EP2520779A2 - Cooling medium circuit - Google Patents

Abstract

The coolant circuit (1) has a heat accumulator (12) by which the cold coolant is heated. The heat accumulator with the coolant is operated as a storage medium and is designed such that the storage temperature of the charged heat accumulator lies above the operating temperature of the coolant circuit. The heat accumulator is bypassed a bypass line and is provided with an electric heater (14). The coolant is water or glycol mixture.

Description

The invention relates to a coolant circuit of a drive according to the preamble of patent claim 1.

In modern internal combustion engines and also in alternative drive concepts, such as hybrid drives and electric drives, there is a problem in that only very little or virtually no heat loss arises, which can be used in particular for conditioning the vehicle interior in winter. In addition, there is still the requirement for internal combustion engines and hybrid drives to bring the engine as soon as possible to operating temperature during a cold start, so that on the one hand the wear and on the other hand the pollutant emissions and fuel consumption is minimized. This problem occurs especially in short-haul traffic, where modern machines can not reach the optimum operating temperature. In short-haul traffic and also in normal operation does not generate enough power loss to bring the coolant circuit of the vehicle to operating temperature. In modern engines, therefore, the lack of power loss is compensated by targeted supply of heat energy. Known here are so-called "Zuheizer", as described by the applicant, for example in the EP 0 350 528 B1 are described.

In the DE 42 35 883 A1 and the EP 0 214 517 A2 In each case, a coolant circuit for an internal combustion engine is described in which a latent heat accumulator is charged via the cooling water. This is - similar to a thermos - so well insulated that it can hold the stored heat energy for a long time, for example, over a period of several days. These latent heat storage consist of a material, such as a salt, which is liquid at the normal operating temperature of the engine and in the range of phase change temperature, for example, a temperature of 60 - 90 ° C, solidifies (Phase Change Material (PCM)). By cooling this melt, the released phase transformation or crystallization enthalpy can be used to change the heat exchange Medium, for example, the cooling water to heat up. When the engine is cold-starting, the cooling water is in heat exchange with the latent heat storage, so that the liquid material is cooled and finally crystallized, using the heat released to heat the cooling water, so that it can be brought to operating temperature. When the coolant circuit is heated, the latent heat accumulator is then charged again so that it is ready for the next cold start.

Such solutions contribute to the reduction of pollutant emissions and wear during cold start, but especially in short-haul traffic, the power loss of the engine is not sufficient to charge the latent heat storage and to exceed the phase change temperature. Another disadvantage of such latent heat storage is that the conversion of the liquid phase into the crystalline phase takes a relatively long time, so that the above-described heating of the cooling water may take several minutes due to the low heat transfer rate. When using paraffins as PCM, this heat transfer rate can be improved, but the thermal conductivity of this material is relatively low, so further measures to improve the heat transfer rate must be provided. Thus, the thermal diffusivity can be improved, for example, by a matrix of highly thermally conductive material, for example a graphite composite material in the PCM - however, such latent heat accumulators are very expensive due to their complex construction.

In the EP 0 791 497 A2 In general, a coolant circuit is described in which an unspecified heat accumulator can be charged via an electric heater, this heater is provided with a connection for an external power source, such as charging the heat accumulator and heating the coolant circuit before the start of the drive is possible.

In the DE 10 2008 015 283 B3 is a coolant circuit disclosed in the cold start of the vehicle, first a "small" coolant circuit is heated and then switched to a large coolant circuit. This heating can take place via a heater which can be activated when the drive is switched off.

The DE 103 44 018 A1 describes a coolant circuit in which the entire coolant is conveyed when switching off the drive in a so-called hot water tank, from which the coolant is returned when starting the drive in the coolant circuit.

Although these solutions allow in principle the heating of the coolant circuit before starting the drive, the device and control technical effort required for this purpose is relatively high.

In contrast, the present invention seeks to provide a coolant circuit of a drive, which can be brought to operating temperature with relatively little effort and in a short time.

This object is achieved by a coolant circuit of a drive having the features of patent claim 1.

Advantageous developments of the invention are the subject of the dependent claims.

According to the invention, the coolant circuit of a drive, such as an internal combustion engine, an electric drive or a hybrid drive, a heat storage, can be heated by the cold coolant by heat exchange to operating temperature. The heat storage is designed with the coolant itself as a storage medium, the storage temperature with charged heat storage is above the operating temperature of the coolant circuit.

The invention thus turns away from conventional solutions in which complex PCM materials are used as the storage medium. The use of the coolant as a storage medium reduces the device complexity considerably. By compared to the operating temperature higher storage temperature of the storage medium, the heat transfer rate can be significantly improved due to the larger temperature gradient compared to the solutions described above, in which the coolant is stored at operating temperature. One Another advantage is that even with a longer standstill of the drive and even with the best insulation inevitable drop in the storage temperature of the storage medium over the conventional solutions significantly longer time a sufficient temperature difference is present, which can be used for heat exchange with the coolant.

According to the invention it is preferred if the heat accumulator can be bypassed via a bypass channel, which can be brought via a valve arrangement in fluid communication with the heat accumulator or against this shut off. In this way, the heat storage can be thermodynamically switched on, for example, in a cold start of the drive, so that the coolant can be brought to operating temperature very quickly.

In order to heat the storage medium in the heat storage to a storage temperature which is above the operating temperature of the coolant circuit, the heat storage is preferably carried out with an electric heater.

This electric heater can also be used to prevent a drop in temperature in the heat storage at a longer shutdown of the drive.

In an energetically very advantageous solution of the invention, the heating via an electrical machine, such as a generator, supplied with energy, which is designed such that during operation released kinetic energy, such as braking energy, is convertible into electrical energy for operating the heater.

The heater can also be provided with a connection, so that the heat storage is charged externally, for example, overnight.

The structure of the coolant circuit is particularly compact when the heater is integrated in the heat accumulator.

In one embodiment, it is provided that the operating temperature is below 100 ° C, for example, at about 95 ° C, while the "excessive" storage temperature is in the range of more than 120 ° C, for example at 130 ° C. This temperature difference is particularly well suited for a coolant circuit in which a water / glycol mixture is used as the coolant. In such a coolant significantly higher temperatures (> 160 ° C) should be avoided, since then the water / glycol mixture can decompose. In principle, however, it is also possible to use other coolants that are stable even at higher temperatures. At such high temperatures, however, care must be taken that evaporation of the coolant in the actual coolant circuit is prevented - this can be controlled for example by appropriate design of the thermal resistance of the heat transfer from the coolant in the heat storage to the coolant in the actual coolant circuit.

In a further embodiment, it is provided that the "excessive" storage temperature is in a range of more than 130 ° C, but below the decomposition temperature. Advantage here is the larger storable amount of energy. However, the heat accumulator must then be decoupled from the "rest" of the coolant circuit due to the resulting increased system pressure, which can be up to 8 bar. This decoupling is possible for example by suitable valves. For this system must then be provided for the emptying of the memory, a controlled pressure equalization between the storage tank and the coolant circuit to avoid vapor bubbles when relaxing.

To avoid vapor bubbles in the heat storage in the supply of electrical heating energy, this may be provided with a circulation pump through which a partial flow of the refrigerant withdrawn at the outlet of the heat accumulator and conveyed back to the input - in this way a uniform heating of the storage medium is ensured.

In one embodiment of the invention, the heat accumulator is arranged in the coolant circuit between a radiator and the drive.

• Figur 1 ein Blockschaubild eines ersten Ausführungsbeispiels eines Kühlmittelkreislaufs;
• Figur 2 ein Blockschaubild eines Kühlmittelkreislaufs, bei dem der Wärmespeicher über einen Bypass umgehbar ist und
• Figur 3 ein Blockschaubild eines Kühlmittelkreislaufs mit einer Umlaufpumpe.

Preferred embodiments of the invention are explained below with reference to schematic drawings. Show it:

• FIG. 1 a block diagram of a first embodiment of a coolant circuit;
• FIG. 2 a block diagram of a coolant circuit in which the heat storage is bypassed by a bypass and
• FIG. 3 a block diagram of a refrigerant circuit with a circulation pump.

FIG. 1 shows an extremely simplified block diagram of a coolant circuit 1 of an internal combustion engine 2. Here, a water / glycol mixture is used as the coolant. The heated by the engine 2 coolant can according to FIG. 1 be used to increase the vehicle interior temperature via an interior heating. In this case, the heated in the engine 2 to its operating temperature of about 95 ° C coolant is fed to a heat exchanger 4 an air conditioner to heat the vehicle interior to be supplied air. The slightly cooled after this heat exchange with the vehicle interior air coolant is supplied downstream of the heat exchanger 4 a cooler 6 and cooled there, for example, by wind and / or a fan. The cooler 6 can be bypassed during cold start of the engine by means of a bypass line 8, which can be opened or closed via a bypass valve 10. When cold starting the engine, the radiator 6 is bypassed by controlling the bypass line 8, so that the coolant can be brought to operating temperature as quickly as possible.

In the illustrated embodiment, the bypass valve 10 is designed as a 3-way valve, in principle, of course, another valve arrangement with valves upstream and / or downstream of the radiator 6 can be used.

Downstream of the radiator 6, a heat accumulator 12 is provided according to the invention, the concrete structure of which is explained in a parallel patent application of the applicant. A special feature of this heat accumulator 12 is that as Storage medium, the coolant itself is used, which is heated with charged heat storage 12 to a temperature above the operating temperature. This heating can be done for example via an electric heater 14. This may for example be a heating cartridge or the like, which heats the storage medium - in the present case the coolant - in the heat accumulator 12. This is designed with a very good thermal insulation, which ensures that the stored heat is maintained even with a longer standstill of the vehicle.

To power the heater 14, for example, a generator 15 may be provided which has a much higher power output than conventional generators and in cooperation with electrical energy storage, not shown, provides the required electrical energy. Such a generator does not have to be driven directly by the internal combustion engine, but can be coupled to the outlet of a transmission, so that, for example, during "sailing" with the combustion engine disengaged, the generator 15 is driven via the wheels of the vehicle. Such a circuit also makes it possible to drive the generator 15 when braking the vehicle via the recuperation of braking energy, so that the energy consumption for driving the vehicle can be considerably reduced. By interacting with a start-stop mode and the drive of the generator during the operating modes "braking" (recuperation) and "sailing" the energy emitted in conventional concepts only as heat loss to supply the electrical loads, in particular the heater 14 can be used. In this case, the generator 15 supports the actual brake system during the braking process, so that the braking performance is improved.

The coolant circuit 1 further has a coolant pump 16, via which the coolant in the coolant circuit 1 is circulated.

In a cold start of the internal combustion engine 2, the bypass valve 10 is turned on, so that the radiator 6 is bypassed. The circulated by the coolant pump 16 coolant is brought by heat exchange or admixture with the coolant in the heat storage 12 very quickly to operating temperature, so accordingly Also, the internal combustion engine 2 reaches its operating temperature in a very short time and thus pollutant emissions and excessive wear can be prevented.

In principle, it is also possible to charge the heat accumulator 12 to temperatures above 130.degree. This results in an increased pressure. For heat exchange with the coolant in the coolant circuit then appropriate measures would have to be taken to relax the coolant when emptying the heat accumulator 12. As explained above, in such a variant suitable means must be provided for decoupling the pressure-operated heat accumulator, which is elevated in relation to the coolant circuit, and for releasing the coolant received in the accumulator at elevated pressure, so that a pressure equalization with the coolant takes place in the actual coolant circuit. In the simplest case, the pressure build-up in the heat accumulator takes place due to the temperature increase of the coolant in the heat accumulator 12. In thermodynamic connection of the heat accumulator with the actual coolant circuit then the pressurized pressure medium must be relaxed via suitable throttles or the like.

After conventional internal combustion engines 2 are designed to a coolant temperature in the range of about 95 ° C, appropriate measures must be taken to decouple the heat accumulator 12 on reaching the operating temperature of the coolant circuit, so that no overheating of the coolant or more preferably the internal combustion engine 2 takes place.

FIG. 2 shows a possibility over which the heat accumulator 12 can be decoupled from the coolant circuit. The basic structure of in FIG. 2 shown coolant circuit corresponds to that of FIG. 1 , so that only the differences are discussed and, moreover, reference is made to the above statements. To decouple the heat accumulator 12 from the actual coolant circuit, a bypass line 18 is provided, which can be opened or closed via a bypass valve arrangement 20. When the bypass line 18 is actuated, the heat accumulator 12 is bypassed by the coolant circulated via the coolant pump 16 and is thus thermally decoupled from the coolant circuit. About the heater 14 can then Coolant can be heated in the heat storage 12 to a storage temperature above the operating temperature. The insulation of the heat accumulator 12 ensures that this storage temperature can be maintained over a comparatively long period without activation of the heater 14. During cold start of the internal combustion engine 2, the stored in the heat storage 12, to a temperature higher than that permitted for the engine heated coolant is optionally mixed by suitable control of the bypass valve assembly 20 with "cold" coolant and fed to the engine 2 with operating temperature, so this is heated very quickly. This mixing with "cold" coolant is advantageous to prevent stresses in the engine block. The mixing ratio of the coolant from the heat accumulator 12 and the "cold" coolant may be adjusted via the bypass valve assembly 20. A discharge of the heat accumulator 12 may for example also take place if, after phases of "sailing", rapid heating of the internal combustion engine 2 is required. After discharging the heat accumulator 12, this can be charged very quickly to its storage temperature by the above-explained control of the heater 14, in which case of course the bypass line 18 is turned on to thermally decouple the heat accumulator 12 from the coolant circuit.

Also, the bypass valve assembly 20 is exemplified as a 3-way valve, of course, a different valve arrangement, for example with valves at the entrance and at the output of the heat accumulator 12 can be used. The valve assemblies 10 and 20 are preferably designed as electrically adjustable by the engine control valves.

When loading the heat accumulator 12 via the heater 14, local overheating of the storage medium in the heat accumulator 12 may occur under certain circumstances. This is possible, for example when the engine is stopped in sailing mode. To avoid this, according to the variant in FIG. 3 a circulation pump 22 are provided, which is arranged in a circulation line 24, can be withdrawn via the coolant at an output 26 of the heat accumulator 12 and fed back to an input 28, so that a uniform heating of the heat accumulator 12 recorded coolant (storage medium) is ensured and the Formation of gas bubbles can be avoided by thermal overheating. Instead of the circulation can also be taken to ensure that the coolant is mixed in the heat accumulator 12, for example via a kind of stirrer or by suitable flow guidance to avoid local overheating.

According to the invention, the heater 14 may additionally be provided with an external connection via which the heater 14 can be controlled, for example, overnight in a garage or the like, in order to charge the heat accumulator 12 so that it is ready for operation even during prolonged engine stoppage.

This external connection can be designed so that the heating system is supplied with energy directly or via the vehicle battery.

Disclosed is a coolant circuit of a drive, for example an internal combustion engine, a hybrid drive or an electric drive, in which coolant can be brought to operating temperature via a heat accumulator. According to the invention, coolant is used as the storage medium of the heat accumulator, this being heated to a storage temperature which is significantly above the operating temperature of the coolant circuit.

LIST OF REFERENCE NUMBERS

1

Coolant circuit

2

internal combustion engine

4

heat exchangers

6

cooler

8th

bypass line

10

bypass valve

12

heat storage

14

heater

15

generator

16

Coolant pump

18

bypass line

20

Bypass valve assembly

22

circulating pump

24

circulation line

26

output

28

entrance

Claims (13)

Coolant circuit of a drive which is temperature-controlled via a coolant to operating temperature and with a heat storage (12), can be heated via the cold coolant, characterized in that the heat accumulator (12) operates with the coolant as a storage medium and is designed such that the storage temperature when the heat accumulator (12) is charged above the operating temperature of the coolant circuit. Coolant circuit according to claim 1, wherein the heat accumulator (12) via a bypass line (18) is bypassed, which can be brought via a bypass valve assembly (20) in fluid communication with the heat accumulator (12) or against this shut off. Coolant circuit according to one of the preceding claims, wherein the heat accumulator (12) is provided with an electric heater (14). Coolant circuit according to claim 3, wherein the heater (14) via a generator (15) is supplied with electrical energy, so that during operation released kinetic energy into electrical energy for operating the heater (14) is convertible. Coolant circuit according to claim 3, wherein the heater (14) is powered by a vehicle battery with electrical energy. Coolant circuit according to claim 3, 4 or 5, wherein the heater (14) has an external connection. Coolant circuit according to one of the claims 3 to 6, wherein the heater (14) is integrated in the heat accumulator 12. Coolant circuit according to one of the preceding claims, wherein the operating temperature can be below 100 ° C and the storage temperature above 120 ° C. Coolant circuit according to claim 8 wherein the storage temperature is in the range between 130 ° C and 160 ° C, so that in the heat accumulator (12) adjusts an increased pressure. Coolant circuit according to one of the preceding claims, wherein the coolant is a water / glycol mixture. Coolant circuit according to one of the preceding claims, with a circulation over which a coolant flow can be withdrawn circumferentially at an output (26) of the heat accumulator (12) and fed back to an input (28). Coolant circuit according to one of the preceding claims, wherein the heat accumulator (12) is designed with a means for mixing the coolant. Coolant circuit according to one of the preceding claims, wherein the heat accumulator (12) in the coolant flow path between a radiator (6) and the drive (2) is arranged.

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