SU983298A1 - Charging member with skewing cutoff edge for disengagement of a cylinder, used in high-pressure pumps of diesel engines - Google Patents

Abstract

A fuel delivery element having a piston (1) with an oblique control edge (3) co-operable with a spill port (not shown) in a cylinder (2), for injection pumps of diesel engines, in which pumps the pistons of all the delivery elements are rotatable through equal angles during regulation and some of the pistons have no effective delivery stroke, or a smaller effective delivery stroke than the remaining pistons, during the no-load and low load positions. The oblique control edge (3) of each said piston has a uniform slope and is provided in the effective range of no-load and low load positions with a recessed surface (60) of such small depth that a throttle gap of extremely small cross-sectional area is produced. <IMAGE>

Description

(5) DELIVERY ELEMENT WITH COSOU CUTTING

EDGE FOR DISCONNECTING A CYLINDER USED IN HIGH-PRESSURE DIESEL PUMPS

one

The invention relates to an oblique cut-off discharge element for shutting off a cylinder used in high-pressure pumps of diesel engines, and in a high-pressure pump all pistons of pump elements can be turned by the same angle during adjustment, their cut-off edge has a known uniform slope, and for discharge elements that are shut off at idle and at low load, there is a shallow depth area, forming a throttle slit with a small cross section.

From the description of DE P1, it is known that in conventional high-pressure radial pumps, the metering system has several injection elements in which the design of the piston is changed in such a way that when idling and in the mode of lowest load, the effective motors can no longer occur.

The fuel injection stroke. This can be implemented as an oblique cut-off edge with different slopes on the pump piston.

. (Fig. 6 in DE P1 576 SJ) and by expanding the return groove in the direction that shortens the oblique cutting edge circumferentially (Fig. 2 in OE P1 576310) JO While the cut edge is with different slopes when decreasing engine load causes a gradually intensifying reduction in fuel delivery

15 compared with other cylinders, the expansion of the return groove entails a sharp cessation of supply.

The described down-regulation processes mainly depend only on

Claims (1)

20 from the position of the adjusting rail, and not from the number of revolutions of the engine. This is a disadvantage, since the disconnected cylinders remain off until reaching a nominal 39 revolutions j, which leads to increased fuel consumption. Furthermore, from the description of US Pat. No. 3,197,810, it is known that in the pumping element of the type described it can be switched off at idle and A low load has a shallow depth field, forming a choke slot with a small cross section. In this case, this plate may be limited parallel to the upper edge of the piston. The disadvantage of this solution is. the fact that the bearing surfaces on the piston are not unfavorably distributed, which accelerates its wear. From the description of DE-OS 2, the design of an element with an oblique sipe groove and a centrally transverse hole in the wall of the piston, which is especially effective at low load and at idle. In this way, under low load conditions and with decreasing engine speed, enhanced down regulation is achieved. Thus, depending on the number of revolutions, smooth transitions arise for the gradual shutdown of the supercharger: elements at low loads and revolutions. Through the centrally located hole in the piston and the small transverse hole of the piston, the fuel drains away from the bypass hole in the element cylinder. This prevents effective . injection flow rate when the engine is idling and in the lower partial load range. As the number of revolutions increases, the amount of fuel displaced by the piston gradually increases, and at the same time a small cross section of the opening opening gradually decreases to the same extent, which causes the supply of fuel, depending on the number of revolutions, earlier. As the number of revolutions increases, the connecting point of the disconnected cylinders moves in the direction of all smaller steps of the adjusting rail. The disadvantage of the solution described in DE-OS 2 429.23 is that it is applicable only to pumps whose pistons have a centrally located opening . For discharge elements with a return groove and cutting edge, which, in low load and at idle, compared to other injection elements, produce an inefficient discharge flow, turning to the same angle, a dynamic shutdown characteristic should be achieved depending on from the number of revolutions. At the same time, the design change provided for in accordance with the invention should ensure a more favorable distribution of the supporting surfaces on the piston. The invention proceeds from the task of creating such a construction of an injection element with an oblique cut-off edge of the type described so that as the engine speed decreases, the dynamic characteristic of a smooth decrease in the amount of injected fuel and a complete shutdown of the fuel supply at low load and idling as well as reliable development of production are provided. such a pumping element in relation to its lapping and compliance with the required tolerances of the throttle gap. The task is solved by the fact that the platform is located parallel to the return groove, which is parallel to the axis of the piston, at a certain distance of the groove, which is less than the same width, and the diameter of the bypass hole is smaller. The platform may extend in a known manner, at a certain distance from the upper edge of the piston. In addition, the platform may at the same time have an internal constraint, made at a sharper angle than the spit cut-off edge. Thus, a better distribution of the support bar on the piston can be realized, which in turn provides a more favorable wear characteristic. For dynamic disconnection, depending on the load and speed, and increasing fuel consumption with the main open mode, only in the lower throttling gap are achieved. The conditions for the dynamic flow of fuel through an elongated slot, with only one outlet cross-section of the slot. The production of the proposed injection element can be more reliably mastered with regard to the lapping of this element and the achievable tolerances of the throttle gap. The invention prevents the formation of an unwanted sharp edge at the junction of the throttle slit to the axial groove, which, due to the spread occurring during production, can have a different shape, which in turn causes a large spread of the dynamic characteristic of the throttling effect. This design allows for obtaining a reliably reproducible dynamic response for reducing and shutting off fuel supply. In FIG. Figure 1 shows an injection element with a piston having a platform located parallel to the return groove, running parallel to the axis of the piston at a certain distance from this groove; in fig. and a cylinder and a piston with a partial section A-A in FIG. 2; view from above; in fig. 2 an injection element with a piston having a platform, the internal limitation of which has a sharper angle than the spit cut-off edge 3; in fig. Figure 3 shows the flow of fuel QC .. supplied by known and assumed injection elements depending on the movement of the regulator in idle and partial load modes at various speeds n and rpm in FIG. k is the flow diagram of the fuel supplied by the proposed and known injection elements depending on different speeds within n - f 2 at the same position of the adjusting plate, and RWU. I The delivery element consists of a piston 1, which is lapped in cylinder 2, the piston 1 having an oblique cut-off edge 3 which starts from the return groove 5. The effective pressure stroke of the piston t is achieved by turning the piston with respect to the stationary cylinder 2, and the flow is only That is the time when the bypass hole k in the cylinder 2 is blocked by a zone of piston 1 between the upper edge 7 of the piston and oblique cut-off edge 3. The piston 1 (Fig. 1) within the limits of the bypass hole k when idling and low load area e 86 ku 60, This platform at a certain distance 71 from the upper edge of the piston 7 and from a distance of 51 from the gate gate 5 passes in the direction of travel of the oblique cut-off edge 3. The platform 60 is formed as a result of running grinding of the piston in the region shown in FIG. . 1a The distance 01 from the return groove 5 is smaller than the diameter of the bypass hole i. Platform 62 (FIG. 2) is made as an oblique notch starting at a distance of 51 from the return groove 5 and extending to the oblique cut-off edge 3. The bounding edge 8 thus forms a sharper angle than the cut-off edge 3 to. with respect to the piston axis, the return groove 5. The fuel consumption supplied by separate injection elements (Fig. 3) is shown depending on the movement of the regulator R in idling and small load conditions with two constant speeds in the form of parameters in n and hg. The feed curves N are a characteristic of ordinary injection elements, the number of revolutions n corresponding to the number of revolutions of the idling, and n ,, the nominal number of revolutions. The letter E denotes the flow curves corresponding to the given speed for the proposed injection element (Fig. 1). From these characteristics it can be seen that, at idling speed f, the proposed injection element begins to flow only after moving the regulator larger than the movement of the known injection element. At nominal speed p with load, the supply, carried out by the proposed injection element, is less than the supply of a known element, but reaches its supply over the partial load area, 0. (Fig. 3) indicates the amount of fuel injected, and the position of the rail with the adjusted amount of fuel injected in idle mode. From the feed characteristic Qe at a constant position of the rail, the speed range n, - P2 (FIG.), It can be seen that the supply of the ordinary pressure element N increases approximately linearly, while the element according to the invention increases more than the idle speed p, starting with O, according to the Measurement of the increase in the number of revolutions increases nonlinearly The feed characteristic of the proposed element, as can be seen from Fig. t, is well reproducible. used in high-pressure pumps of diesel engines, and in the high-pressure pump all the pistons of the pumping elements when adjusting, turn to the same angle, their spit from the cross-sectional edge has a known uniform slope, and for injection elements that are shut off at low speed and under low load. there is a shallow depth area, forming a choke slit with a small cross section, characterized in that the space 60 is parallel to the return groove 5 running parallel to the axis of the piston at a certain distance 51, and this distance 51 is narrower than its diameter 51 bypass hole k. 2, an element according to claim 1, characterized in that the pad 60 passes in a known manner at a certain distance 71 from the top, pQ, 7 pistons, 3. The element according to claim 1, due to the fact that the pad 62 has an internal limitation of 8, made with a sharper angle, the spit has an edge 3. It is recognized as an invention according to the results of an examination carried out by the Office for the Invention of the German Democratic Republic. AlA 4l./d