The invention is based on a gear pump, in particular for pumping fuel from a fuel tank to a high-pressure fuel pump, as generically defined by the preamble to claim 1.
One such gear pump is known from German Patent Disclosure DE 101 34 622 A1. This gear pump has a housing, in which a pump chamber is formed in which a pair of gear wheels meshing with each other on their outer circumference is disposed. The gear wheels pump the medium to be pumped along pumping conduits, formed between their outer circumference and adjacent circumferential walls of the pump chamber, from a suction chamber into a pressure chamber. In operation of the gear pump, a tooth gap of one gear wheel reaches the pressure chamber, and a tooth gap of the other gear wheel reaches the pressure chamber after it, in chronological succession. The angle of rotation of the gear wheels corresponding to this spacing amounts here to 360°/2z in each case, where z is the number of teeth of the gear wheels.
Upon the entry of a tooth gap into the pressure chamber, the volume of the pressure chamber is increased, causing the pressure in the pressure chamber to drop. In operation of the gear pump, pressure pulsations thus occur in the pressure chamber, which have a period corresponding to half the tooth pitch angle of the gear wheels. For a number of teeth z=10, the period is thus 18°, relative to the respective axes of rotation of the gear wheels. In other words, after 18° of an angle of rotation of each of the gear wheels, one tooth gap enters the pressure chamber, and the pressure chamber volume is increased. The pressure pulsations lead to high mechanical stress on the gear pump, which must be taken into account by means of an expensive construction of the gear pump that has the requisite strength. Moreover, the pressure pulsations reduce the pumping capacity of the gear pump. To reduce these pulsations, it has been proposed in DE 101 34 622 A1 that grooves be provided, by which the radial spacing between the outer circumference of the gear wheels and the circumferential walls is increased. By means of this provision, it has already been possible to achieve a significant reduction in the amplitudes of the pressure pulsations.
The invention has the object of furnishing a gear pump with further reduced amplitudes of the pressure pulsations are achieved.
The gear pump according to the invention having the characteristics of claim 1 has the advantage that as a result of the different radial spacings of the grooves in the circumferential walls of the pump chamber, a further reduction the pressure pulsations is attained. As a result, the mechanical stress on the gear pump is reduced, so that the pump can be manufactured more economically. Moreover, the pumping capacity of the gear pump is improved as a result.
In the dependent claims, advantageous features and refinements of the gear pump of the invention are disclosed.
One exemplary embodiment of the invention is shown in the drawings and described in further detail in the ensuing description.
In
The pump chamber 12 has circumferential walls 20, 22, which are oriented toward the outer circumferences of the gear wheels 14, 16 and are suitably curved in concave fashion. The gear wheels 14, 16 mesh approximately in the middle of the pump chamber 12; originating with the tooth engagement of a gear wheel 14, 16 on the side pointing in the directions of rotation 18, 19, a suction chamber 24 is formed in the pump chamber 12, and on the side pointing counter to the directions of rotation 18, 19, a pressure chamber 26 is formed in the pump chamber 12. Beginning at the suction chamber 24, one pumping conduit 28, 30 each is formed between the outer circumference of the respective gear wheel 14, 16 and the adjoining circumferential wall 20, 22 of the pump chambers 12 In operation of the gear pump, fuel is [verb missing: surely “pumped”] out of the suction chamber 24 along the pumping conduits 28, 30 into the pressure chamber 26 by the gear wheels 14, 16 in their tooth gaps. An inlet from the fuel tank discharges into the suction chamber 24, and a communication with the high-pressure fuel pump leads away from the pressure chamber 26.
In the circumferential wall 20 of the pump chamber 12 oriented toward the gear wheel 14, a groove 32 is embodied, by which the radial spacing between the outer circumference of the gear wheel 14 and the circumferential wall 20 is increased. The first groove 32 extends in the direction of rotation 18 of the gear wheel 14 as far as the beginning of the pressure chamber 26. In a first angular range α1 of the first groove 32, there is a radial spacing Ar1 between the circumferential wall 20 and the first gear wheel 14. In a second angular rangeα2 of the first groove 32, there is a radial spacing Ar2 between the circumferential wall 20 and the first gear wheel 14, and Ar1 is not equal to Ar2. In the exemplary embodiment shown in
In the circumferential wall 22 of the pump chamber 12 oriented toward the gear wheel 16, a second groove 34 is embodied, by which the radial spacing between the outer circumference of the gear wheel 16 and the circumferential wall 22 is increased. The second groove 34 extends in the direction of rotation 19 of the gear wheel 16 as far as the beginning of the pressure chamber 26. In a first angular range β1 of the second groove 34, there is a radial spacing Ar1 between the circumferential wall 22 and the second gear wheel 16. In a second angular range β2 of the second groove 34, there is a radial spacing Ar2 between the circumferential wall 22 and the first gear wheel 14, and Ar1 is not equal to Ar2. In the exemplar embodiment shown in
As a result of this embodiment of the grooves 32, 34 a further reduction in the pressure pulsations is attained. Alternatively, the same effect can also be attained by means of a purposeful arrangement of a plurality of grooves, each of constant cross section. However, that variant is more expensive to produce and has a greater tendency to cavitation.
To prevent cavitation phenomena: the transition regions 36 between the first angular ranges α1, β1 on the one hand and the second angular ranges α2, β2 on the other are rounded. In a simplified embodiment, the transition regions 36 may also be shortened or even be omitted entirely.
In
A comparison of the first line 38 and the second line 40 makes it immediately clear that the amplitudes of the pressure pulsations in the gear pump of the invention can be reduced even more markedly, compared to the gear pump known from DE 101 345 622 A1. As a result, the gear pump of the invention can not only be made lighter in weight and produced more economically, but the pressure regulation in the low-pressure region of the fuel injection system is also improved on the intake side of a downstream high-pressure fuel pump.
Number | Date | Country | Kind |
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10 2006 045 932.6 | Sep 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP07/57821 | 7/30/2007 | WO | 00 | 10/9/2009 |