DE102007058229A1 - Fuel injection system controlling method for internal-combustion engine of motor vehicle, involves controlling pump based on operating temperature and actual fuel pressure to enable accelerated starting in subsequent starting phase - Google Patents

Abstract

The method involves controlling a pre-supply pump (3) based on an operating temperature and an actual fuel pressure of an internal-combustion engine (42), during operation of the internal-combustion engine in a stop phase, to enable accelerated starting of the internal-combustion engine in a subsequent starting phase. The pre-supply pump is disconnected during the stop phase, when an actual fuel pressure exceeds a predetermined upper pressure threshold value. The pre-supply pump is cyclically switched on when the operating temperature exceeds a preset temperature threshold value. An independent claim is also included for a computer program for executing a method for controlling a fuel injection system of an internal-combustion engine with a start-stop operation.

Description

State of the art

The The present invention relates to a method for controlling a Fuel injection system of an internal combustion engine with start-stop function, the fuel injection system comprising a high pressure pump, that of a prefeed pump Fuel supplied becomes.

Out The prior art are already internal combustion engines with so-called start-stop functions known. Such internal combustion engines are usually at a standstill for consumption reduction or fuel savings through an injection suppression automatically turned off. To restart the internal combustion engine a new start request is generated, eg. By a user the internal combustion engine, so that one of the internal combustion engine assigned Starter actuated is to perform a restart by starter rotation.

at such internal combustion engines is the reconnection after one Stop phase. in usually dependent from the generated start request, so that the required to restart Start time to avoid loss of comfort is as low as possible. Furthermore, every restart restricts the on-board power supply and can be too unwanted and subjectively perceive as unpleasant noises, especially when a required for restarting control of the feed pump the internal combustion engine can occur.

Disclosure of the invention

A The object of the present invention is therefore a method and a To provide apparatus in an internal combustion engine with start-stop function after a stop phase a restart with shortened starter runtime enable.

This Problem is solved by a method of controlling a fuel injection system Internal combustion engine with start-stop function. The fuel injection system includes a high-pressure pump, which is supplied by a prefeed pump fuel. In a stop phase during operation of the internal combustion engine, the prefeed dependent on driven by operating parameters of the internal combustion engine to a accelerated starting of the internal combustion engine in a subsequent start-up phase to enable.

The Invention allows Thus, in an internal combustion engine with start-stop function a shortening of Restart time after a stop phase and in particular a restart with shortened Starter runtime.

According to the invention the operating parameters of the internal combustion engine one of the high pressure pump generated actual fuel pressure, wherein the prefeed pump during the stop phase at least is cyclically switched on when the actual fuel pressure is a predetermined lower Pressure threshold falls below. If the actual fuel pressure is one exceeds predetermined upper pressure threshold, the prefeed pump turned off. Furthermore, the operating parameters include the internal combustion engine according to the invention one of the prefeed pump produced actual prefeed pressure, the prefeed pump while the stop phase is at least cyclically switched on when the Actual prefeed a predetermined lower Vorförderdruckschwellwert below. If the actual prefeed pressure is a predetermined upper Pre-delivery pressure exceeds threshold, can the prefeed pump turned off.

Consequently It can essentially be prevented from being too low Actual prefeed or actual fuel pressure in one of the high pressure pump associated High-pressure accumulator vapor bubbles are formed and / or air out the fuel is outgassed. Furthermore, it can be prevented that the fuel pressure in the high-pressure accumulator when restarting a exceeds specified maximum pressure.

According to the invention the operating parameters of the internal combustion engine also an operating temperature the internal combustion engine, wherein the prefeed pump at least cyclically during the stop phase is turned on when the operating temperature is a predetermined Temperature threshold exceeds. For determining the operating temperature of the internal combustion engine is measured or simulated a temperature that is at least one based on the following temperature values: fuel, cooling water, Intake air, oil and ambient temperature.

There the vapor bubble formation in the high-pressure accumulator not only on the pressure conditions, but also depends on the operating temperature of the internal combustion engine can thus achieving an effective prevention of vapor bubble formation become.

According to the invention, the operating parameters of the internal combustion engine further include an intake valve opening pressure of the high pressure pump, wherein the prefeed pump is driven during the stop phase such that the this produced prefeed pressure is smaller than the intake valve opening pressure.

The Invention allows thus, a filling the high pressure pump in the stop phase over the To prevent intake valve.

According to the invention Pre-feed pump to Setting a preset feed pressure with control parameters controlled, which are derived from assigned characteristic fields.

Consequently can quickly and easily suitable control parameters for control the pre-feed pump be determined.

Of Furthermore, the internal combustion engine is preferably controlled in such a way that that the pre-feed pump operated in the stop phase with reduced power.

hereby the load of the on-board power supply can be effectively reduced.

The The aforementioned problem is also solved by a computer program to carry out a method for controlling a fuel injection system an internal combustion engine with start-stop function, wherein the fuel injection system a high-pressure pump, which is supplied by a prefeed pump fuel. The computer program controls during a stop phase during operation of the Internal combustion engine, the pre-feed pump dependent on from operating parameters of the internal combustion engine to an accelerated Starting the internal combustion engine in a subsequent start-up phase to enable.

The The aforementioned problem is also solved by an internal combustion engine with a fuel injection system and a start-stop function, the fuel injection system comprising a high pressure pump, that of a prefeed pump Fuel supplied becomes. In a stop phase during operation of the internal combustion engine is the prefeed dependent on operated by operating parameters of the internal combustion engine to a accelerated starting of the internal combustion engine in a subsequent Start phase to allow.

Brief description of the drawings

following is an embodiment of Present invention explained in more detail with reference to the accompanying drawings. there demonstrate:

1 a schematic representation of a fuel injection system of an internal combustion engine with a high-pressure pump;

2 a schematic representation of the high pressure pump of 1 with quantity control valve;

3 a schematic representation of a method for controlling the fuel injection system of 1 ,

Embodiment of the invention

1 shows a schematic representation of a fuel injection system 1 an internal combustion engine 42 with a start-stop function. This includes a fuel tank 2 from which a prefeed pump 3 over a line 4 with a corresponding feed pressure fuel to one about a cam 30 driven high-pressure fuel pump 10 inflated. At the high pressure pump 10 is a low-pressure side a quantity control valve 20 intended. By means of the quantity control valve 20 is the flow rate of the high pressure pump 10 set. The cam 30 is from the internal combustion engine 42 driven, z. B. from an associated cam or crankshaft and may also be part of this cam or crankshaft.

The high pressure pump 10 preferably has a delivery chamber with a check valve disposed on the input side, as in 2 is described in detail, compresses the fuel to a very high pressure and delivers it via a pipe 5 in a high-pressure accumulator 40 , in which the fuel is stored under very high pressure and which is also referred to as "rail" or "rail". At these are several injectors or injectors 41 connected, the fuel directly into them associated combustion chambers of the engine not shown in detail 42 inject. The internal combustion engine 42 serves z. B. to drive a motor vehicle.

The actual fuel pressure in the high-pressure accumulator 40 is from a pressure sensor 43 detected. Its signals are transmitted by the pressure sensor 43 to a control and regulating device 46 , the input side also with a temperature sensor 45 and one on the internal combustion engine 42 arranged speed sensor 44 connected is. On the output side is the control and regulating device 46 with the pre-feed pump 3 and the quantity control valve 20 connected.

The control and regulating device 46 implements the start-stop function of the internal combustion engine 42 and causes an injection suppression for automatically switching off the internal combustion engine 42 in a so-called "engine stop", that is to say when the internal combustion engine is at a standstill, in particular to reduce fuel consumption or save fuel, in a stop phase of the internal combustion engine following the shutdown 42 will the prefeed 3 according to a preferred embodiment form of the invention as a function of operating parameters of the internal combustion engine 42 activated to accelerate the starting of the internal combustion engine 42 in a subsequent start-up phase. This leads z. B. the control and regulating device 46 a corresponding method for controlling the prefeed pump 3 with suitable drive parameters, as stated below 3 will be described by way of example. According to the invention, these drive parameters at least take account of the pressure sensor 43 determined actual fuel pressure in the high-pressure accumulator 40 , one with the temperature sensor 45 determined operating temperature of the internal combustion engine 42 and / or one with the speed sensor 44 determined instantaneous speed of the internal combustion engine 42 ,

According to a preferred embodiment of the invention, the method for controlling the prefeed pump 3 implemented as a computer program by the control equipment 46 is executable. This computer program is z. B. on an electronic storage medium 47 stored with the control and regulating device 46 is usable. Thus, the invention with already existing components of the internal combustion engine 42 be realized easily and inexpensively.

2 shows a schematic representation of the high-pressure pump 10 with the quantity control valve 20 from 1 according to an embodiment of the invention. This will be over the line 4 in which a filter 101 is arranged, fuel supplied. For low-pressure side damping of pulsations of the high-pressure pump 10 is in front of the quantity control valve 20 hydraulically a pressure damper 102 provided, further to ensure a high degree of delivery of the high-pressure pump 10 also with high turning and cam numbers serves.

As mentioned above, the quantity control valve is used 20 for adjusting the flow rate of the high-pressure pump 10 and this accordingly measures an amount of fuel required for this, with a slide 201 one or more control openings 207 in a cylinder 202 depending on demand at least partially opens or closes, so in the cylinder 202 Fuel from a first room 205 through the control openings 207 to a connection 208 can flow. The slider 201 or the position of an associated control edge 206 relative to the control openings 207 is with an actor 203 set, the z. B. can be designed as an electromagnet.

This actor 203 move the slider 201 against the force of a spring element 204 so the control edge 206 depending on the applied actuator force, the control openings 207 at least partially releases. If the actor 203 is not actuated, the spring element relaxes 204 and acts on the slide like this 201 that the control edge 206 the control openings 207 closes. This state of the quantity control valve, referred to as the "normally closed" state 20 is in 2 shown.

The thus metered fuel is via an inlet valve 103 in a workroom 104 a pump cylinder 106 the high pressure pump 10 sucked, its available volume of the position of one in the pump cylinder 106 provided pump piston 105 depends. How out 2 can be seen, the work space 104 enlarged in the illustrated embodiment, when the pump piston 105 one from the cam drive 30 controlled downward movement and this sucks fuel. The sealing of the pump piston 105 with regard to the cam drive 30 is through a sealing element 107 guaranteed. After such a downward movement or intake phase followed by one of the cam drive 30 caused upward movement of the pump piston 105 in which the in the work space 104 sucked fuel compressed to relatively high pressures and via an exhaust valve 108 into the pipe 5 and about this in the high-pressure accumulator 40 is encouraged. A possible piston leakage due to a pressure difference in a corresponding piston gap 111 on the pump piston 105 can arise over a line 112 back to the line 4 led on the low pressure side.

The pump piston 105 is in the stop phase of the internal combustion engine 42 preferred as in 2 shown at top dead center, to an unwanted pressure increase in the high-pressure accumulator 40 to prevent or at least restrict. To make this possible, the cam drive 30 According to the invention to a corresponding stop position of the internal combustion engine 42 Voted. In addition, to avoid an unwanted pressure increase in the high-pressure accumulator 40 For high-pressure pumps with intake valve control, the quantity control valve 20 be switched so that an associated inlet valve is kept open in the stop phase and an unused amount of fuel thus via the open inlet valve to the inlet side of the high-pressure pump 10 can be promoted back.

To limit one in the pump cylinder 106 buildable fuel pressure to a maximum pressure value is between the working space 104 and the line 5 a pressure relief valve 109 intended. Furthermore, it is parallel to the quantity control valve 20 and the pump cylinder 106 a bypass valve 110 arranged over the fuel in the high-pressure accumulator 40 can reach if that Quantity control valve 20 remains closed in operation due to an error occurring. This bypass valve 110 remains in normal operation of the internal combustion engine 42 due to the high pressure in the high-pressure accumulator 40 closed.

To be in a stop phase of the internal combustion engine 42 the occurrence of unwanted filling of the working space 104 over the piston gap 111 or one between slides 201 and pump cylinders 202 of the quantity control valve 20 occurring leakage gap 209 To prevent, the feed pump 3 according to a preferred embodiment of the invention as a function of operating parameters of the internal combustion engine 42 driven. In addition to the control of the feed pump according to the invention 3 Optionally an outlet valve 113 in the pipe 112 be provided to the piston leakage 111 to minimize.

According to the invention comprises a suitable control of the prefeed pump 3 in the event that the prefeed pump 3 is adjustable, an adjustment of the prefeed pressure generated by this. Accordingly, in the context of the present invention, turning off the prefeed pump includes 3 lowering the prefeed pressure and switching on the prefeed pump 3 a raising of the pre-feed pressure.

3 shows an embodiment of a flowchart illustrating an example method 300 for controlling the fuel injection system 1 the internal combustion engine 42 from 1 and 2 for accelerating a restart of the internal combustion engine 42 represents after a stop phase. According to the invention, the method 300 exclusively in such stop phases of the internal combustion engine 42 executed, ie it ends after a respective restart.

The procedure 300 begins in step S301, in which it is determined whether the internal combustion engine 42 is operated in a stop phase or if there are operating conditions that require a transition from normal operation to a stop mode. For example, at one over that of the speed sensor 44 generated speed signal detected standstill of the internal combustion engine 42 a transition from normal operation to the stop mode is requested or initiated. If it is determined in step S301 that the internal combustion engine 42 is not operated in stop mode, is the normal operation and the feed pump 3 remains on in step S302. Otherwise, the pre-feed pump 3 depending on operating parameters of the internal combustion engine 42 is driven, wherein in step S303 first a corresponding operating parameter is evaluated to determine whether it exceeds a lower threshold.

According to the invention, this operating parameter can be determined by the high-pressure pump 10 be generated actual fuel pressure, which is compared with a corresponding lower pressure threshold, and / or one of the prefeed pump 3 generated actual prefeed pressure, which are compared with a lower Vorförderdruckschwellwert. In this case, the lower threshold values are preferably predetermined such that vapor bubble formation in the high-pressure accumulator 40 is prevented.

If the actual fuel pressure and / or the actual prefeed pressure exceed the lower pressure threshold value or the lower prefeed pressure threshold value, the pressure conditions required for a rapid restart are given, and the prefeed pump 3 is turned off in step S304. Otherwise, the pre-feed pump 3 to increase the pressure conditions in step S305 turned on or turned on again. For example, the actual fuel pressure or the actual prefeed pressure may be due to leaks in the fuel injection system 1 fall and are thus raised according to the invention again.

After turning on the pre-supply pump in step S305, it is checked in step S306 whether that of the high-pressure pump 10 generated actual fuel pressure exceeds an associated upper pressure threshold and / or that of the prefeed pump 3 produced actual prefeed pressure exceeds an associated upper Vorförderdruckschwellwert. In this case, the upper threshold values can match the lower threshold values due to the application and are preferably predetermined in such a way that, in the case of a restart after the stop phase, a permissible maximum pressure in the high-pressure accumulator 40 is not exceeded.

If the actual fuel pressure and / or the actual prefeed pressure exceed the upper pressure threshold and the upper Vorförderdruckschwellwert, the process returns to step S304, in which the Vorförderpumpe 3 is turned off. Otherwise, the procedure returns 300 to step S305, that is, the prefeed pump 3 stays on and the check in step S306 is repeated.

After switching off the pre-feed pump 3 In step S304, it is checked in step S307 whether the one from the high-pressure pump 10 generated actual fuel pressure is less than the lower pressure threshold and / or whether the pre-feed pump 3 produced actual prefeed pressure is smaller than the lower Vorförderdruckschwellwert. If the actual fuel pressure is less than the lower pressure threshold and / or if the actual prefeed pressure is less than the lower Vorförderdruckschwellwert, the prefeed pump 3 turned on in step S305. Otherwise the Ver drive 300 to step S304, that is, the prefeed pump 3 remains off and the check in step S307 is repeated.

As a rule, the prefeed pump 3 in the above-described embodiment of the method 300 during a stop phase at least cyclically switched on or off. This can be achieved by the inventive control of the prefeed pump 3 or a suitable raising or lowering of the prefeed pressure generated by this can be prevented on the one hand, that in the high-pressure accumulator 40 generated actual fuel pressure exceeds a permissible maximum pressure. On the other hand, an accelerated starting of the internal combustion engine 42 reached in a start phase following the stop phase.

As mentioned above, the vapor bubble formation in the high-pressure accumulator depends 40 not only on the pressure conditions, ie on the actual fuel pressure in the high-pressure accumulator 40 and the actual prefeed pressure on the low-pressure side, but also on the operating temperature of the internal combustion engine 42 , Accordingly, an operating temperature of the internal combustion engine 42 descriptive, with the temperature sensor 45 measured or simulated temperature value z. B. be taken into account in the determination of the lower thresholds. In addition, a temperature threshold can be specified, wherein the prefeed pump 3 is at least cyclically switched on during the stop phase when the operating temperature exceeds this predetermined temperature threshold. Suitable temperature values, individually or combined to determine the operating temperature of the internal combustion engine 42 can be measured or simulated include z. B. fuel, cooling water, Ansaugluft-, oil and ambient temperature.

Furthermore, the opening pressure of the intake valve can also be 103 as operating parameters of the internal combustion engine 42 in the procedure 300 be taken into account. Here, a corresponding intake valve opening pressure of the intake valve 103 the high pressure pump 10 are taken into account, wherein the prefeed pump is controlled during the stop phase such that the prefeed pressure generated by this is smaller than the intake valve opening pressure. Thus, according to the invention, a filling of the working space 104 via the inlet valve 103 be prevented.

In addition, further measures for optimizing the activation of the prefeed pump according to the invention 3 be implemented. For example, the prefeed pump 3 be set to set a predetermined feed pressure with control parameters derived from assigned characteristic fields. Such characteristics fields can also specify a plurality of different thresholds, for. B. depending on different operating temperatures and / or different, adjustable Vorförderdrucken. Also, the prefeed pump 3 be operated in the stop phase with reduced power to the load of the on-board power system and the noise of the pre-feed pump 3 to reduce in the stop phase. Furthermore, structural measures can also be applied. In 2 is this z. B. the above-described, optional outlet valve 113 shown. This is used according to the invention, a filling of the working space 104 in a stop phase of the internal combustion engine 42 with pre-feed pump switched on 3 over the piston gap 111 to prevent. However, since such a filling also on the leakage gap 209 is possible, is the exhaust valve 113 merely as an optional construction measure.

Claims (12)

Method for controlling a fuel injection system ( 1 ) an internal combustion engine ( 42 ) with start-stop function, wherein the fuel injection system ( 1 ) a high pressure pump ( 10 ) supplied by a prefeed pump ( 3 ) Fuel is supplied, characterized in that during a stop phase during operation of the internal combustion engine, the prefeed pump ( 3 ) as a function of operating parameters of the internal combustion engine ( 42 ) is controlled in order to accelerate starting of the internal combustion engine ( 42 ) in a subsequent start-up phase. Method according to Claim 1, characterized in that the operating parameters of the internal combustion engine ( 42 ) one of the high pressure pump ( 10 ) comprise the actual fuel pressure generated, wherein the prefeed pump ( 3 ) is at least cyclically switched on during the stop phase, when the actual fuel pressure falls below a predetermined lower pressure threshold. Method according to claim 2, characterized in that the prefeed pump ( 3 ) is turned off during the stop phase when the actual fuel pressure exceeds a predetermined upper pressure threshold. Method according to one of the preceding claims, characterized in that the operating parameters of the internal combustion engine ( 42 ) one of the prefeed pump ( 3 ), wherein the prefeed pump ( 3 ) is switched on at least cyclically during the stop phase, when the actual prefeed pressure falls below a predetermined lower Vorförderdruckschwellwert. Method according to claim 4, characterized in that the prefeed pump ( 3 ) is turned off during the stop phase when the actual prefeed pressure exceeds a predetermined upper prefeed pressure threshold. Method according to one of the preceding claims, characterized in that the operating parameters of the internal combustion engine ( 42 ) an operating temperature of the internal combustion engine ( 42 ), wherein the prefeed pump ( 3 ) is turned on at least cyclically during the stop phase when the operating temperature exceeds a predetermined temperature threshold. A method according to claim 6, characterized in that for determining the operating temperature of the internal combustion engine ( 42 ) a temperature is measured or simulated based on at least one of the following temperature values: fuel, cooling water, intake air, oil and ambient temperature. Method according to one of the preceding claims, characterized in that the operating parameters of the internal combustion engine ( 42 ) an intake valve opening pressure of the high pressure pump ( 10 ), wherein the prefeed pump ( 3 ) is controlled during the stop phase such that the prefeed pressure generated by this is smaller than the intake valve opening pressure. Method according to one of the preceding claims, characterized in that the prefeed pump ( 3 ) is controlled to set a predetermined prefeed pressure with control parameters, which are derived from associated characteristic fields. Method according to one of the preceding claims, characterized in that the internal combustion engine ( 42 ) is controlled such that the prefeed pump ( 3 ) is operated in the stop phase with reduced power. Computer program for carrying out a method for controlling a fuel injection system ( 1 ) an internal combustion engine ( 42 ) with start-stop function, wherein the fuel injection system ( 1 ) a high pressure pump ( 10 ) supplied by a prefeed pump ( 3 ) Fuel is supplied, characterized in that the computer program at a stop phase in the operation of the internal combustion engine, the prefeed pump ( 3 ) as a function of operating parameters of the internal combustion engine ( 42 ) to accelerate starting of the internal combustion engine ( 42 ) in a subsequent start-up phase. Internal combustion engine ( 42 ) with a fuel injection system ( 1 ) and a start-stop function, wherein the fuel injection system ( 1 ) a high pressure pump ( 10 ) supplied by a prefeed pump ( 3 ) Fuel is supplied, characterized in that during a stop phase during operation of the internal combustion engine, the prefeed pump ( 3 ) as a function of operating parameters of the internal combustion engine ( 42 ) is controllable to an accelerated starting of the internal combustion engine ( 42 ) in a subsequent start-up phase.