WO2012175281A1 - High-pressure pump for a fuel injection device of an internal combustion engine - Google Patents

Abstract

The invention relates to a high-pressure pump, in particular for a fuel injection device of an internal combustion engine, having at least one pump piston (5) which is driven at least indirectly by a drive shaft (2) in a reciprocating movement, wherein the drive shaft (2) is driven by the internal combustion engine at a rotational speed which is proportional to the rotational speed of the internal combustion engine. The drive shaft (2) has at least one single or multiple cam (3) for driving the at least one pump piston (5). The at least one pump piston (5) delimits a pump working chamber (6) which has a swept volume. The suction phases of the at least one pump piston (5) are dimensioned in such a way that, at a low rotational speed of the drive shaft (2) and of the internal combustion engine, in particular the starting rotational speed of the internal combustion engine, the swept volume of the pump working chamber (6) is filled at least substantially completely with fuel in the suction phase of the at least one pump piston (5), and that, at a high rotational speed of the drive shaft (2) and of the internal combustion engine, the swept volume of the pump working chamber (6) is filled only partially with fuel in the suction phase of the at least one pump piston (5).

Description

 High-pressure pump for a fuel injection device of an internal combustion engine

The present invention relates to a high-pressure pump for a

Fuel injection device of an internal combustion engine according to the preamble of claim 1.

State of the art

Such a high-pressure pump is known from DE 10 2008 041 934 A1. This high-pressure pump has a pump piston, of a

Pump drive shaft is driven by a cam. The

Pump drive shaft is mechanically driven by the internal combustion engine, so that the rotational speed of the pump drive shaft is proportional to the speed of the internal combustion engine. Through the pump piston is a

Pump working space limited with a defined displacement. The high-pressure pump feeds fuel into a high-pressure region, for example a high-pressure accumulator, and can be injected at the internal combustion engine. To reduce the fuel consumption and the CO 2 emission of the internal combustion engine is aimed at this missing

Drive demand, for example, when a standstill equipped with the internal combustion engine motor vehicle, off. This is also called a start-stop system. When the internal combustion engine is stopped by the high pressure pump no fuel is promoted. Subsequently, however, a quick start of the internal combustion engine is required, which in turn requires a quick fuel delivery through the high-pressure pump. In order to enable a quick starting of the internal combustion engine must by the

High pressure pump already at low speed a large amount of fuel to be promoted. A corresponding design of the high pressure pump according to However, the prior art leads to the fact that a high torque for driving the pump drive shaft is required and that the required drive torque also varies widely. In addition, more fuel may be delivered by the high-pressure pump at high speed than is required in each operating state of the internal combustion engine.

Disclosure of the invention

Advantages of the invention

The high-pressure pump according to the invention with the features of claim 1 has the advantage that on the one hand even at low speed the required for a quick start of the engine fuel quantity is promoted on the other hand, however, at high speed not too much fuel is promoted. The stroke volume of the pump working space can according to the quantity requirement for starting the

Internal combustion engine are designed.

In the dependent claims are advantageous embodiments and

Further developments of the high pressure pump according to the invention indicated. The embodiment according to claim 2 has the advantage that the shortening of the suction phases compared to the delivery phases of the pump piston both the filling of the pump working chamber is reduced at high speed, since the delivery of the high-pressure pump at high speeds deteriorates, but this effect can by increasing the Hubvolumens be compensated. In addition, the required drive torque for driving the high-pressure pump can be reduced, since a larger rotation angle range of the pump drive shaft is available for the delivery phases. Of the

Construction costs are virtually unchanged compared to a previously known high-pressure pump. The embodiment of claim 4 allows a sufficiently large displacement of the pump working space without high

Speeds and accelerations of the pump piston and resulting high and fluctuating drive torques for the

Pump drive shaft occur. Advantageous developments of the invention are also to be taken from the drawings, in which an illustrated in the figures embodiment of the invention is described in more detail.

Brief description of the drawings

Show it:

Figure 1 is a sectional view of an inventively designed

 Piston pump,

FIG. 2 shows a diagram with a representation of a known piston stroke and a piston stroke of a pump camshaft designed according to the invention and FIG

3 shows a diagram with a representation of a piston speed of a known cam and a cam designed according to the invention of a pump camshaft.

The pump illustrated in FIG. 1 is designed as a fuel lift pump for a fuel injection device, in particular a common rail injection system, a self-igniting internal combustion engine operated with diesel fuel and designed to deliver diesel fuel at a pressure of more than 1600 bar into a high-pressure accumulator. The piston pump has a pump housing 1, in which a designed as a pump camshaft 2 pump drive shaft is rotatably mounted. The pump camshaft 2 has a double cam 3, which in a rotational movement of the

Pump camshaft 2 cooperates with a roller tappet 4 and a pump piston 5 a translational up and down movement of the pump piston 5 causes. The pump camshaft 2 is mechanically by the

Internal combustion engine driven and the speed of the pump camshaft 2 is proportional to the speed of the internal combustion engine.

A pump working chamber 6 is in a pump cylinder head 7 of

High-pressure pump, with the pump cylinder head 7 continues is integrally formed with a pump cylinder 8. The pump cylinder 8 projects into a recess 9 of the pump housing 1 and is aligned with the center axis of the pump camshaft 2.

The roller tappet 4 has a tappet body 10, which is guided inwardly on the pump cylinder 8 and is secured against rotation by means of an anti-rotation device 1 1. Similarly, the roller tappet in the pump housing 1 could be externally guided and secured against rotation. Furthermore, the plunger body 10 has an up to an inner annular flange 18 extending

Pump camshaft side recess into which a roller shoe 12 is inserted. The roller shoe 12 has a hollow cylindrical recess 13 into which a roller 14 is inserted captive. The roller 14 runs at a rotational movement of the camshaft 2 on the cam track and thus transmits the rotational movement of the camshaft 2 in a translational movement of the pump piston 5. The pump piston 5 has a

Pumpenkolbenfuß 15, which via a clamping device 16 with the

Roller plunger 4 and the plunger body 10 is connected by pinching between the roller shoe 12 and the inner annular flange 18. Not shown in the figure is a pump spring which presses the roller tappet 4 in the direction of the camshaft 2. The pump spring is arranged in a space 17 below the pump cylinder 8 between this and the inner annular flange 18 of the plunger body 10.

The pump working chamber 6 is in communication with a suction valve, via which fuel is supplied from a low-pressure system and wherein the suction valve opens during a suction stroke (downward movement) of the pump piston 5 and thus fuel is admitted into the pump working chamber 6. In a delivery stroke (upward movement) of the pump piston 5 closes the suction valve and

Fuel is delivered from the pump working chamber 6 via a fuel line, a check valve and a continuing line in the high-pressure accumulator.

The pump piston 5 has, for example, a diameter of about 6 mm to 9 mm, in particular from about 6.5 to 7.5 mm and the stroke of

Pump piston 5 is about 5 mm to 8 mm, in particular about 5 to 6.5 mm. Preferably, the diameter of the pump piston 5 is greater than the stroke of the pump piston 5. At a certain displacement of the

Pump working space 6 result in large diameter of the

Pump piston 5 and small stroke of the pump piston 5 lower

Speeds and accelerations of the pump piston 5 than at the same stroke volume with a smaller diameter and larger stroke of the pump piston. 5

The diagram of Figure 2 has an abscissa on which the cam angle in degrees pump camshaft 2 is shown, while the ordinate the

 Indicates piston stroke in millimeters. A well-known standard cam for one

Pump camshaft 2 with a double cam 3 has a cam profile, which is reached from 0 mm piston stroke at 0 ° pump camshaft 2 a maximum piston stroke of 6.5 mm at approximately 90 ° pump camshaft 2 and then drops again to a piston stroke of 0 mm at

180 ° pump camshaft 2. The inventively designed cam 3 (start-stop cam) has the same maximum piston stroke of approximately 6.5 mm, but this piston stroke is only achieved at a later cam angle of approximately 105 °. The suction phase of the pump piston 5 extends in the cam 3 according to the invention over a cam angle of about 75 ° and the delivery phase of the pump piston 5 extends over a

Cam angle of about 105 °.

In the diagram of Figure 3, the cam angle in degrees pump camshaft 2 is again given on the abscissa, while the ordinate the

 Piston speed in m / s at a speed of 1, 000 revolutions of the pump camshaft 2. A well-known standard cam is designed so that this pump piston 5, starting from a

Piston speed from 0 m / s up to a maximum value of 0.6 m / s accelerates at approximately 20 ° pump camshaft 2 and then at this value over a cam angle of approximately 40 ° to a

Cam angle of 60 ° pump camshaft 2 remains. From the cam angle of 60 ° pump camshaft 2, the piston speed is reduced to a standstill at 90 ° pump camshaft (OT), then negative to a minimum value of approximately -0.7 m / s (negative piston speed at the downward movement of the pump piston) at about 135 °, then up to a cam angle of 180 ° Pumpenmnockenwelle 2 again up to a piston speed of 0 m / s (standstill in UT) increase. The cam 3 according to the invention (start-stop cam) reaches the maximum speed even at approximately 10 ° pump camshaft 2

Piston speed of just over 0.4 m / s, which is kept constant over a cam angle of approximately 70 ° to a cam angle of approximately 80 °. Thereafter, the piston speed - the standstill in TDC at approximately 105 ° pump camshaft 2 reaches - to a negative value of -

0.8 m / s at approximately 150 ° cam angle reduced, then to rise to 180 ° pump camshaft 2 again to 0 m / s (standstill in UT). Clearly recognizable is the over a wide cam angle of about 70 °

Pump camshaft 2 reduced during the funding phase

Piston speed, which allows a significant reduction in the drive torque of the pump camshaft 2 of the piston pump.

The stroke volume of the pump working space 6 is dimensioned such that at low speed of the pump drive shaft 2 and the internal combustion engine, in particular at the starting speed of the internal combustion engine, in the suction phase of

 Pump piston 5 of the pump chamber 6 is at least substantially completely filled with fuel, and thus by the pump piston 5 is a sufficient to start the engine fuel quantity is promoted. The starting speed of the internal combustion engine is the speed with which, for example, an electrically operated starter can drive the engine. At high speed of the pump camshaft 2 and the

Internal combustion engine is no longer completely filled the pump working chamber 6 because of the suction phase of the pump piston 5 shortened compared to the delivery phase during the suction stroke of the pump piston 5, so that the delivery rate of the high-pressure pump is reduced at high speed. The displacement of the

 Pump work space 6, however, is sized so large that despite the

Degree of reduction even at the speed in an operating condition of the internal combustion engine for the highest torque and / or the highest power the required amount of fuel through the pump piston 5 is promoted.

Claims

Patent Proverbs 1 . High-pressure pump, in particular for a fuel injection device of an internal combustion engine, with at least one pump piston (5) which is driven by a drive shaft (2) at least indirectly in a lifting movement, wherein the drive shaft (2) of the  Internal combustion engine with the speed of the internal combustion engine proportional speed is driven, wherein the drive shaft (2) at least a single or multiple cam (3) for driving the at least one pump piston (5), wherein by the at least one pump piston (5) a pump working space ( 6) is limited, which has a stroke volume, characterized in that the suction phases of the at least one pump piston (5) are dimensioned so that at low speed of the drive shaft (2) and the internal combustion engine, in particular starting speed of  Internal combustion engine, the stroke volume of the pump working space (6) in the suction phase of at least one pump piston (5) is at least substantially completely filled with fuel, and that at high speed of the drive shaft (2) and the internal combustion engine in the suction phase of the at least one pump piston (5 ) the stroke volume of the pump working space (6) is only partially filled with fuel. 2. High pressure pump according to claim 1 characterized in that the at least one single or multiple cam (3) of the drive shaft (2) is formed so that based on the angle of rotation of the drive shaft (2) the suction phases of the at least one pump piston (5) over a smaller angle of rotation of the drive shaft ( 2) extend as the delivery phases of the at least one pump piston (5). 3. High-pressure pump according to claim 1 or 2,  characterized in that the displacement of the  Pump work space (6) is dimensioned so that in one  Operating state of the internal combustion engine with maximum torque and / or maximum power of the internal combustion engine also at  Partial filling of the stroke volume of the pump chamber (6) the required amount of fuel is promoted. 4. High-pressure pump according to one of claims 1 to 3,  characterized in that the stroke of the at least one  Pump piston (5) is smaller than the diameter of the at least one pump piston (5). 5. High-pressure pump according to one of the preceding claims,  characterized in that the at least one pump piston (5) has a diameter of about 6 to 9 mm, preferably about 6.5 to 7.5 mm, and that the stroke of the at least one pump piston (5) about 5 to 8 mm, preferably is about 5 to 6 mm.