JP2002364474A - Fuel system for supplying fuel for internal combustion engine and internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a start characteristic and an operation characteristic of an internal combustion engine equipped with a fuel system at a high operation temperature and prolong an endurance life of the fuel system. SOLUTION: A shut-off valve device 66 hydraulically operated is placed in a leakage guide pipe 64. The shut-off valve device is controlled by a pressure in a section positioned upstream side of a shut-off device 26 of a fuel connection part 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel system for supplying fuel for an internal combustion engine, comprising a storage container, a first fuel pump having an inlet connected to the storage container, and a fuel pump. A second fuel pump having an inlet connected to an outlet of the first fuel pump via a fuel connection, and a fuel chamber connected to an outlet of the second fuel pump and at least indirectly transferring fuel. At least one injection device, which can be supplied to a fuel supply, and a shut-off device for preventing fuel from flowing back into the storage container from at least one section of the fuel connection;
A leakage conduit leading from the second fuel pump to the storage container.

[0002]

2. Description of the Related Art Such fuel systems are commercially available. In known fuel systems, an electrically driven fuel pump delivers fuel from a fuel reservoir via a fuel conduit to a high pressure fuel pump driven by an internal combustion engine. The high pressure fuel pump delivers fuel at a very high pressure to a fuel collecting conduit (also called a "rail"). From there, the fuel reaches at least one injection valve, via which the fuel finally reaches the combustion chamber of the internal combustion engine.

In known fuel systems, a one-cylinder piston pump is used as a high-pressure fuel pump. Leaked fuel passing through the gap between the cylinder and the piston via the leak conduit is returned from the high pressure fuel pump to the storage container. This reduces the load on the piston seal of the one-cylinder piston pump used. Behind the outlet of the electric fuel pump there is a check valve which prevents the fuel from flowing back through the fuel pump and into the storage container.

A fundamental problem in fuel systems is that fuel is supplied to the combustion chamber of the internal combustion engine during the starting process. In known fuel systems, the valve device comprises:
During the starting process, an electrically driven fuel pump supplies fuel to the injector at an elevated supply pressure. In many cases, this increased pressure is sufficient to start the internal combustion engine in a very short time. Due to the increased supply pressure, air bubbles are likely to be compressed in the fuel connection between the electrically driven fuel pump and the fuel pump driven by the internal combustion engine, often resulting in a reliable internal combustion engine. A good start is guaranteed.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve a fuel system of the type mentioned at the outset and to further improve the starting and operating characteristics of an internal combustion engine with the fuel system even at high operating temperatures. It is to improve and extend the service life of the fuel system as much as possible while at the same time making the fuel system as simple as possible.

[0006]

According to the device of the invention, a hydraulically operated shut-off valve device is arranged in the leaking conduit, and the shut-off valve device is provided with a hydraulically operated shut-off valve device. , Which is controlled by the pressure in a section of the fuel connection upstream of the shut-off device.

[0007]

By providing the shut-off valve device in the leak line, the increased pre-pressure is maintained in the fuel connection between the first and second fuel pumps after the internal combustion engine has stopped. can do. By shutting off the leaking conduit, i.e. after shutting down the internal combustion engine, fuel passes through the gap between the movable pump element of the second fuel pump and the boundary of the pump chamber and into the storage container. Flow back is prevented. This results in a gradual decrease in the pressure in the fuel connection downstream of the first fuel pump.

By maintaining the pressure, the formation of air bubbles at the connection between the first fuel pump and the second fuel pump after shutting down the hot internal combustion engine is prevented.
Such bubbles form when the fuel in the fuel conduit between these fuel pumps is heated by heat transfer from the internal combustion engine. However, if the pressure that is possible in the fuel system according to the invention is maintained even in a stopped internal combustion engine, the generation of such bubbles can be largely avoided. This significantly improves the starting characteristics of the internal combustion engine with the fuel system according to the invention.

The hydraulic operation of the shut-off valve device can be realized reliably and simply in this case, in other words at a low cost.
The control of the shut-off valve device by pressure in the section of the fuel connection downstream of the shut-off device allows a quick response of the shut-off valve device to the shut-off or connection of the first fuel pump. .

In this section, when the fuel pump is connected, that is, very quickly, a pressure build-up of the ambient pressure in the rest state to the normal operating pressure of the first fuel pump results. Conversely, the pressure in this section of the fuel connection is
When shutting down the first fuel pump, a drop from the normal operating pressure to the ambient pressure occurs very quickly, so that the shut-off valve arrangement can be reliably connected in this case.

[0011]

Advantageous developments of the invention are described in the dependent claims.

In a first development, the shut-off valve device is controlled by the pressure at the outlet of the first fuel pump. Here, the pressure change during the shut-off and connection of the first fuel pump is most directly detectable. Upon shut-off of the first fuel pump, the shut-off valve device can thereby be closed very quickly, which leads to an early leakage of the fuel from the leakage conduit and the fuel connection into the storage container. To block. The pressure in the fuel connection can thereby be maintained at the highest possible level.

In a fuel system having a constant prestress, the shut-off valve device opens only when a control pressure which is within the normal operating pressure of the first fuel pump is applied, and It is particularly advantageous for the deployment to be closed when the pressure drops to a control pressure below the normal operating pressure of one fuel pump.

In a fuel system with variable prestress, the above arrangement is subject to the following condition: the opening pressure of the shut-off valve device is within the range of the lowest operating pressure of the first fuel pump. And the closing pressure is below this minimum operating pressure.

[0015] This ensures that the shut-off valve device is opened and the pressure in the leaking conduit drops to ambient pressure only when the fuel pump produces sufficient work after connection and a delay-free start of the internal combustion engine is possible. Is guaranteed. Conversely, however, it is also ensured that the shut-off valve device is closed immediately after shutting off the first fuel pump.

In this case, it is particularly advantageous if the shut-off valve device has a preload element, for example a spring, which loads the valve element into a closed rest position.

It is further possible for a pressure limiting valve to be provided downstream of the shut-off device. The following situation is obtained by this pressure limiting valve. After shutting down the hot internal combustion engine, shutting down the first fuel pump and consequently closing the shut-off valve arrangement, heating of the fuel and consequently expansion of the fuel in the fuel connection can be tolerated within this range. May cause no pressure rise. Such unacceptable pressure build-up is prevented by the pressure limiting valve. The components in the fuel connection and in the leakage conduit are thereby protected against unacceptably high pressures even when the internal combustion engine is shut down, which increases its service life. In addition, inexpensive components configured for low pressure can be used.

[0018] In a preferred configuration, downstream of the shut-off device, a return line from the fuel connection to the storage vessel branches off and a pressure limiting valve is arranged in this return line.

Furthermore, between the outlet of the first fuel pump and the shut-off device of the fuel connection, a conduit branches off towards the storage container, in which a flow restrictor is arranged, and This conduit is connected to the control connection of the shut-off valve device. Such a restriction accelerates and facilitates the generation of a stable pressure in the fuel connection between the first fuel pump and the second fuel pump when connecting the first fuel pump. become. The amount of fuel discharged to the storage container via the flow restrictor can advantageously be used to operate a suction jet pump for supplying the first fuel pump. The fuel flow required for the control of the shut-off valve device is not important in this case.

[0020] Alternatively, the control connection of the shut-off valve device can be connected to the deaeration connection of the first fuel pump. Advantageously, this solution, together with the return amount, is used when the suction jet pump is not operated. For the efficiency of the first fuel pump, it is advantageous if the control variable is not subtracted from the main fuel transport.

It is also possible for the shut-off valve device to have a pressure limiting function in addition to the shut-off function. In this case, a separate pressure limiting valve can be omitted, which reduces the construction cost of the fuel system according to the invention.

Furthermore, due to the constructional costs, it is advantageous if the shut-off valve device is arranged in the region of the storage container, in particular in the region of the first fuel pump. In this case, it is particularly advantageous if the first fuel pump and the shut-off valve device are part of a tank-containing unit.

The present invention relates to an internal combustion engine, in particular an automotive internal combustion engine, comprising a fuel system, the fuel system supplying fuel to at least one combustion chamber. In this case, it is advantageous if the fuel system is configured in the manner described above.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, the fuel system is indicated generally by the reference numeral 10. This fuel system is part of an internal combustion engine 11 and has a low pressure range 12 and a high pressure range 14.
And

The low pressure area 12 has a storage container 16 in which fuel 18 is stored. Fuel 18 is pumped from storage container 16 by a first fuel pump 20. First
Is an electric fuel pump and is controlled by a timing module (Taktmodul) 22.
An electric fuel pump 20 conveys fuel through outlet 23 into low pressure fuel conduit 24. In this low-pressure conveying conduit, behind the electric fuel pump 20, looking in the direction of flow,
A check valve 26 and then a filter 28 are arranged.

In front of the check valve 26 in the direction of flow, a branch line 30 branches off from the low-pressure fuel line 24 and returns to the storage container 16. A flow restrictor 32 is arranged in the branch conduit 30. From the area of the low-pressure fuel line 24 which lies between the check valve 26 and the filter 28, a further branch line 34 branches off, which is also returned to the storage container 16 and in which a pressure limiter is provided. A valve 36 is arranged. The pressure in the section of the low pressure fuel conduit 24 downstream of the check valve 26 is sensed by a pressure sensor 38.

The low pressure fuel conduit 24 is connected to a second fuel pump 40
Leads to. This second fuel pump is driven by the crankshaft of the internal combustion engine 11 in a manner not shown here in detail. The second fuel pump 40 is a one-piston high-pressure pump. Upstream of the high pressure pump 40, a pressure buffer 42 and a check valve 44 are further arranged in the low pressure fuel conduit 24.

On the outlet side, high pressure pump 40 is connected to fuel line 46
And the fuel conduit is passed through a check valve 48,
It leads to a fuel collecting conduit 50. This fuel collection conduit is commonly referred to as a "rail." A plurality of fuel injection valves 52 are connected to the fuel collecting conduit 50 itself, and these fuel injection valves inject fuel into a combustion chamber (not shown) of the internal combustion engine 11. The pressure in the fuel collecting conduit 50 is detected by a pressure sensor 54.

In order to prevent an overpressure in the fuel collecting line 50 from impairing the function of the injection valve 52, a pressure limiting valve 56 is provided in the fuel collecting line 50. Is fluidly connected to the low pressure fuel conduit 24 via a conduit 58. In short, the high pressure range 1 of the fuel system 10 in the fuel conduit 46 and the fuel collecting conduit 50
4 is controlled via a quantity control valve 60 which is connected to a check valve 48 and a high pressure pump 40 of the fuel line 46.
Between the low-pressure fuel conduit 24 and the check valve 44.
And the pressure buffer 42 are connected to a range.

The fuel system 10 also has a control and regulation device 62, which receives, inter alia, the signal of a pressure sensor 54. A signal is supplied from the pressure sensor 38 to the control and adjustment device 62. On the exit side, a control and regulation device 6
2 is connected, inter alia, to the timing module 22 and the quantity control valve 60 of the first fuel pump 20.

From the high pressure pump 40, a leak conduit 64 returns to the storage vessel 16. A shut-off valve device 66 is present in the leak conduit 64. The shut-off valve device has an open switching position 68 and a closed switching position 70. In the closed switching position, the shut-off valve device 66 is provided by a compression spring 72 as a preload element. In the open switching position, the shut-off valve device 66 is
Is provided by a piston 74 shown only schematically in FIG. Via control conduit 76, piston 74
Is loaded with the pressure in the branch conduit 30.

The electric fuel pump 20, the check valve 26, the filter 28, the pressure sensor 38, the pressure limiting valve 36, the flow restrictor 32, and the shut-off valve device 66 include a tank built-in unit 75.
Part.

Next, the high-pressure pump 40 and the shut-off valve device 66 will be described in detail with reference to FIG.

The high-pressure pump 40 is a one-piston type pump. The piston 77 is driven via a cam drive 78. The piston 77 is guided in a cylinder casing 80. The upper side of the piston 77 and the cylinder casing 80 partition the pump chamber 82. The pump chamber is sealed with respect to the cam drive unit 78 by a gap seal formed between the piston 77 and the cylinder casing 80. Further, a stationary piston seal 84 is provided on the casing. Leakage conduit 64
Is branched from a ring groove 86 immediately above the piston seal 84. Thereby, during operation, the piston seal 84
Is reduced.

The shut-off valve device 66 has a casing 88 in which the piston 74 is guided. That,
At the upper end as viewed in FIG. 2, the piston 74 has a head 90 whose diameter is significantly larger than the diameter of the piston 74. The head 90 is also tightly guided in a correspondingly wide range of the valve housing 88.
The head 90 is loaded by a compression spring 72 by which the lower end of the piston 74 is loaded on a ring web 92 which is formed in the flow chamber 94 behind the inlet 96 of the shut-off valve device 66. ing. In the flow chamber 94, a radial outlet 97 is provided, to which the section of the leakage conduit 64 leading to the storage container 16 is connected.

The casing 88 of the shut-off valve device 66 is closed upward by a cover 98 which has a pin (not numbered) on its inner surface facing the head 90.
The compression spring 72 is centered by this pin. The cover 98 of the shut-off valve device 66 is irremovably connected by a valve casing 88 and a caulking portion 99. Below the head 90, another pressure chamber 100 is provided between the head 90, the piston 74 and the valve casing 88.
Are formed. This pressure chamber is connected to a control conduit 76 via a radial bore 102. Compression spring 72
Are guided in a cylindrical notch (unsigned) in the upper surface of the head 90. Flow passage 1 from the bottom of the notch
04 communicates downwardly in the piston 74 and further radially outwardly into the flow chamber 94.

The fuel system 10 shown in FIGS. 1 and 2 works as follows.

In normal operation of the internal combustion engine 11, the fuel 18
Is transported from the storage container 16 by the electric fuel pump 20 into the low-pressure fuel line 24 and further into the high-pressure pump 40. The high pressure pump 40 conveys the fuel 18 precompressed by the electric fuel pump 20 at a higher pressure into the fuel conduit 46 into the fuel collecting conduit 50. The pressure sensor 54 and the quantity control valve 60 are part of a closed regulation circuit through which the quantity of fuel delivered from the high-pressure pump 40 into the high-pressure range 14 of the fuel system 10 and its pressure are regulated. .

When the electric fuel pump 20 is connected,
The pressure in the low pressure fuel conduit 24 is increased by a control and regulation device 62 to a predetermined value, which is controlled via a pressure sensor 38 and a timing module 22. In the case of a hot start, the pressure is approximately 6 bar with a pressure limiting valve 3
The opening pressure is increased to 6. In the entire operating range, the pressure in the low pressure range 12 is varied between approximately 1.5 and approximately 6 bar. Flow restriction 32
This pressure is also dominating in the branch conduit 30 where is located. The pressure is therefore controlled by control conduit 76
Through the pressure chamber 100 of the shut-off valve device 66.

The pressure surface below the head 90 and the compression spring 72 are matched to each other as follows. That is, at a pressure just below the minimum operating pressure of 1.5 bar, the head 90 and thus the piston 74
It is moved upward against the force of the compression spring 72. This causes the piston 74 to move away from the ring web 92 and open the path of the leak conduit 64 through the shut-off valve device 66 to the storage container 16.

This allows fuel that has reached the ring groove 86 through the gap seal between the piston 77 and the cylinder casing 80 to flow through the flow chamber 94, the radial outlet 97 and the leak conduit 64 and into the storage vessel 16. It is possible to flow back to. This means that the piston seal 8
4 significantly reduced load.

When the internal combustion engine is stopped, the electric fuel pump 20 is also shut off. Thus, within the low pressure fuel line 24 located upstream of the check valve 26, the pressure drops to the ambient pressure prevailing in the storage vessel 16. The same is true for branch conduit 30, control conduit 76 and pressure chamber 100. By means of the compression spring 72, the head 90 and the piston 74 are now pushed downward again, the piston 74 abutting on the ring web 92 and the connection of the leakage conduit 64 to the storage container 16 being interrupted.

As already mentioned above, the pressure surface and the compression spring 72 located below the head 90 are coordinated with each other as follows. That is, the closing of the shut-off valve device 66 already takes place at a pressure just below 1.5 bar. When the shut-off valve device 66 is closed, however, the entire area of the leak line 64 between the shut-off valve device 66 and the high-pressure pump 40 and the low-pressure fuel line between the high-pressure fuel pump 40 and the check valve 26 The area is closed from the surroundings. In this range, therefore, the system pressure at the time of shutdown, even in a stopped internal combustion engine,
Will be maintained.

After shutting down the internal combustion engine, heat transfer may cause heating of the low pressure fuel conduit 24. This also heats and expands the fuel 18 in the low pressure fuel conduit 24. This results in a pressure increase in the just-mentioned closed area of the low-pressure fuel conduit 24. In order to avoid damage to the low-pressure fuel line 24 or the components of the low-pressure area 12 as a whole, the pressure limiting valve 36 is connected to the branch line 34.
Is connected to this area of the low-pressure fuel conduit 24.

In some cases, the end faces of the compression spring 72 and the piston 74 within the ring web 92 can be coordinated with one another as follows. That is, the piston 74 moves away from the ring web 92 when the pressure in the leak conduit 64 rises above a threshold. The corresponding pressure level is preferably the pressure limiting valve 3
6 is located above a predetermined pressure level. In this case, the shut-off valve device 66 creates an additional safety pressure limiting device for the low-pressure fuel line 24 and the leak line 64.

Via the flow passage 104, the chamber in which the compression spring 72 is located is connected to a radial outlet 97 of the shut-off valve device 66, which itself communicates with the storage container 16. ing. Since the ambient pressure is usually dominant there, this flow passage 104
The occurrence of pressures that disrupt the force relationship in the chamber in which the compression spring 72 is located is avoided.

In a non-illustrated embodiment, the control line does not lead from the shut-off valve device to the branch line, but to the deaeration connection present in the electric fuel pump. Advantageously, this solution is used if the suction jet pump is not operated due to the return amount. This has the advantage that no controlled quantity is derived from the main quantity of fuel, which improves the efficiency of the electric pump.

[Brief description of the drawings]

FIG. 1 shows a schematic block diagram of one embodiment of a fuel system.

FIG. 2 shows a schematic detail of the second fuel pump of FIG. 1 as well as the shut-off valve arrangement of the fuel system.

[Explanation of symbols]

Reference Signs List 10 fuel system, 11 internal combustion engine, 12 low pressure range, 14 high pressure range, 16 storage container, 18
Fuel, 20 first fuel pump, 22 timing module, 23 outlet, 24 low pressure fuel conduit,
26 check valve, 28 filter, 30 branch conduit,
32 flow restrictor, 34 branch conduit, 36 pressure limiting valve, 38 pressure sensor, 40 second fuel pump,
42 pressure buffer, 44 check valve, 46 fuel line, 48 check valve, 50 fuel collecting line, 52 fuel injection valve, 54 pressure sensor, 56 pressure limit valve,
58 conduit, 60 quantity control valve, 62 control and regulating device, 64 leaking conduit, 66 shut-off valve device, 6
8 open switching position, 70 closed switching position, 72 compression spring, 74 piston, 75 tank built-in unit, 76 control conduit, 77 piston, 78 cam drive, 80 cylinder casing, 82 pump chamber, 84 piston seal, 8
6 ring groove, 88 casing, 90 head,
92 ring web, 94 flow chamber, 96 inlet, 97 outlet, 98 cover, 99 caulking section, 100 pressure chamber, 102 holes, 104 flow passage

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Helmut Lembold, inventor Germany Stuttgart Ehringer Strasse 27 (72) Inventor Jens Wolber, Germany Gehrlingen Pappelweg 6

Claims (13)

[Claims] A fuel system (10) for supplying fuel (18) for an internal combustion engine, comprising a storage container (1).
6), a first fuel pump (20) whose inlet is connected to the storage container (16), and an outlet of the first fuel pump (20) via a fuel connection (24) ( 2
A second fuel pump (40) connected to 3) and an outlet of the second fuel pump (40) and capable of supplying the fuel (18) to the combustion chamber at least indirectly. At least one injector (52) and a fuel (1);
8) a blocking device (26) for preventing backflow from at least one section of the fuel connection (24) into the storage container (16), and a storage device (16) from the second fuel pump (40). )), Wherein a hydraulically operated shut-off valve arrangement (66) is arranged in the leak conduit (64). Supplying fuel for an internal combustion engine, characterized in that the device is controlled by the pressure in a section of the fuel connection (24) upstream of the shut-off device (26). For the fuel system. 2. The fuel system according to claim 1, wherein the shut-off valve device is controlled by a pressure at an outlet of the first fuel pump. 3. The shut-off valve device (66) opens only when a control pressure within the normal operating pressure range of the first fuel pump (20) is applied, and the first fuel pump (20) is closed. 3. The fuel system according to claim 1 or 2, wherein the fuel system is adapted to close when the pressure drops to a control pressure below the normal operating pressure. 4. The shut-off valve device (66) opens only when a control pressure within the range of the lowest operating pressure of the first fuel pump (20) is applied and the first fuel pump (20) 3.) The fuel system according to claim 1, wherein the fuel system is adapted to close when the pressure drops to a control pressure below the lowest operating pressure of (a). 5. The shut-off valve device (66) has a preload element (72), which loads the valve element into a closed rest position. 5. The fuel system according to 4. 6. The fuel system according to claim 1, wherein a pressure limiting valve (36) is provided downstream of the shut-off device (26). 7. Downstream of the shut-off device (26), a backflow conduit (34) from the fuel connection (24) to the storage vessel (16) branches off and a pressure limiting valve (36) 7. The fuel system according to claim 6, wherein the fuel system is disposed in a conduit (34). 8. A conduit (30) branches towards the storage container (16) between the outlet of the first fuel pump (20) and the shut-off device (26) of the fuel connection (24). A flow restrictor (32) is arranged in this conduit,
The fuel system according to claim 6 or 7, wherein the conduit (30) is connected to a control connection (102) of the shut-off valve device (66). 9. The control connection of the shut-off valve device is connected to the deaeration connection of the first fuel pump.
The fuel system according to any one of the preceding claims. 10. The fuel system according to claim 1, wherein the shut-off valve device has a pressure limiting function in addition to the shut-off function. 11. The storage valve (1) includes a shut-off valve device (66).
11. The fuel system according to claim 1, wherein the fuel system is arranged within 6), for example within the first fuel pump (20). 12. The first fuel pump (20) and the shutoff valve device (66) are part of a tank built-in unit.
The fuel system according to claim 11. 13. An internal combustion engine (11), for example for a motor vehicle, provided with a fuel system (10), which supplies fuel (18) to at least one combustion chamber. An internal combustion engine of the type, characterized in that the fuel system (10) has the configuration according to one of the preceding claims.