EP2414675A1

EP2414675A1 - High-pressure pump

Info

Publication number: EP2414675A1
Application number: EP10702693A
Authority: EP
Inventors: Werner Vallon; Otto Mueller
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2009-04-02
Filing date: 2010-02-08
Publication date: 2012-02-08
Anticipated expiration: 2030-02-08
Also published as: CN102378861A; CN102378861B; EP2414675B1; WO2010112253A1; DE102009002132A1

Abstract

The invention relates to a high-pressure pump for a fuel injection device of an internal combustion engine, in particular for a common-rail system, comprising a cam power train, wherein the rotational movement of a cam shaft is transformed by means of at least one cam into a stroke movement of a pump piston of the high-pressure pump, wherein a cam contour of the cam is designed in a way such that during a suction phase of the high-pressure pump in a range from a top dead center to a bottom dead center, in which fuel is sucked into a pump working chamber, the stroke of the pump piston follows a sinusoidal course as a function of the cam rotational angle.

Description

description

Title High pressure pump

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

High-pressure pumps are used, for example, in common-rail systems of motor vehicles to provide or supply pressurized fuel to a high-pressure accumulator under all operating conditions. Such high-pressure diesel pumps usually have either eccentric drives or cam drives. The advantage of cam-driven high-pressure pumps is that in this case it is possible to design for a desired application a cam profile adapted thereto, which represents the piston stroke via a rotation angle of the drive shaft or the camshaft. For example, a slow delivery phase and a fast suction phase of the high pressure pump can be realized via an asymmetric cam profile, whereby an advantage is achieved by the resulting low maximum drive torque, which must apply the motor to drive the high pressure pump.

However, in order to reduce the variety of parts in the production, substantially symmetrical cam contours have been developed in the prior art, which have the same stroke course in the suction and delivery phase. A cam contour designed in this way can therefore also be used both for the right-handed and for the anti-clockwise rotation. Although the symmetrically designed cam contours have the advantage described above that the number of parts is kept small, they have the disadvantage that the fundamental differences that arise for the suction phase and the delivery phase of the high-pressure pump, are not taken into account or included.

In the case of high-pressure pumps known from the prior art, moreover, the cams used for their drive shafts were also optimized with regard to their cam contour only with regard to the delivery phase. However, the resulting cam contours gave unfavorable properties for the filling behavior of the element space or the pump working space of the high-pressure pump in the suction phase.

Therefore, it is necessary to provide a high-pressure pump for fuel injection devices and in particular for common rail systems, which has a

Has cam contour, which is also optimized in terms of the suction phase.

Disclosure of the invention

Advantages of the invention

According to the invention, a high-pressure pump is provided for a fuel injection device of an internal combustion engine, in particular for a common rail injection system, which has a cam engine in which the rotational movement of a camshaft is converted via at least one cam into a lifting movement of a pump piston of the high-pressure pump, wherein a cam contour of the Cam is designed so that in a suction phase of the high pressure pump in a range from a top dead center to a bottom dead center, in which fuel is sucked into a pump working space, the piston stroke of the pump piston as a function of the cam rotation angle follows a sinusoidal course. Due to the sinusoidal design of the cam contour, the filling behavior of the element space or of the pump working space of the high-pressure pump in the suction phase is improved, and strong variations in the fuel delivery rate as a function of the rotational speed are reduced. Farther The range is improved in the pressure reduction after top dead center of the cam.

According to a preferred embodiment, the at least one cam has an asymmetrical cam contour. This allows adaptation to special requirements, for example with regard to the suction phase and the delivery phase.

According to a further preferred embodiment, the sinusoidal curve in the suction phase corresponds to a falling edge of a sinusoidal function, which starts at a top dead center of the cam and ends at a bottom dead center of the cam. By means of the "half-sine cam" with, for example, 2 × 6 mm stroke according to the embodiment, clear increases in delivery can be achieved in comparison with conventional cams with, for example, 2 × 6 mm stroke, for example, the delivery rate increases from 160 l / h when using a conventional cam to 178 l / h, when the "semi-sine cam" according to the embodiment is used. In addition, this can reduce flow rate fluctuations over the speed, for example, a two-piston pump and the Abspringverhalten the plunger assembly of the high-pressure pump is improved in the suction phase. A correction or compensation of flow rate fluctuations over the speed and reduced flow rates by increasing the piston stroke is no longer necessary, which improves the durability of the high-pressure pump. In particular, by the configuration described above, a high load on the plunger spring, a high drive torque of the high-pressure pump and high Umpumpverluste, resulting in an additional consumption of

High pressure pump leads, avoided.

It is particularly preferred if the falling edge is formed from a sum of harmonic functions. By forming the falling edge of the cam profile from a sum of harmonic functions, the performance of the high pressure pump is further optimized. In particular, the lift-off properties of the plunger body of the high-pressure pump are improved, and depending on the acceleration curve of the rising flank in the delivery phase, larger acceleration stages in the transition region to the suction phase are avoided. In particular, this refinement of the speed and loading accelerated course of the pump piston and the Hertzian pressure improved.

According to yet another preferred embodiment, the sinusoidal curve in the suction phase at the top dead center of the cam corresponds to a maximum delivery stroke of the pump piston. By this configuration, the suction phase is further optimized, the course or the cam contour of which takes place before the suction phase promotion phase is irrelevant and can follow an already optimized cam contour. The sinusoidal characteristic is characterized by a slow and harmonic decrease or increase in the piston stroke, the piston speed and the piston acceleration after and before the dead centers. The high piston speed in the mid-range of the delivery phase was previously the reason for high drive torques of the high-pressure pump and was not enforceable in the requirements previously imposed on the high-pressure pumps in the prior art. However, the slow, harmonic decay after top dead center results in an improved suction phase and lower negative torques during pressure build-up. Due to the slow approach to the bottom dead center, the suction valve of the high-pressure pump can begin earlier with its closing operation and delivery losses due to a late closing of the suction valve are significantly reduced.

According to yet another preferred embodiment, the sinusoidal curve in the suction phase at the bottom dead center of the cam corresponds to a minimum delivery stroke of the pump piston.

Preferably, the cam contour is designed so that in the suction phase of the high-pressure pump, the piston speed of the pump piston performing a downward movement follows a sinusoidal course as a function of the cam rotation angle.

Preferably, the cam contour is designed so that in a delivery phase of the high pressure pump, in which the fuel is compressed in the pump working space and supplied to a delivery valve, an acceleration of the pump piston as a function of the cam rotation angle follows a course, which consists of sinusoidal, linear, tangential or arcuate Composed of sections. Brief description of the drawings

Hereinafter, embodiments of the invention will be described in more detail with reference to the accompanying drawings. It shows:

1 shows a section through a high pressure pump according to the prior art.

FIG. 2 is a graph illustrating the delivery rate versus rotational speed of a prior art cam and a cam according to an embodiment; FIG.

Fig. 3 is a diagram of the course of the piston stroke in response to the

Cam rotation angle;

4 shows a diagram of the course of the piston speed as a function of the cam rotation angle; and

5 shows a diagram of the course of the piston acceleration as a function of the cam rotation angle.

Embodiments of the invention

In Fig. 1 is a section through a high pressure pump 1 for a fuel injection device of an internal combustion engine is shown, as it is known from the prior art. The high-pressure pump 1 has a multipart pump housing 2 in which a drive shaft or camshaft 3 driven in rotation by the internal combustion engine is arranged. The camshaft 3 is rotatably supported, for example, via two bearing points spaced apart from one another in the direction of the axis of rotation 4 of the camshaft 3. The bearings can be arranged in different parts of the pump housing 2, for example, a first bearing in a base body 5 of the pump housing. 2 and a second bearing point may be arranged in a flange part 6 connected to the main body 5.

In a region lying between the bearing points, the camshaft 3 has a cam 7, which may also be designed as a multiple cam.

The high pressure pump 1 has at least one or more arranged in the housing 2 pump elements 8, each with a pump piston 9 which is driven by the cam 7 of the camshaft 3 in a lifting movement in at least approximately radial direction to the axis of rotation 4 of the camshaft 3. Upon rotation of the cam 7, the pump piston 9 is set in a reciprocating or upward and downward movement. This results in a cyclic change in the volume of a pump working chamber 14 delimited by the pump piston 9. In the region of each pump element 8, a pump housing part 10 connected to the main body 5 is provided, which is designed as a cylinder head. The pump housing part 10 has a voltage applied to an outer side of the main body 5 and a flange 1 1 through an opening in the main body 5 to the camshaft 3 out, at least approximately cylindrical projection 12 with respect to the flange 1 1 smaller diameter. The pump piston 9 is guided in a tightly displaceable manner in a bore 12 formed in the ZyMn derbohrung 13 in the pump housing part 10 and limited with its side facing away from the camshaft 3 end face in the cylinder bore 13 the pump chamber 14. The cylinder bore 13 may extend into the flange 1 1 inside , in which then the pump working space 14 is arranged. The pump working chamber 14 has a connection with a fuel feed, for example a feed pump (not shown), via a fuel feed channel 15 running in the pump housing 2. At the mouth of the fuel inlet channel 15 into the pump working chamber 14, an opening into the pump working chamber 14 inlet valve 16 is arranged. The pump working chamber 14 also has, via a fuel outlet passage 17 extending in the pump housing 2, a connection to an outlet, which is connected to a high-pressure accumulator 18, for example. One or more injectors 19 arranged on cylinders of the internal combustion engine are connected to the high-pressure accumulator 18, through which fuel is injected into the cylinders of the internal combustion engine. At the mouth of the fuel outlet channel 17 into the pump working chamber 14, an outlet valve or delivery valve 20 which opens out of the pump working chamber 14 is arranged. During the suction stroke of the pump piston 9 or in the suction phase, in which the

Pump piston 9 moves radially inward, the pump working chamber 14 is filled with fuel through the fuel inlet channel 15 with open inlet valve 16, which acts as a suction valve, wherein the delivery valve 20 is closed.

During the delivery stroke of the pump piston 9 or in the delivery phase, in which the pump piston 9 moves radially outward, the pump piston 9

Fuel under high pressure through the fuel outlet passage 17 with open

Delivery valve 20 is conveyed to the high-pressure accumulator 18, wherein the inlet valve 16 is closed.

Between the pump piston 9 and the cam 7 of the camshaft 3, a plunger 21 is arranged, via which the pump piston 9 is at least indirectly supported on the cam 7 of the camshaft 3. The plunger 21 is formed in a hollow cylindrical shape with a round outer cross section and is in a bore 22 of the

Main body 5 of the pump housing 2 in the direction of the longitudinal axis 23 of the pump piston 20 slidably guided. The longitudinal axis of the plunger 21 is thus at least substantially identical to the longitudinal axis 23 of the pump piston 9. In the plunger 21 in the camshaft 3 end facing a support member 24 is inserted, in which a roller 25 is rotatably mounted on the cam 7 of the camshaft 3 rolls. The axis of rotation 26 of the roller 25 is at least approximately parallel to the axis of rotation 4 of the camshaft 3. The support member 24 has on its side facing the camshaft 3 a recess 27 in which the roller 25 is rotatably mounted. The support member 24 and the plunger 21 may also be integrally formed.

On the plunger 21 or on the pump piston 9 engages a prestressed spring 28, which is designed as a return spring, which is supported on the pump housing part 10. By the spring 28 of the pump piston 9 and the plunger 21 are applied to the cam 7 of the camshaft 3 out, so that the system of the role

25 is also ensured on the cam 7 when directed toward the camshaft 3 suction stroke of the pump piston 9 and even at high speed of the camshaft 3. The pump piston 9 may be coupled to the plunger 21, at least in the direction of its longitudinal axis 23. Alternatively, the pump piston 9 may not be connected to the plunger 21, then by the return spring 28, the system of the pump piston 9 is secured to the plunger 21. It can be be seen that the return spring 28 engages, for example via a spring plate 29 on an enlarged diameter piston base of the pump piston 9, which is thereby held in abutment against a on the plunger 21 of the jacket inwardly projecting flange, which in turn held in contact with the support member 24 is, so that the entire composite of pump piston 9, plunger 21 and support member 24 is acted upon with roller 25 to the cam 7 of the camshaft 3 out.

In the direction of the axis of rotation 26, a support 30 is arranged laterally next to the roller 25 for this purpose, by which the roller 25 is prevented from moving out of the support element 24 in the direction of its axis of rotation 26. The roller 25 may be convexly curved at its side facing the support 30 side surfaces, for example, curved at least approximately spherical. The surface of the support 30 facing the side surfaces of the roller 25 may be at least approximately planar or curved. The support 30 may be formed as a ring surrounding the roller 25 or may be arranged only laterally adjacent to the side surfaces of the roller 25.

2 shows a diagram representing the delivery rate of a high-pressure pump 1 as a function of the rotational speed of a cam 7 on the one hand according to the prior art and of a further cam 7 on the other hand according to an embodiment which is determined according to a simulation. The simulation of the production rates or comparison of delivery rates were based on the conditions of a pressure of 1800 bar and a temperature of 40 ⁰ C carried leads. Furthermore, on the one hand a radial piston pump according to the prior

Technique compared with a conventional cam 7 with 2 x 6 mm stroke with a radial piston pump with a cam 7 according to an embodiment of the invention, which has a cam contour with respect to the suction phase, which follows a sinusoidal course. The cam 7 according to the embodiment is hereinafter referred to as a half-sine cam. As can be seen from the diagram, according to the simulation, the delivery rate of 160 l / h achieved by the conventional cam 7 increases to 178 l / h for the half-sine cam at a speed of about 5000 rpm.

3 shows a diagram of the course of the piston stroke as a function of the

Cam rotation angle. The promotion phase is in the left half of the diagram shown over a cam rotation angle range of 0 ° to 90 °, in which the curve of linear, sinusoidal, tangential or arcuate acceleration ranges is composed. However, it is important that in the suction phase the cam contour follows a sinusoidal course in a cam rotation angle range of 90 ° to 180 °. Starting at the top dead center of the cam 7 indicated by reference numeral 31 at a cam rotation angle of 90 °, the piston stroke smoothly drops until it approaches zero at a cam rotation angle of 180 ° at the bottom dead center of the cam 7 indicated by reference numeral 32 , Due to the slow, harmonic drop in the beginning of the flank after passing through top dead center 31 and a subsequent rapid suction phase, inter alia, an improved suction phase and lower negative torques are achieved during pressure reduction.

The falling edge 33 of the cam contour can also be formed from a non-pure sinusoidal function, the falling edge 33 of the cam contour then being obtained from a sum of harmonic functions, whereby a further optimization latitude in the cam design can be obtained.

If the falling edge 33 is composed of the sum of harmonic functions of different orders, then the piston stroke results from the following equation:

Hub = AO + A1 ^* sin (1 ^* (α + Q ₀ )) + A2 ^* sin (2 ^* (α + Q ₁ )) + A3 ^* sin (3 ^* (α + α ₂ )) +

For reasons of spring excitation, contributions from the 4th order may only be less than 1% of the 1. Be alright A1.

4 shows a further diagram in which the progression of the piston speed is shown as a function of the cam rotation angle in a delivery phase and in the intake phase. Again, the piston velocity in the suction phase again follows a sinusoidal course.

Finally, FIG. 5 shows a diagram of the course of the piston acceleration as a function of the cam rotation angle. Again in the sucking phase the a sinusoid following course, while the course of the delivery phase of sinusoidal and linear regions is composed.

The sinusoidal piston acceleration results from the formula:

b = bo ^* sin (a ₀ ^* (α + α ₀ )) + c.

The piston speed and the piston stroke result from appropriate integration of the piston acceleration.

Overall, it is created with the high-pressure pump 1 according to the invention with an optimized suction phase, whereby the delivery rate can be increased and flow rate drops can be avoided.

Claims

claims

1 . High-pressure pump (1) for a fuel injection device of an internal combustion engine, in particular for a common rail system, which has a cam engine, in which the rotational movement of a camshaft (3) via at least one cam (7) into a stroke movement of a pump piston (9) the high pressure pump (1) is implemented, characterized in that a cam contour of the cam (7) is designed so that in a suction phase of the high pressure pump (1) in a range from a top dead center (31) to a bottom dead center ( 32), in which fuel is sucked into a pump working space (14), the piston stroke of the pump piston (9) follows a sinusoidal course as a function of the cam rotation angle.

2. High-pressure pump (1) according to claim 1, characterized in that the at least one cam (7) has an asymmetric cam contour.

3. High-pressure pump (1) according to claim 2, characterized in that the sinusoidal curve in the suction phase of a falling edge (33) corresponds to a sine function which starts at a top dead center (31) of the cam (7) and a bottom dead center (32 ) of the cam (7) ends.

4. High-pressure pump (1) according to claim 3, characterized in that the falling edge (33) is formed of a sum of harmonic functions.

5. High-pressure pump (1) according to claim 3 or 4, characterized in that the sinusoidal curve in the suction phase at the top dead center (31) of the cam (7) corresponds to a maximum delivery stroke of the pump piston (9).

6. High-pressure pump (1) according to one or more of claims 3 to 5, characterized in that the sinusoidal course in the suction phase at the bottom dead center (32) of the cam (7) corresponds to a minimum delivery stroke of the pump piston (9).

7. High-pressure pump (1) according to one or more of claims 1 to 6, characterized in that the cam contour is designed so that in the suction phase of the high-pressure pump (1), the piston speed of a reciprocating motion exporting pump piston (9 ) follows a sinusoidal course as a function of the cam rotation angle.

8. High-pressure pump (1) according to one or more of claims 1 to 7, characterized in that the cam contour is designed so that in a delivery phase of the high-pressure pump (1), in which fuel in the pump working space (14) compressed and a delivery valve ( 20), the piston stroke of the pump piston (9) follows a sinusoidal course as a function of the cam rotation angle.

9. High-pressure pump (1) according to one or more of claims 1 to 7, characterized in that the cam contour is designed so that in a delivery phase of the high pressure pump (1), in which the fuel in the pump working space (14) compressed and supplied to the delivery valve (20), the acceleration of the pump piston (9) as a function of the cam rotation angle follows a course, which is composed of sinusoidal, linear, arcuate or tangential sections.