FR3147849A1 - Thermal control device for a vehicle gearbox. - Google Patents

Abstract

Thermal regulation device for a vehicle gearbox. The invention relates to a thermal regulation device (10) for a gearbox (2) of a motor vehicle (1), the thermal regulation device (10) comprising a shell (11) intended to at least partially envelop an external casing (3) of such a gearbox (2) to facilitate the temperature rise of the gearbox (2), in particular when starting such a motor vehicle (1). Abstract figure: fig. 2

Description

Thermal control device for a vehicle gearbox. Technical field of the invention

The invention relates to a thermal control device for a gearbox of a motor vehicle. The invention further relates to an arrangement comprising a gearbox and such a thermal control device. The invention further relates to a method of operating such a thermal control device. The invention further relates to a motor vehicle comprising such an arrangement or such a thermal control device.

State of the prior art

A motor vehicle comprises a powertrain. Such a powertrain comprises at least one heat engine and/or at least one electric motor and at least one gearbox. Such a gearbox is generally arranged between the engine(s) and at least one transmission shaft intended to transmit torque to at least one means in contact with the ground such as a wheel. Such a gearbox generally comprises pinions meshing with each other and uses oil for its lubrication. Such a lubricating oil comprises an operating temperature range within which its lubricating power is optimal.

However, when starting one or more engines, particularly in cold weather, the gearbox oil only reaches the optimum operating temperature range after a certain period of time. Furthermore, particularly in hot weather and/or at high engine speeds and/or high gearbox speeds, the gearbox oil exceeds the optimum operating temperature range.

More specifically, at a temperature below such a temperature range, the oil is viscous, which creates a loss of efficiency of the gearbox, leading to excess consumption of the vehicle in terms of electricity and/or fuel. Conversely, at a temperature above such a temperature range, the oil film between gears meshing together is not thick enough, which causes premature wear of the gears. In the long term, such wear causes abnormal noises from such a gearbox, or even malfunctions, or even breakage of gears, which leads to deterioration of the gearbox and makes it unusable.

This situation is not acceptable.

Presentation of the invention

The present invention aims to provide a thermal regulation device for a gearbox which overcomes the above drawbacks. In particular, the invention makes it possible to reach the optimum operating temperature range of the oil more quickly when starting the engine(s) and not to exceed this temperature range when revving up the engine(s) and consequently the gearbox, and/or in hot weather.

To achieve this objective, the invention relates to a thermal regulation device for a gearbox of a motor vehicle, the thermal regulation device comprising a shell intended to at least partially envelop an external casing of such a gearbox to facilitate the temperature rise of the gearbox, in particular when starting such a motor vehicle.

The thermal control device may include an air inlet duct to facilitate cooling of the gearbox.

The air inlet duct may comprise an air inlet, the inlet having a non-constant section, in particular a truncated cone, so as to capture more air.

The air inlet duct may include a closing and opening means, in particular of the shutter type.

The thermal regulation device may comprise a control means configured to control the means for closing and opening the air inlet duct.

The invention also relates to an arrangement for a motor vehicle, the arrangement comprising a gearbox, the gearbox comprising an external casing, the arrangement comprising a thermal regulation device as defined above, the shell being arranged relative to the external casing so as to create a circulation space for an air flow between the shell and the external casing.

The thermal regulation device may be arranged so as to capture air substantially longitudinally, in particular at the level of a front face of such a motor vehicle.

The arrangement may comprise a radiator and the thermal control device may be arranged to capture air at the radiator in the longitudinal direction, in particular next to the radiator or above or below the radiator in a vertical and transverse plane,
or the thermal regulation device may be arranged so as to capture air in front of the radiator in the longitudinal direction.

The arrangement may comprise a radiator and the thermal regulation device may be arranged to capture air behind the radiator in the longitudinal direction, the radiator may comprise means for closing and opening an air flow passing through the radiator, the means for closing and opening the radiator may regulate the air flow between the shell and the external casing of the gearbox.

The invention also relates to a method of operating a thermal regulation device as defined above, the method comprising:
- measuring the temperature of a gearbox, then
- if the temperature is less than or equal to a first threshold, placing the closing and opening means in the closed position, and
- if the temperature is greater than or equal to a second threshold, the second threshold being strictly greater than the first threshold, placing the closing and opening means in the open position.

The invention also relates to a motor vehicle comprising an arrangement as defined above, or a thermal regulation device as defined above.

Presentation of figures

These objects, characteristics and advantages of the present invention will be explained in detail in the following description of an embodiment of a thermal regulation device and of variants, of an embodiment of a method of operating the thermal regulation device made without limitation in relation to the attached figures among which:

There is a schematic view of a motor vehicle according to one embodiment of the invention.

There is a partial schematic view of the vehicle according to the embodiment of the invention.

There is a partial perspective view of the vehicle according to the embodiment of the invention.

There is a partial bottom view of the vehicle according to the embodiment of the invention.

There is a side view of a thermal regulation device according to the embodiment.

There is a front view of the thermal regulation device according to the embodiment.

There is a graph illustrating the method of operation of the means for closing and opening an air inlet duct of the thermal regulation device according to the embodiment.

Detailed description

The direction in which a vehicle, in particular a motor vehicle, moves in a straight line is defined as the longitudinal direction X. By convention, the direction perpendicular to the longitudinal direction, located in a plane parallel to the ground, is called the transverse direction Y. The third direction, perpendicular to the other two, is called the vertical direction Z. Thus, a direct XYZ reference frame is used in which X is the longitudinal direction in the front-rear direction of the vehicle, therefore directed towards the rear, Y is the transverse direction directed towards the right and Z is the vertical direction directed upwards. The forward direction corresponds to the direction in which the vehicle usually moves in the longitudinal direction and is opposite to the rear direction.

As illustrated in the , a motor vehicle 1 comprises a GMP powertrain. Such a powertrain comprises at least one engine 8. The engine 8 is for example of the internal combustion engine type, or electric, or even hybrid. The vehicle 1 comprises a gearbox 2. The gearbox may comprise at least one electric machine operating for driving the vehicle and/or for generating current for recharging a traction battery. The gearbox 2 comprises an external casing 3.

Preferably, the motor vehicle 1 comprises a front face 5. Advantageously, a radiator 6 is arranged at this front face 5. The radiator 6 is for example of the air/liquid exchanger type, a liquid of the coolant type for the engine(s) 8 being able to flow through the radiator 6 in order to be cooled. Alternatively, several radiators, for example superimposed or substantially superimposed, are arranged at the front face.

The vehicle 1 comprises an engine compartment 9. The engine compartment 9 generally accommodates at least the engine(s) and the gearbox 2. Advantageously, as illustrated in FIGS. 1 and 2, the engine compartment 9 is arranged at the front of the vehicle. Thus, the radiator 6 arranged near the front face 5 of the vehicle is close to the engine 8 and the gearbox 2.

The motor vehicle 1 further comprises an arrangement 4. The arrangement 4 comprises the gearbox 2 and the external casing 3 of the gearbox 2. The arrangement 4 further comprises a thermal regulation device 10 for the gearbox 2. As will be seen later, the thermal regulation device 10 is arranged so as to capture the air in a substantially longitudinal direction, preferably at the front face 5 of the motor vehicle 1.

More specifically, as illustrated in FIGS. 2, 4, 5 and 6, the thermal regulation device 10 comprises a shell, or cover, or casing 11. The shell 11 is intended to envelop at least in part the external casing 3 of the gearbox 2. Preferably, the shell 11 is arranged relative to the external casing 3 to create a circulation space E for an air flow F between the shell 11 and the external casing 3 ( ). Thus, preferably, the shell 11 does not come into full contact with the external casing 3 of the gearbox 2. Preferably, the shell 11 comprises an insulating material. For example, the shell 11 is covered, on the side of its face facing the external casing 3 and/or on the side of its opposite face, with an insulating material, for example rock wool.

Advantageously, as illustrated in FIGS. 2, 3, 4, 5 and 6, the thermal regulation device 10 comprises an air inlet duct 20, for example of the tubing type. Preferably, the section of the duct 20 is circular, or substantially circular, in particular so as to obtain a flow of air within the duct with low pressure losses. Thus, as illustrated in FIG. , the air flow F enters the duct 20 and passes between the external casing 3 of the gearbox 2 and the shell 11, in other words in the space E for circulation of the flow F. Note that this space E extends in front of, and/or below and/or above the external casing 3.

Advantageously, the air inlet duct 20 comprises an intake, an inlet, an inlet 21 for the air. The intake 21 preferably has a non-constant section, for example frustoconical, so as to capture more air. In this case, a section 22 arranged at the front of the intake 21, in a vertical and transverse plane, has a greater area than an area of a section 23 arranged at the rear of the intake, in a vertical and transverse plane, as illustrated in particular in FIGS. 3, 5 and 6. For example, as illustrated in FIGS. , the rear section 23 of the intake 21 is identical, or substantially identical, to the section of the air inlet duct 20. The front section 22 of the intake is for example circular in shape, or square in shape, or rectangular in shape, or rectangular in shape with at least one chamfered corner 24, as illustrated in the . In any case, the front section 22 of the intake 21 is shaped so as to integrate as easily as possible at the level of the front face 5 of the vehicle 1, preferably by capturing a maximum of air.

As schematically illustrated in the , the air inlet duct 20 preferably comprises a closing and opening means 30. Preferably, the means 30 is arranged within or at the intake, i.e. between the front and rear sections 22, 23. Alternatively, the means 30 may be arranged within the duct 20, outside the fresh air intake area. For example, the closing and opening means 30 is of the flap or butterfly type, pivoting about an axis extending for example vertically or transversely. In this case, preferably, the thermal regulation device 10 comprises a control means 13 configured to control the closing and opening means 30 of the air inlet duct 20. The control means 13 comprises for example a means for measuring the temperature, for example of the probe type, of the external casing 3 and/or the temperature of the oil present in the gearbox 2 and/or the coolant temperature of the engine 8. Thanks to the control means 13, the means 30 is for example opened from a measured high threshold temperature. By "open", it is meant that the flap 30 lets air pass into the duct 20. By opening the flap 30, the air or flow F illustrated in the , circulates around the gearbox in particular in space E. Alternatively, preferably in addition, the means 30 is for example closed as long as a measured low threshold temperature is not reached. By "closed" is meant that the flap does not allow air to pass, or substantially does not allow air to pass.

Alternatively or in addition, the thermal regulation device 10 is arranged so as to capture the air at the radiator 6 in the longitudinal direction. For example, the intake 21 is arranged next to the radiator 6, or above, or below the radiator 6 in a vertical and transverse plane. Alternatively, the thermal regulation device 10 is arranged so as to capture the air in front of the radiator 6 in the longitudinal direction.

Alternatively, according to a first variant not illustrated, it may be provided that the thermal regulation device does not have a means of closing and opening the air duct. In this case, as soon as there is a movement of the vehicle, an air flow is created in the air duct and propagates around the gearbox, more precisely between the external casing and the shell. Thus, any movement of the vehicle towards the front, in the event of an air intake arranged substantially longitudinally and opening towards the front, causes cooling of the gearbox and/or of the lubricating oil of this gearbox. In this case, without movement of the vehicle, no air flow is created.

Alternatively, according to a second variant not illustrated, the thermal regulation device is arranged so as to capture the air behind the radiator in the longitudinal direction. In this case, preferably the radiator 6 comprises a means 7 for closing and opening an air flow passing through the radiator(s) 6 (closing and opening means 7 illustrated in the ). The intake is then arranged behind the radiator 6 (embodiment not illustrated), the means of closing and opening 7 of the radiator 6 then making it possible to regulate the flow of air entering the intake. Thus, it is the means of regulating the radiator which authorizes or not the creation of an air flow within the air duct and consequently in the space between the shell and the external casing of the gearbox.

For example, the intake 21 or scoop is made of polypropylene (PP). For example, the intake duct or tube or sleeve 20 is made of polypropylene and/or Ethylene-Propylene-Diene Monomer (EPDM). Preferably, the gearbox is rigidly fixed relative to the engine while the engine is fixed relative to the body via vibration filtration means. In addition, the shell 11 is preferably fixed directly to the external casing 3 of the gearbox. Thus, movements are possible between the shell secured to the gearbox and the air inlet duct, for example fixed to the body. Thanks to the EPDM type material in particular, such movements are tolerated where appropriate by the duct 20 without risk of cracking and/or breakage of the duct and/or at a junction 12 between the duct 20 and the shell 11 (junction 12 illustrated in FIGS. 5 and 6).

A mode of execution of a method of operation of the thermal regulation device 10 will now be described.

In a first step, a temperature of the gearbox 2 is measured. This measurement, preferably carried out with a temperature probe, is carried out in the lubricating oil, for example at the bottom of the gearbox. Alternatively, or in addition, a temperature measurement is carried out on the external casing, for example on an internal wall of the external casing. Alternatively, or in addition, a temperature measurement is carried out in the coolant of the engine 8.

Then, the measured temperature is compared to a first threshold or first threshold value, and to a second threshold or second threshold value. Note that the second threshold is strictly higher than the first threshold.

If the measured temperature is less than or equal to the first threshold, then the closing and opening means 30 is placed in the closed position, or left in the closed position if the means 30 is already in the closed position. This has the effect of promoting the temperature rise of the gearbox as will be specified later.

If the measured temperature is greater than or equal to the second threshold, then the closing and opening means 30 is placed in the open position, or left in the open position if the means 30 is already in the open position. This has the effect of cooling the gearbox as will be specified later.

In particular, when measuring the temperature of the lubricating oil, the first threshold is preferably a low temperature in the optimum operating range of the oil, or even a temperature slightly below this range. In this case, the second threshold is preferably a high temperature in the optimum operating range of the oil, or even a temperature slightly above this range. The optimum operating range of the oil is understood to mean a temperature range in which the oil has optimum or even maximum lubricity. For example, this range is 70 to 90 degrees Celsius.

There illustrates an opening/closing law of means 30 (level of opening of the intake flap expressed in percentages on the ordinate) as a function of the measured temperature of the gearbox oil (temperature of the lubricating oil expressed in degrees Celsius on the abscissa).

For example, on the , the first oil temperature threshold value is 70 degrees C and the second oil temperature threshold value is 90 degrees C. Thus, in the event of a measured temperature value less than or equal to 70 degrees C, the flap 30 is, or remains, closed. In the event of a measured temperature value greater than or equal to 90 degrees C, the flap 30 is, or remains, fully open. In the temperature range between the first threshold and the second threshold, i.e. above 70 degrees C and below 90 degrees C, the flap is preferably opened gradually, proportionally to the change in temperature for example, according to a slope P illustrated in the . These two thresholds make it possible to avoid oscillations of the shutter likely to generate noise and consequently wear of such a shutter and/or its pivoting means where applicable. Thanks to such a control, the duration between two temperature measurements can be short without generating recurrent oscillations of the shutter 30.

Alternatively, a single temperature threshold value is defined and the shutter opens as soon as the measured temperature exceeds this threshold value and closes as soon as the measured temperature falls below this threshold value. This operation causes oscillations of the shutter as soon as the measurements are around the threshold value. Preferably, in this case, the time between two measurements is increased so as to limit the oscillations in opening/closing of the shutter 30.

In the case of control with temperature measurement, the control of the shutter is therefore independent of the speed of the vehicle. As a reminder, the control is therefore done according to the temperature of the oil and/or the temperature of the gearbox (for example its external casing), and/or the temperature of the coolant of the engine(s) connected to the gearbox.

In the case of the first variant, i.e. without means of closing and opening the air inlet duct, the cooling of the gearbox depends on the speed of the vehicle.

In summary, the solution involves a thermal envelope for a gearbox allowing active blowing on the external casing of the gearbox.

In particular, the solution is suitable for a gearbox coupled to an electric motor in order to improve the efficiency of the gearbox, in particular to generate a shorter warm-up time for the gearbox, in particular with a view to the WLTP approval cycle, coming from the Anglo-Saxon expression "Worldwide harmonised Light vehicles Test Procedure", generally of the order of 30 minutes. As a reminder, reducing the warm-up time of the gearbox reduces friction within it.

Note that the solution can be used for a gearbox coupled to a hybrid engine or adapted to a reducer or a gearbox with manual gear change.

Advantageously, the thermal envelope or shell 11 around the gearbox is arranged essentially on the front face and/or under the gearbox.

When starting, particularly in cold weather, the shell 11 creates an insulated enclosure and facilitates the temperature rise of the gearbox. For example, the shell is made of polyamide, possibly caulked, insulated on at least one face of the shell. Thus, a volume of air heats up quickly between the shell 11 and the external casing 3, particularly when the vehicle is not running and/or when the flap 30 is closed. The small volume of air rapidly heated at the space E promotes the temperature rise of the gearbox, which quickly improves its efficiency and limits the consumption of electrical energy and/or fuel. Indeed, the low value of the optimum temperature range of the gearbox is quickly reached. In other words, the disadvantages of a low-temperature oil, particularly in terms of viscosity, only last for a short time.

Once the gearbox is hot, for example from a measured temperature threshold value as seen previously, fresh air is introduced between the shell 11 and the external casing 3 of the gearbox via the opening of the intake 21 of the fresh air inlet duct 20. The opening of the flap 30 makes it possible to circulate fresh air in the space E and to prevent the external casing 3 as well as the oil present in the gearbox from reaching excessively high temperatures. By thus limiting the maximum temperature of the oil, temperatures are prevented from reaching temperatures for which the oil film between the gears is too thin. In other words, the reliability of the gearbox at high temperatures is guaranteed, in particular at high speeds, for example when driving on the motorway. As a reminder, this blowing is obtained by capturing air preferably at the front, for example in front of or at the radiator 6.

As seen previously, preferably the closing and opening means 30 of the air inlet duct 20 is controlled as a function of the temperature of the oil in the gearbox 3 so as to promote a lowering of the oil temperature (in the event of significant stresses on the gearbox, in particular when driving on the motorway and/or high outside temperatures) or to promote a rise in the oil temperature (in the event of a cold start, in particular in cold weather, for example negative outside temperatures).

Thanks to the solution, the gearbox oil and its structure can be maintained within an optimum temperature range, for example between 60 or 70 degrees Celsius and 90 degrees Celsius. This results in improved efficiency of the gearbox, which is thus wrapped and equipped with a ventilated external housing if necessary. The solution therefore reduces heat losses from the gearbox when cold while ensuring its reliability when hot.

Furthermore, by avoiding reaching excessively high temperatures, for example of the order of 100 degrees Celsius, any deterioration in the mechanical strength of the gear teeth and/or bearings and/or rollers of the gearbox is avoided. By reducing the operating time below the temperature range, for example below 60 degrees Celsius, the efficiency of the gearbox is improved.

The solution therefore helps to reduce the consumption of the powertrain during the start-up phase, particularly during a homologation cycle (WLTP as mentioned above), while ensuring excellent mechanical resistance of the gearbox components once the start-up phase is complete and/or during high loads, particularly when driving at high speeds.

In the second variant using the means 7 for closing and opening the flow passing through the radiator(s) 6 instead of the intake flap, it is possible to take advantage of the opening/closing phases of the means 7 in terms of control. Optionally, a compatible control law for the radiator(s) and the gearbox can be determined. This second variant makes it possible to limit costs since no flap must be designed and mounted on the vehicle.

Advantageously, the geometric shapes of the intake 21 and/or the duct 20 and/or the shell 11, in particular with respect to the external casing 3 concerning the shell 11, are determined so as to maximize the flow of fresh air for cooling (intake 21 open if necessary) and so as to isolate the external casing for heating the gearbox (intake closed if necessary). For example, the shell 11 “follows”, or substantially follows, the shapes of the external casing 3, in particular under the gearbox, leaving a gap extending perpendicularly with respect to the external casing of the order of 2 cm to 3 cm. In other words, the air circulation space E (open intake and/or vehicle moving in the forward direction) or air stagnation space (closed intake and/or vehicle stationary) includes an air gap, for example of the order of 2 to 3 cm thick, around the external casing.

For example, the presence of the shell increases the oil temperature by around 7 degrees Celsius and opening the intake causes a drop of around 12 degrees Celsius, particularly at high vehicle speeds.

For example, at an ambient temperature of around minus 7 degrees Celsius, the presence of the thermal regulation device makes it possible to increase the temperature of the gearbox quickly by around 10 degrees, or even by around 20 degrees Celsius compared to a gearbox not having this equipment. This increase in temperature makes it possible to quickly reach around 50 degrees C for the gearbox, i.e. to reach a value close to the optimum temperature range for the gearbox.

The thermal regulation device therefore allows, when starting the engine(s) in particular, in particular in cold weather, for the gearbox oil to reach the optimum operating temperature range quickly. Conversely, in particular in hot weather and/or at high engine speed(s) and/or at high gearbox speed, the gearbox oil remains within the optimum operating temperature range without exceeding it. Thus, the gearbox equipped with the regulation device operates for a very short time with viscous oil, which is synonymous with a loss of gearbox efficiency and causes excess consumption of the vehicle in terms of electricity and/or fuel. In addition, the oil film between the gears meshing together remains sufficiently thick and prevents any premature wear of the gears at high speed and/or high ambient temperature. This avoids wear that could cause abnormal noises from the gearbox, or even malfunctions, or even breakage of gears leading to deterioration of the gearbox.

As a side note, the solution therefore achieves the desired objective of making a motor vehicle gearbox more reliable and has the advantage of being able to be adapted for another motorized vehicle, for example a motorcycle, a snowmobile, a tractor, a construction machine or even a train.

Claims (11)

Thermal regulation device (10) for a gearbox (2) of a motor vehicle (1), characterized in that the thermal regulation device (10) comprises a shell (11) intended to at least partially envelop an external casing (3) of such a gearbox (2) to facilitate the temperature rise of the gearbox (2), in particular when starting such a motor vehicle (1). Thermal control device (10) according to claim 1, characterized in that the thermal control device (10) comprises an air inlet duct (20) to facilitate cooling of the gearbox (2). Thermal regulation device (10) according to the preceding claim, characterized in that the air inlet duct (20) comprises an inlet (21) for the air, the inlet (21) having a non-constant section, in particular frustoconical, so as to capture more air. Thermal regulation device (10) according to one of claims 2 or 3, characterized in that the air inlet duct (20) comprises a closing and opening means (30), in particular of the shutter type. Thermal regulation device (10) according to the preceding claim, characterized in that the thermal regulation device (10) comprises a control means (13) configured to control the closing and opening means (30) of the air inlet duct (20). Arrangement (4) for a motor vehicle (1), the arrangement (4) comprising a gearbox (2), the gearbox (2) comprising an outer casing (3), the arrangement (4) comprising a thermal regulation device (10) according to one of the preceding claims, the shell (11) being arranged relative to the outer casing (3) so as to create a circulation space (E) for an air flow between the shell (11) and the outer casing (3). Arrangement (4) according to the preceding claim, characterized in that the thermal regulation device (10) is arranged so as to capture the air substantially longitudinally, in particular at the level of a front face (5) of such a motor vehicle (1). Arrangement (4) according to one of claims 6 or 7, characterized in that it comprises a radiator (6) and in that the thermal regulation device (10) is arranged so as to capture air at the radiator (6) in the longitudinal direction, in particular next to the radiator (6) or above or below the radiator (6) in a vertical and transverse plane, or
in that the thermal regulation device (10) is arranged so as to capture air in front of the radiator (6) in the longitudinal direction. Arrangement (4) according to one of claims 6 or 7, characterized in that it comprises a radiator (6) and in that the thermal regulation device (10) is arranged so as to capture the air behind the radiator (6) in the longitudinal direction, the radiator (6) comprising a means (7) for closing and opening a flow of air passing through the radiator (6), the means (7) for closing and opening the radiator (6) regulating the flow of air between the shell (11) and the external casing (3) of the gearbox (2). Method of operating a thermal regulation device (10) according to one of claims 4 or 5, characterized in that it comprises:
- measuring the temperature of a gearbox (2), then
- if the temperature is less than or equal to a first threshold, placing the closing and opening means (30) in the closed position, and
- if the temperature is greater than or equal to a second threshold, the second threshold being strictly greater than the first threshold, placing the closing and opening means (30) in the open position. Motor vehicle (1), characterized in that it comprises an arrangement (4) according to one of claims 6 to 9, or a thermal regulation device (10) according to one of claims 1 to 5.