Heating system and method for heating a vehicle interior of a vehicle having an internal combustion engine

A heating system for heating a vehicle interior of a vehicle having an internal combustion engine by using a heat exchanger includes three temperature sensors, wherein a first temperature sensor measures the coolant temperature at a coolant outlet of the internal combustion engine, a second temperature sensor measures the coolant temperature at a coolant inlet of the internal combustion engine, and a third temperature sensor measures the coolant temperature upstream of at least one heat source. A first heat circuit couples the heat exchanger to the internal combustion engine, whereas a second heat circuit bypasses the internal combustion engine. The first heat circuit operates solely with the internal combustion engine as a heat source when a target inlet temperature of the heat exchanger is above a preset value; otherwise an additional heat source is switched in, optionally operating in addition to the internal combustion engine.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is the U.S. National Stage of International Application No. PCT/EP2014/000876, filed Apr. 2, 2014, which designated the United States and has been published as International Publication No. WO 2014/166607 and which claims the priority of German Patent Application, Serial No. 10 2013 006 155.5, filed Apr. 10, 2013, pursuant to 35 U.S.C. 119(a)-(d).

BACKGROUND OF THE INVENTION

The invention relates to a heating system for heating a vehicle interior of a vehicle having an internal combustion engine. The invention also relates to a heating strategy for heating a vehicle interior by using the heating system according to the invention.

It is known that the engine heat is used for heating the vehicle cabin in vehicles having internal combustion engines that are coupled with a heat exchanger of the air conditioner of the vehicle. In hybrid vehicles, an electric drive is used in addition to the internal combustion engine, wherein the internal combustion engine and the electric drive are controlled so as to achieve the most optimal energy efficiency. However, the heat generation of the internal combustion engine is kept low as a result and the engine heat is therefore not always adequate to heat the vehicle interior, so that electric heat sources, for example a high-voltage PTC add-on heater (HV-PTC), are used.

Therefore, heating systems and heating strategies are required for hybrid vehicles that optimally use the available heat sources of the vehicle in terms of energy efficiency and electrical range of the hybrid vehicle.

A generic heating system for a vehicle with an internal combustion engine is known from DE 10 2008 035 955 A1, wherein the internal combustion engine is coupled by way of a coolant inlet and a coolant outlet with a first heat circuit having a heater for the interior of the vehicle. Furthermore, a bypass line of the first heat circuit is provided between the coolant inlet and the coolant outlet of the internal combustion engine for forming a second heat circuit. This bypass line is controlled by a bypass valve and has an electrically or exhaust-gas-heated heat source and a temperature sensor, wherein the heat source and the associated temperature sensor can also be arranged in the first heat circuit in the flow direction upstream of the heater provided for the interior. When a certain temperature is detected at a temperature sensor disposed at the coolant outlet of the engine, an inlet valve at the coolant inlet of the internal combustion engine is opened such that coolant passes through both the internal combustion engine and through the bypass line. This bypass valve is not closed until a thermostat opens a coolant circuit to a vehicle cooler, since otherwise the heat supplied via the additional heat source would be discharged via the coolant circuit to the vehicle cooler. When the internal combustion engine is started, the coolant is fed directly through the bypass line and the additional heat source to the heater for the interior, when the bypass valve is open and inlet valve at the coolant inlet of the internal combustion engine is closed. Thus, coolant will not flow through the heater during a cold start of the engine, while at the same time the coolant is heated by the heat source.

An obvious disadvantage of this known heating system is that the highest possible energy efficiency cannot always be achieved in all operating states of travel when used in a hybrid vehicle.

SUMMARY OF THE INVENTION

With this prior art in mind, it is an object of the invention to improve a heating system of the aforementioned type so that a high energy efficiency is attained with the available heat and heat sources when used in a vehicle, in particular in a hybrid vehicle. It is another object of the invention to provide a heating strategy for heating the vehicle interior of a vehicle by using the heating system according to the invention.

The first-mentioned object is achieved by a heating system with the features of claim1and with the features of claim2.

According to a first aspect of the invention, a heating system for heating of a vehicle interior of a vehicle having an internal combustion engine by means of a heat exchanger from a heater, includesa first heater circuit coupling the heat exchanger with the internal combustion engine and having a coolant flowing therethrough,a bypass line of the first heat circuit bypassing the internal combustion engine with a bypass valve to form a second heat circuit,at least one heat source arranged in flow direction of the coolant downstream of the bypass line, anda first temperature sensor for measuring the coolant temperature at a coolant outlet of the internal combustion engine, is characterized according to the invention in thata second temperature sensor for measuring the coolant temperature is provided at a coolant inlet of the internal combustion engine,a third temperature sensor for measuring the coolant temperature in the flow direction of the coolant is provided upstream of the at least one heat source, andin the presence of a first condition, where the first temperature sensor detects at least one predetermined nominal inlet temperature of the heat exchanger, the first heat circuit is operated exclusively with the internal combustion engine as a heat source, and in the absence of the first condition and in the presence of a second condition where the first temperature sensor detects during the operation of the first heat circuit a coolant temperature above the coolant temperature detected with the second temperature sensor, the at least one heat source is operated as an additional heat source, or where during the operation of the second heat circuit the first temperature sensor detects a coolant temperature above the coolant temperature detected by the third temperature sensor, the first heat circuit is operated in conjunction with the at least one heat source.

According to a second aspect of the invention, a heating system includesa first heat circuit having a coolant flowing therethrough and coupling the heat exchanger with the internal combustion engine,a bypass line of the first heat circuit bypassing the internal combustion engine and having a bypass valve to form a second heat circuit,at least one heat source arranged downstream of the bypass line in a flow direction of the coolant,a first temperature sensor for measuring a coolant temperature at a coolant outlet of the internal combustion engine, anda second temperature sensor for measuring the coolant temperature is provided at the inlet of the bypass valve,wherein in the presence of a first condition, where the first temperature sensor detects at least one predetermined nominal inlet temperature of the heat exchanger, the first heat circuit is operated exclusively with the internal combustion engine as a heat source, and wherein in the absence of the first condition and in the presence of a second condition, where during operation the first heat circuit, the first temperature sensor detects a coolant temperature above the coolant temperature detected by the second temperature sensor, the at least one heat source is operated as an additional heat source, or where during operation of the second heat circuit, the first temperature sensor detects a coolant temperature above the coolant temperature detected by the second temperature sensor, the first heat circuit is operated in conjunction with the at least one heat source.

With such an inventive heating system in accordance with the aforementioned solutions, the energetically ideal time for switching from the first heat circuit, wherein the engine heat of the internal combustion engine is available, to the second heat circuit, wherein the internal combustion engine is bypassed by way of the bypass line, and vice versa, is ensured by using two or three coolant temperature sensors arranged at suitable locations in the heat circuit. The appropriate switching between the two heat circuits is governed by specific relations of these determined temperatures. Furthermore, the robustness of the switching behavior between these two heat circuits can be maximized by using these three temperature sensors.

The second-mentioned solution differs from the first-mentioned solution in that the second temperature sensor also takes over the function of the third temperature sensor by being arranged upstream of the bypass valve in the flow direction of the coolant so that the temperature of the coolant is measured at the appropriate location both when the first heat circuit is activated as well as when the second heat circuit is activated. This solution can thus be used when the lengths of the lines of the two heat circuits is very short so that only negligible heat losses occur.

Another advantage of the two solutions of the invention is that only a small application effort is required for realizing the heating system according to the invention, because there is no need to develop accurate characteristic diagrams for the various operating points for each combination of variants of internal combustion engines and heat exchangers.

Finally, a better heating dynamics is obtained with such an inventive heating system in accordance with the two solutions, because less coolant needs to be heated by timely switching to the second heat circuit, when the internal combustion engine can no longer serve as a heat source and is therefore bypassed by the bypass line.

When, according to one embodiment of the invention, neither the first nor the second condition is satisfied, only the second heat circuit with the at least one heat source is operated as the heat source. In this case, when both conditions are not satisfied, the internal combustion engine would be a heat sink. This approach prevents the internal combustion engine from being heated electrically with the heat source which is preferably a heat exchanger and/or a PTC resistor and/or a fossil fuel add-on heater.

A heating strategy according to the first aspect of the invention for heating of a vehicle interior of a vehicle having an internal combustion engine with a heat exchanger is implemented by usinga first heater circuit coupling the heat exchanger with the internal combustion engine and having a coolant flowing therethrough,a bypass line of the first heat circuit bypassing the internal combustion engine with a bypass valve to form a second heat circuit,at least one heat source arranged in flow direction of the coolant downstream of the bypass line, whereinin the presence of a first condition, where the coolant temperature at a coolant outlet of the internal combustion engine reaches at least one predetermined nominal inlet temperature of the heat exchanger, the first heat circuit is operated exclusively with the internal combustion engine as a heat source, and in the absence of the first condition and in the presence of a second condition, where during the operation of the first heat circuit, the coolant temperature at the coolant outlet of the internal combustion engine is above the coolant temperature at a coolant inlet of the internal combustion engine, in addition the at least one heat source is operated as an additional heat source, or where during the operation of the second heat circuit, the coolant temperature at the coolant outlet of the internal combustion engine is above the coolant temperature upstream of the at least one heat source in the flow direction of the coolant, the first heat circuit and in addition the at least one heat source are operated.

A heating strategy according to the second aspect of the invention for heating of a vehicle interior of a vehicle having an internal combustion engine with a heat exchanger is implemented by operating, in the presence of a first condition where the coolant temperature at a coolant outlet of the internal combustion engine reaches at least one predetermined nominal inlet temperature of the heat exchanger, the first heat circuit exclusively with the internal combustion engine as a heat source, and in the absence of this first condition and in the presence of a second condition, where during the operation of this first heat circuit the coolant temperature at the coolant outlet of the internal combustion engine is above the coolant temperature at the inlet of the bypass valve, by operating the at least one heat source additionally as an additional heat source, or where during the operation of the second heat circuit the coolant temperature at the coolant outlet of the internal combustion engine is above the coolant temperature at the inlet of the bypass valve, by operating the first heat circuit and in addition the at least one heat source.

The advantages mentioned in connection with the heating system of the invention also apply to this heating strategy.

Advantageously, in a further development, when neither the first nor the second condition is satisfied, only the second heat circuit with the at least one heat source is operated as the sole heat source.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The structure of a heating system of a hybrid vehicle for heating its interior according toFIGS. 1 and 2includes an internal combustion engine1as well as a heat exchanger2, which is part of an air conditioning system of the hybrid vehicle. The internal combustion engine1and the heat exchanger2are coupled to each other via a heat circuit.

This heat circuit is composed, on the one hand, of a connecting line L1connecting the heat exchanger2via an electric cooling water pump5and a ⅔-way valve3with a coolant inlet1.2of the internal combustion engine1and, on the other hand, a connecting line L2connecting a coolant outlet1.1of the internal combustion engine1via a heat source4with the heat exchanger2.

Furthermore, this heat circuit includes a bypass line L bypassing the internal combustion engine1which can be opened or closed by the ⅔-way valve3as a bypass valve. A first temperature sensor S1is provided to measure the coolant temperature T1at the coolant outlet1.1of the internal combustion engine in the direction of the heat exchanger2.

This first temperature sensor S1is arranged in the cooling circuit of the internal combustion engine1so that coolant flows around it independent of the switching state of bypass valve3, thereby always providing a representative value for the coolant temperature.

The coolant temperature T2at the coolant inlet1.2of the internal combustion engine1is detected with a second temperature sensor S2. A third temperature sensor S3, which is arranged downstream of the location where the inlet of the bypass line L opens into the connection line L2, measures the coolant temperature T3in the flow direction of the coolant directly upstream of the heat source4. Lastly, a fourth temperature sensor S4is arranged upstream of the heat exchanger2in the connection line L2for measuring the inlet temperature.

When the bypass line L is closed by this bypass valve3, a first heat circuit W1is formed wherein a coolant flows from the heat exchanger2via the cooling-water pump5and the bypass valve3into the internal combustion engine1and from there back into the heat exchanger2via the connecting line L2. This first heat circuit W1is indicated graphically inFIG. 1with respect to the connection lines L1and L2by thicker lines as compared to the bypass line L. Upon activation of this first heat circuit W1, the waste heat from the internal combustion engine1is used as a heat source for the heating system and thus for heating the interior of the vehicle.

Conversely, when the bypass line L is opened by the bypass valve3, a second heat circuit W2is formed, wherein the coolant flows back from the heat exchanger2via the cooling-water pump5, the bypass valve3, and thereafter via the bypass line L into the heat exchanger2. This second heat circuit W2from the connection line L1to the bypass valve3, the bypass line L and the remaining connecting line L2to the heat exchanger2is highlighted inFIG. 2by thick lines. Upon activation of this second heat circuit W2, only the heat source4is used as a heat source for heating the coolant and thus for heating the interior of the vehicle.

The heating strategy performed with the heating system in accordance withFIGS. 1 and 2will now be explained in reference to the flow diagram ofFIG. 3.

To perform this heating strategy, the temperature values of the temperature sensors S1to S4are cyclically interrogated in accordance with the flow diagram ofFIG. 3, are compared with one another, and different actions are performed, namely one of the actions1to3in accordance with the flowchart ofFIG. 3, when certain relationships between these temperatures conditions occur.

According toFIG. 3, a first condition B1is checked after the start whether the coolant temperature T1at the coolant outlet1.1of the internal combustion engine1is greater than a predetermined nominal inlet temperature T4,sollupstream of the heat exchanger2(T1>T4,soll). If this first condition B1is satisfied, then the first heat circuit W1is activated as Action1, i.e. the bypass valve3closes the bypass line L, so that only the internal combustion engine1then used as the sole heat source for the heat circuit and hence for heating the interior of the vehicle.

If this first condition B1is not satisfied, the existence of a second condition B2which has two sub-conditions B21and B22is checked in additional steps.

If according to the sub-condition B21, the first heat circuit W1in accordance withFIG. 1is activated and the coolant temperature T1at the coolant outlet1.1of the internal combustion engine1is greater than the coolant temperature T2at the coolant inlet1.2of the internal combustion engine1(T1>T2), the heat source4is activated additionally as Action2as an additional heat source, i.e. in addition to the internal combustion engine1as a heat source.

If this sub-condition B21is not satisfied, then the second sub-condition B22is checked. If the second heat circuit W2according toFIG. 2is activated in accordance with this sub-condition B22and if the coolant temperature T1at the coolant outlet1.1of the internal combustion engine1is greater than the coolant temperature T3upstream of the heat source4(T1>T3), then a switchover to the first heat circuit W1takes place as Action2, so that, in addition to the heat source4as a heat source for the heat circuit, the internal combustion engine1is also used as an additional heat source for heating the interior of the vehicle.

This second condition indicates that the internal combustion engine is integrated as a heat source for heating the vehicle interior, as soon as the internal combustion engine1is able to do so.

If the second condition B2is not satisfied, i.e. neither the sub-condition B21nor the sub-condition B22is satisfied, a switchover to and activation of the second heat circuit W2takes place according toFIG. 3as Action3, so that only the heat source4is used as a heat source for the heat circuit. The internal combustion engine1is disconnected as a heat source when the bypass line L is opened by the bypass valve3, since the internal combustion engine1would otherwise represent a heat sink for the heat generated by the heat source4. This would be the case when the internal combustion engine1is first used as a heat source while the first heat circuit W1is active, but subsequently cools down to a temperature where it would represent a heat sink for the coolant and would therefore be heated by the heat that is electrically generated by a heat source4or by a plurality of such heat sources4. This would be contrary to an energy-efficient use of existing heat source.

If the heat source4were not available in the latter case, the first heat circuit W1would be activated again, with the heating system then using only the waste heat from the internal combustion engine1.

To ensure a robust, in particular a stable operation of the heating strategy according to the invention, the aforementioned temperature relationships are idealized and must be supplemented for their practical implementation with appropriate hysteresis and minimum dwell times in order to prevent, for example, continuous switching between the first and second heat circuit W1and W2.

FIG. 4shows an optional structure of a heating system according to the invention for a hybrid vehicle, which differs from that of the heating system according toFIGS. 1 and 2in that the function of the third temperature sensor S3is taken over by the second temperature sensor S2; however, in that case, this second temperature sensor S2is connected in the coolant circuit in the flow direction of the cooling medium upstream of the bypass valve3, i.e. it is located between the bypass valve3and the coolant pump5. This second temperature sensor S2is hence located in both the first heat circuit W1and in the second heat circuit W2. This structure according toFIG. 4can be used when the lengths of the lines are very short so that heat losses rarely occur. The associated heating strategy differs from that according toFIG. 3only in that the temperature T2of the second temperature sensor S2is used in the secondary condition B22instead of the temperature T3. The heating system in accordance withFIG. 4has advantageously a smaller number of temperature sensors, since the third temperature sensor T3corresponding to the heating system in accordance withFIGS. 1 and 2is not required.

In the aforedescribed embodiments, only a single heat source4is used; of course, several such heat sources may also be used. PTC heaters, as for example, HV-PTCs and/or heat exchangers of the heat pumps and/or fossil heaters are suitable as a heat source.

This heating strategy according to the invention ensures the energetically ideal time for switching from the first heat circuit W1, wherein the engine heat of the internal combustion engine1is available, to the second heat circuit W2, wherein the internal combustion engine1is bypassed by the bypass line L, and vice versa, by way of three or two coolant temperature sensors S1to S3and S1and S2, respectively, arranged at suitable locations in the heating system. This prevents the internal combustion engine from being heated by the heat source(s) when heating electrically. This heating strategy makes it possible to utilize the internal combustion engine as a heat source or as a heat sink by using the temperature sensors, thereby implementing, depending on the particular situation, the most efficient interconnection and optionally additional activation of the additional heat source(s) for heating the interior of the vehicle.

For example, when a particular coolant inlet temperature is required for the heat exchanger for heating the interior, this requirement is energy-efficiently fulfilled with the heating strategy according to the invention by using the “most advantageous” heat source, in this case the waste heat from the internal combustion engine. When using multiple heat sources, these are activated by taking into account the best coefficient of performance (COP).

If, for example, a hybrid vehicle is started in a cold state and is initially driven only electrically, then the interior space is heated exclusively by the additional heat sources4, with the engine being detected as a heat sink, and the second heat circuit is activated, preventing the heated coolant from flowing via the “cold” combustion engine1. If the engine1is started during the drive, for example, due to a high speed, the engine1becomes increasingly warmer. As soon as the internal combustion engine1has heated up to the point where its waste heat can contribute to heating the interior space, i.e. when the coolant temperature T1satisfies the second condition, then the internal combustion engine1is integrated by way of the first heat circuit W1so that the interior is heated by both the waste heat of the internal combustion engine and by the heat source4as a heat source. However, once the coolant temperature T1has reached the inlet temperature of the heat exchanger2due to the increasing waste heat, which depends on the temperature setting, the additional heat source4or several such heat sources4are switched off in stages, so that only the internal combustion engine1as a the sole heat source takes over heating the interior space.

Only the aforementioned temperature sensors S1to S3or S1and S2are required to carry out this heating strategy, independent of the engine variants and air conditioning equipment variants. The energy balance of the internal combustion engine and the heat exchanger are measured exclusively with the temperature sensors S1to S3, thus obviating the need for specific thermal models of the internal combustion engine and heat exchanger in a corresponding application software.

The application costs are low, because accurate characteristic curves for the various operating points need not be developed for each combination of variants of the internal combustion engine and heat exchanger.