DE10248625A1 - Device for throttling the amount of liquid sucked in by a feed pump - Google Patents

Abstract

The invention relates to a device (24; 38) for throttling the amount of liquid flowing via a line system (28, 30) to a suction side (15) of a liquid feed pump (14), with a liquid upstream of the feed pump (14) in the flow direction of the liquid. throttle cross-section (26; 60, 70) arranged in the line system (28, 30). The device is characterized in that the throttle cross section (60) is variable during the operation of the feed pump (14).

Description

State of the art

The invention relates to a device to throttle the amount of over a line system to a suction side of a liquid feed pump flowing liquid with one in the flow direction the liquid in front of the feed pump throttle cross section arranged in the line system.

Such devices are, for example. in common rail fuel injection systems for diesel engines used. Such systems include a low pressure feed pump to promote from diesel from a tank to a high pressure pump that has an injection pressure level from currently 1350 bar to 1600 bar in a fuel storage, the Common rail. The amount delivered by the low pressure feed pump in principle depends on diesel fuel from the suction pressure that the low pressure pump generates. Furthermore hangs the funded Quantity from the inlet pressure, which is already in operation without the Low-pressure feed pump before the low pressure feed pump established. With conventional fuel systems for internal combustion engines this is the first approximation the atmospheric pressure.

While the suction pressure of the low pressure feed pump, which is driven by the internal combustion engine over wide speed ranges, especially for medium-sized and high engine speed is almost constant, the inlet pressure is larger fluctuations subjected. Such fluctuations are caused, for example, by an operation of the internal combustion engine at different heights with different air pressures as well through the usual Air pressure fluctuations when changing between high pressure and low pressure weather conditions caused. To the delivery rate the low pressure feed pump at high inlet pressures limit, the suction side of the low pressure feed pump in known systems, a simple throttle with a constant throttle cross section (opening or flow cross-section) upstream. The dimensioning of this The throttle must be set in such a way that, even with minimal inlet pressure, can drop to values of 0.5 bar, for the greatest possible performance of the internal combustion engine needed Amount of fuel is supplied to the high pressure pump. Through this Dimensioning flows at higher Inlet pressure necessarily more liquid, or diesel, in the low pressure feed pump. The low pressure feed pump promotes in this case, more fuel than is required by the internal combustion engine. The funded too much Crowd is about an overflow valve back passed into the tank.

A disadvantage of this known system is that the simple suction throttle from the above Reasons the minimum inlet pressure must be designed. This leads to higher Inlet pressure to a correspondingly higher flow rate and thus to a higher Energy consumption of the feed pump.

Another disadvantage results from the fact that diesel fuel injection systems are equipped with fuel filters. Because the filter capacity with regard to the maximum possible output of diesel fuel must be dimensioned when using the known simple suction throttle with a larger fuel filter the associated cost and weight disadvantages become.

In addition, increases accordingly the increase in delivery rate too the back pressure against which the low-pressure feed pump delivers the fuel. This does not lead only to a higher one Energy consumption of the feed pump, but also causes a higher one mechanical load on the feed pump. The feed pump is therefore more mechanically stable, which is also and brings cost disadvantages.

Against this background, the The object of the invention is to provide a device for throttling Amount of over a line system to a suction side of a liquid feed pump flowing liquid state at which the above Disadvantages are at least reduced.

This task is done with a device of the type mentioned in that the throttle cross section while the operation of the feed pump mutable is.

Advantages of invention

Ideally, the low pressure feed pump delivers a constant amount of liquid independent of the inlet pressure. It has been shown that the device according to the invention with the during operation the feed pump variable Throttle cross section is a good approximation of this ideal state delivers while the well-known simple throttle to an increasing inlet pressure steadily increasing flow rate over the Low-pressure feed pump leads. It has also been shown that the maximum flow through the low pressure feed pump reduce by about 30% with the help of the invention presented here leaves. Advantageously, the dimensions of the fuel filter can be adjusted accordingly to reduce. Moreover takes place in an operation with high inlet pressure (sea level) Relief of the low pressure feed pump due to reduced back pressure of up to 0.5 to 1 bar in comparison to known fuel supply systems for common rail injection systems, equipped with the well-known simple, constant choke are. Another advantage is a lower energy consumption the low pressure feed pump at high inlet pressure.

It is preferred that the line system has a first part arranged in front of the device and a second part arranged between the device and the feed pump, and that the throttle cross-section changes during operation of the feed pump such that the stop changes diminished a pressure fluctuation occurring in the second part compared to the extent of an associated pressure fluctuation occurring in the first part.

This configuration causes further approximation the ideal of a constant amount of liquid that is independent of the inlet pressure, that of the low pressure feed pump sucked in and conveyed becomes.

It is further preferred that the throttle cross section from a first variable throttle cross section and a second constant throttle cross section are arranged in parallel in the device, the first changeable Throttle cross section depending from the difference delta_P = P1 - P2 the pressures P1 changeable in the first part and P2 in the second part of the pipe system is. According to this configuration, the variable cross section is at maximum pressure difference delta P, i.e. maximum inlet pressure P1, closed. The constant, permanently open cross-section is like this dimensioned that at a maximum pressure difference, for example Common rail injection system maximum needed Quantity from the low pressure feed pump can be sucked in.

As the inlet pressure drops, the second throttle cross section released to the lower flow by balancing the first constant throttle. With minimal inlet pressure the variable throttle is complete open. The flow through the constant and through the variable throttle must with a minimum pressure difference equal to the maximum amount required of liquid be, for example, the maximum amount of diesel required for a common rail injection system.

This configuration causes that the low-pressure pump an amount that is almost independent of the inlet pressure promotes.

It is further preferred that the Device has a guide body, in which a sliding element (piston) is movably sealed, and that of at least part of the liquid flowing to the feed pump via the Flow through throttle cross-section is, the throttle cross section through an opening of the guide body in a slideway of the sliding element is determined, the opening through the sliding element is at least partially coverable and the Burr of the cover is determined by the position of the sliding element in the guide body becomes.

This configuration enables constructively easy to master realization of a changeable Throttle cross section with the desired Characteristics.

It is further preferred that the position of the sliding element depending on the pressure of the liquid changes in the first part of the piping system.

This configuration advantageously enables the desired change of the throttle cross section depending from the inlet pressure.

It is further preferred that the Throttle cross section between a minimum value and a maximum value is variable and between these extreme values with increasing pressure is reduced in the first part of the pipe system and with falling pressure is enlarged in the first part of the pipe system.

This configuration provides the desired properties So a largely constant, from the fluctuations in the inlet pressure almost independent output the low pressure feed pump.

It is further preferred that the Sliding an end face to which the existing in the first part of the pipe system Pressure acts so that the pressure on the end face is in the direction of the slideway generates first force acting on the sliding element.

This configuration causes that an increasing inlet pressure can shift the sliding element that the sliding element in turn as a result of its displacement reduced the throttle opening cross section.

It is further preferred that the Device at least one element for generating a on the sliding element acting second force, whose direction to the direction of first force is opposite.

This has the advantage that there is a balance between the first and second forces leaves, which as a result the stable attitude of one to the size of the first Strength and thus the amount of Inlet pressure suitably assigned opening of the variable throttle allowed.

It is further preferred that the called element is an elastic element.

An elastic element draws is characterized by the fact that larger forces have greater deformations more Cause restoring forces. The use of an elastic element in that described here Context provides the advantage of an automatic one Establishing a balance between the two mentioned forces and thus a suitable stable setting of the opening cross section of the variable throttle dependent on from the inlet pressure.

It is further preferred that the second, constant throttle cross section through a centrally in the sliding element arranged breakthrough is realized.

This configuration enables particularly compact and therefore weight and cost-saving implementation the invention.

There are further advantages the description and the attached Characters.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination indicated in each case, but also in other combinations or on their own, without the To leave the scope of the present invention.

drawings

Embodiments of the invention are shown in the drawings and are described in the following Description closer explained. Show it:

1 schematically shows a known throttle device in connection with other components of a fuel supply system for a common rail injection system of an internal combustion engine (Otto or Diesel) as a possible environment in which the invention unfolds its effect;

2 an embodiment of a device with features that has the above advantages and properties;

3 Development of delivery rates of a feed pump over the inlet pressure using a simple throttle with a constant opening cross-section and using the subject of the present application.

description

The digit 10 in the 1 denotes parts of a fuel supply system of an internal combustion engine. Fuel from a tank 12 is powered by a low pressure feed pump 14 over their suction side 15 sucked in and over a fuel filter 16 to a high pressure pump 18 promoted. The high pressure pump 18 generated in a fuel storage 20 , the common rail, a supply of fuel under the fuel injection pressure of 1350 to 1600 bar. Fuel is supplied from the common rail to the combustion chambers of the internal combustion engine via injection valves (not shown). The feed pump 14 always has to deliver a little more fuel than the high pressure pump 18 in the fuel storage 20 is delivered later. Not from the high pressure pump 18 Fuel delivered is via an overflow valve 22 in the tank 12 returned.

To limit the delivery rate of the low pressure feed pump 14 is their suction side 15 a throttle device 24 upstream. In known systems, this throttle device 24 a choke 26 with a constant opening cross-section. The throttle device 24 is in a piping system 28 . 30 arranged that the tank 12 with the suction side 15 the feed pump 14 combines.

A first part 28 of the pipe system 28 . 30 directs fuel from the tank 12 to the throttle device 24 , In this first part 28 of the pipe system 28 . 30 the so-called inlet pressure P1 prevails, which usually corresponds to the ambient pressure which varies depending on the weather and operating altitude. In the second part 30 of the pipe system 28 . 30 on the other hand, there is that of the feed pump 14 on the suction side 15 generated suction pressure P2.

The digit 38 in the 2 denotes an embodiment of a device according to the subject matter of the present application. In the environment of 1 replaced the one in the 2 with the number 38 designated device the known throttle device 24 ,

The device 38 has a two-part construction from a tank connector for constructional and manufacturing reasons 40 and a pump connector 42 on. The tank connector 40 For example, an internal thread 44 own with whom the line 28 from the 1 to the device 38 is connected. The pump connector can do the same 42 have an internal thread 46 with which the in 1 to the suction side 15 the feed pump 14 leading management 30 to the device 38 is connected.

In the configuration according to the 2 forms the tank connector 40 a guide body 40 in which a sliding element (piston) 48 is movably guided. Here is the sliding element 48 along a slideway 50 inside the guide body 40 displaceable.

The sliding element 48 has an end face 52 on that connecting the first part 28 of the pipe system 28 . 30 and thus the tank-side connection of the device 38 is facing. The inlet pressure P1 therefore acts on the end face 52 and created in connection with this face 52 a first, on the sliding element 48 in the direction of the slideway 54 Acting force.

An elastic element 56 , for example a metal spring, supports the sliding element 48 against the first force by applying a second force (restoring force) in the event of deformation, which is in the direction 58 that affects the direction 54 is opposite. Depending on that on the face 52 of the sliding element 48 acting inlet pressure P1 (or depending on the pressure difference delta P) and the spring constant of the elastic element 56 this results in an equilibrium position of the sliding element 48 in the guide body 40 on.

If the inlet pressure P1 is sufficiently low, the elastic element presses 56 the sliding element 48 in the representation of the 2 all the way to the left. If the inlet pressure P1 is sufficiently large, the sliding element 48 however, pushed all the way to the right. On the other hand, if the flow pressure P1 is in a middle range, the position of the sliding element changes 48 in the guide body 40 between the extreme positions mentioned.

The guide body 40 has at least one opening 60 in the slideway 50 on, about the liquid from the first part 28 of the pipe system 28 . 30 in a the circumference of the sliding element 48 circumferential recess (ring groove) of the sliding element 48 can flow. From this recess 62 can have fluid over holes 64 and a hollow interior 65 of the guide body 40 into the pump connector 42 and thus in the second part 30 of the pipe system 28 . 30 and on to suction 15 the feed pump 14 stream.

Through the at least one opening 60 is in interaction with the movable sliding element 48 a first variable throttle cross section realized.

In the position shown, the elastic element presses 56 the sliding element 48 to its left stop position, which corresponds to a low inlet pressure P1. As a result, the opening is at this low inlet pressure P1 60 completely free, which corresponds to a maximum opening cross-section and thus a minimum throttling.

With increasing pressure P2, the pressure increases on the end face 52 of the sliding element 48 acting force that the sliding element 48 against the restoring force of the elastic element 56 shifts to the right. As a result, the opening 60 initially partly from the sliding element moving to the right 48 covered, so that a reduction in the first variable throttle cross section occurs as a result of an increase in the inlet pressure P1.

When the inlet pressure P1 is sufficiently high, the sliding element closes 48 by opening it further to the right 60 completely, so that the first variable throttle cross section becomes minimal or disappears.

In the representation of the 2 is the first variable opening cross-section, which is due to the interaction of the opening 60 with the position of the sliding element 48 is realized, a second constant throttle cross section connected in parallel. This second constant throttle cross section is shown in the 2 through a throttle opening 70 in connection with a breakthrough 68 through a central area of the sliding element 48 realized.

The device 38 thus shows a parallel connection of a first variable opening cross section 60 and a second constant opening cross section 70 on. As already mentioned at the beginning, the suction pressure is P2 of the feed pump 14 largely constant. The variable cross section is closed at the maximum pressure difference, that is to say the maximum inlet pressure P1. That means the opening 60 completely through the sliding element 48 is covered. The constant, permanently open cross-section 70 is dimensioned so that at maximum pressure difference the maximum amount required by the feed pump from the common rail system 14 can be sucked in.

With falling inlet pressure P2, the sliding element 48 the second throttle cross section (opening 60 ) released the lower flow through the first constant throttle 70 compensate. The variable throttle is fully open at minimum inlet pressure. The flow through the constant and maximum open variable throttle must be equal to the maximum required amount of the common rail system with a minimum pressure difference.

In the 3 denotes the number 72 the course of a feed pump 14 amount of liquid Q delivered per unit of time depending on the inlet pressure P1 when using a known throttle 24 with constant opening cross-section. As can be clearly seen from the illustration, the delivery rate increases monotonically with increasing inlet pressure P1.

In contrast, the one with the number shows 74 designated course a largely constant course of the delivery rate depending on the inlet pressure P1. The curve 74 results when using the device presented 38 instead of the known device 24 , The hatched area 76 represents the reduction in the excess output. This reduction results in the advantages of the invention mentioned at the beginning. At low values of P1 (P1 <P1_0) the variable choke is 60 fully open. The parallel connection of the variable choke 60 and the constant choke 70 is dimensioned in this case, for example, in such a way that the same flow rate results as in the known constant throttle. However, while the flow through the known throttle increases undesirably at higher P1 values, the flow remains approximately constant when using the throttle shown here, because the variable throttle increases with increasing pressure P1 60 . 48 increasingly closes.

Claims (10)

Contraption ( 24 ; 38 ) for throttling the amount of via a pipe system ( 28 . 30 ) to a suction side ( 15 ) a liquid feed pump ( 14 ) flowing liquid, with a in the direction of flow of the liquid upstream of the feed pump ( 14 ) in the pipe system ( 28 . 30 ) arranged throttle cross section ( 26 ; 60 . 70 ), characterized in that the throttle cross section ( 60 ) during the operation of the feed pump ( 14 ) is changeable. Contraption ( 24 ; 38 ) according to claim 1, characterized in that the line system ( 28 . 30 ) one in front of the device ( 24 ; 38 ) arranged first part ( 28 ) and one between the device ( 24 ; 38 ) and the feed pump ( 14 ) arranged second part ( 30 ) and that the throttle cross section ( 60 ) during the operation of the feed pump ( 14 ) changed so that the extent of one in the second part ( 30 ) occurring pressure fluctuation compared to the extent of an associated, in the first part ( 28 ) occurring pressure fluctuations are reduced. Contraption ( 38 ) according to claim 2, characterized in that the throttle cross-section ( 60 . 70 ) from a first variable throttle cross section ( 60 ) and a second constant throttle cross section ( 70 ) composed in the device ( 38 ) are arranged parallel to one another, the first variable throttle cross section ( 60 ) depending on the difference delta_P = P1 - P2 of the pressures P1 in the first part ( 28 ) and P2 in the second part ( 30 ) of the pipe system ( 28 . 30 ) is changeable. Contraption ( 38 ) according to one of claims 1 to 3, characterized in that the device ( 38 ) a guide body ( 40 ) in which a sliding element ( 48 ) is movably guided, and that of at least part of the feed pump ( 14 ) flowing liquid over the throttle cross section ( 60 ) is flowed through, the throttle cross section ( 60 ) through an opening ( 60 ) of the guide body ( 40 ) in a slideway ( 50 ) of the sliding element ( 48 ) is determined, the opening ( 60 ) through the sliding element ( 48 ) is at least partially coverable, and the degree of coverage is determined by the position of the sliding element ( 48 ) in the guide body ( 40 ) is determined. Contraption ( 38 ) according to claim 4, characterized in that the position of the sliding element ( 48 ) depending on the pressure of the liquid in the first part ( 28 ) of the pipe system ( 28 . 30 ) changes. Contraption ( 38 ) according to claim 5, characterized in that the throttle cross-section ( 60 ) is variable between a minimum value and a maximum value and between these values with increasing pressure in the first part ( 28 ) of the pipe system ( 28 . 30 ) is reduced and with falling pressure in the first part ( 28 ) of the pipe system ( 28 . 30 ) is enlarged. Contraption ( 38 ) according to claim 6, characterized in that the sliding element ( 48 ) an end face ( 52 ) to which the first part ( 28 ) of the pipe system ( 28 . 30 ) existing pressure acts so that the pressure on the end face ( 52 ) one towards ( 54 ) the slideway ( 50 ) on the sliding element ( 48 ) acting first force. Contraption ( 38 ) according to claim 7, characterized in that the device ( 38 ) at least one element ( 56 ) to generate a on the sliding element ( 48 ) acting second force, whose direction ( 58 ) to direction ( 54 ) is opposite to the first force. Contraption ( 38 ) according to claim 8, characterized in that the element ( 56 ) an elastic element ( 56 ) is. Contraption ( 38 ) according to one of claims 3 - 9, characterized in that the second throttle cross-section ( 70 ) by a centrally in the sliding element ( 48 ) arranged breakthrough ( 68 ) is realized.