EP3705631B1 - Working machine with electric drive and cooling device - Google Patents

Description

The invention relates to a work machine with an electric drive, in particular a construction machine such as an excavator, a loader or a dump vehicle.

In the past, a diesel engine has proven to be the most effective drive for such work machines. This engine operates a hydraulic circuit with which the driving and working movements of the work machine can be effected, e.g. by driving a hydraulic circuit.

However, just as in the passenger car sector, it is also expected that combustion engines (e.g. diesel engines) will increasingly be converted to electric drives for such work machines.

The operation of such electric drives usually causes the components involved to heat up considerably, in particular the electrical drive components such as electric motors, inverters (power electronics, motor control), voltage converters (DC/DC converters), on-board chargers (e.g. AC/DC converters) and electrical energy storage devices or batteries. The heat generated can lead to damage during continuous operation, as is common with such machines, and must therefore be dissipated.

Liquid cooling is known to provide cooling for the drive components, but this increases the complexity of the entire system and requires additional space in the machine. In addition, liquid cooling is technically complex and leads to considerable additional costs.

Since the machines in question are usually only used stationary or have only a small radius of movement, no airflow is generated that could contribute significantly to cooling the drive components.

The design of cooling fins can also be disadvantageous in such machines because the machines are often used in a dirty environment (dust, sand, mud), so that the cooling fins can be covered with a heat-insulating crust of dirt after only a short period of use.

Out of JP 2004 203566 A and JP 2014 149992 A Electrically driven forklift trucks are known in which heat-generating components of the control electronics are arranged in the rear counterweight of the forklift truck, whereby heat transfer from the components to the counterweight is sought in order to effect cooling of the components.

In the EP 3 176 334 A1 describes an excavator with a hybrid drive that has an internal combustion engine and an electric motor. To cool the engines and other components, a fan is provided to generate a cooling air flow, with an energy storage device arranged in the cooling air flow.

The invention is based on the object of providing a simplified cooling possibility for the electrical, i.e. electronic, drive components of an electric drive in a work machine.

The object is achieved according to the invention by a work machine having the features of claim 1. Advantageous embodiments are specified in the dependent claims.

A work machine is specified, with a drive device with an electric drive and with structural components that are selected from the group of basic structure, machine frame, chassis base plate, counterweight and/or engine compartment housing. The electric drive has an electric motor and heat-generating electrical, in particular electronic, drive components, wherein at least one of the drive components is attached to one of the structural components in such a way that the heat generated by the drive component can be at least partially conducted into the component.

By coupling the heat-generating drive component to the structural component, a cooling device for the drive component is formed.

The work machine can in particular be a mobile work machine, especially a construction machine, such as an excavator, a (wheel) loader or a dumper vehicle (dumper, dump truck).

The electric drive can be constructed in a known manner and have various components, namely in particular an electric motor and electrical (or electronic) drive components such as inverters, power electronics, motor control, voltage converters or on-board chargers. Electrical energy storage devices or batteries are also among such electrical drive components.

The structural components form the "framework" or "skeleton" of the working machine and thus the central physical structures of the working machine. They consist in particular of steel or steel construction or of grey cast iron (such as the counterweight). The basic frame can be welded or bolted together from steel components. All other components of the working machine, including the chassis, the driver's cab, the engine compartment and the components required to effect the working movement, are attached to it. In this sense, the basic structure can also be understood as a machine frame or a chassis base plate.

This is the main support structure, which is also relevant for the central strength of the working machine. The chassis base plate can be constructed in a plate-like manner, while the basic structure or machine frame can also be connected to higher structures.

The counterweight can be provided on certain construction machines, such as an excavator, and can be arranged opposite to compensate for a boom with respect to a vertical axis of rotation. In excavators in particular, a solid counterweight made of gray cast iron is provided opposite the boom (e.g. excavator arm) to compensate for the weight of the excavator arm and in particular the load that the excavator has to bear during operation and to prevent the excavator from tipping over.

This makes it possible according to the invention to use the structural components already present in a work machine for the targeted dissipation of heat from the electrical or electronic drive components. In the case of work or construction machines of this type in particular, the structural components have a simple structure on the one hand and a large mass on the other. In addition, they are usually made of a material with good thermal conductivity (steel, gray cast iron) and are therefore able to absorb or conduct larger amounts of heat. In this way, it can be ensured that the electronic drive components do not require any additional or separate cooling, in particular no additional fluid cooling or additional fans or cooling fins.

The structural components serve as heat sinks for the electronic drive components. The thermal coupling of a drive component in question with a structural component is also understood in this context as a "cooling device". The steel components can absorb and dissipate the heat flow well due to their weight and large cross-sections. The other steel components, sheets and cladding parts attached to the central framework structures can act in a similar way to cooling fins. They represent an additional mass that can absorb heat. They also increase the surface area to the environment so that the heat can be released into the ambient air. In this way, for example, the basic framework of the working machine itself becomes the heat sink.

There can be a contact surface between the drive component and the structural component to which the drive component is attached, whereby an increased heat transfer is possible via the contact surface, which is greater than heat transfer via an air gap. The contact surface thus forms a surface contact between the parts involved. In particular, direct contact between the parts is possible in order to achieve good heat transfer. For example, the contact surface can be flat in order to easily attach the drive component to the structural component - already present on the work machine. The aim should be to achieve as direct, surface contact as possible between the parts, because only then can a heat flow from the drive component into the component be achieved.

A heat conducting element can be arranged in the contact surface between the drive component and the structural component. This heat conducting element can serve as an "adapter" or adaptation element, so to speak, in order to adapt the drive component, which in turn is usually a purchased part that can no longer be changed in terms of design, to the structural component as flatly as possible. The structural component of the working machine is also usually already there and should not have to be changed for cost reasons, but also for design reasons. With the help of the heat conducting element, it is therefore possible to achieve good heat transfer or good heat conduction from the drive component to the component.

The heat conducting element can be designed, for example, as a metal body or as a metal plate in order to serve as a heat sink with respect to the drive component. The heat conducting element should have a contact surface with the drive component on the one hand and a contact surface with the component on the other. Design constraints can easily be implemented by adapting the heat conducting element accordingly, without the drive component or the structural component having to be changed in terms of design. This makes it easy to achieve the desired "adapter function".

It was stated above that a contact surface may be present between the drive component and the structural member. If the above-mentioned heat-conducting element is also present, this contact surface is considered to be the Contact surface between the drive component and the heat conducting element.

In one embodiment, this contact surface can be at least 20% of the entire outer surface of the drive component. In this way, a significant portion of the heat generated in the drive component can be conducted into the structural component via the contact surface - possibly also via the heat-conducting element. The contact surface is preferably at least 30% of the entire outer surface of the drive component. The contact surface is particularly preferably at least 40% of the entire outer surface.

In one embodiment, at least 30% of the heat generated by the drive component can be conducted into the structural component. The heat can be conducted into the component in particular via the contact surface. Preferably, at least 40% of the heat generated by the drive component can be conducted into the structural component. Particularly preferably, at least 50% of the heat generated by the drive component can be conducted into the structural component.

In one variant, the structural component can be a counterweight, with a recess provided on the inside of the counterweight into which the heat-generating drive component can be inserted. It has already been explained above that the counterweight can be used, for example, in an excavator to balance the boom (excavator arm) and the load carried by it. Additional counterweights are often installed, particularly in construction machinery, to prevent the machines from tipping over.

The inside of the counterweight is directed towards the boom or the load-bearing device. There can be a recess in the counterweight into which the heat-generating drive component is inserted directly or with the help of a heat-conducting element. When the working machine is in operation, the heat generated in the drive component can then be conducted directly into the counterweight. Due to its size and the associated mass of the counterweight, the counterweight is easily able to absorb larger amounts of heat. It therefore heats up slightly during operation. The heat can in turn be dissipated to the environment via the outside of the counterweight.

It can be particularly advantageous if the drive component can be integrated into the installation space occupied by the counterweight, because in this way the installation space can be used particularly efficiently.

In addition to the electric drive, the drive device can have a hydraulic circuit that is driven by the electric drive to generate a travel movement and/or a working movement. The work machines in question here are typically moved, i.e. moved, via a hydraulic circuit. The additionally required working movement (for example the lifting and swiveling movement of an excavator arm or a loader bucket) can be effected by the same or by a separate hydraulic circuit.

Such a hydraulic circuit is known per se. The electric drive can rotate a hydraulic pump, which enriches hydraulic fluid (e.g. hydraulic oil) with energy and delivers it under pressure in a hydraulic circuit. The hydraulic circuit has corresponding consumers connected to it, such as hydraulic motors or linear drives (piston-cylinder units). The hydraulic motors can be provided on the wheel axles, for example, and drive wheels with which the travel movement can be achieved. The linear drives can cause swivel and lifting movements, for example for booms, excavator arms, shovels, etc.

The hydraulic circuit may comprise a cooling device with a fan and a heat exchanger, wherein the fan generates a cooling air flow for the heat exchanger, and wherein the cooling air flow is guided upstream of the heat exchanger such that it sweeps over a surface of the heat-generating drive component and/or a surface of the structural component to which the drive component is attached.

In this variant, the cooling air flow in the intake area of the fan is guided in such a way that not only the hydraulic components of the hydraulic circuit, in particular the hydraulic fluid circulating there via the heat exchanger, are cooled, but also the heat-generating drive component or the structural component to which the drive component is attached and which is thus heated by the drive component during operation. This can achieve an additional cooling effect for the drive component. The hydraulic circuit and the corresponding hydraulic components are typically present in such a work device anyway, so that A heat exchanger with a fan is also usually provided to cool the hydraulic fluid. The cooling air flow from this fan is used to cool the electrical or electronic drive components. The structural component can also be cooled to improve the cooling effect.

An electrical energy storage device can be provided for the electric drive and/or for the electric motor, with the cooling air flow being guided upstream of the heat exchanger in such a way that it passes over the electrical energy storage device. The electrical energy storage device can in particular be a battery that supplies the electric motor with electrical energy. In this variant, the cooling air flow generated by the hydraulic circuit fan can thus also cool the electrical energy storage device in advance and keep it at a suitable operating temperature.

An engine compartment can be provided with an engine compartment housing in which the following components are housed: electric motor, fan of the cooling device of the hydraulic circuit, energy storage for the electric drive, at least one of the heat-generating drive components. A main inlet opening for the cooling air flow can be provided in the engine compartment housing, wherein the cooling air flow is guided in such a way that it flows through the engine compartment. The engine compartment is thus defined by the engine compartment housing or a corresponding engine compartment cover. Through clever design and suitable attachment of the main inlet opening, the fan can generate a cooling air flow that at least partially covers all the components to be cooled within the engine compartment.

In addition to the main inlet opening, an engine cooling air opening can be provided in the engine compartment housing, through which the cooling air specifically for the electric motor enters the engine compartment. The electric motor in particular generates considerable heat during operation. Accordingly, it is expedient to provide a separate opening for the electric motor, namely the engine cooling air opening, through which cooling air from the environment can be specifically introduced and passes over the electric motor in the engine compartment.

In one variant, the structural component can have a cavity that is filled with and/or through which a liquid can flow, which absorbs heat from the structural component. The structural component thus experiences additional cooling through the liquid. The flow through the component can be achieved by a suitable conveying device, e.g. a pump such as a coolant pump.

The work machine can in particular be a construction machine such as an excavator, a loader or a dump truck. An excavator is typically characterized by having an undercarriage and an upper carriage mounted on it so that it can rotate about a vertical axis. The upper carriage is usually provided with a boom (excavator arm), at the end of which a bucket (bucket) can be pivotably mounted.

A loader or wheel loader has a chassis with wheels. It can also have a height-adjustable bucket or a telescopic boom (telescopic loader).

A dump truck has a dump truck that can be adjusted in height. Such vehicles are also called dumpers.

Fig. 1

den schematischen Aufbau einer Kühlvorrichtung für eine Arbeitsmaschine in Seitenansicht;

Fig. 2

eine besondere Ausführungsform der Kühlvorrichtung in einem Gegengewicht;

Fig. 3

eine schematische vertikale Schnittdarstellung eines Motorraums;

Fig. 4

eine horizontale Schnittdarstellung bei der Variante von Fig. 3;

Fig. 5

ein Beispiel für eine Arbeitsmaschine als Bagger mit Gegengewicht; und

Fig. 6

ein Beispiel für eine Arbeitsmaschine als Radlader.

These and other features and advantages of the invention are explained in more detail below using examples with the aid of the accompanying figures. They show:

Fig.1

the schematic structure of a cooling device for a working machine in side view;

Fig. 2

a special embodiment of the cooling device in a counterweight;

Fig. 3

a schematic vertical sectional view of an engine compartment;

Fig.4

a horizontal sectional view of the variant of Fig.3 ;

Fig.5

an example of a working machine as an excavator with counterweight; and

Fig.6

an example of a working machine as a wheel loader.

Fig.1 shows a highly simplified representation of a structure for cooling a heat-generating electronic drive component 1.

The drive component can be, for example, a converter, power electronics, motor control, voltage converter or part of an on-board charger. It has electronic components, some of which are subjected to high electrical currents and generate large amounts of heat. This heat must be dissipated to prevent the drive component from overheating and ultimately destroying it.

For this purpose, the drive component 1 is surface-coupled to a structural component 2. The component 2 is, for example, a structural part of a working machine, i.e., for example, part of a steel construction basic structure or machine frame, as is usually provided for such working machines.

The drive component 1 is coupled to the structural component 2 via a heat conducting element 3 that serves as a heat sink. The heat conducting element 3 can, for example, be in the form of a metal plate. It has a first contact surface 4 to which the drive component 1 is connected and via which the heat from the drive component 1 flows into the heat conducting element 3. The heat conducting element 3 also has a second contact surface 5 via which the heat conducting element 3 touches the structural component 2 and via which the heat from the heat conducting element 3 can be conducted into the component 2.

The heat conducting element 3 can thus be understood as an adapter between the drive component 1 and the structural component 2 in order to ensure optimal heat transfer from the drive component 1 to the component 2.

In addition, a housing 6 can be provided which surrounds the drive component 1 and thus protects it from external influences. In addition, the housing 6 can also have a heat-insulating effect in order to prevent heat from the drive component 1 from reaching other areas of the drive machine in an undesirable manner. This applies in particular if the aim is for the heat generated by the drive component 1 to be conducted as far as possible, for example more than 50%, into the structural component 2.

Fig.2 shows a further development of the embodiment of Fig.1 The structural element 2 is designed in the form of a counterweight 7.

As already explained several times above, counterweights are used in excavators in particular to balance the weight of the boom (excavator arm) and the load attached to it. Accordingly, the counterweights are usually made of very solid steel or gray cast iron.

At the Fig.2 In the embodiment shown, a recess 8 is formed on an inner side of the counterweight 7 directed towards the boom (not shown), into which the arrangement of Fig.1 is used.

This means that the heat from the drive component 1 can be introduced into the counterweight 7 via the heat conducting element 3. The counterweight 7 thus heats up when the working machine is in operation. Since the outside 9 of the counterweight 7 is exposed to the environment, it is constantly cooled by the ambient air so that the heat can be released to the environment. The counterweight 7 has a large surface on its outside 9, which enables a good cooling effect.

How Fig.2 shows, the recess 8 can be used to ensure that the installation space does not have to be enlarged or not significantly enlarged. Rather, the recess 8 can be used to create a space inside the counterweight 7 in comparison to the original installation space 10, in which space the drive component 1 can be inserted.

Fig.3 shows a special design of an engine compartment 12 in vertical section.

The engine compartment 12 is formed by an engine compartment housing 13 or an engine compartment cover. Various components are arranged inside the engine compartment housing 13, namely a heat exchanger 14 for a hydraulic circuit, a fan 15 for generating a cooling air flow 16 inside the engine compartment housing 13, which mainly passes through the heat exchanger 14 in order to cool the hydraulic fluid contained therein. The hydraulic fluid is used as a working medium for operating a travel drive and/or a working drive, as already explained above.

An electric motor 17 is also arranged in the engine compartment 12, which drives, for example, a hydraulic pump (not shown), with which the hydraulic circuit can be operated. Several electronic drive components 1 are arranged in the engine compartment 12 to operate the electric motor 17. These can be control units, power electronics, etc.

The heat-generating drive components 1 are attached to the structural component 2. This can be, for example, part of a machine frame or chassis.

Furthermore, an electrical energy storage device 18 is provided in the engine compartment 12 for storing the electrical energy for the electric motor 17.

Opposite the fan 15, a main inlet opening 19 is provided in the engine compartment housing 13, through which cooling air from the environment can flow into the engine compartment 12 to form the cooling air flow 16. The main inlet opening 19 can of course consist of many smaller openings or an opening grille to prevent the penetration of larger particles and to ensure safe operation.

Furthermore, an engine cooling air opening 20 is provided on the underside of the engine compartment housing 13, through which cooling air from the environment can flow into the engine compartment 12 in order to specifically cool the electric motor 17 located above it.

How Fig.3 shows, the cooling air flow 16 is guided in such a way that all components including the structural element 2 are swept over in order to achieve a certain degree of cooling.

Fig.4 shows the arrangement of Fig. 3 in the top view.

A further heat-generating drive component 1 is provided, which this time is installed on the inside of the counterweight 7, as already shown above with reference to Fig. 2 shown.

This means that a combination of Fig. 3 and 4 Drive components 1 can be mounted on the underside, i.e. on the machine frame, and on the counterweight 7, in order to to distribute the heat generated evenly across the structural components 2 of the working machine.

Fig.5 shows an excavator as an example of a work machine or construction machine.

In a known manner, a movable undercarriage 21 is provided on which an upper carriage 23 is mounted so as to be rotatable about a vertical axis of rotation Z.

On one side of the rotation axis Z, a boom 23 is provided as an excavator arm, while - opposite to the rotation axis Z - a counterweight 7 is attached. One or more drive components can be provided inside the counterweight 7 - as explained above.

In Fig.5 The engine compartment housing 13 and a machine frame 24 can also be seen.

Fig.6 shows another example of a working machine in the form of a wheel loader. The machine frame 24 is partially covered by covers in order to effectively protect it against contamination.

Claims (7)

1. Working machine, comprising

   - a drive device having an electric drive; and comprising

   - structural components (2) which are selected from the group

   + basic framework

   + machine frame (24)

   + chassis base plate

   + counterweight (7)

   + motor compartment housing (13)

   + running gear frame

   wherein

   - the electric drive comprises an electric motor (17) and heat-generating electric drive components (1); and wherein

   - at least one of the drive components (1) is attached to one of the structural components (2) such that the heat generated by the drive component (1) can be directed at least partially into the component (2);

   - the drive device comprises a hydraulic circuit which is driven by the electric drive in order to generate a driving movement and/or a working movement;

   - the hydraulic circuit comprises a cooling device having a fan (15) and a heat exchanger (14);

   - the fan (15) generates a cooling air flow (16) for the heat exchanger (14);

   - the cooling air flow (16) is guided upstream of the heat exchanger (14) such that it sweeps over a surface of the heat-generating drive component (1) and/or a surface of the structural component (2), to which the drive component (1) is attached;

   - an electric energy store (18) is provided for the electric drive and/or for the electric motor (17); and wherein

   - the cooling air flow (16) is guided upstream of the heat exchanger (14) such that it sweeps over the electric energy store (18);
   characterised in that

   - the structural component is a counterweight (7); and in that

   - a recess (8) is provided on an inner side of the counterweight (7), the heat-generating drive component (1) being inserted into the recess.
2. Working machine as claimed in claim 1, wherein

   - a contact surface (4) is provided between the drive component (1) and the structural component (2), to which the drive component (1) is attached; and wherein

   - increased heat transfer is possible via the contact surface (4), said increased heat transfer being larger than heat transfer via an air gap.
3. Working machine as claimed in claim 2, wherein a heat-conducting element (3) is arranged in the contact surface (4) between the drive component (1) and the structural component (2).
4. Working machine as claimed in claim 2 or 3, wherein the contact surface (4) amounts to at least 20 percent of the entire outer surface of the drive component (1).
5. Working machine as claimed in any one of the preceding claims, wherein

   - a motor compartment (12) is provided, having a motor compartment housing (13) in which the following components are accommodated:

   + electric motor (17)

   + fan (15) of the cooling device of the hydraulic circuit

   + energy store (18) for the electric drive

   + at least one of the heat-generating drive components (1)

   - a main inlet opening (19) for the cooling air flow is provided in the motor compartment housing (13); and wherein

   - the cooling air flow (16) is guided such that it flows through the motor compartment (12).
6. Working machine as claimed in claim 5, wherein, in addition to the main inlet opening (19), a motor cooling air opening (20) is provided in the motor compartment housing (13), via which cooling air enters the motor compartment (12) in a targeted manner for the electric motor (17).
7. Working machine as claimed in any one of the preceding claims, wherein

   - the structural component (2) comprises a hollow space which is filled with a fluid and/or through which a fluid can flow, said fluid absorbing heat from the structural component (2).

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