Patent Grant
7713041
The invention relates to a pump, in particular an oil pump for internal combustion engines, comprising a pump case, with the pump case comprising a pump lid and a pump flange, with at least one toothed wheelset being arranged between the pump lid and the pump flange, and the pump lid and the pump flange are connected to one another via at least one distance element.
The development of automobiles with low fuel consumption requires the optimization of vehicle and motor components. Here, for the energy consumption of the vehicle in the frequently occurring short-distance and city traffic the loss caused, among other things, by driving secondary power trains is particularly important. The drive performance of oil pumps, among other things, ensuring the lubrication of the motor can result in the reduction of the actual motor performance, which drastically increases the fuel consumption.
Up to 40° C. below zero, the function of the motor lubrication and a sufficiently fast motor lubrication must be ensured and during hot idling up to 160° C. the oil supply must not show any defects. The hot idling operation is characterized in a high internal leakage of the oil pump and a relatively high oil consumption of the motor. The hot idling operation is an essential operating point for sizing the oil pump.
In general, in the classical sizing of the pump the oil pump is designed for this operating point. In normal vehicle operation, this leads to an oversized oil pump, because the oil absorption line of the internal combustion engine progresses digressively over the rotation, with the characteristic pump line of the oil pump rising approximately linear in reference to the rotation. The excess supply of oil resulting therefrom is blown off via a pressure control valve in an energy consuming manner.
The above-described problem is enhanced in that the automotive industry, in particular, requests the use of oils with lower viscosity. Although this improves the function of pumps at temperatures below freezing, the volumetric effectiveness worsens at high temperatures.
Another problem is the fact that almost all pump cases are made from different materials in reference to the toothed wheelsets used. A multitude of pump cases are made from aluminum die casting, for example, for reasons of weight reduction, while the toothed wheelsets are produced from steel, in particular sintered steel. The different heat expansion coefficients of the pump case and the toothed wheelsets cause the necessarily designed end play between the toothed wheelset and the pump case to change during the increase and/or reduction of the temperature. At an increase of temperature, an approximately linear increase of the end play occurs, so that it results in an additional loss of volumetric effectiveness, which can amount to 50 to 60%. The volumetric effectiveness of a pump drops approximately linear at rising temperatures.
The above-described problem is shown in greater detail using an example of a vane cell pump with the following characteristics:
The end play of the pump is designed to 0.07 mm at 20° C.
Temperature difference 130° C. (20° C. to 150° C.)
Expansion of aluminum case:
46.07 mm+46.07 mm*0.0000238° C.−1*130° C.=46.213 mm
expansion of sintered steel wheelset:
46.00 mm+46.00 mm*0.000012° C.−1*130° C.=46.07 mm
This results in an end play of 0.143 mm.
Temperature difference 60° C. (−40° C. to 20° C.):
Shrinkage of aluminum case:
46.07 mm−46.07 mm*0.0000238° C.−1*60° C.=46.004 mm
shrinkage of sintered steel wheelset
46.00 mm−46.00 mm*0.000012° C.−1*60° C.=45.967 mm
This results in an end play of 0.037 mm. p Due to the different heat expansion of the materials the end play increases at 150° C. to 0.143 mm and reduces to 0.037 mm at 40° C. Doubling the end play and reducing the viscosity of the medium leads to a loss of volumetric effectiveness by 50 to 60%. At low temperatures, due to the reduction of the end play, malfunctions can occur and result in considerable worsening of the mechanic effectiveness. An increase of end play by 0.01 mm results in approximately 1 liter/min reduction of flow at 100° C., 5.5 bar RPM (statement TV-H November 98). When designing an oil pump this volumetric loss has to be considered and the pump must be sized respectively bigger. Due to the bigger sized pump an excess supply of oil occurs at higher rotations, which has to be removed under power consumption.
The object of the invention is to design a pump, which is provided with an end play changing little at a temperature range from negative 40° C. to 160° C. and which has a volumetric effectiveness that drops only little over said temperature range.
The object is attained according to the invention in a pump, in particular an oil pump for internal combustion engines, comprising a pump case, with the pump case comprising a pump lid and a pump flange, with at least one toothed wheelset being arranged between the pump lid and the pump flange, and the pump lid and the pump flange being connected to one another via at least one distance element, with the distance element having a lower heat expansion coefficient than the pump lid, the pump flange, and/or the toothed wheelset.
The pump designed according to the invention allows an improvement of the volumetric effectiveness of a pump by 40 to 50% in reference to pumps having a pump case made from aluminum die casting and a toothed wheelset made from steel. The volumetric effectiveness of the pump according to the invention is higher by approx. 20 to 25% in reference to pumps having a pump case and a toothed wheelset made from steel. Furthermore, at low temperatures the mechanical effectiveness is improved. Another advantage relates to the effect on the pump design, because the size of the pump can be reduced. Further, a reduction of the power input and the weight of the pump is possible and, primarily, a reduction of the fuel consumption. By the design of the pump according to the invention the best possible end play can be calculated for almost all types of pumps with the best effectiveness possible. In many types of pumps this optimization can be retrofitted cost-effectively.
The advantages of the design of the pump according to the invention are shown using an example of a vane cell pump mentioned in prior art:
Optimized vane cell pump:
Heat expansion coefficient Invar=0.0000015° C.−1
Expansion of the distance element made from Invar (nickel steel):
46.09 mm+46.09 mm*0.0000015° C.−1*130° C.=46.098 mm
Expansion of the toothed wheelset made from sintered steel:
46.00 mm+46.00 mm*0.000012° C.−1*130° C.=46.072 mm
This results in an end play of 0.026 mm.
Shrinkage of the distance element made from Invar (nickel steel):
46.09 mm−46.09 mm*0.0000015° C.−1*60° C.=46.086 mm
Shrinkage of the toothed wheelset made from sintered steel:
46.00 mm−46.0 mm*0.000012° C.−1*60° C.=45.96 mm
This results in an end play of 0.119 mm.
By implementing a distance element with a heat expansion coefficient of 0.0000015° C.−1 the end play reduces to 0.026 mm at 150° C. and increases to 0.119 mm at −40 ° C. Therefore, it shows that the implementation of a distance element into the pump case, for example made from nickel steel (Invar) with 36% nickel content (heat expansion coefficient 0.0000015), converts the negative effect of the heat expansion into a positive one, i.e., at high temperatures the end play reduces and at low temperatures the end play increases.
The effect of the heat expansion with regard to the changes of the end play over the temperature is shown in the graph of
The graph shows that in a combination of a pump case made from steel with a wheelset made from steel the intended end play remains constant over the temperature, because the pump case and the wheelset have an identical heat expansion coefficient. A pump case made from aluminum—die casting, optimized with regard to its weight, in combination with a wheelset made from sintered steel shows the increasing end play at higher temperatures and the leakages resulting therefrom, which are undesirable. The combination according to the invention of a light pump case made from aluminum die casting with a wheelset made from sintered steel and distance elements with a heat expansion coefficient smaller than the one of the wheelset and the pump case shows an end play reducing at rising temperatures.
Further, by the graph shown in
It is clearly discernible that at 20° C. the volumetric effectiveness of a pump made according to prior art drops by approximately 7% at an increasing pressure. At a temperature increased to 80° C. the volumetric effectiveness drops by approximately 30%.
However, the graph of
Pump case: grey iron with integrated distance sockets made from Invar (nickel steel with 36% nickel content)
It is discernible that the volumetric effectiveness of a pump according to the invention drops approximately 7% only under rising pressure and is almost independent from the temperature.
An advantageous embodiment of the invention provides that a circular pump disc is arranged between the pump lid and the pump flange, with at least one toothed wheelset being supported on it, with the circular pump disc having the same heat expansion coefficient as the distance element or a greater one.
Another advantageous embodiment of the invention is provided such that the heat expansion coefficient of the distance element is smaller than the respective heat expansion coefficient of the pump lid, the pump flange, the toothed wheelset, and/or the circular pump disc by at least the factor 10.
In a particularly advantageous embodiment of the invention it is provided that the heat expansion coefficient of the distance element is smaller than 0.00002° C.−1.
In a useful embodiment of the invention it is provided that the distance element is made from nickel steel, preferably with a nickel content of 36%.
In another useful embodiment of the invention it is provided that the distance element is a sintered piece. The sintered metal component can be provided with respective alloy elements in order to achieve a distance element with a heat expansion coefficient adjusted to the specific application.
In an advantageous embodiment of the invention it is provided that a planetary rotor set is supported concentrically in the circular pump disc, with the interior rotor being connected to a drive shaft and the pump lid, the circular pump disc, and the pump flange being separated from one another in a sealed manner, with distance elements being provided, whose height is greater than the height of the planetary rotor set by the amount of the intended end play and the height of the circular pump disc is smaller than the height of the distance element by the amount of the heat expansion coefficient, with the expansion gap located between the pump lid, the circular pump disc, and the pump flange being sealed by sealing elements.
In a particularly advantageous embodiment of the invention it is provided that the pump lid is connected to a collar, which extends into the circular pump disc and a planetary rotor set is supported in the circular pump disc, with the circular pump disc being penetrated by at least one distance elements, which contacts the pump lid and the pump flange.
In another advantageous embodiment of the invention it is provided that the pump lid and the pump flange are provided with a collar, which extends into the circular pump disc and a planetary rotor set is supported in the circular pump disc, with the circular pump disc, being penetrated by at least one distance element, which contacts the pump lid and the pump flange.
The invention is shown in the following, using schematic drawings of exemplary embodiments. They show:
The distance sockets 5 are adjusted such to the height of the planetary rotor set that the distance sockets 5 are higher than the height of the planetary rotor set 4 by exactly the amount of the intended end play 24. The difference in the height between the distance sockets 5 and the planetary rotor set 4 is equivalent to the end play 24 at normal temperature.
The circular pump disc 6 is to be adjusted to the distance sockets 5 such that the circular pump disc 6 is smaller than the distance socket 5 by the amount of the heat expansion coefficient (heat expansion coefficient (circular pump disc)*height (circular pump disc)* temperature). This is equivalent to the expansion gap 15.
When screwing the pump 1 together, the pump lid 2 and the pump flange 3 are pressed onto the distance sockets 5. An expansion gap 15 forms between the pump lid 2, the circular pump disc 6, and the pump flange 3, which is sealed by the elastic O-rings 11.1 and 11.2.
The material of the distance sockets 5 is selected such that the heat expansion coefficient is always smaller than the one of the wheelset 4 and the circular pump disc 6. In the present case it is advantageous to use a nickel steel with 36% nickel content (Invar) as the material for the distance sockets 5. This material has a heat expansion coefficient of 0.0000015° C.−1, which is therefore smaller by the factor 10 than the heat expansion coefficient of sintered steel or steel. It is also advantageous for the wheel set 4 to be formed from sintered aluminum Si 14.
In the pump according to the invention, as seen in
Therefore, at 150° C. an end play of 0.0227 mm would develop.
Therefore, at negative 40° C. an end play of 0.0625 mm develops.
ATF—transmission oil at 150° C. approx. 3.4 mm2/s (cSt)
ATF—transmission oil at −40° C. approx. 100002/s (cSt)
For the construction according to the invention the following values result:
Length of distance sockets: width of wheelset+collar length+end play=12.04
temperature difference:=130° C.
expansion distance sockets: (Invar)
12.04 mm+12.04 mm*0.0000015° C.−1*130° C.=12.0423 mm
expansion wheelset (sintered steel)
5.0 mm+5.0 mm*0.000012° C.−1*130° C.=5.0078 mm
expansion length of collar, aluminum
7.0 mm+7.0 mm*0.0000238° C.−1*130° C.=7.021 mm
Therefore, at 150° C. an end play develops of:
12.0423 mm−5.0078 mm−7.021 mm=0.013 mm
Another constructive possibility is to make the circular pump disc from nickel steel with 36% nickel content (Invar). Alternatively, the circular pump disc can also be made from brass or red bronze with the heat expansion coefficient then being approximately 0.000018° C.−1.
L2*(heat expansion coefficient(case)*temperature+L2*(heat expansion coefficient(distance element)*temperature
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 31 979 | Jul 2003 | DE | national |
This is a continuation of application no. PCT/EP2004/007729, filed Jul. 12, 2004, which claims priority to German application no. 103 31 979.4-15, filed Jul. 14, 2003, the entireties of each is incorporated herein by reference.
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| Number | Date | Country | |
|---|---|---|---|
| 20060140811 A1 | Jun 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2004/007729 | Jul 2004 | US |
| Child | 11332523 | US |
