EP1570173A1

EP1570173A1 - Electromagnetically controlled connecting unit for a cam-actuated injection system of an internal combustion engine

Info

Publication number: EP1570173A1
Application number: EP04797953A
Authority: EP
Inventors: Günter Kampichler
Original assignee: Motorenfabrik Hatz GmbH and Co KG
Current assignee: Motorenfabrik Hatz GmbH and Co KG
Priority date: 2003-11-25
Filing date: 2004-11-17
Publication date: 2005-09-07
Also published as: WO2005059351A1; DE10354919A1

Abstract

Disclosed is an electromagnetically controlled connecting unit for controlling the passage of a fluid-conducting junction between the high-pressure system and the low-pressure system of a cam-actuated injection system in a self-igniting internal combustion engine. Said electromagnetically controlled connecting unit comprises: - a driving slide (1) that is guided in a precisely fitting manner within an axial guiding bore (32) of a slide cylinder (3), which is fluidically connected to the high-pressure system (37); - an overflow chamber (39) that is fluidically connected to the guiding bore (32) via an electrically controlled magnetic valve (9, 10, 2) while being fluidically connected to the low-pressure system (38) via an overflow chamber bore (50); - a transversal bore (42) that crosses the guiding bore (32) and is connected to the high-pressure system (37) at one end and to the low-pressure system (38) at the other; - a block control bore (17) which extends into the guiding bore (32) downstream of the transversal bore (42) in the direction of displacement of the driving slide counter to the restoring force of the slide spring (12), said block control bore (17) being fluidically connected to the low-pressure system (38).

Description

Electromagnetically controlled switch-on unit for cam-operated injection system of an internal combustion engine

According to its type, the present invention relates to an electromagnetically controlled activation unit for controlling the passage of a fluid-conducting connection between the high-pressure system brought to high fluid pressure and a low-pressure system of a cam-operated injection system in a self-igniting internal combustion engine. Such control of the passage of a fluid-conducting connection between the high-pressure system and the low-pressure system serves to regulate the amount of fuel injected into the combustion chamber.

In cam-controlled injection systems for internal combustion engines of the pump-line-nozzle or pump-nozzle type, the amount of fuel injected is regulated mechanically-hydraulically via speed and load or electronically via a map.

In automotive engineering, for example, mechanical centrifugal governors are used as final speed controllers. In the case of a centrifugal governor, the governor hub is driven by the injection pump camshaft. Two opposing centrifugal weights are mounted in the regulator hub via two angle levers, which move an adjusting bolt, which acts on the regulating rod via a regulating lever, as a result of which the position of the control edges of the pump pistons relative to the element suction hole is changed. Top speed controllers only regulate the idling and maximum speed. Between these limit values, the driver controls using the accelerator pedal.

Electronic control of the amount of fuel supplied to the combustion chamber is considerably more complex, but fulfills significantly lent more features. The full load characteristics can be freely selected, whereby the smoke limit is always maintained. The amount of fuel injected can be adjusted in an almost optimal manner in accordance with a measurement of the air, coolant and fuel temperature. Furthermore, the fuel quantity can be limited as a function of the air mass and the speed, the driving speed can be regulated and in particular limited, and self-diagnosis or diagnostic help can be provided and the fuel consumption can be displayed.

In order to carry out electronic control, sensors transmit measured values about the operating state of the overall system to a microprocessor-controlled control device. In the control unit there is a comparison between the actual value of the fuel quantity supplied to the combustion chamber and a target value resulting from the recorded measured values, for which purpose the data necessary for the comparison are stored in the form of a map in a memory unit of the control unit. After the adjustment has taken place, the control unit outputs correction signals for actuating an actuating magnet for the control rod until the setpoint and actual value are the same. Another control circuit, in which the actual value of the start of spraying is recorded by a needle movement sensor, serves to control a start-of-actuating magnet which actuates a slide valve via a linkage and an eccentric.

Although there are numerous advantages associated with the electronic control of the injected fuel quantity, its use is often not practicable due to the higher costs compared to mechanical-hydraulic systems and the increased maintenance effort. For this reason, it would be highly desirable, even with mechanically-hydraulically controlled inputs Spray systems to supply the flow rate with simple means of a map control.

In contrast, it is an object of the present invention to provide an activation unit for cam-operated injection systems, by means of which the delivery rate of such injection systems can be supplied to a map control in a simple manner.

This object is achieved according to a proposal of the invention by an electromagnetically controlled activation unit for controlling the passage of a fluid-conducting connection between a high-pressure system brought to high fluid pressure and a low-pressure system of a cam-operated injection system in a self-igniting internal combustion engine according to the features of claim 1.

An intrusion unit according to the invention accordingly comprises a traction slide which is guided in a precisely fitting manner in an axial guide bore of a slide cylinder which is fluidly connected to the high pressure system. The traction slide is axially displaceable against the restoring spring force of a slide spring between a rest position caused by the spring force and an end stop position caused by the fluid pressure. An essential feature of the invention is that two control grooves that surround the circumference in a ring are recessed in the lateral surface of the driving slide perpendicular to the direction of displacement. The override unit according to the invention further comprises an overflow space which is connected in a fluid-conducting manner to the guide bore for the driving slide via an electrically controlled magnetic valve. Furthermore, the activation unit according to the invention comprises a transverse bore crossing the guide bore, which has one end connected to the high-pressure system and is connected at the other end to the low-pressure system of the injection system. The transverse bore is arranged such that the axial length of the driving slide is dimensioned such that in the rest position of the driving slide the transverse bore is closed by the lateral surface of the driving slide. On the low pressure side, a pressure control valve closes the cross hole. In addition, a block control bore, which is connected to the low-pressure system in a fluid-conducting manner, opens into the guide bore of the driving slide. The mouth of the block control bore is arranged in such a way that the block control bore opens into the guide bore in the direction of the displacement of the driving slide against the restoring force of the slide spring after the transverse bore. In addition, the block control bore in the rest position of the driving slide must not be closed by its outer surface. Furthermore, an overflow space bore is provided, through which the overflow space space is connected in a fluid-conducting manner to the low-pressure system.

A characteristic feature of the invention is that the two control grooves are arranged in such a way that, in the event of an axial displacement of the drive slide against the restoring force of the slide spring, the block control bore is only closed by the lateral surface of the drive slide when the leading control groove has already passed the transverse bore and before the trailing control groove comes at least partially opposite to the transverse bore. In other words, the block control bore is only closed by the lateral surface of the driving slide if the transverse bore is closed by the lateral surface located between the control grooves and before the trailing control groove reaches the block bore. It is also essential that the trailing control groove in the end stop position of the Driving slide in at least partial juxtaposition to the cross hole.

The invention further relates to a cam-operated injection system in an internal combustion engine, which is coupled to an activation unit according to the invention.

The invention will now be explained in more detail using an exemplary embodiment, reference being made to the accompanying drawings. Show it

Fig. 1 is a schematic overview of an injection system with a coupled activation unit according to the invention;

2 shows an axial section through an activation unit according to the invention in a functional state before the start of the pre-injection (phase I); in the small diagram, which schematically shows the injection process, the functional state of the activation unit is identified by the vertical line;

3 shows an axial section through the activation unit according to the invention from FIG. 2 in a functional state during the pre-injection (phase II); in the small diagram, which schematically shows the injection process, the functional state of the activation unit is identified by the vertical line;

4 shows an axial section through the activation unit according to the invention from FIG. 2 in a functional state between the pre-injection and the main injection. tongue (phase III); in the small diagram, which schematically shows the injection process, the functional state of the activation unit is identified by the vertical line;

5 shows an axial section through the activation unit according to the invention from FIG. 2 in a functional state during the main injection (phase IV); in the small diagram, which schematically shows the injection process, the functional state of the activation unit is identified by the vertical line;

6 shows an axial section through the activation unit according to the invention from FIG. 2 in a functional state at the end of the main injection (phase V); In the small diagram, which schematically shows the course of the injection, the functional state of the activation unit is identified by the vertical line.

First of all, consider the schematic overview representation of a cam-controlled injection system of the pump-line-nozzle type with a coupled activation unit from FIG. 1.

An injection pump 20 is supplied with fuel from a tank 19 via a low pressure line 24. The injection pump

20 conveys the fuel via a high-pressure line 22 to the injection nozzle 21, from where the fuel is injected into the combustion chamber (not shown). From the injector

21 leads a so-called leak oil line 23 fuel under low pressure back to the tank 19. The switch-on unit 28 according to the invention is connected to the high pressure line 22 via the connecting line 29 and to the leak oil line via the overflow line 30. device 23 fluidly connected so that - depending on the respective flow resistance within the activation unit - fuel can be discharged via the activation unit 28 to the leakage oil line 23. For the sake of completeness, it should be mentioned that a leak oil line 25 also leads from the injection pump 20 back to the fuel tank 19.

The override unit 28 is supplied with electrical control signals by a control unit 26 via an electrical connecting line 27. In the control unit 26, the amount of fuel to be injected into the combustion chamber for a specific operating state of the internal combustion engine is stored in the form of a map. In order to determine the actual state of the internal combustion engine, the control unit 26 receives the state values 31 of the internal combustion engine, eg. B. speed, air temperature, exhaust gas composition and the like. After the detected actual state has been compared with the target state determined on the basis of the characteristic diagram, the control unit sends electrical control signals to the activation unit 28 via the electrical connection line 27, as a result of which the flow resistance within the activation unit for the fuel which is directed from the high-pressure line 22 to the leakage oil line 23 is changed. A high flow resistance means that little or no fuel is diverted from the high-pressure line 22 into the leakage oil line 23, whereas with a small or a negligibly low flow resistance, the pressure in the high-pressure system drops sharply due to the deactivation of fuel, as a result of which an injection process can be prevented.

Although the override unit according to the invention was connected to the high-pressure and low-pressure line of an injection pump of the pump-line-nozzle type in FIG. 1, it is the same Possible way to connect the intrusion unit according to the invention with the high-pressure and low-pressure chamber of an injection pump of the pump-nozzle type, which is possible without additional connecting lines.

To illustrate the structure and function of the intrusion unit according to the invention, reference is made to FIGS. 2 to 6.

FIG. 2 shows an axial section through an activation unit 28 according to the invention in a functional state before the start of the pre-injection (phase I). The small diagram shows the complete injection process in the form of the pressure plotted against time in the high-pressure system of the injection system. The functional status of the activation unit in phase I is indicated by the vertical line.

The switch-on unit according to the invention comprises a slide cylinder 3 surrounded by a slide housing 4, a slide housing cover 6 fastened to the front of the slide housing 4, and a magnet housing 5 fastened to the bottom of the slide housing 4 Pump-nozzle housing 36 of an injection pump are screwed, firmly connected.

An axial guide bore 32 is formed in the slide cylinder 3, in which a drive slide 1 is guided with a precise fit. The driving slide 1 is axially displaceable against the restoring force of a slide spring 12. The slide spring 12 is arranged in a slide spring chamber 33 formed as part of the guide bore 32. In the outer surface of the Slider 1, perpendicular to the direction of displacement, around the circumference, two annular control grooves 34, 51 are recessed.

The valve housing cover 6, which is attached to the valve housing 4 on the end face, comprises an inlet 34 in the form of an inlet sealing cone and an outlet 35. The inlet 34 is connected at one end to a high-pressure chamber 37 formed in the pump-nozzle housing 36 in a fluid-conducting manner. At its other end, the inlet 34 is fluidly connected to the guide bore 32. As a result, the slide valve 1 is acted upon by the fluid pressure of the fluid from the high-pressure chamber 38. The traction slide can be transferred by the fluid pressure from a rest position brought about by the spring force of the slide spring 12 into an end stop position. The outlet 35 is connected in a fluid-conducting manner to the leak oil line 38 formed in the pump-nozzle housing 36. An O-ring 13 ensures a fluid-tight connection between the outlet 35 and the leak oil line 38.

The magnet housing 5 is attached to the bottom of the slide housing 4 via an O-ring 14. The magnet housing 5 comprises an overflow chamber 39 connected to the slide spring chamber 33. In the overflow chamber 39 there is a solenoid valve which is composed of a magnet winding 9, a coil magnet core 11, a magnet armature 10 and a control ball 2 which interacts with the magnet armature. In the closed position of the solenoid valve, the control ball 2 is seated on a sealing seat 40. The sealing seat 40 is formed in a top piece 41 placed tightly on the slide cylinder 3. In the closed position, the solenoid valve closes the fluid-conducting connection between slide spring chamber 33 and overflow chamber 39, while the solenoid valve opens the passage in the open position. The solenoid valve can be energized by a corresponding energization of the magnet winding 9 via an electrical (not shown in FIG. see connecting line 27 between control unit 26 and opening unit 28 are brought into the open or closed position. In addition, the override unit shown in FIG. 2 has a magnetic return spring 18, by the spring force of which the magnet armature 10 is pressed against the control ball 2, as a result of which the control ball 2 is seated on its sealing seat 40.

The override unit according to the invention is further provided with a transverse bore 42 crossing the guide bore 32. The transverse bore 42 is connected at one end to the inlet 34 via an axial bore 43 and a cutout 44 in the valve housing cover 6. At its other end, the transverse bore 43 is connected to the drain 35 via a bore 45 which is widened compared to the transverse bore 43. The drain 35 is designed in the form of a screw hole.

In the functional state of the override unit (phase 1) shown in Fig. 2, in which the traction slide 1 by the restoring force of the slide spring 12 against the stop 47 of the slide housing cover 6, i. H. is pressed into its rest position, the passage of the transverse bore 42 is blocked by the lateral surface of the driving slide 1. By axially displacing the driving slide 1 counter to the restoring force of the slide spring 12, the control grooves 34 can each come into juxtaposition with the transverse bore 42, so that the two parts of the transverse bore 42 opening into the guide bore 32 are connected in a fluid-conducting manner by the control grooves 34 of the driving slide 1 and thus creating a fluid-conducting connection between the high-pressure system and the low-pressure system.

The transverse bore 42 is closed on the outlet side of the driving slide 1 by a pressure maintaining valve. The pressure control valve consists of a leaf spring 16 and a control ball 15 which interacts with the leaf spring. The control ball 15 is pressed onto its sealing seat 48 by the leaf spring, as a result of which the transverse bore 42 is closed. The sealing seat 48 results from a conical transition of the widened bore 45 into the transverse bore 42. The leaf spring 16 is clamped into a cutout which consists of a part of a cutout 46 formed in the circumferential surface of the slide cylinder 3 and a cutout adjacent to this cutout 46 48 composes. The widened transverse bore 45 opening into the outlet 35 crosses the cutout 46 in the lateral surface of the slide cylinder 3, so that the cutout 46 is connected to the outlet 25 in a fluid-conducting manner.

The pressure valve can be opened by a fluid pressure above a certain opening pressure, which is preferably between 20 and 50 bar. The size of the opening pressure can be regulated by the spring force of the leaf spring 16.

Furthermore, the activation unit according to the invention has a connecting channel for the fluid-conducting connection of the overflow chamber 39 and the slide spring chamber 33 to the outlet 35. For this purpose, the connecting channel comprises an overflow space bore 50 opening into the overflow space 39 and a bore 49 connecting the overflow space bore 50 with the cutout 46, as a result of which a fluid-conducting connection is created with the outlet 35, since the cutout 46 via the widened bore 45 downstream of the pressure valve is fluidly connected to the outlet 35. The extension of the bore 49 which connects the overcurrent space bore 50 to the cutout 46 in a fluid-conducting manner opens into the block control bore 17, which opens into the slide spring space 33. So the shooting Spring chamber connected via fluid control to block control bore 17, bore 49, cutout 46 and bore 45 with drain ^* 35.

In the functional state of the override unit (phase I) shown in FIG. 2, in which the driving slide 1 is pressed against its stop 47 within the cutout 44 of the slide housing cover 6 by the restoring force of the slide spring 12, the block control bore 17 is from the lateral surface of the driving slide 1 not blocked, so that there is a fluid-conducting connection between slide spring chamber 33 and outlet 35.

The axial length of the driving slide 1 according to the invention is dimensioned such that in the rest position of the driving slide 1 shown in FIG. 2, the transverse bore is closed by the lateral surface of the driving slide 1.

The control grooves 34, 51 are arranged such that, in the event of an axial displacement of the driving slide 1 against the restoring force of the slide spring 12, the block control bore 17 is only closed by the lateral surface of the driving slide 1 when the leading control groove 34 has already passed through the transverse bore 42 and before the trailing control groove 51 arrives at least partially opposite the transverse bore. Furthermore, the trailing control groove 51 arrives in the end stop position of the driving slide 1 in an at least partially opposite position to the transverse bore.

Phase I represents the starting position of the driving slide 1 before the start of the pre-injection. The solenoid valve is closed. The driving slide is in a rest position in which it is moved by the spring force of the slide spring 12. against the stop 47 of the valve housing cover 6 (right in the drawing) is pressed. The pressure in the high-pressure chamber 37 and inlet 34 corresponds to the standing pressure of the high-pressure system between two injection processes, and is generally between 5 and 50 bar. The system stand pressure acts on the slide valve 1, but is not sufficient to move the slide valve 1 against the restoring force of the slide spring 12. In the other cavities filled with fuel, there is a fluid pressure which results from the fluid pressure in the low-pressure supply system (leakage oil line). This is generally between 0.5 and 5 bar.

The start of delivery of the injection pump coupled to the activation unit can be regulated, for example, via an overhead control edge of the pump plunger. If the pump plunger begins its delivery at the time when the control edge located above closes the element suction hole, the fluid pressure in the high-pressure system increases and the pre-injection begins. The rise in the fluid pressure in the high-pressure chamber 34 causes the driving slide 1 to be displaced counter to the restoring force of the slide spring 12. This functional state of the activation unit (phase II) is shown in FIG. 3.

FIG. 3 shows an axial section through the activation unit according to the invention from FIG. 2 in a functional state during the pre-injection (phase II). The small diagram shows the complete injection process in the form of the pressure plotted against time in the high-pressure system of the injection system. The functional status of the activation unit in phase II is indicated by the vertical line.

In FIG. 3, as well as in FIGS. 4, 5 and 6, the elements that are the same as in FIG. 2 are designated with the same reference numbers. Around To avoid repetitions, only the differences in the respective functional states of the intrusion unit are shown.

FIG. 3 shows the driving slide 1, which is displaced against the restoring force of the slide spring 12 (to the left in the drawing) in a position immediately before the end of the pre-injection. The solenoid valve is closed. The pressure in the high-pressure system is now generally between 200 and 300 bar. The displaced slide valve 1 releases the cutout 44 of the valve housing cover 6, as a result of which the pressure of the high-pressure system also prevails in the bore 43 and the part of the transverse bore 42 connected therewith. In all other cavities filled with fuel there is still a pressure which results from the pressure in the low pressure supply system (leakage oil line). At this time, the high-pressure cross bore 42 is still closed by the outer surface of the driving slide 1.

Phase II, however, only lasts very briefly because the rapidly increasing pressure in the high-pressure system brings the leading control groove 34 of the driving slide 1 in opposition to the transverse bore 42. This functional state of the driving slide 1 (phase III) is shown in FIG. 4.

As can be seen in FIG. 4 (phase III), the leading control groove 34 connects the parts of the transverse bore 42 opening into the guide bore 32. A fluid-conducting connection between the high-pressure and low-pressure system is thus created via the transverse bore 42, as a result of which the pressure in the high-pressure system abruptly collapses, the nozzle needle closes and the pre-injection is ended. The duration of the pilot injection thus depends on the running behavior of the slide valve 1 in turn depends on the area ratio of the pump ram / traction slide area, as well as on the overlap lengths of the transverse bore 42 and the circumferential surface closing this until the leading control groove 34 is reached. The longer it takes for the leading control groove 34 to face the transverse bore 42 and to open the passage of the transverse bore 42, the longer the pilot injection takes, and vice versa.

The opening pressure of the pressure holding valve closing the transverse bore 42 results in a holding pressure in the high pressure system of approximately 20 to 50 bar. Downstream of the pressure control valve, as well as in all other cavities filled with fuel, there is a fluid pressure which results from the fluid pressure in the low pressure supply system (leakage oil line). The solenoid valve is still closed.

The pump piston continues its delivery and drives the slide valve 1 with the holding pressure of approximately 20 to 50 bar until the trailing edge of the leading control groove 32 closes the transverse bore 42. This results in a design criterion for the spring force of the slide spring 12, according to which the driving slide 1 is to be brought into abutment against the stop 47 by the restoring force of the slide spring 12 at the beginning of phase I, but is axially displaced by the holding pressure against the restoring force of the slide spring 12 should.

As soon as the trailing edge of the leading control groove 34 closes the transverse bore 42, the pressure in the high-pressure system rises quickly and the main injection begins. The duration of phase III, ie the decoupling distance between the pre-injection and the main injection, depends on the specific design of the activation unit. The decoupling distance results from the running behavior of the driving slide 1, as well as from the overlap lengths of the transverse bore 42 and the leading control groove 3. The faster the driving slide 1 is displaced against the restoring force of the slide spring 12, the greater the decoupling distance between the pre-injection and the main injection given a constant overlap length of the transverse bore 42 and the leading control groove 34. The greater the overlap length of the transverse bore 42 and the leading control groove 34, the greater the decoupling distance between the pre-injection and the main injection with a constant running behavior.

After the start of the main injection (phase IV), the fluid pressure of the high-pressure system is present in the high-pressure chamber 37, inlet 34, milling 44, bore 43 and the inlet-side part of the transverse bore 42. This is generally between 250 and 1000 bar. The holding pressure of the pressure holding valve (25 to 50 bar) prevails in the drain-soapy part of the transverse bore 42 up to the pressure holding valve, since the inlet-side part of the transverse bore 42 and the drain-side part of the transverse bore 42 are separated by the outer surface of the slide valve 1. In all other cavities filled with fuel, there is a fluid pressure which results from the fluid pressure in the low pressure supply system (leakage oil line). The solenoid valve is still closed.

Due to the pressure in the high-pressure system, the driving slide 1 is displaced further against the restoring force of the slide spring 12. The axial dimension of the driving slide 1 and the spatial distance between the two control grooves 34, 51 are such measure that, when the driving slide 1 is displaced counter to the restoring force of the slide spring 12, the leading lateral surface of the driving slide 1 closes the block control bore 17 as long as the transverse bore 42 is closed by the lateral surface of the driving slide 1 located between the two control grooves 34, 51, ie before the trailing control groove 51 fluidly connects the inlet-soapy part of the transverse bore 42 and the drainable part of the transverse bore 42.

If the traction slide 1 passes over the block control bore 17 with its leading lateral surface, hydraulic blocking of the traction slide 1 is achieved as long as the solenoid valve is kept closed.

This functional state of the activation unit (phase IV) is shown in FIG. 5. By closing the block control bore 17, the fluid pressure in the slide spring chamber 33 increases very rapidly when the solenoid valve is closed. The axial displacement of the driving slide 1 counter to the restoring force of the slide spring 12 is blocked hydraulically, so that the trailing control groove 51 does not reach the transverse bore 42 and can release the passage of the transverse bore. The main injection continues.

If the solenoid valve is now opened by energizing the solenoid coil, i.e. if the control ball 2 releases the passage between slide spring chamber 33 and overflow chamber 39, the hydraulic blocking of the slide valve 1 is released and the slide valve is immediately pressed into its end stop position by the pressure of the high pressure system the trailing control groove 51 reaches the cross bore 42 opposite. In the end stop position of the driving slide 1 Passage of the transverse bore 42 is thus released through the control groove 51, the pressure in the high-pressure system drops suddenly, the nozzle needle closes quickly and the main injection is ended.

This functional state (phase V) of the activation unit is shown in FIG. 6. The trailing control groove 51 is located opposite the transverse bore 42 and establishes a fluid-conducting connection between the high-pressure system and the low-pressure system. In its end stop position, the slide valve 1 with its abutment surfaces 53 comes to rest against the stop 52 of the attachment piece 41.

As soon as the pressure in the high-pressure system drops below the opening pressure of the pressure control valve, the pressure control valve closes. As a result, there is a holding pressure in the high pressure system corresponding to the opening pressure of the pressure holding valve, which is generally between 20 and 50 bar. According to the design of the slide spring 12, this pressure is sufficient for the slide valve 1 to remain in its end stop position. Only when the lower control curve of the pump plunger releases the element suction hole and the delivery of the pump plunger has ended, does the pressure in the high-pressure system drop below the holding pressure and the driving slide is returned to its starting position by the restoring force of the slide spring 12, ie to its rest position in the stop 47 of the Slider housing cover 6 is pressed. In this functional state, which corresponds to phase I, the high-pressure system stand pressure is present in the high-pressure chamber 37, in the inlet 34, in the bore 43 and in the transverse bore 42 between two injection processes. In all other cavities filled with fuel, there is a fluid pressure which results from the fluid pressure in the low pressure supply system (leakage oil line). The magnet valve til is closed by energizing the armature coil or solely by the spring force of the spring 18. The control ball 2 rests on its sealing seat.

The following should be noted regarding the dimensioning of the solenoid valve and the pressure control valve. The solenoid valve can become very small due to the small amounts of fluid flowing through. For this purpose, the ball seat advantageously has a cross-sectional area which corresponds to 5 times the cross-sectional area of a nozzle spray hole. Due to the comparatively small opening of the solenoid valve and the resulting low forces, it is sufficient to use small solenoid coils and cores. A fast switching (open - close) solenoid valve can be dispensed with due to the large amount of time available (generally up to 720 ° KW) until the start of the next injection process. Rather, it is sufficient for the solenoid valve to open quickly, which can always be guaranteed by simply disconnecting the solenoid from the power supply and by supporting the pressure in the hydraulic block in the slide spring chamber. Typically, the solenoid valves used have a power consumption of less than 20 W, preferably less than 5 W. The control ball of the solenoid valve is not at risk from cavitation due to the low flow rates.

Something else applies to the pressure control valve, since the entire amount of fuel delivered by a pump plunger must be shut off in this way, for example when the engine is stopped. For the cross-sectional area of the transverse bore, this means that it should be at least 10 times the cross-sectional area of a nozzle spray hole. A typical size for the diameter of the cross hole is approx. 1 mm. Since there are no requirements for high pressure ke are to be set, a low flow rate can be easily realized. If the diameter of the cross hole is approx. 1 mm, the diameter of the control ball of the pressure control valve is typically 2 mm.

The end face of the control slide exposed to the fluid pressure of the high-pressure system is preferably approximately 30 times the cross-sectional area of a nozzle spray hole. The diameter of an end face of the control slide which is circular in cross section is typically 3 mm.

The delivery unit of the injection, the end of delivery and thus the injection quantity is influenced by the push-on unit according to the invention via the drive slide, control grooves, hydraulic blocking of the drive slide and the electrically controlled solenoid valve. The static start of delivery is usually regulated via an overhead control edge of the pump plunger. The lower control edge of the pump plunger has no function for the delivery end when the connection unit is connected, in contrast to the prior art. The delivery end is instead brought about by a forced pressure drop in the high-pressure system with the aid of a regulation of the passage of a fluid-conducting connection between the high-pressure system and the low-pressure system through the activation unit according to the invention. A map control is possible by activating the activation unit according to the invention via a control unit.

Existing purely mechanically-hydraulically controlled cam-controlled injection systems can be retrofitted in a simple and economical manner with the activation unit according to the invention in order to supply the important functions of injection end and injection quantity to a map control. moreover Pre-injection can be implemented in an extremely advantageous manner without having to rely on fast-switching solenoid valves for this purpose. Since the electrical switching power can generally be less than 20 W, the switch-on unit can be made very small.

The activation unit according to the invention can be coupled to injection systems of the pump-nozzle or pump-line-nozzle type.

Of course, the invention is not restricted to the exemplary embodiment shown, but is accessible to a large number of modifications without departing from the scope of protection of the invention. In particular, it is at the discretion of the person skilled in the art to provide the drive slide of the activation unit according to the invention with only a single control groove and thus to dispense with the preinjection being implemented.

Claims

Expectations

Electromagnetically controlled switch-on unit for controlling the passage of a fluid-conducting connection between the high-pressure system and the low-pressure system of a cam-operated injection system in a self-igniting internal combustion engine, which switch-on unit comprises:

a slide valve (1), which is guided in an axial guide bore (32) of a slide cylinder (3), which is fluidly connected to the high-pressure system (37), the slide valve (1) against the restoring spring force of a slide spring (12) between one by the Spring force caused rest position and an end stop position caused by the fluid pressure is axially displaceable, and two control grooves (34, 51) surrounding the circumference are recessed in the lateral surface of the driving slide (1) perpendicular to the direction of displacement;

an overflow chamber (39) which is connected in a fluid-conducting manner to the guide bore (32) via an electrically controlled solenoid valve (9, 10, 2);

a transverse bore (42) crossing the guide bore (32), one end of which is connected to the high-pressure system (37) and the other end of which is connected to the low-pressure system (38), the transverse bore (42) being in the rest position of the driving slide (1) is closed by the outer surface of the traction slide; a pressure holding valve (15, 16) closing the transverse bore (42) on the low pressure side; a block control bore (17), which opens in the direction of the displacement of the driving slide against the restoring force of the slide spring (12) after the transverse bore (42) into the guide bore (32), the block control bore (17) being fluidly connected to the low pressure system (38) ; an overflow space bore (50) through which the overflow space (39) is connected in a fluid-conducting manner to the low-pressure system (38); The two control grooves (34, 51) are arranged in such a way that when the drive slide (1) is axially displaced, against the restoring force of the slide spring (12), the block control bore (17) is closed by the lateral surface of the drive slide (1) after the leading control groove (34) has passed the transverse bore (42) and before the trailing control groove (51) comes at least partially opposite to the transverse bore (42); - ^* and - the trailing control groove (51) in the end stop position of the driving slide (1 ) in at least partial juxtaposition to the transverse bore (42).

2. intrusion unit according to claim 1, characterized in that the opening pressure of the pressure holding valve is between 20 and 50 bar.

3. intrusion unit according to claim 1, characterized in that the electrically controlled solenoid valve has a power consumption of less than 20 watts.

4. intrusion unit according to claim 1, characterized in that the electrically controlled solenoid valve has a power consumption of less than 5 watts.

5. Activation unit according to claim 1, characterized in that the cross-sectional area of the through opening of the solenoid valve is substantially 5 times the cross-sectional area of a nozzle spray hole of an injection system coupled to the activation unit.

6. Activation unit according to claim 1, characterized in that the cross-sectional area of the transverse bore (42) is at least 10 times the cross-sectional area of a nozzle spray hole of an injection system coupled to the activation unit.

7. Activation unit according to claim 1, characterized in that the surface of the driving slide (1) exposed to the fluid pressure is substantially 10 times the cross-sectional area of a nozzle spray hole of an injection system coupled to the activation unit.

8. intrusion unit according to claim 1, characterized in that the solenoid valve has an additional solenoid valve spring, by the spring force of the solenoid valve is transferred to a closed position.

9. cam-operated injection system in an internal combustion engine coupled to an intrusion unit according to one of the preceding claims.