WO2012028370A1

WO2012028370A1 - Delivery device of a fuel supply system of an internal combustion engine

Info

Publication number: WO2012028370A1
Application number: PCT/EP2011/061945
Authority: WO
Inventors: Peter Roth; Peter Schenk
Original assignee: Robert Bosch Gmbh
Priority date: 2010-08-31
Filing date: 2011-07-13
Publication date: 2012-03-08
Also published as: DE102010039974A1

Abstract

In a delivery device 10 of a fuel supply system of an internal combustion engine having a high-pressure piston pump 12, a delivery chamber 30, an inlet valve 14 and an outlet valve 16, it is proposed that it comprises a flow restrictor 28 which connects a region 18 which lies downstream of the outlet valve 16 to the delivery chamber 30.

Description

Description title

Conveyor of a fuel supply system of an internal combustion engine prior art

The invention relates to a delivery device of a fuel supply system of an internal combustion engine with a high-pressure piston pump, a delivery chamber, an inlet valve and an outlet valve.

From the market conveyors are known, the one

High-pressure piston pump, designed as a quantity control valve inlet valve, and designed as a check valve exhaust valve include. The

High-pressure piston pump is driven by a camshaft of an internal combustion engine. The high-pressure piston pump promotes the one

Low-pressure system provided fuel into a rail, which is also referred to as common rail.

The common rail is part of the high pressure system and supplies the

Injectors with high pressure fuel. A pressure sensor detects the pressure prevailing in the common rail and transmits it to an electronic control unit. The control unit controls among others in

Dependence of the accelerator pedal position and the pressure in the rail, the flow rate of the high-pressure piston pump. This happens because, by opening the inlet valve of the high-pressure piston pump, a filling of a delivery chamber of the high-pressure piston pump and thus a quantity of fuel delivered by the high-pressure piston pump is controlled.

If a fuel delivery interrupted by a shutdown of the internal combustion engine or a fuel cut, a last set pressure in the high pressure system is maintained. In the case of an overrun fuel cutoff, they remain at a rotating speed Internal combustion engine, the injection valves closed. Due to the waste heat of the internal combustion engine, the fuel remaining in the common rail heats up and expands. This so-called reheating leads to a further increase in pressure. A pressure limitation is carried out by a

Pressure relief valve, with an opening pressure far above a pressure typically prevailing in the high-pressure system. The high pressure leads to inadvertent leakage from the interfaces in the system, such as fittings, gaskets and valve seats. Disclosure of the invention

The problem underlying the invention is achieved by a

Fuel supply system solved according to the features of claim 1.

Advantageous developments are specified in subclaims. Features important to the invention can also be found in the following

Description and in the drawing, wherein the features both alone and in different combinations for the invention may be important, without being explicitly referred to again.

A basic idea of the invention is to reduce the pressure in the high pressure system with interrupted fuel delivery by means of a defined leakage between high pressure system and low pressure system with existing components. This avoids unintentional leakage at the interfaces in the system, such as fittings, gaskets, and valve seats, and eliminates the need for sealing that causes high manufacturing costs. Another advantage of the invention is that with activated overrun fuel cutoff and rotating engine, the pressure in the high-pressure system increases less or not at all due to the so-called post-heating. As a result, the injectors do not have to open against the high system pressure in the subsequent re-insertion of the injection and inject the small injection low injection quantity with very short, time-dependent activation times. This reduces consumption and emissions.

The invention advantageously also prevents the formation of a negative pressure in the high-pressure system. This results from a cooling of the fuel and the associated contraction. The negative pressure in the high pressure system causes oxygen bound in the fuel to outgas and form vapor bubbles.

The invention enables a backflow of the fuel from the

Low-pressure system via the open inlet valve or, with the inlet valve closed, via a piston gap. This reduces the formation of vapor bubbles and the starting behavior when restarting the

Internal combustion engine is improved.

An advantageous embodiment of the invention provides that the

Flow restrictor is integrated in the exhaust valve. As a result, the design effort on the conveyor itself remains low and the size of the conveyor unit is not affected.

A production-technically simple solution is that the flow throttle comprises a notch in a valve seat of the exhaust valve. This component is particularly inexpensive to manufacture.

In addition, it is proposed that the flow restrictor in one

Bypass line is arranged, which is parallel to the exhaust valve. Thus, the exhaust valve remains unchanged and the invention can be used with existing

Components in combination with a low overhead for the

Bypass line can be realized.

In addition, it is proposed that the inlet valve be forcibly,

preferably electrically, is openable. As a result, the intake valve can be controlled particularly easily. After switching off the internal combustion engine, the fuel flows from the high-pressure system into the delivery chamber of the

High pressure piston pump and from there via the open inlet valve in the low pressure system. This results in a quick pressure reduction.

When the inlet valve is closed, the fuel escapes through the piston gap and the speed of the pressure reduction is reduced. In this way, the invention enables, depending on whether the inlet valve is open or closed, a rapid pressure reduction or a certain pressure maintenance, which accelerates a restart of the internal combustion engine. Furthermore, a method is proposed for operating a conveyor of the type described above. The above-described

Advantages of the invention also realized.

It is also proposed that when switching off the internal combustion engine, the inlet valve is controlled so that a maximum delivery capacity of the high-pressure piston pump is achieved. This will reduce the pressure in the

High pressure system increases when stopping and combination with the method described above for pressure maintenance results in a favorable extension of the availability of a minimum pressure, a fast

Restart of the internal combustion engine allows.

Short description of the drawing

Hereinafter, an embodiment of the present invention will be explained in detail with reference to the accompanying drawings. In the drawings show

1 shows a schematic representation of a fuel supply system of an internal combustion engine

Fig. 2 is a sectional view of an exhaust valve of a

Fuel supply system of Fig. 1 and

3 is a flowchart of the method according to the invention

Description of the embodiment

In Fig. 1, a fuel system is shown. The delivery device 10 comprises a fuel pump configured as a high-pressure piston pump 12, an inlet valve 14 arranged on the suction side and an outlet valve 16 arranged on the pressure side. The high-pressure piston pump 12 is driven in a manner not shown in the figure by a camshaft of an internal combustion engine. In a downstream region 18, a high pressure system 20 connects to the exhaust valve 16. The high pressure system 20 includes a common rail 22 and, arranged thereon, a plurality of injectors 24 and a pressure sensor 26th

Arranged parallel to the outlet valve 16 is a flow restrictor 28, which connects the high-pressure system 20 via a bypass line 29 to a delivery chamber 30 of the high-pressure piston pump 12. The flow restrictor may be integrated into the outlet valve 16.

From the high pressure port 18, a return line 32 leads back to the delivery chamber 30 of the high pressure piston pump 12. In the return line 32 is arranged a pressure relief valve 34th

The inlet valve 14 designed as a quantity control valve is electrically actuated and is connected by a low-pressure connection 36 to a low-pressure system 38, which comprises a fuel tank 40 and an electric fuel pump 42. Arranged on the low-pressure connection 36 is a pulsation damper 44. An electronic control unit bears the reference numeral 46.

The above-described conveyor 10 operates as follows: The pressure sensor 26 detects the pressure prevailing in the common rail 22 pressure and transmits it to the electronic control unit 46. Depending on the pressure in the common rail 22 and other input variables, the controller 46 causes an opening of the inlet valve 14. Durch the open inlet valve 14 flows fuel from the low pressure system 38 into the delivery chamber 30 of the

High-pressure piston pump 12, as long as the inlet valve 14 is opened and the piston of the high-pressure piston pump 12 is in the suction stroke. The

High-pressure piston pump 12 subsequently increases the pressure of the inflowing fuel and conveys it further to the high-pressure system 20.

When the fuel cut, the injectors 24 remain closed when the internal combustion engine. Due to the waste heat of the internal combustion engine, the fuel remaining in the common rail 22 heats up and expands. A portion of the fuel escapes through the flow restrictor 28 in the

Delivery chamber 30 of the high pressure piston pump 12 and flows through the open inlet valve 14 back into the low pressure system 42. This is a

unwanted increase in pressure in the high pressure system 20 prevented. If no fuel is to be delivered when switching off the internal combustion engine, the inlet valve 14 is opened, so that the fuel located in the common rail 22 and pressurized by the flow restrictor 28 of the exhaust valve 16 according to the invention back into the delivery chamber 30 of

High-pressure piston pump 12 flows. From there, the fuel flows through the open inlet valve 14 back into the low pressure system 38. Thus, the pressure in the high pressure system 20 is rapidly reduced. When the inlet valve 14 is closed, the fuel can not over the

Inlet valve 14 flow back into the low pressure system 38 so that it passes through the piston gap of the high pressure piston pump 14 in the low pressure system 38. This reduces the pressure reduction speed. As a result, a predeterminable minimum pressure is maintained longer in the high-pressure system 20.

A further extension of the pressure maintenance can be inventively achieved in that when stopping the engine by

Control of the intake valve 14, the flow rate is increased. This increases the pressure in the common rail 22 and the time until the pressure drops to the minimum pressure is extended.

In Fig. 2, designed as a check valve outlet valve 16 is shown in detail. A ball 52 is held by a spring 54 downstream against the valve seat 50 and thus closes the fuel passage 48. In the valve seat 50 is incorporated a notch 56th

If fuel is delivered by the high-pressure piston pump 12, the ball 52 is pressed against the pressure generated by the high-pressure piston pump

Spring force lifted from the valve seat 50 and the fuel flows through the now open fuel ka na I 48 in the high pressure system 20. Promotes the high pressure piston pump 12 no fuel, the spring force pushes the ball 52 on the valve seat 50 and the fuel channel 48 is closed. The notch 56 in the valve seat 50 generates a defined leakage, the backflow of the Fuel ensured in the delivery chamber 30 of the high-pressure piston pump 12, with the valve closed

FIG. 3 shows a flow chart of the method according to the invention. It starts in a start block 58.

In a query block 60, it is checked whether the internal combustion engine with

Thrust shutdown operated or shut down.

In the case of stabling, a branch is made to a block 62 in which a conditional branch is made.

If the first condition 62.1 is satisfied, then the internal combustion engine is turned off and at the same time the inlet valve 14 is opened. As a result, a rapid pressure reduction takes place in the high pressure area and the unwanted leakage of fuel is effectively prevented. Thereafter, the inventive

Stopping completed.

This shutdown always takes place when the internal combustion engine is to be turned off for a long time. For example, such shutdown occurs when the engine is shut down by the driver by turning off the engine

Remove the key.

If the second condition 62.2 is satisfied, then the internal combustion engine is switched off and at the same time the inlet valve 14 is activated in such a way that the delivery rate of the high-pressure piston pump 12 is maximized,

This shutdown takes place whenever the internal combustion engine is switched off by the engine control, examples of such a shutdown is the start-stop mode or the shutdown of the internal combustion engine in hybrid vehicles

Subsequently, it is checked in a query block 64 whether the pressure in

High pressure system 20 has exceeded a predetermined maximum value (p _max ). If the pressure in the high-pressure system 20 is undesirably high, the inlet valve 14 is opened in the function block 66. Subsequently, it is checked in query block 68 whether a predefinable minimum pressure has been reached. If this is not the case, the system branches again to the query block 64. If the minimum pressure is reached in the Function block 70, the inlet valve 14 is closed. This reduces the pressure reduction rate and the inventive method is completed.

In the case of overrun fuel cutoff is branched directly to query block 64. Thereafter, the process proceeds as described above.

Claims

claims

1 . Conveying device (10) of a fuel supply system of a

Internal combustion engine with a high-pressure piston pump (12), a

Delivery chamber (30), an inlet valve (14) and an outlet valve (16), characterized in that it comprises a flow restrictor (28) which connects a downstream of the outlet valve (16) located region (18) with the delivery chamber (30).

Second conveyor (10) according to claim 1, characterized in that the flow restrictor (28) in the outlet valve (16) is integrated.

3. conveying device (10) according to claim 2, characterized in that the flow restrictor (28) has a notch (56) in a valve seat (50) of the

Exhaust valve (16) comprises.

4. conveying device (10) according to claim 1, characterized in that the flow restrictor (28) in a bypass line (29) is arranged, which is parallel to the outlet valve (16).

5. conveying device (10) according to any one of the preceding claims, characterized in that the inlet valve (14) forcibly, preferably electrically, is apparent.

6. A method for operating a conveyor (10) according to one of

preceding claims, characterized in that

Control of the inlet valve (14) a pressure reduction rate is set.

7. The method according to claim 6, characterized in that when stopping the internal combustion engine, the inlet valve (14) is opened when a first Condition (62.1) is present, so that the pressure in the high-pressure region (20) is rapidly reduced.

8. The method according to claim 6, characterized in that when stopping the internal combustion engine, the inlet valve (14) is controlled so that the delivery rate of the high pressure piston pump (12) is increased when a second condition (62.2) is present.

9. The method according to any one of claims 6 to 8, characterized in that when stopping the internal combustion engine, the inlet valve (14) is opened when the pressure in the high pressure system (20) has exceeded a predetermined maximum value (Pmax) when the internal combustion engine operated with fuel cut becomes.