DE102010013047B4 - Method for utilizing the waste heat of an internal combustion engine, in particular a piston engine, by means of a heat accumulator and cooling system for carrying out the method - Google Patents

Abstract

Cooling system of an internal combustion engine (10) of the piston type with a cylinder head and a coolant circuit (12), which has a cooler branch (12a) containing a cooler (14), which can be separated from the coolant circuit (12) via a thermostatic valve (16), and a second one with a heat store (24) comprises a line branch (12b) which can be connected via a controllable valve (52), the heat accumulator (24) at a connection point (28) with the lowest-lying line element (50) of the second line branch (12b) via a controllable valve (52) containing coolant line (48), the second line branch (12b) in its highest position has a compensation volume (40) with a ventilation opening, the heat accumulator (24) has a conveying device (38; 54; 62) for transferring the coolant from the heat accumulator ( 24) is assigned to the second line branch (12b) and the heat accumulator (24) is provided with a ventilation line (46), d ie at the level of the compensation volume (40) opens into the ambient air, characterized in that the capacity of the heat accumulator (24) is dimensioned such that it can at least absorb the coolant volume from the cylinder head (transfer volume), the ventilation line (46) being a shut-off valve (58) contains and between the shut-off valve (58) and the heat accumulator (24) an air intake line (56) opens into the ventilation line (46), which contains an air pump (54) as a conveying device, which is followed by a check valve (61).

Description

Technical field of the invention

The invention relates to a method and apparatus for utilizing the waste heat of a cooled by a coolant circuit cylinder head of a piston engine type internal combustion engine by means of a heat accumulator, wherein the guided over the cylinder head coolant circuit in a cooler containing a radiator branch and a parallel, connectable to the heat storage second leg divided and the flow path can be shut off via the radiator.

The prior art are cooling systems in which the second leg is a heating branch containing a heating heat exchanger to which a bypass containing the heat accumulator is switched on and off in parallel. In this case, the coolant can circulate without passing through the heat storage only on the Heizungswärmtauscher and the cylinder head, or it can alternatively flow through the heat storage. This detour is used to charge the accumulator with hot coolant, or to increase the coolant temperature by admixing the hot coolant from the heat accumulator when the engine is to be heated rapidly in a cold start to avoid harmful exhaust emissions.

Problems with the state of the art

The main problem with the prior art is the cooling of the coolant and the mass of the engine in contact with the coolant or the cold environment compared to the operating temperature of the engine, and optionally also of the heating heat exchanger, during the stoppage of the engine. Although the admixing of the stored in the heat accumulator hot partial volume of the coolant to the cooled residual volume of the coolant is an improvement of the coolant circuit during cold start, the time that elapses after the cold start to reach the operating temperature of the system remains unsatisfactory. The result is still relatively high exhaust emissions and increased fuel consumption when cold starting the engine.

This current problem is weighing heavily on efforts to improve the combustion efficiency of combustion engines in terms of energy efficiency and low exhaust emissions, so that by reducing fuel consumption and exhaust emissions they will protect the environment and meet legislative requirements in the future.

The DE 196 35 044 A1 discloses a coolant temperature control system for vehicles in which the coolant temperature is determined after stopping the engine by means of a water temperature sensor. Optionally, coolant is removed for other use.

The DE 41 05 199 A1 discloses an internal combustion engine with a heat transfer circuit, in which there is a latent heat storage. After a start of the internal combustion engine, the heat transfer medium is passed through the cylinder head of the internal combustion engine and passes from this via a surge tank back to the latent heat storage.

The DE 10 2006 017 246 A1 discloses a waste heat utilization system for an automotive engine. An engine cooling water stored in a heat storage tank is circulated by a pump so that the hot water is supplied to the engine before the engine operation is started.

The DE 41 36 910 A1 discloses a method for rapid adjustment of the operating temperature of a mass by a free-flowing or free-flowing heat carrier, in particular for rapid heating of a motor vehicle engine during cold start.

The DE 103 44 018 A1 discloses a method for controlling the temperature of an internal combustion engine and a cooling system for an internal combustion engine, in which when switching off the engine substantially all of the coolant is conveyed from a coolant circuit in a hot water reservoir, from which the coolant is returned to the coolant circuit at a start of the engine to shorten the phase of the cold start.

The FR 2 771 771 A1 discloses a cooling system of an internal combustion engine according to the preamble of claim 1.

Object of the invention

It is therefore an object of the invention to drastically reduce the heat losses of the system during standstill and the thereby occurring cooling of the engine and thus already at cold start, especially during cold start of an internal combustion engine for motor vehicles to promote the efficient treatment of the fuel-air mixture and while at the same time minimizing the investment and manufacturing costs of the required technology.

Inventive solution

When stopping the motor described at the beginning, the following steps can be taken:
Blocking the flow path via the radiator and subsequent emptying and venting of the cylinder head by transfer of the coolant volume from the cylinder head into the heat accumulator,
Storing this volume of coolant (transfer volume) in the heat accumulator until the engine is restarted,
when restarting the stored coolant volume back into the cylinder head and at the same time its vent,
as well as when reaching a threshold temperature of the coolant in the engine compartment open the radiator circuit.

The term "cylinder head" is to be understood here as a general term for the areas of the engine through which the coolant flows, that is to say including the cooling area for the cylinder jacket.

While in the prior art after stopping the engine not only the metallic volume of the cylinder head, but also the volume of coolant contained in the cylinder head cools down and this large volume must be reheated when restarting the engine, the heat losses are on the cylinder head when using the present invention limited the cooling of its low heat-active metallic mass. When restarting the engine is achieved by the inflow of hot coolant from the heat storage, the optimum operating temperature in a short, measured in seconds deadline.

An advantageous embodiment of the method consists in a coolant circuit, the second line branch includes a heater core in that when stopping the engine, the coolant volume from the cylinder head plus the coolant contained in the heat exchanger coolant volume (transfer volume) emptied from the cylinder head and until the engine is restarted in the heat storage stored and returned to the heater core when restarting the engine.

Preferably, when restarting the engine, the transfer volume is supplied to the heater core via the engine.

The emptying of the cylinder head and optionally the heating heat exchanger includes the associated line elements of the second leg.

Preferably, the piston movement is delayed when the engine starts and it is first the coolant volume from the heat storage in the second leg and fed back the cylinder head heated by the coolant.

One embodiment is that when stopping the engine, the coolant is discharged into a lower-lying heat storage. If the conditions in the engine compartment do not allow this variant, according to another variant, the transfer volume of the coolant can be transferred by suitable conveying means, preferably pumps, into the heat accumulator or removed therefrom. become.

A cooling system according to the invention of an internal combustion engine of the piston type comprising a cylinder head and a coolant circuit comprising a radiator branch containing a radiator and separable by a thermostatic valve from the coolant circuit and a second, connected to a heat accumulator via a controllable valve leg, is generally designed in such a way that the heat accumulator is connected at a junction with the lowest-lying line element of the second leg via a coolant line containing the controllable valve, the second leg has in its highest position a compensating volume exhibiting a vent, the heat accumulator a conveyor for transferring the refrigerant from the heat accumulator to the second Line branch is assigned and the heat accumulator is provided with a vent line in the amount of the vent opening of the compensation volume into the ambient air, wherein the capacity of the heat accumulator is dimensioned so that it can absorb at least the volume of coolant from the cylinder head (transfer volume).

In this case, an advantageous embodiment is that the second line branch contains a heating heat exchanger as a heating branch, wherein the capacity of the heat storage ( 24 ) is dimensioned so that it can accommodate at least the volume of coolant from the cylinder head and the heater core (transfer volume).

The conveyor device is preferably a coolant pump in the coolant line. Alternatively, the vent line may include a shut-off valve, wherein between the shut-off valve and the heat accumulator, an air intake line opens into the vent line, which includes a conveyor as an air pump, which is connected downstream of a check valve.

Preferably, between the heater core and the connection point a the Return flow to the heater exchanger preventing backflow arranged to direct after the restart of the engine, the transfer volume initially on the cylinder head of the engine and to optimize its heating.

An embodiment variant is that the heat accumulator is arranged below the mentioned lowest lying line element. Thus, the refrigerant can be transferred under the action of gravity in the heat storage as soon as the controllable valve is opened. This variant assumes that there is sufficient space in the engine area to be able to position the heat storage sufficiently low. However, this possibility does not always exist. There is therefore a further embodiment in that the conveying device can be switched over between two opposite conveying directions, so that the coolant can be transferred into the heat accumulator by the operation of the conveying device.

On the basis of the following description of exemplary embodiments of the present invention referring to the drawings, this will be explained in more detail,

Brief description of the drawings

1 is the schematic representation of the coolant circuit of a piston engine of the prior art with a heat storage for keeping hot a portion of the coolant during a break in operation.

2 is the schematic representation of the coolant circuit of a piston engine internal combustion engine with a heat storage for keeping warm at least a portion of the coolant of the engine during a service break of the engine,

3 shows an arrangement according to the invention,

4 shows a variant of an arrangement and

5 shows a further variant of an arrangement.

Description of preferred embodiments

First, referring to 1 The prior art explained in more detail from which the present invention proceeds.

About a four-cylinder internal combustion engine shown only schematically 10 leads a total of 12 designated coolant circuit, a cooler branch 12a and a heating branch 12b having.

The radiator branch 12a leads from the engine 10 over a cooler 14 and via a thermostatic valve 16 to a coolant inlet of the engine 10 adjacent coolant pump 18 and from there back to the engine 10 , The thermostatic valve 16 is designed as a three-way valve. To that the engine 10 Cooling leaving coolant will be the cooler 14 leaving coolant from the thermostatic valve 16 to the coolant pump 18 directed. If the coolant temperature is below a predetermined threshold value, the thermostatic valve interrupts the connection to the coolant pump 18 and closes the radiator branch 12a bypassing the engine 10 over a line branch 20 short.

The heating branch 12b leads from the engine 10 via a heating heat exchanger 22 and the coolant pump 18 back to the engine 10 , Parallel to that between the heater core 22 and the coolant pump 18 extending section of the heating branch 12b is a heat storage 24 arranged, whose inflow through a three-way valve 26 can be opened or closed, and its outflow at 28 back in the heating branch 12b opens. The three-way valve 26 directs the coolant flow either through the heat storage 24 (Branch) or past it (flow). Upstream from the three-way valve 26 and downstream of the confluence 28 is each a temperature sensor 30 respectively. 32 arranged. These temperature sensors 30 and 32 supply their temperature readings to a comparison circuit 34 that is capable of giving a control pulse to the three-way valve 26 to switch it to flow when the difference in the two temperature readings falls below a given threshold, indicating that the cold and warm volumes of the refrigerant have sufficiently mixed and temperatures of the total refrigerant volume are substantially equalized. Another coolant output to the circuit from the heat storage 26 can not cause any further increase in the coolant temperature. The control pulse from the comparison circuit 34 therefore switches the three-way valve 26 on flow. After this switching of the three-way valve, the comparison circuit 34 inactivated. Only when it is determined that the coolant or the system has reached its desired operating temperature, the three-way valve 26 switched back to diversion, the heat storage 26 Coolant is supplied to operating temperature and the coolant is supplied until the engine is switched off 10 through the radiator 14 and the thermostatic valve 16 kept at the operating temperature.

In order for the desired operating temperature to be reached, the waste heat resulting from the engine operation must be supplied to the coolant. Is the three-way valve 26 On flow, the volume of coolant to be heated by the engine waste heat is reduced by the volume that is in the over the heat accumulator 24 leading branch 36 of the coolant circuit is located. When the operating temperature is reached, the thermostatic valve opens 16 the cooler branch 12a to prevent a further increase in the coolant temperature.

Since the fuel consumption and the exhaust emissions are high when the engine is cold, the control of the system is expediently designed such that initially the coolant temperature in the engine 10 raised with the help of the hot coolant from the heat storage to the temperature compensation and then only the engine 10 is started. If, however, the drive of the coolant pump 18 is mechanically connected to the engine crankshaft, the coolant pump 18 Do not pump coolant before starting engine. In this case, in the over the heat storage 26 leading branch 36 another, electrically operable pump 38 provided, which is suitable after switching the three-way valve 26 on branch, the coolant circuit through the heat storage 24 to start and thus to carry out the preheating of the engine. For this purpose, for example, when opening the door lock a control pulse can be triggered, the pump 38 put into operation.

When cold starting the engine 10 can the three-way valve 26 be on flow, then it is by a pulse at engine start or when starting the pump 38 switched to diversion. At this time prevails at the temperature sensors 30 and 32 approximately the same temperature, namely that of the cooled coolant outside the heat accumulator 26 What if immediate activation of the comparison circuit 34 this would cause the three-way valve 26 immediately switch back to flow, which is why the start pulse only with a short delay, during which the out of the heat storage 26 supplied hot coolant through the junction 28 to the temperature sensor 32 penetrates and thereby a sufficiently large temperature difference to the temperature sensor 30 manufactures to the provision of the three-way valve 26 To prevent a second pulse follows, the comparison circuit 34 activated again.

This prior art cooling system and its operation have the inadequacies discussed at the outset, and it is possible to drastically shorten, without much effort, the time that elapses between the start of the cooled engine and the time at which the engine arrives 10 has reached the operating temperature. The 2 shows a suitable system for operating an internal combustion engine 10 , for elements that match those of 1 the same reference numerals are used and to that extent a detailed description is dispensed with, but following on from the known construction, which, for example, in the DE 195 35 027 A1 is disclosed, changed design features and different functional features will be discussed in more detail.

As in the prior art is an internal combustion engine 10 with a coolant circuit 12 provided in a cooler branch 12a and a heating branch 12b is divided. The heating branch 12b leaves the cylinder head of the engine 10 , passes through the heating heat exchanger 22 and returns via the coolant pump 18 to the engine 10 back. Between the engine 10 and the heater core 22 is with the heating branch 12b a compensating volume communicating with the outside air in the form of a surge tank 40 connected to the highest section of the heating branch 12b represents and is open to the outside over the ambient air. Its function will be explained later.

Deeper than this heating branch 12b is a heat storage 24 arranged, the known construction of an outer container 42 and an inner container 44 There is a vacuum insulation space between them. Heat insulated are in the inner container 44 one at the level of the expansion tank 40 open air line 46 and a coolant line 48 introduced. The air line 46 opens in the inner container 44 whose upper wall portion adjacent to, the coolant line 48 near its bottom. The coolant line 48 is at 28 with the deepest, below engine 10 and heating heat exchanger 22 lying conduit element 50 of the heating branch 12b connected. Between the heat storage 24 and the connection point 28 leads the coolant line 48 via a feed pump 38 , which at standstill counter to the conveying direction

Will the operation of the engine 10 finished, the shut-off valve 52 opened, The in the heating branch 12b including engine 10 , Surge tank 40 and heating heat exchanger 22 , located coolant runs by gravity into the heat storage 24 and displaces the air via the air line 46 from the heat storage 24 , With the transfer of the coolant volume from the heating branch 12b this fills up over the expansion tank 40 with air.

When restarting the engine 10 is through the pump 38 the hot coolant through the opened shut-off valve 52 Pressed up until it surge tank 40 achieved, which is determined by a suitable sensor, whereupon the shut-off valve 52 closed and the pump 38 is switched off. The expansion tank 40 Ensures that the coolant circuit is free of trapped air during engine operation and, on the other hand, the drained heater branch 12b filled with air. The from the heat storage 24 in the heating branch 12b recirculated coolant is now withdrawn the heat required for heating the cooled metal volume, which is soon replaced by the heat of combustion of the running engine.

Preferably, in the conduit element 50 a check valve 51 provided that a flow from the connection point 28 to the heating heat exchanger 22 prevented. This ensures that in the return of the heat storage 24 stored coolant in the heating branch 12b through the pump 38 for the heating heat exchanger 22 certain coolant mass first the engine 10 flows through and causes its preheating, before the specific for the engine coolant mass in the engine 10 enter and continue to heat it up. The flow rate through the engine is thereby 10 increases and ensures the turbulence of the flow mass, whereby the heat transfer coefficient between the coolant and the engine wall is maximized. The turbulence creates a plug flow in the coolant at the highest possible rate for the heat transfer between the coolant and the engine. The rapid heating of the engine walls is an important prerequisite for the efficient and low-emission combustion of the fuel when cold starting the engine.

In a four-cylinder engine, for example, a coolant volume of 2 liters is stored. The delivery rate of the pump 38 is for example 600 liters / hour. The transfer volume of 2 liters is thus promoted in 12 seconds. Due to the high thermal conductivity of the metallic elements of the heating branch 12b is the time between switching on the coolant pump 38 and reaching the desired operating temperature of the engine 10 in the same order of magnitude. Using a delay circuit to a flow of the pump 38 to cause before starting the engine according to said short period of time, the cylinder head already has the optimum operating temperature when the piston movement in the engine 10 starts. As a result, in addition to the reduction of fuel consumption and exhaust emissions, the wear caused by the cold start is avoided without the need for expensive technical equipment.

The 3 shows a variant of the invention, in which the pump 38 deleted because their job is an air pump 54 takes over, by one in front of the heat storage 24 with the air line 46 at 60 connected, a check valve 61 containing suction line 56 Ambient air in the heat storage 24 presses and thereby the hot coolant in the heating branch 12b pushes back. There is one on the heat storage 24 opposite side of the junction 60 in the air line 46 provided shut-off valve 58 closed. Will after switching off the engine 10 the valve 52 opened, is also the shut-off valve 58 open so that in the heat storage 26 incoming coolant, the air from the heat storage 26 can push into the open air. Instead of the air pump 54 Another on-board compressed air source can also be used.

The embodiments described above are suitable, the heat storage 24 filling coolant volume under the action of gravity in the heat storage 24 to transfer who occupies the lowest position in the system. Where this position is not available for receiving the heat accumulator is an arrangement according to 4 suitable. The heat storage 24 is there in a position higher than the line element 50 , In the coolant line 48 is a coolant pump 62 arranged, the conveying direction is switched such that each with the valve open 52 Either the coolant in the heat storage 24 is transferred, or in the opposite direction back into the line branch 12b ,

All embodiments described above have in common that the at rest of the internal combustion engine from the cylinder head and optionally the heating heat exchanger in the heat storage to be transferred coolant volume after opening a valve 52 over a line 48 in the heat storage 24 passes and over the same line 48 returned back to the cylinder head and optionally the heat exchanger and thereby the heat storage 24 is then discharged through the valve during engine operation 52 from the coolant circuit 12 is disconnected.

The 5 shows a design variant, which is particularly suitable for internal combustion engines, which are used in areas where to be reckoned with relatively low temperatures. The operating method of the coolant transfer is similar in construction to the 2 applied, whose reference numerals are adopted accordingly, but with a heat storage 24a is used, in its thermally insulated interior three lines 46 . 48 and 64 are guided.

The administration 64 replaces the one from the heating heat exchanger 22 leaving line 50 and causes the coolant circuit of the heating branch 12b during engine operation constantly on the heat storage 24a and continue via the pump 38 and the line 48 is led back to the cylinder head and heater core. Will the internal combustion engine 10 shut off, the essential part of the outside of the heat accumulator 24a located coolant volume (transfer volume) in the heat storage 24 be transferred.

In the above based on the 2 - 4 described embodiments, the capacity of the heat accumulator 24 such that it can absorb the transfer volume. If the transfer volume at engine start in the heating branch 12b is transferred, remains the heat storage 24 empty until he turns off the engine 10 is filled again.

In the embodiment according to 5 is when the engine is switched off 10 the heat storage 24a not empty, because it is included in the coolant circuit. It is therefore to accommodate the transfer volume an extension of the storage volume, ie an increase in the heat storage 24a required, for example, increases the storage volume to twice the transfer volume. During engine operation, the heat accumulator is then filled only in the lower region with the coolant passed through. The inflow and outflow of air from the heat storage 24a takes place according to the changes in the coolant volume within the heat accumulator 24a over the air line 46 ,

The advantage of this embodiment is that at engine start the cooled areas of the heating branch 12b a volume of hot coolant is supplied, which is substantially greater than the transfer volume, and thus also transported a correspondingly larger amount of heat, whereby the heating of the cold engine mass is accelerated, especially at low ambient temperatures.

To the inflow of air in the derivation of the transfer volume in the heat storage 24a To allow for emptied heating branch and after the engine start the complete filling of the heating branch 12b Secure is at the highest section of the heating branch 12b an expansion tank opened to the atmosphere 40 intended.

Claims (8)

Cooling system of an internal combustion engine ( 10 ) of the piston type with a cylinder head and a coolant circuit ( 12 ), which is a cooler ( 14 ), via a thermostatic valve ( 16 ) from the coolant circuit ( 12 ) separable cooler branch ( 12a ) and a second, with a heat storage ( 24 ) via a controllable valve ( 52 ) connectable line branch ( 12b ), wherein the heat storage ( 24 ) at a connection point ( 28 ) with the lowest line element ( 50 ) of the second branch ( 12b ) via a controllable valve ( 52 ) containing coolant line ( 48 ), the second line branch ( 12b ) in its highest position a compensating volume having a ventilation opening ( 40 ), the heat storage ( 24 ) a conveyor device ( 38 ; 54 ; 62 ) for transferring the coolant from the heat accumulator ( 24 ) in the second line branch ( 12b ) is assigned and the heat storage ( 24 ) with a vent line ( 46 ) equal to the equalization volume ( 40 ) opens into the ambient air, characterized in that the capacity of the heat storage ( 24 ) is dimensioned so that it can absorb at least the volume of coolant from the cylinder head (transfer volume), wherein the vent line ( 46 ) a shut-off valve ( 58 ) and between the shut-off valve ( 58 ) and the heat storage ( 24 ) an air intake line ( 56 ) in the vent line ( 46 ), which serves as a conveying device an air pump ( 54 ) containing a check valve ( 61 ) is connected downstream. Cooling system according to claim 1, characterized in that the second line branch ( 12b ) as heating branch a heating heat exchanger ( 22 ), wherein the capacity of the heat storage ( 24 ) is dimensioned such that it at least the volume of coolant from the cylinder head and the heating heat exchanger ( 22 ) (Transfer volume) can record. Cooling system according to claim 2, characterized in that between the heating heat exchanger ( 22 ) and the connection point ( 28 ) one the return flow to the heating heat exchanger ( 22 ) preventing backflow barrier ( 51 ) is arranged. Cooling system according to one of claims 1 to 3, characterized in that the conveying device ( 38 ; 62 ) a coolant pump in the coolant line ( 48 ). Cooling system according to one of claims 1 to 4, characterized in that the heat storage ( 24 ) below this lowest-lying line element ( 50 ) is arranged. Cooling system according to one of claims 1 to 4, characterized in that the conveying device ( 62 ) is switchable between two opposite conveying directions. Cooling system according to one of claims 1 or 2, characterized in that the heat storage ( 24a ) with three connecting cables ( 46 . 48 . 64 ) provided and in series with the heating heat exchanger ( 22 ) in the heating branch ( 12b ), that its input through a line ( 64 ) with the heating heat exchanger ( 22 ) and its output through a line ( 48 ) via a coolant pump ( 38 ) with the cylinder head of the engine ( 10 ), wherein the capacity of the heat storage ( 24a ) is greater than the transfer volume. Cooling system according to claim 7, characterized in that the capacity volume of the heat storage ( 24a ) is at least twice as large as the transfer volume.

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