Input control method for model-based adjustment of a hot path temperature in an air conditioning unit of a motor vehicle, air conditioning unit with control unit for carrying out the input control method and motor vehicle with such an air conditioning unit

Abstract

A pre-control method (500) for setting a hot path temperature in an air conditioning unit (100) of a motor vehicle (200) is described, wherein the pre-control method (500) comprises the following steps: Model-based setting (S501) of a first hot path temperature setpoint (TWs) as a function of at least one air conditioning parameter (KP) detected outside the hot path (106); Setting (S502) of an electrical power consumption of at least one electrical heating element (108) as a function of the first hot path temperature setpoint (TWs); Model-based calculation (S503) of a hot path temperature model value (TWm); Comparison (S504) of the hot path temperature model value (TWm) with the hot path temperature setpoint (TWs);Determine (S505) an initial time (t0) when the warm-path temperature model value (TWm) reaches a lower or upper limit setpoint (Tgu, Tgo), wherein the lower and upper limit setpoints (Tgu, Tgo) form a temperature band around the first warm-path temperature setpoint (TWs); Determine (S506) a time period (td) from the initial time (t0) to a predetermined end time (t1), provided the warm-path temperature model value (TWm) lies within the temperature band; where, upon reaching (S507) the end time (t1), a new model-based adjustment (S501) of the first warm path temperature setpoint (TWs) takes place depending on at least one air conditioning parameter (KP) detected outside the warm path (106).

Description

[0001] The invention relates to a pre-control method according to the preamble of claim 1 for setting a hot path temperature in an air conditioning unit of a motor vehicle, an air conditioning unit with a control unit for carrying out the pre-control method and a motor vehicle with such an air conditioning unit.

[0002] A heating element with a control unit for carrying out such a process is known, for example, from EP 2 082 920 A1 or DE 10 2016 120 201 A1.

[0003] The outlet temperature control in an air conditioning unit, also known as an air conditioner, is primarily achieved by adjusting the mixing ratio of two air mass flows. These consist of a fresh air mass flow (cold) and an air mass flow in the warm air path, which passes through one or more heating elements or sources (warm / hot). The mixing ratio is actively regulated via temperature dampers to set the desired outlet temperature. For comfortable air conditioning, it is also necessary to set the desired outlet temperature at a specific mixing ratio, a process known as stratification. To achieve this stratification, a target temperature is set for the warm air path mass flow to ensure the desired outlet temperature is reached at the desired mixing ratio.In previously known air conditioning units, this target temperature is regulated in a subordinate control loop in the hot path based on several temperature measuring points or temperature sensors downstream of the heating device or heat source.

[0004] It has been shown that determining the hot path setpoint is difficult in practical applications because the exact mass flow rates are unknown. To compensate for inaccuracies, it is therefore common practice to continuously adjust the hot path setpoint in a control system to achieve the desired discharge temperature at a given mixing ratio.

[0005] This approach requires, in particular, a subordinate control loop at the heat source, which includes several temperature sensors (up to eight). Furthermore, this approach exhibits a high tendency for the coupled control loops to oscillate at medium settling speeds. This is especially evident when the air mass flow rates change, and / or when the outlet temperature setpoints change, and / or when control limits (power) are reached.

[0006] The object underlying the invention is seen as being to provide a method that avoids the above disadvantages and in particular also leads to a constructive simplification of the air conditioning unit.

[0007] This problem is solved by a pre-control method, an air conditioning unit, and a motor vehicle with the features of the respective independent patent claims. Advantageous embodiments with appropriate further developments are specified in the dependent patent claims.

[0008] A pre-taxation procedure is therefore proposed for setting a hot path temperature in an air conditioning unit of a motor vehicle, wherein the pre-taxation procedure comprises the following steps: Model-based setting of a first warm path temperature setpoint depending on at least one air conditioning parameter measured outside the warm path; Setting the electrical power consumption of at least one electrical heating element as a function of the first hot path temperature setpoint; Model-based calculation of a warm path temperature model value; comparison of the warm path temperature model value with the first warm path temperature setpoint; Determining an initial time when the warm-path temperature model value reaches a lower or upper limit setpoint, where the lower and upper limit setpoints form a temperature band around the first warm-path temperature setpoint; Determining a time period from the start time to a predetermined end time, provided the warm path temperature model value lies within the temperature band; where, upon reaching the end time, the first warm path temperature setpoint is reset based on a model, depending on at least one air conditioning parameter recorded outside the warm path.

[0009] Such a feedforward control method, particularly a model-based one, eliminates the need for a subordinate control loop with multiple temperature sensors located downstream of the heating element, resulting in a simplified and more cost-effective air conditioning unit. In other words, this feedforward control method replaces the control loop for setting a hot path temperature. Furthermore, this type of feedforward control method reduces the tendency for oscillation.

[0010] The necessary accuracy of the actual hot path temperature is achieved through an iterative process, whereby the first hot path temperature setpoint is repeatedly set or adjusted if the hot path temperature model value remains within the temperature band for a certain period of time, which usually only occurs when a certain operating point of the air conditioning unit is reached, in which the parameters underlying the model-based feedforward control do not change or change only slightly.

[0011] In the pre-control method, one or more of the following parameters can be used as air conditioning parameters: an air temperature before entering the warm air path, an ambient air temperature, an air mass flow rate supplied to the warm air path, an indoor air temperature, or the position of a temperature damper in the air conditioning unit. Furthermore, active power limits can also be taken into account, such as a maximum or minimum supplied air mass flow rate, a maximum or minimum power consumption in a heating device, and the like.

[0012] In the input control method, the lower limit setpoint and the upper limit setpoint form a temperature band of approximately 4 to 6°C around the hot path temperature setpoint, so that the starting time is determined when the amount of a difference between the hot path temperature model value and the hot path temperature setpoint is 2 or 3°C.

[0013] Furthermore, an air conditioning unit for a motor vehicle is proposed, comprising at least one fan device; at least one evaporator connected to a refrigeration system; at least one heating device arranged downstream of the evaporator, in particular a heating coil connected to the refrigeration system, and at least one electric heating element, wherein the heating device is arranged within a hot path of the air conditioning unit; at least one cold path bypassing the hot path; at least one temperature flap arranged downstream of the hot path and the cold path; a mixing chamber formed downstream of the temperature flaps; and several outlets that can be fluidically connected to an interior of the motor vehicle; wherein the air conditioning unit has a control unit configured to carry out the above-described, in particular model-based, feedforward control method.

[0014] The air conditioning unit can be free of sensor devices for measuring the temperature of the warm air generated by the heating device downstream of the heating device and upstream of the temperature damper associated with the hot path.

[0015] Furthermore, the air conditioning unit can have at least one temperature sensor upstream of the heating device and downstream of the temperature flaps, particularly in the area of ​​a relevant outlet.

[0016] In other words, no temperature sensors are arranged in the hot path downstream or on the output side of the heating device because they are not necessary if the control unit is able to determine the hot path temperature model value using a model-based approach and compare it with the hot path temperature setpoint.

[0017] Furthermore, a motor vehicle with a refrigeration system and an air conditioning unit as described above is proposed.

[0018] Further advantages and details of the invention will become apparent from the following description of examples, which may also be embodiments, with reference to the figures. These show: Fig. 1 a simplified and schematic representation of an air conditioning unit in a motor vehicle; Fig. 2 a simplified and schematic flowchart of an input tax procedure; Fig. 3 Two simplified and schematic time / temperature diagrams to illustrate the input tax procedure.

[0019] In Fig. Figure 1 is a highly simplified and schematic representation of a motor vehicle 200 with an air conditioning unit 100, also illustrated only schematically.

[0020] The air conditioning unit 100 comprises at least one heat exchanger 102, in particular an evaporator for cooling and / or dehumidifying the supplied air L. The air L, or an air mass flow, is conveyed, in particular, by a fan or blower 103. Downstream of the evaporator 102, simplified air ducts 104 for cooled air, which can also be referred to as the cold path, and air ducts 106 for air to be heated, which can also be referred to as the hot path, are shown.

[0021] The air conditioning unit 100 has electric heating elements 108 in the air ducts 106 or in the warm air path, which are configured to heat the supplied air L as required. Alternatively or additionally, a heat exchanger 109, in particular a heating coil, connected to a refrigeration system of the motor vehicle 200, can be arranged in the warm air path, particularly upstream of the electric heating elements 108. The heat exchanger 109 and / or the heating elements 108 can be more generally referred to as the heating device of the air conditioning unit 100.

[0022] The air ducts 104, 106 can be (partially) opened or (partially) closed by means of actuators 110, such as flaps or the like. This allows the volume of air flowing through each air duct 104, 106 to be adjusted. The actuators 110 can also be referred to as temperature flaps.

[0023] Downstream of the temperature flaps 110, a mixing chamber 112 is arranged in which air introduced from the hot path 106 or the cold path 104 is at least partially mixed or stratified.

[0024] The air conditioning unit 100 also has several outlets 114 which can be fluidically connected to or are connected with an interior of the motor vehicle 200.

[0025] The air conditioning unit 100 further comprises a control unit 150, which is configured to control individual components of the air conditioning unit 100, such as a refrigeration system connected to the evaporator 102 and the heating coil 109, and / or the electric heating elements 108. The control unit 150 can also be part of a higher-level vehicle control unit.

[0026] The air conditioning unit 100 can also have several temperature sensors. For example, a temperature sensor 116a can be provided to detect the air temperature before it enters the warm air path 106. For example, a temperature sensor 116b can be provided to detect the ambient air temperature. Furthermore, the air outlets 114 can each be assigned their own temperature sensor 116c to detect the respective outlet air temperature. For example, an interior air temperature sensor 116d can be provided in the interior of the motor vehicle 200.

[0027] It is pointed out that in the Fig. 1. For reasons of better visibility, the reference symbol 114 is not shown for all outlets, and a temperature sensor 116c is not shown for every outlet.

[0028] The temperature sensors 116a-d shown as examples in the air conditioning unit 100 are all arranged outside the hot path 106. In other words, the hot path 106 is free of temperature sensors that detect an air temperature in the hot path 106, particularly downstream of the heating register 109 and / or downstream of the electric heating elements 108 and upstream of the temperature dampers 110.

[0029] In Fig. Figure 2 shows a simplified and schematic process for an input tax procedure 500 for an air conditioning unit 100. Such an input tax procedure can be implemented, in particular, by means of the control unit 150.

[0030] In the pre-taxation procedure 500, according to step S501, a model-based setting of a first warm path temperature setpoint WTs is carried out depending on at least one air conditioning parameter KP recorded outside the warm path 106.

[0031] According to step S502, an electrical power consumption of at least one electrical heating element 108 is set depending on the first hot path temperature setpoint WTs.

[0032] In step S503, a model-based calculation of a warm path temperature model value WTm is performed.

[0033] In step S504, the warm path temperature model value WTm is compared with the warm path temperature setpoint WTs.

[0034] In step S505, an initial time t0 is determined when the warm path temperature model value WTm reaches a lower or upper limit setpoint Tgu, Tgo, where the lower and upper limit setpoints Tgu, Tgo form a temperature band around the first warm path temperature setpoint WTs.

[0035] According to step S506, a time period td is determined from the start time t0 to a predetermined end time t1, provided that the warm path temperature model value WTm is within the temperature band.

[0036] According to step S507, the end time t1 is reached and the procedure returns to step S501, in which a new model-based adjustment of the first warm path temperature setpoint WTs takes place depending on at least one air conditioning parameter detected outside the warm path 106.

[0037] The air conditioning parameter KP used as an input variable in step S501 can, for example, be one or more of the following: an air temperature TL before entering the warm air path 106, an ambient air temperature TU, an air mass flow mL conveyed into the warm air path, an indoor air temperature TI, a position TK of a temperature damper 110 of the air conditioning unit 100.

[0038] In the input control procedure 500, the lower limit setpoint Tgu and the upper limit setpoint Tgo can form a temperature band of approximately 4 to 6°C around the hot path temperature setpoint WTs, so that the initial time t0 is determined when the difference between the hot path temperature model value WTm and the hot path temperature setpoint WTs is 2 or 3°C. In other words, t0 is set when |WTm - WTs| = 2 or 3, or |WTs - WTm| = 2 or 3.

[0039] The above-described input control method 500 is subsequently illustrated using two temperature / time diagrams of the Fig. 3 explained.

[0040] In the diagram of Fig. 3A shows the warm path temperature setpoint TWs as a solid black line. The model-based determined warm path temperature model value WTm is shown as a dashed line. An interior temperature setpoint Tls, which can also be understood or referred to as the climate temperature setpoint, is shown on the vertical axis. The lower and upper limit setpoints Tgu and Tgo are shown as longer dashed lines above and below the curve for the warm path temperature setpoint TWs.

[0041] In the diagram of Fig. 3B shows the target indoor temperature Tis as a closely spaced dashed line. The course of a measured indoor temperature value TI is shown as a dashed line (three lines, two dots).

[0042] Furthermore, the diagram shows the Fig. 3 partially illustrates the steps according to the procedure 500 described above, in particular steps S501, S505 and S507.

[0043] Starting from a starting point that is the origin of the diagrams of the Fig. When the value is 3, step S501 is executed in the pre-control procedure. For example, a target indoor temperature value Tis is specified. Settings are made on the air conditioning unit 100 using the control unit 150, such as a specific power consumption in the electric heating elements 108, a specific airflow rate using the blower 103, and the like.

[0044] Based on one or more such air conditioning parameters KP, a warm path temperature setpoint TWs is determined or set (solid line in Fig. 3A) and continuously calculates a model-based development of the warm path temperature model value TWm (dashed line in Fig. 3A).

[0045] If the model-based calculated warm path temperature model value TWm reaches the lower limit setpoint Tgu (step S505), an initial time t0 is determined. If the calculated warm path temperature model value TWm remains within the temperature band defined by the limit setpoints Tgu and Tgo, a stable operating state is assumed to have been reached. The system monitors whether this stable operating state persists for a specific duration td and then reaches an end time t1.

[0046] If this is the case, for example at the end time t1, it can be compared whether the indoor temperature value TI has already reached the indoor temperature setpoint TIs, which in Fig. 3B is evident. This is after the first stable operating phase in Fig. 3A or Fig. 3B is apparently not yet the case. It should be taken into account that the indoor temperature TI is a mixed temperature with heat losses.

[0047] The advantage of the model temperature monitoring, i.e., of TWm in relation to TWs, lies in particular in the fact that disturbances or limitations in the air conditioning unit 100 can be detected, such as whether the electrical heating elements 108 provide enough power to heat the air mass flow L to the setpoint level.

[0048] Regarding the Fig. 3B means that at the first time point t0, it is initially determined that sufficient power or energy has not yet been provided to reach the indoor temperature setpoint TIs.

[0049] During the stable operating state (t0 to t1), it can be checked, for example, whether an increase in the power consumption at the heating elements 108 is possible on the system side at all, in particular whether sufficient electrical energy can be provided that is not otherwise needed in the motor vehicle.

[0050] Step S501 is executed again, and the warm path temperature setpoint WTs is set to a higher level based on newly acquired air conditioning parameters. According to the new settings, the warm path temperature model value TWm is continuously calculated using a model until it reaches the lower limit setpoint Tgu again (second temperature band in). Fig. 3A). The test for a stable operating state is repeated by determining the start time t0, the duration td and the end time t1.

[0051] The measured interior temperature value TI is higher at this point than the interior temperature setpoint TIs ( Fig. 3B), so that another adjustment is made by executing procedure 500 starting with step S501.

[0052] From the Fig. 3A shows that the input tax procedure 500 with the model-based calculated hot path temperature model value TWm is repeated or iteratively carried out when a stable operating state is reached.

[0053] Based on this approach, it is possible to do without temperature sensors, which are usually located downstream of the heating elements 108 and / or downstream of the heating register 109 and upstream of the temperature damper 110.

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