KR20180061207A - An assembly having a drive unit and a cooling unit - Google Patents

Abstract

The present invention relates to a frequency converter having a cooling section for an electric motor for driving a hydrostatic pump. Cooling is effected by the working pressure medium delivered by the pump. The channel of the cooling section may form part of the hydraulic circuit supplied by the pump, or the working pressure medium may be taken out of the tank and sent out to a separate cooling circuit line.

Description

An assembly having a drive unit and a cooling unit

The present invention relates to a drive unit comprising a hydrostatic pump, an electric motor and a frequency converter to be cooled. The invention also relates to an assembly comprising such a drive unit.

Prior art discloses driving a static pressure pump for supplying to a hydraulic consumer, for example, a motor or a cylinder, through an oil hydraulic circuit by an electric motor. A frequency converter is provided between the power supply and the electric motor, and the frequency converter generates waste heat. Most of the waste heat is generated in the power electronics or in the bipolar transistor (s) (IGBT) with insulated gate electrodes and in the rectifier. In order to optimally transfer the waste heat to the heat sink, the frequency converter or the IGBT and / or the rectifier are mostly screwed directly onto the heat sink. The heat sink is made of a material having a high thermal conductivity, for example, aluminum. A thermally conductive paste is provided between the frequency converter or IGBTs and / or the rectifier and the heat sink for optimization of heat transfer.

The additional waste heat is generated in the additional capacitor in the inner chamber of the frequency converter. Since such waste heat is very small, there is no need for cooling by a heat sink. The waste heat is transferred to ambient air by natural convection or by forced convection using a housing fan.

As an alternative, the prior art discloses that a special cooling liquid, for example water, is passed through the heat sink. Which is guided through a bore or recess in the inner chamber of the heat sink. Even in the case of a water-cooled heat sink, the IGBT and / or the rectifier can be screwed directly to the heat sink using a thermally conductive paste, so that good heat transfer can be achieved. Heat sinks, including water cooled parts, have greater cooling power due to higher heat transfer or higher heat capacity of most of the water.

A drawback of such a drive unit comprising an electric motor with a frequency converter that is cooled with a water-cooled heat sink is the device technology complexity of the water circuit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an assembly and a drive unit with a cooling section with reduced cooling capacity of the water-cooled section and reduced device technical complexity.

This problem is solved by a drive unit comprising a pump, an electric motor and a cooled frequency converter having the features of claim 1. [

The drive unit according to the invention comprises an electric motor, which can be connected to or preferably connected to the pump for driving a static pressure pump. The electric motor is electrically connected to the frequency converter, and the frequency converter is cooled by the cooling device. The cooling device can be cooled by an operating pressure medium, and in particular can be perfused, and said working pressure medium is located directly in an operating circuit which is actuated by a pump, or at least obtained in said operating circuit.

The problem is also solved by an assembly having a static pressure pump which can be driven by an electric motor electrically connected to a frequency converter cooled by a cooling device. The cooling device can be cooled by an operating pressure medium, and in particular can be perfused, and the working pressure medium is located in at least an operating circuit which is actuated by a pump, or at least obtained in the operating circuit.

By cooling the frequency converter with an operating pressure medium in accordance with the invention, a technically simple but effective cooling of the frequency converter and in particular of the bipolar transistor (IGBT) and / or rectifier with the power electronics of the frequency converter and the insulated gate electrode No special coolant circuit with special coolant is needed in this case.

If the working pressure medium is a hydraulic oil, its corrosion inhibiting effect can be utilized.

Other preferred embodiments of the invention are described in the dependent claims.

If the frequency converter comprises a housing, protection against dust and / or splashes and / or an increase in the degree of protection can be achieved. That is, a protection degree of at least IP54 can be realized.

Moreover, in an improvement including, in particular, housing, the frequency converter is not to be placed in the switch cabinet, but can be spatially assigned to the drive unit according to the invention or to the assembly according to the invention. Thus, a modular, more compact drive unit or modular compact assembly can be formed. In addition, the frequency converter discharges its waste heat into the switch cabinet, and the switch cabinet is prevented from having to be cooled again complicatedly.

Preferably, a bipolar transistor (IGBT) and / or a rectifier having a maximum heat generating section of the frequency converter, for example a power electronics or an insulated gate electrode, is arranged directly adjacent to the heat sink.

The heat sink may be a cold plate or a cold plate in the preferred embodiment. The plate can be in the form of a disc, so that if the tank and the housing are cylindrical, a compact assembly can be formed.

An internal cooling water channel may be additionally provided in accordance with the first improvement example for the release of the heat absorbed by the heat sink.

Another disk and at least one fan or ventilator may be provided in accordance with the second improvement example to release the heat absorbed by the heat sink to ambient air. The heat generated by the electric motor through other discs can also be released to ambient air.

Preferably, the frequency converter is fixed in a heat conducting manner (for example with a thermally conductive paste provided therebetween) in the region of the heat sink, and in this region a channel for the working pressure medium is also inserted in the heat sink. The wall thickness between the channel and the frequency converter or IGBT and / or rectifier shall be minimum.

In a particularly preferred first variant of the drive unit according to the invention the channel for the working pressure medium forms at least one section of the return line of the circuit and the consumer can be supplied by the pump through said section. In a corresponding particularly preferred first variant of the assembly according to the invention, the channel for the working pressure medium forms at least one section of the return line from the low pressure side consumer connection of the assembly towards the tank of the assembly.

In a second preferred variant of the drive unit according to the invention, the channel for the working pressure medium forms at least one section of the suction line arranged upstream of the pump. In a correspondingly preferred second variant of the assembly according to the invention, the channel for the working pressure medium forms at least one section of the suction line arranged upstream of the pump connecting the tank to the pump.

In a third preferred variant of the drive unit according to the invention the channel for the working pressure medium forms at least one section of the supply line or pressure line arranged downstream of the pump. In a correspondingly preferred third variant of the assembly according to the invention, the channel for the working pressure medium is arranged downstream of the pump to form at least one section of the supply line or pressure line connecting the pump to the high pressure side consumer connection.

In a fourth preferred variant of the assembly according to the invention, the channel for the working pressure medium forms at least one section of a separate cooling circuit line or bypass connected to the tank at the input side and at the output side.

In this case, the cooling circuit line or the piping may comprise a cooling pump and / or a filter and / or an oil cooler. The oil cooler may be an oil-air heat exchanger.

In a particularly preferred refinement, the assembly is a compact assembly, in which the frequency converter is fixed to the first side (upper side) of the cooling plate while the electric motor is fixed to the second side (lower side) of the cooling plate.

If the housing for the frequency converter is disposed on the first side, protection against dust and / or splashes and / or an increase in the degree of protection can be achieved. Further, the housing may be formed such that the air of the fan is guided through the disk pack and the side discharge of the air is blocked.

In this case, the pumps may be arranged in the region of the second side (lower surface) - preferably on the side of the electric motor remote from the cooling plate.

In this case, the tank may be disposed in the area of the second surface (lower surface).

In a particularly preferred embodiment of the compact assembly, the tank completely surrounds the electric motor and / or the pump.

Preferably the tank has a bottom in the form of a circular ring formed integrally with the wall and is closed by a cooling plate.

It is particularly preferred that a disk thermally connected to the cooling plate through a heat pipe is disposed inside the tank to cool the working pressure medium that has absorbed the waste heat of the frequency converter according to the present invention. The pressure medium may flow through the disk upon entry into the tank, and may in particular emit pre-absorbed heat by a frequency converter.

If the cooling plate, the electric motor, the pump and the tank of the compact assembly are concentric to each other, this is desirable for design and manufacturing reasons.

The assembly may include a frequency adjuster. In this case, the pressure in the feed line or pressure line is measured by a pressure sensor, and the signal can be delivered to a frequency converter with an integrated PID-regulator for constant pressure regulation. The frequency converter adjusts the frequency of the power supply of the electric motor. Thereby, it is achieved that the pressure inside the supply line is kept constant in accordance with the volume flow rate in the supply line determined by the hydraulic system. For example, if the consumer requires more volumetric flow because the hydraulic cylinder must travel very quickly, the frequency converter will accelerate the electric motor according to the regulating circuit (pressure sensor-frequency converter-motor-pump) .

A number of embodiments of an assembly according to the present invention including a drive unit according to the present invention are shown in the drawings. The present invention will be described in detail with reference to the drawings.

1 is a circuit diagram of an assembly according to the invention according to the first embodiment;
2 is a circuit diagram of an assembly according to the present invention according to a second embodiment;
3 is a circuit diagram of an assembly according to the invention in accordance with the third embodiment;
4 is a circuit diagram of an assembly according to the invention in accordance with the fourth embodiment;
Figure 5 is a cross-sectional perspective view of the assembly of Figure 1;

Figure 1 shows a circuit diagram of an assembly according to the invention according to the first embodiment. The assembly includes a drive unit having an electric motor (M) and a static pressure pump (1). The electric motor (M) of the drive unit is operated by the frequency converter (2). The assembly also includes a pressure medium, for example a tank T for hydraulic oil.

Since the frequency converter 2 is connected between the power supply 4 and the electric line 6, the electric motor M is supplied with electric power through the electric line 6 in the frequency control mode and the rotational speed control mode. The pump 1 is driven by the electric motor M via the shaft 8 to vary the rotational speed. The pump 1 draws the pressure medium from the tank T through the suction line 10 and sends the pressure medium through the supply line 12 to the high pressure side consumer connection 14 of the assembly. A consumer is connected to the consumer connection 14 through a valve, and the consumer may be, for example, a cylinder. The consumer is only shown symbolically with the valves and is indicated at 16.

Pressure medium through the low pressure side consumer connection 18 back into the assembly from the consumer 16. More precisely, the pressure medium flows from the consumer connection 18 to the tank T via return line 20.

According to the invention, the return line 20 is formed entirely or partially by the channel 22, which is formed in the interior of the cooling plate 24. The frequency converter 4 is connected to the cooling plate 24 so that the power electronics 28 is placed in the immediate vicinity of the cooling plate 24 and in particular the channel 22 with a bipolar transistor (IGBT) Threaded. In the first embodiment according to FIG. 1, the frequency converter 2 and in particular the power electronics 28 of the frequency converter are cooled by an operating pressure medium flowing back from the consumer 16.

The frequency converter 2 and the power electronics 28 of the frequency converter comprise a housing 26 and the housing is connected to the cooling plate 24 in a sealing manner as far as possible so that a degree of protection IP54 is achieved.

In the first embodiment according to Fig. 1, a constant pressure regulation is achieved. To this end, a supply line 12 is provided with a pressure sensor 30, and the signal of the pressure sensor is transmitted to the frequency converter 2 via a signal line. The frequency converter adjusts the frequency for the electric line (6) and the electric motor (M) according to the pressure signal.

Figure 2 shows a circuit diagram of an assembly according to the invention in accordance with the second embodiment. 1 is that the channel 22 formed in the cooling plate 24 forms a section of the feed line 12 or of the feed line 12. In this case, This allows the frequency converter 2 and in particular the power electronics 28 of the frequency converter to be cooled by the pressure medium and the pressure medium from the pump 1 to the high pressure side consumer connection 14 and through the valves to the consumer The drawing candidates 16 of FIG.

Figure 3 shows a circuit diagram of a third embodiment of an assembly according to the invention. The crucial difference with the two preceding embodiments in this case is that the channel 22 formed in the cooling plate 24 forms a section of the suction line 10 or of the suction line 10, T is connected to the input of the pump 1. Whereby the frequency converter 2 and in particular the power electronics 28 of the frequency converter are cooled by the pressure medium and the pressure medium flows from the tank T towards the pump 1.

In the first three embodiments according to Figs. 1 to 3, the frequency changer 2 is respectively cooled by the pressure medium flowing directly in the operating circuit of the assembly according to the invention, while in the fourth embodiment Basically offers a different solution. More precisely, there is provided a special cooling circuit 30 with a special drive unit for the cooling circuit 30, the drive unit consisting of an electric motor and a pump. The pump of the drive unit 32 sucks the pressure medium used for cooling the frequency converter 2 and the power electronics 28 of the frequency converter directly from the tank T and directly returns the pressure medium to the tank T). In this case the pressure medium is fed from the pump of the drive unit 32 first through the heat exchanger 34 and then through the filter 36 and finally through the frequency converter 2 and especially to the power electronics of the frequency converter 28 flow through the channel 22 of the fixed cooling plate 24.

Figure 5 shows the structural configuration of the compact assembly of Figure 1 in a cross-sectional perspective view. The assembly has a generally cylindrical periphery, in which case a disc cooling plate 24 is provided in the central region. The long frequency converter 2 with the power electronics 28 is fixed on the first side (upper side in Fig. 5) of the cooling plate 24. From the low pressure side consumer connection 18 to the return filter 38 within the cooling plate 24 along the long side of the frequency converter 2 where the frequency converter 2 contacts the cooling plate 24, And the returning pressure medium absorbs the waste heat of the frequency converter 2, and in particular the power electronics 28 of the frequency converter, when the channel is perfused.

An electric motor M is disposed concentrically with the damping member 40 on the second side of the cooling plate 24 (the lower side in Fig. 5), and the surface of the electric motor remote from the damping member 40 A pump (1) is disposed. The drive unit composed of the electric motor M and the pump 1 is surrounded by the tank T concentrically on the outer periphery and the tank is fixed to the second surface of the cooling plate 24 . In this case, the cooling plate 24 closes the end surface of the tank T while the other end surface of the tank T is closed by a disk-shaped bottom 42 formed integrally with the two cylindrical walls.

Two disk packs 44 opposed to each other are provided in the interior of the tank T and only one of the disk packs 44 is shown in FIG. Each disk pack 44 is made up of a number of individual disks in approximately semicircular form. The disks of each disk pack 44 are thermally connected to the other disk packs 48 provided on the first side (top surface in FIG. 5) of the cooling plate 24 through a plurality of heat pipes 46 .

The pressure medium flowing back from the low pressure side consumer connection 18 flows through the channel 22 of the cooling plate 24 and absorbs the waste heat of the frequency converter 2 and especially the power electronics 28 of the frequency converter. The pressure medium then flows along the gravity through the two disk packs 44 toward the bottom 42 of the tank T and in this case releases the heat to the two disk packs 44. Heat is guided from the two disk packs 44 to the upper surface of the cooling plate 24 toward the other disk pack 48 through the heat pipe 46 and the other disk pack emits heat to the ambient air .

The drive unit is disposed in the center of the compact assembly. The drive unit is surrounded by a tank T containing a pressure medium. The cover of the tank T is embodied as a cooling plate 24. The cooling plate 24 is made of a good thermally conductive material, such as aluminum.

A frequency converter (2) is installed on the cooling plate (24). Since the frequency converter 2 used here has only the degree of protection IP22, the frequency converter is surrounded by the housing 26. [ The housing raises the protection rating for the frequency converter to> IP54.

The countercurrent pressure medium is here cooled by the heat pipe cooling section. The heat pipe cooling section comprises a disk pack 44, which penetrates the tank T and absorbs the thermal energy of the pressure medium. The heat pipe 44 is preferably implemented as a thermal siphon and conveys the heat energy to another disk pack 48 against gravity, and the other disk pack releases heat to ambient air. Additional fans (not shown) are installed to increase heat transfer from the other disk pack 48 to ambient air.

Even though the cooling plate 24 is made of a good thermally conductive material, for example aluminum, the thermal resistance of the frequency converter 2 can be too large (from the IGBT through the cooling plate 24 toward the heat pipe and finally Thermal resistance toward external disk pack 48). Therefore, in order to absorb and discharge the heat energy of the frequency converter 2, a reverse flow medium is used. The returning pressure medium flows through the cooling plate 24 (from the right in FIG. 5) into the channel 22 in the lower face of the frequency converter 2 and into the return filter 38 incorporated in the cooling plate 24 do. The return filter 38 may not necessarily be installed and the pressure medium may reach the tank T from above immediately after the perfusion of the cooling plate 24. [

The electric motor M is also cooled by the heat pipe cooling section. The bores are integrated in the housing of the electric motor in the gravitational direction, and a heat pipe (not shown) is inserted into the bore in a favorable thermal conduction manner, for example using a thermally conductive paste. The heat pipe conveys the thermal energy of the electric motor (M) to another disk pack (50), where the heat energy is released to ambient air.

The channel 22 for the pressure medium, preferably countercurrent, is very close to the power electronics 28 (IGBT) of the frequency converter 2. As a result, the thermal resistance is further reduced, the cooling power is increased, or the overheat of the frequency converter 2 is prevented.

A frequency converter having a cooling section for an electric motor for driving a static pressure pump is described. Cooling is effected by the working pressure medium delivered by the pump. In this case, the channel of the cooling section may form part of the hydraulic circuit supplied by the pump, or the working pressure medium may be obtained from the tank and sent out to a separate cooling circuit line.

1 pump
2 frequency converter
4 Power Supply
6 Electric line
8 shafts
10 Suction line
12 supply lines
14 High-voltage side consumer connection
Consumer with 16 valves
18 Low-voltage side consumer connection
20 return line
22 channels
24 cooling plate
26 Housing
28 Power electronics
30 Pressure sensor
31 Cooling circuit
32 drive unit
34 Heat exchanger
36 filters
38 return filter
40 damping member
42 floor
44 disk pack
46 heat pipes
48 different disk packs
50 different disk packs
M electric motor
T tank

Claims (16)

A drive unit comprising an electric motor (M), the electric motor being connected to the static pressure pump for driving a hydrostatic pump (1), the electric motor (M) being electrically connected to the frequency converter And the frequency converter is cooled by a heat sink cooled by a cooling liquid,
Wherein the cooling liquid is an operating pressure medium of the pump (1). The drive unit according to claim 1, characterized in that the frequency converter (2) comprises a housing (26). A drive unit according to claim 1 or 2, wherein the heat sink is a cooling plate (24). 4. The drive unit according to any one of claims 1 to 3, wherein the heat sink comprises an internal cooling water channel. 5. A drive unit according to any one of claims 1 to 4, characterized in that the disks (48, 50) and at least one fan are arranged on the heat sink. 6. A drive unit according to any one of claims 1 to 5, characterized in that a channel (22) for the working pressure medium is provided in the heat sink and the channel forms a return line (20). 6. A pump according to any one of the preceding claims, characterized in that a channel (22) for said working pressure medium is provided in said heat sink and said channel forms a suction line (10) for said pump . 6. A pump according to any one of the preceding claims, wherein a channel (22) is provided in the heat sink for an operating pressure medium, the channel forming a supply line (12) disposed downstream of the pump And the drive unit. An assembly comprising a drive unit according to any one of claims 1 to 5, wherein a channel (22) for an operating pressure medium is provided in a heat sink, said channel forming a line of the cooling circuit (31) Wherein the cooling circuit is connected to the tank (T) at an input side and an output side. 10. The assembly according to claim 9, wherein the cooling circuit (31) comprises a cooling pump and / or a heat exchanger (34) and / or a filter (36). An assembly comprising a drive unit according to claim 3 or claims cited therein, wherein the assembly is a compact assembly, a frequency converter (2) is fixed on a first side of the cooling plate (24) Wherein an electric motor (M) is fixed to a second side of the assembly. 12. The assembly according to claim 11, wherein the cooling plate (24) is cooled by an operating pressure medium and the working pressure medium flows back into the tank (T) via a return filter (38). 13. An assembly according to claim 11 or 12, characterized in that the pump (1) is arranged on the second side. 14. The assembly according to any one of claims 11 to 13, wherein a tank (T) is disposed on the second surface. 15. The assembly according to claim 14, wherein the tank (T) completely surrounds the electric motor (M) and / or the pump (1). A system according to claim 14 or 15, characterized in that the disks (44) are arranged inside the tank (T) and the disks are connected to the cooling plate by a heat pipe (46) and / ≪ / RTI >

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