FR3120426A1 - Method for controlling a refrigerant circuit - Google Patents

Abstract

Method for controlling a refrigerant circuit The present invention relates to a method for controlling a refrigerant circuit (2) comprising a main branch (6), a first branch (7) and a second branch (8), the main branch (6) comprising a device for compression (27) of the refrigerant fluid, and a temperature determination device (18), the first branch (7) comprising a first heat exchanger (11) and a first expansion member (13), the second branch (8) comprising at least a second heat exchanger (12) and a second expansion device (14), characterized in that: - in a first step, the second expansion device (14) is opened according to a minimum opening and an opening of the first expansion device (13) is reduced, - in a second step, the opening of the second expansion device (14) is increased. (figure 1)

Description

Method for controlling a refrigerant circuit

The present invention relates to the field of heat treatment systems, and more particularly relates to a method for controlling a refrigerant circuit integrated within such heat treatment systems.

Motor vehicles are commonly equipped with a heat treatment system comprising at least one refrigerant circuit and at least one heat transfer fluid circuit, both used to participate in a heat treatment of different areas or different components of the vehicle. It is in particular known to use the refrigerant circuit and/or the heat transfer fluid circuit to thermally treat a flow of air sent into the passenger compartment of the vehicle equipped with such a circuit.

In another application of this circuit, it is known to use the heat transfer fluid circuit to cool electrical or electronic components of the vehicle's traction chain, such as for example an electrical storage device, the latter being used to supply energy to an electric motor capable of setting the vehicle in motion. The heat treatment system thus supplies the energy capable of cooling the electrical storage device during its use in the driving phases.

The coolant is circulated in the coolant circuit by a compression device. By circulating within the refrigerant circuit, the refrigerant undergoes various changes of state and temperature in accordance with the refrigeration cycle. However, it happens that the refrigerant undergoes too much overheating, in particular during the cooling operation of the electrical or electronic elements. A refrigerant fluid circulating at too high a temperature in the refrigerant fluid circuit risks damaging the components of the refrigerant fluid circuit, but also creating difficulties in the heat treatment of said refrigerant fluid, for example during its expansion.

The present invention makes it possible to overcome this problem by proposing a method for controlling a refrigerant circuit, through which a refrigerant fluid passes, for a vehicle comprising a main branch, a first branch and a second branch, both in series with the main branch. , the main branch comprising at least one device for compressing the refrigerant fluid, a first heat exchanger configured to effect a heat exchange between the refrigerant fluid and a first fluid, and at least one temperature determination device estimating the temperature of the fluid refrigerant at the outlet of the compression device, the first branch comprising at least a first heat exchanger configured to effect a heat exchange between the refrigerant fluid and a heat transfer fluid flowing through a heat transfer fluid circuit, the second branch comprising at least a second heat exchanger configured to effect a heat exchange between the refrigerant fluid and the heat transfer fluid of the heat transfer fluid circuit, the second branch further comprising a device for accumulating the refrigerant fluid, the first branch and the second branch being in parallel with each other and joining in a first convergence point arranged downstream of the accumulation device and upstream of the compression device with respect to a direction of circulation of the refrigerant fluid, the first branch and the second branch respectively comprising a first expansion member arranged upstream of the first exchanger and a second expansion member arranged upstream of the second heat exchanger, the first expansion member being at least partially open beforehand, characterized in that during said control method:

- in a first step, the second expansion device is opened according to a minimum opening and an opening of the first expansion device is reduced when the temperature of the refrigerant fluid at the outlet of the compression device is greater than or equal to a maximum temperature threshold,

- in a second step, if the temperature of the refrigerant fluid at the outlet of the compression device is still greater than or equal to the maximum temperature threshold, the opening of the second expansion device is increased as long as the temperature of the refrigerant fluid at the outlet of the device compression is greater than or equal to the maximum temperature threshold.

By virtue of such a process, the temperature of the refrigerant fluid at the outlet of the compression device can be controlled, in particular be lowered in the event of an excessive increase that risks impairing the operation of the components through which the refrigerant fluid passes or even causing undesirable thermal effects.

Within the refrigerant fluid circuit, the refrigerant fluid is circulated by the compression device. The latter compresses the refrigerant in the vapor state and brings it to high pressure and high temperature. The temperature determination device is arranged so as to be able to measure the temperature of the refrigerant fluid at the outlet of the compression device. The temperature of the coolant at the outlet of the compression device is continuously monitored during operation of the coolant circuit, in order to compare said temperature with the maximum temperature threshold.

The first heat exchanger is installed downstream of the compression device and allows at least partial condensation of the refrigerant fluid thanks to the heat exchange carried out between the refrigerant fluid and the first fluid. By way of example, the first fluid can be a flow of air outside the vehicle. In order to be able to be arranged across a path of the flow of outside air, the first heat exchanger can for example be installed within a grille located on the front face of the vehicle, where the flow of outside air can s engulf.

Downstream of the first heat exchanger, the first branch and the second branch are both installed in series with the main branch. The refrigerant fluid can circulate from the main branch to the first branch, or be divided into two fractions, a first fraction of refrigerant fluid circulating in the first branch and a second fraction circulating in the second branch, the first branch and the second branch being parallel to each other. The first branch and the second branch each comprise, in an order corresponding to the direction of circulation of the refrigerant fluid, an expansion member and a heat exchanger. The first expansion member and the second expansion member make it possible to expand the refrigerant fluid in order to lower its temperature before it passes through the first heat exchanger and the second heat exchanger respectively. The opening of each of the expansion devices can be increased or reduced in order to regulate the flow of refrigerant fluid circulating in the first branch and/or in the second branch.

The first expansion member being opened beforehand, the refrigerant fluid circulates in the first branch, and therefore through the first heat exchanger. The first heat exchanger makes it possible to operate a heat exchange between the low-temperature refrigerant fluid and the heat transfer fluid circulating in the heat transfer fluid circuit. The heat transfer fluid circuit corresponds to a closed loop where the heat transfer fluid is cooled by the refrigerant fluid via the heat exchanger(s), then cools the electrical or electronic element requiring heat treatment. The refrigerant fluid, passing through the heat exchangers, therefore participates in the heat treatment of the electrical or electronic element, the latter being likely to release heat during its operation and thus risking rising to a temperature such that its operation may be s find it degraded.

At the outlet respectively from the first heat exchanger and from the second heat exchanger, the first branch and the second branch join together at the first point of convergence, so as to be both connected to the main branch, upstream of the compression device. The second branch has the particularity of comprising the accumulation device, arranged between the second heat exchanger and the first convergence point. Any fluid circulating in the second branch therefore passes through the accumulation device.

During the circulation of the refrigerant fluid, the latter is in the vapor state during its compression by the compression device, passes at least partially in liquid form by crossing the first heat exchanger, then passes completely in liquid form during its relaxation by the organs of relaxation. The refrigerant is then evaporated by the heat transfer fluid during the heat exchange occurring within the heat exchangers. However, it may happen that the refrigerant does not evaporate completely. The accumulation device therefore has the function of retaining a potential fraction of refrigerant fluid maintained in the liquid state before said liquid fraction circulates to the compression device, the latter being able to be damaged in the event of circulation of refrigerant fluid. in liquid form.

The accumulation device is arranged on the second branch. In other words, any fluid passing through the first branch bypasses the accumulation device and flows directly to the compression device. Bypassing the accumulation device is advantageous in that such bypassing makes it possible to reduce the pressure drop of the refrigerant fluid. On the other hand, the risk of the refrigerant overheating is greater when the latter bypasses the accumulation device.

The control method according to the invention is in particular configured to bring about a drop in the temperature of the refrigerant fluid when it overheats following circulation exclusively within the first branch.

Thus, when the temperature of the refrigerant at the outlet of the compression device is greater than or equal to the maximum temperature threshold, the first step of the control process is launched with the aim of lowering this temperature. The second expansion device is therefore open in order to allow the circulation of the refrigerant fluid in the second branch. Parallel to the opening of the second expansion member, the opening of the first expansion member is reduced in order to maintain substantially the same flow rate of refrigerant fluid circulating in the refrigerant circuit. By implementing the first step of the control method, the electrical or electronic element is still cooled via the heat exchange carried out within the first heat exchanger and the second heat exchanger, but the flow of refrigerant fluid bypassing the device of accumulation is reduced, thus causing the temperature of the refrigerant at the outlet of the compression device to drop.

In order to avoid as much as possible the loss of pressure linked to the passage of the refrigerant fluid through the accumulation device, the second expansion device is open according to a minimum opening in order to limit the flow of refrigerant fluid circulating in the second branch. If this minimum opening of the second expansion member is not sufficient to regulate the temperature of the refrigerant fluid at the outlet of the compression device, the control method passes to the second step in order to increase the opening of the second expansion member in the aim of increasing the flow rate of refrigerant fluid circulating in the second branch, and thus of forcing a drop in the temperature of the refrigerant fluid at the outlet of the compression device. The opening of the second expansion device is gradual until the temperature of the refrigerant fluid at the outlet of the compression device is below the maximum temperature threshold.

According to one characteristic of the process, it comprises a third step, subsequent to the second step, where the opening of the first expansion device is further reduced. Like the first step where the opening of the first trigger member is reduced parallel to the opening of the second trigger member, the opening of the first trigger member is again reduced when the opening of the second trigger member relaxation is increased during the second stage.

According to a characteristic of the method, the opening of the second expansion member and the reduction of the opening of the first expansion member are proportional to each other. This proportionality makes it possible to maintain a constant total bit rate, said total bit rate corresponding to the sum of the bit rates circulating within the mutually parallel branches. The flow must be kept constant so that the compression device can properly compress the refrigerant.

According to a characteristic of the process, the maximum temperature threshold is between 120°C and 125°C. The temperature of the refrigerant fluid at the outlet of the compression device must therefore be kept below a temperature of between 120° C. and 125° C. so that the operation of the refrigerant fluid circuit is correctly ensured. When the temperature of the refrigerant at the outlet of the compression device reaches or exceeds a temperature between 120°C and 125°C, the control method is implemented so that the temperature of the refrigerant at the outlet of the compression device becomes lower again. at this temperature between 120°C and 125°C.

According to a characteristic of the process, during the first step, the minimum opening of the second expansion device corresponds to a section of 0.07mm² at +/- 10%. This is the minimum section allowing a flow of refrigerant fluid sufficient to act on the cooling of the electrical or electronic element. For a circular opening, a section of 0.07mm² corresponds to a diameter of 0.3mm.

According to a characteristic of the method, a temperature check is implemented after the third step. The temperature check makes it possible to determine whether, after the increase in the opening of the second expansion device and the reduction in the opening of the first expansion device, the temperature of the refrigerant fluid at the outlet of the compression device is again lower at the maximum temperature threshold.

According to one characteristic of the method, the second step, the third step and the temperature verification are repeated iteratively as long as the temperature of the refrigerant fluid at the outlet of the compression device is greater than or equal to the maximum temperature threshold. The objective being to reduce the temperature of the refrigerant while ensuring circulation within the second branch as low as possible in order to limit the pressure drop, the temperature check is done cyclically so that the section of the opening of the second expansion device is as small as possible. Such an iterative repetition continues until the temperature of the refrigerant fluid at the outlet of the compression device is below the maximum temperature threshold.

The invention also covers a refrigerant fluid circuit comprising a main branch provided with a compression device, a temperature determination device configured to measure a temperature of the refrigerant fluid at the outlet of the compression device and a first exchanger heat, a first branch comprising a first expansion member and a first heat exchanger, a second branch comprising a second expansion member, a second heat exchanger and an accumulation device, said refrigerant circuit implementing a method of control as described above.

According to one characteristic of the invention, the refrigerant circuit comprises a third branch in series with the main branch and in parallel with the first branch and the second branch, the third branch comprising at least one second heat exchanger configured to operate a heat exchange between the refrigerant fluid and an interior air flow sent into the passenger compartment of the vehicle, the second branch and the third branch joining at a second convergence point arranged on the second branch, between the second heat exchanger and the storage device. The third branch cools the vehicle interior via the second heat exchanger. The second heat exchanger is disposed at a path of the indoor air flow. The second heat exchanger is configured so that the coolant circulates there at low temperature in order to cool the interior air flow which is subsequently sent to the passenger compartment of the vehicle. As a result, the third branch comprises a third expansion member making it possible to expand the refrigerant fluid, and possibly to regulate the flow rate of the latter. The second heat exchanger can be installed within a ventilation, heating and/or air conditioning installation, which circulates the interior air flow in a cyclic manner in order to cool or heat the passenger compartment according to a mode operation of the heat treatment system.

When the heat treatment system operates according to an operating mode intended to ensure the cooling of the passenger compartment of the vehicle, the refrigerant fluid must then circulate both in the first branch and possibly in the second branch in order to cool the electrical or electronic element. to be heat-treated, but also in the third branch to ensure the comfort of the vehicle cabin. Since the internal air flow may not be at a sufficiently high temperature to completely evaporate the refrigerant fluid, the third branch is connected to the second branch so that a liquid fraction of refrigerant fluid coming from the third branch can be stopped by the device. of hoarding.

According to one characteristic of the invention, the main branch comprises a third heat exchanger arranged between the compression device and the first heat exchanger, the third heat exchanger being configured to effect a heat exchange between the refrigerant fluid and a second fluid which may be the interior air flow. The third heat exchanger ensures the comfort of the vehicle cabin in the event of low ambient temperature. The third heat exchanger is arranged downstream of the compression device and is therefore traversed by the high-temperature refrigerant fluid. The latter is therefore able to heat the second fluid, for example the flow of interior air which is subsequently sent to the passenger compartment of the vehicle.

Other characteristics and advantages of the invention will become apparent through the description which follows on the one hand, and several embodiments given by way of indication and not limiting with reference to the appended diagrammatic drawings on the other hand, on which :

represents a heat treatment system provided with a refrigerant circuit capable of implementing a control method according to the invention,

is a flowchart for breaking down the different stages of the control process,

represents the circulation of a coolant in the coolant circuit operating according to a cooling mode of a passenger compartment of a vehicle, during the progress of the control method,

represents the circulation of the coolant in the coolant circuit operating according to a heating mode of the passenger compartment of the vehicle, during the progress of the control method.

On the , a refrigerant circuit is illustrated in solid lines. In FIGS. 3 and 4, the portions traversed by the refrigerant fluid are in solid lines and the portions without circulation of refrigerant fluid are in dotted lines. Furthermore, the circulation of the refrigerant fluid is illustrated by indicating its direction of circulation by arrows. The solid lines indicating the circulation of fluid are also of different thickness concerning the refrigerant circuit. More precisely, the thickest solid lines correspond to portions where the refrigerant fluid circulates at high pressure and the thinnest solid lines correspond to portions where the refrigerant fluid circulates at low pressure.

The terms "first", "first", "second", etc. used in the description are not intended to indicate a level of hierarchy or order the elements they accompany. These terms make it possible to distinguish the elements that they accompany and can be interchanged without reducing the scope of the invention.

There represents a refrigerant circuit 2 without indication of fluid circulation. The refrigerant circuit 2 is configured to form part of a heat treatment system 1, for example within a vehicle. The refrigerant can for example be a fluid of the R134a or R1234yf type.

The refrigerant circuit 2 comprises in particular a main branch 6 provided with a compression device 27. The compression device 27 makes it possible to circulate the refrigerant fluid and to compress it at very high pressure. Thanks to the compression device 27, the refrigerant fluid can thus circulate in the main branch 6. In order to compress the refrigerant fluid, the compression device 27 is capable of entering into rotation. The higher the speed of rotation of the compression device 27, the greater the flow rate of compressed refrigerant fluid. The main branch 6 comprises a temperature determining device 18 arranged at the outlet of the compression device 27. The temperature determining device 18 can however be arranged at another zone of the refrigerant circuit 2, the essential being that it is capable of determining the temperature of the refrigerant fluid after it has been compressed by the compression device 27. The temperature determination device 18 can carry out a direct measurement of the temperature of the refrigerant fluid, or else a measurement another parameter of the refrigerant allowing its temperature to be deduced therefrom.

The main branch 6 comprises a first heat exchanger 21 configured to effect a heat exchange between the refrigerant fluid and a first fluid. As shown on the and in the following figures, the first fluid corresponds by way of example to a flow of air 4 outside a passenger compartment of the vehicle. The main branch 6 also comprises an expansion device 16 configured to expand the refrigerant fluid before the latter passes through the first heat exchanger 21. The first heat exchanger 21 is arranged downstream of the compression device 27, and the expansion device 16 is arranged upstream of the first heat exchanger 21 and downstream of the compression device 27. The expansion device 16 allows the expansion of the refrigerant fluid after the latter has been placed under high pressure by the compression device 27. The expansion device expansion device 16 nevertheless has the ability to let the coolant pass without expanding it. Thus, the refrigerant fluid can pass through the first heat exchanger 21 at high pressure or at low pressure, the pressure of the refrigerant fluid depending on an operating mode of the refrigerant circuit 2.

Downstream of the first heat exchanger 21, the main branch 6 is divided into a first branch 7, a second branch 8 and a third branch 9, all arranged in series with the main branch 6. The first branch 7, the second branch 8 and the third branch 9 are therefore arranged in parallel with respect to each other. The first branch 7 and the third branch 9 both begin at a first point of divergence 31 where the main branch 6 ends. The second branch 8 begins for its part at a second point of divergence 32 located on the main branch 6, upstream of the first point of divergence 31.

The first branch 7 comprises a first heat exchanger 11 as well as a first expansion member 13 arranged between the first point of divergence 31 and the first heat exchanger 11. The first heat exchanger 11 is configured to effect a heat exchange between the fluid refrigerant circulating in the first branch 7 and a heat transfer fluid circulating within a heat transfer fluid circuit 3. The first expansion device 13 is arranged on the first branch 7, between the first point of divergence 31 and the first heat exchanger 11 The first expansion device 13 makes it possible to expand the refrigerant fluid before the latter passes through the first heat exchanger 11.

The heat transfer fluid circuit 3 is part of the heat treatment system 1, and is intended to heat treat at least one electric or electronic element 25 necessary for the proper operation of the motor vehicle, for example an electric motor or an electric storage element. Such an electric or electronic element 25 is likely to release heat during its operation. The heat transfer fluid therefore has the particular function of cooling the electrical or electronic element 25 in order to preserve the optimal functioning of the latter. The electrical or electronic element 25 therefore has a need for cooling which must be met by the heat transfer fluid, and therefore by analogy the refrigerant fluid.

The heat transfer fluid circuit 3 comprises a pump 26 capable of circulating the heat transfer fluid so that the latter passes through the first heat exchanger 11. The low-temperature refrigerant fluid therefore makes it possible to cool the heat transfer fluid during the heat exchange taking place in the first heat exchanger 11. The cooled heat transfer fluid can subsequently cool the electrical or electronic element 25. Once the heat transfer fluid has captured the calories generated by the electrical or electronic element 25, the heat transfer fluid can again be cooled by the refrigerant passing through the first heat exchanger 11.

The second branch 8 comprises a second heat exchanger 12 and a second expansion device 14 installed between the second point of divergence 32 and the second heat exchanger 12. When the refrigerant fluid is authorized to circulate in the second branch 8, it is expanded by the second expansion member 14, then passes through the second heat exchanger 12. The heat transfer fluid circulating in the heat transfer fluid circuit 3 can therefore be cooled simultaneously thanks to the first heat exchanger 11 and the second heat exchanger 12, thus ensuring the cooling of the heat transfer fluid on the electrical or electronic element 25.

The first branch 7 and the second branch 8 join the main branch 6 at a first point of convergence 41, arranged upstream of the compression device 27, within which the refrigerant fluid can again be compressed there.

In order to prevent a fraction of non-evaporated refrigerant fluid from passing through the compression device 27, the second branch 8 comprises an accumulation device 17. The latter corresponds to a container making it possible to retain any liquid fraction of the refrigerant fluid so that this does not circulate as far as the compression device 27. The accumulation device 17 is arranged between the second heat exchanger 12 and the first point of convergence 41. In other words, the refrigerant fluid circulating in the first branch 7 bypasses the accumulation device 17 while the refrigerant fluid circulating in the second branch 8 passes through the accumulation device 17.

Bypassing the accumulation device 17 makes it possible to avoid the loss of charge of the refrigerant fluid. The circulation of the refrigerant fluid via the first branch 7 is therefore privileged with respect to the second branch 8. On the other hand, by bypassing the accumulation device 17, there is a risk of overheating of the refrigerant fluid when the latter is compressed by the compression device 27. Circulating a coolant at too high a temperature in the coolant circuit 2 can cause malfunctions within the latter. A refrigerant that is too hot can, for example, damage components through which the refrigerant passes and which are not designed to withstand excessively high temperatures. The heat exchanges occurring in the refrigerant fluid circuit can also be made difficult to perform if the refrigerant fluid is too hot. It is therefore essential to ensure that the refrigerant at the outlet of the compression device is maintained at a temperature below a temperature limit threshold called the maximum temperature threshold. If this maximum temperature threshold is reached or exceeded, a control process can be launched in order to regulate the temperature of the refrigerant fluid. The temperature determining device 18 therefore participates in the launch of the control process by determining the temperature of the refrigerant fluid at the outlet of the compression device 27.

The third branch 9 begins for its part at the level of the first point of divergence 31, and ends at the level of a second point of convergence 42 arranged on the second branch 8 between the second heat exchanger 12 and the accumulation device 17. The refrigerant fluid circulating in the third branch 9 therefore passes through the storage device 17.

The third branch 9 comprises a third expansion member 15 and a second heat exchanger 22 configured to effect a heat exchange between the refrigerant fluid and an interior air flow 5 intended to be sent to the passenger compartment of the vehicle in order to cool this one. Thus the second heat exchanger 22 is configured to be traversed by the low-temperature refrigerant fluid in order to cool the interior air flow 5. As such, the second heat exchanger 22 can be arranged within a ventilation, heating and/or air conditioning installation, configured to cause the interior air flow 5 to circulate in a closed circuit in order to constantly respond to the cooling of the passenger compartment of the vehicle. The third expansion device 15 makes it possible to expand the refrigerant fluid in order to lower its temperature before passing through the second heat exchanger 22. The refrigerant fluid circulates in the third branch 9 when the passenger compartment of the vehicle needs to be cooled, by example following a manual command from a user of the vehicle. The refrigerant circuit 2 then operates according to a cooling mode of the passenger compartment of the vehicle.

The refrigerant circuit 2 also comprises a third heat exchanger 23, arranged on the main branch 6 downstream of the compression device 27. The third heat exchanger 23 is therefore traversed by the refrigerant at high pressure and at high temperature. , and is configured to effect a heat exchange between the refrigerant fluid and a second fluid. On the , as well as in the following figures, the second fluid corresponds to the internal air flow 5. The heat exchange taking place within the third heat exchanger 23 is therefore operated between the high temperature refrigerant fluid and the flow of interior air 5 in order to heat the latter, which is then sent to the passenger compartment of the vehicle in order to heat the latter. The refrigerant circuit 2 then operates according to a heating mode of the passenger compartment of the vehicle. Therefore, the third heat exchanger 23, like the second heat exchanger 22, can be installed within the ventilation, heating and/or air conditioning installation. Depending on the mode of operation of the refrigerant circuit 2, the ventilation, heating and/or air conditioning installation may include flaps that can guide the interior air flow 5 so that the latter only crosses the heat exchanger relating to the requested mode of operation.

The refrigerant circuit 2 can also comprise a fourth heat exchanger 24 configured to effect a heat exchange between the refrigerant fluid and the outside air flow 4. The fourth heat exchanger 24 is installed on the main branch 6, between the first heat exchanger 21 and the second point of divergence 32. The fourth heat exchanger 24 is therefore installed in series with the first heat exchanger 21, and upstream of the latter with respect to a direction of circulation of the flow of outside air 4. The fourth heat exchanger 24 can thus act as a sub-cooler in order to condense the refrigerant fluid. Sub-cooling the refrigerant fluid allows more effective expansion thereof by the expansion devices 13, 14, 15.

The main branch 6 comprises a third point of divergence 33 between the first heat exchanger 21 and the fourth heat exchanger 24. The refrigerant circuit 2 comprises a fourth branch 51 starting at this third point of divergence 33 and ending at the second point of convergence 42. The fourth branch 51 allows the refrigerant fluid to bypass the heat exchangers 11,12 as well as the second heat exchanger 22, and directly join the accumulation device 17. The fourth branch 51 thus allows a function of heat pump of the refrigerant circuit 2. The fourth branch 51 comprises a first valve 61 authorizing or not the circulation of the refrigerant fluid in the fourth branch 51.

The refrigerant circuit finally comprises a fifth branch 52 starting at a fourth point of divergence 34 located between the third heat exchanger 23 and the expansion device 16, and ending at a third point of convergence 43 located on the main branch 6 between the fourth heat exchanger 24 and the second point of divergence 32. The fifth branch 52 allows the refrigerant fluid to bypass the first heat exchanger 21 and the fourth heat exchanger 24 in order to directly reach the first branch 7 and/or the second branch 8 and/or the third branch 9. The fifth branch 52 comprises a second valve 62 authorizing or not the circulation of the refrigerant fluid in the fifth branch 52. So that the refrigerant fluid circulating in the fifth branch 52 does not circulate towards the fourth heat exchanger 24 once at the third point of convergence 43, the main branch 6 comprises a non-return valve 63 arranged cé downstream of the fourth heat exchanger 24.

There represents a flowchart of the control method 100 mentioned previously. The control method 100 makes it possible to regulate the temperature T at the outlet of the compression device so that it is kept below the maximum temperature threshold Tmax, corresponding to a maximum temperature limit before a potential appearance of malfunctions within the fluid circuit refrigerant.

The control method 100 is therefore launched when the temperature T of the refrigerant fluid at the outlet of the compression device is greater than or equal to the maximum temperature threshold Tmax. This determination is in particular established by the temperature determination device referenced 18 on the . The maximum temperature threshold Tmax can for example be between 120°C and 125°C.

Following this determination, the control method 100 is launched with a first step 110 which consists of a minimum opening 101 of the second expansion device, in order to authorize the circulation of the refrigerant fluid in the second branch. The minimum opening 101 can for example be of a section of 0.07mm² at +/- 10% or of a diameter of 0.3mm if said section is circular.

The first step 110 also includes a reduction in the opening 102 of the first expansion member in order to maintain a constant flow of coolant fluid between the first branch, the second branch and possibly the third branch if the cooling mode of the passenger compartment of the vehicle is active. The reduction in the flow rate of refrigerant fluid in the first branch also makes it possible to potentially lower the temperature T of the refrigerant fluid at the outlet of the compression device. Therefore, once the minimum opening 101 and the opening reduction 102 have been carried out, a temperature check is implemented in order to check whether the temperature T of the refrigerant fluid at the outlet of the compression device is still greater than or equal to the maximum temperature threshold Tmax, or else if the first step 110 has enabled the temperature T of the refrigerant fluid at the outlet of the compression device to again be lower than the maximum temperature threshold Tmax. If the temperature T of the refrigerant fluid at the outlet of the compression device is lower than the maximum temperature threshold Tmax, this means that the temperature T of the refrigerant fluid has been correctly regulated and the control method 100 can end with an end step 103.

If the temperature T of the refrigerant at the outlet of the compression device is still greater than or equal to the maximum temperature threshold Tmax, the control method 100 continues with a second step 120, which consists of an increase in opening 104 of the second organ expansion, to intensify the flow of refrigerant flowing in the second branch. The second step 120 is linked with a third step 130 where the reduction in opening 102 of the first expansion device is again applied in order to maintain the total flow rate of refrigerant fluid constant.

The objective being to carry out the control of the temperature T of the refrigerant fluid at the outlet of the compression device while minimizing the pressure drop of the refrigerant fluid, the control method 100 therefore implements the second step 120 and the third step 130 so that the increase in aperture 104 and the reduction in aperture 102 are as small as possible. Thus, once the second step 120 and the third step 130 have been carried out, a temperature check is again carried out in order to determine whether the temperature T of the refrigerant fluid at the outlet of the compression device is still greater than or equal to the maximum temperature threshold Tmax , or else if the second step 120 and the third step 130 have enabled the temperature T of the refrigerant fluid at the outlet of the compression device to again be lower than the maximum temperature threshold Tmax. If the temperature T of the refrigerant fluid at the outlet of the compression device is lower than the maximum temperature threshold Tmax, this means that the temperature T of the refrigerant fluid has been correctly regulated and the control method 100 can end with the step of end 103.

If the temperature T of the refrigerant fluid at the outlet of the compression device is still greater than or equal to the maximum temperature threshold Tmax, the second step 120 and the third step 130 are repeated in order to increase the flow rate of refrigerant fluid circulating in the second branch and to reduce the flow rate of refrigerant fluid circulating in the first branch. Then the temperature check is performed again. The second step 120 and the third step 130 are repeated iteratively until the temperature T of the refrigerant fluid at the outlet of the compression device is lower than the maximum temperature threshold Tmax, thus leading to the end step 103.

There illustrates the circulation of the refrigerant fluid FR in the refrigerant fluid circuit 2 when the latter operates according to the cooling mode of the passenger compartment of the vehicle and during the control method. Thus, the refrigerant fluid FR is circulated within the main branch 6 and is compressed at high pressure by the compression device 27. The refrigerant fluid FR then passes through the third heat exchanger 23 without influencing the temperature of the flow of indoor air 5 thanks to the shutters of the ventilation, heating and/or air conditioning installation mentioned above.

The refrigerant fluid FR then reaches the expansion device 16 which allows the refrigerant fluid FR to pass without expanding the latter. The refrigerant fluid FR continues its circulation in the main branch 6 by crossing the first heat exchanger 21 then the fourth heat exchanger 24 in which the refrigerant fluid FR is cooled and at least partially condensed by the flow of outside air 4.

The refrigerant fluid FR continues to circulate within the main branch 6 as far as the second point of divergence 32, where a first fraction of refrigerant fluid FR continues to circulate within the main branch 6, while a second fraction of fluid refrigerant FR circulates in the second branch 8, is expanded by the second expansion device 14 and then passes through the second heat exchanger 12 in order to cool the heat transfer fluid within the heat transfer fluid circuit 3. At the same time, the pump 26 makes it possible to put circulation of the heat transfer fluid from the heat transfer fluid circuit 3 so that the heat exchange can be carried out at the level of the second heat exchanger 12. The circulation of the refrigerant fluid FR is authorized within the second branch 8 given that the process of control is being implemented.

At the outlet of the second heat exchanger 12, the circulation of the refrigerant fluid FR continues in the second branch 8 as far as the storage device 17 where a potential liquid fraction of refrigerant fluid FR is retained there. The refrigerant FR then joins the main branch 6 via the first convergence point 41 before being compressed again by the compression device 27.

The first fraction of refrigerant fluid FR circulates as far as the first point of divergence 31 and separates into two sub-fractions. A first sub-fraction circulates within the first branch 7 with the aim of cooling the heat transfer fluid which itself will cool the electrical or electronic element 25, while a second sub-fraction circulates in the third branch 9 in the purpose of cooling the interior air flow 5 so that it cools the passenger compartment of the vehicle.

The first sub-fraction of refrigerant fluid FR is therefore expanded by the first expansion device 13 which is kept at least partially open during the control process, then passes through the first heat exchanger 11. The heat transfer fluid is then cooled, and can then cool the electrical or electronic element 25. At the outlet of the first heat exchanger 11, the refrigerant fluid FR then joins the first convergence point 41 bypassing the accumulation device 17 and is compressed again by the compression device 27.

The second sub-fraction of refrigerant fluid FR circulating in the third branch 9 is expanded by the third expansion member 15, then passes through the second heat exchanger 22 in order to cool the interior air flow 5. At the outlet of the second heat exchanger heat 22, the refrigerant fluid FR then joins the second branch 8 at the level of the second point of convergence 42, circulates within the accumulation device 17 where a potential liquid fraction of refrigerant fluid FR is retained there, then joins the main branch 6 via the first convergence point 41 before being compressed again by the compression device 27.

During the control process, the flow rate of refrigerant fluid FR circulating in the first branch 7 and in the second branch 8 can vary, the opening of the first expansion member 13 being able to decrease while the opening of the second expansion member 14 may increase.

There illustrates the circulation of the refrigerant FR in the refrigerant circuit 2 when the latter operates according to the heating mode of the passenger compartment of the vehicle and during the control method. Thus, the refrigerant fluid FR is circulated within the main branch 6 and is compressed at high pressure by the compression device 27. The refrigerant fluid FR then passes through the third heat exchanger 23 at high temperature, thus making it possible to heat the interior air flow 5 so that it is sent therein into the passenger compartment of the vehicle to heat the latter.

The refrigerant fluid FR then reaches the fourth point of divergence 34. The second valve 62 being open, a first fraction of refrigerant fluid FR passes through the fifth branch 52 while a second fraction continues its circulation in the main branch 6.

The first fraction passes through the fifth branch 52 and joins the main branch 6 via the third convergence point 43 bypassing the first heat exchanger 21 and the fourth heat exchanger 24. The first fraction continues its circulation within the main branch 6 to the second point of divergence 32, where a first sub-fraction of refrigerant fluid FR continues to circulate within the main branch 6, while a second sub-fraction of refrigerant fluid FR circulates in the second branch 8, is expanded by the second expansion device 14 and then passes through the second heat exchanger 12 in order to cool the heat transfer fluid within the heat transfer fluid circuit 3. At the same time, the pump 26 makes it possible to circulate the heat transfer fluid of the fluid circuit coolant 3 so that the heat exchange can be operated at the level of the second heat exchanger 12. The circulation of the refrigerant fluid FR is at the authorized within the second branch 8 since the control method is being implemented.

At the outlet of the second heat exchanger 12, the second sub-fraction of refrigerant fluid FR continues in the second branch 8 as far as the accumulation device 17 where a potential liquid fraction of refrigerant fluid FR is retained there. The refrigerant FR then joins the main branch 6 via the first convergence point 41 before being compressed again by the compression device 27.

The first sub-fraction circulates as far as the first point of divergence 31 and circulates exclusively within the first branch 7, access to the third branch 9 being blocked by the third trigger member 15 which is completely closed.

The first sub-fraction is expanded by the first expansion member 13 which is at least partially open throughout the control process, then passes through the first heat exchanger 11. The heat transfer fluid is then cooled, and can then cool the element electric or electronic 25. At the outlet of the first heat exchanger 11, the refrigerant FR then joins the first convergence point 41 bypassing the accumulation device 17 and is compressed again by the compression device 27.

Concerning the second fraction of refrigerant fluid FR having formed at the level of the fourth point of divergence 34, the latter continues its circulation in the main branch 6, is expanded by the expansion device 16, then passes through the first heat exchanger 21 in which the external air flow 4 is cooled by the expanded refrigerant FR. At the outlet of the first heat exchanger 21, the refrigerant FR reaches the third point of divergence 33. The first valve 61 being open, the refrigerant FR circulates within the fourth branch 51, and directly joins the second point of convergence 42 The refrigerant fluid FR then circulates within the accumulation device 17 where a potential liquid fraction of refrigerant fluid FR is retained there, then joins the main branch 6 via the first convergence point 41 before being compressed again by the compression device 27.

During the control process, the flow rate of refrigerant fluid FR circulating in the first branch 7 and in the second branch 8 can vary, the opening of the first expansion member 13 being able to decrease while the opening of the second expansion member 14 may increase.

Of course, the invention is not limited to the examples which have just been described and many adjustments can be made to these examples without departing from the scope of the invention.

The invention, as it has just been described, achieves the goal it had set itself, and makes it possible to propose a control method making it possible to avoid the circulation of overheated refrigerant fluid within a circuit. of refrigerant fluid. Variants not described here could be implemented without departing from the context of the invention, provided that, in accordance with the invention, they include a control method in accordance with the invention.

Claims (10)

Method (100) of controlling a refrigerant fluid circuit (2), through which a refrigerant fluid (FR) passes, for a vehicle comprising a main branch (6), a first branch (7) and a second branch (8) all two in series of the main branch (6), the main branch (6) comprising at least one device (27) for compressing the refrigerant fluid (FR), a first heat exchanger (21) configured to effect a heat exchange between the refrigerant fluid (FR) and a first fluid, and at least one temperature determination device (18) estimating the temperature of the refrigerant fluid (FR) at the outlet of the compression device (27), the first branch (7) comprising at least one first heat exchanger (11) configured to effect a heat exchange between the refrigerant fluid (FR) and a heat transfer fluid flowing through a heat transfer fluid circuit (3), the second branch (8) comprising at least one second heat exchanger ( 12) configured to operate a heat exchange between the refrigerant fluid (FR) and the heat transfer fluid of the heat transfer fluid circuit (3), the second branch (8) further comprising a device (17) for accumulating the refrigerant fluid (FR), the first branch (7) and the second branch (8) being parallel to each other and join at a first point of convergence (41) disposed downstream of the accumulation device (17) and upstream of the compression (27) with respect to a direction of circulation of the refrigerant fluid (FR), the first branch (7) and the second branch (8) respectively comprising a first expansion member (13) arranged upstream of the first heat exchanger (11 ) and a second expansion member (14) arranged upstream of the second heat exchanger (12), the first expansion member (13) being previously at least partially open, characterized in that during said control method (100) :
- in a first step (110), the second expansion member (14) is opened according to a minimum opening and an opening of the first expansion member (13) is reduced when the temperature (T) of the refrigerant fluid (FR) at the outlet of the compression device (27) is greater than or equal to a maximum temperature threshold (Tmax),
- in a second step (120), if the temperature (T) of the refrigerant fluid (FR) at the outlet of the compression device (27) is still greater than or equal to the maximum temperature threshold (Tmax), the opening of the second expansion device (14) as long as the temperature (T) of the refrigerant fluid (FR) at the outlet of the compression device (27) is greater than or equal to the maximum temperature threshold (Tmax). Control method (100) according to claim 1, comprising a third step (130), subsequent to the second step (120), in which the opening of the first expansion member (13) is further reduced. Control method (100) according to claim 1 or 2, in which the opening of the second expansion member (14) and the reduction of the opening of the first expansion member (13) are proportional to each other. the other. Control method (100) according to any one of the preceding claims, characterized in that the maximum temperature threshold (Tmax) is between 120°C and 125°C. Control method (100) according to any one of the preceding claims, during which, during the first step (110), the minimum opening of the second expansion member (14) corresponds to a section of 0.07mm² at + /- 10%. A control method (100) according to any one of the preceding claims, combined with claim 2, during which a temperature check is implemented after the third step (130). Control method (100) according to the preceding claim, during which the second step (120), the third step (130) and the temperature verification are repeated iteratively as long as the temperature (T) of the refrigerant fluid (FR) at the output of the compression device (27) is greater than or equal to the maximum temperature threshold (Tmax). Refrigerant fluid circuit (2) comprising a main branch (6) provided with a compression device (27), a temperature determination device (18) configured to measure a temperature of the refrigerant fluid (FR) at the outlet of the compression device (27) and a first heat exchanger (21), a first branch (7) comprising a first expansion member (13) and a first heat exchanger (11), a second branch (8) comprising a second expansion member (14), a second heat exchanger (12) and an accumulation device (17), said refrigerant circuit (2) implementing a control method (100) according to any one of the claims previous ones. Cooling fluid circuit (2) according to the preceding claim, comprising a third branch (9) in series with the main branch (6) and in parallel with the first branch (7) and the second branch (8), the third branch (9) comprising at least a second heat exchanger (22) configured to effect a heat exchange between the refrigerant fluid (FR) and an interior air flow (5) sent into the passenger compartment of the vehicle, the second branch ( 8) and the third branch (9) joining at a second convergence point (42) arranged on the second branch (8), between the second heat exchanger (12) and the storage device (17). Cooling fluid circuit (2) according to the preceding claim, in which the main branch (6) comprises a third heat exchanger (23) arranged between the compression device (27) and the first heat exchanger (21), the third heat exchanger (23) being configured to operate a heat exchange between the refrigerant fluid (FR) and a second fluid which may be the interior air flow (5).