KR100350875B1 - Fuel injection pump for diesel engine - Google Patents

Abstract

PURPOSE: A fuel injection pump is provided to reduce the amount of exhaust gas, while allowing fuel injection characteristics to be easily controlled. CONSTITUTION: A reduced pipe(20) is connected to the inlet of an injector(5), and a plunger is mounted at the entrance of the reduce pipe in such a manner that the plunger is interlinked with a spool(26) accommodated in a barrel(24). The barrel is divided into a first hydraulic chamber(28) and a second hydraulic chamber(30) by the spool. The first hydraulic chamber has an accumulator(36), and the second hydraulic chamber is connected to a flow channel(40) branched off from a fuel supply pump(38). A flow channel is connected to the reduce pipe. The second hydraulic chamber is connected to a pilot valve(48) for reducing the pressure of the second hydraulic chamber, and to a groove(52) of the spool through a connection port(50). The barrel has a flow channel(54) which is open to the groove of the spool when the spool moves, wherein the flow channel has a shutter valve. The degree of opening of first to fourth variable orifices(32,42,46,58) and the pilot valve is controlled by an ECU(60).

Description

Fuel injection pump of diesel engine

The present invention relates to a fuel injection pump of a diesel engine, and more particularly, to allow the plunger to be driven by the hydraulic pressure of the fuel, so that the control of the driving speed and the like is easy and thus the fuel injection characteristics of the diesel engine can be freely adjusted. It relates to an injection pump.

The structure of a diesel engine is almost similar to that of a gasoline engine, but there is a big difference in the injection system between a gasoline engine, a spark ignition engine and a diesel engine, a compression ignition engine.

In other words, diesel engines do not require an electric ignition device, but need an injector that injects fuel into the combustion chamber at an appropriate pressure and time.

Exemplary Drawings FIG. 1 is an explanatory view showing an injection system of such a diesel engine. The functions required for an injector of a fuel system are to feed fuel, adjust an appropriate injection amount required for an engine, and form spray.

The fuel is sucked up from the fuel tank 2 by the feed pump 1, filtered by the filter 3, and then supplied to the injection pump 4 and injected from the injector 5.

The injection of the fuel, the adjustment of the amount thereof, and the timing of the injection are determined by the injection pump 4, and based on this, the governor 5 and the timer 6 are configured to mechanically control fuel injection suitable for the vehicle driving state.

Therefore, the injection pump 4 is a core part of the fuel system of the diesel engine, and an exemplary view for explaining this in detail FIG. 2 (A) is a conceptual view showing a fuel injection pump.

Shown is a thermal injection pump typically used in diesel engines, in which a pump housing (8) for receiving fuel delivered from a fuel supply pump is formed, and a delivery valve (9) and a holder (10) are mounted thereon. In addition to the threaded portion, fuel inlet and outlet passages are provided.

The camshaft 11 is driven from the crankshaft via the timing gear, and operates the plunger 13 up and down via the tappet 12, and also drives the fuel feed pump 1.

The structure has the cams 14 and the cams for operating the fuel feed pump as many as the number of cylinders of an engine as shown, and the drive shaft of the camshaft 11 has the said timer, and the governor is mounted on the opposite side.

The fuel is fed to the injector through the injection pipe 15 through the driving of the camshaft 11 and the plunger 13, and the operating state of the plunger is illustrated in the drawing of FIG. 2 (b).

In the suction stroke, the plunger 13 is lowered and the suction port 17 of the barrel 16 is opened. At this time, the delivery valve 9 is closed.

Subsequently, in the oil feeding stroke, the plunger 13 is raised to close the inlet 17, and at the same time, the delivery valve 9 is opened and the fuel is fed through the injection pipe 15.

Here, the length of the upper end of the plunger 13 and the lead 18 is the effective stroke (a), and if the lead 18 is positioned in the inlet 17 even though the plunger 13 continues to rise, the lead 18 Since the fuel comes out to the inlet 17, the injection is finished.

On the other hand, the output characteristics and exhaust characteristics of the diesel engine vary greatly depending on the performance of the fuel spray injected into the combustion chamber.

In particular, in the direct injection type diesel engine, the formation of the mixer is important, so the condition of the mixer formation is required from the engine side and determined by the injection measurement. The supply conditions of the injection system are divided into time and space.

The temporal characteristic of fuel refers to the injection characteristics exhibited by the injection pump described above as a matter of injection timing, injector, injection rate, and abnormal injection, and the spatial characteristics are represented in the injector such as spraying distance, angle, particle size distribution or injection degree. Say characteristic.

In particular, the exhaust gas countermeasures by the said injection characteristic are urgently urgent currently required for restricting exhaust gas.

In other words, diesel engines emit more particulate emissions than gasoline engines because they have to finish diffuse spray combustion in a short time in a cylinder.

Moreover, due to the surplus oxygen contained in the exhaust gas of the diesel engine, the three-way catalyst of the gasoline engine and the corresponding air-fuel ratio feedback process cannot be carried out. Therefore, the emissions of nitrogen oxides, which are photochemical smog and acid rain, are significantly higher than those of the gasoline engine. .

For this reason, emissions of diesel engines are focused on reducing nitrogen oxides and particulate matter.

The emission measures of diesel engines are divided into pre-treatment through engine modulation and post-treatment of exhaust system. Engine modification is focused on three components: injection system, intake and exhaust system, and combustion chamber system. Is an exhaust gas countermeasure by adjusting the injection characteristic.

Three pathways are known for the generation of nitrogen oxides: thermal NO generated under high temperature atmosphere, fuel NO generated from nitrogen contained in fuel, and prompt NO generated at relatively low temperature when fuel is decomposed in a combustion chamber.

Among them, the generation control of thermal NO is controlled by engine modulation.

In other words, most of the countermeasures against nitrogen oxides caused by engine modulating are the same as the excess air ratio, the lower the combustion gas temperature, and the shorter the holding time at that temperature, the lower the amount of NO produced, and If the holding time is the same, the smaller the excess air rate, the less the amount of NO is produced.

Representative methods are a reduction in the combustion gas temperature and a shortening of the hot gas holding time due to the delay of the injection timing, which is adjusted to perform the cam and the timer of the injection pump described above.

As described above, the fuel injection of the diesel engine is performed by the injection pump, which is performed by the cam 14 of the injection pump driving the plunger 13, which perceives the injection timing by the cam 14 and the timer. To reduce the emission of nitrogen oxides.

However, this reflects the increase of particulate matter and hydrocarbons, and the deterioration of thermal efficiency and startability. Therefore, the presently enthusiastically developed pilot injection and reduced initial injection rate methods are used.

In other words, nitrogen oxides emitted from diesel engines are generated in large amounts as the amount of premixed combustion that explosively combusts the mixture formed during the ignition delay period. Therefore, it is effective to shorten the ignition delay period. Injecting and burning a small amount of fuel prior to the main injection increases the temperature and pressure in the cylinder in advance, thereby reducing nitrogen oxides without delaying the injection timing.

In addition, the initial injection reduction method injects a small amount at the beginning of the injection and increases the amount of injection therefrom, thereby preventing a sudden increase in pressure caused by sudden injection and the rapid development of the combustion chamber in the high temperature atmosphere.

However, this pilot injection or initial injection reduction has been a problem that can not be performed with the above-described simple mechanical injection pump, and also in the pilot injection injection system capable of main injection of high pressure high injection rate to prevent combustion deterioration during diffusion combustion There was also a problem that is essential.

Accordingly, an object of the present invention is to provide an injection pump of a diesel engine to solve the above problems.

The present invention for this purpose is to replace the inner diameter of the discharge port of the injection pipe with a reduction tube smaller than its inlet and to install a plunger at the inlet of the reduction tube to determine the transport pressure and the flow rate of the fuel in accordance with the movement of the plunger, The movement is linked to the hydraulically operated spool of fuel. The barrel in which the spool is installed is divided into two hydraulic chambers by the spool, and the hydraulic chamber is connected to the flow path along with the pilot valve, the shutter valve, and the variable orifice. While connected, the pilot valve and the orifice are controlled by an ECU (Electronic Control Unit) that performs the overall control of the engine to control the movement of the spool, and as a result, the injection of fuel to achieve the pilot injection and initial reduction injection The characteristics are adjusted.

1 is an explanatory diagram of a diesel engine fuel system;

2 (a) is an explanatory view of the appearance of the fuel injection pump;

(B) is a conceptual diagram illustrating a conventional injection pump,

3 and 4 are schematic views showing the structure of the present invention and its operating state.

-Explanation of symbols for main parts of the drawing

20-miniature tube, 22-plunger,

24-barrel, 26-spool,

28-1st hydraulic chamber, 30-2nd hydraulic chamber,

32-first variable orifice, 34-euro,

36-accumulator, 38-feed pump,

40-euro, 42-second variable orifice,

44-euro, 46-third variable orifice,

48-pilot valve, 50-connection port,

52-groove, 54-euro,

56-shutter valve, 58-fourth variable orifice,

60-ECU, 62-solenoid,

64-flow meter.

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

In the present invention, the reduction tube 20 is connected to the inlet (5) inlet of the diesel engine, the plunger 22 is installed to interlock with the spool 26 inserted into the barrel 24 at the inlet of the reduction tube (20). On the other hand, the barrel 24 is divided into the first and second hydraulic chambers 28 and 30 by the spool 26 and the hydraulic chamber 28 (in the flow path 34 together with the first variable orifice 32) ( 30 is connected, and the accumulator 36 is installed at the first hydraulic chamber 28 side, and the second hydraulic chamber 30 has one flow passage 40 branched from the fuel supply pump 38. It is connected with the second variable orifice 42, the other flow path 44 is connected to the reduction tube 20 so as to be closed simultaneously with the oil movement of the plunger 22, and at the same time the third variable orifice 46 in the flow path 44 Is installed, the second hydraulic chamber 30 is connected to the pilot valve 48 for reducing the pressure thereof and at the same time it is connected to the groove 52 of the spool 26 through the connection port 50. Work of barrel 24 A flow path 54 opening to the groove 52 and a shutter valve 56 are installed at the side of the spool 26 for oil movement, and the flow path 54 is branched so that the fourth variable orifice 58 is installed. The first, second, third and fourth variable orifices 32, 42, 46 and 58 and the pilot valve are controlled by the ECU 60 so that the oil supply pressure and discharge amount of the reduction tube 20 are adjusted. It is a fuel injection pump of a diesel engine that is controlled.

3 and 4 are conceptual views showing the structure and operation of the present invention. The present invention moves the spool 26 by the hydraulic pressure of fuel delivered by the fuel supply pump, which drives the plunger 22. It was fed through the reduction tube 20 so that the initial reduction injection with the pilot injection can be performed.

That is, the conventional injection pump was not able to perform pilot injection and initial reduction injection, but the simple driving of the plunger by the rotation of the cam linked with the rotation of the engine crankshaft, in the present invention, the spool 26 is the plunger 22 Since the spool 26 is operated by the hydraulic pressure of the fuel, controlling the hydraulic pressure of the fuel is expected to move the spool 26 to be diversified, and thus, pilot injection for initially injecting a small amount and performing main injection. The initial reduction injection is performed by increasing the injection rate during the injection period.

In addition, by controlling the moving speed of the spool 26 to form a high pressure, which is further pressurized through the reduction tube 20 can prevent combustion worsening during diffusion combustion in the pilot injection as described above.

The spool 26 for this purpose is inserted into the barrel 24, and the barrel 24 is divided into the first and second hydraulic chambers 28 and 30 by the spool 26 and at the same time, the first and second hydraulic chambers ( 28 and 30 are connected to the flow path 34 together with the first variable orifice 32.

In addition, in the second hydraulic chamber 30, one flow passage 40 branched from the fuel supply pump 38 is connected with the second variable orifice 42, and the other flow passage 44 is connected to the third flow passage 44. It is connected to the reduction tube 20 together with the orifice 46.

In addition, a pilot valve 48 is connected to the second hydraulic chamber 30, and the first, second, and third variable orifices 32, 42, 46 are controlled by the ECU 60, and the pilot The valve 48 is also adapted to be controlled by the ECU 60 by the solenoid 62.

Therefore, injection fuel is introduced from the flow path 44 in the reduction pipe 20 for supplying fuel to the injector 5, and both ends of the spool 26 supply hydraulic pressure through the flow path 40 and the flow path 34. I am getting it.

Here, a flow meter 64 is installed in the flow path 44 so that the ECU 60 checks the amount of fuel oil, and through the transmission signal of the flow meter 64 and the control of the third variable orifice 46. The amount of fuel introduced into the reduction tube 20, that is, the amount of fuel injected into the injector 5 is controlled.

In addition, the solenoid 64 of the pilot valve 48 is in a state where the ECU 60 controls the first and second variable orifices 32 and 42 to balance the first and second hydraulic chambers 28 and 30. By driving), the second hydraulic chamber 30 is depressurized, its balance is broken, and the spool 26 is oil-transferred, wherein the opening amount and pilot of the first and second variable orifices 28 and 30 are moved. It is possible to control the opening speed of the valve 48 to control its moving speed.

That is, by slowly moving the spool 26 and injecting a small amount of fuel prior to the main injection, the initial stage of the pilot injection described above is performed, and the speed is gradually increased to perform initial reduction injection.

On the other hand, the groove 52 of the spool 26 is connected to the second hydraulic chamber 30 by the connecting port 50, the flow path 54 to be opened when the oil movement of the spool 26 on one side of the barrel 24 Is formed, and this is branched so that one is provided with a shutter valve 56, and the other is connected with a fourth variable orifice 58, which is also under the control of the ECU 60.

Therefore, when the spool 26 moves slowly by the pilot valve and the flow path 54 is opened, the hydraulic pressure of the second hydraulic chamber 30 is dropped by the shutter valve 56 and the fourth variable orifice 58. As a result, the spool 26 is rapidly moved toward the second hydraulic chamber 30 to form a strong pressure wave.

Meanwhile, the rapid moving speed of the spool 26 is controlled by adjusting the opening amount of the fourth variable orifice 58 based on the hydraulic pressure provided by the first and second variable orifices 32 and 42. As described above, since the opening amount of the first and second variable orifices 32 and 42 is also adjusted, the moving speed of the spool 26 is diversified by the combination of these, and thus the number of cases where the injection characteristics are innumerable is controlled. This is a natural result.

Subsequently, when the oil feeding stroke of the spool 26 is finished, the residual pressure of the reduction tube 20 exerts a force to return to the plunger 22, and the hydraulic pressure of the second pressure chamber 30 is reduced by the hydraulic adjustment of the variable orifice. The spool 26 is returned by being higher than the first pressure chamber 28, and the first and second pressure chambers 28 and 30 are balanced again, and the above process is repeated.

According to the invention as described above, the spool 26 drives the plunger 22 and this spool 26 is operated with the hydraulic pressure of the fuel, the hydraulic pressure of the fuel being controlled by the ECU 60 and accordingly the spool 26. ) Is diversified, the pilot injection for initial injection of a small amount and the main injection and the initial reduction injection to increase the injection rate during the injection period is performed to reduce the exhaust gas of the diesel engine .

Claims (1)

The reduction tube 20 is connected to the inlet 5 of the diesel engine, and the plunger 22 is installed at the inlet of the reduction tube 20 so as to be interlocked with the spool 26 inserted into the barrel 24. The barrel 24 is divided into the first and second hydraulic chambers 28 and 30 by the spool 26, and the hydraulic chambers 28 and 30 are transferred to the flow path 34 together with the first variable orifice 32. The accumulator 36 is installed at the side of the first hydraulic chamber 28, and the second hydraulic chamber 30 has a second variable flow path 40 branched from the fuel supply pump 38. It is connected with the orifice 42, the other flow path 44 is connected to the reduction tube 20 so as to be closed at the same time as the oil movement of the plunger 22, and at the same time the third variable orifice 46 is installed in the flow path 44 On the other hand, the second hydraulic chamber 30 is connected to the pilot valve 48 for reducing the pressure of the micro, and at the same time connected to the groove 52 of the spool 26 through the connection port 50, the barrel ( On one side of the spool ( A flow path 54 opening to the groove 52 and a shutter valve 56 are installed in the oil movement of the 26, and the flow path 54 is branched to provide a fourth variable orifice 58. 1,2,3,4 variable orifices (32) (42) (46) (58) and pilot valves are fuel injection pumps for diesel engines whose structure is controlled by the ECU (60).

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