EP1130250A1 - High pressure fuel injection pump - Google Patents

Abstract

Pump has housing with working chamber, reciprocally moving piston rotatably mounted about its longitudinal axis and at least one inlet opening. Opening in piston casing is connected to working chamber, interacts with inlet opening and is designed so liquid flowing into working chamber can be adjusted to turn the piston, which has radial groove with radial depth of at least one per cent of piston diameter. The pump has a pump housing (2) with a working chamber (3), a reciprocally moving piston (4) rotatably mounted about its longitudinal axis (A) and at least one inlet opening (21). An opening (5) in the piston casing is connected to the working chamber, interacts with the inlet opening and is designed so the liquid flowing into the working chamber can be adjusted to turn the piston. A groove (8) extending along the periphery of the piston has a radial depth amounting to at least one per cent of the piston diameter. Independent claims are also included for the following: the use of the pump for a diesel fuel injection system for a large diesel engine and a large diesel engine with a drainage coil pump.

Description

The invention relates to a suction throttle pump for conveying Liquids, especially fuel, according to the preamble of independent claim 1.

EP-A-0 863 308 discloses a piston pump which in particular as a high-pressure pump for the injection system Diesel engine is suitable. Since this piston pump is also suitable for heavy oil , it can also be used to deliver fuel to the injection system a large diesel engine can be used. Such large diesel engines that usually with heavy oil as fuel and injection pressures of up to Operated at 2000 bar can be found, for example, as main drive units for ships and in stationary systems for power generation. To the amount of fuel delivered to the desired load state of the To adjust the motor, means must be provided on the high pressure pump with which the amount of fuel delivered per work cycle between approximately zero and a full load amount is adjustable.

EP-A-0 863 308 therefore proposes a piston pump which includes a Has pump housing with a work space, a back and forth movable piston for enlarging and reducing the working space, and at least one inlet opening for introducing the fuel into the Working space. The piston is mounted rotatably about its longitudinal axis and points in its outer surface one connected to the work area and with the Inlet opening cooperating recess. This recess is designed so that the amount of fuel flowing into the work area is adjustable by rotating the piston about its longitudinal axis. If the piston in the area of its bottom dead center (maximum volume of the Work area), the recess in the piston and the overlap Inlet opening so that the fuel from the inlet opening through the Recess can flow into the work area. The size of the There is overlap by rotating the piston about its longitudinal axis adjustable. In other words, depending on the angular position of the piston Flow connection between the inlet opening and the work area not, partially or fully open when the piston is in the area its bottom dead center. In this way it is per work cycle amount of fuel entering the work area and thus the amount delivered Fuel quantity adjustable. One such disclosed in EP-A-0 863 308 Piston pump, in which the one entering the work area Liquid volume through an adjustable throttling on the Entry opening, that is to say on the suction side, is adjustable as Suction throttle pump called.

Although the suction throttle pump disclosed in EP-A-0 863 308 is in the Practice has proven itself very well in operating states in which the Pump has to pump no or only very small volume flows, problems shown. If the suction throttle pump, for example, as a high pressure pump for the injection system of a large diesel engine is used in a ship, Such conditions occur in the lower partial load range, or when the engine is turned off, but the crankshaft by the connected to it Propeller continues to be turned. Then the piston also moves the suction throttle pump, which is usually driven by the crankshaft back and forth, but without fuel being promoted. In such Operating states occur increasingly wear and tear Signs of wear on. The piston has a significantly increased Eating tendency, and there is a risk of a piston eater, leading to considerable and costly damage.

It is therefore an object of the invention to provide a suction throttle pump to improve the way explained above in that the Wear and the tendency to eat especially in such Operating states in which there are no or only low volume flows promoted, significantly reduced.

The suction throttle pump solving this task is characterized by the features of characterized independent claim 1.

According to the invention, a suction throttle pump is used to convey Liquids, especially fuel, proposed with a Pump housing, which has a working space with a back and forth Movable piston to enlarge and reduce the Working space, which piston is rotatably mounted about its longitudinal axis, and with at least one inlet opening for introducing the liquid into the Working space, one in the outer surface of the piston with the Work space connected and interacting with the inlet opening Recess is provided, which is designed so that the in the Liquid volume flowing into the work area by turning the piston its longitudinal axis is adjustable. Furthermore, a groove is provided, which is extends along the entire circumference of the piston, and its radial Depth is at least one percent of the diameter of the piston.

This deep groove, which is independent of the angular position of the piston each cycle of the piston fills with the liquid, serves as a reservoir and as Distributor. During the stroke movement of the piston, it is in the groove existing liquid distributed along the running surface of the piston, from which very good lubrication of the piston results. Especially in such Operating conditions in which very little or no liquid flows through the Recess in the piston in the working area of the pump guaranteed the liquid present in the deep groove that the piston is sufficient is lubricated to reliably prevent the piston from seizing. For each The operating state of the suction throttle pump is therefore always sufficient liquid for lubricating the piston.

To increase the cross-sectional area of the groove, the axial height is the groove preferably at least ten percent of the diameter of the Piston.

Preferred configurations are those in which the radial depth of the groove at least six percent, in particular about ten percent, of The diameter of the piston is approximately and the axial height of the groove fifteen percent of the diameter of the piston. These dimensions have proven themselves in practice to provide particularly good lubrication of the Ensure piston.

To further improve lubrication and lower Stress peaks in the material, it is advantageous if the groove is rounded Has edges.

Furthermore, with regard to the filling of the groove, it is advantageous if the groove is arranged with respect to its axial position so that it the inlet opening fully or partially opposite when the piston is in its top dead center. This measure is namely the open one Flow cross section between the inlet opening and the groove just then maximum or particularly large if the piston speed is minimal.

The suction throttle pump according to the invention is particularly suitable for Use as a high pressure pump to deliver fuel, especially heavy oil, for the injection system in a diesel engine.

Since the suction throttle pump is suitable for pumping heavy oil, it is suitable itself to feed the fuel into the injection system Large diesel engine.

Further advantageous measures and preferred configurations of the Invention result from the dependent claims.

Fig. 1:

ein Ausführungsbeispiel der erfindungsgemässen Saugdrosselpumpe mit den wesentlichen Teilen, teilweise im Schnitt,

Fig. 2:

den Kolben des Ausführungsbeispiels im unteren Totpunkt, und

Fig. 3:

den Kolben des Ausführungsbeispiels im oberen Totpunkt.

The invention is explained in more detail below using an exemplary embodiment and the drawing. The schematic drawing shows:

Fig. 1:

An embodiment of the suction throttle pump according to the invention with the essential parts, partly in section,

Fig. 2:

the piston of the embodiment in bottom dead center, and

Fig. 3:

the piston of the embodiment at top dead center.

In the following description, reference is made to the specific application referred to that the suction throttle pump as a high pressure pump for pumping heavy oil for the injection system a large diesel engine is used.

Fig. 1 shows the parts essential for an understanding of the invention Embodiment of the suction throttle pump according to the invention, the is generally designated with the reference number 1, in part cut and partially symbolic representation.

The suction throttle pump 1 comprises a pump housing 2, in which a Work space 3 is provided, and a back and forth arranged piston 4, which by its oscillatory movement between two reversal points periodically enlarged and downsized. Below is the reversal point, which is a minimum Volume of the work space 3 corresponds to, referred to as top dead center and the turning point, the maximum volume of the work space corresponds as bottom dead center. Fig. 1 shows the piston 4 in its lower Dead center. The piston 4 is essentially cylindrical and pivoted about its longitudinal axis A. For this there is a piston 4 Driver bushing 7 is provided with teeth. By means of a Control rod 6, which is provided with teeth which engage with the Teeth of the driver bush 7 are, the piston 4 is through accordingly moving the control rod 6 in the direction of Double arrow B in both directions C rotatable about its longitudinal axis A.

The stroke movement of the piston can e.g. B. in a conventional manner a cam 11 arranged on a shaft 10 and a cam follower 12 are driven. The shaft 10 is, for example, by the Crankshaft of the engine set in rotation. The cam 11 presses the Piston 4 against the force of a piston spring, not shown as shown upwards.

The suction throttle pump 1 further comprises at least one inlet opening 21 for introducing the liquid (heavy oil) into the work area 3 and one Outlet opening 22 through which the pressurized heavy oil is pushed out. The inlet opening 21 is connected via a suction line 13 connected to a low pressure system for the heavy oil. That under pressure Heavy oil that has been placed enters through outlet opening 22 via Check valve 14 in a pressure line 15 which to the injection system of Motors, for example for the pressure accumulator of a common rail system, leads.

2 shows a view of the piston 4 for better understanding Direction of the inlet opening 21, which is indicated by dashed lines. The piston 4 is at its bottom dead center. The pump housing is in section indicated. Fig. 3 is analogous to Fig. 2, but the piston 4 is in his shown top dead center. In Fig. 2 and Fig. 3 the piston 4 is in an angular position in which only a very small amount of liquid is pumped becomes.

In the lateral surface of the piston 4 there is one with the working space 3 connected and interacting with the inlet opening 21 5 is provided, which is used to adjust the position in the work area 3 Fuel quantity and thus serves to regulate the delivery rate. In which The embodiment 5 described here extends the recess 5 initially in the form of a groove 51 (see FIGS. 2 and 3) of the Working space 3 facing end face 49 of the piston 4 along the Lateral surface of the piston parallel to its longitudinal axis A and then goes in a substantially V-shaped portion 52 which extends in the circumferential direction of the piston 4 is tapered. The inlet opening 21 is arranged so that it is at the same height (with respect to the longitudinal axis A) as the V-shaped one Part 52 of the recess 5 when the piston 4 in its lower Dead center is (see Fig. 2). To those that occur in the material To lower voltage peaks are the edges of the recess 5 rounded. This applies in particular to the edges of the groove 51 in the Mouth area in the end face 49, for the edges in the transition area between the groove 51 and the V-shaped part 52 and for the edge on the Tip of the V-shaped part 52.

For reasons of the most symmetrical possible pressure distribution are preferred at least two substantially identical recesses 5 in the The outer surface of the piston 4 is provided, preferably diametrically are arranged opposite each other and up to the Work area 3 facing end face 49 of the piston 4 extend. Naturally can also be provided more than two such recesses 5, the preferably evenly distributed in the lateral surface of the piston 4 are arranged. It is understood that in such cases where several Recesses 5 are also arranged in the outer surface of the piston more than one inlet opening 21 can be provided in the pump housing. Since it is sufficient for understanding, only one of the possibly considered several recesses 5.

The recess 5 is used in the operating state for the controllable introduction of Heavy oil in the work area 3. The piston is located in FIGS. 1 and 2 4 roughly at its bottom dead center. In this state the Recess 5 (in the angular position of the piston 4 shown) Connection between the inlet opening 21 and the work space 3. The for The heavy oil prepared for combustion passes through the suction line 13 Inlet opening 21, as symbolically represented by the one with the reference symbol BE provided arrow is indicated, and from there through the recess 5 in the work area 3. During the subsequent stroke movement of the piston the piston closes the inlet opening 21 and reduces the size Workroom 3, which puts the heavy oil in it under pressure becomes. This passes through the outlet opening 22 and the check valve 14 into the pressure line 15. During the subsequent downward movement of the Piston 4 or when this is in the area of its bottom dead center is located, a connection is again formed between the inlet opening 21 and the work space 3 through the recess 5, so that for the next Heavy oil work cycle can get into work area 3.

With the generic suction throttle pump, the load-dependent takes place Regulation of the amount of heavy oil extracted by regulating the in the Working area 3 entering heavy oil quantity. For this purpose, the recess 5 geometrically designed such that, depending on the angular position of the piston 4 relative to the pump housing 2 more or less fuel in the Working space 3 can reach when the piston 4 is in its lower Dead center is located. As can be seen in particular from FIG. 2, the Coverage between the recess 5 and the inlet opening 21 depending on the angular position of the piston 4. For example, the Delivery increased compared to the situation shown in Fig. 2 the piston 4 is activated by operating the control rod 6 rotated counterclockwise as shown. This gives the Recess 5 a larger part of the inlet opening 5 free when the Piston 4 is at its bottom dead center, so more fuel in the Work area 3 can flow. Conversely, turning the Piston 4 in a clockwise direction (as shown in Fig. 2 and Fig. 3) Coverage between the recess 5 and the inlet opening 21 reduced in size so that less fuel can flow into the work space 3, when the piston 4 is at its bottom dead center. Will the Piston 4 turned so far that none in its bottom dead center Coverage between the inlet opening 21 and the recess 5 is present, the flow rate of the suction throttle pump 1 is zero.

With regard to the design of the recess 5 and especially its geometry numerous variants are possible. In this regard, reference is made to the one already cited EP-A-0 863 308. In particular, it also explains how about the geometry of the recess 5 different control characteristics (Relationship between displacement of control rod 6 or Angular position of the piston 4 and change in the funded Amount of liquid) can be realized.

According to the invention, a groove 8 is provided in the suction throttle pump 1, which extends along the entire circumference of the piston 4, and whose radial depth T is at least one percent of the diameter D of Piston 4 is. With the radial depth is the depth in the Longitudinal axis A of the piston 4 meant the vertical direction. Preferably the axial height H of the groove 8 is at least ten percent of Diameter D of the piston 4. With the axial height is the expansion of the Groove 8 meant in the direction of the longitudinal axis A. In particular, it has in the Proven in practice if the radial depth T is at least six percent is specifically about 10 percent of the diameter D. For the axial height the groove 8 has a value of approximately fifteen percent of the diameter D. proven. "Approximately" denotes dimensions that are up to ± 30% from corresponding nominal value may differ.

Preferably, the groove 8 is in relation to the axial direction, with which the Direction of the longitudinal axis A is meant, arranged so that the groove 8 is the same height as the inlet opening 21 and thus this opposite when the piston is at top dead center. This is 3 can be seen in particular. Of course, the groove 8 with respect to Axial direction can also be arranged so that it the inlet opening 21st only partially opposite when the piston 4 is at top dead center is located, that is, the inlet opening 21 is partially at the top dead center covered by the piston 4.

It has proven to be advantageous if the groove 8 has rounded edges 81 has, as shown in Fig. 2 and Fig. 3. The edges 81 which limit the groove 8 with respect to the radial direction to the outside each rounded down. As a result, the lubrication of the piston 4 can still continue to improve, and the stress peaks in the material are reduced.

Furthermore, are in the embodiment described here as shown, several relief grooves 9 below the groove 8 provided for pressure equalization, each along the entire Extend circumference of the piston 4 and ensure that around the circumference the piston 4 around there is essentially the same pressure everywhere. The Relief grooves 9 are usually with respect to their respective axial Height and their respective radial depth significantly smaller than that Slot 8.

The groove 8 ensures in particular in such operating states Suction throttle pump 1, in which only very small or no volume flows are promoted, so very little or no fuel in the Workspace 3 arrives, ensuring that it is not a defective one Lubrication of the piston 4 comes.

3, the groove 8 is a large one Cross-sectional area, with each working cycle with the inlet opening 21 connected when the piston 4 is at top dead center. Consequently fills the groove 8 - regardless of the respective angular position of the Piston 4 - with each stroke in the area of top dead center with fuel, which can flow into the groove 8 from the inlet opening 21. In the subsequent downward and upward movement as shown, the fuel located in the groove 8 along the tread of the Piston 4 distributed and thus ensures good lubrication of the piston 4th At the end of the upward movement, the piston 4 returns to the upper one Dead center, fuel can flow in from the inlet opening 21, so that the groove 8 is filled again. The groove 8 serves as a storage and distribution element for the lubricant that is identical to the fluid being pumped.

The groove 8 thus ensures that even in such Operating states in which the suction throttle pump 1 has no or only very much promotes small amounts of liquid, always sufficient lubrication of the Piston 4 is present so that there is no excessive wear, heavy wear or the piston 4 may seize. This significantly increases the operational safety of the suction throttle pump 1.

Of course, the groove 8 can also deviate from that in FIGS. 1-3 Design shown cross-sectional areas other than a square have, for example, a partially curved or rounded Cross-section. The terms axial height and radial depth then denote the maximum axial height or the maximum radial depth.

The suction throttle pump according to the invention is suitable for delivery any liquids. A preferred use is as High pressure pump to deliver fuel to the injection system of a Diesel engine. In particular, the suction throttle pump according to the invention especially as a high-pressure fuel pump in a fuel oil-powered one Large diesel engine suitable. There, the suction throttle pump 1 is preferred driven by the crankshaft of the large diesel engine and promotes that Heavy oil under a pressure of up to 2000 bar, for example approximately 1200 bar into the injection system of the large diesel engine. If this after The suction throttle pump feeds the common rail principle Heavy oil under high pressure in the pressure accumulator (accumulator) of the common Rail systems. The possibility of each in the work room 3 of Regulating the amount of heavy oil brought in by pump 1 can Delivery capacity of the suction throttle pump to the desired one Load condition of the large diesel engine can be adjusted. Through the groove 8 is thereby ensures that even in operating conditions in which no heavy oil is pumped and the pump works in "idle", always sufficient There is lubrication of the piston. This increases the Operational safety of the entire large diesel engine.

Claims (8)

Suction throttle pump for pumping liquids, especially of Fuel, with a pump housing (2), which has a work space (3), with a reciprocating piston (4) to enlarge and reduce the working space (3), which pistons is rotatably mounted about its longitudinal axis (A), and with at least one Inlet opening (21) for introducing the liquid into the work area (3), one in the outer surface of the piston (4) with the Working space (3) connected and with the inlet opening (21) cooperating recess (5) is provided, so is designed such that the flowing into the work space (3) Liquid quantity by turning the piston (3) around its longitudinal axis (A) is adjustable, characterized by a groove (8), which is extends along the entire circumference of the piston (4), and the radial depth (T) at least one percent of the diameter (D) of the Piston (4). Suction throttle pump according to claim 1, wherein the radial depth (T) the groove (8) at least six percent, in particular about ten Percent, the diameter (D) of the piston (4). Suction throttle pump according to claim 1 or 2, wherein the axial Height (H) of the groove (8) at least ten percent of the diameter (D) of the piston (4). Suction throttle pump according to one of the preceding claims, which the axial height (H) of the groove (8) about fifteen percent of Diameter (D) of the piston (4). Suction throttle pump according to one of the preceding claims, which the groove (8) has rounded edges (81). Suction throttle pump according to one of the preceding claims, which the groove (8) is arranged with respect to its axial position so that it faces the inlet opening (21) completely or partially, when the piston (4) is at top dead center. Use of a suction throttle pump according to one of the preceding claims as a high pressure pump for conveying Fuel, especially heavy oil, for the injection system in a diesel engine. Large diesel engine with a suction throttle pump according to one of the Claims 1-6 for conveying the fuel into the injection system.

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