WO2023232464A1

WO2023232464A1 - Electric actuator for motor vehicle comprising a safety valve

Info

Publication number: WO2023232464A1
Application number: PCT/EP2023/063181
Authority: WO
Inventors: Philippe Bourlon
Original assignee: Hitachi Astemo France
Priority date: 2022-05-30
Filing date: 2023-05-16
Publication date: 2023-12-07
Also published as: FR3135941B1; FR3135941A1

Abstract

The invention relates to an electric actuator (4) for a brake (2) of a motor vehicle (1), comprising: - a housing (5), and - filtering means (8) which are supported by the housing (5) and allow circulation of water vapour between the inside (9) and the outside of the housing (5) and prevent circulation of liquid water between the inside (9) and the outside of the housing (5). Part of the filtering means (8) is supported by a safety valve (10) which is mounted so as to be movable on the housing (5) between a closed rest position in which it is inactive and an open safety position in which it is active. The safety valve (10) is configured to move into the open safety position when the pressure inside (9) the housing (5) reaches, or exceeds, a predetermined pressure threshold.

Description

Electric actuator for a motor vehicle comprising a safety valve

Technical field of the invention

The invention relates to the field of electric actuators for motor vehicle brakes.

Technical background

A braking system of a motor vehicle generally comprises mechanical means for applying the brake including in particular friction means, such as brake pads or shoe linings, connected to an actuator capable of moving these friction means in direction of a rotor linked in rotation to a wheel of the vehicle to grip it and thus brake the vehicle by friction, or move them apart in order to stop braking. In the case of an electromechanical brake, the mechanical clamping means are controlled by an electric actuator intended to provide the clamping force. The electric actuator usually comprises a housing inside which is housed an electric motor equipped with a rotating shaft which drives the mechanical clamping means. The actuator housing also generally includes other electrical or electronic components necessary for the proper functioning of the brake. Thus, it is desirable to avoid as much as possible the presence of foreign elements, in particular liquid water, inside the actuator housing in order to reduce the risk of damaging the components housed there, which would affect the proper functioning of the brake.

For this, it is known to manufacture the electric actuator in such a way that its housing is hermetically closed once mounted on the brake, in particular with an envelope protection index of IP67 or IP68 according to the international standard IEC 60529. However, during manufacturing, the air trapped in the case has a humidity level which is not zero. Consequently, when a thermal shock occurs, for example due to an increase in the temperature inside the case due to the heat emitted during braking, the water vapor present in the case condenses and can cause corrosion of the electrical and electronic components present in the case. Such corrosion is undesirable because it is likely to cause malfunctions in the braking system and therefore create a risk of accident.

To combat this condensation, it is known to add to the housing of the electric actuator one or more filtration devices allowing the circulation of water vapor and preventing the circulation of liquid water between the inside and the outside. of the case. These filtration devices include, for example, a filtration membrane which is permeable to water vapor and impermeable to liquid water. Thus, by allowing ventilation of the internal space of the case, we reduce the risk that the water vapor present will condense there and therefore that a corrosion phenomenon will occur. However, this solution has drawbacks.

Indeed, over the life of the brake, the filtration device becomes less and less efficient because residues, such as dust or braking particles, are deposited on the filtration membrane and block it at least partially. part. As the surface area of the filtration membrane that is sealed increases, the capacity of the membrane to allow the circulation of water vapor between the interior and exterior of the housing decreases. As a result, the risk that the water vapor present inside the case condenses and causes corrosion of the electrical and electronic components increases.

The invention aims in particular to provide an electric actuator for a motor vehicle brake for which the risk of corrosion of the components present inside the actuator housing is reduced.

To this end, the subject of the invention is an electric actuator for a motor vehicle brake, comprising:
- a box, and
- filtration means carried by the housing and allowing circulation of water vapor between the interior and exterior of the housing and preventing circulation of liquid water between the interior and exterior of the housing,
in which part of the filtration means is carried by a safety valve movably mounted on the housing between a closed rest position in which it is inactive and an open safety position in which it is active,
the safety valve being configured to move to the safety open position when the pressure inside the housing reaches or exceeds a predetermined pressure threshold.

During the life of the electric actuator, the capacity of the filtration means to allow the circulation of water vapor between the interior and exterior of the housing decreases. This is particularly the case, for example, when the filtration means include a filtration membrane which is likely to be blocked by dust, such as braking particles, and therefore to become less effective during the life of the device. the actuator. Consequently, when the temperature inside the housing increases, for example following braking or operation of the electric motor, the pressure in the internal space of the housing also increases because the air circulation using filtration means is reduced. The increase in pressure inside the housing therefore reflects the reduction in the filtration capacity of the filtration means. Thus, by increasing the capacity for circulation of water vapor via the safety valve when the pressure inside the box reaches or exceeds a predetermined threshold, it is possible in a simple and effective way to reduce the risk that steam water present inside the case condenses.

The pressure threshold is predetermined according to the characteristics of the electric actuator so that it corresponds to a pressure reflecting an operation deemed insufficient of the filtration means with regard to the circulation of water vapor between the interior and exterior of the case. In other words, the safety valve constitutes an emergency filtration means which is mobilized when necessary. In normal conditions, that is to say when the filtration means allow sufficient circulation of water vapor between the interior and exterior of the housing, the safety valve is in the closed rest position and does not is therefore little or not exposed to foreign elements which could clog it. Thus, when an increase in filtration capacities is necessary, the safety valve can effectively fulfill its filtration function.

The safety valve is inactive when it is in the closed rest position, that is to say it does not participate in the filtration function of the filtration means. In other words, when it is inactive, the safety valve does not allow circulation of water vapor between the inside and outside of the housing and also does not allow circulation of liquid water between the inside and the outside of the case.

The safety valve is active when it is in the safety open position, that is to say when it participates in the filtration function of the filtration means. In other words, when active, the safety valve allows circulation of water vapor between the interior and exterior of the housing and prevents circulation of liquid water between the interior and exterior of the housing.

It is understood that in normal operation, the filtration means comprise, for example, a filtration device allowing circulation of water vapor between the interior and exterior of the housing and preventing circulation of liquid water between the interior and exterior of the case. According to a particular embodiment, the filtration device comprises at least one filtration membrane permeable to water vapor and impermeable to liquid water.

The invention may also include one or more of the following optional features, taken alone or in combination.

The predetermined pressure threshold is between 0 and 0.5 bar. This range of pressure threshold values advantageously covers the pressure threshold values which best reflect a reduction in the capacity of the filtration means to allow circulation of water vapor between the interior and exterior of the housing which is likely to generate a significant risk of condensation of water vapor present inside the housing. The lower limit of the range of pressure threshold values is therefore sufficiently low not to cause activation of the safety valve while the capacity of the filtration means to circulate water vapor between the interior and the exterior of the housing is still sufficient for safe operation of the electric actuator. The upper limit of the range of pressure threshold values is sufficiently high not to risk non-activation of the safety valve while the capacity of the filtration means to circulate the water vapor between the interior and exterior of the housing has decreased so as to cause a risk of condensation of water vapor inside the housing.

The safety valve is configured to move from its closed rest position to its open safety position according to a sliding movement relative to the housing, this sliding being caused by a pressure difference between the pressure inside the housing and the pressure outside the case. The transition from the closed rest position to the open safety position is thus obtained in a simple and economical manner. Furthermore, it is understood that the sliding movement of the safety valve advantageously makes it possible to rid the safety valve of possible foreign elements, for example braking particles, which may have become fixed on it. This improves the lifespan of the safety valve and therefore of the electric actuator. The fact that the passage between the two positions of the safety valve is carried out thanks to the pressure difference between the inside and the outside of the box is advantageous because it is an economical solution which does not require a special order. Alternatively, according to another embodiment, the electric actuator comprises a pressure sensor intended to measure the pressure inside the housing, the electric actuator being configured to control a passage of the safety valve into the safety open position when the pressure sensor detects that the pressure inside the housing has reached or exceeded a predetermined pressure threshold.

The safety valve includes a filtration membrane that is permeable to water vapor and impermeable to liquid water. This is a simple and effective way for the safety valve to perform its filtration function when activated, that is to say when it is in the safety open position. We understand that the use of a membrane for the filtration function is advantageous because it is space-saving, simple to implement and economical.

According to one embodiment, the filtration membrane is made of expanded polytetrafluoroethylene. Such membranes are also known by the trade name goretex membrane and offer good performance in liquid water impermeability and water vapor permeability.

Advantageously, the actuator further comprises a safety valve activation detector intended to detect when the safety valve is in the safety open position. It is thus possible to warn a user of the vehicle or an operator carrying out a maintenance operation on the vehicle that the safety valve is in the safety position. Thus, the vehicle user or operator understands that the safety valve is activated and therefore that a change of the main filtration means is necessary to ensure optimal operation of the electric actuator. According to one embodiment, the electric actuator comprises an electronic control unit configured to control the emission of a signal, for example the lighting of a warning light on the dashboard, when the activation detector of the safety valve detects that the safety valve is in the safety open position. In this embodiment the signal emitted is a visual signal. According to another embodiment, the signal emitted is a sound signal.

According to one embodiment, the safety valve activation detector comprises:
- a first detection member fixed on the housing, and
- a second detection member fixed on the safety valve,
the safety valve activation detector being configured so that, when the safety valve is in the closed rest position, the first and second detection members are not in contact with each other, and that , when the safety valve is in the safety open position, the first and the second detection members are in contact with each other. This is a simple and effective way to detect safety valve activation. According to one embodiment, the detection elements are connected to an electronic control unit. The electronic control unit thus receives the contact information between the detection elements and interprets it to determine the position of the safety valve.

The safety valve is fixed to the box by clipping. This is a simple, reliable and economical way to attach the safety valve to the housing. Advantageously, the safety valve can be easily separated from the housing by unclipping it. We understand that maintenance operations on this valve or its replacement are then facilitated. According to other embodiments, the safety valve is fixed in another way on the housing, for example by screwing, by gluing or by welding.

The number of safety valves is between two and thirty. We understand that the higher the number of safety valves, the safer the use of the electric actuator over time. Indeed, when a first safety valve is activated following reaching the predetermined pressure threshold, it is in the safety open position and therefore likely to become clogged. The filtration function of this first safety valve is therefore also likely to decrease over time. The presence of several safety valves makes it possible to maintain a satisfactory filtration function for longer since once the filtration capacities have decreased so as not to allow sufficient circulation of water vapor between the inside and the outside of the housing, the pressure inside the housing increases until it once again reaches the predetermined pressure threshold, thus allowing the activation of a second safety valve. Thus, the greater the number of safety valves present, the longer the life of the electric actuator.

The invention also relates to a brake for a motor vehicle comprising an electric actuator as described above.

Finally, the invention also relates to a motor vehicle comprising a brake as described above.

Brief description of the figures

The invention will be better understood on reading the description which follows, given solely by way of non-limiting example and made with reference to the appended drawings in which:

there is a schematic top view of a vehicle in which a brake comprising an electric actuator according to the invention is mounted;

there is a perspective view of a brake according to the invention;

there is a schematic sectional view of a part of an electric actuator according to a first embodiment of the invention in which a safety valve is shown in the closed rest position (A) and in the open safety position (B) .

there is a schematic sectional view of a part of an electric actuator according to a second embodiment of the invention in which the safety valve is shown in the closed rest position (A) and in the open safety position (B) .

detailed description

We represented on the a motor vehicle 1 in which a brake 2 according to the invention, of the electromechanical type, is arranged on at least two wheels 3, advantageously on the four wheels 3.

The invention applies to any type of brake, in particular those intended to equip motor vehicles of the tourism type, SUV (English acronym for “Sport Utility Vehicles”), two wheels (in particular motorcycles), airplanes, industrial vehicles chosen from vans, “heavy goods vehicles” – i.e. metros, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering machinery -, or other transport or handling vehicles. The invention also applies to non-motorized vehicles such as a trailer, a semi-trailer or a caravan.

In the present case, brake 2 is of the floating caliper disc type. Thus, it conventionally comprises at least two friction elements (not shown) intended to cooperate by friction respectively with opposite faces of a disc (not shown) integral in rotation with one of the wheels 3 of the vehicle 1.

The brake 2 comprises an electric actuator 4 intended to provide the clamping force necessary to move the friction elements and carry out braking. In the present case, the electric actuator 4 notably comprises an electric motor (not shown) housed inside a housing 5, an electronic control unit 6, a heat sink 7 and filtration means 8.

The housing 5 defines an interior space 9 dimensioned so as to be able to accommodate the electric motor and other electrical or electronic components (not shown) useful for the operation of the electric actuator 4. The housing 5 is fixed at one of its ends to the brake 2 so as to put a rotary shaft of the electric motor into communication with means for converting the rotational movement of the rotary shaft into translational movement and allow the movement friction elements. This transmission and conversion of the rotational movement of the rotary shaft of the electric motor is carried out in a conventional manner and will not be detailed in more detail here.

The heat sink 7 is fixed at the end of the housing 5 opposite to that by which the housing 5 is fixed to the rest of the brake 2. The heat sink 7 makes it possible to dissipate the heat from the electric actuator 4, in particular the heat generated during operation of the electric motor. This heat dissipation function of the electric actuator 4 is classic and will not be detailed here.

The filtration means 8 are carried by the housing 5. They allow a circulation of water vapor between the interior 9 and the exterior of the housing 5 and prevent a circulation of liquid water between the interior 9 and the exterior of the housing 5. According to the first embodiment presented in Figures 1 to 3B, part of the filtration means 8 is carried by a safety valve 10. The other part of the filtration means 8 is carried by two filtration devices 11 (see ).

The filtration devices 11 represent main filtration means. In normal operation, it is the filtration devices 11 which ensure the function of the filtration means 8 aimed at allowing the circulation of water vapor between the interior 9 and the exterior of the housing 5 and preventing the circulation of liquid water between the interior 9 and the exterior of the housing 5. In the present case, the two filtration devices 11 are identical and each include a filtration membrane made of expanded polytetrafluoroethylene which is permeable to water vapor and impermeable to water. liquid water. The two filtration devices 11 are each fixedly mounted on the housing 5 of the electric actuator 4. According to other embodiments, the number of filtration devices 11 is different, for example between one and thirty. The greater the number of filtration devices 11, the greater the risk that the function of the filtration means 8 aimed at allowing circulation of water vapor between the interior 9 and the exterior of the housing 5 is impaired. This delays the moment when the use of the safety valve 10 is necessary. According to other embodiments, the filtration devices 11 are not all identical to each other. It is understood in particular that at least one of the filtration devices 11 may comprise a filtration membrane which is not made of expanded polytetrafluoroethylene but of another material permeable to water vapor and impermeable to liquid water.

The safety valve 10 is movably mounted on the housing 5 between a closed rest position (Figure 3A) in which it is inactive and an open safety position (Figure 3B) in which it is active. Thus, when the safety valve 10 is inactive, that is to say when it is in the closed rest position, it does not participate in the filtration function of the filtration means 8. In other words, when it is inactive, the safety valve 10 does not allow a circulation of water vapor between the interior 9 and the exterior of the housing 5. When the safety valve 10 is active, this is that is to say when it is in the safety open position, it participates in the filtration function of the filtration means 8. In other words, when active, the safety valve 10 allows a circulation of water vapor between the interior 9 and the exterior of the housing 5 and prevents a circulation of liquid water between the interior 9 and the exterior of the housing 5. In the present case, the safety valve 10 is fixed on the housing 5 by clipping. According to other embodiments, the safety valve 10 is fixed in another way on the housing 5, for example by screwing, by welding or by gluing.

In the present case, the safety valve 10 is configured to move from its closed rest position (Figure 3A) to its open safety position (Figure 3B) in a sliding movement relative to the housing 5. According to other modes embodiment, this passage can be made following a movement other than sliding.

The safety valve 10 is fixed on the housing 5 at the level of an opening made in the wall 12 of the housing 5. The safety valve 10 is generally cylindrical in shape with a circular section. It is hollow and is open at its internal end, that is to say its end located inside 9 of the housing 5 and is sealed in a sealed manner by a sealing disc 13 at its external end. , that is to say its end located outside the housing 5. The internal end has a shoulder configured to abut against an internal face of the wall 12 of the housing 5 when the safety valve 10 is in safety open position so as to limit the sliding of the safety valve 10. The outer end also has a shoulder formed by the shutter disc 13. A first O-ring seal 14 is fixed on the face of the shutter disc 13 which faces the external face of the wall 12 of the housing 5 (Figures 3A and 3B). Thus, when the safety valve 10 is in the closed rest position, the seal 14 is pressed between the shutter disc 13 and the wall 12 of the housing 5 so as to ensure tight closure of the safety valve 10.

The safety valve 10 comprises a filtration membrane 15 permeable to water vapor and impermeable to liquid water. In the present case, the filtration membrane 15 is made of expanded polytetrafluoroethylene. According to other embodiments, the membrane is made of another material which allows the membrane to be permeable to water vapor and impermeable to liquid water. The membrane is fixed in the internal space delimited by the cylindrical body of the safety valve 10. It is understood that the presence of the shutter disc 13, in addition to ensuring the sealing of the safety valve 10 when in the closed rest position, prevents any particles, for example dust or braking, from settling. on the filtration membrane 15. As a result, as long as the safety valve 10 is in the closed rest position, it is not likely to become clogged. Thus, when the filtration function of the safety valve 10 is necessary, it is fully operational.

The safety valve 10 comprises transverse openings delimiting an air passage channel 16 allowing, when the safety valve 10 is in the safety open position (FIG. 3B), the circulation of water vapor between the interior 9 and the exterior of the case 5.

The safety valve 10 further comprises a second O-ring seal 17 located near the internal end of the safety valve 10 and extending all around the cylindrical wall forming the safety valve 10 (Figures 3A and 3B). The second seal 17 is configured so as to be pressed between the external wall of the safety valve 10 and the wall 12 of the housing at the level of the opening in which the safety valve 10 is mounted, in order to ensure the seal around the safety valve 10 when it is in the safety open position (Figure 3B).

The safety valve 10 is configured to go into the safety open position when the pressure inside 9 of the housing reaches or exceeds a predetermined pressure threshold. Thus, the activation of the safety valve 10 makes it possible to mobilize an additional filtration capacity of the filtration means 8 when the filtration capacity of the main filtration means formed by the filtration devices 11 is no longer sufficient. In this case, the predetermined pressure threshold is between 0 and 0.5 bar.

In the present case, the filtration means 8 comprise a single safety valve 10. According to other embodiments, the filtration means 8 comprise a greater number of safety valves 10, for example between two and thirty safety valves 10. The higher the number of safety valves 10, the greater the filtration capacity reserve of the filtration means 8.

When the filtration capacity of the filtration means 8 decreases, for example when the filtration devices 11 become clogged, the circulation of water vapor between the interior 9 and the exterior of the housing decreases. There is therefore a risk that during a thermal shock the water vapor present inside 9 of the housing 5 will condense and cause corrosion of the elements housed in the housing 5. This reduction in the filtration capacity of the means 8 filtration is accompanied by an increase in the pressure inside 9 of the housing 5, in particular when the temperature of the electric actuator 4 increases. The predetermined pressure threshold is therefore determined as a function of the characteristics of the electric actuator 4 to correspond to the moment when the filtration capacity of the filtration means 8 is considered insufficient and the risk that the water vapor presents inside 9 of housing 5 condenses is too important.

The safety valve 10 is configured so that, when the predetermined pressure threshold is reached, the pressure difference between the interior 9 of the housing 5 and the exterior of the housing 5, which is at atmospheric pressure, causes the sliding according to the direction P of the safety valve 10 from its closed rest position to its open safety position. We thus activate this part of the filtration means 8 which was not previously used, thus increasing the filtration capacities of the filtration means 8 and consequently reducing the risk of water vapor being present inside 9 of the housing 5 condenses.

Figures 4A and 4B illustrate a second embodiment of an electric actuator 4 according to the invention.

The second embodiment differs from the first embodiment only in that the electric actuator 4 further comprises a detector 18 for activating the safety valve 10. This detector 18 for activating the safety valve 10 is intended to detect when the safety valve 10 is activated, that is to say when it is in the safety open position (FIG. 4B). It is thus possible to warn a user of the vehicle 1 or an operator carrying out a maintenance operation on the vehicle 1 that the safety valve 10 is in the safety open position and therefore that the filtration capacity of the filtration devices 11 has greatly reduced .

In the present case, the safety valve activation detector 18 comprises a first detection member 19 fixed on the housing 5 and a second detection member 20 fixed on the safety valve 10. The detector 18 for activating the safety valve 10 is configured so that, when the safety valve 10 is in the closed rest position (FIG. 4A), the first and second detection members 19, 20 are not in contact. with each other, and that, when the safety valve 10 is in the safety open position (FIG. 4A), the first and second detection members 19, 20 are in contact with each other. The first and second detection members 19, 20 are connected to the electronic control unit 6 and transmit a signal to it when they are in contact with each other. The electronic control unit 6 interprets this signal as information that the safety valve 10 is in the safety open position. According to one embodiment, the electronic control unit 6 is configured to emit a signal when it detects contact between the first and second 19, 20 detection members. This signal is of a different nature depending on the embodiments. For example, the signal is visual when the electronic control unit 6 controls the lighting of a warning light on the dashboard or the inscription of a written message on this dashboard. Alternatively or additionally, the signal is audible, the electronic control unit 6 controlling, for example, the emission of an audible alert or a voice message.

The invention is not limited to the embodiments presented and other embodiments will be clear to those skilled in the art.

Reference list

1: motor vehicle
2: brake
3: wheel
4: electric actuator
5: case
6: electronic control unit
7: heat sink
8: filtration means
9: interior of the case
10: safety valve
11: filtration device
12: wall of the box
13: shutter disc
14: first seal
15: filtration membrane
16: air passage channel
17: second seal
18: safety valve activation detector
19: first detection organ
20: second detection unit

Claims

Electric actuator (4) for brake (2) of automobile vehicle (1), comprising:
- a box (5), and
- filtration means (8) carried by the housing (5) and allowing circulation of water vapor between the interior (9) and the exterior of the housing (5) and preventing circulation of liquid water between the the interior (9) and the exterior of the case (5),
characterized in that part of the filtration means (8) is carried by a safety valve (10) movably mounted on the housing (5) between a closed rest position in which it is inactive and an open safety position in which it is active,
the safety valve (10) being configured to go into the safety open position when the pressure inside (9) of the housing (5) reaches or exceeds a predetermined pressure threshold.
Electric actuator (4) according to claim 1, in which the predetermined pressure threshold is between 0 and 0.5 bar.
Electric actuator (4) according to claim 1 or 2, in which the safety valve (10) is configured to move from its closed rest position to its open safety position in a sliding movement relative to the housing (5), this sliding being caused by a pressure difference between the pressure inside (9) of the housing (5) and the pressure outside the housing (5).
Electric actuator (4) according to any one of the preceding claims, in which the safety valve (10) comprises a filtration membrane (15) permeable to water vapor and impermeable to liquid water.
Electric actuator (4) according to claim 4, in which the filtration membrane (15) is made of expanded polytetrafluoroethylene.
Electric actuator (4) according to any one of the preceding claims, further comprising a safety valve (10) activation detector (18) intended to detect when the safety valve (10) is in the safety open position .
Electric actuator (4) according to the preceding claim, in which the detector (18) for activation of the safety valve (10) comprises:
- a first detection member (19) fixed on the housing (5), and
- a second detection member (20) fixed on the safety valve (10),
the detector (18) for activating the safety valve (10) being configured so that, when the safety valve (10) is in the closed rest position, the first and second detection members (19, 20) do not are not in contact with each other, and that, when the safety valve (10) is in the safety open position, the first and second detection members (19, 20) are in contact with each other the other.
Electric actuator (4) according to any one of the preceding claims, in which the safety valve (10) is fixed to the housing (5) by clipping.
Electric actuator (4) according to any one of the preceding claims, in which the number of safety valves (10) is between two and thirty.
Brake (2) for a motor vehicle (1), characterized in that it comprises an electric actuator (4) according to any one of claims 1 to 9.
Motor vehicle (1), characterized in that it comprises a brake (2) according to the preceding claim.