DE102009027857A1 - Electromechanical device e.g. starter, for internal-combustion engine of motor vehicle, has cooling device comprising heat reservoir with phase change materials that exhibit temperature in operating range of operating temperature - Google Patents

Abstract

The device has a device part heated at operating temperature during operation of the device and designed as a stator or a rotor. A cooling device (11) comprises a heat reservoir with phase change materials (13) for cooling the device, where the phase change materials exhibit phase conversion temperature in an operating range of the operating temperature. The heat reservoir comprises a closed container (12), and a heat pipe is arranged above a contact surface of the container. The phase change materials are metals such as tin, lead or bismuth, or metal alloys. An independent claim is also included for a method for operating an electromechanical device.

Description

State of the art

The The invention relates to an electromechanical device a device part resulting in the operation of the electromechanical Device heated to an operating temperature, and with a cooling device having a heat storage with a phase change material.

The The invention also relates to a method for operating the electromechanical device, wherein in a first step, a device part heated by the operation and in a second step at least for a time t the temperature of the device part by a heat absorption a heat storage kept substantially constant becomes.

Further The invention also relates to the use of the cooling device.

electrical Machines heat up mainly due to resistive Resistors and magnetically induced eddy currents and must be cooled to minimize the operating temperature be about to increase the efficiency of the machine or also limit the maximum temperature of individual components and to ensure a long service life.

It There are numerous cooling circuit arrangements and types of movement a coolant. Typically, the heat transfer by forced convection of the coolant, for example through a fan. The possible Volume flow of the coolant and thus also the effect of Fans increase with its diameter and its speed of rotation.

at very compact or low-speed machines Forced convection is often inadequate. An improvement in the Cooling efficiency, for example by means of liquid Refrigerant and heat exchanger or decoupling Of fan and machine drive, often fails due to of space requirements and cost aspects.

Machinery, the short heat cycles are exposed, such as electrical Starters, can be sized to the time constant the warming is greater than that of the Heat cycle. A big heat capacity The components are usually about the increase the component mass, ie at the expense of a weight reduction achieved.

It is known, phase transformation material in heat accumulators use, such materials at a phase transition Energy is so-called "latent heat" isothermal absorb or release.

The DE 1901221 describes a machine having a heating machine part that has a cavity with phase change material whose phase transition temperature is above a predetermined operating temperature and below a maximum allowable temperature. Thus, in the case of a brief high load of the machine, overheating is avoided by the loss of heat leading to the phase transformation of the phase change material and the heating of the machine part being limited by the phase transition temperature.

The EP 0208369 B1 describes a latent heat storage as a thermal insulation layer between a momentarily heated, heat-emitting component and an adjacent cooler, heat-sensitive area.

The EP 1343243 A1 describes the cooling of a generator with high-speed rotor by spraying with oil, whereby the cooling capacity is increased by the evaporation of the cooling oil.

The US 5,770,903 describes a reflux condenser for an electromechanical device operating with a continuously evaporating and re-condensing refrigerant. In order to ensure the coexistence of the liquid and gaseous phase of the coolant, the coolant is protected against overheating with a further, additional phase change material.

It Object of the invention, an electromechanical device and to provide a method of operating the same in or in which an extension of the component life allows becomes.

Disclosure of the invention

According to the invention the object by the subject of the claims 1 and 11 solved. The dependent claims define preferred developments of the invention.

It is an idea of the invention to utilize phase change material for cooling the electromechanical device when its phase transition temperature is in the operating range of the operating temperature, wherein at least one device part heats to at least that operating temperature during operation of the electromechanical device. In this case, the cooling device according to the invention cools at least the device part, wherein it has a heat accumulator with the phase change material to from the Vorrich receive heat emitted part, and leads quasi to an increase in the heat capacity of the device or the device part. The phase transition temperature is therefore not only below a maximum allowable temperature of the device part, but also in the temperature range, which is assumed in the regular operation of the device. Thus, the cooling device can also act in regular operation and thereby increase the component life.

Reached the device part when heating the phase transformation temperature, so will a further increase in temperature, especially at continuous Heat supply, at least as long prevented until the phase change material has completely completed the phase transition, so that for the duration of the phase transition the temperature of the device part by the heat absorption of the heat accumulator is kept substantially constant.

In order to allows the invention, the temperature rise of the device part to slow down, delay or even completely prevent if during the duration of the phase transition, approximately due to a subsequent operating state with lower power loss, the heat flow into the heat storage is stopped. This also reduces the maximum operating temperature both the device part and surrounding device parts. Consequently, the thermal load of components is reduced and their life extended.

Preferably is the electro-mechanical device for a cyclic Operation designed or operated cyclically. Under a cyclic operation is subsequently an operation with at least two cyclically repeating operating states, in which the device part each have different operating temperatures assumes, so in about two stages. It basically corresponds an operating state of the off state of the device and another state of full load operation, wherein a cyclic operation with only these two states is preferred.

at Such a cyclic operation also changes the operating temperature the device part cyclically, according to the invention itself heated the device part in a first step and then in a second step, the temperature of the device part the heat absorption of the heat storage substantially isothermal, ie kept constant, at least for a time t. During this time t is flowing Heat storage heat from the device part to and leads to a progressive phase transformation of the Phase change material.

Of the The device part heating operating state can also over stop the duration of the full phase transformation, so that the device part after keeping the temperature constant is further heated and the cooling device so leads to the said decrease in temperature rise. However, this warming condition is followed, possibly already before the complete phase transformation, ie during keeping the temperature constant, a subsequent operating state, which leads to a cooling of the device part. During this operating condition, the heat storage release the previously absorbed heat and can the phase change material perform a phase transformation in the opposite direction.

The Result is the slowing down of the temperature gradients and the Smoothing of temperature peaks in cycle mode. As consequence can the device for a higher number of Cycles are operated without exceeding a permissible maximum temperature. In addition, given a number of cycles, a lower maximum temperature be achieved, resulting in higher durability, durability and lower material requirement leads.

The Electromechanical device may be an electric machine, for example an electric motor, especially a compact powerful Motor, and the device part a housing part, a Rotor and / or comprise a stator.

Preferably is the electromechanical device as a starter, a generator or a combination of starter and generator, such as for an internal combustion engine of a motor vehicle.

The phase change material is preferably bound or included in a phase change material shell prior to, during, and after the phase transition, the shell serving to thermally bond the phase change material to the device portion. The phase transformation material may be chemically and / or physically bound in the shell, for example due to a molecular structure or a spongy structure of the shell. The melting temperature of the phase change material sheath must be sufficiently larger than the phase transition temperature of the phase change material to ensure sufficient strength of the structure. In addition, the phase change material sheath serves the thermal connection of the phase change material to the device part, wherein a connection to the temperature most sensitive components is preferred.

at In a preferred embodiment, the heat accumulator comprises a, preferably closed container with phase change material at the inside. The container can therefore be the case or else only part of the shell. So the cooling device, but at least the heat storage, independent from the electromechanical device and also for different ones Devices are made equally suitable.

Preferably has at least one wall of the container metal or is made of metal and can heat the wall as a heat pipe with the highest possible thermal conductivity for heat flow into or out of the phase change material. The melting temperature of the container is preferably above the phase transformation temperature of the phase change material and / or over the maximum permissible temperature of the device or the device part.

Of the Container is increasingly preferred in this order at least 50%, 75% or 90% of its volume filled with phase change material, so that the cooling device at a possible store small volumes of heat as much as possible can.

Of the Heat transfer between the device part and the heat storage can significantly by heat conduction, so negligible by convection or thermal radiation, done so that the Cooling device of simple mechanical construction can, wherein in a favorable embodiment the cooling device only from the container with phase change material consists.

Preferably the heat accumulator forms a heat conduction a contact surface of the container, which is connected to a heated surface of the device part adjacent. there is "adjoin" so to understand that the contact surface, preferably a container wall, by means of a heat conduction, such as a thermal paste or a heat conducting foil, or also directly, for example by pressing together by means of screwing, Welding, soldering or gluing, directly with the device or the device part can be connected to a good Heat conduction between contact surface and heated To allow area.

The Cooling device and / or the contact surface can be arranged inside the device and can adjoin an inner surface of the device. So the cooling device as close as possible be attached to a heat source and thus extend the life of components. Furthermore, the cooling device can be constructed in such a way that they do not have the outside dimensions of the device protrudes so that a compact design can be achieved. Especially even with a starter as a device, the cooling device preferably in the air space between rotor, windings and housing be installed.

Furthermore The cooling device may be at a during the operating moving part of the device, such as the rotor attached be. Such parts are conventionally difficult to cool, because heat due to a frictionless as possible Storage mostly bad due to heat conduction to the outside can be led or even a connection to a closed Coolant circuit is expensive. For the application on rotating parts, a phase change material can be used be whose volumetric expansion coefficient in the liquid Phase is greater than that of the solid phase. In addition, the sheath can be sufficiently stiff, so that the contact surface macroscopically uninterrupted and the phase change material, especially in the liquid Phase, bubble-free remains. So can the phase transformation material be macroscopically homogeneous at all times, such as the formation of dynamic Prevent imbalances.

Furthermore is particularly preferred that the phase change material in the phase transformation temperature is a phase transition between a solid and a liquid phase, so that unlike the transition to a gaseous Phase the smallest possible change in volume Phase transition occurs as solid and liquid Phase have approximately equal densities. So can the Container of the heat accumulator only low pressure loads exposed and, as shown above, with as much as possible Phase transformation material to be filled.

The Selection of phase transformation material is also provided by the Operating temperature determined. The phase transition temperature is in this order increasingly preferably at least about 30 ° C, 40 ° C, 50 ° C or 70 ° C and preferably over the ambient temperature of the device, in particular via the lowest of the operating temperatures during operation of the device with a plurality of operating states. Furthermore For example, the phase change temperature may increase in this order preferably at most about 400 ° C, 350 ° C, 300 ° C or 250 ° C and in particular under a maximum allowable maximum temperature of Device or the device part lie around this or surrounding components to protect against heat damage.

As the phase change material, the usual materials may be selected, for example, salts or paraffins. Preferably, a Metal or a metal alloy used as a phase change material whose solid-liquid phase transition can be at the aforementioned temperatures, can be adjusted by means of concentration ratios of the alloy components suitable phase transformation temperatures. For example, with soft solders, the melting temperatures can already be at temperatures of about 70 ° C to about 180 ° C and of course also higher. In this case or independently thereof, the phase transformation material may comprise at least one substance from the group tin, lead and bismuth. Generally, the phase change material is most suitable which has the largest heat capacity in the entire operating range and also the highest enthalpy of fusion.

It It is understood that the above and below to be explained features not only in the specified Combination, but also usable in other combinations.

Brief description of the drawings

The Invention will be described below with reference to the drawings explained in more detail. Show it:

1 a schematic representation of a cross section through a cooling device,

2 a schematic representation of an inventive electromechanical device with the cooling device,

3 a schematic representation of another electromechanical device according to the invention with a plurality of cooling devices and

4 a temperature profile of the operating temperature of a device part of an inventive electromechanical device in a cyclic operation.

The 1 shows a cooling device 11 using a heat accumulator with a metal alloy as the phase change material 13 , namely a soft solder with the main components tin and lead and with a melting temperature PCM-T of about 250 ° C, in a container 12 having. The cuboid container 12 is made of metal with a significantly higher melting temperature than that of the soft solder 13 made and is complete with the soft solder 13 filled. The container 12 may be adjacent to a heated surface of the device part with one or a plurality of its walls as contact surfaces.

The 2 shows a schematic representation of an inventive electromechanical device, namely an electric machine in the form of a starter 21 an internal combustion engine in a motor vehicle, with a cooling device 25 and a stator 22 , The cooling device 25 is a container filled with solder according to 1 attached to an outer surface of the starter housing 24 is welded, so that a container wall as a contact surface heat conduction to that through the stator 22 heated outside surface forms.

The starter 21 is designed for cyclic operation in the 4 will be explained in more detail, wherein the cyclic operation comprises a switched-on operating state A and a switched-off operating state B. When the operating state A is switched on, at least the stator heats up 22 due to ohmic power loss during current flow through a stator winding 23 and gives heat to the starter housing 24 which heats up in a first step, especially on the outer surface. In a second step, as in the 4 shown, the temperature of the starter housing 24 and thus also the stator 22 and the stator winding 23 in the operating range of the operating temperature T _e by the heat absorption of the heat accumulator of the cooling device 25 kept substantially constant.

The 3 shows a schematic representation of a device according to the invention, namely also a starter 31 an internal combustion engine in a motor vehicle. Unlike the one in the 2 Illustrated herein are a variety of cooling devices 35 . 36 . 37 . 38 according to 1 inside the starter 31 attached, including other combinations of cooling devices or even a single cooling device, and at the same time cooling devices inside and outside of the starter 31 are feasible. The in 3 shown starter 31 However, so experiences no increase in its external dimensions due to the cooling devices 35 . 36 . 37 . 38 and can directly a conventional starter without cooling device according to the invention 35 . 36 . 37 . 38 replace. Due to the material mix of stator, rotor and cooling device a reduction of the maximum component temperature at low weight is possible. The reduction of the temperature leads to improved efficiency, higher operating times, higher cycles and longer service life.

Incidentally, here have all the cooling facilities 35 . 36 . 37 . 38 same phase transformation material. However, different cooling devices with phase change materials of different phase transition temperatures PCM-T are also possible for different operating ranges of the operating temperatures of different device parts.

The cooling device 37 is on an inner surface of the starter housing 34 welded. The other cooling facilities 35 . 36 . 38 are in this example on moving parts, namely on the front of the rotor 32 , inside the rotor 32 or in the commutator 39 , attached, essentially by an electrical power loss in the rotor winding 33 heat. The containers of the heat storage are completely filled with phase change material to an imbalance in the rotational movement of these parts 32 . 33 . 39 to avoid.

The 4 shows comparatively the course of the operating temperatures T _e , T _{k of} an inventive electromechanical device (solid line), namely a starter of an internal combustion engine of a motor vehicle, and a conventional electromechanical device without inventive cooling device (dashed line) in a cyclic operation with the two operating states A, B are shown, wherein the switched-operating state A corresponds to a full-load operation of the respective starter. With the start of the switched-on operating state A, the operating temperatures T _e , T _{k of} both devices increase and the corresponding device parts heat up. Part of the energy is also released to the environment. Once the phase transition temperature PCM-T is reached, the phase transformation of the phase change material commences, so that the operating temperature T _{e of} the electromechanical device according to the invention for the phase transformation time t1, ie until complete phase transformation of all phase transformation material in the heat storage from the solid to the liquid phase, substantially constant is held and thereby delayed, while in the conventional device in this time t1, the operating temperature T _k continues to rise. As soon as the phase transformation has been completed, ie after the duration t1, the operating temperature T _{e of} the device according to the invention is kept constant and the operating temperature T _e continues to increase, provided that the switched-on operating state A continues. In this period, namely, until the time of the transition to the deactivated operating state B, the operating temperature T _{e of} the device according to the invention, however, is significantly lower than the operating temperature T _{k of} the conventional device. Likewise, the maximum operating temperature T _{e, max of} the device _{according to} the invention is well below the maximum operating temperature T _{k, max of} the conventional device. Thus, the thermal load of the device or the device parts can be reduced and their life can be extended.

During the switched-off operating state B no further heat supply takes place and the heat stored in the device and also in the heat accumulator is emitted above the phase transition temperature accompanied by a cooling of the devices, in particular to their surroundings. When the phase transition temperature PCM-T is reached, the operating temperature T _{e of} the device according to the invention remains constant for the duration t 2 of the phase transformation, now from the liquid to the solid phase. After the release of the latent heat from the heat storage, the operating temperatures T _e , T _{k of} the invention as well as the conventional device continue to decrease, approximately to the respective ambient temperature and / or until the next onset of the switched-on operating state A.

The 4 clearly shows that a delayed increase in temperature and also a lower maximum temperature T _{e, max are} achieved by the phase change material, in particular in a regular cyclical operation of the device. There are 4 the temperature profile of a starter with a cooling device with tin as a phase change material again and is the isothermal heat storage duration, ie the duration t1 of the phase transformation, several seconds and the reduction of the maximum temperature several tens of Kelvin.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 1901221 [0009]
• EP 0208369 B1 [0010]
• - EP 1343243 A1 [0011]
• US 5770903 [0012]

Claims (13)

Electromechanical device ( 21 . 31 ) with a device part ( 22 . 32 ), which occurs during operation of the electromechanical device ( 21 . 31 ) is heated to an operating temperature (T _e ), and with a cooling device ( 25 . 35 . 36 . 37 . 38 ) having a heat storage with a phase change material, characterized in that the phase change material has a phase change temperature (PCM-T) in the operating range of the operating temperature (T _e ). Electromechanical device ( 21 . 31 ) according to claim 1, characterized in that the device is designed for cyclic operation. Electromechanical device ( 21 . 31 ) according to one or more of the preceding claims, characterized in that the device ( 21 . 31 ) an electric machine and the device part a rotor ( 32 ) and / or a stator ( 22 ). Electromechanical device ( 21 . 31 ), characterized in that the device ( 21 . 31 ) is designed as a starter, a generator or a combination of starter and generator. Electromechanical device ( 21 . 31 ) according to one or more of the preceding claims, characterized in that the heat accumulator a closed container ( 12 ) with phase transformation material ( 13 ) in the interior and a heat conduction over a contact surface of the container, which contact surface to a heated surface of the device part ( 32 ) is adjacent, is formed. Electromechanical device ( 31 ) according to claim 5, characterized in that the contact surface to an inner surface of the electromechanical device ( 31 ) adjoins. Electromechanical device ( 21 . 31 ) according to one or more of the preceding claims, characterized in that the phase change material at the phase transition temperature (PCM-T) has a phase transition between a solid and a liquid phase. Electromechanical device ( 21 . 31 ) according to one or more of the preceding claims, characterized in that the phase transition temperature (PCM-T) is at least about 30 ° C and / or at most about 400 ° C. Electromechanical device ( 21 . 31 ) according to one or more of the preceding claims, characterized in that the phase change material is a metal or a metal alloy. Electromechanical device ( 21 . 31 ) according to one or more of the preceding claims, characterized in that the phase-change material comprises at least one substance from the group tin, lead and bismuth. Method for operating an electromechanical device ( 21 . 31 ), in particular according to one or more of claims 1 to 10, in which a device part ( 22 . 32 ) is heated by the operation and the operating temperature (T _e ) of the device part ( 22 . 32 ) is kept substantially constant by a heat absorption of a heat accumulator, characterized in that the electromechanical device ( 21 . 31 ) is cyclically operated. A method according to claim 11, characterized in that after keeping constant the operating temperature (T _e ), the device part ( 22 . 32 ) is further heated by the operation. Use of a cooling device having a heat accumulator with a phase change material for cooling an electromechanical device ( 21 . 31 ) according to one or more of claims 1 to 10.

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