JPS61123723A - Fuel injection device for diesel engine - Google Patents

Abstract

PURPOSE:To check a noise while bringing advantages in a variable valve opening pressure type injection nozzle into the maximum, by installing a device for reducing a timing advance value of a timer mechanism which controls fuel injection timing for its spark advance in time of engine's low speed, low load running. CONSTITUTION:A fuel injection pump 10 applies pressure to fuel inside a pressure chamber 28 in accordance with motion of a plunger 16 being free of rotation and axial slide motion, and feeds an injection nozzle 38 of each cylinder via a distributing port 30 and a delivery valve 34. Control of injection timing for this injection pump 10 is performed by a timer mechanism 48 which varies phase of a cam plate 14 to a roller 18 according to motion of a timer piston 52 via a slide pin 50 whereby it controls the injection timing. At the above- mentioned, the high pressure side 56 of the time position 52 os the time mechansim 48 is connected to a spring chamber 58 at the low pressure side through a relief passage 60, and a solenoid valve 62 is interposingly installed in the said passage 60, thus a spark advance reducing device is constituted.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel injection device for a diesel engine.

[Prior art]

In a diesel engine, fuel is pumped by a fuel injection pump with fuel injection timing and injection amount depending on engine operating conditions, and is injected from a fuel injection nozzle into a combustion chamber or a pre-combustion chamber.

The opening pressure of the fuel injection nozzle is generally adjusted to a preset value by adjusting the center load of a pressure spring that biases the nozzle needle with an adjustment screw.

When the valve opening pressure is set high, the penetrating force of the fuel spray increases, so the amount of smoke generated at high speed and high load is reduced, and high output is obtained. Particularly in a supercharged diesel engine, the in-cylinder pressure is high, so it is necessary to set the valve opening pressure high to avoid blowback into the injection nozzle.

On the other hand, during low-speed, low-load operation such as idling, when the valve opening pressure is high, the penetrating force of the fuel spray is large, so the fuel adheres to the combustion chamber wall in liquid form and leaves unburned residue, so that tends to increase. This tendency is particularly noticeable in swirl chamber type diesel engines. Also, the noise during idling (idle knock) is loud. Therefore, it is desirable to set the valve opening pressure low.

Therefore, in the prior art, variable valve opening pressure injection nozzles have been proposed that are capable of changing valve opening pressure according to engine operating conditions. For example, JP-A-57-1735
In the injection nozzle described in Japanese Patent No. 57, the valve opening pressure is made variable by increasing or decreasing the cent load of the pressure spring using a cam mechanism. Also, a method is commonly used in which a solenoid actuator is used to change the cent load of a pressure spring, and the valve opening pressure is changed by controlling energization to the solenoid.

[Problem to be solved]

However, in an injection device equipped with this type of variable opening pressure injection nozzle, when the injection nozzle opening pressure is reduced, the injection nozzle opens earlier in the injection pump plunger's pumping stroke, and the actual injection The time will be earlier. As a result, the noise cannot be sufficiently reduced, or the noise increases.

[Purpose of the invention]

The present invention was devised in view of the above-mentioned problems, and an object of the present invention is to provide a fuel injection device that can suppress noise while maximizing the advantages of a variable valve opening pressure type injection nozzle. That is.

[Means for solving problems]

The present invention provides a fuel injection device including a fuel injection pump equipped with a timer mechanism for advance control of fuel injection timing, and a variable valve opening pressure fuel injection nozzle operatively connected to the fuel injection pump. The invention is characterized in that means is provided for reducing the amount of advance of the timer mechanism during low-speed, low-load operation of the engine.

〔Example〕

FIG. 1 shows the overall arrangement of the fuel injection device of the present invention. The fuel injection pump IO is a slightly modified version of a commercially available distribution type injection pump, and is the same as the conventional one except for a timer mechanism which will be described later. Since this type of injection pump is well known, its construction and operation will only be briefly described. A drive shaft 12 that rotates in synchronization with the engine crankshaft is force-knob-ringed to a cam plate 14 and a plunger 16, and when the cam face of the cam plate 14 rides on a roller 18 supported by a roller ring, the plunger 16 moves into the cylinder 20. It is designed so that it can perform a stroke and rotate in synchronization with the drive shaft 12. The fuel is supplied by a Hoene-type feed pump 22 that is rotated by the drive shaft 12 (for convenience, it is shown rotated by 90 degrees in FIG. 1, but in reality, this feed pump rotates around the drive shaft 12). It is pressurized, enters the inner chamber 25 of the pump housing 24, is sucked from there into the pressurizing chamber 28 through the suction port 26, is pressurized by the plunger 16, and is distributed from the distribution port 30 to the distribution passage 32 of each cylinder, It is supplied to the injection nozzle of each cylinder via the delivery valve 34 and the vibrator 36. The injection amount is controlled by operating a spill control lever 44 using a solenoid actuator 42 controlled by a control circuit 40 to determine the position of the spill ring 46.

On the other hand, control of the injection timing is performed by a timer mechanism 48, and by angularly displacing a slide pin 50 connected to a roller ring carrying a roller 18 by a timer piston 52, the cam plate 14 is shifted in phase with respect to one column 16. to advance or retard the injection timing (for convenience, the timer piston 52 is shown as 9 in FIG. 1).
Since the timer piston 52 is configured so that the fuel pressure in the inner chamber 25 acts on it, the injection timing is basically determined by the discharge pressure of the feed pump 22, i.e. The rotation speed of the drive shaft 12 is controlled according to the rotation speed of the drive shaft 12, and is supplementarily corrected by an advance angle reduction means, which will be described later.The rotation speed of the drive shaft 12 is detected by a rotation speed sensor 54, and The signal is input to control circuit 40.

The above configuration and operation are substantially the same as those of conventional distribution injection pumps.

Now, according to the invention, the timer mechanism 4 of the injection pump IO
8 is a combination of advance angle amount reducing means.

This means includes a solenoid valve 62 (hereinafter referred to as a timer control valve) provided in a swing leaf passage 60 that connects the high pressure 56 of the timer piston 52 and the low pressure side spring chamber 58. This timer control HALPRO 2 reduces the amount of advance of the timer mechanism 48 by relieving fuel from high overwhelm 56 to low overwhelm 58 (which is connected to the suction side of the feed pump 22) when the valve is opened. It is something that makes you The timer control HAL PRO 2 is electronically controlled by a control circuit 40. timer piston 52
The displacement of the slide bin 50 and the angular position of the slide bin 50 are determined by a timer position sensor 6 connected to the timer piston 52.
4, and its output signal is input to the control circuit 40. The control circuit 40 receives a signal from, for example, an 0N10FF type accelerator switch 66 connected to an accelerator pedal. The accelerator switch 66 is, for example,
It can be configured so that it is turned on when the load is higher than a relatively low set load and turned off when it is lower than that.

FIG. 2 is a block diagram of the control circuit 40, in which 68 is an A/D converter or counter that converts the analog output from the rotational speed sensor 54 into a digital value, 70 is a microprocessor, 72 is a memory, and 74 is a D/D converter. A converter, 76
78 is a subtracter that subtracts the output value of the timer position sensor 64 from the output value of the D/A controller 4, and 78 is a driver that amplifies the output of the subtracter 76 and outputs it to the timer control HAL PRO 2.

Next, to explain the operation, the microprocessor 7
0 detects that the engine speed and load are respectively below set values, and sends a signal corresponding to the injection timing to the converter 74. The output from the timer position sensor 64 is input to the subtracter 76 as a feed bank signal. Subtractor 76 outputs the difference between the output from converter 74 and the output from sensor 64, and this output is amplified by driver 78 and sent to timer control valve 62 to open it (timer control When it is desired to control the duty ratio of the opening degree of the pulp 62, the dry huff 8 is configured with a pulse width modulation device, and the subtracter 7
The analog output from 6 can be converted into a pulse signal with a required duty ratio and supplied to the timer control valve 62. ). Therefore, when the engine is running at low speed and under low load, the fuel acting on the high overwhelm 56 of the timer piston 52 is relieved through the relief passage 60 to the low overwhelm 58 according to the opening degree of the timer control pulp 62, and the timer mechanism 48 The amount of advance angle is corrected to the retard side.

The graph in Figure 3 shows the injection rate curve of the injection device of the present invention in comparison with that of a conventional injection device. shows. As shown by curve B, when the opening pressure of the injection nozzle is simply lowered, the injection timing is advanced. Curve C shows the injection rate curve at low speed and low load in the device of the present invention, and the injection timing can be delayed to the same extent as curve A.

FIG. 4 shows another embodiment, in which a solenoid actuator 80 is used to correct the injection timing. When the solenoid 82 is energized, the plunger 84 is attracted to the right in the figure, increasing the cent load on the timer spring 86, thereby increasing the rightward biasing force on the timer piston 52 and reducing the amount of advance. In this embodiment, the timer position sensor 64 is not required.

FIG. 5 shows an embodiment using negative pressure as the power source. Since the set load of the timer spring 86 is now corrected by the negative pressure actuator 88, the working negative pressure of the actuator 88 is controlled by controlling the negative pressure of an accumulator 92 connected to a vacuum pump 90 for a brake booster, for example, by a solenoid valve 94. obtain.

Alternatively, as shown in FIG. 6, a motor 96 and gearbox 98 may be used to articulate the cent load of the timer spring 86.

In the above embodiment, it is assumed that the opening pressure of the injection nozzle 38 is electromagnetically increased or decreased.
An injection nozzle of the type in which the valve opening pressure can be varied by a cam mechanism as described in Japanese Patent No. 557 may also be used.

It is also possible to connect a water temperature sensor to the control circuit 40 shown in FIGS. 1 and 2 to correct the injection timing according to the cooling water temperature. Furthermore, the control subcircuit 40 can be constructed using hardwired logic instead of the microprocessor 70.

〔Effect of the invention〕

According to the present invention, since the advance amount of the timer mechanism is reduced at the same time as the valve opening pressure of the variable valve opening pressure type injection nozzle is reduced, it is possible to prevent the actual injection timing of the injection nozzle from advancing. Therefore, fuel injection can be started at the optimal rank angle even when the valve opening pressure decreases, so noise such as idle knock can be effectively suppressed while enjoying the maximum effect of the variable valve opening pressure type injection nozzle. This has a remarkable effect.

[Brief explanation of drawings]

FIG. 1 is a schematic overall view of a fuel injection device according to a first embodiment of the present invention, FIG. 2 is a block diagram of a control circuit, FIG. 3 is an injection rate curve of an injection nozzle, and FIGS. FIG. 6 is a sectional view of a part of another embodiment. 10...Fuel injection pump, 38...Variable valve opening pressure type injection nozzle, 40...Control circuit, 48...Timer mechanism,
50... Slide pin, 52... Timer piston, 60... Relief passage, 62... Timer control valve, 64... Timer position sensor, 40, 60, 62...
Advance angle reduction means.

Claims (1)

[Scope of Claims] A fuel injection pump equipped with a timer mechanism for advance control of fuel injection timing, and a variable valve opening pressure fuel injection nozzle operatively connected to the fuel injection pump. What is claimed is: 1. A fuel injection device for a diesel engine, characterized in that the fuel injection device is provided with means for reducing the amount of advance of the timer mechanism during low-speed, low-load operation of the engine.