts the valve body 42 to communicate the communication passage 40,
When the solenoid is turned off, the valve body 42 is projected to shut off the communication passage 40.

The drive shaft 2 projects toward the pump chamber 12 and is connected to the cam plate 28 via a coupling. The cam plate 28 is fixed to the plunger 16 and is pressed against the roller 32 by the spring 50. Therefore, the cam plate 28 is rotated by the drive shaft 2, and the roller 32 and the cam plate 28 are rotated.
The cam crest of the cam plate 28 rides on the roller 32 according to the contact state of the above, so that the plunger 16 is reciprocated by the same number of rotations as the number of cylinders during one rotation.

At the bottom of the fuel injection pump, a hydraulic timer (90 ° deployment) is used to change the phase of the drive shaft 2 and the cam plate 28 that drives the plunger 16 to change the fuel injection timing by utilizing the change in the fuel feed pressure. 52) is provided. According to this timer 52, the spring 5
4 pushes the timer piston 56 in the injection delay direction, and when the engine speed rises, the oil feeding pressure rises and the piston 56 is pushed against the elastic force of the spring 54, so that the rod 58 is pushed. The roller ring 30 is rotated in the direction opposite to the rotation direction of the injection pump, and the fuel injection timing is advanced in proportion to the oil pressure. The ignition timing is determined by controlling the hydraulic pressure acting on the piston 56 by the solenoid valve 48 so that the actual ignition timing coincides with the target ignition timing (determined from the engine speed and the engine load) predetermined by the engine condition. To be done.

A signal rotor 60 is fixed to the tip of the drive shaft 2 coaxially with the drive shaft 2, and
A pickup 62 is attached to this so as to face the peripheral surface of the signal rotor 60. Signal rotor 60
A plurality of convex teeth are arranged at a predetermined angle (for example, 5,625 °), and the convex teeth are cut out at equal intervals as the number of cylinders to form toothless portions. That is, in the case of a 4-cylinder diesel engine, as shown in FIG.
Plural convex teeth 60α, 60β, etc. are arranged every 5,625 ° (corresponding to 11, 25 ° CA) and 90 °
The toothless portions 60a to 60d are formed for each (corresponding to 180 ° CA). Accordingly, when the signal rotor 60 rotates, the convex teeth move toward or away from the pickup 62, and the pickup 62 moves the fourth tooth from the pickup 62 by electromagnetic induction.
The pulse signal shown in the figure is output. The wide valley portion of this pulse signal acts as a reference position signal, and the other portions act as rotation angle signals. Further, the pickup 62 and the signal rotor 60 are arranged such that one of the toothless portions approaches the pickup 62 before the plunger 16 is moved forward in the direction in which the high pressure chamber is contracted, that is, before the plunger 16 is lifted. The relative position is determined so that the pickup 62 outputs the reference position signal, that is, the width of the valley portion of the pulse signal is widened.

Further, the pump housing 10 is provided with a fuel injection cut valve 64 that stops fuel injection by blocking the intake port 14.

The delivery valve 36 is connected to a fuel injection valve 68 mounted so as to project into the auxiliary combustion chamber of the diesel engine 66. A glow plug 70 and an ignition timing sensor 72 for detecting ignition of fuel are attached to the auxiliary combustion chamber so as to project therefrom. The ignition sensor 72 is composed of an optical fiber and a phototransistor, and is configured to convert the light of the flame transmitted through the optical fiber into an electric signal by the phototransistor.

Incidentally, 74 is an accelerator sensor for detecting the accelerator opening,
Reference numeral 76 is a pressure sensor for detecting the intake pipe pressure, 78 is a water temperature sensor for detecting the engine cooling water temperature, and 80 is a glow relay. Further, 84 is a pulsar arranged at the same number as the number of cylinders (90 ° interval in the case of a 4-cylinder engine) on the fuel injection drive pulley 3, and 86 is a specific position (for example, the top dead center of the engine as the pulsar 84 passes. ) Is a pickup that outputs a crank angle reference signal, and 90 is a starter.

FIG. 5 shows the mounting state of the pulsar 84 and the pickup 86. In the figure, the fuel injection pump 10A is positioned by a pump mounting flange 88. A drive pulley 3 is screwed to the drive shaft 2 that drives the fuel injection pump 10A. On the side surface of the drive pulley 3 on the flange 88 side, the same number of pulsars 84 as the number of cylinders are arranged at equal intervals. This pulsar 84
In case of a 4-cylinder engine, four units are arranged every 90 °. Further, the flange 88 is attached so that a crank angle reference signal is output as the pulsar 84 passes. The relative mounting position between the pulsar 84 and the pickup 86 is
The crank angle reference signal is set to be output when the plunger of the fuel injection pump 10A reaches a position corresponding to a specific position (for example, the top dead center of each cylinder) during one cycle of each cylinder. The drive pulley is illuminated at the timing triggered by the crank angle reference signal.

The pickup 62, the ignition timing sensor 72, the accelerator sensor 74, the pressure sensor 76, the water temperature sensor 78, and the pickup 86 are connected to the input port of the microcomputer 82. The output port of the microcomputer 82 is connected to the glow plug 70 via the glow relay 80, and the solenoid 46 of the solenoid valve 44,
It is connected to the solenoid of the solenoid valve 48 and the solenoid of the fuel cut valve 64. Further, a starter signal is input from the starter 90 to the microcomputer 82.

The microcomputer 82 has buffer circuits 82a, 82b, 82c, 82d, 8 as shown in FIG.
2e, 82f, waveform shaping circuits 82g, 82h, 82i,
Multiplexer 82j, A / D converter 82k, CPU 821 having input / output port, ROM, RAM, drive circuits 82m, 82n, 82p, 82q, current detection circuit 82r.
The output signals of the water temperature sensor 78, the pressure sensor 76, and the accelerator sensor 74 are buffer circuits 82a, 82b, and 82c, a multiplexer 82j, and A /
It is supplied to the CPU 821 via the D converter 82k. Further, among the variations in the injection amount of the fuel injection pump, the output signal of the phase corrector 94 for setting the correction value for correcting the phase variation in the rotation angle direction of the fuel injection pump by the voltage value, and the responsiveness of the solenoid valve 44. The output signals of the τ corrector 96, which sets the correction value for correcting the variation by the voltage value, are buffer circuits 82d and 82e and the multiplexer 82, respectively.
It is supplied to the CPU 821 via the A / D converter 82K.

Further, the output signal of the pickup 62 that outputs the rotation angle signal is supplied to the CPU 821 via the waveform shaping circuit 82g, and the pickup 8 that outputs the crank angle reference position signal.
The output signal of 6 is sent to the CPU 82 via the waveform shaping circuit 82h.
1 is being supplied. Furthermore, the output signal of the ignition timing sensor 72 is supplied to the CPU 821 via the waveform shaping circuit 82i. The output signal of the starter 90 is supplied to the CPU 821 via the buffer circuit 82f.

The ROM of the CPU 821 stores various data such as various control programs and numerical data for determining the fuel injection amount, control data for the fuel injection cut valve 64, and the solenoid valves 48, 44. The CPU 821 performs various calculations based on the output signals of the water temperature sensor 78, the pressure sensor 76, the accelerator sensor 74, and the like, and a drive signal for controlling the drive of the fuel injection cut valve 64, the solenoid valves 48, 44, and the display 92. Drive circuits 82m and 82
It is configured to output to n, 82p, and 82q.
The drive circuits 82m to 82q each have a switching element such as a power transistor, and can drive the fuel injection cut valve 64, the solenoid valve 48, and the display 92 by a drive signal from the CPU 821.

In the drive circuit 82p of the drive circuits, the current detection circuit 8
2r is provided, and the drive circuit 82p is controlled by the constant current control of the current detection circuit 82r so that the current value of the drive signal supplied to the solenoid valve 44 is always constant.
Further, the ROM stores various control programs and various map data such as duty ratio map data associated with the engine water temperature as shown in FIGS. 7 and 8.

The present embodiment has the above-mentioned structure, and its operation will be described below with reference to the flowchart of FIG.

In FIG. 9, the microcomputer 82 first takes in the detection output of the water temperature sensor 78, reads the engine water temperature (step 100), and proceeds to the processing of step 102. In step 102, the output signal from the starter 90 is monitored, and it is determined whether or not the engine is starting. In this step, the starter signal when the starter 90 is turned on is supplied to the microcomputer 82, and when it is determined that the start is made, the process proceeds to step 104.

In step 104, the detection output of the pickup 62 is fetched and it is determined whether the engine speed NE is 200 rpm or less. If YES is determined in this step, the process proceeds to step 106 and FTDuty = 0%
And perform the process. That is, the engine speed NE is 200
When the speed is equal to or lower than rpm, a control signal having a duty ratio of 0% is output to the solenoid valve 48, and a process for setting the fuel injection timing to the most advanced angle is performed.

On the other hand, if NO at step 104, the routine proceeds to step 108, where it is determined whether the engine speed NE is 500 rpm or less. If YES at this step, the routine proceeds to step 110. That is, when the engine speed NE is between 200 rpm and 500 rpm, the duty ratio determined by the engine speed NE and the engine coolant temperature is calculated. The following equation (1) is used in the calculation of the duty ratio.

FTDuty = 36 × NE-TDthw (1) Here, NE represents the engine speed detected by the pickup 62, and TDthw represents a numerical value obtained from the map data shown in FIG. 7. That is, step 110
In the above, since the engine speed NE is higher than that at the time of step 106, the control signal of the duty ratio for advancing the phase retarded from the maximum advance is output to the solenoid valve 48.

If NO in step 108, the process proceeds to step 112, where the engine speed NE is 1000 rpm.
It is determined whether or not the following. Then, if YES is determined in this step and the engine speed NE is 1000 rpm or less, the process proceeds to step 114. Step 11
At 4, the process of calculating FTDuty shown in FIG. 8 is performed. That is, in this step, FTDuty shown in FIG. 8 is obtained from the detection output of the water temperature sensor 78, and a process of outputting a control signal of the duty ratio for retarding the angle to that in step 110 to the control valve 48 is performed. .

On the other hand, the ON signal is no longer output from the starter 90,
When NO is determined in step 102 and step 1
If NO is determined in step 12, both steps 1
Move to processing of 16. In this step, the target ignition timing determined by the engine speed NE and the engine load (accelerator opening by the detection output of the accelerator sensor 74) is compared with the actual ignition timing by the detection output of the ignition sensor 72, and the actual ignition timing is set as the target. A control signal of a duty ratio for matching the ignition timing is output to the solenoid valve 48, and ignition timing feedback control for injecting fuel at a timing for matching the actual ignition timing with the target ignition timing is performed. By this processing, all processing in this routine is completed. That is, in this embodiment, the engine speed NE is equal to the high speed set speed (1
(000 rpm), the engine can sufficiently rotate without the aid of the starter 90, so ignition timing feedback control is performed.

〔The invention's effect〕

As described above, according to the present invention, when the engine is started, the ignition timing feedback control is not executed, and the fuel is injected at the timing determined from the engine speed and the engine cooling water temperature, so that the ignition phenomenon is unstable. Even at the time of starting, the fuel is injected at the optimum timing, and the excellent effect that the startability can be improved is obtained.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining the present invention, and FIG.
FIG. 3 is a block diagram of an embodiment to which the present invention is applied, and FIG.
FIG. 4 is a schematic diagram of the configuration of the signal rotor shown in FIG. 4, FIG. 4 is a schematic diagram of a pulse signal output from the pickup accompanying the rotation of the signal rotor shown in FIG. 3, and FIG. FIG. 6 is a diagram for explaining the configuration of the microcomputer, FIG. 7 is a characteristic diagram of the timer duty water temperature correction term according to the present invention, FIG. 8 is a characteristic diagram of FTDuty according to the present invention, and FIG. 3 is a flowchart for explaining the operation of the device shown in FIG. 48 ... Electromagnetic valve, 56 ... Timer piston, 62, 86 ... Pickup, 68 ... Fuel injection valve, 72 ... Ignition timing sensor, 74 ... Accelerator sensor, 78 ... Water temperature sensor, 82 ... Microcomputer, 90 ... Starter.

Claims (1)

[Claims] Claims: 1. Ignition timing feedback control is used, in which a target ignition timing determined from an engine speed and an engine load is compared with an actual ignition timing, and fuel is transported at a timing at which the actual ignition timing coincides with the target ignition timing. In the method for controlling the fuel injection timing of a diesel engine, the fuel injection timing control method does not execute the ignition timing feedback control at the time of engine start, but injects fuel at a timing determined from the engine speed and the engine cooling water temperature. Timing control method.