JPH089389Y2 - Fuel injection system for direct injection diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a fuel injection device for a direct injection diesel engine.

[Conventional technology]

Generally, in order to obtain a good combustion performance in a direct injection diesel engine, it is necessary to distribute the finely pulverized fuel as uniformly as possible in the combustion chamber.

FIG. 3 shows a fuel injection device for a direct injection diesel engine. In the figure, reference numeral 1 is a feed pump for pressure-feeding the fuel in a fuel tank 3 to a fuel filter 5. The feed pump 1 is a side surface of an injection pump 7. And is driven by an eccentric cam provided on the injection pump cam shaft.

Then, the fuel filtered by the fuel filter 5 is pressurized by the injection pump 7, passes through the fuel supply passage 9, and is injected at high pressure into the combustion chamber by the fuel injection nozzle 11. Also, the fuel delivery amount of the feed pump 1 is usually determined by the fuel injection nozzle 11
It is set to be larger than the injection amount from the injection pump 7
Excess fuel from the overflow valve 13 installed on the
The fuel tank 3 overflows through the fuel recirculation passage 15. Thus, as the excess fuel overflows from the overflow valve 13, the temperature inside the injection pump 7 becomes low, and the temperature of the fuel sent to the fuel injection nozzle 11 becomes low, so that the thermal expansion of the fuel occurs. And uniform fuel injection becomes possible.

As shown in FIG. 4 showing the relationship between the overflow amount and the feed pressure, where the horizontal axis is the overflow amount and the vertical axis is the feed pressure (the gallery pressure of the fuel pump 7), the conventional fuel injection device When the pressure sent from the feed pump 1 exceeds a constant valve opening pressure P ₀ , the overflow valve 13 opens the flow path to overflow the fuel into the fuel tank 3 as described above. The higher the value, the more overflow. Further, at high speed, the temperatures of the injection pump 7 and the engine rise and the temperature of the fuel rises, so the feed pressure P is higher and the overflow amount is increased as the speed is higher.

As shown in the characteristic map of the feed pressure P in FIG. 5 in which the horizontal axis represents the engine speed and the vertical axis represents the load, the higher the engine speed, the higher the rotation of the feed pump and the fuel pump, and the higher the feed pressure P. However, the overflow amount is the difference between the amount sent out by the feed pump and the injection amount, and the injection amount consumes more fuel as the load increases, so the flow rate is larger. Because it is small, it increases.

Therefore, in combination with what has been already described in the relationship between the overflow amount and the feed pressure in FIG. 4, in the conventional fuel injection device, the feed pressure becomes higher as the speed and load are increased.

In other words, at low speed and high load such as when traveling uphill, the feed pressure is low as shown in FIG.
High-pressure injection cannot be obtained, a sufficient overflow amount cannot be obtained, and the cooling effect of the fuel pump cannot be improved.

[Problems to be solved by the device]

In order to solve the above-mentioned problems, the technology of increasing the injection pressure in the low speed range compared to the past by changing the position of the fuel pump plunger at the beginning of refueling is "Automotive Technology" Vo
l.40 No.10 1986 pages 1263 to 1269 (especially page 1265 page 4
Figure).

However, in such a prior art, since the tamming at the beginning of oil feeding is changed, the injection timing is changed at the same time as the oil feeding rate, and the injection tamming cannot be controlled independently.

Therefore, the fuel deteriorates, NO _X and smoke are generated,
Fuel efficiency deteriorates. However, the structure of the fuel pump was complicated and the cost was high.

The present invention has been devised in view of such circumstances, and provides a fuel injection device capable of performing high-pressure injection at a low speed and a high load with a simple structure, reducing NO _X and smoke, and improving fuel consumption.

[Means for solving the problem]

In order to achieve such an object, a fuel injection device for a direct injection diesel engine according to the present invention includes a variable displacement feed pump driven by the engine in a fuel supply passage extending from a fuel tank to a fuel injection nozzle. And a controller for mounting the engine load and rotation speed detection means on the engine, and controlling the feed pressure of the feed pump to increase as the engine becomes low speed and high load by a signal from each detection means. It is a thing.

[Action]

According to the present invention, when the engine becomes low speed and high load, the feed pressure of the variable displacement feed pump is increased by the command from the control which receives the signal from the load and the rotation speed detecting means.

Therefore, at low speed and high load, high pressure injection is performed, and the combustion is improved by synchronizing the injection tamming.

Further, even under a high load, a sufficient amount of overflow can be obtained, the cooling effect of the engine can be enhanced, and the output can be improved.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same parts as those of the above-mentioned conventional example are designated by the same reference numerals, and their structural description will be omitted.

FIG. 1 is a schematic view of a fuel injection device according to a first embodiment of the present invention. In the drawing, reference numeral 17 is a variable capacity type installed in a fuel supply passage 19 from a fuel tank 3 to a fuel filter 5. The feed pump of the variable displacement feed pump 17
Is driven by the engine 21 to pump fuel to the fuel filter 5. Then, to the variable displacement feed pump 17, a normally closed type electromagnetic proportional valve 25 driven by a command from the controller 23 is connected, and a load sensor 27 and an engine rotation sensor 29 attached to the engine 21 Signal is above controller 23
To the feed pressure P according to the map of FIG.
Then, open and close the solenoid proportional valve 25 and feed pump 17
By changing the feed pressure of the variable displacement feed pump 17 as the engine 21 becomes low speed and high load
It is designed to increase the feed pressure of.

That is, the variable displacement feed pump 17 is provided with a variable device 31 for varying the displacement thereof connected to the solenoid proportional valve 25 via the operating circuits 33, 35, and the solenoid proportional valve 25 is also provided.
Operating circuits 39 and 41 are connected to the fuel recirculation passage 15 and the fuel supply passage 37 on the downstream side of the fuel filter 5, respectively. Then, the controller 23, which receives the signals from the load sensor 27 and the engine rotation sensor 29, sends a command to the solenoid proportional valve 25 to operate the variable device 31, thereby controlling the feed pressure of the variable displacement feed pump 17. It is supposed to do.

Since the present embodiment is configured in this way, when the engine becomes low speed and high load, the solenoid proportional valve 25 operates (the envelope of the proportional solenoid valve 25 moves) in response to a command from the controller 23, and the variable displacement type The feed pressure of the feed pump 17 will increase.

Therefore, according to the present embodiment, high-pressure injection is performed even at low speed and high load, or the fuel is improved by tuning the injection tamming, so NO _X and smoke are reduced, and fuel efficiency is improved. . However, since a sufficient amount of overflow can be obtained even under high load, the cooling performance of the fuel pump 7 is improved, and as a result, the output can be increased.

Figure 2 shows an engine equipped with a unit injector 43.
The fuel injection device according to the present invention is applied to 21A. A variable fuel injection device having the same configuration as that of the first embodiment is provided upstream of the fuel filter 5 in the fuel supply passage 19 from the fuel tank 3 to the unit injector 31. A capacitive feed pump 17 is provided. Since the other configurations are similar to those of the first embodiment, the same components are designated by the same reference numerals and their structural description is omitted.

Therefore, according to the present embodiment, as in the first embodiment,
High-pressure injection is performed from the unit injector 43 even at a low speed, and the fuel is improved by synchronizing the injection tamming, so that NO _X and smoke are reduced. Of course, a sufficient amount of overflow can be obtained even under high load,
It became possible to enhance the cooling effect of the engine.

[Effect of device]

As described above, according to the present invention, the variable displacement feed pump driven by the engine is provided in the fuel supply passage from the fuel tank to the fuel injection nozzle, and the engine load and rotation speed detection means is provided. Since it is attached to the engine and is provided with a controller for increasing the feed pressure of the feed pump as the engine becomes low speed and high load by a signal from each of the detection means, it is possible to control the fuel injection nozzle even at low speed. Since high-pressure injection is performed and the fuel is improved by synchronizing the injection tamming, NO _X and smoke are reduced and fuel efficiency is improved. In addition, a sufficient amount of overflow can be obtained even under high load, so that the engine cooling effect is enhanced and the output can be improved.

However, the variable displacement feed pump driven by the engine has a simple structure like a general feed pump and has a simple structure.

[Brief description of drawings]

1 is a schematic configuration diagram of a fuel injection device according to a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a fuel injection device according to a second embodiment of the present invention, and FIG. 3 is a conventional fuel injection device. FIG. 4 is a schematic configuration diagram of the apparatus, FIG. 4 is an explanatory diagram showing the relationship between the feed pressure and the overflow amount, and FIG. 5 is a conventional feed pressure characteristic map.
FIG. 6 is a feed pressure characteristic map in the present invention. 3 ... Fuel tank 5 ... Fuel filter 7 ... Fuel pump 11 ... Fuel injection nozzle 13 ... Overflow valve 17 ... Variable displacement feed pump 19,37 ... Fuel supply passage 21 ... Engine 23 ... Controller 25 …… Electromagnetic proportional valve 27 …… Load sensor 29 …… Engine rotation sensor 31 …… Variable device 33,35,39,41 …… Operating circuit 43 …… Unit injector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, written by Kitamura, 1-chome, Ii-chome, Ageo-shi, Saitama, Nissan Diesel Industry Co., Ltd. (72) Keiichi Niimura, 1-chome, Io-chome, Ageo, Saitama Prefecture Co., Ltd. (72) Inventor Shuichi Nakamura 1-chome, Ichome, Ageo City, Saitama Prefecture Nissan Diesel Industry Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A variable displacement feed pump driven by an engine is provided in a fuel supply passage extending from a fuel tank to a fuel injection nozzle, and an engine load and rotational speed detecting means is attached to the engine. A fuel injection device for a direct injection diesel engine, comprising a controller for controlling the feed pressure of the feed pump to increase as the engine becomes low speed and high load in response to signals from the respective detection means.