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Title:
ARRANGEMENT FOR A FUEL INJECTION SYSTEM FOR DIESEL ENGINES
Document Type and Number:
WIPO Patent Application WO/2019/126858
Kind Code:
A1
Abstract:
The invention concerns an arrangement for a fuel injection system (1 ) for diesel engines which comprises an injector (5), a control valve unit (CVU) (4), which is connected to the injector (5) through the second high pressure pump (18), an electronic control unit (ECU) (6), which electronically controls the opening and closing of the connection (34) of the CVU, and a pump (3), where the pump (3) is connected to the CVU (4) through a first high pressure pipe (17).

Inventors:
MARTINS DE SOUZA, Avelino Elias (Avenida República Argentina, 2500 apart. 10, Portão -260 Curitiba - PR, 80610-260, BR)
Application Number:
BR2018/050484
Publication Date:
July 04, 2019
Filing Date:
December 27, 2018
Export Citation:
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Assignee:
ROBERT BOSCH LIMITADA (Via Anhanguera, Km 98 Vila Boa Vista, -900 Campinas - SP, 13065-900, BR)
International Classes:
F02M55/02; F02M55/04; F02M59/46; F02M63/00
Domestic Patent References:
WO1991012421A11991-08-22
Foreign References:
GB2193262A1988-02-03
JPS6011670A1985-01-21
US20040076530A12004-04-22
US5749717A1998-05-12
Attorney, Agent or Firm:
DANNEMANN, SIEMSEN, BIGLER & IPANEMA MOREIRA (Rua Marquês de Olinda, n° 70 - Botafogo, -040 Rio de Janeiro - RJ, 22251-040, BR)
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Claims:
CLAIMS

1. Arrangement for a fuel injection system (1 ) of diesel engines, which comprises

an injector (5),

a control valve unit (CVU) (4), which is connected to the in jector (5) through a second high pressure pipe (18),

an electronic control unit (ECU) (6), which electronically con trols the opening and closing of the connection (34) of the CVU, and a pump (3),

characterized by the fact that the pump (3) is connected to the CVU (4) through a first high pressure pipe (17).

2. Arrangement in accordance with claim 1 , characterized by the fact that the length and diameter of the first high pressure pipe (17) are dimensioned so that the loss of additional charge generated by the first high pressure pipe (17) in the system (1 ) is compensated by the stability generated by the volume of additional damping and by the re duction in the length of the second high pressure pipe (18).

3. Arrangement in accordance with any of the previous claims, characterized by the fact that the CVU (4) comprises a low pres sure fuel passage (31 ) and a high pressure fuel passage (32).

4. Arrangement in accordance with any of the previous claims, characterized by the fact that the high pressure passage of the CVU (32) is connected to the second high pressure pipe (18) through the snubber valve (25).

5. Arrangement in accordance with any of the previous claims, characterized by the fact that the CVU (4), in the open position, allows for the flow of fuel from the low pressure passage (31 ) to the high pressure passage (32).

6. Arrangement in accordance with any of the previous claims, characterized by the fact that the CVU (4), in the closed position, blocks the flow of fuel from the low pressure passage (31) to the high pressure passage (32).

7. Arrangement in accordance with any of the previous claims, characterized by the fact that the ECU (6) determines the open- ing and closing of the CVU (4) due to the volume and temperature of the air admitted, position of the crankshaft, position of the cam and the torque demand.

Description:
Descriptive Report of a Patent for an“ARRANGEMENT FOR A FUEL INJECTION SYSTEM FOR DIESEL ENGINES".

[001 ] This invention concerns an arrangement for a fuel injection system for diesel engines, more specifically for small scale diesel en gines.

DESCRIPTION OF THE STATE OF THE ART

[002] Electronically-controlled fuel injection systems have been used in diesel engines since the 1980s. In comparison with mechanically controlled injection systems, the electronic injection systems of diesel engines allow for more flexible control of the begin of injection (BOI - "Begin Of Injection") and the duration of injection (DOI - "Duration Of Injection"), in addition to variations in such parameters regarding the temperature of the fuel, the volume of air admitted, atmospheric pres sure, oil pressure, the position of the cam, the position of the crankshaft, the rotation of the engine, and the demands of the user, among others.

[003] As a consequence of the more flexible control of the opera tion, the diesel engines which comprise an electronic injection system offer a superior level of emissions of pollutants (gases and particles) into the atmosphere through the optimization of the injection and, conse quently, the burning of fuel.

[004] Document US 5.749.717 presents an example of a pump unit for the electronically controlled fuel injection systems of diesel engines. This document of the state of the art comprises a solenoid valve coupled to one of its ends. The pump unit is positioned in contact with a cam in the engine. A high pressure pipe is responsible for the transference of fuel and connects the pump unit to the injector, which in turn is positioned on the cylinder head of the combustion engine, and is responsible for transporting the fuel.

[005] Small scale diesel engines require, in turn, compact equip ment that can be coupled to the engine without the need to alter the existing constructive arrangements. The pump units for diesel engines described in the state of the art, such as the aforementioned example, combine a pump and a valve in a single non-compact unit, which renders impossible the use of such equipment in many diesel engines available on the market.

[006] In addition to this, the high pressure pipe which connects the pump unit to the injector, when it is long, presents undesirable behav iours for an injection system, such as loss of charge and potentially un stable injection due to the pressure waves generated inside the system.

BRIEF DESCRIPTION OF THE INVENTION

[007] A first objective of the arrangement for the fuel injection sys tem of this invention is to ensure a more stable response from the hy draulic system in terms of fuel injection, which is to say, less variation in the volume of fuel injected between each injection and less variation in the injection pressure in the combustion chamber of the engine.

[008] A second objective of this invention is to provide a fuel injec tion system with flexibility of installation in engines with spatial limita tions. In addition to this, the system is capable of converting a mechani cally controlled injection system into an electronically controlled injection system without major constructive alterations to the engine.

[009] A third objective of this invention is to provide an arrangement for a fuel injection system capable of realizing an electronic injection of fuel with precise and flexible control of the BOI and DOI regarding the operational parameters of the engine.

[0010] The arrangement for a fuel injection system for diesel en gines of this invention comprises a mechanical pump, a first high pres sure pipe (Pump - CVU), a control valve unit (CVU), an electronic control unit (ECU), a second high pressure pipe (CVU-lnjector), an injector, where the pump connects with the CVU through the first high pressure pipe, the CVU connects with the injector through the second high pres sure pipe, and the ECU electronically controls the opening and closing of the CVU connection.

[001 1 ] The length and diameter of the first high pressure pipe are dimensioned so that the loss of additional charge generated by the first high pressure pipe in the system is compensated by the stability gener ated by the volume of additional damping and by the reduction in the length of the second high pressure pipe.

[0012] The introduction of a new segment of high pressure pipe (first high pressure pipe) connecting the original pump to the CVU provides new resources for the optimization of the injection, such as the internal diameter of the pipe, minimizing the loss of charge in the filling of the piston chamber of the pump during the downward movement of the pis ton and in the pressure building movement during the upward movement of the piston with the CVU closed. The injection systems of the state of the art do not possess this degree of freedom provided by the additional dead volume of the first high pressure pipe and, thus, do not possess this resource for optimizing the stability of the injection.

[0013] In addition to this, the CVU itself comprises a low pressure fuel circuit and a high pressure fuel circuit. The high pressure passage of the CVU connects to the second high pressure pipe through a snubber valve. The CVU in the open position and with the downward movement allows for the filling of the high pressure circuit of the injection system through the opening between the valve and the body. The CVU in the open position and with the upward movement of the piston enables the return of the volume transferred by the piston to the low pressure circuit in the direction of the tank. The CVU in the closed position with the up ward movement of the piston isolates the high pressure circuit from the low pressure circuit, causing a rise in pressure in the high pressure cir cuit and achieving the opening pressure of the mechanical injector. As a consequence, the injection of diesel into the combustion chamber of the engine is begun.

BRIEF DESCRIPTION OF THE DESIGNS

[0014] This invention shall be described in more detail below based on an example of execution represented in the designs. The figures show the following:

[0015] Figure 1 - is a schematic diagram of the fuel injection system of this invention;

[0016] Figure 2 - is a frontal view of the fuel injection system of this invention; and

[0017] Figure 3 - is a lateral cross-section view of the pump unit - CVU of the fuel injection system of the present invention.

[0018] Figure 4 - shows an example of the materialization of the in vention.

DETAILED DESCRIPTION OF THE FIGURES

[0019] Figure 1 presents a schematic diagram of the arrangement for a fuel injection system 1 in accordance with the present invention. The system comprises a fuel tank 2, a pump 3, a control valve unit * (CVU - "Control Valve Unit") 4, an injector 5, an electronic control unit (ECU - "Electronic Control Unit") 6 and a number of sensors 7, 8.

[0020] The fuel tank 2 is responsible for storing the fuel and is con nected to the CVU 4 through a low pressure pipe system which com prises a fuel supply pipe 9, a fuel return pipe 10 and a supply/fuel return pipe 1 1. The supply/fuel return pipe 1 1 is connected to the supply and return pipes 9, 10 by means of a Y-shaped connector 12. The fuel supply pipe 9 comprises a fuel filter 13 and a retention valve 14 which allows for the flow of fuel only in the direction of the CVU. The fuel return pipe 10, in turn, comprises a retention valve 15 which allows for the flow of fuel only in the direction of the fuel tank 2. The flow of fuel in the low pressure pipe system occurs through gravity, without the need for the use of a pipe or other suction elements.

[0021 ] The system also comprises a low pressure short pipe 16, a high pressure first pipe 17 and a second high pressure pipe 18 which will be described below.

[0022] Figure 2 shows a pipe unit - CVU - injector with the low pres sure 1 1 , 16 and high pressure pipes 17, 18. The fuel supply/return pipe 1 1 is connected to a low pressure entrance present in the CVU through a first low pressure connection 19. The low pressure short pipe 16 con nects the low pressure outlet of the CVU to the low pressure entrance of the pump through a second low pressure connection of the CVU 20 and a low pressure connection of the pump 21 respectively. The first high pressure pipe 17 connects the high pressure outlet of the pump to the high pressure entrance of the CVU through a high pressure connection of the CVU 23 respectively. The second high pressure pipe 18 connects the high pressure outlet of the CVU to the injector 5. The second high pressure pipe 18 is connected to the injector 5 through a high pressure connection 24, while the connection with the CVU 4 is achieved through a snubber valve ("snubber valve") 25.

[0023] Unlike the CVUs of the state of the art used in fuel injection systems, the CVU 4 of the present invention is not directly coupled to the pump 3 of the injection system, but rather to the pump 3 through the low pressure short pipe 16 and the high pressure short pipe 17. This instal lation characteristic confers greater flexibility on the system for installa tion in small scale diesel engines which possess spatial limitations. The pump units-CVUs for diesel engines known to the state of the art require a certain arrangement of the external characteristics of the engine, such as the physical space between the different elements, so that their in stallation is physically viable, since the positioning of the CVU is fixed in relation to the end of the pump unit. As in the pump unit - CVU of this invention, the CVU does not possess this physical limitation, the fuel in jection system 1 of the present invention can be installed in a greater range of engines when compared with conventional electronic injection systems.

[0024] Another advantage conferred by the use of the first high pres sure pipe 17 on the injection system 1 of the present invention is the possibility of reducing the length of the second high pressure pipe 18 due to the greater proximity of the CVU 4 to the injector 5. Depending on the characteristics required by the engine, the CVU 4 may be positioned closer to the injector 5 through variation in the length of the first and sec ond high pressure pipes 18, 17. The reduction in the length of the second high pressure pipe 18 causes a reduction in the loss of charge and a reduction in the dead volume of the cited pipe leading to the generation of more stable pressure waves in the system during the injection. As a result, more stable conditions of the opening and closing of the injector 5 are obtained, which is to say, less variation in the volume of fuel in jected between each injection and less variation in the pressure of injec tion in the combustion chamber of the engine.

[0025] Despite also generating a greater loss of charge, the inclu sion of the first high pressure pipe 17 in the system 1 creates a dead volume which reduces the fall in pressure between the pump 3 and the CVU 4. In addition to this, the inclusion of the first high pressure pipe 17 allows for a reduction in the length of the second high pressure pipe 18 with a consequent reduction in the loss of charge and an increase in the stability of the system.

[0026] As such, the length and pressure of the first high pressure pipe 17 must be carefully dimensioned to compensate for this loss of additional charge. This dimensioning must be realized in order that the loss of additional charge generated by the first high pressure pipe 17 is compensated by the stability generated by the additional damping vol ume and by the reduction in the length of the second high pressure pipe 18. The cited dimensioning varies in accordance with the specifications of each engine. In addition to this, the length of the second high pressure pipe 18 must be dimensioned in accordance with the external character istics of the engine and the length of the first high pressure pipe 17, run ning the lowest possible distance between the CVU 4 and the injector 5.

[0027] Figure 3 presents details of the internal characteristics of the pump unit - CVU. The CVU 4 presents an internal configuration similar to the CVUs known to the state of the art, comprising a valve body 26, a solenoid housing 27, a valve needle 28 and a valve spring 29, in addition to the high 23, 22 and low pressure 19, 20, 21 connections and the pre viously described snubber valve 25.

[0028] In the CVU 4 of this invention, the solenoid housing 27 is cou pled to the side of the valve body 26 and comprises a coil and a magnetic nucleus (not shown). The valve body 26 comprises a valve chamber 30, a low pressure fuel passage 31 and a high pressure fuel passage 32. The valve chamber 30 is responsible for connecting the low pressure passage 31 to the high pressure passage 32 so that the fuel can flow freely between the passages 31 , 32 of the CVU 4. The coil, when ener gized by the ECU 6 through the terminals 33, moves the valve needle 28, which is responsible for closing and opening the connection 34 be tween the high pressure passage 32 and the valve chamber 30 to begin and end the injection of fuel respectively. In other words, the activation of the solenoid controls the flow of fuel from the fuel tank 2 to the injector 5. The functioning of the system as a whole will be explained in detail below.

[0029] The inside of the pump 3 comprises a high pressure fuel pas sage 35, a low pressure fuel passage 36, a high pressure chamber 37, a piston 38 and a piston coil 39. The pump piston is responsible for var ying the internal volume of the high pressure chamber 37 through the action of a cam 40 present in the engine. The cam 40 acts mechanically with a roller 41 present at one of the ends of the pump 3 which, in turn, moves the pump piston 38 in a direction opposite to that of the force applied by the coil 39. The coil 39 present inside the pump 3 ensures the return of the piston 38 to the initial position after its movement by the cam 40 of the engine, also ensuring a permanent contact between the piston 30 and the roller 41. This effect results in greater stability in the pressure generated in the system and less wear of the components act ing in the movement of the piston 38.

[0030] The fuel present in the high pressure chamber 37 may occa sionally flow in an undesirable manner between the pump piston 38 and the pump body 42. This fuel is kept in a surplus fuel chamber (not shown) which is connected to the low pressure fuel passage of the pump 36. This passage 36 is responsible for returning the fuel from the high pres sure chamber 37 to the low pressure pipes of the injection system.

[0031 ] The high pressure fuel passage 35 present inside the pump connects the high pressure chamber of the pump 37 to the first high pressure pipe 17. While the first high pressure pipe 17 connects the high pressure passage of the pump 35, through a high pressure connection of the pump 22, to the high pressure passage of the CVU 32, through a high pressure connection of the CVU 23. The second high pressure pipe 18 connects the high pressure passage of the CVU 32 to the injector 5.

[0032] The snubber valve 25 present between the high pressure passage of the CVU 32 and the second high pressure pipe 18 protects the system against disturbances generated by waves continuously pre sent in injection systems. The snubber valve 25 acts as a restriction de vice which absorbs the energy of the waves generated by the opening and closing of the injector 5. As a consequence, the valve 25 reduces the fluctuation in the pressure and, simultaneously, maintains a residual pressure on the inside of the second high pressure pipe 18. These re sulting effects ensure more stable operating conditions for the injection system 1 of this invention.

[0033] The CVU 4 possesses two operating positions, one open po sition and one closed position. The open position occurs when there is no tension being applied to the solenoid coil and, consequently, the valve needle 28 remains in an extended position due to the force applied by the valve coil 29. In this case, the connection 34 between the high pres sure passage 32 and the valve chamber 30 is not blocked and the fuel may flow from the fuel tank 2 to the high pressure chamber of the pump 37 and vice-versa.

[0034] As the cam 40 moves the pump piston 38, the fuel present inside the high pressure chamber 37 is compressed and forced to flow through the high pressure passage 35 to the first high pressure pipe of the CVU 32.

[0035] With the CVU 4 in the open position, the fuel flows to the valve chamber of the CVU 30 and returns to the supply/fuel return pipe 1 1 through the low pressure passage of the CVU 32. In this case, the injection is not begun due to the low pressure of the fuel in the second high pressure pipe 18, which is not sufficient to open the injector 5.

[0036] At a moment determined by the ECU 6, during the movement of the piston 38 by the cam 40, the solenoid coil is energized through the terminals 33 and the valve needle 28 is moved to the withdrawn position. In this case, the CVU passes to the closed position, since the connection 34 between the high pressure passage 32 and the valve chamber 30 is blocked and the fuel is prevented from returning to the tank 2. Conse quently, the pressure generated by the movement of the piston 38 is sent to the second high pressure pipe 18 and to the injector 5, positioned in the engine cylinder and partially inserted in the fuel chamber of the cyl inder. On reaching a given pressure, the injector 5, which is activated by the pressure of the fuel, opens and the fuel is injected into the fuel cham ber of the engine.

[0037] The fuel injection ends when the ECU 6 stops energizing the solenoid and the connection 34 between the high pressure passage 32 and the valve chamber 30 is opened again. This allows for the return of the fuel through the supply/return pipe 1 1 , causing a fall in pressure in the second high pressure pipe and resulting in the closure of the injector 5. As such, the BOI and DOI of the injection are independent of the ac tion of the cam 40 on the pump piston 38. These parameters are defined by the ECU 6 through the activation of the CVU 4.

[0038] The series of sensors 7, 8 of the system is responsible for obtaining important information about the parameters which influence the BOI and DOI of the injection. The principal parameters in question are the volume of air admitted, the temperature of the air admitted, the position of the crankshaft, the position of the cam and the torque de mand. Other parameters also influence the BOI and DOI of the injection, but in a less significant manner, resulting in mere adjustments to their controls.

[0039] Figure 4 shows an example of the materialization of the cou pling of the fuel injection system of this invention in a small scale diesel engine. From the figure it is possible to observe the constructive ad vantages of the fuel injection system of the present invention. The flexi bility of the positioning of the CVU 4 in the vicinity of the engine allows for the installation of the pump unit- CVU of this invention even when the space available is limited or the spatial arrangement of the external structure of the engine is unusual.

LIST OF REFERENCES

1 - fuel injection system 2 - fuel tank

3 - pump

4 - control valve unit (CVU)

5 - Injector

6 - electronic control unit (ECU)

7, 8 - series of sensors

9 - fuel supply pipe

10 - fuel return pipe

11 - fuel supply/return pipe

12 - Y-shaped connector

13 - fuel filter

14 - supply pipe retention valve

15 - return pipe retention valve

16 - low pressure short pipe

17 - high pressure short pipe

18 - second high pressure pipe

19 - first low pressure connection of the CVU

20 - second low pressure connection of the CVU

21 - low pressure connection of the pump

22 - high pressure connection of the pump

23 - high pressure connection of the CVU

24 - high pressure connection of the injector

25 - snubber valve

26 - valve body

27 - solenoid housing

28 - valve needle

29 - valve coil

30 - valve chamber

31 - low pressure fuel passage of the CVU

32 - high pressure fuel passage of the CVU 33 - terminals

34 - connection between the high pressure passage and the valve chamber

35 - high pressure fuel passage of the pump

36 - low pressure fuel passage of the pump

37 - high pressure passage of the pump

38 - pump piston

39 - piston coil

40 - cam

41 - roller

42 - pump body