WO2012146428A1

WO2012146428A1 - Plate spring for a plunger assembly of a high-pressure pump, and high-pressure pump

Info

Publication number: WO2012146428A1
Application number: PCT/EP2012/054002
Authority: WO
Inventors: Jochen Aleker
Original assignee: Robert Bosch Gmbh
Priority date: 2011-04-27
Filing date: 2012-03-08
Publication date: 2012-11-01
Also published as: DE102011017571A1

Abstract

The invention relates to a plate spring for a plunger assembly (2) of a high-pressure pump in a fuel injection system, wherein the plate spring (1) is in particular a punched part, and wherein the plate spring (1) has a central recess (3) for receiving a pump piston (4). According to the invention, the plate spring (1) also has at least two arcuately running recesses (5), which are arranged around the central recess (3), for forming a radially inner support ring (6) and a radially outer support ring (7) which are connected to one another via substantially radially running webs (8), wherein the radially inner support ring (6) has apertures (9) via which the central recess (3) is connected to the arcuately running recesses (5), such that the radially inner support ring (6) is divided into parts which form spring arms (10). The invention also relates to a high-pressure pump for a fuel injection system having a plate spring (1) of said type.

Description

description

title

Spring plate for a ram assembly of a high pressure pump and high pressure pump

The present invention relates to a spring plate for a plunger assembly of a high pressure pump having the features of the preamble of claim 1. Furthermore, the invention relates to a high pressure pump with such a spring plate.

State of the art

A spring plate of the type mentioned above or a high-pressure pump with such a spring plate is exemplified in the published patent application DE 103 55 027 A1. The high-pressure pump described herein has at least one pump element with a pump piston which delimits a pump working space and which can be driven at least indirectly by a drive shaft against the spring force of a restoring spring in a lifting movement. For this purpose, the pump piston is indirectly supported via a sleeve-shaped plunger on the drive shaft. To connect the pump piston with the plunger, a spring plate is provided, which engages behind the piston of the pump piston. About the return spring, which is supported on the spring plate, plunger and pump piston are held in contact with the drive shaft.

The plunger has a radially inwardly extending annular collar on which on the one hand the spring plate and on the other hand abut a support member for rotatably supporting a roller. Between the support element and the spring plate, the piston foot of the pump piston comes to rest. Due to manufacturing tolerances, an axial play is often present between the components, which in particular in the areas of the movement reversal of the pump piston, for example during the transition from the delivery phase into the suction phase, is passed through dynamically by the pump piston. As a result, the components strike against each other and are therefore subject to increased wear.

In DE 103 55 027 A1 it is therefore proposed that the spring plate, which connects the pump piston with the plunger, is elastically deformable. Preferably, the stiffness of the spring plate is less than that of the return spring chosen, so that the deformation of the spring plate by means of the spring force of the return spring is effected. For this purpose, the return spring bears against a peripheral region of the spring plate and presses it in the direction of a spring plate support formed on the plunger. The piston base of the pump piston accommodated in the spring plate serves as a die, so that the spring plate is bent around the piston foot. An axial clearance in the area of the piston foot receptacle can be compensated in this way - at least in one direction of movement of the pump piston.

When passing through an axial clearance of the pump piston undergoes high accelerations, which cause the pump piston strikes the spring plate at high speed. In addition to the unwanted noise developments, this can lead to an overload of the spring plate and this in turn to break the spring plate. Furthermore, an axial clearance in the area of the piston foot receptacle has an effect on the delivery tolerances of the high-pressure pump. Based on the above-mentioned prior art, it is an object of the present invention to further develop an elastically deformable spring plate for a plunger assembly of a high-pressure pump such that the compensation of an axial clearance in the region of the piston receptacle is simplified. The object is achieved by a spring plate with the features of claim 1. Advantageous developments of the invention are specified in the subclaims. The object is further achieved by a high pressure pump having the features of claim 7. Disclosure of the invention

Proposed is a spring plate for a plunger assembly of a high-pressure pump in a fuel injection system, wherein the spring plate is in particular a stamped part and has a central recess for receiving a pump piston. According to the invention, the spring plate has at least two curved recesses arranged around the central recess for forming a radially inner support ring and a radially outer support ring, which are connected to one another via essentially radially extending webs. The radially inner support ring in this case has openings, via which the central recess is connected to the arcuate recesses, so that the radially inner support ring is divided into spring arms forming sections.

The spring arms forming portions of the radially inner support ring cause elastic deformability of the spring plate, so that the spring plate can be installed under an axial bias in the plunger assembly of a high-pressure pump. When installed, the spring arms of the spring plate are biased on the pump piston, so that it is preferably clamped between the spring plate and a support member of the plunger assembly. Depending on the specific design of the pump piston, the spring arms of the spring plate are supported on a piston foot of the pump piston or on a preferably radially extending groove flank of a peripheral groove of a pump piston, for example through-ground. The available space specifies the degree of axial preload. Preferably, the measure of the axial preload is chosen such that the spring plate remains still elastically deformable to allow a "soft ^'' intercepting the movement of the pump piston, during a movement reversal. The elastic deformation of the spring arms of the spring plate is preferably effected by means of the spring force of a return spring, which bears against the spring plate and holds the plunger assembly including the pump piston in contact with the cam or eccentric drive shaft. An axial bias of the spring plate counteracts both unwanted noise and overloading of the spring plate. The Danger of spring plate breakage can thus be significantly reduced. At the same time, the filling efficiency of the high-pressure pump is increased.

The spring plate according to the invention is preferably designed as a highly elastic leaf spring which can be installed under axial prestressing and can be subjected to bending. As a plane-parallel component, the spring plate is also inexpensive to produce from a flat band.

According to a preferred embodiment of the invention, the substantially radially extending webs between the arcuate recesses are arranged at the same angular distance from each other. This results in a uniform bending load as possible of the spring arms forming sections of the radially inner support ring.

Further preferably, the number of openings of the radially inner support ring corresponds to the number of webs. Each section of the radially inner support ring is therefore connected via a web to the radially outer support ring. Each section thus forms together with an associated web an elastically deformable spring arm. The number of webs is preferably two, three or four.

Advantageously, the openings of the radially inner support ring are arranged at the same angular distance from each other. The same angular distance of the apertures to each other causes a subdivision of the radially inner support ring in the same length sections. Alternatively or additionally, it can be provided that the apertures are arranged offset by an angle α to the webs. As a result, the length of a subsequent to a web portion of the radially inner support ring and a spring arm is maximized. Preferably, the angle α is selected such that a web meets centrally on a portion of the radially inner portion. This means that the angle α preferably corresponds to half the angular distance between the webs. An opening is therefore arranged in each case centrally between two webs. In this way, a uniform deformation of the spring arms of the spring plate is guaranteed when exposed to an axial force. Furthermore, it is proposed that the openings in total extend over an angular range which is greater than 180 °. This means that the openings extend over a larger angular range than the sections of the radially inner support ring.

According to a preferred embodiment of the invention, the apertures each extend over an angular range which is substantially equal to the angular distance of the webs to each other. The length of the sections of the radially inner support ring therefore corresponds substantially to the width of the adjoining webs. The reduced to the width of the webs sections can be formed for example by an extension of the webs, whereby the production of the spring plate is simplified.

The further proposed to solve the object mentioned high-pressure pump for a fuel injection system has at least one pump element with a spring plate according to the invention. The spring plate is part of a plunger assembly, via which a hubbeweglich guided pump piston is indirectly supported on a cam or eccentric drive shaft. About the drive shaft of the pump piston against the spring force of a return spring is driven to a lifting movement. The spring plate serves for the positive connection of the pump piston with the plunger assembly. Due to the openings of the radially inner support ring of the spring plate forms elastically deformable spring arms, which rest under axial bias on the pump piston. The axial preload can compensate for an axial clearance in the region of the receptacle of the pump piston. The spring plate thus prevents the pump piston from abutting the adjacent components when there is a reversal of motion and sounding banging occurs. In addition, the movement of the pump piston is "softly" trapped via the elastically deformable spring plate, so that the risk of spring plate fractures is also reduced.Furthermore, the filling efficiency of the high-pressure pump is increased since the pump piston is always tracked.

Advantageously, the spring plate of a high-pressure pump according to the invention is supported via the radially inner support ring on the pump piston and via the radially outer support ring on a plunger body of the plunger assembly. In this arrangement, an axial bias of the spring plate on the Spring force of the return spring realized. When assembling the plunger assembly an elastic deformation of the voltage applied to the pump piston spring arms and thus the axial bias is effected via the spring force of the return spring. The pump piston serves as a die. An axial play in the area of the piston seat can be completely compensated in this way. Since the spring plate is designed as a plane-parallel component, the installation direction of the spring plate is irrelevant. The elastic deformability of the spring arms is given in both directions, so that assembly errors are effectively prevented.

In order to effect the axial bias of the spring plate via the return spring, the stiffness of the spring plate is preferably selected to be less than the stiffness of the return spring. Further preferably, the stiffness of the return spring is three times larger than that of the spring plate chosen. The spring plate is thus always biased statically even with dynamic overshoots in the operation of the high-pressure pump.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

FIG. 1 shows a sectional view, partially in perspective, of a high-pressure pump according to the invention in the region of the plunger assembly,

2a shows a longitudinal section through a plunger assembly with a fiction, contemporary spring plate in a relaxed state,

FIG. 2 b shows an enlarged detail of FIG. 2 a,

Figure 3 is a plan view of a first preferred embodiment of a spring plate and

Figure 4 is a plan view of a second preferred embodiment of a spring plate according to the invention. Detailed description of the drawings

The high-pressure pump according to the invention shown in detail in FIG. 1 comprises at least one pump element with a liftably guided pump piston 4, which is supported via a plunger assembly 2 on a cam 11 of a drive shaft 12. The plunger assembly 2 causes a conversion of the rotational movement of the drive shaft 12 in a translational movement of the pump piston 4. The plunger assembly 2 comprises a sleeve-shaped plunger body 14 and a support member 15 received therein, in which a roller 16 is rotatably mounted. With the roller 16, the plunger assembly 2 is located on the outer peripheral side of the cam 1 1 of the drive shaft 12 at. A return spring 13 holds the plunger assembly 2 in abutment with the cam 1 first

The sleeve-shaped plunger body 14 has on the inner circumference an annular collar 18 on which on the one hand the support element 15, on the other hand, a spring plate 1 is supported. The spring plate 1 has a central recess 3 for receiving the pump piston 4. This is inserted into the spring plate 1 such that the radially inner support ring engages behind a piston foot 17 of the pump piston 4. In this way, a positive connection of the pump piston 4 is achieved with the plunger assembly 2. The spring plate 1 is made of metal, in particular steel, preferably spring steel.

As can be deduced from FIGS. 2a and 2b, the area of the piston foot receptacle due to production has an axial play a, which is dynamically traversed by the pump piston 4 when the movement is reversed. The axial clearance a, which may be 0.1 mm, for example, causes the pump piston 4 does not join the complete axial movement, but after a change of direction at the dead center passes through the game and then hits hard. This results in a disturbing noise, on the other hand, the wear of the spring plate is increased. Furthermore, an overload of the spring plate to the same result. In a high pressure pump according to the invention, therefore, the piston base 17 of the pump piston 4 is clamped between the spring plate 1 and the support element 15. The clamping action is effected by an axial bias of the spring plate 1, which according to the invention elastically deformable spring arms 10, with which the spring plate 1 rests on the piston 17 of the pump piston 4. A first preferred embodiment of a spring plate 1 according to the invention is shown in FIG. The spring plate 1 is designed as a stamped part with a central recess 3 and concentrically arranged arcuately extending recesses 5. The central recess 3 serves to receive the pump piston 4, while the arcuate recesses 5 allow the flow through the spring plate 1 during operation of the high-pressure pump. The shape of the arcuate recesses 5 may also be referred to as kidney-shaped. In the present case, three such recesses 5 are arranged at the same angular distance from one another about the central recess 3. The angular distance is therefore 120 °. The recesses 5 are separated from each other by webs 8, which extend from a radially outer support ring 7 radially inward. Adjacent to the central recess 3, the webs 8 form a radially inner support ring 6 with openings 9, via which the central recess 3 is connected to the arc-shaped recesses 5. The number of openings 9 corresponds to the number of webs 8 and the arcuate recesses 5. In the present case, the radially inlying support ring 6 accordingly three openings 9, which are arranged at the same angular distance from each other and in this way the radially inner support ring. 6 in the same amount of time

Divide pieces. The apertures 9 extend over an angular range, which corresponds essentially to the angular spacing of the webs 8 relative to one another, so that the sections of the radially inner support ring 6 are reduced substantially to the width of the webs 8. Each section forms together with a web 8 a spring arm 10, which is elastically deformable such that the spring plate 1 can be used under axial bias in a plunger assembly 2 of a high-pressure pump.

FIG. 4 shows a second preferred embodiment of a spring plate 1 according to the invention. In contrast to the embodiment of Figure 3, this has a perforated radially inner support ring 6, in which the openings 9 extend over a much smaller angular range. The sections of the radially inner support ring 6 therefore have a greater length. The openings 9 are also arranged centrally between two webs 8, so that the webs 8 each center on the

Pieces of the radially inner support ring 6 meet. The spring arms 10 are therefore each formed by a radially extending web 8 and a portion of the radially inner support ring 6, which extends on both sides of the web 8 along a circular arc. The spring arms 10 of the present embodiment accordingly have a greater length and are therefore easier to elastically deform than the spring arms 10 of the embodiment of FIG

FIG. 3. The embodiment of FIG. 4 is accordingly suitable for forming a highly elastic spring plate 1.

Claims

claims

1 . Spring plate for a plunger assembly (2) of a high-pressure pump in a fuel injection system, wherein the spring plate (1) is in particular a stamped part and wherein the spring plate (1) has a central recess (3) for receiving a pump piston (4),

characterized in that the spring plate (1) furthermore has at least two arcuate recesses (5) arranged around the central recess (3) for forming a radially inner support ring (6) and a radially outer support ring (7) essentially radially extending webs (8) are interconnected, wherein the radially inner support ring (6) has openings (9) through which the central recess (3) with the arcuate recesses (5) is connected, so that the radial inside support ring (6) in spring arms (10) forming sections is divided.

2. spring plate according to claim 1,

characterized in that the substantially radially extending webs (8) are arranged at the same angular distance from each other.

3. spring plate according to claim 1 or 2,

characterized in that the number of perforations (9) corresponds to the number of webs (8), wherein the number of webs (8) is preferably two, three or four.

4. Spring plate according to one of the preceding claims,

characterized in that the openings (9) of the radially inner support ring (6) at equal angular distance from each other and / or offset by an angle α to the webs (8) are arranged, wherein the angle α preferably half the angular distance of the webs (8 ) corresponds to each other. Spring plate according to one of the preceding claims,

characterized in that the openings (9) extend overall over an angular range which is greater than 180 °.

Spring plate according to one of the preceding claims,

characterized in that the apertures (9) each extend over an angular range which is substantially equal to the angular distance of the webs (8) to each other.

High-pressure pump for a fuel injection system with at least one pump element comprising a spring plate (1) according to one of the preceding claims, wherein the spring plate (1) is part of a plunger assembly (2), via which a stroke movably guided pump piston (4) indirectly on a cam (1 1 ) or eccentric of a drive shaft (12) is supported, via which the pump piston (4) against the spring force of a return spring (13) is drivable for a lifting movement.

High-pressure pump according to claim 7,

characterized in that the spring plate (1) via the radially inner support ring (6) on the pump piston (4) and via the radially outer support ring (7) on a plunger body (14) of the plunger assembly (2) is supported.

High pressure pump according to claim 7 or 8,

characterized in that the stiffness of the spring plate (1) is less than the stiffness of the return spring (13) is selected, wherein the stiffness of the return spring (13) is preferably three times greater than that of the spring plate (1).