EP0482378B1 - Aircooler for hydraulic oil pumps - Google Patents

Abstract

The air cooler for hydraulic oil pumps is a so-called "cooling pump carrier", that is the cooler is incorporated into the pump carrier for flange-mounting the pump on the drive motor. The cooler has a radial fan (10) mounted on the drive shaft (11) with axial intake chamber and a cooling element arranged concentrically around this chamber. This cooling element is divided into a plurality of, preferably two, separate cooling elements (5, 5a), to which a corresponding number of separate pressure chambers (1, 1a) lead, the intake openings on the circumference leading to the intake chamber being offset in relation to the cooling elements. Two cooling elements (5, 5a) and a corresponding number of intake openings are advantageously provided which on the circumference each lie opposite one another on a diameter, these diameters being perpendicular to one another. This results in an especially advantageous embodiment by means of which any mixing of entering and emerging cooling air is avoided. In addition standard "straight" cooling elements can be used. <IMAGE>

Description

The invention relates to an air cooler according to the preamble of claim 1.

Such air coolers, which are also referred to as cooling pump carriers, are used to cool the hydraulic oil by means of air in order to dissipate the heat loss. The amount of heat to be dissipated is generally at least 15 to 25% of the installed drive power. For this reason, the use of appropriate coolers is necessary if the heat radiation surface of the oil tank and the other units is not sufficient. A distinction is made between oil-water coolers and oil-air coolers, the latter mostly being preferred because of the lower installation effort and the lower operating costs.

In the oil-air coolers, a distinction is made in the oil hydraulics to separately arranged coolers, in which the air is blown through the cooling fins by means of an electrically operated axial fan and, on the other hand, so-called cooling pump carriers onto which the invention is directed. In known coolers of this type, the air from the radial fan mounted on the drive shaft is blown through the heat sink arranged concentrically around the fan.

In contrast to the separate cooler, the cooling pump bracket is a space-saving solution, since the cooler is integrated in the bellhousing, which is required anyway to flange the pump onto the motor. As a result of this, the installation space available for the cooler is very limited, since this is largely determined by the diameter of the motor on the one hand and by the installation length of the bellhousing on the other hand. The wavelength of the motor and pump and the installation dimensions of the shaft coupling have an influence on the latter dimension.

From DE-B 27 50 967 a bellhousing cooler is known, in which the cooler extends over the entire circumference of the radial fan. For reasons of simpler and more economical construction, the cooler is composed of four elements which adjoin one another in terms of their circumference. The cooling channels formed by the elements are flowed through in the circumferential direction by the pump medium to be cooled and air flows all around radially between the cooling fins. In one embodiment of this known bellhousing cooler, the air enters in the area of two elements lying opposite one another and in the area of the other two elements displaced by 90 ° in the circumferential direction. Overall, the cooler extends over the entire circumference and there is a screw on the pressure side of the radial fan in which the air is whirled around in a circle. The air sucked in through the suction openings is deflected several times so that it can reach the internal suction area of the radial fan. This causes considerable flow losses.

While in the ring coolers the tool costs and the manufacturing costs are very expensive, the cheaper tube coolers have the disadvantage that the required amount of heat is not dissipated in most applications. Due to the small cross-section, the finned tube only allows part of the oil flow to be cooled or only the leak oil to pass through, and the relatively short tube length also does not offer a sufficiently large cooling surface. In addition, the tubes are smooth-walled on the inside, so that generally no turbulent but only a laminar flow is formed in the oil flow, which leads to an unfavorable heat transfer due to the layer formation in the liquid flow. For these reasons, the effect of the tube cooler is unsatisfactory.

A common design feature of bellhousing coolers that have become known so far is that cooling air inlet and outlet take place directly alongside one another on the entire circumference of the cooler. This has two major drawbacks. In terms of flow technology, at least one air boundary layer results from the opposing air movements, in which vortex formation occurs, the movement components of which cancel each other out. On the other hand, at least some of the heated, exiting air can return to the cooler with the intake air and heat up continuously in a cycle. The heating of the intake air leads to a decrease in the temperature difference between air and oil, with which the thermal output of the cooler is reduced proportionally. In addition, there is the described reduction in the flow velocity of the air and thus the amount of air per unit of time, which likewise have a very disadvantageous influence on the air-side heat transfer and the amount of heat dissipated.

The invention has for its object to provide an air cooler of the type mentioned, i.e. to create a cooling pump carrier, which has an improved cooling effect and can therefore be used not only as a leak oil cooler, but in particular as a main flow cooler due to sufficient cross sections. Not only should the efficiency be improved, but it should also be possible to produce at low cost.

This object is basically achieved by the characterizing part of claim 1, an advantageous embodiment being the subject of claims 2 and 3.

According to the invention, the cooling air inlet and cooling air outlet are separated from one another on the circumference. The cooler, which is divided into individual heat sinks, is only arranged where the air is discharged. The free areas serve the cooling air entry, so that a mixture of emerging, heated cooling air and suction air is avoided. This improves efficiency. By dividing the heat sink into several, preferably two, opposite and separately arranged heat sinks, commercially available, straight or prismatic heat sinks can be used, which can be dimensioned sufficiently to achieve any desired liter output (flow rate), are much cheaper than ring coolers, for example, and which dissipate a significantly higher heat output than the tube coolers described. The heat sink can also be arranged so that the pressure chambers can be designed as pressure channels, depending on how much space is available. This enables a largely straight-line air flow through the cooling fins. Depending on what is structurally permissible, the coolers can be pulled apart to achieve an optimal length of the pressure channels and thus an optimal flow of air.

The heat sinks are essentially straight, mass-produced and commercially available components that are integrated into the bellhousing, preferably so that they face each other. On the circumference by 90 ° and slightly offset in the axial direction, the suction openings - again preferably two - are through which the cooling air enters the suction chamber and finally axially into the radial fan.

A further increase in the oil flow rate can be achieved in that the two heat sinks (claim 2) are connected in parallel, so that two parallel or even two separate cooling circuits are possible.

An advantageous embodiment has been found to be that according to claim 4, which essentially has a symmetrical configuration, since the heat sink and the suction openings lie opposite each other on one diameter, the diameters being perpendicular to one another. In the axial direction, the heat sink and suction openings are slightly offset from one another, i.e. they are not in one plane.

If the air cooler is designed as specified in claim 5, then a good and fluidically effective division of the cooling air exiting radially from the radial fan is ensured. The cooling air is distributed evenly over the heat sinks, ensuring that the cooling air enters the heat sinks as effectively as possible.

The invention is explained in more detail below with reference to the drawing using exemplary embodiments.

Fig. 1

einen schematischen Querschnitt durch eine Ausführungsform eines Pumpenträgerkühlers nach der Erfindung;

Fig. 2

einen Längsschnitt durch den Pumpenträger- Kühler nach Fig. 1;

Fig. 3

eine Seitenansicht einer Ausführungsform eines Kühlers mit Motor und Pumpe in senkrechter Anordnung;

Fig. 4

eine der Fig. 3 entsprechende Darstellung, jedoch in waagerechter oder liegender Anordnung; und

Fig. 5

eine schematische Ansicht, jedoch in Parallelschaltung des Ölstromes durch zwei Kühlkörper.

It shows:

Fig. 1

a schematic cross section through an embodiment of a bellhousing cooler according to the invention;

Fig. 2

a longitudinal section through the bellhousing cooler according to Fig. 1;

Fig. 3

a side view of an embodiment of a cooler with motor and pump in a vertical arrangement;

Fig. 4

a representation corresponding to Figure 3, but in a horizontal or lying arrangement. and

Fig. 5

a schematic view, but in parallel connection of the oil flow through two heat sinks.

The bellhousing cooler 9 shown in the drawing is arranged between a drive motor 6 and a pump 7 or screwed to these parts, an elastic, structure-borne sound-absorbing intermediate element 8 being provided between bellhousing cooler 9 and pump 7.

The bellhousing cooler consists of a radial fan 10 which is mounted on the drive shaft 11 in the area of a clutch 12.

1, it becomes clear that two heat sinks 5 and 5a are arranged on the circumference of the radial fan 10, which are so-called "straight" heat sinks. In FIG. 2, the intake openings 3 and 3a for the cooling air are offset by 90 ° on the circumference, namely slightly offset in the axial direction, ie in a different plane, as is also clear when considering FIGS. 3 and 4.

At the radial air outlet from the radial fan 10, pressure chambers 1 and 1a are provided, which are separated from one another by lugs 2 and 2a, as is apparent when viewing FIG. 1. These lugs 2, 2a also serve as air guiding surfaces which direct the cooling air in such a way that it strikes the air channels of the heat sinks 5 and 5a as perpendicularly as possible. The pressure chambers 1 and 1a practically form pressure channels, by means of which it is possible to blow the escaping air as straight as possible through the cooling fins. Depending on the installation conditions, these pressure channels can be designed in such a way that optimal flow conditions and thus a correspondingly good cooling are guaranteed.

The air enters through suction openings 3 and 3a into a suction chamber 13 on one side of the radial fan 10 (see FIG. 2). The inlet opening for the cooling air in the radial fan is formed by edges 4, so that a kind of funnel is created for axial entry into the interior of the radial fan.

In the illustrated embodiment, the two heat sinks 5 and 5a are opposite to each other. The same applies to the suction openings 3 and 3a, these being slightly offset in the axial direction from the heat sinks. The scope is divided so that there are separate areas for cooling air inlet and cooling air outlet, so that there is no undesired mixing.

The heat sinks are of conventional construction, so that so-called turbulator plates are used both in the oil-carrying channels and in the air passages. As a result, laminar flow in the oil channels is avoided even with smaller amounts of oil and at speeds of oil and air, and good heat transfer is thus achieved.

Splitting the cooler into at least two separate heat sinks enables operation as indicated in Fig. 5, i.e. the heat sinks are connected in parallel. If two parallel liquid flows - and not two separate cooling circuits - are provided, then the arrangement of the heat sinks according to FIG. 5 is selected such that the sum of the frictional resistances of the liquid flow through the heat sink 5 is equal to the sum of the frictional resistances through the heat sink 5a, so that a uniform distribution of the cooling flows between the two heat sinks is guaranteed.

The design of the bellhousing cooler is chosen so that it can be mounted in a vertical arrangement on a lid, for example the container lid of a hydraulic tank, as shown in FIG. 3, as well as in FIG. 4 in a horizontal arrangement in connection with a foot motor or separately on Bellhousing foot to be flanged.

Claims (5)

1. Air cooler for hydraulic oil pumps, which is integrated into the pump bracket for flanging the pump (7) to the drive motor (6), with a radial-flow fan (10) having an axial intake chamber (13) mounted on the drive shaft (11) and a cooler arranged around the same, characterized in that the cooler is subdivided into several, preferably two, separate, circumferentially based cooling bodies (5, 5a), to which lead a corresponding number of separate cooling air flows (1, 1a) and that the intake openings (3, 3a) leading to the intake chamber are circumferentially displaced to the cooling bodies in the area defined by the spacing.
2. Air cooler according to claim 1, characterized in that the cooling bodies (5, 5a) are connected in parallel with respect to the hydraulic oil flow to be cooled (Fig. 5).
3. Air cooler according to claim 1 or 2, characterized in that the two cooling bodies (5, 5a) and the intake openings (3, 3a) circumferentially face one another on in each case one diameter, in which the diameter on which the cooling bodies are located is substantially perpendicular to the diameter on which the intake openings are located.
4. Air cooler according to one or more of the preceding claims, characterized in that the pressure chambers (1, 1a) formed by the separate air flows are separated from one another by noses (2, 2a) running tangentially and externally onto the fan edge and which are so arranged and constructed that the cooling air substantially perpendicularly meets the entry face of the associated cooling body (5, 5a).
5. Air cooler according to one or more of the preceding claims, characterized in that the axial air entry from the intake chamber (13) into the radial-flow fan (10) is funnel-shaped through an all-round, drawn-in edge (4).

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