JPS59171803A - Detecting device for fuel injection timing for internal combustion engine - Google Patents

Abstract

PURPOSE:To control a timing of injection accurately by providing a means to detect a solenoid current of an electrohydraulic valve and a current variation detecting means to detect the discontinuous variation of a rise waveform of the solenoid current which occurs at the time of the suction of the valve. CONSTITUTION:CPU7 delivers an injection signal to a power transistor Tr2 through a driver 5. Thereby Tr2 is turned ON, and thus a current starts to flow from a power source to a series circuit of a solenoid 1, Tr2 and a resistor 3, while counting by a counter 9 is started simultaneously. A voltage at a point B is read repeatedly in CPU7 through an A/D converter 4 and an I/O port 10 for a prescribed period after the current starts to flow. Then the values of the current obtained at the preceding and present times are compared with each other to detect a time at which the value has turned from a decrease into an increase, and the value of a time (t) thus detected is stored in RAM8. When the solenoid 1 is electrified subsequently, said detected value is used for correcting the timing of delivery of the injection signal by the amount of variation of the time (t), and thus the time of injection is controlled accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection timing detection device for an internal combustion engine having an electronic hydraulic fuel injection valve side @nucleation function.

In internal combustion engines that have an electrohydraulic valve mechanism in the injection valve body and perform electronic hydraulic fuel injection valve control that uses valve adsorption as a trigger to start injection, normally, current begins to flow to the solenoid of the electrohydraulic valve. A certain period of time after that is considered to be the injection start time. In other words, when the current begins to flow, the attraction force of the solenoid is almost zero and the valve is still opening. Therefore, it is necessary to confirm in advance through experiments, etc., the delay until the valve actually operates. Control is performed with the time when this delay time has elapsed since the time when the flow started being set as the injection start time.

However, the delay time changes depending on various conditions, for example, when the solenoid heats up, the resistance increases and the current rises and falls is delayed, and the steady current value also changes, increasing the delay time. Therefore, if the delay time is treated as a constant, there is a problem that the injection timing cannot be controlled accurately. The purpose of this device is to provide a fuel injection timing detection device for internal combustion observation, which includes a current detection means for detecting the solenoid current of an electrohydraulic valve, and a discontinuity in the rising waveform of the solenoid current that occurs when the valve is attracted. The present invention is characterized by comprising a current change detection means for detecting a change in the solenoid current, and an arithmetic means for feeding back to the control circuit the time when the discontinuous change in the solenoid current is detected as the injection start time.

The present invention will be described in detail below with reference to FIG. 1, which shows an example of changes in solenoid current. In the figure t. is the time when the current begins to flow through the solenoid υ, the current begins to increase rapidly, and the magnetomotive force of the solenoid generates magnetic flux in the movable iron core, which interacts with the magnetizing force due to the magnetomotive force of the solenoid to create an attractive force. occurs. When the iron core is attracted and begins to move, the rate of increase in current decreases due to the back electromotive force caused by the movement, and the current temporarily decreases in the latter half of the stroke. When the movable iron core finishes moving, the current increases rapidly again. Point A in the figure is the change point where the current reverses from decreasing to increasing, and the movement of the movable iron core is completed at this time 11. Therefore, by detecting such a sudden change in the solenoid current, it is possible to know exactly when the valve is suctioning, and the present invention detects the presence or absence of the solenoid current that occurs when the valve is suctioned. Continuous: Leopard change detected, time t. The difference t between the temperature and temperature tl is used for control, and the actual valve adsorption timing is directly detected.
y: Even if the operating time t of the valve changes due to changes, etc., it is possible to accurately control the injection timing.

Next, the present invention will be specifically explained with reference to illustrated embodiments.

In Figure 2, (1) is the solenoid of the electrohydraulic valve, (
2) A power transistor used as a switch element, (3) a current detection resistor, (4) an A/D converter, (5) a driver that controls the power transistor (2), (6) ha microcomputer, (7) i
d CPU.

(8) is RAM, (91 is counter, fIO+Id
It is an I10 port.

To explain the operation with reference to the control flowchart in Fig. 3, a typical value is set as the initial value of t, and the time when injection should truly start is set as T, and at the timing of T-t, the CPU t7+ An injection signal is sent to the power transistor (2) via the driver (5). At this point, the power transistor (2) is turned on, and current begins to flow from the power source to the series circuit of the solenoid (1), power transistor m2, and resistor (3), and at the same time, the counter (9) starts counting. Since the current value can be determined by the terminal voltage of the resistor (3), that is, the voltage at point B, the voltage at point B is input to the A/D converter (4) for a certain period of time after the current starts flowing. ) through CP
U (7) is repeatedly read, and the read values of the previous time and this time are compared to detect the time when the decrease changes to an increase, and the kakunt value at that time, that is, the detected value at the time t when it was actually detected, is calculated. Store in RAM f8).

Then, when the solenoid (1) is energized next time, this detection target is used to correct the timing of outputting the injection signal by the amount of time 12Xit, thereby accurately controlling injection synchronization. This timing correction is carried out at appropriate intervals by means such as an incremental timer or an interrupt.

Detection of point A in FIG. 1 can also be carried out without using the method described in -A. For example, a differential calculator and a comparator are used instead of the A/D converter (4) to convert the pulse waveform into After conversion, it is also possible to add to the CPU [7+, i). FIG. 4 shows the waveform in this case. Waveform C obtained by differentiating the current waveform in FIG. Pulse wave E
This is sent to the CPU (7) as an injection timing detection signal.

As described below, the present invention detects the actual valve suction timing by discontinuous changes in the solenoid current, and by checking this detection result, it is possible to check the heat generation of the solenoid F and the ambient temperature. The fuel injection timing can be accurately controlled by compensating for fluctuations in the valve operation timing due to changes in the fuel injection rate and operating the valve at a predetermined timing.

[Brief explanation of the drawing]

Fig. 1451 is a current waveform diagram explaining the principle of the present invention, Fig. 2 is a block diagram of 81 essential points of the first embodiment, Fig. 3 is a flowchart of the same system 1, and Fig. 4 is a flow chart of the same system. il) Solenoid, (2j...power transistor, (3)...current detection resistor, (6)...microcomputer, (7)...CPU, f8i loss u(
,,f9)・Kakunta. Special liver applicant Yanmar Tiesel Co., Ltd. Tomo Yono Patent attorney Shino 1) Jiichi-t→

Claims (1)

[Claims] (1) In an internal combustion engine that has an electrohydraulic valve mechanism in the injection valve body and performs sideward fuel injection in a system that uses valve adsorption as a trigger to start injection, a current detection means for detecting the solenoid current of the electrohydraulic valve; , a current change detection means for detecting a discontinuous change in the rising waveform of the solenoid current that occurs during valve adsorption, and a calculation for feeding puncture into the control circuit by setting the time when the discontinuous change in the solenoid current is detected as the injection start time. A fuel injection timing detection device for an internal combustion engine, comprising: means.