Title of Invention

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES

Abstract The present invention provides a fuel injection pump for internal combustion engines, comprising pump cylinder a pump-piston which is driven to and fvo in a pump cylinder and is rotatable by means of a control device, and which encloses with its end face in the pump cylinder a pump work area which is connected through at least one of the control port provided in the outer surface of the pump cylinder to a fuel area remaining under low pressure, which control port is closed, at the start of the stroke of the pump piston through one of the control edges provided on its end face, and at the end of the stroke of the pump piston, permanently connected to the pump work area through a oblique control edge which extends obliquely to axis of the pump piston a depression and a longitudinal groove is opened again, and at a distance from the first control edge joins itself with an additional control edge displaced away from the end face characterized in that the oblique control edge is subdivided into a first oblique control edge allocated to the first control edge and at least one additional oblique control edge allocated to the additional control edge and which is offset relative to the first oblique control edge towards the end face of the pump piston and the distance of the end of the additional oblique control edge at the side of the first oblique control edge from the end of the additional control edge to the first control edge in circumferential direction is smaller than the distance of the extend of the control port in circumferential direction and the extend of the control port in alignment of the pump piston axis being greater than the smallest distance of the additional control edge from the additional oblique control edge as its transition to first oblique control edge and an additional control port provided in the wall of the pump cylinder which overlaps with an additional longitudinal groove emanating from the longitudinal groove in axis direction, when the control port is located, in relation to the circumference of the outer surface, in the region between the first control edge and the subsequent additional control edge and of the transition between the first oblique control edge and the subsequent additional oblique control edge.
Full Text The invention proceeds from a fuel-injection pump as classified in patent claim 1. In such a fuel-injection pump known from DE 4,225,803, a longitudinal groove is arranged in the outer surface of the pump piston between a first control edge and a second control edge, said longitudinal groove constantly connecting the pump working space to the recess delimited by the oblique control edge and taking the form of annular groove. The latter separates the control-edge region provided for a hot-running internal-combustion engine from the control region provided for running with a cold internal-combustion engine. This longitudinal groove constitutes a stop groove, by means of which, with the internal-combustion engine running hot, the internal-combustion engine can be brought to a standstill, without having to pass over the injection-quantity range having a high injection quantity and provided for running with a cold internal-combustion engine. As a result of this stop groove, a specific rotary-angle range of a pump piston is occupied and therefore the possible regulating rotary-angle range of the pump piston is restricted. This is a disadvantage particularly also when the pump piston has a double-flow design, that is to say when two control bores are activated simultaneously by control edges and oblique control edges corresponding to one another.
Avantages of the invention
In contrast to this, the advantage of the fuel-injection pump according to the invention, having the defining features of patent claim 1, is that, on the one hand, it is possible, in the range of fuel-injection

quantity control for the hot-running internal-combustion engine, to bring about a plurality of start-of-injection ranges, the mutually offset oblique control edges, in conjunction with the given diameter of the control port, achieving a smooth transition between the fuel-injection quantity setting at the end of one range and the fuel-injection quantity setting at the start of the other range. The design according to the invention, particularly in conjunction with the control edge offset relative to the first control edge and with the oblique control edge offset relative to the first oblique control edge, in cooperation with the control port and the additional longitudinal groove with the additional control port, ensures that, without an interruption in the control ranges between the hot-running internal-combustion engine and cold internal-combustion engine, with the assignment to the first control edge no inter¬mediate groove reducing the regulating travel has to be provided and, nevertheless, a stop effect is achieved in the range between these said operating ranges, with a zero feed. Via the additional longitudinal groove with the additional control port and the overlap of the control edge offset relative to the first control edge with the oblique control edge offset relative to the first oblique control edge via the control port, there is a sufficiently large available flow-off cross section, via which the pump working space can be effectively relieved of pressure and injection is thus terminated.

Accordingly the present invention provides a fuel injection pump for internal combustion engines, comprising pump cylinder, a pump piston which is driven to and fro in the pump cylinder and is rotatable by means of a control device and which encloses with its end face, in the pump cylinder, a pump working space which is connected to a fuel injection valve and which is connected to a low pressure fuel space by at least one control port arranged in an outer surface of the pump cylinder, said at least one control port serving for filling and relieving the pump working space, said control port, at a start of a feed stroke of the pump piston, is closed by a control edge arranged on one end face of the pump piston and, at another end of the feed stroke of the pump piston, is reopened by an oblique control edge on pump piston which extends obliquely relative to an axis of the pump piston and is a limiting edge of a recess which merges circumferentially into a longitudinal groove connected continuously to the pump working space and is located in the outer surface of the pump piston, the control edge on the end face of the pump piston comprising a first control edge which has adjoining said first control edge in the direction of increasing distance of the oblique control edge from the end face, at least one additional control edge offset relative to the first or the preceding control edge, and at least one additional oblique control edge which is assigned to the additional control edge and which is offset relative to the first oblique control edge towards the end face of the pump piston, with a transitional edge extending

in alignment with the axis of the pump piston between the first control edge and additional control edge of which the distance from the transitional edge in the circumferenctial direction is smaller than the width of the control port in the circumferential direction, the extent of the control port in alignment with the pump-piston axis being greater than a smallest distance between the additional control edge following the first control edge and the additional oblique control following the first oblique control edge at its transition to the first oblique control edge and with an additional control port which is provided in the wall of the pump cylinder and which overlaps an additional longitudinal groove starting fiom the longitudinal groove in the axial direction, when the control port is located, in relation to the circumference of the outer surface, in the region of a transition between the first control edge and the following additional control edge and of a transition between the first oblique control and the following additional oblique control edge.
The invention will now be described in more detail with reference to embodiments given by way of example and shown in the accompanying drawings, in which;
Figure 1 shows a cutout fi'om a fuel-injection pump having the design according to the invention of the pump piston and pump cylinder, and Figure 2 shows a developed view of the outer surface of the pump piston in the region of the control edges and oblique control edges with associated control bores.

Figure 1 shows a so-called pump element consist¬ing of a cylinder liner 3 which forms a pump cylinder 2 and which is conventionally inserted into a housing of an in-line fuel-injection pump not shown any further. Guided sealingly displaceably in this pump cylinder 2 is a pump piston 5 which is driven to and fro by a cam drive, not shown further, synchronously with the rotational speed of the associated internal-combustion engine and which can be rotated by means of a regulating device, not shown, in order to set the fuel-injection quantity per pxomp-piston stroke. This can take place by means of a mechanical regulator or by means of an electronically controlled regulator. Such regulators are known and therefore need not be shown in more detail in the present application.
The pump piston moving to and fro in the pump cylinder 2 encloses with its end face 6, in the pump cylinder, a pvimp working space 7. For this purpose, the cylinder liner 3 inserted into the associated in-line fuel-injection pump is closed on the end face in a way not shown here and, on this end face, has an injection conduit, likewise not shown further here, which leads to the associated fuel-injection valve on the internal-combustion engine, to which fuel-injection valve the pump piston 5 feeds fuel under injection pressure during its feed stroke. Provided in the cylinder liner are two control ports 8 which are located diametrically opposite one another and which connect the pump cylinder to a fuel low-pressure space surrounding the cylinder liner 3. During the suction stroke of the pump piston, after its end face 6 has opened the connection of the control ports 8 to the inside of the pump cylinder, the pump working space is supplied with fuel from said fuel low-pressure space. During the upstroke after the control ports have been closed, a high fuel pressure can then build up in the pump working space and, when the injection pressure set on the fuel-injection valve is exceeded, is injected. This injection is terminated when the control ports are opened again by a control edge of the pump piston and, at the same time, a connection between the pump working

space 7 and the control ports is made. The fuel quantity being injected is the greater, the greater the stroke of the pump piston between the closing of the control ports 8 and their reopening.
To control the fuel-injection quantity, the pump piston has in its outer surface 10 two longitudinal grooves which are located diametrically opposite one another and which open into the end face 6 of the pump piston. Furthermore, the outer surface of the pump piston has worked into it, in each case, two first ground-down portions 14 located diametrically opposite one another and two second ground-down portions 15 located diametri¬cally opposite one another, said first and second ground-down portions being of different width, starting from the end face 6 of the pump piston, as seen in the longitudi¬nal direction of the pump axis. These ground-down por¬tions can be seen more clearly particularly in Figure 2 which is a developed view of the pump piston. The first ground-down portion 14, adjacent to the longitudinal groove 12 on the left, is made adjacent to a first control edge 16. The first ground-down portion is placed horizontally in such a way that it forms, together with the outer surface of the pump piston, a second control edge 17 which, like the first control edge, extends in a radial plane relative to the axis of the pump piston, but is shifted away from the end face 6 of the first control edge 16 towards the drive side of the pump piston. The transition is formed in the circumferential direction by a limiting edge 19 of the first ground-down portion, said limiting edge extending parallel to the axis of the pump piston. The second ground-down portion 15 partially overlaps the first ground-down portion 14 and is designed with a larger width, in such a way that it forms, together with the outer surface of the pump piston, a third control edge 18 which is shifted even further from the second control edge away from the end face of the pump piston toward the drive side, with an axis-parallel transition 27. Depending on the rotary position of the pump piston, the control ports 8 shown in Figure 2

cooperate either with the first, the second or the third control edges. As a result, with an increasing rotation of the pump pison to the right, an increasingly later closing of the control ports 8 by control edges 16 to 18 is achieved.
The reopening of the control ports 8 takes place by means of the control edges of a third ground-down portion 2 0 and of a fourth ground-down portion 21 which are likewise in each case formed diametrically opposite one another in pairs. These ground-down portions in the outer surface of the pump piston are made oblique to the pump-piston axis. The third ground-down portion inter¬sects the longitudinal groove 12 and forms a first oblique control edge 22 toward the side of the end face of the pump piston. The fourth ground-down portion is adjacent thereto at a distance from the longitudinal groove after a specific rotary-angle range and, at the same time, is arranged offset in such a way that a limiting edge formed by said fourth ground-down portion and pointing toward the end face 6 forms a second oblique control edge 23 which is offset parallel to the first oblique control edge towards the pump-piston end face and merges with an axis-parallel limiting edge 24 into the first control edge 22. As seen in the circumferential direction of the pump piston, the limiting edges 24 are at a greater distance from the limiting edges 27 than the width or diameter of the control ports 8.
Worked into the outer surface is in each case an additional longitudinal groove 25 which axially adjoins the end of the longitudinal groove 12 and is made sub-stantially narrower and which cooperates in each case with an additional control port 26 in the cylinder liner. The control ports 26, like the control ports 8 too, connect the interior of the pump cylinder to a fuel low-pressure space. They are offset in the circumferential direction relative to the control ports 8.
By means of the design provided here, a sub-division of the operation of a fuel-injection quantity with different injection times and injection quantities.

both in a cold internal-combustion engine and in a hot-running internal-combustion engine, is possible, at the same time taking into account the requirements of the internal-combustion engine for fuel injection in these operating ranges. In the position shown in Figure 2, the pump piston 5 is in a rotary position corresponding to operation in a still cold internal-combustion engine shortly before transition to operation in a hot internal-combustion engine. In the range when the internal-combustion engine is cold, the control port 8 cooperates with the first control edge 16 which determines the start of high-pressure feed. When the first control edge 16 has passed over the port 8, injection takes place, this being terminated when the first oblique control edge 22 opens the control port toward the third ground-down portion 20. The latter then makes a connection from the pump working space 7 via the longitudinal groove 12 and the control port 8 to the fuel low-pressure side. At the same time, the pump working space 7 is relieved and the high-pressure injection of fuel is interrupted. The remaining fuel fed by the pump piston flows off toward the fuel low-pressure space, without injection taking place.
When the associated control device recognizes that the internal-combustion engine is running hot, the pump piston is moved further, in such a way that the control ports 8 now come into the effective range of the second control edges 17. As a result of their axial distance from the end face 6, the start of high-pressure feed takes place at a later point in time, thus signify¬ing an adjustment of the start of injection. When the control port 8 is subsequently closed after the second control edge 17 has passed over it, high-pressure injection then takes place, as before, and this is terminated when the second oblique control edge 23 preceding the first oblique control edge 22 toward the end face of the pump piston makes a connection between the control port 8 and the fourth ground-down portion 21. The latter is connected to the third ground-down portion in such a way that, here too, a relief of the pump

working space via the longitudinal groove 12, the third ground-down portion 2 0 and the fourth ground-down portion 21 as well as the control port 8 to the low-pressure space takes place. The smallest pump-piston stroke effective for injection in a position of the control port toward the side of the longitudinal groove 12 in the region of this second oblique control edge 23 can be smaller than the stroke effective for the injection with the internal-combustion engine still cold, when the control port is located in the region of the first control edge 16. In this operating mode with a cold internal-combustion engine, an excess quantity of fuel is necessary in order to guarantee the operation of the internal-combustion engine.
By means of the third control edge 18, it is possible to achieve an even later start of injection, particularly in the case of a high load. According to the rotary position of the pump piston, the third control edge 18 then cooperates with the control port 8 which, after the feed stroke, is once again opened by the second oblique control edge 23.
Such measures for advancing the start of injec¬tion can be further refined if additional ground-down portions are provided. However, limits are placed on this on the grounds of the overflow cross sections which are necessary for relieving the pump working space. If the overflow cross sections are too small, this results in undesirable throttle effects which, with an increasing rotational speed, become noticeable in an unintended increase in the feed duration and consequently in an unintended increase in the fuel-injection quantity.
In order to stop an internal-combustion engine again, regular use is made of the longitudinal groove 12 which, in known designs, is provided for this purpose. For switching off, the pump piston is then rotated to the left, so that the control ports 8 come into connection with the longitudinal groove 12. In the event of a subdivision into a working range for a cold internal-combustion engine and for a hot internal-combustion

engine, if the longitudinal groove were used as a common stop groove the entire cold control range would have to be traversed. This is not desirable and, moreover, also loads the regulating capacity of the regulator. It is necessary also to have a switch-off possibility in the transitional range between a hot-running internal-combustion engine and a cold internal-combustion engine, as in the state of the art mentioned in the introduction. In the present case, the design of ground-down portions 14 and ground-down portions 20 and 23 is such that, in the transitional range between the first control edge and the second control edge 17, there is a position for the control port 8, in which the latter, between the state of not yet being closed by the control edge 17 and the state of being reopened by the second oblique control edge 23, in the intermediate range constantly makes a connection between the fourth ground-down portion 21 and the first ground-down portion 14. For reasons of space, however, this connection is still throttled to an undesirable extent, so that, at a high rotational speed, some pres¬sure can nevertheless build up in the pump working space and can lead to the injection of small injection quan¬tities. For this position which corresponds virtually to the stop position for switching off the internal-combustion engine, the additional longitudinal grooves 25 are now additionally provided, these coming in this range into overlap with the additional control ports 26. This provides an additional flow-off cross section, the result of which is now that injection is completely prevented in this rotary position of the pump piston. At the same time, the advantage of the additional longitudinal groove is that it is in a region of the outer surface of the pump piston which is noncritical for the regulation of the fuel-injection quantity.
The reduced width of the additional control port 2 6 and of the additional longitudinal groove 25 guarantees that the longitudinal groove 25 is connected to the control port 2 6 only in this narrow range where a switch-off of the internal-combustion engine is desired.

Immediately thereafter, control of the fuel-injection quantity, with the internal-combustion engine running hot, can then take place by a utilization of a maximum possible regulating range.


WE CLAIM:
1. A fuel injection pump for internal combustion engines, comprising pump cylinder (2), a pump piston (5) which is driven to and fro in the pump cylinder (2) and is rotatable by means of a control device and which encloses with its end face (6), in the pump cylinder (2), a pump working space (7) which is connected to a fuel injection valve and which is connected to a low pressure fuel space by at least one control port (8) arranged in an outer surface (10) of the pump cylinder (2)said at least one control port serving for filling and relieving the pump working space (7), said control port (8), at a start of a feed stroke of the pump piston (5), is closed by a control edge (16, 17, 18) arranged on one end face of the pump piston and, at another end of the feed stroke of the pump piston, is reopened by an oblique control edge (22,23) on pump piston which extends obliquely relative to an axis of the pump piston (S) and is a limiting edge of a recess (20, 21) which merges circumferentially into a longitudinal groove (12) connected continuously to the pump working space (7) and is located in the outer surface (10) of the pump piston (5), the control edge on the end face (6) of the pump piston comprising a first control edge (16) which has adjoining said first control edge in the direction of increasing distance of the obUque control edge from the end face (6), at least one additional control edge (17, 18) offset relative to the first or the preceding control edge (16), and at least one additional oblique control edge (23) which is assigned to the additional control edge (17,18) and which is offset relative to the first

oblique control edge (22) towards the end face (6) of the pump piston (5), with a transitional edge (24) extending in alignment with the axis of the pump piston and located, in relation to a circumference of an outer surface, in a region of the edge (19), likewise extending in alignment with the axis of the pump piston (5), between the first control edge (16) and additional control edge (17), of which the distance from the transitional edge (24) in the circumferenctial direction is smaller than the width of the control port (8) in the circumferential direction, the extent of the control port (8) in alignment with the pump-piston axis being greater than a smallest distance between the additional control edge (17) following the first control edge (16) and the additional oblique control (23) following the first oblique control edge (22), at its transition to the first oblique control edge (22), and with an additional control port (26) which is provided in the wall of the pump cylinder (2) and which overlaps an additional longitudinal groove (25), starting fi-om the longitudinal groove (12) in the axial direction, when the control port (8) is located, in relation to the circumference of the outer surface, in the region of a transition between the first control edge (16) and the following additional control edge (17) and of a transition between the first oblique control (22) and the following additional oblique control edge (23).
2. The fuel injection pump as claimed in claim 1 wherein the control edges (16,17,19) extend in the radial plane relative to the axis of the pump piston (5).

3. The fuel injection pump as claimed in claim 1 or 2, wherein the
oblique control edge (2223) extend parallel to one another, the first oblique
control edge (22) is provided for controlling the fuel injection when the
internal combustion engine is not yet running hot and the at least one
additional oblique control edge (23) is provided for controlling the fuel
injection when the internal-combustion engine is running hot, and the
control port (8) being brought into the effective range of the respective
oblique control edge (22,23) by the control device.
4. The fuel-injection pump as claimed in one of the preceding claims, wherein two control bores (8) located diametrically opposite one another and two additional control bores (26) located diametrically opposite one another are provided in the pump cylinder (2), in each case with control edges (16, 17, 18) and oblique control edges (22, 23) assigned to these and designed according to one or more of the preceding claims.
5. A fuel-injection pump for internal combustion engines, substantially as herein described with reference to the accompanying drawings.
1

Documents:

990-mas-95 abstract.pdf

990-mas-95 claims.pdf

990-mas-95 correspondence others.pdf

990-mas-95 correspondence po.pdf

990-mas-95 description (complete).pdf

990-mas-95 drawings.pdf

990-mas-95 form-1.pdf

990-mas-95 form-26.pdf

990-mas-95 form-4.pdf

990-mas-95 form-9.pdf

990-mas-95 petition.pdf


Patent Number 193009
Indian Patent Application Number 990/MAS/1995
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date
Date of Filing 02-Aug-1995
Name of Patentee ROBERT BOSCH GMBH
Applicant Address POSTFACH 30 02 20, 70442 STUTTGART
Inventors:
# Inventor's Name Inventor's Address
1 KARL RAPP GOLDBACHER WEG 14, 70453 STUGGART
2 ALEXANDER TYROLT SCHNELLENSTR. 37, 73770 DENKENDORF
3 KARSTEN HUMMEL FICHTENSTR. 2/1, 71717 BEILSTEIN
4 WERNER FAUPEL POST OFFICE BOX 919, USA-4950 WYOMING
5 HANS-JOACHIM PETERS MITTENFELDSTR. 81, 70499 STUGGART
PCT International Classification Number F02M59/26
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA