Method for operating a heating system in a vehicle

Abstract

A method for operating a heating system (10) in a vehicle, wherein the heating system (10) comprises a preferably fuel-operated heater (12) with a first heat exchanger arrangement (16) for transferring heat provided in the heater (12) to a heat transfer medium circulating or circulating in a heat transfer medium circuit (18), in which method, in a start-up operating phase, the heater (12) is operated with a start-up heating power and the heat transfer medium is circulated at a start-up delivery rate in the heat transfer medium circuit (18), wherein as the temperature of the heat transfer medium increases, the delivery rate is increased starting from the start-up delivery rate, wherein the delivery rate is increased when the temperature of the heat transfer medium reaches or approaches a predetermined first reference temperature, characterized in thatthat when a predetermined second reference temperature is reached in a continued operation following the start-up operating phase, the delivery rate and the heating power are varied to maintain the temperature of the heat transfer medium in the range of the second reference temperature, wherein in the continued operation, in addition to varying the delivery rate to maintain the temperature of the heat transfer medium in the range of the second reference temperature, the heating power is only varied when a deviation between the temperature of the heat transfer medium and the second reference temperature exceeds a predetermined extent.

Description

[0001] The present invention relates to a method for operating a heating system in a vehicle, wherein the heating system comprises a preferably fuel-operated heater with a first heat exchanger arrangement for transferring heat provided in the heater to a heat transfer medium circulating or circulating in a heat transfer medium circuit.

[0002] When operating such heating systems in a vehicle, for example as auxiliary heaters or parking heaters, the general objective is to use the thermal energy provided, for example, by the combustion of a liquid and vaporized or atomized fuel as efficiently as possible to heat or precondition a vehicle. This means that, particularly at the start of operation of such a heating system, it should be ensured as quickly as possible that this system is capable of heating the vehicle. After a start-up phase, heat transfer should be as efficient as possible, i.e., with the greatest possible efficiency.

[0003] A method for operating a heating system in a vehicle according to the preamble of claim 1 is known from DE 35 21 372 A1.

[0004] It is the object of the present invention to provide a method for operating a heating system in a vehicle, with which the thermal influence of a vehicle can be started and continued efficiently.

[0005] According to the invention, this object is achieved by a method for operating a heating system in a vehicle according to claim 1. The heating system comprises a preferably fuel-operated heater with a first heat exchanger arrangement for transferring heat provided in the heater to a heat transfer medium circulating or circulating in a heat transfer medium circuit. In the method according to the invention, in a start-up operating phase, the heater is operated with a start-up heating output and the heat transfer medium is circulated in the heat transfer medium circuit at a start-up delivery rate, wherein as the temperature of the heat transfer medium increases, the delivery rate is increased starting from the start-up delivery rate.

[0006] In the procedure according to the invention, the system is initially operated in the start-up operating phase with a flow rate of the heat transfer medium in the heat transfer medium circuit intended for this operating phase, which flow rate is lower than the flow rate that ensures efficient heat transfer for subsequent continued operation. The result of this is that a comparatively low flow rate at the start of operation ensures that only comparatively little heat is removed from the area of the heater itself, so that the heater itself can be brought up to operating temperature very quickly and can therefore operate with high efficiency very early on. At the same time, however, by providing at least slight circulation of the generally liquid heat transfer medium, it is ensured that this too is already heated and that heat build-up in the area of the heater itself orthe first heat exchanger arrangement cannot occur. If the temperature of the heat transfer medium then increases, which is an indicator that the heater itself is sufficiently heated and, to the extent that the heat provided there can then be transferred to the heat transfer medium, the flow rate can be increased to increase the energy output from the heater and thus increase the amount of heat that can be transferred, for example, to the air being introduced into a vehicle interior.

[0007] The procedure is such that the flow rate is increased when the temperature of the heat transfer medium reaches or approaches a predetermined first reference temperature. In particular, it is possible to select a temperature as the first reference temperature that ensures the most efficient heat transfer of the heat transported in the heat transfer medium, for example, to the air to be introduced into a vehicle interior.

[0008] Additionally, it can be provided that the flow rate is increased when the temperature change rate of the heat transfer medium reaches or approaches a predetermined reference change rate. This allows for the fact that if the temperature of the heat transfer medium changes relatively rapidly, it will soon reach its optimal operating temperature, for example, so that increased energy can be removed from the heater area at an early stage by increasing the flow rate.

[0009] It should be noted here that this increase in the production rate when reaching or approaching the various reference values can be carried out in stages or in a more or less continuous transition.

[0010] Furthermore, in the method according to the invention, upon reaching a predetermined second reference temperature, the delivery rate and the heating power are varied to maintain the temperature of the heat transfer medium in the range of the second reference temperature, wherein it can advantageously be provided that the second reference temperature corresponds to the first reference temperature. Thus, a control of the delivery rate or the heating power is provided as a function of the change in the temperature of the heat transfer medium, so that, even depending on the heat extraction from the heat transfer medium during continued operation, it can be ensured that the temperature of the heat transfer medium is maintained, for example, in the range of the temperature at which operation with the highest efficiency is possible.According to the invention, priority is given to changing the delivery rate in that, in the continued operation following the start-up operating phase, in addition to varying the delivery rate to maintain the temperature of the heat transfer medium in the range of the second reference temperature, the heating power is also varied if a deviation between the temperature of the heat transfer medium and the second reference temperature exceeds a predetermined extent.

[0011] The heating output of the heater can, for example, be variable in steps. Furthermore, it can be provided that a second heat exchanger arrangement is provided for transferring heat transported in the heat transfer medium to air to be introduced into a vehicle interior. A heating output which is determined, for example, beforehand in a test for a specific heater and which cannot be exceeded in subsequent operation by control measures, for example because a control or operational limitation is provided, for example on the amount of fuel to be conveyed and / or the amount of hot air. In the second heat exchanger arrangement, heat transported in the heat transfer medium can be transferred to the air to be introduced into a vehicle interior, i.e. a further heat transfer medium. The setting of the optimal orThe desired or regulated temperature of the heat transfer medium in the heat transfer medium circuit can then be determined depending on the heat transfer medium temperature at which this second heat exchanger arrangement has the highest efficiency.

[0012] The present invention will be described below with reference to the attached Fig. 1, which illustrates a vehicle heating system in principle.

[0013] The vehicle heating system 10 comprises, as an essential component, a heater generally designated 12, which is fuel-operated here, for example. This heater comprises a burner region 14, to which fuel, for example gasoline or diesel fuel, is supplied by a fuel supply arrangement (not shown), and combustion air is supplied by a combustion air supply arrangement (likewise not shown). The combustion taking place in the burner region 14 provides heat, which is transferred in a first heat exchanger arrangement 16 to a generally liquid heat transfer medium, for example water or the like, circulating in a heat transfer medium circuit 18. For this purpose, a heat transfer medium pump 20 can be provided, with which the heat transfer medium is driven for circulation in the heat transfer medium circuit 18.

[0014] In a second heat exchanger arrangement 22, heat transported in the heat transfer medium can be transferred to another heat transfer medium, for example, the air L to be introduced into a vehicle interior. For this purpose, a fan 24 can be provided, which conveys the air through the second heat exchanger arrangement 22.

[0015] A drive unit 26, for example an internal combustion engine, can be integrated into the heat transfer medium circuit 18 so that, on the one hand, it can be preconditioned using the heater 12, but on the other hand, heat provided in the drive unit 26 can also be used to heat the air L to be introduced into the vehicle interior in the second heat exchanger arrangement 22. A valve arrangement 28 makes it possible to switch the heat transfer medium circuit 18 between two states, in one state in which the heat transfer medium flows through the drive unit 26, while in the other state such flow is excluded. In particular, in a start-up operating phase, the drive unit 26 can be decoupled from the heat transfer medium circuit 18, since this generally acts as a temperature sink and makes rapid heating of the heat transfer medium more difficult.

[0016] The heater 12, the valve 28, and the heat transfer medium pump 20 can be controlled by a control device generally designated 30. Depending on the required operation, these system areas can thus be brought into the desired operating state. For example, in the heater 12, the heating output to be provided there can be influenced by appropriate control, for example, a fuel delivery arrangement or combustion air delivery arrangement. Likewise, the delivery rate of the heat transfer medium in the heat transfer medium circuit 18 can be influenced by appropriate control of the heat transfer medium pump 20.

[0017] A temperature sensor 32 is assigned to the heat transfer medium circuit 18, the signal of which is passed to the control device 30 so that, as explained below, the operation of various system areas can be influenced depending on the temperature of the heat transfer medium.

[0018] In an operating mode provided according to the invention, in a start-up operating phase, i.e., when starting up the heater 12, for example, to preheat the interior of a vehicle, the heater 12 can initially be controlled such that it operates with a start-up heating output that can correspond to a maximum heating output to be provided for the heater 12 in the heating system 10. In this way, the fastest possible heating is ensured. In this start-up operating phase, the heat transfer medium pump 20 can also be controlled such that the heat transfer medium circulates in the heat transfer medium circuit 18, but at a comparatively low start-up flow rate.In this way, it is ensured that the heater 12 reaches operating temperature very quickly, i.e. initially little heat energy is extracted, while the circulation of the heat transfer medium, which nevertheless exists, prevents heat build-up in the area of the first heat exchanger arrangement 16.

[0019] Once the heater 12 itself has reached operating temperature in this operating state, increased heat energy will be transferred to the heat transfer medium, so that this heat transfer medium, which is still being pumped at a comparatively low flow rate, is heated more intensively. If its temperature reaches a predetermined reference temperature, which may, for example, correspond to a temperature at which the second heat exchanger arrangement 22 can operate with the greatest efficiency, the heating output of the heater 12 can be reduced, wherein a step-like reduction in steps of, for example, 0.5 kW can preferably be provided. Along with this reduction in heating output, the flow rate of the heat transfer medium can also be increased by appropriately controlling the heat transfer medium pump 20.A higher delivery rate of the heat transfer medium results in increased heat being removed from the heater 12, i.e. the heat exchanger arrangement 16, and being transferred in the direction of the second heat exchanger arrangement 22 and, by operating the fan 24, being transferred to the air L to be introduced into the vehicle interior.

[0020] During this continued operation following the initial operating phase, the flow rate of the heat transfer medium in the heat transfer medium circuit 18 is adjusted or regulated such that the heat transfer medium has a substantially constant temperature, for example, within the range of this optimal temperature. In addition to influencing the flow rate, the heating power is also used as an influencing variable, so that in the event of an excessive temperature drop, which can be detected by the temperature sensor 32, the heating power can be increased, for example, if a corresponding temperature drop cannot be compensated for by changing, e.g., throttling, the flow rate.Here too, for example, in order to use energy as efficiently as possible, it can be provided that the heater 12 is operated with a heating output which, within the range of available heating outputs, ensures the greatest efficiency, including in heat transfer in the area of the first heat exchanger arrangement 16, wherein the temperature of the heat transfer medium in the heat transfer medium circuit 18 is then kept constant by influencing the flow rate, i.e., by appropriately controlling the heat transfer medium pump 20. Only when an excessive deviation occurs here is the temperature of the heat transfer medium influenced by changing the heating output in order to keep it within the desired temperature range.

[0021] It should be noted that, for example, the same reference temperatures can be used for the transition to continued operation, i.e., increasing the flow rate of the heat transfer medium in the heat transfer medium circuit 18 and for adjusting to a constant temperature. It is also possible to influence the flow rate depending on the temperature change of the heat transfer medium, so that if a comparatively rapid temperature increase is apparent, the flow rate can be increased even before the reference temperature is reached in order to correspondingly increase the heat output from the heater 12.

[0022] The present invention ensures that the system can efficiently utilize the energy used through the various control interventions and the resulting rapid heating of the heat transfer medium to a reference temperature and also maintaining it at this reference temperature. This approach has the advantage that it can be controlled independently of, for example, the operation of the fan 24. This means that the inventive approach does not involve any control-related integration of the fan 24, whose operation can be adjusted, for example, depending on other operating variables, such as the vehicle interior temperature or the like.

Claims

[1] A method for operating a heating system (10) in a vehicle, wherein the heating system (10) comprises a preferably fuel-operated heater (12) with a first heat exchanger arrangement (16) for transferring heat provided in the heater (12) to a heat transfer medium circulating or circulating in a heat transfer medium circuit (18), in which method, in a start-up operating phase, the heater (12) is operated with a start-up heating power and the heat transfer medium is circulated at a start-up delivery rate in the heat transfer medium circuit (18), wherein as the temperature of the heat transfer medium increases, the delivery rate is increased starting from the start-up delivery rate, wherein the delivery rate is increased when the temperature of the heat transfer medium reaches or approaches a predetermined first reference temperature, characterized bythat when a predetermined second reference temperature is reached in a continued operation following the start-up operating phase, the delivery rate and the heating power are varied to maintain the temperature of the heat transfer medium in the range of the second reference temperature, wherein in the continued operation, in addition to varying the delivery rate to maintain the temperature of the heat transfer medium in the range of the second reference temperature, the heating power is only varied when a deviation between the temperature of the heat transfer medium and the second reference temperature exceeds a predetermined extent. [2] Method according to claim 1, characterized by that the heating output can be varied in stages. [3] Method according to one of claims 1 or 2, characterized by that the starting heating output is a maximum heating output or in the range of the maximum heating output. [4] Method according to one of claims 1 to 3, characterized bythat a second heat exchanger arrangement (22) is provided for transferring heat transported in the heat transfer medium to air (L) to be introduced into a vehicle interior.

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