JPS58204938A - Controller of fuel injection timing in diesel engine with supercharger - Google Patents

Abstract

PURPOSE:To release advance timing control at supercharge time, by connecting a pressure air chamber in an altitude timing control compensator of fuel injection timing to an intake system in the downstream of a supercharger. CONSTITUTION:A pressure air chamber 74 in an altitude timing control compensator 66 of fuel injection timing is connected to an intake pipe 22 in the downstream of a supercharger 24. The compensator 66 fully opens a valve body 73 on the flatland despite a load and speed of an engine. While on the highland, a decrease of air pressure displaces the valve body 73 downward, and a bleed amount to a pump chamber 38 is decreased to advance timing control earlier than the timing control on the flatland, however at high speed operation of the engine, the valve body 73 is displaced upward by supercharge pressure and fully opened, and the timing control is released.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high altitude compensation device for fuel injection timing in a supercharged diesel engine.

When driving at high altitudes with a diesel engine, the temperature of the compressed air is insufficiently raised due to the decrease in air density, resulting in poor ignition performance and poor drivability due to white smoke emissions and misfires. As a countermeasure against this problem, it is effective to advance the fuel injection timing, and a device has already been proposed that completely corrects the fuel injection timing according to the altitude, that is, the atmospheric pressure. This device has a valve member connected to a pressure sensitive member sensitive to absolute air pressure, which valve member bleeds fuel in the pump chamber of the injection pump to the pump suction side in response to air pressure. Therefore, the pressure in the pump chamber changes depending on the atmospheric pressure (ie, altitude). In this way, the timer piston, which is opened and moved by the pressure in the pump chamber, can compensate the relative angular position between the two-sided cam and the low sill ring, which are integrated with the plunger, depending on the altitude, that is, the fuel injection timing.

However, if the above-mentioned type of fuel injection timing control device is adopted as is, it will be at a significant disadvantage in terms of noise during high loads without the risk of white smoke and misfires, and advancing the injection timing itself will increase noise. It is.

By the way, in a supercharged engine, there is no need to advance the fuel injection timing at high loads and high speeds even if the engine is at full altitude. That is, since the air density and intake air temperature are increased by supercharging, there is no risk of white smoke or misfire. Therefore, even when driving at high altitudes, when the supercharging pressure on the high load side and high rotation side increases, by delaying the injection timing, it is possible to suppress the noise level without causing white smoke or misfires.

Therefore, the present invention provides a diesel engine with a supercharger,
An object of the present invention is to provide a device that can release the advance of fuel injection timing during supercharging.

In order to achieve this object, in the present invention, the air pressure chamber of the pressure sensitive section serving as the high altitude advance compensation device is connected to the intake system downstream of the supercharger. As a result, the pressure sensitive member controls the fuel pressure in the pump chamber so that the advance angle is released during cylinder load and high engine speed when supercharging pressure is generated.

To explain with reference to the drawings below, in FIG. 1, 10 is a cylinder block of a diesel engine, and a piston 12
is provided. A cylinder head 14 is located on the cylinder block 10, and an intake valve 16 and a fuel injection valve 18 are provided. An intake boat 20, which is opened and closed by the intake valve 16, is connected to an outlet of a supercharger 24 through an intake pipe 22.

Reference numeral 26 denotes a so-called distribution type fuel injection pump, which includes an input shaft 28 that is rotatably supported within a housing 27 and rotationally driven by a crankshaft (not shown). A vane-type feed pump 30 (shown in a 90° expanded state in FIG. 1) is mounted on the input shaft 28. When the feed pump 30 rotates as shown by arrow A, it sucks fuel from a fuel pipe 32 connected to a fuel tank (not shown) through a suction boat 34, and discharges the fuel into a pump chamber 38 through a discharge boat 36. A plunger 40 is provided within a cylinder 42, and a two-sided cam 44 is provided at its end. The two-wheeled blade 44 is still in contact with a roller 46 attached to the housing 27, so that the plunger 40 reciprocates from side to side in the figure a number of times corresponding to the number of cylinders during one rotation of the face cam 44. During the suction stroke in which the plunger 40 moves to the left in the figure, the fuel in the pump chamber 38 is introduced into the pressurizing chamber 52 through one of the recesses 50 formed at the tip of the plunger for the number of cylinders, as shown by arrow B. Ru. During the pumping stroke in which the plunger 40 moves to the right in the figure, the recess 50 is disconnected from the pump chamber 38, and the fuel in the pressurizing chamber 52 flows through the center hole 54.
The fuel is supplied to the fuel injection valve 18 through one of the delivery holes 56 formed in the cylinder 42 for the same number of cylinders, the delivery valve 58, and the delivery pipe 60.

A roller 46 that drives the plunger 40 left and right is connected to a timer piston 64 (90° in FIG. 1) via a rod 62.
Shown in expanded state. ). timer piston 64
The suction pressure acts on the 0- side, and the discharge pressure of the pump chamber 38 acts on the other side. Therefore, the differential pressure between the discharge pressure and the suction pressure is p-24
6, 7=the relative angular position with respect to the iscam 44 changes, and as a result, the pumping stroke start timing of the plunger, in other words, the fuel injection timing is controlled.

Reference numeral 66 denotes an altitude advance compensator, and 70 bellows are provided in a case 68, and the bellows are connected to a valve body 73 that opens and closes a pipe 72 that connects the pump chamber 38 to the suction pipe 32 to the pump. The inside of the bellows 70 becomes a vacuum,
A pneumatic chamber 74 is formed on the outside.

The above configuration is similar to that of the prior art, but in this case, the pneumatic space 74 is rarely opened to the atmosphere. Then, since the atmospheric pressure (absolute pressure) is large when driving on flat ground, the bellows 70 contracts and the valve body 7
3 is displaced upward. Therefore, the amount of suction pressure bleed into the pump chamber 38 increases, the internal pressure of the pump chamber 38 decreases, and the timer piston 64, which receives the pump chamber pressure, corrects the roller 62 to retard the injection timing. The relationship between the -1797 rotation speed and the advance angle at this time is expressed as shown in Figure 2 (one-point neckline of Rono) for full load and partial load, respectively.On the other hand, when driving at high altitude, the air pressure chamber 74 The pressure of -T decreases
Therefore, the bellows 70 expands and the valve body 73 moves downward, reducing the amount of suction pressure bleeding into the pump chamber 38. As a result, the internal pressure Q in the pump chamber 38 increases relatively, and the timer piston 64 corrects the injection timing of the roller 62 in the direction of supplying oxygen. This is represented by the broken line in (b) in FIG.

Such conventional control has the drawbacks mentioned above in that it not only unnecessarily advances the fuel injection timing under high loads but also increases noise. That is, in an engine equipped with a supercharger, the intake pressure increases in absolute pressure when the engine is under high load and when the engine speed is high.

On the other hand, the required advance angle from the white smoke and misfire limit is smaller as the pressure is higher, as shown in Figure 3. However, in the past, the advance angle characteristics were simply switched between the dashed line and the dotted line in FIG. 2 for highlands and flatlands. Therefore, even though there was no need to advance the engine angle under high load, the engine angle was advanced when driving at high altitudes.

111 In the present invention, as shown in FIG. 1, the air pressure chamber 70 of the high altitude advance compensation device is connected to the intake pipe 22 downstream of the supercharger 24 via a pipe 80. To describe the operation of the configuration of the present invention, the pressure inside the intake pipe 22 becomes as shown by the dashed line in FIG. On flat ground, regardless of the engine speed and under full load or partial load, the intake pipe pressure is at the level at which the valve body 73 of the ground compensator 66 is in the fully open position (see Fig. 2 (if
The level of t corresponding to 9 mmHg) is always exceeded. Therefore, the advance angle characteristic is related to the engine speed, as shown by the dashed-dotted line in FIG. 2 (b).

In some areas, when the engine speed is lower than r or r2, the boost pressure is lower than the reference level t for fully opening the valve body 73, and the valve body 73 is displaced downward, causing a bleed to the pump chamber 38. Increase the internal pressure of the presser pump.

Therefore, the angle is advanced below this number of revolutions, but not advanced above that number of revolutions, as shown by the solid line in Figure 2 (b). (Low rotation) Full advance height only for Ill, ・1.:
.

Since the advance angle is released on the load side, noise can be reduced without producing white smoke or the problematic sounds of misfires.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of the system of the present invention, and FIG. 2 is a schematic graph showing intake pipe pressure (a) and advance angle characteristics (b) with respect to engine speed yc. FIG. 3 is a schematic graph showing the rectification angle characteristics at the white smoke and misfire limit with respect to the intake pipe pressure. IO...Cylinder block, 12...Piston, 1
8... Fuel injection valve, 22... Intake pipe, 24... Supercharger, 26... Fuel injection pump, 38... Pump chamber, 4o... Plunger, 44... Face cam , 4
6... Cam roller, 52... Pressure chamber, 64... Timer piston, 66, High altitude compensation device, 70... Bellows, 74... Air pressure chamber, 80... Air pressure chamber Pipe connecting downstream of the feeder Patent applicant: Toyota Automobile Industry Co., Ltd. Patent application agent: Patent attorney: Akira Aoki, Patent attorney: Kazuyuki Nishidate, Patent attorney: Kyosuke Tsuchinakayama, Patent attorney: Akiyuki Yamaguchi

Claims (1)

[Claims] A diesel engine with a supercharger, in which an injection pump has a pump chamber that receives fuel at a discharge pressure corresponding to the engine rotation speed, and a cam means that reciprocates a cam roller and a plunger according to the pressure in the pump chamber. and an injection timing control mechanism for controlling the relative angular position of the injection pump, and the pump chamber is connected to the suction side of the injection pump by a valve member connected to a pressure-sensitive member that is sensitive to feed air pressure.
In a device that controls fuel injection timing according to altitude, the chamber that receives the air pressure of the pressure-sensitive member is connected to the engine intake system downstream from the supercharger, and the chamber that receives the air pressure from the pressure-sensitive member is connected to the engine intake system downstream of the supercharger, and the pressure is controlled according to the intake pipe pressure. A fuel injection timing control device that corrects the fuel injection timing.