WO2011069713A2

WO2011069713A2 - External gear pump

Info

Publication number: WO2011069713A2
Application number: PCT/EP2010/065181
Authority: WO
Inventors: Siamend Flo; Heinz Siegel; Juergen Arnold
Original assignee: Robert Bosch Gmbh
Priority date: 2009-12-08
Filing date: 2010-10-11
Publication date: 2011-06-16
Also published as: EP2510239A2; WO2011069713A3; CN102648350B; CN102648350A; DE102009047610A1

Abstract

An external gear pump (14) comprises two rotatable gear wheels (100, 102) that mesh with each other. According to the invention, at least one gear wheel (100) is mounted, in relation to the rotational axis (132) thereof, in the radial direction by the contact of tooth tips (162) directed radially outward with a mounting surface (136) located radially outward. The operating behavior and efficiency of the external gear pump (14) according to the invention are improved by optimized guidance of the liquid to be delivered both on the suction side and on the pressure side by means of openings (170, 174) and channels (172, 176).

Description

description

title

External gear pump prior art

The invention relates to an external gear pump according to the preamble of claim 1.

From DE 10 2006 056 843 AI an external gear pump is known, which has two rotatable, meshing gears. The gears are mounted in a housing. During operation of the external gear pump, a fluid is sucked in on a suction side, pressurized and fed to a pressure side.

From the post-published DE 10 2008 054 751.4 is a

External gear pump known in which the meshing gears are mounted in a housing ring on the tooth heads. This housing ring is between a first housing part and a second housing part

taken, wherein the axial guide / bearing of the gears via the first and the second housing part takes place.

If this external gear pump for highest flow rates, what

In particular, by an increase in the tooth width of the gears and a corresponding adjustment of the housing ring is easily possible, it can be in unfavorable operating points, ie at high speed of the external gear pump come to that on the suction side of the external gear pump due to the throttle losses in the suction channel vapor bubbles arise, which are then sucked into the tooth spaces and there to

can lead to undesirable cavitation effects.

Disclosure of the invention

The object of the present invention is to provide an external gear pump which has sufficiently large flow cross sections even on a large flow, especially on the suction side, so that vapor bubbles do not form or only to a small extent at all operating points.

In addition, the external gear pump according to the invention should be particularly easy to manufacture and durable.

This object is achieved by an external gear pump with the features of claim 1. Advantageous developments are specified in subclaims. In addition, find important features for the invention in the following description and in the drawing, the features both alone and in different combinations for the

Invention may be important, without being explicitly referred to again.

Due to the inventive design of the housing ring, it is possible to hydraulically connect the suction and the low pressure channel with a first approximate twice as large cross-section. This significantly reduces the pressure loss on the suction side of the external gear pump. As a result, no cavitation occurs even with external gear pumps with very wide gears and correspondingly high flow rate.

Since the additional flow paths according to the invention, namely the

Breakthrough and at least one channel, are arranged in the housing ring and this housing ring must be as thick as the tooth width of the gears, it is readily possible to provide this housing ring always with the apertures and channels according to the invention in the housing ring when the flow rate is especially big. Then namely the tooth width of the gears and the thickness of the housing ring are also large. Therefore, then in the housing ring is always enough material to the

cut out breakthroughs and channels according to the invention.

Furthermore, it is possible to provide different versions of the external gear pump according to the invention with different delivery rates, wherein These different versions differ in terms of the width of the gears and the thickness of the housing ring. In the versions with increased delivery line, the openings and channels according to the invention are then additionally formed in the housing ring.

As a result, a significant cost reduction is achieved because the gear pumps with low flow and accordingly thinner Gehäuseringen get along without the openings and channels, while the housing rings for

External gear pump with a large flow rate are correspondingly thicker and then have the breakthroughs and channels according to the invention. All other components can be used for both pump versions.

The additional flow cross section according to the invention by an opening which connects the two end faces of the housing ring together and recessed at the end faces channels which connect the openings with the suction region and the pressure range of the external gear pump made. This shape is particularly advantageous because it has a symmetrical structure, which is in terms of

Flow conditions and the pressure forces acting on the gears positively affects. Furthermore, this shape is also very suitable for production by sintering, since the aperture and the channels can be produced easily with a two-part sintering tool. Also, the manufacturing costs are kept low.

In the case of the housing ring according to the invention, a web is provided between the two channels running on the end faces of the housing ring.

This ensures that the wrap angle of the housing around the gears and thus the storage of the gears in the housing ring is not reduced by the channels according to the invention. As a result, even with gear pumps with high flow, a very good storage of

Gears over their tooth tips to the corresponding circular

Recesses in the housing ring given.

In a further advantageous embodiment of the gear pump according to the invention it is provided that the first housing part, the second housing and the

Housing ring are welded together on the outer circumference. As a result, the three components mentioned are fixed relative to each other. This type of fixation is particularly well suited for mass production because it is easy to automate and is very reliable to operate. So that the weld does not protrude radially outward beyond the outer diameter of the housing parts or of the housing ring, a chamfer is provided on the housing parts and / or the housing ring. The weld is laid in this chamfer.

As a result, the further advantage is achieved that weld spatter does not adhere to the cylindrical outer surface of the housing ring and housing parts, which would adversely affect the manufacture and assembly of the welded components in the outer housing of the gear pump according to the invention.

The invention further relates to a fuel injection system with an external gear pump described above. Their embodiments and advantages have already been explained above. These explanations are hereby incorporated by reference.

Hereinafter, an embodiment of the invention will be explained with reference to the accompanying drawings. In the drawing show:

Figure 1 is a schematic view of a fuel injection system with an internal combustion engine and with an external gear pump for the delivery of fuel;

FIG. 2 shows a view of the external gear pump according to FIG. 1 along a section line designated II-II in FIG. 3;

FIG. 3 shows a view of the external gear pump according to FIG. 1 along a section line designated III-III in FIG.

Figure 4 is an enlarged view of the gear arrangement of

External gear pump according to Figure 1 and

FIG. 5 shows a longitudinal section through the housing ring 72 along a section line designated IV-IV in FIG.

A fuel injection system designated overall by the reference numeral 10 in FIG. 1 for supplying an internal combustion engine 12 with fuel comprises an external gear pump 14. The fuel injection system 10 has a reservoir 16 for storing fuel. With the aid of a prefeed pump 18, which preferably by means of a controllable drive device, in particular in the form of a

Electric motor 20 is driven, fuel is conveyed from the reservoir 16 in a low-pressure line 22. By using a controllable

Drive device for the prefeed pump 18, the flow rate of the fuel injection system 10 can be adjusted so that delivery losses can be reduced, which results by promoting an excess amount of fuel, which then has to be returned to the reservoir 16. To limit the fuel pressure in the low pressure line 22 is a

Low-pressure limiting valve 24 is provided, by means of which at

Exceeding a predefinable maximum pressure fuel from the

Low pressure line 22 is guided back into the reservoir 16.

The low pressure line 22 opens at an input 26 of the

External gear pump 14. This acts on the supplied via the input 26 fuel at high pressure. The pressurized fuel passes through an output 28 of the external gear pump 14 to a

High-pressure line 30, which leads to a fuel collecting device in the form of a rail 32. The rail 32 supplies injectors 34 with pressurized fuel. The injection valves 34 are each one of the combustion chambers of

Assigned internal combustion engine 12 and allow direct injection of fuel into the combustion chambers.

The pressure in the rail 32 is detected by means of a pressure sensor 36. A voltage signal corresponding to the detected pressure can be detected by means of a

Data line 38 are supplied to a control unit 40. The control unit 40 is coupled to the electric motor 20 by means of a control line 42.

The internal combustion engine 12 comprises sections shown

Internal combustion engine housing 44, for example in the form of a cylinder head. The engine housing 44 has an outwardly facing

Housing surface 46 on. Furthermore, the internal combustion engine 12 includes a

Shaft, in particular in the form of a camshaft which is rotatably mounted about a shaft axis 50 on the engine housing 44 and forms a drive shaft 48 for the external gear pump 14. Alternatively, the drive shaft 48 may be formed by a separate from a shaft of the internal combustion engine 12 shaft. In the engine housing 44 is a housing opening 52nd

provided, which is penetrated by the drive shaft 48, so that a

Shaft end 54 extends beyond the housing surface 46 into the environment of the internal combustion engine 12.

The external gear pump 14 has a pot-shaped outer housing 56, which is connected in particular by means of a welded flange 58 to the engine housing 44, for example by means of a screw connection. The outer housing 56 has a housing projection 60 which extends in the direction of the internal combustion engine 12 and which is inserted into the housing opening 52 of the internal combustion engine 12. Of the

Housing projection 60 has a circular cross-section

Housing recess 62, which allows passage of the drive shaft 48.

The outer housing 56 of the external gear pump 14 and the

Internal combustion engine housings 44 are sealed against each other by means of an annular seal 64.

In the outer housing 56 a plurality of housing parts are arranged, namely a first housing part 66, a second housing part 68 spaced therefrom and a third housing part 70 acting as a housing cover. The third housing part 70 is welded to the outer housing 56. It is preferred if the

Have housing parts 66, 68 and 70 mutually parallel planar surfaces, so that the housing parts form metallic sealing surfaces with these flat surfaces. In this case, with the aid of the third housing part 70, a sealing force can be generated, which pushes the housing parts 66 and 68 into the outer housing 56.

In the axial direction between the first housing part 66 and the second

Housing part 68 is a housing ring 72 is arranged, in which a

Gear arrangement 74 is arranged. The gear arrangement 74 forms the actual conveying unit of the external gear pump 14. The gear arrangement 74 is mounted in the axial direction between the first housing part 66 and the second housing part 68. The housing ring 72 serves for the radial mounting of the

Gear arrangement 74.

In order to position the housing parts 66 and 68 and the housing ring 72 relative to one another, these are welded together by welds 168 (see FIG. 2). The welds 168 need not be liquid-tight; she can also be interrupted. In Figure 3, the welds 168 are divided into two angular segments of about 100 °. The weld 168 is preferably provided where the housing ring 72 has a large material thickness. So that the welds 168 do not protrude in the radial direction beyond the housing parts 66 and 68 and the housing ring 72, a chamfer is on these components

formed (without reference numeral) in which the welds 168 lie.

The external gear pump 14 has a low-pressure side connected to the input 26 low-pressure channel 76, which is formed in the third housing part 70. The low-pressure channel 76 opens at a suction kidney 78 (see FIG. 1), which is formed in the second housing part 68. The first

Housing part 66 has one of the shape of the suction kidney 78 corresponding

Counter kidney 80 (see Fig. 2) on.

On the pressure side, the external gear pump 14 has a high-pressure channel 82 connected to the outlet 28, which is formed in the third housing part 70. The high-pressure passage 82 is connected to a pressure kidney 84, which is formed in the second housing part 68. In the first housing part 66 is a counter kidney 86 corresponding to the shape of the pressure kidney 84

arranged. With the help of Gegennieren 80 and 86 is achieved that the

Gear assembly 74 is charged evenly from both sides with pressure.

Furthermore, the external gear pump 14 includes a pressure relief valve 88 (see FIG. 2), by means of which a fluid connection between the high-pressure channel 82 and the low-pressure channel 76 can be produced when a predeterminable operating pressure is exceeded. The pressure limiting valve 88 is arranged in a connecting channel 90 which extends between the high-pressure channel

82 and the low pressure channel 76 extends. The pressure limiting valve 88 has a valve seat 92 pressed into the connection channel 90, a valve body 94 cooperating with the valve seat 92 and a valve spring 96 which presses the valve body 94 against the valve seat 92. Of the

Connecting channel 90 is formed in the form of a blind hole and closed at the open end by means of a pressed-in stopper 98.

The integration of the input 26 and the output 28 and the

Pressure limiting valve 88 in the third housing part 70 allows a substantial waiver of additional sealing elements and thus a further reduction in the number of components of the external gear pump fourteenth The gear assembly 74 includes a first gear 100 that meshes with a second gear 102. The first gear 100 has a smaller diameter than the second gear 102. The first gear 100 is driven by the second gear 102 (see FIGS. 2 and 3).

The second gear 102 is about an axis of rotation associated with this gear

104 rotatable (see Figure 4). The axis of rotation 104 is at least approximately collinear with the shaft axis 50 of the drive shaft 48.

The second gear 102 has a central opening 106 into which the shaft end 54 of the drive shaft 48 is inserted. The drive shaft 48 has a main portion 108 which extends within the

Internal combustion engine housing 44 extends. The main section 108 is followed, in the direction of the external gear pump 14, by a shaft shoulder 110, a shaft-guiding surface 112 that is in particular convex-shaped, a shaft section 114, and a shaft journal 116 arranged on the front side.

The shaft shoulder 110 penetrates the housing recess 62 of the

Outer housing 56. For sealing the drive shaft 48 relative to the external gear pump 14, a sealing device 118 is provided, which is designed in particular in the form of a radial sealing ring. This is arranged within the housing projection 60 and comprises a schematically illustrated first sealing lip 120, by means of which an ingress of oil from the

Inside the internal combustion engine 12 is prevented in the external gear pump 14 inside. Furthermore, the sealing device 118 comprises a second

Sealing lip 122, by means of which a leakage of fuel from the interior of the external gear pump 14 out into the interior of the internal combustion engine 12 is prevented.

The shaft guide surface 112 is mounted in a cylindrical bearing surface 124, which is formed on the first housing part 66. The bearing surface 124 is adjoined by a centering surface 126 inclined relative to the bearing surface 124, by means of which the insertion of the shaft guide surface 112 into the bearing surface 124 is facilitated.

The shaft section 114 has, for example, a polygonal profile, in particular a hexagonal profile. This profile works with a

Hexagonal profile of the central opening 106 of the second gear 102nd

together. The opening 106 is slightly larger than the profile of the Shaft portion 114, so that the second gear 102 is connected in the radial direction play with the drive shaft 48.

In order to insert the drive shaft 48 with the external gear pump 14, the drive shaft 48 and the external gear pump 14 are moved toward each other in one of the joining directions designated 128 and 130. The joining directions 128 and 130 are collinear with the axis of rotation 104 of the second gear 102 and with the shaft axis 50 of the drive shaft 48.

The shaft journal 116 is preferably cylindrical and serves during the insertion of the shaft end 54 in the external gear pump 14 as a further insertion aid. In the simplest case, the external gear pump 14 is attached to the free shaft end 54. Damage to the sealing device 118 during the joining of the drive shaft 48 and the second gear 102 is prevented by the shaft journal 116 first engaging the central opening 106 of the second gear 102 before the shaft shoulder 110 is inserted into the housing recess 62 and into engagement with the shaft Sealing lips 120 and 122 is brought.

The first gear 100 is rotatable about a rotation axis 132. The position of the axis of rotation 132 of the first gear 100 and the axis of rotation 104 of the second gear 102 relative to a plane of rotation of the gears is play-related. In the radial direction, the gears 100, 102 are supported by their meshing engagement in a Kämmbereich 134 and by contact with a respective one of the gears 100, 102 associated bearing surface.

The first gear 100 is mounted on a sectionally cylindrical jacket-shaped first bearing surface 136. The first bearing surface 136 extends over an angular segment 138 of, for example, about 70 degrees to about 90 degrees

Degree. The first housing surface 136 merges into a first housing surface 140, which likewise has a cylinder-shaped jacket.

For storage of the second gear 102 is a sectional way

cylinder jacket-shaped second bearing surface 142, which extends over an angular segment 144 of, for example, about 30 degrees to about 50

Degree extends. The second bearing surface 142 merges into a second housing surface 146, likewise in the form of a cylinder jacket, in sections.

The bearing surfaces 136 and 142 and the housing surfaces 140 and 146 wrap around the gears 100, 102. Due to the fact that the gears 100, 102 have a significantly different diameter, the wrap angle of said surfaces is particularly large.

The bearing surfaces 136 and 142 and the combing region 134 define between them a suction region 148, by means of which the outer gear pump 14 is a medium to be conveyed fed. On the pressure side, the combing area 134, together with a transition between the housing surfaces 140 and 146, delimits a pressure region 150 of the external gear pump 14.

The external gear pump 14 comprises a first force-generating device 152, which is designed in particular in the form of a pressure chamber 154. The pressure chamber 154 has a chamfer geometry, see also Figure 2. The

Pressure chamber 154 extends around first gear 100 along with first housing surface 140.

The external gear pump 14 further includes a second one

Force generating device 156 in the form of a second pressure chamber 158. Also, this pressure chamber has a chamfer geometry and extends

together with the second housing surface 146 around the second gear 102 around.

Relative to a plane of rotation of the gears 100, 102 are the

Pressure chambers 154 and 158 each two times on both sides of the gears 100, 102 arranged so that the gears 100, 102 are loaded in the axial direction from both sides with the same pressure.

The gears 100, 102 each have a plurality of teeth 160. The teeth 160 have radially outwardly facing tooth head surfaces, which are correspondingly curved in the curvature of an associated bearing surface 136, 142.

During operation of the external gear pump 14, this is about the

Input 26 supplied fluid to be delivered. With the aid of the drive shaft 48, the second gear 102 is driven in a drive direction 164. In this way, a fluid to be delivered from the suction region 148 along the bearing surfaces 142 and 136 and along the housing surfaces 140 and 146 of the

Pressure range 150 supplied.

With the help of the force generating means 152 and 156 in the form of

Pressure chambers 154 and 158 is generated by means of the pressurized fluid to be conveyed a force which a gear 100, 102 against a This gear associated bearing surface 136, 142 presses. As a result, the tooth head surfaces 162 of the toothed wheels 100, 102 facing radially outwards each come into sealing contact with an associated bearing surface 136, 142. In this way, it is possible to support the toothed wheels 100, 102 in the radial direction exclusively on these bearing surfaces and in the combing region 134 and at the same time to achieve a good sealing effect for separating the suction region 148 from the pressure region 150.

According to the invention, an opening 170, 174 is formed in each extension of the high-pressure channel 82 and / or the low-pressure channel 76 in the housing ring 72. About also in the housing ring 72 formed channels 172, 176, the openings 170 and 174 with the tooth chambers of

Gear assemblies 74 hydraulically connected. This will be the

Flow cross-section increases both in the suction region 148 and in the pressure region 150 of the gear assembly 74, which has a positive effect on the performance and efficiency of the gear pump.

Between the channels 172 and 176, a web 178 remains (see Figure 5), so that the wrap angle of the bearing mounted on the top gear 100, 102 remains unchanged.

Claims

claims

External gear pump (14) with two rotatable, intermeshing gears (100, 102), wherein the gears (100, 102) in a housing ring (72) are arranged, characterized in that in the housing ring (72) has a hydraulic connection between a low-pressure channel (76) and a suction region (148) is formed.

External gear pump (14) with two rotatable, intermeshing gears (100, 102), wherein the gears (100, 102) in a housing ring (72) are arranged, characterized in that in the housing ring (72) has a hydraulic connection between a high pressure passage (76) and a pressure area (150) is formed,

External gear pump (14) according to claim 1 or 2, characterized

characterized in that a first opening (170) is present in the housing ring (72) such that the first opening (170) extends in extension of the first opening (170)

Low pressure channel (76) is arranged, and that the first opening (170) via at least one first channel (172) is connected to the suction region (148).

External gear pump (14) according to claim 2 or 3, characterized

characterized in that a second opening (174) is present in the housing ring (72), that the second opening (174) extends in extension of a

Pressure channel (150) is arranged, and that the second opening (174) via at least one second channel (176) to the pressure region (150) is connected.

External gear pump (14) according to claim 2 or 3, characterized

in that a web (178) is present in the housing ring (72) between the two first channels (172) and / or the two second channels (176).

6. external gear pump (14) according to any one of the preceding claims, characterized in that the housing ring (72) between a first housing part (66) and a second housing part (68) is arranged, and that the housing ring (72) relative to the first housing part (66) and / or the second housing part (68) is fixed by a welded connection (168).

7. external gear pump (14) according to any one of the preceding claims, characterized in that the housing ring (72), the first housing part (66) and / or the second housing part (68) are made by sintering, in particular of a weldable sintered material.

8. Fuel injection system (10) with an external gear pump (14) according to one of the preceding claims.