DE102008043237A1 - High-pressure fuel pump for an internal combustion engine - Google Patents

Abstract

The present invention relates to a high-pressure fuel pump (10) for a direct injection internal combustion engine (9), having a low-pressure region (12) and a quantity control device (28). The quantity control device (28) comprises a switching valve, which is arranged upstream of an inlet valve (22) of the high-pressure fuel pump (10) and has a first switching position and at least one second switching position, wherein the switching positions differ in their throttle effect.

Description

State of the art

The The invention relates to a high-pressure fuel pump for a Internal combustion engine with direct injection according to the preamble of Claim 1. In addition, the subject of the invention Method for operating a high pressure fuel pump for an internal combustion engine with direct injection, a control and / or Control device and a computer program according to the preamble of corresponding independent claim.

today Fuel systems for internal combustion engines with direct injection usually have a volume-controlled high-pressure fuel pump in an input area (low pressure area), where the volume control essentially by a speed-synchronous operation an intake valve of the high-pressure fuel pump takes place. In order to is a very precise volume control possible. The switching times The quantity control valves used for this purpose are due to the speed-synchronous Control very short. Furthermore, the volume control is a pressure sensor used in a high pressure area. A control and / or regulating device compares an actual pressure with a target pressure in the high pressure range and corrects, if necessary, the control for the quantity control valve.

From the EP 0 299 337 A2 . EP 0 837 986 B1 . EP 0 974 008 B1 and DE 196 12 413 A1 Devices are already known to control the fuel pressure. From the DE 103 27 411 A1 a pressure relief valve for a high-pressure fuel pump is known.

Disclosure of the invention

task The invention is a high-pressure fuel pump for an internal combustion engine of the type mentioned to create or continue to develop, which works reliably and compact is. In addition, the fuel high-pressure pump is inexpensive be.

The Task is performed by a high-pressure fuel pump for one Internal combustion engine having the features of claim 1, and a method of operating a high pressure fuel pump for an internal combustion engine, a control and / or regulating device and a computer program according to the characteristics of each sibling Claim. Find important features for the invention Furthermore, in the following description and in the drawing, the features being both unique and different Combinations may be important to the invention without being explicitly pointed out. advantageous Further developments can be found in the dependent claims.

By the invention will greatly simplify the fuel system and inexpensive. In the simplest case is this a quantity control device with two switch positions is sufficient. The two switch positions usually represent a partial delivery position with weakened, more throttled fuel mass flow and a full development with a substantially unhindered or unthrottled fuel mass flow. The realization of more than two stages, for example for a fuel delivery a small amount, a middle subset and a full load amount is possible if required. A regulation of the switch valve happens through a simply constructed control loop, depending on an easily determinable operating size from the Switching the fuel high-pressure pump section. So only has to be recognized, whether in the more throttling switch position a delivery of fuel is still sufficient or whether switched to a less strongly throttling switch position must become. On the other hand, must in the less strong throttling switch position be recognized that the delivery of fuel at Partial funding sufficient for the current operation is and thus on the more throttling switching position can be switched. These decisions can be made in an easy-to-configure and therefore inexpensive control and / or Control device are taken.

It It is suggested that the switching valve be an electromagnetic Actuator comprises. The operation the switching valve via an actuator of an electromagnet provides a reliable and inexpensive solution In this case, the switching valve for each direction of movement be associated with an electromagnet; but it can only be an electromagnet to work against a spring force of a spring when switched on and then after switching off the spring force the Return the actuator to its original position. In a quantity control device with two switch positions this solution is particularly advantageous. Because the switching can be performed comparatively slowly, there are only low demands on the switching time, over the switching valve with solenoid are sufficiently solved can. Thus, both the switching valve and an associated electrical power amplifier be relatively simple. That too is cost-cutting and saves installation space. Since switching only sporadically with less Switching speed occurs, the noise is through the switching low.

It is also proposed that the switching valve in the unactuated state is in the switching position with the lowest throttle effect. For example. can in Failure occur an interruption of the control line to the switching valve. Even a failure of the power amplifier in a control unit is possible. In these cases of error, a control of the switching valve is no longer possible, it is "unactuated" or "de-energized". Due to the measure according to the invention, despite such a fault, an (emergency) operation of the internal combustion engine is still possible.

alternative For this purpose, it is proposed that the switching valve in the unactuated Condition in a switching position with increased throttle effect is. There is a focus when operating the high-pressure fuel pump on a consumption optimization in the internal combustion engine, so must in the case of error described above, in addition to the mechanical drive line the high pressure pump and the electrical power of the switching valve be taken into account. Namely, the internal combustion engine operated mainly at part load, (and that is at an average Driving style predominantly the case), can by the suggested Measure the energy consumption to be lowered.

additional For this purpose, it is proposed that the throttle effect in a switching position is designed to have a flow rate of about 10-20% the maximum volume flow allows. The interpretation of Throttling effect in the partial delivery position should be like this take that drive power of the high-pressure fuel pump for a certain operating cycle in total is minimal. For motor vehicles can z. B. an MVEG cycle (European Driving cycle for emission and consumption measurements on chassis dynamometers) be based on. According to this cycle will on average only about 10 to 20 percent of the maximum flow the high pressure pump is needed and represented thus a sizing optimum. By the said interpretation the throttle effect can in this switching position a large Part of the operating time of the internal combustion engine are optimally covered.

Advantageous is also when the high-pressure fuel pump is a pressure control valve comprising a high pressure area of the high pressure fuel pump with a low pressure region of the high pressure fuel pump connects and so the pressure in the high pressure region at least substantially constant can hold. In normal operation can in both positions of the switching valve the delivery of the high-pressure pump larger be as the amount requirement of the internal combustion engine. To damage from the high-pressure fuel pump and in particular to a fuel rail To avoid that, the excess amount is going to be Fuel through the proposed pressure control valve from the high pressure area in the low pressure area returned. The pressure in The fuel manifold is thus essentially dependent from an opening pressure of the pressure regulating valve.

additional For this purpose, it is proposed that the pressure regulating valve purely mechanical / hydraulic works, preferably is a check valve. this is a particularly inexpensive, but effective solution, as a pressure sensor and an evaluation of the pressure sensor signals in a control and / or regulating device can be dispensed with. Further It is proposed that the control of the switching valve of a Signal of a pressure sensor, which is a pressure prevailing in the high pressure area detected and / or a driving time of at least one injection valve depends. At a pressure drop in the high pressure area of High-pressure fuel pump must have an actual activation time of the injection valve be extended to those for optimal combustion a fuel / air mixture required amount of fuel to be able to inject into a combustion chamber of an internal combustion engine. At a pressure increase in the high pressure range is the ACTUAL activation time shortened accordingly. The drive time can thus as Characteristic for the pressure in the high-pressure range be considered. Exceeding a given upper or lower limit value of the activation time (DESIRED activation time) is thus an indication of the switching, which causes is that in the low pressure range, the flow of fuel the investigations in the high-pressure area is adjusted. It is the Ansteuerzeit a known operating size in the Control and / or regulating device and can be easily evaluated. This can be a switching time for the switching valve be determined easily and without much effort. The pressure in the high pressure area However, it can also be determined by a sensor and then in the control and / or regulating device with an upper and lower Pressure limit are compared.

additional For this purpose, it is proposed that the control of the switching valve from a pump speed, a prefeed pressure and / or a fuel temperature depends. The evaluation of this Operating variables enable even more precise switching the switching valve, which saves energy and fuel and emissions be reduced.

Brief description of the figures

following is an embodiment of the invention with reference to the figures exemplified. Show it:

1 a schematic representation of a fuel injection system according to the invention;

2 a schematic representation of the switching valve 1 ; and

3 a flow diagram of the method according to the invention.

Detailed description

1 shows a schematic representation of a fuel system 8th for an internal combustion engine 9 with a high-pressure fuel pump 10 , The fuel system 8th is, as will be explained, in an in 1 low pressure area shown on the left 12 and a high pressure area shown on the right 14 divided. One in the low pressure range 12 arranged prefeed pump 16 pumps fuel from a fuel storage tank 18 via a low pressure line 20 with a prefeed pressure to an inlet nozzle 22 the fuel high-pressure pump 10 , In the high-pressure fuel pump 10 are in the low pressure area 12 a filter 24 and a pressure damper 26 arranged. The pressure damper 26 dampens in the high-pressure fuel pump 10 resulting pulsations on the low pressure side and ensures a high degree of delivery even at high rotation and cam numbers.

Via a switching valve 28 and subsequently an inlet valve 30 the fuel is in a working space 32 the fuel high-pressure pump 10 sucked. The switching valve 28 will be described later. The volume of the work space 32 depends on the position of a pump piston 34 in a pump cylinder 36 from. During a downward movement of the pump piston 34 becomes the workroom 32 increases, whereby fuel is sucked. During the upward movement of the pump piston 34 the fuel is highly compressed and via an exhaust valve 38 and one to the high pressure area 14 belonging outlet 40 via a high pressure line 42 continue in a rail 44 promoted. To the rail 44 are injection valves 46 connected the fuel directly into combustion chambers 48 the internal combustion engine 9 inject.

Since in normal operation, the delivery rate of the high-pressure fuel pump 10 larger than that of the single point valves 46 may be injected fuel amount, the unnecessary amount of fuel from the high pressure area 14 via a pressure regulating or pressure limiting valve 50 back to the low pressure area 12 recycled. The pressure relief valve 50 can be configured, for example, as a check valve. The pressure in the high-pressure accumulator 44 then corresponds essentially to the opening pressure of the pressure relief valve 50 , The pressure relief valve 50 is via a high pressure line 52 with the high pressure area 14 and via a low pressure line 54 with the low pressure area 12 connected. Also in the high pressure area 14 arise in particular when using single-cylinder pumps pulsations, with multi-cylinder pumps are also in use but generate pulsations to a lesser extent. The pulsations affect the pressure control function negatively. For decoupling can be a throttle 56 hydraulically before (upstream) the pressure relief valve 50 be arranged, whereby the pulsations in front of the pressure relief valve 50 be steamed.

The pump piston 34 is via a cam 58 powered by the internal combustion engine 9 is driven - for example, via a cam or crankshaft (not shown). The cam 58 can also be part of the cam or crankshaft. A seal of the pump piston 34 to the cam 58 via a sealing element 60 , A piston leakage, in the gap between the pump piston 34 and the pump cylinder 36 is created, is via a return line 62 in the low pressure area 12 recycled.

A control unit 64 controls the switching function of the switching valve 28 via a control line 66 , Furthermore, via control lines 68 the injectors 46 controlled (in 1 is for simplicity's sake only one line 68 shown). The internal combustion engine 9 also includes a speed sensor 70 , which detects the rotational speed of a crankshaft, not shown, and a temperature sensor 72 that detects an operating temperature of the internal combustion engine, for example, a cylinder head temperature or a cooling water temperature. A computer program for performing the control of the switching valve 28 is on a storage medium 74 stored in the control unit 64 located.

The detailed structure and function of the switching valve 28 will with 2 explained in more detail. On the left side is the switching valve 28 in a switching position "partial conveying", shown on the right side in a switching position "full promotion". The switching valve 28 essentially comprises an actor 76 that is a switching element 78 moves, and a spring element 80 , The actor 76 For example, it can be designed as an electromagnet or at least operated electromagnetically and in the energized state against the spring element 80 work. The switching element 78 points in 2 in a lower area a passage with a throttle 82 for partial funding. About it is in 2 for a substantially uninfluenced full promotion a passage 84 arranged.

As a parameter for identification of the need for switching the switching valve 28 becomes a driving time for the actuation of the injectors 46 used. It could also be determined by a sensor, not shown pressure in the rail 44 be used. At a pressure drop in the high pressure area 14 the fuel high-pressure pump 10 must be an actual activation time of the injection valve 46 be extended to the optimum Combustion of a fuel / air mixture required amount of fuel into the combustion chamber 48 the internal combustion engine 9 to be able to inject. At a pressure rise in the high pressure range 14 the actual activation time is shortened accordingly. Exceeding a predetermined upper or lower limit value of the activation time (desired activation time) is thus an indication of the changeover, which causes the delivery quantity of fuel in the low-pressure region to be adapted to the conditions in the high-pressure range.

3 shows a flowchart with the sequence of the method, in particular the method for an adaptation of a switching time of the switching valve 28 , The procedure is in a computer program that is in the control unit 64 expires, implemented. In the query 100 it is determined if the switching valve 28 works in partial conveying (switching position 82 ). If this is the case, will be in 110 to an increase in fuel quantity demand in the high-pressure fuel pump 10 detected, for example, the actual driving times of the injectors 46 recorded and evaluated. In 120 a query is made as to whether the current ACTUAL activation time has exceeded a predetermined upper DESIRED limit value. If this is the case, then in 130 the switching valve 28 on full delivery (shift position 84 ) switched. If this is not the case, then the next actual activation times are compared with the setpoint limit value.

Will in the query 100 found that the switching valve 28 already in full delivery (switch position 84 ) works, so in 140 to a reduction in the fuel quantity requirement in the high-pressure fuel pump 10 detected, in turn, by detecting and evaluating the actual activation times of the injectors 46 , In 150 a query is made as to whether the current ACTUAL activation time has fallen below a predefined lower SET limit value. If this is the case, then in 160 the switching valve 28 on partial conveying (switching position 82 ) switched. If this is not the case, then the next actual activation times are compared with the setpoint limit value. After switching is in 170 the switching time in the control unit 64 stored. When determining the switching time, influences of further operating variables, such as an engine speed, a prefeed pressure and a fuel temperature in the computer program of the control unit 64 considered. Additional, further operating variables, the pressure in the high pressure area 14 or affect the fuel quantity requirement are quite conceivable and can be considered in further embodiments.

To determine if the fuel high pressure pump 10 then when the switching valve in the switching position 82 (Sub-promotion) is sufficient fuel promotes the actual power or the actual torque or its course and / or an actual speed can be evaluated. If a power loss is detected, and can be assigned due to a suitable evaluation of this performance loss of insufficient fuel delivery, this can be used as a switchover criterion to full (switching position 84 ) be used.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 0299337 A2 [0003]
• - EP 0837986 B1 [0003]
• - EP 0974008 B1 [0003]
• - DE 19612413 A1 [0003]
• - DE 10327411 A1 [0003]

Claims (12)

Fuel high pressure pump ( 10 ) for an internal combustion engine ( 9 ) with direct injection, with a low pressure range ( 12 ) and a quantity control facility ( 28 ), characterized in that the quantity control device ( 28 ) comprises a switching valve which upstream of an inlet valve ( 22 ) of the high-pressure fuel pump ( 10 ) is arranged and has a first switching position and at least one second switching position, wherein the switching positions differ in their throttle effect. Fuel high pressure pump ( 10 ) according to claim 1, characterized in that the switching valve ( 28 ) an electromagnetic actuator ( 76 ). Fuel high pressure pump ( 10 ) according to one of claims 1 or 2, characterized in that the switching valve ( 28 ) is in the unactuated state in the switching position with the lowest throttle effect. Fuel high pressure pump ( 10 ) according to one of claims 1 or 2, characterized in that the switching valve ( 28 ) is in the unactuated state in a switching position with increased throttle effect. Fuel high pressure pump ( 10 ) according to one of the preceding claims, characterized in that the throttling action is designed in a switching position so that it allows a volume flow of about 10-20% of the maximum volume flow. Fuel high pressure pump ( 10 ) according to one of the preceding claims, characterized in that it comprises a pressure regulating valve ( 50 ) comprising a high pressure area ( 14 ) of the high-pressure fuel pump ( 10 ) with a low pressure area ( 12 ) of the high-pressure fuel pump ( 10 ) and thus the pressure in the high pressure area ( 14 ) at least substantially constant. Fuel high pressure pump ( 10 ) according to claim 6, characterized in that the pressure regulating valve ( 50 ) works purely mechanically / hydraulically, preferably a check valve. Method for operating a high-pressure fuel pump ( 10 ) according to one of the preceding claims, characterized in that the activation of the switching valve ( 28 ) of a signal of a pressure sensor, which detects a pressure prevailing in the high-pressure region and / or a driving time of at least one injection valve ( 46 ) depends. Method according to claim 8, characterized in that the switching valve ( 28 ) is switched from a more throttling switching position into a less strongly throttling switching position when the actuation time of the injection valve ( 46 ) exceeds a limit. Method according to one of claims 8 or 9, characterized in that the activation of the switching valve ( 28 ) depends on a pump speed, a prefeed pressure and / or a fuel temperature. Control and / or regulating device ( 64 ) for a high-pressure fuel pump ( 10 ), characterized in that it is programmed for use in a method according to any one of claims 8 to 10. Computer program, characterized in that it for use in a method according to any one of the claims 8 to 10 is programmed.