Control system for a heating system and method for operating a heating system

Abstract

A control system and method for a heating system of an electric vehicle or hybrid vehicle is embodied such that when there is a heating request for a passenger compartment of the vehicle, a heating mode is set in order to heat the passenger compartment by heat from a heating circuit. In a mixed mode, an excess heat in the heating circuit is output to the surroundings, or in an excess mode, the excess heat is retained in the heating system, in order to satisfy a heating request. In the mixed mode, a degree of opening of the heating circuit is set such that only a partial quantity of coolant from the heating circuit is exchanged with a cooling circuit. The mixed mode is activated if the excess heat in the heating circuit exceeds a threshold value which is determined in accordance with an external temperature.

Claims

1. A system for a heating system of an electric vehicle or hybrid vehicle, comprising: a control system configured to execute a process such that: when there is a heating request for a passenger compartment of the vehicle, a heating mode is set in order to heat the passenger compartment by heat from a heating circuit, in a mixed mode, an excess heat in the heating circuit is output to surroundings via a surroundings cooler in a cooling circuit, or in an excess mode the excess heat is retained in the heating system, in order to satisfy a heating request, in the mixed mode, a degree of opening of the heating circuit is set in such a way that only a partial quantity of coolant from the heating circuit is exchanged with the cooling circuit and as a result the excess heat is output to the surroundings, the mixed mode is activated if the excess heat in the heating circuit exceeds a threshold value which is determined in accordance with an external temperature.

2. The system according to claim 1, wherein the control system is further configured such that: the threshold value becomes lower as the external temperature rises.

3. The system according to claim 1, wherein the control system is further configured such that: in the mixed mode, the degree of opening is increased as the excess heat in the heating circuit increases.

4. The system according to claim 1, wherein the control system is further configured such that: the degree of opening is determined as a function of the external temperature and the excess heat on the basis of a characteristic diagram.

5. The system according to claim 1, wherein the control system is further configured such that: the excess heat is determined on the basis of a difference between a heating circuit actual temperature of the coolant in the heating circuit and a heating circuit setpoint temperature or corresponds to this difference.

6. The system according to claim 1, wherein the control system is further configured such that: in the excess mode, the excess heat is retained in the heating circuit, in order to satisfy the heating request from the heating circuit.

7. The system according to claim 1, wherein the control system is further configured such that: in the excess mode, the excess heat is retained in the cooling circuit, and in order to satisfy the future heating request it is transferred from the cooling circuit into the heating circuit by a heat pump of the heating system.

8. The system according to claim 1, wherein the control system is further configured such that: in the heating mode, the heating circuit is opened if a heating circuit setpoint temperature is lower than a coolant actual temperature upstream of the heating circuit.

9. The system according to claim 1, wherein the control system is further configured such that: if neither the heating mode nor a cooling mode is activated, the heating circuit is closed in accordance with a heating circuit actual temperature if the heating circuit actual temperature is higher than the external temperature, and is opened if the heating circuit actual temperature is lower than the external temperature or corresponds thereto.

10. The system according to claim 1, wherein the control system is further configured such that: in the heating mode, a fan rotational speed of a fan of the heating system is set in accordance with a coolant actual temperature and a minimum coolant temperature, and in a cooling mode, the fan rotational speed of the fan is set in accordance with the coolant actual temperature.

11. The system according to claim 1, wherein the control system is further configured such that: in the heating mode, a pump rotational speed of a cooling circuit pump is set in a cooling circuit of the heating system in accordance with a coolant actual temperature and a minimum coolant temperature, and in a cooling mode, the pump rotational speed of the cooling circuit pump is set in accordance with the coolant actual temperature.

12. The system according to claim 1, wherein the control system is further configured such that: in the heating mode, a degree of opening of one or more air flaps of the heating system are/is set in accordance with a coolant actual temperature and a minimum coolant temperature, and in a cooling mode, the degree of opening of the one or more air flaps is set in accordance with the coolant actual temperature.

13. The system according to claim 1, wherein the control system is further configured such that: in the heating mode, a compressor of the heating system is activated predictively even before a heating circuit actual temperature undershoots a heating circuit setpoint temperature, in order to avoid a heat deficit or in order to avoid activation of an additional heater in the heating circuit.

14. A method for operating a heating system via a control system, the method comprising the steps of: making a heating request for a passenger compartment of the vehicle and in response to the heating request a heating mode is set in order to heat the passenger compartment by heat from a heating circuit; in a mixed mode, an excess heat in the heating circuit is output to surroundings via a surroundings cooler in a cooling circuit, or in an excess mode the excess heat is retained in the heating system, in order to satisfy a heating request; in the mixed mode, a degree of opening of the heating circuit is set in such a way that only a partial quantity of coolant from the heating circuit is exchanged with the cooling circuit and as a result the excess heat is output to the surroundings; and the mixed mode is activated if the excess heat in the heating circuit exceeds a threshold value which is determined in accordance with an external temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram showing a heating system and a control system.

(2) FIG. 2 shows a refrigeration circuit of the heating system.

(3) FIG. 3 shows a variant of the refrigeration circuit.

(4) FIG. 4 is a characteristic diagram for controlling a heating circuit of the heating system.

(5) FIG. 5 shows control concepts for a fan, air flaps and a cooling circuit pump.

(6) FIG. 6 shows a control concept for a compressor.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) FIG. 1 shows a heating system 2 and a control system 4 for controlling various components of the heating system 2. The heating system 2 is designed for use in an electric vehicle or hybrid vehicle (not shown in more detail) which is also referred to merely as a vehicle. The heating system 2 has an overall cooling circuit 6 and a refrigeration circuit 8, which is not illustrated in FIG. 1. Two variants of the refrigeration circuit 8 are shown in FIGS. 2 and 3. The heating system 2 in FIG. 1 illustrates a preferred embodiment, but the aspects which are described below, specifically with respect to the interconnection of two respective components to one another, can also be applied individually.

(8) The overall cooling circuit 6 has a plurality of circuits 10, 12, 14, specifically a cooling circuit 10, an HVAC circuit 12 and a heating circuit 14. A high-voltage accumulator 16 is connected to the HVAC circuit 12 in order to supply an electric drive train of the electric vehicle or hybrid vehicle. Furthermore, an HVAC additional heater 18 is connected to the HVAC circuit 12. Furthermore, a chiller 20 is connected to the HVAC circuit 12 and is also connected to the refrigeration circuit 8. Furthermore, an HVAC centrifugal pump 22 is arranged in the HVAC circuit 12, in order to circulate coolant.

(9) A heat source 24 of the vehicle is connected to the cooling circuit 10. The heat source 24 is, for example, an electric machine of the vehicle or a power electronics system or a charging electronics system. Downstream of the heat source 24 a first surroundings cooler 26 is connected to the cooling circuit 8 in order to exchange heat with the surroundings. A fan 27 is arranged downstream of the first surroundings cooler 26 in a surroundings air path. The first surroundings cooler 26 is combined in the exemplary embodiment shown with a second surroundings cooler 28 to form a cooler package. However, basically a refinement without the second surroundings cooler 28 is also possible. One or more air flaps 29 are arranged in the surroundings air path upstream of the two surroundings coolers 26, 28 in order to control the supply of air to the surroundings coolers 26, 28. The exchange of heat with the surroundings can therefore be set by actuating the fan 27 and the air flaps 29. Furthermore, a cooling circuit pump 30 is arranged in the cooling circuit 10, here downstream of the first surroundings cooler 26 and upstream of the heat source 24.

(10) The heating circuit 14 serves to control the temperature of the passenger compartment. A heating heat exchanger 32 is connected to the heating circuit 14 in order to heat passenger air for a passenger compartment 34 of the vehicle. Furthermore, a condenser 36 is connected to the heating circuit 14 and also connected to the refrigeration circuit 8 and forms together with the chiller 20 a heat pump which is designed to transfer heat from the chiller 20 into the heating circuit 14. Furthermore, a heating circuit pump 38 and an additional heater 40 are arranged in the heating circuit 14. In the exemplary embodiment shown, the condenser 36, the heating circuit pump 38, the additional heater 40 and the heating heat exchanger 32 are arranged in the specified sequence downstream of one another on a main branch of the heating circuit 14. The heating circuit 14 is connected to the cooling circuit 10 via a heating circuit feedline 42 and a heating circuit return line 44 in such a way that the main branch and the components connected thereto are arranged in series with the first surroundings cooler 26.

(11) The HVAC circuit 12 is also connected to the cooling circuit 8, but not to the heating circuit 14. The HVAC circuit 12 is connected upstream and downstream of the heat source 24 and downstream of the chiller 20. As a result, a series connection or a parallel connection of the high-voltage accumulator 16 and the heat source 24 is optionally possible and is also set given corresponding demand.

(12) The heating system 2 also has a compensation volume 52 for the coolant. Furthermore, a number of temperature sensors 54 are arranged in the overall cooling circuit 6 in order to measure the temperature of the coolant.

(13) In order to control the temperature of the passenger compartment, the heating system 2 has an air-conditioning evaporator 56 which is connected to the refrigeration circuit 8. As is shown in FIGS. 2 and 3, the air-conditioning evaporator 56 is connected parallel to the chiller 20 in the refrigeration circuit 8. In order to set the cooling capacity of the air-conditioning evaporator 56, an expansion valve 58 is connected upstream thereof. An expansion valve 60 is also connected upstream of the chiller 20. The heating heat exchanger 32 and the air-conditioning evaporator 56 are together part of an air-conditioning device by means of which the passenger compartment 34 is heated, cooled and also dehumidified. The refrigeration circuit 8 in FIG. 2 additionally has two internal heat exchangers 64, in each case one for the air-conditioning evaporator 56 and one for the chiller 20. In the variant in FIG. 3, just one internal heat exchanger 64 is arranged for both evaporators. In a variant which is not shown no internal heat exchanger 64 is present.

(14) In order to switch over the heating system 2 between various switched states and in order to set various operating modes various actuators, here valves 66, 68, 70, 72 are arranged in the overall cooling circuit 6. A shut-off valve 66 in the heating circuit feedline 42 serves to shut off the heating circuit 14, that is to say to open or close it. Alternatively, the shut-off valve 66 is arranged in the heating circuit return line 44. Furthermore, three 3/2-way valves 68, 70, 72 are arranged, said valves permitting, depending on the switched position, various series connections and parallel connections of the first surroundings cooler 26, chiller 20, heat source 24 and high-voltage accumulator 16. The heating circuit 14 can be shut off independently thereof in each case.

(15) The control system 4 is embodied in such a way that when there is a heating request for a passenger compartment 34 of the vehicle a heating mode is set in order to heat the passenger compartment by means of heat from the heating circuit 14. In a mixed mode, excess heat dT in the heating circuit 14 is output to the surroundings via the surroundings coolers 26, 28 in the cooling circuit 10 or in an excess mode it is retained in the heating system 2 in order to satisfy a future heating request. In the mixed mode, a degree of opening of the heating circuit 14 is set in such a way that only a partial quantity of coolant from the heating circuit 14 is exchanged with the cooling circuit 10, as a result the excess heat dT is output to the surroundings. In contrast, the remaining part of the coolant circulates in the heating circuit 14 and serves, in particular, to heat the passenger compartment. The degree of opening is set in the exemplary embodiment shown by a clocking system of the shut-off valve 66. The mixed mode is activated if the excess heat in the heating circuit 14 exceeds a threshold value S1 which is determined in accordance with the external temperature Ta. This relationship is explained in more detail below with reference to FIG. 4.

(16) The excess heat dT is therefore not necessarily automatically discharged in the heating system 2 but rather, if appropriate, stored, specifically in the coolant, in a way which is adapted to the situation. This is done here by taking into account the external temperature Ta in the decision as to whether or not the excess heat dT is discharged from the heating circuit 14 to the surroundings by means of the mixed mode, and instead is retained in the heating system 2 in the excess mode.

(17) In the mixed mode, the heating circuit 14 is only partially opened and is operated in a clocked fashion here by means of the shut-off valve 66, to discharge the excess heat dT from the heating circuit 14 in the mixed mode. As a result of the recurring opening and closing, sometimes heat is retained in the heating circuit 14 in order to heat the passenger compartment, and sometimes heat is output into the cooling circuit 10 in order to be output to the surroundings. The mixed mode is set as a result of the fact that the shut-off valve 66 is opened and closed periodically. In a variant which is not shown but is equivalent, instead of the shut-off valve 66 a proportional valve with a variant flow cross section is used.

(18) The excess mode serves to retain heat, and this can be implemented in different ways. For example, the heating circuit 14 is, as in the pure heating mode, continuously closed and the heat is stored in the heating circuit 14. Alternatively or additionally, the supply of surroundings air to the surroundings coolers 26, 28 is interrupted by means of the air flaps 29 so that heat is not exchanged with the surroundings. Alternatively or additionally, the supply of coolant to the surroundings coolers 26, 28 is stopped, e.g. in that the cooling circuit pump 30 is deactivated or its pump rotational speed PD is reduced. The heat is alternatively or additionally stored in the cooling circuit 10.

(19) FIG. 4 shows a characteristic diagram K1 for controlling the heating circuit 14, i.e. for determining and setting the degree of opening. The characteristic diagram K1 shows three regions R1, R2, R3 which predefine the degree of opening in accordance with the external temperature Ta and the excess heat dT and contain the latter, for example, directly as a value. The excess heat dT corresponds here to the difference between a heating circuit actual temperature T-HK-I of the coolant in the heating circuit 14 and a heating circuit setpoint temperature T-HK-S. In the region R1 the heating circuit 14 is closed, in the region R2 the mixed mode is set, and in the region R3 the heating circuit 14 is completely open, i.e. the degree of opening is set to a maximum value. On the basis of the heating mode in the region R1, the mixed mode is activated in the region R2 if the threshold value S1 for the current excess heat dT is exceeded. The heating circuit 14 is then partially opened, i.e. the maximum possible degree of opening is not set but rather part of the heat continues to be used to heat the passenger compartment. As the external temperature Ta rises here, the threshold value S1 becomes lower. As a result of this dependence on the external temperature Ta, the start of the opening of the heating circuit 14 shifts, so that in corresponding cases premature discharging of heat is prevented. Correspondingly, the mixed mode is also prevented, with positive consequences for the acoustic behavior and the wear of the heating system 2. Within the region R2, the degree of opening is increased further as the excess heat dT in the heating circuit 14 increases. In the case of a further increase in the excess heat dT, the region R3 is then reached and a cooling mode is automatically set and the heating circuit 14 is opened to the maximum extent. The degree of opening is correspondingly set to a maximum value.

(20) If neither the heating mode nor the cooling mode is activated, the heating circuit 14 is closed in accordance with the heating circuit actual temperature T-HK-I if the heating circuit actual temperature T-HK-I is higher than the external temperature Ta, and opened if the heating circuit actual temperature T-HK-I is lower than the external temperature Ta or corresponds to it.

(21) Furthermore, the control according to characteristic diagram K1 for FIG. 4 is modified here in certain situations by means of a further control concept and the determined degree of opening is, if appropriate, overwritten. Therefore, the heating circuit 14 is continuously opened here if the heating circuit setpoint temperature T-HK-S is lower than the coolant actual temperature T-KM-I upstream of the heating circuit 14. As a result, an excess mode is set, which overwrites the degree of opening which is determined for the heating mode or for the mixed mode from the regions R1, R2 and sets it to its maximum value.

(22) FIG. 5 now shows control concepts for the fan 27, the air flaps 29 and the cooling circuit pump 30. The fan 27 has an adjustable fan rotational speed LD. This is set in the heating mode in accordance with a coolant actual temperature T-KM-I and a minimum coolant temperature T-KM-min. The minimum coolant temperature T-KM-min specifies a lower limiting value which prevents the coolant at the surroundings coolers 26, 28 from being cooled to such an extent that the latter ice up. For this purpose, the minimum coolant temperature T-KM-min is determined e.g. by means of a characteristic diagram (not shown) in accordance with the external temperature Ta. In the cooling mode, the fan rotational speed LD is set in accordance with the coolant actual temperature T-KM-I by means of corresponding characteristic diagrams K2, K3, K4, in such a way that when heat is discharged via the surroundings coolers 26, 28 and when the coolant actual temperature T-KM-I rises, a higher fan rotational speed LD is set in order to cool the correspondingly warmer coolant to a greater extent. In the excess mode of the cooling circuit, control of the fan 27 is dispensed with and for this purpose, it is deactivated, since an exchange of heat with the surroundings is not desired in this case. The specified concepts for actuating the fan 27 are in parallel with respect to one another, as is clarified in FIG. 5, and are linked via a maximum selection M which selects the respective highest fan rotational speed LD.

(23) As shown in FIG. 5, the control concepts for the fan 27 are applied analogously here also to the air flaps 29 and the cooling circuit pump 30, but in each case with separate individual characteristic diagrams K2, K3, K4. The air flaps 29 are actuated here by means of a degree of opening which indicates how far the air flaps 29 are opened or closed. The cooling circuit pump 30 is actuated by means of a pump rotational speed PD. The input parameters for controlling the fan 27, the cooling circuit pump 30 and the air flaps 29 are accordingly the same. The interpretation of these parameters is, however, adapted to the respective component by means of separate and individual characteristic diagrams K2, K3, K4.

(24) The compressor 62 in the refrigeration circuit 8 is operated with a specific compressor rotational speed VD and then generates a corresponding refrigeration capacity. FIG. 6 shows a closed-loop control concept with a closed-loop controller R, by means of which the capacity of the compressor 62 is subjected to closed-loop control in that the compressor rotational speed VD is subjected to closed-loop control. In the heating mode, closed-loop control in which the heating circuit actual temperature T-HK-I is used as closed-loop control variable is carried out by means of the control system 4. The heating circuit setpoint temperature T-HK-S is used as a guide variable for the closed-loop control, as shown in FIG. 6. During such closed-loop control of the compressor 62, intermittent operation of the compressor 62 usually then occurs in the region of the heating circuit setpoint temperature T-HK-S, since said compressor 62 is deactivated when the heating circuit setpoint temperature T-HK-S is exceeded if it is at its minimum permissible compressor rotational speed VD, and is activated again when subsequent undershooting occurs. In order to avoid a heating deficit owing to this clocking sequence of the compressor 62, the compressor 62 is predictively activated even before the heating circuit actual temperature T-HK-I undershoots the heating circuit setpoint temperature T-HK-S. For this purpose, in the exemplary embodiment in FIG. 6 an offset HK-offs is added to the heating circuit actual temperature T-HK-I, with the result that the closed-loop controller R for the compressor 62 activates said compressor prematurely. The predictive actuation then intervenes effectively in the closed-loop control of the compressor 62.

LIST OF REFERENCE SYMBOLS

(25) 2 Heating system

(26) 4 Control system

(27) 6 Overall cooling circuit

(28) 8 Refrigeration circuit

(29) 10 Cooling circuit

(30) 12 HVAC circuit

(31) 14 Heating circuit

(32) 16 High-voltage accumulator

(33) 18 HVAC additional heater

(34) 20 Chiller

(35) 22 HVAC centrifugal pump

(36) 24 Heat source

(37) 26 First surroundings cooler

(38) 27 Fan

(39) 28 Second surroundings cooler

(40) 29 Air flaps

(41) 30 Cooling circuit pump

(42) 32 Heating-type heat exchanger

(43) 34 Passenger compartment

(44) 36 Condenser

(45) 38 Heating circuit pump

(46) 40 Additional heater

(47) 42 Heating circuit feedline

(48) 44 Heating circuit return line

(49) 46 Cooler branch

(50) 52 Compensation volume

(51) 54 Temperature sensor

(52) 56 Air-conditioning evaporator

(53) 58 Expansion valve (of the air-conditioning evaporator)

(54) 60 Expansion valve (of the chiller)

(55) 62 Compressor

(56) 64 Internal heat exchanger

(57) 66 Shut-off valve

(58) 68 3/2-way valve

(59) 70 3/2-way valve

(60) 72 3/2-way valve

(61) dT Excess heat

(62) HK-offs Offset

(63) K1-K4 Characteristic diagram

(64) M Maximum selection

(65) ÖG Degree of opening of flaps

(66) PD Pump rotational speed

(67) R Closed-loop controller

(68) R1,R2,R3 Region

(69) S1 Threshold value

(70) Ta External temperature

(71) T-HK-I Heating circuit actual temperature

(72) T-HK-S Heating circuit setpoint temperature

(73) T-KM-I Coolant actual temperature

(74) VD Compressor rotational speed

(75) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.