JPS638298B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection timing control device for a diesel engine.

Retarding the fuel injection timing is an effective means of reducing harmful components emitted by diesel engines, especially NOx. However, in a normal diesel engine, the fuel injection timing is advanced in response to the engine speed in order to reduce the fuel consumption rate. Particularly in the case of a distribution type fuel pump, the feed pump and pressure regulating valve built into the pump generate oil pressure according to the engine speed, and by adding that oil pressure to the injection timing adjustment (timer) piston, the engine speed is increased. The injection timing is advanced according to the number of fuels. However, such injection pumps do not have a function to adjust the injection timing in accordance with other engine operating conditions, which poses an obstacle to purifying exhaust gas and the like.

The purpose of the present invention is to precisely control fuel injection timing in accordance with engine operating conditions in a diesel engine without being particularly affected by fluctuations in fuel feed pressure, thereby reducing fuel consumption and reducing exhaust gas. An object of the present invention is to provide a fuel injection timing control device that achieves purification.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a fuel injection timing control device according to the present invention. The distribution type fuel injection pump 1 moves the timer piston 3 to the left against the timer spring 4 by the fuel feed pressure applied to the pressurizing chamber 7. By displacing the roller ring 6 via the timer slide pin 2, the roller 5 incorporated in the roller ring 6 is displaced, and the roller 5 and face cam (not shown) come into contact and rotate. Plunger (not shown)
The pump is driven to determine fuel pumping and fuel injection timing. FIG. 1 shows a state in which the timer piston 3 has moved to the farthest left (most advanced). This condition is achieved by using a timer spring 4 that is relatively weak relative to the fuel feed pressure. The operation of the injection timing control device is to reduce the fuel feed pressure using the on-off valve 9 and retard the injection timing (suppressing the advancement of the injection timing) from the advance state to the appropriate injection timing according to the operating conditions. It is to be. In the figure, a fuel line 8 is a line through which fuel discharged from an on-off valve 9 passes, and is connected to a return fuel line that returns fuel to a fuel tank (not shown).

To set an appropriate injection timing according to the operating conditions, an optimal injection timing map determined by the rotation speed and load is programmed in the control calculation section 11 in advance, and the load detection signal 12 and engine rotation signal 13 are inputted. A rotation-synchronized pressure detector 1 detects fuel feed pressure using an electric signal (reference signal) corresponding to the optimal injection timing determined by the above and an engine rotation signal 13 or a pulse signal 14 that is an integral multiple thereof as a trigger.
The output signal 15 of 0 is compared and an opening/closing signal is sent to the opening/closing valve 9.

FIG. 2 shows an example of a control block for synchronizing the operating cycle of the on-off valve 9 with the engine speed. The signal 17 is obtained from the optimal injection timing map based on the rotational speed and load, for example. This is a reference signal indicating a reference injection timing according to operating conditions. This reference signal 17 and the pressure signal 15 from the rotation synchronized pressure detector 10 are connected to a comparator 18, which compares the reference value and the pressure level. The output after comparator 18 is
The low/high level signals are input to the adder circuit 26 via the proportional constant setter 19. On the other hand, the operating cycle and opening time of the on-off valve 9 are determined as follows. The engine rotation signal 13 is input to a waveform shaping circuit 20 . This engine rotation signal 13 is obtained, for example, from an electromagnetic pickup provided on the crank pulley. A pulse signal input to the waveform shaping circuit 20 that determines the operating period is frequency-divided by a frequency dividing circuit 21 and connected to a monostable circuit 22 . The pulse signal is then divided into two parts, one is sent to the adding circuit 26 via the integrating circuit 23, and the other is sent to the integrating circuit 2 via the integral constant setting device 24 to determine the valve opening time width.
Connected to 5. This output is input to the adder circuit 26 together with the output from the proportional constant setter 19 described above. Here, the operating cycle and valve opening time width are determined according to the engine rotation, and the drive circuit 28 operates the on-off valve 9 in synchronization with the engine rotation via the amplifier circuit 27.

Figure 3 shows the pressurizing chamber 7 of the hydraulic timer in the upper stage.
(Fig. 1), the middle part shows the engine rotation signal 13, and the bottom part shows the operating status of the on-off valve 9. The fuel is forced into the injection pump by the feed pump, and the housing of the injection pump is in communication with the pressurizing chamber 7 of the hydraulic timer.
Pressure fluctuations in the pressurizing chamber 7 are synchronized with the engine speed. That is, in a four-cylinder diesel engine, if the engine rotation pulse 13 appears every 180 degrees as shown in the figure, pressure fluctuations occur twice every time the engine rotation pulse appears.

In the present invention, as described above, the on-off valve 9 (FIG. 1)
The operating cycle and engine speed are synchronized. For example, as shown in the lower part of FIG. 3, the operating cycle of the on-off valve 9 is twice the engine rotation pulse 13 (180° pulse). In this way, the operating period of the on-off valve and the engine rotation period are synchronized so that they are integral multiples of each other. In FIG. 3, the opening time of the on-off valve 9 for each pulse is shown to be constant, but control may be performed to increase or decrease the opening time for each pulse.

According to the present invention, by using a configuration in which the operating cycle of the on-off valve (pressure reducing valve) is synchronized with the engine rotation cycle, the fuel injection timing is determined in synchronization with the movement of the plunger that discharges the fuel. It is now possible to reduce pressure fluctuations in the fuel feed pressure without destroying the synchronization relationship with the plunger, and by controlling the injection timing precisely and setting the operating cycle to an integral multiple of the rotation cycle. Does not impair responsiveness. In addition, by using a rotation-synchronized pressure or displacement detector, it is possible to always detect a certain period of the above-mentioned fluctuations, eliminating the need for control based on erroneous values due to fluctuations, and making it possible to control the injection timing. Can be controlled more precisely.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a distribution type fuel injection pump, schematically showing a fuel injection timing control device of the present invention, and FIG. 2 is a diagram showing an embodiment of a control block in the present invention. FIG. 3 is a diagram showing the relationship among fluctuations in fuel feed pressure of the hydraulic timer section, rotation pulses, and operating cycles of the on-off valve. DESCRIPTION OF SYMBOLS 1... Distribution type fuel injection pump, 3... Timer piston, 9... Pressure reduction opening/closing valve, 11... Control block.

Claims (1)

[Claims] 1. In a device that moves a timer piston in accordance with the fuel feed pressure of a diesel engine, advances the injection timing by moving the timer piston, and controls the injection timing by reducing the fuel feed pressure with an on-off valve. , a pressure detection means for detecting the feed pressure in synchronization with the engine rotation speed, a reference signal setting means for presetting a signal indicating the optimum injection timing according to the engine operating condition, and a signal output from the reference signal setting means. and an actuation signal output means for outputting an actuation signal synchronized with engine speed to the on-off valve based on the difference between a reference signal and a pressure signal output from the pressure detection means. .