JP3519089B2 - Method of operating hydraulically operated fuel pump for internal combustion engine and hydraulically operated fuel pump - Google Patents

Description

The present invention is directed to a fuel conduit for supplying fuel to a fuel pump at a primer pump pressure, a high pressure conduit for supplying a pressurized hydraulic fluid different from the fuel to the fuel pump, and a fuel pump. A pump piston that is pushed out of the chamber, is driven forward in the discharge stroke by the actuator piston in the actuator cylinder, and fills the pump chamber with fuel from the fuel conduit, and is driven backward in the return stroke. And the actuator piston is controlled by an electronically actuated control valve, which allows the pressure chamber in the actuator cylinder to be supplied with hydraulic fluid from a pressure conduit or connected to a drain port. Relates to a method of operating a hydraulically operated fuel pump for an internal combustion engine, in particular a two stroke crosshead engine It

Such a method is described in Danish Patent No. 1511 of the applicant.
No. 45, known, according to this patent, the displacement of a fuel pump is controlled by the rotation of a pump piston, which is connected to an actuator piston.
At the end of the discharge stroke, the pump piston can be pulled back by the actuator piston while at the same time refilling the pump chamber with a compression spring that pushes the actuator piston rearward. Pumps are complex designs with many separate parts, many of which must be machined with great precision in order for the pump and actuator pistons to function correctly.

Hydraulic pumps have long been known (1928).
Applicant's Danish Patent No. 41046), this pump uses fuel as hydraulic fluid, and in one embodiment the pump displacement is supplied from a cam-controlled feed pump In the embodiment of the invention, as determined by a cam-controlled control valve, the drive of the camshaft of the control valve provides more energy to the engine at high speeds than at low speeds, thus Depending on the speed of the control valve, the control valve reacts in different states as a result of which it does not provide a specific starting position or a specific delivery volume for the pump piston. The filling of the pump chamber is carried out hydraulically or by a suction force exerted by an actuator piston, so that the pump piston is pushed backwards by a spring.

U.S. Pat.No. 3,516,395 shows a fuel pump whose filling is controlled by a motorized valve and the actuation of the injection is synchronized with the rotation of the crankshaft and controlled by a second valve. Fuel is used as the hydraulically driven fluid.

For many years it has been impossible to use fuel as hydraulic fluid in large diesel engines. The reason is that the properties of such fuels make them unsuitable for hydraulic purposes. A typical fuel is a heavy oil fuel that requires preheating and contains active and abrasive components. Most modern engines can also use liquid gas as fuel, but such gas is also unsuitable as a hydraulic fluid due to the risk of ice formation during explosion and cooling.

In known hydraulically driven pumps since recent years, the fuel is kept completely separated from the hydraulic fluid, and the fuel supply in these pumps is carried out by the rotation of the pump pistons, which results in an oblique cutoff. The position of the edge changes with respect to the blocking hole in the side wall of the pump cylinder. In addition to the above Danish patent, one example of such a pump is US Pat. No. 4,907,555. In this case, the control valve that supplies the high-pressure hydraulic fluid is
It can be either cam operated or electronically controlled. Furthermore, an electronically actuated control valve for a hydraulically driven fuel pump is known from the applicant's Danish patent 170121, whose control valve is precise and quick-acting.

It is an object of the invention to simplify hydraulically operated fuel pumps and to achieve high pump reliability in terms of design, operation and maintenance.

In view of this, the method according to the invention provides for the pump piston to return to a constant starting position during each injection process by the action of the pressure of the fuel exerted on the end face of the pump piston in the pump chamber, When the desired amount is discharged, the discharge amount of the fuel pump is electronically controlled by the control valve that shuts off the supply of the hydraulic fluid to the pressure chamber.

Fuel primer Pump pressure to bring the pump piston back to a constant starting position, and control the discharge rate by shutting off the hydraulic fluid supply at the very moment the pump has delivered the desired volume. There are several advantages. In this way, the interruption time can be adjusted until the moment when the interruption actually occurs. When the discharge rate changes, the new adjustment takes effect immediately, acting on the cylinder in which the injection takes place, and during the same revolution of the engine, during subsequent injections, can be used in other cylinders. This quick-acting electronic control of pump discharge is 1
An injection sequence can be provided, which can be varied as desired from one continuous injection to a series of closely spaced injections, so-called intermittent injections.

Further, the present invention provides for mechanical return and filling as well as
It is possible to dispense with the known mechanical elements for controlling the blowoff rate, which offers the advantage that many options are possible for the design of the fuel pump. It is also possible to omit the commonly used fuel oil accumulators, also called shock absorbers. It is a further advantage that the return to the starting position takes place over a relatively long period of time, since the injection takes place during a short engine cycle. Also, no specific rotation angle is required between the pump piston and the pump cylinder or actuator piston. The simplification of the operation and the accompanying mechanical simplification substantially reduce the risk of pump failure.

Furthermore, this method has the important effect that the energy losses associated with the operation of the pump are minimized. One reason for this is that the consumption of the pump piston and the high pressure hydraulic fluid stop at the end of the fuel discharge, instead of relieving the pressure in the pump chamber and continuing at the same time as is usual with known pumps. Because it does. Yet another reason is that a constant starting position allows to minimize the dead volume in the pressure chamber of the actuator and thus to minimize the amount of hydraulic fluid to be pressurized immediately after opening the control valve. Because.

Fuel for internal combustion engines, during combustion, it is known that can be mixed with water to reduce the occurrence of undesired NO _X compounds. In known fuel pumps, the engine must operate with a fixed amount of water mixed in, or it must be stopped and reconfigured for operation without the addition of water. This is one problem. The possibility according to the method of the invention of varying the discharge rate of the fuel pump during operation as desired is preferably applied as follows: the electronic control unit controls the fuel flow at the engine load. Switching the pump to deliver an additional amount at the same engine load, reaching 1-60% of the amount, and at the same time the fuel is mixed with an amount of water corresponding to the additional fuel amount To do so. Changes to this low NO _X operation mode can be easily performed while the engine is running, the ratio of the amount of fuel constituted by the additional amount is varied depending on the desired during operation it can, thus, additional amount of water can be continuously adjusted according to other operating conditions decrease, such as temperature and humidity of the engine load and the intake air of a desired NO _X. The possibility of this sudden change to another operating mode is
It is particularly advantageous if the engine is a propulsion engine for a ship that periodically navigates water bodies subject to NO _x emission limits.

SUMMARY OF THE INVENTION The present invention is a pump piston that is longitudinally displaceable within a pump cylinder, the pump piston having a front end surface that defines a pump chamber with the pump cylinder, and an actuator cylinder disposed within an extension of the pump piston. A longitudinally displaceable actuator piston having a piston surface disposed in the pressure chamber, the piston surface facing away from the pump piston, and substantially greater than a cross-sectional area of the pump piston. Actuator piston having a relatively large area,
For an internal combustion engine, in particular a two-stroke diesel engine, comprising at least one fuel inlet passage with a check valve opening into the pump chamber and at least one fuel outlet passage leading from the pump chamber to at least one exhaust port. Further relates to hydraulically actuated fuel pumps.

When the method of the present invention is applied, fuel pump design is conveniently simplified, as adjustment of fuel delivery conditions, both in terms of volume and time, does not impose the usual restrictions on fuel pump design. It The fuel pump according to the present invention is a device in which the pump cylinder and the actuator cylinder are separated from each other by an annular intermediate separating member, and
The pump cylinder is characterized in that it has a lower part that projects downwards into the separating member and an upper part that projects radially with respect to the lower part and is mounted by means of cover studs.

The two cylinders are manufactured as independent devices, stacked during assembly of the pump, separated by an intermediate member, also aligning the axes of the cylinders relatively coarsely with each other, and the cylinder shaft plugs are radiused. It is almost unnecessary to consider whether or not they are displaced from each other in the direction. The fact that the two cylinders do not have to fit together very accurately substantially simplifies the manufacture and installation of the parts. Dividing the pump casing into two cylinders and an intermediate member and assembling with cover studs, i.e. axial bolts, occurs when the pump chamber is pressurized and faces upwards with respect to the upper wall in the chamber. This has the advantage that tensile stresses acting on forces are eliminated. Since the intermediate member only has to withstand the compressive load from the assembly, the degree of fixation between the intermediate member and the two cylinder devices can be made relatively small.

During the discharge stroke, the pistons are pushed away from each other by the propulsive pressure acting on the piston face of the actuator piston, and during the return stroke, the pistons are driven by the relatively small force of the return pressure due to the inflow of fuel into the pump chamber. Stay close to each other. In addition, during operation, a slight radial displacement of the rear end face of the pump piston relative to the front end face of the actuator piston allows the two pistons to be positioned relative to each other, which allows for the separation between the individual parts of the pump. It is possible to automatically compensate for changes in temperature and pressure, reduce wear of the pump, and improve reliability. The piston is controllable to some extent radially by means of an element arranged between the two pump cylinders, for example a pressure gauge which sends data to the electronic control device on the current pressure of the pump chamber to the pump piston relative to each other. It can be arranged between the facing end faces.

The modular construction of the fuel pump with two separate pump cylinders further offers the advantageous possibility that only the actuator cylinder with the associated piston needs to be replaced with another device. In this case, the diameter of the actuator piston is larger than that of the original device so that the maximum injection pressure of the pump can be varied, depending on the pressure of the fluid in the high pressure conduit and the area ratio between the actuator piston and the pump piston. Increase or decrease.

In one preferred embodiment, which fully enjoys the advantages of mutually independent pistons, the pump piston is
It is guided only radially by the associated cylinder bore of the pump cylinder, the actuator piston is guided only radially by the cylinder bore of the associated actuator cylinder, and the two pistons are freely adjustable relative to each other in the radial direction. This embodiment has a minimal number of elements, resulting in simplification of manufacture and high reliability.

In one embodiment, the actuator cylinder is an annular device having an axially extending cylinder bore, the fuel pump is mounted on top of the distributor block, and the cylinder bore of the actuator cylinder is
Located adjacent to the extension of the exhaust port on the upper surface of the distributor block, whereby the pressure chamber is defined radially by the actuator cylinder and axially by the piston surface of the actuator piston and the upper surface of the distributor block, respectively. Is defined as The axially extending cylinder bore of the actuator cylinder makes the actuator design extremely simple to manufacture. The reason is that the actuator consists of only two main parts: an annular bottomless cylinder device and a cylindrical actuator piston. The pressure chamber of the actuator is formed by mounting the fuel pump on the top surface of the distributor block. This is because this attachment constitutes the bottom surface that axially defines the chamber. At the same time, the upper surface of the distributor block functions as a stop for the lowering movement of the two pistons and thus determines the starting position of the pistons. In this position, the pressure chamber
Most of the hydraulic fluid has been discharged. Electronically actuated control valve
Since it is typically mounted on or within the dispenser block, there are only short passages to the discharge ports on the top of the dispenser block. For this reason,
The amount of hydraulic fluid between the control valve and the actuator piston is suitably small so that the control valve will
When opening up to the pressure in the high-pressure conduit, the advantage is realized that the energy consumption for pressurizing this fluid quantity is negligible. At the same time, minimizing dead volume in the pressure chamber makes the time delay after actuation of the valve due to the build-up of the required pressure negligible, so that the electronically actuated control valve Serves to improve rapid actuation characteristics.

The cover stud allows a three-part pump casing to be fastened to the top of the distributor block,
This offers several advantages in terms of fuel pump inspection. When the cover stud is loosened, the pump cylinder with its associated piston can be lifted with the intermediate member as far as possible, leaving the actuator cylinder with its associated piston in the distributor block. The actuator prevents dust from entering the lower hydraulic device while the pump is removed. Since most inspections are performed only on the fuel-affected pump cylinder, it is very advantageous to be able to lift the pump piston together with the associated cylinder, both in terms of equipment maintenance and safety. is there.

When a fuel pump is used for injection of liquid gas, heating of the pump is unnecessary. The pump according to the invention is substantially simpler than known pumps for heavy fuel oil, but when using heavy fuel oil and when the engine is in start standby mode, the preheated oil flows through the pump. Being able to flow would be one advantage. To achieve this, the outer surface of the lower portion of the pump cylinder can be provided with an annular recess which is pressure sealed at the top and bottom with respect to the surrounding inner surface of the separating member,
The fuel inlet formed in the wall of the intermediate member reaches into the annular chamber formed by the recess and the intermediate member, and the discharge passage having the reduced pressure flow restrictor can be continuously connected to the annular chamber. Thus, the fuel flows from the inlet through the annular chamber and is discharged from the discharge passage, the flow restriction in the passage prevents pressure drop in the annular chamber, and the preheated fuel is pumped by circulation. Heat the cylinder.

The above advantages of leaving the actuator as a loose dust cover of some kind on the sensitive hydraulic components in the distributor block are due to the upstanding annular wall having an inner diameter larger than the cylinder bore of the actuator cylinder. Further improvement by the upper surface of the actuator cylinder provided and by positioning an upwardly closed cup-shaped shield at the lower end of the pump piston at a distance from the lower surface of the pump cylinder extending downward around the annular wall. be able to. When the pump cylinder and piston are lifted, the upright wall around the cylinder bore of the actuator causes dust particles to enter the top of the actuator piston, and when continuously operated from this position, dust particles between the cylinder and piston. It is prevented from being carried to the air gap and consequently damaging the sliding surface by wear. The cup-shaped shield of the pump piston, along with the wall, protects fuel from leaking downwards to the actuator piston during operation. This is because a certain amount of fuel leaks through the annular gap between the pump piston and the land of the cylinder on the top of the shield. As the shield extends downwards around the wall, fuel from the top of the shield will flow down only along the outer surface of the wall, which prevents fuel from reaching the actuator piston. The fuel drain port in the cavity between the actuator and pump can prevent large amounts of fuel from collecting around the wall.

The cup-shaped shield is located in a cavity formed by the height of the intermediate member, which cavity participates in the movement of the pump piston and also separates the fuel and hydraulic devices as described above. There is no practical use other than providing space for it. in this way,
The three-part construction makes it possible to utilize the cavity for other purposes. In practice, all known elements that mechanically determine the displacement of the pump by the rotation of the pump piston are replaced by adjusting the volume through temporal control of the supply of hydraulic fluid to the actuator. In particular, when the control valve connects the pressure chamber of the actuator to the high pressure conduit, the delivery of hydraulic fluid may be slightly different between the pumps, resulting in a slight change in the delivery of the pump. By continuously measuring one or more combustion parameters in the cylinder,
It is possible to compensate for these parameters by identifying such changes in pump displacement and then electronically actuating the control valve. Alternatively, the wall thickness of the cup-shaped shield is reduced downward and at least two sensors are provided on the intermediate member on both sides of the shield to detect the intermediate position of the pump piston. The available space in the cavity may be used to design the fuel pump as desired. These two two-sided sensors measure the position of the piston at the same time, so that the electronic control device receiving the measurement signal may arise due to the possibility of the piston being freely positioned in the radial direction. It is possible to compensate for changes in the measured values at one sensor. These sensors are well known and may be, for example, inductively measuring the position of the piston.

Electronically controlling the delivery rate of the fuel pump by stopping the delivery stroke of the pump piston, starting from a constant lower starting position, includes a lower portion that fits in a pressure-tight manner about the pump piston, A pump cylinder having a chamber portion having an inner diameter larger than that of the lower portion, a fuel inlet passage opening into a side wall of the chamber portion, and at least two fuel outlet passages starting from the side wall of the chamber portion, thereby improving pump reliability. It offers the preferred possibility of further improvement. It is well known from prior art pumps having pressure relief holes that are opened or closed by the edges of the piston by passing through the fuel outlet passages and / or passages or holes. That is, rapid changes in pressure in the control edge passage of the piston can cause cavitation and can also cause other corrosive damage to the piston and cylinder. By providing the chamber portion with a larger inner diameter than the low pressure pressure seal portion in accordance with this preferred embodiment of the present invention, the cylinder surface of the pump piston moves radially a predetermined distance within the chamber portion sidewall. The inlet and outlet passages for the fuel end or start at the side wall of the chamber part, which means that the fuel is fully accessible to the passage opening of the pump chamber regardless of the position of the piston and continuously. Means This is because at this opening there is at least one annular region filled with fuel between the cylinder face of the piston and the side wall of the chamber part. This region eliminates abrupt corrosive pressure changes and improves the reliability of the fuel pump. Furthermore,
Abrasive particles in the fuel can cause wear at the edges of the passage openings. The fact that the opening is located at a certain radial distance from the cylinder surface of the pump piston prevents damage due to wear of the edge of the hole from spreading to the piston in the form of scratches, That further improves reliability.

In one embodiment, the diameter of the upper portion of the pump cylinder can be increased to further simplify the fuel pump design. In this embodiment, the fuel outlet passage is connected to the upward discharge port and the flange for the pressure conduit leading to the fuel injector is mounted on the upper surface of the upper part of the pump cylinder. This facilitates the mounting of the pressure conduits and allows them to be designed without bending near their mounting location on the pump. Sufficient space on the top surface of the pump cylinder allows mounting of up to four pressure conduits on the top surface.

One embodiment allows the pump cylinder in the region above the chamber portion to have a smaller diameter portion which constitutes an upwardly closed damping chamber and the pump piston to have a height greater than that of the damping chamber. It is possible to have a top portion with a height corresponding to, and an outer diameter slightly smaller than the diameter of the damping chamber. This damping chamber improves the reliability of the fuel pump. The reason is,
The risk of pump damage is reduced when the high pressure to the pressure chamber of the actuator cannot be stopped, for example due to a temporary stop of the control valve or a delay or lack of an electronic switching signal to the control valve. Is. As the pump piston is driven to the top of the pump chamber due to the lack of such a signal, the pump piston continues to rise into the damping chamber, with the side walls of this closed chamber,
The piston forms an annular cavity through which fuel in the damping chamber is forced, simultaneously increasing the pressure in the damping chamber and substantially slowing the movement of the piston. Thus, the damping chamber constitutes a hydraulic buffer that prevents the pump piston from hitting hard on the top of the chamber. The advantage is that the uppermost part of the pump piston occupies a volume approximately equal to the damping chamber and when the piston is in its starting position the total amount of fuel in the pump cylinder is not substantially increased by the addition of the damping chamber. Bring Energy savings are realized by minimizing this amount, as the entire volume of fuel has to be pressurized so that the opening pressure of the injector can be achieved before injecting fuel. The reason is that the stroke distance of the pump piston for this pressurization is short, which minimizes the consumption of high-pressure hydraulic fluid.

Advantages for the operator are realized in that the actuator piston has a recess near its lower surface and that a stopper mounted on the wall of the actuator cylinder projects into this recess. This stopper is
Prevents the actuator piston from falling out of the cylinder when the cylinder is lifted. This feature is particularly important when the actuator is disassembled after long hours of operation by an unskilled person who does not know that the actuator cylinder does not have a bottom.

One preferred embodiment of the present invention will now be described in detail below with reference to the schematic drawings. 1 is a side view of the outline of a fuel pump according to the present invention mounted on a cylinder in an internal combustion engine.

  2 is a longitudinal sectional view of the fuel pump of FIG.

  FIG. 3 is a view of the fuel pump viewed from above.

The fuel pump 1 is mounted on the upper surface of a distributor block 2 supported by a console 3. The console is connected to a high-pressure conduit for hydraulic fluid, which is supplied with hydraulic fluid from a pump station (not shown), for example at a pressure in the range 125 to 325 bar. This pressure may be constant, but is preferably adjustable with respect to engine load. The pump station can be supplied from a storage tank and the hydraulic fluid can be, for example, standard hydraulic oil, although engine lubricating oil is preferably used as the hydraulic fluid, and The device is preferably supplied from the sump of the engine.

The internal combustion engine may be a medium speed four stroke engine, but is typically a low speed two stroke crosshead engine which is the propulsion engine of a ship or the stationary prime mover of a power plant. The engine can be designed in various sizes with a power output per cylinder of 400 kw to 5500 kw, and the engine can range from, for example, 200 rpm for the smallest engine to, for example, 60 rpm for the largest engine. It can be designed so that the full load value speed is achieved. Typically, at specific fuel consumptions in the range of 160g / kwh to 185g / kwh, the required amount of fuel per injection stroke at full load is about 6g for the smallest engine to the largest engine. It can be changed up to about 250g. The fuel pump according to the invention is particularly suitable for injecting a large quantity of fuel, for example a fuel quantity of 30 g or more at full load.

The high pressure conduit from the pump station is attached to the side of a console 3, which supports the distributor block 2 on its upper surface. A pressure conduit 4 extends from the block to the actuator of the exhaust valve. Several pressure tubes 5, such as three, are connected from the fuel pump 1 to the injector 6.
Extending to the injection device for injecting fuel into the combustion chamber of the engine cylinder 7. The lower flange 8 of the pressure pipe is bolted to the pump 1.

Each of the cylinders of the engine is associated with an electronic control unit 9 which receives signals for synchronizing and controlling as a whole via line 10 and controlling electronic control signals via line 12. Transmit to valve 11. The controller can receive a signal from the control valve via line 13 regarding the immediate position of the control valve. The cylinders can each be provided with one control device 9 or several cylinders can be associated with the same control device. The controller may also receive signals from the overall controller common to all cylinders.

In the console, a passage 14 separate from the pressure conduit
Causes the pressurized hydraulic fluid to flow through the high pressure port of the control valve 11.
The passage 14 is provided with a number of fluid accumulators 15, which supply most of the fluid volume when the control valve is open and while the control valve is closed. Resupplied from the high-pressure line. Via a relatively short passage 16 in the distributor block, the control port on the control valve is connected to the exhaust port on the upper surface 17 of the block.

The control valve also has a tank port connected via a passage 18 to a return conduit for the used hydraulic fluid. The pressure in the return conduit is in the range of atmospheric pressure to overpressure of a few bar.

When the fuel pump should start supplying fuel, the control device 9
A control signal from actuates control valve 11 to a position that connects the high pressure port to the control port, so that high pressure fluid is freely accessible to the exhaust port via passage 16. When the discharge stroke of the pump is to be stopped, the control valve is actuated to the position connecting the tank port to the control port, which causes the high pressure in the passage 16 to drain.

Therefore, the control valve 11 has at least three ports and at least two positions. The control valve may include a rapidly actuated pilot slider that hydraulically adjusts the main slider. The control valve can, for example, be of the type described in the Applicant's Danish patent 170121.

The upper surface of the fuel pump 1 has a cover 19 for the engine cylinder.
It is lifted by the console 3 to almost the same height as
For this reason, the pressure pipe 5 has a short length, and therefore the amount to be pressurized at the start of each injection is preferably small.
The fuel pump is kept fueled by a fuel conduit 20, which is typically a primer pump at an overpressure in the range of 4 to 15 bar, typically 8 bar. Distributes fuel to the pump by. The branch conduit 21 extends from the fuel conduit to the fuel inlet 22 illustrated in FIG. This pump is further connected to a drainage conduit 23 which removes fuel leaks.

The fuel pump comprises two cylinder devices, an actuator cylinder 24 and a pump cylinder 25. These cylinders are separated from each other by an intermediate member 26, the lower surface of which is in contact with the upwardly facing annular surface of the actuator cylinder and whose upper surface is in contact with the downwardly facing annular surface of the pump cylinder. ing. The intermediate member is annular and substantially cylindrical and has a relatively thin wall thickness which is less than or equal to half the wall thickness of the two cylinders. The intermediate member is fastened to the two cylinders by means of small machine screws 27 so as to hold the three parts of the casing together when the pump is driven.

The pump cylinder 25 includes a substantially circular tubular lower portion 28.
And an upper portion 29 having an outer diameter substantially larger than the lower portion. The downwardly facing annular surface for abutting the intermediate member 26 is formed by the lower surface of the radially projecting portion of the upper portion and is located just outside the lower portion 28, so that said portion is formed on the outer surface of the lower portion. Two O-rings 29 arranged in the groove formed are pressure-sealed to the inner surface of the intermediate member at the top and bottom of its cylindrical outer surface.

Between these two axially separated pressure seals,
The outer surface of the lower portion has a recess which, together with the inner surface of the intermediate member, defines an annular chamber 30. The annular chamber 30 is in part in communication with the fuel source 22 and in part in communication with an exhaust passage 31 extending from the annular chamber to a circulation conduit (not shown) for the preheated fuel. Throttle means 32 is provided at the connection of the circulation circuit, and the throttle means is provided with a flow restrictor that regulates the amount of circulating fuel.

When mounted on the upper surface 17 of the distributor block, the fuel pump is positioned such that the actuator cylinder is positioned around the exhaust port of passage 16 and the pump cylinder is fastened to the distributor block by cover studs 33. It The cover stud 33 is inserted into a through hole 34 in the protruding portion of the upper portion 29 of the cylinder.

The actuator cylinder 24 is a pressure-sealed, annular device having an axial through cylinder bore 35 which receives a longitudinally displaceable actuator piston 36. The actuator piston is machined so that its lower edge has a slightly smaller diameter, which actuator recess has an annular recess 37 with a stopper 38 in the form of a screw end. Projecting into the recess 37 of the, the screw is inserted through a bore extending diagonally through the cylinder wall. The front portion of the screw fits into the associated bore in a pressure-sealed condition, and in addition, below the screw head, a pressure-sealed gasket is located. When removing this screw, the actuator piston can be moved down and out of the cylinder. The lower surface 59 of the actuator piston, together with the cylinder bore and the upper surface 17, define a pressure chamber 60, which
The lower surface of the 60 is in contact with the upper surface 17, so that it is substantially empty in the illustrated starting position.

A longitudinally displaceable pump piston 39 is inserted in the pump cylinder. The lower part 40 of the pump cylinder fits in a pressure-tight manner around the pump piston. The lower part has, via a conical part, an upper adjacent chamber part 41 having a larger inner diameter than the lower part 40.
Continuing into, and at the top of the chamber portion, the cylinder bore continues into the upper adjacent damping chamber 42.

The actuator piston has a planar upward end face 43 perpendicular to the actuator longitudinal axis,
The pump piston also has a downwardly facing end surface 44 which abuts the end surface 43 at the illustrated piston starting position. These two end faces are between the pump piston 39 and the cylinder part 40, and between the actuator piston 36 and the cylinder bore 35.
Under the action of a guiding force between them and in a radial direction independent of each other. It should be understood that the up and down directions shown are used for clarity and apply to the illustrated fuel pump mounting. Other mounting methods are also possible, such as mounting laterally on a vertical surface. In addition, front and rear or front and rear directions may also be used, where front and front shall indicate the direction in which the pump piston moves during the active delivery stroke.

Mounted at the top of the actuator cylinder 24 within the cavity 45 formed by the intermediate member 26 is an upstanding annular wall 46 having an inner diameter greater than the cylinder bore 35.
A cup-shaped shield 47 that is closed upward is attached to the lower end of the pump piston. Side wall 48 of the shield extends downwardly and runs downward around the outer surface of wall 46. The shield and walls prevent impurities such as leaked fuel and dust particles from entering the upper surface of the actuator piston. As an alternative to the attachment of the shield 47 shown in the drawing, when the shield is pressed onto a conical guide surface by a nut screwed into the end of the pump piston, the shield 47
Can be interference-fitted into the cylindrical guide surface of the pump piston. A drain opening, not shown, near the top surface of the actuator cylinder connects the cavity 45 to the drain conduit 23.

The thickness of the side wall 48 of the shield is thinned down. Intermediate member 26
At, two sensors 49 are mounted on the diametrically opposite sides of the side wall 48 and transmit signals to the control device 9 via line 50. This signal may be, for example, a voltage, the magnitude of which may correspond to the distance between the end of the sensor and the outer surface of sidewall 48. This wall is sloping and therefore lengthens as the pump piston moves upwards, so that the sensor provides the controller with feedback information regarding the immediate position of the piston.

The fuel inlet passage 51 connects the pump chamber 52 with the annular chamber 30 through the discharge passage 31. A check valve 53 that allows only the flow of fuel into the pump chamber is arranged in the flow path between the discharge passage 31 and the pump chamber. When the pressure in the pump chamber exceeds the primer pump pressure in the annular chamber 30, the check valve closes, and when the discharge process of the pump piston is completed, the pressure in the pump chamber drops again. At this time, the check valve reopens and allows fuel to flow in at the primer pump pressure. This check valve is screwed into the lateral bore 54 of the upper part 29, providing the advantage that the check valve does not take up space on the upper surface of the pump cylinder.

Three fuel outlet passages 55 start from chamber portion 41,
Upper discharge port 56 at the connection of the pressure pipe to the injector 6
Is over. Each of the passages 55 comprises a radial bore having an outer end interrupted by one threaded element 57 and an axial bore. As shown in FIG. 3, these three radial bores and bores 51, 54 can be evenly distributed in the circumferential direction of the cylinder. With regard to the connection of the pressure line, if desired, a check valve can be placed in the pressure line after the end of the discharge process to prevent fuel from flowing back into the pump chamber. Further, an axial central bore 58 extending upwardly from the top of the damping chamber 42 can be formed. The bore 58 is blocked by one element 57 but serves to insert a lifting tool which can be screwed onto the top of the pump piston, if desired, so that said piston can be lifted with the pump cylinder. You can

The pump piston comprises an annular radially outermost portion 61,
And a stepped front end surface having a central radially innermost portion 62 displaced upward relative to the outer portion 61.
Between these two parts, the pump piston has an uppermost part 63, the height of which corresponds to the height of the damping chamber 42, the outer diameter of which is greater than the inner diameter of the damping chamber. Is also slightly smaller.

The fuel pump operates as follows. That is, the control valve
11 drains the pressure chamber 60 in the actuator,
That is, when kept connected to the valve tank port, the fluid pressure in the pressure chamber will be low, such as an overpressure of 0.5 bar. As used herein, drain refers to the possibility of draining used hydraulic fluid as a whole. Therefore, the drain is not always at atmospheric pressure. The drain port connected to the tank port of the valve can be pressurized to a slight overpressure, eg 0.5 bar above. While the chamber is connected to the drain port, the check valve 53 opens and allows fuel to flow into the pump chamber 52 at the primer pump pressure so that the pressure in the chamber is:
For example, an overpressure of 8 bar. When the drainage pressure is adjusted to be higher than atmospheric pressure, the ratio of the actuator piston area to the pump piston area should be such that the downward force applied to the pump piston exceeds the lifting force applied to the actuator piston. Less than the ratio of the primer pump pressure in the chamber to the drainage pressure in the pressure chamber of the actuator. In the illustrated embodiment, the ratio between the areas of the pistons is 4: 1, while the ratio between the absolute values of pressure is about 6: 1.

As long as the control valve 11 is in the above position, the pump piston and the actuator piston are pushed downwards by the pressure in the pump chamber and thus move back to the illustrated starting position, the pistons abut each other and the actuator The lower surface 59 of the piston abuts the upper surface 17 of the distributor block.

When the control valve is actuated to connect its high pressure port to passage 16, the pressure in pressure chamber 60 suddenly increases, for example, to 25
It rises to a pressure in the conduit as high as 0 bar. Due to this pressure, the actuator piston is pushed forward and drives the pump piston into the pump chamber 52, and the rise in pressure in this pump chamber causes the check valve 53 to close,
The pressure in the pressure pipe 5 rises. After the piston has traveled a short distance, the pressure of the fuel in the pressure pipe 5 reaches the operating pressure of the injector, which can be, for example, 400 bar, and the injection of fuel begins.

When the injection is interrupted by the control device 9 and the control device transmits an actuation signal for switching the control valve 11, the passage 16 is reconnected to the tank port and the pressure in the pressure chamber drops sharply to the drain pressure, At the same time, the pressure in the pump chamber simultaneously drops to the primer pump pressure and the pump piston stops. After that, the check valve 53 opens,
The fuel again begins to flow into the pressure chamber, which pushes the pump piston and actuator piston back into their starting position, after which the process can be repeated during the subsequent injection process.

During the return operation, the pump chamber may be supplied with an amount of fuel corresponding to the amount injected in the preceding process, and the injection in the two-stroke engine is performed by It is worth noting that it is typically done during 15 revolutions, so that 14/15 revolutions of the engine are used for piston return or for injection into other cylinders by the same pump. . Even if the downward force on the piston is relatively small, there is sufficient time for the piston to return to its constant starting position.

Naturally, many modifications can be embodied in the above embodiment. For example, it is possible to design an actuator cylinder with a closed bottom by providing the cylinder with a supply passage to the pressure chamber. It is also possible to provide a different design, such as a step, to the upper surface of the actuator piston without taking any further measures, and one upright stud on the actuator piston can also be used for the cup-shaped shield. It is possible to obtain the effect of supporting the body 47 and allowing the lower surface of the pump piston to loosely abut the upper surface of the shield. A pump piston design without a shield can be used when position signals are not needed. Although it is possible to design the fuel pump with a casing capable of absorbing tensile stress in a conventional manner, this is not desirable. Furthermore, the two pump cylinders can be integrated so that there are no actual cavities, the cylinder bore of the actuator extending, for example stepwise or conically, into the cylinder bore of the pump, so that the upright inner wall or the inside It can be a short length fuel pump without a shield. If the pump supplies fuel to the four injectors, the flow restrictor can be located in the lateral bore, as in the check valve. Further, the exhaust port 56 can be oriented laterally so that the pressure tube 5 can be attached to the side wall of the pump. Also, the fuel pump can be mounted so that the actuator cylinder is located above the pump cylinder, while at the same time the annular wall 46 and the cup-shaped shield 47 can be omitted, which will prevent fuel leakage. This is because there is no possibility of mixing with the hydraulic fluid that has run down and leaked. This leaked hydraulic fluid is typically discharged to a sump of a diesel engine. Also, the fuel pump
It may be located below or beside the dispenser block, or elsewhere, such as in the cylinder cover 19.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Senker, Paul Deko, Kingdom of Denmark 2770 Castle, Lestrupwei 68 (56) References JP-A-1-15460 (JP, A) JP-A 64-352 ( JP, A) JP 4-301176 (JP, A) JP 9-32686 (JP, A) JP 54-111013 (JP, A) Actual opening 57-134358 (JP, U) Actual opening Sho 60-23248 (JP, U) Actually open 2-139359 (JP, U) Actually open 63-61573 (JP, U) Actually open 2-40974 (JP, U) Special table 8-511072 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 59/48 F02M 47/00 F02M 59/10

Claims (10)

(57) [Claims] 1. A pump piston (39) displaceable in the pump cylinder (29) in a longitudinal direction, the pump piston having a front end surface defining a pump chamber (52) together with the pump cylinder, and the pump piston. An actuator piston (36) disposed in the extension of the actuator and displaceable longitudinally in the actuator cylinder (24), the actuator piston (36) having a piston surface (59) disposed in the pressure chamber and At least one fuel inlet passageway (51) having an actuator piston pointing away and having an area substantially larger than the cross-sectional area of the pump piston and a check valve (53) opening into the pump chamber.
And at least one fuel outlet passageway (55) extending from the pump chamber to at least one exhaust port,
In a hydraulically operated fuel pump for an internal combustion engine, especially a two-stroke diesel engine, the pump piston is not constrained to the actuator piston, the pump cylinder (25) and the actuator cylinder (2
4) is a separate device separated from each other by an annular intermediate separating member (26), and the pump cylinder has a lower portion (28) protruding downward into the separating member, and Having a radially projecting upper portion (29) and a cover stud (33) for mounting the fuel pump on the distributor block (2), leaving the actuator cylinder on the distributor block. A hydraulically operated fuel pump, characterized in that the fuel pump can be inspected. 2. A hydraulically actuated fuel pump according to claim 1, wherein the pump piston (39) is guided only radially by the associated cylinder bore of the pump cylinder (25) and the actuator piston (36). Is guided only radially by the cylinder bore (35) of the associated actuator cylinder, the two pistons being radially adjustable relative to each other, a hydraulically actuated fuel pump. 3. The hydraulically actuated fuel pump according to claim 1, wherein the actuator cylinder (24) is
An annular unit having a cylinder bore (35) extending axially therethrough, the cylinder bore (35) of the actuator cylinder being located adjacent the extension of the discharge port on the top of the distributor block, which causes the pressure chamber to ,
A hydraulically actuated fuel pump, characterized in that it is defined radially by an actuator cylinder and axially by a piston surface of an actuator piston and an upper surface of a distributor block, respectively. 4. The hydraulically actuated fuel pump according to claim 1, wherein an outer surface of a lower portion (28) of the pump cylinder has an outer surface with respect to an inner surface surrounding the intermediate member (26). An annular recess, which is pressure-sealed at the top and bottom, and a fuel inlet (22) formed in the wall of the intermediate member, has an annular chamber (30) formed by the recess and the intermediate member. ) And a discharge passage (31) having a reduced pressure flow restrictor connected continuously with the annular chamber. 5. The hydraulically actuated fuel pump according to claim 1, wherein the actuator cylinder (24) has an upright surface having an inner diameter larger than a cylinder bore of the actuator cylinder. Ring wall (4
6) and that the upwardly closed cup-shaped shield (47) is positioned at the lower end of the pump piston (39) at a distance from the lower surface of the pump cylinder that extends downward around the annular wall. And a hydraulically actuated fuel pump. 6. The hydraulically actuated fuel pump according to claim 5, wherein the thickness of the wall of the cup-shaped shield (47) is thinned downward, and the intermediate position of the pump piston (39) is detected. Therefore, at least two sensors (49) are attached to the intermediate member at both sides of the shield, so that the hydraulically operated fuel pump is provided. 7. A hydraulically actuated fuel pump according to claim 1, wherein the pump cylinder fits in a pressure-tight manner around a pump piston (39). And a chamber portion (41) having an inner diameter larger than that of the lower portion, and a fuel inlet passageway (51).
Opening into the side wall of the chamber part and at least two fuel outlet passages (55) starting from the side wall of the chamber part. 8. The hydraulically actuated fuel pump according to claim 7, wherein the fuel outlet passage (55) is connected to the upward discharge port (56) and reaches the fuel injector (6). Hydraulically actuated fuel pump, characterized in that a flange (8) for the pressure pipe (5) is mounted on the upper surface of the upper part of the pump cylinder. 9. The hydraulically actuated fuel pump according to claim 7, wherein the pump cylinder (25) in the region above the chamber portion (41) comprises an upwardly closed damping chamber (42). Having a smaller diameter portion, and the pump piston has a height corresponding to the height of the damping chamber,
And a hydraulically actuated fuel pump having an uppermost portion (63) having an outer diameter slightly smaller than the diameter of the damping chamber. 10. The hydraulically operated fuel pump according to claim 1, wherein the actuator piston (36) has a recess (37) near its lower surface.
And a stopper (38) attached to the wall of the actuator cylinder protruding into the recess.
Hydraulically operated fuel pump.