WO2006079315A1

WO2006079315A1 - Directional control valve arrangement and fuel injection system

Info

Publication number: WO2006079315A1
Application number: PCT/DE2006/000075
Authority: WO
Inventors: Werner Reith; Nguyen-Xuan Binh
Original assignee: Bosch Rexroth Ag
Priority date: 2005-01-26
Filing date: 2006-01-19
Publication date: 2006-08-03
Also published as: DE102005003659A1

Abstract

The invention relates to a direction control valve arrangement and to a fuel injection system provided with this direction control valve arrangement, comprising a main stage (2) that is pilot-controlled by a servo-pilot valve (14). By applying a control pressure, the servo-pilot valve can be switched into a final position in which the main stage is subjected to the action of a control pressure difference in order to bring it into a preferred position (a).

Description

description

Directional control valve arrangement and fuel injection system

The invention relates to a directional control valve arrangement according to the preamble of patent claim 1 and a fuel injection system designed with such a directional control valve arrangement.

Such directional valve arrangements are used, for example, in fuel injection systems of heavy, slow-running diesel engines, such as engines of construction machinery or marine engines, to produce a particular injection pressure profile. The modulated by the directional control valve output pressure acts on the low pressure side of a hydraulic pressure booster, via which the fuel is subjected to high pressure and injected via an injection nozzle into a cylinder. Fuel injection valve arrangements are described, for example, in DE 30 09 752 C2 and DE 100 00 027 A1. The hydraulic pressure modulation on the low-pressure side can take place via a directional control valve arrangement, as shown in EP 0 628 731 B1. In this known solution, the directional control valve assembly is designed with a main stage, which is controlled via a servo-pilot valve to move a valve spool of the main stage out of its spring-biased home position. In this case, depending on the position of the servo pilot valve, two oppositely acting control surfaces of the valve slide of the main stage are subjected to a control pressure difference. Between the servo pilot valve and the main stage, an electrically actuated switching valve is provided in the known solution, which in its spring-biased basic position, that is, when de-energized solenoid, both Control surfaces pressurized with tank pressure. The servo pilot valve will only become effective after switching the switching valve. In the event of a malfunction, for example in the event of a power failure, the switching valve is switched to its normal position and the valve slide of the main stage is moved via the spring arrangement to its basic position, which corresponds to the preferred position.

If this known directional control valve arrangement is used in a fuel injection system, the main stage would be returned to its basic position in the event of a malfunction - but this basic position is usually not the same position which causes a safe shutdown of the cylinder in a fuel injection system.

The invention has for its object to provide a directional valve arrangement and a fuel injection system designed therewith, in which the main stage in the event of a malfunction is reliably and with little device complexity in a preferred position displaced.

This object is achieved by a directional control valve arrangement with the combination of features of patent claim 1 and by a fuel injection system having the features of patent claim 11.

According to the invention, the directional control valve arrangement has a main stage, which is pilot-controlled via a servo-pilot valve. The servo pilot valve is associated with a switching valve via which in its basic position a servo pressure chamber of the servo pilot valve can be acted upon by a control pressure such that the servo pilot valve is moved into an end position, so that the main stage is subjected to a control pressure difference and its valve slide is moved to the preferred position. This preferred position does not correspond - as in the above-described prior art - the basic position predetermined by the valve spring of the main stage, but actively sets a position which is optimal for the device, which in each case is hydraulically connected. D. H. , According to the invention a completely different control concept is realized, in which the servo pilot valve is adjusted, while in the prior art, only the connection between the servo pilot valve and the main stage is interrupted.

In a particularly preferred embodiment, the servo pressure chamber is delimited by a piston, which in turn delimits a control chamber with the valve gate of the main stage, wherein the control chamber-side end face of the piston is preferably smaller than the servo pressure chamber side end face.

The additional piston of the servo pilot valve is advantageously designed as a stepped piston.

Sealing with a stepped piston can prevent seizing after a longer "normal" service life.

In a particularly preferred embodiment, the diameter of the smaller end face of the piston is equal to the adjacent end face of the closing piston, so that the amount of control oil in this control chamber of the main stage relative to the basic version of the servo pilot valve does not change, in which this control chamber instead by the above-described piston according to the invention by a Closure plug is locked. The switching valve for acting on the servo pilot valve with a control pressure can be embodied as an electrically actuated 2-way poppet valve, wherein a servo control line extending from the 2-way poppet valve to the servo pressure chamber is connected to the tank via a nozzle so that there is always a certain control oil volume flow flows to the tank. These losses can be reduced by using a 3-way seat valve instead of the 2-way seat valve, which opens the connection to the tank in a switching position, so that the servo pressure chamber is depressurized.

The main stage is preferably formed by a continuously adjustable directional control valve with a pressure port, two working ports and two tank connections, so that two different consumers or facilities can be actuated and the pressure fluid from these in each case flows through its own tank line and pressure fluctuations in the tank line of a circle does not affect the pressure in the other circle.

This directional control valve is preferably designed with an integrated position control for the valve spool.

This directional valve arrangement can be used in a fuel injection system, wherein a working port of the main stage is connected to the low pressure side of a pressure booster, so that upon pressurization of the low pressure side of the fuel to be injected at the high pressure side is correspondingly high pressure and injected via an injection nozzle into the cylinder. When pressure is applied to the power booster, a hydraulically actuated exhaust valve connected to the other port is closed. At the end of the injection process, ie, when connecting the low pressure side of the pressure booster with the tank, the other working port is pressurized, so that the exhaust valve is opened.

Other advantageous developments of the invention are the subject of further subclaims.

In the following a preferred embodiment of the invention will be explained in more detail with reference to schematic drawings. Show it:

Figure 1 is a view of a directional control valve assembly according to the invention, which is part of a fuel injection system;

Figure 2 shows the hydraulic sense of the directional control valve assembly of Figure 1 and

3 shows a representation to illustrate the interaction of a 2-way seat valve and a servo pilot valve of the directional control valve arrangement from FIG. 1.

Figure 1 shows a side view of a directional control valve arrangement 1 according to the invention, which is designed as a plate assembly valve. The directional control valve assembly 1 is part of a fuel injection system of a low-speed marine engine, wherein j edem cylinder one of the directional control valve assemblies 1 is assigned. This directional control valve arrangement is designed such that its dynamics and flow are large enough to be able to generate the injection pressure profiles required for diesel injection. The output pressure modulated by a position control loop of the directional control valve arrangement 1 acts on a low pressure side of a pressure booster and this is designed so that at a low pressure of approx. 200 bar on the high pressure side of the intensifier in diesel fuel Pressures up to approx. 1000 bar can be achieved. The injection takes place via a fuel injection valve connected to the high pressure side of the pressure booster. Within the time interval in which the injection rests, via the directional control valve arrangement, an exhaust valve of the cylinder can be actuated.

The purpose of this task directional control valve assembly 1 has a main stage 2, which is designed as a continuously variable 5-way valve. The main stage has a pressure port P _7, two tank ports Ty ^, Tp ^ and two working ports CyA '^ FI and a leakage port L. In FIG. 1, the connections P, Tp _j and T _{VA are in} each case formed by two bores opening into an end face of the valve plate 4, wherein the geometry is selected according to a customer-specific connection diagram. The main stage 2 has a in Figure 1 only partially visible valve slide 6, which is received axially displaceable in a valve bore 8. This valve bore 8 is introduced directly into the valve plate 4 in the illustrated embodiment, so that the hardened valve spool 6 is guided by the webs of the valve plate 4. The axial displacement of the valve spool 6 of the main stage 2 is detected by a displacement transducer 10 only indicated and controlled by an integrated position control loop. The required control electronics 12 is integrated into the main stage 2. The actuation of the valve slide 6 of the main stage 2 by means of a servo pilot valve 14 which is designed so that the time required to generate the injection pressure profile accelerations of the valve spool 6 can be achieved.

If a fault occurs on a cylinder of the marine engine, it should be switched to idle. For this purpose, in the directional control valve arrangement 1 according to the invention, the main stage 2 is switched to a preferred position, in which the low-pressure side of the pressure booster is connected to the tank and the pressure at the pressure connection P keeps the outlet valve open. These Preferred position is set in the directional control valve assembly 1 according to the invention by means of a 2-way valve 16, which is designed for leak-free shut-off as a seat valve.

Details of the hydraulic circuit of the directional control valve arrangement will be explained with reference to Figure 2, which shows the hydraulic sense of the directional control valve assembly 1 of Figure 1.

FIG. 2 schematically shows the valve plate 4 which is designed with the above-described customer-specific connection diagram, with the two working connections Cy 1, Cp _j , the two tank connections Tpi, ^T VA _{, the} pressure connection P and the leakage connection L.

The port Cpi (FI: Fuel Inj ection) is connected to the low pressure side of the above-mentioned pressure booster of the fuel injection system and the other working port Cy ^ (Valve Actuation) is connected to an actuator of the exhaust valve. The two separate tank lines Tp ₁ , T _VA are provided so that the pressure booster can not be actuated by the tank pressure peaks of the exhaust valve.

In the valve plate 4, the main stage 2, the 2-way seat valve 16 and the servo pilot valve 14 are integrated or attached to this. As mentioned above, the main stage 2 is designed as a continuously variable 5-way valve, which is pre-controlled via the servo pilot valve 14. The main stage 2 has a pressure connection P ', a tank connection R, a tank connection T and two working connections A, B. The working port A is via a working channel 18 with the working port Cpi, the working port B via a working channel 20 with the working port CyA ' ^the two tank ports R, T of Main stage 2 are connected via tank channels 22 and 24 to the two tank connections Ty _A and Tp _j and the pressure connection P 'of the main stage 2 is connected to the pressure connection P of the valve plate 4 via a pressure channel 26.

The main stage 2 is shown in FIG. 2 in a preferred position (a) in which the pressure port P 'is connected to the working port B and the working port A is connected to the tank port R so that the pump pressure applied to the port P is present at the port Cy ^ and the port Cpj is relieved to the tank port Tpj. D. h, in this preferred position (left end position of the valve spool 6), the outlet valve is opened and the pressure booster depressurized, so that no fuel is injected. In a designated with (0) basic position of the main stage 2, the pressure port P ^{1 is} shut off and the two working ports A, B with the j respectively assigned tank port R or T connected, so that correspondingly the pressure port P of the valve plate 4 is shut off and the two working lines

associated tank connections Ty ^ and Tpj are connected.

In the positions indicated by (b) (move the valve spool 6 from the illustration of Figure 2 to the right over the basic position (0)), the pressure port P to the working port Cpj and the other working port Cy ^ connected to the associated tank port Ty ^ , the tank port Tpj is shut off - in these positions of the valve spool 6 is the fuel injection, the exhaust valve is closed. The adjustment of the valve spool 6 via the servo pilot valve 14, the output terminals A, B via pilot channels 28, 30 are connected to control chambers of the main stage 2. A pressure port P of the servo pilot valve 14 is connected via a pressure control channel 32 to the pressure channel 26 and a tank port T via a tank control channel 34 to the tank channel 24.

The executed as a 4-way valve servo pilot valve 14 may be performed substantially in conventional construction, as is known for example from the data sheet RD 29 564 of the applicant, so that detailed explanations are unnecessary. Such a servo pilot valve consists of an electromechanical converter, a hydraulic booster, which can be designed, for example, according to the principle nozzle - baffle plate and a servo piston, which is coupled via a mechanical feedback to the electromechanical converter (torque motor).

The peculiarity of the servo pilot valve 15 is that this is adjustable by means of a control pressure in the end position shown (a), in which the pressure port P to the port A and the tank port T is connected to the other port B, so that in the pilot port 28 of the Pump pressure or another control pressure and in the pilot channel 30 the tank pressure is applied. Due to the resulting pressure difference of the valve spool 6 is moved to its preferred position shown (a). The adjustment of the servo pilot valve 14 in the end position (a) by means of the 2-way seat valve 16, which is biased by a spring 36 in its illustrated opening position in which a servo control line 38 is connected to a branch channel 40 which from the pressure control channel 32 branches off. The servo control line 38 opens into a servo pressure chamber 42, which is indicated in Figure 2 with an arrow. In the spring-biased basic position of the 2-way seat valve 16, a control pressure is therefore present in the servo pressure chamber 42, through which the servo piston 44 of the servo pilot valve 14 is inserted into the illustrated put end position (a) can be moved. As will be described in more detail below, the pressure in the servo pressure chamber 42 does not act directly but via an interposed piston 46 (see FIG. 3) on the servo piston.

By energizing the switching magnet 47 of the 2-way seat valve 16, it is shifted to its blocking position, in which the servo control line 38 is shut off without leakage relative to the pressure control channel 32 and thus the pressure channel 26. The discharge of the servo pressure chamber 42 via a connected to the tank control channel 34 return passage 48, in which a nozzle 50 is arranged. Via the return channel 48 and the nozzle 50, a control oil leakage stream always flows to the tank connection 1-pχ even when the switching magnet 47 is not energized.

In the shut-off position of the 2-way valve 16, the servo pressure chamber 42 is thus pressure-relieved - the servo pilot valve 14 then does not differ in function from conventional servo pilot valves. This can be moved by means of its hydraulic preamplifier from a central position in which there is no control pressure difference at the main stage 2 in the above-described, marked with (a) control positions or in the positions (b), in which the pressure port P to the port B and the port A is connected to the tank port T, so that accordingly the control pressure in the pilot passage 30 is applied and thus the valve spool 6 relative to the illustration in Figure 2 to the right in its (b) marked positions is displaced to effect the fuel injection and the Close the outlet valve. For example, detects the control of the marine diesel engine a fault that requires that the directional control valve assembly 1 (control valve) or more precisely, the main stage 2 must be switched to the preferred position, the power supply for the 2-way valve 16 is turned off, so that this by the force the spring 36 is switched to its passage position. Accordingly, the servo piston 44 is then moved to the end position (a), so that the valve spool 6 of the main stage 2 is moved to the preferred position (a), in which the exhaust valve is actuated and the power injector of the fuel injection system is depressurized.

The control of the servo piston 44 via the 2-way valve 16 will be explained below with reference to Figure 3, which shows the connection region between the servo pilot valve 14 and the 2-way seat valve 16. The latter is carried out in cartridge design and has a closing cone 52 which is pressed at energizing the electromagnet 47 against a valve seat 54 and lifts off when the electromagnet 47 is de-energized from the valve seat 54 to aufzusteuern the connection from the branch channel 40 to the servo control line 38, which - as from Figure 2 explains - is connected via the return passage 48 and the nozzle 50 to the tank port Tpi. The servo control line 38 is connected to a control terminal Y of the servo pilot valve 14, which is connected via a helical channel 56 with the servo pressure chamber 42, which is formed in a housing cover 58 of the servo pilot valve 14. The servo pressure chamber 42 extends coaxially to a servo valve bore 60, in which the servo piston 44 is guided axially displaceable. In the embodiment shown, this servo valve bore 60 is formed in a valve bushing 64 inserted into the housing 62 of the servo pilot valve 14. In the area between the adjacent end face of the servo piston 44 and the end face of the servo pressure chamber 42, a piston 46 is axially displaceably guided, whose rear end face has a diameter D which is greater than the diameter d of the servo piston 44 facing end face. D. H. , the piston 46 is designed as a stepped piston, wherein the larger end face with the diameter D limits the Servodruck- space 42 and the smaller end face with the diameter d together with the adjacent end portion of the servo piston 44 limits a control chamber 66 which via the hydraulic amplifier of the Servo pilot valve can be acted upon by a pilot pressure. At the outer circumference of the piston 46 seals 68 are arranged. The limited by the stage of the piston 46 annular space is connected to atmosphere. The seals 68 on the piston 46 seal this annular space to the servo pressure chamber 42 and the control chamber 66 out. The stroke limitation takes place in that the servo valve piston 44 moves against its left stop (not visible in the section of FIG. 3). The left in Figure 3 end portion of the piston 46 is guided in the valve sleeve 64 and sealed by the second seal.

When switching off the electromagnet 47, the 2-way seat valve 16 is brought into its passage position, so that in the servo control line 38, the pump pressure is applied. This acts via the inclined channel 56 also in the servo pressure chamber 52, so that the piston 46 is displaced to the left against the pressure in the control chamber 66 from the position shown and the servo piston 44 in its final position (a) moves according to Figure 2, in which generates a control pressure is moved by the main stage 2 in its preferred position (a). The area difference (Dd) causes the piston 46 to be displaced even if the pressure in the servo control line 38 and the servo-internal control pressure are equal can be and thus the servo piston 44 is turned on.

In order to keep the changes as low as possible compared with conventional servo-pilot valves, the dimensions of the piston 46 and its position are selected such that the control oil volume in the control chamber 66 corresponds to that of conventional servo-pilot valves in which the servo-valve bore 60 is shut off laterally by a sealing plug ,

The seals 68 and the seat cone of the 2-way seat valve 16 cause that during the long operation time to a fault, the stepped piston 46 and the seat cone itself, not stuck by "silting", but remain functional.

Furthermore, even with long downtimes of the cylinder no leaks occur that can lead to a setting of slides or can cause an adjustment of the main stage 2 from the preferred position out.

Due to the above-described geometry of the piston 46, conventional servo pilot valves 14 can be rebuilt in a simple manner to be used in the directional control valve arrangement according to the invention.

As mentioned, a small pilot oil flow always flows through the tank line Tp _j during the standstill time via the nozzle 50. To avoid this, instead of the 2-way seat valve 16, a 3-way seat valve can be used, through which a connection to the tank can be opened to relieve the servo pressure chamber 42, so that the return channel 48 and the nozzle 50 no longer have to be provided. Of course, the piston 46 can also be arranged so that the servo pilot valve 14 is moved to its end position (b), so that then in the preferred position, the main stage 2 is moved to the marked with (a) end position in which the pressure port P connected to the work connection Opχ.

Disclosed are a directional control valve arrangement and a fuel injection system designed with such a directional valve arrangement with a main stage, which is pilot-controlled via a servo-pilot valve. The servo pilot valve can be switched by applying a control pressure in an end position in which the main stage is supplied with a control pressure difference to bring them into a preferred position.

LIST OF REFERENCE NUMBERS

1 way valve arrangement

2 main stage

4 valve plate

6 valve slide

8 valve bore

10 transducers

12 control electronics

14 servo pilot valve

16 2-way seat valve

18 working channel

20 working channel

22 tank channel

24 tank channel

26 pressure channel

28 pilot channel

30 pilot channel

32 pressure control channel

34 tank control channel

36 spring

38 Servo control cable

40 branch channel

42 servo pressure chamber

44 servo pistons

46 pistons

47 solenoid

48 return channel

50 nozzle

52 cones

54 valve seat

56 inclined channel

58 housing cover

60 servo valve hole

62 housing Valve bushing Control chamber Seal

Claims

claims

1. Directional control valve arrangement with a main stage (2), whose valve slide (6) delimits at least one pressure chamber, which is acted upon for adjusting the valve spool (6) via a servo pilot valve (14) with a control pressure, wherein in a control line (38, 40) between the servo pilot valve (14) and the pressure chamber (42) is arranged a device in whose

Basic position of the valve slide (6) in a preferred position (a) is adjustable, characterized in that a servo pressure chamber (42) of the servo pilot valve (14) via a valve (16) can be fed with a control pressure to a servo piston (44) in an end position (a) to move such that in the pressure chamber of the main stage (2) a control pressure is applied to the valve spool (6) to adjust its preferred position (a).

2. Directional control valve arrangement according to claim 1, wherein the servo pressure chamber (42) by a piston (46) is limited, which in turn with the servo piston (44) delimits a control chamber (66).

3. Directional valve arrangement according to claim 2, wherein the control-space-side end face (d) of the piston (46) is smaller than the servo-pressure chamber-side end face (D).

4. Directional control valve arrangement according to one of the preceding claims 2 to 3, wherein on the outer circumference of the piston (46) seals (68) are arranged.

5. Directional valve arrangement according to one of the claims 2 to 4, wherein the smaller end face (d) of the piston (46) with the same diameter as the adjacent end face of the valve spool (6) is executed.

6. directional control valve arrangement according to one of the preceding claims, wherein the valve (16) is an electrically operated 2/2-way poppet valve, the pressure connection with a pressure medium source and its Arbeitsbeanschluss via a servo control line (38) with the servo pressure chamber (42 ) connected is .

7. Directional valve arrangement according to claim 6, wherein the servo control line (38) via a nozzle (50) with a tank (Tpj) is connected.

8. Directional valve arrangement according to one of the claims 1 to 5, wherein the seat valve is a 3/2-way seat valve with a pressure port, a working port and a tank port.

9. Directional valve arrangement according to one of the preceding

Claims, wherein the main stage (2) is formed by a continuously adjustable directional control valve, which has a pressure port (P '), two working ports (A, B) and two tank ports (R, T), wherein in each case a tank port and a working port one Consumers are assigned.

10. Directional valve arrangement according to claim 9, wherein the directional control valve with a position control (10, 12) is executed.

11. Fuel injection system, wherein the fuel is acted upon by a pressure booster with high pressure, the low-pressure side via a directional control valve arrangement (1) according to one of the preceding claims with pressure medium is applied, wherein a blank run by switching the directional control valve arrangement (1) in a preferred position (a) is adjustable, in which the pressure booster is depressurized.

12. Fuel injection system according to claim 11, wherein in the preferred position (a) via the directional control valve arrangement (1), an outlet valve is actuated.