EP0129645A1 - Air-operated oil cooler - Google Patents

Abstract

A ventilated oil cooler (4) with an oil-supply tank (6) for stationary or mobile hydraulic units has an extremely small volume, a temperature sensor (18) being provided in the oil circuit and a regulating valve (2) controlled by the temperature sensor (18) being provided in the feed line (1) to the oil tank in such a way that oil is fed solely to the oil tank (6) when the oil is cold during the starting phase, and hot oil is fed solely to the oil cooler (4) during high operating load and is fed in part streams to the oil tank (6) and the oil cooler (4) during intermediate load states. This ensures that the oil quickly reaches the optimum temperature during the starting phase and this optimum temperature is kept constant within narrow limits during high load and during varying load by mixing the oil flowing in directly and the oil flowing in via the oil cooler (4). The temperature sensor (18) can be arranged either upstream of or in the regulating valve (2) or in the line (7) leading to the pump, while the oil cooler (4) is arranged in an air-lift funnel (12) optimised for air flow. <IMAGE>

Description

The invention relates to an air-flowed oil cooler with an associated and connected with it oil storage tank for stationary or mobile hydraulic systems, for an open or closed oil circuit, in which the oil cooler in the cooling flow has lines through which the oil can flow and with effective outer surfaces.

In hydraulic systems, the energy loss generated during operation is converted into heat, which leads to increasing heating of the oil. Depending on the condition of the hydraulic system and the type of oil, this energy loss can amount to 10 to 25% of the power consumption of the oil pump when it is warm. With cold oil, the energy loss is very high because the oil has a higher viscosity due to the temperature. Due to the increasing heating of the oil due to operation, the energy loss is reduced. However, if an optimal oil temperature, which is dependent on the type of oil used, is exceeded, the viscosity of the oil becomes so low that the risk of damage to the hydraulic system can occur because the connection of the lubricating oil films is disturbed.

For energy-related reasons, it is therefore advisable to design hydraulic systems so that the lossy start-up phase, in which the oil heats up to the optimum temperature, is kept as short or as short as possible. On the other hand, it must be ensured that the optimal temperature during operation, be it at maximum load or alternating load, within a certain fluctuation range, the upper limit of which is the optimum temperature of the respective used oil remains.

In practice, however, this requirement is not met in known hydraulic systems; There are not only relatively long start-up phases, during which the system works with high losses because the oil is too low, but also lossy operating phases, in which the system works with oil temperatures that are far below the optimal temperature, because one wants to prevent that the oil temperature at peak load rises above the optimal temperature in dangerous areas with insufficient lubricity.

Hydraulic systems are known which do not have an oil cooler, but in which the oil reservoir has four to ten times (and more) the capacity of the pump delivery rate per minute. The heat storage capacity of the oil content in the tank should prevent overheating in these systems. For this, however, it must be accepted that large-volume oil tanks are required, that the systems are large and heavy due to the high weight of such oil tanks; and it is inevitable that the start-up phase, during which the system operates with losses because the oil is not heated to the optimum temperature, will last for a long time. Such systems therefore work with increased energy expenditure, with the costs for the large amount of oil also playing a major role in the periodic replacement,

In other known hydraulic systems, oil coolers are therefore used, which are equipped with a correspondingly large heat-emitting surface, which bypass are connected to the oil reservoir by means of lines and valves. In the oil coolers, the oil is cooled either with the help of water or with the help of flowing air. The use of water is expensive because it requires an additional cooling water circuit. The use of flowing air is also expensive in the known systems because a fan is used to generate the cooling air flow. In both cases, energy must be used to remove the heat in the oil.

There are systems in which this fan is arranged on the same axis as the oil pump, so that the oil cooling is constantly in operation. The operating behavior of these systems is similar to that of systems without a cooler, because since cooling is carried out from the beginning, the oil temperature remains at low start phases for a long time and remains, with the exception of peak load, well below the optimum temperature during the usual alternating load phases. In addition to the losses due to low oil temperature, these systems also accept the loss of energy to operate the fan. The construction costs for the fan are disadvantageous and lead to complicated, heavy and large-volume systems, even if the fan is driven separately by an electric or hydraulic motor. The noise emission of the fan can also be regarded as disadvantageous. In addition, operational safety is jeopardized because, due to operational vibrations and shocks, cable connections in electrically driven fan motors are easily knocked off. The advantage of the additional cooling units is, however, that the capacity of the stock can be selected comparatively small in relation to systems without an oil cooler.

Based on this prior art, the invention has for its object to develop a ventilated oil cooler with oil storage tank of the type mentioned that the advantages of oil tanks without cooling units are combined with those that have additional cooling units while avoiding the specific disadvantages of both types, particular emphasis should be placed on the generation of an intensive cooling air flow, ease of maintenance and adjustment as well as convenient accommodation and low space requirements.

To solve this problem, the above-mentioned unit consisting of an air-cooled oil cooler with an associated oil reservoir is characterized in accordance with the invention in that a control valve is arranged in the supply line to the oil tank, which outlet side has a line leading to the oil tank and a line leading to the air-flowing oil cooler either itself depending on the temperature or depending on a temperature sensor arranged in the oil circuit, controls the cold oil flow to shorten the start-up time either exclusively into the oil tank or the hot oil flow towards the oil cooler or, in the case of intermediate operating conditions, the oil flow is partly directed to the oil tank and the air-flowed oil cooler at the same time, and that the oil cooler is arranged in the lower end of an air buoyancy chimney surrounding it and both at a distance from a standing surface or wall surface that is sufficiently large for the low-loss air inflow Supports or hangers are held, and in which the from the oil flowing through the lines or similar cooling surfaces of the oil cooler, heat given off to the surrounding air is the driving force for a cooling air flow.

Reaching and maintaining the optimum temperature is achieved very quickly and precisely according to the invention, because the control valve remains closed in the direction of the oil cooler until the oil temperature in the container has almost reached the optimum temperature, so that the starting phase is very short in time. When there is an alternating load, the control valve directs partial flows through the cooler, the cool oil of which mixes in the reservoir with the hot, directly supplied oil to an average temperature which is close to the optimum temperature. At peak loads, the entire amount of oil can be led through the cooler so that optimal oil temperatures are maintained in the tank.

A very significant advantage of the unit designed according to the invention is the use of an oil cooler, the cooling air flow of which without a fan, ie. H. that is, without consuming mechanical energy. All disadvantages, such as noise emissions, operational uncertainty, additional construction costs for engines, etc., are saved. In addition, due to its design as an air buoyancy chimney with low flow loss design, the oil cooler designed according to the invention can also be used in the case of changing ambient temperatures and small dimensions, ie. H. So small space requirement, cause intensive cooling.

According to two further developments of the unit, the temperature sensor can either control the control valve be arranged in the feed line to the oil tank, namely upstream of the control valve or on the control valve itself or in the line leading from the oil tank to the pump. The arrangement of the temperature measurement in the supply line is particularly advantageous when there are strongly changing operating conditions (strongly fluctuating oil temperatures) because disproportionate heating of the oil is immediately reduced in the cooler, while the arrangement in the line leading to the pump has the advantage of a very high temperature consistency guaranteed in the event of irregular withdrawals from the oil container.

The arrangement of the control valve and the temperature sensor outside of the oil tank selected according to the main claim and subclaims is of extraordinary advantage because maintenance and replacement work can be carried out very easily without major oil losses, in particular also changes to the control valve or changes in the proportionality between the temperature sensor and control valve in the case of changing oil types or changing operating conditions are very easy to carry out.

In an advantageous development of the unit designed according to the invention for achieving small dimensions and weights, the air inlet in the lower opening of the air lift chimney, preferably angled or curved air guiding surfaces and deflection plates, are arranged in order to reduce the draft losses (entry losses).

. It is also advantageous if a flow-accelerating hood that narrows from bottom to top is provided at the air inlet to the cooler.

It is also advantageous that, in order to reduce the leakage losses, the air buoyancy chimney is expanded at least in the region of its upper open end or over the entire height above the oil cooler, the angle of inclination of the air buoyancy chimney walls widening up to 20 ° to the flow axis.

Air flow losses in the buoyancy chimney are optimally avoided by the two measures mentioned and there is nevertheless a highly effective air flow with a small space requirement of the air buoyancy chimney. Entry and exit losses form a significant part of the air propulsion balance for the generation of the flow velocity. Savings in flow losses are sensibly used in the heat transfer to the oil cooler elements. Depending on the design of the cooling elements, the heat transfer from oil to air increases approximately in proportion to the air speed. This measure ensures that the oil tank with the oil cooler can be made smaller and lighter overall than in systems with motor-driven fans.

The unit designed according to the invention is characterized by a high variability of the loads in relation to oil quantities and oil temperature. Since the oil cooler is forced to flow through the oil circuit when the control valve is open, it is irrelevant for its function where the oil reservoir is located. For example, it can be arranged separately from the oil cooler at the same height or below or above the oil cooler. This configuration has the advantage that the housing of the oil container is free, depending on the spatial design of the hydraulic system, can be selected and contributes to compact overall systems.

According to the invention, in addition to further saving in space and weight, it is also possible for the oil container to form part of the outer wall or to surround the oil cooler as an annular body and to form part or all of the outer wall of the air buoyancy chimney.

In these configurations, the oil reservoir and the oil cooler form a compact unit with low weight and small external dimensions, which can always be easily accommodated.

Another possibility is that the oil container has the shape of a low-loss flow around the body and is arranged within the air lift chimney.

The aforementioned development is particularly suitable when a comparatively high cooling capacity of the oil cooler is combined with a comparatively low capacity of the oil container,

The design with a separate oil container is particularly advantageous for closed hydraulic circuits, because in these the reservoir is under pressure and is therefore preferably drum-shaped.

The capacity of the oil container can advantageously be less than twice the pump delivery rate per minute.

According to the invention, it is possible to make the oil container extremely small. It is only important to ensure that the volume of the container does the secondary tasks, namely storing a reserve for leakage oil losses, sedimentation of solids, which, for. B. caused by coking, volume expansion of the oil by heating, as well as foaming oil to give space, met. If these tasks are fulfilled, an oil tank can also be made significantly smaller than twice the delivery rate per minute of the pump. This has the advantage that the hydraulic system turns out to be small and light due to the small container, operates at low cost for oil and in particular reaches the optimum temperature extremely quickly because only a small amount of oil has to be heated.

• Fig. 1 - eine Seitenansicht,
• Fig. 2 - eine Stirnansicht einer Ausführungsform der erfindungsgemäß ausgebildeten Einheit,
• Fig. 3 - eine Seitenansicht,
• Fig. 4 - eine Draufsicht auf eine Weiterbildung, bei welcher ölbehälter und Luftauftriebskamin eine gemeinsame Wandung haben,
• Fig. 5 - eine Teil-Schnitt-Seitenansicht,
• Fig. 6 - eine Draufsicht auf eine Weiterbildung mit ringförmigem ölbehälter und von den Innenwandungen des Behälters begrenztem Luftauftriebskamin,
• Fig. 7 - eine strömungstechnisch besonders günstige Ausgestaltung in Seitenansicht,
• Fig. 8 - eine Seitenansicht einer strömungstechnisch günstigen Ausgestaltung des Luftauftriebskamines mit beigeordnetem ölbehälter, der eine Seitenwand des Kamines begrenzt,
• Fig. 9 - eine Draufsicht auf die Ausführung gemäß Fig. 8,
• Fig.10 - eine Seitenansicht einer Ausgestaltung, bei welcher strömungstechnisch optimierter Luftauftriebskamin und den Kamin auf einem Teil seiner Höhe ringförmig umgebender Ölbehälter vereinigt sind,
• Fig.11 - eine Draufsicht auf die Ausführung gemäß Fig. 10,
• Fig.12 - eine Schema-Seitenansicht mit innerhalb des Luftauftriebskamines angeordnetem ölvorratsbehälter,
• Fig.13 - eine Draufsicht auf die Ausgestaltung nach Fig. 12.

Embodiments of the unit according to the invention, consisting of a ventilated oil cooler with a storage container, are shown in the drawings. It shows:

• 1 - a side view,
• 2 - an end view of an embodiment of the unit designed according to the invention,
• 3 - a side view,
• 4 - a top view of a further development in which the oil tank and the air buoyancy chimney have a common wall,
• 5 - a partial sectional side view,
• 6 shows a plan view of a further development with an annular oil container and an air buoyancy chimney delimited by the inner walls of the container,
• 7 - a particularly favorable fluidic design in side view,
• 8 is a side view of an aerodynamically favorable configuration of the air buoyancy chimney with an associated oil container which delimits a side wall of the chimney,
• 9 - a top view of the embodiment according to FIG. 8,
• 10 shows a side view of an embodiment in which the aerodynamically optimized air buoyancy chimney and the chimney are combined in an annular manner around the part of its height,
• 11 - a top view of the embodiment according to FIG. 10,
• 12 shows a schematic side view with an oil reservoir arranged inside the air buoyancy chimney,
• Fig. 13 - a top view of the embodiment according to Fig. 12.

1 shows a schematic sectional view, in which the configuration of an embodiment of an oil container 6 with an associated oil cooler 4 is shown, in which the overall height is not very limited. Figure 2 shows the side view.

The unit consisting of both the oil tank 6 and the cooler 4 is supplied with warm oil via an inlet line 1 coming from the hydraulic system and introduced into a control valve 2 which is self-regulating or controlled as a function of temperature. This control valve 2 has a line 3 on the downstream side which leads to the oil cooler 4 and a further line 5 which opens out directly into the oil reservoir 6. From the reservoir 6, the oil is fed via a line 7 to the pump, not shown, and further to the hydraulic system.

In this example, the oil cooler 4 is formed from individual lines 9, coils or the like. The oil passes through the line 3 into the collector 6, from which the coils 9, forming the cooling system 4, exit. Instead of the line 9, with or without a collector 8, other heat-transferring elements (such as finned tubes, elliptical or lenticular tubes, etc.) can also be selected. A collector 10 leads the oil out of the lines 9 and leads it via a line 11 into the reservoir 6.

The control valve 2 is provided in the embodiment according to FIGS. 1 and 2 with a temperature sensor which is not designed separately. Measurements and corresponding control adjustments are made by temperature sensors that are directly connected to valves and their seats. Due to the temperature sensor control in the control valve til 2, the oil coming from the supply line, if it is cold and does not correspond to the optimal oil temperature, flows directly through line 5 into the reservoir 6.Oil, which threatens to exceed the optimum temperature with its temperature, is adjusted accordingly in the control valve 2 passed through line 3 into the oil cooler 4 and emerges cooled from this back into the oil container 6. If there is a high heat build-up in the oil, ie an extremely high peak load, the control valve will block line 5 so that the entire oil flow runs through the oil cooler 4. In intermediate states, the oil coming from the feed line 1 is branched into partial flows. The result of this control activity of the control valve 2 is that the reservoir 6 contains oil with a temperature which is established as the mixing temperature of the oil components coming from line 5 and from oil line 11. This mixing temperature fluctuates only slightly below the optimal temperature of the oil. For some needs, this has the advantages that more oil can be removed at an optimal temperature for a short time than it corresponds to the return flow quantity.

In order to achieve intensive cooling of the oil in a small space, the oil cooler 4 is accommodated in a straight air lift chimney 12, which is held on supports 13 with its lower open end at a distance from a standing surface. For limited overall heights, to improve the cooling air flow, ie to reduce inlet flow losses, 12 air flow losses reducing, preferably angled, but possibly also curved air guiding surfaces 14 and equally designed deflection plates 15 are provided below the lift chimney orderly. The large arrows in the figures indicate the direction of air flow.

The oil tank 6 has in the upper area the usual oil filler neck 16, which can also serve as a vent in open systems; At the lowest point of the oil circuit in the example according to FIGS. 1 and 2 on the lower header 10 of the oil cooler 4, a drain port 1.7 is provided.

In the design according to 3 and 4, compact space-saving training is important in that the air buoyancy chimney 12 and the oil container 6 have a common wall.

5 and 6, the space- and weight-saving saving is further increased by the oil container 6 being configured in a ring shape and forming the walls of the air lift chimney 12 with the inner walls delimiting a cavity. In order to reduce the deflection loss, wing-like deflections 15a (wing deflection) are provided in the inlet to the (cooling air-driving) lift chimney 12 and container interior 6,

The development according to FIG. 7 is varied in particular with regard to particularly effective cooling, that is to say optimal generation of a cooling air flow with additionally low outlet losses. In this system, the oil tank 6 is arranged separately from the air lift chimney 12. The temperature sensor 18 already mentioned is accommodated in the line 7 leading from the oil tank 6 to the pump and is connected via an electrical connection 19 to a proportionality amplifier 20 which is adjustable and in turn to the control valve 2 is connected in terms of control technology. The oil container 6 can, for. B. be designed as a pressure vessel drum and the container can be attached to save space below and next to the air outlet chimney 12 and diffuser 21.

In order to optimize the air buoyancy flow in the air buoyancy chimney 12 (reduction of the buoyancy losses, therefore lower required height of the air outlet chimney 12 or increase of the buoyancy speed for the same air outlet chimney height and thus more effective heat transfer from the oil to the air flowing past), the air exit chimney 12 expands in a diffuser manner to the outlet 21. Depending on the flow conditions, the wall can be inclined up to “20 ° from the flow axis 12a. The exit losses have a significant share in the train loss balance.

8 and 9 show an embodiment in which the oil container 6 forms a side wall of the air buoyancy chimney, in an area in which this air buoyancy chimney 12, similarly to the embodiment according to FIG. 7, is strongly inclined outwards on the container side to form a diffuser-like widening 21. Of course, it is also possible to leave the diffuser axis in the direction of the cooling axis and one communicating container each on the left and right and below the diffuser. 21 to arrange.

10 and 11, the device is formed on a standing wall in a hanging version. The oil container 6 has an annular, in this case circular shape and surrounds the oil cooler like a ring. The lower open end of the air buoyancy chimney 12 has, below the oil cooler 4, a funnel-shaped hood 22 which extends downwards and which, by slowly and steadily accelerating the cooling air to approximately air speed in the oil cooler 4, causes a low-loss inflow of air, while above the oil cooler 4, the one already mentioned diffuser-like extended attachment 21 is provided. The device is held by means of hooks or brackets 23 on the wall. It is also possible to set up this device on a level floor using supports.

12 and 13, the air buoyancy chimney 12 is divided into two and at the same time is formed like a diffuser above the cooler 4. Between these diffuser-like channels, the oil reservoir 6 is arranged as a body which is shaped to be air-flow-friendly.

vergrößern (Re = Reynoldsche Zahl (Maß der Turbulenz), w = Luftgeschwindigkeit, d_Hydr. = Abmessung im Luftschacht, y = kinematische Zähigkeit) und damit die Lufttemperaturim Luftaustrittskamin 12 über den gesamten Querschnitt homogenisieren, die Auftriebskräfte gleichmäßig gestalten und eine gleichmäßige Luftbeaufschlagung mit gleichbleibendem guten Wärmeübergang im Kühler 4 erzielen.By using the diffuser-like attachments 21, the overall height of the oil cooler 4 or the air lift chimney 12 can be reduced by reducing the outlet losses - the outlet losses increase with the square of the air outlet velocity from the air outlet chimney - the turbulence

increase (Re = Reynold's number (measure of turbulence), w = air speed, d _hydr . = dimension in the air shaft, y = kinematic toughness) and thus homogenize the air temperature in the air outlet chimney 12 over the entire cross-section, make the buoyancy forces uniform and even air pressure Achieve consistent good heat transfer in the cooler 4.

The described embodiments therefore make it possible to create auxiliary hydraulic systems which have small-volume oil tanks and relatively small coolers and which, compared to known designs with tanks and oil coolers, with motor-driven fans, are also weight-saving in smaller systems and require small construction volumes. Despite this significantly space-saving design, security for higher ambient air temperatures, extreme peak loads, etc. can be provided. It is further achieved that the oil in the oil container 6 can mix intimately and the entire oil content is available for sudden additional withdrawals at the optimal temperature.

Drive energy for fans is saved, noise emissions are avoided, space and weight are saved and the entire hydraulic system always works close below the optimum temperature of the oil. This optimal temperature is reached quickly due to the small capacity of the oil tank on the one hand and the activity of the control valve on the other. Low oil consumption due to the small volume represents a considerable cost saving. The operational safety is increased compared to known designs because no motor-driven fan can fail or require maintenance. The entire, consisting of cooler and oil tank 4 or 6, unit is very easy to maintain and use, because all possible to be operated or converted facilities, eg. B. the control valve 2, the filler neck 16, etc. are easily accessible.

Claims (10)

1. Air-flowed oil cooler with an associated oil reservoir for stationary or mobile hydraulic systems, for an open or closed oil circuit, in which the oil cooler has lines in the cooling flow that can be flowed through by the oil and have effective outer surfaces,
characterized,
that in the feed line (1) to the oil tank (6) a control valve (2) is arranged, which on the outflow side leads to the oil tank (6) line (5) and to the air-flowing oil cooler (4) line (3) either depending on the temperature or depending on a temperature sensor arranged in the oil circuit, controls such that the cold oil flow to shorten the start-up time either exclusively into the oil tank (6) or the hot oil flow towards the oil cooler (4) or, in the case of intermediate operating conditions, the oil flow proportional to the oil temperature, partly simultaneously to the oil tank (6 ) and to the air-cooled oil cooler (4),
and that the oil cooler (4) is arranged in the lower end of an air buoyancy chimney (12) surrounding it and both are held at a sufficient distance for a low-loss air inflow from a standing surface or wall surface by means of supports (13) or hangers (23), and in which the heat given off by the oil flowing through the lines (9) or similar cooling surfaces of the oil cooler (4) to the surrounding air is the driving force for a cooling air flow. 2. Air-flowed oil cooler according to claim 1, characterized in that the temperature sensor (18) in the feed line (1) to the oil container (6) is optionally arranged in front of or on the control valve (2). 3. Air-flowed oil cooler according to claim 1, characterized in that the temperature sensor (18) is arranged in the line (7) leading from the oil container (6) to the pump. 4. Air-flowed oil cooler according to one or more of claims 1 to 3, characterized in that to reduce the draft losses (entry losses) of the air inlet in the lower opening of the air lift chimney (12) reducing air flow losses, preferably angled or curved air guiding surfaces (14) and deflection plates ( 15) are arranged. 5, air-flowed oil cooler according to one or more of claims 1 to 4, characterized in that at the air inlet to the cooler (4) a flow-accelerating hood (22) narrowing from bottom to top is attached. 6. Air-flowed oil cooler according to one or more of claims 1 to 5, characterized in that to reduce the leakage losses of the air buoyancy chimney (12) is expanded at least in the region of its upper open end or over the entire height above the oil cooler (4) upward , the angle of inclination of the air lift chimney walls extending up to 20 ° to the flow axis (12a). 7. Air-flowed oil cooler according to one or more of claims 1 to 6, characterized in that the oil container (6) is arranged separately from the oil cooler (4) at the same height or above or below the oil cooler (4). 8. Air-flowed oil cooler according to one or more of claims 1 to 6, characterized in that the oil container (6) forms part of the outer wall or surrounds the oil cooler (4) as an annular body and forms part or all of the outer wall of the air lift chimney (12) . 9. Air-flowed oil cooler according to one or more of claims 1 to 6 and / or 8, characterized in that the oil container (6) has the shape of a body with low loss flow and is arranged within the air buoyancy chimney (12). 10. Air-flowed oil cooler according to one or more of claims 1 to 9 _1, characterized in that the capacity of the oil container (6) can be less than twice the pump delivery rate per minute.

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