DK174035B1 - Fuel pump with hydraulic setting at the time of injection - Google Patents

Description

DK 174035 B1 i

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a fuel pump with hydraulic adjustment of the injection point and comprising a stationary pump cylinder having an axially movable pump piston having at least one guide edge which, when interacting with an opening in the wall of the pump cylinder, determines the pump delivery amount during a delivery stroke, a roller guide with a roller, which, under the action of a cam on a camshaft, can move the roller guide and thus the pump piston upwards in a delivery stroke, and a setting device located between the pump piston and the roller guide with a pressure chamber which is defined by a cylinder part and a piston part, where the injection time of the pump is adjustable by at least one opening into the pressure chamber for supplying or discharging hydraulic fluid which is fed to the pressure chamber from a source of hydraulic fluid through a non-return valve, thereby changing the axial distance between the pump piston and the roller.

A mechanism of the kind mentioned initially is known from DE-C2-3 510 223. When supplying hydraulic fluid to the pressure chamber, a spring is compressed depending on the pressure of the hydraulic fluid. By changing the pressure it is possible to set the injection time steplessly. The calibration of setting 25 occurs by inserting a plurality of rings between the cylinder member and the spring stop. Calibration thus requires separation of the pump and it cannot be performed while the pump is in operation.

DE-A-3 911 160 describes a fuel pump with 30 variable injection timing. At this pump, a quantity of hydraulic fluid contained in a cup-shaped element and a piston part enclosed can be enclosed, the amount of which depends on the turning position and the piston in the cup-shaped element. When the desired position 35 between the two parts is obtained, they are hydraulically locked until a piston rotation takes place so that a cutting edge exposes a combined drainage and supply opening and additional hydraulic fluid. Due to the hydraulic locking, a setting can not be made steplessly in either direction.

Numerous methods and mechanisms are known for setting the injection time in an internal combustion engine. The setting is crucial for the performance of the engine, for the operating economy 10 and for the thermal load on the motor elements. The best operating conditions are achieved by speeding up the injection time at lower engine loads, which in experience lowers the temperature level of the combustion of the fuel, so that the lubricating oil decomposition 15 becomes smaller and thus the engine elements get better operating conditions and longer service life. The earlier injection also gives a higher combustion pressure and thus a better utilization of the fuel.

Electronically controlled systems known to operate on the high pressure side of the pump are known. These systems are often complicated and require external control and monitoring systems and possibly mechanical emergency systems in the event of electronics failure. Systems operating on the fuel pump are also known, for example, by an axially slidable slide exposing a drain hole which communicates with the pump chamber, or by the pump cylinder itself being axially slidable between two outer positions, giving two different settings of the injection time. These systems suffer from the disadvantages that the seals between the moving parts are difficult to manufacture, which can cause fuel oil leakage into the underlying camshaft lubrication system, the frictional conditions are not quite the same in the various pumps on the engine, and 35 that due to the close fit between the parts 3 DK 174035 B1 a considerable force influence has to be applied to the control, which makes it difficult to achieve a uniform adjustment of all the pumps.

For many years various designs have been worked on the class of Variable Injection Timing (VIT) mechanisms, which is based on the insertion of a hydraulically acting adjusting device between the pump piston and the roller guide which can change the distance between the pump piston and the roller . An example of such a fuel pump is known from GB-A-2,257,206, in which the cylinder part of the roller guide has several openings which lie at different heights in the cylinder wall or have different diameters. To each opening is connected one or two hydraulic lines with associated control valves which can connect the line to a drain or to a pressure source.

Each opening allows for one discreet setting of the injection time. The system is complicated and requires many wiring with associated valves and valve control if more than two discrete 20 settings of injection time are desired.

From DE-PS 1 107 025 a fuel pump is known, the cylinder part of the roller guide having a number of openings in the same level. If the openings are supplied with hydraulic fluid, the piston part of the pump piston is moved up to a stop towards 25. The design only allows setting between two discrete settings while the engine is running. A similar fuel pump is known from DE-C2 35 10 223 where the stop at the top of the cylinder part is adjustable by means of insert rings, so that several pumps 30 on the engine can be adjusted to give the same acceleration of the injection time at the same pressure in the hydraulic fluid. This setting is labor intensive and can only be made while the engine is out of service.

As the pressure springs in the pumps will over time change to DK 174035 B1 4 to give different compressive forces, the setting must be repeated at regular intervals.

The present invention has for its object to provide a stepless, reliable adjustment of the fuel pump injection time by a mechanically simple construction, based on the supply of hydraulic fluid under pressure, but without the requirement of precise pressure, and in which setting and individual adjustment of several pumps can happen during operation.

This object is fulfilled according to the invention in that the t fuel pump is characterized in that the non-valve connection to a source of hydraulic fluid is arranged to supply a certain 15 volume of hydraulic fluid for each pressure stroke of the rotary piston and that the chamber has a drainage channel located in one of the two elements, while the other has a cutting edge extending about its axis, which, when moving the piston member into the cylinder member, causes the drainage channel to enclose one of the two elements' rotational positions. depending on the volume of the pressure chamber.

During the downward suction stroke of the pump piston, the roller guide is moved downwards and the pressure in the pressure chamber of the adjusting device becomes so low that through an inlet opening hydraulic fluid can be fed into the chamber. As the cam then moves the roller and roller guide upward, the pressure in the pressure chamber increases, and the piston member and the cylinder member adjust to the mutually axial position where the inclined guide edge 30 precisely locks the associated opening into the pressure chamber, whereupon any remaining amount of hydraulic fluid inside the chamber is blocked. , so that the upward movement of the roller guide is transferred to the pump piston. As the guide edge is inclined, a mutual rotation of the cylinder and piston members causes a change of the axial position to the position where the guide edge on one part precisely locks the corresponding opening on the other part.

As a hydraulic fluid is fed to the pressure chamber after each downward movement of the roller guide, the adjusting device is insensitive to leaks from the pressure chamber. The amount of hydraulic fluid in the pressure chamber is solely determined by the rotational position of the cylinder and piston parts, which gives the advantage that variations in, for example, the hydraulic fluid's feed pressure for different pumps on the same engine have no influence on the setting of the injection times. Thus, it is uncomplicated to achieve a uniform setting of several fuel pumps, whether these are worn to varying degrees or have compression springs which give different spring forces.

The inclined guide edge provides the essential advantage that the setting of the fuel pump injection time can be done steplessly to any intermediate position 20 between the two outer positions while the engine is in operation, by simply rotating the piston and cylinder parts mutually. This rotation can be carried out in a completely uncomplicated manner, for example by means of a longitudinally displaceable rack which rotates the part connected with the pump-piston to the adjusting device.

This is a mode of adjustment which corresponds to the setting of the pump's supply quantity by turning the pump's temple, and this has for many years proved its high reliability. It is possible to use a separate 30 rack for setting the injection time.

The camshaft lubrication system can be made unaffected by leaks from the adjusting device by the hydraulic fluid being lubricating oil, preferably camshaft lubricating oil.

In a preferred embodiment, the cylinder part 35 is axially fixed to the lower end of the pump piston and has a downwardly open circular cylindrical bore with an upper end wall, and the piston part projects from the roller guide and is inserted into the bore. This gives the advantage that the end wall and thus the pressure chamber are higher than the cylindrical sealing faces against one another on the piston and cylinder parts, and therefore a little hydraulic fluid will seep down and lubricate these surfaces, even if they are only moved for a very short period of time. in relation to each other.

Alternatively, the piston member may be constituted by the lower end of the pump piston inserted into an upwardly open circular cylindrical bore in a cylinder portion of the roller guide which bore has a lower end wall. This provides a simpler representation of the roller guide.

In a further preferred embodiment, the opening to the pressure chamber is located in the cylinder surface of the bore spaced from the end wall, and the oblique guide edge lies on the cylindrical periphery of the piston portion adjacent to the opening and extends helically over an axial distance at least as large as that of the aperture. distance from the end surface. This embodiment is simple to manufacture by milling a sloping recess into the circumferential surface of the piston, and it is also particularly advantageous in the case where the opening in the peripheral surface of the bore 25 acts as a drainage opening which is intended to drain away only lubricating oil, since the oil can only run out on the outside of the cylinder part and down into the camshaft housing.

The invention will now be explained in more detail with reference to the very schematic drawing, in which FIG. 1 is a longitudinal section through a first embodiment of the fuel pump according to the invention; FIG. 2 is an enlarged sectional view of the adjusting device of the pump of FIG. 1, FIG. 3 is a sectional view taken along line III-III of FIG. 1 and 7 DK 174035 B1 fig. 4 is a longitudinal section through the adjusting device in another embodiment of the fuel pump.

In FIG. 1, a generally designated 1 fuel pump is shown for a large two-stroke slow-moving cross-head motor having a fuel pump for each working cylinder. The pumps are driven by a camshaft common to all the pumps, and for each pump the shaft has a cam 2 on which a roller 4 mounted in a roller guide 3 runs. The roller guide is axially displaceable in the lower part of the housing of the fuel pump 5.

The fuel pump has a stationary pump cylinder 6 in which a pump piston 7 is axially displaceable. Above the pump piston there is a pump chamber 8 which is connected via a discharge duct 9 in the top cover 10 of the pump housing 15 to a high pressure line (not shown) which leads to the injector valve or valves which can inject the fuel into the combustion chamber of the working cylinder.

The pump cylinder is surrounded by an annulus 11 which, through a fuel supply duct 12, is kept filled with 20 fuel at pre-pump pressure. At least one cut-off opening 13 in the wall of the pump cylinder connects the annulus with the pump chamber 8 when the upper side 14 of the pump s temples is at a lower level than the cut-off opening, so that fuel can flow into the pump chamber during the downward suction stroke of the pump piston 25.

The lower end of the pump is pumped axially, by means of a bayonet coupling, to a cylinder part 15 of an adjusting device. The bayonet coupling part 16 of the cylinder part also acts as a spring guide for a pressure spring 17, the upper end of which abuts the stationary pump housing 5, so that the spring pushes the cylinder part downwards in the direction of the roller guide 3.

The cylinder part 15 has a downwardly open circular cylindrical bore in which a piston part 18 is axially displaceable. The piston portion 18 is formed as a circular cylindrical pin raised from DK 174035 B1 8, which is pressure-sealed into the bore of the cylinder part, so that between the upper end wall 19 of the bore and the upper side 20 of the pin is a pressure chamber 21 (see Fig. 2). hydraulic fluid can be supplied from a 5 central opening in the upper side via a roller 22 formed in the roller guide, which is connected to a source for supply of pressurized hydraulic fluid via an inlet channel 23 in the pump housing wall and via an axially directed elongated recess 24 in the peripheral surface of the roller guide 10. next to the access channel. The recess 24 may be longer in length than the stroke of the pump piston, so that the channel 22 is held in communication with the inlet channel throughout the downward movement of the roller guide.

The conduit 22 contains a check valve 25 in the form of a spring-loaded ball which prevents the return of hydraulic fluid from the pressure chamber.

In addition to the downward pressure of the spring 17, the roller guide 3 is also pressed down against the cam 2 by a pressure spring 26, the upper end of which touches the stationary pump housing 5 and the lower end depresses the upper side of the roller guide.

In FIG. 3, the cylinder part 15 has on its outer side a projection 27 which extends in the axial direction and is longitudinally disposed in a groove in a control guide 28. The side faces of the groove lie with little clearance outside the opposite side surfaces of the projection 27, so that the cylinder part participates. in the control movements of the control board. An upper radially protruding rim 41 on the control guide is provided with at least 30 parts of its circumference with a tooth which is engaged by a longitudinally displaceable rack 29 housed in the housing 5, so that a displacement of the rack causes a rotation of the cylinder part. 15th

A second control guide 30 is in known manner 35 arranged around the pump piston 7 under the pump cylinder 9 DK 174035 B1 6 and is axially displaceably accommodated in a recess in the housing 5. The rim 31, like the rim 41, is provided with a tooth which is in engagement with a longitudinally displaceable rack 32 housed in the housing 5. Two opposite planar faces 33, 34 are incorporated in the lower section of the pump piston and the regulating guide has at its lower end two inwardly projecting guides, with little clearance beyond the faces 33 , 34, so that the pump piston is longitudinally displaceable relative to the regulator 30, but is forced to participate in its pivotal movements.

The upper side of the pump piston 7 acts as a first guide edge which, at the passage of the cut-off hole 13 during the upward pump stroke, blocks this, so that the fuel delivery begins. The pump piston further has a second oblique guide edge 35 which, when passing through the cut-off hole 13, connects this to the pump chamber 8 via a recess 36 in the piston's peripheral surface, thereby interrupting the fuel delivery. Since the guide edge 35 is inclined, 20 the amount of pump delivery per pump stroke can be adjusted by turning the pump piston by means of the rack 32.

It is well known that the guide edge or edges may be formed in other ways which also provide a definite relationship between the piston's rotational position and the amount of delivery, and as an alternative to the embodiment shown in the drawing, the piston may be formed with such known guide edges.

As can be seen most clearly in FIG. 2, the piston member 18 has a recess having a lower inclined guide edge 37 which extends from the upper side 20 helically along a portion of the cylindrical periphery of the piston member down to an end point located at an axial distance below the upper side 30 which is equally large or larger. than the largest longitudinal displacement of the pump piston for setting the injection time of DK 174035 B1 10, cf. the following explanation of the operation of the invention.

The cylinder part 15 has in its inner cylinder surface a drainage opening 38 which is connected via a channel 39 to the lower cavity 40 of the pump housing, which communicates with the cavity in the underlying camshaft housing. If lubricating oil is not used as hydraulic fluid, the cavity 40 may instead be drained into a hydraulic fluid tank. The upper point of the drainage opening 38 may be at an axial distance from the end wall 19 which is at least as large as the largest desired longitudinal displacement of the pump piston relative to the roller guide, and it is preferred that the distance of the opening from the end wall be less than the largest edge of the guide edge 37. distance from the top 20 so that the adjusting device can be adjusted to an outer position where the top 20 abuts the end wall 19.

The fuel pump works as follows. When the roller 4 is at the lowest section of the cam, the pump piston is at a lower level than the cut-off opening 20 14. In the continued rotation of the cam, the roller runs up to the cam profile so that the roller guide 3 is lifted and the upward movement is transferred via the adjusting device to the pump piston 7. When its top side 14 passes past cut-off hole 13, delivery of fuel oil 25 to the fuel valve begins.

The start time of the fuel delivery can be controlled by means of the setting device by changing the distance of the pump piston to the roller guide. When the cylinder part is rotated to its one outer position, the opening 30 38 is located over the deepest portion of the guide edge 37 and the pressure chamber 21 is in continuous communication with the drainage channel 39, the pressure chamber is substantially emptied of hydraulic fluid and the upper side 20 abuts against the end wall 19. In this position, the pump piston 35 is as close as possible to the roller guide, and the fuel delivery 11 DK 174035 B1 starts as late as possible in the motor cycle late, which is used in the upper load range of the engine.

At lower engine loads, the start time can be accelerated by rotating the barrel member relative to the piston member in a direction whereby the opening 38 is made to expose an intermediate portion of the guide edge 37. At the start of the upward movement of the roller guide, the liquid in the pressure chamber 21 can flow out through the opening 38 at the same time as the top 20 moves up towards the end wall 19. When the guide edge 37, as shown in FIG. 2, is moved up to the top of the opening, the hydraulic fluid is prevented from flowing through the opening 38, and the fluid trapped in the chamber then transfers the lifting force of the roller guide to the cylinder part 15 and 15 thus to the pump piston 7, which is below the remaining part of the delivery stroke. locked in the current axial position relative to the roller guide. Therefore, the upper face 14 of the pump piston will, at an earlier point in the motor cycle, block the cut-off opening 13.

20 The earliest possible injection is obtained by turning the cylinder part to the second outer position, where the opening 38 is completely or almost completely free of the guide edge, so that the rim of the upper side 20 can block the opening and the pressure chamber 21 will be filled with enclosed liquid down to the top point of opening 38.

Since the rack 29 can be adjusted infinitely between the outer positions, the injection time can be adjusted infinitely to any intermediate position while the engine is running. Since the pump piston is rotated by its own rack 32 30 to set the delivery amount, it is possible to regulate the engine with any desired ratio between the fuel quantity and the injection time. As the quantities of leakage from the fuel pumps increase as the pumps wear out, over time it will be necessary to turn the pump piston to a position with greater effective stroke length to maintain a certain amount of delivery to the injector valve. It is an advantage here that the adjustment of the effective stroke length by turning the pump piston can be done without simultaneously changing the injection time 5.

During the downward suction stroke of the pump piston, the spring 17 is relieved so that the hydraulic fluid can flow from the inlet duct 23 and duct 22 up past the check valve 25 and into the pressure chamber 21, moving the upper side of the piston member 10 away from the end wall 19 and exposing the drainage opening 38. When the roller is lifted upward again, the liquid in the pressure chamber again avoids until the cylindrical periphery of the piston part again blocks the drain opening 38. Since the spring 26 acts directly on the roller guide and keeps the roller in contact with the cam, the spring 17 only has to provide a relatively small spring force for securing because the cylinder part follows the downward acceleration of the roller guide. Since the hydraulic pressure in the pressure chamber is only to overcome the influence of the spring 17, this contributes to the hydraulic fluid being able to flow into the pressure chamber at a low pressure of, for example, 2 bar.

Instead, as mentioned above, the guide edge and the drain opening may be formed on the cylinder part and the piston part, respectively, and the piston part may alternatively be placed on the pump piston, while the cylinder part is then placed on the roller guide.

Claims (9)

13 DK 174035 B1 A fuel pump (1) with hydraulic adjustment of the injection point and comprising a stationary pump cylinder (6) having an axially movable pump piston (7) having at least one guide edge which, when cooperating with an opening (13) in the wall of the pump cylinder, determines the pump a quantity of delivery during a delivery stroke, a roller guide (3, 3 ') with a roller (4) which, under the influence of a cam (2) on a camshaft, can move the roller guide and thus the pump piston upwards in a delivery stroke, and one between the pump piston and the roller controlled positioning device having a pressure chamber defined by a cylinder part (15, 15 ') and a piston part (18, 18'), the pump injection time being adjustable by supplying or discharging hydraulic fluid through at least one opening into the pressure chamber. supplied to the pressure chamber from a source of hydraulic fluid through a non-return valve, thereby changing the axial distance between the pump piston and the roller, 20ke characterized in that the counter-valve connection to a source of hydraulic fluid is arranged to supply for each pump stroke of the swivel piston a certain volume of hydraulic fluid and that the chamber has a drain channel located in one of the two elements, while the other has a cutting edge extending around its axis in axis which, when moving the piston part into the cylinder part, causes the drainage channel to cover and enclose one of the two elements' rotational position depending on the volume in the pressure chamber. Fuel pump according to claim 1, characterized in that the cylinder part is axially fixed to the lower end of the pump piston (7, 7 ') and has a downwardly open, circular cylindrical bore with an upper end wall, and the piston part (18, 18). ') protrudes from the roller guide and is inserted into the bore. Fuel pump according to claim 1 or 2, characterized in that the piston part is axially 5 fixed to the lower end of the pump piston and the cylinder part forms part of the roller guide. 4. A fuel pump according to claims 1-3, characterized in that the cut-off edge is located at the end surface of the piston part, the drainage channel being positioned 10. the cylinder wall of the cylinder part. 5. A fuel pump according to claims 1-4, characterized in that the cut-off edge is located along the edge of the cylinder part at its open end, the drain channel extending from the end surface of the piston part to a point on its cylindrical side surface. A fuel pump according to claims 1 to 5, characterized in that the drainage channel opens into a part of the roller guide, which is formed as a cup and in which there is a hydraulic fluid reservoir with a liquid mirror during operation of the pump, which is located higher than the drainage channel. Fuel pump according to any one of claims 1-6, characterized in that the hydraulic fluid is oil which is part of the camshaft lubrication system. Fuel pump according to claim 6 or 7, characterized in that the opening (38, 38 ') into the pressure chamber is located in the cylinder surface of the bore at a distance from the end wall (19) and that the inclined guide edge (37, 37') is on the cylindrical periphery of the piston member 3. adjacent to the aperture and extends helically over an axial distance at least equal to the distance of the aperture (38, 38 ') from the end surface. Fuel pump according to any of the preceding claims, characterized in that the oil-filled chamber is arranged to be filled to its maximum volume at each stroke.