JPS6053777B2 - Injection timing control method for distributed fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection timing control method for controlling injection timing by electrically controlling the pressure in a timer piston high pressure chamber of a distribution type fuel injection pump.

In recent years, there have been social demands for stricter exhaust gas regulations and the development of vehicles with better fuel efficiency for automobiles, and in order to achieve these demands, highly accurate injection timing control has become necessary.

As one control method, for example, a detection signal from an injection timing detector is used as a feedback signal to open and close a pressure regulating valve that adjusts the pressure in the timer piston high pressure chamber according to the error value between the injection timing target value and the injection timing detection value. In the control method that determines the time ratio, the flow rate of fuel flowing out through the pressure regulating valve changes within a unit time due to changes in engine operating conditions, which increases pressure pulsations in the timer piston high pressure chamber and deteriorates control accuracy. There's a problem. In order to solve such problems, the present invention opens and closes a pressure regulating valve that adjusts the pressure in the timer piston high pressure chamber according to the error value between the target injection timing value determined by the engine operating state and the actual injection timing. By changing the time ratio and further changing the rate of change in the opening/closing time ratio with respect to the error value according to the signal representing the engine speed, pressure pulsations in the timer piston high pressure chamber are suppressed and control accuracy of injection timing is improved. It is an object of the present invention to provide a method for controlling injection timing of a distribution type fuel injection pump. The present invention will be explained below with reference to embodiments shown in the drawings.

FIG. 1 shows the parts of the distribution injection pump that are related to the present invention, and the others are omitted. The distribution injection pump is driven by a pump camshaft, and fuel is sucked up from the fuel tank 1 and supplied to the pump internal pressure chamber 6.
The position of the timer piston 4 is determined by the differential pressure between the high pressure chamber B and the low pressure chamber C and the load of the timer spring 5, and the roller ring 2 is rotated via the pin 3 to determine the injection timing. The pump internal pressure chamber 6 and the high pressure chamber B communicate with the low pressure side via a throttle 12 and an electric pressure regulating valve 13. As shown in FIG. 2, the control device 14 includes a central processing unit (C
PU) 141, memory (ROM) 142, memory (RA
M) 143 is the main element.

Built-in microcomputer and other waveform shaping circuit 1
44, an A/D converter 145, at least one rotational speed sensor 20 for detecting the operating state of the engine, an accelerator position sensor 26 for detecting the accelerator position, and a water temperature sensor (or injection pump) for detecting the warm-up state of the engine. 22, an intake pressure sensor 22 that detects the amount of air taken into the engine, an intake air temperature sensor 23, and a spill ring position sensor 21 that indirectly detects the injection amount. Calculate the target injection timing that is most suitable for the engine operating condition. The error value between this target injection timing and the output value of the timer piston position sensor 15, which serves as an injection timing detector that detects the actual injection timing, is detected, and the pressure regulating valve 13 is opened according to this error value. By changing the valve time and controlling the pressure in the timer piston high pressure chamber B, the timer piston 4 is moved and the injection timing is feedback-controlled. In this feedback control, the opening/closing time ratio (duty As mentioned above, when the fuel flow rate is determined, the flow rate of fuel flowing out through the pressure regulating valve 13 within a unit time changes even with the same duty ratio due to changes in the operating state of the engine.
Pressure pulsations in the timer piston high pressure chamber B become large and control accuracy deteriorates.

Below, we will use Figure 3 to illustrate this situation. This section explains how to solve this problem. Figure 3 shows the pump internal pressure PA
When the engine speed N is low, the overflow valve 8 is closed and the pressure PA in the pump internal pressure chamber 6 supplied by the oil feed pump 7 rises as shown in Figure 3a.
When the rotational speed further increases and the pressure PA reaches the opening pressure of the overflow valve 8, even if the rotational speed N increases thereafter, the pressure PA does not increase and remains constant.

Note that FIG. 3C shows the characteristics of the pressure PA when the pressure regulating valve 13 is fully open, and FIG. 3B shows the timer piston high pressure chamber pressure Pc. Figure 4 shows the error in the actual timer piston position relative to the target position of the timer piston 4 and the duty ratio correction amount ΔD (frequency is fixed) at that time.As the error becomes larger (advanced angle side), the duty ratio is corrected. This shows the characteristic that the amount increases. A case will be described in which the control shown in FIG. 4 is performed at points A and B in FIG. 3. The pressure at point A is P
. 、． P1 at point A'', P2 at point B, P3 at point B''
shall be. The control period T of the pressure regulating valve is constant and is 20W1.
, sec (frequency is 50 Hz). Unit hour when pressure regulating valve 13 is opened during control at point A. The amount of fuel flowing out from the timer piston high pressure chamber B during this period is
1, and the amount flowing into the high pressure chamber B is 1.

From equations (1) and (2), the pressure fluctuation in the timer piston high pressure chamber is as follows.

Similarly, in the case of d - hi ◆v
Easy-t●Exploratoryt ●4V! It becomes 1.

In addition, P2>PO. ．． Since Pl-PO>P2- et al., ΔPTB>ΔPTA. In other words, when controlling at points A and B, an error occurs due to disturbance, and if the duty ratio of the pressure regulating valve 13 is determined based on this error (the duty ratio at points A and B is the same), the What is the pressure fluctuation compared to point A? ? Y? It becomes double. Therefore, as shown in FIG. 4, the duty ratio correction amount characteristic for the timer piston position error is changed depending on the rotation speed. For example, when the rotation speed is NA, the slope (gain) G is set to GA=j-. (NB (N8)
T$O-T$0200NA), the slope is GB=L1-11, and G8ΔP=
If determined as shown in GA×-”, point A and point B ΔP
Pressure fluctuations (responsiveness) at TB can be made the same.

By determining the gain G in this manner according to the engine speed N, it is possible to make the responsiveness the same in the entire range and to suppress pressure fluctuations. This gain G is, for example, GccK
It can be obtained by calculation such as rN (K3 is a constant), GCC buttock (K4 is a constant), or depending on the rotation speed in advance,
It is obtained by mapping G (GA..GB). Figures 5, 6, and 7 show the timer piston position (injection timing) with respect to the rotation speed N when the gain G is changed.
Figure 5 shows G=a for a relatively large constant a, and Figure 6 shows G=a for a relatively small constant b.
b1 FIG. 7 shows the characteristics when G=g×N+a.

Here, a>b at NO, and NO is the rotation speed constant on the high rotation side.

Note that the target value of the injection timing is shown by a dotted line, and the injection timing characteristic is shown by a solid line. When G is set to a large value in Fig. 5, the timer piston position is stable on the low rotation side, but the flow rate flowing through the pressure regulating valve 13 on the high rotation side is at a low rotation speed relative to the unit valve opening time. Because it is larger than the side,
The injection timing (timer piston position) pulsates. In addition, when G is set to a small value in Figure 6, it becomes stable at high rotation speeds, but since the flow rate per unit valve opening time is small at low rotation speeds, the error with respect to the target injection timing becomes large. . In Fig. 7, the G on the low rotation side is large and the G on the high rotation side is small, which compensates for the shortcomings in Figs. 5 and 6 and stabilizes the injection timing accurately over the entire range of rotation speed changes. be able to. . Furthermore, instead of changing the gain G using the rotational speed as a parameter, similar control is possible by changing the gain G according to the characteristics of the internal pressure of the pump, which represents the rotational speed. FIG. 8 is a schematic flowchart when the above-described injection timing control is performed by the control device shown in FIG. 2.

In step 101, the engine rotation speed is calculated by inputting the signal from the rotation speed sensor, and in step 102,
A target injection timing TA (target timer piston position) is calculated according to the above-mentioned operating state signal. Step 103
Then, the current timer piston position is determined from the output value of the timer piston position sensor, and in step 104, the error T between the target timer piston position determined in step 102 and the current timer piston position is determined. Calculate RR=TP-TA. In step 105, the rotation speed obtained in step 101 is used as a parameter, and the gradient G(a)N) of the duty ratio correction amount straight line is calculated according to the rotation speed by map interpolation. The duty ratio correction amount is determined from the error Tadir and the value of G obtained in step 105, and the duty ratio of the pressure regulating valve 13 is calculated. Then, in step 107, the duty ratio signal obtained in step 106 is output to the pressure regulating valve 13, and the pressure in the timer piston high pressure chamber B is controlled to control the injection timing. Thereafter, the processes from steps 101 to 107 are repeated for each pressure regulating valve control cycle. In the above embodiment, the duty ratio correction amount is first calculated to determine the duty ratio of the pressure regulating valve, but it is also possible to calculate the linear duty ratio according to the error of the timer piston position from the target position. good.

As described above, the present invention changes the opening/closing time ratio of the pressure regulating valve that adjusts the pressure in the timer piston high pressure chamber according to the error value from the target value of the injection timing, and further changes the opening/closing time ratio with respect to the error value. Since the injection timing is controlled by changing the ratio in accordance with the signal representing the engine speed, there is an excellent effect that pressure pulsations in the timer piston high pressure chamber can be suppressed and the injection timing can be controlled with high precision.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram showing an injection timing control section of a distribution type fuel injection pump to which the method of the present invention is applied, FIG. 2 is a block configuration diagram of a control device including the microcomputer shown in FIG. 1, and FIG. is a characteristic diagram showing the relationship between the injection pump internal pressure or the timer piston high pressure chamber pressure with respect to the engine rotation speed, and Fig. 4 shows the relationship between the duty ratio correction amount and the error between the actual timer piston position and the target timer piston position. 7 is a characteristic diagram showing the relationship between the timer piston position and the rotational speed, and FIG. 8 is a flowchart showing the arithmetic processing procedure in the control device shown in FIG. 2. 4...Timer piston, 6...Pump internal pressure chamber, 13...Pressure regulating valve, 14...
-Control device, 15...Timer piston position sensor, 20...Rotation speed sensor, B...Timer piston high pressure chamber.

Claims (1)

[Claims] 1. In an injection timing control method in which the pressure in the timer piston high pressure chamber of a distribution type fuel injection pump is electrically controlled by a pressure regulating valve to control the fuel injection timing, the operating state of the engine is detected. Calculate an optimal injection timing target value, change the opening/closing time ratio of the pressure regulating valve according to the error value between this target value and the actual injection timing, and calculate the rate of change of this opening/closing time ratio with respect to the error value. An injection timing control method for a distribution type fuel injection pump, characterized in that the injection timing is controlled by changing it in accordance with a signal representing the rotational speed of the engine. 2. The injection timing control method for a distribution type fuel injection pump according to claim 1, wherein the signal representing the rotational speed of the engine is a pressure value signal of an internal pressure chamber of the injection pump.