EP1798415B1 - High pressure pump - Google Patents

Description

The invention relates to a high-pressure pump.

High-pressure pumps are subject to heavy loads when exposed to pressures of, for example, 2000 bar. Such comparatively high pressures make both high demands on the material of the high-pressure pump and on their construction. At the same time large forces must be absorbed by such high-pressure pumps.

In the GB 301,821 discloses a high-pressure compressor having the structural features as defined in the preamble of claim 1, and in which power is transmitted from a drive unit to the compressor piston via a piston unit interposed therebetween.

The EP 0 400 693 A2 discloses a high-pressure pump in which the pressure generated by a drive device and at least one piston in a hydraulic fluid via transfer membranes on a pressurized fluid is transferable, each piston having two separation membranes are assigned.

The US Pat. No. 1,516,032 discloses a pump having a cylinder in which a piston is disposed at each end of the cylinder, and another piston is disposed between the two pistons, and at least two of the pistons are movable in the same direction.

The object of the invention is to provide a high-pressure pump, which is low even at high pump pressures Wear is subject to and allows reliable and accurate operation.

The object is solved by the features of the independent claims. Advantageous embodiments of the invention are characterized in the subclaims.

The invention is characterized by a high pressure pump with a pump housing and at least one pump unit with a cylinder chamber having a longitudinal axis in which a high-pressure piston is arranged axially movable. The drive of the high-pressure pump via a drive shaft, the drive shaft is in operative connection with a first piston of the at least one pump unit and a pressure chamber of the at least one pump unit is acted upon by the first piston with a first pressure. The pressure chamber is in operative connection with a second piston of the at least one pump unit, which in turn is in operative connection with the high-pressure piston stands. The second piston has a surface facing the pressure chamber and delimiting the same, and the high-pressure piston has a surface facing the cylinder chamber and delimiting it which is smaller than the surface facing the pressure chamber and the limiting surface, and the first piston is relative to the second piston arranged so that the first piston and the second piston are movable in the same direction when used as intended. The first piston is designed as a push cup. The plunger cup has an annular end surface which forms a boundary surface of the pressure chamber.

Since the cylinder chamber facing and this limiting surface of the high-pressure piston is smaller than the pressure chamber facing and this limiting surface of the second piston, a pressure boost in terms of pressure increase from the pressure chamber to the cylinder chamber allows. The pressure ratio results from the ratio of the pressure chamber facing and this limiting surface of the second piston and the cylinder chamber facing and this limiting surface of the high-pressure piston. Due to the pressure ratio even a low pressure in the pressure chamber is sufficient to produce a high pressure in the cylinder chamber. Thus, only a small pressure, which is smaller than the pressure in the cylinder chamber, to be generated in the pressure chamber, which can be achieved with a suitable choice of pressure ratio in a simple manner via the drive shaft and the first piston in operative connection with it. This has the advantage that occur in the pressure chamber only relatively low stresses on the drive shaft and the first piston.

By the arrangement of the first piston relative to the second piston such that the first and the second piston when intended Insert are movable in the same direction, is a simple and compact design of the high-pressure pump, in particular the at least one pump unit, possible. By forming the first piston as a push cup, a better guidance of the first piston in the pump housing can be achieved, in particular if parts of the push cup can be guided in the pump housing. Due to the design of the annular end face of the tappet cup as a boundary surface of the pressure chamber, a particularly space-saving arrangement of the tappet cup in the pump housing is possible, whereby in particular the overall length of the at least one pump unit can be reduced.

In an advantageous embodiment of the invention, the first piston is arranged coaxially with the high-pressure piston. This can in particular represent a simplification of the production of the high pressure pump, since the holes for the cylinder chamber, the pressure chamber and other arranged in the pump housing chambers and chambers can be realized in one operation.

In a further particularly advantageous embodiment of the invention, the pressure chamber is filled with a pressurized fluid, which can be zufüllbar via a pressure chamber inlet line, and the pressure chamber inlet line has a pressure chamber inlet valve. This allows a particularly simple way of supplying pressurized fluid, in particular in the event of leakage.

In a further particularly advantageous embodiment of the invention, the pressure chamber inlet valve is a volume flow control valve. This allows a particularly precise metering of pressurized fluid, which is necessary to compensate for a leakage of pressurized fluid. By a precise metering of pressurized fluid, a particularly uniform transfer behavior from the first piston to the second piston and the high-pressure piston can be achieved.

In a further particularly advantageous embodiment of the invention, the pressure chamber inlet valve is a check valve. This is a particularly simple and inexpensive type of valve, in which a reliable metering of pressure fluid for pressure fluid leakage compensation is possible and the backflow of pressurized fluid can be prevented in the pressure chamber inlet line.

In a further particularly advantageous embodiment of the invention, the high-pressure pump is a radial piston pump with at least two pump units. With such a pump, particularly high injection pressures can be realized.

In a further particularly advantageous embodiment of the invention, the high-pressure pump is a series piston pump with at least two pump units.

Embodiments of the invention are explained in more detail below with reference to the schematic drawings.

• Figur 1 eine schematische Ansicht einer Hochdruckpumpe in einer ersten Ausführungsform in einem Längsschnitt, und
• Figur 2 eine Pumpeneinheit einer weiteren Ausführungsform der Hochdruckpumpe in einem Längsschnitt.

Show it:

• FIG. 1 a schematic view of a high-pressure pump in a first embodiment in a longitudinal section, and
• FIG. 2 a pump unit of another embodiment of the high-pressure pump in a longitudinal section.

FIG. 1 shows a high-pressure pump 10 with a pump housing 12 and three pump units 13, 13a, 13b, which is arranged at an angle of 120 degrees to each other.

The high-pressure pump 10 has centrally a drive shaft 14, which is in operative connection with an eccentric ring 16 and is rotatably mounted in a rotational direction D in the pump housing 12 in the counterclockwise direction. Instead of the eccentric ring, a camshaft can be used as the drive shaft 14. In this case, the number of delivery and compression strokes on the number of cams can be specified. The number of conveying or compression strokes corresponds to the number of cams.

The pump units 13, 13a, 13b are constructed identically. In the following, the pump unit 13 will also be described as representative of the other two pump units 13a, 13b.

The pump unit 13 consists essentially of a first piston 18, a second piston 24 and a high pressure piston 30, which are arranged coaxially with each other. The second piston 24 and the high pressure piston 30 may be integrally formed as individual components or with each other. Between the first piston 18 and the second piston 24, a pressure chamber 22 is arranged, between the pump housing 12 and the second piston 24 on the side remote from the pressure chamber 22 side of the second piston 24, an intermediate chamber 26 is arranged, which is hydraulically coupled to the pressure chamber 22 , and on the The cylinder chamber 32 has a preferably central longitudinal axis L, which forms the central longitudinal axis of the entire pump unit 13 in the embodiment shown here, the intermediate chamber 26 side facing away from the high-pressure piston 30.

The first piston 18 is mounted axially movable in a bore in the pump housing 12 and is in operative connection with the eccentric ring 16. The first piston 18 is held by means of a first spring 20 in constant contact with the eccentric ring 16. Thus, a lifting and re-impact of the first piston 18 can be avoided on the eccentric ring 16, which could lead to damage to both the eccentric ring 16 and the first piston 18.

Between the pump housing 12 and the second piston 24, a second spring 28 is disposed in the intermediate chamber 26, which counteracts a compression stroke of the high-pressure piston 30. The second spring 28 is preferably supported on the pump housing 12 and on the second piston 24. The second spring 28 exerts a force on the second piston 24 and the high-pressure piston 30 connected to it, through which they can reach their starting position without the action of further forces.

In order to be able to fill the cylinder chamber 32 with fluid, it has a cylinder chamber inlet line 33, in which a cylinder chamber inlet valve 34 is preferably arranged. The cylinder space inlet valve 34 facilitates the filling of the cylinder space 32 and prevents the backflow of the fluid from the cylinder space supply line 33 during filling. The cylinder space 32 further has a cylinder space drain line 35 and a cylinder chamber arranged in this Cylinder space outlet 36 on. This fluid can be ejected from the cylinder chamber 32.

The first piston 18 is in operative connection with the pressure chamber 22. During the compression stroke of the first piston 18, the first piston 18 pressurizes the pressure chamber 22 with a first pressure P1. The pressure chamber 22 is also in operative connection with the second piston 24. Thus, the second piston 24 is acted upon by the pressure prevailing in the pressure chamber 22 and impressed by the first piston 18 first pressure P1. Due to the pressurization, the second piston 24 is moved out of its rest position in the same direction as the first piston 18 and thereby performs a stroke. Since the second piston 24 is in operative connection with the high-pressure piston 30, the high-pressure piston 30 also carries a stroke in the same direction as the first piston 18 and the second piston 24 and acts on the cylinder chamber 32 with a second pressure P2.

The second piston 24 has a pressure chamber 22 facing and this limiting surface 52. The high-pressure piston 30 has a cylinder space 32 facing and this limiting surface 54. The latter is smaller than the pressure chamber 22 facing and this limiting surface 52 of the second piston 24th

The pressure ratio P2 / P1 results from the formula P2 / P1 = A1 / A2. Here, P1 is the first pressure in the pressure chamber 22, P2 the second pressure in the cylinder chamber 32, A1, the surface measure of the pressure chamber 22 facing and this limiting surface 52 and A2, the surface dimension of the cylinder chamber 32 facing and this limiting surface 54. Due to the pressure ratio leaves yourself with a relatively small one first pressure P1 in the pressure chamber 22 a relatively large second pressure P2 in the cylinder chamber 32 produce. With a ratio of the area dimensions of A1 / A2 = 20, for example, at a first pressure P1 = 100 bar, a second pressure P2 = 2000 bar results. Despite the high second pressure P2 in the cylinder chamber 32, the eccentric ring 16 and the first piston 18 are only slightly loaded since they only have to absorb a pressure of P1 = 100 bar. The high pressures occur exclusively between the high-pressure piston 30 and the second piston 24. However, these high pressures are unproblematic for the two pistons 24, 30, since there is no relative movement between the high-pressure piston 32 and the second piston 24, as is the case between the eccentric ring 16 and the first piston 18.

The pressure chamber 22 is filled with a substantially incompressible pressure fluid. As a pressurized fluid is particularly suitable a lubricating oil. By using a lubricating oil, the moving parts of the high-pressure pump are simultaneously lubricated. An additional lubricant supply is thus not required, which simplifies the construction of the high-pressure pump. By lubricating the moving components, the friction is reduced, thereby significantly increasing the life of the high-pressure pump.

In order to compensate for a leakage flow of the pressure fluid from the pressure chamber 22, the pressure chamber 22 has a pressure chamber supply line 37. In the pressure chamber inlet line 37, a pressure chamber inlet valve 38 is arranged, which is preferably a check valve. The designed as a check valve pressure chamber inlet valve 38 facilitates the filling of the pressure chamber 22 and prevents when filling the backflow of the pressurized fluid from the pressure chamber inlet line 37th

The intermediate chamber 26, which is hydraulically coupled to the pressure chamber 22, has a pressure chamber outlet line 39 and a pressure chamber outlet valve 40, which is preferably a check valve. This pressure fluid can be drained from the intermediate chamber 26 and the pressure chamber 22 hydraulically coupled with this if necessary.

Due to the coaxial arrangement of the first piston 18 to the high pressure piston 30, a direction equal movement of the first piston 18, the second piston 24 and the high pressure piston 30 is achieved. This coaxial arrangement leads to a particularly simple and compact construction of the high-pressure pump 10.

The following is the operation of the first embodiment of the high pressure pump according to FIG. 1 be described in detail:

In the initial state, the first piston 18, the second piston 24 and the high-pressure piston 30 should be in a position in the pump unit 13 in which they each have a minimum distance from the drive shaft 14.

By a rotational movement of the drive shaft 14 in the direction of rotation D counterclockwise, the first piston 18 is axially moved away from the drive shaft 14 by the eccentric ring 16 and compressed in the pressure chamber 22 pressurized fluid to a first pressure P1. The pressure P1 acts on the pressure chamber 22 facing and this limiting surface 52 of the second piston 24. The second piston 24 is in operative connection with the intermediate chamber 26. By the voltage applied to the surface 52 P1 of the second piston 24, the second piston 24 and the form-fittingly connected to the high pressure piston 30 can perform a movement in the same direction as the first piston 18. The cylinder chamber inlet valve 34 and the cylinder chamber outlet valve 36 are closed. By the movement of the high-pressure piston 30, a compression of the fluid located in the cylinder chamber 32 can take place. The compressed fluid may be expelled after the compression stroke via the now open cylinder chamber outlet valve 36 and the cylinder chamber drain line 35. If the high-pressure pump is, for example, a high-pressure fuel pump of an injection system of an internal combustion engine, the fluid subjected to high pressure can reach a high-pressure fuel reservoir, the so-called common rail.

In order to be able to reduce the pressure P1 in the intermediate chamber 26 that is created by the compression stroke, the pressure chamber outlet valve 40 is opened during the compression stroke and the pressure fluid located in the intermediate chamber 26 is pushed out via the pressure chamber drain line 39.

Furthermore, the first piston 18 is moved by the counterclockwise movement D of the drive shaft 14 by means of the eccentric ring 16 radially to the drive shaft 14 back. In this case, the pressure chamber 22 is filled via the formed as a check valve pressure chamber inlet valve 38 and the pressure chamber inlet line 37 with pressurized fluid. The high pressure piston 30 is moved together with the second piston 24 by the spring force of the second spring 28 in the same direction with the first piston 18 to the drive shaft 14 back. About the cylinder space inlet valve 34 and the Cylinder space supply line 33 while the cylinder chamber 32 is filled with fluid. The pistons 18, 24, 30 have now reached their initial state with a minimum distance to the drive shaft 14. Subsequently, a new stroke for compression of the media can take place again.

In FIG. 2 a pump unit 13 of a second embodiment of the high-pressure pump is shown.

In the pump housing 12, the first piston 18 is mounted axially movable, wherein the first piston 18 is formed as a push cup. The first piston 18 designed as a push cup has a bottom portion 42 and an adjoining annular side wall portion 44. The side wall portion 44 has in its upper region an annular end face 46 and the bottom portion 42 in its lower region an end face 50. About the end face 50 of the bottom portion 42 of the first piston 18 of the first piston 18 is connected to a camshaft, not shown, or an eccentric ring, not shown in operative connection. In this case, the first piston 18 by means of the first spring 20, which is arranged in the pressure chamber 22, held in constant contact with the camshaft or the eccentric ring.

The side wall portion 44 is guided in an annular gap 56 of the pump housing 12. In the side wall portion 44 of the first piston 18 seals 48 are introduced.

The designed as a push cup first piston 18 is connected via the annular end face 46, which forms a boundary surface of the pressure chamber 22, with the pressure chamber 22 in operative connection. During a compression stroke of the as Stößelbecher formed first piston 18 is acted upon by the first piston 18 via the annular end face 46, the pressure chamber 22 with the first pressure P1. Via the surface 52, which faces the pressure chamber 22 and limits this, the pressure chamber 22 is in operative connection with the second piston 24, whereby it is acted upon by the pressure prevailing in the first pressure chamber 22 first pressure P1. Thus, the second piston 24 can be moved out of its rest position in the same direction with the first piston 18 and execute a stroke. The second piston 24 in turn is in operative connection with the high-pressure piston 30, so that the high-pressure piston 30 in the same direction with the first piston 18 and the second piston 24 perform a compression stroke and thus the cylinder chamber 32 can act on the second pressure P2. The ratio of second pressure P2 to first pressure P1 again arises, as shown in detail for the first embodiment, from the ratio of the surface dimensions A1 and A2.

Due to the design of the first piston 18 as a push cup with a boundary surface of the pressure chamber 22 forming annular end surface 46 and the space in the pump housing 12 space-saving pressure chamber 22 is a particularly space-saving design of the pump unit 13 and thus the entire high-pressure pump 10 is possible.

Between the pump housing 12 and the second piston 24, the second spring 28 is arranged, which counteracts the compression stroke of the high-pressure piston 30. The second spring 28 ensures that the second piston 24 and the high-pressure piston 30 coupled to it return to its initial position following the compression stroke, which is characterized by the minimum distance of the pistons 24, 30 from the drive shaft 14. The second spring 28 is supported advantageously on the housing 12 and the second piston 24 from.

In the pressure chamber inlet line 37, the pressure chamber inlet valve 38 is arranged, which is preferably designed as a flow control valve to allow a particularly precise metering of pressurized fluid.

The other structure of the pump unit 13 of the second embodiment of the high-pressure pump is identical to the first embodiment.

The pump unit 13 can be used both in a radial piston pump and in a high-pressure pump designed as a linear piston pump.

In the following, the operation of the second embodiment of the high-pressure pump 10 will be described in detail with reference to the pump unit 13. In this case, the functional differences of the second embodiment of the high-pressure pump compared to the first embodiment will be discussed essentially.

If the first piston 18 moves upwards, the pressure fluid in the pressure chamber 22 is compressed and subjected to the first pressure P1. This first pressure P1 acts on the pressure chamber 22 to the pressure chamber 22 facing and this limiting surface 52. The pressure on the space 22 facing and this limiting surface 52 applied pressure P1 causes the second piston 24 and the high-pressure piston 30 in the same direction with the first piston 18 are moved upward and perform a compression stroke. This is done, as already detailed in the first embodiment described, a compression of the fluid located in the cylinder chamber 32. The compressed fluid may be expelled via the cylinder space drain line 35 subsequent to the compression stroke. If the high-pressure pump 10 is a high-pressure fuel pump, the cylinder space drain line 35 can be connected to the common rail.

Upon completion of the compression stroke, the second spring 28 moves the second piston 24 and the high pressure piston 30 back to their original positions. At the same time, fluid is sucked into the cylinder space 32 via the cylinder space supply line 33. At the same time, the first piston 18 is moved back in the same direction as the second piston 24 and the high-pressure piston 30 and in the pressure chamber 22, the leakage can be compensated via the pressure chamber inlet valve 38.

Due to the design of the pressure chamber inlet valve 38 as a flow control valve, pressure fluid 22 can be metered particularly precisely to the pressure chamber 22. This may be particularly important in the partial load range of the high-pressure pump, since in this case a reduction in the amount of pressurized fluid is possible.

Claims (7)

1. High pressure pump (10),

   - with a pump housing (12),

   - and at least one pump unit (13) having a cylinder space (32) with a longitudinal axis (L), in which a high pressure piston (30) is arranged in an axially movable manner, wherein

   - the high pressure pump (10) is driven via a drive shaft (14),

   - the drive shaft (14) is operatively connected to a first piston (18) of the at least one pump unit (13),

   - a pressure space (22) of the at least one pump unit (13) can be charged with a first pressure (p1) by the first piston (18),

   - the pressure space (22) is operatively connected to a second piston (24) of the at least one pump unit (13), which piston, for its part, is operatively connected to the high pressure piston (30),

   - the second piston (24) has a surface (52) which faces the pressure space (22) and delimits the latter, and the high pressure piston (30) has a surface (54) which faces the cylinder space (32), delimits the latter and is smaller than the surface (52) which faces the pressure space (22) and delimits the latter, and

   - the first piston (18) is arranged relative to the second piston (24) in such a manner that, during correct use, the first piston (18) and the second piston (24) are movable in the same direction,

   characterized in that the first piston (18) is designed as a tappet cup, and the tappet cup has an annular end surface (46) which forms a delimiting surface of the pressure space (22).
2. High pressure pump (10) according to Claim 1, characterized in that the first piston (18) is arranged coaxially with respect to the high pressure piston (30).
3. High pressure pump (10) according to one of the preceding claims, characterized in that the pressure space (22) is filled with a pressure fluid which can be supplied via a pressure-space inflow line (37), and the pressure-space inflow line (37) has a pressure-space inlet valve (38).
4. High pressure pump (10) according to Claim 3, characterized in that the pressure-space inlet valve (38) is a volumetric-flow-regulating valve.
5. High pressure pump (10) according to Claim 3, characterized in that the pressure-space inlet valve (38) is a non-return valve.
6. High pressure pump (10) according to one of the preceding claims, characterized in that the high pressure pump is a radial piston pump with at least two pump units (13).
7. High pressure pump (10) according to one of Claims 1 to 5, characterized in that the high pressure pump is an in-line piston pump with at least two pump units (13).

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