KR20170131266A - Method for operating a low pressure pump - Google Patents

Abstract

The present invention relates to a method to operate a low pressure pump included in a fuel supply system of an internal combustion engine comprising a high pressure system including a high pressure pump, wherein fuel is supplied to a high pressure pump through the low pressure pump included in the low pressure system, thereby reducing energy consumption. According to the present invention, the low pressure pump is operated in a first operation mode (B_1) wherein the low pressure pump is operated by a pressure adjusted in consideration of a target value with respect to a supply pressure of the high pressure pump, and is operated in a second operation mode (B_2) wherein the low pressure pump is operated by a flow rate controlled in consideration of the amount of fuel required for the high and lower pressure systems. In this case, the first mode (B_1) or the second mode (B_2) is used in accordance with one or more operation parameters (L, n) of the fuel supply system.

Description

METHOD FOR OPERATING A LOW PRESSURE PUMP [0001]

The present invention relates to a method of operating a low pressure pump in a fuel supply system of an internal combustion engine, and to a computer unit and a computer program for performing such a method.

In recent vehicles equipped with an internal combustion engine, an electric fuel pump in the form of a so-called pre-feed pump or a low-pressure pump is used in the fuel low-pressure system, in other words, in the low-pressure region of the fuel supply portion. From the tank the fuel is transferred to the high pressure pump.

As a result, the fuel transfer can be performed as needed. To this end, the electric fuel pump requires a unique open circuit control or a closed-loop control, and may have an electronic device which can be integrated into the fuel pump, for example, or separately installed for this purpose.

In DE 10 2008 001 240 A1, for example, a flow control method for operating a low pressure pump is known, in which the amount of fuel supplied from the low pressure pump is adjusted according to the amount of fuel required by the high pressure pump or high pressure system .

DE 10 2010 001 150 A1 discloses a low-pressure pump operating method in which the actual fuel quantity supplied from the low-pressure pump is determined, for example, on the basis of geometrical parameters or operating parameters of the low-pressure pump.

According to the present invention, a method of operating a low pressure pump, having the features of the independent patent claims, and a computer unit and computer program for implementing such a method are proposed. The preferred embodiments are subject of the dependent claims and the following detailed description.

The method according to the invention is suitable for operating a low pressure pump, for example an electric fuel pump, in the fuel supply system of an internal combustion engine with a high pressure system comprising a high pressure pump, the fuel being supplied to the high pressure pump via a low pressure pump . Then, fuel can be supplied to the high-pressure accumulator, for example, through a high-pressure pump, and the fuel is again introduced into the internal combustion engine through the fuel injector. In this case, the low-pressure pump can be operated in the first operating mode in which the low-pressure pump is operated under pressure in consideration of the target value for the supply pressure of the high-pressure pump, or in particular according to such a target value. In this case, the low-pressure pump can be operated under pressure, in particular electrically or electronically, in particular also by means of a sub-rpm control circuit, i.e. it can not be operated mechanically, for example with centrifugal force control. To this end, the pressure value (in particular the supply pressure for the high pressure pump) can be collected by the sensor and compared with the target value (in particular the target supply pressure for the high pressure pump) in the execution side computer unit. In this case, for example, the number of pump revolutions (of the low-pressure pump) is considered as a control variable. The low pressure pump can also be operated in a second operating mode in which the low pressure pump is operated in a flow controlled manner rather than in a pressure regulating manner, especially considering the amount of fuel required in the high pressure system and optionally in the low pressure system . For this purpose, the target rotation speed of the low-pressure pump is preset in accordance with the required fuel amount. In operation of the low pressure pump, a first operating mode or a second operating mode is now used in accordance with one or more operating parameters of the fuel supply system.

The first operating mode, also referred to as supply pressure regulation, is preset by the provision of a supply at the cooling throttle of the high-pressure pump so that sufficient fuel for lubrication or cooling flows through the high-pressure pump in the state in which the super- Thereby making it possible to ensure sufficient lubrication or cooling of the high-pressure pump for a limited operating range using fuel. This can be accomplished, for example, by an electrical supply pressure regulator connected to a cooling throttle in a high pressure pump. Therefore, sufficient lubrication or cooling can be ensured. In the case of a cooling throttle, the supply pressure can be adjusted so that sufficient fuel flows for lubrication or cooling for a limited operating range (motor rpm, load, fuel temperature) even in a high-pressure pump with a small bearing clearance and thus a small leakage.

A second mode of operation, also referred to as flow control, makes it possible to ensure essentially increased lubrication or cooling of the high pressure pump for high load operating conditions. At this time, the amount of fuel required can be achieved, for example, by setting the number of revolutions of the low-pressure pump, and the pressure regulation can be made through a mechanical pressure regulator in the open-flow valve in the high-pressure pump, not through the electrical pressure regulation. In this case, however, the predetermined tolerances in the individual low-pressure pumps can be considered on the one hand and the variable properties of the fuel, in particular the viscosity of the fuel, can be taken into consideration, More fuel is delivered. In other words, the second operating mode is provided only for the high load operating state because unnecessary high energy is consumed by using the second operating mode over the entire operating range of the fuel supply system.

The proposed method now takes advantage of the fact that the two operating modes have different advantages in different operating regions of the fuel supply system. The two operating modes can be used more precisely according to the current value of the operating parameters of the fuel supply system, so that the energy consumption can be reduced if the time slice is high in the normal mode with a low load on the one hand, On the other hand, a rigid boundary condition can be guaranteed for the high-pressure pump under extreme conditions (motor rpm, load, fuel temperature).

Preferably, the first operating mode is used when one or more operating parameters are below an associated threshold. In other words, in other words, it can be changed from the first operating mode to the second operating mode if one or more operating parameters reaches an associated threshold value or exceeds an associated threshold value. At this time, when a plurality of operation parameters are used for each operation parameter, one unique threshold value may be provided. It is also conceivable that, although a plurality of operating parameters are monitored, only one of the plurality of parameters reaches the associated threshold value or exceeds the associated threshold value, it is already changed from the first operating mode to the second operating mode. It will be appreciated that additional or other conditions that vary between the two operating modes, as desired or needed, may also be used for operating parameters and associated thresholds. In this way, energy consumption can be minimized effectively.

Preferably, the at least one operating parameter is selected from the group consisting of fuel temperature, the number of revolutions of the internal combustion engine or the high-pressure pump, the load of the internal combustion engine, the pressure inside the high-pressure accumulator of the high-pressure system, the injection quantity of the fuel injector, do. The operating parameters mentioned affect the amount of fuel required to be delivered or provided by the low pressure pump and / or by the high pressure pump.

In the second operating mode, it is preferable that the low-pressure pump is operated by presetting the target value of the revolution number or the feed amount of the low-pressure pump and / or by adjusting the revolution number of the low-pressure pump. In this way, very simple flow control is possible, in which case the open-circuit control or closed-loop control of the number of revolutions can be carried out very simply through a suitable pump control device.

In a preferred manner, it is desirable for the purpose of adjusting the flow of cooling fuel by means of a high-pressure pump (and thus not for the purpose of conveying, that is to say through the cooling system or cooling line, A swirling valve and / or a cooling throttle are provided in the return line of the high-pressure pump. If a cooling throttle and an overflow valve are both provided, the cooling throttle can be integrated inside the overflow valve (in this case the throttle flow through the piston in the overflow valve is switched according to the pressure) As shown in FIG. Through the overflow valve, the required supply pressure is mechanically ensured over a wide range of perfusion, after the opening pressure has been exceeded by the corresponding amount of overflow, while through the cooling throttle, that is to say through the high pressure pump, Through the throttle in the feedback line, sufficient lubrication or cooling of the high-pressure pump can be achieved even at low pressures. This fact is particularly desirable when the low pressure pump is operated with the overflow valve closed, as can be done in the first operating mode. Alternatively, in the second operating mode, it is desirable to operate the low pressure pump with the overflow valve open, for example to provide a sufficiently high fuel volume for cooling the high pressure pump under high load.

A control unit of a computer unit according to the present invention, for example an automobile, is designed, in particular programatically, to carry out the method according to the invention.

It is also desirable to implement the method in the form of a computer program, since this approach results in particularly low costs, especially if the running-side control device is also used for other tasks anyway. Data carriers suitable for providing computer programs are, in particular, magnetic disks, such as hard disks, flash memories, EEPROMs, DVDs, optical memories and electronic memories. It is also possible to download the program via a computer network (Internet, intranet).

Further advantages and embodiments of the present invention refer to the detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is schematically illustrated in the drawings with reference to an embodiment, and will be described below with reference to the drawings.

Figures 1a and 1b are schematic diagrams of alternative embodiments of a portion of a fuel supply system with a low pressure pump in which the method according to the invention can be carried out.
2 is a graph schematically illustrating ranges for two operating modes depending on operating parameters when carrying out the method according to the invention in a preferred embodiment;
3 is a graph schematically illustrating ranges for two operating modes depending on the return flow rate and differential pressure of the high pressure pump when implementing the method according to the present invention in a preferred embodiment;
Figures 4A and 4B are schematic block diagrams of a sequence of a method according to the present invention implemented in the preferred embodiments.

Figure 1a shows a portion of a fuel supply system 100 of an internal combustion engine having a low-pressure pump 120 formed as an electric fuel pump here and in which the method according to the present invention may be implemented, schematically and illustratively Respectively. In this case, the fuel is transferred from the fuel tank 110 to the high-pressure pump 130 through the two filters 111 and 112 by the low-pressure pump 120.

In the high pressure pump 130 surrounded by the high pressure system 145, the fuel is supplied to the inlet valve 136 via a flow control valve 131 and an inlet valve 136 as shown, for example, or alternatively, To the piston 135 disposed in the engine compartment 132 and in the cylinder there. The piston 135 is coupled to one shaft of the internal combustion engine 150 and is driven through the shaft. Through the discharge valve 137, the fuel can be supplied to, for example, a high pressure accumulator (not shown in this figure).

In addition, the overflow valve 133 and, for example, two storage leaks 134 and 138 are shown through which the fuel flows back into the fuel tank 110 via the return line 146. Through the overflow valve 133, the fuel may flow out, for example, when the predetermined pressure value is exceeded. In addition, a cooling throttle 139 integrated in the overflow valve 133 is provided so that the fuel having a low volumetric flow through the cooling throttle can flow permanently for cooling the high pressure pump 130, There is a possibility of being opened by pressure.

As section A differs from FIG. 1A, as can be seen in FIG. 1B, alternatively, the cooling throttle 133 may be arranged in parallel with the overflow valve 133, so that fuel with a low volumetric flow is introduced into the high- 130 to cool down.

The low pressure pump 120 is in the low pressure system 140 of the fuel supply system 100. The low pressure system 140 includes in particular a pressure sensor 141, a fuel tank 110, filters 111 and 112, a low pressure pump 120, a super flow valve 133, a cooling throttle 139, And a fuel line communicating with the interior. For completeness, the low pressure system 140 may also pass partially through the housing and bearings 134 and 138 of its high pressure pump for the purpose of, for example, lubrication and / or cooling of the high pressure pump 130.

The fuel pump 120 is assigned a computer unit 170 which is formed as a pump control device which is provided for the control and / or regulation of the low pressure pump 120 and which may be, for example, a microcontroller, A measuring device, and suitable software.

In addition, a microcontroller not shown in the drawing is provided, to which the pump control device 170 is connected to transmit data, and the microcontroller is connected to the fuel supply system 100 via the fuel supply system 100, The fuel pump 120 is triggered as desired by providing the pump controller 170 with a corresponding command, such as, for example, the number of revolutions or the volume flow, while the control of the internal combustion engine supplied with the fuel is started.

Figure 2 schematically illustrates the ranges for the two operating modes depending on the operating parameters when carrying out the method according to the invention in a preferred embodiment.

For example, in the present embodiment, the load L of the internal combustion engine and the rotation number n of the internal combustion engine or the high-pressure pump are shown as operation parameters of the fuel supply system, and the first operation mode B ₁ ) and the range for the second operation mode (B ₂ ) can be determined.

It is apparent that other parameters, such as, for example, the fuel temperature, can also be used as operating parameters to determine the range in which one of the two operating modes is used.

As to the load L, for example, the threshold value L _S provided by the rail pressure is shown, and the threshold value n _s is shown for the rotation number n. Now, Within the scope of the proposed method, for example, if the underlying of the internal combustion engine load, number of revolutions, as well as (L) (n) until the relevant thresholds (L _S or n _s) has a first operating mode (B ₁ Is selected. Alternatively, the second operating mode (B ₂ ) is selected as soon as one of the thresholds has been reached or the threshold has been exceeded. Alternatively, a threshold value or a characteristic curve depending on other variables such as an injection quantity as a function of the number of revolutions of the internal combustion engine may be used as the threshold value.

For completeness, the second operating mode (B ₂₎ line to restrict a second operating mode (B ₂₎ generally indicates a range, but, in this case, when all thresholds from the scope of the proposed method below, the The first operating mode (B ₁ ) must be used.

3 schematically shows the ranges for the two operating modes depending on the differential pressure AP and the feedback flow M _R of the high pressure pump when carrying out the method according to the invention in a preferred embodiment.

The feedback flow (M _R ) shown by the solid line passes through the supercooling valve 133 and the integrated cooling throttle 139 from the engine compartment 132 in the fuel supply system shown in FIG. 1, for example, Is an amount of fuel within the return line 146 of the high-pressure pump, such as occurs within a range reaching into the interior of the tank 110. [

At this time, the differential pressure AP of the high-pressure pump corresponds to the pressure drop across the high-pressure pump, i.e., substantially between the supply (to the filter 112) and the return line 146.

Further, by the broken line M ' _R , a so-called throttle curve for the cooling throttle integrated in the overflow valve is furthermore shown, which, when closed by the overflow valve, passes through only the cooling throttle valve, Dependent flow dependence. In this case, the value DELTA _PD describes the pressure when the throttle cross section is completely opened.

It can be seen from the profile of the feedback flow (M _R ) that the profile follows a throttle curve substantially for a low differential pressure, but unlike the pressure threshold value ΔP _S , the feedback flow (M _R ) . The opening pressure of the vortex valve is used as the pressure threshold value (ΔP _S).

The profile of the return flow in an alternative variant in which the cooling throttle is connected in parallel to the overflow valve is described in accordance with the dash-and-dot line (M " _R ).

Now, within the scope of the proposed method, the first operating mode (B ₁ ) is selected, for example when the pressure differential is small and the throttle is open while the swirl valve is not yet open. The overflow valve is opened and thereby the differential pressure is boosted, whereby the second operation mode B ₂ is selected. In this case, the throttle is also held in the open state.

4A and 4B, a sequence of a method according to the present invention implemented in the preferred embodiments is shown schematically as a block diagram. For example, operational parameters such as the number of revolutions, the load and the fuel fuel can be determined continuously or repeatedly during operation.

Now, in FIG. 4A, in step 401, the actual value of the number of rotations n may be compared with the associated threshold value n _s . Correspondingly, in step 402, the actual value of the load L may be compared to the associated threshold L _S , and in step 403 the actual value of the fuel temperature T may be compared to the associated threshold T _S have.

Now, in step 410, the results obtained from steps 401, 402 and 403 may be collected and evaluated to determine which of the two operating modes should be used or whether the operating mode should be replaced. In this case, for example, the first operating mode B ₁ may be selected as long as all three operating parameters are below the relevant threshold values. Alternatively, if more than one operating mode is placed on the associated threshold value, a second operating mode B ₂ may be selected. In this way, the change between the two modes of operation can be simplified and this situation leads to energy efficient operation.

Alternatively, as shown in FIG. 4B, an intermediate variable, e.g., the required feedback flow M _R , may be used as the switching criterion. In this case, for example, the operating parameters n, L and T define the required return flow rate, and this return flow rate is continuously compared with the threshold value M _RS . By continuously comparing the feedback flow rate M _R required as a whole with the threshold value M _RS , for example, in the case of M _R <M _RS , the operating mode B ₁ is selected and in the other case the operating mode B ₂ is Is selected. In this case, as the load, one or more of the different parameters such as the injection amount, the rail pressure, the accelerator pedal position, or the high-pressure feed amount may be considered again.

The preferred fact in this case is that the thresholds are not fixedly defined and rather the interdependency of one operating parameter with respect to one or more other parameters can be shown in the characteristic field. This fact makes it possible to limit the extent to which the operating modes B ₁ and B ₂ can be extended.

Another advantage is that, in addition to the other calculation variables, the calculated intermediate variable can still be used in the operating mode (B ₂ ) for forming the target feed quantity of the direct feed pump.

The current or actual value of the individual operating parameters may then be determined, for example, by a suitable sensor or model or in another suitable manner. Therefore, the number of revolutions of the low-pressure pump can generally be detected / detected or preset in the associated pump control device in any case.

Claims (14)

A method of operating a low pressure pump (120) in a fuel supply system (100) of an internal combustion engine (150) having a high pressure system (145) including a high pressure pump (130) The fuel is supplied to the high-pressure pump 130 through the low-pressure pump 120,
The low pressure pump 120 can be operated in the first operation mode B _{1 in} which the low pressure pump 120 is operated under pressure in consideration of the target value for the supply pressure of the high pressure pump 130,
The low pressure pump 120 can be operated in a second mode of operation B _{2 in} which the low pressure pump 120 is operated in flow control under consideration of the amount of fuel required in the high pressure and low pressure systems 145,
Wherein a first operating mode (B ₁ ) or a second operating mode (B ₂ ) is used in accordance with one or more operating parameters (L, n, T) of the fuel supply system (100). The method of operating a low pressure pump according to claim 1, wherein in the first operating mode, the low pressure pump (120) is flow controlled and operated through a preset speed or speed regulation. A method according to any one of the preceding claims, wherein in the first mode of operation the low-pressure pump is operated electrically or electronically under pressure. 3. A method according to claim 1 or 2, wherein the first operating mode (B ₁₎ is used in less than the one or more operating parameters (L, n, T) related to the threshold value (L _S, n _S, T _S), How the low pressure pump works. 3. The method according to claim 1 or 2, wherein the at least one operating parameter includes at least one of a fuel temperature (T), a rotational speed (n) of the internal combustion engine (150), a rotational speed of the high- Pressure in the high-pressure accumulator of the high-pressure system 145, the amount of injection of the fuel injector, the amount of high-pressure feed, and the position of the accelerator pedal. The method according to any one of claims 1 to 10, wherein in the second operating mode (B ₂ ), by presetting the target value of the rotation speed (n) or the feed amount of the low pressure pump (120) Wherein the low-pressure pump (120) is operated by adjusting the number of revolutions (n). The system according to any one of the preceding claims, wherein an overflow valve (133) and / or a cooling throttle (139) are provided in the return line (146) of the high- pressure pump (130) to regulate the flow of cooling fuel through the high- ) Is provided. The method of operating a low pressure pump according to claim 7, wherein a super flow valve (133) and a cooling throttle (139) are provided, and said cooling throttle (139) is integrated within the super flow valve (133). The method of operating a low pressure pump according to claim 7, wherein the overflow valve (133) and the cooling throttle (139) are provided, and the cooling throttle (139) is installed in parallel with the overflow valve (133). In a first operating mode (B ₁₎ in the vortex valve 133 is a method of operating a low-pressure pump that operates a low-pressure pump 120 in a closed state according to claim 7. In the second operating mode (B ₂₎ in the vortex valve 133 is operated in a low-pressure method low-pressure pump, pump 120 is operated in the opened state according to claim 7. A computer unit (170) designed to perform the method according to any one of the preceding claims. A computer program stored on a machine-readable storage medium, the computer program being executable on a computer unit (170) to cause the computer unit (170) to perform the method according to any one of claims 1 or 2. 14. A machine-readable storage medium having stored thereon a computer program according to claim 13.

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