KR101835301B1 - Method for operating a fuel system of an internal combustion engine - Google Patents

Abstract

The present invention relates to a method of operating a fuel system (1) of an internal combustion engine, characterized in that, in at least one first operating situation, the fuel pump (3) The fuel pump 3 does not deliver fuel into the pressure region 16 by the corresponding adjustment of the valve device 14 in at least one second operating situation, The valve device 14 is at least intermittently controlled so that the fuel in the delivery chamber 36 is compressed but is not delivered into the pressure region 16. [

Description

TECHNICAL FIELD [0001] The present invention relates to an internal combustion engine,

The invention relates to a method according to the preamble of claim 1 and to a computer program and a control and / or control device according to other independent claims.

In the case of modern direct injection internal combustion engines with demand-controlled fuel delivery, the piston-high pressure pump (HDP) required for this operation is sometimes operated temporarily without delivery, depending on the operating conditions of the vehicle. This is done in the prior art systems, especially with the overrun cutoffs, in which the fuel does not need to be delivered since the internal combustion engine does not need fuel. Because these steps are often relatively short (for example, less than 5 minutes), HDP overcomes these steps without damage.

The possibility of a damage mechanism of a piston pump used as an HDP can be explained as follows: If the capacity control valve connected upstream of the HDP and controlling the amount of fuel supplied is not controlled for a longer period of time, Since there is no pressure difference between the so-called "staging chamber" and the high-pressure delivery chamber, no significant fuel exchange takes place in the gap between the piston and the piston bushing of the HDP. However, replacement of the fuel is important for lubrication of the piston and centering of the piston in the piston bushing. Also, as no or low pressure results, the fuel may evaporate at relatively high temperatures in the HDP, as the case may be. Without lubrication at the contact points between the piston and the piston bushing, the HDP can be damaged in the long term (piston seizure).

In this respect, dual fuel drive systems in which the internal combustion engine is operated with gas (CNG) instead of liquid fuel (gasoline or diesel) during longer intervals may be particularly critical. In the meantime, the high pressure pump (HDP) is normally operated without delivery, and the high pressure pump can be relatively hot. Thus, the above-mentioned damage mechanism appears.

Likewise, in this regard, hybrid systems may be critical, during which the HDP is exposed to similar conditions as in combined fuel-gas-operation.

Both of the cases described above can have long periods of high fuel temperature while at the same time preventing the delivery of the HDP. In particular, in normal operation, cooling of HDP caused by fuel flow is not achieved.

Disclosed techniques in this field are for example DE 198 34 121 A1, US 20080208439 A1, US 20070163536 A1, US 20060037583 A1, US 20060196475 A1, US 20060102149 A1 and US 20050098155 A1.

An object of the present invention is to provide a method of operating a fuel system of an internal combustion engine that increases the fatigue strength of the fuel pump. It is also an object of the present invention to provide a computer program and a control and / or control device for carrying out the method.

The problem is solved by a computer program and a control and / or regulating device according to the method according to claim 1 and according to other independent claims. Preferred embodiments are set forth in the dependent claims. In addition, important features of the present invention can be found in the following detailed description and drawings, and the features may be important to the invention alone and in different combinations, which are not explicitly recited.

As an advantage of the present invention, the fuel can flow into the delivery chamber of the fuel pump in the operating state of the fuel system where the fuel pump does not deliver the fuel into the pressure region of the fuel system, and the movable members of the fuel pump, It is lubricated by flowing fuel. As a result, the fatigue strength of the fuel pump can be increased. In particular, the method according to the present invention can be carried out only by the changed control of the valve device of the fuel pump, i.e. by software.

The underlying idea of the present invention is that, during operation of the internal combustion engine, operating conditions occur in which the fuel is not combusted in the combustion chambers of the internal combustion engine and therefore the fuel is not delivered by the fuel pump. This may occur, for example, in the so-called "overrun cutoff" steps, or alternatively it may also occur in vehicles comprising internal combustion engines and hybrid drive devices operated with liquid fuel or gas. A first operating state of the fuel system in which normal delivery of fuel into the pressure region occurs and a second operating state in which fuel is not delivered or discharged into the pressure region may be defined.

According to the present invention, the valve apparatus for measuring the amount of fuel supplied to the fuel pump is sucked from the low-pressure region in which the fuel is upstream at the first stage of the operation of the fuel pump at least intermittently in the second operating state, And in the third stage, the remaining amount of fuel is pressurized between the movable members of the fuel pump and their guides or bearings and is lubricated.

The transition from the three steps, particularly the second step to the third step, or the transition from the third step to the second step is controlled by the valve device according to the invention. For example, the controllable inlet valve of the valve device is open during both initial steps and closed during the third step. Preferably, the third step starts just before reaching the top dead center of the piston and ends at the top dead center. The three steps can be repeated periodically by the motion of the piston.

According to an embodiment of the method, the control of the valve device is performed periodically for each stroke of the fuel pump in the second operating condition. As a result, for example, the lubrication of the piston can be maximally achieved, so that the fatigue strength of the fuel pump can be significantly increased.

According to another embodiment of the method, the control of the valve device is performed occasionally or periodically in the second operating state, and no control is made at the intervals therebetween. As a result, sufficient lubrication may be possible, according to a specific embodiment of the fuel pump, while at the same time there is no probability of undesired delivery of the fuel into the pressure region of the fuel system - and thus an overshoot of the limiting pressure .

According to a further embodiment of the method, the control of the valve device is carried out continuously for a first number of strokes of the fuel pump, respectively, in a second operating situation, and thereafter for a second number of strokes of the fuel pump, Control is not performed. The method according to the invention can therefore be carried out alternately during a plurality of operating strokes of the fuel pump and subsequently not during a plurality of strokes. In this way there are many possibilities for the implementation of the method, and the possibilities can be flexibly adjusted in accordance with the operating conditions or operating parameters of the fuel pump and / or the internal combustion engine.

If the angle of the drive shaft of the fuel pump at which compression is initiated by proper adjustment of the valve device is detected in consideration of one or more operating parameters of the internal combustion engine without fuel being delivered into the pressure region (zero delivery angle) , The method is performed more favorably. Therefore, on the one hand, it can be achieved that the fuel pump is sufficiently lubricated and on the other hand, undesired delivery of the fuel is prevented, depending on one or more operating variables.

If the non-delivery angle is detected using one or more characteristic curves under consideration of multiple operating variables, the method can be implemented more accurately. A number of operating variables can therefore be used to control the valve arrangement, and with one or more characteristic maps, additional information can be used without additional computation time of the control and / or regulating device of the internal combustion engine or the vehicle. Therefore, the implementation of the present invention is generally improved, the computation time is saved, and the cost can be reduced.

In particular, the ejection angle is determined in consideration of one or more of the following variables.

- the speed of the internal combustion engine,

- torque of the internal combustion engine,

- the temperature of the internal combustion engine,

- the temperature of the fuel,

- the fuel pressure in the pressure zone and / or

- operating conditions of the internal combustion engine, especially overrun cutoffs.

Using these parameters, in particular, the first operating condition can be distinguished from the second operating condition, and as a result a "switch-on condition" for this method can be derived. In particular, since the variables are used to accurately detect the point in time for the transition from the second stage to the third stage, sufficient lubrication of the fuel pump is achieved and at the same time undesired delivery of fuel into the pressure zone can be prevented .

Further, if the pressure in the pressure region rises at a rate greater than the limit value, the delivery angle can be changed so that the rate remains below the limit value. Thus, it can be said that the " predicted "throw angle can be adjusted, thus reducing the safety of undesired delivery of the fuel and minimizing the probability of exceeding the limit pressure in the pressure region.

The control of the valve device for carrying out the method is further improved in consideration of the pressure rise due to the heating of the fuel in the pressure region as the operating time increases. This makes it possible to better distinguish whether a pressure rise has occurred or is occurring as a result of undesired delivery of fuel or as a result of heating of the fuel. If the pressure rise is caused by the heating of the fuel, the non-delivery angle need not be further reduced, so that the optimal lubrication of the fuel pump can be maintained.

In the following, embodiments of the present invention will be described with reference to the drawings.

1 is a schematic view of a fuel system of an internal combustion engine;
2 is a schematic view of the fuel pump of the fuel system of FIG.
3 is a time diagram including different steps of the operating movement of the fuel pump.
4 is a flow diagram of a computer program for processing in a control and / or regulating device of an internal combustion engine.

In the drawings, the same reference numerals are used for functionally equivalent components and variables, even if the embodiments are different.

In Figure 1, the fuel system 1 of the internal combustion engine is shown schematically. The fuel tank 9 is connected to the fuel pump 3 through a suction line 4, a preliminary delivery pump 5 and a low pressure line 7. The high-pressure accumulator 13 ("common rail") is connected to the fuel pump 3 via a high-pressure line 11. The high pressure line 11 and the high pressure accumulator 13 together form a pressure region 16 of the fuel system 1. Electromagnetically actuated switching valve 14, hereafter referred to as valve device 14, comprises an electromagnetically actuating device 15, hereinafter referred to as electromagnet 15, Is arranged hydraulically in the low-pressure line (7) between the pumps (3). The electromagnet 15 is controlled by the computer program 8 of the control and / or regulating device 19 using the characteristic maps 6. The fuel pump 3 also includes a cam 17 disposed on the drive shaft 10, and the cam can move the piston 18 vertically in the figure. Other components, such as the outlet valve of the fuel pump 3, are not shown in Fig. Of course, the valve device 14 may be formed as a unit including the fuel pump 3. For example, the valve device 14 may be formed as an inlet valve forcibly opened to the fuel pump 3 in the sense of a so-called "capacity control valve ".

During operation of the fuel system 1, the pre-dispensing pump 5 delivers the fuel from the fuel tank 9 into the low-pressure line 7. In this case, the valve device 14 determines the amount of fuel to be supplied to the delivery chamber 36 of the fuel pump 3.

2, a fuel pump 3 of Fig. 1 is schematically shown. The fuel pump 3 has a housing 20 in which the electromagnet 15 is arranged with the coil 22, the armature 24 and the armature spring 26 in the left region of the housing. The fuel pump 3 also includes an inlet 28 connected to the low pressure line 7 and an inlet valve 30 and an outlet 32 connected to the high pressure line 11 and an outlet valve 34. The inlet valve 30 includes a valve spring 31 and a valve body 33. The valve body 33 can be moved by a valve needle 35 coupled with an armature 24, which is horizontally movable in the figure. When electric current is supplied to the electromagnet 15, the inlet valve 30 can be closed by the force of the valve spring 31. If no current is supplied to the electromagnet 15, the inlet valve 30 can be forced open by the force of the armature spring 26. [ In the delivery chamber 36, the piston 18 is arranged to be movable in the vertical direction in the figure. The piston 18 is able to move in the cylinder 37 via the roller 40, in this case an elliptical cam 17. The cylinder 37 is formed in an area of the housing 20. The inlet valve 30 is hydraulically connected to the delivery chamber 36 through an opening 38.

In the first operating state of the fuel system 1, the fuel pump 3 delivers fuel from the inlet 28 to the outlet 32 and the outlet valve 34 is connected between the delivery chamber 36 and the outlet 32 Lt; RTI ID = 0.0 > and / or < / RTI > The inlet valve 30 is operated by the pressure difference between the inlet 28 and the delivery chamber 36 but also by the valve needle 35 or the electromagnet 15. The inlet valve 30 can be closed and the fuel in the delivery chamber 36 can be supplied to the electromagnet 15 from the point of time during the delivery stroke into the low pressure line 7 But is sent out into the high-pressure accumulator 13 ("rail"). The volume of the fuel pump 3 disposed in the housing 20 is actually filled with fuel.

Fig. 3 shows a second operating situation of the fuel system 1 in which the fuel pump 3 should not deliver or deliver fuel into the pressure region 16. Fig. A time diagram including two coordinate systems is shown in the lower region of the drawing. The current I flowing in the coil 22 with respect to time t in the lower coordinate system is plotted on the vertical axis. The stroke 44 of the piston 18 between the bottom dead center UT and the top dead center OT is plotted on the vertical axis for time t with the same time magnitude in the upper coordinate system.

Further, the three steps of the actuation motion of the piston 18, that is, the suction step PH1, the backwashing step PH2 and the delivery step PH3 are divided into broken lines. The dispensing phase PH3 corresponds to the dispensing angle 46 of the driving shaft 10 and the dispensing angle is defined in the temporal negative direction starting from the top dead center OT on the right side in the figure. The transition from the backwashing step PH2 to the delivery step PH3 is performed at the time point t1. The sum of the steps PH1 to PH3 shown in Fig. 3 between the illustrated both tops OT corresponds to one period of the actuating movement of the piston 18, Or the half rotation of the drive shaft 10. In addition, the shaded area 48 represents the dispensing step PH3.

The states of the fuel pump 3 corresponding to the three steps PH1 to PH3 in the upper region of Fig. 3 are symbolically assigned according to Fig.

In the second operating state of the fuel system 1, the intake step PH1 starts from the top dead center OT on the left side of the drawing. No current is supplied to the coil 22 of the electromagnet 15. The inlet valve 30 is opened by the pressure control and the outlet valve 34 is closed. Fuel may flow from the inlet 28 into the delivery chamber 36 through the open inlet valve 30 and through the opening 38. [ The delivery chamber 36 is simultaneously enlarged by the downward movement of the piston 18 in the direction of the arrow 52. [ The volume of the fuel pump 3 disposed in the housing 20 is actually filled with fuel even in the second operating condition. The suction step PH1 ends at the bottom dead center UT.

The inlet valve 30 is open and the outlet valve 34 is closed in the back-flow phase PH2 starting at the bottom dead center UT. Further, no current is supplied to the coil 22. The volume of the delivery chamber 36 is reduced by the upward movement of the piston 18 in the direction of the arrow 54. [ In this case the fuel in the delivery chamber 36 is at least partly urged again through the opening 38 and the inlet valve 30 along arrow 56 and into the low pressure line 7. The backwashing step PH2 ends at the time point t1.

Current is supplied to the coil 22, so that the transition from the backflow step PH2 to the subsequent delivery step PH3 is performed. To this end, the current I has, for example, the profile shown in the lower coordinate system of Fig. Further, the piston 18 is positioned just before the top dead center OT in the upward motion. The armature 24 and the valve needle 35 move to the left by the magnetic force in the drawing. By virtue of the force of the valve spring 31, the valve body 33 is also supported by the fluid force - possibly to the left - resulting in closing the inlet valve 30. The outlet valve 34 is kept closed. The fuel in the delivery chamber 36 is compressed by the residual stroke of the piston 18 to the top dead center OT as a result of the closing of the inlet valve 30 and the closing of the outlet valve 34 and the hydraulic pressure is transmitted to the delivery chamber 36 . Because of this hydraulic pressure or the pressure difference to the areas outside the housing 20, a small amount of fuel is pressurized between the circumferential surface of the piston 18 and the cylinder 37 in the direction of the arrow 58 in the figure. The piston 18 is lubricated due to the resulting leakage flow.

The delivery angle 46 is maintained such that the outlet valve 34 is kept closed at all of the steps PH1 to PH3 when the hydraulic pressure in the pressure chamber 16 does not exceed the pressure in the delivery chamber 36, So as not to be sent out into the region (16). This delivery angle 46 is also referred to as a "delivery angle" in which delivery of fuel is not effected. This is achieved by suitably controlling the electromagnet 15 by means of the control and / or regulating device 19. This allows, on the one hand, the maximum lubrication of the fuel pump 3, on the one hand, and the undesired delivery into the pressure region 16, on the other hand. The non-delivery angle may be related to the angle of the drive shaft 10 of the fuel pump 3.

The control of the electromagnet 15 can be carried out, for example, every stroke 44 of the fuel pump 3. Alternatively, the control may be performed only occasionally or periodically, and no control is made at intervals therebetween. Another alternative is to control the valve device 14 every stroke 44 during a first limited number of strokes 44 and then not to control during a second limited number of strokes 44. [

For the optimum control of the electromagnet 15, the control and / or regulation device 19 is characterized in that it uses one or more characteristic maps 6 to determine, among the following variables representing the operating parameters of the internal combustion engine at the time of detection of the non- Consider one or more of:

- the speed of the internal combustion engine,

- torque of the internal combustion engine,

- the temperature of the internal combustion engine,

- the temperature of the fuel,

The fuel pressure in the pressure region 16, and / or

- operating conditions of the internal combustion engine, especially overrun cutoffs.

Figure 4 shows a flow chart for processing the method in the computer program 8 of the control and / or regulating device 19. Starting at the start block 70, it is determined whether a switch-on condition for the implementation of the method is given in the query block 72. For this, the first operating condition is distinguished from the second operating condition by the above-mentioned operating parameters. However, this is not shown in detail in FIG. If the internal combustion engine is actually in the first operating state, there is no switch-on condition and the program branches back to start block 70.

On the other hand, if the switch-on condition is given, the dispatch angle 46 (dispense angle) is detected from the characteristic map 6 at 74 in the next block and also taking into account the above-mentioned operating parameters. The electromagnet 15 is controlled in the second operating state in accordance with the detected delivery angle 46 so that the fuel pump 3 is operated in a manner similar to that of Fig.

The pressure in the pressure region 16 is then detected at block 76, from which the rate or gradient of the pressure is detected. In this case, the pressure increase due to the heating of the fuel in the pressure region 16 can be considered as the time of the second operating condition increases.

Thereafter, it is checked in query block 78 whether the detected rate is greater than the limit value 80. [ If not, a branch is made to restart block 70 and the program continues there.

However, if the detected rate is greater than the limit value 80, then in the next block 82 the dispatch angle 46 is stepped down by one step first. This safety function can shorten the dispensing phase PH3 or the dispensing angle (dispense angle) 46 so that the pressure in the dispensing chamber 36 is made smaller and, as a result, the outlet valve 34 It works more strongly in the closed position. That is, the risk that undesirable fuel is delivered into the pressure region 16 becomes smaller. Then thereafter again branches to the start block 70 and the program continues there.

1: Fuel system
3: Fuel pump
14: Valve device
16: Pressure area
36: transmission room

Claims (11)

A method for operating a fuel system (1) of an internal combustion engine, comprising: a fuel pump (3) compressing fuel in a delivery chamber (36) by a corresponding adjustment of a valve device (14) 16), and wherein the fuel pump (3) does not deliver fuel into the pressure region (16) by corresponding adjustment of the valve arrangement (14) in one or more second operating situations The method comprising:
Wherein the valve device (14) is controlled at least intermittently so that fuel in the delivery chamber (36) is compressed but not delivered into the pressure region (16) in the second operating state Lt; / RTI > 2. A method according to claim 1, characterized in that the control of the valve device (14) is carried out periodically at every stroke (44) of the fuel pump (3) in the second operating condition. 2. The fuel system according to claim 1, characterized in that the control of the valve device (14) is carried out only occasionally or periodically in the second operating state and no control is made in the intervals therebetween Way. 4. A method according to any one of claims 1 to 3, wherein the control of the valve device (14) is carried out continuously for a first number of strokes (44) of the fuel pump (3) , And then the valve device (14) is not controlled for a second number of times (44) of the fuel pump (3), respectively. 4. A method according to any one of claims 1 to 3, characterized in that the compression is initiated by corresponding adjustment of the valve arrangement (14) without fuel being delivered into the pressure area (16) Characterized in that the angle of the drive shaft (10) of the fuel pump (3) is detected in consideration of one or more operating parameters of the internal combustion engine. 6. A method according to claim 5, characterized in that the non-delivery angle is detected using one or more characteristic maps (6) under consideration of a number of operating variables. 6. The method according to claim 5,
- the speed of the internal combustion engine
- torque of the internal combustion engine
- the temperature of the internal combustion engine
- the temperature of the fuel
- the fuel pressure in the pressure zone (16) and / or
- the operating state of said internal combustion engine, and - the operating state of said internal combustion engine. 6. A method according to claim 5, characterized in that when the pressure in the pressure zone (16) rises at a rate greater than the limit value (80), the delivery angle is changed such that the rate is kept below the limit value Wherein the operation of the fuel system of the internal combustion engine is performed. 9. A method as claimed in claim 8, characterized in that pressure rise due to heating of the fuel in the pressure region (16) is taken into account as the operating time increases. A computer-readable recording medium on which a computer program is recorded, wherein the computer program is programmed to carry out the method according to any one of claims 1 to 3, Recording medium. A control device (19) for an internal combustion engine, characterized in that the control device includes the computer-readable recording medium according to claim 10.

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