Air conditioning unit for a motor vehicle, as well as an air conditioning system including the air conditioning unit and a method for operating the air conditioning unit.

Abstract

Air conditioning unit (1) for a motor vehicle, comprising a housing with at least one first air inlet (3a) for the inlet of fresh air from the environment and a second air inlet (3b) for the inlet of recirculated air from a passenger compartment, and each an air guide device (4a, 4b) for independently varying the flow cross-sections of the air inlets (3a, 3b), wherein the air guide device (4a, 4b) is each designed as an air flap which is movably mounted between two end positions, wherein a bypass flow channel (7) with a dynamic air guide device (8) is formed for the first air inlet (3a), wherein the dynamic air guide device (8) is designed as an air flap movably mounted between two end positions in such a way as to completely close the bypass flow channel (7) in one end position, and the bypass flow channel (7) has a smaller flow cross-section than the first air inlet (3a).

Description

[0001] The invention relates to an air conditioning unit for a motor vehicle. The air conditioning unit has a housing with at least one first air inlet for drawing in fresh air from the environment, a second air inlet for drawing in recirculated air from a passenger compartment, and an air guide device for independently varying the flow cross-sections of the air inlets. The air guide device is designed as an air flap, which is movably mounted between two end positions.

[0002] The invention also relates to an air conditioning system for a motor vehicle comprising means for conveying, cooling and heating air as well as the air conditioning unit and a method for operating the air conditioning unit.

[0003] In motor vehicles, the increasing number of technical components and rising comfort demands necessitate optimization not only in terms of installation volume but also of the functionality of the components. This includes increasing the effectiveness of the air conditioning system components.

[0004] Air conditioning units of this type have an air intake housing with an air inlet for outside air drawn in from outside the vehicle's passenger compartment, also known as fresh air or ambient air, and an air inlet for recirculated air drawn from the passenger compartment. The air is drawn into the air conditioning unit via the inlets by a fan, then conditioned and discharged into the passenger compartment through suitable distribution openings, also known as air outlets.

[0005] The position of at least one flap located within the air intake housing determines whether the intake air mass flow consists of pure fresh air, pure recirculated air, or a mixture of fresh air and recirculated air. The flap is adjustable within the housing between two end positions, and is usually pivotable. A mixture of the intake air mass flow is achieved by an intermediate position of the flap between the two end positions.

[0006] German patent DE 199 15 966 ​​A1 discloses an air intake housing for a heating and / or air conditioning system of a motor vehicle. The air intake housing comprises an inlet for outside air, an inlet for recirculated air, an outlet connected to a fan, and a flap. The flap is pivotally mounted within the housing between an outside air position and a recirculated air position and can assume intermediate positions.

[0007] In air intake housings known from the prior art, undesirable bypass flows occur when the flap is in intermediate positions between the fresh air inlet and the recirculated air inlet. In these cases, fresh air flows around the flap and is introduced into the passenger compartment of the vehicle through the recirculated air inlet without being conditioned. As a result of such a bypass mass flow, for example, excessively cold or excessively warm outside air can enter the passenger compartment directly.

[0008] The cause of bypass airflow is driving the vehicle at high speed. This results in high stagnation pressure at the fresh air intake, which must be compensated for to maintain a constant airflow rate from the blower and to prevent outside air from flowing directly into the recirculated air intake, and thus into the passenger compartment. Particularly with low fresh air volumes and high stagnation pressures, the cross-sectional area for the fresh air intake must be significantly reduced. This situation is occurring more and more frequently in electric vehicles, as the air conditioning system operates with less fresh air and more recirculated air to conserve electrical energy and maximize the vehicle's range. Consequently, the stagnation pressure control in the air conditioning system is becoming increasingly important.

[0009] In ram pressure compensation or ram pressure control, the cross-sectional area of ​​the air intake is reduced depending on the vehicle speed. Ram pressure compensation thus refers to a throttling of the high back pressure generated by high vehicle speed in the intake area of ​​the air intake housing.

[0010] Since, on the one hand, the fresh air inlet has a large flow cross-section, especially to generate the lowest possible air resistance at operating points of the air conditioning system with large quantities of fresh air, it is, on the other hand, a major challenge to close the fresh air inlet with a single flap in such a way that sufficient dynamic pressure control is ensured when only small quantities of fresh air are required.

[0011] It is known from the prior art to implement ram pressure control directly via a flap, also known as a fresh air flap, which varies the flow cross-section of the fresh air inlet. This flap continuously closes the flow cross-section of the fresh air inlet as the ram pressure increases. However, at high ram pressures and low fresh air flow rates, this pressure-dependent closing of the fresh air inlet results in very narrow, slit-like flow cross-sections between the fresh air flap and the air conditioning unit housing. With such small fresh air inlet flow cross-sections, the necessary ram pressure control is extremely difficult or impossible, both technically (due to the backlash inherent in controlling the flap movement with a conventional stepper motor) and physically.Furthermore, insufficient flow cross-sections promote disturbing noise development, such as rushing or whistling.

[0012] To reduce the high ram pressure in the air intake duct in front of the fresh air flap at high vehicle speeds, ram pressure flaps are conventionally used upstream in the air inlet area, since it is not sufficient to adjust the fan speed to the vehicle speed, for example, to control the vehicle speed-dependent ram pressure of the outside air.

[0013] In known air intake housings with a single flap that allows for "fresh air" and "recirculated air" or "partial recirculated air" positions, an additional second flap is therefore required for ram pressure compensation. This applies particularly when, in the "partial recirculated air" position, a portion of the air is drawn from the passenger compartment. However, the upstream ram pressure flap used for compensation requires sufficient installation space in the air intake of the air conditioning unit.

[0014] DE 10 2004 004 165 B3 discloses an air inlet for a ventilation, heating, or air conditioning system of a motor vehicle, comprising an outside air duct supplying outside air, a recirculated air duct supplying recirculated air, a ram air damper for controlling the outside air duct, and a recirculation damper for controlling the recirculation duct. The recirculation damper and the ram air damper are designed as a combined ventilation damper, which, when the recirculation duct is closed, allows for throttling of the air mass flow through the outside air duct.

[0015] US Patent 2014 / 0 194 048 A1 describes a heating, ventilation, and / or air conditioning unit for the passenger compartment of a motor vehicle. The unit comprises a housing with a first air inlet and a second air inlet for directing an internal airflow, which enters the housing through at least one of the air inlets. At least one heat exchanger is arranged within the housing. The housing also includes an air recirculation duct as a bypass flow channel to the heat exchanger and an air inlet duct for directing the internal airflow through the heat exchanger. The air inlet duct is bounded by an outer wall of the housing and an inner wall located within the housing. The inner wall, extending from the first air inlet, is situated between the heat exchanger located in the air inlet duct and the air recirculation duct.

[0016] As the demands on the efficient operation of the air conditioning system and the required level of comfort increase, the air volumes or mass flows to be controlled become smaller and are confined to narrow, predetermined ranges. Small air volumes are difficult to regulate precisely using control dampers that close off a larger flow cross-section, as, for example, small opening angles of a rotatable control damper already expose a larger flow cross-section than is necessary to allow the desired air mass flow to pass through. As dynamic pressure increases, sensitive control of the air mass flow becomes even more difficult.

[0017] The systems known in the state of the art also have the characteristic that they feature very complex additional elements, which also require more space and control, resulting in higher costs, additional assembly effort and corresponding maintenance effort.

[0018] Furthermore, the flap geometries known from the state of the art result in strong flow noise.

[0019] The object of the present invention is to provide an air intake for a motor vehicle air conditioning unit that enables the intake of fresh air, recirculated air, and partial recirculated air (a mixture of fresh and recirculated air). When partially recirculated air is introduced, a continuous, speed-dependent stagnation pressure compensation must be provided to ensure passenger comfort. Bypass airflow from the fresh air intake to the recirculated air intake must be prevented. Even at high stagnation pressures and low volumes of fresh air, the air intake should function robustly, reproducibly, and acoustically neutrally, and be optimally controllable. Targeted airflow design should minimize the installation space required and associated costs, for example, for control systems, manufacturing, assembly, and maintenance.

[0020] The problem is solved by the subject matter with the features of the independent patent claims. Further developments are specified in the dependent patent claims.

[0021] The problem is solved by an air conditioning unit for a motor vehicle according to the invention. The air conditioning unit has a housing with at least one first air inlet for the intake of fresh air from the environment of the motor vehicle and a second air inlet for the intake of recirculated air from a passenger compartment, as well as an air guide device for independently varying the flow cross-sections of the air inlets. The air guide device is designed as an air flap that is movably mounted between two end positions.

[0022] According to the invention, a bypass flow channel with a ram air guide device for compensating ram pressure is provided for the first air inlet for the intake of fresh air from the environment. The ram air guide device is arranged as an air damper movably mounted between two end positions and is designed to completely close the bypass flow channel in one end position. The ram air guide device is advantageously arranged within the bypass flow channel.

[0023] The bypass flow channel preferably extends parallel to the fresh air intake from the environment, particularly to a closing cross-sectional area of ​​the air intake. The bypass flow channel branches off in the direction of fresh air flow upstream of the closing cross-sectional area of ​​the air intake and rejoins the air intake downstream of the closing cross-sectional area, so that fresh air guided through the bypass flow channel can be routed around the closing cross-sectional area of ​​the air intake.

[0024] The ram air duct system, in conjunction with the air duct system of the first air intake, serves to compensate for the ram pressure within the first air intake for the intake of fresh air. This achieves a complete reduction of the overpressure in the first air intake relative to the second air intake for the intake of recirculated air from the passenger compartment, thus preventing a direct airflow of fresh air entering the passenger compartment through the second air intake. Ram air pressure compensation is ensured by adjusting the positions of the ram air duct system and the first air duct system at different vehicle speeds, thereby varying the degree of fresh air restriction.

[0025] According to the invention, the bypass flow channel has a smaller flow cross-section than the first air inlet.

[0026] The ram air guidance device is advantageously movable independently of the first air guidance device for varying the flow cross-section of the first air inlet and thus serves to vary only a portion of the flow cross-section of the fresh air from the environment, which is composed of the flow cross-section of the first air inlet and the flow cross-section of the bypass flow channel.

[0027] According to a preferred embodiment of the invention, the air guide devices of the first air inlet and / or the second air inlet, designed as air flaps, and / or the ram air guide device for varying the flow cross-section of the bypass flow channel, are each pivotably mounted about an axis of rotation. Alternatively, the air flaps can, for example, also be designed to be displaceable.

[0028] The ram air guide is pivotable in such a way that, in its individual positions during partial recirculation (i.e., between the end positions), the air mass flow of fresh air entering the air conditioning unit through the bypass channel is throttled according to the vehicle-specific pressure upstream of the bypass channel or the first air inlet. The gap created between the housing and the ram air guide during rotation is adjusted to the required throttling of the fresh air flow in the free flow cross-section.

[0029] In order to compensate for the ram pressure by appropriately positioning the ram air guide device and the first air guide device at different speed ranges of the motor vehicle with varying degrees of throttling of the fresh air, combinations of the respective positioning of the first air guide device and the ram air guide device and thus of varying the flow cross-sections of the first air inlet and the bypass flow channel as the total flow cross-section of the fresh air are possible.

[0030] The ram air guide device for varying the flow cross-section of the bypass flow channel and / or the first air guide device for varying the flow cross-section of the first air inlet can each be designed as a centrally mounted rotary flap, which is pivotably mounted about the axis of rotation between a first end position "closed" and a second end position "fully open". The axis of rotation can be located in the area of ​​the cross-sectional area of ​​the air inlet to be closed.

[0031] The housing of the air conditioning unit preferably comprises a blower housing for accommodating a blower and an air inlet housing with the air inlets. The blower housing is arranged downstream of the air inlet housing in the direction of airflow drawn into the air conditioning unit.

[0032] A further advantage of the invention is that the ram air guide device can be continuously adjusted to intermediate positions on a travel path between the two end positions to open the flow cross-section of the bypass flow channel with different degrees of opening, wherein the ram air guide device in the first end position is “closed” against the housing, in particular against the air inlet housing of the housing, sealing the bypass flow channel.

[0033] According to a further development of the invention, the air guide device for varying the flow cross-section of the second air inlet is designed as a rotary flap which is pivotably mounted about the axis of rotation between a first end position "closed" and a second end position "fully open". In contrast to a centrally mounted rotary flap, the axis of rotation is arranged at a distance from the cross-sectional area of ​​the air inlet to be closed.

[0034] The respective air guide devices of the first air inlet for the intake of fresh air from the environment and of the second air inlet for the intake of recirculated air from the passenger compartment can be continuously adjusted along a travel path between the two end positions to intermediate positions for opening the corresponding flow cross-section of the air inlet with varying degrees of opening. In the first end position, the air guide device rests against the air inlet housing, sealing the air inlet.

[0035] A further advantageous embodiment of the invention consists in the provision of seals on the end faces of the surfaces of the air guide devices of the air inlets or the ram air guide device. The seals, which extend completely along the end faces and are firmly connected to the air guide device or the ram air guide device, are configured, in conjunction with the air guide device or the ram air guide device, to close the respective air inlet or bypass flow channel in one of the end positions, depending on the position of the air guide device or the ram air guide device.

[0036] According to a preferred embodiment of the invention, the first air guidance device and the ram air guidance device are each connected to a drive element or, via a drive mechanism, to a common drive element which drives both the first air guidance device and the ram air guidance device, so that only one drive element is provided for actuating both air guidance devices.

[0037] The drive element is advantageously designed as a stepper motor. Alternatively, the drive element can also be designed as a DC motor.

[0038] The object of the invention is furthermore achieved by an air conditioning system according to the invention for a motor vehicle with means for conveying, cooling and heating air as well as the air conditioning unit according to the concept.

[0039] Furthermore, the object of the invention is solved by an inventive method for operating the conceptually designed air conditioning unit for a motor vehicle.

[0040] This involves adjusting the composition of the air mass flow drawn into the air conditioning unit, consisting of pure fresh air from the environment, pure recirculated air from the passenger compartment, or a mixture of fresh air and recirculated air, by adjusting the positions of the air guide devices and the ram air guide device to independently vary the flow cross-sections of the air inlets and the bypass flow channel.When the air conditioner is operating in a ram air compensation mode, the mass flow of fresh air through the flow cross-section of the bypass flow channel is throttled by moving the air guide device located in the flow cross-section of the fresh air inlet to the "closed" end position and adjusting the ram air guide device located in the bypass flow channel independently of the air guide device of the fresh air inlet around the axis of rotation such that an open gap is formed between a wall of the air conditioner housing and the ram air guide device and the flow cross-section of the fresh air inlet is opened depending on the orientation of the ram air guide device.

[0041] An advantage is that the ram air guidance device, in conjunction with the first air guidance device, is used to maintain a constant flow of fresh air and thus the air conditioning unit is increasingly closed as the speed of the vehicle increases. This is achieved by using different positions of the ram air guidance device in combination with the first air guidance device for different speed ranges of the vehicle, ensuring a throttling of the fresh air adapted to the speed of the vehicle.

[0042] The air conditioning unit according to the invention can advantageously be operated at particularly low air volumes in critical operating points where precise control of the fresh air supply is required. In this case, the proportion of fresh air to be controlled is reduced accordingly by the bypass flow channel and can be precisely adjusted by the ram air guide device, which closes off the smaller flow cross-section of the bypass flow channel compared to the fresh air inlet. This is because a small rotation angle of the ram air guide device also results in only a small flow cross-section being opened for the fresh air, thus achieving the desired accuracy in controlling the fresh air supply.

[0043] By incorporating the ram air guide device into the bypass flow channel for the fresh air intake, the desired small flow cross-section of the fresh air can be precisely adjusted by closing the large flow cross-section of the fresh air intake and opening the smaller flow cross-section of the bypass flow channel. The ram air guide device, located in the bypass flow channel and narrower than the air guide device at the fresh air intake, allows for more precise gap control than the change in the fresh air flow cross-section per rotation angle of the corresponding air guide device. Consequently, the smaller opening cross-section and opening angle of the ram air guide device, compared to the air guide device at the fresh air intake, enables more accurate control of the gap-shaped flow cross-section.The corresponding difference becomes clearly visible in the velocity compensation modes with throttling of high fresh air stagnation pressure. Static pressure compensation is thus ensured when operating with the recirculation air duct open, especially when operating with partial recirculation, and when operating exclusively with fresh air.

[0044] In this process, a large volume of fresh air is reduced to a smaller volume as it flows through the bypass air channel, allowing the required air volume to be robustly adjusted using practical rotation angles of the ram air guide. The volume of fresh air to be regulated by the ram pressure induced by the vehicle's speed is reduced by design before it reaches the ram air guide.

[0045] In summary, the air conditioning unit according to the invention has several other advantages: - a speed-dependent, continuous compensation of the dynamic pressure, thereby preventing the flow of fresh air into the air intake for the intake of recirculated air and thus into the passenger compartment, - optimal and reliable controllability even at high back pressures and low volumes of incoming fresh air with minimal susceptibility to malfunctions, - minimal energy consumption for air conditioning, especially for heating and cooling the air for the passenger compartment, thereby - minimum necessary battery capacity, especially for electrically powered vehicles, and minimal consumption of resources as well as maximum range, also through minimal weight, as well as - minimal installation space with minimal material usage and minimal effort for manufacturing, assembly and maintenance of the air conditioning unit.

[0046] Further details, features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1a: a first air conditioning unit for a motor vehicle comprising a blower housing with a blower and an air inlet housing with two air inlets and an air guide device for varying the flow cross-sections of the air inlets, from the prior art in a sectional view, Fig. 1b: a second air conditioning unit of a motor vehicle with the blower housing with the blower and the air inlet housing with two air inlets and each an air guide device for independently varying the flow cross-sections of the air inlets from the prior art in a sectional view, Fig. 2a and Fig. 2b: a third air conditioning unit from the prior art in comparison with an air conditioning unit of a motor vehicle according to the invention, each with the air inlet housing having two air inlets and each with an air guide device for independently varying the flow cross-sections of the air inlets, each in a sectional view, wherein a first air inlet is completely open and a second air inlet is closed, Fig. 2c and Fig. 2d: the third air conditioning unit from the prior art in comparison with the air conditioning unit according to the invention from the Fig. 2a and Fig. 2b each with the first closed air intake and the second fully open air intake in a sectional view, Fig. 3a and Fig. 3b: a detailed view of the first air guide device within the air inlet housing of the third air conditioning unit. Fig. 2a in an intermediate position for stagnation pressure compensation, Fig. 4a to 4c: each the air conditioning unit according to the invention with the air inlet housing with two air inlets and the bypass flow channel to the first air inlet as well as an air guide device for varying the flow cross-sections of the air inlets and the bypass flow channel in a perspective view, Fig. 5a: a sectional view of the air conditioning unit according to the invention made of Fig. 4a, wherein the first air inlet is closed and the bypass flow channel for dynamic pressure compensation and the second air inlet are each fully open and Fig. 5b: a detailed representation of the bypass flow channel of the air conditioning unit according to the invention Fig. 4a, wherein the first air inlet is closed and the bypass flow channel for dynamic pressure compensation is partially open, as well as Fig. 5c: a sectional view of the air conditioning unit according to the invention made of Fig. 4a, wherein the first air inlet is closed and the bypass flow channel for dynamic pressure compensation is fully open and the second air inlet is closed.

[0047] In Fig. 1a is a first air conditioning unit 1-1' of a motor vehicle with a blower housing 2 with a blower 5 and an air inlet housing 3 with two air inlets 3a, 3b and an air guide device 4b-1' for varying the flow cross-sections of the air inlets 3a, 3b from the prior art shown in a sectional view.

[0048] The single air guide device 4b-1', mounted as an air flap pivotable about a rotary axis, serves to simultaneously vary the flow cross-sections of a first air inlet 3a for the inflow of fresh air from the environment and a second air inlet 3b for the inflow of recirculated air from the passenger compartment. The first air inlet 3a is therefore designed as a fresh air inlet, while the second air inlet 3b is designed as a recirculated air inlet. The air inlets 3a and 3b are opened or closed independently of each other.

[0049] The blower 5 comprises a drive component, in particular an electric motor, and a blower wheel. The air drawn in by the blower 5 through the air inlet housing 3 into the blower housing 2 is conditioned and introduced into the passenger compartment through air outlets (not shown). The composition of the drawn-in air mass flow is varied by adjusting the position of the air guide device 4b-1', choosing between pure fresh air, pure recirculated air, or a mixture of fresh air and recirculated air. The air guide device 4b-1' is pivotable between two end positions about its axis of rotation. This axis of rotation is spaced apart from the cross-sectional area of ​​the air inlets 3a, 3b to be closed, and thus lies outside the area to be closed.

[0050] The mixing of the intake air mass flow is adjusted via an intermediate position of the air guide device 4b-1' between the two end positions.

[0051] In intermediate positions of the air guide device 4b-1', bypass flows can occur in which the air guide device 4b-1' is surrounded by fresh air flowing into the air inlet housing 3 through the first air inlet 3a, and the fresh air flows unintentionally into the passenger compartment of the vehicle without conditioning through the second air inlet 3b for recirculation, so that either too cold or too warm outside air enters the passenger compartment directly.

[0052] With the first air conditioning unit 1-1' designed in this way, no dynamic pressure control is possible. The flow cross-section of the first air inlet 3a cannot be controlled for throttling the fresh air flowing in through the first air inlet 3a, so that in certain operating modes of the air conditioning unit 1-1', the fresh air is unintentionally directed into the passenger compartment without conditioning through the second air inlet 3b.

[0053] Out of Fig. 1b shows a second air conditioning unit 1-2' of a motor vehicle with the blower housing 2 with the blower 5 and the air inlet housing 3 with the two air inlets 3a, 3b and each an air guide device 4a', 4b-2' for independently varying the flow cross-sections of the air inlets 3a, 3b from the prior art in a sectional view.

[0054] The air guide devices 4a', 4b-2', each mounted as an air flap pivotable about an axis of rotation, are designed as centrally mounted rotary flaps and are themselves pivotable between two end positions about an axis of rotation. The axis of rotation is located in the area of ​​the cross-sectional area of ​​the air inlets 3a, 3b to be closed, and thus within the cross-sectional area to be closed.

[0055] The air guidance devices 4a', 4b-2' serve to independently vary the flow cross-sections of the first air inlet 3a for the inflow of fresh air from the environment and of the second air inlet 3b for the inflow of recirculated air from the passenger compartment.

[0056] The air guide devices 4a', 4b-2' have various intermediate positions along their travel path from a first end position "closed" to a second end position "fully open", which allow for different opening degrees of the air inlets 3a, 3b. In the first end position "closed", the air guide devices 4a', 4b-2' are in a sealing position against the air inlet housing 3. (See illustration from...) Fig. 1b means the first air intake 3a is “fully open”, while the second air intake 3b is “closed”.

[0057] With the design of the independently pivoting air guide devices 4a', 4b-2', independent control of fresh air and recirculated air into the air inlet housing 3 with ram pressure control at the first air inlet 3a is possible when the first air guide device 4a' is moved to the "closed" end position, but has not yet reached it. However, slightly open flow cross-sections of the first air inlet 3a for ram pressure compensation are difficult to control, since even a minimal rotation of the first air guide device 4a' causes a large change in the flow cross-section.

[0058] In the Fig. 2a and Fig. Figures 2b, 2c, and 2d each show a third air conditioning unit 1-3' from the prior art in comparison with an air conditioning unit 1 of a motor vehicle according to the invention, each with the air inlet housing 3 having two air inlets 3a, 3b and each with an air guide device 4a', 4a, 4b for independently varying the flow cross-sections of the air inlets 3a, 3b for the inflow of fresh air from the environment and of recirculated air from the passenger compartment, each shown in a sectional view.

[0059] The air conditioning unit 1 according to the invention has a bypass flow channel 7 with an air guide device, in particular a dynamic air guide device 8, for opening and closing the bypass flow channel 7. The bypass flow channel 7 extends parallel to the air inlet 3a for the inflow of fresh air from the environment, in particular parallel to the closing cross-sectional area of ​​the air inlet 3a. The bypass flow channel 7 branches off upstream of the cross-sectional area of ​​the air inlet 3a to be closed and opens into the air inlet 3a downstream of the cross-sectional area of ​​the air inlet 3a to be closed.

[0060] According to the Fig. 2a and Fig. 2b, the first air inlet 3a for the inflow of fresh air is fully open, and the second air inlet 3b for the inflow of recirculated air is closed, so that only fresh air is drawn in through the first air inlet 3a. The ram air guide device 8 and thus the bypass flow channel 7 of the air conditioning unit 1 are according to Fig. 2b closed. According to the Fig. 2c and Fig. 2d, the first air inlet 3a for fresh air intake is closed, and the second air inlet 3b for recirculated air intake is fully open. The ram air duct 8, and thus the bypass flow channel 7 of the air conditioning unit 1, are according to Fig. 2d is also closed, so that only recirculated air flows into the air intake housing 3 through the second air inlet 3b.

[0061] The first air guide devices 4a', 4a are each configured as an air flap or a centrally mounted rotary flap, pivotably mounted between two end positions about a rotational axis 6. The rotational axis 6 is located in the area of ​​the cross-sectional area of ​​the first air inlet 3a to be closed. The second air guide devices 4b are also each configured as an air flap, pivotable between two end positions about a rotational axis, which is spaced apart from the rotational axis 6 of the first air guide device 4a', 4a and the cross-sectional area of ​​the air inlets 3b to be closed.

[0062] In the third air conditioning unit 1-3' of the prior art, the dynamic pressure control is carried out directly via the first air guide device 4a', which varies the flow cross-section of the first air inlet 3a. The first air guide device 4a' is moved continuously to close the flow cross-section of the first air inlet 3a as the dynamic pressure increases.

[0063] The ram air guide 8 of the bypass flow channel 7 serves to vary the flow cross-section of the bypass flow channel 7 for the inflow of fresh air from the environment into the air conditioning unit 1, independent of the position of the air guide 4a of the first air inlet 3a. Along its travel path from a first end position "closed" to a second end position "fully open," the ram air guide 8 has various intermediate positions, which allow for different degrees of opening of the bypass flow channel 7. In the first end position "closed," the ram air guide 8 is in a sealing position against the air inlet housing 3.

[0064] Particularly at vehicle speeds that cause only a low ram air pressure, the ram air guide device 8 is closed, so that the amount of fresh air flowing into the air conditioning unit 1 is adjusted by means of the first air guide device 4a.

[0065] The Fig. 3a and Fig. Figures 3b each show a detailed view of the first air guide device 4a' of the first air inlet 3a within the air inlet housing 3 of the third air conditioning unit 1-3' from the Fig. 2a and Fig. 2c in an intermediate position for stagnation pressure compensation.

[0066] The pressure-dependent closing of the first air inlet 3a by rotating the first air guide 4a' about the axis of rotation 6 results, at high pressures and low volumes of fresh air, in very narrow gaps 9 between the first air guide 4a' and the air inlet housing 3, or very narrow, slit-like flow cross-sections of the first air inlet 3a. The open flow cross-section is formed between the end faces of the first air guide 4a' and the wall of the air inlet housing 3. The gaps 9, which have very small radial dimensions, are controlled by very small rotation angles of the first air guide 4a about the axis of rotation 6. This can be further supported by suitably designed contours on the air inlet housing 3 in the area of ​​the stops of the air guide 4a'.

[0067] Dynamic pressure control is not possible with very small openings of the first air inlet 3a due to the backlash-free control of the movement of the first air guide device 4a' by a conventional stepper motor. Furthermore, the small opening and the volume of air flowing through it can cause disturbing noises such as hissing or whistling.

[0068] From the Fig. Figures 4a to 4c show a perspective view of the air conditioning unit 1 of a motor vehicle according to the invention, comprising the air intake housing 3 with two air inlets 3a, 3b and the bypass flow channel 7 to the first air inlet 3a, as well as an air guide device 4a, 4b for independently varying the flow cross-sections of the air inlets 3a, 3b and a ram air guide device 8 for independently varying the flow cross-section of the bypass flow channel 7. The first air guide device 4a is shown in the end position "fully open".

[0069] The ram air guide device 8, designed as an air flap and also referred to as a ram air flap, is configured to completely close the bypass flow channel 7. The bypass flow channel 7 has a significantly smaller flow cross-section than the first air inlet 3a.

[0070] Since fresh air from the environment flows into the air conditioning unit 1 through both the first air inlet 3a and the bypass flow channel 7, the flow cross-sections of the first air inlet 3a and the bypass flow channel 7 together constitute a flow cross-section for the fresh air. The ram air guide 8 is movable independently of the first air guide 4a and thus serves to vary only a portion of the total flow cross-section for the fresh air. The flow cross-section of the bypass flow channel 7, which represents a portion of the flow cross-section for the fresh air, can be varied by means of the ram air guide 8, in particular by being opened and closed.

[0071] The first air guide device 4a and the ram air guide device 8 are each designed as centrally mounted rotary flaps and are pivotable between the two end positions "closed" and "fully open" about a rotary axis 6, 10. The first air guide device 4a and the ram air guide device 8 each have various intermediate positions along their travel path between the end positions, which allow different opening degrees of the air inlet 3a and the bypass flow channel 7, respectively.

[0072] The axes of rotation 6, 10 are each arranged in the area of ​​the cross-sectional area to be closed, in particular the first air inlet 3a or the bypass flow channel 7.

[0073] Out of Fig. Figure 5a shows a sectional view of the air conditioning unit 1 according to the invention. Fig. 4a. The first air inlet 3a is closed, and the bypass flow channel 7 for the inflow of fresh air for ram pressure compensation, as well as the second air inlet 3b for the inflow of recirculated air, are each fully open. The intake air mass flow is therefore composed of a mixture of fresh air and recirculated air.

[0074] After Fig. 5b, which shows a detailed representation of the bypass flow channel 7 of the air conditioning unit 1 according to the invention. Fig. Figure 4a shows that the first air inlet 3a is closed and the bypass flow channel 7 for ram pressure compensation is partially open. Fig. 5b the ram air guide device 8 is aligned in an intermediate position for ram air pressure compensation at high ram air pressure, while the ram air guide device 8 in the arrangement according to Fig. 5a is designed in the "fully open" final position for stagnation pressure compensation at lower stagnation air pressure.

[0075] The first air guide 4a is fixed in the "closed" end position, while the ram air guide 8, located within the bypass flow channel 7, is independently adjustable about the axis of rotation 10. This adjustment provides an open gap 11, or a slit-shaped, open flow cross-section of the bypass flow channel 7, and thus of the flow cross-section for the fresh air, between the air inlet housing 3 and the ram air guide 8. The fresh air flows in the direction of flow 12 between the end faces of the ram air guide 8 and the wall of the bypass flow channel 7 of the air inlet housing 3, and thus through the open flow cross-section of the bypass flow channel 7.

[0076] The front edges of the first air guide device 4a abut the wall of the air inlet housing 3, thus closing the flow cross-section of the first air inlet 3a. A sealing element is advantageously provided between the first air guide device 4a and the wall of the air inlet housing 3. In contrast to the first air guide device 4a, the ram air guide device 8, arranged within the bypass flow channel 7, is adjusted about the axis of rotation 10 such that the flow cross-section of the bypass flow channel 7 is partially opened as required, or an open gap 11 is provided between the air inlet housing 3 and the ram air guide device 8. The flow cross-section for fresh air is at least partially open in the area of ​​the bypass flow channel 7.

[0077] The first air guidance device 4a and the dynamic air guidance device 8, each designed as centrally mounted rotary flaps, can each be connected to a drive element, each of which is designed as an actuator, in particular as a linear or continuous actuator or as a stepper motor.

[0078] Alternatively, the first air guidance device 4a and the dynamic air guidance device 8 can be controlled via a common or coupled mechanism, so that only one actuator, for example a stepper motor, is necessary to actuate both air guidance devices.

[0079] By separately controlling the ram air control device 8 to control the first air control device 4a, and thus completely closing the first air control device 4a and at least partially opening the ram air control device 8, significantly smaller flow cross-sections for the fresh air can be set than with the first air control device 4a alone.

[0080] The design of the bypass flow channel 7 with the ram air guide device 8 enables very fine control of the gap 11 as the flow cross-section for the fresh air, since the change in the flow cross-section for the fresh air depending on the rotation angle of the ram air guide device 8 is significantly smaller than the change in the flow cross-section of the first air inlet 3a depending on the rotation angle of the first air guide device 4a. The ram pressure compensation can thus be controlled very precisely.

[0081] In an operating mode with a mixture of recirculated air and only a small proportion of fresh air, for example, only the small amount of fresh air needs to be heated when the fresh air is at a very low temperature, while only the small amount of fresh air needs to be cooled when the fresh air is at a very high temperature, which leads to a considerable energy saving, especially in electrically powered vehicles, and thus affects the vehicle's range, which is significantly increased.

[0082] In the closed end state of the ram air guide device 8, for example according to the Fig. 2b and Fig. 2d, the end faces of the ram air guide device 8 rest against the wall of the air inlet housing 3, closing off the flow cross-section of the bypass flow channel 7. A sealing element is advantageously provided between the wall of the air inlet housing 3 in the area of ​​the bypass flow channel 7 and the ram air guide device 8.

[0083] In Fig. Figure 5c is a sectional view of the air conditioning unit 1 according to the invention. Fig. Figure 4a shows an orientation of the air guide devices 4a, 4b in which the first air inlet 3a is closed and the bypass flow channel 7 for the inflow of fresh air for stagnation pressure compensation is fully open, and the second air inlet 3b for the inflow of recirculated air is closed. Consequently, only fresh air is drawn into the air conditioning unit 1.

[0084] Depending on the required air volume and control accuracy, various embodiments of the bypass flow channel 7 with the dynamic air guide device 8 are conceivable. In addition to the bypass flow channel 7 shown in the figures on a first side of the air inlet 3a, the bypass flow channel can also be configured on a second side differing from the first, or on both sides of the air inlet. Furthermore, depending on the available installation space, hybrid configurations with bypass channels on different sides of the fresh air inlet are possible. LIST OF REFERENCE MARKS 1, 1-1', 1-2', 1-3' Air conditioner 2 blower housings 3 air intake housings 3a first air intake 3b second air intake 4a, 4a' first air guidance device 4b, 4b-1', 4b-2' (second) air guidance device 5 blowers 6 Rotation axis first air guide device 4a, 4a' 7 Bypass flow channel 8. Ram air guidance system 9 Gap first air guide device 4a, 4a' 10 Rotary axis ram air guide device 8 11 Gap ram air guide device 8 12 Flow direction

Claims

[1] Air conditioning unit (1) for a motor vehicle, comprising a housing with at least one first air inlet (3a) for the inlet of fresh air from the environment and a second air inlet (3b) for the inlet of recirculated air from a passenger compartment, and each an air guide device (4a, 4b) for independently varying the flow cross-sections of the air inlets (3a, 3b), wherein the air guide device (4a, 4b) is each designed as an air flap which is movably mounted between two end positions, wherein a bypass flow channel (7) with a dynamic air guide device (8) is formed for the first air inlet (3a), wherein the dynamic air guide device (8) is designed as an air flap movably mounted between two end positions in such a way as to completely close the bypass flow channel (7) in one end position, and the bypass flow channel (7) has a smaller flow cross-section than the first air inlet (3a). [2] Air conditioning unit (1) according to claim 1, characterized by , that the ram air guidance device (8) is movable independently of the air guidance device (4a) to vary the flow cross-section of the first air inlet (3a). [3] Air conditioning unit (1) according to claim 1 or 2, characterized by , that the air guide device (4a) of the first air inlet (3a) and / or the air guide device (4b) of the second air inlet (3b) and / or the dynamic air guide device (8) for varying the flow cross-section of the bypass flow channel (7) is / are each mounted pivotably about an axis of rotation (6, 10). [4] Air conditioning unit (1) according to claim 3, characterized by , that the ram air guidance device (8) is designed as a centrally mounted rotary flap which is pivotably mounted about the axis of rotation (10) between a first end position “closed” and a second end position “fully open”. [5] Air conditioning unit (1) according to claim 3 or 4, characterized by , that the air guidance device (4a) for varying the flow cross-section of the first air inlet (3a) is designed as a centrally mounted rotary flap which is pivotably mounted about the axis of rotation (6) between a first end position “closed” and a second end position “fully open”. [6] Air conditioning unit (1) according to any one of claims 1 to 5, characterized by , that the housing comprises a blower housing (2) for receiving a blower (5) and an air inlet housing (3) with the air inlets (3a, 3b) and the bypass flow channel (7). [7] Air conditioning unit (1) according to any one of claims 1 to 6, characterized by, that the ram air guide device (8) can be continuously adjusted to intermediate positions on a travel path between the two end positions to open the flow cross-section of the bypass flow channel (7) with different degrees of opening, wherein the ram air guide device (8) in a first end position is “closed” against the housing, in particular against an air inlet housing (3) of the housing, sealing the bypass flow channel (7). [8] Air conditioning unit (1) according to any one of claims 3 to 7, characterized by , that the air guide device (4b) for varying the flow cross-section of the second air inlet (3b) is designed as a rotary flap which is mounted pivotably about the axis of rotation between a first end position “closed” and a second end position “fully open”, wherein the axis of rotation is spaced apart from the cross-sectional area of ​​the second air inlet (3b) to be closed. [9] Air conditioning unit (1) according to any one of claims 1 to 8, characterized by , that the air guide device (4a, 4b) can be continuously adjusted to intermediate positions on a travel path between the two end positions to open the flow cross-section of the air inlet (3a, 3b) with different degrees of opening, wherein in a first end position ‘closed’ the air guide device (4a, 4b) is in a sealing position against the air inlet housing (3) and the air inlet (3a, 3b). [10] Air conditioning unit (1) according to claims 1 to 9, characterized by , that the air guidance device (4a) of the first air inlet (3a) and the ram air guidance device (8) are each connected to a drive element or via a drive mechanism to a common drive element. [11] Air conditioning unit (1) according to claim 10, characterized by that the drive element is designed as an actuator motor. [12] Air conditioning system for a motor vehicle comprising means for conveying, cooling and heating air, comprising an air conditioning unit (1) according to any one of claims 1 to 11. [13] Method for operating an air conditioning unit (1) for a motor vehicle according to any one of claims 1 to 11, wherein a composition of an air mass flow drawn into the air conditioning unit (1) consisting of pure fresh air from the environment, pure recirculated air from the passenger compartment or a mixture of fresh air and recirculated air is set by adjusting the positions of air guide devices (4a, 4b) and a ram air guide device (8) for independently varying the flow cross-sections of air inlets (3a, 3b) and a bypass flow channel (7), wherein in an operating mode of ram air compensation a mass flow of fresh air through the flow cross-section of the bypass flow channel (7) is throttled,by moving an air guide device (4a) arranged in the flow cross-section of an air inlet (3a) of the fresh air into a "closed" end position and adjusting a ram air guide device (8) arranged in the bypass flow channel (7) independently of the air guide device (4a) of the air inlet (3a) of the fresh air such that an open gap (11) is formed between a wall of a housing of the air conditioning unit (1) and the ram air guide device (8) and the flow cross-section of the air inlet (3a) of the fresh air from the environment is opened depending on the orientation of the ram air guide device (8).

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