WO2023110197A1

WO2023110197A1 - Method for operating a refrigerant circuit of a motor vehicle and motor vehicle

Info

Publication number: WO2023110197A1
Application number: PCT/EP2022/079503
Authority: WO
Inventors: Christian Rebinger; Dirk Schroeder
Original assignee: Audi Ag
Priority date: 2021-12-13
Filing date: 2022-10-24
Publication date: 2023-06-22
Also published as: DE102021132800A1

Abstract

The invention relates to a method for operating a refrigerant circuit (10) of a motor vehicle, in which method a compressor (12) conveys a minimum mass flow of refrigerant and a parameter is detected which indicates a refrigerating performance of at least one evaporator (20, 42) located in the refrigerant circuit (10). The evaporator (20, 42) provides the refrigerating performance as a result of refrigerant conveyed by the compressor (12) being supplied. At least a first partial flow of the refrigerant, which partial flow is supplied to the evaporator (20, 42), is expanded by means of an expansion member (18, 40). Depending on the refrigerating performance of the evaporator (20, 42) that is provided with the minimum mass flow of the refrigerant, a second partial flow of the refrigerant conveyed by the compressor (12) flows through a return line (32). The second partial flow is conveyed via the return line (32) from a high-pressure side (30) of the refrigerant circuit (10) to a suction side (24) of the compressor (12), bypassing the evaporator (20, 42). The invention further relates to a motor vehicle comprising a refrigerant circuit (10).

Description

Method for operating a refrigerant circuit of a motor vehicle and motor vehicle

DESCRIPTION:

The invention relates to a method for operating a refrigerant circuit of a motor vehicle, in which a compressor arranged in the refrigerant circuit delivers a minimal mass flow of refrigerant. In the method, at least one parameter is recorded, which specifies a refrigerating capacity of at least one evaporator arranged in the refrigerant circuit. The at least one evaporator provides the refrigerating capacity as a result of exposure to refrigerant conveyed by the compressor. At least a first partial flow of the refrigerant that is fed to the at least one evaporator by means of the compressor is expanded by means of an expansion element of the refrigerant circuit. Furthermore, the invention relates to a motor vehicle with a refrigerant circuit and with a control device for carrying out the method.

DE 10 2016 005 782 A1 describes a method for operating a vehicle air conditioning system with a refrigerant circuit, with a first evaporator being arranged in a first branch of the refrigerant circuit. A second branch of the refrigerant circuit, in which a second evaporator designed as a chiller is arranged, is connected in parallel with the first branch. If a refrigerant compressor arranged in the refrigerant circuit is operated at a minimum speed, a valve cross-sectional area of an expansion element connected upstream of the chiller can be gradually increased in order to reduce the cooling capacity of the first evaporator. In such a method, refrigerating capacity is additionally dissipated at the second evaporator designed as a chiller, so that the chiller functions as a heat sink. However, such an operating mode of the refrigerant circuit is not always desirable or realizable.

DE 26 57 654 A1 describes a refrigerant circuit in which, from an outlet side of a refrigerant cooler or from a device downstream of the refrigerant cooler for separating gas and liquid from refrigerant, a return line is used to return to a low-pressure side of a compressor of the refrigerant circuit. A recirculation device comprising the recirculation line can be provided for starting up or shutting down the compressor and for operating the compressor at low throughput.

DE 34 28 704 A1 describes a method for controlling the cooling capacity of a refrigeration system which is part of an air conditioning system in a motor vehicle. In this case, a bypass is routed from a pressure side of a compressor of the refrigeration system to a suction side of the compressor, with the bypass branching off a gaseous refrigerant. The bypass contains a control valve, which releases the bypass in the opposite direction to the set cooling capacity. The control valve keeps the bypass closed at maximum refrigeration demand and it opens the bypass at less than maximum refrigeration demand.

Such a method is comparatively uneconomical since the bypass is used almost constantly and is only closed when an evaporator of the refrigeration system is providing maximum cooling capacity or refrigeration capacity.

US Pat. No. 5,740,681 A describes a refrigerant circuit of a motor vehicle, which is used to heat a passenger compartment of the vehicle. In this case, an evaporator of the refrigerant circuit can be used as a heat exchanger that gives off heat. In the operation of a refrigerant circuit of a motor vehicle, it can also be provided that the compressor or refrigerant compressor is alternately switched off and then switched on again in low-load operation or low-load operation, ie when the compressor delivers a minimal mass flow of refrigerant. In this way it can be prevented that the evaporator of the refrigerant circuit is set as a result of a permanently comparatively low

Evaporation temperature levels iced. However, such a mode of operation of the compressor in the form of a two-point control operation is unfavorable. This is because there is an increased load on the compressor if it is switched on and off repeatedly and, in particular, at short intervals.

In addition, such an operating mode is unfavorable with regard to the fact that the switching on and off of the compressor can be audible to the occupants of the motor vehicle and can therefore cause disruptive acoustic effects. This is also disadvantageous.

The object of the present invention is to specify a method of the type mentioned at the outset in which icing of the at least one evaporator is avoided in a particularly simple manner when conveying the minimum mass flow of refrigerant, and a motor vehicle with a control device designed to carry out the method to accomplish.

This object is achieved by a method having the features of patent claim 1 and by a motor vehicle having the features of patent claim 10 . Advantageous configurations with expedient developments of the invention are specified in the dependent patent claims and in the following description.

In the method according to the invention for operating a refrigerant circuit of a motor vehicle, a compressor arranged in the refrigerant circuit delivers a minimal mass flow of refrigerant. It at least one parameter is recorded, which specifies a refrigerating capacity of at least one evaporator arranged in the refrigerant circuit. The at least one evaporator provides the refrigerating capacity as a result of exposure to refrigerant conveyed by the compressor. At least one first partial flow of the refrigerant that is fed to the at least one evaporator by means of the compressor is expanded by means of at least one expansion element of the refrigerant circuit. In the method, depending on the cooling capacity of the at least one evaporator provided at the minimum mass flow of the refrigerant, a return line of the refrigerant circuit is flowed through by a second partial flow of the refrigerant conveyed by the compressor. In this case, the second partial flow is routed via the return line from a high-pressure side of the refrigerant circuit, bypassing the at least one evaporator, to a suction side of the compressor.

The second partial flow of the minimum mass flow of refrigerant that is routed via the return line therefore does not circulate through the at least one evaporator. Rather, this second partial flow is returned directly to the suction side of the compressor, bypassing any evaporator of the refrigerant circuit. Consequently, this second partial flow does not contribute to the refrigerating capacity which is provided at the at least one evaporator. Due to the return of the second partial flow via the return line to the suction side of the compressor, the refrigeration capacity of the at least one evaporator is lower than would be the case if the at least one evaporator were subjected to the entire minimum mass flow of refrigerant that the compressor delivers. This prevents the at least one evaporator from icing up. Consequently, icing of the at least one evaporator is avoided in a particularly simple manner.

The minimum mass flow or minimum mass flow is thus only partially conveyed through the refrigerant circuit with the release of cooling capacity, which takes place at the at least one evaporator in the form of heat absorption. Because the second partial flow passes through the Return line directly, ie without flowing through the at least one evaporator, from the high-pressure side of the refrigerant circuit to the suction side of the compressor.

The compressor or refrigerant compressor can thus be operated permanently or continuously, with the compressor permanently conveying at least the minimum mass flow of refrigerant. As a result, a particularly component-friendly continuous operation of the compressor or refrigerant compressor can be achieved. This continuous operation involves less stress on the compressor than would be the case if the compressor or refrigerant compressor were alternately switched off and then on again. This is also advantageous with regard to the fact that a long service life of the compressor or refrigerant compressor can be achieved in this way.

In addition, acoustic disturbances, which can accompany the switching on and off of the compressor, are avoided. And acoustic abnormalities due to fluctuations in the speed of the refrigerant compressor and/or due to changes in the speed of the refrigerant compressor can also be reduced.

The corresponding advantages are particularly important when the compressor is comparatively large or comparatively powerful, as is the case in particular with electrically driven compressors, which can be used in an electric vehicle or hybrid vehicle, for example.

If the compressor or refrigerant compressor is operated with a minimum capacity and thus delivers the minimum mass flow of refrigerant, stable operation of the compressor is ensured. However, this stable operation can no longer be ensured if the compressor delivers a lower mass flow than the minimum mass flow of refrigerant. Since the present always at least the minimum mass flow is conveyed by means of the compressor, stable continuous operation of the compressor is achieved.

Optionally, ie depending on the design of the refrigerant circuit, the refrigerant circuit can map a heat pump function or be operated as a heat pump.

The return line is preferably released by at least partially opening a shut-off device. As a result, it is possible to react in a very targeted manner to a situation in which the at least one evaporator to which at least the first partial flow of the refrigerant is applied provides a critical or undesirably high refrigerating capacity. This can be countered by at least partially opening the shut-off device and thus releasing the return line.

A size of a cross section of the shut-off device through which the second partial flow can flow is preferably set as a function of the cooling capacity of the at least one evaporator provided at the minimum mass flow of the refrigerant. In this way, the refrigerating capacity provided by the at least one evaporator can be reduced very easily and precisely as required.

For this purpose, the shut-off device can be designed in particular as a controllable, preferably steplessly adjustable valve element. Then, by readjusting this valve or valve element, it can be directly brought about that a refrigerating capacity of the at least one evaporator that is better not to be exceeded or permissible is reliably maintained.

The second partial flow can be fed to the suction side of the compressor via an internal bypass line of the compressor. Accordingly, the recirculation line can be designed as an internal bypass line or internal bypass, or one associated with the compressor. A space-saving, compact integration of the recirculation line into the compressor is thus achieved. This is particularly in view of a simple accommodation of the return line in the Motor vehicle advantageous. Furthermore, there is no need to assemble the return line during manufacture of the refrigerant circuit if the return line is designed in the form of the internal bypass line of the compressor as part of the compressor.

Additionally or alternatively, the second partial flow can be fed to the suction side of the compressor via a bypass line that is external to the compressor. Then no structural changes need to be made to the compressor to provide the return line. This is particularly advantageous with regard to retrofitting an existing refrigerant circuit, which may be desirable, by installing the return line.

The second partial flow is preferably branched off from a high-pressure-side line of the refrigerant circuit by means of the external bypass line downstream of the compressor and introduced via the external bypass line into a low-pressure-side line of the refrigerant circuit. In this way, the direct recirculation of the second partial flow from the suction side of the compressor can be implemented particularly easily, bypassing the at least one evaporator.

The second partial flow can be branched off from the high-pressure-side line by means of the external bypass line downstream of the compressor and upstream of a condenser of the refrigerant circuit. This is particularly advantageous if the line on the high-pressure side is easily accessible at this point in the refrigerant circuit. Because this simplifies the integration of the return line into the refrigerant circuit.

Furthermore, the second partial flow can be branched off from the high-pressure-side line of the refrigerant circuit by means of the external bypass line downstream of a condenser of the refrigerant circuit. In this case, the condenser advantageously ensures cooling of the second partial flow of the refrigerant that is returned to the suction side of the compressor. Consequently, an undesirably large increase in the temperature of the Refrigerant at the outlet of the compressor or on the high-pressure side of the compressor can be easily avoided or at least limited in an advantageous manner.

A temperature of the second partial flow can be reduced by means of a cooler integrated in the compressor. This is also advantageous with regard to the fact that the second partial flow, which has a reduced temperature, is already fed to the suction side of the compressor. Consequently, an undesirably strong increase in the temperature of the refrigerant can be avoided or at least limited initially at the inlet of the compressor and thus finally or subsequently also at the outlet of the compressor.

According to a further aspect, the return line can be used to introduce heat into the refrigerant inflow to the compressor, in particular when converting or providing low refrigeration capacities of the refrigerant circuit. In this way, the refrigerant supplied to the suction side of the compressor can be re-evaporated in a targeted manner, in particular to avoid wet suction of the compressor that would otherwise be possible, ie to avoid a situation in which the compressor draws in partially liquid refrigerant. This is conducive to stable operation, in particular continuous operation, of the compressor.

It is particularly simple and efficient if the cooler integrated into the compressor is designed as a cooling jacket for the return line. This is because such a cooling jacket can be used to achieve very good heat dissipation from the refrigerant which flows through the return line in the form of the second partial flow.

In a further advantageous embodiment, the cooler integrated in the compressor, in particular the cooling jacket, can be connected to power electronics of the compressor. The cooler can then ensure that electronic components of the power electronics are cooled, in particular if critically high temperatures should occur in the area of the power electronics. Additionally or alternatively, a temperature of the second partial flow can be reduced by means of a cooler integrated into the return line. In particular, if such a cooler is designed as a component that is external to the compressor, a particularly good cooling performance can be achieved by means of the cooler.

The cooler integrated into the return line can also be designed as a cooling jacket which encloses the return line and has a space through which a cooling medium can flow. Accordingly, heat contained in the refrigerant can be dissipated via the cooling medium.

To reduce the temperature of the second partial flow, the cooler can be charged with air and/or with a liquid coolant. In particular, by using a liquid coolant, a very high heat transfer performance or a very high heat dissipation from the refrigerant to the coolant can be achieved.

The second partial flow is preferably brought to a temperature by means of the cooler, which is essentially the same as a temperature of the first partial flow of the refrigerant coming from the at least one evaporator. In this way it can be avoided to a particularly large extent that the compressed refrigerant leaving the compressor is heated to an undesirably high degree due to the recirculation of the second partial flow, bypassing the at least one evaporator. This is also advantageous with regard to undisturbed continuous operation of the compressor.

Flow through the return line is preferably temporarily prevented as a function of a temperature of the refrigerant on a high-pressure side of the compressor. The entire mass flow of refrigerant conveyed by the compressor is therefore temporarily passed through the at least one evaporator and cooled in the at least one evaporator. In other words, if it turns out that due to the routing of the second partial flow via the return line on the high-pressure side of the compressor, the temperature of the refrigerant is too high, the flow through the return line can be prevented in a subsequent step for a specific period of time . And by expanding the refrigerant at the at least one evaporator by means of the at least one expansion element, the temperature of the refrigerant can be easily reduced during this period of time, which is then fed from the at least one evaporator to the suction side of the compressor.

Such an operating mode of the refrigerant circuit is particularly advantageous when no other cooler is provided for reducing the second partial flow flowing through the return line or such a cooler does not have sufficient cooling capacity. In addition, the temporary suppression of the flow through the return line can be implemented in a particularly inexpensive manner. This applies in particular if there is no separate cooler associated with the return line or if such a cooler is present but is of very simple and inexpensive design.

The motor vehicle according to the invention has a refrigerant circuit which includes a compressor designed to deliver a minimal mass flow of refrigerant. A detection device is used to detect at least one parameter which specifies a refrigerating capacity of at least one evaporator arranged in the refrigerant circuit. The at least one evaporator is designed to provide the refrigerating capacity as a result of being acted upon by the refrigerant conveyed by the compressor. At least one first partial flow of the refrigerant that can be fed to the at least one evaporator by means of the compressor can be expanded by means of at least one expansion element of the refrigerant circuit. The motor vehicle includes a control device, which is designed to function as a function of the minimum mass flow of the refrigerant provided refrigeration capacity of the at least one evaporator to cause a return line of the refrigerant circuit to be flowed through with a second partial flow of the refrigerant conveyed by the compressor. In this case, the return line leads from a high-pressure side of the refrigerant circuit, bypassing the at least one evaporator, to a suction side of the compressor. By using the return line, icing of the at least one evaporator when conveying the minimum mass flow of refrigerant can be avoided in a simple manner.

The control device is consequently designed to operate the refrigerant circuit according to the method according to the invention or an embodiment thereof.

The invention also includes the control device for the motor vehicle. The control device can have a data processing device or a processor device that is set up to carry out an embodiment of the method according to the invention. For this purpose, the processor device can have at least one microprocessor and/or at least one microcontroller and/or at least one FPGA (Field Programmable Gate Array) and/or at least one DSP (Digital Signal Processor). Furthermore, the processor device can have program code which is set up to carry out the embodiment of the method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device.

In particular, the control device can be supplied with measurement signals and/or sensor values which allow conclusions to be drawn about the current operating situation or a respective operating point of the refrigerant circuit. Depending on such variables, the control device can intervene in the operation of the refrigerant circuit, in particular by activating or deactivating a valve element or the like arranged in the return line. The advantages and preferred embodiments described for the method according to the invention also apply to the motor vehicle according to the invention and vice versa.

The invention therefore also includes developments of the motor vehicle according to the invention, which have features as have already been described in connection with the developments of the method according to the invention. For this reason, the corresponding developments of the motor vehicle according to the invention are not described again here.

The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus.

The invention also includes the combinations of features of the described embodiments. The invention also includes implementations that each have a combination of the features of several of the described embodiments, provided that the embodiments were not described as mutually exclusive.

Exemplary embodiments of the invention are described and shown schematically below. For this shows:

1 shows a refrigerant circuit of a motor vehicle, in which a partial flow of a mass flow of refrigerant conveyed by a compressor can be returned directly from the high-pressure side of the compressor to the suction side of the compressor via a return line or bypass line;

2 shows a variant of the compressor in which the return line is designed as an internal bypass of the compressor; 3 shows a further variant of the compressor, in which the return line is designed as an external bypass in relation to the compressor; and

FIG. 4 shows the motor vehicle which has the refrigerant circuit according to FIG.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and that each also develop the invention independently of one another. Therefore, the disclosure is also intended to encompass combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.

In the figures, the same reference symbols designate elements with the same function.

In Fig. 1, a refrigerant circuit 10 is shown schematically, in which a compressor 12 is arranged. The compressor 12 can be embodied as an electrically driven refrigerant compressor or as a mechanical refrigerant compressor which is driven by means of a drive motor (not shown) of a motor vehicle 14 having the refrigerant circuit 10 (cf. FIG. 4).

In the present case, the compressor 12 is operated continuously, so that at least a minimum mass flow of refrigerant is always delivered by the compressor 12 when the refrigerant circuit 10 is in operation. Such continuous operation of the compressor 12 can be provided in particular when air conditioning operation of the refrigerant circuit 10 is required, for example because an air flow which can be introduced into a passenger compartment 22 of the motor vehicle 14 (cf. FIG. 4) is to be dehumidified. The refrigerant conveyed by the compressor 12 is first fed to a condenser 16 or gas cooler in a manner known per se. The refrigerant cooled in the condenser 16 , in particular below its condensation temperature and thus condensed, is then expanded in an expansion element 18 and fed to an evaporator 20 which is arranged in the refrigerant circuit 10 downstream of the expansion element 18 . By means of the evaporator 20, for example, the air flow which is to be introduced into the passenger compartment 22 of the motor vehicle 14 (cf. FIG. 4) can be cooled and thus dehumidified. The expanded refrigerant coming from the evaporator 20 is then fed back to a suction side 24 of the compressor 12 .

If the compressor 12 conveys the entire, minimum mass flow of refrigerant to the evaporator 20, then in this low-load operation of the compressor 12, an undesired icing of the evaporator 20 can occur. Such icing of the evaporator 20 can occur in particular when the air to be introduced into the passenger compartment 22 of the motor vehicle 14 (compare FIG. 4) and cooled by the evaporator 20 already has a comparatively low temperature before it flows through the evaporator 20 .

The compressor 12 therefore provides a minimum refrigerant mass flow, which leads to the provision of a refrigerating capacity above a required refrigerating capacity of the evaporator 20 at the evaporator 20 . This in turn means that temperatures of around 0° C. and below can set in on the evaporator 20 . Moisture separated and condensed from the air flow in this operating state then condenses on the surface of the evaporator 20 and freezes to form ice.

In order to prevent such an undesirable icing of the evaporator 20, the compressor 12 can be alternately switched off and then switched on again. Such a two-point operation of the compressor 12 is accompanied, however, by an undesirably heavy load on the compressor 12 .

In the present case, such a two-point operation of the compressor 12 and at the same time icing of the evaporator 20 are avoided in a particularly simple manner. For example, the temperature of the air can be detected by means of a detection device, for example in the form of a temperature sensor 26 , after the air has flowed through the evaporator 20 . The cooling capacity of the evaporator 20 can be determined on the basis of the temperature of this air. The temperature sensor 26 is preferably placed or arranged on the air outlet side of the evaporator 20 at a point at which the coldest temperature of the air occurs during operation of the refrigerant circuit 10 .

Depending on the cooling capacity provided by the evaporator 20 at the minimum mass flow of the refrigerant, a control device 28 of the motor vehicle 14 can ensure that a partial flow of the minimum mass flow does not reach the evaporator 20 at all, but rather from a high-pressure side 30 of the compressor 12 a return line 32 is returned directly to the suction side 24 of the compressor 12 . This partial flow thus remains in the vicinity of the compressor 12 or refrigerant compressor and bypasses the evaporator 20 and reaches the suction side 24 of the compressor 12. This leads to a reduction in the cooling capacity provided by the evaporator 20 or at the evaporator 20.

As shown by way of example in FIG. 1 , a parallel line 36 of the refrigerant circuit 10 can branch off from a main line 38 of the refrigerant circuit 10 at a branch point 34 upstream of the expansion element 18 . In the present case, a further expansion element 40 or a second expansion element 40 is arranged in this parallel line 36 . The refrigerant expanded by means of the second expansion element 40 and routed through the parallel line 36 can be fed to a further evaporator of the refrigerant circuit 10 , which in the present case is designed as a chiller 42 . At the chiller 42 , in a manner not shown in detail here, heat is absorbed by the refrigerant expanded by means of the second expansion element 40 from a coolant, which flows through a coolant circuit 44 shown only in a highly schematic and partial manner in FIG. 1 . The coolant cooled by means of the chiller 42 can be used in particular for cooling an electrical energy store (not shown) of the motor vehicle 14 and/or an electrical drive motor (likewise not shown) of the motor vehicle 14 .

The expanded refrigerant leaving the chiller 42 is introduced into the main branch 38 at a junction point 46 of the refrigerant circuit 10 at which the parallel branch 36 again opens into the main branch 38 . The confluence point 46 is located downstream of the evaporator 20. From the confluence point 46, the expanded refrigerant is fed to the suction side 24 of the compressor 12.

If the partial flow of the minimum mass flow of refrigerant conveyed by the compressor 12 is returned via the return line 32 directly from the high-pressure side 30 of the compressor 12 to the suction side 24 of the compressor 12, then this partial flow is also bypassed in the present case as the chiller 42 further evaporator of the refrigerant circuit 10 to the suction side 24 of the compressor 12 out.

Accordingly, to avoid icing of the at least one evaporator, in particular an evaporator to which air has been applied, when compressor 12 delivers the minimum mass flow of refrigerant, the at least one evaporator of refrigerant circuit 10, in this case evaporator 20 and/or chiller 42, only a first partial flow of the entire minimum mass flow of refrigerant is supplied, while the second partial flow reaches the suction side 24 of the compressor 12 directly from the high-pressure side 30 of the compressor 12 via the return line 32 . Whether the return line 32 is to be used is determined by the control device 28 is decided in particular depending on which refrigeration capacity the evaporator 20 provides as a result of the application of refrigerant, while the compressor 12 promotes the minimum mass flow of refrigerant.

According to FIG. 1, a shut-off device in the form of a valve 48 is arranged in the return line 32 . The valve 48 can preferably be closed or brought into a closed position in which a flow through the return line 32 is prevented. Furthermore, in the present case, an opening width or a flow cross section of the valve 48 can preferably be set by means of the control device 28 or such a control device. In particular, the opening width or the flow cross section of the valve 48 can be continuously adjusted by means of the control device 28 .

By activating the valve 48 by means of the control device 28, a bypass flow or leakage flow of refrigerant can thus be set, which throttles from the high pressure present on the high pressure side 30 of the compressor 12 to the low pressure level present on the suction side 24 of the compressor 12 in the form of the suction pressure can be.

Preferably, the switchable valve 48 with its flowable cross section and/or a line cross section of the return line 32 are designed in such a way that when the second partial flow is released, there is no sudden pressure equalization between a line section downstream of the compressor 12 and a line section upstream of the compressor 12 or to a sudden drop in pressure occurs. If neither a reduction in the line cross-section of the return line 32 nor an adjustment of the flow-through cross-section of the valve 48 can be represented, such an abrupt pressure equalization can also be avoided by means of a simple orifice. In order to protect such reduced flow cross-sections against any contamination, they can be secured and thus protected with filter elements and/or screens. In Fig. 2, the compressor 12 is shown schematically in an exemplary embodiment. Accordingly, the return line 32 can be designed as an internal bypass line 50 of the compressor 12 . According to FIG. 2, this bypass line 50, which is internal or integrated into the compressor 12, connects a high-pressure connection 52 arranged on the high-pressure side 30 of the compressor 12 to the suction side 24 of the compressor 12, on which a suction-pressure connection 54 is formed in the present case. This internal bypass line 50 or this internal bypass ensures a particularly compact integration of the return line 32 into the refrigerant circuit 10. Accordingly, the valve 48 serving as a bypass throttle can also be integrated into the compressor 12.

If the compressor 12 is designed as an electrically drivable refrigerant compressor, then the compressor 12 comprises an electric motor 56 shown schematically in FIG. 2, which can drive a compression unit 58 of the compressor 12. Furthermore, power electronics 60 of the compressor 12 are indicated schematically in FIG. 2 .

In the variant of the compressor 12 shown in Fig. 2, the second partial flow of the minimum mass flow of refrigerant delivered by the compressor 12, which is throttled to the suction pressure level by means of the valve 48, is cooled by means of a cooler, preferably to the temperature of the temperature generated by the evaporator 20 coming first partial flow of the refrigerant. The cooler used for this according to FIG. 2 can in particular be designed as a cooling jacket 62 which runs around the bypass line 50 or at least partially encloses the bypass line 50 .

As an alternative to the embodiment illustrated in FIG. 2 , the partial flow of the refrigerant that is routed through the bypass or the internal bypass line 50 can also be cooled before the throttling by means of the valve 48 . Accordingly, the valve 48 can be related to the cooling jacket 62 downstream of the direction of flow of the second partial flow through the bypass line 50 .

In a variant of the cooling jacket 62 (not shown in the figures), provision can be made for the cooling jacket 62 to extend as far as the power electronics 60 of the compressor 12 or refrigerant compressor. The cooling jacket 62 can then also cool the power electronics 60 in particular in the case of high thermal loads in or on the power electronics 60 .

As a rule, the cooling requirements of the power electronics 60 and the partial refrigerant flow are opposite to one another with regard to the ambient temperatures. At low loads, provision can therefore be made for cooling jacket 62 to be used primarily for cooling the refrigerant, while at high loads and therefore high ambient temperatures, cooling jacket 62 can be used primarily for cooling power electronics 60 .

3 shows a variant of the compressor 12 in which the second partial flow is fed to the suction side 24 of the compressor 12 via a bypass line 64 that is external to the compressor 12 . Here, the second partial flow is branched off by means of the return line 32 (compare Fig. 1) in the form of the external bypass line 64 (compare Fig. 3) downstream of the compressor 12 from a high-pressure-side line 66 of the refrigerant circuit 10 (compare Fig. 1) and via the external Bypass line 64 introduced into a low-pressure-side line 68 of the refrigerant circuit 10 (see FIG. 1). The line 66 on the high-pressure side is accordingly connected to the high-pressure connection 52 of the compressor 12 . Similarly, the line 68 on the low-pressure side or suction-pressure line is connected to the suction-pressure connection 54 of the compressor 12 .

The bypass line 64 that is external to the compressor is thus designed as an external bypass, via which the second partial flow of the refrigerant is returned or returned to the suction side 24 of the compressor 12 . Also in this variant of the compressor 12 can an actuation of the valve 48 by means of the control device 28, the second partial flow or bypass flow or leakage flow of the refrigerant can be set and, for example, throttled from the high pressure level to the suction pressure level.

Furthermore, a cooler 70 can also be provided in the variant shown in FIG. This cooler 70 can also be designed as a cooling jacket that surrounds the bypass line 64 in at least one section.

Air and/or a liquid coolant can be used as a cooling medium for dissipating heat by means of the cooler integrated into the compressor 12, for example in the form of the cooling jacket 62 (compare FIG. 2) or by means of the external cooler 70 (compare FIG. 3).

Provision can also be made for such a cooling jacket 62 and/or cooler 70 to be dispensed with, for example in order to reduce the complexity of the refrigerant circuit 10 . If, in such a case, it is determined, for example by means of a sensor 72 (cf High-pressure side 30 of the compressor 12 exceeds a predetermined upper threshold value, the bypass function can be temporarily dispensed with. In other words, a flow through the return line 32 can be temporarily prevented.

Then, during this temporary period of time, the entire minimum mass flow of the refrigerant conveyed by the compressor 12 is passed through the at least one evaporator, in this case through the evaporator 20 and/or through the chiller 42, and is cooled as it flows through this at least one evaporator. If it is subsequently determined that a further, lower threshold value of the pressure and/or the temperature of the refrigerant after the compressor 12, i.e. on the high-pressure side 30 of the compressor 12, falls below again, the bypass function can be picked up again and the second partial flow can accordingly be routed again via the return line 32.

According to the configuration of the refrigerant circuit 10 shown schematically in FIG. 1 , the return line 32 can branch off from the high-pressure-side line 66 of the refrigerant circuit 10 upstream of the condenser 16 . From this tap located upstream of condenser 16, the second partial flow of the minimum mass flow delivered by compressor 12 is then correspondingly returned via the controllable or closable throttle or a corresponding expansion element, for example in the form of valve 48, back to the inlet of compressor 12, i.e towards the suction side 24 of the compressor 12.

In this variant, too, provision can be made to briefly or temporarily interrupt the bypass flow, i.e. to temporarily prevent the flow through the return line 32, for example if the pressure and/or the temperature of the refrigerant at the outlet of the compressor 12 exceeds the first or upper threshold value.

Additionally or alternatively, according to FIG. 1 , provision can be made for the second partial flow to be branched off from the high-pressure-side line 66 of the refrigerant circuit 10 downstream of the condenser 16 by means of the return line 32 designed as an external bypass line 64 (cf. FIG. 3 ). Accordingly, in this variant, a connection point 74 of the return line 32 , at which the return line 32 branches off from the line 66 on the high-pressure side, is arranged downstream of the condenser 16 , but in the present case upstream of the branch point 34 . In this variant, too, the valve 48 , which is preferably arranged in the return line 32 , can be actuated by the control device 28 , as shown in FIG. 1 . In a further variant (not shown in the figures) of the refrigerant circuit 10, the return line 32 can be placed on the low-pressure side. For example, the return line 32 can branch off from a line section of the refrigerant circuit 10 formed between the first expansion element 18 and the evaporator 20 and lead from this line section to a line section of the refrigerant circuit 10 arranged downstream of the evaporator 20 . In this variant, the return line 32 represents a bypass line of the evaporator 20. In further variants, the return line 32 can branch off from any other point of a low-pressure-side section of the refrigerant circuit 10 and from there, bypassing the evaporator 20, ultimately lead to the suction side 24 of the compressor 12.

In this variant, the refrigerant is introduced into the return line 32 already expanded and cooled and then supplied to the compressor 12 via the return line 32 . In this variant, too, the valve 48 or a similar shut-off device having a shut-off function is preferably arranged in the return line 32, by means of which a partial mass flow of the refrigerant flowing through the return line 32 can preferably be regulated or adjusted.

1 also shows a further sensor 76, by means of which a pressure and/or a temperature of the coolant supplied to the suction side 24 of the compressor 12 can be detected. The sensor 76 can be arranged upstream or downstream of a point at which the return line 32 (compare FIG. 1 ) opens into the low-pressure-side line 68 of the refrigerant circuit 10 , for example in the form of the bypass line 64 (compare FIG. 3 ).

In all of the variants described, when the bypass is activated, i.e. when the return line 32 or bypass line 50, 64 is activated, only a partial mass flow in the form of the first partial flow reaches the at least one evaporator, in this case towards the evaporator 20 or towards the evaporator 20 and the Chiller 42. The size of this first partial flow is based on a target cooling capacity, which the at least one heat exchanger is intended to provide, for example in the form of the evaporator 20 . And the setting of a target cross-section of the bypass, in this case the setting of the flow-through cross-section of valve 48, is preferably based on the desired or required refrigeration capacity of the at least one evaporator, in this case in particular evaporator 20 to which air is applied during operation.

In particular, the refrigerant circuit 10 can be operated in such a way that, if there is an excess of refrigerating capacity at the evaporator 20, the valve 48 arranged in the agitator line or the return line 32 is opened until the required refrigerating capacity of the evaporator 20 corresponds to the refrigerating capacity present at the evaporator 20. Conversely, when the valve 48 is open and there is a cooling capacity deficit, the valve 48 can first be closed until the required cooling capacity corresponds to the cooling capacity present at the evaporator 20 . If the valve 48 is completely closed and the cooling capacity deficit cannot be covered or compensated for, the speed of the compressor 12 can be increased until the actual cooling capacity of the evaporator 20 corresponds to the target cooling capacity of the evaporator 20 .

Overall, the examples show how continuous operation of the compressor 12 embodied, for example, as an electric refrigerant compressor can be provided using the bypass or the return line 32 or the bypass line 50 , 64 .

Claims

PATENT CLAIMS: Method for operating a refrigerant circuit (10) of a motor vehicle (14), in which a compressor (12) arranged in the refrigerant circuit (10) delivers a minimum mass flow of refrigerant, and in which at least one parameter is recorded, which has a cooling capacity of at least of an evaporator (20, 42) arranged in the refrigerant circuit (10), the at least one evaporator (20, 42) providing the refrigerating capacity as a result of exposure to the refrigerant conveyed by the compressor (12), and at least one 12) the first partial flow of the refrigerant supplied to the at least one evaporator (20, 42) is expanded by means of at least one expansion element (18, 40) of the refrigerant circuit (10), characterized in that depending on the cooling capacity provided at the minimum mass flow of the refrigerant at least one evaporator (20, 42), a return line (32) of the refrigerant circuit (10) is flowed through by a second partial flow of the refrigerant delivered by the compressor (12), the second partial flow being fed via the return line (32) from a high-pressure side (30) of the refrigerant circuit (10) bypassing the at least one evaporator (20, 42) to a suction side (24) of the compressor (12). Method according to Claim 1, characterized in that the return line (32) is released by at least partially opening a shut-off device (48), the size of a cross-section of the shut-off device (48) through which the second partial flow can flow depending on the minimum mass flow of the Refrigerant provided cooling capacity of the at least one evaporator (20, 42) is set.

24 Method according to one of the preceding claims, characterized in that the second partial flow is fed to the suction side (24) of the compressor (12) via an internal bypass line (50) of the compressor (12). Method according to one of the preceding claims, characterized in that the second partial flow is fed to the suction side (24) of the compressor (12) via a bypass line (64) external to the compressor (12), the second partial flow being fed by means of the external bypass line ( 64) is branched off downstream of the compressor (12) from a high-pressure-side line (66) of the refrigerant circuit (10) and introduced via the external bypass line (64) into a low-pressure-side line (68) of the refrigerant circuit (10). Method according to Claim 4, characterized in that the second partial flow is branched off from the high-pressure-side line (66) by means of the external bypass line (64) downstream of a condenser (16) of the refrigerant circuit (10). Method according to one of the preceding claims, characterized in that a temperature of the second partial flow is controlled by means of a cooler (62) integrated in the compressor (12), in particular designed as a cooling jacket of the return line (32), and/or by means of a cooler (62) integrated in the return line (32 ) integrated cooler (70) is reduced. Method according to Claim 6, characterized in that air and/or a liquid coolant is applied to the cooler (62, 70) in order to reduce the temperature of the second partial flow. Method according to claim 6 or 7, characterized in that the second partial flow is brought to a temperature by means of the cooler (62, 70) which is essentially the same as a temperature of the first partial flow of the refrigerant coming from the at least one evaporator (20, 42). Method according to one of the preceding claims, characterized in that depending on a temperature of the refrigerant on a high-pressure side (30) of the compressor (12), a flow through the return line (32) is temporarily prevented, with all of the compressor (12) delivered Mass flow of the refrigerant is passed through the at least one evaporator (20, 42) and cooled in the at least one evaporator (20, 42). Motor vehicle with a refrigerant circuit (10), which includes a compressor (12) designed to deliver a minimum mass flow of refrigerant, and with a detection device (26) for detecting at least one parameter which indicates a cooling capacity of at least one evaporator arranged in the refrigerant circuit (10). (20, 42), wherein the at least one evaporator (20, 42) is designed to provide the refrigeration capacity as a result of exposure to refrigerant delivered by the compressor (12), and wherein at least one The first partial flow of the refrigerant that can be supplied to the evaporator (20, 42) can be expanded by means of at least one expansion element (18, 40) of the refrigerant circuit (10), characterized in that the motor vehicle (14) comprises a control device (28) which is designed to Depending on the refrigerating capacity of the at least one evaporator (20, 42) provided at the minimum mass flow of the refrigerant, a return line (32) of the refrigerant circuit (10) is allowed to flow through with a second partial flow of the refrigerant delivered by the compressor (12). effect, the return line (32) from a high-pressure side (30) of the refrigerant circuit (10) bypassing the at least one evaporator (20, 42) to a suction side (24) of the compressor (12).

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